High-sensitive Fabry-Perot cavity-enhanced optical resonator for photoacoustic sensing with wide frequency range

Highly sensitive broadband acoustic detectors are needed to expand the capabilities of geological exploration, photoacoustic imaging, and industrial inspection techniques. However, while pursuing miniaturization, it is difficult to combine high sensitivity and wide acoustic detection frequency range. Meanwhile, the consistency and mechanical stability of the manufacturing process become important challenges for optical sensors in practical applications. To address this issue, we present a new silicon-based cavity-enhanced Fabry-Pérot interferometer photoacoustic sensor and fully characterize its acoustic performance. Micro-resonant cavity-enhanced photoacoustic sensor with broadband acoustic responses up to 50 Hz-10 k Hz has been fabricated. The detection sensitivity is also impressive, reaching -120.23 dB re rad/µPa @ 1 k Hz, with a noise equivalent pressure (NEP) of 88.7 µPa/√Hz @ 1 k Hz. This approach will help design photoacoustic sensors to improve detection sensitivity and bandwidth with limited fabrication accuracy and size.