Abstract

Fiber Raman soliton lasers have been extensively used to generate femtosecond pulses in the near-IR region around 1.3 μm. We have investigated the amplitude and phase noise properties of these lasers. Pump pulses from a second harmonic cw mode-locked Nd:YAG laser are launched into 300 m of single-mode optical fiber, generating Raman-shifted pulses that are compressed by the soliton effect. For a single-pass compressor, an amplitude noise floor of ≥50 dB above shot noise at 2 mA of photocurrent was observed, substantially higher than the ≈20-dB excess noise at 1-MHz offset observed in a standard fiber-grating pulse compressor. The amplitude noise is white, which implies that the amplitude fluctuations are uncorrelated from pulse to pulse. The Raman-soliton timing jitter increases to 5.2 ps with increasing pump power (1.6 W_max) given ≈2-ps jitter from the Nd:YAG pump. Using a synch-pumped ring cavity improved the timing jitter but did not improve the amplitude noise substantially due to the very low Q cavity.

© 1988 Optical Society of America