The influence of feedback intensity on longitudinal mode properties and optical noise in index-guided semiconductor lasers

Theory and experiments on optical feedback effects in index-guided single-mode semiconductor lasers are presented. Evidence is found for the existence of a characteristic parameter which indicates the relative strength of the optical feedback. Near the transition ( ) from low to high feedback, the feedback-induced low-frequency intensity noise shows a maximum. At higher feedback hysteresis and instabilities are dominant, whereas the feedback-induced noise is low again.