Optimization of radiation pressure in dielectric nanowaveguides

Stimulated Brillouin scattering (SBS) processes have been allowing important technological breakthroughs in integrated photonics and nano-optomechanics, by exploiting light-sound (photon-phonon) interactions at the nanoscale. These nonlinear processes are created by two main effects: radiation pressure and electrostriction; however, the former is the predominant one in high-index-contrast nanowaveguides. In this letter, we derive a simple set of analytical expressions that can be used for optimizing the radiation pressure on the waveguide boundaries, for any optical mode, polarization, and wavelength. We observe a very strong influence of the waveguide geometric parameters on the optimal radiation pressure value. Furthermore, we explain how the existence of such optimal geometric dimensions is physically related to the minimization of the electromagnetic momentum flow in the propagation direction. This work provides a novel and robust method, yet simple, to optimize the radiation pressure in dielectric nanowaveguides, which may be of great relevance for designing integrated photonic-phononic devices.