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 $G_B\mathrm{/}{Q}_m$ = 0.43 W${}^{-1}$m${}^{-1}$ in standard ridge waveguides