Fig. 1. Energy level diagram of the Er³⁺

Fig. 2. Principle of the experimental setup. (a) Schematic diagram of experimental setup; (b) vertical view of the laser system; (c) side-view of the grating laser cavity

Fig. 3. Photoluminescence spectra of Er∶YSGG crystal under different pumping powers

Fig. 4. Laser output spectra of the grating cavity

Fig. 5. Output power of the grating cavity laser under different pump power