The polarization states of light in metastructures

Abstract

In this talk, we present our recent work on controlling the polarization states of light with metastructures. First, we illustrate an approach to tune efficiently the phase difference of light in two orthogonal directions by controlling the time retardation with a microstructured surface. Second, we demonstrate the general mechanism to construct the dispersion-free metastructure, in which the intrinsic dispersion of the metallic structures is perfectly cancelled out by the thickness-dependent dispersion of the dielectric spacing layer. By selecting the structural parameters, the polarization states of light can be freely tuned across a broad frequency range, and all of the polarization states on the Poincare sphere can be realized dispersion free. Third, two examples are given: one is that we have achieved high-efficiency generation of circularly polarized light via symmetry-induced anomalous reflection in a metasurface; the other is that we have realized a freely tunable polarization rotator for broadband terahertz waves using a metastructure, which can conveniently rotate the polarization of a linearly polarized terahertz wave to any desired direction with nearly perfect conversion efficiency. The investigations provide some guidelines to control the polarization state of light at subwavelength scale.