1. Articles from Norihiko Nishizawa

    1-24 of 28 1 2 »
    1. Signal-to-background ratio and lateral resolution in deep tissue imaging by optical coherence microscopy in the 1700 nm spectral band

      Signal-to-background ratio and lateral resolution in deep tissue imaging by optical coherence microscopy in the 1700 nm spectral band

      We quantitatively investigated the image quality in deep tissue imaging with optical coherence microscopy (OCM) in the 1700 nm spectral band, in terms of the signal-to-background ratio (SBR) and lateral resolution. In this work, to demonstrate the benefits of using the 1700 nm spectral band for OCM imaging of brain samples, we compared the imaging quality of OCM en-face images obtained at the same position by using a hybrid 1300 nm/1700 nm spectral domain (SD) OCM system with shared sample and reference arms. By observing a reflective resolution test target through a 1.5 mm-thick tissue phantom, which had ...

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    2. High-spatial-resolution deep tissue imaging with spectral-domain optical coherence microscopy in the 1700-nm spectral band

      High-spatial-resolution deep tissue imaging with spectral-domain optical coherence microscopy in the 1700-nm spectral band

      We present three-dimensional (3-D) high-resolution spectral-domain optical coherence microscopy (SD-OCM) by using a supercontinuum (SC) fiber laser source with 300-nm spectral bandwidth (full-width at half-maximum) in the 1700-nm spectral band. By using low-coherence interferometry with SC light and a confocal detection scheme, we realized lateral and axial resolutions of 3.4 and 3.8  μm in tissue ( n   =  1.38), respectively. This is, to the best of our knowledge, the highest 3-D spatial resolution reported among those of Fourier-domain optical coherence imaging techniques in the 1700-nm spectral band. In our SD-OCM, to enhance the imaging depth, a full-range method was ...

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    3. Wavelength Dependence of Ultrahigh-Resolution Optical Coherence Tomography Using Supercontinuum for Biomedical Imaging

      Wavelength Dependence of Ultrahigh-Resolution Optical Coherence Tomography Using Supercontinuum for Biomedical Imaging

      Optical coherence tomography (OCT) is a noninvasive cross-sectional imaging technique with micrometer resolution. The theoretical axial resolution is determined by the center wavelength and bandwidth of the light source, and the wider the bandwidth, the higher the axial resolution. The characteristics of OCT imaging depend on the optical wavelength used. In this paper, we investigated the wavelength dependence of ultrahigh-resolution (UHR) OCT using a supercontinuum for biomedical imaging. Wideband, high-power, low-noise supercontinua (SC) were generated at λ = 0.8, 1.1, 1.3, and 1.7 μ m based on ultrashort pulses and nonlinear fibers. The wavelength dependence of OCT imaging was ...

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    4. Axial resolution and signal-to-noise ratio in deep-tissue imaging with 1.7-μm high-resolution optical coherence tomography with an ultrabroadband laser source

      Axial resolution and signal-to-noise ratio in deep-tissue imaging with 1.7-μm high-resolution optical coherence tomography with an ultrabroadband laser source

      We investigated the axial resolution and signal-to-noise ratio (SNR) characteristics in deep-tissue imaging by 1.7 - μ m 1.7-μm optical coherence tomography (OCT) with the axial resolution of 4.3    μ m 4.3  μm in tissue. Because 1.7 - μ m 1.7-μm OCT requires a light source with a spectral width of more than 300 nm full-width at half maximum to achieve such high resolution, the axial resolution in the tissue might be degraded by spectral distortion and chromatic dispersion mismatching between the sample and reference arms. In addition, degradation of the axial resolution would also lead to ...

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    5. Full-range ultrahigh-resolution spectral-domain optical coherence tomography in 1.7 µm wavelength region for deep-penetration and high-resolution imaging of turbid tissues

      Full-range ultrahigh-resolution spectral-domain optical coherence tomography in 1.7 µm wavelength region for deep-penetration and high-resolution imaging of turbid tissues

      For the first time, we developed a full-range ultrahigh-resolution (UHR) spectral-domain optical coherence tomography (SD-OCT) technique working in the 1.7 µm wavelength region. This technique allowed high-resolution, deep-tissue imaging. By using a supercontinuum source operating at a wavelength of 1.7 µm, an axial resolution of 3.6 µm in a tissue specimen was achieved. To enhance the imaging depth of UHR-SD-OCT, we performed full-range OCT imaging based on a phase modulation method. We demonstrated the three-dimensional (3D) imaging of a mouse brain with the developed system, and specific structures in the mouse brain were clearly visualized at depths ...

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    6. Wideband ultrafast fiber laser sources for OCT and metrology

      Wideband ultrafast fiber laser sources for OCT and metrology

      Fiber lasers, which use optical fibers as ideal waveguides, have been attracting a great deal of attention as stable, practical, and maintenance-free lasers. Using a combination of an ultrashort-pulse fiber laser and a nonlinear fiber, we can realize wideband highly functional ultrafast fiber laser sources. The generation of ultrashort pulses with wide wavelength tunability and supercontinua based on fiber lasers and nonlinear fibers has been demonstrated. These techniques are useful for laser applications, especially for imaging and metrology. In this topical review, the fundamentals of and recent progress in wideband ultrafast fiber laser sources and their applications are reviewed mainly ...

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    7. Development of a Fiber-Optic Optical Coherence Tomography Probe for Intraocular Use

      Development of a Fiber-Optic Optical Coherence Tomography Probe for Intraocular Use

      Purpose : To evaluate the performance of a newly developed 23-G optical coherence tomography (OCT) probe in animal and human eyes. Methods : The probe is a side-imaging OCT device with a scanning beam set 43° to the optical axis and a working distance of 1.5 to 2.0 mm. The performance of the OCT probe was tested during vitrectomy in porcine cadaver eyes and rabbit eyes in situ. Optical coherence tomography images of a normal retina, retinal break, optic disc, pars plicata of the ciliary body, and intraoperative surgical manipulations were recorded. The probe was also tested in a pilot ...

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    8. Optical coherence microscopy in 1700 nm spectral band for high-resolution label-free deep-tissue imaging

      Optical coherence microscopy in 1700 nm spectral band for high-resolution label-free deep-tissue imaging

      Optical coherence microscopy (OCM) is a label-free, high-resolution, three-dimensional (3D) imaging technique based on optical coherence tomography (OCT) and confocal microscopy. Here, we report that the 1700-nm spectral band has the great potential to improve the imaging depth in high-resolution OCM imaging of animal tissues. Recent studies to improve the imaging depth in OCT revealed that the 1700-nm spectral band is a promising choice for imaging turbid scattering tissues due to the low attenuation of light in the wavelength region. In this study, we developed high-resolution OCM by using a high-power supercontinuum source in the 1700-nm spectral band, and compared ...

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    9. High-power supercontinuum generation using high-repetition-rate ultrashort-pulse fiber laser for ultrahigh-resolution optical coherence tomography in 1600 nm spectral band

      High-power supercontinuum generation using high-repetition-rate ultrashort-pulse fiber laser for ultrahigh-resolution optical coherence tomography in 1600 nm spectral band

      We describe the generation of a high-power, spectrally smooth supercontinuum (SC) in the 1600 nm spectral band for ultrahigh-resolution optical coherence tomography (UHR-OCT). A clean SC was achieved by using a highly nonlinear fiber with normal dispersion properties and a high-quality pedestal-free pulse obtained from a passively mode-locked erbium-doped fiber laser operating at 182 MHz. The center wavelength and spectral width were 1578 and 172 nm, respectively. The output power of the SC was 51 mW. Using the developed SC source, we demonstrated UHR-OCT imaging of biological samples with a sensitivity of 109 dB and an axial resolution of 4 ...

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    10. Highly functional ultrashort pulse fiber laser sources and applications for optical coherence tomography

      Highly functional ultrashort pulse fiber laser sources and applications for optical coherence tomography

      We have been investigating highly functional ultrashort pulse fiber laser sources for highly sensitive, ultrahigh resolution optical coherence tomography (UHR-OCT). The coherent, low-noise, and Gaussian like wideband super-continuum (SC) sources were developed at five different wavelength regions between 0.8 and 1.7 um in order to investigate the wavelength dependence of OCT imaging. A real-time imaging was achieved with spectral domain OCT system. A fiber laser based, rapid, widely wavelength tunable narrow linewidth source was also developed. The UHR-OCT imaging of biological samples were demonstrated using the developed OCT systems.

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    11. 0.54 μm resolution two-photon interference with dispersion cancellation for quantum optical coherence tomography

      0.54 μm resolution two-photon interference with dispersion cancellation for quantum optical coherence tomography

      Quantum information technologies harness the intrinsic nature of quantum theory to beat the limitations of the classical methods for information processing and communication. Recently, the application of quantum features to metrology has attracted much attention. Quantum optical coherence tomography (QOCT), which utilizes two-photon interference between entangled photon pairs, is a promising approach to overcome the problem with optical coherence tomography (OCT): As the resolution of OCT becomes higher, degradation of the resolution due to dispersion within the medium becomes more critical. Here we report on the realization of 0.54  μ m resolution two-photon interference, which surpasses the current record resolution ...

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    12. Non-destructive cross-sectional imaging of tomato using ultra-high resolution optical coherence tomography

      Non-destructive cross-sectional imaging of tomato using ultra-high resolution optical coherence tomography

      Optical coherence tomography is an optical imaging technique that performs non-destructive cross-sectional imaging of micrometer-scale structures in samples. In this report, we demonstrated the visualization of inner structures in tomato fruits and leaves with ultra-high resolution optical coherence tomography (UHR-OCT) using fiber based laser source with ultra-broadband continuous spectrum around 1.7 μm wavelength. We confirmed that our UHR-OCT system allows us to perform cross-sectional imaging of tomato fruits and leaves at ∼ 2.8 μm axial resolution.

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    13. High-speed ultrahigh-resolution spectral domain optical coherence tomography using high-powersupercontinuum at 0.8 µm wavelength

      High-speed ultrahigh-resolution spectral domain optical coherence tomography using high-powersupercontinuum at 0.8 µm wavelength

      We demonstrated high-speed ultrahigh-resolution (UHR) optical coherence tomography (OCT) in the 800 nm wavelength region. A high-power coherent supercontinuum (SC) and a high-speed line scan camera were used to construct a spectral domain OCT. The axial resolution was 3.1 µm in air and 2.3 µm in tissue. The dependence of sensitivity on the SC power and A-scan rate was examined. For the A-scan rate of 70 kHz, the sensitivity of 104 dB was achieved for the SC power higher than 60 mW. High-speed in vivo UHR-OCT imaging was demonstrated for zebrafish embryo and swimming medaka.

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    14. Dispersion cancellation in high-resolution two-photon interference

      Dispersion cancellation in high-resolution two-photon interference

      The dispersion cancellation observed in Hong-Ou-Mandel (HOM) interference between frequency-entangled photon pairs has been the basis of quantum optical coherence tomography and quantum clock synchronization. Here we explore the effect of phase dispersion on ultranarrow HOM dips. We show that the higher-order dispersion, the linewidth of the pump laser, and the spectral shape of the parametric fluorescence have a strong effect on the dispersion cancellation in the high-resolution regime with several experimental verifications. Perfect dispersion cancellation with a linewidth of 3 μ m is also demonstrated through 25 mm of water.

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    15. Supercontinuum generation for ultrahigh-resolution optical coherence tomography at wavelength of 0.8µm using carbon nanotube fiber laser and similariton amplifier

      Supercontinuum generation for ultrahigh-resolution optical coherence tomography at wavelength of 0.8µm using carbon nanotube fiber laser and similariton amplifier

      We demonstrated supercontinuum (SC) generation for ultrahigh-resolution optical coherence tomography (UHR-OCT) in the 0.8 µm wavelength region using an ultrashort-pulse fiber laser system. An Er-doped ultrashort-pulse fiber laser with single-wall carbon nanotubes was developed as the seed pulse source. A 46 fs, highest quality, pedestal-free, clean, ultrashort pulse was generated with a similariton amplifier. Then, a 60 fs ideal ultrashort pulse was generated at a wavelength of 0.8 µm with a second-harmonic generation (SHG) crystal, and a Gaussian-like SC was generated in a photonic crystal fiber. UHR-OCT was demonstrated using the generated SC, and precise images of a ...

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    16. Highly functional wideband fiber lasers for metrology

      Highly functional wideband fiber lasers for metrology

      Spectrum compression of soliton pulses generates a narrow-linewidth pulse source that is rapidly wavelength-tunable across a broad range, making it suitable for novel applications. Advances in ultrashort-pulse laser technology have generated several new applications in the fields of laser processing, biomedical optics, opto-electronics, and related fields. 1, 2 However, conventional ultrashort-pulse lasers are limited by a requirement of quiet laboratory environments and water cooling. In addition, spectroscopy, optical coherence tomography (OCT), and nonlinear microscopy require both a wideband light source and a wavelength-tunable narrow-linewidth source. 2, 3 Moreover, tuning range is generally limited by the laser's gain bandwidth. Although ...

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    17. Generation and application of high-quality supercontinuum sources

      Generation and application of high-quality supercontinuum sources

      Ultrawideband supercontinua have been generated using ultrashort pulses and zero-dispersion highly nonlinear fiber. However, they have inherent large noise and spectral fine structure. We generated a widely and flatly broadened, low-noise, highly coherent, high-quality supercontinuum and used it to demonstrate ultrahigh-resolution optical coherence tomography in several wavelength regions.

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    18. Feature Of The Week 4/8/12: Researchers at Osaka and Nagoya University Investigate The Use of Ultrahigh Resolution OCT for Imaging Protein Crystals

      Feature Of The Week 4/8/12: Researchers at Osaka and Nagoya University Investigate The Use of Ultrahigh Resolution OCT for Imaging Protein Crystals

      technique used for atomic-resolution protein-structure studies, and currently, robotic automation is often used to monitor and optimize crystallization conditions. However, it is often difficult to identify, by conventional light microscopy, crystals that can be used for X-ray crystallography when micro-size, needle, and salt crystals are also present in the crystallization medium.For the work reported herein, we demonstrated that micro-scale, non-invasive, three-dimensional (3D) cross-sectional, μm-resolution imaging of protein crystals could be achieved using optical coherence tomography (OCT).A wideband, ultra-high resolution, OCT spectrum (supercontinuum) was generated using an ultrashort laser pulse and optical fibers as the light source. Given the ...

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    19. Three-dimensional, non-invasive, cross-sectional imaging of protein crystals using ultrahigh resolution optical coherence tomography

      Three-dimensional, non-invasive, cross-sectional imaging of protein crystals using ultrahigh resolution optical coherence tomography

      Micro-scale, non-invasive, three-dimensional cross-sectional imaging of protein crystals was successfully accomplished using ultra-high resolution optical coherence tomography (UHR-OCT) with low noise, Gaussian like supercontinuum. This technique facilitated visualization of protein crystals even those in medium that also contained substantial amounts of precipitates. We found the enhancement of the scattered signal from protein crystal by inclusion of agarose gel in the crystallization medium. Crystals of a protein and a salt in the same sample when visualized by UHR-OCT showed distinct physical characteristics, suggesting that protein and salt crystals may, in general, be distinguishable by UHR-OCT. UHR-OCT is a nondestructive and rapid ...

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    20. Feature Of The Week: 1/15/12: Review of Work by Nagoya University on Development & Application of Ultrashort Pulse Fiber Lasers

      Feature Of The Week: 1/15/12: Review of Work by Nagoya University on Development & Application of Ultrashort Pulse Fiber Lasers
      Passively mode-locked fiber lasers are stable and practical ultrashort pulse sources. We have been investigating the highly functional wideband ultrashort pulse fiber laser sources using ultrafast fiber nonlinear effects. These novel light sources are useful for multi-photon memory, multi-photon miscropscopy, spectroscopy, ultrahigh resolution optical coherence tomography, etc. In this talk, the development and applications of the highly functional ultrashort pulse fiber lasers are explained. Recently, single wall carbon nanotube (SWNT) absorbs a lot of attention as the new nonlinear optical devices. It shows the saturable absorption properties and the recovery time is ~1 ps. The environmental stability is one of ...
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    21. Quantitative comparison of contrast and imaging depth of ultrahigh-resolution optical coherence tomography images in 800–1700 nm wavelength region

      Quantitative comparison of contrast and imaging depth of ultrahigh-resolution optical coherence tomography images in 800–1700 nm wavelength region
      We investigated the wavelength dependence of imaging depth and clearness of structure in ultrahigh-resolution optical coherence tomography over a wide wavelength range. We quantitatively compared the optical properties of samples using supercontinuum sources at five wavelengths, 800 nm, 1060 nm, 1300 nm, 1550 nm, and 1700 nm, with the same system architecture. For samples of industrially used homogeneous materials with low water absorption, the attenuation coefficients of the samples were fitted using Rayleigh scattering theory. We confirmed that the systems with the longer-wavelength sources had lower scattering coefficients and less dependence on the sample materials. For a biomedical sample, we ...
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    22. Generation of broadband spontaneous parametric fluorescence and its application to quantum optical coherence tomography

      Generation of broadband spontaneous parametric fluorescence and its application to quantum optical coherence tomography
      Optical coherence tomography (OCT) based on Michelson interferometer has widely been utilized in biology and medicine as a type of optical biopsy and quantum optical coherence tomography (QOCT) based on Hong-Ou-Mandel interferometer has recently been demonstrated. By use of quantum entangled photon pairs generated via spontaneous parametric down conversion (SPDC) process, axial resolution of QOCT can be better than that of OCT in principle for a source of same bandwidth and group velocity dispersion (GVD) effect for QOCT can be automatically cancelled thanks to the frequency correlation of entangled photon pairs. To realize high-resolution QOCT, we need a broadband quantum ...
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    1-24 of 28 1 2 »
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    1. (28 articles) Norihiko Nishizawa
    2. (27 articles) Nagoya University
    3. (9 articles) Osaka University
    4. (9 articles) Hiroyuki Kawagoe
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    In vivo Ultrahigh-Resolution Ophthalmic Optical Coherence Tomography Using Gaussian-Shaped Supercontinuum Ultrahigh-Resolution Optical Coherence Tomography in 1.7 µm Region with Fiber Laser Supercontinuum in Low-Water-Absorption Samples Generation of broadband spontaneous parametric fluorescence and its application to quantum optical coherence tomography Quantitative comparison of contrast and imaging depth of ultrahigh-resolution optical coherence tomography images in 800–1700 nm wavelength region Feature Of The Week: 1/15/12: Review of Work by Nagoya University on Development & Application of Ultrashort Pulse Fiber Lasers Three-dimensional, non-invasive, cross-sectional imaging of protein crystals using ultrahigh resolution optical coherence tomography Feature Of The Week 4/8/12: Researchers at Osaka and Nagoya University Investigate The Use of Ultrahigh Resolution OCT for Imaging Protein Crystals High-speed ultrahigh-resolution spectral domain optical coherence tomography using high-powersupercontinuum at 0.8 µm wavelength Highly functional ultrashort pulse fiber laser sources and applications for optical coherence tomography High-power supercontinuum generation using high-repetition-rate ultrashort-pulse fiber laser for ultrahigh-resolution optical coherence tomography in 1600 nm spectral band 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