Increasing Q-Factor of Planar Dielectric Resonators with Whisper Gallery Modes

Abstract

Planar dielectric resonators (DR) with height significantly lower than the operating wavelength are investigated as a new class of disk dielectric resonators of the millimeter wavelength range with whispering gallery (WG) modes. It is known that in the open state, such resonators based on the WG modes are not excited due to high radiation losses. It is shown that the solution of this problem is the partial shielding of the disk dielectric structures with a plane-parallel screen by placing the disk between two flat conducting mirrors. It has been established that by introducing an air gap between the flat base of the dielectric disk and one of the conductive mirrors, it is possible to increase the quality factor of the planar DR almost twice. One of the reasons for this is the partial displacement of the resonant field of the WG modes from the dielectric region to the air gap, where the dielectric losses are lower. In addition, an increase in the air gap in the range of optimal values, comparable to half the working wavelength, leads to a decrease in ohmic losses. The above causes an increase in the quality factor of planar DR as an air gap is extended.