Microwave-optical coupling via Rydberg excitons in cuprous oxide [dataset]

We report exciton-mediated coupling between microwave and optical fields in cuprous oxide (Cu2O) at low temperatures. Rydberg excitonic states with principal quantum number up to n= 12 were observed at 4 K using both one-photon (absorption) and two-photon (second harmonic generation) spectroscopy. Near resonance with an excitonic state, the addition of a microwave field significantly changed the absorption lineshape, and added sidebands at the microwave frequency to the coherent second harmonic. Both effects showed a complex dependence on n and angular momentum, l. All of these features are in semi-quantitative agreement with a model based on intra-band electric dipole transitions between Rydberg exciton states. With a simple microwave antenna we already reach a regime where the microwave coupling (Rabi frequency) is comparable to the nonradiatively broadened linewidth of the Rydberg excitons. The results provide a new way to manipulate excitonic states, and open up the possibility of a cryogenic microwave to optical transducer based on Rydberg excitons.