Brillouin cavity optomechanics with microfluidic devices

TL;DR

This paper demonstrates Brillouin cavity optomechanics in microfluidic devices, enabling optical excitation of mechanical modes in liquids confined within hollow resonators, opening new avenues for liquid-phase optomechanical studies.

Contribution

It introduces a novel microfluidic resonator platform for cavity optomechanics with liquids, overcoming previous challenges of acoustic energy leakage in non-solid phases.

Findings

Achieved optical excitation of mechanical whispering-gallery modes in liquids from 2 MHz to 11,000 MHz.

Sustained vibrations in liquids with viscosity higher than blood.

Demonstrated optical coupling from dry side with integrated microfluidic inlet.

Abstract

Cavity optomechanics allows the parametric coupling of phonon- and photon-modes in microresonators and is presently investigated in a broad variety of solid-state systems. Optomechanics with superfluids has been proposed as a path towards ultra-low optical- and mechanical-dissipation. However, there have been no optomechanics experiments reported with non-solid phases of matter. Direct liquid immersion of optomechanics experiments is challenging since the acoustic energy simply leaks out to the higher-impedance liquid surrounding the device. Conversely, here we confine liquids inside hollow resonators thereby enabling optical excitation of mechanical whispering-gallery modes at frequencies ranging from 2 MHz to 11,000 MHz (for example, with mechanical Q = 4700 at 99 MHz). Vibrations are sustained even when we increase the fluid viscosity to be higher than that of blood. Our device enables optomechanical investigation with liquids, while light is conventionally coupled from the outer dry side of the capillary, and liquids are provided by means of a standard microfluidic inlet.