A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

A topical review of numerical and experimental studies of supercontinuum generation in photonic crystal fiber is presented over the full range of experimentally reported parameters, from the femtosecond to the continuous-wave regime. Results from numerical simulations are used to discuss the temporal and spectral characteristics of the supercontinuum, and to interpret the physics of the underlying spectral broadening processes. Particular attention is given to the case of supercontinuum generation seeded by femtosecond pulses in the anomalous group velocity dispersion regime of photonic crystal fiber, where the processes of soliton fission, stimulated Raman scattering, and dispersive wave generation are reviewed in detail. The corresponding intensity and phase stability properties of the supercontinuum spectra generated under different conditions are also discussed.

Supercontinuum generation in photonic crystal fiber

Switches, and Actuators Masahiro Irie,*,† Tuyoshi Fukaminato,‡ Kenji Matsuda, and Seiya Kobatake †Research Center for Smart Molecules, Rikkyo University, Nishi-Ikebukuro 3-34-1, Toshima-ku, Tokyo 171-8501, Japan ‡Research Institute for Electronic Science, Hokkaido University, N20, W10, Kita-ku, Sapporo 001-0020, Japan Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510, Japan Department of Applied Chemistry, Graduate School of Engineering, Osaka City University, Sugimoto 3-3-138, Sumiyoshi-ku, Osaka 558-8585, Japan

Photochromism of Diarylethene Molecules and Crystals: Memories, Switches, and Actuators

Objective: To demonstrate optical coherence tomography for high-resolution, noninvasive imaging of the human retina. Optical coherence tomography is a new imaging technique analogous to ultrasound B scan that can provide cross-sectional images of the retina with micrometer-scale resolution. Design: Survey optical coherence tomographic examination of the retina, including the macula and optic nerve head in normal human subjects. Settings Research laboratory. Participants: Convenience sample of normal human subjects. Main Outcome Measures: Correlation of optical coherence retinal tomographs with known normal retinal anatomy. Results: Optical coherence tomographs can discriminate the cross-sectional morphologic features of the fovea and optic disc, the layered structure of the retina, and normal anatomic variations in retinal and retinal nerve fiber layer thicknesses with 10- μm depth resolution. Conclusion: Optical coherence tomography is a potentially useful technique for high depth resolution, cross-sectional examination of the fundus.

Optical Coherence Tomography of the Human Retina

Current medical imaging technologies allow visualization of tissue anatomy in the human body at resolutions ranging from 100 micrometers to 1 millimeter. These technologies are generally not sensitive enough to detect early-stage tissue abnormalities associated with diseases such as cancer and atherosclerosis, which require micrometer-scale resolution. Here, optical coherence tomography was adapted to allow high-speed visualization of tissue in a living animal with a catheter-endoscope 1 millimeter in diameter. This method, referred to as "optical biopsy," was used to obtain cross-sectional images of the rabbit gastrointestinal and respiratory tracts at 10-micrometer resolution.

In Vivo Endoscopic Optical Biopsy with Optical Coherence Tomography

High resolution and high penetration depth OCT is demonstrated with Gaussian shaped, center wavelength tunable, 230 nm wide bandwidth, high power supercontinuum at 1.65–1.73 µm wavelengths region using ultrashort pulse fiber laser based system.

1.7 µm wavelength tunable supercontinuum source for optical coherence tomography

48 pJ, 413 fs, chirp-free, sech2-shaped, coherent, ultrashort pulse was generated from an incoherent light of super luminescent diode using pulse trapping and amplification by an ultrashort soliton pulse in a 400 m-long birefringent fiber.

Coherent ultrashort pulse generation from incoherent light by trapped pulse amplification in birefringent fibers

Characteristics of ultrashort pulse propagation in optical fibers at the wavelength region of 1.55 μm are experimentally analyzed using the cross-correlation frequency resolved optical gating (X-FROG) technique. In the anomalous dispersive fibers, widely wavelength tunable femtosecond soliton pulse is generated. The spectrogram of almost transform limited soliton pulse around 2 μm is observed. In the dispersion shifted fibers, the wavelength tunable soliton pulse and anti-stokes pulse are generated. As the results of X-FROG measurement, it is clarified that the anti-stokes pulse is overlapped with the soliton pulse and trapped by the soliton pulse. In the highly nonlinear optical fibers, 1.2-2.1 μm ultra-widely broadened super continuum and 1.46-1.68 μm linearly chirped one are generated. The spectrograms of generated super continuum are observed. The phenomenon of pulse trapping is also observed in generated super continuum.

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Experimental Analysis of Ultrashort Pulse Propagation along Optical Fibers Using the Technique of Cross-Correlation Frequency Resolved Optical Gating.

Long ring-cavity, all-polarization maintaining, Er-doped fiber laser using single wall carbon nanotube polyimide film was demonstrated. Output pulses with pulse energy of 0.7∼2.6 nJ were obtained at ultra low repetition rate of 943∼154 kHz.

154 kHz, ultra-low repetition rate, high-energy pulse, polarization maintaining, Er-doped fiber laser using single wall carbon nanotube polyimide film

Three dimensional measurement system with high sensitivity of 99 dB and high longitudinal resolution of 10 μm is demonstrated using ultrashort pulse fiber laser and fiber interferometer. Precise image is obtained from 1.5 m distance.

Norihiko Nishizawa

Papers

1.7 µm wavelength tunable supercontinuum source for optical coherence tomography

Coherent ultrashort pulse generation from incoherent light by trapped pulse amplification in birefringent fibers

Experimental Analysis of Ultrashort Pulse Propagation along Optical Fibers Using the Technique of Cross-Correlation Frequency Resolved Optical Gating.

154 kHz, ultra-low repetition rate, high-energy pulse, polarization maintaining, Er-doped fiber laser using single wall carbon nanotube polyimide film

Highly Sensitive Three Dimensional Measurement Using Ultrashort Pulse Fiber Laser and Fiber Interferometer