Free-space optomechanical liquid probes using a twin-microbottle resonator

TL;DR

This paper introduces a free-space, probe-based twin-microbottle resonator system for high-sensitivity liquid sensing, enabling in-situ measurements in arbitrary media with potential biomedical and rheological applications.

Contribution

It presents a novel twin-microbottle resonator architecture that allows active free-space optomechanical sensing in liquids, overcoming limitations of fixed-structure fluidic methods.

Findings

Achieved high optical quality factor (~10^7) in the readout bottle.

Demonstrated detection of thermomechanical motion in liquid-immersed resonator.

Enabled optomechanical sideband drive in a liquid environment.

Abstract

Cavity optomechanics provides high-performance sensor technology, and the scheme is also applicable to liquid samples for biological and rheological applications. However, previously reported methods using fluidic capillary channels and liquid droplets are based on fixed-by-design structures and therefore do not allow an active free-space approach to the samples. Here, we demonstrate an alternate technique using a probe-based architecture with a twin-microbottle resonator. The probe consists of two microbottle optomechanical resonators, where one bottle (for detection) is immersed in liquid and the other bottle (for readout) is placed in air, which retains excellent detection performance through the high optical-Q (~107) of the readout bottle. The scheme allows the detection of thermomechanical motion of the detection bottle as well as its optomechanical sideband drive. This technique could lead to in-situ metrology at the target location in arbitrary media, and could be extended to ultrasensitive biochips and rheometers.