Fig. 1. Experimental setup. (a) The 200-ps Stokes pulse and 5-ns pump pulse are generated at the front end. (b) The Stokes pulse is frequency-shifted by an amount determined by the chosen SBS medium. (c) Block diagram of the experimental setup. (d) Energy is transferred from the pump pulse to the Stokes pulse in an SBS cell.

Fig. 2. Experimental results. (a) Output Stokes intensity varies with the input intensity; input Stokes and pump intensities are the same. (b) Probability distribution of the output pulse width when the output Stokes pulse widths are in the range 150–200 ps. (c) Temporal intensities of the Stokes and pump pulses for input pump intensity of $150~\text{MW}/\text{cm}^{2}$. The output Stokes pulse width is 165 ps. The pump is not exhausted. (d) Temporal intensities of SBS amplification results for an input pump intensity of $398~\text{MW}/\text{cm}^{2}$. The output Stokes pulse width is 170 ps. Energy is efficiently transferred from the pump pulse to the Stokes pulse.

Fig. 3. Theoretical analysis of Brillouin amplification within nonlinear absorption: comparison between Brillouin amplification with and without considering nonlinear absorption.

Fig. 4. Phase-modulated pump spectrum.

Fig. 5. Temporal intensities of the Stokes and pump pulses of the phase-modulated laser.

Fig. 6. (a) Variation of the interaction length with the crossing angle at $20~\text{mm}\times 20$  mm. (b) Variation of the interaction length with the crossing angle at $370~\text{mm}\times 370$  mm.