Quanta-Ray Lab-Series Pulsed Nd:YAG Lasers

User’s Manual

1335 Terra Bella Avenue Mountain View, CA 94043

Part Number 0000-311A, Rev. A June 2003

Preface

This manual contains information you need in order to safely install, align, operate, maintain and service your Quanta-Ray Lab-Series pulsed Nd:YAG laser on a day-to-day basis. Also described is the installation and operation of the HG harmonic generator and IHS internal harmonic separator. The system comprises three main elements: the Lab-Series laser head, the power supply and a table-top controller. (The system can also be controlled remotely via the front panel RS-232 serial port.) An optional Model WA-1 heat exchanger may also be present. The “Introduction” contains a brief description of these three components and is followed by an important chapter on laser safety. The Lab-Series is a Class IV laser and, as such, emits laser radiation which can permanently damage eyes and skin, ignite fires and vaporize substances. Moreover, focused back-reflections of even a small percentage of its output energy can destroy expensive internal optical components. This section contains information about these hazards and offers suggestions on how to safe- guard against them. To minimize the risk of injury or expensive repairs, be sure to read this chapter—then carefully follow these instructions. This chapter also contains information regarding system compliance to CDRH and CE regulations. “Laser Description” contains a short section on laser theory regarding the Nd:YAG crystal rods that are used in the Lab-Series laser. Also included is a discussion of the second, third and fourth harmonic laser output generated by the system. Following this is a more detailed description of the Lab-Series laser system, concluding with system specifications and outline drawings. The next few chapters describe the Lab-Series controls and interconnects, and guide you through its installation, alignment and operation. The last part of the manual covers maintenance and service and includes a replacement parts list and a list of world-wide Spectra-Physics service centers you can call if you need help. Appendix A is a Programming Reference Guide for those who wish to operate the laser system automatically. Whereas the “Maintenance” section contains information you need to keep your laser clean and operational on a day-to-day basis, “Service and Repair” is intended to help you guide your Spectra-Physics field service engineer to the source of any problems. Do not attempt repairs yourself while the unit is still under warranty; instead, report all problems to Spectra- Physics for warranty repair.

iii Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

This product has been tested and found to conform to “Directive 89/336/ EEC for electromagnetic Compatibility.” Class A compliance was demonstrated for “EN 50081-2:1993 Emissions” and “EN 50082-1:1992 Immu- nity” as listed in the official Journal of the European Communities. It also meets the intent of “Directive 73/23/EEC for Low Voltage.” Class A compliance was demonstrated for “EN 61010-1:1993 Safety Requirements for Electrical Equipment for Measurement, Control and Laboratory use” and “EN 60825-1:2001 Radiation Safety for Laser Products.” Refer to the “CE Declaration of Conformity” statements in Chapter 2. Should you experience any problems with any equipment purchased from Spectra-Physics, or you are in need of technical information or support, please contact Spectra-Physics as described in “Customer Service.” This chapter contains a list of world-wide Spectra-Physics service centers you can call if you need help. Every effort has been made to ensure that the information in this manual is accurate. All information in this document is subject to change without notice. Spectra-Physics makes no representation or warranty, either express or implied, with respect to this document. In no event will Spectra-Physics be liable for any direct, indirect, special, incidental or consequential dam- ages resulting from any defects in this documentation. Finally, if you encounter any difficulty with the content or style of this manual, or encounter problems with the laser itself, please let us know. The last page of this manual is a form to aid in bringing such problems to our attention. Thank you for your purchase of Quanta-Ray Spectra-Physics instruments.

iv CE Environmental Specifications

CE Electrical Equipment Requirements For information regarding the equipment needed to provide the electrical service listed under “Service Requirements” at the end of Chapter 3, please refer to specification EN-309, “Plug, Outlet and Socket Couplers for Indus- trial Uses,” listed in the official Journal of the European Communities.

Environmental Specifications The environmental conditions under which the laser system will function are listed below: Indoor use Altitude: up to 2000 m Temperatures: 10° C to 40° C Maximum relative humidity: 80% non-condensing for temperatures up to 31° C. Mains supply voltage: do not exceed ±10% of the nominal voltage Insulation category: II Pollution degree: 2

Table of Contents

Preface ...... iii CE Environmental Specifications...... v CE Electrical Equipment Requirements ...... v Environmental Specifications ...... v Warning Conventions ...... xiii Standard Units ...... xv Unpacking and Inspection ...... xvii Unpacking Your Laser ...... xvii System Components ...... xvii Accessory Kit ...... xvii Chapter 1: Introduction ...... 1-1 The Quanta-Ray Lab-Series Pulsed Nd:YAG Lasers ...... 1-1 The Laser Head ...... 1-1 The Controller ...... 1-2 The Power Supply ...... 1-2 The Lab-Series Advantage ...... 1-3 Patents ...... 1-3 Chapter 2: Laser Safety...... 2-1 Precautions For The Safe Operation Of Class IV High Power Lasers ...... 2-1 Safety Devices ...... 2-3 Emission Indicator ...... 2-3 MONITOR: PoWeR ON Indicator ...... 2-3 MONITOR: INTERLOCK Indicator ...... 2-4 REMOTE INTERLOCK Connector ...... 2-4 Cover Safety Interlocks ...... 2-4 POWER Keyswitch ...... 2-5 POWER Circuit Breaker ...... 2-5 Focused Back-Reflection Safety ...... 2-6 Maintenance Necessary to Keep this Laser Product in Compliance with Center for Devices and Radiological Health (CDRH) Regulations ...... 2-6 CE/CDRH Radiation Control Drawing ...... 2-7 Label Translations ...... 2-8 CE Declaration of Conformity ...... 2-9 Sources for Additional Information ...... 2-10 Laser Safety Standards ...... 2-10 Equipment and Training ...... 2-11

vii Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Chapter 3: Laser Description ...... 3-1 A Brief Review of Ion Laser Theory ...... 3-1 Emission and Absorption of Light ...... 3-1 Population Inversion ...... 3-2 Nd:YAG as an Excitation Medium ...... 3-4 Q-switching ...... 3-5 Resonant Optical Cavity ...... 3-6 Longitudinal Modes and Linewidth ...... 3-7 Producing Other Wavelengths ...... 3-8 Resonator Structural Considerations ...... 3-9 Pulse Triggering Sequence and Timing ...... 3-9 General Note on Specifications ...... 3-11 Laser Output Specifications ...... 3-12 Outline Drawing ...... 3-14 Chapter 4: Controls, Indicators and Connections ...... 4-1 The Laser Head ...... 4-1 End Connector Panel ...... 4-3 The Marx Bank ...... 4-4 The Seeder Control Panel ...... 4-4 The Emission Indicator ...... 4-5 The Power Supply Front Panel ...... 4-6 The Power Supply Rear Panel ...... 4-8 The Controller ...... 4-9 The GUI Software Menus ...... 4-11 Main Menu ...... 4-11 Setting Menu ...... 4-13 Information Menu ...... 4-14 Chapter 5: Installation and Alignment...... 5-1 Installing the Laser ...... 5-1 Connecting the Electrical Service ...... 5-1 Connecting the Power Supply and Laser Head ...... 5-3 Connecting the Harmonic Generator ...... 5-3 Filling the Cooling System ...... 5-4 Installing the Lab-Series GUI Software for Remote Control ...... 5-5 Alignment ...... 5-6 Chapter 6: Operation...... 6-1 Operation Using the Controller ...... 6-1 Quick Start/Stop Procedure ...... 6-2 Standard Operation ...... 6-2 Operation Using the GUI Interface ...... 6-5 Quick Start/Stop Procedure ...... 6-5 Standard Operation ...... 6-6 Moving the Laser System ...... 6-8 Chapter 7: Harmonic Generator...... 7-1 Harmonic Generator Controls ...... 7-1 Harmonic Generator Temperature Controller Controls ...... 7-3 Installing the Harmonic Generator ...... 7-3

viii Table of Contents

Operation ...... 7-5 Type I and II Crystals ...... 7-5 Second Harmonic (types I and II), and Third and Fourth Harmonic Generation ...... 7-5 Chapter 8: Internal Harmonic Separator ...... 8-1 Dichroics ...... 8-1 IHS System Description ...... 8-1 System Configurations ...... 8-2 Removing the Beam Dump ...... 8-3 Installing the IHS Mirror Mounts ...... 8-3 Replacing the Dichroic Mirrors ...... 8-5 Operating the IHS ...... 8-6 Removing/Replacing the Beam Dump ...... 8-6 Chapter 9: Maintenance ...... 9-1 Preventive Maintenance ...... 9-1 Cleaning Laser Optics ...... 9-1 Equipment Required ...... 9-2 Cleaning Prisms, Mirrors and Windows ...... 9-3 Maintaining the Cooling System ...... 9-3 Maintaining the Harmonic Generator ...... 9-4 Replacing the Deionizing Water Filter ...... 9-4 Tools needed: ...... 9-4 Procedure ...... 9-5 Replacing the Particulate Filter ...... 9-6 Tools needed: ...... 9-6 Procedure ...... 9-6 Replacing the Air Filters ...... 9-7 Tools needed: ...... 9-7 Procedure ...... 9-7 Replacing the Flash Lamps ...... 9-8 Procedure ...... 9-8 Chapter 10: Service and Repair ...... 10-1 General Operation ...... 10-1 Enabling Signals ...... 10-1 Analog Signals ...... 10-1 Local/Remote Operation ...... 10-2 Q-switch Delay ...... 10-2 Q-switch Advanced Sync Generator ...... 10-2 Mode Switch ...... 10-3 Q-switch Drivers ...... 10-3 Single-Shot Operation ...... 10-3 LAMP ON Switch ...... 10-3 STOP/ENABLE buttons ...... 10-4 Interlock Logic ...... 10-4 Pulse-Forming Network ...... 10-4 Flash Lamp Simmer Supply ...... 10-5 Shipping the Laser and Power Supply ...... 10-5 Draining the Cooling System ...... 10-5 Replacement Parts ...... 10-7

ix Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Chapter 11: Customer Service...... 11-1 Customer Service ...... 11-1 Warranty ...... 11-1 Return of the Instrument for Repair ...... 11-2 Service Centers ...... 11-3 Appendix A: Status/Error Codes ...... A-1 Appendix B: Programming Reference Guide ...... B-1 Notes Report Form for Problems and Solutions List of Figures Figure 1-1: The Lab-Series Laser Head ...... 1-1 Figure 1-2: The Lab-Series Controller ...... 1-2 Figure 1-3: The Lab-Series Power Supply ...... 1-2 Figure 2-1: This CE standard safety warning labels would be appropriate for use as an entry warning sign (EN 60825-1, ANSI 4.3.10.1)...... 2-2 Figure 2-2: Optical Beam Dump, Model BD-5 ...... 2-2 Figure 2-3: Laser Head Emission Indicator ...... 2-3 Figure 2-4: The Lab-Series Power supply Control Panel...... 2-3 Figure 2-5: The Lab-Series Power supply Rear Panel...... 2-4 Figure 2-6: Interlock Switches, Laser Head...... 2-4 Figure 2-7:Interlock Switch, Power Supply...... 2-5 Figure 2-8: CE/CDRH Radiation Control Drawing ...... 2-7 Figure 3-1: Electrons occupy distinct orbitals that are defined by the probability of finding an electron at a given position, the shape of the orbital being determined by the radial and angular dependence of the probability. Shown is an “s” orbital on the left, a “p” type on the right. 3-2 Figure 3-2: A Typical Four-level Transition Scheme ...... 3-3 Figure 3-3: Energy Level Scheme for the Nd:YAG Laser Source ...... 3-4 Figure 3-4: The Q-switch comprises a polarizer, a quarter-wave polarization rotator, and a Pockels cell...... 3-5 Figure 3-5: Stable and Unstable Resonator Configurations ...... 3-6 Figure 3-6: Frequency distribution of longitudinal modes for a single line ...... 3-7 Figure 3-7: Simplified Block Diagram of the Lab-Series electronics...... 3-10 Figure 3-8: Lab-Series Timing Schematic ...... 3-11 Figure 3-9: Outline Drawing ...... 3-14 Figure 4-1: An isometric view of the internal components of the Lab-series laser head...... 4-1 Figure 4-2: Laser Head Rear Panel Controls and Connections...... 4-3 Figure 4-3: The Laser Head Side Panel Injection Seeder Controls ...... 4-4 Figure 4-4: Laser Head Emission Indicator ...... 4-5 Figure 4-5: The Power Supply Front Control Panel ...... 4-6 Figure 4-6: The 9-Pin SERIAL COM Port ...... 4-7 Figure 4-7: The Power Supply Rear Connector Panel ...... 4-8 Figure 4-8: The Controller ...... 4-9 Figure 4-9: The Main Menu Showing all Controls ...... 4-11 Figure 4-10: The Setup Menu ...... 4-13 Figure 4-11: The Information Menu ...... 4-14 Figure 5-1: The location of the autotransformer in the power supply. Taps shown for operating voltages ranging from 190 to 260 Vac...... 5-2 Figure 5-2: Location of system fuses...... 5-2

x Table of Contents

Figure 5-3: The Lab-series laser head showing connections for the umbilical...... 5-3 Figure 5-4: Cooling System Component Identification ...... 5-4 Figure 6-1: The Controller ...... 6-1 Figure 6-2: Burn Patterns ...... 6-3 Figure 6-3: The Main Menu ...... 6-5 Figure 6-4: Burn Patterns ...... 6-7 Figure 7-1: HG and Temperature Controller Component Identification. The controller is located inside the laser head near the HG...... 7-1 Figure 7-2: Controller shown behind the HG...... 7-2 Figure 8-1: The various mounting and output options for the Lab-Series laser...... 8-2 Figure 8-2: Single wavelength: second, third or fourth harmonic...... 8-2 Figure 8-3: Dual wavelength: Second, third or forth harmonic plus the fundamental...... 8-3 Figure 8-4: The IHS dichroic mirrors shown in the “normal” position...... 8-4 Figure 8-5: The IHS Mirror Holder ...... 8-5 Figure 8-6: Model BD-6 water-cooled beam dump showing mounting screws...... 8-6 Figure 9-1: Lens Tissue Folded for Cleaning ...... 9-2 Figure 9-2: Cooling system component identification...... 9-3 Figure 9-3: Short together posts A and B to prevent shock when servicing the flash lamps...... 9-8 Figure 10-1: Cooling system component identification...... 10-6 Figure 10-2: Laser head showing coolant connections on the left...... 10-6 List of Tables Table 2-1 : Label Translations...... 2-8 Table 3-1 : Power Specifications...... 3-12 Table 3-2 : Performance ...... 3-12 Table 3-3 : Mode and Pulse Specifications...... 3-13 Table 3-4: Beam Specifications ...... 3-13 Table 3-5: Service Requirements ...... 3-13 Table 4-1: The SERIAL COM Port Connections ...... 4-7 Table 7-1: Controller Settings ...... 7-4 Table 7-2: Summary of Translation Arm Positions ...... 7-6 Table 7-3: Summary of HG Settings ...... 7-7 Table 10-1: Replacement Parts ...... 10-7 Table A-1: Status/Error Codes ...... A-1

xi Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

xii Warning Conventions

The following warnings are used throughout this manual to draw your attention to situations or procedures that require extra attention. They warn of hazards to your health, damage to equipment, sensitive procedures, and exceptional circumstances. All messages are set apart by a thin line above and below the text as shown here.

Danger! Laser radiation is present. Laser Radiation

Danger! Condition or action may present a hazard to personal safety.

Danger! Condition or action may present an electrical hazard to personal safety.

Warning! Condition or action may cause damage to equipment.

Warning! Action may cause electrostatic discharge and cause damage to equip- ESD ment.

Caution! Condition or action may cause poor performance or error.

Note Text describes exceptional circumstances or makes a special reference.

Don't Do not touch. Touch!

Appropriate laser safety eyewear should be worn during this opera- Eyewear Required tion.

Refer to the manual before operating or using this device.

xiii

Standard Units

The following units, abbreviations, and prefixes are used in this Spectra- Physics manual:

Quantity Unit Abbreviation mass kilogram kg length meter m time second s frequency hertz Hz force newton N energy joule J power watt W electric current ampere A electric charge coulomb C electric potential volt V resistance ohm Ω inductance henry H magnetic flux weber Wb magnetic flux density tesla T luminous intensity candela cd temperature celcius C pressure pascal Pa capacitance farad F angle radian rad

Prefixes tera (1012) Tdeci(10-1) d nano (10-9) n giga (109) G centi (10-2) cpico(10-12) p mega (106) M mill (10-3) mfemto(10-15) f kilo (103) kmicro(10-6) µatto(10-18) a

Unpacking and Inspection

Unpacking Your Laser Your Quanta-Ray Lab-Series pulsed Nd:YAG laser was packed with great care, and its container was inspected prior to shipment—it left Spectra- Physics in good condition. Upon receiving your system, immediately inspect the outside of the shipping containers. If there is any major damage (holes in the containers, crushing, etc.), insist that a representative of the carrier be present when you unpack the contents. Carefully inspect your laser system as you unpack it. If any damage is evident, such as dents or scratches on the covers or broken knobs, etc., immediately notify the carrier and your Spectra-Physics sales representative. Keep the shipping containers. If you file a damage claim, you may need them to demonstrate that the damage occurred as a result of shipping. If you need to return the system for service at a later date, the specially designed container assures adequate protection.

System Components The following components comprise the Lab-Series pulsed Nd:YAG laser system: • Nd:YAG laser head • Power supply • Controller Verify all three components are present. Each component is shipped in a separate container.

Accessory Kit Included with the laser system is this manual, a packing slip listing all the parts shipped, and an accessory kit containing the following items: • US or European (German) power cord for the controller, 2 m • table clamp kit: 4 clamps and hardware • a Bondhus SAE Allen wrench set 5 •a /32 in. ball driver • 0–1 SCFH air flow gauge for nitrogen purge • purge hose adaptor couplings • garden hose couplings with ½ in. barbs • spare fuses

xvii Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

• alignment pinhole • Infrared card • CD-ROM with GUI software for remote operation from a Windows- based PC.

xviii Chapter 1 Introduction

The Quanta-Ray Lab-Series Pulsed Nd:YAG Lasers The Quanta-Ray Lab-Series Nd:YAG laser comprises the laser head (Fig- ure 1-1 with the cover removed), a table-top controller (Figure 1-2) and a power supply (Figure 1-3). The system is controlled locally using the small controller that is provided with the system, or remotely via a computer connected to the RS-232 serial port located on the front of the power supply. Provided on the side of the laser head are controls for operating the optional injection seeder. Chapter 3 explains how the laser works. Chapter 4 explains the functions of all the various system parts and controls. The following is a brief description of the system.

The Laser Head The Lab-Series Nd:YAG laser is a pulsed, oscillator-only system configured with either two pump chamber assemblies with one flash lamp each (for high power), or a single pump chamber assembly with two flash lamps (for high rep. rate). The 1064 nm oscillator is typically followed by the optional harmonic generation (HG) stage that can be set to generate 532, 355 or 266 nm output wavelengths. The HG is followed by a pair of dichroic mirrors that reflect the desired harmonic as laser output, while transmitting the undesired wavelengths into a beam dump.

Figure 1-1: The Lab-Series Laser Head

1-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

The Controller

Figure 1-2: The Lab-Series Controller The easy-to-use controller employs conventional knobs and switches for setting and controlling the various system parameters. It provides control from virtually any point in the laboratory via an 8-foot cable that plugs into the REMOTE connector on the front of the power supply. For remote control from a computer or terminal, an RS-232C serial port is provided on the front of the power supply. In addition, an IEEE-488 interface can be optionally installed for system control.

The Power Supply

Figure 1-3: The Lab-Series Power Supply The power supply houses the ac/dc power supplies, the PFN simmer power supply (which stores the power required to flash the lamps at a given rate) and the flash lamp power supplies (which provides the energy in the first place). An RS-232C serial port is provided on the front panel for remote control of the system. An optional IEEE-488 parallel interface is also available for remote control.

1-2 Introduction

The power supply is water cooled and requires an external source of clean cooling water. (The optional Model WA-1 water-to-air heat exchanger can be used for this purpose when plentiful clean water is not available.) For electrical power, 190–250 Vac, 35 A is required for 10 Hz systems, 40 A for 30 Hz system and 55 A for 50 Hz systems.

The Lab-Series Advantage • Easy-to-use controller • Dichroic mirror mounts that provide excellent beam pointing performance (±50 µrad) • Diffused gold reflectors for optimum mode control over time • Sealed dust tubes with nitrogen purge to improve system cleanliness • Highest damage threshold optics in the industry • Single-rod oscillator design for high rep-rate operation • Dual-rod oscillator design for high power models • Ventilated cover design for system stability

Patents The Quanta-Ray Lab-Series laser systems are manufactured under one or more of the following U. S. patents: 4,156,209 4,232,276 4,197,513 4.955,725 4,936,932 4,232,272 4,310,808 4,342,113 4,360,925 5,001,716

1-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

1-4 Chapter 2 Laser Safety

Danger! This Spectra-Physics Quanta-Ray Lab-Series Laser is a Class IV–High Laser Radiation Power Laser whose beam is, by definition, a safety and fire hazard. Take precautions to prevent accidental exposure to both direct and reflected beams. Diffuse as well as specular beam reflections can cause severe eye or skin damage. Because the 1064 nm output beam and some of its harmonics are invisible, they are especially dangerous. Infrared radiation passes easily through the cornea, which, when focussed on the retina, can cause instantaneous permanent damage.

Precautions For The Safe Operation Of Class IV High Power Lasers • Wear protective eyewear at all times; selection depends on the wave- Eyewear length and intensity of the radiation, the conditions of use and the Required visual function required. Protective eyewear is available from suppliers listed in the Laser Focus World, Lasers and Optronics, and Photonics Spectra buyer’s guides. Consult the ANSI and ACGIH standards listed at the end of this section for guidance. • To avoid unnecessary radiation exposure, keep the protective cover on the laser head at all times. • Avoid looking at the output beam; even diffuse reflections are hazardous. • Avoid blocking the output beam or its reflections with any part of the body. • Avoid wearing reflective jewelry while using the laser. • Use an infrared detector or energy detector to verify the laser beam is off before working in front of the laser. • Operate the laser at the lowest beam intensity possible, given the requirements of the application. • Operate in the “long pulse” mode whenever possible, especially during alignment of the experiment. • Expand the beam whenever possible to reduce beam intensity. • Establish a controlled access area for laser operation. Limit access to those trained in the principles of laser safety. • Set up experiments so the laser beam is either above or below eye level.

2-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

• Provide enclosures for beam paths whenever possible. • Maintain a high ambient light level in the laser operation area so the eye’s pupil remains constricted, reducing the possibility of damage. • Set up shields to prevent any unnecessary specular reflections. • Post prominent warning signs near the laser operating area (Figure 2-1). • Set up an energy absorbing beam trap to capture the laser beam and prevent accidental exposure to unnecessary reflections or scattering (Figure 2-2).

VISIBLE AND/OR INVISIBLE* LASER RADIATION AVOID EYE OR SKIN EXPOSURE TO DIRECT OR SCATTERED RADIATION CLASS 4 LASER PRODUCT Nd: YAG/1.5J/8ns

*SEE MANUAL 0451-8090

Figure 2-1: This CE standard safety warning labels would be appropriate for use as an entry warning sign (EN 60825-1, ANSI 4.3.10.1).

hysics ctra-P Spe

Figure 2-2: Optical Beam Dump, Model BD-5

Caution! Use of controls or adjustments, or performance of procedures other than those specified herein may result in hazardous radiation exposure.

Operating this laser without due regard for these precautions or in a manner that does not comply with recommended procedures may be dangerous. At all times during installation, maintenance or service of your laser, avoid unnecessary exposure to laser or collateral radiation* that exceeds the accessible emission limits listed in “Performance Standards for Laser Prod- ucts,” United States Code of Federal Regulations, 21CFR1040.10(d). Follow the instructions contained in this manual to ensure proper installation and safe operation of your laser.

* Any electronic product radiation, except laser radiation, emitted by a laser product as a result of or necessary for the operation of a laser incorporated into that product.

2-2 Laser Safety

Safety Devices

Emission Indicator When on, the amber lamp on the laser head (Figure 2-3) indicates that power is being supplied to the laser head and that emission is present or imminent.

Figure 2-3: Laser Head Emission Indicator

MONITOR: PoWeR ON Indicator When on, this green LED in the upper left corner of the power supply (Fig- ure 2-4) indicates that ac power is applied to the system. However, the system will not turn on until the interlock keyswitch is also turned on.

COMPUTER RS232C

SHOTS X100

MONITOR INPUT OUTPUT REMOTE

PWR INTERLOCK LOW LASER Q-SW LAMP ANALOG Q-SW LAMP Q-SW ON FAULT WATER ID TRIG TRIG STROBE SYNC SYNC ADV SYNC

POWER

Figure 2-4: The Lab-Series Power supply Control Panel.

2-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

SPECTRA-PHYSICS LASERS Reservoir Level P.O. BOX 7013 MT. VIEW, CALIFORNIA 94039-7013

MANUFACTURING DATE:

MODEL

S/N NORMAL THIS LASER PRODUCT COMPLIES Remote Interlock Indicator WITH 21 CFR 1040 AS APPLICABLE OPERATING MADE IN U.S.A. RANGE

REMOTE Umbilical Connector INTERLOCK System WATER IN Connector

Power Cord WATER IN System WATER OUT Connector Power Requirement Label WATER OUT

Figure 2-5: The Lab-Series Power supply Rear Panel.

MONITOR: INTERLOCK Indicator When on, this LED indicates there is a system interlock fault. Once the fault is corrected, this light turns off.

REMOTE INTERLOCK Connector This safety interlock connector on the power supply rear panel (Figure 2-5) provides a means to include an external normally closed safety switch in the interlock loop that turns off the laser in the event the safety switch is opened. To use this interlock, remove the jumper plug from the INTERLOCK connector, and either remove the jumper inside or use a similar connector without a jumper to wire to a perimeter safety switch. The switch can be attached to an access door or to other auxiliary safety equipment. Wire the switch as “normally closed” so that when the door or safety device is opened and the switch opens, the power to the laser is immediately turned off, thus preventing unaware personnel from getting hurt. The power supply is shipped with a 2-pin shorting jumper plug installed that defeats (closes) this interlock when it is not used. This jumpered connector or an external safety switch wired to it must be in place in order for the laser to operate.

Cover Safety Interlocks

Figure 2-6: Interlock Switches, Laser Head.

2-4 Laser Safety

Figure 2-7:Interlock Switch, Power Supply. The LASER HEAD connector is also part of the interlock loop: if the laser head cable is disconnected, the diode pump laser in the power supply is turned off. The laser head and power supply covers are interlocked. Therefore, the laser shuts off whenever either cover is removed. For troubleshooting, a bypass is built into each switch so that the service engineer can pull up on the switch to close the interlock with the cover off. For safety, replacing the cover will activate the switch again and turn off the laser.

Danger! Collateral radiation! While the laser head cover is removed, be Laser Radiation extremely careful to avoid exposure to laser or collateral radiation.

POWER Keyswitch Located in the lower right-hand corner of the power supply control panel (Figure 2-4), the POWER keyswitch provides interlock safety to prevent unauthorized personnel from using the Lab-Series system when the key is turned to the “off” position and is removed from the switch. Turning the key to the “on” position closes the interlock and allows the system to be energized if all the other interlocks are closed and the circuit breaker switch is on. If the keyswitch is set to off but the circuit breaker is on, power is still supplied to the harmonic generator ovens to keep the crystals warm.

POWER Circuit Breaker Provides ac power to the system and to the harmonic generator ovens. The power keyswitch must also be on in order for the system to operate. Turn- ing off the power circuit breaker removes all ac power from the system and turns off the harmonic generator ovens.

2-5 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Focused Back-Reflection Safety Focused back-reflections of even a small percentage of the output energy of any Lab-Series laser can destroy its optical components. To illustrate, consider an uncoated convex lens, which reflects about 4% of the energy incident on each of its surfaces. While the reflection off the first surface diverges harmlessly, the reflection off the second surface focuses, and the power density at the point of focus is high enough to destroy the Q-switch, Nd:YAG rod and the output coupler of the laser. Even anti-reflection coated optics can reflect enough energy to damage laser optical components. To avoid laser damage, minimize back-reflections of its output beam and, where they are unavoidable, direct them away from the optical axis.

Warning! Your Quanta-Ray warranty does not cover damage caused by focused back-reflections.

Maintenance Necessary to Keep this Laser Product in Compliance with Center for Devices and Radiological Health (CDRH) Regulations This laser product complies with Title 21 of the United States Code of Fed- eral Regulations, chapter 1, subchapter J, parts 1040.10 and 1040.11, as applicable. To maintain compliance with these regulations, once a year, or whenever the product has been subjected to adverse environmental conditions (e.g., fire, flood, mechanical shock, spilled solvent, etc.), check to see that all features of the product identified below function properly. Also, make sure that all warning labels remain firmly attached (refer to the CDRH/CE drawing later in this chapter). 1. Verify removing the AUXILIARY INTERLOCK plug on the power supply prevents laser operation. 2. Verify the laser will only operate with the key switch in the ON position, and that the key can only be removed when the switch is in the OFF position. 3. Verify the emission indicator on the laser head works properly; that is, it emits a visible signal whenever the laser is on. 4. Verify the time delay between turn-on of the emission indicator and starting of the laser gives enough warning to allow action to avoid exposure to laser radiation. 5. Verify that removing the laser head or power supply cover shuts off the laser. 6. Verify that when the laser head cover interlock is defeated, the defeat mechanism is clearly visible and prevents installation of the cover until it is removed.

2-6 Laser Safety

CE/CDRH Radiation Control Drawing

Interlock Switch 1 2 3 Power On LED 11 VISIBLE AND INVISIBLE* LASER RADIATION IS EMITTED FROM THIS APERTURE *SEE*SEE MANUALMANUAL AVOIDAVOID EXPOSUREEXPOSURE 8 Remote Keyswitch SPECTRA-PHYSICS LASERS P.O. BOX 7013 MT. VIEW, CALIFORNIA 94039-7013

MANUFACTURING DATE:

MODEL NORMAL S/N FUSES THIS LASER PRODUCT COMPLIES WITH 21 CFR 1040 AS APPLICABLE Interlock 30A/250VAC OPERATING MADE IN U.S.A. WA-1 RANGE INTERFACE 10 REMOTE INTERLOCK Power Breaker WATER IN Switch WATER OUT

Laser Head, Output End Power Supply, Water Supply End Power Supply, Control Panel

7 2

Interlock Switch

STBY ON RESET Q-SW PIEZO FREQ VISIBLE AND/OR INVISIBLE* LASER RADIATION AVOID EYE OR SKIN EXPOSURE TO DIRECT OR SCATTERED RADIATION ON MNL DSBL BLD UP TIME VOLT OFFSET CLASS 4 LASER PRODUCT AUTO Nd: YAG/1.5J/8ns Controller Emission 4 3 11 12 5 6 Laser Head, Side View 7 Indicator Quanta-Ray SIMMER ERROR

START 10 START 10 MIN MAX MIN MAX MIN MAX OSC AMP ADV SYNC VARIABLE Q-SW DELAY

VAR LP LAMP ENERGY FIXEDEXT Q-SW EXT

VISIBLE SOURCE MODE AND INVISIBLE* LASER RADIATION IS SINGLE SHOT INHIBIT OFF ON INT EMITTED FROM THIS APERTURE *SEE*SEE MANUALMANUAL AVOIDAVOID EEXPOSUREXPOSURE FIRE REP COMPUTER LAMP ON STOP ENABLE

CDRH Aperture CE Aperture CE Certification Lamp Inhibit Power On Label (1) Label (2) Label (3) Switch Emission Indicator

VISIBLE AND/OR INVISIBLE* CAUTIONC A U T I O N DANGERD A N G E R DANGERD A N G E R LASER RADIATION AVOID EYE OR SKIN EXPOSURE TO DIRECT OR VISIBLE AND INVISIBLE SCATTERED RADIATION VISIBLE AND INVISIBLE LASER RADIATION WHEN OPEN VISIBLE AND INVISIBLE* CLASS 4 LASER PRODUCT HAZARDOUS ELECTROMAGNETIC AND INTERLOCK DEFEATED. LASER RADIATION WHEN RADIATION WHEN OPEN AND AVOID EYE OR SKIN EXPOSURE OPEN-AVOID SKIN OR EYE Nd: YAG/1.5J/8ns INTERLOCK DEFEATED* TO DIRECT OR SCATTERED EXPOSURE TO DIRECT OR RADIATION.* SCATTERED RADIATION *SEE MANUAL 0451-8090 *SEE MANUAL *SEE MANUAL *SEE MANUAL

CE Danger Label CDRH Caution Label CDRH Danger Label CDRH Danger Label (4) Interlock Defeated EMI (5) Interlock Defeated (6) Non-Interlocked (7)

FUSES or FUSES 30A/250VAC 50A/250VAC SPECTRA-PHYSICS LASERS Spectra-Physics Lasers P.O. BOX 7013 1330 TERRA BELLA AVENUE Fuse Label MT. VIEW, CALIFORNIA 94039-7013 MOUNTAIN VIEW, CALIF. 94043 THIS PRODUCT IS MANUFACTURED Near Fuses Inside (8) MANUFACTURING DATE: 190 – 260V~,60/50Hz, 30 A UNDER ONE OR MORE OF THE MODEL FOLLOWING U.S.A. PATENTS: 4,156,209 4,32,2762 S/N REPLACE THE BATTERY WITH THE SAME OR EQUIVALENT or 4,197,513 4,955,725 TYPE RECOMMENDED BY THE MANUFACTURER. THIS LASER PRODUCT COMPLIES 4,935,932 4,232,272 4,310,808 4,342,113 DISPOSE OF USED BATTERIES ACCORDING WITH 21 CFR 1040 AS APPLICABLE 4,360,925 5,001,716 TO THE MANUFACTURER'S INSTRUCTIONS. 190 – 260V~,60/50Hz, 50 A MADE IN U.S.A. 0004-0363

Battery Replacement Input Voltage Serial Number Label Patent Label (12) Label (9) Labels (10) CDRH (11)

Figure 2-8: CE/CDRH Radiation Control Drawing

2-7 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Label Translations For safety, the following translations are provided for non-English speak- ing personnel. The number in parenthesis in the first column corresponds to the label number listed on the previous page. Table 2-1: Label Translations

Label # French German Spanish Dutch Aperture Ouverture Laser - Expo- Austritt von sichtbarer Por esta abertura se Vanuit dit apertuur wordt Label sition Dangereuse - Un und unsictbarer Laser- emite radiacion laser zichtbare en niet zicht- (1) Rayonnement laser visi- strahlung; nicht dem visible e invisible; evite bare laser-straling gee- ble et invisible est emis Strahl aussetzen. la exposicion. miteerd; vermijd par cette ouverture. blootstellilng. European Rayonnement Laser vis- Sichtbare und/oder Radiacion Laser visible Zichtbare en niet zicht- Safety ible et invisible. Expos- unsichtbare Laserstrahl- y/o invisible. Evite que bare laserstraling. Ver- (4) tion dangereuse de l’oeil ung. Bestrahlung von los ojos y la piel queden mijd blootstelling van ou de la peau au Rayon- Aude oder Haut durch expuestos tanto a la huid of oog aan directe nement direct ou diffus. direkte oder Streustrahl- Radaicion derecta como straling of weerkaatsin- Laser de classe 4; Nd: ung vermeiden. Laser- a la dispersa. Producto gen. Klasse 4 Laser YAG/1.5 J/8 ns. classe 4; Nd: YAG/1.5 J/ Laser Clase 4; Nd: YAG/ Produkt; Nd: YAG/1.5 J/ 8 ns. 1.5 J/8 ns. 8 ns. Caution, Attention. Rayonne- Achtung! Sichtbare und Precaución, radiación Let op. Zichtbare en Defeatable ment visible et invisible unsichtbare schädliche peligrosa electromag- onzichtbare gevaarlijke Interlock dangereux en cas elektromagnetische nética visible e invisible electromagnetische (EMI) d’ouverture et lorsque la Strahlung wenn Abdec- con el dispositivo de straling indien geopend (5) sécurité est neutralisée. kung geöffnet und Sich- seguridad abierto o con en interlock overbrugd. erheitsverriegelung su indicación alterada. überbrückt. Bedienung- sanleitung beachten! Danger, Attention. Rayonne- Vorsicht; Austritt von Peligro, al abrir y retirer Gevaar; zichtbare en Defeatable ment Laser visible et sichtbarer un unsicht- el dispositivo de segu- niet zichtbare laser- Interlock invisible en cas barer Laserstruhlung, ridad exist radiacion straling wanneer geo- (6) D’Ouverture et lorsque wenn Abdeckung geoff- laser visible e invisible; pend en bij uitgeschak- la securite est neutra- net und Sicherhetiss- evite que los ohos o la elde interlock; Vermijd lisse; exposition dan- chalter uberbruckt; piel queden expuestos blootstelling van oog of gereuse de l’oeil ou de Bestrahlung von Auge tanto a la radiacion huid aan directe stral- la peau au rayonnement oder Haut durch direkte dircta como a la dis- ing of weerkaatsingen dirct ou diffus. oder Streustreustrahl- persa. daarvan. ung vermeiden. Danger, Attention; Rayonnement Vorsicht; beim Offnen Peligro, Cuando se abre Gevaar; zichtbare en Non- Laser Visible et Invisi- Austritt von sichtbare existe Radiacion Laser niet zichtbare laser- Interlocked ble en Cas D’Ouverture; und unsichtbare Laser- Visible e Invisible; Evite straling wanneer geo- (7) Exposition Engereuse strahlung; Bestrahlung que los ojos y la piel end; vermijd blootsteling de L’Oeil ou de la Peau von Auge oder Haut queden expuestos tanto aan huid of oog aan dis- au Rayonnement Direct durch direkte oder Streu- a la radaicion directa ecte straling of weer- ou Diffus. strahlung vermeiden. como a la dispersa. kaatsingen. Battery Remplacer la pile par le Batterie nur durch gle- Reemplazar la batería Vervang batteryen door Warning même modèle ou un ichen oder baugleichen con el mismo tipo, o de zelfde, of door de Label modèle équivalent. Se Typ gemäß Herstelle- equivalente, recomen- fabrikant geadviseerde (9) débarasser des piles rangaben ersetzen. Ver- dado por el fabricante. equivalente typen. Voer usagées conformément brauchyte Batterien Pelegro. Deshacerse de de gebruikte battereien au recommandations du ordnungsgemäß entsor- las baterías usadas de af volgens de instructies fabricant. gen. acuerdo con las instruc- van de fabrikant. ciones del fabricante. Patent Label Ce produits est fabriqué Dieses Produkt wurde Este producto esta fab- Dit product is gefabri- (12) sous l’un ou plusieurs unter Verwendung einer ricado con una o más ceerd met een of meer des brevets suivants. oder mehrerer der fol- de las siguientes pat- van de volgende USA genden US-Patente entes de los Estados patenten. hergestellt. Unidos.

2-8 Laser Safety

CE Declaration of Conformity

We, Spectra-Physics, Inc. Solid-State Lasers 1330 Terra Bella Avenue Mountain View, CA. 94043 United States of America declare under sole responsibility that the: Quanta-Ray Lab-Series pulsed Nd:YAG laser system with power supply, analog remote, or pc-based controller running Windows-based GUI control software, Manufactured after December 1, 1995, meets the intent of EMC Directive 89/336/EEC: 1989, for electromagnetic compatibility and Directive 73/23/EEC, the Low Voltage directive. Compliance was demonstrated to the following specifications as listed in the official Journal of the European Communities: EMC Directive 89/336/EEC: 1989 EN 50081-2:1993 Emissions: EN55011 Class A Radiated EN55011 Class A Conducted EN 50082-1:1992 Immunity: IEC 801-2 Electrostatic Discharge IEC 801-3 RF Radiated IEC 801-4 Fast Transients Low Voltage Directive 73/23/EEC: 1973 EN 61010-1: 1993 Safety Requirements for Electrical Equipment for Measurement, Control and Laboratory use: EN 60825-1: 2001 Safety for Laser Products. I, the undersigned, hereby declare that the equipment specified above conforms to the above Directives and Standards.

Bruce Craig Vice President and General Manager

Spectra-Physics, Inc. Solid-State Lasers January 1, 2003

2-9 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Sources for Additional Information The following are some sources for additional information on laser safety standards, safety equipment, and training.

Laser Safety Standards Safe Use of Lasers (Z136.1: 1993) American National Standards Institute (ANSI) 11 West 42nd Street New York, NY 10036 Tel: (212) 642-4900 Occupational Safety and Health Administration (Publication 8.1-7) U. S. Department of Labor 200 Constitution Avenue N. W., Room N3647 Washington, DC 20210 Tel: (202) 693-1999 A Guide for Control of Laser Hazards, 4th Edition, Publication #0165 American Conference of Governmental and Industrial Hygienists (ACGIH) 1330 Kemper Meadow Drive Cincinnati, OH 45240 Tel: (513) 742-2020 Internet: www.acgih.org/home.htm Laser Institute of America 13501 Ingenuity Drive, Suite 128 Orlando, FL 32826 Tel: (800) 345-2737 Internet: www.laserinstitute.org Compliance Engineering 70 Codman Hill Road Boxborough, MA 01719 Tel: (978) 635-8580 International Electrotechnical Commission Journal of the European Communities EN60825-1 TR3 Ed.1.0—Laser Safety Measurement and Instrumentation IEC-309—Plug, Outlet and Socket Coupler for Industrial Uses Tel: +41 22-919-0211 Fax: +41 22-919-0300 Internet: http://ftp.iec.c.h/ Cenelec European Committee for Electrotechnical Standardization Central Secretariat rue de Stassart 35 B-1050 Brussels Document Center 1504 Industrial Way, Unit 9 Belmont, CA 94002-4044 Tel: (415) 591-7600

2-10 Laser Safety

Equipment and Training Laser Safety Guide Laser Institute of America 12424 Research Parkway, Suite 125 Orlando, FL 32826 Tel: (407) 380-1553 Laser Focus World Buyer's Guide Laser Focus World Penwell Publishing 10 Tara Blvd., 5th Floor Nashua, NH 03062 Tel: (603) 891-0123 Lasers and Optronics Buyer's Guide Lasers and Optronics Gordon Publications 301 Gibraltar Drive P.O. Box 650 Morris Plains, NJ 07950-0650 Tel: (973) 292-5100 Photonics Spectra Buyer's Guide Photonics Spectra Laurin Publications Berkshire Common PO Box 4949 Pittsfield, MA 01202-4949 Tel: (413) 499-0514

2-11 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

2-12 Chapter 3 Laser Description

A Brief Review of Ion Laser Theory

Emission and Absorption of Light* Laser is an acronym derived from Light Amplification by Stimulated Emis- sion of Radiation. Thermal radiators, such as the sun, emit light in all directions, the individual photons having no definite relationship with one another. But because the laser is an oscillating amplifier of light, and because its output comprises photons that are identical in phase and direction, it is unique among light sources. Its output beam is singularly directional, monochromatic, and coherent. Radiant emission and absorption take place within the atomic or molecular structure of materials. The contemporary model of atomic structure describes an electrically neutral system composed of a nucleus with one or more electrons bound to it. Each electron occupies a distinct orbital that represents the probability of finding the electron at a given position relative to the nucleus. Each orbital has a characteristic shape that is defined by the radial and angular dependence of that probability, e.g., all s orbitals are spherically symmetrical, and all p orbitals surround the x, y, and z axes of the nucleus in a double-lobed configuration (Figure 3-1). The energy of an electron is determined by the orbital that it occupies, and the over-all energy of an atom—its energy level—depends on the distribution of its electrons throughout the available orbitals. Each atom has an array of energy levels: the level with the lowest possible energy is called the ground state, and higher energy levels are called excited states. If an atom is in its ground state, it will stay there until it is excited by external forces. Movement from one energy level to another—a transition—happens when the atom either absorbs or emits energy. Upward transitions can be caused by collision with a free electron or an excited atom, and transitions in both directions can occur as a result of interaction with a photon of light. Con-

sider a transition from a lower level whose energy content is E1 to a higher one with energy E2. It will only occur if the energy of the incident photon matches the energy difference between levels, i.e.,

ν h = E2 – E1 [1] where h is Planck’s constant, and ν is the frequency of the photon.

* “Light” will be used to describe the portion of the electromagnetic spectrum from far infrared to ultraviolet.

3-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Figure 3-1: Electrons occupy distinct orbitals that are defined by the probability of finding an electron at a given position, the shape of the orbital being determined by the radial and angular dependence of the probability. Shown is an “s” orbital on the left, a “p” type on the right.

Likewise, when an atom excited to E2 decays to E1, it loses energy equal to E2 – E1. The atom may decay spontaneously, emitting a photon with energy hν and frequency

E – E ν = ------2 1 [2] h Spontaneous decay can also occur without emission of a photon, the lost energy taking another form, e.g., transfer of kinetic energy by collision

with another atom. An atom excited to E2 can also be stimulated to decay to ν E1 by interacting with a photon of frequency , emitting energy in the form of a pair of photons that are identical to the incident one in phase, frequency, and direction. This is known as stimulated emission. By contrast, spontaneous emission produces photons that have no directional or phase relationship with one another. A laser is designed to take advantage of absorption, and both spontaneous and stimulated emission phenomena, using them to create conditions favor- able to light amplification. The following paragraphs describe these conditions.

Population Inversion The net absorption at a given frequency is the difference between the rates of emission and absorption at that frequency. It can be shown that the rate of excitation from E1 to E2 is proportional to both the number of atoms in the lower level (N1) and the transition probability. Similarly, the rate of stimulated emission is proportional to the population of the upper level (N2) and the transition probability. Moreover, the transition probability depends on the flux of the incident wave and a characteristic of the transition called its “cross section.” The absorption coefficient depends only on the difference between the populations involved, N1 and N2, and the flux of the incident wave.

3-2 Laser Description

When a material is at thermal equilibrium, there exists a Boltzmann distribution of its atoms over the array of available energy levels with most atoms in the ground state. Since the rate of absorption of all frequencies exceeds that of emission, the absorption coefficient at any frequency is positive. If enough light of frequency ν is supplied, the populations can be shifted until N1 = N2. Under these conditions the rates of absorption and stimulated emission are equal, and the absorption coefficient at frequency ν is zero. If the transition scheme is limited to two energy levels, it is impossible to drive the populations involved beyond equality; that is, N2 can never exceed N1 because every upward transition is matched by one in the opposite direction. However, if three or more energy levels are employed, and if their relationship satisfies certain requirements described below, additional excitation can create a population inversion where N1 > N2. A model four-level laser transition scheme is depicted in Figure 3-2. A ν photon of frequency 1 excites—or “pumps”—an atom from E1 to E4. If the E4 to E3 transition probability is greater than that of E4 to E1, and if E4 is short lived, the atom will decay almost immediately to E3. If E3 is metasta- ble, i.e., atoms that occupy it have a relatively long lifetime, the population will grow rapidly as excited atoms cascade from above. The E3 atom will ν eventually decay to E2, emitting a photon of frequency 2. Finally, if E2 is unstable, its atoms will rapidly return to the ground state, E1, keeping the ν population of E2 small and reducing the rate of absorption of 2. In this way the population of E3 is kept large and that of E2 remains low, thus establish- ing a population inversion between E3 and E2. Under these conditions, the ν absorption coefficient at 2 becomes negative. Light is amplified as it passes through the material, which is now called an “active medium.” The greater the population inversion, the greater the gain.

4 -1 E3 F3/2 11502 cm

ν2 ν1

4 -1 E2 I11/2 2111 cm

4 3+ E1 I9/2 Nd

Figure 3-2: A Typical Four-level Transition Scheme A four-level scheme has a distinct advantage over three-level systems, where E1 is both the origin of the pumping transition and the terminus of the lasing transition. Also, the first atom that is pumped contributes to the population inversion in the four-level arrangement, while over half of the atoms must be pumped from E1 before an inversion is established in the three-level system.

3-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Nd:YAG as an Excitation Medium The properties of neodymium-doped yttrium aluminum garnet (Nd:YAG) are the most widely studied and best understood of all solid-state laser media. Its transition scheme is compared to the model in Figure 3-2b and its energy level diagram is depicted in Figure 3-3. The active medium is tri- ply ionized neodymium, which is optically pumped by a flash lamp whose output matches principle absorption bands in the red and near infrared. Excited electrons quickly drop to the F3/2 level, the upper level of the lasing transition, where they remain for a relatively long time (about 230 µs).

20 Pump Bands 18

16 4F3 -1 14 /2 11502 cm R2 11414 R1 4 3 12 F /2 Laser Transition 4 Laser I15/2 10 Transition ~6000 cm-1

8 4 13 I /2 ~4000 cm-1 4 I15/ 6 2 2526 4 11 2473 4I13 I /2 4 /2 2146 2111 4 11 2 I /2 2029 4 9 4 2001 I /2 I9/2 0 848 Ground Level 311 197 134 0 Figure 3-3: Energy Level Scheme for the Nd:YAG Laser Source

The most probable lasing transition is to the I11/2 state, emitting a photon at 1064 nm. Because electrons in that state quickly relax to the ground state, its population remains low. Hence, it is easy to build a population inversion. At room temperature the emission cross section of this transition is high, so its lasing threshold is low. While there are competing transitions from the same upper state—most notably at 1319, 1338, and 946 nm––all have lower gain and a higher threshold than the 1064 nm transition. In normal operation, these factors and wavelength-selective optics limit oscillation to 1064 nm. A laser comprising just an active medium and resonator will emit a pulse of laser light each time the flash lamp fires. However, the pulse duration will be long, about the same as the flash lamp, and its peak power will be low. When a Q-switch is added to the resonator to shorten the pulse, output peak power is raised dramatically.

3-4 Laser Description

Q-switching Because the upper level of the transition has a long lifetime, a large population of excited neodymium ions can build up in the YAG rod, much in the same way a capacitor stores electrical energy. If oscillation is prevented while the population inversion builds, and if the stored energy can be quickly released, the laser will emit a short pulse of high intensity light. To do this, an electro-optic device (a Q-switch) is added to the cavity, which introduces high cavity loss and prevents oscillation. This allows energy to build up. It is then quickly switched to a very low loss state that allows oscillation to occur and the cavity dumps its energy in the form of a light pulse. As shown in Figure 3-4, the Q-switch comprises a polarizer, a quarter-wave plate, and a Pockels cell. A high voltage applied to the Pockels cell crystal changes its polarization retardation characteristics, which determine whether the Q-switch is open (low loss) or closed (high loss).

5 µs

4 kV High Reflector

Quarter-Wave Pockels Cell Polarizer Plate

Figure 3-4: The Q-switch comprises a polarizer, a quarter-wave polarization rotator, and a Pockels cell. With no voltage applied, the Pockels cell does not affect the polarization of light passing through it, and the Q-switch functions as follows. The polarizer horizontally polarizes light entering the Q-switch, and the quarter- wave plate converts it to circular polarization. As the circularly polarized light returns from the high reflector, the quarter-wave plate converts it to vertical polarization. Because the polarizer only transmits horizontally polarized light, it reflects the light out of the resonator, so the cavity loss is high. With voltage applied, the Pockels cell cancels the polarization retardation of the quarter-wave plate, so the light remains horizontally polarized and suffers minimal loss. During Q-switched operation, the flash lamp excites the Nd ions for approximately 200 µs to build up a large population inversion. At the point of maximum population inversion, a fast high-voltage pulse applied to the Pockels cell changes the Q-switch from high to low loss. The resultant pulse width is <10 ns, and the peak optical power is tens of megawatts. This short pulse of high peak power is the key to the usefulness of the pulsed Nd:YAG laser. Its high peak power permits wavelength conversion through several nonlinear processes, e.g., frequency doubling, frequency mixing, dye laser pumping, or Raman frequency conversion. A short pulse provides excellent temporal resolution of fast phenomena like rapid chemi- cal reactions or high-speed motion.

3-5 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

An alternative “long pulse” mode of operation is built in to the Lab-Series laser. Voltage is applied to the Pockels cell as soon as the flash lamp fires, and the Q-switch is held open for the entire lamp firing. The result is a train of pulses about 200 µs long, with a separation between individual pulses of 2 to 4 µs. The total energy of the pulse train is similar to that of a single Q- switched pulse. This long pulse mode allows safer alignment and set-up, and is useful in experiments where total pulse energy, not its distribution in time, is the critical factor.

Resonant Optical Cavity A resonant cavity, which is defined by two mirrors, provides feedback to the active medium. Photons emitted parallel to the optical axis of the cavity are reflected, returning to interact with other excited ions. Stimulated emission produces two photons of equal energy, phase and direction from each interaction. The two become four, four become eight, and the numbers continue to increase geometrically until an equilibrium between excitation and emission is reached. Both mirrors are coated to reflect the wavelength, or wavelengths, of interest while transmitting all others. One of the mirrors (the output coupler) transmits a fraction of the energy stored in the cavity, and the escaping radiation becomes the output beam of the laser. There are two major types of optical resonators: stable and unstable (see Figure 3-5). The difference between them lies in what happens to a ray of light traveling close to, and parallel with the optical axis. In the stable resonator the ray is reflected toward the optical axis by its cavity mirrors, so it is always contained along the primary axis of the laser. By contrast, a ray travelling in an unstable resonator can be reflected away from the axis by one of the cavity mirrors.

Stable

Unstable Figure 3-5: Stable and Unstable Resonator Configurations Stable resonators can only extract energy from a small volume near the optical axis of the resonator, which limits the energy of the output. Con- versely, unstable resonators can have large beam diameters. Thus, they can efficiently extract energy from active media whose cross-sectional area is large, like that of typical Nd:YAG laser rods. The output coupler in an unstable resonator can take one of three forms. In the first case, a small high reflector is mounted on a clear substrate and placed on the optical axis of the resonator. Energy escapes the resonator by diffracting around this dot, which gives the “diffraction coupled resonator”

3-6 Laser Description

(DCR) its name. A second form employs a partially reflective coating that uniformly covers the whole substrate. The third is a variation on the first, where the small high reflector is replaced by a partial reflector with radially variable reflectivity (an RVR optic). This reflector is capable of producing gaussian or near-gaussian spatial profile at the laser output, and is, therefore a gaussian coupled resonator, or GCR. This Lab-Series laser uses the latter variation. If the energy of the output beam is to be uniformly distributed, the Nd:YAG rod must be uniformly illuminated. Placing the flash lamp at one focus of an elliptical chamber causes all the light it produces to be reflected through the rod, which is placed at the other focus. Uniform cooling is also essential to optimal performance of pulsed Nd:YAG lasers. When heated, the Nd:YAG rod becomes a lens whose focal length depends on the average power absorbed. For optimal performance, the high reflector must be matched to the focal length of the rod, which must remain stable during operation. The thermal gradient of the rod also causes a radially variable polarization rotation that must be carefully controlled for the best beam quality.

Longitudinal Modes and Linewidth A laser oscillates within a narrow range of frequencies around the transition frequency. The width of the frequency distribution—the linewidth— and its amplitude depend on the active medium, its temperature and the magnitude of the population inversion. Linewidth is determined by plotting the net gain of each frequency and measuring the width of the curve where the gain has fallen to one-half maximum (full width at half maximum) as shown in Figure 3-6.

Laser Gain Profile 200 MHz Spacing Laser Cavity Longitudinal Modes

Half-max point 30 GHz Linewidth

ν Figure 3-6: Frequency distribution of longitudinal modes for a single line The output of the laser is discontinuous within the homogeneously broad- ened line. A standing wave propagates within the optical cavity, and any frequency that satisfies the resonance condition mc ν = ------[3] m 2L

3-7 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

ν will oscillate, where m is the frequency, c is the speed of light, L is the optical cavity length and m is an integer. Thus, the output of a given line is a set of discrete frequencies—called “longitudinal modes”—spaced such that c ∆ν = ------[4] 2L Producing Other Wavelengths The high peak power of Q-switched pulses permit frequency conversion in nonlinear crystals like potassium dideuterium phosphate (KD*P). In the simplest case, the 1064 nm Nd:YAG fundamental interacts with the crystal to produce a secondary wave with half the fundamental wavelength. For maximum efficiency the waves must maintain the same speed and phase relationship throughout the crystal. The index of refraction of most materials depends on the wavelength and decreases as the wavelength gets longer. However, some materials are birefringent, i.e., their index of refraction depends on the polarization of the propagating waves. In these materials, if the ordinary index of one wavelength matches the extraordinary index of the other, the waves propagate in phase and at the same speed. Fre- quency conversion is most efficient under these “phase matching” conditions. Phase matching is critically dependent on the temperature of the crystal and on the angle between the direction of polarization and the axes of the crystal. With KD*P, two phase matching alternatives exist. In type I phase matching, the input is along the ordinary axis and the output is polarized along the extraordinary axis. This leaves the residual input wavelength linearly polarized. In type II, the input polarization is at an angle between the extraordinary and ordinary axes, while the output remains polarized along the extraordinary axis. The residual input wavelength is elliptically polarized. Although either type of phase matching can be used to generate the second harmonic of Nd:YAG in KD*P, type II is more widely used because of its higher conversion efficiency. However, some experiments require lin- ear polarization of the residual 1064 nm light for highest efficiency and, for these cases, Type I doubling may yield better overall system performance. The resultant 532 nm wave can be doubled again by passing it through a second crystal to yield a 266 nm wave. It can also be mixed in KD*P with the residual 1064 nm fundamental to produce a 355 nm wave. These four wavelengths—1064, 532, 355, and 266 nm—cover the electromagnetic spectrum from the near infrared to the ultraviolet, which enhances the usefulness of the Nd:YAG laser. 532 and 355 nm light is useful for pumping dye lasers with high conversion efficiency. 355 and 266 nm light is useful for dissociation and photodestructive studies of many molecules. 1064 nm and 266 nm light is widely used for optical modification of materials and probing of semiconductors. These fixed frequencies can be extended further through Raman shifting or by using them to pump a dye laser or an OPO. The latter results in continuously tunable output over a wide range of wavelengths.

3-8 Laser Description

Resonator Structural Considerations The stability of the oscillating frequency depends on the design of the resonator structure. Small changes in cavity length caused by temperature changes and mechanical shifts, among other sources, cause corresponding changes in the resonant frequency. Cavity length changes due to temperature can be expressed as

∆L = αL∆T [5]

where L is the cavity length, α is the thermal expansion coefficient of the resonator structure and ∆T is temperature change. In order to eliminate frequency drift, either α or ∆T must be zero. The choice of materials affects the length stability of the structure. The ideal material has both a low thermal expansion coefficient and a high abil- ity to distribute heat evenly, causing a constant ∆T along the length of the structure. Graphite composite, such as that used in the Lab-Series resonator, has the lowest thermal expansion coefficient of any currently used structural material. Since its coefficient is also negative, the thermal compensation system of the resonator structure can be kept simple. The negative expansion of the graphite rods offsets the positive expansion of the metal parts, so the net change remains near zero over a wide range of temperatures. Frequency stability also depends on the mechanical rigidity of the resonator structure. Modulation due to “jitter,” the microphonic movement of cavity mirrors, can be caused by an external shock to the resonator structure or acoustic noise. Isolation of the resonator from the case that surrounds the laser helps reduce this jitter.

Pulse Triggering Sequence and Timing Figure 3-7 is a block diagram of the Lab-Series electrical system. It also depicts the order and timing of control signals within the system. This simplified diagram provides a means for understanding the operation of the laser and the nomenclature of its input and output signals. Figure 3-8 shows the Lab-Series timing relationships. The source switch selects one of three possible lamp triggering sources: a fixed rate setting (10, 30, 50), a variable setting that is ±10% of the laser design frequency (using an internal oscillator), or an externally set setting (applied to the lamp trigger input) that can vary the laser frequency ±10% of its design frequency. Signal A is the trigger source for all subsequent functions. It fires the SCR gate current generator for the pulse forming network and the Q-switch delay. SCR gate current B fires the pulse forming network, whose discharge produces a critically damped current pulse C through the lamp. The Q- switch delay prevents the opening of the Q-switch until the population inversion has built up in the Nd:YAG rod. After approximately 210 ns, its output D increases the Q of the cavity to maximum by applying high voltage I to the Pockels cell.

3-9 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

HI Fixed Q-SW Repetition Fixed Pulse Marx Q-switch Delay Generator Bank H.V. Rate

A D External Q-switch Ext Q-SW K Input Delay trig input Pulse Q-switch Generator Sync. Out Variable Variable Pulse Q-switch Repetition Delay Generator Adv. Sync. Rate E F Out

J Pulse Lamp Generator Sync. Out

Simmer Current Pulse Generator

Switching C Supply

Lamp Figure 3-7: Simplified Block Diagram of the Lab-Series electronics. The mode switch selects the configuration of the Q-switch. The Pockels cell can be fired internally (normal mode), externally by a trigger pulse at the Q-SW TRIG input (external mode), or in a long pulse mode that provides a pulse of low peak power that is useful for system alignment. In normal mode, the Q-switch delay D fires a fixed delay G. Subsequently, the pulse generator is fired H, providing a sync signal and triggering the electro-optic driver (Marx bank). The high voltage output of the Marx bank I changes the polarization retardation characteristic of the Pockels cell, which opens the Q-switch after a total delay of D+G. The Q-switch advanced sync signal is also derived from the Q-switch delay D. Signal D triggers both the fixed delay G described above and a variable delay E, setting up a race between these two pulses. The variable delay pulse is adjustable, so it can end either before or after the end of the fixed delay pulse. The variable delay pulse triggers the advanced sync pulse generator F, whose output either precedes or follows the opening of the Q- switch I. This creates a pre- or post-trigger pulse with a range of 0 to 500 ns. In the long pulse mode, the Pockels cell is triggered at the moment of lamp firing. It is internally charged to provide a long, high voltage pulse that yields a long optical pulse. The Q-switch sync output is inhibited in this mode.

3-10 Laser Description

T = 0

>500 ns 50 Ω Input Positive Edge Trigger 2.5 – 6 V TTL Compatible A Ext. Lamp Trigger Input

5 ms 50 Ω Input 2.5 V Into 50 Ω TTL Compatible J Lamp Sync Output

FWHM = 180 µs C Lamp Current

500 µs Max 60 ms Min 210 µs Nom D Q-Switch Delay

>500 ns 50 Ω Input Positive Edge Trigger 2.5 – 6 V TTL Compatible L Ext. Q-Switch Trigger Input

5 ms Ω Ω 50 Input 2.5 V Into 50 TTL Compatible K Q-Switch Sync Output

– 700 to +500 ns 50 Ω Input Ω 5 ms Pulse Width 2.5 V Into 50 TTL Compatible F Q-Switch Advanced Sync Ouput 500 ns

6.5 V Into 50 Ω H Marx Bank Trigger

I Q-Switch High Voltage

3.5 kV 8 – 12 ns FWHM 1064 nm Light Output (Normal)

2.5 ns FWHM 1064 nm Light Output (Fast)

Figure 3-8: Lab-Series Timing Schematic

General Note on Specifications Specifications for Lab-Series pulsed Nd:YAG lasers are given in good faith and are set at levels that ensure manufacturability and allow reliable long- term operation. Due to the complexity involved in measuring many of the individual specifications, we cannot demonstrate all performance parameters at your site. We will ensure that all energy specifications are met by making the appropriate energy measurements, and that copies of our final test beam profiles and burn patterns are included with the installation of each laser. Pulse width and single-mode operation can also be demonstrated. All other specifications can be demonstrated either at your site or at the Spectra-Physics manufacturing facility. Contact your local Spectra- Physics representative for further information.

3-11 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Laser Output Specifications Note that, unlike ion lasers, the output power of the Lab-Series YAG laser is not variable and is based on the model of laser purchased. Output frequency can be varied ±10% of the nominal frequency. Table 3-1: Power Specifications

Model1 Lab-130- Lab-150- Lab-170- Lab-190- Rep Rate (Hz) 10 30 50 10 30 50 10 30 50 10 30 50 100 Energy (mJ/p)2 1064 nm 450 275 200 650 500 300 850 700 550 1000 800 600 325 532 nm 200 100 70 300 200 100 450 325 210 500 400 250 120 355 nm 90 40 30 150 100 40 220 175 100 250 200 100 50 EEO-3553 ––––––240––300––– 266 nm 50 25 15 70 35 25 90 60 30 110 60 25 20 1 All specifications, unless otherwise stated, are for Q-switched operation at 1064 nm, and are subject to change without notice. 2 Harmonic energies are specified after separation using dichroic mirror pairs. 532 nm energies are specified using type II second harmonic generation (SHG). 355 nm energies are specified using type II SHG. A 10% increase in 355 nm energies can be specified when type I SHG is used. 3 High UV output option designed for OPO pumping, including injection seeder, harmonic generator, 355 nm dichroic separators and beam dump. Table 3-2: Performance

Wavelength Pulse Width1 Short-Term Energy Stability2 Long-Term Power Drift3 1064 nm 8–12 nm ±2% <3% 532 nm 1–2 nm <1064 nm ±3% <5% 355 nm 2–3 nm <1064 nm ±4% <6% 266 nm 3–4 nm <1064 nm ±8% <10% 1 Nominal full width half maximum (FWHM) pulse width 8–10 ns, except Lab-130 and -190 10 Hz versions, which will be 9–12 ns. The short pulse mode, standard on all Lab-series lasers, reduces the 1064 nm pulse width to approximately 2.5 ns and reduces the pulse energy by approximately 10%. (Short pulse mode is available on seeded versions by special request only). 2 Pulse-to-pulse stability for >99% of pulses, measured over a 1-hour period. 3 Over an 8-hour period with temperature variations of less than ±3°C.

3-12 Laser Description

Table 3-3: Mode and Pulse Specifications

Mode Pulse Spatial Mode Profile1 Standard Fit ESM Fit3 Line Width4 Near Field (1 m) >70% >85% ±5% Standard <1.0 cm-1 ∞ >95% Far Field ( ) >95% Injection Seeded <0.003 cm-1 Modulation2 <40% <20%

Beam Diameter5 <10 mm – Timing Jitter6 <0.5 ns 1 Near field spatial profiles measured 1 m from laser using a commercially available beam diagnostic system. 70% refers to the correlation between the actual beam profile and the best least-squares fit Gaussian profile. Far field profiles are measured at the focal plane of a 2 m focal length lens. 2 Refers to the maximum deviation from the best-fit Gaussian profile measured in the near field (1 m) between the FWHM points. 3 Enhanced spatial mode options can be tailored to meet your application needs. To obtain >85% Gaussian fits, energy can be reduced by 30%. 4 Insertion losses for systems using the Model 6350 injection seeder are <15% at 1064 nm, 532 nm and 266 nm. 5 Actual beam diameter will vary depending on laser configuration. 6 rms jitter from Q-switch sync pulse. Jitter is ≤1 nm rms when using the Model 6350 injection seeder at 10 Hz, ≤1.5 ns at 30 Hz, and ≤2 ns at 50 Hz. Table 3-4: Beam Specifications

Pointing Stability1 <±50% µrad Beam Divergence2 <0.5 mrad Lamp Lifetime3 30 million pulses 1 Long-term average pointing drift after warm-up over 8 hours ±3°C. Shot-to-shot pointing stability <±25 µrad. 2 Full angle measured at FWHM points. 3 IR energy within 10% of specified value. Table 3-5: Service Requirements

Water Service 10 Hz1, 30 Hz, 50 Hz 7.6 l/min (2.0 US gal/min)2 Electrical Service 10 Hz <35 A 30 Hz <40 A 50 Hz <55 A Voltage 3 190–260 Vac, Single Phase, 50/60 Hz Umbilical Length 3 m (10 ft) Controller Cord Length 3 m (10 ft) Weight Laser Head 55 kg (120 lb) Power Supply 68 kg (150 lb) 1 Lab 130-10 and 150-10 Hz units are air-cooled as standard. Water-cooled versions require WAT 100 (3.8 liters/min. or 1.0 U.S. gal/min.). All seeded lasers must be water- cooled. 2Minimum pressure 40 psi. Maximum pressure 60 psi. 3 Input transformer has taps at 190, 200, 210, 220, 230, 240, 250 and 260 V. Once a tap is chosen, actual input voltage differing by more than ±10% from nominal voltage may affect operation of the laser.

3-13 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Outline Drawing

13.00 330 46.16 5.01 4.00 1172 127 102

12.04 306 7.62 193

32.0 7.0 2.06 9.00 813 178 52,3 228 Lab-Series Laser Head

30.3 21.2 770 538

17.22 437

19.8 2.5 502 64 25.2 640 Lab-Series Power Supply

Quanta-Ray SIMMER ERROR

START 10 START 10 MIN MAX MIN MAX MIN MAX OSC AMP ADV SYNC VARIABLE Q-SW DELAY

VAR LP 7.28 LAMP ENERGY FIXEDEXT Q-SW EXT 185 SOURCE MODE SINGLE SHOT INHIBIT OFF ON INT

FIRE REP COMPUTER LAMP ON STOP ENABLE

inches 7.90 3.25 All dimensions in 201 82,5 mm Controller

Figure 3-9: Outline Drawing

3-14 Chapter 4 Controls, Indicators and Connections

This chapter describes the controls, indicators and connections of the Lab- Series laser head, power supply, controller and GUI control software. Fig- ure 4-1 shows the various components inside the Lab-Series laser head.

The Laser Head

High Reflector M1 Pockels Cell and λ /4 Plate (Q-Switch) Marx Bank Location Polarizer Pump Chambers (2 Places)

Injection Seeder 2

1 HG Temperature Controller

Base Pan Aluminum Base Plate

Output Coupler M2

Injection Seeder Controls Harmonic Generator (HG)

Dichroic Mirror DM1

Dichroic Mirror DM2 Beam Dump Figure 4-1: An isometric view of the internal components of the Lab-series laser head.

4-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Referring to Figure 4-1, the laser head components are described, starting from the rear mirror and moving forward.

Rear mirror M1—one of two oscillator cavity end mirrors. It reflects all laser light back into the cavity. Vertical and horizontal controls allow you to align the oscillator cavity and to optimize output power and mode quality. These controls are only accessible when the cover is off. λ /4 (quarter-wave) plate—rotates the polarized cavity light 90° and is used in conjunction with the polarizer and Pockels cell to set the Q-switch holdoff, i.e., when properly aligned, there will be no laser oscillation until the Q-switch is fired, no matter how much oscillator PFN voltage there is (8 V max.).The waveplate is aligned by rotating the knurled ring around the high reflector. Pockels cell—a high-voltage device (crystal) used as an optical high-speed shutter to Q-switch pulses. It is opaque (blocks light) until voltage is applied to it. There are no local controls. Polarizer—a coated optic placed in the beam path that allows only polarized light with a select polarization alignment to pass through. It is used in λ conjunction with the /4 plate to select light of a certain polarization for transmission. The polarizer is aligned by rotating the optic in its holder. A clamping screw holds it in place. Pump chambers (1 to 2 chambers in one of 2 types)—a rectangular box that contains a single parabolic chamber with a flash lamp placed at one focus point and a YAG rod at the other, or a dual parabolic chamber with a flash lamp at the focus of each chamber and the rod placed at the focus common to each chamber. The YAG rod is the lasing media which is pumped by the lamp(s). The number and type of chambers found in the oscillator depends on the laser model and its output power capacity. There are no controls on the chambers. Two terminals provide attachment for the high-voltage wires for the lamp(s). Marx bank—provides power to drive the Pockels cell and uses a TTL- trigger source from the power supply controller to turn on and off the cell. Injection seeder—(optional) provides a small amount of single-frequency laser light of the desired wavelength to stimulate emission at that wavelength in the oscillator once the proper threshold for lasing is reached in the rod. Its controls are provided on one of the laser side panels. Refer to “Side Panel” later in this chapter for a description of these controls. Base pan—encloses the bottom of the laser to keep it clean and to provide emf and safety shielding.

Output coupler M2—one of two cavity end mirrors. Whereas rear mirror M1 reflects all light back into the cavity, output coupler M2 allows a small percentage of it to pass through as the oscillator output laser beam. Its vertical and horizontal controls allow you to align the oscillator cavity and to optimize output power and mode quality. These controls are only accessible when the cover is off. Harmonic generator (HG)—contains various crystals that, depending on their sequence and orientation to the incoming beam, generate second,

4-2 Controls, Indicators and Connections

third and fourth harmonics from the primary wavelength. There are two control arms for positioning and rotating the optics inside. Refer to Chapter 7, “Harmonic Generator,” for detailed information on using this device. HG temperature controller—stabilizes the temperature of the HG crystals, thus maintaining stable output despite changes in ambient temperature. Refer to Chapter 7, “Harmonic Generator,” for information describing the use and setting of these controls.

Dichroic mirror 1 (DM1)—reflects certain wavelengths and routes this output to DM2 for transmission while transmitting residual 1064 and/or 532 nm to the beam dump. Vertical and horizontal controls allow you to adjust the routing of the beam.

Dichroic mirror 2 (DM2)—like DM1, it selects certain wavelengths for reflection, then routes this output beam out the laser. Vertical and horizontal controls allow you to adjust the routing of the beam. Beam dump (BD-6) — water-cooled, absorbs the residual 1064 nm output. Aluminum base plate—provides a rigid and thermally stable platform upon which to mount the laser components.

End Connector Panel

Q-Switch Connector

Inlet Outlet Inlet Control High Voltage Neutral/ Coolant Purge Cable Connector Ground Connector Connector Connector Connector Figure 4-2: Laser Head Rear Panel Controls and Connections. Coolant input connector—provides attachment for the umbilical male hose connector to bring coolant to the laser head from the power supply. Coolant output connector—provides attachment for the umbilical female hose connector that returns the coolant to the power supply. Q-Switch input connector (BNC)—provides attachment for the umbilical coaxial connector to receive the Q-switch triggering signal from the power supply. Nitrogen purge input connector—attaches to the nitrogen flow regulator unit provided in the accessory kit. Nitrogen is used to purge the laser head and harmonic generator to keep them clean longer. Control cable connector—attaches to one of the large umbilical connectors from the power supply and provides controls signals for the various components in the laser head.

4-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

High voltage connector—attaches to one of the large umbilical connectors from the power supply that provides high voltage for the flash lamps, simmer supply, and Q-switch. Neutral/ground connector—attaches to one of the large umbilical connectors from the power supply and provides a return path and safety grounding for the high voltage system.

The Marx Bank The the Marx bank control box is located inside the laser head near the rear panel. The connections are made at the factory, but instructions are provided here in the event they are accidentally disconnected.

Danger! 5 kV is present at the Marx bank connectors. Shut off the laser (press the stop button) before changing outputs.

Marx bank INPUT connector (BNC)––accepts the Q-switch control signal from the end panel connector. Marx bank OUTPUT: FAST connector (MHV)––transmits a Q-switch control signal for a 2.5 ns optical pulse from the cavity. Marx bank OUTPUT: SLOW connector (MHV)––transmits a Q-switch control signal for an 8 ns (nominal) optical pulse from the cavity.

The Seeder Control Panel Located on the side of the laser (Figure 4-3), this panel provides control of the optional Model 6350 injection seeder. Refer to the Seeder user’s manual for signal level requirements and instructions on using the seeder. The following control descriptions are provided here for convenience.

STBY ON RESET Q-SW PIEZO FREQ

ON MNL DSBL BLD UP TIME VOLT OFFSET AUTO Figure 4-3: The Laser Head Side Panel Injection Seeder Controls Power ON indicator—glows amber to show the seeder is powered on. STANDBY/ON switch—sets the system to standby (STBY) or active mode (ON). In standby, all temperature control circuits are operational but the laser seeder is disabled. In active mode, the seeder is enabled. Mode switch—allows you set the seeder to manual mode (MNL) or auto- matic mode (AUTO), or to disable it (DSBL). Use the MNL position to set the piezoelectric voltage to the center of its range. The AUTO position allows a servo to reset the piezoelectric to its center whenever the piezoelectric voltage reaches the end of its range (auto-centering). DISABLE prevents the servo from resetting the system automatically.

4-4 Controls, Indicators and Connections

RESET indicator—glows yellow whenever the servo is resetting the piezoelectric voltage to the center of its range. RESET connector (BNC)—(output) provides a means to remotely monitor when the servo reset is active. Output is a 5 V active high TTL-level signal. Q-switch buildup timing connector (BNC)—(output) provides attachment for an oscilloscope cable for sweep timing. A TTL-level output pulse is presented to the connector and remains high for the duration of the Q- switch hold-off. PIEZO/VOLT connector — (output) not used on this system. FREQuency OFFSET connector—(input) provides connection for a user- supplied input voltage that fine tunes the injection seeder to center it on the gain bandwidth of the YAG laser. It works in conjunction with the manual frequency adjustment (see below). Manual frequency adjust—provides local control to fine tune the injection seeder to center it on the gain bandwidth of the YAG laser. This signal is summed with any signal applied to the FREQuency OFFSET connector (see above).

The Emission Indicator

The EMISSION ENABLE indicator on the side panel glows whenever the laser is capable of emitting laser radiation.

Figure 4-4: Laser Head Emission Indicator

4-5 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

The Power Supply Front Panel

COMPUTER RS232C

SHOTS X100

MONITOR INPUT OUTPUT REMOTE

PWR INTERLOCK LOW LASER Q-SW LAMP ANALOG Q-SW LAMP Q-SW ON FAULT WATER ID TRIG TRIG STROBE SYNC SYNC ADV SYNC

POWER

Figure 4-5: The Power Supply Front Control Panel MONITOR: PWR ON indicator—glows when utility power is applied to the system and the circuit breaker and key switch are turned on. MONITOR: INTERLOCK FAULT indicator—glows when there is a system interlock fault: either the laser head or power supply cover is off, or the remote interlock is open (see Remote Interlock Connector below). Once the fault is corrected, the light turns off. MONITOR: LOW WATER indicator—glows when water in the reservoir falls below the safety level. When this happens, turn off the system and add distilled water immediately. MONITOR: LASER ID indicator—glows when there is a mismatch between the power supply and laser head with regard to the optimized repetition rate. When glowing, the power supply cannot be turned on. Requested frequency must be within ±10% of the laser design frequency. INPUT: Q-SWitch TRIGger connector (BNC)—accepts a 5 V signal to fire the Q-switch (input impedance = 700 Ω). The circuit is overload protected. An external time delay is required. INPUT: LAMP TRIGger connector (BNC)—accepts a 5 V signal to trigger the flash lamp ±10% of the rated frequency rate of the laser (input impedance = 700 Ω). The circuit is isolated and overload protected. INPUT: ANALOG STROBE connector (BNC)—provides connection for an enabling signal that gates analog information from the controller to allow analog programming to be completed before the laser fires. A high TTL- level signal enables transmission, a low level disables it. It may be operated as a level or edge-triggered device. The circuit is overload protected (input

4-6 Controls, Indicators and Connections

impedance = 16 kΩ). Refer to Chapter 10, “Service and Repair: Analog Signals,” for details on using this strobe function. OUTPUT: LAMP SYNC connector (BNC)—provides an output timing pulse synchronous with lamp firing for use with other equipment. The pulse width is approximately 0.5 ms and has an amplitude of 2 V and a rise time of approximately 20 ns (into a 50 Ω load). OUTPUT: Q-SWitch SYNC connector (BNC)—provides an output timing pulse synchronous with the Q-switching of the laser for use with other equipment. Pulse width is approximately 4.5 ms with an amplitude of 2 V and a rise time of approximately 20 ns (into a 50 Ω.load). OUTPUT: Q-SWitch ADVance SYNC connector (BNC)—adjusts the output sync signal from 700 ns before Q-switch firing to 500 ns after it fires to allow synchronization to auxiliary equipment. The pulse width is approximately 4.5 ms with an amplitude of 2 V and a rise time of approximately 20 ns (into a 50 Ω load). REMOTE connector—provides attachment for the 37-pin D-sub connector of the controller cable. COMPUTER: RS-232C connector—provides attachment for a 9-pin, RS-232C serial control device. Any computer or terminal that is compliant with the IBM 9-pin standard can use this port to control the laser system. The pinout and specifications for this connector are given in Table 4-1 below. Chapter 6, “Operation,” provides information on operating the laser using a Win- dows*-compatible computer using the GUI software provided with this system. “The GUI Software Menus” section later in this chapter explains the software menus. Appendix B is a Programming Guide for those wishing to write a program to operate the laser directly and automatically.

69 Figure 4-6: The 9-Pin SERIAL COM Port

Table 4-1: The SERIAL COM Port Connections Computer or Terminal Lab Power Supply RS-232-C Signal Pin No. Pin No. Pin No. Signal Signal Name (25-Pin) (9-Pin) Transmit Data TXD 2 3 3 RXD Receive Data RXD 3 2 2 TXD Not Connected RTS 4 7 – CTS Not Connected CTS 5 8 – RTS Not Connected DSR 6 6 – DTR Not Connected DCD 8 1 – DCD Not Connected DTR 20 4 – DSR Signal Ground 755 Protective Ground 1SHELLSHELL

*Windows is a registered trademark of the Microsoft corporation.

4-7 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

POWER: ON key switch—applies power to the control electronics. Both the circuit breaker and key switch must be turned on before the controller can provide control to the system. When the key switch is turned on, the power LED on the power supply front panel and the OFF lamp on the analog controller turn on. POWER circuit breaker—applies ac power to the power supply circuitry and turns on the MONITOR: PWR ON lamp.

The Power Supply Rear Panel Reservoir level indicator—shows how much water is in the power supply reservoir. When the water level falls midway between the level markers, the MONITOR: LOW WATER lamp on the front panel turns on to warn you that the water is getting low. Always maintain the water level between the two level markers during operation. Umbilical connector—provides connection for the umbilical to the laser head. Power cord—provides facility ac power to the laser system. The cord is permanently attached to the power supply. Refer to the Specification tables in Chapter 3 for electrical service requirements.

SPECTRA-PHYSICS LASERS Reservoir Level P.O. BOX 7013 MT. VIEW, CALIFORNIA 94039-7013

MANUFACTURING DATE: MODEL S/N NORMAL THIS LASER PRODUCT COMPLIES Remote Interlock Indicator WITH 21 CFR 1040 AS APPLICABLE OPERATING MADE IN U.S.A. RANGE

REMOTE Umbilical Connector INTERLOCK System WATER IN Connector

Power Cord WATER IN System WATER OUT Connector Power Requirement Label WATER OUT

Figure 4-7: The Power Supply Rear Connector Panel Remote interlock connector—allows other safety interlock devices to be included in the interlock chain, e.g., a safety switch mounted on the door of the laser operation area. If this were the case, the laser would automatically shut off when the door was opened. Wire remote interlocks using shielded twisted-pair wires that are isolated from ground. If no auxiliary interlock is to be used, verify the black shorting plug is inserted to close the interlock circuit. The laser will not operate while these pins are open. System WATER IN connector—allows attachment for a facility water hose to provide cooling water to the laser and power supply. For reliable operation, do not swap the hose attached to this connection with the one attached to the WATER OUT connector. Refer to the Specifications table in Chapter 3 for required flow rates.

4-8 Controls, Indicators and Connections

System WATER OUT connector—allows attachment for a facility water hose for removing the laser-heated water from the system. Attach the other end of this hose to a drain or to a water-to-air cooling device, such as the Model WA-1. For reliable operation, do not swap the hose attached to this connection with the one attached to the WATER IN connector. Hose used should be designed for hot water usage.

The Controller

The controller plugs into the 37-pin REMOTE connector on the power supply. Its controls and indicators are shown in Figure 4-8 and are listed and described here from top to bottom, left to right. OSCillator SIMMER indicator—glows whenever the oscillator flash lamp simmer current is on. AMPlifier SIMMER indicator— (is not used on the Lab-Series system) OSCillator LAMP ENERGY control—sets the output energy of the oscillator flash lamp(s). The scale is relative and is marked START – 10. AMPlifier LAMP ENERGY control—(is not used on the Lab-Series system)

Quanta-Ray SIMMER ERROR

START 10 START 10 MIN MAX MIN MAX MIN MAX OSC AMP ADV SYNC VARIABLE Q-SW DELAY

VAR LP LAMP ENERGY FIXEDEXT Q-SW EXT

SOURCE MODE

SINGLE SHOT INHIBIT OFF ON INT

FIRE REP COMPUTER LAMP ON STOP ENABLE

Figure 4-8: The Controller ADVanced SYNC control—adjusts the output sync signal from 700 ns before Q-switch firing to 500 ns after it fires to allow synchronizing to auxiliary equipment. The signal is available at the Q-SW ADV SYNC output connector on the power supply. Rep Rate ERROR indicator—blinks if the remote control source has selected more than one source to fire the lamp.

4-9 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Rep Rate VARIABLE control—sets the lamp firing rate in a range that is approximately 1 Hz to +5% from the system fundamental FIXED frequency setting as denoted by the laser model number. Q-SWITCH ERROR indicator—blinks if the remote control source has selected more than one mode to trigger the Q-switch. Q-SWitch DELAY control—adjusts the Q-switch firing delay timing from 50 to 300 µs. Rep Rate SOURCE selector—selects the source of the lamp firing pulse: FIXED, VARIABLE, or EXTernal source. FIXED selects the repetition rate as denoted by the laser model number. VARIABLE allows you to vary the pulse rate from approximately 1 Hz to +5% of the system fixed frequency. The EXTERNAL setting requires a firing pulse to be presented at the LAMP TRIG input on the power supply, but is constrained by the same limitations of the VARIABLE setting. Do not exceed this rating. Q-switch MODE selector—selects the source for the timing of the Pockels cell firing: Q-SW, LP and EXT. When set to Q-SW, the Pockels cell is fired after the flash lamps with a time delay set by the Q-SW DELAY control (see above). When set to LP (Long Pulse), the Pockels cell and flash lamp are fired synchronously. When set to EXT (external), the Pockels cell is fired by a signal presented at the power supply Q-SW TRIG input.

Note Be careful when using the Q-switch MODE selector that the Q-switch DELAY setting above it is not disturbed, since laser output power is sensitive to the DELAY setting.

SINGLE SHOT/FIRE switch—when pressed, a single pulse is triggered that is synchronized to the next available flash lamp firing signal, regardless of its source. SINGLE SHOT/REP switch—sets the laser to fire repetitively or one pulse at a time. When set to the REP position, the rep rate SOURCE selector controls the firing rate and the FIRE switch is defeated. When set to the SINGLE SHOT position, the FIRE button is enabled. INTernal/COMPUTER switch—selects the controller or a remote terminal or computer for the control source. This switch remains active when the laser is under computer control, thus allowing you to restore manual control by simply switching it back to INTernal. INHIBIT indicator—glows when the LAMP ON switch has been pressed to turn off the flash lamp. It is off when the lamp is flashing. LAMP ON switch—turns on and off the flash lamp power supply and, therefore, the lamp. If the switch is in the INHIBIT position (up position), the lamps cannot flash and the INHIBIT indicator glows. This button is functional even when the INTernal/COMPUTER switch is set to COMPUTER. OFF indicator—glows whenever the power supply is on but the laser is off. STOP switch—turns off the laser (sets it to standby) but power is still applied to the system. The OFF indicator glows when this button is pressed. This button is functional even when the INTernal/COMPUTER switch is set to COMPUTER. 4-10 Controls, Indicators and Connections

ON indicator—glows whenever the laser is on and capable of emitting light. This indicator also serves as the CDRH emission indicator. ENABLE switch—allows the laser to begin emission and turns on the ON indicator. The ENABLE switch operates only after the power supply circuit breaker is closed and its keyswitch is set to the on position. This button is functional even when the INTernal/COMPUTER switch is set to COMPUTER.

The GUI Software Menus When using the GUI software, the Main menu is the primary monitor and control device. Figure 4-9 shows all the controls available on that menu. These controls can be hidden or displayed by toggling the check next to the associated name in the pull-down list under the View tab. Two other menus, Setup and Info, are available under the Window tab. These three menus and their controls are described below. The program “Exit” button is under the File tab.

Figure 4-9: The Main Menu Showing all Controls

Main Menu This is the first menu that appears when the software is started. It will “remember” the controls that were present the last time the program was used. INTERLOCK fault indicator—turns on whenever an interlock fault has occurred. To clear the fault, turn off the laser (press the ON/OFF button), fix the fault (refer to the MONITOR lamps on the power supply), then turn the laser on again. ADVANCED SYNC control—adjusts the output sync signal from 700 ns before Q-switch firing to 500 ns after it fires to allow synchronizing to aux-

4-11 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

iliary equipment. This signal is available at the Q-SW ADV SYNC output connector on the power supply. QSWITCH selector—selects the source for the timing of the Pockels cell firing. • NORMAL (Q-switched)—the Pockels cell is fired after the flash lamps with a time delay set by the Q-SW DELAY control on the Setup menu. • LONG PULSE—the Pockels cell and flash lamp are fired synchronously. • EXTERNAL—the Pockels cell is fired by a signal presented at the power supply Q-SW TRIG input. EMISSION indicator—when the laser is on or capable of emitting laser light, “Emission” is displayed in black letters on a red background, warning that laser output is available or imminent. PUMPS indicator—when on, indicates the pump is on and system has pressure. If this lamp turns off, either the pump has failed, the reservoir is low on fluid or there is a blockage or kink in the coolant line. SIMMER indicator— glows whenever the oscillator flash lamp simmer current is on and turns off if simmer current is not available. HIGH VOLTAGE indicator—when on, indicates the high-voltage circuits are working properly; when off, the high-voltage system is not on yet or has failed. ON/OFF switch—toggles the laser on and off. When the button has been pushed to turn on the laser, the button turns green. Otherwise, the button is gray when the laser is off. REPETITIVE/SINGLE/FIRE slide control—provides a means to set the laser system to repetitive pulse mode or single shot mode, and to fire single shots at will. To select the desired mode, click on the lever and slide it to that position. To fire single shots, click on the lever while it is in the single-shot position. • REPETITIVE—this position fires the lamps automatically at a rate set by either the VAR RATE control or the source selected using the LAMPS TRIGGER selector. • SINGLE—this position takes the system out of repetitive pulse mode and allows the operator to fire the lamps one pulse at time. • FIRE—fires the lamp(s) a single time when the lever is pressed. Actual firing is synchronized to the next pulse from the selected lamp trigger source. VAR RATE control—sets the lamp firing rate in a range that is approximately 1 Hz to +5% above the system fundamental FIXED frequency setting as denoted by the laser model number. LAMPS TRIGGER selector—inhibits firing or selects the source of the lamp firing pulse. • INHIBIT—prevents the lamps from firing. • FIXED—sets the repetition rate to that denoted by the laser model number.

4-12 Controls, Indicators and Connections

• VARIABLE—allows the pulse rate to be varied from approximately 1 Hz to +5% above the system fixed frequency rate using the VAR RATE control. • EXTERNAL—requires a pulse to be presented at the LAMP TRIG input on the power supply to fire a laser pulse, but this function is constrained by the same limitations of the VAR RATE setting. Do not exceed this rating.

Setting Menu

Figure 4-10: The Setup Menu This menu allows the operator to set the oscillator pfn in terms of percent of available power, set the Q-Switch delay time and to tell the system that a new lamp has been installed. OSC PFN window—allows the user to enter the PFN voltage in terms of percent of total power by pressing the up/down arrows on the window or by typing the desired value from 0 to 100 percent in the window. Q-SWITCH DELAY selector— allows the operator to delay the firing of the Q-Switch down to 60 and up to 500 µs from the actual firing pulse and shows the delay time in the window. Use this timing function to optimize the output pulse. Enter the setting by turning the knob, pressing the up/ down arrows on the window, or typing the desired time delay in the window. NEW LAMP INSTALLED button—tells the system that a new lamp has been installed and resets the shot counter.

Information Menu

Figure 4-11: The Information Menu

4-13 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

This menu displays information about the Lab-Series system. LASER MODEL number—is the model number as read from the system. The last number denotes the standard firing repetition rate. LAB SOFTWARE REVision number—displays the current software revision for the control pc board in the power supply. SOFTWARE REVision number—displays the current GUI software revision. LAMP SHOTS number—displays the total shots fired since the lamp was installed, which gives the operator an idea of how long he can expect the lamp(s) to last. This number cannot be changed on-screen. However, if a lamp is replaced, this number must be reset to zero using the “Shots” command described in Appendix B, “The Programming Reference Guide.” This command can also be used to reset to the count to a number other than zero if a lamp is replaced with a lamp that has already been used in the system. HISTORY buffer window—displays the last 16 status/error code entries made by the system (refer to Appendix A. These codes are used for diagnostic purposes only. The most recent entry is to the left.

4-14 Chapter 5 Installation and Alignment

Installing the Laser The following installation procedure is provided for reference only; it is not intended as a guide to the initial installation and set-up of your laser. Please call your service representative to arrange an installation appointment, which is part of your purchase agreement. Allow only personnel qualified and authorized by Spectra-Physics to install and set up your laser system.

Caution! The use of controls or adjustments or the performance of procedures other than those specified herein may result in hazardous radiation exposure.

Warning! Purge the laser with dry nitrogen only or you will void your warranty!

1. Place the laser head on a suitable optical table and place the controller near it. 2. Place the power supply on the floor within 3 m (10 ft) of the facility power source (the length of the power cord) and within 3 m of the laser head (the length of the umbilical).

Caution! The air vents on the power supply provide cooling for components inside. These vents are strategically placed for air flow management. Allow about 0.5 m (2 ft) clearance around the power supply for proper air movement.

3. Loosen the two screws on each side of the power supply and carefully lift off the cover.

Connecting the Electrical Service The main autotransformer is located in the power supply on the lower tray near the heat exchanger (Figure 5-1). 1. Connect the white wire to the tap that most closely matches your facility line voltage. The autotransformer has several taps, each marked with a different operating voltage (Figure 5-1). The range of the autotransformer is 190 to 260 Vac. The operating range of the laser is ±10% of this voltage.

5-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Figure 5-1: The location of the autotransformer in the power supply. Taps shown for operating voltages ranging from 190 to 260 Vac. 2. Verify the correct fuses are installed for your system configuration. Figure 5-2 shows the location of the fuses in the power supply. A label listing the proper fuse size is located near the fuses. The specification tables at the end of Chapter 3 list the system power requirements for the different configurations.

Main Fuses Figure 5-2: Location of system fuses. 3. Connect the 3 m (10 ft.) power cord to your facility service outlet. Ver- ify the green wire is connected to earth ground, not neutral.

5-2 Installation and Alignment

Connecting the Power Supply and Laser Head Connecting the power supply and laser head entails attaching the umbilical to the laser head and hooking up a nitrogen purge to the laser head. All the umbilical connections at the laser head are polarized so that they cannot be inadvertently swapped. In addition, the three electrical connections contain interlock sensors that prevent the laser from starting if one or more is disconnected. Refer to Figure 5-3.

Q-Switch Connector

Inlet Outlet Inlet Control High Voltage Neutral/ Coolant Purge Cable Connector Ground Connector Connector Connector Connector Figure 5-3: The Lab-series laser head showing connections for the umbilical. 1. Connect the three large electrical connectors by pushing them in, then screwing on the outer shell. 2. Connect the input to the nitrogen purge flow regulator (included in the accessory kit) to the dry nitrogen tank. You need to supply the hose fittings for attaching the regulator hose to your nitrogen supply. 3. Connect the flow regulator output hose to the purge input port on the laser head. Simply push the hose fitting in until it clicks. To remove the hose, push in on the retaining wire clip and pull the hose out. 4. Connect the Q-switch BNC control cable to the laser head panel. 5. Connect the two coolant water hoses to the laser head connector panel. The hoses are polarized. Simply push the hoses on until they click. to remove a hose, push on the metal retaining tab and pull the hose out. Be careful of water spillage when removing hoses. This completes the procedure to connect the power supply to the laser head.

Connecting the Harmonic Generator If a harmonic generator (HG) was ordered with the laser or ordered later, or if the HG was removed for some reason, mount it after completing the installation of the laser. When ready, refer to Chapter 7, “HG Harmonic Generator: Installing the HG.” The HG must be purged with nitrogen. A gauge and hose fittings are part of your accessory kit. Connect the nitrogen tank to the gauge and the gauge to the Inlet Purge Connector on the umbilical end of the laser head (see Figure 5-3).

5-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Filling the Cooling System

Warning! To prevent damage caused by freezing, the laser cooling system was drained before initial shipment. The system must be filled with water before operating the laser for the first time. Your Spectra-Physics service representative will perform this task during initial installation. Before he arrives, obtain 20 l (5 gal) of distilled water for filling and flushing the system.

During the following process, water will have to be added to the reservoir in the power supply (Figure 5-4) several times as the system fills. Rather than remove and replace the reservoir cover several times, it is easier to use a long-necked funnel placed in the return hose entry of the reservoir cover to add water as needed.

Level Sensor Return Hose Deionizing Filter Reservoir Particle Filter Cooling Pump

Figure 5-4: Cooling System Component Identification 1. Pull the small return hose from the coolant reservoir cover. Take care not to spill any water that may still be in the hose. 2. Place a long-necked funnel in the vacated hole in the reservoir cover. 3. Fill the reservoir with distilled water.

Warning! Avoid spilling water on any electrical components. When power is reap- plied, some components will contain high voltage and damage can occur. If you do spill water, clean it up immediately.

4. Set these system controls as follows:

Control Setting Circuit breaker (power supply) Closed Keyswitch (power supply) ON LAMP ON switch (controller) OFF (INHIBIT light is on)

5-4 Installation and Alignment

Refer to Chapter 4, “Controls, Indicators and Connections,” for control descriptions. 5. Hold the coolant return hose over a drain or bucket, then press the ENABLE button on the controller to start the cooling system pump. 6. As water is pumped to the head and removed from the reservoir, add water, keeping it full, until water flows from the return hose. Do not let the reservoir run dry. If the reservoir gets close to empty, press the POWER OFF button immediately, then add water and try again. 7. Once water flows from the return hose, allow the water in the reservoir to drop to below the upper fill level on the power supply rear panel, then press the POWER OFF button. If the water dropped below the upper fill level, add water. 8. Remove the funnel and shove the return line back into the hole in the reservoir cover. 9. Replace the power supply cover and tighten the screws. Air vents—provide air cooling for components inside the power supply. These vents are strategically placed for air flow management. Allow about 0.5 m (2 ft) clearance around the power supply for proper air movement. This completes the installation of the Lab-Series laser.

Installing the Lab-Series GUI Software for Remote Control The Lab-Series GUI control software is supplied on CD-ROM for installation on your own Windows®*-based personal computer or notebook. Alter- natively, a remote computer or terminal can be used to run your own software program to control the Lab-Series laser automatically. If you choose the latter, refer to Appendix B, “Programming Reference Guide,” for instructions on using the programing commands. 1. If you are going to use the GUI control software to control your system, verify your computer meets these minimum requirements. • 486 (or higher) processor, 66 MHz or higher • 16 MB RAM or more, (32 MB RAM recommended) • 3 MB available disk space for installation • a Windows-compatible pointing device, such as a mouse • a video display with 640 x 480 (VGA) or higher resolution (800 x 600 to 1024 x 768 preferred) • an available RS-232 serial port properly configured for 9600 baud, 8 bits, 2 stop bits, no parity. • Microsoft® Windows 95, 98, ME, 2000 or XP operating system. 2. Place your computer in a convenient location. 3. Using a standard 9-pin serial extension cable, connect the computer to the RS-232 connector on the front of the power supply. Refer to Chap- ter 4 for connector and pin specifications.

*Windows and Microsoft are registered trademarks of Microsoft Corporation.

5-5 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

4. Install the GUI control software: a. Place the CD-ROM in the drive, then double-click “My Computer” > “D:” > “Setup.exe.” The software will create a directory on drive C by default, but will allow you to place it wherever you wish. It will then install itself in that directory. b. Follow the on-screen instructions to complete the installation. It will install LabWindows run-time components into the “c:/windows/system” directory and place an icon on the desktop for convenient program startup. An uninstall program is also placed in the selected directory in the event you wish to remove these program components from your system at a later date (e.g., when you wish to change or upgrade the host computer). 5. Refer to Chapter 6, “Operation: Operation Using the GUI Interface” for instructions on setting the computer to communicate with the power supply and to run the laser. Refer to Chapter 4 for descriptions of the menus and their controls.

Alignment

Danger! Your Lab-Series laser was aligned at the factory by specially trained professionals and again when it was first set up at your site. It should not require further alignment in the field. Furthermore, the laser contains lethal high voltage and generates an enormous amount of optical power that can cause damage and even injury. Therefore, do not attempt to align the laser yourself, you may void your warranty. Instead, call your Spectra-Physics service representative.

5-6 Chapter 6 Operation

The Lab-Series Nd:YAG laser system is controlled locally using the table- top controller provided with the system. It can be controlled remotely via the 9-pin RS-232 serial port on the power supply using the Windows®*- based software provided with the system. It emulates the controller functions on a computer. It also can be controlled remotely using your own software program running on a computer. Appendix B, “Programming Reference Guide,” explains the Lab-Series RS-232 command language and how it is used to control the laser system. (Note: an optional IEEE-488 port is also available for remote control of the system.) Chapter 5 explains how to connect the system and explains how to install the Lab-Series GUI software. This chapter assumes this has already been done if you are going to use it. This chapter is divided into two major sections. The first describes laser operation using the provided local controller. The second describes laser operation using the GUI software provided. The

Operation Using the Controller

Quanta-Ray SIMMER ERROR

START 10 START 10 MIN MAX MIN MAX MIN MAX OSC AMP ADV SYNC VARIABLE Q-SW DELAY

VAR LP LAMP ENERGY FIXEDEXT Q-SW EXT

SOURCE MODE

SINGLE SHOT INHIBIT OFF ON INT

FIRE REP COMPUTER LAMP ON STOP ENABLE

Figure 6-1: The Controller

*Windows is a registered trademark of the Microsoft Corporation 6-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Quick Start/Stop Procedure The standard start-up procedure follows this section.

Start-up 1. Turn on the power supply front panel POWER circuit breaker. 2. Turn on the power supply front panel POWER key switch. 3. Set the controller as follows:

Control Setting OSC LAMP ENERGY knob START SOURCE switch FIXED MODE switch Q-SW INT/COMPUTER switch INT SINGLE SHOT/REP switch REP LAMP ON switch Lamp on (INHIBIT lamp is off) Q-SWitch DELAY knob mid-range

4. Verify all covers are on. 5. Temporarily depress the ENABLE switch. 6. After the start-up delay, slowly increase the OSC LAMP ENERGY knob to 10. 7. Adjust the Q-SWitch DELAY knob until energy output is at its max.

Shut-down 1. Decrease OSC LAMP ENERGY to START. 2. Press the STOP switch. 3. Allow the water to flow for an additional 5 to 10 minutes to cool down the lamp(s) and rod(s). This is important for proper cool-down! 4. Turn off the external cooling water supply, or the heat exchanger, if one is used.

Standard Operation

Start-up For day to day operation after you have some experience operating this system, you may want to use the Quick Start/Stop Procedures above to save time. The following detailed procedures are provided for those who are not familiar with the system. 1. Set the controller as follows:

Control Setting Oscillator (OSC) LAMP ENERGY knob START Rep rate SOURCE switch FIXED Q-SWitch MODE switch Q-SW

6-2 Operation

Control Setting INT/COMPUTER switch INT SINGLE SHOT/REP switch SINGLE SHOT LAMP ON switch Lamp on (INHIBIT lamp is off)

2. Verify the power supply POWER circuit breaker is open (off), then apply utility power to the system. 3. Close the power supply POWER circuit breaker. 4. Turn on POWER key switch. 5. Press the ENABLE button. 6. When the simmer light turns on, turn the OSC LAMP ENERGY knob to position 7.

Danger! In the following step, do not look at the film when taking a burn pattern. Laser Radiation The light will be very bright.

7. Obtain a burn pattern to check for proper alignment and any optical damage. a. Place a piece of unexposed but developed Polaroid film into a transparent plastic bag, then place it in the beam path about 1 m from the laser. b. Press the SINGLE SHOT: FIRE button once. 8. If the burn pattern is symmetrical (Figure 6-2), set the MODE switch to Q-SW and adjust the Q-SW DELAY control for maximum output energy. You can safely raise the LAMP ENERGY control to maximum and increase the repetition rate by setting the SOURCE switch to VARiable and increasing the rate to the level desired.

Good Clipped Diffraction Evident Misaligned HR Misalligned OC Figure 6-2: Burn Patterns If the burn pattern is asymmetrical or has flared edges, set the MODE switch to Q-SW and adjust the Q-SW DELAY control for maximum output energy, then reset the system for single shot and repeat these last two steps to take a second burn pattern. If this pattern is asymmetrical or has flared edges, call your Spectra-Physics service representative.)

Warning! Only allow personnel trained and authorized by Spectra-Physics to align your Lab-Series laser. Misalignment can permanently damage cavity optics. Such damage is not covered by warranty.

6-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Interlock Faults An interlock fault shuts off the laser to minimize the risk of damage to system components. This is either caused by something that has failed, or there is a possibility of laser radiation exposure. Interlocks include: water flow sensor, auxiliary interlock connector, laser head water temperature sensor, power supply cover switch, and laser head cover switches. Also included in the interlock chain are the cables to the power supply Control pc board and Power pc board (both inside the power supply), the controller and the laser head. When a fault occurs, the interlock fault MONITOR lamps on the power supply glow.

Note It is normal for the INTERLOCK FAULT indicator to glow when the circuit breaker and key switch are on but the laser is off because there is no cooling water flow. Press the ENABLE button to start the coolant pump and clear the fault.

Restarting the Laser after an Interlock Fault 1. Clear the fault. Refer to the MONITOR indicators on the power supply to find out what caused the fault. 2. Turn the OSC LAMP ENERGY control to START. 3. Press the ENABLE switch to start the laser, or issue a start command via the computer if the system is set for computer control.

Single-Shot Operation Single-shot operation is typically only used for setup and test. Firing a single shot requires two signals: an enabling signal, such as pressing the SIN- GLE SHOT switch on the controller panel or issuing a fire command from a remote computer, and one to fire it, which is the next available pulse from the continuously running system frequency generator. This pulse fires the Marx bank once, and until the firing circuit is armed again, subsequent pulses are inhibited. (Remote operation is covered in Appendix A.) This completes the procedures for standard laser start-up using the controller.

Shut-down You can damage the laser if you do not shut it down properly. When finished using the laser, perform the following steps in the order they are presented. 1. Reduce the output to zero by turning the LAMP ENERGY control to START. 2. Allow the water to flow for an additional 5 to 10 minutes to cool down the lamp(s) and rod(s). This is important for long lamp and rod life! 3. Press the STOP button, turn off the key switch on the power supply, and turn off the circuit breaker.

6-4 Operation

4. Turn off the external cooling water supply (or the heat exchanger if one is used). 5. Do not turn off the purge supply. Let it flow 24 hours a day at 2 scfm. This completes the shut down procedure using the controller.

Operation Using the GUI Interface Refer to Figure 6-3 while performing these procedures. Refer to Chapter 4 for descriptions of the controls.

Figure 6-3: The Main Menu

Quick Start/Stop Procedure The standard start-up procedure follows this section.

Start-up 1. Turn on the power supply front panel POWER circuit breaker. 2. Turn on the power supply front panel POWER key switch. 3. Set the Main menu controls as follows:

Control Setting LAMPS TRIGGER knob FIXED QSWITCH knob NORMAL INT/COMPUTER switch (on controller if COMPUTER plugged into the power supply) Single shot/rep switch REPETITIVE Q-SWITCH DELAY knob (on Setup menu) mid-range

6-5 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

4. Verify the laser head and power supply covers are on. 5. Click on the ON/OFF button to start the cooling pump and start the laser. 6. Once the system is at full power, adjust the Q-SWITCH DELAY knob until energy output is at its max.

Shut-down 1. Press the ON/OFF button. 2. Once the laser has turned off, allow the water to flow for an additional 5 to 10 minutes to cool down the lamp(s) and rod(s). Proper cool- down is important for long lamp and rod life! 3. Turn off the external cooling water supply (or the heat exchanger if one is used).

Standard Operation

Start-up For day-to-day operation after you have gained some experience operating this system, use the Quick Start/Stop Procedures above to save time. The following detailed procedures are provided in the event you are not yet familiar with the system. 1. Set the controller as follows:

Control Setting LAMPS TRIGGER knob FIXED QSWITCH knob NORMAL INT/COMPUTER switch (on controller if COMPUTER plugged into the power supply) Single shot/rep switch SINGLE Q-SWITCH DELAY knob (on Setup menu) mid-range

Danger! In the following step, do not look at the film when taking a burn pattern. Laser Radiation The light will be very bright.

6. Obtain a burn pattern to check for proper alignment and any optical damage. a. Place a piece of unexposed but developed Polaroid film into a transparent plastic bag, then place it in the beam path about 1 m from the laser. b. Press the FIRE button once.

6-6 Operation

7. If the burn pattern is symmetrical (Figure 6-4), set the QSWITCH knob to NORMAL and adjust the Q-SW DELAY control for maximum output energy. You can safely increase the repetition rate by setting the LAMPS TRIGGER switch to VARIABLE and increasing the rate to the level desired.

Good Clipped Diffraction Evident Misaligned HR Misalligned OC Figure 6-4: Burn Patterns If the burn pattern is asymmetrical or has flared edges, set the QSWITCH knob to NORMAL and adjust the Q-SW DELAY control for maximum output energy, then reset the system for single shot and repeat these last two steps to take a second burn pattern. If this pattern is asymmetrical or has flared edges, call your Spectra-Physics service representative.)

Warning! Only allow personnel trained and authorized by Spectra-Physics to align your Lab-Series laser. Misalignment can permanently damage cavity optics. Such damage is not covered by warranty.

Interlock Faults If an interlock fault is detected, the laser shuts off to minimize the risk of damage to system components. Such a fault is caused either by something that has failed or a condition where there is a possibility of laser radiation exposure. Interlocks include: water flow sensor, auxiliary interlock connector (for a user-installed switch), laser head water temperature sensor, power supply cover switch, and laser head cover switches. Also included in the interlock chain are the signal cables to the power supply Control and Power pc boards, the controller and the laser head. When a fault occurs, the interlock fault MONITOR lamps on the power supply glow.

Note It is normal for the power supply INTERLOCK indicator to glow when the circuit breaker and key switch on the power supply are on and the laser is off because there is no cooling water flow. Click on the ON/OFF button to start the coolant pump and start the laser.

When an interlock fault occurs, an interlock warning window will pop up on the computer screen with a list of possible fault areas.

Restarting the Laser after an Interlock Fault 1. Refer to the interlock warning pop-up window for a list of possible faults. Also refer to the MONITOR indicators on the power supply to find out what caused the fault.

6-7 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

2. Once resolved, press the ON/OFF button to clear the fault and start the laser. If multiple faults have occurred, the system will refuse to start and a second pop-up window will appear. When all faults have been resolved, press the ON/OFF button to clear the final fault and start the laser

Single-Shot Operation Single-shot operation is typically only used for setup and test. Otherwise the system is set to repetitive mode.

Shut-down The laser can be damaged if it is not shut down properly. When finished using the laser, perform the following steps in the order presented. 1. Click on the on/off button to turn off the laser. 2. Allow the water to flow for an additional 5 to 10 minutes to cool down the lamp(s) and rod(s). Proper cool-down is important for long lamp and rod life! 3. Turn off the key switch on the power supply, and turn off the circuit breaker. 4. Turn off the external cooling water supply (or the heat exchanger if one is used). 5. Do not turn off the purge supply. Let it flow 24 hours a day at 2 scfm.

Moving the Laser System Take extreme care when moving the laser system to another location. Typi- cally, the laser head can be placed on top of the power supply along with the controller, and the whole system can be moved to another nearby location. If the unit is to be shipped anywhere, or if it is to be moved off site (out of the building), it is highly recommended that the system be disconnected and each component moved separately. Refer to Chapter 5, “Installation and Alignment,” and disconnect the power supply, laser head and controller in reverse order of assembly. Refer to Chapter 10, “Service and Repair: Shipping the Laser and Power Supply,” for information on draining the coolant from the power supply and laser head.

Warning! Make sure that, before shipping the laser or the power supply, the coolant is completely drained from each. The temperature in an aircraft cargo hold can freeze the coolant and can cause several components to burst. Such damage is not covered under your warranty!

6-8 Chapter 7 Harmonic Generator

Warning! The harmonic generator (HG) uses KD*P crystals. These crystals are sensitive to thermal shock, so change temperatures slowly. They are also hygroscopic, i.e., they are water soluble. Avoid getting them wet, and keep the humidity in their environment low. To ensure a low-humidity environment, it is recommended the power supply circuit breaker be left on even when the other equipment is turned off (including the power supply keyswitch) so that the HG heater remains on. This also dramatically reduces warm-up time when the system is used the next time.

Harmonic Generator Controls

1st Stage Crystal Translation Arm

Input Window Output Window (Shown Covered) (Shown Covered)

2nd Stage Crystal Translation Arm

HG TEMPERATURE CONTROLLER

Power ON LED

ON SHG THG/FHG ON

Power Switch Power Switch PWR INC HTR HTR INC OFF TEMP TEMP

SHG Adjust Warming LED Warming LED THG/FHG Adjust

Figure 7-1: HG and Temperature Controller Component Identifica- tion. The controller is located inside the laser head near the HG.

7-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Figure 7-2: Controller shown behind the HG. Input polarization rotator—rotates the polarization of the 1064 nm input beam to optimize it with the crystal for maximum conversion efficiency. Crystal translation arm (one for each stage)—slides the crystals in and out of the beam path and serves as a lever for angle tuning the crystals. The first stage crystal translation arm serves as an indicator of the polarization of the output beam. Notches in the arms lock the crystals in position. Refer to Table 7-2 and Table 7-3 at the end of this chapter for arm settings.

Note As a rule, the polarization of the harmonic is perpendicular to the tuning axis of the crystal.

Angle tuning knob (one for each tuning arm)—adjusts the angle of the crystal for the most efficient harmonic generation, optically aligning it with the input beam. Main housing—rotates about the optical axis to change the polarization for different harmonic crystals. The output polarization is always vertical. Clamping screws lock the HG in the desired orientation.

7-2 Harmonic Generator

Harmonic Generator Temperature Controller Controls The temperature controller provides power to heat the HG crystals, then stabilizes their temperature to maintain a stable output despite changes in ambient temperature. And because the crystals are hygroscopic, keeping the crystals warm also minimizes unwanted optical effects caused by water absorption. It also dramatically reduces system warm-up time. The ideal temperature setting is one that allows the affected crystal to produce the most harmonic generated light. PWR ON switch—turns on the temperature controller and the Channel 1 heater. SHG HEATER indicator—glows as the controller heats the second harmonic generator (SHG) crystals. The lamp will turn on and off periodically as the controller maintains the temperature. SHG INCrease TEMPerature control—sets the temperature of the second harmonic crystals. Its range is approximately 30–50° C over 20 turns. THG/FHG HEATER indicator—glows as the controller heats the third and fourth harmonic generator (THG and FHG) crystals. The lamp turns on and off periodically as the controller maintains the temperature. THG/FHG INCrease TEMPerature control—sets the temperature of the third and fourth harmonic crystals. Its range is approximately 30–50° C over 20 turns. THG/FHG ON/OFF switch—turns on the heater for the third and fourth harmonic crystals. Control cable—attaches to the HG heater input connector to provide power from the controller for the heaters in the HG and sensor signals from the HG to the controller.

Installing the Harmonic Generator The HG was optically aligned at the factory. Therefore, the following procedure should allow optimal harmonic generation from all crystals in the unit. If the HG was not purchased with the Lab-Series laser but added later, a Spectra-Physics service representative will install both the HG and the temperature controller as part of your warranty agreement.

Warning! Never move the crystal into or out of the beam while the laser is running.

1. Remove wrapping, tie-downs and restrainers from the HG. 2. Install the HG base plate on the L-frame (three spring-loaded screws hold it down). Three setscrews, each located next to a hold-down screw, work against the springs to adjust the HG vertically. 3. Plug the control cable from the temperature controller into the back of the HG. The connector is keyed and only goes in one way.

7-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

4. Place the HG so that the four elongated holes on its yoke line up with the corresponding threaded holes in the base plate. Start all four mounting screws, but leave them loose to allow horizontal movement of the HG. 5. Slide both crystal translation arms to the “0” position (pushed all the way in: note the markings on the arm) to move the crystals out of the beam path. 6. Start the laser, then set controls on the controller as follows (do not use the GUI interface during this installation): Table 7-1: Controller Settings

Control Setting LAMP ENERGY Near threshold Q-SW DELAY Optimum SOURCE FIXED MODE Long Pulse INT-COMPUTER switch INTernal SINGLE SHOT switch REPetitive LAMP ON switch OFF (INHIBIT light is on)

Danger! Use protective eyewear throughout the rest of this procedure. Make all Laser Radiation adjustments with the laser near the lasing threshold and in Long Pulse mode.

7. Adjust the HG horizontally and vertically to center the input and exit windows on the laser beam. Reduce the ambient light in the room and use an infrared (IR) card as a detector for the input beam. If the HG must be moved vertically more than its spring-loaded screws allow, “walk” the vertical adjustment by simultaneously loosening one spring-loaded screw and tightening the vertical adjustment screw next to it. Repeat with the other vertical adjustments. 8. Connect the purge system to the HG and purge for 15 minutes before proceeding. 9. Check for clipping of the output beam (use an IR card.) Adjust the base plate of the HG if the crystal clips the beam. Turn the HG to the other polarization orientation and check again for clipping.

Note The rate of rotation of the beam polarization is twice that of the polarization rotator.

7-4 Harmonic Generator

Operation 1. Verify purge flow is set to 0.5 SCFH, and purge the system for 15 minutes before proceeding. 2. Set the crystal translation arms for the wavelength of interest (refer to Table 7-2 and Table 7-3 at the end of this chapter for arm settings). Example: to obtain the second harmonic from a type I SHG crystal: a. Slide the first stage crystal translation arm to “I,” which places the type I crystal in the beam path. b. Slide the second stage crystal translation arm to “O,” which moves the second stage crystals out of the beam path. 3. Turn the main housing on its yoke to orient the output for vertical polarization (it should always be vertical). Example: to obtain vertically polarized second harmonic output, turn the main housing on its yoke until the first stage translation arm is vertical. This orients the axis of rotation horizontally for tuning the crystal. 4. Switch to Q-SWitch mode, then angle-tune the crystal for maximum output at the wavelength of interest. 5. Adjust the polarization rotator for maximum output.

Type I and II Crystals The type I crystal creates a 1064 nm residual fundamental that is linearly polarized and is useful when mixing frequencies. It produces up to 10% more third harmonic power than a type II crystal, even though its doubling process is less efficient. The type II crystal creates a 1064 nm residual fundamental that is elliptically polarized and has a slightly higher conversion efficiency than a type I. It is typically used for dye laser applications.

Second Harmonic (types I and II), and Third and Fourth Harmonic Generation 1. Turn on the temperature controller and the SHG channel heater. 2. Select crystals and output polarization as described in Table 7-2 and Table 7-3 for the desired wavelength. 3. Turn on the laser and adjust the HG for maximum output at this wavelength. 4. Watch the HEATER indicators. They should remain on for several minutes while the crystals warm up, and both lamps will blink periodically when the temperature is stable (there is a slow oscillation around a set point as the controller turns the heater on and off to keep the crystal temperature constant). Set the crystal temperature just above room temperature, and monitor the indicators to make sure the crystal temperature remains stable.

7-5 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

If either lamp turns off and stays off, turn the associated INC TEMP control clockwise to increase the temperature a little. The lamp should turn on, glow continuously for a short time, and blink after that. If either lamp continues to glow after 10 minutes of operation, turn the associated INC TEMP pot counterclockwise just until the lamp shuts off. It should stay off for a short time and blink after that. 5. The fourth harmonic crystal is temperature dependent. In addition to generating UV, it also absorbs IR. When too warm, it approaches its critical phase-matching angle and output power will diminish. At this point, either reduce the input power or turn off the SHG channel heater and let the crystal cool off. In the tables below, find the combination of wavelength, polarization, and SHG crystal for the output of interest on the left-hand side of the table and set the HG as described on the right-hand side. All output wavelengths are collinear; they can be separated by dichroic beam splitters or dispersive prisms (or equivalent optics).

Note It is easy to determine the polarization plane of the last harmonic generated by the HG. It is in the same plane as (in-line with) the long control arm that is associated with the crystal generating that harmonic.

Table 7-2: Summary of Translation Arm Positions1

Stage Arm Position Crystal Position 1st O First stage crystals out of beam path I Type I SHG2 crystal in beam path II Type II SHG2 crystal in beam path 2nd O Second stage crystals out of beam path T THG3 crystal in beam path F FHG4 crystal in beam path 1 Table describes an HG with a full complement of harmonic generation crystals. 2 Second Harmonic Generation (532 nm). 3 Third Harmonic Generation (355 nm)––occurs by summing the fundamental (1064 nm) and its second harmonic. Type I second harmonic produces optimal third harmonic performance. 4 Fourth Harmonic Generation (266 nm)––occurs by generating the second harmonic of the second harmonic of the fundamental. Type II second harmonic produces optimal fourth harmonic performance.

7-6 Harmonic Generator

Caution! The table below provides both vertical and horizontal polarization options available from your HG unit. The IHS dichroics have been optimized for vertical polarization.

Table 7-3: Summary of HG Settings

Output of HG Settings1 Interest λ (nm) Polarization SHG Main 1st 2nd Crystal Housing Stage Stage Stage Position Position Position Position 1064 Horizontal 0 0 532 Vertical I Horizontal I 0 Horizontal I Vertical I 0 Vertical II Horizontal II 0 Horizontal II Vertical II 0 355 Vertical I Vertical I T Horizontal I Horizontal I T Vertical II Vertical II T Horizontal II Horizontal II T 266 Vertical I Vertical I F Horizontal I Horizontal I F Vertical II Vertical II F Horizontal II Horizontal II F 1 Table describes an HG with a full complement of harmonic generation crystals.

7-7 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

7-8 Chapter 8 Internal Harmonic Separator

Warning! The internal harmonic separator (IHS) transmits and modifies Class IV- High Power Laser beams. These beams are eye, skin, and fire hazards; therefore, take precautions to prevent accidental exposure to both direct and reflected beams. Diffuse as well as specular reflections can cause severe eye or skin damage.

Dichroics Dichroic mirrors are used to separate the second, third and fourth harmonic from the Nd:YAG fundamental in the Lab-Series laser. The small amount of unwanted harmonics in the beam is regarded as inconsequential for OPO operation, and the convenience and flexibility of dichroic separation when used in other applications has led to the creation of the internal dichroic harmonic separator for general-purpose use. Dichroic mirrors are characterized by high reflectivity at one range of wavelengths and low reflectivity elsewhere. Advanced optical coating techniques now allow excellent color separation with high damage thresholds, even into the ultraviolet (UV).

IHS System Description The IHS system provides high throughput of various combinations of the second, third and fourth harmonics as well as the fundamental 1064 nm beam. The system has two basic parts: the optics sets that transmit the desired wavelengths and the wave plate sets that adjust the polarization state of residual beams. The illustrations on the following pages show the possible combinations. Note: some setups require the removal of the beam dump.

Dichroic mirrors DM1 and DM2 are mounted in standard mounts and have vertical and horizontal mirror adjustments. For repeatability, a knurled ring holds each mirror against a 3-ball seating surface. Refer to “Replacing the Dichroic Mirrors” later in this chapter for instructions on changing mirrors. The following components comprise the IHS system: IHS-532—a pair of mounted 532 nm dichroic beam splitters that separate the second harmonic from the fundamental. This set is included in the basic IHS but is also available separately. IHS-355—a pair of optional, mounted 355 nm dichroic beam splitters that separate the third harmonic from the fundamental and second harmonic.

8-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

IHS-266—a pair of optional, mounted 266 nm dichroic beam splitters that separate the fourth harmonic from the fundamental and second harmonic. WP-3—an optional waveplate set that orients the polarization of 532 nm output. The orientation of the harmonic generator on the pump laser deter- mines the polarization of the shortest harmonic input. WP-4—an optional wave plate set that linearly polarizes the 1064 nm residual fundamental output of the Lab-Series laser after type II second harmonic generation. It orients the polarization after type I second harmonic generation.

System Configurations The modularity of the IHS allows several system configurations by using a combination of the optics sets listed above to provide selected output. The more common configurations are shown in Figure 8-1 to Figure 8-3. Two windows in the front bezel on 4 in. standard Quanta-Ray spacing provide selected wavelength output. Figure 8-1 shows the possible placement of these optics. Some configurations require the removal of the beam dump (refer to “Removing the Beam Dump” below).

Laser Head

4 in.

HG Beam Dump

Figure 8-1: The various mounting and output options for the Lab- Series laser. Single wavelength—for second, third or fourth harmonic only, use the IHS- 532 or IHS-266 or IHS-355 as shown in Figure 8-2.

Laser Head

IHS-XXX 1064, 532, 355 or 266 nm

4 in.

HG Beam Dump

Figure 8-2: Single wavelength: second, third or fourth harmonic.

8-2 Internal Harmonic Separator

Dual wavelengths––for second, third, or fourth harmonic plus fundamental, use the IHS-532, IHS-355 or IHS-266, and the WP-4 as shown in Figure 8-3.

Laser Head

IHS-XXX 532, 355 or 266 nm

4 in.

1064 nm

HG Beam Dump WP4 Removed

Figure 8-3: Dual wavelength: Second, third or forth harmonic plus the fundamental.

Removing the Beam Dump Some configurations require that the water-cooled beam dump be removed. When removing the beam dump, remove one cooling line at the harmonic generator and the other at the beam dump. Then attach the end removed at the beam dump to the vacant barb on the HG. Verify you have properly reattached the water lines to the harmonic generator before you turn on the laser. When replacing the beam dump, reverse this process to include the beam dump in the cooling loop.

Installing the IHS Mirror Mounts There are times when a different wavelength or output port must be used and a different mirror arrangement is required. Use the following instructions when the IHS mirror mounts were removed and must be re-installed or when they have to be moved to another location.

Danger! During installation, always operate the Nd:YAG laser at low levels to prevent injury to yourself or damage to the system or both. To pump with the second harmonic, the low level setting should be un-Q- switched. The same conditions apply to the third and fourth harmonic, except that a UV fluorescent card can be used to detect the beam. Safety goggles or glasses are required any time the laser is on, even at low energy.

8-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

HG Temperature Controller

IHS Dichroic Mirror DM2

Harmonic Generator Aluminum Base Plate

IHS Dichroic Mirror DM1

Beam Dump

Figure 8-4: The IHS dichroic mirrors shown in the “normal” position. 1. Remove the laser head cover (4 screws) and install the shortest wavelength dichroics at this time. 2. Install the optic mounts in the desired location (refer to Figure 8-1 through Figure 8-3). Use two screws to fasten the mount to the base plate. 3. Put a power meter or beam dump at the output ports to be used. 4. Turn on the laser in Long Pulse mode. 5. Adjust the dichroic mirror mounts vertically and horizontally to center the harmonic beam on the selected output port. 6. If you want to use additional second-harmonic dichroics, turn off the laser and install them along with the required wave plates (WP-3 or WP-4). Turn on the laser and set it to a safe power level again. 7. Check the alignment of the second harmonic beam and wave plates. 8. Verify the harmonic generator is set so that the shortest harmonic is vertically polarized (refer to Chapter 7). 9. Turn off the laser. 10. Install the appropriate windows and absorption filters in the beam paths as required, or enclose the beam path in dust tubes. 11. Replace the cover. This completes the installation procedure.

8-4 Internal Harmonic Separator

Replacing the Dichroic Mirrors When changing output wavelengths of the harmonic generator, (from 2nd to 3rd or 3rd to 4th etc.), it is necessary to change dichroic separator mirrors. Note: a change in HG setting typically causes the output beam to be dis- placed from its original path. A slight offset can be compensated for by adjusting the IHS mirrors. 1. Prior to changing the HG setting and the dichroic mirrors, note the location of the beam on a far-field target.

2. Unscrew the knurled retaining ring on DM2 (see Figure 8-5).

Adjustments Horiz. Vert.

Mirror Mount Ring

Mounting Holes Figure 8-5: The IHS Mirror Holder 3. Remove the finger spring and dichroic optic. 4. Install the new dichroic optic with the arrow on the barrel facing towards the incoming laser beam. The optic should rest against the 3- ball mirror seat. 5. Place the finger spring into the knurled retaining ring with the fingers facing towards the dichroic optic. 6. Tighten the retaining ring to compress the finger spring against the dichroic optic and hold it in place. 7. Repeat the procedure for the second dichroic optic. 8. Change the HG setting to the desired wavelength(s).

9. Slightly readjust the vertical and horizontal controls of DM2 to place the beam back on target.

8-5 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Operating the IHS Since the IHS is a completely passive device, no special procedures or alignments are required during routine operation. When harmonic separation is required, install the appropriate mirror set into the mounts.

Removing/Replacing the Beam Dump The optional Model BD-6 water-cooled beam dump is positioned after the

first dichroic mirror, DM1. It lets you dump the residual 1064 and 532 nm light and allows you to position the OPO, dye laser, experiments, etc., closer to the output of the Lab-Series laser. Water cooling removes excess heat that would otherwise build up in the laser head. The beam dump can be conveniently moved out of the beam path by simply loosening the two 8-32 beam dump mounting screws and sliding the beam dump assembly down (see Figure 8-6). Use the following procedure to remove the beam dump entirely. 1. Turn off the laser. 2. Disconnect one of the beam block water hose connections at the in- line coupler between the HG and the beam dump and, holding both hose ends as high as possible for a moment, allow the water inside to drain back to the power supply. Wipe up any spilled water. 3. Disconnect the second hose from the HG, then connect the two system hose connectors together, leaving the beam dump out of the cooling loop. Connect the two beam dump hoses together to prevent dripping. 4. Remove the 10-32 base mounting screw from the beam dump base. 5. Lift the beam dump out and set it aside. To install the beam dump, reverse this procedure.

8-32 Beam Dump Mounting Screws

10-32 Base Mounting Screw

Figure 8-6: Model BD-6 water-cooled beam dump showing mounting screws.

8-6 Chapter 9 Maintenance

Preventive Maintenance • The top cover of the Lab-Series laser protects the internal components from outside contamination and also prevents unwanted stray optical radiation from escaping the system. Always operate the unit with the top cover in place. • Inspect daily all windows for contamination or damage. The windows should be cleaned with acetone and lens tissue any time contamination is suspected or observed. Damaged windows should be immediately replace. • It is highly recommended that you annually check the safety features of the laser to ensure safety is maintained (see Chapter 2, “Laser Safety,” for details).

Cleaning Laser Optics Losses due to unclean optics, which might be negligible in ordinary optical systems, can disable a laser. Dust on mirror surfaces can reduce output power or cause total failure due to damage. Cleanliness is essential, and the maintenance techniques used with laser optics must be applied with extreme care and attention to detail. “Clean” is a relative description; nothing is ever perfectly clean, and no cleaning operation ever completely removes contaminants. Cleaning is a process of reducing objectionable material to acceptable levels. Since cleaning simply dilutes contamination to the limit set by solvent impurities, solvents must be as pure as possible. Use spectroscopic, electric or reagent grate solvents and leave as little solvent on the surface as possible. As any solvent evaporated, it leaves impurities behind in proportion to its volume. Avoid re-wiping a surface with the same swab; a used swab and solvents will redistribute contamination, it won’t remove it. Both methanol and acetone collect moisture during prolonged exposure to air. Avoid storage in bottles where large volume of air is trapped above the solvent; instead, store solvents in squeeze bottles from which trapped air can be removed. Laser optics are made by vacuum-deposited microthin layers of materials of varying indices of refraction on glass substrates. If the surface is scratched to a depth as shallow as 0.01 nm, the operating efficiency of the optical coating will be reduced significantly.

9-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

The condition of the laboratory environment is the primary factor affecting your periodic maintenance schedule. The coated surfaces of the dichroic mirrors, windows, and wave plates are the elements most subject to environmental contamination. In these laser systems, where the peak power is very high, contaminated optics damage much more easily than clean optics. Do not allow smoking in the laboratory. Careful handling of optics during installation and configuration changes is the best maintenance. Always use clean finger cots or powder-free latex gloves when handling optics, and do not remove the dichroics and wave plates from their mounts except for cleaning. Stick to the following principles whenever you clean any optical surface: • Remove and clean one optical element at a time. If all of the optics are removed and replaced as a group, all reference points will be lost, making realignment extremely difficult. • Work in a clean environment, over and area covered by a soft cloth or pad. • Wash you hands thoroughly with liquid detergent and use finger cots. Body oils and contaminants can render otherwise fastidious cleaning practices useless. • Use dry nitrogen, canned air or a rubber squeeze bulb to blow dust or lint from the surface before cleaning with solvent. Permanent damage may occur if dust scratches the glass or mirror coating. • Use spectroscopic, electronic or regent grade solvents. Do not try to remove contamination with a cleaning solvent that may leave other impurities behind. • Use photographic lens tissue to clean optics. use each piece only once: dirty tissue merely redistributes contamination.

Equipment Required • Dry nitrogen, canned air or rubber squeeze bulb • Photographic lens tissue • Spectroscopic grade methanol • Forceps • Hemostat

Figure 9-1: Lens Tissue Folded for Cleaning

9-2 Maintenance

Cleaning Prisms, Mirrors and Windows 1. Blow away dust particles or lint using nitrogen or air. 2. Fold a piece of lens tissue into a pad about 1 cm in a side and clamp it in a hemostat (see Figure 9-1). Saturate the pad with methanol, shake off the excess, resaturate and shake again. 3. Wipe one surface—bottom to top—in a single motion. Be careful that the tip of the hemostat does not scratch the surface. Repeat the operation with a clean tissue on the second optic surface. A clean optical surface will scatter little or no light when the laser is operating. 4. Install the optical assembly back into its base and adjust the mirror vertically and horizontally for maximum optical output power.

Warning! Always follow the instructions in Chapter 6, “Operation,” for turning off the laser. Ignoring the shutdown procedure can permanently damage the lamps and/or rods.

Maintaining the Cooling System

Level Sensor Return Hose Deionizing Filter Reservoir Particle Filter Cooling Pump

Figure 9-2: Cooling system component identification.

Danger! Be wary every time you remove the power supply cover that there is lethal high voltage inside.

1. Circulate water through the system for 30 minutes every week when the laser is not in use.

9-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Warning! It is important that you follow this instruction for the well-being of your system. Failure to do so can cause sediment build-up and restricted cooling.

2. Inspect the water level in the reservoir through the window in the power supply rear panel every time you use the laser. Keep the reservoir at least half full. Drain the coolant and replace it with fresh deionized, water every three months. 3. Check the deionizing filter (Figure 9-2) monthly and replace the filter when all the yellow resin in it has changed color to light brown. Refer to “Replacing the Deionizing Water Filter” later in this chapter. 4. Replace the particulate filter whenever you replace the deionizing filter. Refer to “Replacing the Particulate Filter” later in this chapter. 5. Replace the air filter monthly or when the blue indicator turns pink.

Maintaining the Harmonic Generator

Warning! Do not attempt to clean, remove, replace or add crystals. Allow only factory-trained service engineers to open your harmonic generator (HG).

1. Keep the crystals sealed, purged and heated at all times. 2. Use only spectroscopic grade methanol and photographic lens tissue to clean window surfaces.

Replacing the Deionizing Water Filter To prevent air from getting into the water pump and causing the pump to lose prime, the deionizing filter cartridge must be replaced while water is still in the system. Doing so means there is the possibility of water spillage. The following procedure allows you to replace the filter cartridge with minimum chance of spillage. Table 10-1 lists the part number for the cartridge. After you replace the deionizing filter, proceed to “Replacing the Particle Filter” below for instructions on replacing this filter as well.

Tools needed: 5 • /32 in. Allen (hex) wrench • Small cork for plugging end of cartridge • Small bucket • An absorbent towel

9-4 Maintenance

Procedure 1. Loosen the two screws on each side of the power supply, and lift off the cover. 2. Remove the “T” Clip-Lok™ fitting from the top of the filter cartridge, and allow the water in the filter to drain back into the reservoir. This may take several minutes. 3. Place a towel under the bottom “T” fitting to catch any water that may leak from the hose or cartridge when the lower fitting is removed. 4. Remove the “T” Clip-Lok fitting from the bottom of the filter cartridge, and place the cork in the now vacant hole on the “T” fitting. Allow the remaining water in the filter to drain into the absorbent towel. 5 5. Loosen the two /32 in. screws located on the filter restraint structure and remove the filter. Place the filter in the bucket. 6. Place the new filter cartridge in the restraint structure and tighten the screws. 7. Install both “T” fittings onto the new cartridge and verify they seal properly. 8. Clean up any spilled water. 9. Turn on the power supply circuit breaker and key switch, and press the ENABLE button on the controller to start the pump. If the pump does not prime itself, prime it by removing the large supply hose from the reservoir and, using a long-necked funnel, pouring water into the hose. 10. Run the pump for about 10 minutes. 11. If the MONITOR: LOW WATER indicator lights, shut off the power supply and add deionized water to the reservoir. Refer to Chapter 5, “Installation and Alignment: Filling the Cooling System.” 12. Replace the power supply cover. 13. Dispose of the used filter cartridge properly. This completes the procedure for replacing the deionizing filter. Continue with “Replacing the Particle Filter” below.

Clip-Lok™ is a registered trademark of Anarak, Inc.

9-5 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Replacing the Particulate Filter Replace the particulate filter (Figure 9-2) in the power supply whenever the deionizing filter is replaced. Follow the instructions in the above procedure for purging the cooling system of water.

Tools needed: • Wire cutters • Needle-nose pliers

Procedure 1. Loosen the two clamping screws on each side of the power supply, and lift off the cover. 2. Locate the opaque plastic particulate filter next to the deionizing filter on the upper tray. 3. Remove the output hose from the reservoir. 4. Remove the input hose where it is attached to the Clip-Lok fitting on the deionizing filter. 5. Cut the two tie-wraps holding the existing filter in place with the wire cutters, and discard the tie-wraps. 6. Thread the new tie-wraps through the fasteners. 7. Note the orientation of the existing filter, then replace it with the new one so the new filter is oriented in the same direction. 8. Place the long output hose into the reservoir. 9. Attach the remaining hose to the Clip-Lok fitting, and verify it is securely seated. 10. Using the needle-nose pliers, tighten the tie-wraps around the filter so it is securely fastened to the tray. 11. Install the power supply cover. This completes the procedure for replacing the cooling system particle filter.

9-6 Maintenance

Replacing the Air Filters Three air filters in the laser head comprise a single filter assembly: the input oil filter, the output particle filter, and the desiccant filter. Replace all of them at one time, not individually. Table 10-1 lists the part number for this assembly.

Tools needed: • Wire cutters

Procedure 1. Verify the system is off and that there is no power to the system. 2. Remove the laser head cover by removing the 4 screws, then lifting off the cover. 3. Locate the air purge filter assembly under the tray. It is toward the umbilical end of the laser head, below the Marx bank. 4. Detach the assembly Clip-Lok fittings from the input panel fitting and from the manifold “T.” 5. Lift up on the small black tap on the desiccant filter restraining straps to release the catch mechanism, and remove the straps. 6. If there is a tie-wrap holding the desiccant filter in place (used only during initial shipment), use wire cutters to remove it. 7. Note the orientation of the filter assembly, then remove it. 8. Lay the new filter assembly in place, then refasten the black restraining straps around the desiccant filter. 9. Fasten the input hose to the input panel fitting and the output hose to the manifold “T.” Pull on the fittings to verify they latched properly. 10. Install the head cover and tighten the 4 screws. This completes the procedure for replacing the air filter assembly.

9-7 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Replacing the Flash Lamps For optimal performance, lamps should be replaced after 1000 hours for 10 Hz systems, 330 hours for 30 Hz systems, and 200 hours for 50 Hz systems. Table 10-1 lists the part number for this assembly.

Procedure

Danger! Be wary every time you remove the power supply cover that there is lethal high voltage inside.

1. Turn off the laser according to the instructions in Chapter 6, then open the power supply circuit breaker.

Danger! As an extra precaution, open the circuit breaker and disconnect the power cord.

2. Allow 5–10 minutes for the heads to cool. 3. Remove the laser head cover by removing the 4 screws, then lifting off the cover. 4. Remove the plastic high voltage shield that covers the lamp housings. 5. Short together terminal posts A and B (Figure 9-3) on each pump chamber using shorting wires. 6. Disconnect the lamp leads from the terminal posts. 7. Disconnect the water hose located at the top of the lamp house assembly. This allows the water in the head to drain back into the power supply. Use a towel to catch or wipe up any spilled water.

Terminal Posts Terminal Posts A B A B

Figure 9-3: Short together posts A and B to prevent shock when servicing the flash lamps.

9-8 Maintenance

8. Loosen and remove the thumb screws and block from both ends of the lamp(s). 9. Remove each lamp by moving it toward the middle and pulling it out. 10. Clean the new lamp with methanol. 11. Reverse Steps 6 through 10 to install each lamp. a. Depending on clearance, insert the proper end of the lamp first. The anode end is identified by a red mark on its electrode and an “A” on the red anode lead. The anode electrode is solid, while the cathode electrode is segmented and cone-shaped. b. Make sure all O-rings are seated snugly in the groove of the lamp housing. c. Tighten all thumb screws evenly and snugly. Do not overtighten. d. Bend the ends of the lamp wire down at 90 degrees. 12. Remove the shorting connector from terminal posts A and B. 13. Connect the water hose to the top of the rod assemblies. 14. After installation, test for water leaks as follows: a. Defeat the cover interlock. b. Press the ON button long enough to move cooling water into the lamp housing. c. If no leaks occur, turn on the water pump and inspect for leaks again at full pressure. If there are no leaks after 5 seconds, the seals are tight. d. Turn off the laser, deactivate the cover interlock defeat, and install the laser head cover. 15. If a leak occurs: a. Turn off the laser and observe the danger warning in Step 1. b. Remove the thumb screws and blocks. c. Center the lamp in its housing, and check the seating of the O- rings. This completes the procedure for replacing the flash lamps.

9-9 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

9-10 Chapter 10 Service and Repair

This chapter is divided into four parts. The first is a general description to give you a better idea of how the system works at the technical level in the event you encounter problems while operating your unit. Do not attempt repairs yourself while the unit is still under warranty; instead, report all problems to Spectra-Physics for warranty repair. The second part contains the troubleshooting guide that is for you, the user. It is meant to assist in isolating some of the problems that might arise while using the system. A complete repair procedure is beyond the scope of this manual. For information concerning the repair of your unit by Spectra- Physics, please call your local service representative or refer to Chapter 11, “Customer Service.” The third part is a replacement parts list of components (and their part numbers) that are most likely to break or get lost, as well as those you may simply want to order as spares or substitutes. The final part gives directions on how to drain and disassemble the system for shipping. Be sure to read this section before you move your system.

General Operation This section describes briefly how various parts of the system operate and what modifications, if any, can be made. References are made throughout this section to control devices. The first reference is to the control on the controller provided with the system. The second reference (in parentheses) is to the control on the GUI interface software also shipped with the system.

Enabling Signals Enabling signals are used to control laser start-up, analog strobe triggering, flash lamp firing, select the lamp trigger oscillator, set the Q-switch triggering mode and to select single-shot or repetitive operation. The controller supplies enabling signals directly. When the system is operated remotely, enabling commands may be sent via the RS-232C port or the optional IEEE-488 interface. Refer to Appendix A for instructions.

Analog Signals Analog voltages control the flash lamp energy, the variable oscillator, the Q-switch triggering delay, and the timing of the Q-switch advanced sync signal. The controller supplies analog signals directly. The computer control interface (CCI) supplies these analog signals when commanded to do so by the attached computer or terminal.

10-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

The analog strobe function can be either edge-triggered or level controlled, depending on the placement of jumper W3 on the Control pc board. The standard Lab-Series laser is shipped from the factory set for level-controlled, which provides continuous analog data transfer. Changing Jumper W3 to its alternative setting allows edge triggering of a 5 ms gate aperture. This mode accepts triggered analog data transfers from the computer bus with a time-restricted window. When the standard Lab-Series laser is set to internal control and the INPUT: ANALOG STROBE connector terminals are either shorted or have a logic 0 (0 V) signal applied to them, the system holds (latches) the last data setting and does not respond to any subsequent change in signal. Alternatively, when the system is set to internal control and the INPUT: ANALOG STROBE connector terminals are either not terminated or have a logic 1 (5 V) signal applied to them, the system responds immediately to changes in input signal. When set for computer control, an Analog Strobe logic 1 command allows data to transfer while a logic 0 command latches the last data entered.

Local/Remote Operation

The INT/COMPUTER button on the controller selects the attached computer/ terminal for remote control, or the controller for manual local control. The RS-232C serial and optional IEEE-488 parallel ports are enabled when COMPUTER is selected, but only one port can be used at a time.

Q-switch Delay After the firing signal emerges from the computer test delay, it passes through a one-shot pulse generator that shapes the wave form to meet the drive requirements of the voltage-programmable Q-switch delay. The Q- SWITCH: DELAY control provides an adjustable delay of 50 to 300 ms that allows the population inversion to develop before Q-switch triggering. this allows the Q-switch to open at the peak of stored energy.

Q-switch Advanced Sync Generator The signal splits, passing through a pair of delays, one fixed (850 ns) and one voltage-programmable (300 to 1300 ms). The variable delay controls the timing of the “pre-trigger” signal at the Q-SWitch ADVance SYNC connector on the power supply panel. The fixed delay provides the timing reference against which the variable delay is compared. The advance sync pulse generator shapes the waveform to meet output signal requirements: pulse width = 5 ms 2V (50Ω) rise time = 20 ns (50 Ω oscilloscope input)

10-2 Service and Repair

Mode Switch

The MODE switch on the controller (or the QSWITCH knob on the Main menu) enables one of three sources of Q-switch trigger signals. When set to Q-SW (NORMAL), a signal from the voltage-programmable delay opens the Q-switch momentarily at the point of maximum inversion. When set to LONG PULSE, the flash lamp and Pockels cell are triggered simultaneously, holding the Q-switch open throughout the lamp pulse. When set to EXTER- NAL, a signal at the INPUT: Q-SW TRIG connector on the power supply fires the Pockels cell. The source of the enabling signal depends on the setting of the INT/COM- PUTER selector on the controller and, if set to COMPUTER, on the computer when a computer is connected to the RS-232 interface and the REMOTE jumper plug is installed (see “Local/Remote Operation” above). All external Q-switch triggering signals enter through the INPUT: Q-SW TRIG connector on the power supply regardless of the INT/COMPUTER setting.

Q-switch Drivers

The output of the SOURCE: FIXED delay switch (LAMPS TRIGGER) passes through the MODE switch (QSWITCH) when Q-switch mode is enabled and fires the Marx bank pulse generator. The result is a pulse a few millisec- onds long that becomes amplified by the Marx bank buffer to produce the signal that drives the Marx bank. The Q-switch pulse generator stretches the output of the Marx bank pulse generator to produce a signal that appears at the OUTPUT: Q-SW SYNC connector on the power supply: 2V (50Ω) pulse width 5 ms with 20 ns rise time

Single-Shot Operation Firing a single shot requires two signals: one to enable the single-shot flip- flop and one to fire it. The enabling signal is from either the SINGLE SHOT: REP switch on the controller or the slide bar control on the Main menu. The arming signal (get ready to fire signal) is from either the SINGLE SHOT: FIRE button on the controller or the FIRE position on the Main menu slide bar control. Once armed, the single-shot circuit fires the Marx bank on the next available pulse from the lamp trigger signal. Until it is armed again, the flip-flop prevents the passage of subsequent lamp trigger pulses.

LAMP ON Switch

When the LAMP ON switch (GUI: ON button) is turned off, voltage is applied to the reset line of the lamp sync pulse generator to prevent lamp firing. It also turns on the INHIBIT lamp (GUI: LAMPS TRIGGER knob points to INHIBIT). The inhibit and source fault signals pass through an OR gate that allows either of them to inhibit firing. The LAMP ON switch remains active even when under computer control so that the laser can always be shut off at the controller.

10-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

STOP/ENABLE buttons

The function of the STOP and ENABLE buttons (ON/OFF SWITCH) depends either on the INT/COMPUTER selector on the controller and, if set to COM- PUTER, on the computer when a computer is connected to the RS-232 interface and the REMOTE jumper plug is installed (see “Local/Remote Operation” above). Under INT control, pressing the ENABLE button (toggle ON) closes the main relay and activates all power supply circuits. After a 10 second delay, the laser starts. Under COMPUTER control, two signals are require: an enabling signal that is derived by pressing the controller ENABLE button or by using the REMOTE jumper plug, and an “on” signal from the computer by toggling the ON/OFF SWITCH to “on.” The lighted buttons on the controller identify the operating status of the laser, regardless of the position of the INT/COMPUTER switch. The line dropout detector shuts off the laser if it senses a loss of line voltage. The initializing circuits prevent transfer of laser control until all power supplies have energized. They also prevent mishaps due to errors in logic start-up.

Interlock Logic The interlock logic examines several sensors to ensure safe, trouble-free operation: external interlock, laser head and power supply cover switches, and cooling water temperature and flow. The auxiliary interlock connector on the back of the power supply is included for simple installation of environmental safety devices such as a door switch. If an interlock fault occurs, the logic trips the main contactor, shutting off power to the switching supply and simmer transformer. Logic power remains on. The logic circuit also receives input from the lamp voltage level sensor which prevents the laser from starting until lamp energy is reduced to nearly zero. This prevents accidental high power output upon start-up. If no interlock faults occur, the logic circuit enables the turn-on delay, and, after 10 seconds, the laser starts. If one or more faults occur, the laser will not start and the INTERLOCK FAULT lamp on the power supply and Main menu turn on. The auxiliary interlock connector operates from a 15 Vdc source in the power supply and must be wired to a sensing switch using twisted-pair wire. Because the auxiliary interlock is a possible source of noise, shield the wire in hostile environments. This shield should be grounded to the power supply chassis near the auxiliary interlock connector. Use any one of the chassis mounting screws. Do not attach the shield at any other point.

Pulse-Forming Network The pulse-forming network (PFN) produces a critically-damped pulse when the SCR is fired. This pulse drives the flash lamp(s) that pump the Nd:YAG rods. The switching power supply transforms line voltage (208 Vac, nominal) into dc voltage for the PFN. The PFN voltage (Vpfn) is programmable:

Vpfn = 187.5 x V where V = 0 to 8 Vdc.

10-4 Service and Repair

A PFN voltage monitor is provided at TP24 on the Control pc board in the power supply. The value can also be obtained by query via the computer (see Appendix A). A resistive network is connected across the PFN capacitor as a bleeder to discharge the energy stored in the capacitor when the laser is switched off. The lamp sync pulse generator provides a 5 ms signal to the SCR pulse generator, to the OUTPUT: LAMP SYNC connector on the power supply, and to the lamp-triggered signal for the PFN voltage monitor. The SCR pulse generator conditions the output of the lamp sync pulse generator for the SCR driver. This sends a 1 A pulse through the pulse transformer to fire the SCR.

Flash Lamp Simmer Supply This supply provides dc voltage to the flash lamp start circuit (200 V), the Marx bank (550 V), and the flash lamp simmer current circuit. The start circuit supplies a capacitively-coupled, high-voltage pulse through the lamp housing which breaks down the lamp. After the lamp starts, simmer current flows, is sensed, and the start circuit shuts off. For information on monitoring the simmer supply via the computer, refer to Appendix A.

Shipping the Laser and Power Supply

Warning! Before shipping the laser or the power supply, completely drain the coolant from each. The temperature in an aircraft cargo hold can freeze the coolant and can cause several components to burst. Such damage is not covered under your warranty!

Draining the Cooling System 1. Move the power supply into an open area. 2. Loosening the two screws on each side of the power supply, and carefully lift off the cover. 3. Pull the small return hose from the coolant reservoir cover (Figure 10-1). Take care not to spill any water that may still be in the hose. 4. Using the controller, set its controls as follows:

Control Setting Power supply POWER circuit breaker Closed (On) Power supply POWER key switch On LAMP ON switch Off (INHIBIT lamp on)

10-5 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Level Sensor Return Hose Deionizing Filter Reservoir Particle Filter Cooling Pump

Figure 10-1: Cooling system component identification. 5. Hold the coolant return hose over a drain or bucket, then press the ENABLE button to start the cooling system pump. 6. When the system runs dry, press the STOP button to shut off the pump.

Q-Switch Connector

Inlet Outlet Inlet Control High Voltage Neutral/ Coolant Purge Cable Connector Ground Connector Connector Connector Connector Figure 10-2: Laser head showing coolant connections on the left. 7. Decouple the inlet coolant hose from the laser head (Figure 10-2) and allow the remaining fluid to drain back down into the reservoir. 8. Use a siphon or hand pump to remove the rest of the water from the reservoir. 9. Replace the return hose back into the reservoir cover. 10. Replace the power supply cover. This completes the procedure for draining the coolant from the system.

10-6 Service and Repair

Replacement Parts

Table 10-1: Replacement Parts

Description Part Number Maintenance Flash lamps 0450-9080 Deionizing cartridge, cooling system 9800-0600 Particle filter, cooling system 9800-0620 Air filter assembly, Includes: desiccant filter assembly, 9800-0610 particle (micron) filter, and oil filter. Electrical Control pc board assembly 0449-7900S Power pc board assembly 0447-0510S Fan controller pc board assembly 2203-0071 Simmer pc board 0447-2220 Start circuit assembly 0004-2986S Marx bank assembly 0004-2087-2S Contactor 4501-0361 Thyristor, dual, SCR 4802-2482 Switch, circuit breaker 5102-0640 Fuse kit with 0.25 A FB, 0.5 A FB, 0.5 A SB, 1.5 A SB, 4 A 9850-0650 SB, switching regulator, 1 A SB, 1 A FB, 1/8 A SB, 1/16 A FB, and 30 A SB Optical Thin film polarizer 0005-0021 Output mirror contact factory Q-switch, 10 mm 0100-4460 Q-switch, 13 mm 0447-3300 Gold pump cavity consult factory High reflector contact factory Nd:YAG rods consult factory Dichroic mirror, 532 nm 0441-6070 Dichroic mirror, 355 nm 0449-5370 Dichroic mirror, 266 nm 0449-5360 Half-wave plate, 1064 nm 0002-0053 Half-wave plate, 532 nm 0002-0050 Quarter-wave plate, 1064 nm, Laser 0005-0140 HG WIndow 0002-0061 HG Window Quartz 0002-0061-1 Mechanical Model BD-5 Beam Dump BD-5 Model BD-6 Beam Dump BD-6

10-7 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

10-8 Chapter 11 Customer Service

Customer Service At Spectra-Physics, we take great pride in the reliability of our products. Considerable emphasis has been placed on controlled manufacturing meth- ods and quality control throughout the manufacturing process. Neverthe- less, even the finest precision instruments will need occasional service. We feel our instruments have excellent service records compared to competi- tive products, and we hope to demonstrate, in the long run, that we provide excellent service to our customers in two ways: first by providing the best equipment for the money, and second, by offering service facilities that get your instrument repaired and back to you as soon as possible. Spectra-Physics maintains major service centers in the United States, Europe, and Japan. Additionally, there are field service offices in major United States cities. When calling for service inside the United States, dial our toll free number: 1 (800) 456-2552. To phone for service in other countries, refer to the “Service Centers” listing located at the end of this section. Order replacement parts directly from Spectra-Physics. For ordering or shipping instructions, or for assistance of any kind, contact your nearest sales office or service center. You will need your instrument model and serial numbers available when you call. Service data or shipping instructions will be promptly supplied. To order optional items or other system components, or for general sales assistance, dial 1 (800) SPL-LASER in the United States, or 1 (650) 961- 2550 from anywhere else.

Warranty This warranty supplements the warranty contained in the specific sales order. In the event of a conflict between documents, the terms and conditions of the sales order shall prevail. Unless otherwise specified, all parts and assemblies manufactured by Spectra- Physics, except optics, are unconditionally warranted to be free of defects in workmanship and materials for a period of two years following delivery of the equipment to the F.O.B. point. All optics are warranted for 90 days. Liability under this warranty is limited to repairing, replacing, or giving credit for the purchase price of any equipment that proves defective during the warranty period, provided prior authorization for such return has been given by an authorized representative of Spectra-Physics. Spectra-Physics will provide at its expense all parts and labor and one-way return shipping

11-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

of the defective part or instrument (if required). In-warranty repaired or replaced equipment is warranted only for the remaining unexpired portion of the original warranty period applicable to the repaired or replaced equipment. This warranty does not apply to any instrument or component not manufactured by Spectra-Physics. When products manufactured by others are included in Spectra-Physics equipment, the original manufacturer's warranty is extended to Spectra-Physics customers. When products manufactured by others are used in conjunction with Spectra-Physics equipment, this warranty is extended only to the equipment manufactured by Spectra- Physics. This warranty also does not apply to equipment or components that, upon inspection by Spectra-Physics, discloses to be defective or unworkable due to abuse, mishandling, misuse, alteration, negligence, improper installation, unauthorized modification, damage in transit, or other causes beyond the control of Spectra-Physics. Simple misalignment and unclean optics are the most probable causes of low power or instrument failure and are excluded from warranty protection. A service charge will be assessed if an instrument shipped to Spectra-Physics for warranty repair can be returned to operating condition by routine cleaning or adjustment. This warranty is in lieu of all other warranties, expressed or implied, and does not cover incidental or consequential loss. The above warranty is valid for units purchased and used in the United States only. Products with foreign destinations are subject to a warranty surcharge.

Return of the Instrument for Repair Contact your nearest Spectra-Physics field sales office, service center, or local distributor for shipping instructions or an on-site service appointment. You are responsible for one-way shipment of the defective part or instrument to Spectra-Physics. We encourage you to use the original packing boxes to secure instruments during shipment. If shipping boxes have been lost or destroyed, we recom- mend that you order new ones. Spectra-Physics can return instruments only in Spectra-Physics containers.

Warning! Always drain the cooling water from the laser head and power supply before shipping. Water expands as it freezes and will damage the laser. Even during warm spells or summer months, freezing may occur at high altitudes or in the cargo hold of aircraft. Such damage is excluded from warranty coverage.

11-2 Customer Service

Service Centers

Benelux Telephone: (31) 40 265 99 59

France Telephone: (33) 1-69 18 63 10

Germany and Export Countries* Spectra-Physics GmbH Guerickeweg 7 D-64291 Darmstadt Telephone: (49) 06151 708-0 Fax: (49) 06151 79102

Japan (East) Spectra-Physics KK East Regional Office Daiwa-Nakameguro Building 4-6-1 Nakameguro Meguro-ku, Tokyo 153 Telephone: (81) 3-3794-5511 Fax: (81) 3-3794-5510

Japan (West) Spectra-Physics KK West Regional Office Nishi-honmachi Solar Building 3-1-43 Nishi-honmachi Nishi-ku, Osaka 550-0005 Telephone: (81) 6-4390-6770 Fax: (81) 6-4390-2760 e-mail: [email protected]

United Kingdom Telephone: (44) 1442-258100

United States and Export Countries** Spectra-Physics 1330 Terra Bella Avenue Mountain View, CA 94043 Telephone: (800) 456-2552 (Service) or (800) SPL-LASER (Sales) or (800) 775-5273 (Sales) or (650) 961-2550 (Operator) Fax: (650) 964-3584 e-mail: [email protected] [email protected] Internet: www.spectra-physics.com

*And all European and Middle Eastern countries not included on this list. **And all non-European or Middle Eastern countries not included on this list.

11-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

11-4 Appendix A Status/Error Codes

Table A-1 lists the status and error codes for the Lab-Series laser system. The codes are generated by the embedded controller in the power supply. When Spectra-Physics GUI control software is used, these codes are displayed in the history buffer window located at the bottom of the Info panel. When user-written software is used, these codes can be accessed via queries. Appendix B, “Programming Reference Guide,” at the end of this manual contains information on how to do this. These codes are three-digit numbers. The fist digit relates to internal laser conditions that are useful for Spectra-Physics diagnostics and debugging, but may be ignored by the system operator. The second and third digits indicate the actual error being reported. Thus, error codes 101, 201 and 301 should all be interpreted as reporting the same error, 01, which is “interlock error.” Table A-1: Status/Error Codes

Status Code Description 01 Interlock error 02 Laser ID mismatch 03 Low water 04 Reserved 05 AC dropout detected 06 Unexpected loss of internal power. 07 Oscillator SIMMER failure 08 N/A 09 Reserved 10 Reserved 11 Watchdog timeout 12–98 Reserved 99 Unknown error

A-1

Appendix B Lab-Series Programming Guide

Introduction ...... B-2 Conventions for this manual, and the Lab-Series laser ...... B-2 Section 1: General Purpose Commands ...... B-3 Section 1.1: Basic Commands ...... B-3 HELP...... B-3 *IDN?...... B-3 ON...... B-3 OFF...... B-4 LAMPs ...... B-4 LAMPs? ...... B-4 QSWitch ...... B-4 QSWitch ...... B-4 QSWitch ADVance [value]...... B-4 QSWitch DELay [value] ...... B-4 QSWitch ADVance?...... B-4 QSWitch DELay? ...... B-4 QSWitch?...... B-4 APFN ...... B-5 APFN?...... B-5 OPFN...... B-5 OPFN? ...... B-5 *STB?...... B-5 *RST?...... B-5 SHOTs? ...... B-6 Section 1.2: Communications Setup ...... B-6 ECHo ...... B-6 ECHo?...... B-6 WATChdog ...... B-7 BAUD...... B-7 Section 1.3: Diagnostics...... B-7 READ:OPFN? ...... B-7 READ:APFN? ...... B-7 READ:OMON?...... B-8 READ:AMON? ...... B-8 READ: QSWADV?...... B-8 READ: QSWDEL? ...... B-8 READ: SHOTs? ...... B-8 READ: VARiable?...... B-8 Section 2: Status/Error Reporting Commands...... B-9 Section 2.1: Status Registers ...... B-9 *STB?...... B-9 STATus:QUEStionable? ...... B-10 *CLS...... B-11 READ:HISTory?...... B-11 Section 2.2: ‘C’ Language Example – Using the Status Byte to check for Interlocks ...... B-11

B-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Introduction

The command language for the Quanta-Ray laser system is based on the SCPI (Standard Commands for Programmable Instruments) protocol. The specification for that language can be found at www.SCPIConsortium.org. The Quanta-Ray laser is not 100% compliant with the standard, but does use it as a guide.

Conventions for this manual, and the Lab-Series laser

Å indicates a line of text sent to the laser Æ indicates the laser’s response indicates an integer parameter indicates a floating-point parameter is the ASCII Carriage Return character (hex 0x0D) is the ASCII Line Feed character (hex 0x0A) is the Space character

Commands to the laser may be terminated with , , or both. Responses from the laser are normally terminated with can be modified (refer to ECHO Command).

Every command has both a “short” and “long” form. This document uses a special notation to differentiate the short form command from the long form of the same command. The long form of the command is shown, with the short form portion shown in uppercase characters, and the rest of the keyword is shown in lowercase characters. However, commands sent to the laser are not case sensitive. Consider the listing for the command to set lamp trigger mode. The laser would consider any of these commands to be equivalent:

Å lamp fix (all lower case, all short form) Å lamps fixed (all lower case, all long form) Å LAMP fixed (part upper case short form, part lower case long form) Å LaMpS fIX (mixture of upper & lower case, short & long form)

However,

Å LAMPs FIXE?

would be invalid ---- “FIXE” doesn’t match either the short form “fix” or the long form (“fixed”) subcommand.

Most commands take parameters, separated by a space. The READ and STATus commands take subcommands separated by a colon. Queries return a value and “units.” The units can be used to verify that the laser’s answers are synchronized with your control computer’s questions. Units may consist of a traditional unit. For example, “QSWitch DELay?” returns a string such as “191.075 171.1 231.1 µs ”. “191.075 µs” is the value that Q-switch delay is set for and “171.1 231.1 µs ” are the minimum and maximum value of Q-switch delay respectively.

B-2 Lab-Series Programming Guide

Section 1: General Purpose Commands

General-purpose commands include all commands except those specifically relating to detecting errors. Examples of commonly used commands are turning the laser on and off, changing lamp trigger source, or changing Q-switch trigger mode.

Section 1.1: Basic Commands

HELP

Help command returns the available command.

Å HELP Æ SETUP commands: Æ ECHo HELP Æ OPERATIONAL commands: Æ *CLS *ESR *IDN *RST *STB Æ APFN BAUD BLOK DLOK LAMPs Æ OFF ON OPFN QSWitch READ Æ SHOTs STATus WATChdog

*IDN?

This command returns the product identification string as defined by the SCPI standard. The response to the IDN command contains four fields (manufacturer, model, serial number, and firmware version) separated by commas. A typical response from the laser would be

Spectra Physics,QUANTA-RAY-LAB170-10,2404l,0452-0023A/0456-6600A (company name) (product id) (Serial No) (GCR firmware) / (FPGA firmware)

Examples: Å *IDN? Æ Spectra Physics,QUANTA-RAY-LAB170-10, 2404l,0452-0023A/0456-6600A

This command is used to turn on the laser. The normal sequence is:

1 Close the contactor. 2 Wait 15 seconds. 3 Simmer the lamps and begin firing. 4 Ramp up the PFN power supplies to the last commanded value.

The *STB? command can be used to monitor the turn-on sequence.

Example: Å ON turn on the system

B-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

OFF

This command is used to turn off the laser. The normal sequence is:

1 Turn off the PFN and simmer power supplies. 2 Turn off the water pump 20 seconds after the last lamp trigger.

The *STB? command can be used to monitor the turn off sequence.

Example: Å OFF turn off the system

LAMPs LAMPs? Mode=EXTernal, FIXed, VARiable, INHibit

This command is used to select or identify the lamp trigger source. It is also used to set the variable trigger rate.

Example: Å LAMP FIX Lamp trigger is set to Fixed. Å LAMP EXT Lamp trigger is set to External Source. Å LAMP VAR Lamp trigger is set to Variable. Å LAMP VAR 8.2 Variable Rate is set to 8.2 pulses per second. Å LAMP VAR? To what value is the lamp Variable Rate trigger set? Æ 10.0 VAR Lamp trigger is set to Variable and repetition rate is 8.2 pulses per sec. Å LAMP INH Lamp trigger(s) are Inhibited. Å LAMP? Identify lamp trigger. Æ INHibit Indicates the lamp is Inhibited.

QSWitch QSWitch QSWitch ADVance [value] QSWitch DELay [value] QSWitch ADVance? QSWitch DELay? QSWitch? Modes = EXTernal, LONGpulse, NORMal Types = FIRe, REPetitive, SINGleshot

This command controls the Q-Switch modes, type and timing. The modes are: External, Long Pulse and Normal. The types are: Fire, Repetitive and Single-Shot

Example: Å QSW LONG Sets the Q-switch to its Long Pulse mode. Å QSW SING Sets the Q-switch to Single-Shot type. Å QSW FIRe Fires the Q-switch once. Å QSW? What is the Q-switch setting?

B-4 Lab-Series Programming Guide

Æ LONGpulse SINGleshot Indicates the Q-switch is set to Long Pulse mode and Single- Shot type.

Reminder: QSWitch DELay and ADVance are only meaningful in NORMal mode.

Å QSW ADV 250 Sets the Q-switch Advance Sync to 250.00. Å QSW ADV? To what value is Q-switch Advance Sync set? Æ 250.00 –700.0 500.0 ns Indicates the Q-switch Advance Sync is 250.0, the min value is –700.0 ns and the max value is 500.0 ns. Å QSW DEL? To what value is Q-switch Delay set? Æ 210.00 120.0 250.0 µs Indicates the Q-switch Delay is set to 210.0 µs, the min value is – 120.0 µs and the max value is 250.0 µs.

APFN APFN? Range: n = 0 – 100%

The APFN command sets the Amplifier PFN voltage as a percentage of factory full scale.

Example: Å APFN 100 Sets the APFN voltage to 100.0%. Å APFN? To what value is APFN set? Æ 100.0 % Indicates APFN is set to 100.0%.

OPFN OPFN? Range: n = 0-100%

The OPFN command sets the Oscillator PFN voltage as a percentage of factory full scale.

Example: Å OPFN 100 Sets the OPFN voltage to 100.0%. Å OPFN? To what value is OPFN set? Æ 100.0 % Indicates OPFN is set to 100.0%.

*STB?

The status byte is the central component of the SCPI status system. Properly interpreting this byte allows the operator to determine the overall operating condition of the laser system. See “Section 2: Status/Error Reporting” for information on interpreting the status byte and other status registers.

*RST?

This command resets the laser head pc board.

B-5 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

SHOTs?

This command returns the number of shots on the lamps, or resets the counter when the lamp is replaced. Note: this command returns the actual number of shots while the mechanical counter on the front panel reports shots rounded to the nearest 100.

Example: Å SHOT? How many shots are on the lamps? Æ 1134 1134 (the mechanical counter on the power supply would report 1100) Å SHOT 0 resets the lamp shots counter to zero

Section 1.2: Communications Setup

ECHo ECHo?

This command modifies the way the control computer interacts with the laser. The parameter is an integer that specifies a bit pattern. The bits are defined as follows:

Bit Description 0 show prompts 1 the laser echoes characters as they are received 2 shows error messages 3 output at least a line feed for every command (even ones that do not normally generate a response) 4 terminate responses with , rather than just 5 use XON/XOFF handshaking for data sent to the laser (No handshaking is used for data sent from the laser)

The previous Echo mode is replaced at power up and is unaffected by the *RST command. When Echo is set to zero, the laser will not issue a response unless a command requires it, and the response will be terminated with a character.

Examples: Å ECH? What is the current Echo mode? Æ 0 The system responds: ECHO 0. Å ECH 1 Set to Echo 1 mode. Æ !Ready Laser prompts that it is ready. Å ECH 17 Request both prompt and termination. Æ !Ready Laser prompts that it is ready. Å ECH 21 Request prompt and error messages. Æ !Ready Laser prompts that it is ready. Å LMP FIX Send an illegal command (should be LAMPs FIXed). Æ What? Laser prompts that it does not understand the command. Æ !Ready Laser prompts that it is ready. Å ECH 8 Request for all commands, no prompts or warnings. Æ The verifies that a command was received

B-6 Lab-Series Programming Guide

WATChdog Range: 0 to 110 seconds.

This is the RS-232 laser/control computer communication watchdog timer. If the laser does not receive communications from the control computer within the specified time, it turns itself off. The default value is zero (disabled).

This command allows users to set their own comfort level for a safety check on their control computer. Values from 3 to 10 seconds are typical.

Example: Å WATC 5.1

BAUD Values for n = 2400, 4800, 9600, 19200, 38400

This command sets the communications speed between the laser embedded computer and the user’s control computer. At power-up, the laser always communicates at 9600 baud. The baud rate is not affected by the *RST command.

Example: Å BAUD 38400

Section 1.3: Diagnostics

The READ commands are used to learn what the laser is actually doing, as opposed to what it has been asked to do. A few reasons the READ commands can return something different than what was commanded by a control computer are:

1 The control computer is not actually in control. A remote panel or an external BeamLok controller is in control. 2 The system may be in a turn-on or turn-off sequence. For example: when the system is turned off, it is normal for APFN? to indicate a commanded value of 100%, and READ:APFN to report an actual value of 0%. 3 Under certain conditions the system will automatically decrease the PFN voltages to 90% of the nominal settings in order to prevent optical damage. A typical example is when the Q-Switch is set to Single-Shot type.

READ:OPFN? READ:APFN?

These queries return the oscillator or amplifier PFN command setting in percent (i.e., what the PFN power supply is being asked to do).

Example: Å READ: APFN? Æ 0.0 %

B-7 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

READ:OMON? READ:AMON?

These queries return the oscillator or amplifier PFN monitor in percent (i.e., what the PFN power supply is actually doing).

Example: Å READ: AMON? Æ 0.0%

READ: QSWADV?

This query returns the current Q-Switch Advanced Sync setting.

Example: Å READ:QSWADV? Æ –200.0 ns

READ: QSWDEL?

This query returns the Q-Switch delay setting.

Example: Å READ:QSWDEL? Æ 210.0 µs

READ: SHOTs?

This query returns the number of shots.

Example: Å READ:SHOT? Æ 429

READ: VARiable?

This query returns the lamp trigger rate, unless the lamp trigger source is external.

Example: Å READ:VAR? Æ 10.1 VAR

B-8 Lab-Series Programming Guide

Section 2: Status/Error Reporting Commands

One of the most powerful (and therefore complex) parts of the SCPI protocol is its error reporting facility. Status is reported in a tree-like structure where the root of the tree is the status byte. Users should regularly check this byte for information about basic conditions such as laser emission, water pump on, and interlock status. It also discloses any “questionable” conditions that might exist. “Questionable” conditions are those that might raise doubts about laser system performance (such as a power supply that cannot properly charge the high voltage capacitor). If “questionable” conditions are reported, then further information can be requested.

Section 2.1: Status Registers

*STB?

This query returns the status byte, which is the top level of the SCPI information data structure. The value returned is an integer representing a 32-bit value, which, when properly interpreted, discloses the condition of the laser.

A programming example of how to use this status byte to access the SCPI data structure is included at the end of this appendix.

Bit Description Number 0 Laser emission can occur 1 (reserved) 2 Data is in the error log, use READ:HIST? 3 Check STAT:QUES bits 4 (reserved) 5 Check *ESR bits 6 (reserved) 7 Check STS:OPER bits 8 Main contactor is energized 9 Oscillator simmer is on 10 Amplifier simmer is on 11 Oscillator PFN is at target 12 The laser has recently fired 13 15 Vdc power supply failure 14 Laser cover interlock open 15 One or more of the following interlocks is open: CDRH plug, power supply cover, laser head cover, laser head temperature, water pressure, water flow 16 Remote panel disconnected 17 Internal 208 Vac failure 18 CDRH enable failure 19 Laser ID fault 20 Low water fault

B-9 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

21 Interlock fault 22 A remote panel is connected 23 the remote panel indicates that the computer is in control. 24 The main contactor should be on 25-31 (reserved)

To properly interpret the power supply interlock state, first consider bits 13 through 21. The laser has three interlock priorities: bits 19, 20, and 21, with bit 19 being the most important. Bits 13 through 18 do not contain useful information unless bit 21 is true (high).

If bit 23 is low, the remote panel is in control, and commands that attempt to set a value (such as LAMPs or QSWitch) have no effect on the laser. Any command that asks for information (such as READ:SHOTs?) operate as expected. The ON and OFF commands will operate as expected, even if the remote panel is in control.

Example: Å *STB? Send status byte. Æ 139 The requested status byte states that the laser has emission, the shutter is open and something is questionable about the laser. Use the STATus:QUES command to determine which conditions have set the questionable bit.

STATus:QUEStionable?

This query returns the questionable condition register. It is an extension of the basic status byte, and it can give more information about subsystems within the laser. Bit 3 of the status byte (*STB?) is a logical-OR of bits 9, 10, and 11. If Bit 3 of the status byte is false (low), there is no need to check the STATus:QUEStionable register for additional information.

Bits 0 through 8 and 12 through 15 are undefined and are reserved for future use.

Bit 9 is set if the oscillator high-voltage (HV) power subsystem does something unexpected. If bit 9 is true (high), then bits 16 through 23 should be examined to identify the fault. If Bit 9 is false, bits 16 through 23 should be ignored.

Bit 10 is set high if the amplifier high-voltage (HV) power subsystem does something unexpected. If bit 10 is true, bits 24 through 31 should be examined to identify the fault. If bit 9 is false, bits 24 through 31 should be ignored.

Bit 11 is set when an EXTernal LAMPs trigger has occurred at a rate that is outside the specified MIN and MAX limits.

Bit Description number 0 – 8 (reserved) 09 Oscillator HV failure 10 Amplifier HV failure 11 External Trigger Rate out of range

B-10 Lab-Series Programming Guide

12 De-ionized water low 16 OSC HVPS # 1 EndOfCharge 17 OVerLoad 18 OVerTemp 19 OVerVolt 20 OSC HVPS # 2 EndOfCharge 21 OVerLoad 22 OVerTemp 23 OVerVolt 24 AMP HVPS # 1 EndOfCharge 25 OVerLoad 26 OVerTemp 27 OVerVolt 28 AMP HVPS # 2 EndOfCharge 29 OVerLoad 30 OVerTemp 31 OVerVolt

Example: Å STAT:QUES? What is the status of the system? Æ 512 The system reports that the oscillator high-voltage is not ok.

*CLS

This command clears the status byte and status questionable register. Use it to make sure there is no “left over” information in these registers from a previous error. The history buffer (READ:HISTory) is not affected by *CLS, even though bit 2 of the status byte remains zero until a new error occurs.

READ:HISTory?

This query returns up to 16 status/error codes from the system history buffer. If the laser has shut itself off or the system is behaving erratically, investigate the answer to this query. The first element in this history buffer is the most recent. A complete listing of the laser history buffer error codes is included in Appendix A. This query returns at lest two lines of information, each of which consists of two numbers. The first number in the first line is the number of items in the buffer. The second number in first line is the number of seconds since power up. The final line is always “0 0”. Intermediate lines contain the error code followed by the system time when the error occurred.

Example: Å READ:HIST? Request for history buffer Æ 1 827 1 error has occurred, current time is 827 sec Æ 301 810 Error code 301 occurred at 810 sec Æ 0 0 End of history buffer

Section 2.2: ‘C’ Language Example – Using the Status Byte to check for Interlocks

B-11 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

#defineSTB_LASER_ID BIT_19 #defineSTB_LO_WATR BIT_20 #defineSTB_ILK_NOK BIT_21 #defineSTB_INTERLOCK1 BIT_13 #defineSTB_INTERLOCK2 BIT_14 #defineSTB_INTERLOCK3 BIT_15 #defineSTB_INTERLOCK4 BIT_16 #defineSTB_INTERLOCK5 BIT_17 #defineSTB_INTERLOCK6 BIT_18 int StbTimer ( void) { long stb; static char buff[255]; sprintf(buff, "*STB?\n\r"); WriteBuf_CurSerialPort(buff, strlen(buff));//This function writs the buffer to serial port ReciveBuf_CurSerialPor( );//This function receives the responds from laser and saves it in InputBuffer stb=atoi( InputBuffer); if(stb ^ Last_Stb) // Last_Stb is global variable and initially is sets to zero CheckStatus(stb); } void CheckStatus(long stb) { Last_Stb = stb; if(stb&STB_LASER_ID || stb&STB_LO_WATR || stb&STB_ILK_NOK ) { if(stb&STB_LASER_ID ) { sprintf (ErrorMessage, " LASER ID FAULT. \n\n" " Unable to run the laser,\n"); DisplayPanel(ErrorMessage); //This function displays the error message. } if (stb&STB_LO_WATR) { sprintf (ErrorMessage, " LOW WATER INTERLOCK DETECTED. \n\n" " Unable to run the laser,\n" " Please fill up the reservoir \n" " Then Press OK"); DisplayPanel(ErrorMessage); //This function displays the error message. } if(stb&STB_ILK_NOK) {

if(stb & STB_INTERLOCK1 ) { sprintf (ErrorMessage, " 15 VOLTS P.S INTERLOCK DETECTED. \n" " Unable to run the laser.\n\n\n\n");

B-12 Lab-Series Programming Guide

DisplayPanel(ErrorMessage); //This function displays the error message. } else if(stb & STB_INTERLOCK2) { sprintf (ErrorMessage, "P.S. COVER INTERLOCK DETECTED. \n\n" " Unable to run the laser,\n\n\n\n"); DisplayPanel(ErrorMessage); } else if(stb & STB_INTERLOCK3) { sprintf (ErrorMessage, " ONE OR MORE OF THE FOLLOWING PROBLEMS HAS BEEN DETECTED. \n\n" " 1-Water Flow \n" " 2-CDRH \n" " 3-Power Supply Cover Interlock \n" " 4-Head Cover \n" " 5-Head Thermistor \n" " 6-External Water Pressure \n\n" " Unable to run the laser."); DisplayPanel(ErrorMessage); } else if(stb & STB_INTERLOCK4) { sprintf (ErrorMessage, " REMOTE CONTROL INTERLOCK DETECTED. \n" " Unable to run the laser,\n\n\n\n"); DisplayPanel(ErrorMessage); } else if(stb & STB_INTERLOCK5) { sprintf (ErrorMessage, " INTERNAL 208 AC POWER INTERLOCK DETECTED. \n" " Unable to run the laser,\n\n\n\n"); DisplayPanel(ErrorMessage); } else if(stb & STB_INTERLOCK6) { sprintf (ErrorMessage, "CDRH TRNSISTOR INTERLOCK DETECTED. \n\n" " Unable to run the laser,\n\n\n\n"); DisplayPanel(ErrorMessage); } } } }

B-13 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

B-14 Notes

Notes-1 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Notes-2 Notes

Notes-3 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Notes-4 Notes

Notes-5 Quanta-Ray Lab-Series Pulsed Nd:YAG Laser System

Notes-6 Report Form for Problems and Solutions

We have provided this form to encourage you to tell us about any difficul- ties you have experienced in using your Spectra-Physics instrument or its manual—problems that did not require a formal call or letter to our service department, but that you feel should be remedied. We are always interested in improving our products and manuals, and we appreciate all suggestions. Thank you.

From: Name Company or Institution Department Address

Instrument Model Number Serial Number Problem: