Laser Focus World

November 2015

Photonics Technologies & Solutions for Technical Professionals Worldwide www.laserfocusworld.com QCL arrays target IR spectral analysis PAGE 36

Positioning equipment— the foundational tools PAGE 27 Measuring aspheres with interferometry PAGE 41 Tunable laser diode combines QDs and SiP PAGE 45

® Optical coherence tomography angiography, NIR fluorescence- guided surgery PAGE 55

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1511lfw_1 1 11/2/15 11:52 AM Photonics Technologies & Solutions for Technical NOVEMBER 2015 ■ VOL. 51, NO. 11 Professionals Worldwide

newsbreaks world news

9 15 Orbital Angular Momentum Natural catenary Pancharatnam lens acts as structures create perfect OAM beams improved diffractive lens 16 Silicon Photonics Standard wire-bonding technique doubles waveguide Ge detector bandwidth X-ray pumped laser produces 1.4 Å narrow-linewidth hard x-ray emission Gold wire G G G 10 S S G Ultrafast lasers simplify fabrication G of 3D hydrogel tissue scaffolds Al Ge SiO2 Si 12 17 Multimode holographic waveguides Mid-infrared Lasers CMOS silicon-on-sapphire tackle in vivo biological imaging process produces broad mid-IR supercontinuum

20 Fiber-optic Components Fiber Y-splitter Silk gel handles seven-core optical fiber XYZ translation stage

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7 THE EDITOR’S DESK 80 BUSINESS FORUM 25 LETTERS 79 ADVERTISING/WEB Built on a solid foundation Effective communication INDEX W. Conard Holton is fundamental to 69 NEW PRODUCTS Associate Publisher/Chief Editor success in photonics 79 SALES OFFICES Milton Chang 78 BUSINESS RESOURCE CENTER

75 MANUFACTURERS’ PRODUCT SHOWCASE

LASERS ■ OPTICS ■ DETECTORS ■ IMAGING ■ FIBER OPTICS ■ INSTRUMENTATION

2 November 2015 www.laserfocusworld.com Laser Focus World

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27 Photonic Frontiers: Positioning and 45 Tunable Lasers Support Equipment Quantum dots and silicon Looking Back/Looking photonics combine in 36 COVER STORY Forward: Positioning broadband tunable laser A 200 cm-1 prototype equipment—the challenge A new wavelength-tunable laser diode quantum-cascade-laser of building a solid combines quantum-dot technology (QCL) array with 32 foundation for optics and silicon photonics with large QCLs is shown prior to beam combining and Stability and precision have been optical gains around the 1310 nm packaging. (Courtesy of crucial for optics since the 19th telecom window. Tomohiro Kita and Pendar Technologies) century. Jeff Hecht Naokatsu Yamamoto

36 Mid-IR Sensing 49 Optics Characterization Monolithic DFB QCL Shack-Hartmann wavefront array aims at handheld sensor enables flexible IR spectral analysis characterization of lenses Many QCLs combined on a single A Shack-Hartmann wavefront sensor chip demonstrate fully electronic can replace an interferometer or wavelength tuning for stand-off stylus profilometer for measuring IR spectroscopy of explosives lens properties in a lab or production and other materials. Mark F. Witinski, environment. Ralf Dorn and Johannes Pfund Romain Blanchard, Christian Pfluegl, Laurent Diehl, Biao Li, Benjamin Pancy, 52 Modeling Daryoosh Vakhshoori, and Federico Capasso Computer modeling boosts Coming laser device development 41 Photonics Products: Interferometers A full quantitative understanding of in December Numerous ways exist laser devices is boosted by computer to interferometrically modeling, which is not only essential Next month includes special measure aspheres for efficient development processes, articles to highlight what’s Aspheric optics can be measured but also for identifying the causes of hot in many important areas: using a Fizeau interferometer, or by unexpected behavior. Rüdiger Paschotta using an optical profiler containing an • A continuation of our interferometer. John Wallace Looking Back/Looking Forward series will investigate the many LASER FOCUS WORLD PRESENTS types of optical design software. • Senior editor John Wallace will examine the top 20 ® technology stories of 2015. 55 Editor’s Column 58 Optical Coherence Tomography/ • Articles on Optics profile up among neuroscientists Ophthalmology magnetorheological Barbara Gefvert OCT angiography: A new finishing (MRF) and Editor in Chief, BioOptics World approach with ‘gold standard’ high-power laser capabilities and more Chieh-Li Chen, calibration and Qingin Zhang, Anqi Zhang, and Ruikang K. Wang 56 BioOptics News & Breakthroughs characterization. In BioOptics World, we will Neuro15 exhibitors meet exacting 63 Fluorescence-guided Surgery demands: Part 1 have articles on optoacoustic Advanced surgery: NIR fluorescence guidance imaging and optical filtering arrives David J. Burrington for the life sciences.

Laser Focus World www.laserfocusworld.com November 2015 3

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1511lfw_4 4 11/2/15 11:52 AM laserfocusworld.online More Features, News & Products

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Focus on Positioning & Support Blog: Photon Focus Laser Focus World covers optical mounting, positioning, and Strategies Unlimited isolation equipment available for everything from simple senior analyst Allen Nogee optics to confocal microscopes and interferometers. Here gives his thoughts on a are three of our most recent articles on this topic. Kickstarter campaign for a laser-powered razor Kirigami thin-film in development. Keep photovoltaic cells coming back to our blog flex to track the sun for more hot topics, cool A team of researchers has commentary, and other come up with a way to events-related musings! tilt solar cells in a simple, http://bit.ly/14RIfUO compact way such that the whole apparatus can fit within a flat solar panel. Technical Digests dig into http://bit.ly/1LIB7ye technology topics Laser Focus World offers Get the most out of your microscope by free downloadable understanding your site environment technical digests that Measuring and analyzing environmental noise before the installation provide an in-depth of a precision microscope resource on photonics enables the end user to and optoelectronics save time, money, and topics, including free- resources by preparing form optics and military the installation location laser systems. appropriately for the http://bit.ly/ViD38v incoming instrument. http://bit.ly/201ovMm Webcasts let you make new Matter wave discoveries from your desktop interferometry cools Whether you are looking to learn about laser atoms and should damage to optics or finite element modeling cool molecules of laser material processing, we’ve got Researchers demonstrated webcasts aplenty to meet your educational needs. for the first time a new laser http://bit.ly/Onhs9J cooling method—based upon the interference of matter waves—that could White papers offer detailed tech be used to cool molecules. http://bit.ly/1RqXv2x specs on many products Our library of technical white papers delves into performance attributes of several optics and photonics products available on the market, including LED lens component CORRECTION The cover photo in the October 2015 issue should have been credited to Optimax Systems and not Thin Film Center. Laser Focus World regrets the error. optimization software and nanostructured substrates for optical diagnostics. http://bit.ly/1BUCpTf www.laserfocusworld.com

Laser Focus World www.laserfocusworld.com November 2015 5

1511lfw_5 5 11/2/15 11:52 AM 1511lfw_6 6 11/2/15 11:52 AM editor’s desk Built on a solid foundation

Stability and precision are critical characteristics of photonics tools, and represent a recurrent theme of this issue. The characteristics are essential in interferometers, as noted by senior editor John Wallace in his Photonics Products feature exploring the different products and methods available for interferometrically measuring aspheres (see page 41). Contributing editor Jeff Hecht, continuing his 50th year cele- bration of Laser Focus World, furthers the theme by telling tales of how optical positioning equipment was developed to put interferometers, holography systems, and many other optical systems on a stable footing. As he recounts, we have come a long way from some initial lab setups that had tabletops rest- ing on the inner tubes of truck tires (see page 27). Greater stability and precision in biophotonics tools are also evident in our BioOptics World section this month, where researchers explain recent, significant advances in two fields: near-infrared fluorescence guidance for advanced surgery techniques (see page 63) and optical coherence tomography angiography (OCTA), which, aided by data processing, promises to be useful in clinical monitoring and therapeutic treatment of the retina (see page 58). Products have always been the most reliably popular topic in our website and magazine, and of course in our Buyers Guide. They are the tools that scientists and engineers actually use or specify in their work. To illustrate, the Photonics Products article on interferometers that I described earlier is part of John Wallace’s widely read, bi-monthly series on products, and I’m happy to say that the series becomes monthly in 2016, with senior editor Gail Overton also contributing with product survey articles on topics such as specialty fibers, spectrometers, high-speed cameras, and nanopositioners. I am confident that these articles will contribute to the continued stability and precision found in W. Conard Holton Laser Focus World over the past 50 years. Associate Publisher/ Editor in Chief [email protected]

Alan Bergstein Group Publisher, (603) 891-9447; [email protected] EDITORIAL ADVISORY BOARD W. Conard Holton Editor in Chief, (603) 891-9161; [email protected] Stephen G. Anderson, SPIE; Gail Overton Senior Editor, (603) 305-4756; [email protected] www.pennwell.com Dan Botez, University of Wisconsin- John Wallace Senior Editor, (603) 891-9228; [email protected] Madison; Walter Burgess, Power EDITORIAL OFFICES Lee Dubay Associate Editor, (603) 891-9116; [email protected] Technology; Connie Chang-Hasnain, Laser Focus World UC Berkeley Center for Opto-electronic CONTRIBUTING EDITORS PennWell Corporation Nanostructured Semiconductor 98 Spit Brook Road, LL-1, Nashua, NH 03062-5737 Technologies; Pat Edsell, Avanex; David A. Belforte Editor in Chief, Industrial Laser Solutions, (603) 891-0123; fax (603) 891-0574 Jason Eichenholz, Open Photonics; (508) 347-9324; [email protected] www.laserfocusworld.com Thomas Giallorenzi, Naval Research Barbara Gefvert Editor in Chief, BioOptics World, Laboratory; Ron Gibbs, Ron Gibbs (603) 891-9194; [email protected] CORPORATE OFFICERS Associates; Anthony M. Johnson, Jeff Hecht Photonic Frontiers, (617) 965-3834; [email protected] Center for Advanced Studies in Robert F. Biolchini Chairman Photonics Research, University of Meg Fuschetti Editorial Creative Director Frank T. Lauinger Vice Chairman Maryland Baltimore County; Sheila Ward Production Manager Mark C. Wilmoth President and Chief Kenneth Kaufmann, Hamamatsu Chris Hipp Senior Illustrator Executive Officer Corp.; Larry Marshall, Southern Cross Venture Partners; Jan Melles, Gillian Hinkle Marketing Manager Jayne A. Gilsinger Executive Vice President, Photonics Investments; Debbie Bouley Audience Development Manager Corporate Development and Strategy Masahiro Joe Nagasawa, TEM Co. Ltd.; Alison Boyer Ad Services Manager Brian Conway Senior Vice President, Finance David Richardson, University of and Chief Financial Officer Southampton; Ralph A. Rotolante, SUBSCRIPTION INQUIRIES Vicon Infrared; Samuel Sadoulet, TECHNOLOGY GROUP T (847) 763-9540; fax (847) 763-9607; e-mail: [email protected] Edmund Optics; oby Strite, Christine A. Shaw Senior Vice President / IPG Photonics. web: www.lfw-subscribe.com Group Publishing Director

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1511lfw_8 8 11/2/15 11:53 AM newsbreaks

Pancharatnam lens acts as improved diffractive lens In a “Pancharatnam” phase-modifying optical (2.26 µm) f/2.1 Pancharatnam lens using a tive lenses, it does have a strong wavelength device, the polarization state of a circularly polarization holography alignment technique. dependence. The researchers fabricated an polarized wavefront passing through the device The technique, which is low-cost, could be ap- experimental device for a 632 nm wavelength is modified by the device as a continuous func- plicable to a wide size range. using a photoalignment layer that shows a tion of the position across the device. strong orientational response to the lo- For example, a Pancharatnam lens is Optical path difference (µm) cal polarization axis of light, and is ex- basically a half-wave retarder, with 0 posed in a holographic setup to provide the retarder’s local optical axis aligned -50 the desired half-wave retarder orien- with the azimuthal angle at that point. tation. The result is a polarization axis -100 Such a lens—when designed as a that is a function of the radial distance positive lens for, say, right-handed, cir- -150 from the center of the pattern with a Aspherical lens cularly polarized light—focuses light -200 gradually decreased grating pitch to the as a positive lens should, but becomes Pancharatnam lens edge. The design of the fabricated de- Polynomial fit a negative lens when left-handed -250 vice had a parabolic phase profile and circularly polarized light is passed -300 showed the expected imaging proper- through the lens. Pancharatnam lenses -350 ties, which were good imaging quality for have previously been fabricated by 0.0 0.5 1.0 1.5 2.0 2.5 low f numbers and some degradation for Radius (mm) microrubbing, creating a space-variant higher f numbers. A design modeling the subwavelength dielectric grating, or via holo- Unlike a conventional diffractive lens, a Pan- optimal diffraction-limited asphere would avoid graphic alignment. Now, a group at Kent State charatnam lens does not diffract light into un- the image degradation. Reference: K. Gao et al., University (Kent, OH) has made an ultrathin desired orders. However, like ordinary diffrac- Opt. Express, 23, 20, 26086 (Oct. 5, 2015).

X-ray pumped laser produces Two-color XFEL 8 keV & 9 keV XFEL pulse 2-stage focusing system 1.4 Å narrow-linewidth from SACLA for x-ray laser Kα laser hard x-ray emission 1st mirrors Spectrometer SASE XFEL 2nd mirrors Cu foil In 2011, Japanese researchers achieved coherent x-ray free- ASE Kα laser electron laser emission of 1.2 Å from the SPring-8 Angstrom Compact Free Electron Laser (SACLA; Hyogo, Japan), which Seeded Kα laser Photon energy today routinely produces < 1 Å hard x-ray pulses (photon en- ΔE = 40 eV ergy on the order of 10 keV) with 1020 W/cm2 maximum fo- Photon energy ΔE = 5 eV cus intensity. Now, in an effort to further the study of the movement of Photon energy ΔE = 1.7 eV electrons within materials and, hence, gain crucial light-matter interaction information that governs nearly all physical pro- eV—smaller than the natural width defined by the lifetime of cesses, researchers at the University of Electro-Communica- the atomic transition because of the uncertainty principle. The tions and the University of Tokyo (both in Tokyo, Japan), RIKEN narrower linewidth denotes the effective decay time of 1 s in and JASRI (Hyogo, Japan), and Osaka and Kyoto University artificially suppressed vacancy ions. In this SACLA-seeded laser, have developed a 1.4 Å (0.14 nm) hard x-ray laser from a cop- strong induced emission occurs and the branching ratio of the per target with an inner-shell electron excitation scheme. By us- relaxation process of the K-shell vacancy (Kα1, Kα2, and Auger ing a two-color pulse from the SACLA system, they successful- process) is changed from its nominally constant values. This al- ly seeded the hard x-ray laser to maximize temporal coherence lows pure Kα1 or Kα2 laser emission with high efficiency. Refer- at almost ideal limits. The narrowest bandwidth obtained is 1.7 ence: H. Yoneda et al., Nature, 524, 446–449 (Aug. 27, 2015).

Laser Focus World www.laserfocusworld.com November 2015 9

1511lfw_9 9 11/2/15 11:53 AM newsbreaks

Ultrafast lasers simplify fabrication of 3D hydrogel tissue scaffolds Femtosecond lasers are improving fabrication of tissue scaffolds and implants without Silk gel needing nonbiocompatible photoinitiators

or chemical cross-linking materials typically XYZ translation used in 3D printing. Direct micropatterning stage leveraging multiphoton absorption (MPA) of ultrafast laser light has been demonstrat- Polarizer ed by Tufts University (Medford, MA) re- 10× searchers within an elastomeric silk fibro- objective in hydrogel formula that is transparent to Shutter visible light, allows initiation of MPA at low powers (a few nanojoules) without self-fo- Half-wave cusing, is biocompatible and biodegrad- plate able, and allows laser light to create 10- to 400-µm-diameter voids (with a 5 µm later- of an 810 nm, 80 MHz repetition-rate, 100 µm in length were easily fabricated (in vol- al resolution) over a large 3D volume in the fs pulse-width femtosecond laser was in- umes up to 100 cm3) by scanning the hydrogel through penetration depths up to put to a microscope objective and focused stage at speeds between 50 and 100 µm/s. 1 cm—1.5 orders of magnitude deeper than into the silk hydrogel fixed to a three-ax- Typical fabrication time for the helix or ves- other biocompatible materials. is translation stage. Test patterns such as sel structure is around 1 hr., depending on To fabricate complex features or voids a 200-µm-diameter, two-turn helix and a the shape/size of object. Reference: M. B. within the hydrogel that function as tissue blood-vessel-like branching structure be- Applegate et al., Proc. Nat. Acad. Sci., 112, scaffolds for cell growth, the < 2 nJ output ginning 300 µm deep and extending 100 39, 12052–12057 (Sept. 29, 2015).

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Multimode holographic waveguides tackle in vivo biological imaging

The ability to image biological struc- microscopy, and endoscopy. Challenged Alliance (Glasgow, Scotland), has built on tures and tissues deep within the human by the tradeoff of imaging resolution vs. earlier work to improve understanding body is met with varying levels of suc- depth, a researcher at the University of of holographic light transport process- cess through such methods as optical co- Dundee (Dundee, Scotland), with sup- es through optical fibers, enabling in vivo herence tomography (OCT), multiphoton port from the Scottish Universities Physics imaging through flexible multimode fibers—a feat not previously possible.

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ORBITAL ANGULAR MOMENTUM Natural catenary structures create perfect OAM beams

The natural curve formed by a free-hanging chain, known in on metallic surfaces using varying patterns of catenary struc- architectural circles as a catenary structure, had no known appli- tures. The structures consisted of repeating scales or petals of cations in photonics until researchers at the Chinese Academy volumes bordered by two catenary curves, with a length Λ and of Sciences (Chengdu, China), Swinburne University of Technol- a separation at the midsection (or shift) called Δ (see figure). ogy (Hawthorn, Victoria, Australia), and the National Univer- Phase and polarization equations define how the catenary sity of Singapore created planar catenary arrays capable of gen- parameters produce light with a particular OAM value. erating optical beams with various degrees of orbital angular To evaluate broadband performance of the resulting OAM momentum (OAM).1 beams, three lasers with wavelengths of 532, 632.8, and 780 Unlike OAM beams formed by spiral phase plates, computer- nm were adopted to illuminate the catenary structures and the generated holograms, optical nanoantenna arrays, ring resona- resultant beams were analyzed. An analysis of the efficiency of tors, and even chiral forms, catenary OAM beams have broader conversion—defined as the ratio of the OAM-carrying beam to bandwidth and can be created from nanometers-thick structures. the overall transmitted power—for the ascending wavelengths revealed conversion efficiency values of 23.2, 39.8, and 54.4%, Broadband OAM which is at least a 30-fold enhancement compared to circular Orbital angular momentum has emerged as a useful attribute nanoslit structures. for applications in optical communications, quantum informa- Subsequently, the catenary structures were used to realize tion processing, and so many other emerging applications that it more complex functionalities involving OAM. Except for the now has a dedicated annual conference venue. phase control being in the azimuthal direction, the researchers With a goal to generate light with a geometrical phase and added additional phase variations along the radial direction. In spatially continuous and spectrally achromatic distribution, such a way, the OAM beam could be either focused into a small the researchers fabricated two-dimensional (2D) structures doughnut or converted to a high-order Bessel beam, which is famous for its nondiffractive property. y I I I I I I a) c) I = -3 x y total x y total It is also possible to construct catenary x λ = 532 nm Λ z = 27 µm structures using dielectric rather than metallic 6π Circular polarization 3π λ = 632.8 nm 0 z = 25 µm materials as a way to enhance energy effi- λ = 780 nm ciency, albeit with a sacrifice in achievable z = 20 µm Δ ξ(x) d) I = -6 2 µm y x λ = 532 nm bandwidth. z = 25 µm “The generation of OAM is just one of the many b) 6π 12π λ = 632.8 nm 3 µm 0π z = 22 µm applications of optical catenaries,” says Xiangang λ = 780 nm z = 18 µm Luo, director of the State Key Laboratory of Optical e) I = 12 λ = 532 nm Technologies on Nano-Fabrication and Micro-Engi- z = 8 µm neering at the Chinese Academy of Sciences. “In 0 λ = 632.8 nm 12π z 24π = 9 µm fact, we have recently extended the concept of λ = 780 nm z = 10 µm catenary optics to other applications, such as polarization-controlled surface plasmon manipulation Two catenary curves enclose a volume (a) with length Λ and mid-axis separation of and invisibility cloaking.”—Gail Overton Δ. The structures are arranged in a repeating scallop pattern (b) and in a series of concentric or spiraling circles that define a particular phase distribution. Different REFERENCE patterns (c-e) with different topological charges define different types of OAM or 1. M. Pu et al., Sci. Adv., 1, 9, e1500396 (Oct. 2, 2015). circularly polarized beam profiles. (Image credit: Chinese Academy of Sciences)

Laser Focus World www.laserfocusworld.com November 2015 15

1511lfw_15 15 11/2/15 11:53 AM world news

SILICON PHOTONICS Standard wire-bonding technique doubles waveguide Ge detector bandwidth

Some forms of active silicon photonic operation because the introduced induc- circuits benefit from the use of germa- tance counteracts part of the influence of nium (Ge) as a photodetector material, the capacitance. creating a hybrid system. These Ge wave- Avoiding the creation of any compli- guide-coupled photodetectors can take cated on-chip inductors, the research the form of either vertical or lateral p-i-n group simply wire-bonds gold wires to junction structures. While lateral struc- the Ge detector, creating an “off-chip” tures have reached a 3 dB bandwidth inductor (although the wires actually of 120 GHz, the easier-to-make vertical reside at the Ge detector itself). To do this, structures have had difficulty exceeding a they change the detector’s single conven- 3 dB 30 GHz bandwidth using many but tional integral electrode to three separate very complicated techniques. parts (see figure), leaving the actual pho- Now, researchers from the Huazhong todetection section unchanged. Then, University of Science and Technology they introduce two gold wires to connect (Wuhan, China) and Huawei Technol- the two discrete ground electrodes—the ogies (Shenzhen, China) have come up section of wire forms the inductor, with with a straightforward way of boosting its inductance value depending on the the speed of conventional vertical p-i-n size and length of the wire.

Gold wire G G G S S G G

Al Ge

SiO2 Si A conventional vertical p-i-n junction Ge detector, with its single integrated electrode, is seen at left. A modified Ge detector with three separate electrodes is shown at right—these electrodes can be connected with gold wires via the standard wire-bonding process to form a single electrode that has increased inductance, raising the bandwidth of the detector.

junction Ge detectors from 30 to 60 For example, a detector can be made GHz.1 The technique involves using using a gold wire about 450 µm long and standard wire-bonding technology to with a 25 µm diameter, which provides introduce gold wires into the detector’s an inductance and resistance of 1 nH/ discrete ground electrodes. mm and 2 Ω/mm, respectively, over a The so-called RC parasitic parame- wide frequency range. For this device, ter (R and C refer to the photodetector calculations show the doubling of the equivalent circuit’s resistance and capaci- detector’s bandwidth from 30 to 60 GHz. tance components, respectively) places a limit on how fast a detector can operate. Experiment verifies concept However, introducing an inductor (L) into An experimental Ge photodetector was the detector’s RC circuit to create a so- fabricated on a silicon wafer using a 0.18 called RLC circuit can help high-speed µm CMOS process at the Institute of

16 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_16 16 11/2/15 11:53 AM MID-INFRARED LASERS Microelectronics in Singapore. First, a single-mode channel waveguide with a 500 nm width was fabricated in the silicon, along with a grating coupler etched to a depth of 70 nm for vertically coupling light into the detector. CMOS silicon-on- Next, doped layers of Ge totaling about 700 nm were deposited and then sapphire process etched, and metals were deposited to form the electrodes. Post-fabrication bonding of two pieces of gold wire totaling about 450 µm in length com- produces broad mid- pleted the device. Bonding of the wires slightly decreased the detector’s responsivity from 1 IR supercontinuum to 0.85 A/W at 1550 nm under a –3 V bias voltage, attributed to the resistance of the wires. At a bias voltage of –0.5 V, the bonded wires actually Beyond its well-known photonic capabilities in slightly reduced the dark current from 64 to 61 nA. the telecommunications wavelength band around The detector’s frequency response was measured by coupling light at a 1.5 µm and its functionality in silicon-on-insulator 1550 nm wavelength to the device through a cleaved fiber at a power of (SOI) form up to 2.5 µm, silicon has now entered about 5 dBm. While some jitter was seen in the measurements at higher fre- a new frontier: silicon-on-sapphire (SOS) nanow- quencies because of bandwidth limitations in the electrical cable and connec- ires have been used to demonstrate octave-span- tions used in the measurement, a 3 dB response out past 60 GHz was seen. ning mid-infrared (mid-IR) supercontinuum gen- The researchers note that because wire-bonding technology is a standard eration from 1.9 to just beyond 6 µm.1 part of a Ge waveguide detector’s construction anyway, their method This broadband supercontinuum source is adds no extra fabrication process. In addition, the bonded wire can easily realized using a complementary metal-oxide semi- be removed and a new wire of same or different length and diameter conductor (CMOS) process and is the collaborative rebonded.—John Wallace effort of researchers from the Center for Ultrahigh Bandwidth Devices for Optical Systems (CUDOS) REFERENCE at the University of Sydney, Macquarie Univer- 1. G. Chen et al., Opt. Express (2015); doi:10.1364/OE.23.025700. sity, and Silanna Semiconductor (all in Sydney, IF WE DON’T HAVE IT, WE’LL MAKE IT FOR YOU. THIN FILM COATINGS FOR ANY CATALOG, CUSTOM, OR OEM NEED.

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1511lfw_17 17 11/2/15 11:53 AM world news

Power (10 dB/div) Compact, inexpen- avoid higher multiphoton absorption that sive mid-IR sources are normally occurs in silicon beyond 2.5 µm, 2.5 kW becoming more and the researchers engineered SOS nanowires 1.82 kW more important, espe- that minimized dispersion and optical loss 1.06 kW cially for applications at the pump wavelength via a 2.4 × 0.48 520 W in molecular sensing μm nanowire. By treating the nanowire at part-per-billion and with chemical oxidation and oxide strip- 200 W Pump even part-per-trillion ping to reduce surface roughness, and levels. Although super- by using a relatively wide nanowire to 2500 3750 5000 6250 Wavelength (nm) continuum genera- improve mode confinement, propagation tion using chalcogenide losses are minimized to a level of 1.0 ± 0.3 The power output spectra from a silicon-on-sapphire (SOS)- glass fibers has been dB/cm at 4 µm. based supercontinuum source are shown for input power levels demonstrated out to 13 For supercontinuum generation, the ranging from 200 W to 2.5 kW. (Image credit: CUDOS) µm, the CMOS-com- 3.7 µm, 320 fs pulse-width, 20 MHz rep- NSW, Australia), the CUDOS Laser Physics patible SOS platform offers scalability etition rate output from a tunable optical Center at Australian National University and promises new nonlinear integrated parametric amplifier (OPA) was input (Canberra, ACT, Australia), the Institut (and cost-effective) silicon devices such to the TE mode of the nanowire, colli- des Nanotechnologies de Lyon, CNRS as this mid-IR supercontinuum source mated and sent to a monochromator, and (Lyon, France), and RMIT University (Mel- that operates well beyond the legacy detected with two detectors: lead selenide bourne, Victoria, Australia). The team of silicon window. (PbSe) from 1.5 to 4.8 µm and mercury researchers says that this mid-IR supercon- cadmium telluride (MCT) from 4 to 6.5 tinuum source represents “both the widest Supercontinuum SOS μm. For coupled input peak powers from spectrum and longest wavelength gener- The first SOS waveguides fabricated in 200 W to 2.5 kW, the widest continu- ated to date in any silicon platform.” 2010 had 4.3 dB/cm losses at 4.5 µm.2 To ous output spectrum spans 1.53 octaves from 1.9 to 5.5 µm at the -30 dB signal level for a 1.82 kW input. Even well above the noise floor at -45 dB, light is generated beyond 6 µm (see figure). To achieve a flatter dispersion profile over a wider bandwidth, SOS-based pillar waveguides could be constructed. Further- more, improvements to epitaxial growth of the SOS nanowires are expected to minimize near-IR losses by reducing lattice mismatch at the silicon/sapphire interface. The researchers say that these improvements will make it possible to demonstrate supercontinuum generation over the full transparency spectrum of silicon using a single nanowire. “The silicon-on-sapphire platform paves the way for integration of electronics and photonics on a single device,” says Neetesh Singh of CUDOS, University of Sydney. “This would lead to electrically tunable, on-chip, linear, and nonlinear ultrawide optical operation from near-IR to mid-IR range.”—Gail Overton

REFERENCES 1. N. Singh et al., Optica, 2, 9, 797–802 (Sep- tember 4, 2015). 2. T. Baehr-Jones et al., Opt. Express, 18, 12, 12127–12135 (2010).

18 November 2015 www.laserfocusworld.com Laser Focus World

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1511lfw_19 19 11/2/15 11:53 AM world news

FIBER-OPTIC COMPONENTS Fiber Y-splitter handles seven-core optical fiber

In the past few years, data-transmis- the use of multicore single-mode fiber, The last approach, which often sion rates for experimental fiber-optic which allowed transmission of 255 takes the form of a seven-core trian- systems has reached deep into the tera- Tbit/s over a 1 km fiber length. gular array, is a relatively straightfor- bit-per-second range. Some ward fiber design that can greatly boost configurations that have data rate (as long as crosstalk between Output helped to achieve such rates MCF-1 Output cores is minimized). One thing that is are a combination of orbital MCF-2 not straightforward about using seven- angular momentum (OAM) core fiber, though, is the design of the y-splitter and wavelength-division components that couple light into and multiplexing (WDM), which out of the fibers, as well as manage reached 100 Tbit/s over a z the light during transmission. To help in short length of fiber; hybrid x this respect, Ehab Awad of King Saud integration with differ- y University (Riyadh, Saudi Arabia) has ential-quadrature phase- designed a 2.4-mm-long Y-splitter for Input shift keying, reaching 14 MCF multicore fibers that requires no separa- Tbit/s over a single 160 km tion of the fiber’s multiple cores. Light from the seven cores of an input multicore fiber fiber; an optical fast-Fou- (MCF) is split individually by a Y-splitter based on seven rier-transform (FFT) scheme layers of gradient-index waveguide optics. Both the input Numerically simulated that enabled 26 Tbit/s over and output MCFs are simply cut and placed in contact The design, which so far has been a single 50 km fiber; and with the Y-splitter. numerically simulated for a seven-core

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1511lfw_20 20 11/2/15 11:53 AM The first Orbital Launch The ﬁrst successful orbital launch was of the Soviet unmanned Sputnik 1 on October 4, 1957. The satellite is believed to have orbited Earth at a height of about 250 km (160 mi).

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1511lfw_21 21 11/2/15 11:53 AM world news

fiber but not yet constructed, relies on The simulations indicated a number of differing Y-splitting waveguide layers—one for each core—with that the splitter would all layers having a novel double-hump work well over a graded-index (DHGI) profile that splits optical power equally into two halves broadband region from (see figure). The input and two output 1460 to 1675 nm with fibers are rotated about their axes with respect to the Y-splitter until all of the polarization-insensitive seven cores reside in different horizon- operation, showing tal planes with respect to the splitter. This allows a separate waveguide layer an insertion loss of to access each of the seven cores. around 0.12 dB over all Each single Y-splitter layer contains an expander, a DHGI space-division wavelengths, excess loss splitter (SDS), and a separator. The of 0.13 dB, polarization- seven individual Y-splitters are sur- rounded by a 400 × 125 µm cladding dependent loss of less region. The fiber in the numerical than 0.02 dB, and a model has seven identical step-index single-mode cores with a 40 µm sep- worst-case return loss of aration between adjacent cores, a 35.8 dB. cladding refractive index of 1.45, and a core refractive index of 1.4551. Each splitter has a waveguide height of 9 µm, is separated from the adjacent device and associated optical fibers at waveguide layer by 4 µm of cladding, 1555 nm and other wavelengths, as and splits the input light into two well as eigenmode expansion (EME) outputs separated by 250 µm (twice solutions using software from Lumeri- the diameter of the multicore fiber). cal Solutions (Vancouver, BC, Canada). The input and output fibers are rotated These simulations showed no signifi- by 19° about their axis to create a line- cant cross-coupling between waveguide of-sight view between cores of each layers or cores. single splitter. The simulations indicated that the The waveguide lens embedded in splitter would work well over a broad- each splitter layer is 280 × 60 × 9 µm in band region from 1460 to 1675 nm size and has a gentle parabolic refrac- with polarization-insensitive operation, tive-index profile that expands the showing an insertion loss of around 0.12 beam adiabatically to minimize the pro- dB over all wavelengths, excess loss of duction of higher-order modes. Light 0.13 dB, polarization-dependent loss from the lens enters the DHGI SDS of less than 0.02 dB, and a worst-case portion of the device, which has two return loss of 35.8 dB. The optimum parabolic graded-index humps, each 3 dB splitting ratio fluctuated by less with a size of 995 × 60 × 9 µm. The than 0.1 dB over the entire wavelength dimensions are sized to reliably split the range. A tolerance analysis showed that input beam 50%/50%. The two beams low-loss performance was achieved for are then sent to two separate wave- maximum misalignments of about 0.5 guides and then on to the two output to 1.0 µm (depending on the type of fibers. loss modeled).—John Wallace In the process of designing the Y-splitter, Awad ran finite-difference time- REFERENCE domain (FDTD) simulations of the elec- 1 E. Awad, Opt. Express (2015); doi:10.1364/ OE.23.025661. tromagnetic-field distribution in the

22 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_22 22 11/2/15 11:53 AM Neil Armstrong landed with Apollo 11 on July 20, 1969 and was the ﬁrst human to step onto the Moon.

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1511lfw_23 23 11/2/15 11:53 AM 1511lfw_24 24 11/2/15 11:53 AM LETTERS

I just read Jeff Hecht’s article in Laser Focus A few years after the initial release of the World titled “Spectrometers and Spec- VBG-based diode laser, IPS again revolution- troscopy: Looking Back/Looking Forward: ized the world of handheld Raman when Spectrometers and spectroscopy get faster, they came out with the first fully integrated, better, and cheaper,” and I thought the VBG-stabilized diode laser with a collimated article was very well written and covered output in a TO-56 package (see photo). This many of the key points in the evolution of even further reduced the size and power miniature spectrometers. I was also excited consumption, allowing for the smartphone- to see that he cited an article that I co- size Raman spectrometers that now fit in the authored in LFW back in May 2013. A VBG-stabilized laser diode integrated into a palm of your hand and run off AA batteries. I think you left out one of the major portable Raman spectrometer. (Courtesy of IPS has historically been really bad with milestones in the miniaturization of Raman Snowy Range Instruments – Laramie, WY) PR and over the years, our sales have pri- spectrometers—the commercialization of marily been OEM and private label; there- the volume Bragg grating (VBG)-based compact, low-cost, and low-power-con- fore, outside of the Raman spectroscopy external cavity diode laser by Innovative sumption excitation source that was wave- community, not too many people are aware Photonic Solutions (IPS) in 2003. I know length- and power-stabilized over a wide of IPS’s impact. I know it’s too late to get this statement may seem biased because ambient temperature range. This resulted any of this into the article, but I figured it I am currently employed by IPS, but I had in the IPS laser being used in most of the couldn’t hurt to fill the gap in the story. been a customer of IPS for six years prior first-generation “handheld” Raman spec- Again, overall I really liked the article and I to joining the company in fall 2013, so I trometers. Since then, the VBG-stabi- have already sent it to a few friends. can speak with both perspectives. The lized diode laser has become the industry Robert V. Chimenti is a product line manager at reason why this laser was so important is standard in Raman spectroscopy—in both Innovative Photonic Solutions, Monmouth Junction, it allowed systems integrators to have a handheld and laboratory systems. NJ; e-mail: [email protected].

1511lfw_25 25 11/2/15 11:53 AM A Gift That Keeps On Giving

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1511lfw_26 26 11/2/15 11:53 AM PHOTONIC FRONTIERS: POSITIONING AND SUPPORT EQUIPMENT

LOOKING BACK/LOOKING FORWARD: Positioning equipment—the challenge of building a solid foundation for optics

JEFF HECHT, Contributing Editor

Stability and precision the speed of light. The detect shifts as small as 1% of a fringe— have been crucial for optics measurement required but they failed to find the ether drift since the 19th century. exacting precision, so predicted by classical physics, and thus they assembled a multi- helped launch modern physics. The birth of holography pass Michelson interfer- and other precision ometer on a foot-thick Holography demands stability laser measurements brought a new slab of sandstone mea- Early laser experiments didn’t require generation of equipment, which is now suring 5 ft2 that floated such extreme stability, and typical- feeding the needs of nanotechnology. on liquid mercury in the ly were performed on laboratory ta- basement of a massive bles. Ordinary optical measurements Positioning and stabilizing optics may stone building to isolate it from ther- were made on optical benches, essen- seem a humble task, but it paid off in mal variations and vibrations from pass- tially long, straight rails holding opti- a big way for Albert A. Michelson in ing horse traffic (see Fig. 1). They could cal mounts to align a series of lenses. 1907, when he received the Nobel Prize in Physics “for his optical precision instruments and the spectroscopic and metrological investigations carried out with their aid.” His most famous experiment was an 1887 attempt with Edward Morley to measure how the Earth’s motion affected

FIGURE 1. The Michelson- Morley experiment was performed on this slab in the basement of a stone dormitory at Western Reserve University in Cleveland. (Courtesy of the Special Collections & Archives Department, Nimitz Library, U.S. Naval Academy)

Laser Focus World www.laserfocusworld.com November 2015 27

1511lfw_27 27 11/2/15 11:53 AM POSITIONING AND SUPPORT EQUIPMENT continued

The first issue of Laser Focus lab was on the first floor, so it in January 1, 1965 didn’t men- picked up vibrations when the tion tables, mounts, or other po- elevator went up and down, and sitioning equipment. But it did from passing traffic. The only include a lengthy report on the way to record good holograms then-new subject of three-di- was in the middle of the night, mensional (3D) laser hologra- when no one else was in the phy. We noted that recording building and the elevator slept. holograms with then-avail- After he graduated, able continuous-wave (CW) la- Matthews set out to develop sers required long exposures. better optical tables for hologra- During that time, we wrote, phy. He and Dennis Terry, a su- “the reflecting objects must FIGURE 2. Leith and Upatnieks’ iconic toy train hologram. It looked pervisor in the Caltech machine remain stationary to less than so good because the inside was filled with epoxy to stabilize it. shop, decided to form their own about 1/8 wavelength of the il- company while spending a day lumination of the exposure.” To achieve George. He and fellow grad student John at Newport Beach in 1969. The name that high stability, Emmett Leith and Juris Matthews worked on a homemade optical Newport Research was inspired by the Upatnieks had to fill the HO-gauge toy bench made by floating a massive steel plate beach and their interest in the scientif- train engine in their iconic hologram with on a pair of heavy-duty truck inner tubes. ic market. Matthews developed ways to epoxy and glue it to the tracks (see Fig. 2). I spent the summer after my junior year damp vibrations in the tables, and adapt- “Before holography, you never had to wor- working in that lab, and was quite im- ed a honeycomb structure used in aero- ry about the stability of the tabletop,” recalls pressed by the setup. But it didn’t pro- space for its rigidity and light weight. They Milton Chang, who earned a PhD for holo- vide the several minutes of absolute still- earned $46,000 in their first year working graphic research at Caltech under Nicholas ness needed for serious holography. The in a garage, and then moved into a shop

28 November 2015 www.laserfocusworld.com Laser Focus World

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in nearby Fountain Valley. Chang joined blocks into a box them in 1972 as marketing manager. filled with sand, Artists making holograms took a low- and attached op- end approach to vibration isolation. In tics to them with C 1970, Canadian artist Jerry Pethick and clamps. Soon, ho- laser physicist and holographer Lloyd lographic art was Cross stuck plastic pipes and concrete emerging from basement holographic sandboxes.

A foundation for lasers Optical positioning equipment had be- FIGURE 5. A 20-ft vertical optical table built to support a fiber draw come an important tower, outside Newport’s plant in Fountain Valley, CA. (Courtesy of business by the time Newport/Jim Fisher) of our January 1975 issue. Newport ran stood for Walt E. Disney. The optical ta- a full-page ad dense with information in bles were replacing an assembly of 4 × 4 small type, many photos, and two graphs boards floating on inner tubes in creat- of vibration isolation and damping. They ing special effects for movies like Tron. had plenty of competition. Information- rich ads from Aerotech (Pittsburgh, PA; Robotics and programmable see Fig. 3) and Burleigh Instruments (East positioners Rochester, NY) described “optical erec- The 1980s brought numerical control to tor sets” for holding components. Modern positioning equipment for optics and to Optics (El Monte, CA) advertised opti- industrial laser systems. “The first U.S. in- FIGURE 3. By January 1975, optical cal tables starting at $1000 and precision dustrial laser robot system was installed positioning equipment had become an mirror mounts for $49. And Scientech in 1984. By 1989, industry sources pre- important business, as this ad from Aerotech in the issue described an “optical erector set” (Boulder, CO) offered magnesium-alloy dict that several hundred laser robot sys- for holding components. optical benches for $100 per meter in tems could be in place performing spot lengths to 5 m. welding and cutting operations,” wrote Our main editorial coverage of position- David Belforte in our October 1984 issue. ing equipment was in the products section. Flipping through the rest of that issue One January 1975 entry described CVI showed the emerging trend. An ad from Laser mirror mounts with manual adjust- Oriel Corp. (Stratford, CT) mentioned ments offering 0.5 arcsec angular resolu- computer-compatible stepping motors and tion. But optical mounts sometimes played drives with active control to maintain con- supporting roles on the cover, as shown on stant speed for motorized microposition- our April 1975 cover (see Fig. 4). ers, and Newport advertised a motorized The optical table business was set on end drive with a keypad control. Our prod- by the fiber-optic boom of the late 1970s. ucts section described a positioning sys- “We built some vertical tables for Corning tem that Anorad (Hauppauge, NY) had in the 1970s to support drawing towers,” re- developed for automated laser drilling and calls Larry Mayhew, a senior manufactur- cutting of printed-circuit boards. ing engineer at Newport. The first vertical table stood 20 ft tall (see Fig. 5), and later Nanotechnology and Corning brought assemblies up to 54 ft tall. mountaintop optical tables Another new application emerged in the Our editorial coverage of positioning early 1980s. Mayhew visited a mysterious equipment expanded in the 1990s. A fea- southern California customer called WED ture in our January 1995 issue (see Fig. 6) FIGURE 4. Optical mounts have a Enterprises to make measurements for a listed options for table surfaces that still supporting role on our April 1975 cover. new optical table—and found the WED sound familiar. “Stainless steel is by far the

30 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_30 30 11/2/15 11:53 AM NEED FOR SEED Pure Power.

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FIGURE 6. Skin material options for table surfaces included stainless steel, aluminum, and granite, as reported in January 1995.

most common top-skin material because steel has a high stiffness-to-weight ratio and can be laminated, machined, drilled and tapped, then damped with reasonable effort,” wrote Jerry Hobbs. Aluminum skins are light and easy to machine, but are excelliSCAN — More Productivity more prone to deformation and contamination. Granite can be for Micro-Machining polished flatter, but it is more massive and amplifies a broader range of vibrations. The new premium scan system for industry’s most “Nano” had begun to emerge as a buzzword. Burleigh demanding applications Instruments (Fishers, NY) used the headline “Nanopositioning” ŭŮůŰűŲųŮSCANahead control eleminates tracking for an ad in our January 1995 issue (see Fig. 7) promoting its error and fully utilizes scanner dynamics “inchworm” piezoelectric positioners, able to move up to 200 mm ŭŮŴŵŵŰűŶŷŸűŲŮŹŰźŻŸŵżŮŽŲŻŸżŵŮžŸŷŹŮŲŵŹŶŵſŲŽŮ at speeds of 1 nm to 2 mm/s. A September 1999 feature by Scott thermal management Jordan of Polytec PI (Auburn, MA) told ŭŮdynAXISseŮŽŸżŸŷŶųƀŲŵſŰŽŲƁŮżŶųűŶŵŰƂŲŷŲƁŻŮƃŰƁ highest positioning accuracy how piezoelectric positioners could ŭŮƄƁŲſŸŻŸŰŵŮŶŵŽŮųŰŵżƀŷŲƁƂŮŻŷŶƅŸųŸŷƆŮŸŵŮƇƈƉƊŮŰƋŲƁŶŷŸŰŵ automate alignment ŭŮƌŲŻŷŮſŰŵŷŰźƁŮƃŸŽŲųŸŷƆŮŶŷŮŹŸżŹŮƂŶƁƍŸŵżŮŻƋŲŲŽŻ of single-mode op- ƎźŲŻŷŸŰŵŻŮŶŵŽŮŸŵŽŸűŸŽźŶųŮƁŲƏźŸƁŲƂŲŵŷŻƐŮƑźŻŷŮſŰŵŷŶſŷŮźŻƒ tical fiber for com- ŸŵƃŰƓŻſŶŵųŶƅƔŽŲ munication systems. The late 1990s also saw optical tables reaching new heights at the Keck Observatory on Mauna Kea, Hawaii. Newport supplied more than 50 tables for an optical delay line used for interferometry www.scanlab.de FIGURE 7. Burleigh Instruments’ “inchworm” with the twin 10 m piezoelectric positioners were able to move telescopes. Getting up to 200 mm at speeds of 1 nm to 2 mm/s. the tables up the

32 November 2015 www.laserfocusworld.com Laser Focus World

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mountain was a picnic compared to in- ON, Canada) described a six-axis stage stalling and testing them in the thin air with active alignment that could align a at 14,000 ft, recalls Warren Booth, a se- probe to a 2 µm waveguide with 10 nm nior manufacturing engineer at Newport. resolution within a second or two. That marked a dramatic advance over the 10 The age of nanopositioning minutes needed manually. An ad from A March 2004 feature (see Fig. 8) by Mad City Labs (Madison, WI) offered Steve Kidd of Melles Griot UK and two nanopositioning systems with subnano- colleagues from LNL Optenia (Ottawa, meter precision.

FIGURE 8. A six-axis stage with active alignment could align a probe to a 2 µm waveguide with 10 nm resolution within a second or two.

New cutting-edge research required new positioning techniques. Exacting precision was needed to prevent any relative motion between the ultrashort laser and the acceleration chamber in the Berkeley Laboratory Laser Accelerator (BELLA) at the Lawrence Berkeley Laboratory in California, which we described in June 2013. That required tuning vibration damping of the optical tables at the site rather than in the factory for the first time ever, says Booth of Newport. Vibration isolation is finding applications far beyond optics. The oddest Booth recalls was at a biotechnology company trying to produce genetically engineered rats. The rodents were so finicky that they wouldn’t breed if they could feel any vibration, and the company was near active train tracks. The baby rat population boomed after he installed an isolation table as a foundation for a rat housing proj- ect. (Booth called it a “rat brothel,” but somebody might find that offensive.)

Looking forward One emerging trend is the “smart table,” with a control system that actively identi- fies resonant frequencies and damps them with faster settling time than standard tables. “Some semiconductor companies are

Laser Focus World

1511lfw_34 34 11/2/15 11:53 AM POSITIONING AND SUPPORT EQUIPMENT continued

looking for that now, as a way to improve active systems will become more afford- instruments have become small enough throughput,” says James Fisher, vice pres- able as sensor costs drop and electron- to be installed on higher floors, where ident for optical components and vibra- ics become more powerful, and “people they are more vulnerable to low-frequen- tion control at Newport, which recently will need more active systems” as their cy building vibrations. One recent inqui- introduced one. Figure 9, from our March demands for extreme stability and pre- ry came from a person in the 20th floor 2015 issue, shows how that system im- cision increase. of a Hong Kong building who was hav- proved the quality of nanostructures fab- New technology offers other options. ing problems making measurements with ricated by Steven Koo at MIT in a fifth- The same March 2015 feature described an atomic force microscope. floor laboratory. totally passive negative-stiffness vibra- Valma says the passive negative-stiff- So far, the market for active systems has tion isolators developed by Minus K ness isolators can be made on a wide range been limited to the most sensitive equip- Technology (Inglewood, CA). Based on of scales. NASA’s Johnson Space Flight ment, including atomic force and scan- a combination of coiled springs and neg- Center is using six custom-made isola- ning-probe microscopes as well as semi- ative-stiffness flexures, they have a low tors with capacity of 10,000 pounds each conductor fabrication. But Fisher says natural frequency of 0.5 Hz, making them to test the James Webb Space Telescope more effective at such on the ground. On the other end of the a) b) low frequencies than scale, their smallest units can handle 25 air or active damping, pounds each. Their most interesting ap- says Steve Valma, op- plication so far has been to isolate the erations manager at high-end Döhmann Helix 1 audio turn- 2 µm 2 µm Minus K. They don’t table just introduced by Audio Union. require an air supply At $40,000, the turntable is designed FIGURE 9. Without active damping, nanostructures fabricated or power. They are for serious audiophiles who are very af- at MIT were irregular (a). Turning on the active damping system finding growing ap- fluent—a far cry from a stable table to produced the more regular patterns (b). plications as sensitive coddle fussy rats. Small is the new BIG ſŵƔŰŻŽűŮƝŻűŲŻżŮƀŻžƞűŲŻżƌŮƄŻŽŮƂŸƌŵŽŮƝŲƁŽŻųŸƁŹŲżŲżƇŮƟżŸƙžŵƠ ŭŮ ůŰűŲųŲŴŵŶŮŷŸűŹŮźŻżűŽŻž ŭŮ ƆŲƇŹűŮƈŻƁŸžŮŷžŸżŸŽŲűƅ ŭŮ ſŸżŻųŵűŵŽŮƀƁŸžŵŮƂŲżŵŮ ŭŮ ƆŽŸƉŵƁűŻŽƅƊƋŸƌŵŶŮƂŸƌŵŽŮ Ů ƃżŲƄŻŽųŲűƅ Ů ƆŽŲƇƇŵŽŲżƇŮŮ

ƀƁŽŲƙŲżƇ ƂŲűŹŻƇŽŸŰŹƅ ƚŶŶŲűŲƛŵ ƜŽŲžžŲżƇ ƚƙžŸűŲŻż Newport Motion Solutions now include Smarter Motion Controllers. For more information call ƍƎƏƏƐŮƑƑƑƊƒƓƓƏ or visit ƔƔƔƕżŵƔŰŻŽűƕƁŻųƖųŲƁŽŻųŸƁŹŲżŲżƇƊƗƘ

1511lfw_35 35 11/2/15 11:53 AM MID-IR SENSING

Monolithic DFB QCL array aims at handheld IR spectral analysis

MARK F. WITINSKI, ROMAIN BLANCHARD, CHRISTIAN PFLUEGL, LAURENT DIEHL, BIAO LI, BENJAMIN PANCY, DARYOOSH VAKHSHOORI, and FEDERICO CAPASSO

Many QCLs combined on a single chip beyond advances in IR structure of QCL arrays and (2) their demonstrate fully electronic wavelength hardware, requiring the fully electronic wavelength tuning— tuning for stand-off IR spectroscopy of proper combination of that is, no moving gratings, allow- several areas of exper- ing for much-higher-speed acquisition explosives and other materials. tise: cutting-edge optical through improved amplitude and wave- Advances in infrared (IR) laser sourc- design and laser fabrication, integrat- length stability. When integrated into a es, optics, and detectors promise ma- ed laser electronics, thermally efficient system, the result is robust, stable, and jor new advances in areas of chemical hermetic packaging, statistical signal field-deployable. analysis such as trace-gas monitoring, processing methods, and deep chemi- One of the key advances that has en- IR microscopy, industrial safety, and se- cal knowledge. abled this technology to be fielded is the curity. One key type of photonic device At the core of the approach we have high-yield fabrication of each laser ridge that has yet to reach its full potential taken at Pendar Technologies is the in the QCL array from a single wafer is a truly portable noncontact (stand- monolithic distributed feedback (DFB) such that every channel simultaneously off), chemically versatile analyzer for quantum-cascade laser (QCL) array. meets the specified wavelength, power, fast Fourier-transform infrared (FTIR)- Invented in Federico Capasso’s group at and single-mode suppression ratio. Each quality spectral examination of nearly Harvard University (Cambridge, MA) of these parameters is critical to both ef- any condensed-phase material. and licensed exclusively to Pendar, the ficient beam combining and to obtain- The unique challenges of stand- continuously wavelength-tunable QCL ing high-quality molecular spectrosco- off IR spectroscopy actually extend array source is a highly stable broad- py once integrated. band source With these hurdles largely overcome, a) b) that can be used the payoff in terms of spectrometer per- for illumination formance lies largely in a demonstrat- in reflectance ed shot-to-shot amplitude stability in spectroscopy. pulsed mode of <0.1%—a factor of 50 Each element more stable than is typical for EC QCLs, of the array is even when used in the lab. Most im- individually ad- portantly, the DFB QCL noise is ran- 1 dressable and dom, and averages toward an Allan 0.1 emits at a differ- variance limit quickly such that detec- 0.01 ent wavelength tor-noise-limited, high-quality spectra 0.001 by design. can be obtained for trace levels (for ex- 2 8.8 9.0 9.2 9.4 The advantag- ample, 1–50 µg/cm ) of typical powders Wavelength (µm) es of these QCL in just 100 ms. arrays over ex- FIGURE 1. A 200 cm-1 prototype QCL array with 32 QCLs is shown ternal-cavi- More DFB array advantages prior to beam combining and packaging (a), and experimental spectra ty (EC) QCLs While the stability advantage of DFBs from 32 adjacent QCLs are seen (b). (Courtesy of Pendar Technologies) stem from (1) vs. EC configurations has been well es- the monolithic tablished, there are a few less-obvious

36 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_36 36 11/2/15 11:53 AM aspects to DFB arrays that make them more highest performance regressions against suitable to real-world spectroscopy tools reference spectra while maintaining the and, in particular, portable spectroscopy high-speed identification that the QCL tools. For one, the laser array as a whole array actually enables. can maintain a 100% duty cycle while each With regard to the wavelength regions DC-DC laser in the array requires operation only of interest (see Fig. 2), most of the spectral over a 100/n (%) duty cycle, where n is richness of an IR spectrum is centered in the number of lasers in the array. Put an- two bands, generally referred to as the func- CONVERTERS other way, a laser array consisting of only tional group region (about 3.3–5.5 µm) and pulsed QCLs can operate as a truly con- the fingerprint region (about 7–11 µm). The tinuous-wave (CW) system, allowing for first is typically dominated by the stretch high-measurement duty cycle while possi- modes of certain common bond groups, bly reducing the cost of fabrication. while the latter includes bending modes of In a related way, generating light for an some functional groups as well as lower fre- array that has a 100% aggregate duty cycle quency modes that are characteristic of the (by using, for instance, 32 lasers at 3% duty macromolecule “backbone”—for instance, cycle), the thermal heat-sinking require- the torsional modes of a toluene ring found ments of the source are dramatically re- in many highly energetic materials. With NEW AVP/AVN SERIES! duced. Indeed, our packaged prototypes do support from the Department of Homeland 10,000 VDC Outputs not even require active cooling to keep the Security (DHS)’s Widely Tunable Infrared system cool enough to run. A thermoelec- Source (WTIRS) program and from the Now in Miniature Design tric cooler is built into the package only to Army Research Lab, Pendar is developing stabilize the temperature, which therefore a compact array module that fully covers 0.5” x 1.0” x 0.5” stabilizes the 32 wavelengths (see Fig. 1). 7–11 µm (900–1430 cm-1). Finally, the arbitrary programmabili- • Isolated • High Reliability ty of the QCL array opens up many new System architecture drivers • 6,000, 7,000, 8,000, 9,000, 10,000 VDC, possibilities for experimental optimiza- To maximize signal-to-noise (SNR) while positive and negative output models tion. Certain lasers can be skipped, multi- minimizing the required acquisition time, • 1.25 watt output power, -25˚ to +70˚C ple lasers can fire at once, repetition rates the system architecture is driven by the fol- operating temperature standard, and pulse durations can be set for each el- lowing first-order considerations: no de rating ement, and so on. These advantages are 1. Increasing the laser power enabled • 5-12-15-24 and 28 VDC inputs standard only truly realized when the QCL array by relaxed thermal constraints as the heat • Military Upgrades Available is instrumented into a full system. load is distributed over several modules Expanded operating temperature, -55˚ to Looking holistically at how best to in- (arrays) and laser waveguides. +85˚C available - Selected MIL-STD-883 tegrate this new capability into a full sys- 2. Maximization of the measurement screeening available tem, it is critical to draft the link equations duty cycle enabled by the fast purely elec- • Free review of any additional requirements that govern the use of electrons to pro- tronic control of the array, allowing close and specifications you may have to comply with duce photons, the collection of photons to zero-delay switching between lasers— scattered back, and finally the conversion that is, a laser is on at any time. This is • Fully encapsulated for use in harsh environmental conditions from raw spectral information to chemical also enabled by the distributed heat load identification. In the case of mid-IR ma- among the laser units. For full characteristics of these and the entire PICO product line, see PICOís terial identification, it becomes clear that 3. Improved source stability, wavelength Full line catalog at three aspects are particularly consequen- accuracy, pulse-to-pulse amplitude, and tial: (1) How broad a wavelength range frequency repeatability—all of which are www.picoelectronics.com is needed for the tool to be of maximum needed to ensure that the source noise is specificity without producing redundant not the limiting form of noise (compared to PICO ELECTRONICS, Inc. or useless chemical information (that is, detector or speckle noise). Other research- 143 Sparks Ave., Pelham, New York 10803 how many laser channels should be used, ers have studied the source-noise problem Call Toll Free 800-431-1064 how should they be spaced with respect of commercial EC QCLs as well and con- FAX 914-738-8225 to one another, and over what total wave- cluded that the order-of-magnitude advan- E Mail: [email protected] length regime should they be spaced); (2) tage in minimum detectable absorbance the mechanical and electro-optical design (MDA) offered by a DFB QCL carries of the instrument; and (3) how to get the through the full experiment.

Laser Focus World www.laserfocusworld.com November 2015 37

1511lfw_37 37 11/2/15 11:53 AM MID-IR SENSING continued

Finally, once the spectra are digitized, chemical signatures in the Absorbance EGDN the system must use complex chemomet- reference spectral library 1.6 PETN rics algorithms to ensure confident identi- to reflect the physical and 1.4 Ammonium fication of threats in the presence of chem- environmental conditions nitrate 1.2 ical clutter, deliberate interferents, and of the experiment. A phys- TATP unknown backgrounds, without the inter- ics-based model will thus 1.0 Nitroglycerin vention of an expert user. Our approach be included in the detec- 0.8 Urea nitrate to real-time chemometrics is centered on tion algorithm to help us 0.6 Potassium perchlorate the fact that for chemically cluttered situ- model the variability in a 0.4 Ammonium ations, spectral libraries alone—no matter reference spectrum as a perchlorate 0.2 how large—cannot constitute the sole ba- function of effects such as 0.0 sis for chemometric analysis. Microphysics vapor pressure, deliques- 900 1100 1300 1500 1700 1900 modeling and experimentation are also cence, photochemical life- Wavenumber (cm-1) required, particularly in regard to crystal time, reactive lifetime, de- FIGURE 2. An assemblage of IR spectra of many common size distribution, clutter interactions, and composition products, and explosives shows that each has at least one unique chemical photolysis/reactions. The key ad- so on to facilitate better absorption feature in the wavelength ranges selected. The vance lies in the incorporation of chemical comparison with the mea- blue shaded box indicates strong water interference in the and physical understanding of the targets sured spectrum. troposphere. The figure intentionally spans beyond 1800 cm-1 and their co-indicators. We are current- 2. Situational effects. so as to illustrate that no new information is gained for this ly developing a four-tiered approach to Effects of different sub- chemical class by shifting the longwave-IR (LWIR) source the spectroscopic algorithms challenge: strates and their properties further to the blue until the midwave-IR (MWIR) is reached. 1. Physics-based models. Reliable chem- on the chemical signatures ical detection from standoff measure- and the angular dependence of spectra of physics and chemistry will be exper- ments will involve transformation of the that are not clearly linked to equations imentally evaluated and included in the Etalons

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38 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_38 38 11/2/15 11:53 AM MID-IR SENSING continued

Standardized intensity Acetaminophen addition to the physical mod- handheld demonstration system. Figure 3 3 el—will enable better detec- shows the experimentally obtained spectra 2 tion strategies. for two nonhazardous chemical targets as a 1 3. Feature-based classifica- function of stand-off distance. The yellow 0 0.5 m tion. Extraction of relevant line in each panel shows the library FTIR -1 1 m feature vectors from the ref- (“true”) spectrum for each. Agreements of -2 1.5 m erence library spectra and the r2 > 0.9 were typical. With the prototype -3 Library knowledge of the chemistry to system as an extrapolation point, contin- -4 form a hierarchical decision ued, focused advances in the technology 940 960 980 1000 1020 1040 Wavenumber (cm-1) tree that will help us provide are now underway to open myriad fron- Standardized intensity different levels of classifica- tiers in molecular spectroscopy. Ibuprofen tion based on the customer 5 0.5 m ACKNOWLEDGEMENT requirements. For instance, if 4 1 m Pendar Technologies was formed in August a customer is only interested 3 1.5 m 2015 through a merger between Pendar Med- Library in finding out whether a giv- ical (Cambridge, MA), a portable spectrosco- 2 en chemical is an explosive, py company founded by Daryoosh Vakhshoo- ri (who was previously at Ahura Scientific and 1 then we might save on com- CoreTek), and QCL sensing startup Eos Pho- 0 putational cost by avoiding tonics (Cambridge, MA), a Harvard spinoff -1 searching through the leaves founded by professor Federico Capasso and -2 of the decision tree to find out his postdocs. 940 960 980 1000 1020 1040 -1 Wavenumber (cm ) the exact chemical. Mark F. Witinski is vice president of the 4. Real-time atmospheric Chemical Analysis and Security Unit, Romain FIGURE 3. Standoff spectra of of acetaminophen and measurements. Once validat- Blanchard is a systems architect, Biao Li ibuprofen for three target distances. The black line shows is a senior scientist, Christian Pfluegl is the FTIR of the same using a diffuse reflectance accessory. ed, the model will be suitable vice president of engineering for the Infrared The only data processing shown is the normalization of the for field implementation by the Systems Unit, Laurent Diehl is vice presi- curve areas to a common value. inclusion of an integrated sen- dent of the Mid Infrared Platform, Benjamin sor suite that simultaneously Pancy is an optical engineer, Daryoosh Vakhshoori is chief executive officer, and detection algorithm. In particular, exper- records atmospheric pressure, tempera- Federico Capasso is a board member and imentally measuring such variability will ture, relative humidity, solar flux, wind advisor at Pendar Technologies, Cambridge, help us algorithmically model the variabil- magnitude, and water-vapor mixing ratio. MA; e-mail: [email protected], www. pendartechnologies.com. Capasso is also ity of chemical signatures from some “gold With these design drivers considered, a professor of applied physics at Harvard standard” reference signature, which—in Pendar recently completed the build of a University, Cambridge, MA.

Laser Focus World www.laserfocusworld.com November 2015 39

1511lfw_39 39 11/2/15 11:53 AM CONNECTING MINDS. ADVANCING LIGHT.

PHOTONICS WEST• THE PREMIER EVENT FOR THE PHOTONICS AND LASER INDUSTRIES

BiOS—Biomedical Optics The Moscone Center Translational Research San Francisco, California, USA LASE —Lasers and Sources Conferences & Courses OPTO—Optoelectronic Devices 13–18 February 2016 Green Photonics 3D Printing Photonics West Exhibition Industry Panels and Keynotes 16–18 February 2016

BiOS EXPO 13–14 February 2016

1511lfw_40 40 11/2/15 11:53 AM photonicsproducts INTERFEROMETERS

Numerous ways exist to interferometrically measure aspheres

JOHN WALLACE, Senior Editor

Aspheric optics can be measured require the use of a null displacement. Optical profilers are ca- using a Fizeau interferometer, or by lens, which is placed pable of measuring very steep surfac- using an optical profiler containing an in the interferometer es, including hemispheres. to counteract the op- interferometer; both approaches have a tic’s asphericity. Such The Fizeau interferometric variety of forms. a null lens often takes approach Because aspheric optics—from large the form of a computer-generated ho- Today’s Fizeau interferometer is an in- precision one-off designs to mass-pro- logram (CGH), a diffractive element strument well suited for asphere sur- duced small elements for consumer de- that can be easier to fabricate than a face-form characterization. For ex- vices—are growing in use, the testing refractive null lens. This approach is ample, the Verifire Asphere (VFA), of aspheres is currently a very active widely used. produced by Zygo (Middlefield, CT), area in optics, with improvements to However, null lenses do add com- an Ametek company, is a noncon- the technology occurring rapidly and plexity to the interferometric setup— tact interferometric metrology tool with impressive results. Optical test- not only do they have to be precise- based on the Verifire Fizeau interfer- ing of aspheres takes two major forms: ly made, but they have to be properly ometer that Zygo has produced for interferometric testing and noncontact placed and aligned with respect to the many years. profilers (which can contain their own interferometer and the optic under test. As described by Tyler Steele, prod- interferometers). In response, techniques have been de- uct manager at Zygo, the instrument The archetypal laser interferome- veloped to allow testing of even strong contains a five-axis motorized stage ter—the type that has been used in op- aspheres without the use of null lenses. and two-axis displacement measur- tical labs for decades—is a Fizeau in- In an optical profiler, a spot of laser ing interferometer (DMI) that enables terferometer that uses laser light at 633 light is scanned across the surface of an automatic alignment and acquisition nm to measure spherical optics. For optic to determine its 3D shape point of an aspheric surface under test. A added flexibility, today’s interferom- by point. In some cases, the profiler’s full 3D surface-error map and an ar- eters can be obtained with laser sourc- own optical system includes a laser in- ray of numerical outputs are available es operating at wavelengths ranging terferometer to characterize the spot to characterize surface error for final from ultraviolet (UV) to longwave-infrared (LWIR). FIGURE 1. Measuring aspheric sur- Data from different faces or optical components zones of an on a standard laser inter- aspheric surface ferometer, however, quick- measured by a ly becomes challenging as Verifire Asphere interferometer the asphericity of an op- are combined in tic increases. While weak software to obtain aspheres can be measured the optic’s shape. with a standard interfer- (Courtesy of Zygo) ometer, stronger aspheres

Laser Focus World www.laserfocusworld.com November 2015 41

1511lfw_41 41 11/2/15 11:53 AM INTERFEROMETERS continued

metrology or provide feedback for deter- termed subaperture stitching interferom- (many fringes) over any given subaperture. ministic polishing. etry (SSI), is a mainstay of the company’s The ASI(Q) also can be configured with “An aspheric surface that is aligned to interferometer systems. the optional variable optical null (VON). a Fizeau interferometer produces annu- “Our systems combine a precision The VON corrects for known amounts lar zones of null interference,” says Steele. motion platform, interferometer, novel of coma and astigmatism for any given “The zone radial position is a function of Z stitching algorithms, and custom soft- subaperture, allowing for data capture position of the test surface relative to the ware,” says Paul Murphy, senior optical in subapertures that would otherwise interferometer. As the test part is trans- engineer at QED. “SSI technology en- have fringe densities too high for reliable lated in Z with feedback from the DMI, ables testing spheres of large size (150– interferometric acquisition. Achievable zones are acquired across the test surface 400 mm convex lenses) and high-numer- measurement specifications are part- and (see Fig. 1) and the aspheric surface is re- ical-aperture (hemispherical) optics that environment-dependent, but QED has constructed in software. The output is a have traditionally challenged convention- demonstrated results in the single-nano- deviation from the ideal design, or an op- al full-aperture interferometry. Finally, SSI meter range.” timized asphere base radius and conic con- technology makes aspheric measurement The ASI can handle steep surfaces; in stant can be calculated from the as-mea- possible without dedicated null lenses.” one example by Murphy (which hap- sured best fit surface.” The Aspheric Stitching Interferometer pens to be for a sphere rather than for The VFA is best suited for rotational- with QIS [ASI(Q)] is the latest offering an asphere), a 150-mm-diameter lens ly symmetric aspheres with departure from QED, notes Murphy. The QIS, a with an approximately 500 mm radius from spherical of less than 800 µm and

radius of curvature less than 800 mm, a) b) notes Steele. “The ophthalmic market 17 has benefited from this metrology tech- 18 16 nique, as contact lens surfaces fit within 19 8 15 these conditions,” he says. “Many new 7 9 contact-lens designs are based on aspheric 20 1-4 6 14 surfaces that slightly deviate from spher- 10 5 ical in order to achieve multifocal effects. 13 21 11 26 Accurate metrology of these designs is 12 critical in ensuring the proper prescrip- 22 25 tion, as well as defect inspection and pro- 23 24 cess management.” Large-volume manufacturing areas such as the contact-lens market have driven the FIGURE 2. An ASI(Q) interferometer (a) creates a development of an automation capability subaperture lattice (b), then collects and stitches the for the VFA: a 150 × 150 mm stage and subaperture data. (Courtesy of QED Technologies) automation software enable multiple test parts to be placed in a tray and automatically measured. Relevant results and a was measured and polished. “A 6 in. in- surface-error map are reported, with a terferometer cannot cover a convex part graphical pass/fail interface controlled by of these dimensions, says Murphy. “For an operator. In addition to asphere metrol- coherent imaging, 6-in.-aperture Fizeau a concave part, an f/3 or faster transmis- ogy, the VFA is capable of precision spher- interferometer, is mounted in a multiaxis sion sphere is needed to cover the part ical radius and surface measurements, as machine. The user enters information on without stitching. With stitching, how- well as toric surfaces—each a key surface the part and the software automatically ever, we were able to employ a slower shape in the ophthalmic contact-lens in- recommends a transmission element, de- diverging transmission sphere to obtain dustry, says Steele. signs an appropriate subaperture layout higher magnification and thus superi- One way to allow a Fizeau interferom- (lattice), and collects and stitches the sub- or lateral resolution. Furthermore, we eter to measure strong aspheres without aperture data (see Fig. 2). took advantage of the ASI’s automatic resulting in an unmeasurably high number “The QIS allows for greater than 50% random reference calibration to enable of fringes is to divide the full aperture into more slope capture than a convention- mid-spatial-frequency measurements at subapertures, measure each one, and com- al, incoherent system,” explains Murphy. tenth-nanometer levels. These measure- bine the data. This approach, developed at “This is critical for asphere measurement, ments allowed magnetorheological fin- QED Technologies (Rochester, NY) and as many prescriptions have large slopes ishing (MRF) corrections to improve

42 November 2015 www.laserfocusworld.com Laser Focus World

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the surface form and mid-frequencies “The UltraSurf 4X 300 has the capabil- ideal for measuring large aspheric sur- to better than 1 nm root-mean-squared ity to measure virtually any asphere up to faces as well as aspheres with radical de- (RMS), as well as monitor submillime- 300 mm in diameter,” says Ed Fess, R&D parture. “The UltraSurf is also capable of ter lateral features.” manager at OptiPro. “The 4X 300 model measuring both surfaces of near-meniscus number denotes four axes of motion (X, Z, shapes simultaneously,” he adds. “In this Surface profiling by scanning B, and C) with 300 mm of X-axis travel. case, it can measure the convex, concave, Measuring the surface of an asphere by To achieve high-precision metrology, all and thickness maps in one measurement scanning an optical spot across it in a pre- axes are driven by the latest air-bearing scan. The thickness map can provide a de- determined pattern is another important and linear-motor technology. Each lin- tailed 3D map of any wedge and decenter noncontact technique (contact profilome- ear axis has nanometer resolution, while that might be between the two surfaces.” try, which is yet another important tech- both rotary axes nique, will not be covered in this article). have subarcsecond The UltraSurf noncontact metrolo- resolution. In addi- For More Information gy system, made by OptiPro Systems tion, the UltraSurf (Ontario, NY), uses focused light from 4X 300 can ac- Companies mentioned in this article include: an optical probe to scan aspheric surfaces commodate a va- OptiPro Systems Taylor Hobson for 2D and 3D surface figure error anal- riety of probes op- Ontario, NY Leicester, East Midlands, England www.optipro.com www.taylor-hobson.com ysis for either ground or polished optical erating at different QED Technologies Zygo surfaces (see Fig. 3). Noncontact point wavelengths.” Rochester, NY Middlefield, CT sensors can include a low-coherence in- Fess notes that www.qedmrf.com www.zygo.com terferometer to measure inside and out- the unit’s flexibil- FOR A COMPLETE LISTING OF COMPANIES making interferometers, side surfaces at the same time, or a white ity in both trav- visit the Laser Focus World Buyers Guide (http://buyersguide. light confocal system to measure individ- el and probe com- laserfocusworld.com/index.html). ual optical surfaces. patibility makes it

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1511lfw_43 43 11/2/15 11:53 AM INTERFEROMETERS continued

Fess gives two example applications in uses both coherence scanning interferom- to be expendable for metrology, the pre- which the UltraSurf’s capabilities helped etry (CSI) and 2D vision analysis to make cise molds used to manufacture them re- in a manufacturing process. The first in- subnanometer 3D measurements of opti- quire significantly more care,” he explains. volved a customer who was manufactur- cal surfaces, as well as 2D inspection of “A noncontact solution allows a finished ing an asphere with aspheric departure relevant mounting and alignment param- lens mold to be measured and immedi- on the order of 1000 waves. “The cus- eters of both lenses and injection-mold- ately used, without a final finishing step tomer had an issue during their manu- ing tooling molds. to remove evidence of metrology. In addition, because Compass measures the entire surface of the asphere, it can detect a) b) problems that may escape notice of other techniques.” For example, one issue uncovered by an inspection with the Compass tool was that a customer’s plastic injection process was actually underfilling the lens mold, resulting in an asymmetric lens surface as well as an incorrect surface shape. Line- profiling-based techniques could see the incorrect surface shape, but it wasn’t until the lens was measured with the Compass that the underfill became obvious.

Multiwavelength interferometry A scanning-interferometer-based asphere-measurement system produced by Taylor Hobson (Leicester, East Midlands, England), another Ametek company, is based on multiwavelength interferometry (MWLI), which has the capability of FIGURE 3. An UltraSurf 4X 300 noncontact metrology system (a) scans an aspheric surface measuring absolute distances. As noted by using a stage-mounted single-point optical probe (b). (Courtesy of OptiPro Systems) Erik Stover, business development manager at Taylor Hobson, the LuphoScan facturing process that caused the form “The technique is entirely noncontact system contains a four-wavelength probe. error of the optic to exceed what they and results in 3D topography, deviation, The system contains a fiber-based in- could measure with their interferome- and texture results,” he says. “Users can terferometer with four wavelengths that ter and hologram setup,” says Fess. “We create recipes that automate the process lie in the 1530–1610 nm range, with all were able to use the UltraSurf to mea- of characterizing the entire lens. The non- light coincident at the same point on the sure the optic and provide them with a contact CSI technology leverages the short test optic. The resulting four independent- data map to use with their subaperture coherence length of white-light illumina- ly measured interference signals are digi- polishing process. This allowed them tion to compare the surface of a test region tized and their information combined to to correct the surface shape and utilize to a reference surface built into the micro- produce an absolute distance measure- their process again. We also had a cus- scope objective. Overlapping regions of the ment. The optic under test is scanned by tomer purchase an UltraSurf for the sim- surface are measured and then stitched rotating it on a 360° rotary stage while ple fact that it was not slope-limited like together to form a full 3D map of the moving the interferometer probe radial- contact profilometers, and was not lim- lens topography. The 3D map can then be ly and in Z. ited to how aspheric the profile was.” compared to the optical prescription and The absolute-measurement capability Zygo has developed and commer- a deviation map can be presented, show- allows the system to correlate data mea- cialized a 3D surface mapping system, ing both qualitatively and quantitatively sured successively on different surfac- called the Compass, that is specifically how different the optical element is from es, such as the front and back of a lens, designed to inspect small aspheres typi- the design parameters.” enabling the system to determine de- cally used in consumer electronics devic- The noncontact measurement is im- center, wedge, lens thickness, and lenses. Eric Felkel, product manager at Zygo, portant, notes Felkel. “While small plastic mount positioning as well as asphere sur- says the Compass asphere metrology tool lenses can be made in sufficient volumes face shape.

44 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_44 44 11/2/15 11:53 AM TUNABLE LASERS

Quantum dots and silicon photonics combine in broadband tunable laser

TOMOHIRO KITA and NAOKATSU YAMAMOTO

A new wavelength-tunable laser wavelength-division mul- have a small footprint and low pow- diode combines quantum-dot (QD) tiplexing (WDM) sys- er consumption. Therefore, compact, technology and silicon photonics with tems with dense frequen- low-power wavelength-tunable laser di- cy channels. Because the odes are key devices for use in higher-ca- large optical gains around the 1310 nm frequency channels in pacity data transmission systems that telecom window and is amenable to the conventional band have been designed to use these unde- integration of other passive and active (C-band) at 1530–1565 veloped frequency bands, and our het- components towards a truly integrated nm are overcrowded, the erogeneous tunable wavelength laser photonic platform. frequency utilization ef- diode consisting of a QD optical gain ficiency of such WDM medium and a silicon photonics exter- A new heterogeneous wavelength-tun- systems becomes saturated. However, nal cavity is a promising candidate.5 able laser diode, configured using extensive and unexploited frequency re- quantum dot (QD) and silicon pho- sources are buried in the near-infrared Quantum dot optical amplifier tonics technology, leverages large op- (NIR) wavelength regions such as the Ultrabroadband optical gain media tical gains in the 1000–1300 nm wave- thousand (T) and original (O) bands spanning the T- and O-band are effec- length region using a scalable platform between 1000 and 1260 nm and 1260 tively fabricated by using QD growth for highly integrated photonics devices. and 1350 nm, respectively. techniques on large-diameter galli- A cooperative research effort between Quantum dot-based optical gain me- um-arsenide (GaAs) substrates. Our Tohoku University (Sendai, Japan) and dia have various attractive characteris- sandwiched sub-nano-separator (SSNS) the National Institution of Information tics, including ultrabroad optical gain growth technique is a simple and effi- and Communication Technology bandwidths, high-temperature device cient method for obtaining high-qual- (NICT; Tokyo, Japan) has resulted in stability, and small linewidth enhance- ity QDs (see Fig. 1). the demonstration of broadband tun- ment factors, as well as silicon photonic In the SSNS method, three monolay- ing of 44 nm around a 1230 nm center wire waveguides based on silicon-on-in- ers (each around 0.85 nm thick) of GaAs wavelength with an ultrasmall device sulator (SOI) structures that are easily thin film are grown in an indium GaAs footprint, with many more configura- amenable to constructing highly inte- (InGaAs) quantum well (QW) under the tions with various performance met- grated photonics devices.1-4 QDs. We had previously observed many rics possible. The photonic devices used for short- large, coalescent dots that could induce Recently developed high-capaci- range data transmission are required to crystal defects in QD devices using a ty optical transmission systems use

a) b) c) SOA (2000 μm) p-GaAs FIGURE 1. A cross-section (a) InGaAs QW2 GaAs spacer layer p-AI0.3Ga0.7As shows a quantum dot (QD) device InAs QD GaAs grown using the SSNS technique, IN0.15Ga0.85As InAs QDs resulting in a high-density, high- SSNS SSNS (GaAs sub-nano layer)

7-stacked IN0 Ga0 As quality QD structure (b) that is used (GaAs 3ML) .15 .85 GaAs to create a typical SOA (c) using QD InGaAs QW n-AI0.3Ga0.7As 1 GaAs (001)Sub. 300 nm optical gain. n-GaAs(001) AR coating Facet mirror

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conventional growth technique without cross-section of the semiconductor opti- of indium arsenide (InAs) with 20–30 SSNS. Now, we can obtain high-density cal amplifier (SOA) has an anti-reflection nm diameters were grown within an (8.2 × 1010 cm-2), high-quality QD struc- (AR) coating facet to connect a silicon InGaAs QW. Seven of these QD layers tures since the SSNS technique success- photonics chip with low reflection and a are stacked to achieve broadband optical fully suppresses the formation of coales- cleaved facet used as a reflecting mirror gain. Subsequently, this QD-SOA is used cent dots. in the laser cavity. as an optical gain medium for the hetero- For single-mode transmission, a ridge- To fabricate the SOA, the SSNS growth geneous laser, which can be complement- type semiconductor waveguide was fab- technique was combined with molecular ed by other communication technology ricated for single-mode transmission. The beam epitaxy. Quantum dots comprised devices such as a high-speed modulator, a two-mode laser, and a photoreceiver.6, 7

Silicon photonics ring resonator filter With the QD-SOA fabricated, a wavelength filter is fabricated next using silicon photonics techniques. It includes a spot-size converter that has a silicon oxide (SiOx) core and a tapered Si waveguide that connects the QD-SOA to the Si photonic wire waveguide while minimizing optical reflections and coupling losses (see Fig. 2). The wavelength-tunable filter consists of two ring resonators of different size. The Vernier effect of these two ring resonators allows only light of a specific wavelength to reflect to the QD-SOA. Furthermore, Tantalum micro-heaters formed above the resonators provide a means whereby the laser wavelength can be tuned through application of the thermooptic effect. Essentially, the wavelength tuning operation of the double ring resonator wavelength filter is achieved through Vernier effects wherein a ring resonator acts as a wavelength filter with constant wavelength interval called the free spectral range (FSR), which is inversely propor- tional to the circumference of the ring. The tuning wavelength range is determined from the FSR difference of the two rings with FSR1 and FSR2. A smaller difference in the FSR provides a wider wavelength tuning range, even when the transmittance difference between the main and side peaks is small. On the other hand, a sufficiently large transmittance difference is required to achieve stable single-mode lasing and is obtained using large FSR ring resonators. Silicon photonics allows us to fabricate an ultrasmall ring resonator with large FSR because of the strong light

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1511lfw_46 46 11/2/15 11:53 AM a) Ring 2 Spot size converter

Ta micro heater

50 μm Ring 1

Wavelength tuning range Transmittance b) FSR1 FSR2 difference

Ring 1

Transmittance (dB) Transmittance Ring 2

Wavelength (a.u.)

FIGURE 2. A microscope image (a) shows a silicon-photonics- based wavelength-tunable filter. In a transmittance analysis (b), the red and blue dotted lines indicate the transmittance of a small ring resonator with free spectral range FSR1 and a large ring resonator with FSR2, respectively, and the solid line indicates the product of each transmittance. The tuning wavelength range is determined from the FSR difference of the two rings. A smaller difference in the FSR provides a wider wavelength tuning range, even when the transmittance difference between the main and side peaks is small.

confinement in the waveguide. The ring resonator consists of four circle quadrants and four straight lines and the radius of the circle was chosen to be 10 µm to avoid bending losses. The FSRs of the ring resonators and the coupling efficiency between the bus-waveguide and the ring resonator are optimized to obtain wide wavelength tuning range and sufficient transmittance difference.

Ultra-compact silicon High-quality QD photonics filter

200 nm 50 μm Laser output 1 mm 3 mm

QD gain chip Silicon photonics chip Wavelength controllers

FIGURE 3. A schematic shows how the heterogeneous wavelength- tunable laser diode is constructed.

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The FSRs and the coupling efficien- Optical output (dBm) Measured using a lensed fiber, the cies of the double ring resonators are laser output from the cleaved facet of Wavelength tuning range: 44 nm designed to obtain a 50 nm wave- the QD-SOA shows single-mode las- length tuning range and 1 dB trans- -10 ing characteristics with a laser oscil- mittance difference. We have since -20 lation threshold current of 230 mA. fabricated various wavelength-tun- Maximum fiber-coupled output pow- -30 able laser diodes, including a broader is 0.4 mW when the QD-SOA in- band tunable laser diode, a narrow -40 jection current is 500 mA. spectral-linewidth tunable laser diode, -50 As the ring resonator temperature is and a high-power integrated tunable increased by a heater with 2.1 mW/nm laser diode by using a silicon photon- -60 power consumption, the superimposed ics wavelength filter and a commer- 1.20 1.21 1.22 1.23 1.24 1.25 lasing spectra show a 44 nm wave- Wavelength (μm) cially available C-band SOA.8, 9 length tuning range with more than FIGURE 4. The heterogeneous wavelength-tunable a 37 dB side-mode-suppression ratio The tunable laser diode laser diode has a broad tuning range about its center between the ring resonator’s modes. Using stepper motor controllers, the wavelength. The 44 nm wavelength tuning range QD-SOA—kept at approximately of our heterogeneous QD/Si photon- 25°C using a thermoelectric cooler—and the silicon photonics ics wavelength-tunable laser is, to our knowledge, the broadest wavelength filter are butt-jointed (see Fig. 3). The lasing wave- achieved to date. The 44 nm tuning range around 1230 nm cor- length is controlled by the temperature of a micro-heater placed responds to 8.8 THz in the frequency domain, which is far larger on the ring resonators. With physical footprints of 600 µm × 1 than the 4.4 THz frequency that is available within the C-band. mm and 1 × 2 mm for the wavelength filter and the QD-SOA, Our heterogeneous laser is suitable for use as a light source respectively, the total device size of the tunable laser diode is on a silicon photonics platform that includes other optical just 1 × 3 mm. components such as high-speed modulators and germani- um (Ge)-based detectors. In addition to application as a single-chip broadband optical transceiver for telecommunications, the laser could also be applied to biomedical imaging applications such as optical coherence tomography (OCT), considering the low absorption of NIR light at 1310 nm in the presence of water.

ACKNOWLEDGEMENTS This research was partially supported by the Strategic Information and Communications R&D Promotion Program (SCOPE), of Japan’s Ministry of Internal Affairs and Communications and a Grant-in-Aid for Scientific Research of the Japan Society for the Promotion of Science.

REFERENCES 1. Y. Arakawam and H. Sakaki, Appl. Phys. Lett., 40, 11, 939–941 (1982). 2. D. L. Huffaker et al., Appl. Phys. Lett., 73, 18, 2564–2566 (1998). 3. R. A. Soref, Proc. IEEE, 81, 12, 1687–1706 (1993). 4. B. Jalai and S. Fathpour, J. Lightwave Technol., 24, 12, 4600–4615 (2006). 5. T. Kita et al., Appl. Phys. Express, 8, 6, 062701 (2015). 6. N. Yamamoto et al., Jpn. J. Appl. Phys., 51, 2S, 02BG08 (2012). 7. N. Yamamoto et al., Proc. OFC, Los Angeles, CA, paper W2A.24 (Mar. 2015). 8. T. Kita et al., Appl. Phys. Lett., 106, 11, 111104 (2015). 9. N. Kobayashi et al., J. Lightwave Technol., 33, 6, 1241–1246 (2015).

Tomohiro Kita is assistant professor in the Department of Electrical Engineering at Tohoku University, Sendai, Japan; e-mail: [email protected]; www.ecei.tohoku.ac.jp. Naokatsu Yamamoto is director of the Lightwave Device Laboratory at the National Institution of Information and Communication Technology, Tokyo, Japan; e-mail: [email protected]; www.nict.go.jp.

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1511lfw_48 48 11/2/15 11:53 AM OPTICS CHARACTERIZATION

Shack-Hartmann wavefront sensor enables flexible characterization of lenses

RALF DORN and JOHANNES PFUND

A Shack-Hartmann wavefront sensor methods such as sty- Sensor configuration can replace an interferometer or lus-based surface profi- A Shack-Hartmann wavefront sensor stylus profilometer for measuring lometry. However, op- consists of a 2D array of microlenses tics can be damaged by and a CCD camera detector. After pass- lens properties in a lab or production tactile methods and the ing through the microlens field, a flat environment. measuring device quick- wavefront generates a regular grid of Many devices in today’s market make ly approaches its limits for cases of high points on the detector whose spots have use of optics; in particular, aspherical curvature. the same array separation distance as elements are on the rise because they In contrast, a Shack-Hartmann wave- the microlenses. If the wavefront has a allow optical systems to be designed front sensor assesses optics quickly us- curvature, the spots generated by the more compactly and easily. Although ing current computer power, and can microlens are displaced in x and y cor- functional and quality demands on op- operate using low-coherence light sourc- respondingly. From the shifts of these tics are continuously increasing, main- es. The Shack-Hartmann sensor has a grid points, the wavefront can be recon- taining quality of optics often lags be- very high dynamic measurement range structed. With strongly curved wave- hind because of the lack of sufficiently and functions rapidly enough that the fronts, however, the spots in the prox- flexible measurement technology. Here, measurement process is insensitive to imity of adjacent spots can move out the use of a Shack-Hartmann wave- environmental vibrations, and as a re- of their “home aperture,” or the im- front sensor provides a solution, en- sult is suitable for use in the vicinity of mediate region surrounding the refer- abling a rapid and flexible recording operating machines. ence point’s location. of the characteristic values of optical lenses. A great number of different mea- SHSInspect 1Xpass surement processes and modalities can be integrated into one device so that it SHSCam works efficiently both in manual and Object Telescope automated production environments. under test There are several methods available to test an optical device. The simplest SHSInspect 2Xpass (and at the same time also the slow- est) is to sample the optics using tactile

FIGURE 1. Schematic shows Reference sensor-system configurations for sphere measurement in single (SHSInspect SHSCam 1Xpass; a) and double pass (SHSInspect 2Xpass; b). Telescope Object under test

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Optocraft has developed a Shack- For testing of chromatic effects, a single wavefront Hartmann wavefront-sensing system (SHSLab) that contains a solution to sensor can be used over a wide wavelength range. this problem—a process that reliably as- The basic optical principle of the Shack-Hartmann sensor signs the displaced spots to their proper reference points in the case of high makes it possible to use the sensor not only with light wavefront curvatures (see Fig. 2). The sources of different wavelengths, but also with sources process requires only a single camera image and is thus very fast and simple having low coherence. As a result, low-cost LEDs can to use. The local radius of curvature of be used as a source that provides a large range of a wavefront impinging on the microlens array can be as small as 5 mm, allow- wavelengths for testing. ing wavefronts with extreme curvatures to be measured. the test specimen. The resulting increase in vibrate, induced by running machines or The sensor (SHSCam) can accommo- measurement sensitivity allows the whole motors in the device itself. The high vi- date up to 240 × 160 spots as well as an measurement configuration to be calibrat- bration tolerance of the Shack-Hartmann evaluation rate of up to 1000 Hz. By ed simply by means of a plane mirror and sensor system allows the expense of vi- means of associated software (SHSWorks), a reference sphere. bration damping to be avoided. A fur- a great number of optical measurement ther important requirement for produc- variables can be tested, such as wavefront Integration into R&D and tion quality control is a sufficiently high aberrations, imaging quality (Strehl, MTF, production environments level of measurement precision. The Shack- etc.), focal length, and laser quality. For the optical industry, this type of system Hartmann sensor head by itself achieves One of the complete measurement offers high accuracy and can also be easily a typical uncalibrated base accuracy of systems based around SHSLab is called integrated into an automated production λ/15 peak-to-valley (PV). Depending on SHSInspect (see Fig. 3). The system has environment. One important characteris- the optical structure of the test system, two configurations: with “1Xpass,” the tic is that the system works fast enough to an even higher precision can be achieved measurement beam runs through the measure in real time during the produc- by suitable calibration measures. In the test specimens only once, while with tion cycle. The 1Xpass and 2Xpass sys- case of the 2Xpass, a value of λ/20 PV is “2Xpass,” the light passes twice through tems reach, according to sensor size, frame about typical. the test specimen (see Fig. 1). In the latter rates between 1 and 50 Hz and, in special For testing of chromatic effects, a sin- case, the light is reflected back after the applications, up to 1000 Hz. Ultimately, gle wavefront sensor can be used over a first transition of a mirror. the time required for the insertion of the wide wavelength range. The basic opti- One strength of 2Xpass is that its influ- test specimen into the measuring equip- cal principle of the Shack-Hartmann sen- ence on the measurement beam is doubled ment determines the measuring rate. sor makes it possible to use the sensor not because of the twofold transition through Production environments naturally only with light sources of different wavelengths, but also with sources having low coherence. As a result, low-cost LEDs can be used as a source that provides a large range of wavelengths for testing.

Multifunctional systems SHSInspect (especially in its 2Xpass form) is adaptable to the requirements of the user. Currently, on-axis and off-axis measurements with field angles up to 50° are possible. Larger angles are feasible. By measuring the mechanical and optical characteristics of a lens, both the back focal length (BFL) and the effective focal length (EFL) can be determined. FIGURE 2. A screen capture shows various forms of data captured and produced by Many objective lenses include an ad- SHSLab, including the spot array imaged at the CCD sensor, a 2D wavefront representation, a justable lens provided at a location that wavefront cross-section, and a Zernike evaluation. can be targeted, displaced, and/or tilted,

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In the first case, the test specimen is in- serted manually into the measuring system—the measurements then progress automatically in accordance with a test protocol. However, this loading and unloading can also be implemented by means of a robot. Because of their speed and the reliability of their measurements, Shack-Hartmann wavefront sensors are suitable for the testing of optics both in research and in production. Even wavefronts with extreme curvatures can be measured precisely using corresponding evaluation software in combination with special sensor models. However, to select the proper sensor con- FIGURE 3. SHSInspect operates over a large wavelength range and also works with low- figuration, it is important to first evaluate coherence light sources such as LEDs. the required measurement sensitivity, as for example, to compensate form and po- automatically adjust the return sphere to well as the requirements for integration sition faults of the other fixed-assembly its ideal position. This allows the opera- into the production environment. lenses. With the 2Xpass, the adjustment tor to concentrate on the adjustments of Ralf Dorn and Johannes Pfund are at of such sliding lenses in microscope lenses the test specimen. Optocraft GmbH, Erlangen, Germany; e-mails: is done rapidly, enabled by the motorized In production, measurements can be [email protected] and [email protected]; centering function of the return sphere to implemented partly or fully automatically. www.optocraft.de.

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Computer modeling boosts laser device development

RÜDIGER PASCHOTTA

A full quantitative understanding of on the performance of a it is close to impossible to properly quan- laser devices is boosted by computer Q-switched, single-trans- tify the importance of such effects. modeling, which is not only essential verse-mode laser? The transverse beam profile in a typical for efficient development processes, Obviously, such ques- actively Q-switched Nd:YAG laser var- tions cannot simply be ies with the number of resonator round but also for identifying the causes of addressed with experi- trips (see Fig. 1). In addition to significant unexpected behavior. mental tests since these variations of beam size during the pulse, Computer modeling can give valuable at most reveal what laser output is much stronger effects of that kind associ- insight into the function of laser devices. achieved in a few situations, but ne- ated with a dramatic reduction in beam It can even reveal internal details that glect the full impact of particular effects quality are observed if the path length in could not be observed in experiments, on the performance and do not allow a air is increased from 20 to only 25 mm, and thus allows one to develop a com- full system optimization. which would still be well within the sta- prehensive understanding from which A computer model that takes into ac- bility range of that laser resonator. laser development can enormously prof- count the transverse dimensions concern- This path length increase causes a fre- it. For example, the performance poten- ing beam profiles and excitation in the quency degeneration for higher-order tials of certain technologies can be ful- laser crystal can show in detail how the modes—knowledge that could not be ly exploited and time-consuming and thermal lens with its aberrations affects gained through experiments, but could expensive iterations in the development the beam quality, for example, and to be garnered through modeling exercis- process can be avoided. Some typical what extent the transverse dependence es that quantify the sensitivity of the la- examples clarify the benefits of com- of the laser gain (gain guiding) influ- ser to gain-guiding effects, which de- puter modeling for improved laser de- ences the performance in high-gain sit- pend strongly on the resonator design vice development. uations. Note that the transverse gain and not only on the magnitude of gain profile changes substantially within the and the pump beam size. Such knowl- Example 1: Q-switched lasers pulse duration because of saturation of edge is essential for an efficient optimi- The basic dynamics of pulse genera- the gain medium. Without such a model, zation process. tion in a Q-switched laser can be described with y position (µm) FIGURE 1. Evolution of the 200 helpful formulas that re- transverse beam profile (shown veal the influence of var- with a color scale) and the optical 150 ious laser parameters on power (black circles, in arbitrary 100 certain performance pa- units) in an actively Q-switched 50 rameters such as pulse laser is simulated with RP Fiber energy and duration. Power software using numerical 0 beam propagation. The color However, it is often im- -50 scale is normalized for each portant to understand the round trip according to the time- -100 impact of additional ef- dependent optical power so -150 fects. For example, what that the variation of the beam -200 effects will thermal lens- diameter can be seen. 0 5 10 15 20 25 30 ing and gain guiding have Number of round trips

52 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_52 52 11/2/15 11:53 AM Example 2: Mode-locked lasers details, it allows one 0.1 Pulse energy (J) Today, even fiber lasers can have im- to refine the system ASE energy in 1 ms (J) pressive performance characteristics in design such that all 0.01 the area of ultrashort pulse generation. known potential 1e-3 This, however, requires operation in re- problems are safely 100e-6

gimes where strong nonlinear and dis- avoided. The likeli- 10e-6 persive effects occur. Particularly in such hood of unwelcome 1e-6 cases, the relationships between device surprises in the sub- parameters and performance are often sequent laboratory 100e-9 far from obvious. experiments is then 10e-9 Fiber 1 Fiber 2 Fiber 3 Fiber 4 Among other details, suitable param- much reduced. One 1e-9 0 1 2 3 4 5 6 7 8 9 10 11 eters of saturable absorbers for passive does not have to or- Position (m) mode locking—namely, the required mod- der expensive com- FIGURE 2. ulation depth and the acceptable recovery ponents without The evolution of pulse energy and forward ASE powers in a four-stage fiber amplifier system with various types of ASE time—need to be determined. Only a nu- knowing whether suppression between the stages, calculated with a comprehensive merical model makes it practical to explore they will work in computer model. the limits of pulse stability and optimize practice. performance. A “blind flight” trial-and-er- Modeling can reveal how the pulse en- may be the right choice. Then, the con- ror approach in the lab can easily lead to ergies and forward ASE levels evolve in sultant can evaluate the calculated results time-consuming, costly, and frustrating a four-stage amplifier system (see Fig. 2). together with interpretations and recom- iterations, making it nearly impossible to The ASE is essentially removed by acous- mendations and pass those to the team. develop optimized designs. to-optic modulators after the first and sec- In many cases, an R&D team or re- ond stages, and reduced with a bandpass search group will prefer to do the mod- Example 3: Ultrashort- filter after the third stage. The output is eling work internally using some suitable pulse fiber amplifiers substantial in terms of average power, al- software tools. In that way, the internal High-energy optical pulses can be gener- though the peak power of the amplified developers gain the most solid in-house ated by amplifying low-energy seed puls- pulse is far higher. The same model also expertise. They just need to select soft- es from a pulsed laser diode in a sequence calculates the temporal shape of the re- ware tools that will serve multiple mod- of fiber amplifier stages. Between the am- sulting pulses (with strong distortions be- eling needs in the future. plifier stages, bandpass filters, Faraday cause of gain saturation) and many other isolators, and/or optical switches can quantities of interest. Different user interfaces suppress light resulting from amplified The easiest way to get started is by using spontaneous emission (ASE). It is not obvi- How to get started software that consists of forms in which ous to which extent the mentioned meth- Although laser development can greatly the developer enters various device and op- ods are required. profit from computer modeling, many en- eration parameters like fiber length, input Also, it is essential to know about other gineers and scientists hesitate before us- power levels, and wavelengths desired, and aspects such as occurring optical intensities, ing this powerful method. But some tips then obtains an output in text and graph- pulse distortions because of gain saturation, and simple steps to follow based on prac- ical form that shows, for example, how and possible nonlinear effects, amongst tical experience can ease apprehensions optical power evolves within the device others. For many reasons, an uninformed about the method. or how it changes with time (see Fig. 3). trial-and-error approach is again inefficient. First, an important step is to identify the Using these simple tools, models can be Also, diagnosing problems in an ex- questions that should be answered by a set up quickly and leverage a number of periment can be rather difficult because model. For example, one may identify the predefined diagrams that can make var- one cannot easily measure various essen- need to understand the evolution of ASE ious adjustments through the available tial quantities within the optical fibers or powers along amplifier fibers, including forms. For example, a developer could cal- find out in the lab why such a system does their time dependencies. culate the output power of an amplifier as not work well. Next, a suitable person should be found a function of the pump power. A comprehensive computer model of to actually develop the model—perhaps A common disadvantage of forms, how- a multistage amplifier system can there- just one person within an R&D team or ever, is their lack of flexibility. The types fore be extremely helpful. It can be con- a research group. If there is no such per- of models and generated diagrams are structed in a much shorter time than an son around (or no one has spare time), or more or less limited to those considered experimental prototype and at much low- if such needs do not arise often enough to by the developer of the software. It may er cost. By revealing all relevant internal justify the effort, an external consultant not be practical to put together multi-stage

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STATEMENT OF OWNERSHIP, MANAGEMENT, AND CIRCULATION one from scratch. Also, forms may al- 1. Publication title: Laser Focus World. 2. Publication number: 922-380 3. Filing date: October 1, 2015. 4. Issue frequency: low the user to inject small pieces of Monthly. 5. Number of issues published annually: 12. 6. Annual subscription price: $162.00. 7. Complete mailing script code into the generated script, address of known office of publication: PennWell so that certain details (such as addi- Corporation, 1421 South Sheridan Rd., Tulsa, OK 74112, Tulsa County. 7a. Contact person: Traci Huntsman. 7b. Telephone: tional, special plots in a diagram) can 918-831-9435. 8. Complete mailing address of headquar- ters or general business office of publisher: PennWell Cor- be added without moving to script poration, 98 Spit Brook Rd., Nashua, NH 03062. 9. Full names programming altogether. and complete mailing addresses of Publisher, Editor and Managing Editor: Publisher: Alan Bergstein, 98 Spit Brook Rd., Another possibility is that forms Nashua, NH 03062. Editor: W. Conard Holton, 98 Spit Brook Rd., Nashua, NH 03062. Managing Editor: W. Conard Holton, 98 Spit can be defined within scripts. This Brook Rd., Nashua, NH 03062. 10. Owner: Penn Well Corpora- means that input and output fields, tion, 1421 So. Sheridan Rd., Tulsa, OK 74112, Tulsa County; Successors to the Estate of Helen B. Lauinger, 1421 So. Sheridan possibly including convenient graphi- Rd., Tulsa, OK 74112, Tulsa County. 11. Known Bondholders, Mortgages, and Other Security Holders Owning or Holding cal control elements such as selection 1 Percent or More of Total Amount of Bonds, Mortgages, boxes, can be defined in text form and or Other Securities: None. 12. N/A. 13. Publication Title: FIGURE 3. Form-based software can be used to Laser Focus World. 14. Issue Date for Circulation Data: associated with certain variables or September 2015. model laser devices such as a fiber amplifier. It is functions rather than being hard-cod- 15. Extent and Nature of Circulation: essential that such forms be made or modified by ed in the software. This allows the Average No. No. copies of the user or by technical support, so that they can copies each single issue user to construct forms tailored to issue during published be tailored to specific applications. preceding nearest to a certain modeling purpose, rather 12 months: filing date:

amplifier systems and to simulate complex than being limited to those forms created a. Total number of copies 38,302 38,308 operation cycles if the software developer by the software developer. b. Legitimate paid and/or requested distribution 1. Outside county paid/requested 32,398 32,798 did not offer these variants. Advanced simulation and design soft- mail subscriptions stated Much greater flexibility is obtained ware is an easy path to device modeling on PS form 3541 2. In-county paid/requested mail 0 0 if modeling software also offers a script without being limited to basic tasks. The subscriptions stated on PS form 3541 3. Sales through dealers and 2,529 2,320 language that can be used to define the valuable time of laser engineers and scien- carriers, street vendors, counter considered setup, to trigger calculations, tists can be saved for more complex tasks sales, and other paid or requested distribution outside USPS® and to generate the text or graphical out- rather than being used in overly time-con- 4. Requested copies distributed 0 0 by other mail classes puts in any desired form. With a power- suming learning exercises. through the USPS® ful script language, one can freely imple- c. Total paid and/or 34,927 35,118 requested circulation ment even the most sophisticated models Documentation and support d. Non-requested distribution and operation modes. For example, one For any modeling task, documentation 1. Outside county nonrequested 1,971 1,926 copies stated on PS form 3541 could simulate multiple amplification of methods and results is essential. The 2. In-county nonrequested copies 0 0 stated on PS form 3541 and pumping cycles of an amplifier sys- documentation must not only explain de- 3. Nonreqeusted copies distributed 0 0 tem as the output parameters stay con- tails of the user interface, but must inform through the USPS by other classes of mail stant, or automatically modify system pa- the user what kind of physical model was 4. Nonrequested copies distributed 960 820 rameters such that certain goals are met. used, what simplifying assumptions were outside the mail e. Total nonrequested distribution 2,931 2,746 However, potential users may have con- made, and what limitations need to be f. Total Distribution 37,858 37,864 g. Copies not Distributed 444 444 cerns that such a language would take considered. Unfortunately, software doc- h. Total 38,302 38,308 too long to learn. umentation is often neglected. i. Percent paid and/or requested 92.26% 92.75% circulation These two approaches—modeling In case of doubt, competent technical sup- 16. Electronic Copy Circulation software with forms or with a script lan- port should be available—not only for help- a. Requested and Paid Electronic Copies 33,027 37,423 guage—are so fundamentally different ing with the handling of the software, but b. Total requested and paid print copies 67,954 72,541 + requested/paid electronic copies that moving from forms to scripting may also offering detailed technical and scien- c. Total requested copy distribution + 70,885 75,287 appear overwhelming. Fortunately, there tific advice. For example, a beginner may requested/paid electronic copies d. Percent paid and/or requested 95.87% 96.35% are ways to conveniently combine the two find it difficult to decide which kind of mod- circulation ✔ I certify that 50% of all my distributed copies (electronic and print) approaches. el should be implemented for a certain pur- are legitimate requests or paid copies. One possibility is that the software, pose and which possibly disturbing effects 17. Publication of Statement of Ownership: Will be printed when controlled with forms, can generate need to be considered. Such support should in the November 2015 issue of this publication. 18. Signature and title of Editor, Publisher, Business scripts based on the form inputs. The user come from a competent expert in the field Manager, or Owner: Traci Huntsman, Manager Corporate Assets can then go as far as possible using simple rather than just a programmer. and Postal Compliance. Date: 10/01/2015. I certify that all information furnished on this form is true forms, but when the limits of that approach and complete. I understand that anyone who furnishes false Rüdiger Paschotta is founder and execu- are met, the user can easily switch to script or misleading information on this form or who omits mate- tive of RP Photonics Consulting, Bad Dürrheim, rial or information requested on the form may be subject to programming, starting with the automat- criminal sanctions (including fines and imprisonment) and/or Germany; e-mail: [email protected]; civil sanctions (including civil penalties). ically generated script rather than writing www.rp-photonics.com.

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1511lfw_54 54 11/2/15 11:53 AM a)

LASER FOCUS WORLD PRESENTS

BioOptics News & Optics profile Breakthroughs

56 Neuro15 exhibitors meet up among exacting demands: Part 1 neuroscientists

BioOptics Features While the technology behind amazing advances in neuroscience is still often hard to discern in the conference at the OPTICAL COHERENCE TOMOGRAPHY/OPHTHALMOLOGY Society for Neuroscience (SfN) annual meeting, two things have recently helped bring it out of the shadows: the U.S.’s 58 OCT angiography: A new approach with ‘gold Brain Research through Advancing Innovative Neurotech- standard’ capabilities and nologies (BRAIN) Initiative and a trend toward interdisci- more Chieh-Li Chen, Qingin Zhang, plinary research. Barbara Gefvert Anqi Zhang, and Ruikang K. Wang At the 2015 event (October 17-21)—which attracted Editor in Chief FLUORESCENCE-GUIDED SURGERY approximately 30,000—optogenetics was a star as the fo- [email protected] 63 Advanced surgery: NIR cus of nearly 30 dedicated conference sessions and even fluorescence guidance an SfN-sponsored an Optogenetics Social. (Optogenetics arrives David J. Burrington was mentioned as well in sessions dedicated to other topics.) Op- tical imaging was another hot topic, as several sessions specifically discussed approaches such as two-photon and light-sheet microscopy (and others discussed optical imaging-enabled discoveries), and super-resolution pioneer and Nobel Laureate Stefan Hell was one of seven luminaries to deliver Special Lectures.

online @bioopticsworld.com

Startup to provide access to low- Protein-based sensor IR thermography can detect cost super-resolution microscopy detects viral infection, joint inflammation, helping to A new startup is working to introduce can kill cancer cells improve work ergonomics imaging reagents that provide super- A modular system of proteins can detect A study has found that infrared resolution microscopy capabilities a particular DNA sequence in a cell and (IR) thermography can detect joint on standard single-molecule then trigger a specific response, such inflammation and, therefore, help improve microscopes. http://bit.ly/1LX43pz as cell death. http://bit.ly/1LwVMap work ergonomics. http://bit.ly/1GDr0h5

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1511lfw_55 55 11/2/15 11:53 AM Technical advances in lasers, optics, and imaging for the life sciences NEWS & BREAKTHROUGHS

Neuro15 exhibitors meet exacting demands: Part 1

Increasingly, neuroscientists are work- tion of both the long and short ends noise by 300–500%, while PrimeLo- ing with researchers in disciplines of the bandpass via the instrument or cate automatically detects and trans- such as chemistry and physics. This device such as a computer. Also new fers regions of interest, and easy crop- trend has been noticed by exhibi- from Sutter is its first major new prod- ping reduces file sizes. tors at the Society for Neuroscience uct line in two decades: a suite of elec- And Hamamatsu upped the imag- (SfN) annual meeting (October 17-21, trophysiology recording hardware and ing ante with its ORCA-Flash 4.0 V2 2015; Chicago, IL), and was in evi- software (Integrated Patch Amplifier) sCMOS, promising not only improved dence throughout the conference pro- to enable efficient, low-noise, whole- read noise, but also quantum effi- gram (see figure). Perhaps such col- cell recordings. ciency (QE) up to 82% to detect laboration is why the field of neurosci- very faint signal and reduce exposure ence seems better able to appreciate Smile for the camera innovations times. Other enhancements include the capabilities of technology. For sure, Speaking of low noise, Photomet- enhanced frame rate (100 frames/s exhibitors at Neuroscience dished up rics demonstrated how onboard soft- max at full resolution) and dynamic plenty to entice them. ware in its Prime sCMOS camera can range. To help you gauge the actual Many developers have innovated improve outcomes: Its PrimeEnhance QE that you will achieve (the 82% is at to ease the use of sophisticated tech. feature promises to reduce active shot about 600 nm wavelength), the com- For instance, dura- ble-equipment developer Sutter Instru- ment has paired with high-performance filter developer Sem- rock to offer filter changers specially designed for wavelength selection over a wide spectral range to any given nanometer value. Now, with the release of Semrock’s Versa- Chrome Edge filter technology, which allows selection of bandwidth as well as center wavelength (and blocking outside the passband with an additional filter), Sutter has released the VF-1 Edge system to ease selec- Neuroscience 2015 featured rotating poster presentations in the exhibit hall. (Courtesy of Coherent)

56 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_56 56 11/2/15 11:53 AM pany gave away slide rules that show for commercial release. Future SLM Optogenetics the camera’s photon output using grey development promises more exciting Among the many companies exhibit- levels or analog-to-digital units (the applications. ing optogenetics offering was Migh- measure that your imaging software Meadowlark Optics, a development tex, which showed its Optical Acti- uses to report intensity) in any region partner of BNS, also showed how high- vation, Stimulation and Imaging Sys- of an image. speed SLMs increase the number of 3D tem (OASIS) for in vivo and in vitro neuronal ensembles able to be excited research, and its new optogenetics Advanced spatial light modulators simultaneously. And Phi-Optics pro- starter kits—turnkey solutions for ChR2 While the average neuroscientist may moted Spatial Light Interference Micro- stimulation offering super-high out- not have known that spatial light mod- sopy (SLIM) as an add-on to all major put power (up to 7.2 mW with a 200 ulator (SLMs) can have dramatic impact brands of optical microscopes for quan- µm fiber) and ultra-low power variation on his/her experiments, a few exhib- titative cell imaging. (<2%) during rotation. itors demonstrated just that. Boul- ASI drew attention with an impres- Coherent discussed optogenetics der Nonlinear Systems (BNS) showed sive display of its dual inverted selec- research based on multiphoton exci- how next-generation SLMs are helping tive plane illumination microscopy tation principles for in vivo work: Its to drive scientific advances. The com- (diSPIM), which offers light-sheet exci- Chameleon and Fidelity products pany displayed PocketScope, a porta- tation and emission from both the right support standard imaging with flu- ble single-photon SLM microscope able and left. And Mad City Labs showed off orescent proteins, optogenetic acti- to image or photostimulate different its Kohler Illumination Tower, provid- vation, and monitoring of neuron regions of a sample simultaneously, with ing an extra-long working distance (>30 activity using genetically encoded 3D precision and at high frame rates. mm!) for use with live-cell chambers. Ca+ indicators. BNS is preparing the instrument, devel- Prior Scientific displayed a precision-con- For Part 2 of our Neuroscience cover- oped in the lab of Columbia Univer- trol setup that included a super compact age, please visit www.bioopticsworld.com/ sity neuroscience pioneer Rafael Yuste, 3-axis manipulator from Sensapex. worldview-blog.html.—Barbara Gefvert ULTRA PRECISE PIEZO-Z FOCUSING STAGE

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® OCT angiography: A new approach with ‘gold standard’ capabilities and more

CHIEH-LI CHEN, QINGIN ZHANG, ANQI ZHANG, and RUIKANG K. WANG

Optical coherence tomography angiography (OCTA) is a new imaging technique enabling the visualization of microcirculation in vivo with high resolution. Aided by data processing, it promises usefulness in the clinical monitoring and therapeutic treatment of various retinal pathologies.

Since its first demonstration in a bio- Photons Detected A-scan signals Subtracted signals medical application in 1991, optical A1 A2 coherence tomography (OCT)1 has be- Artery Vein A1 come an indispensable tool in routine Retina t1 Caused by blood flow clinical practice for anatomical (struc- Choroid A2 tural) imaging and therapeutic mon- Sclera itoring—especially in ophthalmology. 2 Recent advances in light sources Photons and detection techniques have enabled Red blood cell A1 A2 Artery OCT to advance and extend dramat- Vein Retina A1 ically, to the point of enabling func- t2 Choroid tional imaging. Now, a newly devel- A2 Sclera oped technique, OCT angiography (OCTA), is allowing the functional FIGURE 1. visualization of blood vessel networks How OCTA works: As moving blood cells pass through vessels, they generate in the eye. Inheriting all the advan- changes in OCT signals. Based on this concept, a blood flow signal can be extracted by tages of OCT—such as the ability to subtracting the OCT signals from the same location but at different time points (red path). The OCT signals will be different at these locations, while OCT signals from surrounding retinal generate cross-sectional images of bi- tissues will remain steady (blue path). ological structures in three dimensions (3D) with high sectioning resolution (1–10 µm)1—OCTA can provide moving particles (for example, red particles (such as red blood cells) in functional information about the dy- blood cells) as the contrast mechanism vessels. The signal from structural tis- namics of blood vessel networks in for imaging functional flows. To give a sue remains steady, while the signal vivo, without exogenous intravenous brief description of its operation, imag- from flowing blood changes over time. dye-injection.3 ine two OCT signals—one backscat- To differentiate the moving particles The concept of OCTA is to use tered from static structural tissue and from static tissue, repeated cross-sec- changes in OCT signals caused by the other backscattered from moving tional scans (B-scans) are performed

58 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_58 58 11/2/15 11:53 AM at the same location. Temporal changes of the OCT signal in adjacent scans a) caused by moving particles generate the angiographic contrast and allow visualization of the microvasculature in OCTA (see Fig. 1).

Compared to the ‘gold standards’ Compared with other functional imaging techniques, a key advantage of OCTA is that it is non-contact and noninvasive. Fluorescein angiography (FA) and indo- cyanine green angiography (ICGA) are the current “gold standards” for diagnosing vasculature abnormality in clinical practice. However, the invasiveness of the dye injection combined with possible adverse reactions, such as nausea or anaphylactic response in some rare cases, makes them unsuitable for widespread ophthalmic b) c) d) screening applications and for frequent monitoring. By contrast, OCTA enables visualization of ocular vessels by detect- ing the differences between cross-sectional scans without intravenous contrast agent or dye injection. Thus, OCTA may be a better alternative in longitudinal disease monitoring—especially for progressive FIGURE 2. (a) Wide-field imagery of the retinal vasculature of a healthy young woman was obtained diseases showing high correlation with by montage scanning protocol of optical microangiography (OMAG). Data are coded with different vessel dysfunction (such as age-related colors for each of three layers: red represents NFL, green is SRL, and blue is DRL. (b-d) exhibit the macular degeneration, diabetic retinop- magnified angiograms located in the white dashed boxes in (a), which better illustrates the high athy, and glaucoma) that may benefit from sensitivity of OMAG. OMAG angiograms corresponding to the white dashed boxes in (b) are shown early intervention or treatment. in (b-d), magnified to demonstrate the detail of blood vessels in different regions, including (b) optic In addition, OCTA is more time-ef- nerve head, (c) fovea, and (d) temporal region. The size of (a) is 12 × 16 mm2, while the size of (b-d) is ficient. It takes 10–30 min. for FA and 2.0 × 2.4 mm2. (Adapted from Q. Zhang et al. with permission5) ICGA imaging, while only a few seconds for OCTA to complete one volumetric Data processing can be roughly categorized, but not lim- scan. Thirdly, OCTA provides visual- Increased interest in OCTA has spawned ited into three groups: ization of in vivo vasculature in 3D with the development of numerous data-pro- 1. OCTA based on both the magni- microscopic resolution. Though FA and cessing algorithms. To classify them, the tude and phase of OCT signal (com- ICGA provide images with a wide field basic concept of OCT signal should be plex signal); of view, the images are two-dimensional introduced: Raw data in Fourier-domain 2. OCTA based on the magnitude of and therefore cannot provide depth in- OCT consists of spectral interferograms OCT signal; and formation of vasculatures. As a depth-re- captured by the detector. Fourier trans- 3. OCTA based on the phase of solved imaging technique, OCTA allows formation is applied to the raw data to ob- OCT signal. visualization of vessel networks at var- tain depth-resolved signals. After Fourier ious depths. These vessel networks can transformation, the OCT signal contains Optical microangiography (OMAG)- be segmented into specific retinal and both magnitude and phase information, based OCTA is one of the leading tech- choroidal layers to determine where the which have both been explored, indi- niques, employing the change of com- disease originates. Furthermore, the high vidually and together, to develop angioplex signal (both intensity and phase axial and transversal resolution of OCT graphic methods for the purpose of con- changes) to contrast blood flow in- systems enable detection of capillaries trasting blood flow within living tissue. formation. OMAG has been shown and visualization of microcirculation. Therefore, the various OCTA approaches to have ultra-high sensitivity to the

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a) b) c) the subjects. Four consecutive B-scans along the transverse direction were acquired at each fixed longitudinal location before the scanning probe pro- ceeded to the next location along the longitudinal direction. A sampling d) e) f) g) interval of approximately 9.8 µm was achieved in both di- rections to guaran- Structural OCT tee high-resolution Superficial layer angiograms. The Deep layer time difference be- Outer layer tween two adjacent B-scans was FIGURE 3. Optical microangiography (OMAG) and fluorescein angiography (FA) images illustrate intermediate, non-proliferative approximately 3.6 MacTel2. (a) An early-phase FA image shows hyperfluorescence in the temporal juxtafoveal region, while (b) a late-phase FA ms. A single-volume image shows increased and diffuse hyperfluorescence and leakage. (c) A composite en face color-coded OMAG demonstrates abnormalities that correspond well to the microvascular abnormalities seen in the early-stage FA image. (d) An en face OMAG dataset can be ac- image from the superficial retinal layer shows microvascular abnormalities in the juxtafoveal region, while (e) an en face OMAG quired in ~4 s. from the deep retinal layer shows the telangiectatic and dilated vessels in the middle retinal layers. (f) And an en face OMAG For later data image from the outer retinal layer shows subtle microvascular alterations in the outer retinal layers. (g) Finally, a horizontal central processing, OMAG B-scan shows the microvascular flow in different colors corresponding to the different segmented layers of the retina. Thinning of uses a complex val- the retina and disruption of the inner segment/outer segment/ellipsoid boundary are observed temporally in an area of abnormal ue differentiation retinal flow (green and blue). The size of (c-f) is 3 × 3 mm2. algorithm to ex- tract in vivo blood microcirculation.3,4 OMAG algorithm same spatial sampling rate as in the typ- flow information. has been implemented both in a 100 ical 3 × 3 mm2 field of view), which in- Retinal layer segmentation can be per- kHz 1 µm swept-source OCT (SS- creases effectiveness of OMAG for clin- formed to isolate specific retinal and OCT) prototype and a CIRRUS HD- ical practice. choroidal layers. Typically, three main OCT 5000 system (both by Carl Zeiss retinal layers are segmented: a superfi- Meditec, Dublin, CA) to conduct clini- Application in human studies cial retinal layer (SRL) that includes the cal evaluations. The CIRRUS HD-OCT OMAG has been widely applied in hu- ganglion cell layer and the inner plexi- 5000 system with AngioPlex OCT an- man eye diseases to provide more infor- form layer; a deep retinal layer (DRL) giography, which uses the OMAG al- mation about retinal and choroidal cir- that includes the inner nuclear layer and gorithm, operates at a central wave- culation. Several studies were conducted the outer plexiform layer; and an out- length of 840 nm and a speed of 68,000 using both a CIRRUS HD-OCT 5000 er retinal layer (ORL) that includes the A-scans/s, and is the first and only prototype with active motion-tracking outer nuclear layer and the external lim- OCTA technology to have received capability and a prototype 1 µm SS-OCT iting membrane. The segmentation can clearance from the U.S. Food and Drug system (with center wavelength at 1060 also be used to separate the choroid into Administration (FDA). nm).6 For the CIRRUS HD-OCT 5000 choriocapillaris and deep choroid layers. A key feature of CIRRUS HD-OCT prototype, a montage scan protocol en- The segmented layers can be adjusted to 5000 is an active eye-tracking mecha- abled by motion-tracking capability cen- provide a better presentation of the vas- nism able to trace and compensate eye tered at the fovea was used to acquire vol- culature for various ocular pathologies. motion in real time, and provide mo- umetric datasets with 10% area overlap Finally, the en face vascular images are tion-artifact-free angiographic images.5 It between adjacent dataset for later mon- created by using a maximum (or aver- allows wide-field imaging (>10 × 10 mm2) taging.5 For the SS-OCT prototype, a sin- age) projection method within the lay- without sacrificing resolution (that is, the gle volumetric scan was acquired from er of interest and then used to correlate

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the findings between OMAG and con- involvement in this disease. But the re- a useful and powerful tool for diagno- ventional methods (FA/ICGA images). sults provided by OMAG hold prom- sis, detection, and monitoring of vari- Figure 2 shows a wide-field OMAG ise for the evaluation of patients with ous ocular pathologies. angiogram enabled by real-time mo- MacTel2 and other diseases affecting tion-tracking of normal retinal vascula- the microvasculature (see Fig. 3).6 One REFERENCES ture, captured with CIRRUS HD-OCT 3D dataset processed with OMAG takes 1. D. Huang et al., Science, 254, 1178–1181 (1991). 5 5000 system. Three layers were seg- <4 s to acquire and has none of the po- 2. C. R. Baumal, Curr. Opin. Ophthalmol., 10, mented to give a better demonstration tential adverse events associated with 182–188 (1999). according to depth. Figure 2a shows the FA. Further studies are needed to quanti- 3. R. K. Wang, IEEE J. Sel. Top. Quantum results of the wide-field OMAG angio- tate vascular caliber, density, and blood Electron., 16, 545–554 (2010). 4. R. K. Wang, L. An, P. Francis, and D. Wilson, 2 gram (~12 × 16 mm ), including nerve flow in the central macula and identi- Opt. Lett., 35, 9, 1467–1469 (2010). fiber layer (NFL), SRL, and DRL. fy whether changes in these parameters 5. Q. Zhang et al., J. Biomed. Opt., 20, 066008 Macular telangiectasia type 2 predict disease progression or response (2015). (MacTel2) is a bilateral retinal disease to future therapeutic interventions. 6. M. R. Thorell et al., Ophthalmic Surg. Lasers Imaging Retina, 45, 369–380 (2014). that presents with asymmetric severity The vascular en face images from during the fifth to seventh decades of OMAG are comparable to the cur- Chieh-Li Chen, Ph.D., Qinqin Zhang, life and affects the juxtafoveal region rent gold standard, and further pro- Ph.D., and Anqi Zhang, Ph.D., are se- of the macula. The pathogenesis of the vide angiograms with high resolution nior research fellows, and Ruikang K. disease is unknown and currently, there and the depth information of patholo- Wang, Ph.D., is a professor, all in the is no proven treatment. Until recently, gies. Though currently there is no stan- Bioengineering & Ophthalmology OCT has been unable to provide infor- dard way of evaluating OCT angiogra- Department at the University of mation on the functional microvascula- phy and new clinical endpoints must be Washington, Seattle, WA; e-mail: ture in the central macula and unable to established with larger studies, OMAG [email protected]; http://depts.washing- provide information about blood flow has demonstrated its potential as being ton.edu/wangast.

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1511lfw_61 61 11/2/15 11:54 AM CONNECTING MINDS.

BiOS• BIOS IS THE WORLD’S LARGEST BIOMEDICAL OPTICS CONFERENCE, PART OF PHOTONICS WEST

BiOS—Biomedical Optics The Moscone Center Translational Research San Francisco, California, USA LASE—Lasers and Sources Conferences & Courses OPTO—Optoelectronic Devices 13–18 February 2016 Green Photonics 3D Printing Photonics West Exhibition Industry Panels and Keynotes 16–18 February 2016

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1511lfw_62 62 11/2/15 11:54 AM FLUORESCENCE-GUIDED SURGERY

Advanced surgery: NIR fluorescence guidance arrives

DAVID J. BURRINGTON

To resect an entire tumor while avoiding healthy tissue, surgeons must be able to see relevant details invisible to the naked eye. Optical imaging with targeted contrast agents have demonstrated efficacy in clinical trials to enable better visualization for better outcomes—now, refinement and commercialization efforts aim to eventually bring them to the surgical suite.

As much as surgeons might wish for Even a thin layer of blood or tissue, cancers are left behind during the initial “x-ray vision,” the reality is that the just hundreds of microns in depth, can surgery,1 resulting in the need for either human brain and eyes are restricted to completely obscure a surgeon’s vision. repeat surgery and/or adjuvant therapy. perceiving a very narrow sliver of the Some objects, such as malignant tu- Conversely, objects such as blood vessels, electromagnetic spectrum called visible mors, need to be resected fully for cure, nerves, and bodily lumens need to be light, which spans roughly 400–700 but finding small collections of cells in avoided, as damage to them during sur- nm. Because of this, many objects able the context of normal tissue remains a gery results in high morbidity.2,3 to provide helpful information during significant challenge. For example, even surgery are invisible to the unaided eye. today, between 30 and 40% of all breast Expanding the surgeon’s view There is a constant tension in modern

800 nm >781 nm oncologic surgery between the diametri- NIR long-pass cally opposed goals of maximizing both camera ≥ 770 nm 700 nm tissue resection and tissue avoidance: D2 685-735 nm NIR • Take out too much tissue and the can- band-pass ≤ 740 nm camera cer might be cured, but complications from the surgery create a lifetime of suffering caused by a combination of Color physical and/or emotional pain and 400-650 nm Module Wavelength(s) D1 video follow-up care costs; or ≤ 650 nm band-pass camera White 400 - 650 nm • Remove too little tissue and the can- 665 nm 665 ± 3 nm 760 nm 760 ± 3 nm cer may spread and kill the patient.

Solving this conundrum is the reason Surgical field John V. Frangioni, M.D., Ph.D., developed FLuorescence-Assisted Resection FIGURE 1. All FLARE imaging systems permit simultaneous, real-time acquisition of color video and Exploration (FLARE) technology4 and provide two independent channels of NIR fluorescence without moving parts. while he was a full-time Professor of

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Medicine and Professor of Radiology at and Europe). NIR-depleted white light Harvard Medical School (Boston, MA). and two independent channels of NIR FLARE is an optical imaging platform excitation light illuminate the field-of- that combines state-of-the-art engineer- view (FOV), while three independent sen- ing and chemistry to solve important bio- sors image the FOV simultaneously and medical problems. Rather than being con- in real time. The table summarizes the strained to visible light, FLARE expands system’s optical characteristics. on the the spectrum of the surgeon’s vision up to Every FLARE imaging system is able to 900 nm. In fact, this critical region from display four independent video streams, cutting 700 to 900 nm, termed the near infra- including a color video image of the sur- red (NIR) “window,” is where the absor- gical field (i.e., what the surgeon is ac- bance curves for biomolecules that consti- customed to seeing), two independent tute living tissue all reach local minima. channels of NIR fluorescence emission But absorbance is not the only rea- (one centered at 700 nm and one at 800 edge son the NIR window is so important. nm), and a merge of all three (see Fig. 2). Wavelength-dependent scatter and auto- The merged image permits a range of op- fluorescence are also much lower in the tions, from simple overlay of images to the most versatile NIR compared to the visible. The final real-time ratiometric imaging—which sCMOS camera portfolio key property of NIR light is invisibility unlocks the potential of next-generation on the market itself. Because the surgeon can perceive contrast agents that respond to environ- NIR light only as a faint red glow with- mental stimuli. out assignment of wavelength or intensi- In fact, FLARE’s dual-NIR channel ca- ty, light used for both excitation and flu- pability solves that longstanding problem small orescent emission can be made invisible. of opposing goals: One NIR channel can deep Being invisible means no change to the be dedicated to tissue resection and high- form factor look of the surgical field—so surgeons lighted using one color in the merged im- cooled can operate as they normally do. age, while the other independent chan- Because of the invisibility of NIR light, nel can be dedicated to tissue avoidance two innovations are needed to make the and highlighted with a different color— technology work: an imaging system that all in real time. generates and “sees” otherwise invisible NIR fluorescent light, and targeted con- Wavelength with targeting trast agents having the desired NIR emis- Developing NIR fluorescence contrast sion wavelength. FLARE accomplish- agents that have the desired emission wave- es the former using the optical system length and desired targeting is a daunting shown diagrammatically in Fig. 1 (which task. FLARE accomplishes this in two is the subject of issued patents in the U.S. ways. The first is the traditional approach of covalently conjugating a Optical characteristics of FLARE targeting ligand to a NIR flu- Aberration correction 400–900 nm orophore. Unlike convention- Parfocality 400–900 nm al NIR fluorophores, however, Transmission ≥ 90% (400–850 nm) FLARE uses a novel and pro- Distortion < 1% prietary class of “zwitterionic” special NIR fluorophores that have new Vignetting < 5% microscopy geometrically balanced, elec- models Telecentricity < 5° readout trically neutral polyionicity.5-7 edge 4.2 LT modes Working distance 12–18 in. (variable) These physicochemical prop- &edge 3.1 FOV 0.9 cm diameter at 12 in. WD to 25 cm erties result in extremely low diameter at 18 in. WD non-specific binding and up- Zoom 15X (motorized) take in vitro and in vivo, and www.pco.de Focus Motorized thus extremely low non-spe- www.pco-tech.com System resolution 70 µm (max. zoom) to 700 µm (min. zoom) cific background. Zwitterionic at 15 in. WD NIR fluorophores are

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available at 700 nm (e.g., ZW700-1 Forte chemistries. The Forte line of zwitterionic The second approach to targeted NIR and its derivatives) and 800 nm (ZW800- NIR fluorophores also provides extraor- fluorophores is called “structure-inher- 1 and its derivatives; see Fig. 3), as well dinarily high (>90% at 24 h) stability in ent targeting.”8 For this class of FLARE as in a variety of conjugation and linker warm serum. molecules, the targeted moieties are graft- ed onto the resonant backbone of a NIR File management, scripting, and settings fluorophore such that targeting and fluorescence is accomplished as a single molecular en- tity. To date, peer-reviewed literature from Dr. Frangioni’s company, Color NIR channel video #1: 700 nm Curadel, has addressed fluorescence structure-inherent targeting to cartilage, bone,

FIGURE 2. FLARE provides real-time data acquisition and data analysis of four independent video streams, and presents this information through a streamlined graphical user interface. For this example, the 700 and 800 nm NIR fluorescence channels are NIR channel #2: Real-time merge of color, pseudo-colored green and red (respectively) in 800 nm fluorescence NIR channel #1, NIR channel #2 the merged image.

ƙƆƏƇƓƚŭƑƋƌƊƍƛƚŮƆŵƊƋƇżƚƜƓƑƋƇƝżƚƞƟƠżƚƁơ ƕƥƜƚƅŮŮƚƗƥŭƢƣƢƥƧƢƧƨƚƩƚƅƪƣƥƙƅƣƢƥƧƚƅƗƗŮƢƫƅƣƢƥƧŭ

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ƎƓƆƏƊƚƫƓƆŴżƚƕŴƊŹŸƇƊƍ ŭƑƊźźƊƇƚƩƚơƫƚƙƓƑƓƇƍ ƥŻƔŸŶůźƇŸŻůůůůƍŴƀƘųƦźŴƤŸƇů ŭŮůŰŭűŲųŴŵůŮŶųŷŸŹźŻŶŷŻżůůŽžſƀſƁƂƀƁƃŽƄů

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ƎƋƏŸŸƐƈŭƑƋƌƊƍƈ ƕŴƊŹŸƇƊƈŭƑƋƌƊƍ ƅƆƇƈƉƊƋƇƆŵƌƍƈ ƗƆƊƘƓƈƙƊƏŻƋŵƆƏƍ ƒƊŹƋźƓƔƍƈ ƉƊƋƐƈŭƑƊƊƇƆŵƌ ƙƆŵƆƈŭƑƋƌƊƍƈ ƕƆƖƊƇƈƅŴƆƌŵƐƊŵƑƈ

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1511lfw_66 66 11/2/15 11:54 AM parathyroid glands, thyroid glands, and a) OO– adrenal glands, to name a few applications.

– – O O O O Availability S S O O Curadel is currently refining and commer- O cializing FLARE technology. Because of + N N the future clinical potential of the technology, and to avoid any possible confusion + + N N by consumers, the company conducts its development and commercialization activi- NEW!NEW! ties through two separate companies, with HLD117 Linear b) Motor Series Stages separate product offerings and labeling. Curadel ResVet Imaging (CRV) already MICROSCOPE AUTOMATION & manufactures and sells NIR fluorescence ILLUMINATION SOLUTIONS imaging systems and contrast agents un- From the highest precision linear der the Lab-FLARE brand for laboratory motor motorized microscope stages research (not for diagnostic or therapeu- to the most advance fluorescence tic use), and will eventually offer prod- illumination systems, Prior Scientific ucts for veterinary applications under manufactures the highest performing the Vet-FLARE brand. CRV launched and most reliable microscope its flagship open-space imaging system, automation equipment available. the Lab-FLARE Model R1 (see Fig. 3) and Fluorescence Illumination its first 11 NIR fluorescent contrast agents FIGURE 3. The carboxylic acid form of at the 2015 World Molecular Imaging zwitterionic NIR fluorophore ZW800-1 (CAS Congress (September 2, 2015; Honolulu, #1239619-02-3) in two dimensions (a) and 3D HI). It will soon launch its first minimal- with positive (red) and negative (blue) charges ly invasive imaging system, the RF1, at geometrically and electrically balanced over the molecular surface (b). the European Molecular Imaging Society

FIGURE 4. The fully mobile, 3R guideline-compliant 6-DOF articulating arm Lab-FLARE Model Sample Handling R1 Open Space Imaging System for Laboratory Research features a long- reach articulated arm that positions Calibration well the imaging head Imaging in 3D space. The head white light source provides illuminance Physiology Solutions of ≥ 20,000 lux at 15 in. WD; ≥ 85 CRI; and a color Scientific temperature of 4500 K. The GPIO laser source generates light Keyboard and switches at 660 nm (4 W total power) and 760 nm (10 W total power) wavelengths, while the NIR excitation fluence Universal Bluetooth AC power rate is ≥ 4 mW/cm2 at 660 wireless footswitch nm and ≥ 10 mW/cm2 at 760 nm. 800-877-2234 www.prior.com

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meeting (March 2016). Over the coming the FLARE imaging system because there ResVet Imaging are registered trademarks of year, CRV will expand its first 11 contrast weren’t enough contrast agents to use on it. Curadel, LLC. agents for laboratory research to over 40 So, once we developed the imaging system, REFERENCES agents capable of a variety of NIR fluores- we turned our attention to contrast agents 1. R. G. Pleijhuis et al., Ann. Surg. Oncol., 16, 10, cence imaging tasks in vitro and in vivo, and invented both zwitterionic NIR fluo- 2717–2730 (Oct. 2009). and it will continue its efforts aimed at rophores and structure-inherent targeting. 2. M. D. Michaelson et al., CA Cancer J. Clin., 58, 4, bringing the Vet-FLARE line of imaging Now we’re told that there is no market for 196–213 (Aug. 2008). 3. W. A. Macrae, Br. J. Anaesth., 101, 1, 77–86 (Jul. systems for veterinary surgery to market. optical imaging, and bringing contrast 2008). The ultimate goal of FLARE is to em- agents to regulatory approval will be too 4. S. Gioux, H. S. Choi, and J. V. Frangioni, Mol. power surgeons to perform better sur- difficult and expensive. Well, OK, but af- Imaging, 9, 5, 237–255 (Oct. 2010). gery. All FDA- and EMA-regulated prod- ter proof of principle of the technology in 5. H. Hyun et al., Mol. Imaging Biol., doi:10.1007/ s11307-015-0870-4 (Jun. 18, 2015). ucts for human use are being developed clinical trials involving over 500 patients 6. H. S. Choi et al., Nat. Biotechnol., 31, 148–153 by Curadel’s second subsidiary, Curadel worldwide, and with all studies published (Feb. 2013). Surgical Innovations (CSI). CSI plans to in peer-reviewed journals, naysayers are 7. H. S. Choi et al., Angew. Chem. Int. Ed., 50, 28, offer imaging systems and contrast agents running out of excuses.” 6258–6263 (Jul. 4, 2011). 8. H. Hyun et al., Nat. Med., 21, 2, 192–197 (Feb. under the Med-FLARE brand. At present, The promise of NIR fluorescence guid- 2015). however, none of CSI’s products have been ance are procedures that are faster, better, approved by regulatory bodies, but efforts and cheaper. Only time will tell if these David J. Burrington, M.Ed., is quality are currently underway to obtain market- goals are met, but at least for the time be- system manager with the Translational ing authorization. ing, NIR fluorescence is finally seeing the Cancer Imaging Facility at Beth Israel For Dr. Frangioni, this has been a 15- light of day. Deaconness Medical Center (Boston, year road that has been neither straight MA); e-mail: centerformolecularimag- ACKNOWLEDGEMENTS nor flat: “When we first started, we were FLARE, Lab-FLARE, Vet-FLARE, Curadel, [email protected]; www.center- told that it was a waste of time to develop Curadel Surgical Innovations, and Curadel formolecularimaging.org/tcif.

Available for femto- and picosecond pump sources Levante IRNSP + HarmoniXX DFG

High Power MIR Source for Spectroscopy

ï Covers 1.4 ... > 15 µm @ 80 MHz repetition rate ï High average power of up to 50 mW @ 6 µm ï Direct excitation of vibrational levels in the MIR

ï Supports bandwidth for few cycle pulses in the MIR (fs version)

ï Narrow bandwidth (10 cm-1) for high resolution (ps version) ï Easy tunability

Angewandte Physik & Elektronik GmbH [email protected] www.ape-berlin.de

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1511lfw_68 68 11/2/15 11:54 AM LASERS ■ OPTICS ■ DETECTORS ■ IMAGING ■ FIBER OPTICS ■ INSTRUMENTATION New products Would you like to be included? Please send your product description with high-resolution digital image to: [email protected]

Tunable Portable optical optical filter profiler The OSG100 is an ultrahigh isolation-programmable The Nomad portable opti- optical filter that enables the creation of arbitrary filter cal profiler enables 3D non- shapes, with isolation exceeding 60 dB for testing and contact metrology on sam- experimentation. The filter allows tuning of frequency, ples that were previously impossible or impractical to passband, and power level in spectrum slices of 12.5 measure. It uses the company’s Coherence Scanning GHz centered on the ITU grid, and is controlled using Interferometry (CSI) and SureScan technologies for an intuitive but powerful graphical user interface for vibration robustness, its range of parfocal objectives generating arbitrary filter shapes. from 1.4 to 100x magnification, and its Mx software InLC Technology for enhanced data visualization and quantification of Gwangju, Korea step heights, texture, and volumetric features. www.inlct.com Zygo Middlefield, CT www.zygo.com

DPSS laser system for lidar The HLS DPSS laser system is designed for airborne Terahertz time-domain spectrometer lidar data collection. It combines a proprietary short-

A terahertz time-domain spectrometer integrates pulse laser with Yb-doped fiber and Nd:YVO4 ampli- sub-surface scanning and 3D imaging functionalities. fiers for up to 2 mJ pulse energies at 532 nm, with 2 Featuring a proprietary dendrimer dipole excitation M <1.5 TEM00 beam quality at 10 kHz and above. It (DDE) continuous-wave (CW) terahertz source, the produces a stable temporal pulse shape of <1.5 ns spectrometer has use in molecular investigations. pulse width at <100 ps jitter. ARPhotonics CEO Laser Harrisburg, PA St. Charles, MO http://arphotonics.net http://cuttingedgeoptronics.com

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3X zoom lens at reduced resolution. Weighing 1.6 kg, the one-piece camera The MicroMate 3X Zoom lens system images has 4, 8, and/or 16 GB memory options. onto a 4/3 in. sensor and retains the same pixel Photron resolution across the entire field. It images onto San Diego, CA sensors with diagonals up to 22.5 mm with no www.photron.com vignetting. With a large field of view and fixed pupil position, the lens offers a fixed NA over UV-enhanced silver mirror coatings the entire zoom range. The #4000 and #4100 silver-based UV-enhanced mirror coat- Navitar ings overcome the inherent reflectivity limitation of silver Rochester, NY below 450 nm and deliver broadband reflectivity >98% from www.navitar.com 400 nm to the mid-IR wavelength range. These coatings High-speed camera are suited for military optics, The FASTCAM Mini AX100 high-speed camera offers light telescopes, spaceflight hard- sensitivity of ISO ware, analytical instruments, 40,000 for mono- and ultrafast Ti:sapphire lasers. chrome and ISO Acton Optics 16,000 for color. It Acton, MA provides 1024 × www.actonoptics.com 1024 pixel resolution at up to 4000 Servo amplifier frames/s and The QD-2000 servo amplifier is a class-0 servo amplifier that 540,000 frames/s features a single output power amp with up to 30 W output power, dual push/pull output, and analog input (+10). Available in single-axis and open-frame Piezo Stages Positioning Technology configurations, it has over/under voltage protections for laser systems and scanning mirrors. Nutfield Technology www.piezosystem.com Hudson, NH Series Scan XY www.nutfieldtech.com ñ Piezo Controlled Movement Scientific OPO platform High Speed Scan Stages for Laser Beam Coupling A scientific optical parametric oscillator (OPO) platform for fully automated, synchronously pumped OPOs features rede- veloped control and Ůŭ Free inside space software architecture, Ůŭ Customized design automated tuning Ůŭ Precise movement and control via a PC, and extensive log files and remote access. It is available for the Levante IRNSPfs, Levante EmeraldNSP, and Ti:sapphire pumped OPONSP-X. APE DE (+49) 36 41 66 88 0 Berlin, Germany US (+1) 508 634 - 6688 www.ape-berlin.de [email protected]

70 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_70 70 11/2/15 11:54 AM New products VCSELs Highest Efficiency(>63%) Optical design software Highest Reliability TracePro v7.7 optical design soft- Highest Power (watts to kW) ware features a Candela plot viewer For all types of illumination- 3D, Virtual and Augmented Reality, Automotive illumination and LIDAR, Pumping, Line generators ìIlluminator for Google Tangoî

Our VCSEL Key Differentiators: ï Low cost surface mount packaging ï High efficiency (>63% ) ï High power- kW from one chip and an automotive lighting toolkit. ï Highest reliability with new Photorealistic rendering capability has process- MTTF of >100 years@70 0C smart stage rotates the pre-mounted been improved for 3D visualization of ï Supply with diffusers for higher aluminum-coated mirror ±20° at up to the output performance of luminaire divergence 1100°/s. Applications include medical or light pipe design. Users may now ï 650 to 1064nm- any wavelength lasers and imaging systems, industrial choose whether to use simulation or measurement and spectroscopy instru- VCSEL with analysis modes for ray tracing. diffuser to ments, and laser printing and engraving. Lambda Research change the New Scale Technologies divergence Littleton, MA Victor, NY angle to ña www.lambdares.com max of- www.newscaletech.com 110x85 deg Imaging spectrographs The MS260i 1/4 m imaging spectro- SLM picosecond laser 2kW-808nm The Pico series laser delivers 10 W of graph is designed for applications in VCSEL side TEM (M2<1.3) at 1064 nm with 150 pumping5W VCSEL the 200–1350 nm spectral range. Each 00 ps pulses at up to 300 kHz. The output modulefrequency pre-configured model comes with a doubled is single longitudinal mode (SLM) with green Laser 10 pm linewidth. The laser requires 24 for laboratory V DC input and is tap water-cooled. applications

Applications include micromachining, ablation, scribing, lidar, nonlinear optics, and other industrial, medical, military, and R&D tasks. Applications: RPMC Lasers ï IR Illumination-security, automotive O’Fallon, MO ï Laser heating ï high-line-density ruled triple grating and www.rpmclasers.com 3D printing ï input slit. Available options include slit 3D Imaging Illumination source- Structured Light, Time of Flight, etc type, number of output ports, and com- UV-curable epoxy system ï Sensor applications, single mode munication interfaces. UV22 is a one-component, nanosilica- devices (mW to 5W single mode) Oriel Instruments filled UV-curable epoxy system that ï Rapid Drying for Printing Irvine, CA ï Frequency doubled blue and green www.newport.com/MS260i lasers ï Pumping- Nd:YAG and Er:Glass Miniature positioning system The DK-M3-RS-U-1M-20 piezoelectric mirror positioning system has a galvo-scanner form factor and mea- www.princetonoptronics.com sures 12 mm in diameter, including the [email protected] embedded closed-loop controller. The (609) 584-9696 ext. 107

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meets NASA low outgassing specifica- Plasma profiling instrument Light-shaping diffusers tions. At 75°F, the system offers viscos- The Plasma Profiling time-of-flight mass for simulation library ity of 1000–8000 cps, tensile strength spectrometer (PP-TOFMS) provides Proprietary Light Shaping Diffusers >7000 psi, abrasion resistance, optical chemical composition as a function (LSDs) have been added to OPTIS’s clarity, and thermal stability up to 350°F. of depth of solid materials. It provides SPEOS optical modeling and simulation It cures quickly when exposed to a UV standard-free, instantaneous semi- library. This adds simulations with light light source via a cationic reaction. using holographic patterns imbedded Master Bond on polycarbonate, acrylic, and poly- Hackensack, NJ ester substrates. The diffusion ability www.masterbond.com allows engineers to design energy-efficient and low-profile subsystems with Bidirectional IL/ high uniformity. RL test system Luminit The OP940-OP725 bidirectional IL/RL Torrance, CA test system has had new revisions to the www.luminitco.com insertion and return loss meter, allow- quantification analysis of a sample with Hyperspectral an atomic concentration range span- sensor systems ning orders of magnitudes in a single AisaKESTREL pushbroom hyperspectral measurement. It can analyze conductive sensor systems are designed for UAVs and non-conductive materials from inor- and other platforms of limited payload ganic to hybrid. Horiba Scientific Edison, NJ www.horiba.com/scientific Adjustable rigid ing direct control via USB link. Operators post mounts may obtain real-time IL/RL results or The HZP Series adjustable rigid post reflectance scans in either direction. The mounts have use in electrophysiology system can also be used as a 2 × 2 opti- applications. Compatible with upright cal switch with the company’s software, and inverted microscopes and available size. The 5 kg sensor detects vegetation, making any source unit bidirectional. in four different heights, they work with water, or soil attributes of minute spec- Sensapex zero-drift solid-state and other tral differences, providing radiometrically OptoTest and spectrally stable data with high sig- Camarillo, CA nal-to-noise ratio and spatial resolution www.optotest.com of 2048 pixels. The AisaKESTREL10 is for High-speed video camera 400–1000 nm and the AisaKESTREL16 for 600–1640 nm. The Hyper Vision HPV-X2 high-speed Specim video camera features a FTCMOS burst Oulu, Finland image sensor that increases photosen- www.specim.fi sitivity by six times more than previous models. It features high-speed record- X-Y stage ing at 10 million frames/s. It has use The KT210-EDLM X-Y Stage features an common micromanipulators. They offer in observing phenomena, such as the internal motor and controller. Measuring interaction of cancer cells, the auto- a 60° sliding dovetail for stable position- motive fuel injection process, and the ing, and are compatible with 1/4-20 and printer ink ejection process. 6 mm optical breadboards. Shimadzu Prior Scientific Kyoto, Japan Rockland, MA www.ssi.shimadzu.com www.prior.com

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50 × 210 mm, it offers travel of 100 × 100 mm and includes low-profile, direct-drive ironless linear motors. Suited for life science, semiconductor, fiber optics, and micromachining applications, accuracy is 13.6 μm with repeatability of 2.7 μm. Steinmeyer Burlington, MA www.steinmeyer.com Fiber laser The Highlight FL series fiber laser delivers output powers to 4 kW. Using a modular architecture, OEM customers and system integrators may select turnkey We have systems or build custom fiber DETECTORS with laser systems. Available at all power levels with various output delivery fiber options, they are Super Powers optimized for cutting and welding metals and alloys. Coherent Santa Clara, CA www.coherent.com High-speed cameras The Phantom v2512, v2012, v1612, and v1212 1 Mpixel ultrahigh-speed cameras are now available with 72, 144, or 288 GB of memory. The cameras use 1 and 2 TB CineMag IV to quickly record data to a large amount of non-volatile storage. All models are equipped with 10 GB Ethernet and are able to transfer data at up to 500 MB/s HP & Super HP Detectors on optimized systems. Vision Research Up to 100 kW Wayne, NJ www.visionresearch.com We have a complete line of High Power Detectors for Tunable lasers measuring multi-kW lasers. The TSL-550 tunable laser features mode-hop-free tuning We offer standard detectors, available off the shelf, with with output power of 10 dBm and signal-to-noise ratio of 90 LEARN regular models up to 12 kW dB/0.1 nm. A unique cavity design is used to lower the optical and custom-made detectors, MORE ASE noise. The fully programmable laser is designed for preci- available on demand and sion optical testing in the 1260–1360/1500–1630 nm wave- designed for your needs. at length ranges. Square, round or even gentec-eo.com/ Santec rectangular apertures are SuperHP Komaki, Japan possible and skyís the limit www.santec.com in terms of maximum power! Optical shaft measurement system Designed to provide fully automatic measurement of smaller shafts and turned parts directly on the shop floor, the

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its own trigger, gate, delay, and width Nanopositioner settings. It provides precise timing up The PIHera Z flexure-guided piezo to 1000 s, with 250 ps width and delay nanopositioning stage has travel ranges of 50 to 250 µm or 400 µm open- loop. Flexure-guided piezo positioning stages provide vibrationless motion. It is equipped with absolute-measuring, direct-metrology capacitance sensors and provide resolution down to 0.1 nm MarShaft SCOPE 250 plus features a in a compact, FEA-optimized package matrix camera with four million pixels. for high stiffness and long lifetime. It measures parts up to 250 mm long PI (Physik Instrumente) and 40 mm in diameter with a maxi- Auburn, MA mum permissible error (MPE) of <1.5 www.pi-usa.us resolution and < 200 ps internal jitter. μm + L/40 for diameter and <3 μm + Optical electrical outputs and inputs L/125 for length. Interferometer are available. Mahr Federal The SP1500 C interferometer from SIOS Saelig Providence, RI Messtechnik GmbH has a measuring Fairport, NY www.mahr.com range of > 15 m and has been designed www.saelig.com for high-precision length, angle, and OTDR platform straightness measurements of linear A suite of optical time-domain reflec- Coordinate measuring axes. It uses a rotatable measuring tometry (OTDR) solutions for embed- machine The XM Series handheld probe coordi- ded network monitoring applications nate measuring machine is designed to achieves instrumentation-level per- be easily installed in any environment formance in a compact form factor. and allow operators to perform accu- Designed for both central office and rate 3D measurements. Operation does field monitoring applications, the not require any foundation or ancillary platform provides a high dynamic range and spatial resolution using low reflector consisting of hollow retro optical power. reflectors and a rotatable Wollaston II-VI prism. Calibration software and a USB Pittsburgh, PA interface are included. www.ii-vi-photonics.com Armstrong Optical Northampton, Northamptonshire, Positioning stage England The Lintech 610 series positioning stage www.armstrongoptical.co.uk provides a 7780 lb. load capacity and is available in stroke lengths from 6 to 60 SXR spectrometer in. The enclosed, screw-driven slide uses The Model 251MX soft x-ray spectrom- a low-friction, preloaded, recirculating eter includes a new gold-coated dif- linear ball bearing system riding on pre- fraction for work from 20 to 80 nm, for cision ground linear rail guides. measurements of soft x-ray, extreme LinTech ultraviolet, and vacuum ultraviolet spec- Monrovia, CA equipment, and operating ranges are tra. It includes an adjustable-width slit www.lintechmotion.com 50°–95°F and 20–80% RH. The system and adjustable detector mount. It oper- -6 -10 automatically records and saves all ates at 10 torr vacuum, with a 10 Pulse generator measurements. torr version available. The Model 577 digital delay/pulse gen- Keyence McPherson erator offers 4 or 8 channels, with each Itasca, IL Chelmsford, MA output individually configurable with www.keyence.com/XMPR09 www.mcphersoninc.com

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1511lfw_74 74 11/2/15 11:54 AM Manufacturers’ Product Showcase

SuperGamut™ High-performance Spectrometer Narrowband Optical Power Measurement BaySpec’s high- Ophir Photonics, performance global leader in SuperGamut™ precision laser spectrometer measurement is designed to equipment cover the full and a Newport spectral range Corporation of 200-2500 nm Company, or your specific introduces a wavelength new system for range with optimized performance and resolution. The narrowband unique turn-key system allows single acquisition for the optical power measurement, the 3A-IS Optical Power Sensor entire wavelength range with ultrafast speed (up to 5K Hz). and AUX-LED Self-Absorption Accessory. The 3A-IS is a Utilizing BaySpec’s patented VPG® grating technology, the compact, easy-to-use integrating sphere and photodiode spectrometer features compact size, high throughput with sensor system. It is designed to measure the optical power low stray light, and no moving parts with superb stability of divergent, narrowband light sources from 350nm–1100nm, and reliability. Numerous SuperGamut have been shipped such as lasers and LEDs. to date covering broad application areas such as OEM integration, light source measurement, radiometry and optical metrology.

www.bayspec.com [email protected] • +1 435-753-3729 [email protected] www.ophiropt.com/photonics

A Quantum Leap in Piezo Nanopositioning 1919-R High Performance Optical Power Meter Aerotech’s QNP Series piezo nanopositioning stages offer Newport’s new 1919-R nanometer-level performance in a compact, high-stiffness High Performance package for X, Optical Power Meter will XY and Z axis be released in October. applications. A It features on-board variety of travel processing for advanced and feedback math and statistics options make functions, a color screen, them ideal for and a comprehensive applications menu structure allowing from microscopy an easy access to key to optics alignment. functions. Best-in-class stiffness and resonant frequency enable high process throughput and fast closed-loop response, and unparalleled geometric performance. The Ensemble QLAB stand-alone, piezo motion controller provides up to four axes of open- or closed-loop control. The front panel interface allows quick execution of simple operations such as jogging and moving to fixed positions. Onboard memory stores programs for more complex operations.

(800) 222-6440 www.aerotech.com www.newport.com

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New Laser Spectrum Analyzer Bristol Instruments has introduced the model 771, a unique instrument that operates as both Award-Winning Illumination a high-accuracy Design, Analysis, and wavelength meter and Optimization Software high-resolution spectrum Luminaire Design analyzer. It is for LED Integration researchers who Light Pipe Design Design Optimization need to know Biomedical Optics the spectral Stray Light Analysis properties of their CW and high-repetition rate pulsed lasers that operate from 375 nm to 12 μm. Absolute laser TracePro streamlines your prototype-to-manufacturing wavelength is measured to an accuracy as high as ± 0.0001 process with: nm, and the laser’s spectrum is determined to a resolution Photorealistic Rendering as high as 2 GHz. What’s more, these specifications Displays luminance and radiance maps as true color, images based are guaranteed by continuous calibration with a built-in on wavelength or as a photorealistic rendering using source and optical properties of the model wavelength standard, thereby ensuring the most meaningful Light Source 2D & 3D CAD Interface Materials experimental results. Includes catalogs of LED Optimization Enables geometry & Surfaces surface sources from major Sophisticated 2D and 3D layout with familiar Applies range of material manufacturers and imports optimizers provide complete CAD tools and gadgets and surface properties source manufacturer ray fi les and interactive control to objects and surfaces

REQUEST A FREE 30-DAY TRIAL TODAY www.lambdares.com

ůŰůűŲųŴűųŵųŶŷŸŷŹŹŹźŻżŽžſƀƁűŽƂžſźƃƀƄŷŷ 25 Porter Road | Littleton, MA 01460 USA ŽƂƅƀƆŻżŽžſƀƁűŽƂžſźƃƀƄ Phone: +1 978-486-0766 | Web: lambdares.com [email protected]

Mid-IR Optical Isolators

ONLINE

EOT’s Mid-IR Optical Isolators maintain excellent beam quality while protecting lasers from back reflections. Our 2µm Faraday Isolator is designed for use with thulium and holmium lasers in the 1900-2100nm region. It provides >30dB isolation for power levels up to 30W with a pulsed damage threshold of 5J/cm2 at 10ns. Our 4.55µm Faraday Isolator is designed for use with QCLs in the 4500 to 4600nm region. It provides >30dB isolation for power levels up to 2.5W and >65% transmission at 22°C.

www.laserfocusworld.com Electro-Optics Technology, Inc. (231) 935-4044 | [email protected] | www.eotech.com

76 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_76 76 11/2/15 11:54 AM Manufacturers’ Product Showcase

ŶƀƁƂƆƃŽŮſƂƆŷŽƎŸƍƃƆŽƎŷŸƌƆŷƂŽ MICRO Spectra ƏŷƍžŽƐƌƄƆŹƅ Laser spectrum analyzer

• 7-20 pm resolution • 7-20 pm abs. accuracy • Long-life calibration • 630-1083 nm range

ŭŮůŰűŲųűŴŰŵűŶŷűŸŲŹŵźŻűżŽűŴŰŵű žſŴŵůŰűƐƔŲƖƗŽųƆŷŸƆƂűŲųűƀƁźŻŵŹű źŮŻŵƂűŹżŲŹŵűŹƂżſŵƂŻűżŽůźƁŹŵŻűŮű ƂŵƀźŮůŵŮƃźŵűŲƁŴƀƁŴűŸŲŹƁźŵűƄżŴŰű ŮŽűƁźŴƂŮƅŰżƆŰƅŻƀŵŵŹűŻŲůƇŵŴƈű ŻƁżŴŮƃźŵűųŲƂűƁŻŵűƄżŴŰ ƑƒŽžƐƉƎƓƔ ŻƁƃƅŽŮŽŲŻŵůŲŽŹűƀƁźŻŵŻƉ ƕŽźƂƉƎƓƔ ƊŲŹŵźŻűƄżŴŰűŸŮƋżŸƁŸűƀƁźŻŵű The MICRO Spectra is best in class in high resolution, ůƁƂƂŵŽŴŻűŲųűƌƉŶžűŴŲűŶƌžűŮƂŵű steady calibration and compactness. ŮſŮżźŮƃźŵƈűƄżŴŰűƀƁźŻŵűƄżŹŴŰŻ ųƂŲŸűƍƌƌűƀŻűŴŲűŶűƁŻƉ ŵƍƃƆƁŽƐƔŲƖƗƐƖƘ Characterize and control your pulsed and cw lasers (ECDL, ƎƏƐƑƈűƒƓƅƔƕƔƈűŮŽŹűŭŴŰŵƂŽŵŴű DFB, DBR, VCSEL and many more) with this accurate and ůŲŽŴƂŲźűŮſŮżźŮƃźŵƉ reliable tool.

ŶŷŸŹŸźŻżŽžſźƀſƁƂżŽƃſƄſƂƅƆƆƄƂŽſƄ ŭŮŭůŰűŲųŴųŰŭŵųƅƄƄƇƈƉƉƊƊƊƋſƌƄƆŹƅƇƀƁƂƆƋŹƍžƉƁſƂƆŷ ŭŮůŰűŲųŴŮůŵŶŷŲŮųŸűŲųŴŮŹŶźŷŰŻżŽžſƀŰƁŻŮŵ [email protected] • www.resolutionspectra.com

Q-Max Compact Precision Servo Stage Q-Max series are stages with a compact envelope suitable for high precision and high stability positioning. The multi-directional high moment loading capability allows payloads of various envelope configurations, including overhanging CG, also in vertical Z-Axis installations. A high resolution linear encoder provides position feedback with standard 50nm resolution and optional 1,2 nanometer for application specific high performance positioning. The custom designed fine pitch ballscrew drive with preloaded nut mechanism guarantees elevated stiffness and secures excellent repeatability. The protective cover assures long term sustained positioning performance. For the high rigidity guide system custom needle bearings rails are deployed featuring 4 rolling motion guide planes and non-recirculating continuous rolling motion elements. Achieves low mechanical noise, high rigidity, near infinite life expectancy and practically zero heat generation.

MECHATRONIC SYSTEMS www.nutec1.com • 631 242 1225 • [email protected]

Laser Focus World www.laserfocusworld.com November 2015 77

1511lfw_77 77 11/2/15 11:54 AM Business Resource Center

Optics / Polarizers Manufacturing Optics / Coatings Manufacturing Optics / Filters Manufacturing

INFRARED OPTICS windows • prisms • lenses • filters Lattice Electro Optical Filters AgBr CdTe KCI Sapphire Optics, Inc. AgCl Csl KRS‑5 Si Infrared, VIS, UV 1324 E. Valencia Dr. Fullerton, CA 92831 AMTIR GaAs LiF SiO2 Bandpass • Longwave-pass www.latticeoptics.com BaF2 Ge MgF2 ZnS Shortwave-pass • Broad-Bandpass T: 714-449-0532, F: 714-449-0531 CaF2 KBr NaCl ZnSe Neutral Density CO LASER OPTICS [email protected] 2 •‑First quality production over-runs lenses • mirrors • beamsplitters reflectors • output couplers Need optics & coatings? •‑>100,000 filters for immediate delivery POLARIZERS •‑Typical size 1 inch dia, most filters can be turned down or diced to smaller dimensions wire grid • free‑standing • far IR Quality, quick service & any quantity 24 hrs turnaround on most optics & coatings •‑3 inch dia Si and Ge filter waters available for FIBER OPTICS specific wavelengths UV‑mid IR single or bundled assemblies CUSTOM optics with a lightening quick delivery One of the largest INVENTORIES in the industry •‑Custom design for prototype or OEM UV SiO2 • GeO • Sapphire • ZrF Chalcogenide • Silver Halide Applications: COATINGS •‑Gas Analysis-•-Moisture Sensors anti‑reflection • hard carbon infrared • metalization •‑Emission/Environmental Monitoring •‑Analytical Instruments-•-Process Control REFLEX Analytical Corporation •‑Medical/Clinical/Respiratory/Agricultural “Serving you across the Spectrum” Then, challenge us! •‑Alcohol Analyzers-•-Astronomical PO Box 119 Ridgewood, New Jersey 07451 •‑Laser Instruments-•-Machine Vision Internet: www.reflexusa.com High power ultrafast laser optics. •‑Thermal Imaging-•-Fluorescence E‑mail: [email protected] High damage threshold optics & coatings. Tel: 201‑444‑8958 Fax: 201‑670‑6737 High damage PBS, high energy beam expanders. Request our FREE catalog Excimer, YAG, CO2 optics. OPO, crystal & laser rod Optical Coatings coatings, prisms mirrors, windows, beamsplitters, Anti-reflection • Beamsplitter polarizing optics, waveplates, filters spherical, High reflections mirror cylindrical & aspheric lenses, Etalons (0.1mm‑20mm thk). •‑Coating Service capabilities 193-20000 nm Coating service (1 day) SPECTROGON Holographic Gratings AR, DAR, TAR, BBAR, PR, HR, Hybrid, Metallic Sweden: [email protected] UV(from 157nm), VIS, NIR, Mid IR, Far IR Tel +46 86382800 USA: [email protected] Holographic Gratings Catalog Tel +1 9733311191 Request our free catalog UK: [email protected] Laser tuning • Telecommunication Tel +44 1592770000 Pulse compression/stretching www.spectrogon.com Monochromators • Spectroscopy

• High efficiency • Extremely low stray light • Straight grooves with uniform profile, plane and concave/convex • Standard sizes 8 × 15 - 120 × 140 mm • Custom made gratings according to spec’s SPECTROGON NEWS & PRODUCTS • DEFENSE & SECURITY Sweden: [email protected] Tel +46 86382800 DETECTORS & IMAGING • LASERS & SOURCES USA: [email protected] Tel +1 9733311191 SPECTROSCOPY • TEST & MEASUREMENT UK: [email protected] Tel +44 1592770000 Free e-Newsletter from www.spectrogon.com LaserFocusWorld

78 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_78 78 11/2/15 11:54 AM Advertiser index

ADVERTISING SALES OFFICES Aerotech, Inc...... 1, 75 Lambda Research Corporation ...... 76 MAIN OFFICE 98 Spit Brook Road, LL-1, Nashua, NH 03062-5737 AFL ...... 13 LightMachinery, Inc...... 18, 38 (603) 891-0123; fax (603) 891-0574 Publisher Alluxa ...... 29 Mad City Labs Inc...... 57 Alan Bergstein (603) 891-9447; [email protected] Ape Angewandte Physik Executive Sales and Marketing Assistant Master Bond, Inc...... 51 Julia Campbell & Elecktronik, GmbH ...... 68 (603) 891-9174; [email protected] Minus K Technology ...... 28 Digital Media Sales Operations Manager Applied Scientific Instrumentation ...... 57 Tom Markley (603) 891-9307; [email protected] Nanoplus GmbH ...... 25 Ad Services Manager Avtech Electrosystems, Ltd...... 77 Alison Boyer-Murray Necsel IP, Inc...... 34, 77 (918) 832-9369; fax (918) 831-9153 BaySpec Inc...... 75 [email protected] Director, List Sales Newport Corporation ...... 35, 75 Kelli Berry Bristol Instruments, Inc...... C2, 76 (918) 831-9782; [email protected] NKT Photonics AS ...... 65 Chroma Technology ...... 24 NORTH AMERICA North America: East & Central NM Laser Products, Inc...... 48 Jeff Nichols, National Sales Manager Continuum ...... C4 (413) 442-2526; fax (413) 442-2527 [email protected] Nufern ...... 11 Cybel ...... 22 North America: West & Mountain AnneMarie St. John-Brooks, Nutec Components ...... 77 (510) 606-0630; [email protected] Discovery Semiconductors, Inc...... 6 INTERNATIONAL Ophir-Spiricon, Inc...... 21, 23, 75 Eagleyard Photonics GmbH ...... 31 Austria, France, Germany, Switzerland, Russian Federation, United Kingdom OptoSigma Corporation ...... 17 Holger Gerisch Edmund Optics ...... 12, 33 +49-(0)8801-9153791; fax +49-(0)8801-9153792 [email protected] PCO AG ...... 64 EKSPLA ...... 46 Hong Kong/China Adonis Mak 852-2-838-6298; fax 852-2-838-2766 PI (Physik Instrumente) L.P...... 66 [email protected] Electro-Optical Products Corporation.....39 India Rajan Sharma 91-11-686-1113; fax 91-11-686-1112 Electro-Optics Technology ...... 76 Pico Electronics, Inc...... 37 [email protected] Israel (Tel Aviv) Dan Aronovic Piezosystem Jena GmbH ...... 70 972-9-899-5813; [email protected] Energetiq Technology, Inc...... 16 Japan Masaki Mori 81-3-6721-9890; [email protected] Fermionics Corporation ...... 10 Princeton Optronics, Inc...... 71 Taiwan Diana Wei 886-2-2396-5128 ext. 270; fax: 886-2-2396-7816 [email protected] FLIR Commercial Systems, Inc...... 4 Prior Scientific, Inc...... 67 For all other international sales, please contact: Alan Bergstein, Publisher (see contact info. above) Gentec Electro-Optics, Inc...... 73 Resolution Spectra Systems ...... 19, 77 For assistance with marketing strategy Santec USA Corp...... 28 or ad creation, please contact: Gooch & Housego PLC ...... 8 Marketing Solutions Vice President Paul Andrews Hamamatsu Corporation ...... 20 Scanlab AG ...... 32 240.595.2352 [email protected] Incubic ...... 26 SPIE ...... 40, 62 Laser Focus World® (ISSN 1043-8092), Volume 51, No. 11. Laser Focus World is published 12 times a year, monthly by PennWell® Corporation, 1421 S. Sheridan, Tulsa, OK 74112. Innovation Photonics ...... 38 Stanford Research Systems ...... C3 Periodicals postage paid at Tulsa, OK 74112 and at additional mailing offices. SUBSCRIPTION PRICES: USA $162 1yr., $310 2 yr., $443 3 yr.; Canada $216 1 yr., $369 2 yr., $507 3 yr.; International $270 1 yr., $435 2 yr., $578 3 yr. POSTMASTER: Send address corrections to Laser Focus World, P.O. Box 3425, Northbrook, IL 60065-3425. Laser Focus iXBlue SAS ...... 43 Sutter Instrument Co...... 61 World is a registered trademark. © PennWell Corporation 2015. All rights reserved. Reproduction in whole or in part without permission is prohibited. Permission, however, is granted for employees of corporations licensed under the Annual Authorization Service offered by the Copyright Clearance Center Inc. (CCC), 222 Rosewood Drive, Danvers, Mass. Kimmon Koha USA, Inc...... 47 United Lens ...... 14 01923, or by calling CCC’s Customer Relations Department at 978-750-8400 prior to copying. We make portions of our subscriber list available to carefully screened companies that offer products and services that may be important for your work. If you do not want to This ad index is published as a service. The publisher does not assume any liability for errors or omissions. receive those offers and/or information via direct mail, please let us know by contacting us at Send all orders & ad materials to: Ad Services Specialist, Laser Focus World, 1421 S. Sheridan, Tulsa OK 74112 List Services Laser Focus World, 98 Spit Brook Rd LL-1, Nashua, NH 03062-5737. Printed in the USA. GST No. 126813153. Publications Mail Agreement no. 40052420.

Laser Focus World www.laserfocusworld.com November 2015 79

1511lfw_79 79 11/2/15 11:54 AM BusinessForum

THE INTERSECTION OF BUSINESS AND PHOTONICS TECHNOLOGY

Effective communication is fundamental to success in photonics

MILTON CHANG

A recent article in a business magazine spective. Define which aspects of your discussion can make an impression and cited that more than 60% of compa- how you might best convey the message to get their full attention. nies polled in a survey consider com- For that, you have to know something about your audience and how they view you. munication skills as the top skill they Then, he told me about a YouTube video showing a blind person begging on a street look for in hiring a new employee. I am corner. His placard states “I am blind, please help me!” He was able to get a few coins surprised it is not 99.9%. from time to time. Then, a passerby—no doubt a marketing professional—changed Effective communication to bring the message to read, “It is a beautiful day, but I can’t see.” Coins rained down on him one’s point across can make such a hence. This video may be staged, but does point out that how you make your case big difference in everything we do does matter—in this example by appealing to a passerby’s emotion vs. stating a fact. because we constantly have to sell our Here are a few useful generalizations I got from Dave and Jeff: ideas, exert influence, and have our Tell a story. Begin with an outline as if you are telling a story—no matter way—to land a job, win a what you are writing, even if it is a research paper. Make the story grant, get funding to start fun, exciting, and suspenseful, as you want to capture the reader’s a company, and convince full attention. If possible, keep the punch line until the end so the people to take our side. reader will read on. Use the so-called Watt’s eight-point story arc: I was fortunate to get The stasis (starting point or status quo), trigger (what sparks off the input from two friends to story), quest (build the story), surprise, critical choice (crucial deci- help me with this essay on sion), climax, reversal, and resolution. Feel free to use adjectives, and the importance of com- even go overboard on superlatives because you can always ratchet munications: David Tytell, MILTON CHANG of back. Always follow the adage, tell them what you’re going to tell manager of marketing and Incubic Management was them, tell them, and then tell them what you told them. president of Newport and communications at MIT, New Focus. He is currently Be brief. It is really important to be able to express yourself clearly and Jeff Hecht, a regular director of mBio without being verbose. Anything more than necessary to make your Diagnostics and Aurrion. contributor to this maga- He is a Trustee of the point only serves to distract the reader. Information overload drowns zine and to New Scientist. California Institute of out the main message—worse, it provides thoughts for objection. Technology and has served Their input is particularly on the SEC Advisory Write it, sleep on it, and edit it again and again. Even experienced germane because both are Committee on Small and writers have difficulty getting started on a text. Write down whatever Emerging Companies and technologists-turned-pro- the Visiting Committee on lead sentences come to mind to choose from later without worrying fessional writers. I para- Advanced Technology of about the wording or even the order of your thoughts because it is easy phrased what they said and the National Institute of to make revisions and move text around. Keep going until the first Standards and Technology, thank them for sharing and the authoring draft is finished. Then, fine-tune the text again and again! You will see their wisdom and insight. committee of the National ways to tell the story succinctly to get your message across, especially Academies’ Optics and Dave stared at me when Photonics: Essential if you wait a few hours between drafts to see the text with fresh eyes. I asked him how to begin Technologies for Our A 20% reduction in length with each pass is not an unrealistic goal. Nation. Chang is a Fellow of and said, pause a moment IEEE, OSA, and LIA. Direct Write frequently. Practice makes perfect! You will even become to contemplate where your business, a better speaker. E-mail writing presents an excellent opportunity to management, and career you stand relative to your questions to him at practice communication skills. A good discipline is to edit the draft at reader or listener before [email protected], least twice and reduce the length by 40% before hitting the send button. and check out his book you start. Decide on the Toward Entrepreneurship at In a future editorial, I will address how to put your writing skills to message from their per- www.miltonchang.com. practical use—for example, pitching to investors.

80 November 2015 www.laserfocusworld.com Laser Focus World

1511lfw_80 80 11/2/15 11:54 AM Programmable DC Power Supplies to 20 kV

SRS has added four new high voltage power supplies to the PS300 series: ñ10 kV, +10 kV, ñ20 kV and +20 kV. All PS300 series supplies offer a wide range of features including programmable current and voltage limits, selectable overload response, short circuit protection, and a GPIB computer interface.

The combination of performance, features and price make the PS300 series the right choice.

ƍƍƍŰŹƎźżƏƐƑƐŰžŻƄƒƂųŻƈŶžŹƁƒƃƐƓůůŰƎŹƄ

ŭŮŮŮůŰůůűŮŲŮųŴŵŶŷŸŹźŻż ŭŮŮŮůŰůŽŮŲŮŸžžŶųŸžſ ŭŮŮŮűŮƀŻŷŹŮųŴƁŻŷŶŹźŻż ŭŮŮŮůŰůůűŽŮŲŮŻŶŹƂŶŹŮųźƂƂŷŴ ŭŮŮŮƃųŻŵųŸƄƄŸƅŷŴŮŷźƄźŹƁŮƆŮŹųźƂƁ ŭŮŮŮƇŻŷŹŸŵŴŮŸżƈŮžŶųųŴżŹŮųŴŸƈŻŶŹƁ ŭŮŮŮƉƃƊƋŮźżŹŴųƌŸžŴ

25 Watt Power Supplies ... $1395 (U.S. list) ŭ PS310 ±1.25 kV ŭ PS325 ±2.5 kV ŭ PS350 ±5 kV

10 Watt Power Supplies ... $2595 (U.S. list) ŭ PS355 ñ10 kV ŭ PS365 +10 kV ŭ PS370 ñ20 kV ŭ PS375 +20 kV

Stanford Research Systems Phone: (408) 744-9040 Fax: (408) 744-9049 [email protected] www.thinkSRS.com

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