Surface acoustic wave displacement amplitude measurements using a curved Fabry-Pérot interferometer

We propose a fiber-optic sensing method for absolute vertical displacement amplitude measurement of surface acoustic waves (SAWs). The sensor is based on a “curved Fabry-Perot” interferometer formed by the endface of a single-mode fiber (SMF) and the curved SAW surface. Amplitudes on the order of a few picometers at 100 MHz on a lithium niobate substrate are derived through a physics-based analytical model. The proposed technique can be used for SAW device characterization and to replace or complement the conventional electrodes used with SAW sensors for higher sensitivity, resolution and sampling rate.