Stimulated Brillouin scattering fidelity with a variable aberrator

Abstract

We have examined stimulated Brillouin scattering (SBS) wavefront reconstruction with a continuously variable aberrator. A tripled single-longitudinal-mode YAG laser at 355 nm was used. The 10-ns laser pulse width was approximately twice the phonon lifetime of liquid hexane (the SBS medium), and the pulse energy was varied from SBS threshold to ~20 times threshold. No light pipes or phase plates were used. The aberrator produced continuously variable optical path differences (OPDs) from 0.14λ to 2.5λ (peak to valley). For pulses with 20 times threshold energy, the SBS accurately reconstructed the wavefront, independent of pump aberration for OPDs from 0.14λ to 2.5λ. For pulses with 7 times threshold energy, the SBS accurately reconstructed the wavefront for OPDs from 0.14λ to 1.3λ, but the fidelity monotonically declined for larger OPD. For pulses slightly above threshold, the fidelity was constant for a lower range of OPDs and declined for large OPD. At all intensities, the decline in fidelity was distinct from a decline in reflectivity, which was observed as the aberrator reduced the pump focal intensity. The onset of fidelity decline always occurred during stronger aberrations than the onset of reflectivity decline.