[OPTICAL REVIEW Vol. 1, No. 2 (1994) 188-190]

Properties of a Two-Beam Laser Diode and Focusing Characteristics of a Two-Beam Optical Head

Masahisa SHINODA and Kenjiro KIME

Imaging Systems Laboratory, Mitsubishi Electric Corporation, 1, Zusho-Baba, Nagaokakyo, Kyoto, 617 Japan

(Accepted September 29, 1994)

Dynamic wavelength shifts of a monolithic, two-beam laser diode for a two-beam optical head in optical disk drives were analyzed with a streak camera system. The wavelength shift did not exceed 3 nm for the recording beam which was operated in a series of pulses, and the reproducing beam which was operated continuously showed no shift. The focusing characteristics on the basis of the wavelength shift and specifications of the optical head were also calculated. The dynamic displacement of the focal points caused by the wavelength shifts was so small as compared with the depth of focus in the optical head that the recording and reproducing characteristics were hardly influenced.

Key words : optical disk, two-beam optical head, two-beam laser diode, focusing characteristic, chromatic aberration, wavelength shift, streak camera