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Find the Newport / New Focus 6300 at our website: Click HERE TLB-6300 Tunable

• New ranges from 630 to 2 µm • Cavity design eliminates mode-hops • Smooth, linear, mode-hop-free tuning

New—2 µm!

U.S. Patent #5,319,668

• Testing and qualifying telecom- munications components • of volatile gases 1600

ations in the atmosphere m 1580 n , h t 1560 g • Seeding of optical parametric n e l 1540 e oscillators (OPOs) to provide v a 1520

W narrow bandwidth

1500 Applic 0 5 10 15 20 25 • Swept-frequency metrology Time, s • FM locking and non-linear optical These curves demonstrate the generation (see page 16) monotonic and continuous tuning of a Model 6328 . They were • Measuring polarization-mode taken using maximum, 20% of maximum, and 10% of maxi- • Spectroscopy and environmental mum tuning-speed settings. sensing of methane, CO, CO2, water vapor and hydrocarbons

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The TLB-6300 (Velocity™ laser) series is our Complete Computer Control and most versatile line of external-cavity tunable LabVIEW™ Programs Power Meters Receivers & Detectors, diode lasers. Designed for your most demanding Anything you can adjust from the front panel applications, these lasers offer continuous can be controlled through RS-232 or GPIB tuning over wide wavelength ranges, fast linear (IEEE-488) interfaces. In remote mode, you sweeps, excellent tuning resolution, and narrow, still have access to the frequency-modulation stable linewidths. input, allowing you to dither the frequency as you perform automated wavelength scans. Choppers Modulators & Optical Our laser-cavity design and proprietary manu- facturing procedure ensure fast mode-hop-free The general-purpose detector input on the back tuning over the entire wavelength range and panel allows you to implement digital-control superior wavelength repeatability and precision algorithms. This allows you to feed in signals with a greater than 40-dB side-mode suppres- from sources as diverse as photodetectors

sion ratio. Our precision-engineered mechanical and frequency discriminators, and is particularly Contr Motion drive-train has a fine-frequency piezo control useful for stable-power wavelength scans, back- that allows you to set the laser’s wavelength ground correction in applied-spectroscopy ol with a resolution of 0.02 pm. And unlike lasers experiments, and wavelength stabilization. driven by stepper motors, the TLB-6300’s tuning is truly continuous and monotonic.

(See page 24.) With a choice of Components Opto-Mechanical from 630 to 2 µm, these lasers are ideal for telecommunications, spectroscopy, metrology, and environmental-sensing applications.

Features:

High-Speed Current Modulation Br W orkstations & eadboar Modulate the laser amplitude with a 3-dB bandwidth of 1 MHz through the controller’s current-modulation input. Applying a signal ds directly to the via a connector on the laser head allows you to modulate the amplitude at rates of at least 100 MHz. Optics

Easy Wavelength Modulation Convenient wavelength modulation for spectroscopy or stabilization experiments is provided by a PZT actuator on the tuning

element. Modulating the PZT through the Solutions OEM modulation input on the back panel of the con- troller allows you to directly modulate the laser wavelength with a small-signal 3-dB bandwidth of 2 kHz. Full 30-GHz frequency modulation can be performed at rates up to 200 Hz. Notes Application Automated Wavelength Scans Easily perform wavelength scans over the entire tuning range of the laser. Just set the start and stop wavelengths and scanning speed (up to 20 nm/s for some models) and press the scan button. Glossar y

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Laser Power: Piezo-Voltage Display: Wavelength and Scan Speed All front-panel functions can Turns on the Shows the percentage of the Display: Indicates operating be controlled remotely through current to voltage applied to the piezo- wavelength, scan speed, and back-panel inputs. the diode. electric transducer for fine- start and stop wavelengths. frequency control of the laser. Accuracy: 0.1 nm.

Fine Frequency Control: Multipurpose Paddles: Current Controls: Sets the voltage to the Used in conjunction with Sets the diode current and piezoelectric transducer the setpoint knobs, this monitors the actual laser that controls the activates and deactivates output power. (Output fine-frequency tuning stable-power mode, and sets power is measured by of the laser. wavelength, scan speed, diverting a small fraction start and stop wavelengths, of the output power to a diode temperature, baudrate monitor photodiode.) and GPIB addressing. Display resolution: 0.1 mW and 0.4 mA. Frequency Modulation Input: Allows Current Modulation Input: you to control the voltage applied to Lets you modulate the amplitude Remote Interfaces: Let you the piezo. It is equivalent to the fine of the laser. It has a 1-MHz band- use either an IEEE-488 or an frequency adjust on the front panel. width. The SMA input on the laser RS-232 computer interface. head has a >100-MHz bandwidth.

Wavelength Output: Results Wavelength Input: Lets you Detector Input: in a 0–10-V linear output that control the laser wavelength Gives you a general- D A N G E R is proportional to the actual (equivalent to the coarse purpose analog

VISIBLE AND/OR INVISIBLE LASER RADIATION wavelength of the laser. adjust on the front panel). input for control AVOID DIRECT EXPOSURE TO BEAM Resolution: 0.01 nm. applications. CLASS IIIb LASER PRODUCT

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Higher power and custom wavelengths are available. Please contact our sales department for information on Power Meters Receivers & Detectors, the latest products at [email protected].

Mode-Hop-Free 632.5– 668– 765– 838– 960– 1055– 1220– Tuning Range 637 nm 678 nm 781 nm 853 nm 995 nm 1075 nm 1250 nm Minimum Power 2 mW 2 mW 5 mW 5 mW 5.5 mW 4 mW 5 mW Typical Maximum Power 5 mW 4 mW 12 mW 7 mW 8 mW 6 mW 7 mW Choppers Modulators & Optical Maximum Coarse-Tuning Speed 6 nm/s 6 nm/s 8 nm/s 8 nm/s 12 nm/s 12 nm/s 20 nm/s Coarse-Tuning Resolution 0.02 nm 0.02 nm 0.02 nm 0.02 nm 0.02 nm 0.02 nm 0.02 nm Typical Wavelength Repeatability 0.1 nm 0.1 nm 0.1 nm 0.1 nm 0.1 nm 0.1 nm 0.1 nm Fine-Frequency 70 GHz 70 GHz 75 GHz 60 GHz 50 GHz 50 GHz 45 GHz Tuning Range (0.09 nm) (0.1 nm) (0.15 nm) (0.14 nm) (0.16 nm) (0.16 nm) (0.3 nm) Fine-Frequency 2 kHz 2 kHz 2 kHz 2 kHz 2 kHz 2 kHz 2 kHz Contr Motion Modulation Bandwidth Current-Modulation BW 100 MHz 100 MHz 100 MHz 100 MHz 100 MHz 100 MHz 100 MHz ol Linewidth <300 kHz <300 kHz <300 kHz <300 kHz <300 kHz <300 kHz <300 kHz Model # TLB-6304 TLB-6308 TLB-6312 TLB-6316 TLB-6320 TLB-6321 TLB-6323 Base System Price* $19,500 $18,500 $20,000 $21,000 $27,000 $25,000 $25,000 Add -D Add -D Add -D Add -D Add -D Add -D Add -D Additional Laser Head* to Model # to Model # to Model # to Model # to Model # to Model # to Model # Components Opto-Mechanical and $11,000 and $10,000 and $11,500 and $12,500 and $18,500 and $16,500 and $16,500 Add -P Add -P Add -P Add -P Add -P Add -P Add -P Fiber Pigtail with to Model # to Model # to Model # to Model # to Model # to Model # to Model # FC/APC Connector*† and $4,500 and $4,500 and $4,500 and $4,500 and $4,500 and $3,500 and $3,500

Mode-Hop-Free 1270– 1470– 1415– 1520– 1550– 1650– 1940– 1970– Br W

Tuning Range 1330 nm 1545 nm 1480 nm 1570 nm 1630 nm 1680 nm 1970 nm 2000 nm orkstations & eadboar Minimum Power 5 mW 4 mW 3 mW 20 mW 4 mW 3 mW 2 mW 2 mW

Typical Maximum 7 mW 10 mW 8 mW 20 mW 4 mW 5 mW 3 mW 3 mW Power ds Maximum Coarse-Tuning 15 nm/s 20 nm/s 20 nm/s 20 nm/s 25 nm/s 20 nm/s 20 nm/s 25 nm/s Speed

Coarse-Tuning 0.02 nm 0.02 nm 0.02 nm 0.02 nm 0.02 nm 0.02 nm 0.02 nm 0.02 nm Optics Resolution Typical Wavelength Repeatability 0.1 nm 0.1 nm 0.1 nm 0.1 nm 0.1 nm 0.1 nm 0.1 nm 0.1 nm Fine-Frequency 50 GHz 30 GHz 30 GHz 30 GHz 30 GHz 30 GHz 20 GHz 20 GHz Tuning Range (0.29 nm) (0.23 nm) (0.24 nm) (0.24 nm) (0.24 nm) (0.24 nm) (0.30 nm) (0.30 nm) Fine-Frequency Modulation 2 kHz 2 kHz 2 kHz 2 kHz 2 kHz 2 kHz 2 kHz 2 kHz Bandwidth

Current-Modulation Solutions OEM BW 100 MHz 100 MHz 100 MHz 100 MHz 100 MHz 100 MHz 100 MHz 100 MHz Linewidth <300 kHz <300 kHz <300 kHz <300 kHz <300 kHz <300 kHz <300 kHz <300 kHz Model # TLB-6324 TLB-6326 TLB-6327 TLB-6328 TLB-6330 TLB-6331 TLB-6334 TLB-6335 Call for Call for Base System Price* $24,000 $24,000 $25,000 $25,000 $25,000 $25,000 Pricing Pricing Add -D Add -D Add -D Add -D Add -D Add -D Add -D Add -D Additional Laser to Model # to Model # to Model # to Model # to Model # to Model # to Model # to Model # Head* and $15,500 and $15,500 and $16,500 and $16,500 and $16,500 and $16,500 (call for price) (call for price) Notes Application Fiber Pigtail with Add -P Add -P Add -P Add -P Add -P Add -P Add -P Add -P FC/APC to Model # to Model # to Model # to Model # to Model # to Model # to Model # to Model # Connector*† and $3,500 and $3,500 and $3,500 and $3,500 and $3,500 and $3,500 (call for price) (call for price)

See page 14 for tuning curves. For special orders or items not contained in this table, please e-mail us at [email protected]. † Typical coupling efficiency is >30% for Model 6304, >40% for Models 6308, 6312, 6316, 6320, 6331, 6334, 6335, and >50% for all other models. Fiber used is polarization-maintaining (PM) PANDA fiber.

Related Products: Photodetectors (pages 60–99) n Modulators (pages 116–119) n Power Meters (pages 56–59) Glossar Definitions of Characteristics (page 11) *For international prices add 10%. y

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Tunable Laser Selection Guide

Whether you need a stand-alone benchtop unit or custom OEM module, turn to the world’s leading supplier of tunable lasers for test and measurement—New Focus™. We offer a wide variety of lasers covering tuning ranges from 400 nm The TLM-8700 to 2 µm, including swept-wavelength sources, narrowly tun- laser modules use a new technology able sources, and new cPCI/PXI module sources. Their to achieve 1-nm/s highly coherent, tunable output is ideal for applications to >1,000-nm/s ranging from telecommunications to atomic and molecular tuning speeds. spectroscopy, interferometry, and metrology.

Tunable Lasers Currently Available Our new TLB-7000-XP Benchtop Lasers Wavelengths Mode-Hop-Free lasers deliver >50 mW Covered Tuning Range at 780 and 850 nm. TLB-6000 400–420 nm, Up to 80 GHz 630–2000 nm 400–420 nm, TLB-6300 630–2000 nm Up to 80 nm 1425–1620 nm, TLB-6500* 1260–1340 nm, Up to 100 nm 960–995 nm 632.5–640 nm, TLB-7000 835–853 nm 150 GHz 767–781 nm, TLB-7000-XP 840–853 nm 15 GHz

Module Lasers Wavelengths Mode-Hop-Free Covered Tuning Range TLM-8700* 1460–1630 nm >110 nm *Custom wavelengths are also available. Call for pricing and lead times.

Available on our Web Site For current off-the-shelf laser solutions, visit www.newfocus.com.

Diagram of Laser Applications and Their Wavelength Regions 300 nm 400 nm 500 nm 600 nm 700 nm 800 nm 900 nm 1 µm 1.1 µm 1.2 µm 1.3 µm 1.4 µm

390–430 nm Spectroscopy of Ca, In, Rb. 710–795 nm 1.25–1.40 µm Spectroscopy of Fr, K, 890–970 nm Spectroscopy of Ar, Li, O , Rb (D1 and D2); Spectroscopy of Cs 2 CH4 (methane), CO, magneto-optical traps (D1), H O; 2 970–1100 nm CO2, O2, water vapor; 630–700 nm for atom cooling. second-harmonic Spectroscopy of He; telecommunications. Spectroscopy of Ca, I, generation. injection seeding of Li, Sr88+; replacement Nd:YAG lasers; for stabilized HeNe; 795–890 nm telecommunications interferometry; optical Spectroscopy of Ar, pump bands; injection data storage; holography. Cs (D2); heterodyne seeding for terahertz experiments; Raman generation; second- spectroscopy; harmonic generation. magneto-optical traps for atom cooling.

Wavelengths from 405 nm–2.0 µm are currently available from New Focus.

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The TLB-7000 StableWave™ laser series The TLB-6000 (Vortex™ laser) series Power Meters Receivers & Detectors, builds upon the popular TLB-6000 (Vortex™ consists of reasonably priced, built- laser) series offering improved performance at to-order lasers with tuning 633 nm and 852 nm with increased rugged- ranges up to 80 GHz—wide ness—ideal for atomic-clock, cooling, metrology, enough for most absorption and phase-shifting-interferometry applications. spectra and metrology applications. Choppers Modulators & Optical The new TLB-7000-XP laser offers a 5 to 10 The TLB-390X laser is ideal for DWDM telecom times improvement in output powers at 780 and test-and-measurement applications 850 nm. With greater than 50 mW of output power, requiring 20 mW of output power these lasers are ideal for atomic cooling and across the C band. clock experiments where you need more power. Contr Motion The swept-wavelength TLB-6500 laser The new TLM-8700 cPCI/PXI tunable laser family offers coverage across all key telecom modules deliver ultrafast tuning of 1,000 nm/s ol bands, low ASE, and an easy-to-use icon- over more than 165 nm of tuning in the C-band. based interface for telecom- They are easily integrated into the PXI platform component characterization with our other modules (swept-wavelength

and fiber-sensing applications. meter and power sensor). Components Opto-Mechanical

The TLB-6300 (Velocity™ laser) series is ideal for FM locking, measuring polarization- mode dispersion, and nonlinear optics. The

980-nm model is useful for characterizing Br W orkstations & EDFA pump components. New this year are And, if you don’t see what you need, let our award-winning, eadboar lasers that cover the wavelength interdisciplinary engineering team work with you to design lasers specifically for your application. With our ISO ranges from 1.6 to 2.0 µm ds for environmental sensing. 9001:2000-compliant quality systems, we will manufacture For other wavelengths, to your specs, on time, and with engineered cost savings.

please contact us. We even have lasers in development for use in space- Optics deployed atomic clocks.

1.5 µm 1.6 µm 1.7 µm 1.8 µm 1.9 µm 2.0 µm 2.1 µm 2.2 µm 2.3 µm 2.4 µm 2.5 µm 2.6 µm Solutions OEM

1.48–1.67 µm 2.10–2.60 µm Spectroscopy of 1.94–2.08 µm Spectroscopy of CO, acetylene, CH4 N O, CH (methane), Spectroscopy of CO2, 2 4 (methane), CO, CO2, NH , water vapor. NH2, water vapor. Kr, NH , water vapor, 2 2 1.70–1.82 µm hydrocarbons; Notes Application Spectroscopy of telecommunications; CH (methane), He, fiber-Bragg gratings 4 NO, water vapor. that measure temperature, pressure, and strain. Glossar

For wavelengths above 2.0 µm please call for availability. y

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What’s Inside Our Tunable Lasers Precision Mechanics Result Laser Cavity Designs for The laser cavities in our external-cavity in a Laser with Truly Continuous, 24/7 Reliability diode laser (ECDL) systems and laser Mode-Hop-Free Tuning Adding our extensive experience in manu- modules are the result of many years of Once the diode is coated, we place it in facturing lasers and opto-mechanics to the experience in designing and manufacturing an external laser cavity that is a modified proprietary AR coating and unique cavity tunable lasers. Their demonstrated quality Littman-Metcalf configuration. In this cavity, design results in a robust and rugged laser and reliability have helped make New a grazing-incidence diffraction grating and that can withstand rough handling and a Focus the leading supplier of tunable a tuning element provide all the necessary variety of environmental conditions. These lasers for test and measurement. dispersion for single-mode operation. In lasers surpass international shipping stan- addition, our cavity design allows mode- dards for shock and vibration and can All New Focus lasers start out as commer- hop-free tuning. The wavelength in our operate in environments with up to 80% cially available semiconductor-diode lasers. modified Littman-Metcalf laser is changed relative humidity from 15–35 ºC. This These diodes typically operate with several by rotating the tuning element, which means that they can survive the long-term, longitudinal modes lasing simultaneously, changes the diffracted wavelength fed 24/7 use (and abuse) found on many leading to low coherence and large back into the cavity. To prevent mode manufacturing floors. linewidths. To ensure high coherence, we hopping, the cavity length must be kept anti-reflection (AR) coat the diodes so at a constant number of wavelengths as they act only as gain elements. The diode the laser tunes. This requires positioning can then be placed in an external cavity the pivot point around which the tuning that contains wavelength-selective optics element rotates with sub-micron accuracy, so that only a single mode lases at any enabling us to produce lasers with no given time. mode hops.

echnical Note Robust, Proprietary AR Coating for Tight Environmental Control Broad Wavelength Tunability for Narrow Linewidth

T True single-mode tuning requires that Once single-mode operation is established the optical feedback is dominated by the by the optics in the external cavity, the external optics, not by reflections from linewidth of the laser can be affected by the diode facet. We use a proprietary AR- acoustic coupling and cavity-temperature coating process to reduce residual diode variations, each of which can change the reflectivities to below 0.001—which guar- cavity length, and electrical-noise coupling, antees true single-mode operation. This which causes changes in the index of process allows us to use nearly any avail- refraction of the diode and in the piezo able single-mode diode laser and achieve length (also affecting the cavity length). low reflectivity over a broad wavelength Every aspect of our laser design aims to range. In addition, since the lifetime of an minimize these effects. For example, our ECDL is commonly limited by that of the laser controllers feature current sources AR coating, our proprietary process ensures with less than 100-nA current noise in that our coatings last. rms a 1-MHz bandwidth.

Wavelength Tuning Tuning Element HR Coating AR Coating

Laser-Diode Chip

Collimating Lens

Diffraction Grating

Laser Output

A modified Littman-Metcalf configuration.

10 [email protected] fax: (408) 919–6083 Artisan Technology Group - Quality Instrumentation ... Guaranteed | (888) 88-SOURCE | www.artisantg.com New Focus™ Tunable Lasers Definitions of Characteristics Absolute Wavelength Accuracy Minimum Power The maximum difference between the measured wavelength The lowest power that the laser will output across its specified and the displayed wavelength of the laser system. tuning range when the current is set to its recommended operating value. Due to changes in diode gain and cavity loss with wave- Amplified Spontaneous Emission (ASE) length, the laser’s output power is not constant as it tunes. (See The ratio of the optical power at the center of the laser linewidth tuning curves on page 14.) to the optical power at a given distance, as measured using an optical spectrum analyzer with a set resolution bandwidth. (See Output Power “Why is the Noise Spectrum Important?” on page 12.) The typical power that the laser will output across the entire tuning range. Coarse-Tuning Resolution The smallest wavelength change you can make with the Power Repeatability coarse-tuning DC motor on the TLB-6300 laser. The typical difference in power between scans for a given wavelength. Current-Modulation Bandwidth The highest rate at which the laser diode’s current can be Power Stability changed. This is the 3-dB frequency of the direct-modulation The maximum deviation in power as the laser sits at a specific input located at the laser head. wavelength over a 1-hour period.

Fine-Frequency Modulation Bandwidth Side-Mode Suppression Ratio The highest rate at which the fine-tuning PZT in the laser The ratio of the carrier to the nearest side mode. cavity can modulate the laser frequency. The specified bandwidth is for a 3-dB drop from a low-frequency baseline Tuning Range under small-signal modulation. The span of wavelengths over which the laser is guaranteed to operate. For the TLB-6300 series, the laser may be able to Fine-Frequency Tuning Range tune outside this range, but this may introduce mode hops. The frequency range over which the laser can be piezoelectrically tuned. (If λ is the wavelength of the laser and c is the speed of Tuning Speed light, the tuning range expressed in frequency, ∆ν, and wave- The speed over which the laser can sweep over the entire length, ∆λ, is related by ∆ν=c•∆λ/λ2. Keep in mind that 30 GHz tuning range. is equivalent to 1 cm–1.) Typical Maximum Power Integrated Dynamic Range The maximum output power you can expect over the laser’s The ratio of the signal to the source emission, integrated over tuning range. Due to changes in diode gain and cavity loss with all wavelengths. This is measured by observing the spectrum of wavelength, the laser’s output power is not constant as it tunes. two cascaded fiber-Bragg gratings with a total rejection ratio of >100 dB and a 0.8-nm window, and is a realistic expectation Wavelength Repeatability of the dynamic range of your measurement. (See “Why is the The largest measured deviation that may occur when the laser Noise Spectrum Important?” on page 12.) returns to a given set wavelength. This is a measure of how well the laser returns to a set wavelength over many attempts and Linewidth when approached from different directions. The laser’s short-term frequency stability. It is measured using a heterodyne beatnote that is recorded over a 50-ms interval. The Wavelength Resolution linewidth varies as a function of integration time. For a graph of The smallest step the laser can tune. the measured frequency stability versus integration time, please see the discussion on page 14. Wavelength Stability The maximum amount of drift the laser will exhibit over a Maximum Coarse-Tuning Speed specified period of time and temperature variation. The highest guaranteed speed at which the TLB-6300 laser can tune using the coarse-tuning DC motor. The actual maximum coarse-tuning speed for individual systems may vary, but will always be at least this fast.

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TLB-6300 (Velocity™ Laser) and TLB-6000 (Vortex™ Laser) Performance Data Tuning Curves 14 These graphs show sample tuning curves 12 for some of our TLB-6300 lasers. The two 10 8 curves represent the maximum and minimum 6 power over a tuning resolution of about 4 2.3-MHz linewidth Power, mW Power, Averaging time 30 s 0.1 nm. This modulation is due to residual 2 Res. BW 2.0 MHz 0 reflectivity at the diode output facet. Since the 960 965 970 975 980 985 990 995

TLB-6300 diodes and laser cavities are simi- Wavelength, nm 5 dB/div lar to those used in the TLB-6000 lasers, Model 6320 you may also use these curves to approxi- 10 MHz/div mate the power output at any wavelength 14 for the narrow-tuning TLB-6000 lasers. 12 Laser Linewidth 10 This beatnote linewidth between two 8 6 external-cavity diode lasers was mea- 4 Power, mW Power, sured over a 30-s interval. The linewidth 14.0 2 12.0 0 was determined using a heterodyne tech- 10.0 1050 1055 1060 1065 1070 1075 1080 nique. The individual laser linewidth over 8.0 Wavelength, nm 6.0 a 50-ms interval was less than 300 kHz. 4.0 Model 6321 Power, mW Power, 2.0 0.0 631 633 635 637 639 10 z 104 H

Wavelength, nm k ,

8 e c echnical Note

n 3

a 10 Model 6304 6 i r a 4 V n 2 a

T 10 l Power, mW Power, l

2 A - t

o 1 0 o 10 R 4.5 1270 1280 1290 1300 1310 1320 1330 10–7 10–6 10–5 10–4 10–3 10–2 10–1 100 101 4.0 Wavelength, nm 3.5 Integration Time, s 3.0 Model 6324 2.5 2.0 Linewidth as a 1.5 Function of Integration Time Power, mW Power, 1.0 25 0.5 The Root-Allan variance, like heterodyne 0 20 666 668 670 672 674 676 678 680 15 linewidth, is a measure of the frequency Wavelength, nm 10 stability of an oscillator. It can be inter- Model 6308 Power, mW Power, 5 preted as the laser linewidth over a 0 given time interval and gives you a very 1520 1530 1540 1550 1560 1570 accurate description of long-term laser Wavelength, nm frequency variations.* The measured 12 Model 6328 Allan variance for two of our lasers 10 shows that the linewidth is narrowest 8 6 2.5 (~50 kHz) at short integration times 4 2.0 and increases with integration time. The Power, mW Power, 2 1.5 short-time fluctuations are mainly due 0 770 775 780 785 790 1.0 to electrical fluctuations. The long-time

Wavelength, nm mW Power, 0.5 fluctuations are mainly due to slow tem- Model 6312 0 perature changes, and the middle-time 1940 1945 1950 1955 1960 1965 1970 spikes are the result of acoustically Wavelength, nm excited mechanical resonances in the Model 6334 laser cavity. The curve fit is based on a

25 model that includes flicker and random- 2.5 20 walk frequency noise. The linewidth at 2.0 15 longer time intervals can be estimated 1.5 10 by extrapolating the line. 1.0 Power, mW Power, 5 Power, mW Power, 0.5 0 * F.L. Walls, and D.W. Allan, “Measurements 828 833838 843 848 853 0 1970 1975 1980 1985 1990 1995 2000 of Frequency Stability,” Proc. IEEE 74, No. 1 Wavelength, nm Wavelength, nm (1986) pp. 162–168. Model 6316 Model 6335

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TLB-6300 and TLB-6000 Lasers Fr

What is the output-beam polarization? than 5 MHz over a 5-second interval. the laser wavelength is by changing the The output beams are linearly polarized The 50-ms linewidth is 300 kHz or less. voltage to the PZT actuator on the tuning equently Asked Questions in a vertical plane, with a polarization ratio Stabilizing the frequency of the laser is element. The small-signal bandwidth of of 100:1 free space. easy with an error feedback signal to the the fine-frequency input is 2 kHz in the frequency-modulation input on the back TLB-6300 lasers and 3.5 kHz in the Does the laser mode hop? panel. Using this technique, wavelength TLB-6000 lasers. How can I tell if it does? drift can be dramatically reduced. How stable is the output amplitude? With the precise pivot-point location of Can I stabilize the frequency of Can I amplitude-stabilize the laser? the tuning element, our lasers do not mode the laser? hop over the specified tuning range. The amplitude stability of our TLB-6300 However, if the laser does mode hop, the The laser can easily be locked either to and TLB-6000 lasers over 10 seconds frequency change would be 3 GHz—equal an atomic line or to an external cavity is better than 0.25% at any given wave- to the external-cavity free-spectral range. using wavelength-modulation techniques length. To prevent optical feedback from (In contrast, for a poorly coated diode to produce a feedback signal. Dither the affecting the laser’s performance, we rec- laser, it can be as much as 100 GHz.) To laser frequency through the frequency- ommend using an optical isolator with our determine if the laser has mode hopped, modulation input. The error signal free-space lasers. For fiber-coupled lasers, you will need a wavelength meter. The generated can then be fed back to the the fiber pigtails have built-in isolators. laser through the drive current. meter will indicate a phase-error signal Are the laser heads interchangeable? and a discontinuous change in frequency What is the minimum observable fre- Yes. The same controller will work with of about 0.1 cm–1. quency shift over >5-second intervals? any laser head in its family. However, We individually test every laser we build The minimum frequency shift that is wavelength calibration for each laser head and ship them with printouts of their tun- observable over the frequency jitter of is guaranteed only when it is used with ing curves, so you’ll know exactly what the laser is 1 MHz. its original controller. Laser heads will not to expect from your laser. (Please contact work with controllers from other families. Can I eliminate coherence effects us if you would like to see sample tuning (When ordering additional laser heads for due to the narrow linewidth? curves in your wavelength range.) a TLB-6300 system, initial calibration of If you’re working with unterminated fibers, the head to the controller may be required.) How is the tuning achieved? you may be concerned about possible For the TLB-6300, we separate wavelength coherence effects due to the narrow How many laser heads can I operate tuning of our lasers into coarse and fine linewidth. For most measurements, a simple at one time? tuning. Coarse tuning is accomplished way to make the linewidth appear much Each controller can operate one laser by using a DC motor to turn a precision broader is to apply a signal to the piezo in head at a time. To operate two lasers screw. An angle sensor incorporated in order to frequency modulate the laser. simultaneously, you need two controllers. the laser cavity feeds back to the micro- Can I modulate the laser amplitude? What if I need to get a specific processor to scan to the desired wave- Will the wavelength be affected? wavelength or higher power? length. On the end of the coarse tuning screw is a piezoelectric actuator (PZT). You can modulate the laser current by We routinely build systems to order. This actuator provides independent fine applying analog voltages to the current- Contact us for more information. modulation input at a rate of up to 1 MHz control of the laser wavelength and can What’s the fiber used in the with a modulation amplitude of up to also be used to modulate the laser fre- TLB-6300 optional fiber pigtail? quency while it is being slowly scanned. 2-mA peak. You can also modulate the Included with this option are all the nec- For the narrow tuning of the TLB-6000 laser’s amplitude with a bandwidth of essary coupling optics and a fiber isolator lasers no DC motor is required, so we 100 MHz and an amplitude of up to which provides at least 30-dB isolation use the PZT to control the wavelength. 10-mA peak through the SMA connector on the laser head. Small changes in over the laser’s entire tuning range. This How precisely can I set the index of refraction of the laser-gain package bolts to the front of the laser the wavelength? medium as a function of laser current lead head and alignment screws are provided For the TLB-6300, the coarse-tuning to changes in the laser wavelength when to peak up the output power. The fiber is mechanism allows you to set the wave- the current is modulated. The wavelength- a polarization maintaining (PM) PANDA length with a resolution of 0.02 nm. The modulation coefficient depends strongly fiber. All pigtails have FC/APC connectors fine-frequency resolution is 10 MHz (about on each laser diode’s characteristics, but standard. The coupling loss from the laser 2×10–5 nm) with a range several times is typically 50 MHz/mA and at most to the fiber pigtail is >3 dB. The PM fiber larger than the coarse-tuning resolution. 1 GHz/mA. is aligned with the polarized axis to within For the TLB-6000, the tuning resolution is two degrees of the output polarization What is the wavelength-modulation wavelength dependent, but is always finer of the laser. This results in an 18-dB to bandwidth? than 1/100 of the tuning range. 20-dB polarization ratio (approximately While you can modulate the wavelength 100:1). For this option, add “-P” to the What’s the frequency stability? by scanning the drive motor (TLB-6300 model number. The frequency drift of the laser is less only) or by changing the laser-drive current, than 0.02 nm over an entire day, and less the most straightforward way to modulate

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TLB-7000-XP, TLB-7000, TLB-6300, and TLB-6000

These pages highlight a few of the wide Mode-Hop-Free Tuning and FM Locking and variety of applications that have used our Narrow Linewidths for Swept- Nonlinear Generation tunable lasers. If you are interested in Frequency Measurements Researchers have used one of our lasers learning more about these applications, Interferometry is widely used to make pre- locked to the atomic lines of rubidium and we will happily fax you the references. cision length and displacement measure- potassium to create frequency standards We’re always interested in hearing how ments ranging from less than a nanometer at 1550 nm. In their setup, the output of you are using (or plan to use) our lasers, to tens of meters. Researchers used our the external-cavity diode laser at 1550 nm so please contact us if you have an 630-nm TLB-6300 laser to perform these was frequency doubled in a periodically types of precision measurements. The graph application you’d like to share. poled LiNbO3 waveguide, then injected below shows a wavelength scan of a into a cell containing either rubidium short-path-length interferometer (a couple or potassium gas. By dithering the laser of centimeters). The interferometer fringes frequency, wavelength-modulation are smooth and evenly spaced, demon- spectroscopic techniques were used to strating that the laser is operating single create an error signal that was then fed mode and mode-hop free over the entire back to the laser to stabilize the laser’s tuning range. The phase-continuous output frequency. Such techniques are (mode-hop-free) tuning over a wide tuning important in developing frequency standards range allows high-resolution measure- for dense wavelength-division-multiplexed 1 ments over large distances. (DWDM) optical-communication and fiber- optic sensing systems. 16 14 12 10 8 1 MHz 6

Power, V 4 Free Running 2 0 0 1000 2000 3000 4000 5000 Time, ms Locked Swept-wavelength measurement of an 0 25 50 75 100 unbalanced interferometer. The scanning Time, s range was 5 nm with a path-length differ- This graph compares the frequency noise of a ence of a few millimeters. New Focus™ laser without any feedback con- trol to the same laser when actively stabilized 2 1G.P. Barwood, P. Gill, and W.R.C. Rowley, Meas. to a sub-Doppler absorption line of rubidium. Sci. Technol. 4 (1993) pp. 988–994. “Laser diodes for length determination using swept- frequency interferometry.”

, a.u. 1.00

0.75

0.50 0.31 nm

0.25

0.00 1538 1539 1540 1541 1542 Second Harmonic Power Pump Wavelength, nm

This phase-matching curve was generated in

a periodically poled LiNbO3 waveguide dou- bler using a New Focus laser at 1540 nm.3

2V. Mahal, A. Arie, M.A. Arbore, and M.M. Fejer, Opt. Lett. 21 (1996) pp. 1217–1219. “Quasi-phase- matched frequency doubling in a waveguide of a 1560-nm diode laser and locking to the rubidium D2 absorption lines.”

3A. Bruner, A. Arie, M.A. Arbore, and M.M. Fejer, Appl. Opt. 37 (1998) pp. 1049–1052. “Frequency stabilization of a diode laser at 1540 nm by locking to sub-Doppler lines of potassium at 770 nm.”

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Absolute Frequency Measurements FM Spectroscopy with our TLB-6000 Model 6013 Tunable Diode Laser Absolute frequency measurements can Tunable Diode Laser be a challenge, but they can be aided The TLB-6000 laser is ideal for frequency- significantly by commercially available tun- modulation (FM) spectroscopy—a powerful able diode lasers. A team at JILA/NIST laser-spectroscopic technique that can has used nonlinear optics to compare achieve a high signal-to-noise ratio with the UV sum frequency generated from a relatively simple experiment. A typical Rb Vapor Cell Model 20X7 Nirvana™ the doubled Nd:YAG output plus 778-nm setup is shown at right. In the simplest FM Auto-Balanced Photoreceiver Ti:Sapphire light with the UV frequency spectroscopy experiment, a laser beam In the FM-spectroscopy setup above, a second obtained by doubling a stabilized, tunable is transmitted through a gas cell contain- 632-nm diode laser. Effectively this experi- laser beam that does not pass through the ing an atomic or molecular vapor. The vapor cell is used to eliminate laser-intensity ment measures the 532-nm frequency wavelength of this continuous-wave laser of an iodine reference transition in terms fluctuations. A dual-balanced photodetector, is modulated at a particular frequency such as the Model 20X7 Nirvana™ photore- of known standards at 633 nm and through direct frequency modulation. As 778 nm. The international team included ceiver (page 76), is used to make a differential the wavelength is scanned across the measurement. French, Russian, Japanese, Australian, and atomic transition, the frequency modula- Chinese scientists, in addition to University tion is converted into amplitude modulation of Colorado students and postdocs. through the optical absorption of the beam. Pictured are: Scott Diddams (JILA/NIST), In the case of the TLB-6000, this is easily Bruce Tiemann (CU), and Lei Hong achieved with the frequency-modulation (from NIST’s sister organization, NRLM, input that has a bandwidth of 3.5 kHz. A in Tsukuba, Japan). Doppler-free saturated absorption spectrum, taken using a TLB-6000 laser, is shown in the graph below.

NOTE: For more information, see page 282 for “Application Note 7: FM Spectroscopy with Tunable Diode Lasers.”

Absorption, a.u. 100 MHz

Frequency

This graph shows Doppler-free absorption lines of rubidium obtained with a TLB-6000 laser and a Nirvana auto-balanced photoreceiver.

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Phase-Shifting Interferometry for Determining Optical Surface Quality

Determining the surface quality of an the fringe centers. Second, measurements While most phase-shifting interferometers optic—the deviation from the intended can be taken at every element in the pho- use HeNe lasers as the source, using shape whether flat, spherical, etc—is critical todetector array directly yielding optical path- an external-cavity tunable diode laser such to optics manufacturing. Traditional methods length differences on a regularly spaced as the TLB-7000 provides significant consist of an interferometer, for example grid. The concept behind phase-shifting advantages. First, the laser wavelength can a Twyman- interferometer (pictured interferometry is to apply a time-varying be chosen to exactly match the operating below) that compares the test optic to a phase shift between the reference and test wavelength of the optics, of particular value reference. Differences in optical path wavefronts. This can be achieved, for exam- when the optics are coated and may not length between the two arms of the inter- ple, by mounting the reference optic on a be reflective at 633 nm. Second, the time- ferometer lead to bright and dark fringes in linear transducer, such as a piezoelectric varying phase shift can be achieved by the photodetector—typically a CCD array. transducer. If the relative phase-shift, α, is unbalancing the two arms and varying the Points lying on the same fringe center are linear in time, the intensity on every point laser wavelength, eliminating the need for at an equal optical path-length difference in the photodetector array, l, will change a linear actuator to translate the reference while points on adjacent centers represent sinusoidally with time optic. When using a tunable laser, the a difference of a half wavelength. Introducing phase shift is given by l(x, y, t)=B(x, y)+A(x, y) cos[φ(x, y)+α(t)] a small tilt between the reference and test α=2π OPD ∆λ/λ2, optic results in an interferogram where any where the bias level, B, and modulation deviation from an evenly spaced straight amplitude, A, are unknown and the optical where OPD is the optical path-length fringe implies an aberration from the test phase difference between the test and difference between the two arms of the optic, as shown below. reference optic, φ, is the quantity to be interferometer, λ is the laser’s center measured. φ is related to the height errors wavelength, and ∆λ is the time-varying While analyzing interferograms is an of the test optic, h, by wavelength change. Therefore using a extremely powerful technique, there are a tunable diode laser such as the TLB-7000 few disadvantages. Finding the location of φ=4πh/λ enables measurements, and increases the the fringe centers, which ultimately limits speed of the measurement. the accuracy of the technique, is a difficult where λ is the laser wavelength. Since there task, and any intensity variations across the are three unknowns, measurement of at interferogram or sensitivity variations in the least three interferograms at known phase photodetector introduce spurious errors. differences is needed to determine φ. For Another drawback is that data is obtained example, by taking data at α=0, π/2, π, and only along the fringe centers not on the 3π/2, one can compute the phase differ- regularly spaced grid that many analysis ence at every point by the simple formula routines demand. Lastly, since a few widely –1 φ(x, y)=tan [(I4(x, y)–I2(x, y))/(I1(x, y)–I3(x, y))], spaced fringes can be measured more accurately than many closely spaced ones, where I1…I4 are the intensities measured at there is a tradeoff between resolution and every photodetector element at times corre- the number of data points. sponding to the phase shifts α=0…3π/2. Since the calculation is performed at every Phase-shifting interferometry overcomes point, variations in intensity and photode- these limitations. First, phase-shifting tector sensitivity are not issues. interferometry does not rely on finding

Reference Optic

Beamsplitter

Beam Laser Expander Test Optic

Imaging Lens

Detector Array

Typical configuration of a Twyman-Green interferometer. Bright and dark fringes of an interferogram.

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