Characterization of transducer arrays by laser interferometry: influence of acousto-optic interactions on displacement measurements in water

This paper deals with the influence of acoustooptic interactions on displacement measurements over transducer array with laser interferometer. Changes on the popular x-t and ω-k diagram of displacement due to interactions between acoustic and laser beams are discussed. A theoretical analysis of acousto-optic phenomenon, based on the plane wave decomposition of radiated field by the array is developed. Theoretical and experimental results are compared, showing first that waves with phase velocity near the one of the fluid are greatly amplified. Second, the interaction of laser beam with edge wave produced by the vertical size of elements induces a parasitic temporal pulse on the x-t diagram and so interference pattern in the ω-k diagram. Several possibilities of filtering are analyzed