Affiliation:
1. Department of Physics, Zhejiang University of Technology 1 , Hangzhou 310023, China
2. Collaborative Innovation Center for Bio-Med Physics Information Technology of ZJUT, Zhejiang University of Technology 2 , Hangzhou 310023, China
Abstract
With the in-depth study of open optical systems, the topological phases of non-Hermitian metasurfaces have attracted increasing attention due to their topological protection properties. Here, in this paper, a tunable non-Hermitian metasurface with bidirectional anisotropism is proposed. By incorporating the phase change material vanadium dioxide (VO2) into the metasurface, two topological exceptional points (EPs) appear in the system by adjusting the conductivity of VO2 and chiral responses appear at both EPs. This research shows that the conductivity significantly affects the reflection of the metasurface, and the zero-reflection points correspond to the EPs of the non-Hermitian system. Further results prove that circling around EPs leads to a 2π phase change, which is topologically protected and independent of the encirclement path. Therefore, this study employs an active control approach to realize two topological EPs. Through comprehensive investigations into the topological properties and chiral performance at EPs, we elucidate the mechanism for the chirality generation in non-Hermitian metasurfaces, which offers feasible solutions for the development of chiral topological devices and light transmission and modulation in future applications.
Funder
Natural Science Foundation of Zhejiang Province
National Natural Science Foundation of China
Fundamental Research Funds for the Provincial Universities of Zhejiang