Abstract

Stable single-frequency, narrow-linewidth, tunable lasers are required in applications such as coherent optical communications, optical fiber sensoring and spectroscopy. One can reduce the frequency drift of semiconductor lasers by locking to a Fabry-Perot interferometer using an automatic-frequency-control loop with feedback to the injection current [1] or temperature [2]. More recently very fast electronic feedback systems have achieved laser linewidth reduction as well as center frequency stabilization [3]. In addition, a variety of methods have been developed to reduce semiconductor laser linewidths by using optical techniques, including direct single-mirror optical feedback, optical injection locking and even optical feedback from fiber reference cavities [4].

© 1987 Optical Society of America