Abstract

Recently all-fiber, self-starting, passive mode-locked lasers with either linear or ring cavities have been proposed based on the intracavity nonlinear Sagnac switch ^[1,2]. Subsequent experiments ^[3,5] have demonstrated that these lasers are capable of generation of pulses with duration of less than 1 ps. In spite of a long cavity length, desired for a proper design of a nonlinear Sagnac switch, and since the repetition rate is not exactly defined at self-starting passive mode-locking, these lasers can operate at any multiple of the fundamental frequency of the cavity. Harmonic mode locking with repetition rates up to tens of gigahertz was observed at cavity resonant frequencies of few megahertz^[3,4]. However, it is difficult to control the repetition rate, namely, the modelocked pulses bunch together and the repetition rate is not fixed. Attaching to the laser the recirculating sub-ring cavity leads to the stabilization of the repetition rate, nevertheless the amplitude of the output pulses still fluctuates^[6].

© 1992 IQEC