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

A compact system of wavelength tunable femtosecond soliton pulse generation is demonstrated using compact fiber laser and optical fibers. The wavelength can be changed linearly and continuously from 1.56 to 1.86 /spl mu/m by changing the power of pump pulse. The experimental results are almost in agreement with the results of numerical simulations. Since this system is very compact and reliable, it is useful as a practical ultrashort pulse light source.

Compact system of wavelength tunable femtosecond soliton pulse generation in 1.56-1.86 /spl mu/m using optical fiber

Squeezed light generation is demonstrated using a new scheme of nonlinear fiber loop mirror. The squeezed light can be generated stably in a compact setup and the phase difference can be changed arbitrarily. Using a 100 ps mode-locked pulse laser at 1.064 µm and 0.85 µm single-mode fiber, the quantum noise reduction of 2.0 dB below the shot noise level is observed in the frequency range of 25–35 MHz. Accounting for the detection efficiency, this corresponds to 2.9 dB squeezing.

Generation and Detection of Squeezed Light with Phase Tunable Fiber Loop Mirror using Polarization Beam Splitter.

We demonstrated an all-optical signal control technique, novel to our knowledge, based on pulse trapping and amplification by ultrashort soliton pulse in a birefringent fiber to implement three functions: amplification, reshaping, and retiming. The signal and control pulses trap each other and copropagate in the fiber. The signal pulse experiences Raman gain and soliton effect by an ultrashort control pulse. The characteristics were investigated both experimentally and numerically. The maximum gain obtained was 28 dB in a 140 m long fiber. The output waveforms were ∼300 fs, chirp-free, sech2-shaped, ultrashort pulses. Delays and advances within ±0.4 ps in the initial signal were compensated for.

Ultrafast all-optical signal regenerator using pulse trapping in birefringent fibers

A device and a method for generating a wavelength-variable short pulse capable of generating a wavelength-variable short pulse light in a visible light wavelength region. When a ultra-short pulse light is beamed into an optical fiber (3), a wavelength-variable ultra-short soliton pulse is generated by a soliton effect and a non-linear optical effect due to Raman scattering. When the time width of this soliton pulse is shortened and a peak strength is increased, a third harmonic having one-third the wavelength can be generated by a tertiary non-linear optical effect, and using this a visible-light-region short wavelength can be obtained.

Wavelength-variable short pulse generating device and method

A high-speed, high-resolution, and large-scanning-range three-dimensional measurement system was demonstrated using an electronically controlled wavelength-tunable orthogonally polarized high-power ultrashort twin pulse source and an all-fiber interferometer. Thanks to the high peak power, the ultrashort optical pulses propagated along a fiber while maintaining the pulse shape by means of the soliton effect, allowing us to demonstrate high-speed, high-resolution, and large-scanning-range measurement. First, the interference was analyzed by numerical calculations and then the measurement system was demonstrated experimentally. A longitudinal scanning range of about 25 mm, a longitudinal resolution of 33 μm, and a scanning speed of 1000 points/s were achieved without moving parts. For a measurement distance of 0.5 m, a sensitivity of 60 dB was obtained. Clear three-dimensional images of a 100 yen Japanese coin and metal samples were obtained using this system.

High-speed, high-resolution, and large-scanning-range three-dimensional optical measurement system using a wavelength-tunable orthogonally polarized ultrashort twin pulse source

Norihiko Nishizawa

Papers

Compact system of wavelength tunable femtosecond soliton pulse generation in 1.56-1.86 /spl mu/m using optical fiber

Generation and Detection of Squeezed Light with Phase Tunable Fiber Loop Mirror using Polarization Beam Splitter.

Ultrafast all-optical signal regenerator using pulse trapping in birefringent fibers

Wavelength-variable short pulse generating device and method

High-speed, high-resolution, and large-scanning-range three-dimensional optical measurement system using a wavelength-tunable orthogonally polarized ultrashort twin pulse source