Generation of transition of dark into bright and harmonic pulses in a passively Er-doped fiber laser using nonlinear multimodal interference technique

Abstract We demonstrate a passively Er-doped fiber lasers in normal dispersion region using nonlinear multimodal interference technique-based modulator, which generate the transition from dark pulse to single bright pulse and harmonic bright pulse. With the pump power set as 210 mW, the dark pulse possessing 40 MHz repetition frequency occurs. When the polarization states are suitable varied in the cavity, single-bright and second harmonic bright pulses can be achieved. The simulation method based on Ginzburg-Landau equation is provided to illustrate the laser physics and reveal the underlying principles of the transition from dark to bright pulses and the generation of harmonic pulses. Polarization modal dispersion resulting from multimode fibers plays a vital role for these phenomena. This proposed fiber laser possessing cost-efficient, versatile, all-fiber structure, provides a promising solution for large integrated networks and photonics.