Abstract
A quartz Bulk Acoustic Wave resonator is designed to coherently trap phonons in such a way that they are well confined and immune to suspension losses so they exhibit extremely high acoustic Q-factors at low temperature, with Q × f products of order 10 18 Hz. In this work we couple such a resonator to a Superconducting Quantum Interference Device (SQUID) amplifier and investigate effects in the strong signal regime. Both parallel and series connection topologies of the system are investigated. The study reveals significant non-Duffing response that is associated with the nonlinear characteristics of Josephson junctions. The nonlinearity provides quasi-periodic structure of the spectrum in both incident power and frequency. The result gives an insight into the open loop behaviour of a future Cryogenic Quartz Oscillator in the strong signal regime.
Highlights
In the past ultra-stable low phase noise photonic frequency sources have been implemented for a range of applications including very high precision probes of fundamental physics, high precision oscillators as local oscillators for atomic clocks and advanced radar systems [1,2,3,4]
The Bulk Acoustic Wave (BAW) resonator can provide very narrow spectral lines, while the superconducting circuit adds the strong nonlinearities required at low powers
In this work we utilizes a Superconducting Quantum Interference Device (SQUID) circuit [31] coupled to a high Q BAW Cavity [27]
Summary
In the past ultra-stable low phase noise photonic frequency sources have been implemented for a range of applications including very high precision probes of fundamental physics, high precision oscillators as local oscillators for atomic clocks and advanced radar systems [1,2,3,4]. The influence on the frequency stability of high-performance quartz oscillators on time scales of order 1–50 s is well-documented and it has been observed that the flicker self-noise decreases with decreasing power of the incident signal, and our recent results confirm that the resonators are thermal noise limited, and flicker-free without the carrier [27].
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