Dynamics of Noise-like pulses in a Thulium-doped mode-locked fiber laser based on a non-linear absorbing loop mirror

Abstract

Nonlinear loop mirrors are widely used as an artificial saturable absorber to design passive mode-locked fiber lasers. Theoretical estimation shows that the nonlinear absorbing loop mirror (NAbLM) in ‘figure-8’ architecture can provide higher modulation depth and generate a larger extinction ratio over other conventional loop mirrors. The transmissivity of both the NAbLM and non-linear amplifying loop mirror (NALM) has been calculated and compared. Accordingly, a mode-locked Thulium fiber laser at around 2 µm has been designed using an NAbLM-based laser cavity. In the stable state, square-shaped broadband noise-like pulses of 3 ns at a repetition rate of 1.77 MHz have been obtained with a pulse energy of 141 nJ.