Noise-like pulse generation in high-power spatiotemporal mode-locked fiber lasers with 41% optical-to-optical efficiency

The spatiotemporal mode-locked (STML) fiber laser provides a new way to construct a higher-power, higher-energy mode-locked fiber laser. In this work, a noise-like pulse STML fiber laser with an average power of 4.1 W and an optical-to-optical efficiency of up to 41% is reported. At the same time, a good beam quality ($<i>M</i><i>x</i>2=1.35,<i>M</i><i>y</i>2=1.41$) of the output beam is also obtained benefiting from the beam self-cleaning. In addition, the 3 dB spectral bandwidth of the output pulse reaches 54 nm due to the strong nonlinear spectral broadening and the weak spectral filtering in this multimode laser cavity. Our research contributes to a better understanding of the behavior of high-power STML lasers and further studies of noise-like pulse STML fiber lasers for practical applications.