Coherent Retroreflective Metasurfaces

TL;DR

This paper introduces coherent retroreflective metasurfaces that use multi-wave illumination to achieve controllable retroreflection, enabling advanced wave control and applications like mode filtering and field localization.

Contribution

It presents a novel design and theoretical framework for coherent retroreflectors using inhomogeneous metasurfaces, expanding wave control capabilities beyond traditional single-wave illumination.

Findings

Demonstrated controllable retroreflection with designed metasurfaces

Showed filtering of undesired modes using coherent illumination

Enabled creation of localized fields in waveguides

Abstract

Inhomogeneous metasurfaces have shown possibilities for unprecedented control of wave propagation and scattering. While it is conventional to shine a single incident plane wave from one side of these metastructures, illuminating by several waves simultaneously from both sides may enhance possibilities to control scattered waves, which results in additional functionalities and novel applications. Here, we unveil how using coherent plane-wave illumination of a properly designed inhomogeneous metasurface sheet it is possible to realize controllable retroreflection. We call these metasurfaces as "coherent retroreflectors" and explain the method for realizing them both in theory and practice. We show that coherent retroreflectors can be used for filtering undesired modes and creation of field-localization regions in waveguides. The latter application is in resemblance to bound states in the radiation continuum.