Fig. 1. (a) Photo of GO saturable absorber; (b) Raman spectrum and SEM image of GO-SAs

Fig. 2. Experimental setup of passively mode-locked Tm, Ho∶LiLuF4 laser

Fig. 3. (a) Curves of crystal absorption efficiency; (b) continuous wave and mode-locked output power versus the absorbed pump power

Fig. 4. Spectrum of the mode-locked laser

Fig. 5. Mode-locked pulsesequences with (a) 1 ms,(b) 20 μs, (c) 2 μs and (d) 10 ns scanning time