High-Power Noise-Like Pulse Generation in a Tm-Ho Co-Doped Fiber Laser

In this study, we demonstrate a high-performance passively mode-locked thulium-holmium (Tm-Ho) co-doped fiber laser utilizing a single-mode fiber–few-mode fiber–single-mode fiber (SMF-FMF-SMF) structure as an effective saturable absorber (SA) for noise-like pulse (NLP) generation. By solely adjusting the output coupling ratio from 30% to 50%, the maximum average output power at a pump power of 4.5 W is significantly increased from 238 mW to 391.2 mW in a single-pulse operation. The corresponding maximum pulse energy reaches 99.5 nJ at a repetition rate of 3.933 MHz, with a broad 3 dB bandwidth of 33.40 nm centered at 1948 nm. The laser exhibits excellent stability, as evidenced by a signal-to-noise ratio (SNR) of 69 dB. These results highlight the effectiveness of the SMF-FMF-SMF structure in improving output power and pulse characteristics, offering a promising approach for advancing high-energy mode-locked fiber lasers.