Various types of visible laser diode have been reported as light sources for optical disk reading, such as audio and video disks. However, among them single-longitudinal-mode lasers need special means, such as super imposing (radio) high frequency on the bias current for applications in video disk reading, which requires about a 30-dB higher SNR than audio disk reading. Because without such means the noise of single-longitudinal-mode lasers increases drastically when a part of the reflected output is returned to the laser diode, resulting in mode jumping. On the other hand, multilongitudinal-mode laser diodes do not show such significant noise deterioration.

© 1982 Optical Society of America

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