  Current theoretical demonstration of the Stimulated Brillouin scattering
(SBS) in waveguides composed of centrosymmetric materials does not capture
physics of the phenomenon in waveguides composed of non-centrosymmetric
materials. The SBS in the latter problem, entails mutual coupling of the
electric and acoustic waves due to piezoelectricity, and ends up to a different
power conversion equation than that in a centrosymmetric material. In this
study, we theoretically investigate Brillouin scattering in chip-scale
waveguides with non-centrosymmetric material when excited by an
Inter-Digital-Transducer. We explain how Brillouin scattering is formulated in
the presence of externally injected acoustic waves. Also we demonstrate the
effect of this external signal on reinforcing Stimulated Brillouin scattering.
As a case study we study SBS in a gallium arsenide nonowire. It is shown that
the Stokes amplification due to electromechanically reinforced SBS in this
waveguide can grow several orders of magnitude higher than the values reported
for the SBS in a silicon nanowire; This enables reducing the waveguide length
required for a given Stokes amplification from centimeters to few hundred
micrometers.
