45 W kHz-linewidth single-frequency fiber laser at 1120 nm

Single-frequency fiber lasers (SFFLs) at 1120 nm have been widely used in biochemical analysis applications by generating 560 nm lasers. Here, we investigate the capacity of large-mode-area Yb-doped fiber for 1120 nm single-frequency laser amplification. By optimizing the length of large-mode-area Yb-doped fiber to balance the amplified spontaneous emission and stimulated Brillouin scattering effect, the output power of the 1120 nm SFFL could be enhanced to 45 W with a slope efficiency of 59.9%. At the maximum power level, the optical signal-to-noise ratio, the linewidth, and the beam quality of the output laser are 45 dB, 7.03 kHz, and M x 2 =1.52/ M y 2 =1.49, respectively. Our study proves that using large-mode-area fiber in cooperation with a gain coefficient and fiber length optimization is promising to improve the output power of 1120 nm SFFL. And the experimental results provide implications for the expansion of Yb-doped single-frequency lasers to the wavelength above 1100 nm.