WGM microprobe device for high-sensitivity ultrasound detection and vibration spectrum measurement

Whispering-gallery-mode (WGM) microcavities have emerged as a promising alternative to traditional ultrasound probes, offering high sensitivity and wide bandwidth. In our research, we propose a novel silica WGM microprobe device, with impressive Q factors up to 10⁷. The side-coupled approach and special encapsulation design make the device compact, robust, and capable of utilizing in both gaseous and liquid environments. We have successfully conducted photoacoustic (PA) imaging on various samples using this device which demonstrates a high sensitivity of 5.4 mPa/√Hz and a broad bandwidth of 41 MHz at -6 dB for ultrasound. And it is capable of capturing the vibration spectrum of microparticles up to a few hundred megahertz. Our compact and lightweight device exhibits significant application potential in PA endoscopic detection, near-field ultrasound sensing and other aspects.