Studies on nonlinear loss and laser dynamics: From multiwavelength CW lasing to multi-pulsing transition

We develop a simple iterative model to simulate a laser with homogeneous gain and intensity dependent loss. Simulation results show that a laser with homogenous gain can operate at multiple wavelengths if the intensity-dependent loss exhibits saturable transmitter characteristics. Our results also show that for nonlinear losses that have both saturable transmitter and saturable absorber characteristics, such as arises from nonlinear optical loss mirrors (NOLM) or nonlinear polarization rotation (NPR), the multiwavelength output power spectrum can become very flat. The laser can also exhibit periodic and chaotic behaviors. We find that the same theoretical model can also be used to describe multipulsing dynamics of mode-locked lasers when the cavity energy increases. Near the multi-pulsing transitions, both periodic and chaotic behavior can be observed as operating states of the laser cavity. Our iterative model provides a simple geometrical description of the entire multi-pulsing transition behavior as a function of increasing cavity energy. The model captures all the key features observed in experiments, including the periodic and chaotic mode-locking regions, and further provides valuable insight into laser cavity engineering for maximizing performance.