980-nm all-fiber mode-locked Yb-doped phosphate fiber oscillator based on semiconductor saturable absorber mirror and its amplifier
Li Ping-Xue†, , Yao Yi-Fei, Chi Jun-Jie, Hu Hao-Wei, Zhang Guang-Ju, Liang Bo-Xing, Zhang Meng-Meng, Ma Chun-Mei, Su Ning
       

RF spectrum of the 980 nm mode-locked fiber laser at a repetition of 20.96 MHz.