All-Fiber 2 µm Mamyshev Oscillator: Mapping of Different Operating Regimes

Abstract

The Mamyshev oscillator is an elegant and versatile method for generating ultrashort and high-energy laser pulses. It is realized in an all-fiber structure, which provides robustness and good beam quality, ensuring reliable and efficient performance. An all-fiber 2 µm Mamyshev oscillator is presented based on two Tm-doped fiber amplifiers separated by a broadband fixed wavelength filter with 11.2 nm −3 dB bandwidth and a tunable narrow bandwidth filter with 1.1 nm −3 dB bandwidth. Three distinct emission regimes are identified and mapped out in terms of the pump power and the filter wavelength separation: 1) no mode-locking if either pump power is insufficient 2) stable mode-locking in a limited region of pump powers, and 3) noise-like pulse mode-locking if one of the pump powers exceeds a threshold. It is demonstrated how the mode-locking region in terms of the two pump powers narrows with increasing filter wavelength separation and the pulses are compressed to 309 fs in standard silica fiber. The map over operation regimes provides a clear relationship between operating regimes and cavity parameters, offering valuable insights into the design of Mamyshev oscillators using filters of significantly different bandwidths.