All-fiber self-starting Mamyshev oscillator based on absorption-induced spectral filtering

A self-starting all-fiber Mamyshev oscillator (MO) at 1550 nm is proposed and experimentally demonstrated based on an absorption filter. A shortpass absorption filter is designed based on the strong absorption of Tm 3+ ions near 1560 nm. The filter is cascaded with a conventional fiber filter, forming an offset spectral filtering stage suitable for MO. The effects of the cutoff depth of the absorption filter and the pump power on the self-starting mode-locking behavior of MO are systematically investigated. Experimental results show that self-starting mode locking is achieved when the pump power in both arms reaches 390 mW. With further pump power scaling, ultrashort pulses with an energy of 6.52 nJ, a pulse duration of 225 fs, and a 20-dB spectral bandwidth of 375.6 nm, an overall spectral bandwidth of 502 nm are generated. The MO also demonstrates excellent self-starting performance. The MO can operate without seed injection or auxiliary starting arms. The straightforward design can enable a novel implementation of a high-energy ultrafast fiber laser.