Fig. 1. The experimental setup of the ns-SFS seed.

Fig. 2. The output characteristics of the ns-SFS seed. The output spectra of the unfiltered ns-SFS (a) and the filtered ns-SFSs (b). (c) The pulse profiles. (d) The fluctuations at the pulse peak of the ns-SFS seed.

Fig. 3. The experimental setup of the ns-SFS amplifier.

Fig. 4. The output spectra (a) and the pulse profiles (b) of the ns-SFS signals at an output power of approximately 18 W.

Fig. 5. (a) The output power and (b) pulse width of amplified ns-SFS signals as a function of pumping power, (c) the pulse profiles and (d) the details of the pulse peak of amplified ns-SFS signals at a pump power of 370 W.

Fig. 6. The SRS of the amplified ns-SFS with various linewidths. (a) The first-order SRS power ratio of seven ns-SFS amplifiers under different pump powers. (b) The output spectra of the ns-SFS amplifiers with a pump power of 370 W. (c) The experimental and fitted output spectra in the case of an 8 nm ns-SFS at a pump power of 370 W in a linear scale; inset, the corresponding spectra in a logarithmic coordinate. (d) The first-order SRS power ratio and the second-order SRS power ratio versus the ns-SFS seed’s FWHM linewidth at a pump power of 370 W.

Fig. 7. The dependence of the ASE power ratio and spectral broadening factor on the FWHM linewidth of the ns-SFS seed at a pump power of 370 W.

Fig. 8. Output performance of the 2 nm ns-SFS amplifier. (a) Output average power (black line) and pulse width (red line) versus pump power. (b) Pulse profiles at different output powers. (c) Output spectra dependence on the operation power. (d) Beam quality at the maximum output power of 602 W.