High performance single-gain-arm Tm-doped Mamyshev oscillator without external seeding

Mamyshev oscillators have attracted extensive attention in the fiber-laser community owing to their high pulse energy, but their practical implementation is hindered by difficult self-starting and complex cavity configurations. Here, we demonstrate a high-performance, single-gain-arm Tm-doped Mamyshev oscillator. By replacing a fixed filter with a tunable bandpass filter based on the multimode interference effect in a single-mode-no-core-single-mode fiber (SMF-NCF-SMF) structure, and employing nonlinear polarization rotation for saturable absorption, mode locking without external seeding is achieved. Aligning the central wavelength of the tunable filter with that of the fixed filter initiates mode locking, and a 73rd-order harmonic mode-locking state with a repetition rate of 793.5 MHz is achieved by increasing the pump power. Furthermore, by detuning the two filters from one another, an average output power of 92 mW is obtained, corresponding to a pulse energy of 8.3 nJ. This compact single-gain-arm design offers a viable route toward high-power pulsed fiber lasers in the 2 µm band.