Supermode noise suppression of the harmonically mode-locked fiber laser through continuous wave injection. Experiment and numerical simulations

We report on the results of experimental and numerical studies enabling deep insight into the physical mechanisms underlying the supermode noise suppression in harmonically mode-locked (HML) fiber laser using the resonant continuous wave (CW) injection. In particular, we have proved experimentally that the supermode noise suppression effect is available only with the CW injected to the long-wavelength side of laser spectrum. Injection to the opposite side destroys the HML operation regime and leads to the formation of tight soliton bunch. Our numerical simulations confirm these specific features. To get the result, we have simulated phase-locking between the CW and a single soliton. Then, the developed model has been applied to the laser cavity operating multiple pulses in the presence of the gain depletion and recovery mechanism responsible for harmonic pulse arrangement. We clearly demonstrate how the CW injection accelerates or destroys the HML process enabling the generation of additional inter-pulse forces.