Broadband focusing ultrasonic transducers based on dimpled LiNbO3 plate with inversion layer

A high-frequency broadband focusing transducer based on dimpled LiNbO₃ inversion layer plate has been fabricated and characterized. A spherical surface with a curvature radius of 6 mm is formed on the half-thickness LiNbO₃ inversion layer plate of Y36° cut orientation. The domain structure in the cross section is observed after a hydrofluoric acid etching process. For transducer fabrication, conductive epoxy is used as the backing material and polymer is deposited on the front face as the matching layer. The center frequency, bandwidth, and insertion loss of the focused transducer are measured to be 72 MHz, 136%, and -32 dB, respectively. The focused transducer has been successfully used for rabbit eyeball imaging and a better imaging capability compared with the planar transducer has been demonstrated. These promising results prove that the dimpled LiNbO₃ inversion layer plate has great potential for fabrication of high-frequency broadband focusing ultrasonic transducers.