1. Articles in category: Tunable Sources

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    1. Tuneable laser source

      Tuneable laser source

      Described herein is a laser (1) having a cavity for supporting oscillation of an electromagnetic signal to provide lasing action. A gain element (5) provides a source of stimulated emission for amplifying the oscillating signal. The laser also includes a wavelength selective element (7), which includes a reflecting element and a polarization modifying element. The reflecting element selectively defines a predetermined wavelength and the polarization modifying element selectively modifies the polarization of the signal component at the predetermined wavelength so as to provide high selectivity. The wavelength selective element (7) rotates the signal polarization at the predetermined wavelength into an ...

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      Mentions: Finisar
    2. Breathing laser as an inertia-free swept source for high-quality ultrafast optical bioimaging

      Breathing laser as an inertia-free swept source for high-quality ultrafast optical bioimaging

      We demonstrate an all-fiber breathing laser as inertia-free swept source (BLISS), with an ultra-compact design, for the emerging ultrafast bioimaging modalities. The unique feature of BLISS is its broadband wavelength-swept operation ( ∼ 60     nm ) with superior temporal stability in terms of both long term (0.08 dB over 27 h) and shot-to-shot power variations (2.1%). More importantly, it enables a wavelength sweep rate of > 10     MHz ( ∼ 7 × 10 8     nm / s )—orders-of-magnitude faster than the existing swept sources based on mechanical or electrical tuning techniques. BLISS thus represents a practical and new generation of swept source operating in the unmet ...

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    3. Coherence improvement in dispersion-tuned swept laser by pulse modulation

      Coherence improvement in dispersion-tuned swept laser by pulse modulation

      The dispersion-tuned swept laser (DTSL) is a fast and wideband swept source applicable in swept-source optical coherence tomography (SS-OCT). However, it suffers from coherence degradation at high sweep rates. The coherence in the DTSL, which can be improved by pulse modulation in place of sinusoidal modulation, is demonstrated. A coherence length of 8 mm is obtained at a sweep rate of 50 kHz using 100 ps pulse modulation.

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    4. Feature Of The Week 11/9/14: Dynamics of a Short Cavity Swept Source OCT Laser

      Feature Of The Week 11/9/14: Dynamics of a Short Cavity Swept Source OCT Laser

      Great advances in OCT speed and sensitivity have been possible due to the introduction of fast frequency swept laser sources. One of the most commonly used swept source devices is a short (~5 cm) cavity Fabry-Perot laser. We present both experimental characterisation and numerical modelling of such an OCT swept source and also analyse the underlying physics to better understand how such sources may be optimised. For the experimental characterisation we use a high-speed digital oscilloscope for real time analysis of the fast temporal intensity and frequency evolution. For the theoretical analysis we use a set of delay differential equations ...

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    5. Wavelength-swept lasers and their application to fiber optic sensors

      Wavelength-swept lasers and their application to fiber optic sensors

      The wavelength swept laser (WSL) is a promising optical source in optical coherence tomography, optical fiber sensor, and optical beat source generation. It is demonstrated by employing a narrowband wavelength-scanning filter, such as a fast rotating polygonal-scanner-filter, a diffraction grating on a galvo-scan mirror, or a fiber Fabry-Perot tunable filter (FFP-TF). In this manuscript, we present our researches on the dynamic fiber-optic sensors. Two kinds of WSLs are used to demonstrate the dynamic measurement in the fiber-optic sensors. One is the WSL using a polygon-scanner-based wavelength filter and the other is the Fourier domain mode-locked (FDML) WSL using a FFP-TF ...

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      Mentions: Min Yong Jeon
    6. System and method for improved resolution, higher scan speeds and reduced processing time in scans involving swept-wavelength interferometry

      System and method for improved resolution, higher scan speeds and reduced processing time in scans involving swept-wavelength interferometry

      A system and method for measuring an interferometric signal from a swept-wavelength interferometer by scanning a tunable laser source over two wavelength ranges, whose centers are separated substantially more than the length of wavelength ranges. The spatial resolution of the measurement is determined by the inverse of the wavelength separation between a first and second wavelength region, as well as by the wavelength range of the first and second regions. An electronically tunable laser may be utilized to produce two wavelength ranges that are widely separated in wavelength. Such a system and method has wide applications to the fields of ...

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    7. All-fiber wavelength swept ring laser based on Fabry-Perot filter for optical frequency domain imaging

      All-fiber wavelength swept ring laser based on  Fabry-Perot filter for optical frequency domain  imaging

      Innovations in laser engineering have yielded several novel configurations for high repetition rate, broad sweep range, and long coherence length wavelength swept lasers. Although these lasers have enabled high performance frequency-domain optical coherence tomography, they are typically complicated and costly and many require access to proprietary materials or devices. Here, we demonstrate a simplified ring resonator configuration that is straightforward to construct from readily available materials at a low total cost. It was enabled by an insight regarding the significance of isolation against bidirectional operation and by configuring the sweep range of the intracavity filter to exceed its free spectral ...

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    8. Praevium Research Receives NIH Grant for VCSEL Technology for Ultrahigh Speed OCT Retinal and Anterior Eye Imaging.

      Praevium Research Receives NIH Grant for VCSEL Technology for Ultrahigh Speed OCT Retinal and Anterior Eye Imaging.

      Praevium Research Receives a 2014 NIH Grant for $426,962 for VCSEL Technology for Ultrahigh Speed OCT Retinal and Anterior Eye Imaging. The principal investigator is Vijaysekhar Jayaraman. The program began in 2012 and ends in 2015. Below is a summary of the proposed work. The ultimate goal of this program is to enable a new generation of high performance, low cost ophthalmic Optical Coherence Tomography OCT technology based on new MEMS-tunable vertical cavity surface-emitting laser (MEMS-VCSEL) swept light sources. This will be accomplished by developing, validating, and commercializing VCSEL technology for swept source OCT (SS-OCT) at 850nm and 1050nm ...

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    9. A Fiber Bragg Grating Sensor Interrogation System Based on a Linearly Wavelength-Swept Thermo-Optic Laser Chip

      A Fiber Bragg Grating Sensor Interrogation System Based on a Linearly Wavelength-Swept Thermo-Optic Laser Chip

      A linearized wavelength-swept thermo-optic laser chip was applied to demonstrate a fiber Bragg grating (FBG) sensor interrogation system. A broad tuning range of 11.8 nm was periodically obtained from the laser chip for a sweep rate of 16 Hz. To measure the linear time response of the reflection signal from the FBG sensor, a programmed driving signal was directly applied to the wavelength-swept laser chip. The linear wavelength response of the applied strain was clearly extracted with an R-squared value of 0.99994. To test the feasibility of the system for dynamic measurements, the dynamic strain was successfully interrogated ...

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    10. Tunable Laser Array System

      Tunable Laser Array System

      A system for swept source optical coherence tomography, the system including a light source emitting multiplexed wavelength-swept radiation over a total wavelength range, the light source including N wavelength-swept vertical cavity lasers (VCL) emitting N tunable VCL outputs having N wavelength trajectories, a combiner for combining the N tunable VCL optical outputs into a common optical path to create the multiplexed wavelength-swept radiation, a splitter for splitting the multiplexed wavelength- swept radiation to a sample and a reference path, an optical detector for detecting an interference signal created by an optical interference between a reflection from the sample and light ...

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    11. Volumetric cutaneous microangiography of human skin in vivo by VCSEL swept-source optical coherence tomography

      Volumetric cutaneous microangiography of human skin in vivo by VCSEL swept-source optical coherence tomography

      We demonstrate volumetric cutaneous microangiography of the human skin in vivo that utilises 1.3-μm high-speed sweptsource optical coherence tomography (SS-OCT). The swept source is based on a micro-electro-mechanical (MEMS)-tunable vertical cavity surface emission laser (VCSEL) that is advantageous in terms of long coherence length over 50 mm and 100 nm spectral bandwidth, which enables the visualisation of microstructures within a few mm from the skin surface. We show that the skin microvasculature can be delineated in 3D SS-OCT images using ultrahigh-sensitive optical microangiography (UHS-OMAG) with a correlation mapping mask, providing a contrast enhanced blood perfusion map with ...

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    12. Versatile Swept Source With Adjustable Coherence Length

      Versatile Swept Source With Adjustable Coherence Length

      An electronically controlled optical swept source at 1550 nm using mode locking in a dispersive ring cavity is described. Active mode-locking was achieved by directly modulating the current of a semiconductor optical amplifier (SOA) used as a gain medium. In the static regime, parameters such as linewidth, tuning bandwidth, and contrast were measured, whereas the axial range was determined dynamically. Two types of fiber, dispersion compensation and single mode, are employed in the laser ring cavity. It is demonstrated that the relative lengths of the two types of fiber have little effect on the linewidth, whereas more control on the ...

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    13. Dynamics of a short cavity swept source OCT laser

      Dynamics of a short cavity swept source OCT laser

      We investigate the behaviour of a short cavity swept source laser with an intra cavity swept filter both experimentally and theoretically. We characterise the behaviour of the device with real-time intensity measurements using a fast digital oscilloscope, showing several distinct regimes, most notably regions of mode-hopping, frequency sliding mode-locking and chaos. A delay differential equation model is proposed that shows close agreement with the experimental results. The model is also used to determine important quantities such as the minimum and maximum sweep speeds for the mode-locking regime. It is also shown that by varying the filter width the maximum sweep ...

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    14. Wide and fast wavelength-swept fiber lasers based on dispersion tuning for real-time OCT

      Wide and fast wavelength-swept fiber lasers based on dispersion tuning for real-time OCT

      Swept-Source Optical coherence tomography (SS-OCT) is a powerful tool for fast medical imaging. For the real-time 3D imaging, the wide tuning range over 100 nm and fast sweep rate over 100 kHz are typically required. We recently proposed a new wavelength-swept laser for SS-OCT. It is based on a principle called dispersion tuning. Since the cavity contains no mechanical components, such as tunable filters, we could achieve the very high sweep rate. In this review paper, we describe the principle of the dispersion-tuned swept lasers in detail and present our recent works on the application to the SS-OCT system.

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    15. Coherence revival multiplexed, buffered swept source optical coherence tomography: 400  kHz imaging with a 100  kHz source

      Coherence revival multiplexed, buffered swept source optical coherence tomography: 400  kHz imaging with a 100  kHz source

      The effective speed of a swept source optical coherence tomography (SSOCT) imaging system was quadrupled using efficient sweep buffering along with coherence revival and spatial multiplexing. A polarizing beam splitter and fold mirror assembly were used to create a dual spot sample arm with a common objective designed for near-diffraction-limited retinal imaging. Using coherence revival, a variable optical delay line allowed for separate locations within a sample to be simultaneously imaged and frequency encoded by carefully controlling the optical path length of each sample path. This method can be used to efficiently quadruple the imaging speed of any SSOCT system ...

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    16. OCT System With Bonded Mems Tunable Mirror Vcsel Swept Source

      OCT System With Bonded Mems Tunable Mirror Vcsel Swept Source

      A microelectromechanical systems (MEMS)-tunable vertical-cavity surface emitting laser (VCSEL) in which the MEMS mirror is a bonded to the active region. This allows for a separate electrostatic cavity, that is outside the laser's optical resonant cavity. Moreover, the use of this cavity configuration allows the MEMS mirror to be tuned by pulling the mirror away from the active region. This reduces the risk of snap down. Moreover, since the MEMS mirror is now bonded to the active region, much wider latitude is available in the technologies that are used to fabricate the MEMS mirror. This is preferably deployed ...

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    17. Optores introduces the worlds first swept laser source with a sweep rate of up to 1.5 MHz for tomorrow's optical coherence tomography system

      Optores introduces the worlds first swept laser source with a sweep rate of up to 1.5 MHz for tomorrow's optical coherence tomography system

      Optores introduces the worlds first swept laser source with a sweep rate of up to 1.5 MHz for tomorrow's optical coherence tomography systems. The Optores swept source is based on all-fiber Fourier-domain mode-locked (FDML) laser technology. Designed for record speed, the Optores swept laser also features long coherence lengths and very high output powers beyond 80 mW. Three configuration variants are available to match your requirements.

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      Mentions: Optores
    18. Swept-source OCT and glaucoma

      Swept-source OCT and glaucoma

      A technology being investigated for use in posterior segment imaging may have a role in glaucoma diagnosis, according to the literature First there was time-domain optical coherence tomography (TD-OCT), then spectral-domain OCT (SD-OCT); now a newer technology—swept-source OCT—may be able to image structures that the previous technologies could not, according to researchers involved in clinical studies of the device. "With swept-source technology, a frequency swept light source and a high speed detector are used to detect the interference signal as a function of time, instead of a spectrometer and camera as in spectral-domain technology," explained James G. Fujimoto ...

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    19. Light Source And Optical Coherence Tomography Apparatus Including The Light Source

      Light Source And Optical Coherence Tomography Apparatus Including The Light Source

      A light source includes an upper electrode layer, a lower electrode layer, and an active layer interposed therebetween. At least one of the upper and lower electrode layers is divided into a plurality of electrodes separated from each other in an in-plane direction of the active layer. The separated electrodes independently inject current into a plurality of different regions in the active layer. The light source emits light by injecting current from the upper and lower electrode layers into the active layer, guide the light in the in-plane direction, and output the light. The plurality of different regions in the ...

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    20. Optical Semiconductor Device, Driving Method Thereof, And Optical Coherence Tomography Apparatus Having The Optical Semiconductor Device

      Optical Semiconductor Device, Driving Method Thereof, And Optical Coherence Tomography Apparatus Having The Optical Semiconductor Device

      The present invention provides an optical semiconductor device which can make a wavelength band of emitted light wider than that of a conventional optical semiconductor device. The optical semiconductor device includes: an active layer including a multiple quantum well structure; and at least one electrode pair for injecting an electric current into the active layer, wherein the multiple quantum well structure has a first quantum well and a second quantum well which is different from the first quantum well, and the first quantum well and the second quantum well are mutually different in at least two out of a composition ...

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    21. PhD scholarship in MEMS Tunable VCSELs for Optical Coherence Tomography at Technical University of Denmark

      PhD scholarship in MEMS Tunable VCSELs for Optical Coherence Tomography at Technical University of Denmark

      Applications are invited for a 3-year PhD position within the field of MEMS tunable VCSELs for optical coherence tomography (OCT). The project is multidisciplinary and will cover topics within the field of semiconductor optical devices, microelectromechanical systems, semiconductor technology and optical measurement systems. The project will be carried out at the Department of Photonics, Technical University of Denmark (DTU). Fast and widely tunable VCSELs are set to revolutionize the applications of tunable lasers for sensing. They promise not only low cost but also new properties like high dynamic coherence not normally associated with fast tunable lasers. Impressive results have been ...

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    22. Feature Of The Week 3/16/14: The University of Hong Kong Demonstrates MHz A-Line SS-OCT via Optical Time Stretching and Raman Amplification of Pulsed Source

      Feature Of The Week 3/16/14: The University of Hong Kong Demonstrates MHz A-Line SS-OCT via Optical Time Stretching and Raman Amplification of Pulsed Source

      We demonstrate all-optical ultrahigh-speed swept-source optical coherence tomography (OCT) based on amplified optical time-stretch (AOT). Such an inertia-free wavelength-swept mechanism, via group velocity dispersion, enables us to realize OCT with an A-scan rate well above MHz. More importantly, the key significance of AOT-OCT is its simultaneous broadband Raman amplification during the time-stretch process–greatly enhancing the detection sensitivity compared with prior attempts to apply optical time-stretch to OCT. Here, we report on an AOT-OCT system which is operated at an A-scan rate of 7.14 MHz, a superior roll-off performance (>2  mm/dB), a record-high sensitivity of time-stretch-based OCT (>80 ...

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    23. Filtered ASE swept source for OCT medical imaging

      Filtered ASE swept source for OCT medical imaging

      An integrated swept wavelength optical source uses a filtered ASE signal with an optical amplifier and tracking filter. This source comprises a micro optical bench, a source for generating broadband light, a first tunable Fabry Perot filter, installed on the bench, for spectrally filtering the broadband light from the broadband source to generate a narrowband tunable signal, an amplifier, installed on the bench, for amplifying the tunable signal, and a second tunable Fabry Perot filter, installed on the bench, for spectrally filtering the amplified tunable signal from the amplifier. A self-tracking arrangement is also possible where a single tunable filter ...

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    24. Integrated dual swept source for OCT medical imaging

      Integrated dual swept source for OCT medical imaging

      An optical coherence analysis system comprising: a first swept source that generates a first optical signal that is tuned over a first spectral scan band, a second swept source that generates a second optical signal that is tuned over a second spectral scan band, a combiner for combining the first optical signal and the second optical signal to form a combined optical signal, an interferometer for dividing the combined optical signal between a reference arm leading to a reference reflector and a sample arm leading to a sample, and a detector system for detecting an interference signal generated from the ...

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