EXICITATION OF WHISPERING GALLERY MODES IN A DISK PLANAR DIELECTRIC RESONATOR BY A COUPLING SLOT

The spectral and energy characteristics of disk planar dielectric resonator (DR) with high-order whispering gallery modes (WGMs) were investigated in Ka-band. The diameter of the planar DR was several wavelengths in the dielectric material, and its height was much smaller than the wavelength. The dielectric disk was placed by flat bases between two conducting mirrors. Thus, electromagnetic field of the resonator was limited by the height of the planar disk by two conducting surfaces. The resonant properties of such structure were determined by the condition of total internal reflection of the waves from the curved surface of the dielectric disk. A method of effective excitation of WGMs in the planar DR by the coupling slot in the metal mirror was proposed. It is shown that with this excitation method, a regime of supercritical coupling with planar DR is achieved. In this case, the mode spectrum of such a resonator is rarefied relatively. It is established that the Q-factor of a planar DR is mainly determined by the losses in its dielectric material and by the ohmic losses in metallic mirrors, since the radiation losses at a necessary ratio of the wavelength and the diameter of the dielectric disk can be small. For a disk made of teflon with a height of 1 mm, a diameter of 78 mm, located between brass mirrors, the Q-factor of the planar DR can reach 1500 at the high-frequency edge of the Ka-band. The recommendations for increasing of Q-factor of the planar DRs and reducing their dimensions are proposed.

disk planar dielectric resonator, whispering gallery modes, supercritical coupling, Q-factor, Ka-band

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