ANALYTICAL AND NUMERICAL STUDY OF AN ACOUSTIC WAVE-CONVERSION IN 2D SURFACE SUPERLATTICES WITH LIQUID LOADING

摘要

A typical ultrasonic 2D phased array is a piezoelectric composite device, the active elements of which are individually excited by electric pulses at programmed delay times. Such delay scheme allows electrically steered dynamic beam control. However, the ultrasonic 2D phased array system has not been used in a wider scale because such a system costs too much. It is mainly due to the complexity due to the very large number of elements, and associated connections with electronic steering systems required to provide a satisfactory performance. The topic of the paper is based on an alternative approach, which employs a doubly - periodic superlattice, with the periodicity in the range of ultrasonic wavelength. In general, a superlattice arises when a periodic spatial modulation is imposed. It can be effected by a variety of means involving such as a 'freezing' of acoustic waves when passing through a critical ferrodistortive regime, by a change of composition or by a modulation of the concentration of impurities.