Reconfigurable graphene-based metamaterial polarization converter for terahertz applications

This study proposes a high-gain polarization converter using a graphene-based metamaterial array, a rectangular array comprising 20 periodic unit-cell elements. Each graphene-based metamaterial unit-cell element contains a rectangular patch with four triangular-shaped graphene parts at its four corners placed over a rectangular substrate backed with a perfect electric conductor and has a relative permittivity of εsub = 3.38. The metamaterial characteristics of the proposed graphene-based metamaterial unit-cell element are obtained over frequencies of 1.5–2.2 terahertz (THz). The graphene-based metamaterial array is placed over a linearly polarized slot antenna operating at 1.8 THz, with a maximum gain of 5.5 dBi. The linearly polarized wave radiated from the slot antenna can be converted into reconfigurable right-handed or left-handed circular polarizations according to the graphene parts’ biasing states. Moreover, the slot antenna’s operating − 10 dB bandwidth (BW) is increased by 22.2%, and the gain is enhanced to 8 dBi at the same operating frequency. A reconfigurable polarization conversion for the slot antenna can be obtained over a wide 3 dB axial ratio BW from 1.75 to 1.92 THz (20%–3 dB BW).