Two-Photon 3D-Printed Fabry–Pérot Interferometric Sensor for Ultrasensitive High-Frequency Ultrasonic Detection

A novel fiber extrinsic Fabry-Pérot interferometric ultrasonic sensor for detecting high-frequency ultrasonic signals is proposed and fabricated. The diaphragm structure features an anti-outer-ring clover design. Finite element simulation is employed to determine optimal parameters before directly printing the sensor onto the fiber tip using two-photon 3D printing technique. Experimental results indicate that the sensor achieves a signal-to-noise ratio of 67 dB@300 kHz, a mechanical sensitivity of 1362 nm/kPa, and a noise equivalent acoustic signal level of 3.98 $\mu$ Pa/Hz $^{1/2}$ @300 kHz. The proposed fiber sensor offers a new approach for sensing weak ultrasonic signals and is expected to be applied in various ultrasonic detection fields.