Abstract
Terahertz (THz) electromagnetic wave absorbers are finding new applications both in military and civilian sectors. This is the reason why constant efforts have been made worldwide to enhance the working performance of these absorbers. One downside of the available absorbers is their response to Transverse Electric (TE) and Transverse Magnetic (TM) waves at different frequency bands. Specific strategic applications require response of an absorber in same frequency band for TE and TM electromagnetic waves, for large inclination and polarization angle of the incoming signal. In this work, we present a metasurface based THz absorber with improved functionality. The fractional bandwidth is 91.64% w.r.t the center frequency of 1.97 THz, that shows an absorptivity of more than 90%. Due to the fourfold symmetry, the absorber is polarization insensitive. It shows more than 80% absorptivity for incoming wave inclinations upto <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$60^{\circ }$</tex-math></inline-formula> . The thickness of the absorber is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim$</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda$</tex-math></inline-formula> /11. The good point is that the absorber shows all these improved performance for both TE and TM incoming signals in the same frequency range. Overall, the designed absorber is a much improved version of its peers available in the literature.
Highlights
B ECAUSE of crowding in the low frequency region, higher frequencies are constantly being explored and the focus is THz region of the spectrum
Wave absorber is one such component [1], [2], and at THz frequency, it has some useful applications like imaging, sensing, and cloaking [3], [4]
The absorptivity of more than 80% has been obtained for different angle of incidence electromagnetic wave up to 60◦, for transverse electric (TE) and transverse magnetic (TM) mode of polarization
Summary
B ECAUSE of crowding in the low frequency region, higher frequencies are constantly being explored and the focus is THz region of the spectrum. In one case the absorption occurs due to the occurrence of Lorentzian electric and magnetic resonance, which leads to the impedance match of the structure to the free space. This in turn power dissipation in the materials. Graphene has attracted considerable attention from researchers due to its unique electromagnetic and electric conductive properties [25] This material has more applications in THz frequency than in the lower region. The graphene layer of unit cell is perforated in a plus shape and circular ring form to get two different nearby resonating frequency bands so that they can form a wide-band of absorption in THz frequency regime. The structure is polarization insensitive for both TE and TM modes
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