Dynamic generation of giant linear and circular dichroism via phase-change metasurface

Abstract

Dichroism, an important property for the manipulation and characterization of polarization states, has been widely studied. However, owing to the inherent relationship between linear and circular polarization, it is difficult to generate high linear dichroism (LD) and circular dichroism (CD) in the same structure. Previous study can only solve this problem in the condition of oblique incidence. Here, a method is proposed to generate high LD and CD under normal incidence without any structural changes. By the design of metamolecule composed of two pairs of twin nanopillars, the polarization-dependent interference from those twin nanopillars can be utilized to achieve giant dichroism. Meanwhile, the phase state of Sb 2 S 3 is introduced as an additional degree of freedom to further control the polarization-dependent interference thus generating LD and CD in the same structure. Moreover, the proposed method can achieve both LD and CD in transmission as well as reflection modes. This full-space feature was not achieved before. Due to the compactness and excellent performance, we envision that this work will advance the development of tunable dichroic devices and flat polarization optical elements in the optical integrated system.