Abstract

Recent experimental studies of feedback-induced noise in single-mode diode lasers have revealed that weak feedback can induce the generation of sidebands separated by 1-3 GHz from the primary optical mode [1,2]. An interesting but unexplained observation was that, for external cavities longer than several millimeters, the sideband frequency did not depend on the length of the optical feedback path. The new analytical and numerical results reported in this paper indicate that feedback-induced high frequency intensity pulsations in single mode diode lasers are caused by the carrier-dependent modal refractive index of the laser cavity. These results fully explain the above observations and establish a simple, yet general, framework for understanding the origin of feedback noise in diode lasers coupled to external cavities of arbitrary length.

© 1982 Optical Society of America