Generation of a steerable ultrasonic beam using a phased array of low power semiconductor laser sources and fiber optic delivery

Abstract

A linear array of optical fibers was used to deliver optical power from 8 low power (1.5 W) semiconductor laser sources to an aluminum plate. The optical fibers were arranged to form a linear phased array. Time delays of up to 520 ns were then utilized to adjust the excitation of the elements in the array, thus allowing the direction of the generated ultrasonic beam to be controlled at angles of up to 18° for an array spacing of 8 mm. Excitation was in the form of 3.6 µJ laser pulses and hence was truly non-destructive. Detection was achieved using piezoelectric transducers or interferometric fiber optic sensors.