Abstract
The present paper describes a computational study of the effects of a truncation coefficient on cross talk and frequency characteristics. The effects result from direct focusing of laser diode elliptical Gaussian beams when the minor axis of a focused beam is adjusted parallel to the track. It was found that a truncation coefficient that yields the minimum cross talk level varies with track spacing. Calculations were carried out on track spacing ranging from 1 to 2μm, which is the range required for practical applications. When the space between tracks was 1.4μm; the wavelength of the laser diode, 780nm; the NA of a objective lens, 0.5; the truncation coefficient which minimized cross talk was 0.7, and the minimum cross talk level was -40 dB. The change in frequency characteristics was less than 1 dB when the truncation ranged from 0.7 to 1.0, and these values did not affect playback characteristics.
