Fig. 1. Schematic of the laser system. ISO, isolator; GM, gold mirror; LD, laser diode; λ/2, half-wave plate; λ/4, quarter-wave plate; DM, dichroic mirror; L, lens.

Fig. 2. Measured output characteristics of the pre-amplifier under a pump power of 10 W. (a) Output spectrum. (b) Autocorrelation trace. (c) RF spectrum with a resolution bandwidth of 10 Hz. (d) Pulse trains in the nanosecond and millisecond time scales.

Fig. 3. Average output power and pulse duration of the main amplifier versus pump power.

Fig. 4. (a) Output spectra and (b) corresponding autocorrelation traces of the main amplifier at different average output power levels. (c) Linear output spectrum of the main amplifier at an average output power of 8.12 W.

Fig. 5. Beam quality measurement of the main amplifier at an average output power of 6.28 W. Inset: the corresponding collimated beam profile.

Fig. 6. (a) Measured long-term stability of the main amplifier for 1 hour at an average output power of 6.28 W. Inset: the corresponding pulse train measured in a 20-ms time scale. (b) RF spectrum with a resolution bandwidth of 10 Hz.