High-spatial-resolution ultrasonic sensor using a fiber-optic Fabry-Perot interferometer

摘要

An all-optical micro ultrasound sensor, consisting of a rigid, fiber-coupled Fabry-Perot interferometer (FPI) with an open micro-cavity is proposed and experimentally demonstrated. The sensor structure comprises a rectangular gold membrane on micro scale that is formed by ultrafast machining technology using femtosecond laser. The processed membrane is easy to be deformed or deflected by the external pressure, making it be a cantilever beam to perceive the dynamic acoustic pressure. The sensing principle relies exclusively on the detection of pressure-induced changes of the interference phase of FPI. This enables inherently linear signal detection over a broad bandwidth by using spectral band-side filtering technology. The theoretical analysis and experimental demonstration are characterized in detail. Thanks to the ultrahigh sensitivity and micro-scale structure of sensor, the sensor presents a high spatial resolution.