Influence of the Refractive Index and Temperature of the Ambient Medium on the Eigenfrequencies of Quasioptical Cylindrical Dielectric Resonators
We have made the first effort to separate the influences of the temperature and refractive index of the ambient air space on the spectrum and energy characteristics of cylindrical Teflon and leucosapphire resonators with the whispering gallery modes in the millimeter wavelength band. It is found that the degree of temperature influence on the resonator eigenfrequencies is greater under the conditions of natural fluctuations of the above-mentioned factors of the external medium under consideration. We demonstrate that quasioptical cylindrical dielectric resonators can be used as sensors of the temperature of the ambient air medium, which ensure an accuracy of 10-4 ^°C when their resonance frequencies are measured with an accuracy of 100 Hz. A method for determination of the refractive index of air has been developed, which involves the use of the considered resonator as temperature sensors and measuring cell of the microwave resonator refractometer. The refractometer sensor has been developed on the basis of two identical resonators with whispering gallery modes. The differential double-resonator refractometer compensates the influence of the changes in the temperature of the ambient medium on the measured difference of the eigenfrequencies of resonators with identical modes. It is found that the accuracy of determination of the refractive index of air is ensured at a level of 10-2, when the frequency difference is measured with an accuracy of 10 Hz.