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 new scheme for a birefringent nonlinear polarization rotation mirror is proposed for pedestal suppression of ultrashort pulses. Environmentally stable and precisely controllable operation is demonstrated. The main pulse and pedestal components are separated and picked out from the different ports. By use of the soliton effect and nonlinear polarization rotation, almost transform-limited pedestal-free 318 and 143 fs ultrashort pulses with peak powers of 0.9 and 1.7 kW are successfully generated. The maximum pedestal-suppression ratio is 24 dB, and the pick-out efficiency is up to 46% including coupling loss. The characteristics are analyzed both experimentally and numerically.

Pedestal suppression of ultrashort pulses by using a birefringent nonlinear polarization rotation mirror

A direct diode pumped continuous-wave Ti:sapphire laser (DDPTS) is presented. A bow-tie geometry with optical diode is chosen for unidirectional single-mode operation. Frequency selection is performed with a standard combination of birefringent filter and etalon. To accomplish mode-hop free frequency tuning the piezo-driven etalon is stabilized to one of the cavity modes via dither-locking method. To suppress environmental fluctuations the cavity-mode is additionally locked to an external optical cavity with low frequency drift. Feasibility of the setup for high-resolution spectroscopy is demonstrated by saturated absorption spectroscopy of the D2 line of Rubidium.

A direct diode pumped Ti:sapphire laser with single-frequency operation for high resolution spectroscopy

Using Er-doped fiber and polarization maintaining highly nonlinear dispersion shifted fiber, ultrabroad supercontinuum is generated. The spectrum expands from 0.9 to 2.7 /spl mu/m, and the bandwidth is over 1.8 /spl mu/m.

http://ieeexplore.ieee.org/iel5/9407/29846/01361502.pdf

0.9 /spl sim/ 2.7 /spl mu/m over one octave spanning ultrabroad supercontinuum generation based on all fiber system

We developed a compact and high-power mode-locked fiber laser for three-dimensional optical memory. Fiber lasers have the potential to be compact and stable light sources that can replace bulk solid-state lasers. To generate high-power pulses, we used stretched-pulse mode locking. The average power and pulse width of the output pulse from the fiber laser that we developed were 109 mW and 2.1 ps, respectively. The dispersion of the output pulse was compensated with an external single-mode fiber of 2.5 m length. The pulse was compressed from 2.1 ps to 93 fs by dispersion compensation. The pulse emitted from this fiber laser has an energy sufficient to generate two photon recording effectively, so the fiber laser we have developed is possible to use as a light source of three-dimensional optical memory.

Compact and High-Power Mode-Locked Fiber Laser for Three-Dimensional Optical Memory

Ultrafast all-optical switching by use of pulse trapping in birefringent optical fiber is demonstrated both experimentally and numerically. The wavelengths of the control soliton pulse and the trapped soliton pulse are shifted to satisfy the condition of group velocity matching. Furthermore, the energy of the trapped pulse is increased through Raman gain of the control pulse. Only a signal pulse in the pulse train with temporal separation of about 1.2 ps is successfully picked off. The repetition frequency corresponds to 0.83 THz. The spectrogram of the optical switching is directly observed using the X-FROG technique. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 158(3): 38–44, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20470

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/eej.20470

Norihiko Nishizawa

Papers

Pedestal suppression of ultrashort pulses by using a birefringent nonlinear polarization rotation mirror

A direct diode pumped Ti:sapphire laser with single-frequency operation for high resolution spectroscopy

0.9 /spl sim/ 2.7 /spl mu/m over one octave spanning ultrabroad supercontinuum generation based on all fiber system

Compact and High-Power Mode-Locked Fiber Laser for Three-Dimensional Optical Memory

Ultrafast all‐optical switching using pulse trapping by ultrashort soliton pulse in birefringent optical fiber