Abstract

The Mode locking of lasers, particularly semiconductor lasers, continues to generate intense interest because of its such potential use as the source of ultrashort optical pulses in a soliton communication system and a general laboratory tool. A large number of different-techniques have been used in recent years, including Kerr-lens mode locking, and additive-pulse mode locking. In this paper we demonstrate a new technique for mode locking that appears to be applicable to a wide variety of lasers including semiconductor lasers for which the short optical-cavity length and resultant high repetition rate make active mode locking very difficult. Our technique makes use of optical feedback from a phase-conjugate mirror (PCM) created by nondegenerate four-wave mixing (FWM), which directly couples pairs of longitudinal modes in a manner similar to active mode locking. The technique is essentially passive, however, because the laser is mode locked, it and the PCM pump laser are operated continuously.

© 1995 Optical Society of America