Analysis of the noise spectra of a laser diode with optical feedback from a high-finesse resonator

Noise spectra of a semiconductor laser with and without optical feedback from an external high-finesse resonator are calculated. Even very small amounts of optical feedback significantly reduce the low-frequency noise power, but the reduction depends on the source of the noise. The effect of various parameters on the noise reduction and on the stability of single-mode operation of the laser are determined, and the results are compared to recent experimental measurements. The results provide guidelines for the design of practical systems for achieving narrow emission linewidths and avoiding instability. The theoretical results show that a semiconductor laser with optical feedback functions as a laser with an optical servoloop and can be considered a self-injection-locked laser