Temperature‐Controlled Optical Activity and Negative Refractive Index

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