Quantum Optics Seminar by Michael R. Vanner

Observation of Brillouin optomechanical strong coupling

Achieving optomechanical strong coupling with high-frequency phonons provides a rich avenue for quantum technology development including quantum state-transfer, memory, and transduction, as well as enabling several fundamental studies of macroscopic phononic degrees-of-freedom. Reaching such coupling with GHz mechanical modes however has proved challenging, with a prominent hindrance being material- and surface-induced-optical absorption in many materials. Here, we circumvent these challenges and report the observation of optomechanical strong coupling to a high frequency (11 GHz) mechanical mode of a fused-silica whispering-gallery microresonator via the electrostrictive Brillouin interaction. Using an optical heterodyne detection scheme, the anti-Stokes light backscattered from the resonator is measured and normal-mode splitting and an avoided crossing are observed in the recorded spectra, providing unambiguous signatures of strong coupling. The optomechanical coupling rate reaches values as high as 39 MHz through the use of an auxiliary pump resonance, where the coupling dominates both the optical (3 MHz) and the mechanical (21 MHz) amplitude decay rates. Our findings provide a promising new approach for optical quantum control using light and sound.

https://arxiv.org/abs/1808.07115  (accepted in Optica)