Whispering gallery mode (WGM) microcavities have been widely used for high-sensitivity ultrasound detection, owing to their optical and mechanical dual-resonance enhanced sensitivity. The ultrasound sensitivity of the cavity optomechanical system is fundamentally limited by thermal noise. In this work, we theoretically and experimentally investigate the thermal-noise-limited sensitivity of a WGM microdisk ultrasound sensor and optimize the sensitivity by varying the radius and a thickness of the microdisk, as well as using a trench structure around the disk. Utilizing a microdisk with a radius of 300 μm and thickness of 2 μm, we achieve a peak sensitivity of 1.18 μPa Hz −1/2 at 82.6 kHz. To the best of our knowledge, this represents the record sensitivity among cavity optomechanical ultrasound sensors. Such high sensitivity has the potential to improve the detection range of air-coupled ultrasound sensing technology.
CITATION STYLE
Yang, H., Cao, X., Hu, Z.-G., Gao, Y., Lei, Y., Wang, M., … Li, B.-B. (2023). Micropascal-sensitivity ultrasound sensors based on optical microcavities. Photonics Research, 11(7), 1139. https://doi.org/10.1364/prj.486849
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