Abstract

Semiconductor lasers are commonly used for the storage and retrieval of information in optical recording systems. Although the relative intensity noise (RIN) of a well-designed semiconductor laser isolated from external reflections remains low (< 120 dB/Hz) and well-behaved, a small fraction of optical feedback renders the RIN unstable and often higher by 20 dB or more. The feedback-induced RIN enhancement can be avoided by a technique known as high-frequency in jection (HFI),^1-4 in which the laser current is modulated at frequencies much higher than the data rate. The experimental results show that the RIN increase does not occur if the modulation frequency is suitably optimized and if the modulation amplitude is large enough to ensure that the laser is below threshold during a part of the modulation cycle.

© 1993 Optical Society of America