Yutaka Iwasaki

Periodic twinning in crystal quartz for optical quasi-phase matched secondary harmonic conversion

We show here the possibility of optical quasi-phase matched secondary harmonic generation in crystal quartz that is a non-ferroelectric crystal. By utilizing a twinning phenomenon, for the first time, we have succeeded infabricating periodic modulation of the nonlinear coefficient by hot pressing. In this method, stress is applied vertically on a quartz surface. We also devised a special press system. The numbers of twins we have achieved are 10 for 500 μm and 17 for 250 μm periods, and the depth of the twinned area is about 50 μm. Our results suggest that the twinned regions can be controlled artificially, and over a few tens of microns of twinned depth can be realized.

Differential interference contrast microscope with differential detection for optimizing image contrast.

A laser scanning differential interference contrast microscope using a differential detection method is proposed. This microscope permits observers to control the differential image contrast with a simple operation. Utilizing this function, the observers are capable of obtaining the optimized differential image whose contrast is most favorable for observation. A simple theoretical analysis and experimental considerations are described.

High-resolution displacement measurement using mode interference in the optical waveguide

Using an optical waveguide, high-resolution displacement measurement is achieved for the first time. The measurement principle is based on the interference between the two (even and odd) modes in the double-mode waveguide. After the light from a laser diode is focused onto the object to be measured, the wavefront gradient of the reflected light is detected using a Ti-indiffused LiNbO/sub 3/ channel waveguide. Although this optical measurement system is very simple, very high resolution (of less than 1 mn) is obtained. Besides, the characteristics of the measurement system do not depend on the surface condition of the object.

A Novel Super Resolution Technique for High-Density Optical Data Storage using Mode Interference in Channel Waveguides

A novel super-resolution system using a waveguide device is proposed and theoretical considerations are given. This system is capable of raising the storage density of optical discs considerably. The detected signal is calculated using scalar diffraction theory and the three-dimensional beam propagation method. The structure of the disc is substantially the same as that of conventional compact discs, which is the outstanding advantage of this method.

Characteristics of a high-resolution displacement sensor using mode interference in the optical waveguide

A high-resolution optical displacement sensing system using an optical waveguide is fabricated and characterized. The measurement principle is based on interference between an even and odd modes in the double-mode waveguide. After the light from a laser light source is focused onto the object to be measured, a wavefront gradient in the converged reflected light beam from the object gives a phase asymmetry at the entrance of the double-mode (DM) waveguide. A change of the phase asymmetry due to the displacement of the object along the optical axis is detected as a change of light intensity distribution at the exit of the DM waveguide. Although the optical system is very simple, experimental results using Ti-indiffused LiNbO3 waveguide device shows a very high resolution less than 1 nm. Next, a compact-type displacement sensor module using silica waveguide is fabricated and shows an identical high resolution. In conclusion, it will be very useful as a built-in component for various kinds of the industrial equipment.

Wide area interaction using telephoto imaging

Conventional interaction researches deal with relatively small spaces with physical proximity or completely distant spaces without physical proximity. However, there is an intermediate range of them. The distance to a target for interaction is longer than physical proximity but the target can be seen in a view. Such situations occur in sport stadiums, construction sites, cities, and so on. We call interaction in such a range as wide area interaction. As for wide area interaction, there are some researches on the infrastructure aspect [Blackstock et al. 2006], but there are few on the practical interaction method. Our approach is to utilize telephoto lens. With telephoto lens, a user can address a distant object and point the exact coordinate on the surface of the object from a distant place.

Characteristics of a Guided-Wave Displacement Sensor Based on Wavefront Detection

The characteristics of a guided-wave displacement sensor based on the wavefront detection are obtained. The displacement is measured by detecting the wavefront gradient of the light reflected from the measured object. The wavefront gradient is determined using the mode interference of the even and odd modes in the double-mode waveguide which is fabricated of silica glass on a Si substrate. The measuring range is 3 µm and the resolution is determined to be less than 1 nm. The object tilting dependence and the stability of the sensor are also measured. Furthermore, sample surfaces are observed and very fine images are obtained using this sensor. The optical system is very simple and the sensor is very compact, hence it will be useful as a built-in component for various kinds of industrial equipment.