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Temperature‐Controlled Optical Activity and Negative Refractive Index

Authors :
Quan Xu
Caihong Zhang
Shaoxian Li
Biaobing Jin
Jiaguang Han
Eric Plum
Meng Liu
Weili Zhang
Hua Li
Chongwen Zou
Xueqian Zhang
Source :
Advanced Functional Materials. 31:2010249
Publication Year :
2021
Publisher :
Wiley, 2021.

Abstract

Chiral media exhibit optical activity, which manifests itself as differential retardation and attenuation of circularly polarized electromagnetic waves of opposite handedness. This effect can be described by different refractive indices for left- and right-handed waves and yields a negative index in extreme cases. Here we demonstrate active control of chirality, optical activity and refractive index. These phenomena are observed in a terahertz (THz) metamaterial based on three-dimensionally (3D) chiral metallic resonators and achiral vanadium dioxide inclusions. The chiral structure exhibits pronounced optical activity and a negative refractive index at room temperature when vanadium dioxide is in its insulating phase. Upon heating, the insulator-to-metal phase transition of vanadium dioxide effectively renders the structure achiral, resulting in absence of optical activity and a positive refractive index. The origin of the structure’s chiral response is traced to magnetic coupling between front and back of the structure, while the temperature-controlled chiral-to-achiral transition is found to correspond to a transition from magnetic to electric dipole excitations. The use of a fourfold rotationally symmetric design avoids linear birefringence and dichroism, allowing such a structure to operate as tunable polarization rotator, adjustable linear polarization converter and switchable circular polarizer.

Details

ISSN :
16163028 and 1616301X
Volume :
31
Database :
OpenAIRE
Journal :
Advanced Functional Materials
Accession number :
edsair.doi.dedup.....83f5ef66d889ab1a61545f1f3e5da9f6
Full Text :
https://doi.org/10.1002/adfm.202010249