The effect of ambient temperature on eigenfrequencies of a quasi-optical cylindrical dielectric resonator

Effects of the temperature and refractive index of ambient air on the eigenfrequencies of a cylindrical dielectric resonator (CDR) featuring whispering-gallery modes have been studied. An attempt to separate the effects of two factors on the spectral and energy characteristics of a fluoroplastic CDR for a millimeter wavelength range has been made for the first time. It is established that the behavior of CDR eigenfrequencies and the stability of Q factors exhibit different characters when the temperature is varied from -60 to +60$^\circ$C and the permittivity of air is changed from 1 to 1.0004. A CDR can be used as a sensor of ambient temperature accurate to within 10$^{-4}$ K, provided that the resonance frequencies in the millimeter wavelength range are measured to within 1 kHz.