Fig. 1. Experimental setup of the single-frequency pulsed Ho:YLF ring laser and the single-pass amplifier.

Fig. 2. Output characters of the single-frequency pulsed Ho:YLF seed laser. (a) Output energy versus pump power; (b) pulse width and line width versus pump power.

Fig. 3. Output energy of the single-frequency Ho:YLF amplifier versus pump power.

Fig. 4. Energy stability of the Ho:YLF amplifier under free-running and single-frequency operation.

Fig. 5. Pulse build-up time of the Ho:YLF amplifier. (a) Under free-running operation; (b) under single-frequency operation.

Fig. 6. Temporal shapes and FFT curves for the Ho:YLF amplifier. (a) Free-running operation; (b) single-frequency operation.

Fig. 7. Laser properties of the single-frequency Ho:YLF amplifier. (a) Beating signals; (b) fast Fourier transform (FFT) spectrum of the beating signals.