Impact of Spectral Filtering on Multipulsing Instability in Mode-Locked Fiber Lasers

We investigate the impact of spectral filtering in mode-locked fiber lasers with an extended geometrical model. Our iterative model, which includes gain, loss, and the pulse shaping effects of chromatic dispersion and self-phase modulation, is used to model the laser cavity dynamics. Simulations show that broadband pulses experience large losses from spectral filtering in the cavity, leading to a number of potential laser instabilities and outcomes such as multipulsing, periodic and chaotic states, or a single pulse which transits to a higher energy state. For narrow band spectral filtering, the laser dynamics is dominated by the gain-loss dynamics in the cavity which causes multipulsing. For broadband spectral filtering, the nonlinearity-induced spectral reshaping of the single pulse can lead to a discontinuous pulse energy transition that circumvents multipulsing. The inclusion of third-order dispersion shows that the multipulsing instability is induced even in the case of broadband spectral filtering.