Study on Heavy Matching Layer Transducer Towards Producing Second Harmonics

Cavitation bubbles are microbubbles which can be incepted by highly negative pressure. Producing such highly negative pressure exceeding the cavitation threshold is difficult to accomplish due to nonlinear propagation followed by focal phase shift. By superimposing the second harmonic to fundamental is a way to significantly reduce the problem. However, the conventional design for an air-backed transducer is not suitable to generate both the second harmonic and fundamental at the same time. In order to overcome this problem, we propose a high impedance matching layer approach. Furthermore, we also construct a study to foresee the impact by adjusting the thickness ratio towards fundamental and second harmonic. Numerical simulation and experimental measurement have shown that by using a high impedance matching layer, efficiently generation of both the second harmonic (2 MHz) and fundamental (1 MHz) at the same time is possible. Besides, by adjusting the thickness ratio between piezocomposite and heavy matching layer will influence the amplitude of acoustic power over squared of voltage of the fundamental and second harmonic.