All-Dielectric Triply-Resonant Cavity Electro-Optic Transducer with Strong Optical Mode Coupling

We report a cavity electro-optic transducer that combines a high-Q, small-mode-volume all-dielectric microwave resonator in LiNbO₃ with a millimeter-scale, high-Q optical cavity with large power handling. We have developed all dielectric resonators that approach the limit of microwave mode volumes, reaching sub cubic millimeter scales, while achieving polarization and phase matching, and triply resonance operation. In this configuration, we demonstrate strong coupling between a pair of optical modes mediated by a large microwave pump. Observing the normal mode splitting allows us to explicitly measure the electro-optic coupling rate, in good quantitative agreement with our simulations. Our system has attained electro-optic cooperativity high enough to optically resolve room temperature thermal microwave state, which in the near term opens up applications in blackbody thermometry and low noise microwave receivers. We have recently developed lower loss optical cavities, which we are integrating with our smallest mode volume microwave resonators to increase cooperativity to approach unity. In the future, operation at cryogenic temperatures targets single-photon-level microwave-to-optical transduction for quantum networks.