Yasuhiro Ishii

Optical Properties of Anthracene Single Crystals

Reflection spectra of anthracene are analysed by Kramers-Kronig method in the wavelength region from 192 to 600 mµ. The oscillator strength of the first electronic transition A 1 g → B 2 u is obtained with Lorentz field correction. The oscillator strength for individual vibronic band at room temperature is in excellent agreement with that obtained in the solution spectrum. The total oscillator strength f a + f b is 0.100 and 0.107 at room and at liquid nitrogen temperatures respectively. The quantity of the ratio of the oscillator strength as well as the absolute value of the oscillator strength is discussed in connection with the ratio of absorption intensities. Result suggests that the first vibronic band involves a contribution which arises from a thermally induced transition. Lorentz field in the anthracene crystal shows large anisotropy with respect to the direction of electric field applied. The oscillator strength obtained by simplified method is compared with that reported by several investigators.

Diaphragm for speaker and method of producing same

A diaphragm for a speaker obtained by forming a diaphragm base by screen processing a mixture of carbon fiber, pulp and polyvinyl alcohol fiber as a binder in a manner similar to that employed for making paper, depositing a thermosetting resin on the diaphragm base by impregnation or coating, and subjecting the diaphragm base, on which the thermosetting resin has been deposited, to electroless plating to deposit a metal film in the interstices between fibers and on the entire fiber surface.

Erasable digital audio disk system.

Following the popularization of the compact disc, much attention has been paid to development of an erasable optical disk. A magnetooptical disk has proved the most useful in our development of a digital audio disk system which cannot only play and record but also has erase and rewrite disks. This system using MO disks is capable of playing 45-min PCM sound on a CD format which makes high-fidelity sound with a low word error rate of 10−9 (after error correction). This system can also be used for the compact disk playback.

Polarized absorption edge and exciton-photon interaction in phenanthrene

Abstract The width at the half-maximum and the steep exponential absorption edge of the first exciton band of phenanthrene provide experimental evidences of a strong exciton-phonon interaction in phenanthrene. Shoulder bands which locate at the exciton absorption edge are interpreted as due to the existence of lattice defects.

Real-Time Recording and Erasure of Information by Optical Head with Laser Diode Array in Magneto-Optical Disk

The realization of an optical data system using magneto-optical disks remains an important subject for research. The functions of such a system would consist of real-time recording and erasure of information. We developed an optical head using a laser diode array with three elements, which successfully performs these functions. We also measured the real-time recording/erasure characteristics as a function of the composition of TbFeCo disks, using the optical head and six TbFeCo disks with different compositions. The characteristics were evaluated on the basis of the carrier-to-noise ratio and block error rate in Compact Disc formats. Real-time recording/erasure could be performed by applying a magnetic field of more than 400 Oe. But TbFeCo disks with compositions in the neighborhood of the magnetic compensation point delivered more stable performance with respect to deviations in the applied magnetic field and the recording power than disks with other compositions. We concluded that TbFeCo disks with 23 to 27 at% Tb are optimal for real-time recording/erasure by an optical head using a laser diode array.