Integrated Optical Microrings on Fiber Facet for Broadband Ultrasound Detection

The miniature optical fiber ultrasound sensor with high sensitivity and bandwidth is important for the field of ultrasonic detection. In this study, a unique fiber ultrasound sensor via integrating optical microrings on a multicore fiber facet is reported. The results demonstrate this sensor can be used in liquid environment and has high sensitivity with broadband bandwidth. The detector's equivalent noise pressure (NEP) can reach 13.2 mPa Hz^−1/2 with a broadband ultrasound response over 250 MHz (103 MHz in −6 dB). Besides, this sensor is resistant to environmental impurities. The sensor is successfully applied to photoacoustic microscopy (PAM) with a lateral resolution of 5 µm and an axial resolution of 6.6 µm. Furthermore, an integrated transceiver structure for ultrasound/photoacoustic detection is proposed, which has great application prospects for using in constrained tiny spaces, such as endoscopy, or closely scanning over uneven surfaces.