1. Articles from Meena Siddiqui

    1-8 of 8
    1. Extended Coherence Length and Depth Ranging Using a Fourier-Domain Mode-Locked Frequency Comb and Circular Interferometric Ranging

      Extended Coherence Length and Depth Ranging Using a Fourier-Domain Mode-Locked Frequency Comb and Circular Interferometric Ranging

      Fourier-domain mode locking has been a popular laser design for high-speed optical-frequency-domain imaging (OFDI), but achieving long coherence lengths, and therefore imaging range, has been challenging. The narrow linewidth of a Fourier-domain mode-locked (FDML) frequency-comb (FC) laser could provide an attractive platform for high-speed as well as long-range OFDI. Unfortunately, aliasing artifacts arising from signals beyond the principal measurement depth of the free spectral range have prohibited the use of an FDML FC laser for imaging so far. To make the increased coherence length of an FDML FC laser available, methods to manage such artifacts are required. Recently, coherent circular ...

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    2. Extended coherence length and depth ranging using a Fourier domain mode-locked frequency comb and circular interferometric ranging

      Extended coherence length and depth ranging using a Fourier domain mode-locked frequency comb and circular interferometric ranging

      Fourier domain mode-locking (FDML) has been a popular laser design for high speed optical frequency domain imaging (OFDI) but achieving long coherence lengths, and therefore imaging range, has been challenging. The narrow instantaneous linewidth of a frequency comb (FC) FDML laser could provide an attractive platform for high speed as well as long range OFDI. Unfortunately, aliasing artifacts arising from signals beyond the principle measurement depth of the free spectral range have prohibited the use of a FC FDML for imaging so far. To make the enhanced coherence length of FC FDML laser available, methods to manage such artifacts are ...

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    3. High-speed optical coherence tomography by circular interferometric ranging

      High-speed optical coherence tomography by circular interferometric ranging

      Existing three-dimensional optical imaging methods excel in controlled environments, but are difficult to deploy over large, irregular and dynamic fields. This means that they can be ill-suited for use in areas such as material inspection and medicine. To better address these applications, we developed methods in optical coherence tomography to efficiently interrogate sparse scattering fields, that is, those in which most locations (voxels) do not generate meaningful signal. Frequency comb sources are used to superimpose reflected signals from equispaced locations through optical subsampling. This results in circular ranging, and reduces the number of measurements required to interrogate large volumetric fields ...

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    4. 16  MHz wavelength-swept and wavelength-stepped laser architectures based on stretched-pulse active mode locking with a single continuously chirped fiber Bragg grating

      16  MHz wavelength-swept and wavelength-stepped laser architectures based on stretched-pulse active mode locking with a single continuously chirped fiber Bragg grating

      We demonstrate a novel high-speed and broadband laser architecture based on stretched pulse active mode locking that provides a wavelength-swept and wavelength-stepped output. The laser utilizes a single intracavity 8.3 meter chirped fiber Bragg grating to generate positive and negative dispersion, and can be operated with or without an intracavity fixed Fabry–Perot etalon to generate wavelength-swept and wavelength-stepped (frequency comb) outputs, respectively. Using a four-path delay line at the output, we achieved 16.3 MHz repetition rates and a 62 nm lasing bandwidth centered at 1550 nm. Single-sided double-pass coherence lengths of 1.25 mm for the wavelength-swept ...

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    5. Compensation of spectral and RF errors in swept-source OCT for high extinction complex demodulation

      Compensation of spectral and RF errors in swept-source OCT for high extinction complex demodulation

      We provide a framework for compensating errors within passive optical quadrature demodulation circuits used in swept-source optical coherence tomography (OCT). Quadrature demodulation allows for detection of both the real and imaginary components of an interference fringe, and this information separates signals from positive and negative depth spaces. To achieve a high extinction (∼60 dB) between these positive and negative signals, the demodulation error must be less than 0.1% in amplitude and phase. It is difficult to construct a system that achieves this low error across the wide spectral and RF bandwidths of high-speed swept-source systems. In a prior work ...

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    6. System, Apparatus And Method Utilizing Optical Dispersion For FOURIER-DOMAIN Optical Coherence Tomography

      System, Apparatus And Method Utilizing Optical Dispersion For FOURIER-DOMAIN Optical Coherence Tomography

      An apparatus can be provided which can include a laser arrangement which can be configured to provide a laser radiation, and can include an optical cavity. The optical cavity can include a dispersive optical first arrangement which can be configured to receive and disperse at least one first electro-magnetic radiation so as to provide at least one second electro-magnetic radiation.

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    7. A rapid, dispersion-based wavelength-stepped and wavelength-swept laser for optical coherence tomography

      A rapid, dispersion-based wavelength-stepped and wavelength-swept laser for optical coherence tomography

      Abstract: Optical-domain subsampling enables Fourier-domain OCT imaging at high-speeds and extended depth ranges while limiting the required acquisition bandwidth. To perform optical-domain subsampling, a wavelength-stepped rather than a wavelength-swept source is required. This preliminary study introduces a novel design for a rapid wavelength-stepped laser source that uses dispersive fibers in combination with a fast lithium-niobate modulator to achieve wavelength selection. A laser with 200 GHz wavelength-stepping and a sweep rate of 9 MHz over a 94 nm range at a center wavelength of 1550 nm is demonstrated. A reconfiguration of this source design to a continuous wavelength-swept light for conventional ...

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    8. Optical-domain subsampling for data efficient depth ranging in Fourier-domain optical coherence tomography

      Optical-domain subsampling for data efficient depth ranging in Fourier-domain optical coherence tomography

      Recent advances in optical coherence tomography (OCT) have led to higher-speed sources that support imaging over longer depth ranges. Limitations in the bandwidth of state-of-the-art acquisition electronics, however, prevent adoption of these advances into the clinical applications. Here, we introduce optical-domain subsampling as a method for imaging at high-speeds and over extended depth ranges but with a lower acquisition bandwidth than that required using conventional approaches. Optically subsampled laser sources utilize a discrete set of wavelengths to alias fringe signals along an extended depth range into a bandwidth limited frequency window. By detecting the complex fringe signals and under the ...

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    1-8 of 8
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  2. Topics in the News

    1. (8 articles) Massachusetts General Hospital
    2. (8 articles) Benjamin J. Vakoc
    3. (7 articles) Harvard University
    4. (3 articles) Massachusetts Institute of Technology
    5. (2 articles) Brett E. Bouma
    6. (1 articles) Cedric Blatter
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    Optical-domain subsampling for data efficient depth ranging in Fourier-domain optical coherence tomography A rapid, dispersion-based wavelength-stepped and wavelength-swept laser for optical coherence tomography System, Apparatus And Method Utilizing Optical Dispersion For FOURIER-DOMAIN Optical Coherence Tomography Compensation of spectral and RF errors in swept-source OCT for high extinction complex demodulation 16  MHz wavelength-swept and wavelength-stepped laser architectures based on stretched-pulse active mode locking with a single continuously chirped fiber Bragg grating High-speed optical coherence tomography by circular interferometric ranging Extended coherence length and depth ranging using a Fourier domain mode-locked frequency comb and circular interferometric ranging Extended Coherence Length and Depth Ranging Using a Fourier-Domain Mode-Locked Frequency Comb and Circular Interferometric Ranging Image contrast correction method in full-field optical coherence tomography Evaluation of posterior vitreous detachment using ultrasonography and optical coherence tomography Optical coherence tomography angiography characteristics of acute retinal arterial occlusion Computed Tomography–Mediated Registration of Trapeziometacarpal Articular Cartilage Using Intraarticular Optical Coherence Tomography and Cryomicrotome Imaging: A Cadaver Study