Rapid and Stable Photoacoustic Imaging System Based on Fiber Ultrasound Detector Array

Photoacoustic imaging (PAI) greatly depends on the quality of the photoacoustic signal detected by ultrasound sensors. Recent research focused on improving the performance of optical ultrasonic detectors with high sensitivity and small size. However, using a single detector requires cooperation with mechanical scanning, which will increase the acquisition time. The use of a galvanometer, which is huge in size and sensitive to alignment, brings about coupling and stability problems in the system. A detector array presents a viable solution to these problems, although it's rarely reported. In this work, a PAI system based on a fiber-based ultrasonic detector array and a high-speed optical switch (OSW) is proposed. The developed array comprises 64 elements made by Fabry-Pérot resonant cavities, offering high sensitivity with a noise equivalent pressure of 0.61 kPa and a broad bandwidth of 38 MHz, which enables the acquisition of high-resolution photoacoustic images. The array is linearly scanned along the sample by a high-speed OSW. This method allows the system to have a nanosecond-level unit scanning rate theoretically, which is faster. It also reduces system disturbance and is 10 times more stable than galvanometer scanning. The proposed fiber ultrasound array system based on OSW provides an effective and stable way for rapid photoacoustic imaging with high resolution.