Brillouin Scattering Selection Rules in Polarization-Sensitive Photonic Resonators

Spontaneous Brillouin scattering in bulk crystallinesolids isgoverned by the intrinsic selection rules locking the relative polarizationof the excitation laser and the Brillouin signal. In this work, weindependently manipulate the polarization of the two by employingpolarization-sensitive optical resonances in elliptical micropillarsto induce a wavelength-dependent rotation of the polarization states.Consequently, a polarization-based filtering technique allows us tomeasure acoustic phonons with frequencies difficult to access withstandard Brillouin and Raman spectroscopies. This technique can beextended to other polarization-sensitive optical systems, such asplasmonic, photonic, or birefringent nanostructures, and finds applicationsin optomechanical, optoelectronic, and quantum optics devices.