Additive pulse mode-locking using a birefringent optical fiber

Abstract

A powerful and increasingly common method to mode-lock a variety of lasers is additive pulse mode-locking (APM). In this technique, a nonlinear medium is placed in an external cavity which is coupled to the main laser cavity. As a result of interference at the common mirror between the pulses returning from each cavity, significant pulse shortening may be obtained. Optical fiber is often used as the nonlinear medium, and polarization effects and fiber birefringence are generally neglected. A computer model has been developed in order to simulate the effect of using a birefringent fiber. The simulations indicate that although the birefringence often has little qualitative effect on the system, in certain cases the birefringence may be exploited for enhanced mode-locking.