Abstract

Considerable activity has been evident recently in the use of lasers coupled to nonlinear external cavities for the generation of short optical pulses. In particular nonlinear optical fibers have been used to effect additive pulse mode-locking (APM).¹ In the present paper we report a theoretical study of the utilization of a fiber laser source coupled to a nonlinear fiber external cavity configured for APM. The model developed in this work is of general application and, for example, includes as a special case a description of pulse effects in fiber laser amplifiers. The model utilizes numerical techniques for solving the nonlinear Schroedinger equation appropriate to both the active gain medium of the fiber laser and the passive external cavity nonlinear fiber.² It is shown in this work that a variety of pulse phenomena may arise in the all-fiber coupled cavity configuration depending upon the operating conditions of the fiber laser. The anticipated pulse narrowing is seen but pulse breakup may also occur. Prospects for high repetition frequency short pulse production are considered.

© 1991 Optical Society of America