1. Articles from Xiaoming Wei

    1-11 of 11
    1. Video-rate centimeter-range optical coherence tomography based on dual optical frequency combs by electro-optic modulators

      Video-rate centimeter-range optical coherence tomography based on dual optical frequency combs by electro-optic modulators

      Imaging speed and range are two important parameters for optical coherence tomography (OCT). A conventional video-rate centimeter-range OCT requires an optical source with hundreds of kHz repetition rate and needs the support of broadband detectors and electronics (>1 GHz). In this paper, a type of video-rate centimeter-range OCT system is proposed and demonstrated based on dual optical frequency combs by leveraging electro-optic modulators. The repetition rate difference between dual combs, i.e. the A-scan rate of dual-comb OCT, can be adjusted within 0~6 MHz. By down-converting the interference signal from optical domain to radio-frequency domain through dual comb beating ...

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    2. Spatio-temporally incremental fiber swept source

      Spatio-temporally incremental fiber swept source

      A spatio-temporally incremental fiber sweep source includes a laser light pulse generator for generating light pulses and a fiber array of individual optical fibers. The fiber array has an input end and an output end, with the fibers at the input end receiving the light pulses substantially simultaneously. The optical fibers at the output end are arranged in a raster scan pattern, e.g., a square pattern, wherein the optical delay in each fiber is greater than the previous one in the scan pattern direction. As a result light exits the array in a completely optical two dimensional raster scan ...

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    3. Sensitivity enhancement in swept-source optical coherence tomography by parametric balanced detector and amplifier

      Sensitivity enhancement in swept-source optical coherence tomography by parametric balanced detector and amplifier

      We proposed a sensitivity enhancement method of the interference-based signal detection approach and applied it on a swept-source optical coherence tomography (SS-OCT) system through all-fiber optical parametric amplifier (FOPA) and parametric balanced detector (BD). The parametric BD was realized by combining the signal and phase conjugated idler band that was newly-generated through FOPA, and specifically by superimposing these two bands at a photodetector. The sensitivity enhancement by FOPA and parametric BD in SS-OCT were demonstrated experimentally. The results show that SS-OCT with FOPA and SS-OCT with parametric BD can provide more than 9 dB and 12 dB sensitivity improvement, respectively ...

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    4. Tri-band optical coherence tomography for lipid and vessel spectroscopic imaging

      Tri-band optical coherence tomography for lipid and vessel spectroscopic imaging

      Optical coherence tomography (OCT) has been utilized for various functional imaging applications. One of its highlights comes from spectroscopic imaging, which can simultaneously obtain both morphologic and spectroscopic information. Assisting diagnosis and therapeutic intervention of coronary artery disease is one of the major directions in spectroscopic OCT applications. Previously Tanaka et al. have developed a spectral domain OCT (SDOCT) to image lipid distribution within blood vessel [1]. In the meantime, Fleming et al. have demonstrated optical frequency domain imaging (OFDI) by a 1.3-μm swept source and quadratic discriminant analysis model [2]. However, these systems suffered from burdensome computation ...

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    5. Tri-band spectroscopic optical coherence tomography based on optical parametric amplification for lipid and vessel visualization

      Tri-band spectroscopic optical coherence tomography based on optical parametric amplification for lipid and vessel visualization

      A tri-band spectroscopic optical coherence tomography (SOCT) system has been implemented for visualization of lipid and blood vessel distribution. The tri-band swept source, which covers output spectrum in 1.3, 1.5, and 1.6μ m wavelength windows, is based on a dual-band Fourier domain mode-locked laser and a fiber optical parametric amplifier. This tri-band SOCT can further differentiate materials, e.g., lipid and artery, qualitatively by contrasting attenuation coefficients difference within any two of these bands. Furthermore, ex vivo imaging of both porcine artery with artificial lipid plaque phantom and mice with coronary artery disease were demonstrated to showcase ...

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    6. 28 MHz swept source at 1.0 μm for ultrafast quantitative phase imaging

      28 MHz swept source at 1.0 μm for ultrafast quantitative phase imaging

      Emerging high-throughput optical imaging modalities, in particular those providing phase information, necessitate a demanding speed regime (e.g. megahertz sweep rate) for those conventional swept sources; while an effective solution is yet to be demonstrated. We demonstrate a stable breathing laser as inertia-free swept source (BLISS) operating at a wavelength sweep rate of 28 MHz, particularly for the ultrafast interferometric imaging modality at 1.0 μm. Leveraging a tunable dispersion compensation element inside the laser cavity, the wavelength sweep range of BLISS can be tuned from ~10 nm to ~63 nm. It exhibits a good intensity stability, which is quantified ...

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    7. High-performance multi-megahertz optical coherence tomography based on amplified optical time-stretch

      High-performance multi-megahertz optical coherence tomography based on amplified optical time-stretch

      As the key prerequisite of high-speed volumetric structural and functional tissue imaging in real-time, scaling the A-scan rate beyond MHz has been one of the major pursuits in the development of optical coherence tomography (OCT). Along with a handful of techniques enabling multi-MHz, amplified optical time-stretch OCT (AOT-OCT) has recently been demonstrated as a viable alternative for ultrafast swept-source OCT well above MHz without the need for the mechanical wavelength-tuning mechanism. In this paper, we report a new generation of AOT-OCT demonstrating superior performance to its older generation and all other time-stretch-based OCT modalities in terms of shot-to-shot stability, sensitivity ...

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    8. Simultaneous dual-band optical coherence tomography for endoscopic applications

      Simultaneous dual-band optical coherence tomography for endoscopic applications

      Dual-band optical coherence tomography (OCT) can greatly enhance the imaging contrast with potential applications in functional (spectroscopic) analysis. A new simultaneous dual-band Fourier domain mode-locked swept laser configuration for dual-band OCT is reported. It was based on a custom-designed dual-channel driver to synchronize two different wavelength bands at 1310 and 1550 nm, respectively. Two lasing wavelengths were swept simultaneously from 1260 to 1364.8 nm for the 1310-nm band and from 1500 to 1604 nm for the 1550-nm band at an A-scan rate of 45 kHz. Broadband wavelength-division multiplexing was utilized to couple two wavelength bands into a common catheter ...

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    9. 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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    10. Broadband fiber-optical parametric amplification for ultrafast time-stretch imaging at 1.0 um

      Broadband fiber-optical parametric amplification for ultrafast time-stretch imaging at 1.0 um

      We demonstrate a broadband all-fiber-optical parametric amplifier for ultrafast time-stretch imaging at 1.0 μm, featured by its compact design, alignment-free, high efficiency, and flexible gain spectrum through fiber nonlinearity- and dispersion-engineering: specifically on a dispersion-stabilized photonic-crystal fiber (PCF) to achieve a net gain over 20 THz (75 nm) and a highest gain of ∼ 6000 (37.5 dB). Another unique feature of the parametric amplifier, over other optical amplifiers, is the coherent generation of a synchronized signal replica (called idler) that can be exploited to offer an extra 3-dB gain by optically superposing the signal and idler. It further enhances ...

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    11. Performance of megahertz amplified optical time-stretch optical coherence tomography (AOT-OCT)

      Performance of megahertz amplified optical time-stretch optical coherence tomography (AOT-OCT)

      Enabled by the ultrahigh-speed all-optical wavelength-swept mechanism and broadband optical amplification, amplified optical time-stretch optical coherence tomography (AOT-OCT) has recently been demonstrated as a practical alternative to achieve ultrafast A-scan rate of multi-MHz in OCT. With the aim of identifying the optimal scenarios for MHz operation in AOT-OCT, we here present a theoretical framework to evaluate its performance metric. In particular, the analysis discusses the unique features of AOT-OCT, such as its superior coherence length, and the relationship between the optical gain and the A-scan rate. More importantly, we evaluate the sensitivity of AOT-OCT in the MHz regime under the ...

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    1-11 of 11
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    1. (9 articles) Kenneth K. Y. Wong
    2. (8 articles) University of Hong Kong
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    Performance of megahertz amplified optical time-stretch optical coherence tomography (AOT-OCT) Broadband fiber-optical parametric amplification for ultrafast time-stretch imaging at 1.0 um Breathing laser as an inertia-free swept source for high-quality ultrafast optical bioimaging Simultaneous dual-band optical coherence tomography for endoscopic applications High-performance multi-megahertz optical coherence tomography based on amplified optical time-stretch 28 MHz swept source at 1.0 μm for ultrafast quantitative phase imaging Tri-band spectroscopic optical coherence tomography based on optical parametric amplification for lipid and vessel visualization Tri-band optical coherence tomography for lipid and vessel spectroscopic imaging Sensitivity enhancement in swept-source optical coherence tomography by parametric balanced detector and amplifier Spatio-temporally incremental fiber swept source Optical Coherence Tomography: Critical Tool to Manage Expectations after Cataract Extraction Improving the characterization of ex vivo human brain optical properties using high numerical aperture optical coherence tomography by spatially constraining the confocal parameters