Abstract-Polarization-independent and angle-insensitive broadband absorber with a target-patterned graphene layer in the terahertz regime

Xin Huang, Wei He, Fan Yang, Jia Ran, Bing Gao, and Wei-Li Zhang

Fig. 1 Proposed broadband metamaterial absorber with a target-patterned graphene layer. (a) Schematic of the proposed broadband tunable metamaterial absorber. (b) Top view of the unit cell, (c) Perspective view of the unit cell. The geometry parameters of the proposed structure are set as (unit:𝜇𝑚$\mu m$): 𝑝=75,ℎ=27,𝑅=23,𝑅11=24,𝑅12=35,𝑔=1,𝑛=0.2$p=75,h=27,R=23,R_{11}=24,R_{12}=35,g=1,n=0.2$.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-26-20-25558

We propose a broadband tunable metamaterial absorber with near-unity absorption in the terahertz regime based on a target-patterned graphene sheet. Due to gradient diameter modulation of the graphene sheet and circular symmetry of the unit cell, broadband and polarization-independent properties are achieved in the absorber. A full-wave numerical simulation is performed, and the results show that the absorber’s bandwidth of 90% terahertz absorption reaches 1.57 THz with a central frequency of 1.83 THz under normal incidence. At oblique incidence, the broadband absorption of the absorber remains more than 75% over a wide incidence angles up to 60°$°$for the transverse electric (TE) mode and 75°$°$for the transverse magnetic (TM) mode. Furthermore, tunable property is implemented and the peak absorption of the absorber can be tuned from 19% to near 100% by changing the Fermi energy of the graphene sheet from 0 to 0.9 eV via electrostatic doping. The absorber is scalable to the infrared and visible frequencies, which could be used as tunable sensors, filters and photovoltaic devices.

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