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

We investigated the root mean square (RMS) timing jitter and RMS intensity noise of the wavelength tunable femtosecond soliton pulses using the technique of radio-frequency spectrum analysis We obtained interesting results that the generated solitons have almost constant RMS timing jitter and RMS intensity noise of approximately 410 fs and 003% in the wavelength region of 1600-1750 nm It is therefore believed that the magnitudes of the jitter and noise are not greatly increased in the process of wavelength tunable soliton pulse generation The wavelength tunable soliton pulse is confirmed to be stable and useful for practical applications

Measurement of Timing Jitter in Wavelength Tunable Femtosecond Soliton Pulses

We have measured the temperature of a Si substrate using an optical low-coherence interferometer employing supercontinuum light (SC). The accuracy of temperature measurement and the minimum measurable thickness of a layer are determined by the maximum resolving power of the optical path length of the medium in low-coherence interferometry, which depends on the coherent length defined by the spectrum profile and the wavelength of the light source. Low-noise, ultraflat, and highly coherent SC, generated using ultrashort laser pulses and optical fibers, was used as a light source. The wavelength dispersion of SC on the Si substrate was compensated by using a silicon mirror as a reference mirror, resulting in shaper interference waveforms of SC at the front and back surfaces of Si substrate than those of the superluminescent diode (SLD) light used as a conventional low-coherence light source. The measurement accuracy of the temperature using SC was improved to be ±0.4 °C from ±1.0 °C for the case of using the SLD. The temperatures of the Si substrate and SiO2 thin film were simultaneously measured using SC on an 800-µm-thick Si substrate with an 8.55-µm-thick SiO2 film. The temperature of the thin film, the thickness of which is several micrometers, was measured using SC and a compensation technique of wavelength dispersion using the silicon reference mirror.

https://iopscience.iop.org/article/10.7567/JJAP.52.026602/pdf

Temperature Measurement of Si Substrate Using Optical-Fiber-Type Low-Coherence Interferometry Employing Supercontinuum Light

1 Ultrahigh-Resolution Optical Coherence Tomography Using Femtosecond Lasers J.G. Fujimoto, A.D. Aguirre, Y. Chen, P.R. Herz, P.-L. Hsiung, T.H. Ko, N. Nishizawa, and F.X. Kärtner . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.

Ultrahigh-Resolution Optical Coherence Tomography Using Femtosecond Lasers

Wavelength dependence of ex-vivo ultrahigh-resolution optical coherence tomography (UHR-OCT) imaging of thyroid gland using supercontinuum at wavelength from 800 to 1700 nm was demonstrated. The wavelength dependence of the thickness of follicular epithelium and fine structures such as round or oval follicles were observed from the UHR-OCT cross sectional images. The reconstructed en-face OCT images at all wavelength regions were obtained and the images of follicles with several different signal intensities were observed in 1060 and 1700 nm UHR-OCT images. To our knowledge, this is the first observation of wavelength dependence of OCT images of thyroid gland structure.

Ex-vivo Imaging of Thyroid Gland Using Ultrahigh-Resolution Optical Coherence Tomography at Wavelength from 800 to 1700 nm

Cross-sectional imaging of isolated rat lungs was demonstrated by ultrahigh-resolution optical coherence tomography using supercontinua at 800, 1060, and 1300 nm wavelengths. The detailed structure of the trachea, including cartilage, mucosa, and annular ligaments, were observed clearly. In the imaging of visceral pleura and alveoli, when phosphate-buffered saline was instilled into the lung, the penetration depth of imaging was improved, and clear images of the fine structure of the lung, including alveoli, were observed owing to the index-matching effect. The wavelength dependence of the light source was discussed for the observation of fine structure and imaging contrast.

Norihiko Nishizawa

Papers

Measurement of Timing Jitter in Wavelength Tunable Femtosecond Soliton Pulses

Temperature Measurement of Si Substrate Using Optical-Fiber-Type Low-Coherence Interferometry Employing Supercontinuum Light

Ultrahigh-Resolution Optical Coherence Tomography Using Femtosecond Lasers

Ex-vivo Imaging of Thyroid Gland Using Ultrahigh-Resolution Optical Coherence Tomography at Wavelength from 800 to 1700 nm

Observation of Fine Lung Structure by Ultrahigh-Resolution Optical Coherence Tomography Using 800, 1060, and 1300 nm Supercontinua