Son et Iumiere

摘要

The confinement of photons in a resonant cavity is the basis of laser operation. A device that has a resonant cavity for acoustic phonons inside an optical cavity enhances the interaction between sound and light. A quintet of physicists has created some interesting 'tunes' using coupled resonant cavities. The double-resonator structures described by Trigo and colleagues' in Physical Review Letters are unusual in that they are designed to resonate at optical frequencies (with photons) and at acoustical frequencies (with phonons)―simultaneously. Resonant cavities are ubiquitous. They form an essential part, for example, of orchestral instruments such as brass and woodwind, of pipe organs, and of the vocal cavities of many species. Their study also has a long and illustrious history. In 1877, Lord Rayleigh published his Theory of Sound, launching, among other things, the study of waves in confining geometries, or resonators. A notable early optical resonator is that of Fabry and Perot, unveiled in 1897, which has served the optical community well over the intervening years, and whose variants are crucial elements in the feedback systems of lasers. The function of a resonator is to provide space for wave propagation within reflective walls, so as to support a standing wave with a particular wavelength, and hence frequency. But to be useful, the resonator walls must not be perfectly reflective ― they must radiate some energy to the outside world.