Abstract-Ultra-broadband terahertz bandpass filter with dynamically tunable attenuation based on a graphene–metal hybrid metasurface

 

Wenli Huang, Xiaoqing Luo, Yuanfu Lu, Fangrong Hu, and Guangyuan Li

https://www.osapublishing.org/ao/abstract.cfm?uri=ao-60-22-6366

We propose an ultra-broadband terahertz bandpass filter with dynamically tunable attenuation based on a graphene–metal hybrid metasurface. The metasurface unit cell is composed of two metal stripes enclosed with a graphene rectangular ring. Results show that when the metasurface is normally illuminated by a terahertz wave polarized along the metal stripes, it can act as an ultra-broadband bandpass filter over the spectral range from 1.49 THz to 4.05 THz, corresponding to a fractional bandwidth of 92%. Remarkably, high transmittance above 90% covering the range from 1.98 THz to 3.95 THz can be achieved. By changing the Fermi level of graphene, we find that the attenuation within the passband can be dynamically tuned from 2% to 66%. We expect that the proposed ultra-broadband terahertz bandpass filter with tunable attenuation will find applications in terahertz communication and detection and sensing systems.

© 2021 Optical Society of America

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