CONCAVE DIFFRACTION GRATINGFOR WHISPERING-GALLERY MODE SELECTION

摘要

Owing to a high Q-quality factor of whispering-gallery modes and relatively small size the dielectric disk resonators are extensively used as an oscillating circuit of high-stable microwave oscillators [I] and serve to measure the electro-physical properties of different materials at microwaves [2]. At the same time, the spectrum of whispering-gallery oscillations represents a rather thick grid of equidistant azimuthal oscillations of both E- and H- polarizations. Here.the fundamental contradiction is hidden: An increase of disk resonator radius .R relative to wavelength results in growing Q-quality of oscillations because the resonator volume and quantity of energy stored in' it are maximized. At the same time the frequency interval between the neighboring azimuthal modes tends to decrease [1]:Δf_(n-(n+1)= c/2πR where c is the velocity of light, n is the azimuthal number, and ε is the permittivity of the dielectric that makes up the resonance cavity.