Gallium phosphide as a piezoelectric platform for quantum optomechanics

TL;DR

This paper demonstrates a gallium phosphide-based piezoelectric optomechanical device with a high-Q optical resonator and a 2.9 GHz mechanical mode, enabling quantum behavior and potential quantum transduction applications.

Contribution

It introduces a novel gallium phosphide device that overcomes optical absorption challenges, enabling quantum optomechanics in integrated piezoelectric systems.

Findings

Achieved quantum behavior in gallium phosphide device.

Demonstrated coupling of mechanical and optical modes at telecom wavelengths.

Enabled potential for microwave-to-optical quantum transduction.

Abstract

Recent years have seen extraordinary progress in creating quantum states of mechanical oscillators, leading to great interest in potential applications for such systems in both fundamental as well as applied quantum science. One example is the use of these devices as transducers between otherwise disparate quantum systems. In this regard, a promising approach is to build integrated piezoelectric optomechanical devices, that are then coupled to microwave circuits. Optical absorption, low quality factors and other challenges have up to now prevented operation in the quantum regime, however. Here, we design and characterize such a piezoelectric optomechanical device fabricated from gallium phosphide in which a 2.9~GHz mechanical mode is coupled to a high quality factor optical resonator in the telecom band. The large electronic bandgap and the resulting low optical absorption of this new material, on par with devices fabricated from silicon, allows us to demonstrate quantum behavior of the structure. This not only opens the way for realizing noise-free quantum transduction between microwaves and optics, but in principle also from various color centers with optical transitions in the near visible to the telecom band.