Nano-optomechanical resonators in microfluidics

TL;DR

This paper presents a high-Q nano-optomechanical micro-wheel resonator integrated in microfluidics, capable of operating in water with low damping, high sensitivity, and supporting thermal Brownian motion observation.

Contribution

It introduces a novel optomechanical micro-wheel resonator with ultra-high optical quality factor and demonstrates its operation in water, overcoming viscous damping challenges.

Findings

Achieved optical Q factor up to 1.5 million in water.

Operates in self-oscillation mode with low threshold power.

Estimated mass sensitivity of attogram level in liquid environment.

Abstract

Operation of nanomechanical devices in water environment has been challenging due to the strong viscous damping that greatly impedes the mechanical motion. Here we demonstrate an optomechanical micro-wheel resonator integrated in microfluidic system that supports low-loss optical resonances at near-visible wavelength with quality factor up to 1.5 million. The device can be operated in self-oscillation mode in air with low threshold power of 45 uW. The very high optical Q allows the observation of the thermal Brownian motion of the mechanical mode in both air and water environment with high signal-to-background ratio. A numerical model is developed to calculate the hydrodynamic effect on the device due to the surrounding water, which agrees well with the experimental results. With its very high resonance frequency (170 MHz) and small loaded mass (75 pg), the present device is estimated to have mass sensitivity of attogram level in liquid environment with bandwidth of 1 Hz.