Single frequency Yb-doped fiber laser based on graphene loop mirror filter

We report a new method for obtaining a stable single-frequency Yb-doped fiber laser by introducing a graphene film into a fiber loop mirror combined with a simple linear cavity. The graphene film acts as a saturable absorber so as to form a dynamic absorbing grating in the 3 dB fiber loop. This grating is like a narrow-band filter for discriminating and selecting longitudinal modes. Moreover, we use a polarization controller in the linear resonator to suppress the spatial hole burning effect. The maximum output power is 16 mW at 1 064 nm with a pump power of 110 mW at 975 nm, the slope efficiency is 15%, and the SNR is about 60 dB. To the best of our knowledge, this is the first demonstration of a 1 064 nm single-frequency laser based on a linear cavity with a graphene-loop mirror filter.