Compound Metaoptics for Amplitude and Phase Control of Wavefronts

TL;DR

This paper introduces a novel compound metaoptic design using two closely spaced metasurfaces to independently control both the amplitude and phase of wavefronts, overcoming previous limitations of passive metasurfaces.

Contribution

The authors develop a systematic design method for compound metaoptics that enable independent control of wavefront amplitude and phase without reflection or absorption.

Findings

Demonstrated independent amplitude and phase control using two metasurfaces

Achieved transformation of complex field distributions without losses

Potential applications in holography and optical system miniaturization

Abstract

Metasurfaces allow tailored control over electromagnetic wavefronts. However, due to the local conservation of power flow, a passive, lossless, and reflectionless metasurface is limited to imparting phase discontinuities -- and not power density discontinuities -- onto a wavefront. Here, we show how the phase and power density profiles of a wavefront can be independently controlled using two closely-spaced, phase-discontinuous metasurfaces. The two metasurfaces, each designed to exhibit specific refractive properties, are separated by a wavelength-scale distance and together form a compound metaoptic. A systematic design procedure is presented, which allows transformation between arbitrary complex-valued field distributions without reflection, absorption, or active components. Such compound metaoptics may find applications in optical trapping of particles, displaying three-dimensional holographic images, shrinking the size of optical systems, or producing custom (shaped and steered) far-field radiation patterns.