1. Articles in category: Tunable Sources

    1-24 of 409 1 2 3 4 ... 15 16 17 »
    1. Frequency-doubled FDML-MOPA laser in the visible

      Frequency-doubled FDML-MOPA laser in the visible

      Wavelength-swept lasers enable high-speed measurements in absorption spectroscopy, Raman spectroscopy, nonlinear Raman hyperspectral microscopy, rapid confocal microscopy, short impulse generation, and most importantly for high-speed optical coherence tomography, with speeds up to video-rate volumetric imaging. Recently, we introduced a pulsed wavelength-swept laser based on the Fourier domain mode-locked (FDML) laser principle combined with a master-oscillator power amplifier (MOPA) architecture. The high peak powers reached with this laser enabled rapid two-photon microscopy and two-photon fluorescence lifetime microscopy and high-speed light detection and ranging measurements. Here, we present the extension of this laser into the visible wavelength range by frequency doubling the ...

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    2. Stepped frequency comb generation based on electro-optic phase-code mode-locking for moderate-speed circular-ranging OCT

      Stepped frequency comb generation based on electro-optic phase-code mode-locking for moderate-speed circular-ranging OCT

      Circular-ranging (CR) optical coherence tomography (OCT) uses frequency comb sources to improve long-range imaging. While the initial development of CR-OCT focused on extremely high-speed imaging (i.e., operation at A-line rates of several to tens of MHz), there are many applications and imaging strategies for which more moderate speeds are preferred. However, we lack suitable frequency comb sources to enable moderate speed CR-OCT imaging. Here, we describe a novel phase-code mode-locking (PCML) laser architecture that can be operated from the kilohertz to megahertz range, while also offering novel features such as dynamic re-configurability and simplified linear-in-time frequency stepping. We demonstrate ...

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    3. 9.4 MHz A-line rate optical coherence tomography at 1300 nm using a wavelength-swept laser based on stretched-pulse active mode-locking

      9.4 MHz A-line rate optical coherence tomography at 1300 nm using a wavelength-swept laser based on stretched-pulse active mode-locking

      In optical coherence tomography (OCT), high-speed systems based at 1300 nm are among the most broadly used. Here, we present 9.4 MHz A-line rate OCT system at 1300 nm. A wavelength-swept laser based on stretched-pulse active mode locking (SPML) provides a continuous and linear-in-wavenumber sweep from 1240 nm to 1340 nm, and the OCT system using this light source provides a sensitivity of 98 dB and a single-sided 6-dB roll-off depth of 2.5 mm. We present new capabilities of the 9.4 MHz SPML-OCT system in three microscopy applications. First, we demonstrate high quality OCTA imaging at a ...

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    4. PhD position on tunable lasers for optical coherence tomography at the University of Kent

      PhD position on tunable lasers for optical coherence tomography at the University of Kent

      We are recruiting for a PhD Studentship in the fields of Optics and Laser Physics, with emphasis on optical coherence tomography for a period of 36 months starting up to 31 January 2021, within the Applied Optics Group, School of Physical Sciences. This is supported by the Marie Curie Innovative Training Network scheme, 860807, EU funded, jointly organised with 14 other universities, companies and hospitals in Europe. You will spend time at the University of Kent and at the other beneficiaries or associated partners. Supervision will be provided in an European setting where specialized and complementary training will be provided ...

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    5. Spectrally shaped tunable short-cavity laser

      Spectrally shaped tunable short-cavity laser

      A tunable source includes a short-cavity laser optimized for performance and reliability in SSOCT imaging systems, spectroscopic detection systems, and other types of detection and sensing systems. The short cavity laser has a large free spectral range cavity, fast tuning response and single transverse, longitudinal and polarization mode operation, and includes embodiments for fast and wide tuning, and optimized spectral shaping. Disclosed are both electrical and optical pumping in a MEMS-VCSEL geometry with mirror and gain regions optimized for wide tuning, high output power, and a variety of preferred wavelength ranges; and a semiconductor optical amplifier, combined with the short-cavity ...

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    6. Highly Stable All-Fiber-Ring Short-Cavity Continuously Tuned Swept Source

      Highly Stable All-Fiber-Ring Short-Cavity Continuously Tuned Swept Source

      In this study, we present a swept source that can intelligently control its sweeping speed while satisfying the commercial stability and miniaturization standards. The source’s central wavelength of the output spectrum is 1300 nm and spectral width is greater than 100 nm. Meanwhile, the scan frequency can be adjusted to range from 20 to 100 kHz, and the stability degree of the optical capacity is less than 0.34%. Additionally, this study establishes a numerical model for the swept-source optical coherence tomography (SS–OCT) system and introduces a numerical simulation of the signal produced during the OCT imaging process ...

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    7. Resolving absolute depth in circular-ranging optical coherence tomography by using a degenerate frequency comb

      Resolving absolute depth in circular-ranging optical coherence tomography by using a degenerate frequency comb

      In Fourier-domain optical coherence tomography, an interference signal is generated that spans an RF bandwidth proportional to the product of three parameters: the imaging range, the imaging speed, and the inverse of the axial resolution. Circular-ranging optical coherence tomography (CR-OCT) architectures were introduced to ease long-range imaging by decoupling the imaging range from the signal RF bandwidth. As a consequence, present CR-OCT systems resolve the relative, but not the absolute, depth location of the scatterers. We introduce here a modified implementation of CR-OCT that uses a degenerate frequency comb source that allows recovery of absolute depth information while only minimally ...

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    8. GaAs-Based InPBi Quantum Dots for High Efficiency Super-Luminescence Diodes

      GaAs-Based InPBi Quantum Dots for High Efficiency Super-Luminescence Diodes

      InPBi exhibits broad and strong photoluminescence at room temperature, and is a potential candidate for fabricating super-luminescence diodes applied in optical coherence tomography. In this paper, the strained InPBi quantum dot (QD) embedded in the AlGaAs barrier on a GaAs platform is proposed to enhance the light emission efficiency and further broaden the photoluminescence spectrum. The finite element method is used to calculate the strain distribution, band alignment and confined levels of InPBi QDs. The carrier recombinations between the ground states and the deep levels are systematically investigated. A high Bi content and a flat QD shape are found preferable ...

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    9. Multimodality Imaging Approach for Combined Central Retinal Vein and Artery Occlusion: The Role of Optical Coherence Tomography Angiography

      Multimodality Imaging Approach for Combined Central Retinal Vein and Artery Occlusion: The Role of Optical Coherence Tomography Angiography

      Combined central retinal artery and vein occlusion is an uncommon vascular pathology that can cause severe and permanent visual impairment. Optical coherence tomography angiography (OCTA) is a newly available, noninvasive imaging technique that can potentially improve understanding of the structural and vascular implications and prognosis of this infrequent pathology. The present report describes the principal clinical findings in a case of combined central retinal artery and vein occlusion, as detected by the different imaging modalities available in a tertiary referral hospital. OCTA wide-field montage images identified an extensive area of nonperfusion on the macula with involvement of the entire retina ...

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    10. Surface emitting laser, information obtaining apparatus, and imaging apparatus

      Surface emitting laser, information obtaining apparatus, and imaging apparatus

      The present invention provides a surface emitting laser the wavelength-tunable band of which is wide. The wavelength-tunable surface emitting laser includes a first reflector (101), an active layer (103) disposed on the first reflector (101), a beam portion (110) disposed over the active layer (103) with an air gap therebetween, and a second reflector (120) disposed on the beam portion (110). The second reflector (120) has a distributed Bragg reflector consisting of a stack of dielectric layers. The beam portion (110) has a distributed Bragg reflector consisting of a stack of conductive semiconductor layers.

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    11. Method for signal processing in optical coherence tomography by means of a tunable light source

      Method for signal processing in optical coherence tomography by means of a tunable light source

      The invention relates to a method for signal processing in optical coherence tomography by means of a tunable light source (swept source), comprising the following steps: tuning the light source and sensing a signal intensity of the light source in linear dependence on the respective wave number (k) of the tunable light source and producing a signal intensity distribution in dependence on k; applying a window function to the sensed signal intensity distribution and producing a weighted signal intensity distribution; and applying a fast Fourier transform (FFT) to the weighted signal intensity distribution; and characterized in that, in the tuning ...

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    12. Thorlabs Extends MEMS-VCSEL Swept-Wavelength Laser Source Offering to Include 1060 nm

      Thorlabs Extends MEMS-VCSEL Swept-Wavelength Laser Source Offering to Include 1060 nm

      Thorlabs announced today that it has released next-generation versions of its MEMS-VCSEL Swept-Wavelength Laser Sources. The new SL10 series, centered at 1060 nm, complements the already well-established SL13 series at 1300 nm and is available with four different sweep rates ranging from 60 kHz to 400 kHz. Based on a patented microelectromechanical system (MEMS) tunable vertical cavity surface emitting laser (VCSEL), these light sources feature a record-breaking coherence length of over 100 mm and include an active power control that maintains constant output power over the lifetime of the laser. All drive electronics and trigger signals needed to seamlessly integrate ...

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      Mentions: Thorlabs
    13. Acousto-optically tuned external-cavity laser diode for optical coherence tomography with continuous wavelet transform

      Acousto-optically tuned external-cavity laser diode for optical coherence tomography with continuous wavelet transform

      We propose an acousto-optically tuned external-cavity laser diode (ECLD) based on the Littrow configuration to expand the wavelength-scanning range and eliminate mechanical motions. The scanning range and tuning rate of our prototype were 68.85 nm and more than 100 kHz, respectively, without any mode hop. Moreover, we implemented this improved ECLD in an optical coherence tomography imaging system and conducted a measurement of the two-dimensional thickness distribution of a thin glass plate via continuous wavelet transform analysis.

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    14. Highly-stable, multi-megahertz circular-ranging optical coherence tomography at 1.3 µm based on a chirped fiber Bragg grating

      Highly-stable, multi-megahertz circular-ranging optical coherence tomography at 1.3 µm based on a chirped fiber Bragg grating

      In Fourier-domain optical coherence tomography (OCT), the finite bandwidth of the acquisition electronics constrains the depth range and speed of the system. Circular-ranging (CR) OCT methods use optical-domain compression to surpass this limit. However, the CR-OCT system architectures of prior reports were limited by poor stability and were confined to the 1.55 µm wavelength range. In this work, we describe a novel CR-OCT architecture that is free from these limitations. To ensure stable operation, temperature sensitive optical modules within the system were replaced; the kilometer-length fiber spools used in the stretched-pulse mode-locked (SPML) laser was eliminated in favor of ...

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    15. Marie Curie PhD Studentship: VCSELs for Optical Coherence Tomography

      Marie Curie PhD Studentship: VCSELs for Optical Coherence Tomography

      Two Marie Curie Early Stage Researcher/PhD positions for 36 months starting from 1st February and 1st of April 2020, respectively, are available within the Institute for Microwave Engineering and Photonics (Photonics group/ Terahertz Devices and Systems group). These are supported by an EU funded Marie Curie Innovative Training Network, 860807, jointly organised with 14 other universities, companies and hospitals in Europe. Students will spend most of their time in Darmstadt, Germany with secondments to at least one University and one industrial partner each. Research will focus on innovative solutions for swept sources for optical coherence tomography based on widely ...

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    16. Wavelength tunable laser device

      Wavelength tunable laser device

      A photonic integrated circuit wavelength tunable laser device includes a gain element integrated into a photonic integrated circuit. The gain element provides optical gain to an optical signal. A tunable filter is integrated into the photonic integrated circuit. A modulator is integrated into the photonic integrated circuit that modulates the optical signal as a function of time, wherein the gain element, the tunable filter, and the modulator form a wavelength tunable laser device having a wavelength that tunes as a function of time.

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      Mentions: Eric A. Swanson
    17. Surface emitting laser, information acquiring apparatus, imaging apparatus, laser array, and method of manufacturing surface emitting laser

      Surface emitting laser, information acquiring apparatus, imaging apparatus, laser array, and method of manufacturing surface emitting laser

      A surface emitting laser having a wide wavelength tunable band is provided. A surface emitting laser includes a first reflecting mirror (102); a second reflecting mirror (116); and an active layer (104) arranged between the first reflecting mirror (102) and the second reflecting mirror (116), a gap being formed between the second reflecting mirror (116) and the active layer (104), an oscillation wavelength being tunable. The second reflecting mirror (116) includes a beam (108) comprising a single-crystal semiconductor, and a dielectric multilayer film (110) supported by the beam (108), and the dielectric multilayer film (110) is arranged in an opening ...

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    18. Real time FPGA resampling for swept source optical coherence tomography

      Real time FPGA resampling for swept source optical coherence tomography

      Real-time swept source OCT data is most often sampled using a specially cut hardware k-clock. The present invention involves mathematically resampling signals within an FPGA-based data acquisition board based on data sampled from a wide free spectral range reference interferometer. The FPGA can then multiply up the reference clock rate to achieve greater imaging depth. The Nyquist fold-over depth can thus be programmed from a standard reference to an arbitrary depth, much as PLL frequency synthesizer can produce many frequencies from a standard stable reference. The system is also capable of real-time performance.

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    19. Laser swept source with controlled mode locking for OCT medical imaging

      Laser swept source with controlled mode locking for OCT medical imaging

      An optical coherence analysis system uses a laser swept source that is constrained to operate in a mode locked condition. This is accomplished by synchronously changing the laser cavity's gain and/or phase based on the round trip travel time of light in the cavity. Many high-speed wavelength swept laser sources emit pulses synchronized with the round trip time of the cavity as part of a nonlinear optical frequency red shifting process. Stable pulsation is associated with smooth tuning and low relative intensity noise. Addition of mode-locking methods to this class of lasers can control and stabilize these lasers ...

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    20. Praevium Research Inc Receives a 2019 NIH Grant for $497,982 for Manufacturable and Reliable Electrically-Pumped Micro-Electromechanically Tunable VCSELs for Low-Cost Ophthalmic SS-OCT

      Praevium Research Inc Receives a 2019 NIH Grant for $497,982 for Manufacturable and Reliable Electrically-Pumped Micro-Electromechanically Tunable VCSELs for Low-Cost Ophthalmic SS-OCT

      Praevium Research Inc Receives a 2019 NIH Grant for $497,982 for Manufacturable and Reliable Electrically-Pumped Micro-Electromechanically Tunable Vertical Cavity Surface Emitting Lasers for Low-Cost Ophthalmic Swept Source Optical Coherence Tomography. The principal investigator is Christopher Burgner. The program began in 2012 and ends in 2020. Below is a summary of the proposed work. The ultimate goal of this effort is to bring advanced ophthalmic swept source optical coherence tomography (SS-OCT) imaging to low cost broadly accessible environments. SS-OCT is a powerful non-invasive diagnostic imaging modality, and an increasingly valuable tool in the early detection and monitoring of a number ...

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    21. Convective Nozaki-Bekki holes in a long cavity OCT laser

      Convective Nozaki-Bekki holes in a long cavity OCT laser

      We show, both experimentally and theoretically, that the loss of coherence of a long cavity optical coherence tomography (OCT) laser can be described as a transition from laminar to turbulent flows. We demonstrate that in this strongly dissipative system, the transition happens either via an absolute or a convective instability depending on the laser parameters. In the latter case, the transition occurs via formation of localised structures in the laminar regime, which trigger the formation of growing and drifting puffs of turbulence. Experimentally, we demonstrate that these turbulent bursts are seeded by appearance of Nozaki-Bekki holes, characterised by the zero ...

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    22. Fourier-domain mode-locked laser combined with a master-oscillator power amplifier architecture

      Fourier-domain mode-locked laser combined with a master-oscillator power amplifier architecture

      Originally introduced in 2005 for high-speed optical coherence tomography, the rapidly wavelength-swept Fourier-domain mode-locked (FDML) laser still, to this day, enables highest imaging speeds through a very high-speed spectral tuning capability. The FDML laser achieves a tuning bandwidth of over 1/10th of its center wavelength and can sweep this entire bandwidth in less than a microsecond. Interestingly, even though it covers a very broad spectral range, instantaneously it has a narrow spectral linewidth that puts it in a unique space compared to other high-speed broadband laser sources, e.g., mode-locked lasers or supercontinuum sources. Although it has been applied ...

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      Mentions: Bahram Jalali UCLA
    23. Agile imaging system

      Agile imaging system

      An agile optical imaging system for optical coherence tomography imaging using a tunable source comprising a wavelength tunable VCL laser is disclosed. The tunable source has long coherence length and is capable of high sweep repetition rate, as well as changing the sweep trajectory, sweep speed, sweep repetition rate, sweep linearity, and emission wavelength range on the fly to support multiple modes of OCT imaging. The imaging system also offers new enhanced dynamic range imaging capability for accommodating bright reflections. Multiscale imaging capability allows measurement over orders of magnitude dimensional scales. The imaging system and methods for generating the waveforms ...

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    24. Temperature stabilized phase reference for MEMS based swept sources

      Temperature stabilized phase reference for MEMS based swept sources

      MEMS tunable lasers are not inherently phase stable because Brownian motion and drive electronics noise make the starting wavelength of the sweep unstable with respect to the electrical sweep trigger. A typical solution to the problem is to use a fiber Bragg reflector wavelength trigger. That is a sub-optimal solution since environmental changes can move both the Bragg peak and the k-clock phase. We have packaged temperature controlled trigger and clock etalons in a butterfly package to solve this environmental problem. By making the wide FSR trigger etalon from silicon and the narrow FSR clock etalon from fused silica, the ...

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