Dynamics of an ultrahigh-repetition-rate passively mode-locked Raman fiber laser

We present an extended study of an ultrahigh-repetition-rate Raman fiber laser passively mode-locked through dissipative four-wave mixing. We demonstrate mode locking at 100 and 160 GHz repetition rates, corresponding to harmonic frequencies more than 400,000 times the cavity resonance frequency. By varying the output coupling ratio we are able to change the threshold and slope efficiency of the laser. The maximum average output power achieved was 926 mW, a further twofold increase of the output power reported previously for this type of laser. Further numerical analysis reveals that the main factor limiting the pulse quality of our setup is supermode noise. Subsequently, we experimentally investigate the use of all-fiber subcavity Fabry-Perot filters to reduce the noise and demonstrate a significant improvement in the laser operation.