A Broadband Graphene Based Multi-Functional mid-THz Polarization Converter

A graphene–based multifunctional polarization converter for the mid–THz band is proposed in this work and its electromagnetic behavior is explained with the help of the physics behind it and the circuital theory. The novelty of the proposed reflector lies in the fact that a linear–to–linear (LL) polarization conversion takes place for a chemical potential in 0.3–0.6 eV and a linear–to–circular (LC) in 0.7–1.0 eV across the mono–layered graphene over a large oblique angle (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\approx$</tex-math></inline-formula> 40<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>) of the incident wave. The fractional 3 dB axial ratio bandwidth in the case of LC polarization conversion is 81%. Moreover, for LL polarization conversion it gives 31% fractional bandwidth for polarization conversion ratio (PCR) more than 85%. The structure maintains a thickness of <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>/7.5 and a lattice size of <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>/18. The proposed multi–functional polarization converter can act as a promising candidate for THz indoor communication.