Analysis of a Thin Tunable Silicon-Based Metamaterial Absorber for Sensing Applications

Here, a tunable graphene based thin absorber which can be applied for sensing different analytes, has been proposed. A graphene ring has been used to tune the absorption characteristics from 4.2 THz – 4.8 THz with varying chemical potential from 0–0.9 eV for both transverse electric (TE) and transverse magnetic (TM) incident waves. When no chemical potential is applied to the graphene ring, greater than 99% absorption is exhibited at 4.4 THz and 5.6 THz respectively. When a chemical potential of 0.4 eV is applied to the graphene ring, single band absorption is registered at 4.3 THz. Both single and multiband sensing have been investigated by full-wave simulations using finite integration technique without altering the absorber geometry. The absorber is thin (0.16λ) and polarization insensitive due to its four-fold rotational symmetry. Highest figure of merit (FOM) of 10 and quality factor (Q\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Q$$\end{document}) of 304.55 is obtained when the absorber is used as a sensor at μ=0eV.\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu =0 eV.$$\end{document} Analytes of different thickness and refractive indices have been used to validate the application of the absorber as a sensor. Maximum frequency sensitivity of the structure is achieved as 0.5 THz per refractive index. An equivalent circuit model is proposed for the sensor for μ=0eV\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu =0 eV$$\end{document} and μ=0.4eV\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\mu =0.4 eV$$\end{document} which corroborates the numerical simulations.