Applications of coupled dielectric resonators using SrTiO3 pucks: Tuneableresonators and novel thermometry

The combination of very low loss dielectric single crystal materials (such as sapphire) with a high-temperature superconductor (HTS) shielding enclosu re has led to the achievement of high Q resonators operated in the temperat ure range 40-70 K, which show great promise for frequency standard applicat ions. A number of problems remain to be solved, We have already reported ho w high frequency stability with minimum temperature control may be achieved by means of composite dielectric pucks, the components having opposite sig ns for their temperature coefficients of permittivity, A second requirement for a frequency standard is that it should possess a specified frequency, sere, we report implementation of electronic tuning of a sapphire dielectri c puck resonator by using a SrTiO3 (STO) tuning element situated in the eva nescent field region outside the sapphire puck. In addition the same struct ure may be used when the sapphire and STO elements act as weakly coupled re sonators so that the resonant frequency becomes a very sensitive function o f temperature, allowing the possibility of very high resolution thermometry .