Theoretical and experimental comprehensive study of GHz-range passively mode-locked fiber lasers

In this paper, we present a theoretical model based on the nonlinear Schrödinger equation to characterize GHz-range passively mode-locked fiber lasers. The modeled cavities of the lasers are configured by a highly doped and polarization-maintaining single fiber of a single type. For different pulse repetition rates, ranging from 1.0 to 10.0 GHz, gain parameters and pump threshold for a stable mode-locked laser emission are studied. Pulse time width, spectral width, and semiconductor saturable absorber mirror (SESAM) properties are defined to achieve stable emission. To experimentally validate our theoretical model, 1.0 and 2.2 GHz laser cavities have been built up and amplified. A stable and robust operation for both frequencies was obtained, and the experimental measurements have been found to match the theoretical predictions. Finally, enhanced environmental stability has been achieved using a cavity temperature control system and an antivibration enclosure.