Abstract

A semiconductor laser (SCL) under external feedback exhibits a variety of instabilities.^[1],[2] Many details of these instabilities depend sensitively on system parameters, such as the amount of feedback, the operating point of the laser, and the ratio of the laser cavity length to the distance between laser output mirror and the feedback mirror. In particular, Sacher el al.^[1] report linewidth broadening (10-25 GHz) and intermittent behavior in the emitted light intensity. We consider a colinear three-mirror composite-cavity configuration with 100%-reflecting end mirrors and an internal mirror of arbitrary reflectivity. The left cavity is a semiconductor laser and the right cavity is passive. We also assume an overall ^[3] and the usual gain linearly proportional to carrier density. By composite-cavity modes we mean the eigenmodes of the combined system of the two coupled cavities when no active material is present. We have found extreme sensitivity of steady-state operating conditions (laser frequency and threshold carrier density) on the external cavity length and studied the dynamical behavior of small length changes.

© 1992 IQEC