Abstract-Broadband switchable terahertz half-/quarter-wave plate based on metal-VO2 metamaterials

 

Juan Luo, Xingzhe Shi, Xiaoqing Luo, Fangrong Hu, and Guangyuan Li

. Schematic of the proposed metamaterial composed of multi-layered metal-VO2${}_2$ hybrid structures. (a) When VO2${}_2$ is in the insulating state, it acts like dielectric, denoted by VO2${}_2$ (D) and indicated by the blue block, the metamaterial functions as an HWP converting linear 𝑦$y$ polarization into linear 𝑥$x$ polarization. (b) When VO2${}_2$ is in the conducting state, it acts like metal, denoted by VO2${}_2$ (M) and indicated by the red block, the metamaterial functions as a QWP converting linear 𝑦$y$ polarization into LCP. (c) Geometric parameters of the unit cell of the multi-layered metamaterial.

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-28-21-30861&id=440195

We propose a metal-vanadium dioxide (VO2) metamaterial with broadband and functionality-switchable polarization conversion in the terahertz regime. Simulation results show that the function of the proposed metamaterial can be switched from a half-wave plate (HWP) to a quarter-wave plate (QWP) over a broad bandwidth of 0.66–1.40 THz, corresponding to a relative bandwidth of 71.8%. The HWP obtained when VO2 is in the insulating state has reflection of 90% and linear polarization conversion ratio exceeding 98% over the bandwidth of 0.58–1.40 THz. By transiting the phase of VO2 into the conducting state, the obtained QWP can convert the incident linearly-polarized wave to circularly-polarized wave with an ellipticity of 0.99 over 0.66–1.60 THz. Additionally, results show that the proposed broadband switchable HWP/QWP has a large angular tolerance. We expect that this broadband and switchable multi-functional wave plate will find applications in polarization-dependent terahertz systems including sensing, imaging, and telecommunications.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement