Pulse Temporal Distance Control in Mamyshev Oscillators Enabled by Gain Depletion and Recovery

Abstract The core mechanism for mode-locking in a Mamyshev oscillator is the synergy between spectral broadening induced by self-phase modulation and offset spectral filtering. However, the long-cavity design required to accumulate sufficient nonlinearity, together with the randomness of the broadened spectral waveform, limits the realization of stable mode locking in the system, causing it to operate in a multi-pulse mode-locking regime under more general operating conditions. To address this issue, this work introduces the gain depletion and recovery mechanism into a Mamyshev oscillator and establishes a corresponding model. By exploiting the perturbation-induced gain depletion and recovery effect to adjust the temporal distances between adjacent pulses, a controllable evolution from a multi-pulse state to a harmonic mode-locking state is achieved. Experimental results show that this mechanism significantly accelerates the equalization of the temporal distances between adjacent pulses and enables stable harmonic mode-locking. Based on this approach, we achieve 95th-order harmonic mode-locking with a repetition rate of 341.12 MHz. These results demonstrate that the gain depletion and recovery mechanism induced by perturbations provides an effective and scalable route toward high-repetition-rate operation in Mamyshev oscillators.