Space-time gradient metasurfaces

TL;DR

This paper introduces space-time gradient metasurfaces that enable advanced light manipulation, including non-reciprocal transmission, by combining spatial and temporal variations to break symmetry constraints.

Contribution

It demonstrates the addition of temporal gradients to metasurfaces, enabling non-reciprocal effects and expanding light control capabilities beyond static designs.

Findings

Achieved non-reciprocal electromagnetic transparency analogue.

Enabled one-way transmission in otherwise opaque surfaces.

Proposed magnetic-free, ultrathin non-reciprocal planar surfaces.

Abstract

Metasurfaces characterized by a transverse gradient of local impedance have recently opened exciting directions for light manipulation at the nanoscale. Here we add a temporal gradient to the picture, showing that spatio-temporal variations over a surface may largely extend the degree of light manipulation in metasurfaces, and break several of their constraints associated to symmetries. As an example, we synthesize a non-reciprocal classical analogue to electromagnetic induced transparency, opening a narrow window of one-way transmission in an otherwise opaque surface. These properties pave the way to magnetic free, planarized non-reciprocal ultrathin surfaces for free-space isolation.