<title>Low-threshold passively mode-locked erbium fiber ring lasers</title>

Abstract

The operating characteristics of a simple self-starting mode-locked erbium fiber ring laser based on a commercial optical fiber gain module are described. The laser produces pulses of the order of 50 mW. In contrast to earlier lasers of the same type, no polarizing element was needed in the ring to initiate mode locking. the implications of this fact relative to possible mechanisms for mode locking are discussed.