A strong coupling regime between light and high-frequency acoustic sound waves was demonstrated by a team from Imperial College London, the University of Oxford, and the National Physical Laboratory. The team’s findings could provide a possible approach to quantum control of light and sound. Light (shown in orange) is injected into an optical microresonator via a tapered optical fiber. The light circulates many thousands of times inside the structure and couples strongly to high-frequency acoustic waves. Courtesy of Quantum Measurement Lab, Imperial College London. The researchers demonstrated strong coupling between an optical whispering-gallery mode of a fused-silica microresonator and an 11-GHz mechanical traveling wave via Brillouin anti-Stokes scattering. Light was injected into the microresonator through a tapered optical fiber. As the light circulated around the circumference of the structure, it interacted with the 11-GHz acoustic vibration, causing light to be scattered in the reverse direction, thus allowing an energy exchange between the light and the sound waves. To prevent decay in the light and sound fields, the researchers used a whispering-gallery microresonator to achieve a coupling rate that was larger than the processes causing the light and sound waves to decay. “It is fascinating that these glass ring resonators can store excessive amounts of light, which can ‘shake’ the molecules in the material and generate acoustic waves,” said researcher Pascal Del’Haye. To the best of the researchers’ knowledge, their platform demonstrates optomechanical strong coupling with the highest mechanical frequency reported to date. Their research could afffect classical- and quantum-information processing and the testing of quantum mechanics at large scales. The team is now preparing its next generation of experiments, which will operate at temperatures close to absolute zero. “This will allow highly sensitive quantum mechanical behavior to be explored and utilized for the development of quantum technologies,” said researcher Michael Vanner. The research was published in Optica, a publication of OSA, The Optical Society (https://doi.org/10.1364/OPTICA.6.000007).