Fig. 1. Schematic diagrams. (a) Pump-probe technique. (b) Collinear polarization splitting configuration. (c) Orbital angular momentum mode division filtering. SPP, spiral phase plate; PBS, polarized beam splitter; λ/4, quarter-wave plate; and LPF, low-pass filter.

Fig. 2. Schematic diagrams. (a) Generic spiral phase imaging. (b) Proposed optical nonlinear operation for on-demand tailoring of Brillouin signal. L, lens; SPP, spiral phase plate; BA cell, Brillouin amplifier cell; and PBS, polarized beam splitter.

Fig. 3. (a0) Input Gaussian beam. (b0) Phase object image. (a1)–(a6) Simulated spatial profiles after spiral phase filtering of ℓ=1, 2, 3, 4, 5, 6, and (b1)–(b6) corresponding output phase profiles. (c0) Experimentally observed phase object image, and (c1)–(c4) experimental transverse profiles for ℓ=1, 2, 4, and 6, respectively.

Fig. 4. Schematic of the experimental setup. Key components include the half-wave plate (HWP), quarter-wave plate (λ/4), polarized beam splitter (PBS), spatial light modulator (SLM), lens (L), spiral phase plate (SPP), Brillouin amplifier cell (BA cell), and charge-coupled device (CCD). f represents the focal length of lens.

Fig. 5. Experimental results. (a1) Observation of the input precoding signals without spiral phase filtering and (a2), (a3) with spiral phase filtering of ℓ=1, 2, respectively. (b1)–(b3) Corresponding amplified output Brillouin signal profiles.

Fig. 6. Experimental results of the output intensity distribution with the spiral phase precoding of (a) ℓ=1 and (b) ℓ=2 for the pump of 5 mJ and the input signal of 1 μJ.

Fig. 7. Experimental results. (a) Energy conversion efficiency versus the pump energy EP. (b) Signal amplification factor versus the input signal energy ESin, including the condition without spiral phase precoding and with spiral phase precoding of ℓ=1, 2.