A 3D-Printed Multicore Fiber-Tip Resonator for Ultrasonic Sensing

Optical fiber sensors have attracted considerable attention for ultrasonic detection, owing to their compactness and superior performance. In this study, leveraging two-photon polymerization technology in micronano fabrication, we have developed an ultrasonic sensor integrated with photonic wire bonding and an optical resonant microdisk, which are fabricated on the optical fiber end-face. The sensor demonstrates an ultrasonic sensitivity of 5.6 mV/kPa@1 MHz, a noise-equivalent pressure of 12.31 mPa/√Hz@1 MHz, and the capability to detect ultrasonic signals over a 180° angular range. Furthermore, the sensor can be employed for the localization and imaging of small-scale objects. We perform a systematic experiment involving the linear translation of the sensor to acquire ultrasonic signals, subsequently reconstructing the two-dimensional spatial profile of the fiber array. This fiber-tip ultrasonic sensor features compact dimensions, broad bandwidth, and elevated sensitivity, which demonstrate significant potential for diverse applications in ultrasonic wave-based sensing, imaging, and nondestructive testing.