Triply Resonant Millimeter Scale Cavity Electro-Optic Transducers*

We explore resonant cavity electro-optic transduction between microwave and optical photons by harnessing Lithium Niobate's (LN) non-liner optical properties. We incorporate LN within a Fabry-Perot optical cavity and build a millimeter scale microwave resonator around it. We have developed several microwave resonator designs with high Q and low mode volumes a fraction of a cubic wavelength. These include 1D dielectric photonic crystal resonators, the fundamental dielectric TE mode of an LN slab, and devices consisting of LN sandwiched between two slabs of high dielectric constant titanium dioxide housed within a copper loop gap resonator. These are tuned to achieve a triply resonant condition where optical pump photons, microwave photons, and photons at the sum of those frequencies are all resonant with electromagnetic modes of our structure, in order to achieve efficient signal transduction. We will report progress toward laser cooling of the microwave cavity, and the transduction of thermal photons at room temperature. Such devices lay the groundwork for an array of systems from quantum networking to sensing of microwave signals. Their room temperature operation will allow for applications such as temperature metrology via optically detecting microwave blackbody photons. When operated in the cryogenic regime we hope to achieve single photon level microwave – optical quantum transduction to coherently couple superconducting qubits to room temperature fiber optic networks.