Stimulated Brillouin scattering by surface acoustic waves in lithium niobate waveguides

We numerically demonstrate that lithium niobate on insulator (LNOI) waveguides may support confined short-wavelength surface acoustic waves that interact strongly with optical fields through backward-stimulated Brillouin scattering in both Z - and X -cut orientation. We conduct fully anisotropic simulations that consider not only moving boundary and photoelastic forces, but also roto-optic forces for the Brillouin interaction. Our results indicate that photoelasticity dominates the Brillouin gain and can reach as high as G B / Q m =0.43W −1 m −1 in standard ridge waveguides.