Abstract

A systematic investigation of optical feedback induced effects on semiconductor laser diodes shows a variety of phenomena; some of them are linked to (left-right) symmetry properties of the system (symmetric solitary device plus optical feedback source). Attention is devoted to the appearance of feedback induced nonlinearities (kinks) in the P-I curves just above threshold [1]. Such nonlinearities are present in the characteristic curves taken from both facets, depend on the feedback ratio, and are reproducible. Kink formation and shaping are not substantially affected by the path between the laser facet and the reflecting surface; in particular they are not dependent on the presence of splices or connectors when a typical transmission line is the subject of investigation. Furthermore the role of optical feedback in destroying the symmetry between light outputs from the (equal reflectivity) front and rear facet of the devices is examined in detail, and a connection is established with the feedback adversely affecting the differential quantum efficiency of the device, in a selected range of values of the feedback ratio.

© 1992 Optical Society of America