Bandwidth improvement of LiNbO₃ultrasonic transducers by half-concaved inversion layer approach

A novel type of half-concaved LiNbO3plate with domain inversion layer has been proposed for fabricating high-frequency broadband ultrasonic transducers. Two opposite ferroelectric polarization layers with a curved boundary are presented after heat treatment in the half-concaved LiNbO3plate with a total thickness of 110 μm. Characterization of the transducers illustrates that, without a matching layer, the self-focusing transducer with the half-concaved LiNbO3plate has achieved 123% bandwidth at the center frequency of 60 MHz, which is a significant improvement over the planar inversion layer transducer.