High-sensitivity Optical Microcavity Acoustic Sensor Covering Free Spectral Range

TL;DR

This paper presents a novel optical microcavity acoustic sensor with an extended dynamic range using an interferometric approach, achieving significantly improved sensitivity and minimal detectable pressure for high-precision acoustic detection.

Contribution

The study introduces a new sensor design combining a Mach-Zehnder interferometer with postselection to extend the dynamic range to the free spectral range in whispering gallery mode microcavity sensors.

Findings

Sensitivity improved by 57.87 dB over traditional methods

Minimal detectable acoustic pressure increased 26 times

Response amplitude enhanced via coherent state and heterodyne detection

Abstract

Optical whispering gallery mode microcavity acoustic sensors have emerged significant potential in high-sensitivity acoustic signal detection, but the narrow dynamic range limits the application prospect. To address the challenge, we propose and experimentally demonstrate a high-sensitivity acoustic sensor in optical whispering gallery mode microcavity. The proposed sensor integrates an extended Mach-Zehnder polarization interferometer with postselection, extending the dynamic range to the free spectral range. The sensing regions can be categorized into phase-drastic and phase-enhanced regions, both of which yield an optimal acoustic response that surpasses traditional transmission method. Experiment results demonstrate improvements of 57.87 dB in detection sensitivity and 26 times in minimal detectable acoustic pressure over the transmission method. Moreover, the application of coherent state and heterodyne detection can enhance response amplitude, further improving the detection sensitivity. Given the wide application range for acoustic dispersion and dissipation response, as well as the performance advantages of high sensitivity and wide dynamic range, the proposed WGM sensor offers a promising solution for acoustic sensing. Potentially, the structural design may be adaptable to other application scenarios involving time-varying signals through optical microcavity sensing.