Low-phase noise temperature-compensated cryogenic whispering gallery mode resonator operated at 63 K in a closed-cycle cooler

We report further progress on whispering gallery (WG) modes in a miniature temperature compensated composite dielectric sapphire and rutile resonator operating in a closed cycle cooler which can exhibit loaded Q_L values above 10⁷ at ~10 GHz. The geometrical size of the dielectric pucks has been increased so that a compact loop-oscillator system is realized at a frequency close to the Cs atomic clock hyperfine frequency and an operating temperature of 63.5 K. Excellent long term temperature control (stability is better than 100 μK) has been achieved. The high Q of the dielectric resonators can be used to produce low phase noise oscillators limited only by the performance of amplifiers and mixers. Effective mechanical vibration isolation is also demonstrated in a Giffard-McMahon cooler