Fig. 1. Energy level structure of Ho∶YAG

Fig. 2. Fluorescence spectrum of Ho∶YAG

Fig. 3. Designed reflectance curve of Ho∶YAG thin disk crystal

Fig. 4. Absorption efficiency curves of thin disk crystal

Fig. 5. Structural model and physical diagram of self-developed 72-pass pump module. (a) Structural model; (b) physical object drawing

Fig. 6. Surface pattern of Ho∶YAG thin disk with diamond heat sink

Fig. 7. Packaged Ho∶YAG thin disk

Fig. 8. Pump spot on thin disk Ho∶YAG crystal

Fig. 9. Schematic of Ho∶YAG thin-disk laser based on 72-pass pumping module

Fig. 10. Output power and optical-optical conversion efficiency versus pump power (D_pump=3.6 mm)

Fig. 11. Output power and optical-optical conversion efficiency versus pump power (D_pump=4.5 mm)

Fig. 12. Power stability recorded at output power of 150 W

Fig. 13. Beam quality and spot of Ho∶YAG thin-disk laser

Fig. 14. Output spectrum of Ho∶YAG thin-disk laser