Metascreen-based acoustic passive phased array with sub-wavelength resolution

Abstract

A phased source array is an array consisting of elementary sources with proper relative phases to steer a wavefront, so as to form desired wave fields of specific property and applications. However, the phased array requires a large number of sources in forming complex wavefront or non-paraxial wave beams, leading to high cost and complexity in the electronics required to operate individual sources of the active array. A passive metascreen is presented here to transmit sound energy from a single source and steer the transmitted wavefront to form desired fields. The metascreen plays a role like a phased array but with a passive way that avoids the complexity of an active array. The screen has a half-wavelength thickness and composes of a series of elements with a dimension of one-tenth of the sound wavelength along the screen. The elements have a hybrid structure designed for high transmission and full range of phase shift. The performance of the screen is numerically simulated and experimentally demonstrated to generate a self-bending beam in non-paraxial region. The screen with its simple configuration and extreme acoustic performance could have applications for sound field shaping in numerous areas where the conventional array would have complexity and limited capability.