Generation of H-shaped pulse rains induced by intracavity Fabry-Perot filtering in a fiber laser

We report the generation of h-shaped pulses and rains in a fiber laser with a Fabry-Perot (F-P) subcavity. An h-shaped pulse state composed of a sharp spike as a leading edge and a long flat-top bunch as a tailing one could be switched to an h-shaped pulse rain state by adjusting the polarization controllers (PCs). F-P filtering was found to play a crucial role in the formation of the h-shaped pulses and rains. The leading and tailing edges of the h-shaped pulse were found to be generated in the primary and secondary F-P filtering profiles, respectively. Furthermore, small discrete pulses could be triggered in the subordinate longer-wavelength F-P filtering profiles by adjusting the PCs. Then, for the first time, h-shaped pulse rains were experimentally observed as many small pulses continuously drifting away from the nanosecond-long h-shaped pulses because of their group velocity mismatch. These results will help contribute to a deep understanding of the dynamics of complex pulse patterns in fiber lasers.

Automated summary

By adjusting the polarization controllers, h-shaped pulses and spikes can be generated in a fiber laser with a Fabry-Perot subcavity. The F-P filtering plays a crucial role in shaping these pulses, with different filtering profiles leading to different pulse characteristics.