A Bit About Us. Optical Coherence Tomography

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1 A Bit About Us Optical Coherence Tomography Thorlabs is well known for its Photonics Tools catalog business: think Sears, Roebuck & Company but for researchers working in the optical sciences. But, perhaps we are not as well known for is our contribution to the development of a number of key technologies for the life sciences. One of those technologies is Optical Coherence Tomography. 1 As the owner and founder of Thorlabs, Alex Cable takes special pride in nurturing new businesses; he s been involved A photograph of Thorlabs first prototype Swept-Source System in six (Menlo, IdestaQE, PicoLuz, labs, Nova Phase, and one soon to be announced), each of which has resulted in the development of substantial new market opportunities. Our First Introduction to : In 2001, Thorlabs added a broadband ASE light source emitting in the 1.3 µm wavelength range to its portfolio. In that same year, we were getting numerous requests from the community for a higher power, broader bandwidth version. As -related sales and interests grew, we naturally paid more attention to the underlying technology. During this time, Cable had several fruitful discussions with Professor James Fujimoto, the founding father of the technique. In 2002, he purchased a copy of the Handbook of Optical Coherence Tomography and within months had built our first timedomain system. Our First Commercial Source: Menlo GmbH was founded in 2001 by Professor Hänsch, Alex Cable, Ronald Holzwarth, and Michael Mei. The company was a spin-off from the renowned Max-Planck-Institute for Quantum Optics and focused their efforts around the optical frequency comb technology, a revolutionary and simple technique for measuring the frequency of light, which earned Professor Hänsch a Nobel Prize in physics in By 2004 Menlo GmbH developed a Benchtop Supercontinuum Source specifically for the market. This source, based on a femtosecond, passively mode-locked fiber laser pumping a supercontinuum photonic crystal fiber, was unique for its time. As we studied the market, it became apparent that the cost of the supercontinuum source took it out of the running as a long-term solution for any of the then emerging markets. Menlo subsequently superseded their source, and Thorlabs Inc. began to develop a swept-source laser based on a semiconductor gain element Our First Swept Source Laser: In January 2004 Thorlabs purchased Radians Innova AB, a manufacturer of external cavity tunable diode lasers. In part, this acquisition was motivated by the desire to design a low-cost, high-speed swept-source laser specifically for. Our Sweden-based laser development team in collaboration with our advanced technologies group based in Newton, NJ produced a 16 khz swept-source laser. This source was featured in an Optics Express article published December 2005 (OE, Vol. 13, No. 26, Page 10523). Thorlabs and Praevium Team to Design Ideal Swept Source Laser: As Axsun Technologies and Santec came on the market with compact 50 khz swept-source lasers in 2010, Cable responded by investing in Praevium Research and working to form a relationship between Praevium and Thorlabs to develop the ideal laser, which would have a sweep speed in excess of a MHz, a coherence length greater than 100 mm, and sufficient power to exceed what can be used on live tissue. 106

2 Thorlabs Purchases a Semiconductor Foundry: As the work with Praevium was ongoing, Thorlabs acquired Covega and its 40,000-sq-ft facility in Jessup, MD in March 2009, which includes 18,000 sq. ft. of class 100 and 10,000 cleanroom facilities. Covega offered full indium phosphide and lithium niobate foundry capabilities and manufactures components and modules for the telecommunications, medical, industrial, defense, and test & measurement markets. This decision to acquire Covega was in large part driven by the desire to preserve the capability of making the best in class gain chips, which today are used throughout the market. Covega has been renamed Thorlabs Quantum Electronics (TQE) and has remained the sole source supplier of gain chips to the major laser manufacturers. Today, the TQE foundry has been expanded to include a MEMS-Tuned VCSEL at both 1 µm and 1.3 µm as well as highpower GaAs laser diodes and MIR Interband and Quantum Cascade Lasers operating in the 3 to 12 µm range. MEMS-Vertical Cavity Semiconductor Laser Débuts: The CLEO 2011 trade show was a major milestone for Thorlabs and its collaborators. Thorlabs with Praevium Research, and MIT, presented the first MEMS-Tuned VCSEL results at a post deadline session. Today, the results of our research and development efforts can be found on the following pages where we discuss our Swept Source and Spectral Domain imaging systems and the ThorImage software designed for use with all our laser scanning microscopy products. 1. D. Huang, E. A. Swanson, C. P. Lin, J. S. Schuman, W. G. Stinson, W. Chang, M. R. Hee, T. Flotte, K. Gregory, C. A. Puliafito, and J. G. Fujimoto, Optical Coherence Tomography, Science 254, (1991). Selection Guide Pages Pages Pages Page Page Page Pages Quick Chapter Guide Fluorescence Imaging 1 u 106 High Content Imaging 156 Optical Tweezers 186 Scientific Cameras 200 Electrophysiology 216 Optogenetics 252 Workstations 272 Accessories

3 2D and 3D Imaging Solutions for Structural Analysis Optical Coherence Tomography () is a noninvasive, non-destructive imaging technique that enables high-resolution, cross-sectional imaging of a wide range of highly scattering media, such as biological tissues. It can provide real-time 2D and 3D images (illustrated by Figures 1 and 2, respectively) of both excised samples and those inside living organisms. has been employed as a valuable imaging modality in fields of scientific and medical research such as ophthalmology, angiology, neurology, dermatology, gastroenterology, embryology, oncology, and cardiology. fills a gap between confocal microscopy and ultrasound (see Figure 3 below). As an optical analog to ultrasound, directs near infrared light into a sample and then measures the "time of flight" and intensity of the back reflected light. Like ultrasound, non-invasively produces cross-sectional and volumetric images. Along with the non-invasive, cross sectional imaging capability, utilizes confocal "gating" techniques to reject backscattered light, thereby producing micron-level resolutions. MEMS-VCSEL Swept Source System 85.0 µm depth µm depth Figure 1. Post processing en face views of a mouse brain through a cranial window taken with the Telesto System. There is a separation of 17 µm between each view µm Resolution 100 µm 10 µm Ultrasound 1 µm Confocal Microscopy 0 µm 0.1 mm 1 mm 10 mm 100 mm Image Penetration Figure 3. fills a niche between ultrasound and confocal microscopy. Figure 2. 3D Volumetric image of a snail in water taken by the Telesto System. Figure 3 above illustrates the advantages of three common imaging modalities used in the scientific and medical research fields: confocal microscopy,, and ultrasound. (shown in blue) fills a niche between the high resolution, shallow penetration depth of confocal microscopy and the low resolution, long penetration depth of ultrasound. The unique properties of can be exploited in various imaging applications. 108

4 2D and 3D Imaging Solutions for Structural Analysis has been used as a high-quality imaging solution in a wide range of applications. Fields that have benefitted from include the following: n Small Animal Imaging n Tissue Characterization n Live Blood Flow Imaging n Developmental Biology n Cell Imaging n Non-Clinical Ophthalmology n Biofilm Inspection n Skin Imaging n Brain Activation n Art Conservation For over 10 years, Thorlabs has been designing and manufacturing imaging systems to meet a wide variety of applications. As a result, Thorlabs offers the widest selection of complete imaging systems in the market. Figure 7 below outlines several of our standard systems and the applications in which they have been used. For further details on a selection of these applications, please see the following pages. We recognize each application possesses unique imaging requirements. Be it high-resolution, highspeed, long imaging range, or some combination of requirements, Thorlabs can provide an optimal imaging solution. Guidance on choosing the best system for your application is provided on pages Figures 4, 5, and 6 below demonstrate the use of in non-clinical ophthalmology, brain activation, and tissue characterization, respectively. Figure 4. Anterior Chamber Imaged with a 1070 nm System µm Depth Figure 5. Mouse Vascular Cranial Imaging (See Page 110 for Application Details) 2 mm Figure 6. Structural Imaging of Mouse Trachea (See Page 111 for Application Details) GANYMEDE GANYMEDE-II TELESTO TELESTO-II OCS1310V1 Vocal Cord Breast Cancer Cochlea Dentistry Esophageal Ophthalmology Anterior Eye Posterior Eye Dermatology Biofilm 4 Angiography Blood Flow 4 4 Brain 4 4 Cell 4 Cardiology Surgical Laser Ablation Monitoring or Intra-Operative Guidance Articular Cartilages Figure 7. Thorlabs have been used in a wide variety of applications. 109

5 Optical Coherence Tomography: Imaging Capabilities Cerebral Vasculature Imaging Through the Cranium Imaging of cerebral vasculature in animal models such as mice is commonly performed to study causes for, or effects of, cerebral ischemia. Researchers at the University of Lübeck, Germany demonstrated non-invasive live mouse brain imaging through the cranium (seen in Figures 8 and 9 to the right) using Thorlabs Telesto-II imaging system. Figure 8. Structural Image of the Mouse Cranium Figure 9. Angiogram Using Speckle Variance of a Mouse Brain Through the Cranium Registered to the Structural Image in Figure 8. The images in Figure 10 below show a series of en face intracranial structure and vasculature images also taken in this study. Each optical slice is separated by 51 μm. For this study, the high-speed, non-invasive imaging capabilities of the Telesto-II enabled acquisition of structural and functional brain images in a live mouse model. Such techniques allow for long-term studies to be performed in the same animal micron depth micron depth micron depth micron depth micron depth micron depth micron depth micron depth micron depth micron depth Figure 10. En face intracranial vascular images overlaid on structural images of a mouse brain. Image provided by Jan Wenzel, Gereon Hüttmann, and Hendrik Spahr, University of Lübeck 3D Renderings 110 Thorlabs systems are ideal for imaging small animals. Figure 11 (to the right) shows images of a chicken embryo before and after subdivision and formation of compartments within the brain, taken by researchers at Washington University. Pre-Compartment Formation These images were acquired using Thorlabs 1325 nm Swept Source Microscope. Transverse cross sections were compiled into volumes, which enabled the generation of 3D volumetric renderings and reconstructions, as shown to the right. Time lapse capabilities built into the software provided real-time, noninvasive visualization of changes in morphology. Post-Compartment Formation Chick Embryo Brain Imaging 3D Reconstructions Transverse CrossSections Transverse CrossSections Figure 11. Reference: B.A. Filas, et al., Annals of Biomedical Engineering 39, , 2011.

6 Optical Coherence Tomography: Imaging Capabilities Imaging a Mouse Trachea Figure 12 to the right shows images of an excised mouse trachea acquired with a Ganymede System. The system was operating in high-speed mode with a 28 khz A-scan rate, and the standard LSM03 scan lens had been removed and replaced with an LSM02-BB scan lens (see page 120 for details on the Ganymede system). During the acquisition of the images, the mouse trachea was kept in solution at room temperature; the cilia were still active, and their movement was detectable with the system. The cilia layer, goblet cell layer, and capillaries are evident in frames (b), (c), and (e), respectively. (b) Cilia Layer (a) Goblet Cell Layer (d) (c) Capillaries Doppler Flow Imaging in a Tadpole Heart Blood flow imaging in developmental biology models such as tadpole or chicken embryo hearts is often performed to study congenital heart diseases. Researchers at the University of Toronto used Thorlabs Swept Source Imaging System with Doppler imaging to noninvasively study the cardiovascular system of living tadpoles. An optical Doppler cardiogram was obtained using a gated technique to provide ultra-high-speed visualization of the blood flow pattern in the heart of developing African frog embryos, as seen in Figure 13. This 4D (3D volume and time) gating method allows detailed visualization of the complex cardiac motion and hemodynamics in the beating heart. The series of images in Figure 14 show in vivo cross-sectional SS- images of a beating tadpole heart superimposed with Doppler blood flow images. (f) (e) Figure 12. En face views of a 2 mm x 2 mm area section of the mouse trachea. There is a separation of ~50 µm between each optical slice. (a) (b) (c) (d) (e) (f) Figure 14. Beating tadpole heart imaged using SS-. Normalized Flow Velocity (h) (g) Reference: A. Mariampillai, B.A. Standish, N.R. Munce, C. Randall, G. Liu, J.Y. Jiang, A.E. Cable, I.A. Vitkin, V.X.D. Yang, Doppler optical cardiogram gated 2D color flow imaging at 1000 fps and 4D in vivo visualization of embryonic heart at 45 fps on a swept source system, Optics Express 15, 1627 (2007). Fig. A Fig. B Figure 13. Fig. A shows the 3D surface reconstruction of the tadpole heart, while Fig. B demonstrates the complex blood flow pattern of the heart via a 3D color Doppler map. 111

7 Optical Coherence Tomography Tutorial Fourier Domain Optical Coherence Tomography (FD-) is based on low-coherence interferometry, which utilizes the coherent properties of a light source to measure optical path length delays in a sample. In, to obtain cross-sectional images with micron-level resolution, an interferometer is set up to measure optical path length differences between light reflected from the sample and reference arms. There are two types of FD- systems, each characterized by its light source and detection schemes: Spectral Domain (SD-) and Swept Source (SS-). In both types of systems, light divides into sample and reference arms of a Michelson interferometer setup, as illustrated in Figure 15. Spectral Domain Broadband Source Swept Source Swept Laser Source SS- uses coherent and narrowband light, whereas SD- systems utilize broadband, low-coherence light sources. Back reflected light, attributed to variations in the index of refraction within a sample, recouples into the sample arm fiber and then combines with the light that has traveled a fixed optical path length along the reference arm. The detection arm of the interferometer measures the resulting interferogram. The frequency of the interferogram measured by the sensor is related to the depth location of the reflector in the sample. As a result, a depth reflectivity profile (A-scan) is produced by taking a Fourier transform of the detected interferogram. 2D cross-sectional images (B-scans) are produced by scanning the sample beam across the sample; by doing so, a series of A-scans are collected to create the 2D image. Similarly, when the beam is scanned in a second direction, a series of 2D images are collected to produce a 3D volume dataset. With FD-, 2D images are collected on time scales of milliseconds, and 3D images can be collected at rates below 1 second. CCD Grating Balanced Detector Spectrometer 1 3 CIR 2 FC FC PC Sample Arm PC Sample Arm Reference Arm VA M C Reference Arm VA M C Figure 15: Schematic diagrams for the typical implementation of two Fourier Domain techniques, Spectral Domain and Swept Source. FC: Coupler; PC: Polarization Controller; C: Collimator; VA: Variable Attenuator; M: Mirror; CIR: Circulator Spectral Domain vs. Swept Source Spectral Domain and Swept Source systems are based on the same fundamental principle but incorporate different technical approaches for producing the interferogram. SD- systems have no moving parts and therefore have high mechanical stability and low phase noise. Availability of a broad range of line cameras has also enabled development of SD- systems with varying imaging speeds and sensitivities. In contrast, SS- systems utilize a wavelength swept light source and photodetector to generate rapidly the same type of interferogram. Due to the rapid sweeping of the swept laser source, high peak powers at each discrete wavelength can be used to illuminate the sample to provide greater sensitivity with little risk of optical damage. Our new swept source lasers are either electro-optically tuned or use robust MEMS tuning elements. 112 FD- Signal Processing In Fourier Domain, the interferogram is detected as a function of optical frequency. With a fixed optical delay in the reference arm, light reflected from different sample depths produces interference patterns with different frequency components. A Fourier transform is used to resolve different depth reflections, thereby generating a depth profile of the sample (A-scan). This process is illustrated in Figure 16. Figure 16. FD- Signal Processing

8 Flow Imaging with Flow imaging is used for vessel mapping or assessing tissue function. Thorlabs systems employ two different methods for optical detection of flow: Doppler and Speckle Variance. Doppler Doppler is an extension of that enables imaging of particle motion within a sample. This imaging capability is ideal for functional vascular imaging, studying embryonic cardiac dynamics, or monitoring vascular treatment response. Principles of Doppler In the most general terms, the Doppler effect is an apparent frequency shift of reflected waves caused by the motion of either the observer or the source, as illustrated in Figure 17 below. Although most commonly associated with sound, the Doppler effect has been observed in all types of waves, including light. Figure 17. The Doppler Effect A moving light source appears bluer (higher frequency) when approaching an observer, and redder (lower frequency) when moving away from one. In Doppler, the Doppler effect caused by moving particles in a sample is determined by measuring a phase shift between consecutive interference fringe signals. Any change in phase between consecutively acquired A-scans can be attributed to a Doppler frequency shift induced by particle motion. The Thorlabs Doppler Imaging Mode displays the phase shift induced by moving particles using a standard Doppler color map where red to yellow indicates flow in the direction toward the sample beam and violet to blue indicates flow away from the beam. This Doppler map can be clearly seen in Figure 18 to the right. The color map is then superimposed onto the composite B-scan to provide structural landmarks to aid in flow analysis. Figure 18. Doppler image of a rotating rod taken by the Telesto System. The red and blue color map is clearly visible on this image. Speckle Variance Speckle Variance uses variation in speckle to represent particle motion. This technique is ideal for microvascular imaging because the movement of highly scattering red blood cells causes the speckle to twinkle like a star, allowing for easy identification. This method for optical detection of flow provides high vascular contrast while minimizing oversampling and allows visualization of flow on the molecular level. It eliminates the need for phase detection because it is sensitive to motion perpendicular to the incident beam. However, unlike Doppler, Speckle Variance is unable to provide information on flow orientation within the sample. Principles of Speckle Variance When a laser illuminates an irregular surface, the highly coherent light generates an interference pattern called speckle. When an object moves, the speckle pattern changes, allowing for the identification of movement within a static sample. The size of the speckle is dependent on the tool being used to observe it. Thus, the size and shape of the speckle pattern does not play a role in movement identification. Figure 19. Speckle Variance image of blood vessels taken with the Telesto-II System. Speckle variance data can be overlaid on top of intensity pictures to provide morphological information. Different color maps can be used to display the multimodal pictures. One such color map and overlay is illustrated in Figure 19 above. 113

9 Optical Coherence Tomography Selection Guide Thorlabs offers a wide variety of Optical Coherence Tomography () imaging systems. We recognize each imaging application has specific requirements. With the growing number of systems available, it can be challenging to decide which system best meets your needs. The Selection Guide below outlines a few key technical specifications for each system as well as some tips on how to choose the best system for your application. Center Wavelength Thorlabs currently offers systems that operate with a center wavelength of 905 nm, 930 nm, or 1300 nm. The center wavelength contributes to the actual imaging depth and resolution of the system. Shorter wavelength systems, such as our 905 nm or 930 nm systems, are ideal for higher resolution imaging compared to systems with a center wavelength of 1300 nm. For imaging samples that have higher optical scattering properties, such as tissue, the longer wavelength systems are recommended. The longer center wavelength is not as affected by scattering, and therefore, the light is able to penetrate deeper into the sample and return for detection. Thorlabs System Name Telesto Telesto-II OCS1310V1 Ganymede Ganymede-II Center Wavelength 1300 nm 930 nm 905 nm A- / Line Rate A single depth profile (Intensity vs. Depth) is called an A-. B-s, or two-dimensional cross-sectional images, are created by laterally scanning the beam and collecting sequential A-scans. The speed with which a B-scan is collected depends on the A- or Line Rate. Thorlabs System Name OCS1310V1 Telesto Telesto-II A- Line Rate 100 khz Up to 91 khz Up to 76 khz For Spectral-Domain systems, the A- rate is determined by the frame rate of the camera in the detection spectrometer. For Swept-Source systems, it is determined by the sweep repetition rate of the swept laser source. There is a tradeoff between A- rate and the sensitivity of an system: a higher A- rate results in lower sensitivity. Sensitivity The sensitivity of an system describes the largest permissible signal attenuation within a sample that can still be distinguished from the noise. In practice, higher sensitivity systems are capable of providing higher contrast images. Since the sensitivity of an system can be increased by increasing the integration time, there is usually a tradeoff between A-scan rate and sensitivity. Ganymede-II Ganymede Thorlabs System Name Telesto Ganymede Ganymede-II OCS1310V1 Up to 30 khz Sensitivity Up to 106 db 105 db Telesto-II Up to 103 db 114

10 Optical Coherence Tomography Selection Guide Field of View The length (L) and width (W) of the Field of View (FOV) is limited by the objective lens properties. All of our systems are equipped with an objective lens that supports a 10 mm x 10 mm (L x W) field of view (FOV). The maximum imaging depth (D) attainable is set by the design of the system. The graphic to the right shows variation in the maximum imaging depth among all of our systems in air. However, the actual penetration depth that will be achieved typically depends on the optical properties of the sample. Our standard systems are designed to provide a balance between imaging depth and axial resolution. For applications requiring greater imaging depth or higher resolution, we offer other objectives. Please see pages for more information. Resolution In, the axial (depth) and lateral resolutions are dependent on different factors. The axial resolution of the system is proportional to the square of the center wavelength of the source divided by the source bandwidth. In practice, the axial resolution is also improved by the index of refraction of the sample. For example, the axial resolution of the Telesto system is <7.5 μm Thorlabs in air or <5.6 μm in waterrich samples such as tissue Lateral System Name Resolution* Ganymede-II 4 µm (n=1.35). Ganymede Telesto Telesto-II OCS1310V1 *Using LSM03 Telecentric Objectives 8 µm 15 µm 25 µm Thorlabs System Name OCS1310V1 Telesto-II Ganymede Telesto Ganymede-II Thorlabs System Name Ganymede-II Telesto-II Ganymede Telesto As with general microscopy principles, the lateral resolution is dependent on the focusing objective in the imaging probe. All of Thorlabs systems come with our LSM03 objective lens, which provides telecentric scans across the entire field of view. Please see pages for information on our other telecentric objective lenses. SPECTRAL DOMAIN Field of View 12 mm 3.5 mm 2.7 mm 2.5 mm 2.0 mm Axial Resolution (In Tissue) 2.9 µm 4.1 µm 5.8 µm 7.5 µm OCS1310V1 16 µm LSM03 Objective Lens SWEPT SOURCE System GANYMEDE GANYMEDE-II TELESTO TELESTO-II OCS1310V1 Center Wavelength 930 nm 905 nm 1300 nm 1300 nm 1300 nm A-/Line Rate Up to 30 khz Up to 91 khz Up to 76 khz 100 khz c Axial (Depth) Resolution a (Tissue) 4.5 µm 2.9 µm <5.6 µm 4.1 µm 12 µm Lateral Resolution a 8 µm 4 µm 15 µm 25 µm Maximum FOV b (L x W x D) 10 mm x 10 mm x 2.7 mm 10 mm x 10 mm x 2.0 mm 10 mm x 10 mm x 2.5 mm 10 mm x 10 mm x 3.5 mm 10 mm x 10 mm x 12 mm Sensitivity Up to 106 db Up to 103 db 105 db Key Performance Feature High-Resolution Video-Rate Imaging Very High Axial Resolution in Tissue Widely Versatile Imaging Highest Resolution at 1.3 µm Unprecedented Imaging Depth Range Catalog Page a Measured with the LSM03 Lens b Field of View c 200 khz MEMS-VCSEL presented on pages (Item # SL1310V ) 115

11 System System Features n 905 nm, 930 nm, and 1300 nm Available n Fully Operational System Right Out of the Box n Complete, Easy-to-Assemble n and OEM Options OCS1310V1 MEMS-VCSEL Swept Source Thorlabs offers several Optical Coherence Tomography () systems to address a wide variety of imaging applications. is a non-invasive, non-destructive imaging technique that enables high-resolution, crosssectional imaging. With the ability to image up to 12 mm (with a 500 MSamples/s DAQ) in depth and achieve better than 5 µm in axial resolution, fills a niche between ultrasound and confocal microscopy. Each system is designed to provide the best balance between imaging depth and axial resolution. All systems include an imaging engine, hand-held probe, mount, computer that is preinstalled with high-performance user software, and a software development kit. The following two pages contain details about each of the components that are included with all of our systems. 116 Imaging Engine All of our systems come with an imaging engine and light source. The OCS1310V1 Swept Source system has these two pieces packaged separately, while our other Spectral Domain systems have them packaged together. The swept source laser for the OCS1310V1 system is packaged in a 321 mm x 320 mm x 150 mm unit. The separate imaging module, which measures 321 mm x 320 mm x 65 mm, conveniently sits on top of the engine (as shown in the photo to the right) and houses the interferometer module, hand-held probe drive electronics, aiming beam, user-adjustable reference arm, and polarization control for this VCSEL-based system. Swept Source Imaging Engine for the OCS1310V1 System with Imaging Module resting on top The imaging engine for all of our other systems contains the light source as well as a spectrometer and all drive electronics in a compact 420 mm x 320 mm x 149 mm package. The reference arm for these systems is located in the probe (see the next page for probe details).

12 System Stand Features n n n Aluminum Breadboard Provides Adaptable Work Surface Breadboard Base has Side Grips and Recessed Feet for Easy Lifting and Transportation of the Stand Includes a Sample Stage with 1" X and Y Travel as well as Rotation SD- Imaging Probe Hand-Held Probe and Stand All Thorlabs systems include a hand-held probe and stand, as shown here. The probe provides X-Y (Transverse) scanning for threedimensional data acquisition. A camera, integrated in the probe, provides live video imaging during data acquisition. The probe easily slips onto the stand for imaging of small samples. Software Development Kit (SDK) Along with high-performance user software (see pages for details), all include a software development kit from which the user application is built upon. C++ and LabVIEW Based Interfaces n Seamless Integration into User s Own Software n High-Speed Processing in Both Programming Languages n Includes Hardware Control, Extensive Processing Routines, Display Options, and Data Import/Export Controls n Figure 20. 3D volumetric rendering of the head of a wasp acquired with a Telesto system High-Performance Software High-performance data acquisition software is included with all systems. The Windows-based software performs data acquisition, processing, scan control, and display of images. Figure 20 above is a screenshot taken from the software during the imaging of a wasp. See pages for more details. 117

13 ThorImage Software ThorImage is high-performance data acquisition software that is included with Thorlabs systems. This 64-bit Windows-based software package is capable of data acquisition, processing, scan control, displaying images, and data archiving. Additionally, NI LabVIEW and C-based Software Development Kits (SDKs) are available. The SDKs provide the means for developing highly specialized imaging software for every individual application. Features n Interactive Position Control through Video Display (Draw and ) n Advanced Dataset Management n High-Speed Volume Rendering of 3D Data n Doppler and Speckle Variance Imaging n Versatile and Acquisition Control Control ThorImage provides numerous scan and acquisition controls. The camera integrated in the probe of our system provides live video images in the application software. Defining the scan line for 2D imaging or the scan area for 3D imaging is accomplished through the easy-to-use "Draw and " feature (as seen in Figure 21 below). Additionally, one can further set processing parameters, averaging parameters, and the speed and sensitivity of the device using device presets. Dataset Management ThorImage software provides advanced dataset management capabilities, which allow opening several datasets simultaneously. Datasets are uniquely defined using an identifier consisting of study (or test series) name and an experiment number. Datasets can be exported in various image formats, such as PNG, BMP, or JPG, as well as other formats suited for post-processing purposes, such as RAW/SRM, FITS, or VFF. ThorImage also features a plug-in that allows the user to open datasets in ImageJ with one click. 2D Mode In the 2D imaging mode the probe beam scans in one direction, thus acquiring cross-sectional images, which are then displayed in real time (as seen in Figure 22 below). Line averaging before or after the Fast Fourier Transform (FFT) is available as well as B- averaging. Image display parameters, such as color mapping, can be controlled manually in this mode. Automatic calculation of the optimum contrast and brightness of the displayed images is also possible. Figure 21. Draw and Feature Used to Define Pattern Figure 22. 2D image of skin with immersion taken with the Telesto-II Imaging System. 118

14 ThorImage Software 3D Mode In the 3D imaging mode, the probe beam scans sequentially across the sample to collect a series of 2D cross-sectional images, which are then processed to build a 3D volumetric image. In the ThorImage software, 3D volume datasets can be viewed as orthogonal cross-sectional planes (Figure 23) and volume renderings (Figure 24). The Sectional View features crosssectional images in all three orthogonal planes, independent of the orientation in which the data was acquired. The view can be rotated as well as zoomed in and out. The Rendering View provides a volumetric rendering of the acquired volume dataset. This view enables quick 3D visualization of the sample being imaged. Planes of any orientation can be clipped to expose structures within the volume. The 3D image can be zoomed in and out as well as rotated. Furthermore, the coloring and dynamic range settings can be adjusted. Figure 23. Sectional View Figure 24. Rendering View Utilizing the full potential of our high-performance software in combination with our high-speed systems, we have included a Fast Volume Rendering mode in ThorImage, which serves as a preview for high-resolution 3D acquisitions. In this mode, high-speed volume renderings can be displayed in real-time, providing rapid visualization of samples in three dimensions. Doppler Mode Doppler imaging comes standard with all systems (available upon request with the OCS1310V1). In the Doppler mode, phase shifts between adjacent A-scans are averaged to calculate the Doppler frequency shift induced by particle motion or flow. The number of lateral axial pixels can be modified to change velocity sensitivity and resolution during phase shift calculation. The Doppler images are displayed in the Figure 25. Doppler image of a rotating rod (taken with Telesto System). main window with a color map indicating forward- or backward-directed flow, relative to the beam, as depicted in Figure 25. Controls Enlarged Speckle Variance Mode ThorImage 4.0 introduces a new acquisition mode, which uses the variance of speckle noise to calculate angiographic images. It can be used to visualize three dimensional vessel trees without requiring significant blood flow and without requiring a specific acquisition speed window. The speckle variance data can be overlaid on top of intensity pictures to provide morphologic information (see Figure 26 to the right). Different color maps can be used to display the multimodal pictures. Figure 26. Speckle variance image of blood vessels in the back of a hand (taken with the Telesto System). 119

15 Ganymede TM Imaging System Features n Turn-Key System Powered by ThorImage Software (See Pages ) n Video-Rate Imaging Speed n A- Rate: Up to 30 khz at 1024 x 1024 Pixels n Three Acquisition Modes for Flexibility in Imaging Speed and Sensitivity n Ideal for Biological Imaging Applications n Large Field of View: 10 mm x 10 mm x 2.7 mm n Configurations Available Thorlabs Ganymede Spectral Domain Imaging System is an excellent general-purpose system for imaging biological samples as well as producing 2D cross-sectional images and 3D volume datasets. It should be used in applications that require highsensitivity and high-resolution images while being somewhat insensitive to imaging speed and depth. This system offers three acquisition speed settings for imaging flexibility. A selection guide that compares all of our is provided on pages SPECIFICATIONS Center Wavelength 930 nm High-Speed Mode: 30 khz A- Line Rate* Medium-Speed Mode: 10 khz High-Sensitivity Mode: 1.25 khz High-Speed Mode: 91 db Sensitivity* Medium-Speed Mode: 97 db High-Sensitivity Mode: 106 db Axial Resolution (Tissue) 4.5 µm Lateral Resolution (with LSM03 Lens) 8 µm Maximum Field of View 10 mm x 10 mm x 2.7 mm *Increasing sensitivity, at the cost of imaging speed, enables higher contrast during imaging, thereby improving detection of very weakly resolved structures in the sample. ITEM # PRICE DESCRIPTION GANYMEDE $ 50, nm, Video-Rate System Imaging a Mouse Trachea These images of a mouse trachea were taken by a Ganymede System with the standard LSM03 objective lens removed and replaced with a LSM02-BB objective lens (see pages for details). The system was operating in High-Speed Mode with a 28 khz A-scan rate. The scans were acquired on an excised mouse trachea in solution at room temperature. The cilia were still active. Figure 1. B-scan with an imaging depth of 2 mm. Figure 2. Suspended, stabilized mouse trachea prior to imaging. Figure 3. 3D rendered volumetric image of a 2 mm x 2 mm trachea section. Figure 4. The resolution limit can be seen in the speckles in this zoomed-in view. In Live Mode, the movement of the speckles indicated cilia movement. 120

16 Ganymede TM -II Imaging System The Ganymede-II, in combination with our LSM02 objective lens (see pages ), bridges the gap between classical imaging, which typically has a 10 µm resolution range, and confocal imaging, which has a 1 µm resolution range. The matched pair of broadband superluminescent diode sources gives the Ganymede-II an axial resolution of 2 µm in tissue and 3.3 µm in air. Compared to the Ganymede, the Ganymede-II offers higher resolution with a slightly shorter imaging depth. The two systems feature comparable imaging speeds and sensitivities. SPECIFICATIONS Center Wavelength 905 nm High-Speed Mode: 30 khz A- Line Rate* Medium-Speed Mode: 10 khz High-Sensitivity Mode: 1.25 khz High-Speed Mode: 91 db Sensitivity* Medium-Speed Mode: 97 db High-Sensitivity Mode: 106 db Axial Resolution (Tissue) 2.9 µm Lateral Resolution (with LSM03 Lens) 4 µm Maximum FOV 10 mm x 10 mm x 2.0 mm *Increasing sensitivity, at the cost of imaging speed, enables higher contrast during imaging, thereby improving detection of very weakly resolved structures in the sample. Features n Complete SD- Turn-Key System n Bridges the Gap Between Classic Imaging and Confocal Imaging n Video-Rate Imaging Speed Powered by ThorImage Software (See Pages ) n Three Acquisition Modes for Flexibility in Imaging Speed and Sensitivity n Ideal for High-Resolution Tissue Imaging n Very High Axial Resolution: 2 µm in Tissue n Three Different Objective Available for Flexibility in Lateral Resolution and Depth of Focus Figure 5: 3M Ear plug. (a) 3mm x 3 mm x 1 mm volumetric view. (b) 3 mm x 2 mm x 1 mm side view slice ITEM # PRICE DESCRIPTION GANYMEDE-II $ 50, nm, Video-Rate System Telecentric Objective Thorlabs selection of scan lenses with 1.6X, 3X, 5X, or 10X magnification are ideal for use with. These objective lenses are offered with an AR coating optimized for 1350 nm or 850/1050 nm. Typically the 5X scan lens (LSM03) comes with each of our systems. However, all of our other objective lenses are also compatible. An adapter kit is available to exchange objective lenses in the field. Alternatively, another lens may be requested during the initial ordering process. Please contact us for more information. (a) (b) Figure 5 to the left shows images of a foam 3M ear plug, obtained with the Ganymede-II system. Frame (a) shows a 3 mm x 2 mm x 1 mm volumetric view, while Frame (b) shows a 3 mm x 2 mm x 1 mm side view slice. LSM03 LSM02 LSM05 See Pages for Details 121

17 Variable-Rate TelestoTM Imaging System Features n n n n n Thorlabs Telesto Imaging System provides the flexibility required for high-speed, deep penetration, and high resolution imaging applications. It utilizes Thorlabs unique superluminescent diode (SLD) design, which was designed and manufactured by our Quantum Electronics group in Jessup, Maryland. This results in an axial resolution of less than 7.5 μm in tissue. The Telesto s three acquisition modes allow this system to combine either high-sensitivity or highspeed imaging, making it very versatile. Figure 1 shows an image acquired in the high-speed mode. Center Wavelength 1325 nm A- Line Rate* High-Speed Mode: 91 khz Video-Rate Mode: 28 khz High-Sensitivity Mode: 5.5 khz Sensitivity* High-Speed Mode: 91 db Video-Rate Mode: 97 db High-Sensitivity Mode: 106 db <5.6 µm Lateral Resolution (with LSM03 Lens) 15 µm Maximum Field of View 10 mm x 10 mm x 2.5 mm *Increasing sensitivity, at the cost of imaging speed, enables higher contrast during imaging, thereby improving detection of very weakly resolved structures in the sample. ITEM # TELESTO Figure 1. Image of a pad of a finger taken with the Telesto System in high-speed mode (91 khz) using the LSM02 Lens. Thorlabs Quantum Electronics (TQE) SPECIFICATIONS Axial Resolution (Tissue) n SD- Turn-Key System Powered by ThorImage Software (Pages ) 1325 nm Center Wavelength Provides Deep Image Penetration in Highly Scattering Samples Cross-Sectional and Volumetric Imaging Three Acquisition Modes for Flexibility in Imaging Speed and Sensitivity Ideal for High-Speed and Biological Imaging Applications High Axial Resolution: Less than 7.5 µm PRICE $ 60, The light sources used in our systems are manufactured at our optoelectronics facility located in Jessup, MD. Here we have a full in-house Indium Phosphide and Gallium Arsenide foundry, as well as a state-of-the-art III-V Semiconductor and Lithium Niobate wafer processing group. Crystal growth, photolithography, etching, thin-film, deposition, cleaving/ dicing, optical coating, laser welding, and auto dye attaching are all preformed at this Maryland facility. DESCRIPTION 1325 nm, Variable-Rate System Flexible Imaging with Telesto (a) 5.5 khz (b) 29 khz (c) 91 khz The Telesto 1325 nm SD- Imaging System boasts the flexibility of user-controlled acquisition speed. With this flexibility, one can achieve high sensitivity or high speed with a single system. Above are images of a fingertip taken at all three speed A- settings: 5.5 khz (a), 59 khz (b), and 91 khz (c). Image size: 4.8 mm x 2.6 mm. 122

18 Variable-Rate Telesto TM -II Imaging System Features n SD- Turn-Key System Powered by ThorImage Software (Pages ) n 1300 nm Center Wavelength Provides a Large Penetration Depth in Highly Scattering Media n New 2048 Pixel Sensor Combines High Resolution and Large Field of View Measurements n Four Acquisition Modes for Even More Flexibility in Imaging Speed and Sensitivity n New 2048 Pixel Spectrometer Utilizes the Full Bandwidth of Thorlabs Unique Matched Pair Superluminescent Diodes Design (See Page 137 for Details) n Highest Axial Resolution at 1300 nm: 4.1 µm in Tissue n Three Different Objective Available for Flexibility in Lateral Resolution and Depth of Focus Images of a Finger Pad These images were taken with the LSM02 (d), LSM03 (e), and LSM04 (f) objective lenses, respectively. They demonstrate the flexibility of the Telesto-II. Our Adapter Kits are required to change the scan lens in any of our systems. Please see pages for details on the objective lenses. LSM02 The Telesto-II system features a new 2048 pixel sensor that combines high resolution and large field of view measurements, simultaneously increasing axial resolution and imaging depth. The Telesto-II offers higher resolution and a longer imaging depth than the Telesto system but requires a slower imaging speed to achieve this resolution. All Thorlabs imaging systems are powered by the ThorImage software package that includes an extensive SDK that allows customization of your imaging experiments (see page 118). LSM03 (Included Lens) SPECIFICATIONS Center Wavelength A- Line Rate* 1300 nm High-Speed Mode: 76 khz Medium Sensitivity Mode: 48 khz Video-Rate Mode: 30 khz High-Sensitivity Mode: 5.5 khz High-Speed Mode: 89 db Medium-Speed Mode: 92 db Sensitivity* Video-Rate Mode: 95 db High-Sensitivity Mode: 103 db Axial Resolution (Tissue) 4.1 µm Lateral Resolution (with LSM03 Lens) 15 µm Maximum Field of View (L x W x H) 10 mm x 10 mm x 3.5 mm *Increasing sensitivity, at the cost of imaging speed, enables higher contrast during imaging, thereby improving detection of very weakly resolved structures in the sample. Magnification: 5X, Max. Area: 10 mm x 10 mm Lateral Resolution in Focus: 13 µm (e) 250 µm LSM04 Magnification: 10X, Max. Area: 6 mm x 6 mm Lateral Resolution in Focus: 7 µm (d) 250 µm Magnification: 3X, Max. Area: 16 mm x 16 mm Lateral Resolution in Focus: 20 µm (f) 250 µm ITEM # PRICE DESCRIPTION TELESTO-II $ 70, nm, Variable-Rate System 123

19 MEMS-VCSEL Swept Source System Thorlabs OCS1310V1 System is based on a patented Micro- Electro-Mechanical (MEMS)-tunable Vertical Cavity Surface Emitting Laser (VCSEL) that is specially designed for optimal performance in applications. Developed in partnership with Praevium, a strategic partner of Thorlabs, this MEMS-VCSEL system provides high-speed imaging at unprecedented imaging depth ranges of 12 mm. The 1300 nm central wavelength and greater than 100 mm coherence length of this swept laser source enable imaging through highly scattering samples with an imaging range of 12 mm (current imaging range and coherence length measurements are solely limited by data acquisition electronics). The OCS1310V1 has the fastest imaging speed and the longest imaging depth of all Thorlabs systems (see in Figure 1 for a sample image). It is ideal for use in applications where these two factors are paramount but sensitivity and resolution are not as critical. Compared to the Ganymede and Telesto technology, the OCS1310V1 system does not suffer from inherent sensitivity degradation at longer imaging depths due to the long coherence length of the laser source. Thorlabs MEMS-VCSEL system is based on our MEMS- VCSEL Swept Laser Source, which boasts over 100 nm wavelength tuning range (see page 130 for details). Features n Complete Turn Key System Powered by ThorImage Software (See Pages ), Doppler Mode Available Upon Request n Long Imaging Range of 12 mm n 2D Cross-Sectional Imaging at 100,000 Lines per Second n High-Speed 2D and 3D Acquisition n 25 µm (Lateral) x 16 µm (Depth) Resolution in Tissue 124 SPECIFICATIONS Center Wavelength 1300 nm A- Line Rate* 100 khz Sensitivity* 100 db Imaging Range 12 mm Axial Resolution (Tissue) 12 µm Lateral Resolution (with LSM03 Objective Lens) 25 µm at Focus Maximum Field of View 10 mm x 10 mm x 3 mm *Increasing sensitivity, at the cost of imaging speed, enables higher contrast during imaging, thereby improving detection of very weakly resolved structures in the sample. Figure 1. En face images of a plant leaf acquired with a MEMS-tunable system operating at a 200 khz line rate. Image size: 6 mm (L) x 6 mm (W) x 100 µm step (D).

20 MEMS-VCSEL Swept Source System Images of Highly-Scattering, Transluscent, 3M Magic Tape Integrated lasing and tuning elements on a single VCSEL device enable artifact-free imaging at exceptionally long imaging ranges. An imaging depth as great as 30 mm is obtainable using a MEMS-tunable VCSEL. These images of a roll of 3M MagicTM brand translucent tape demonstrate the high-quality imaging capability that can be obtained in a single B- measurement at 100 khz line rate. The roll of tape is 11.5 mm thick mm Figure 2a mm display depth (4096 A-scans; 512 pixel display depth) 7.5 mm Figure 2b. 7.5 mm display depth (4096 A-scans; 1024 pixels display depth) A photograph of the roll of tape with the corresponding features of the image labeled. 15 mm Figure 2c. 15 mm display depth (4096 A-scans; 2048 pixel display depth) Tape Region 30 mm Plastic Roll Outer Section Plastic Roll Inner-Most Edge Figure 2d. 30 mm display depth (4096 A-scans; 4096 pixels display depth) taken with the OCS1310V1 MEMS VCSEL system. Coming Soon: 1050 nm MEMS-VCSEL Thorlabs is actively developing a MEMS-VCSEL Swept Laser Source operating with a central wavelength of 1050 nm to target applications in ophthalmology. The long coherence length of the MEMS-VCSEL may improve visualization of deep retinal structures (e.g., choroid and optic nerve head). Figure 3. image of human finger acquired using Thorlabs MEMSVCSEL Swept Laser operating at a 200 khz A- rate. Image Size (W x D): 15 mm x 7.4 mm (1024 A-s, 1024 points per A-) ITEM # OCS1310V1 PRICE $ 67, DESCRIPTION 1300 nm, MEMS-VCSEL System 125

21 Polarization-Sensitive Module PS- System Features n n n n Add-on Module for our SS- System Contrast Based on Birefringence of Material Ideal for Imaging Biological Materials Real-Time Display of Phase Retardation Images PS-1310V1 Polarization-Sensitive Optical Coherence Tomography (PS-) is a cross-sectional birefringence imaging method, ideal for a wide range of biological and engineered materials. PS- is an extension of that is based on measuring the polarization properties of light collected from birefringent samples. Birefringent materials decompose light into two polarization states with an optical delay being imposed on one state. Birefringence only occurs if the material is anisotropic. Materials that exhibit birefringence properties include tissues such as tendons, muscles, teeth, bones, blood vessels, and skin. In samples such as these, PS- provides additional contrast compared to conventional structural images as seen in the images to the right. The real-time, high-resolution imaging capability of PS- makes it well suited for studying glaucoma and other eye diseases, dental 255 π 0 0 (a) (b) structural (a) and PS- phase retardation (b) images of an oxtail sample. The strong birefringence seen in the phase retardation image indicates that highly organized structures such as collagen fibrils exist in the tissue layers. diseases, burn depths in the skin, and vascular imaging to guide plaque excision. Thorlabs has developed a real-time, fiber-based swept source PS- imaging system that provides simultaneous cross-sectional imaging of the intensity and phase retardation of light backscattered from birefringent samples. This system utilizes a standard Thorlabs SS- Imaging with the PS- add-on module. The modularity of the Thorlabs system enables incorporation of PS- imaging capability at any time. Thorlabs software package enables easy display of structural or PS- birefringence images. PS- Images Imaging of a human fingernail bed, a chicken muscle, and a plastic component are shown below. The birefringence of the human fingernail bed and chicken muscle is due to intrinsic ordering of specific areas of biological tissue, while that of the component is induced by residual strain resulting from the manufacturing process. Note the significantly improved contrast in the phase retardation images (b) compared to the intensity-only images (a) typical of conventional systems. (a) (a) (b) (b) Fingernail ITEM # PS-1310V1 126 Chicken Muscle PRICE $ 25, (a) (b) Plastic Component DESCRIPTION Polarization-Sensitive Module

22 on Nikon FN1 Microscope Features n Ideal for Real-Time Imaging of Biological Samples n Utilizes Thorlabs SS- Engine and ThorImage Software n Built Upon the Nikon Eclipse FN1 Upright Microscope n Collinear Optical Design Enables Easy Registration Between and Sub-Micron Microscopy Imaging The OCS1310V1-NIK Nikon FN1 Microscope is built upon Thorlabs Swept Source engine, enabling 2D crosssectional and 3D volumetric imaging, as well as surface profiling. This system includes a 1300 nm Swept Source engine, Nikon FN1 Eclipse Microscope with integrated scanning module, computer (with monitor), and our SS- control and data acquisition software discussed on pages SPECIFICATIONS Center Wavelength 1300 nm Axial Rate >100 khz (Call for Details) Objective* Thorlabs LSM03 Thorlabs LSM02 Magnification 5X 10X Transverse Resolution 20.0 µm 13.0 µm Field of View 10.0 mm x 10.0 mm 5.0 mm x 5.0 mm Axial Resolution Air (Water) 16 µm (12 µm) Max Field of View 10.0 mm x 10.0 mm x 12 mm *See Pages for Objectives OCS1310V1-NIK Microscope with ning Module When combined with a Nikon Eclipse FN1 upright microscope, which is designed specifically for imaging small animals and thick samples, the result is a system capable of imaging. The microscope has a slim body design and long working distance for easy access to and manipulation of the sample. The video-rate imaging capability of makes it an attractive tool for realtime monitoring of experimental procedures " (572 mm) 1.79" (46 mm) Out Position Channel Engagement Slider Adjustable Sample Height 6.91" (176 mm) 8.45" (215 mm) 18.00" (457 mm) CCD Port 12.34" (314 mm) 1.96" (50 mm) Optional Spacer The beam path is collinear with the optical microscopy path of the FN1. This design allows users to quickly switch between and submicron microscopy modalities with a simple pull of a lever. As a result, the sample does not need to be moved to switch between the modalities; hence, registration is closely maintained, and the two images can be overlaid with minimal correction. Flow imaging is also possible with the Doppler Imaging function included in the software. The OCS1310V1-NIK is delivered with Thorlabs 5X LSM03 objective lens. The system is also available with a 10X LSM02 objective lens (see pages ) upon request (please specify at time of ordering). ITEM # PRICE DESCRIPTION OCS1310V1-NIK $ 82, Nikon FN1 Microscope 127

23 2D and 3D Imaging Solutions Thorlabs offers engineering solutions for integrating customized Optical Coherence Tomography () imaging modules into complex host systems. Our groups consist of scientists and engineers with over 10 years of experience in technology and its applications. Both systems and components are manufactured at our facilities in Lübeck, Germany, and Newton, NJ. We look forward to working with you to design a custom system that meets your needs. OEM System for Ophthalmology Project Considerations To successfully integrate advanced imaging technology into a complex host system, there are many factors to consider beyond component development: Selection of the best-suited parameters for the imaging technology within the context of the host system and its application A dedicated engineering team that is in close contact with the host system development team ization of certain components for seamless host system integration A reliable manufacturing process that provides timely delivery of high-quality components Competencies n n n n n Extensive Knowledge in Photonics Technology Vertically Integrated Manufacturing Facilities Over a Decade of Experience Developing Technologies Library of Existing,, and Subassemblies Engineering, ization, and Manufacturing Expertise Experienced Team n n n n Contributions to the Field for Over 10 Years Extensive Portfolio of Developed and Manufactured by Thorlabs Several Hundred Successfully Designed, Manufactured, and Deployed into the Field Over 20 Peer-Reviewed Publications Involving Successful Research Conducted with Thorlabs and 0.5 mm 20 ms Healthy Human Lens Imaged with a 1070 nm System mm 40 ms Anterior Chamber Imaged with a 1070 nm System

24 Engineering Process Thorlabs is committed to working with you at each stage of the development process to ensure the final design meets your unique requirements. 1 Process Analysis Imaging System Application Market 2 Feasibility Evaluation as Imaging Technology 3 Proof of Principle Rapid Testing with Existing 4 5 Demand Identification Module Engineering & Testing Component Requirements, Parameters, and Interfaces ized Prototype 6 Manufacturing Process & Quality Control Imaging Component for System Integration Thorlabs Expertise Thorlabs is a leading photonics company that develops and manufactures a broad portfolio of technologies ranging from optical components to advanced imaging systems. We have implemented imaging solutions for a wide range of applications in various fields with different levels of customization. ized Probe, or Sample Head, Designed to Allow Imaging of Liquid within a Bottle ized Probe Module to Allow Submerged Imaging of Liquids 0.5 mm 1 ms Contact Lens in Water Imaged with a High-Sensitivity System Laminated Foil Measurement Imaged at 2 μm Axial Resolution 0.5 mm 10 ms 129

25 MEMS-VCSEL Laser Source Have you seen our... SLD for SLD1325 See page 136 Features n 1300 nm Benchtop Swept Laser Source Ideal for Optical Coherence Tomography n 200 khz or 100 khz Sweep Speed n Over 100 mm Coherence Length n Single Mode, Mode-Hop-Free Operation n Linear Sweep Trajectory Configurations n 200 khz Sweep Speed 24 mm MZI k-clock Delay (Supports 6 mm Imaging Depth Range at 500 MS/s Sampling Rate) 48 mm MZI k-clock Delay (Supports 12 mm Imaging Depth Range at 1 GS/s Sampling Rate) n 100 khz Sweep Speed 48 mm MZI k-clock Delay (Supports 12 mm Imaging Depth Range at 500 MS/s Sampling Rate) COMMON SPECIFICATIONS Center Wavelength 1300 nm Duty Cycle (Unidirectional Sweep) >65% Wavelength Tuning Range (-20 db) >100 nm Coherence Length >100 mm Average Output Power a >20 mw Relative Intensity Noise (RIN) b <1.0% Ripple Noise Suppression -47 db Humidity >85%, Non-Condensing Environment Supply Voltage c VAC, 50/60 Hz Laser Classification (per IEC ) Class 1M Dimensions (L x W x H) 321 mm x 320 mm x 150 mm (12.4" x 11.6" x 5.75") a Measured at the laser output aperture b Measured using a detector with DC to 400 MHz bandwidth and averaged over all output wavelengths. c The swept laser source has a universal AC input. Coming Soon: 1050 nm MEMS-VCSEL Thorlabs is actively developing a MEMS-VCSEL Swept Laser Source operating with a central wavelength of 1050 nm to target applications in ophthalmology. The long coherence length of the MEMS-VCSEL can provide whole eye imaging in a single shot. References: Ahsen, Osman O.; Tao, Yuankai K.; et al. Swept source optical coherence microscopy using a 1310 nm VCSEL light source Optics Express (July 19, 2013): Tsai, Tsung-Han; Potsaid, Benjamin; et al. Ultrahigh speed endoscopic optical coherence tomography using micromotor imaging catheter and VCSEL technology Biomedical Optics Express 4.7 (June 14, 2013): Jayaraman, V.; Potsaid, B.; et al. High-speed ultra-broad tuning MEMS-VCSELs for imaging and spectroscopy Proceedings of SPIE: Smart Sensors, Actuators, and MEMS VI 8763 (May 31, 2013): doi: / SL1310V LASER RADIATION DO NOT VIEW DIRECTLY WITH OPTICAL INSTRUMENTS CLASS 1M LASER PRODUCT Thorlabs MEMS-VCSEL benchtop laser sources are designed for high-speed, long-range, Swept- Source Optical Coherence Tomography (SS-) applications. Developed in partnership with Praevium, a strategic partner of Thorlabs, these swept laser sources are based on a patented Micro- Electro-Mechanical (MEMS)-tunable Vertical Cavity Surface Emitting Laser (VCSEL). With a record-breaking coherence length, the benchtop sources provide single mode, mode-hopfree operation over a tuning range in excess of 100 nm. They are available in three configurations (listed to the left) that incorporate all of the drive electronics, temperature controllers, and triggers necessary for easy integration into custom SS- systems. Thorlabs MEMS-VCSEL benchtop lasers incorporate all the necessary drive electronics, temperature controllers, trigger signals, and optical isolators for easy operation and integration into any swept source system. Additionally, these benchtop laser sources utilize a specially designed Mach-Zehnder interferometer k-clock that provides a digital output signal for triggering your data acquisition (see the next page for details). The three laser configurations we currently offer are optimized for maximum imaging range at the most common data acquisition rates. configurations are available. Please contact us for more information. Any system based on our swept source laser will likely be limited by other elements in the system, such as the detectors or data acquisition electronics. As these limiting subsystems are improved, they can be utilized to enhance the performance of your imaging system, providing a degree of future proofing.

26 MEMS-VCSEL Laser Source MEMS VCSEL Cavity Module Polarization Controller 1 (PLC1) Input Optical Isolator Boost Optical Amplifier (BOA) Output Optical Isolator Polarization Controller 2 (PLC1) Laser Aperture (FC/APC) Monitoring Photodiode Monitoring Photodiode MZI Clock Module DAQ Trigger (SMA) Cavity Intensity (SMA) Laser Intensity (SMA) DAQ Clock (SMA) Figure 1. Internal Schematic of a MEMS-VCSEL Swept Laser Source The figure above shows a schematic of the MEMS-VCSEL benchtop laser. These lasers consist of a MEMS- VCSEL cavity, a booster optical amplifier (BOA), a fiber-optic monitoring network, and signal generation circuits. The optical output of the MEMS-VCSEL cavity module is connected to the optical input of the BOA. A polarization controller (PLC1) is used to control the polarization states of the light in the fiber when entering the BOA. Another polarization controller (PLC2) is used to control the output fiber polarization before the main laser output. The DAQ Trigger provides a line trigger whereas the DAQ Clock is a digital output from the MZI k-clock to trigger data acquisition that is linear in wavenumber. Laser monitoring ports are also provided from the output of the MEMS-VCSEL Cavity (Cavity Intensity) and after amplification (Laser Intensity). Integrated optical isolators in the benchtop laser sources eliminate the need for additional isolators external to the laser. Wavenumber Triggering Options All Thorlabs SL1310V1 series swept laser sources include an integrated Mach Zehnder interferometer for digital k-clock triggering. The SL1310V laser source provides a 12 mm imaging range at 100 khz sweep speeds when using a 500 MS/s data acquisition card. Comparatively, the SL1310V , which operates at a 200 khz sweep speed, requires a minimum of 1 GS/s data acquisition to achieve a 12 mm imaging range. For applications that require a high sweep speed but not an exceptionally long imaging range, or those that are limited in data acquisition speed, the SL1310V laser source can provide a 6 mm imaging range at 200 khz when using a 500 MS/s data acquisition card. ITEM # SL1310V SL1310V SL1310V Min Typ. Max Min Typ. Max Min Typ. Max Repetition Rate 99 khz 100 khz 101 khz 198 khz 200 khz 202 khz 198 khz 200 khz 202 khz Integrated MZI Interferometer Delay 46 mm 48 mm 50 mm 23 mm 24 mm 25 mm 46 mm 48 mm 50 mm Supported Imaging Depth Range 11.5 mm a 12 mm a 12.5 mm a 5.5 mm a 6 mm a 6.5 mm a 11.5 mm b 12 mm b 12.5 mm b a Measured when using 500 MS/s DAQ b Measured when using 1 GS/s DAQ ITEM # PRICE DESCRIPTION SL1310V $ 35, khz MEMS-VCSEL Swept Laser Source, 48 mm MZI k-clock Delay SL1310V $ 35, khz MEMS-VCSEL Swept Laser Source, 48 mm MZI k-clock Delay SL1310V $ 35, khz MEMS-VCSEL Swept Laser Source, 24 mm MZI k-clock Delay 131

27 High-Speed MEMS-VCSEL for Swept Source Optical Coherence Tomography Thorlabs is dedicated to developing leading-edge Optical Coherence Tomography () systems and components that will help advance our customers research and development efforts. One significant effort is focused on the development of sources that will push the limits with regards to bandwidth, imaging speed, and coherence length. Through a strategic partnership with Praevium Research, we have developed a patented ultrabroadband, 1325 nm superluminescent diode light source that enables high-resolution SD- imaging (see page 136 for details). Building upon the established success of this partnership, Thorlabs and Praevium have developed a high-speed MEMS-VCSEL for high-speed swept source applications in the 1300 nm window. This project is one of great excitement for us at Thorlabs, as well as for the community. In this article we will describe the motivation, goals, and promising preliminary results of a MEMS-VCSEL for Swept Source as we push into new wavelength ranges and sweep speeds. is a noninvasive imaging modality that is capable of rapidly producing micron-scale, crosssectional and volumetric images. Over the past several years, significant technological advancements of related technologies have resulted in major developments in the application of imaging systems to areas of medical imaging such as ophthalmology, dermatology, and cardiology. The ability to noninvasively and rapidly collect 3D volume images allows for the visualization of rapid changes in tissue architecture and sample manipulations, such as taking virtual histological slices. To reach its full Deflecting Membrane Multiple Quantum Well Active Region Fully Oxidized Dielectric Mirror Substrate Diagram of MEMS-VCSEL Emission Air Gap MEMS Dielectric Mirror MEMS Actuator Top Contact Antireflection Coating MEMS Actuator Bottom Contact Praevium s MEMS-VCSEL is an innovative design that offers high speed and broadband emission with long coherence length. This is an ideal combination for an swept laser source. potential, however, there are still some technological barriers where could improve. Challenges that exist in current systems include higher scan speeds, deeper penetration, and higher resolution. To address these challenges, Thorlabs has partnered with Praevium. Founded in 2001, Praevium Research develops semiconductor-based light emitting devices such as superluminescent diodes (SLDs), as well as both edge-emitting and vertical cavity lasers. Praevium s early development work on a wideband tuning VCSEL demonstrated great promise to serve as a light source that will surpass current limitations. Building upon the same model that led to Thorlabs release of the 1325 nm broadband (SLD1325) and extended bandwidth (LS2000B) light sources for, Praevium Research, Thorlabs, and collaborators at MIT have set out to further develop our wideband, high-speed MEMS-VCSEL light source for applications. The LS2000B is a dual fiber-coupled SLD light source. The SLDs are choosen so that the coupled spectral output has a bandwidth exceeding 170 nm. LS2000B 1325 nm Extended Broadband SLD Source (See Page 137 for Details) Emission Intensity (µw) Sample SLD Emission Ch4 SLD A+B < 3 db FWHM ~ 200 nm Wavelength (nm) 132

28 High-Speed MEMS-VCSEL for Swept Source Optical Coherence Tomography VCSEL Vertical Cavity Surface Emitting Lasers (VCSELs) are semiconductor-based devices that emit light perpendicular to the chip surface. VCSELs were originally developed as low-cost, low-power alternatives to edge-emitting diodes, mainly for highvolume datacom applications. The advantages of VCSELs lead to them being preferred light sources over edge-emitters in many applications. Compared to edge-emitting sources, VCSELs offer superior output beam quality, lower manufacturing costs, and single mode operation. MEMS-VCSELs utilize micro-electromechanical mirror systems (MEMS) to vary the cavity length of the laser, thereby tuning the output wavelength. MEMS-VCSELs have existed for several years; however, the limited tuning range and output power of these devices have precluded them from being used in applications. Praevium Research, in collaboration with Thorlabs and MIT, have since developed a MEMS-VCSEL design that overcomes these previous limitations. In order for a MEMS-VCSEL to be successful for applications in, it needs to meet certain standards: Rapid Sweep Speed Long Coherence Length Broad Tuning Range High Laser Output Power Low Cost High Reliability Rapid Sweep Speed Applications using demand high-speed imaging without sacrificing current image quality. Fast imaging rates allow better time resolution, dense collection of 3D datasets, and decreased laser exposure times to the sample or patient. Currently, there exists a few swept laser sources that offer high-speed scanning. Fourier domain mode-locked lasers, for example, achieve extremely high imaging speeds but require the use of very long fiber optic delays in the laser cavity and can only operate in wavelength ranges were fiber loss is low. Of the commercially available high-speed swept lasers, many operate with multiple longitudinal modes or have long cavity lengths, which limits coherence length or tuning speed, respectively. The low mass of the MEMS-tuning mirror in a MEMS-VCSEL and the short single mode cavity both contribute to its high-speed operation. The short cavity length places only one mode in the gain spectrum, enabling single-mode continuous tuning. In addition, the short cavity design enables nearly identical spectra in the forward and backward sweeps. We have recently measured greater than 500 khz sweep rates using a MEMS-VCSEL prototype, without using optical multiplexing to increase the sweep speed. Broad Tuning Range High-resolution imaging depends on the overall tuning bandwidth of the swept laser source. Praevium boasts the broadest bandwidth MEMS-VCSEL that has ever been developed. A unique design incorporating broadband fully oxidized mirrors, wideband gain regions, and thin active regions, has currently resulted in a remarkable 110 nm of continuous mode-hop-free tuning, centered around 1300 nm (see below), efforts to further extend this tuning range are currently underway. Intensity (db) Static Tuning of MEMS-VCSEL 110 nm Wavelength (nm) MEMS-VCSELs can be densely packed on a single wafer to increase the potential yield. Shown to the left is a typical VCSEL wafer. The inset shows a single MEMS-VCSEL device after fabrication. The overall size of the MEMS-VCSEL is approximately 600 µm x 600 µm square MEMS-VCSELs are capable of tuning over 100 nm. Here we show single mode operation over a 110 nm spectral tuning range centered at 1300 nm. 133

29 High-Speed MEMS-VCSEL for Swept Source Optical Coherence Tomography Long Coherence Length A significant limitation to most systems is the depth-ofview (maximum imaging depth range). Especially in clinical applications, where sample thickness, patient motion, and sample location cannot be controlled, a long depth-of-view is advantageous. Image sensitivity also needs to be virtually unaffected throughout the entire depth. Due to the micron-scale cavity length of the VCSEL and single mode operation that is free of mode hops, we have measured coherence lengths of greater than 100 mm from our MEMS-VCSEL with nearly no signal degradation. Currently limited by detector bandwidth, we are confident that the MEMS-VCSEL is able to achieve even longer imaging depths than have been measured to date. This remarkable depth-of-view will not only benefit the medical imaging community but also open doors to other applications such as large objective surface profiling, fast frequency domain reflectometry, and fast spectroscopic measurements with high spectral resolution. High Output Power One advantage of edge-emitting light sources over VCSELs is that they can emit greater output powers. As a general rule, outside of ophthalmetry, most imaging applications need a minimum of 20 mw of laser output power to maintain image quality when operating at faster scan rates. To reach this goal, the MEMS-VCSEL is coupled with a semiconductor optical amplifier (SOA) to achieve greater than 30 mw of power. An additional advantage of this postamplification scheme is that the SOA reshapes the MEMSVCSEL output spectrum such that it is more uniform. Low Cost 134 Fabrication of a MEMS-VCSEL Source The VCSEL wafer process begins with a multiple quantum well (MQW) active region (A) that is grown on an InP substrate (B) and bonded to a GaAs-based mirror (C) grown on a GaAs substrate (D). B A C D The InP substrate is chemically etched down to a strategically located stop-etch layer (E). The GaAs-based mirror is oxidized to create a wideband dielectric mirror (F). E F G H After removal of the stop-etch layer, an AR coating (G) and annular MEMS bottom actuator contact (H) are deposited on top of the MQW active region. I Next, a sacrificial layer (I) of a specifically designed thickness and composition is deposited. K J A membrane layer (J) and annular top MEMS actuator contact (K) are then deposited on top of the sacrificial layer. Finally, a dielectric mirror (L) L Although was originally developed for medical imaging is deposited and patterned. The top MEMS contact is further applications, the high cost is still prohibitive to allowing patterned to complete creation of the actuator. The sacrificial layer wide spread adoption across medical applications, such as is undercut to leave a suspended, dermatology and dentistry, and geographical markets, such movable top mirror above the MQW structure, producing as China and India. A unique aspect about MEMS-VCSELs a VCSEL with MEMS-based compared to other swept laser sources is that both the tuning element in a single device. gain material and tuning element are integrated onto a single chip. Existing laser sources require separate manufacturing and assembly of the gain media and tuning element. Although the manufacturing process of MEMS-VCSELs is more involved than edge-emitters, we envision that the overall cost per source can be less. VCSELs can be tested throughout the manufacturing process, while still at the wafer level including final functional testing. Also, since VCSELs emit from the top surface, they can be more densely packed within a wafer. These two aspects, along with the integrated manufacturing of the gain media and tuning element, potentially result in a much higher device yield, which translates to a lower manufacturing cost per device.

30 High-Speed MEMS-VCSEL for Swept Source Optical Coherence Tomography additional capabilities and equipment are necessary to accommodate mass production of MEMS-VCSELs. Thorlabs is dedicated to building the infrastructure and capabilities towards making these devices available to not only the clinical imaging market but also core researchers who desire such sources for their particular application. a b c The MEMS-VCSEL cavity consists of very few optical components, which can often cause noise and etalon-based artifacts. As shown in this series of images of a roll of scotch tape, the individual layers of the roll of tape can be resolved at different reference arm delays: (a) 0.5 mm, (b) 2.5 mm, and (c) 5.0 mm. The total display depth range in these images is 8 mm. A special feature of the MEMS-VCSEL is that it is scalable for different wavelengths. Through innovative combinations of gain materials and dielectric mirrors, a wide wavelength range in the visible to near infrared can be reached, enabling expansion of this new family of light sources. Along with all the development work required to design a MEMS-VCSEL, Thorlabs is ramping up to support production of these devices. Building off of a thirteen-year history of manufacturing of semiconductor-based components, Thorlabs Quantum Electronics (TQE) division is well positioned for manufacturing these devices at their 40,000 ft2 facility. At TQE there already exists a semiconductor fabrication and device packaging facility that will be further expanded for MEMS-VCSEL manufacturing. Additionally, skilled personnel are already available who have years of experience in volume manufacturing of semiconductor active optical devices such as lasers, SLDs, amplifiers, and modulators. Beyond the already existing wafer fabrication capability and hermetic packaging knowledge, En face (XY) images of a plant leaf acquired with a MEMS-VCSEL system operating at 200 khz line rate. Image size: 6 mm (L) x 6 mm (W) x 100 um step (D) With the proper design, MEMS-VCSELs are capable of advancing optical coherence tomography into new applications. Unlike other commercially available swept laser sources for, the MEMS-VCSEL can provide high speed, a wide spectral tuning range, and long coherence length in a single device. As we develop this light source, we look forward to finding new and exciting applications for its use. Updates on this technology will be posted at Please contact us to discuss how a MEMS-VCSEL may advance your research. Thorlabs Quantum Electronics (TQE) Located in Jessup, MD, our TQE team has fully qualified the 1300 nm MEMS VCSEL as being ready for production. An extensive reliability test plan, including artificial aging, was successfully completed in 2013, culminating in the full release of the 1300 nm swept source lasers. A 1050 nm is following right behind. The manufacturing of the MEMS VCSEL devices will also take place in the TQE foundry. This foundry includes MBE and MOCVD wafer growth, photolithography, etching, thinfilm deposition, dicing, optical coating, laser welding, automated pigtailing, and final device and system-level packaging. This is all housed in a 40,000-square-foot facility that incorporates class 100, 1000, and 10,000 clean rooms. 135

31 Superluminescent Diode Source for Features n Integrated Optical Isolator for Enhanced Output Stability n FC/APC-Terminated Pigtail Minimizes Optical Feedback n Integrated TEC and Thermistor for Temperature Control n Hermetically Sealed 14-Pin Butterfly Package SLD1325 This high-power, broadband 1325 nm Superluminescent Diode (SLD) is hermetically sealed in a 14-pin butterfly package and includes a built-in thermoelectric cooler and thermistor for temperature control. Each device goes through burn-in screening, mechanical robustness testing, and characterization testing before being packaged. The output is coupled into an SM fiber terminated with an FC/APC connector. Normalized Intensity Typical Emission Spectrum of an SLD1325 SLDs in butterfly packages are excellent highpower broadband light sources for use as ASE light sources and in applications like optical coherence tomography () imaging systems and fiber optic gyroscopes (FOGs). Each SLD is shipped with its own characterization sheet. SPECIFICATIONS Center Wavelength Bandwidth (FWHM) 1325 nm >100 nm 0.2 -Coupled Power >10 mw Wavelength (nm) SLD Injection Current (Max) 780 ma Voltage (Max) 4 V Operating Temperature Range 0 to 40 C Pigtail SMF-28e+, 1 m, FC/APC Connector ITEM # PRICE DESCRIPTION SLD1325 $ 3, FC/APC Pigtailed SLD, 1325 nm, >100 nm FWHM Driver Mount Visit for Details Features n Low Noise SLD Driver n High Stability Temperature Controller n Constant Power ITC4001 n External Modulation Input n Two Operation Modes n Constant Current Features n Butterfly Package Mount LM14S2 n Laser-Enabled LED Indicator n User-Defined Pin Out Configuration n Compatible with all 14-Pin Butterfly Laser Diodes, Like the SLD1325 Sold Above ITEM # PRICE DESCRIPTION ITC4001 $ 2, Benchtop Laser Diode/TEC Controller, 1 A/96 W ITEM # PRICE DESCRIPTION LM14S2 $ Universal 14-Pin Butterfly Laser Diode Mount 136

32 Extended Broadband SLD Source for : >170 nm FWHM Features n Dual SLD for Broadband Spectral Output n 1300 nm Center Wavelength n -Coupled Power: > 10 mw In imaging systems, the optical bandwidth of the light source is inversely proportional to the axial resolution. To provide higher axial resolution than currently possible with a single SLD, we offer an extended broadband SLD light source, which contains two handpicked SLDs. The output of the two fiber-pigtailed SLDs are fiber coupled together to provide a single extended bandwidth (>170 nm) light source. This extended light source can be used in imaging systems to produce images with a resolution of ~3 µm in biological (n = 1.33) samples. The LS2000B extended broadband SLD light source packages the matched-pair SLDs into a single compact housing measuring 320 mm x 269 mm x 64 mm. The LS2000B front panel provides independent control of the output of each SLD. In addition, each SLD has a front panel enable/ Emission Intensity (µw) Ch1 SLD A FWHM 80 nm LS2000B Extended Broadband SLD Source for High Resolution Sample SLD Emission FWHM 110 nm Ch 2 SLD B n Independent Enable/Disable and Output Power Control for Each SLD n Remote Control via USB disable output button as well as a reset to the factory configuration. There are four FC/APC fiber connectors in the front panel. Two are for access to the output of each SLD, while the other two provide extended bandwidth output from the combined pair of SLDs. Each combo-channel provides a bandwidth in excess of 170 nm and output power greater than 10 mw. SPECIFICATIONS Matched-Pair SLD Characteristics Channels SLD Output SLD A SLD B A + B Center Wavelength (Typical) 1225 nm 1340 nm 1300 nm FWHM Wavelength (Typical) 80 nm 110 nm 200 nm 10 db Bandwidth (Typical) 100 nm 150 nm 235 nm -Coupled Power >10 mw per channel Noise (Typical) <0.2% (Source Dependent) Controller Characteristics Adjustment Range 0 - Full Power Temperature Control 14 to 30 C Operating Temperature C /Connector SMF-28e+, FC/APC Wavelength (nm) Wavelength (nm) Channels 1 and 2 on the LS2000B are the output* of SLD A and SLD B respectively. Channels 3 and 4 of the LS2000B are both the combined output* of SLD A and SLD B. *Spatial noise from water absorption lines is present in the measurement at wavelength greater than 1350 nm. Emission Intensity (µw) Sample SLD Emission Ch3 SLD A+B < 3 db FWHM ~ 200 nm ITEM # PRICE DESCRIPTION LS2000B $ 12, Extended Broadband SLD Source, 1300 nm, FWHM > 170 nm Ch4 SLD A+B 137

33 Telecentric Objectives Features LSM02 M25 x 0.75 Threading THORLABS LSMO2 EFL=18 LWD=7.5 Ø33 mm 28.1 mm 23.2 mm n Telecentric Objectives Maintain Uniform Spot Size Over 15 Range n >93% Transmission Efficiency from nm n Ideal for Applications n Magnification: 1.6X, 3X, 5X, or 10X n AR Coating: 1315 nm or 850/1050 nm LSM03 M25 x 0.75 Threading THORLABS LSMO3 EFL=36 LWD=25.1 Ø34 mm 30 mm 25.5 mm LSM04 M25 x 0.75 Threading THORLABS LSMO4 EFL=54 LWD=42.3 Ø34 mm 38.5 mm 43 mm LSM05 SM2 (2.035"-40) Threading THORLABS LSMO5-BB EFL= LWD=95.3 Ø59.5 mm 61.0 mm Thorlabs telecentric objectives are ideal for use in laser scanning applications like Optical Coherence Tomography (). These applications benefit from the flat image plane that telecentric objectives offer as a laser beam is scanned across the sample. A flat image plane minimizes image distortion, which in turn creates geometrically correct images without the need for post-image processing. In addition to offering a flat image plane, a telecentric scan lens maximizes the coupling of the light scattered or emitted from the sample into the detection system. The spot size in the image plane is also nearly constant over the entire field of view, resulting in constant image resolution. The LSM02, LSM03, LSM04, and LSM05 are AR coated to minimize back reflections from broadband sources with a central wavelength around 1315 nm, whereas the -BB series is coated for reflection minima centered at 850 and 1050 nm in a single lens mm 138 Adapter Kit for An adapter kit is available that makes it possible to interchange the scan lenses in our systems without sending the system back to us, making the system a more versatile, generalpurpose device. Alternatively, another lens maybe requested during the inital ordering process. Please contact us for more details on this kit. ning Distance (SD): The SD is the distance between the galvo mirror pivot point and the back mounting plate of the objective. The galvo mirror pivot point must be located at the back focal plane of the objective to maximize image resolution. Pupil Size (EP): The size of the EP determines the ideal 1/e2 collimated beam diameter to maximize the resolution of the imaging system. Working Distance (WD or LWD): The distance between the tip of the scan lens housing and the front focal plane of the scan lens is defined as the WD. Depth of View (DOV): The DOV corresponds to the distance between the front focal plane and a parallel plane where the beam spot size has increased by a factor of 2. Field of View (FOV): The FOV is the maximum scan area on the sample that can be imaged with a resolution equal to or better than the stated resolution of the scan lens. Parfocal Distance (PD): The PD is the distance from the scan lens mounting plane to the front focal plane of the scan lens. Angle (SA): The SA is the maximum allowed angle between the beam and the optical axis of a scan lens after being reflected from the galvo mirror. ning Distance Objective Length Working Distance Galvo Mirror Objective Lens FOV Parfocal Distance

34 % Reflectance Typical Reflectance of AR Coatings on BB LSM Lens Elements % Reflectance Typical Reflectance of 1315 nm LSM Lens Elements 1315 ± 65 nm Wavelength (nm) The LSMxx-BB telecentric objectives have a broadband AR coating that maximizes the transmission of the objectives in bands around 850 nm and 1050 nm. 850/1050 nm Telecentric Objectives Wavelength (nm) ITEM # LSM02-BB LSM03-BB LSM04-BB LSM05-BB Magnification 10X 5X 3X 1.6X Design Wavelengths 850 nm 1050 nm 850 nm 1050 nm 850 nm 1050 nm 850 nm 1050 nm Wavelength Range ±40 nm ±50 nm ±40 nm ±50 nm ±40 nm ±50 nm ±40 nm ±50 nm Effective Focal Length (EFL)* mm mm mm mm mm mm 110 mm 110 mm Lens Working Distance (LWD) 7.5 mm 25.1 mm 25.0 mm 42.3 mm 42.2 mm 93.7 mm ning Distance (SD) (Distance from Pupil Position to Mounting Plane) 16.1 mm 18.9 mm 75.5 mm Pupil Size (1/e 2 ) (EP) 4 mm 8 mm Depth of View (DOV) 0.12 mm 0.58 mm 1.15 mm 1.2 mm Field of View (FOV) 4.7 mm x 4.7 mm 9.4 mm x 9.4 mm 14.1 mm x 14.1 mm 28.9 mm x 28.9 mm Parfocal Distance (PD) 30.7 mm 50.5 mm 80.7 mm mm Mean Spot Size (S) (1/e 2 Beam Diameter in the Field of Focus) 9 µm 11 µm 17 µm 21 µm 24 µm 29 µm 19 µm 29 µm Angle (SA) ±7.5º * Changes in the EFL due to wavelength are not the same as chromatic focal shift. A change in the EFL indicates a change in the location of the principal plane and hence the magnification of the scan lens. Chromatic focal shift is a wavelength dependent axial deviation in the position of the beam waist nm Telecentric Objectives ITEM # LSM02 LSM03 LSM04 LSM05 Magnification 10X 5X 3X 1.6X Design Wavelength Wavelength Range 1315 nm Effective Focal Length (EFL)* mm mm mm 110 mm Lens Working Distance (LWD) 7.5 mm 25.1 mm 42.3 mm 93.7 mm ning Distance (SD) (Distance from Pupil Position to Mounting Plane) 16.1 mm 18.9 mm 75.5 mm Pupil Size (1/e 2 ) (EP) 4 mm 8 mm Depth of View (DOV) 0.12 mm 0.58 mm 1.15 mm 1.2 mm Field of View (FOV) 4.7 mm x 4.7 mm 9.4 mm x 9.4 mm 14.1 mm x 14.1 mm 28.9 mm x 28.9 mm Parfocal Distance (PD) 30.7 mm 50.6 mm 80.8 mm mm Mean Spot Size (S) (1/e 2 Beam Diameter in the Field of Focus) 13 µm 25 µm 35 µm 23.5 µm Angle (SA) ±7.5º 850/1050 nm Telecentric Objectives 1315 nm Telecentric Objectives The LSMxx telecentric objectives have an AR coating that maximizes the transmission of the objectives in a band around 1315 nm. * Changes in the EFL due to wavelength are not the same as chromatic focal shift. A change in the EFL indicates a change in the location of the principal plane and hence the magnification of the scan lens. Chromatic focal shift is a wavelength dependent axial deviation in the position of the beam waist. ±65 nm ITEM # PRICE DESCRIPTION LSM02-BB $ 1, X Lens, EFL = 18 mm, AR Coating: nm LSM03-BB $ X Lens, EFL = 36 mm, AR Coating: nm LSM04-BB $ X Lens, EFL = 54 mm, AR Coating: nm LSM05-BB $ X Lens, EFL = 110 mm, AR Coating: nm ITEM # PRICE DESCRIPTION LSM02 $ 1, X Lens, EFL = 18 mm, Design Wavelength = 1315 ± 65 nm LSM03 $ X Lens, EFL = 36 mm, Design Wavelength = 1315 ± 65 nm LSM04 $ X Lens, EFL = 54 mm, Design Wavelength = 1315 ± 65 nm LSM05 $ X Lens, EFL = 110 mm, Design Wavelength = 1315 ± 65 nm Additional specifications for our scan lenses are available on our website. The data includes specifications on the chromatic performance of the lens as well as plots that show spot size as a function of scan angle. 139

35 Dispersion Compensators for LSM Objective Features n Dispersion Compensation up to Second Order LSM02DC LSM03DC n AR Coated: nm n Mounted in an Engraved SM1 Series Lens Tube LSM04DC LSM05DC Thorlabs dispersion compensators are single glass compensation blocks whose glass type and thickness were chosen to match the dispersion of the LSM objective lenses featured on the previous page. Each compensator is mounted in an engraved 1" long SM1-threaded (1.035"-40) lens tube and AR coated for the 800 nm to 1400 nm wavelength range (see graph below). 1.0 Typical Reflectance of LSMxxDC Dispersion Compensators % Reflectance nm Wavelength (nm) 30.5 mm (1.20") ITEM # LSM02DC LSM03DC LSM04DC LSM05DC Compatible LMS02 LMS02-BB LMS03 LMS03-BB LMS04 LMS04-BB LMS05 LMS05-BB Material N-SF8 N-SK4 N-BAK1 H-ZF7LA 29.2 mm (1.15") 26.2 mm (1.03") Wavelength Range nm Diameter 1" (25.4 mm) Clear Aperture Surface Quality 22.8 mm Scratch-Dig SM1 External Thread (1.035"-40) Wavefront Error l/4 Thickness Tolerance ±0.1 mm Diameter Tolerance +0/-0.2 mm ITEM # PRICE DESCRIPTION LSM02DC $ Dispersion Compensating Mirror for LSM02 or LSM02-BB Objective Lens LSM03DC $ Dispersion Compensating Mirror for LSM03 or LSM03-BB Objective Lens LSM04DC $ Dispersion Compensating Mirror for LSM04 or LSM04-BB Objective Lens LSM05DC $ Dispersion Compensating Mirror for LSM05 or LSM05-BB Objective Lens 140

36 Mach-Zehnder Interferometer Module Features n Two Models Available: 850 nm or 1300 nm Center Wavelength n Ideal for Swept Source Output Frequency Monitoring with Balanced Output n Insertion Loss: <3 db n Flat Wavelength Response n Integrated Signal for Power Monitor and k-clock Signals n Compact Design n Power Supply Included INT-MZI-1300 Models & Volume Pricing Available Thorlabs series of Mach-Zehnder interferometer modules are designed to be used for constructing swept source systems with a central wavelength of 850 nm or 1300 nm. The internal fiber couplers are optimized for flat wavelength responses and coupling losses that have a very low polarization dependence, which make the output signals independent of input polarization changes. The modules have an integrated detection circuit with an ultra-low noise, Figure 1. Sample Setup of INT-MZI-1300 high-speed transimpedance amplifier to provide a power monitor signal as well as a k-clock signal to monitor both the output power and wavelength of a swept laser source. Both outputs have a 200 MHz bandwidth, and the k-clock includes a balanced detector to maximize rejection of common mode noise. ITEM # INT-MZI-850 INT-MZI-1300 Wavelength Range nm nm Free Spectral Range* GHz (±5%) Insertion Loss** <1.5 db (Typical), 3 db (Max) <1.0 db (Typical), 3 db (Max) Power Monitor Bandwidth MZI Output Bandwidth DC MHz (3 db) DC MHz (3 db) 780-HP SMF-28e+ Dimensions (W x H x D) 120 mm x 80 x 16 mm (4.72" x 3.5" x 0.63") * models with choice of Free Spectral Range are available; please contact technical support for more information. **Includes connector losses for the input and output pigtail, measured at central wavelength Rapidly swept laser sources typically use sinusoidal tuning elements to achieve the very fast optical frequency sweep speeds required for imaging applications. Accurate and reliable re-calibration of the signal is required so that the final data points are evenly spaced in frequency. The Thorlabs swept source laser features a built-in Mach-Zehnder Interferometer (MZI) with balanced detector output that can be used for just this purpose. A frequency clock is derived from the zero crossings of the MZI interference fringe signal; these zero crossings are equally spaced in optical frequency (k-space). ITEM # PRICE DESCRIPTION INT-MZI-850 $ 1, nm Mach-Zehnder Interferometer INT-MZI-1300 $ 1, nm Mach-Zehnder Interferometer 141

37 Michelson-Type Interferometer Modules INT-MSI-1300B Models & Volume Pricing Available Thorlabs Michelson Interferometer Modules ease the task of building imaging systems for both our research and industry customers. It contains a fiber coupler network with outputs for both reference and sample arms. The internal couplers are optimized to ensure the output signal is insensitive to changes in the input polarization. The INT-MSI-1300 and INT-MSI-1300B have an integrated balanced detector based on two InGaAs photodetectors for use in high sensitivity Swept Source applications. The modules also feature an additional input for a 660 nm (±30 nm) aiming laser to assist in the alignment of the sample arm beam. The housing includes FC/APC-angled fiber adapters for easy coupling to both the sample and reference arms of an system. ning Mirror Reference Arm Sample Sample Arm 50/50 INT-MSI-1300 WDM Circulator Aiming Laser Broadband Source Data Acquisition Device Features n <5 db Coupling Loss n Flat Wavelength Response (See Figure 2) n Input for Aiming Beam (660 nm) to Aid Alignment n Power Supply Included Figure 1: Sample Setup of INT-MSI-1300 in an system n DC to 15 MHz or DC to 100 MHz Bandwidths Available Internal Network Figure 1 above shows a sample setup of the INT-MSI-1300 in an system. The incoming broadband light source, which has a central wavelength of 1300 nm, passes through a circulator and a broadband 50/50 coupler. Back-reflected light from both the sample and reference arms of the interferometer are combined in the 50/50 coupler, generating the interference fringe signals that pass through the circulator and the WDM coupler to the inputs of the balanced detector, the output of which is labeled as the data acquisition device in Fig. 1. Figure 2: Coupling of the INT-MSI-1300/INT-MSI-1300B measured from the 1300 nm IN port to the SAMPLE and REFERENCE ARM ports. ITEM # INT-MSI-1300 INT-MSI-1300B Wavelength Range nm Detector Material/Type InGaAs/PIN Output Bandwidth (3 db) DC to 15 MHz DC to 100 MHz Transimpedance Gain 51 kv/a 100 kv/a Saturation Power** 70 µw 35 µw Input Power Laser (Max)** 250 mw 250 mw Aiming Laser Wavelength Range nm Path Length Difference <0.1 mm (Typical), 0.2 mm (Max) Peak Responsivity 1.0 A/W Type SMF-28e+ Input/Output Port FC/APC Insertion Loss* 1300 nm to Sample Arm and Reference Arm Insertion Loss* for 660 nm to Probe <4.2 db (Typical) 5.0 db (Max) <3.0 db (Typical) 4.5 db (Max) Dimensions (W x H x D) 120 mm x 80 mm x 21 mm (4.72" x 3.15" x 0.83") *Includes connector losses of the input and output pigtail, measured at the central wavelength ** Conversion gain measured with respect to the output power using a high impedance load, the value is halved with a 50 Ω impedance 142 ITEM # PRICE DESCRIPTION INT-MSI-1300 $ 2, nm, 15 MHz Michelson-Type Interferometer INT-MSI-1300B $ 2, nm, 100 MHz Michelson-Type Interferometer

38 Common-Path Interferometer Module Thorlabs Common-Path Interferometer module is designed for common-path applications where the reference and sample arm signals arise from the same optical path. Internal couplers are optimized for flat wavelength response and coupling losses that have a very low polarization dependence. The interferometer module includes FC/APC-angled fiber adapters on all external connections. All internal connections are fusion spliced. To simplify alignment, we have added an additional input for a 660 nm (±30 nm) aiming laser. This module is intended for constructing an system with an interferometer that follows a common path configuration, similar to that shown in Fig. 1 on the previous page. The probe interfaced with this module has a reference arm and sample arm. Reflections from both arms are combined to produce interference fringes that are detected by one channel of the integrated balanced detector. The second channel of the detector may be used to offset the DC component of the interference signal by using an external variable optical attenuator to control the amount of light reaching the second detector channel. The integrated balanced detector utilizes two InGaAs photodetectors. The RF output signal from the ultra-low noise, high-speed transimpedance amplifier is proportional to the difference between the two photocurrents, which reduces common-mode noise. INT-COM-1300 Features n 2.3 db Coupling Loss n Flat Wavelength Response (See Figures 3 and 4 Below) n Input for 660 nm Alignment Beam n Compact Design n Power Supply Included Models & Volume Pricing Available Sample Probe WDM Circulator Aiming Laser Slope Compensation 95/5 Laser Figure 3: Wavelength response of coupling from the input to probe port. Variable Optical Attenuator INT-COM-1300 Data Acquisition Device Figure 1: Sample Setup of INT-COM-1300 in an System SPECIFICATIONS Wavelength Range Insertion Loss from 1300 nm Input to Probe Insertion Loss from 1300 nm Input to VOA Input Insertion Loss from 660 nm Input to Probe Bandwidth (3 db) Dimensions (W x H x D) 1250 nm nm <1.5 db (Typical), 2.3 db (Max) <17 db (Typical), 20 db (Max) <2 db (Typical), 4 db (Max) DC to 15 MHz 120 mm x 80 mm x 20 mm (4.72" x 3.15" x 0.83") Figure 4: Wavelength response of coupling from the input to variable optical attenuator (VOA) input port. ITEM # $ DESCRIPTION INT-COM-1300 $ 2, nm, 15 MHz Common-Path Interferometer 143

39 -Proven Broadband 2 x 2 -Optic Couplers FC APC Features n Operating Wavelengths: 1310 ± 70 nm or 850 ± 40 nm n Flat Spectral Response n Low Insertion Loss n Available Coupling Ratios: 99:1, 90:10, or 50:50 n FC/APC Connectors n ized Lengths and Connectors Available 1300 nm Test Setup Broadband Source (BW > 160 nm) Broadband Source (BW > 160 nm) Optical Coherence Tomography () systems require components that operate over a broad spectral range with minimal spectral dependency. Thorlabs -proven couplers are tested to ensure minimal wavelengthdependent insertion loss variations, making them an ideal choice for integration into many custom-built systems. The FC and FC series of -proven broadband couplers are polarization-independent, passive, 2 x 2 single mode fiber optic components designed for use over larger bandwidths. An important consideration in the design of an system is the flat spectral response of the components in the system. Shown on the next page are the spectral response curves for these couplers. FC/APC FC/APC Optical Spectrum Analyzer Coupler Reference A FC/APC Optical Spectrum Analyzer Coupler Output B Experimental Test Procedure Step 1: A broadband light source is spectrally analyzed, and the trace is saved as Reference A. Step 2: This reference light is sent to the coupler; the output of the coupler is analyzed and saved as trace B (Fig. 1 Below). Step 3: These two traces are normalized to 0 db so that they share a common reference intensity (Fig. 2 Below). Step 4: The difference between these normalized curves is calculated and plotted (Difference = A B) in Fig. 3 below. The result is the spectral uniformity curve for the fiber coupler, showing the variation in db across the wavelength band of interest. Intensity (db) Figure 11: - Raw Spectra Figure 22: - Normalized Spectra Figure 33: - Difference A A-B - B Reference A Coupler Output B Wavelength (nm) Relative Intensity (db) 0-3 Reference A Coupler Output B Wavelength (nm) Difference (db) Difference A-B Wavelength (nm) 144

40 -Proven Broadband 2 x 2 -Optic Couplers Each optical path is analyzed, yielding four traces for each coupler. For an operating bandwidth of 140 nm, the maximum variation of any optical path will not surpass 1.5 db ( nm), and for an operating bandwidth of 100 nm, the maximum variation will not surpass 1.0 db. This guarantees a flat response across a wide wavelength range, making these couplers perfect for broadband experiments and imaging. Spectral Variation (db) Optical Path Blue to Red Blue to White White to Red White to White Spectral Uniformity for FC XX-APC Series Δλ = 100 nm Wavelength (nm) **For reference only** Device-Specific Curves will Vary Specifications SERIES FC APC FC XX-APC SERIES Wavelength Range 850 ± 40 nm 1310 ± 70 nm Type ITEM # PRICE DESCRIPTION FC APC $ Broadband Optic Coupler, 850 nm ± 40 nm, 50:50, FC/APC FC APC $ Broadband Optic Coupler, 1310 nm ± 70 nm, 99:1, FC/APC FC APC $ Broadband Optic Coupler, 1310 nm ± 70 nm, 90:10, FC/APC FC APC $ Broadband Optic Coupler, 1310 nm ± 70 nm, 50:50, FC/APC Have you seen our... Extended Broadband SLD Source LS2000B For more details, see page HP Ø900 µm Hytrel Tubing 500 µm 500 µm Corning SMF-28e+, Ø900 µm Hytrel Tubing Coupling Ratio (%) 50:50 99:1 90:10 50:50 Insertion Loss 4.2/4.2 db 0.4/21.6 db 0.8/12.7 db 3.8/3.8 db Polarization-Dependent Loss (PDL) 0.2 db 0.15 db Excess Loss 1.0 db 0.5 db Directivity 55 db 60 db Port Configuration 2 x 2 Operating Temperature Range -40 to +85 C Storage Temperature Range -40 to +85 C Lead Length and Tolerance 100 ± 10 cm Connectors FC/APC Imaging with a 90 nm bandwidth (FWHM) source provides ~9 µm of axial resolution, as demonstrated in the top image of an onion skin. Incorporating an Extended Broadband SLD, based on matched-pair SLD light sources that together provide a bandwidth of >170 nm (FWHM), enables imaging at axial resolutions less than 4 µm, as demonstrated to the left. The higher resolution provided by the Extended Broadband SLD enables visualization of distinct layers in the onion skin (pink arrows). 145

41 -Proven Broadband Circulator Features n Polarization Independent n Broadband Operating Wavelength Range ( nm) n <1.6 db Insertion Loss n 1 m Single Mode (SMF-28e+) with FC/APC Connectors n Ø900 µm Loose Protective Jacket n ized Length and Connectorization Available CIR APC Port 2 Port 1 Port 3 Circulator Optic Circulators, such as the CIR APC, guide light from the input fiber (Port 1) to the output fiber (Port 2). returning through the output fiber is redirected to a third fiber (Port 3) with minimal no loss. The circulator isolates the input source (Port 1) from light returning from Port 2. Each -Proven Broadband Circulator has been tested for optimal application in imaging system designs. An important consideration in the design of an system is the flat spectral response of the components in the system. The CIR APC was chosen as an -proven broadband circulator because of its flat spectral response over its operating range. SPECIFICATIONS Wavelength Range nm Isolation >28 db Insertion Loss <1.6 db Directivity (Port 1 3) 50 db Return Loss 45 db Polarization-Dependent Loss <0.2 db Polarization Mode Dispersion <0.05 ps Max Optical Power 500 mw Operating Temperature 0 to 70 C Storage Temperature -40 to 85 C Type SMF-28e+ Pigtail Type and Length Ø900 µm Loose Tube, 1.0 ± 0.1 m Connector FC/APC (Angled) for Each Port Normalized Coupling Efficiency 1310 nm Circulator Spectral Transmission 100% 80% 60% 40% 20% P o r t 2 - > 3 P o r t 1 - > 2 0% Wavelength (nm) Normalized coupling efficiency versus wavelength for the two beam propagation paths of a typical -proven 1310 nm circulator (CIR APC). Port 1 2 shows a mean coupling efficiency of 88%. Port 2 3 shows a mean coupling efficiency of 86% and a standard deviation of 12%. ITEM # PRICE DESCRIPTION CIR APC $ Broadband Circulator, nm Integrated Modules ning Mirror Reference Arm Sample Sample Arm WDM 50/50 Circulator INT-MSI-1300B Aiming Laser Broadband Source Data Acquisition Device Schematic of a swept source imaging system. A key component in the imaging system is the INT-MSI-1300B Michelson-Type Interferometer (see page 142), which utilizes a CIR APC. In the interferometer, the circulator guides the light emitted by the broadband light source into the sample and reference arms of the system. The light returning from the sample and reference arms is then guided to the detector. 146

42 Aiming Beam Coupler: 660/1310 nm WDM Our WDM components can effectively combine (or separate) single mode signals at two wavelength ranges. This 660/1310 nm multiplexer is an ideal solution for combining and aiming beam light at 1310 nm and 660 nm (see below). Based on the proven Fused Biconic Taper (FBT) technology, this multiplexer provides a broad operating wavelength range and low insertion loss. All of our WDM couplers are available with any connector style (FC/PC as standard, other connectors available upon request) and include Ø900 µm loose tubing to protect the fibers. Please visit for other WDM wavelengths. Features n Designed for Coupling 660 nm Aiming Laser into 1310 nm System n <0.5 db Insertion 1310 nm n Flat (±3.5%) Spectral Response from 1250 nm to 1360 nm nm nm 2.76" (70.0 mm) Ø0.16" (Ø4.0 mm) Integrated Module with Aiming Beam 1300/660 nm PERFORMANCE SPECIFICATIONS PARAMETERS WD202A2 Operating Wavelength 660/1310 nm Max Insertion Loss* 0.5 db Polarization Dependent Loss <0.1 db Wavelength Bandwidth ± nm Operating Temperature -40 to 85 C Storage Temperature -50 to 85 C Type 0.5 m of SMF-28e+ Jacket Ø900 µm Loose Tubing * Insertion loss will change depending on connector type; specified without connectors ning Mirror Reference Arm Sample Sample Arm 50/50 INT-MSI-1300 WDM Circulator Aiming Laser Broadband Source Data Acquisition Device Setup of INT-MSI-1300 with a Michelson Interferometer module (see page 142). The WD202A2 660/1310 nm WDM is incorporated in Thorlabs SS- Imaging System to provide users with a collinear aiming laser with the imaging beam. Please refer to our website for complete models and drawings. Wavelength Division Multiplexers (WDM) ITEM # PRICE DESCRIPTION WD202A2 $ Proven 660/1310 nm Wavelength Division Multiplexer WD202A2-FC $ Proven 660/1310 nm Wavelength Division Multiplexer, FC/PC Have you seen our... Optical Amplifiers Tapered Optical Amplifiers Single-Angle Facet Gain Chips SOA1013S Semiconductor Optical Amplifiers For more details, please visit 147

43 Polarization Controllers CCC1310-J9 SM is Compatible with SMF-28e+ FPC020 FPC030 If your application includes single mode fiber and requires linearly polarized light, the FPC Series of Polarization Controllers can be easily implemented to convert elliptically polarized light in a single mode fiber into another state of polarization, including linearly polarized light. This polarization conversion Retardance (Waves) Retardance Per Paddle Ø125 µm Clad on FPC Wavelength (µm) Plot of the retardance per paddle for silica fiber with Ø125 µm cladding on the FPC030, which has a loop diameter of 27 mm. 3π 5π/2 2π 3π/2 π π/2 Retardance (Radians) FPC560 For Bend-Sensitive s is achieved by loading the paddles with a prescribed number of fiber loops and adjusting their positions to control the output polarization state. These polarization controllers utilize stressinduced birefringence to create three independent fractional wave plates to alter the polarization of the transmitted light in the single mode fiber by looping the fiber into three independent spools. The miniature FPC020 Polarization Controller achieves the same results with just two paddles. The FPC031, FPC032, FPC561, and FPC562 fiber polarization controllers come preloaded with fiber. Please check our website for detailed operating theory. NOTE: The FPC030 and FPC020 Controllers work well with most of our single mode fibers. For fibers with higher bend loss (e.g., SMF-28e+), we recommend FPC560, which has larger paddles. Retardance (Waves) Retardance Per Paddle Ø125 µm Clad on FPC Wavelength (µm) Plot of the retardance per paddle for silica fiber with Ø125 µm cladding on the FPC560, which has a loop diameter of 56 mm. 5π/2 2π 3π/2 π π/2 Retardance (Radians) Retardance (Waves) Retardance Per Loop Ø125 µm Clad on FPC π/ π π/ π π/ π π/ π π/ Wavelength (µm) Plot of the retardance per paddle for bare silica fiber with Ø125 µm cladding on the FPC020, which has a loop diameter of 18 mm. Retardance (Radians) 148 ITEM # LOOP DIAMETER PADDLE ROTATION FOOTPRINT OPERATING WAVELENGTH CONNECTORS BEND LOSS FPC " (18 mm) ± " x 0.5" (77.7 mm x 12.7 mm) N/A N/A N/A FPC " (27 mm) ± " x 1.0" (216 mm x 25 mm) N/A N/A N/A FPC " (27 mm) ± " x 1.0" (216 mm x 25 mm) nm FC/PC 0.1 db FPC " (27 mm) ± " x 1.0" (216 mm x 25 mm) nm FC/APC 0.1 db FPC " (56 mm) ± " x 1.0" (317.5 mm x 25 mm) N/A N/A N/A FPC " (56 mm) ± " x 1.0" (317.5 mm x 25 mm) nm FC/PC 0.1 db FPC " (56 mm) ± " x 1.0" (317.5 mm x 25 mm) nm FC/APC 0.1 db

44 Polarization Controllers Convert Between Linearly and Elliptically Polarized Input Polarization l/4 l/2 l/4 Output Polarization These fiber polarization controllers allow the user to convert linearly polarized light to elliptically polarized light, to rotate linearly polarized light, or to achieve arbitrary polarization states. These images show an ideal case. The fractional retardance of each paddle depends upon many factors, including the wavelength, the number of fiber loops, and the fiber type. Rotate Linearly Polarized l/4 l/2 l/4 Output Polarization Achieve Arbitrary Polarization States l/4 l/2 l/4 Output Polarization Input Polarization Input Polarization ITEM # PRICE DESCRIPTION FPC020 $ Miniature 2-Paddle Polarization Controller FPC030 $ Paddle Polarization Controller w/ Small Paddles, No FPC031 $ Paddle Polarization Controller w/ Small Paddles, FC/PC Connectors, CCC1310-J9 FPC032 $ Paddle Polarization Controller w/ Small Paddles, FC/APC Connectors, CCC1310-J9 FPC560 $ Paddle Polarization Controller w/ Large Paddles, No FPC561 $ Paddle Polarization Controller w/ Large Paddles, FC/PC Connectors, SMF-28e+ FPC562 $ Paddle Polarization Controller w/ Large Paddles, FC/APC Connectors, SMF-28e+ Compatible with SMF-28e+ Inline Polarization Controller The PLC-900 polarization controller is ideal for applications that require a stable, compact, manual controller. It is designed Features to be used with Ø900 µm jacketed single mode fiber. Simply n Insensitive to Wavelength Variations place the fiber in a channel and hold in place with end-clamps. n For Ø900 µm Tight-Buffered An adjustable knob allows the fiber to be squeezed and rotated, n Compact providing the ability to convert an arbitrary input state of polarization into any other state of polarization; any point on the Poincare Specifications sphere may be set. A separate knob is used to n Insertion Loss: <0.05 db lock the controller into position. n Return Loss: >65 db n Extinction Ratio: >40 db PLC-900 ITEM # PRICE DESCRIPTION PLC-900 $ Inline Polarization Controller for Ø900 µm Tight-Buffered 149

45 Balanced Detectors Swept Source Schematic Diagram of a Swept Source System Swept Laser Source 1 3 CIR 2 FC PC C Reference Arm VA M Balanced Detector See Page 112 for an Tutorial Sample Arm PDB420A Polarization- Independent Balanced Detector OR INT-POL-1300 Polarization-Diversity Balanced Detector Polarization-Independent Balanced Detectors n -Coupled and Free-Space Inputs n Wavelengths Between 320 and 1700 nm n See Pages Polarization-Diversity Balanced Detector n -Coupled Inputs n Wavelengths Between 1270 and 1350 nm n See Page 155 Balanced Detector When building an system, the image quality can be improved by utilizing a balanced detection scheme, which improves the signal-to-noise ratio using common mode rejection and autocorrelated noise suppression. In the diagram above, which shows the light path in a swept-source system, light exiting the fiber coupler (labeled FC) is incident on each photodiode input of the balanced detector. The detector subtracts the two signals to identify and reduce noise. The output voltage can be read using an oscilloscope or other data acquisition device. See pages for interferometer modules for with balanced detectors already integrated into the package. Thorlabs Swept Source imaging systems incorporate polarization-independent balanced detectors. Each of these detectors is optimized for low DC offset and high transimpedance gain. The active lowpass anti-aliasing filter helps to remove the frequency aliasing effect associated with high frequency signal digitization processes. SELECTION GUIDE Wavelength Available Bandwidths Type Page nm DC - 15 MHz DC - 75 MHz nm DC MHz DC MHz 152 Optimized for 1060 nm Optimized for 1300 nm DC MHz DC - 1 GHz DC MHz DC GHz Polarization-Independent nm DC - 15 MHz Polarization-Diversity

46 Polarization-Independent Balanced Detectors: nm Features n nm Wavelength Range n Switchable Power Supply Included n Inputs Adaptable to Free-Space and Applications n Excellent Common Mode Rejection Ratio: >35 db (Typical) These balanced detectors for the nm range each feature a pair of well-matched silicon photodiodes and an ultra-low noise, highspeed transimpedance amplifier. The two photodetectors are matched to achieve an excellent common mode rejection ratio, leading to better noise reduction. Each input features a removable FC input connector, making them suitable for either free space or fiber-coupled applications. The inputs on these detectors are not fibercoupled to the photodiodes. Three SMA electrical connectors provide the balanced output signal plus a fast power monitor for each of the two input signals for all of the balanced detectors. These two monitors can be used as an independent power meter as well as for measuring low frequency modulated signals up to 1 MHz. Repsonsivity (A/W) Si Photodiode Responsivity PDB410A Wavelength (nm) ITEM # PDB440A PDB420A PDB410A PDB460A Detector Type Wavelength Range Si/PIN nm Bandwidth (3 db) DC 15 MHz DC 75 MHz DC 100 MHz DC 200 MHz Peak Responsivity 0.53 A/W 0.50 A/W Active Detector Diameter 0.8 mm 0.4 mm Common Mode Rejection Ratio >35 db >25 db (>35 db Typical) Transimpedance Gain* 51 x 10 3 V/A 250 x 10 3 V/A 50 x 10 3 V/A 30 x 10 3 V/A Conversion Gain RF-Output 27 x 10 3 V/W 133 x 10 3 V/W 26.5 x 10 3 V/W 16 x 10 3 V/W Conversion Gain Monitor Output nm CW Saturation Power RF-Output nm nm nm nm NEP (Min) Optical Inputs Photodiode Damage Threshold RF Output Impedance Post Mounting 6.4 pw/hz 1/2 (DC - 10 MHz) 6.5 pw/hz 1/2 (DC - 10 MHz) 7 pw/hz 1/2 (DC - 10 MHz) FC/PC or FC/APC (Removable) 20 mw 50 W via Included Adapter Plate with 8-32 (M4) Screws Dimensions 85 mm x 80 mm x 30 mm (3.35" x 3.15" x 1.18") Power Supply *Transimpedance Gain is reduced by a factor of two for 50 W loads ± ma, 110 V or 230 V Selectable Input Voltage 13.2 pw/hz 1/2 (DC - 10 MHz) ITEM #* PRICE DESCRIPTION PDB440A $ 1, Balanced Amplified Photodetector, Fixed Gain, Si, 15 MHz PDB420A $ 1, Balanced Amplified Photodetector, Fixed Gain, Si, 75 MHz PDB410A $ 1, Balanced Amplified Photodetector, Fixed Gain, Si, 100 MHz PDB460A $ 1, Balanced Amplified Photodetector, Fixed Gain, Si, 200 MHz *Add -AC to the item number for a version with AC-Coupling. 151

47 Polarization-Independent Balanced Detectors: nm Features 1.2 InGaAs Photodiode Responsivity PDB440C n nm Wavelength Range n Switchable Power Supply Included n Inputs Adaptable to Free- Space and Applications n Excellent Common Mode Rejection Ratio: >35 db (Typical) Repsonsivity (A/W) Wavelength (nm) These balanced detectors for the nm range each feature a pair of well-matched silicon photodiodes and an ultra-low noise, high-speed transimpedance amplifier. The two photodetectors are matched to achieve an excellent common mode rejection ratio, leading to better noise reduction. The inputs of each detector (except the PDB460C) feature a removable FC input connector, making them suitable for either free space or fiber-coupled applications. The inputs on these detectors are not fiber-coupled to the photodiodes. Three SMA electrical connectors provide the balanced output signal plus a fast power monitor for each of the two input signals for all of the balanced detectors. These two monitors can be used as an independent power meter as well as for measuring low frequency modulated signals up to 1 MHz. ITEM # PDB440C PDB420C PDB410C PDB460C Detector Type Wavelength Range InGaAs/PIN nm Bandwidth (3 db) DC 15 MHz DC 75 MHz DC 100 MHz DC 200 MHz Peak Responsivity 1.0 A/W Active Detector Diameter 0.3 mm 0.15 mm Common Mode Rejection Ratio >35 db >25 db (>35 db Typical) Transimpedance Gain* 51 x 10 3 V/A 250 x 10 3 V/A 50 x 10 3 V/A 30 x 10 3 V/A Conversion Gain RF-Output 51 x 10 3 V/W 250 x 10 3 V/W 50 x 10 3 V/W 30 x 10 3 V/W Conversion Gain Monitor Output nm nm nm nm CW Saturation Power RF-Output nm nm nm nm NEP (Min) 3.3 pw/hz 1/2 (DC - 10 MHz) 3.5 pw/hz 1/2 (DC - 10 MHz) 3.8 pw/hz 1/2 (DC - 10 MHz) 6.0 pw/hz 1/2 (DC - 10 MHz) Optical Inputs** FC/PC or FC/APC (Removable) FC/PC or FC/APC (Not Removable) Photodiode Damage Threshold RF Output Impedance Post Mounting 20 mw 50 W via Included Adapter Plate with 8-32 (M4) Screws Dimensions 85 mm x 80 mm x 30 mm (3.35" x 3.15" x 1.18") Power Supply *Transimpedance Gain is reduced by a factor of two for 50 W loads ± ma, 110 V or 230 V Selectable Input Voltage **For Model PDB460C, the FC adapter is not removable 152 ITEM #* PRICE DESCRIPTION PDB440C $ 1, Balanced Amplified Photodetector, Fixed Gain, InGaAs, 15 MHz PDB420C $ 1, Balanced Amplified Photodetector, Fixed Gain, InGaAs, 75 MHz PDB410C $ 1, Balanced Amplified Photodetector, Fixed Gain, InGaAs, 100 MHz PDB460C $ 1, Balanced Amplified Photodetector, Fixed Gain, InGaAs, 200 MHz *Add -AC to the itme number for a version with AC-Coupling

48 Polarization-Independent Balanced Detectors: nm These balanced detectors, optimized for 1060 nm, each feature a pair of well-matched InGaAs photodiodes and an ultra-low noise, high-speed transimpedance amplifier. The photodiodes are connected to the FC/APC optical inputs with exactly length-matched fiber to achieve excellent common mode rejection ratio values across the full detector bandwidth. The fiber-coupled design suppresses line artifacts in the image, which generally occur when detector coupling optics are used. The combination of fiber and photodiodes was chosen to optimize these detectors for 1060 nm ( nm range). The 30 khz GHz bandwidth PDB481C-AC detector is offered in an AC-coupled version only and incorporates the latest design for balanced amplified photodetectors. The ultra-low-distortion output stage supports up to a 2 Vp-p A/D card input range, which, combined with the fiber-coupled design, improves the image quality for applications considerably. Three SMA electrical connectors provide the balanced output signal plus a fast power monitor for each of the two input signals for all of the balanced detectors. These two monitors can be used as an independent power meter as well as for measuring low frequency modulated signals up to 3 MHz. Responsivity (A/W) PDB471C and PDB481C-AC Detector Responsivity Wavelength (nm) The shaded blue region marks the specified wavelength range of the detector, while the vertical blue line indicates 1060 nm. Features n Optimized for 1060 nm ( nm Range) n Switchable Power Supply Included n FC/APC Inputs for Applications n Excellent Common Mode Rejection Ratio: >30 db (Typical) PDB481C-AC ITEM # PDB471C PDB481C-AC Detector Type InGaAs/PIN Operating Wavelength Optimized for 1060 nm ( nm Range) Internal Coupling HI1060 Bandwidth (3 db) DC 400 MHz 30 khz 1.0 GHz Peak Responsivity nm Active Detector Diameter mm Common Mode Rejection Ratio >25 db (30 db Typ.) Transimpedance Gain 10 x 10 3 V/A 16 x 10 3 V/A a Conversion Gain RF-Output 7.2 x nm 11.5 x nm a Conversion Gain Monitor Output nm CW Saturation Power RF-Output nm NEP (Min) 8 pw/hz 1/2 (DC to 100 MHz) 9.0 pw/hz 1/2 (30 khz to 100 MHz) Optical Inputs FC/APC (Not Removable) Photodiode Damage Threshold 5 mw RF Output Impedance 50 W Post Mounting via Included Adapter Plate with 8-32 (M4) Screws Dimensions 85 mm x 80 mm x 30 mm (3.35" x 3.15" x 1.18") Power Supply ± ma 110 V or 230 V Selectable Input Voltage a For a 50 W load ITEM # PRICE DESCRIPTION PDB471C $ 1, Coupled Balanced Amplified Photodetector, 400 MHz, InGaAs PDB481C-AC $ 1, Coupled Balanced Amplified Photodetector, 1.0 GHz, InGaAs, AC Coupled 153

49 Polarization-Independent Balanced Detectors: nm Features n Optimized for 1300 nm ( nm Range) n Switchable Power Supply Included n FC/APC Inputs for Applications n Excellent Common Mode Rejection Ratio: >30 db (Typical) PDB480C-AC 1.0 PDB470C and PDB480C-AC Detector Responsivity 0.8 These balanced detectors, optimized for 1300 nm, each feature a pair of well-matched InGaAs photodiodes and an ultra-low noise, high-speed transimpedance amplifier. The photodiodes are connected to the FC/APC optical inputs with exactly length-matched fiber to achieve excellent common mode rejection ratio values across the full detector bandwidth. The fibercoupled design suppresses line artifacts in the image, which generally occur when detector coupling optics are used. The combination of fiber and photodiodes was chosen to optimize these detectors for 1300 nm ( nm range). The 30 khz 1.6 GHz bandwidth PDB481C-AC detector is offered in an AC-coupled version only and incorporates the latest design for balanced amplified photodetectors. The ultra-low-distortion output stage supports up to a 2 Vp-p A/D card input range, which, combined with the fiber-coupled design, improves the image quality for applications considerably. Three SMA electrical connectors provide the balanced output signal plus a fast power monitor for each of the two input signals for all of the balanced detectors. These two monitors can be used as an independent power meter as well as for measuring low frequency modulated signals up to 3 MHz. ITEM # PDB470C PDB480C-AC Detector Type Operating Wavelength Internal Coupling InGaAs/PIN Optimized for 1300 nm ( nm Range) SMF-28e+ Bandwidth (3 db) DC 400 MHz 30 khz 1.6 GHz Peak Responsivity Active Detector Diameter Common Mode Rejection Ratio nm mm >25 db (30 db Typ.) Transimpedance Gain 10 x 10 3 V/A 16 x 10 3 V/A a Conversion Gain RF-Output Conversion Gain Monitor Output 9 x nm nm 14.4 x nm a CW Saturation Power RF-Output nm NEP (Min) Optical Inputs Photodiode Damage Threshold RF Output Impedance Post Mounting 8 pw/hz 1/2 (DC to 100 MHz) FC/APC (Not Removable) 10 mw 50 W 9.0 pw/hz 1/2 (30 khz to 100 MHz) via Included Adapter Plate with 8-32 (M4) Screws Dimensions 85 mm x 80 mm x 30 mm (3.35" x 3.15" x 1.18") Power Supply a For a 50 W load Responsivity (A/W) Wavelength (nm) The shaded blue region marks the specified wavelength range of the detector, while the vertical blue line indicates 1300 nm. ± ma 110 V or 230 V Selectable Input Voltage 154 ITEM # PRICE DESCRIPTION PDB470C $ 1, Coupled Balanced Amplified Photodetector, 400 MHz, InGaAs PDB480C-AC $ 1, Coupled Balanced Amplified Photodetector, 1.6 GHz, InGaAs, AC Coupled