Abstract: An ultrasonic wave transducer capable of generating a convergent ultrasonic sound beam has been found. The transducer comprises a piezoelectric substrate, at least one interdigital electrode group arranged on the surface of the piezoelectric substrate, each of said groups having a plurality of interdigital electrodes arranged in the longitudinal direction of the fingers of each interdigital electrode, said substrate being positioned in a liquid so that at least said interdigital electrodes contact with the liquid, and said electrodes being applied an alternating voltage with a predetermined phase difference thus providing a convergent sound beam in y-direction based upon the principle of interference between the sound beams, similar to the interference by a diffraction grating. Further, the non-uniform arrangement of the fingers of the interdigital electrodes provides the x-direction convergence, thus, an ultrasonic wave beam focusing at a single point is obtained.

Abstract: The combination of an electro-optic substrate the refractive index of which is changed by an electric field applied to the same and a pair of comb-shaped interdigital diffraction electrodes formed on the surface of said substrate provides an electrically controllable diffraction grating, which can be used as an optical modulator of a laser beam. An example of a substrate is lead-zirconate-titanate ceramic and the electrode can be composed of metal.