Ultrasonic focusing Gaussian source to receive nonlinearly generated second harmonic sound by itself

A focusing source to concurrently detect the nonlinearly generated second h armonic sound contained in the reflected wave has been produced. A 36 degre es rotated Y-cut LiNbO3 plate of 20 MHz fundamental resonance frequency wit h a reversed polarization layer formed by heat treatment is bonded to a pla ne surface of a solid acoustic lens whose thickness is set at a small value so as to avoid the influences of nonlinear distortion and multiple reflect ion within the lens. One of the electrodes on the piezoelectric plate is fa bricated to a 20-point-star shape. The formation of a 20 MHz focused Gaussi an beam and the capability of receiving the 40 MHz second harmonic sound ar e confirmed through experiments.