Metamaterial bricks and quantization of meta-surfaces

TL;DR

This paper introduces quantal meta-surfaces composed of pre-manufactured bricks encoding phase delays, enabling versatile acoustic field control with simplified design and potential for advanced sound modulation applications.

Contribution

It presents a novel approach using analogue-to-digital conversion and wavelet decomposition to create reconfigurable meta-surfaces from metamaterial bricks for acoustic manipulation.

Findings

Experimental demonstration of acoustic focusing and steering.

Successful air-borne acoustic levitation with meta-layers.

Effective multi-bit phase quantization for sound control.

Abstract

Controlling acoustic fields is crucial in diverse applications such as loudspeaker design, ultrasound imaging and therapy, or acoustic particle manipulation. The current approaches use fixed lenses or expensive phased arrays. Here, using a process of analogue-to-digital conversion and wavelet decomposition, we develop the notion of quantal meta-surfaces. The quanta here are small, pre-manufactured three-dimensional units - which we call metamaterial bricks - each encoding a specific phase delay. These bricks can be assembled into meta-surfaces to generate any diffraction-limited acoustic field. We apply this methodology to show experimental examples of acoustic focusing, steering and, after stacking single meta-surfaces into layers, the more complex field of an acoustic tractor beam. We demonstrate experimentally single-sided air-borne acoustic levitation using meta-layers at various bit-rates: from a 4-bit uniform to 3-bit non-uniform quantization in phase. This powerful methodology dramatically simplifies the design of acoustic devices and provides a key-step towards realising spatial sound modulators.