Multiband Polarization Independent Terahertz Absorber for Sensing Applications

In this article, a multiband electromagnetic terahertz (THz) absorber-based biosensor is proposed. The absorber’s unit cell has a dielectric substrate with a metallic ground plane at the bottom and a metallic resonating structure at the top with an overall volume of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$20\times 20\times 3.37~\mu $ </tex-math></inline-formula> m3 (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.09\lambda _{L} \times 0.09\lambda _{L} \times 0.015165\lambda _{L}$ </tex-math></inline-formula>, where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{L} =$ </tex-math></inline-formula> wavelength at 1.35 THz). It has a peak absorption of 92.79%, 94.77%, 98.87%, 99.58%, 97.07%, and 96.27% at the resonance frequencies of 1.35, 2.974, 5.564, 8.574, 10.184, and 12.438 THz, respectively. The full-width at half-maxima (FWHM) of the first three absorption bands are 0.108, 0.239, and 0.718 THz, respectively, and the combined FWHM of remaining three absorption peaks is 4.641 THz with polarization insensitivity and incident angle (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta ^{\circ }$ </tex-math></inline-formula>) stability for <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta \le 50^{\circ }$ </tex-math></inline-formula>. The proposed absorber’s sensor configuration to detect malaria and different cancer cells has a maximum sensitivity of 8.225 THz/RIU and maximum figure of merit (FoM) of 100.3 RIU-1. The proposed absorber and sensor configurations are dominating the available structures in terms of overall volume, number of operating bands, number of peaks, peak absorption, and peak sensitivity.