Abstract

A systematic investigation of optical feedback (OFB)-induced effects on semiconductor laser diodes (SLD) shows a variety of phenomena. The emitted light has always been measured from both laser facets: front facet (FF) is the facet facing the source of OFB, and rear facet (RF) is the opposite one. The results of the investigation show the existence of an asymmetry in the response from the system (solitary device plus OFB source). The threshold current linear reduction, the appearance of a kink just above threshold in the P-I characteristic curve of the oscillations induced in the emitted power by changing the length of the external cavity can be monitored from the FF as well as from the RF. On the contrary the differential quantum efficiency does not show the same behavior from both sides. Its changes from the RF are negligible, but looking at the signal emitted from the FF it is possible to see an increase or a decrease of the slope of the P-I curve. A simple and comprehensive analysis of the asymmetric response from the SLD facets can be performed with an analytical model for single-mode SLD. The rate equations with microscopic parameters are implemented with additional terms describing the contribution of OFB to the dynamics, responsible for the existence of different classes of behavior of the differential quantum efficiency as the feedback ratio is changed.

© 1991 Optical Society of America