Compound Metaoptics for Amplitude and Phase Control of Wave Fronts

Phys Rev Lett. 2019 Mar 22;122(11):113901. doi: 10.1103/PhysRevLett.122.113901.

Abstract

Metasurfaces allow tailored control of electromagnetic wave fronts. However, due to local conservation of power flow, passive, lossless, and reflectionless metasurfaces have been limited to imparting phase discontinuities-and not power density discontinuities-onto a wave front. Here, we show how the phase and amplitude profiles of a wave front can be independently controlled using two closely spaced phase-discontinuous metasurfaces. The two metasurfaces, each designed to exhibit spatially varying refractive properties, are separated by a wavelength-scale distance and together form a compound metaoptic. A method of designing the compound metaoptic is presented, which enables transformation between arbitrary complex-valued field distributions without reflection, absorption, polarization loss, or active components. Such compound metaoptics may find applications in the 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.