119-W Monolithic Single-Mode 1173-nm Raman Fiber Laser

We report a high-power high-efficiency single-mode all-fiber Raman fiber laser (RFL) operating at 1173 nm. With the core pumped by a 144-W 1120-nm Yb-doped fiber laser, an output power of 119 W at a wavelength of 1173 nm was obtained, corresponding to an optical efficiency of 82%. To the best of our knowledge, it is the highest power at the 1150-1200-nm laser band by using common silica fiber. The optical efficiency of the RFL with high output coupler (OC) reflectivity and short fiber length is discussed. We also carefully measured the output Raman spectrums under different cavity parameters and presented primary analysis. The results show that the bandwidth increases near linearly with laser output power, rather than a square-root law concluded for high Q-value and long-cavity RFLs in previous published literatures. Increasing the length of the gain fiber and the reflectivity of the OC would also broaden the output spectral bandwidth.