A Theoretical Framework for Electromechanically Reinforced Brillouin Scattering in Integrated Photonic Waveguides

Abstract: 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.