Bulk Acoustic Wave Resonator-Oscillators and Tests of Fundamental Physics

Quartz Bulk Acoustic Wave resonator-oscillators are amongst the best oscillators for frequency control applications. We will present our latest results for using such oscillators and resonators to improve the precision and test fundamental physics. For instance, we have set up new experiments to test for Lorentz invariance violations, to search for Dark Matter and high frequency Gravitational Wave radiation. The former uses stable room temperature oscillators and the later uses cryogenic resonators cooled to low temperatures. At cryogenic temperatures such resonators have been shown to have record acoustic Q factors of more than a billion near 4 K and above 100 MHz. Such high values also suggest low phase noise and highly frequency-stabilized oscillators should be possible. We have realized a Pound stabilized cryogenic oscillator from one such mode near 116 MHz. Despite the extremely high Q-factors, we find that the power-frequency sensitivity is increased by a factor of 1000 at cryogenic temperatures, which limits the purity of the oscillator signal at low temperatures. To realise the full potential of such a stable oscillator, this dependence must be understood and dealt with. Details of the oscillator stabilisation system and noise floor analysis will be presented.