Fig. 1. Nd³⁺ ion transition energy-level diagram

Fig. 2. Experimental setup of 914-nm laser

Fig. 3. Schematic diagram of a simplified resonant cavity

Fig. 4. Fundamental mode radius in crystals varying with pump power when the cavity length is different

Fig. 5. Experimental setup of 228-nm laser

Fig. 6. Average output power and pulse energy varying with pulse repetition rate for 914-nm laser

Fig. 7. Average output power and the pulse energy varying with pulse repetition rate for 457-nm laser

Fig. 8. Spectrum of 228-nm laser

Fig. 9. Average output power and pulse width varying with repetition rate of 228-nm laser

Fig. 10. Power stability of 228-nm laser

Fig. 11. Pulse sequence and pulse width of 228-nm laser. (a) Pulse sequence and (b) pulse width at 10 kHz; (c) pulse sequence and (d) pulse width at 18 kHz

Fig. 12. Spot intensity distribution diagrams of ultra-violet laser. (a) Two-dimensional spatial intensity distribution; (b) three-dimensional spatial intensity distribution; (c) horizontal intensity distribution; (d) vertical intensity distribution