Brillouin Scattering Selection Rules in Polarization-Sensitive Photonic Resonators

The selection rules governing spontaneous Brillouin scattering in crystalline solids are usually taken as intrinsic material properties, locking the relative polarization of excitation and signal in bulk. In this work, we independently manipulate these polarization states by means of optical resonances in elliptical micropillars and demonstrate a polarization-based filtering scheme for Brillouin spectroscopy in the 20-100 GHz range, important for telecom applications. This strong modification of selection rules using elliptical micropillars can be extended to any optical system with localized, polarization-sensitive modes, such as plasmonic resonators, photonic crystals, birefringent micro-, and nanostructures. Our polarization control protocol will thus find applications in the engineering of light-matter interactions in optomechanical, optoelectronic and quantum optics devices.