Brillouin scattering in hybrid optophononic Bragg micropillar resonators at 300 GHz

BACKGROUND: Inelastic scattering of light by acoustic phonons has potential for the tailored generation of frequency combs, laser-line narrowing, and all-optical data storage. To be efficient, these applications require strong optical fields and a large overlap between the optical and acoustic modes. Control over the shape of the acoustic spectrum is highly desirable. So far, patterned waveguides and photonic crystal fibers have allowed tailoring the acoustic spectrum up to a few tens of gigahertz. Here, we introduce a monolithic Brillouin generator based on embedding a high-frequency nanoacoustic resonator, which is operating at 300 GHz, inside an optical micropillar cavity. It allows independent design of the Brillouin spectrum and the optical device. We develop a free-space filtering technique by using the different spatial patterns of the diffracted excitation laser and the Brillouin signal. The micropillars could be readily integrated into fibered and on-chip architectures, can be engineered to reach the stimulated regime, and are compatible with quantum dots, making them relevant for quantum communication.