Coherent Fiber-Optic Method for Spatially Resolved, Time-Dependent, Picometer-Scale Displacement Amplitude Measurements of Surface Acoustic Waves

This paper presents a compact, noncontact fiber-optic interferometric method for measuring the vertical displacement amplitude of surface acoustic waves (SAWs) at 100 MHz on a lithium niobate substrate with picometer-scale precision. A single-mode fiber serves as the sensor, forming a Fabry-Pérot-like interferometer with reflections from the fiber endface and SAW surface. The method achieves high sensitivity (10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/19