High-sensitivity, high-frequency extrinsic Fabry–Perot interferometric fiber-tip sensor based on a thin silver diaphragm

We propose and demonstrate a fiber-tip sensor based on an ultra-thin silver diaphragm for highly sensitive and high frequency ultrasonic detection. The diaphragm is prepared by the vacuum thermal deposition method and then transferred to the fiber tip. The sensor demonstrated in this letter has a 300 nm thick diaphragm with an inner diameter of 75 μm, leading to a static pressure sensitivity of 1.6 nm/kPa and a resonant frequency of 1.44 MHz. This sensor has potential applications in many fields such as structural health monitoring and medical ultrasonography.