Ultra high quality factor resonators operated in fluids

Maximal quality factors are often a synonym for high performances for resonator based sensing devices. When vibrating within a fluid, several damping mechanisms dramatically reduce their performances. We propose a new concept to drastically reduce acoustic radiation damping. A specifically designed cavity enclosing the resonator is presented, able to couple the radiated field back in the resonator. Experiments on a custom tuning fork have been carried out and a cavity design is presented. This enclosing cavity tenfold its quality factor to reach Q = 75,000 in air at atmospheric pressure, passing through the established physical limits and setting a new record. The presented concept can be extended to many areas of physics employing high quality factor resonators, allowing the exploration of completely new geometries.