Generation of Coherent Phonons via a Cavity Enhanced Photonic Lambda Scheme

TL;DR

This paper reports the generation of coherent phonons in a quartz resonator enhanced by a microwave cavity using a photonic lambda scheme, demonstrating a new method for phonon control via electrostrictive effects.

Contribution

The work introduces a novel cavity-enhanced photonic lambda scheme for generating coherent phonons in a BAW resonator, enabling direct readout and electrostrictive phonon production without threshold.

Findings

Coherent phonons generated via a microwave cavity in quartz BAW resonator.

Phonons produced at the difference frequency between pump and probe.

Process confirmed to be electrostrictive with no back action effects.

Abstract

We demonstrate the generation of coherent phonons in a quartz Bulk Acoustic Wave (BAW) resonator through the photoelastic properties of the crystal, via the coupling to a microwave cavity enhanced by a photonic lambda scheme. This is achieved by imbedding a single crystal BAW resonator between the post and the adjacent wall of a microwave reentrant cavity resonator. This 3D photonic lumped LC resonator at the same time acts as the electrodes of a BAW phonon resonator, and allows the direct readout of coherent phonons via the linear piezoelectric response of the quartz. A microwave pump, $\omega_p$ is tuned to the cavity resonance $\omega_0$, while a probe frequency, $\omega_{probe}$, is detuned and varied around the red and blue detuned values with respect to the BAW phonon frequency, $\Omega_m$. The pump and probe power dependence of the generated phonons unequivocally determines the process to be electrostrictive, with the phonons produced at the difference frequency between pump and probe, with no back action effects involved. Thus, the phonons are created without threshold and can be considered analogous to a Coherent Population Trapped (CPT) maser scheme.