Fig. 1. Experimental arrangement of the 1.3 kW narrowband fiber amplifier.

Fig. 2. (a) Output optical spectra of the 1.3 kW narrowband fiber amplifier under a wide scanning range; (b) power of the Raman Stokes and anti-Stokes lights versus the output laser power.

Fig. 3. (a) Output optical spectra of the 1.3 kW narrowband fiber amplifier under a narrow scanning range; (b) FWHM of the signal laser under different output power.

Fig. 4. Signal laser in the time domain during the amplification process.

Fig. 5. Effective gain enhancement factor along with the normalized phase mismatch ΔB.

Fig. 6. Stokes output power of amplifier A3 along with the laser output power at different RG peak values.

Fig. 7. Stokes gain enhancement factor at different laser powers and absolute phase mismatch values.

Fig. 8. Ratio of anti-Stokes and Stokes power at the RG peak along with laser output power and phase mismatch values.