Researchers at Imperial College London, Oxford University, and the National Physical Laboratory used the whispering gallery effect to confirm the existence of a "strong coupling mechanism" between light and high-frequency sound waves. This discovery not only has a major impact on traditional and quantum information processing technologies, but also allows large-scale testing of quantum mechanical behavior. Related papers were recently published in the famous "Optics" magazine.
The research team mainly used the "whispering gallery mode resonance". This phenomenon is named after an effect observed in St. Paul's Cathedral in the 19th century. In St. Paul's Cathedral, when you speak softly against the wall at one end of the arcade, you will pass through the giant dome of the church and clearly pass to the opposite wall, so that the other person can clearly hear what you are saying.
The researchers injected light into the optical microresonator through a tapered fiber. The light was reflected multiple times around the surface of the tiny circular glass structure and cycled thousands of times inside the structure. Since the glass ring resonator can store a large amount of light, these light energy "Shake" the molecules in the material to produce sound waves.
When light circulates over a circular glass structure, it can interact with 11 GHz acoustic waves, causing light to scatter in the opposite direction. This interaction allows energy to be exchanged between light and sound waves at a rate. However, both the light field and the sound field are attenuated by a friction-like process that prevents the two from coupling. The team used two whispering gallery modes to overcome this challenge and achieved a coupling rate greater than the friction-like process. In a tiny glass structure, light and high frequency sound waves are coupled to each other.
The research team is preparing to conduct further experiments at temperatures close to absolute zero to explore quantum mechanical behavior and develop quantum technology.