RECENTLY PUBLISHED PAPER
The paper outlines the optimal design of a room-temperature whispering-gallery-mode sapphire resonator. In particular, design rules were determined to enable choice of the optimum azimuthal mode number and resonator radius for a given resonance frequency. The coupling probe design was investigated and it was found that straight antenna probes aligned radially and positioned in the mid-plane of the resonator gave the highest unloaded Q-factors because of minimized probe losses. We noted that when coupling through this technique (as compared with a perpendicularly positioned probe) the mode standing wave pattern would lock to some asymmetry in the crystal resonator itself and not to the probe. From this analysis, the highest attainable Q-factor is expected to be (2.1 ± 0.1) x 105 at 9 GHz in a quasi-TM mode.
Authors: Hartnett, J.G., Tobar, M.E., Ivanov, E.N., Luiten, A.N.
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control, 60(6), art. no. 6521054, pp. 1041-1047.