Sapphire loaded microwave resonators with enhanced quality factor

This paper describes the properties of two-dimensional shielded dielectric ring resonators consisting of a few coaxial dielectric layers surrounded by the coaxial metal shield. It is shown that the Q factor of such resonators excited in whispering-gallery modes increases with azimuthal mode number due to the effective concentration of electromagnetic energy outside the dielectric in the inner region of the resonator as well as in the gap between the dielectric layers. At moderately high azimuthal numbers (m=15...25) the Q-factor can significantly (2 to 3 times) exceed the limit imposed by the intrinsic losses in the dielectric.<
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