# Piezo-optomechanical coupling of a 3D microwave resonator to a bulk acoustic wave crystalline resonator

## TL;DR

This paper demonstrates the coupling between a 3D microwave cavity and a bulk acoustic wave resonator via piezoelectric and radiation pressure effects, highlighting potential for high-cooperativity quantum systems.

## Contribution

It introduces a novel system integrating a quartz bulk acoustic wave resonator with a microwave cavity, and models its electromechanical coupling mechanisms.

## Key findings

- Coupling between microwave mode and acoustic wave observed and characterized.
- Finite element simulations quantify electromechanical contributions.
- Potential for high cooperativity in quantum applications identified.

## Abstract

We report the observation of coupling between a 3D microwave cavity mode and a bulk mechanical resonator mediated by piezoelectric and radiation pressure effects. The system is composed of a quartz bulk acoustic wave resonator placed inside a microwave re-entrant cavity, which is designed to act as both the electrodes for piezoelectric actuation as well as a 3D resonator. The cavity electromagnetic mode is modulated by a 5 MHz bulk acoustic wave shear mode, which is modeled and experimentally verified using the input-output formalism. Through finite element method simulations, we calculate the various contributions to the electromechanical coupling and discuss the potential of the system to reach high cooperativities as well as suitable applications.