Spontaneous anti-Stokes backscattering in Brillouin dynamic gratings

Spontaneous Brillouin backscattering, which accompanies the operation of Brillouin Dynamic Gratings (BDG) sensors, is experimentally investigated for the anti-stokes configuration, where the probe wave propagates against the orthogonally polarized high frequency writing pump. Even in the absence of the low frequency writing pump but for a strong enough high frequency writing pump, the observed anti-Stokes reflection of the probe becomes much stronger than its corresponding value under classical anti-Stokes backscattering. It is also shown that, eventually, as the probe reaches a critical value, the anti-Stokes reflection sharply decreases to its classical value.