Magnetic control of scattering field parameters on magnetoplasmonic graphene gratings in the terahertz frequency range

Background. The relevance of the problem of developing new methods for efficient control of THz radiation characteristics is dictated by the needs of the development of THz technology. For practical purposes, the ability to control the polarization and intensity of THz radiation in nanostructured media and change their magneto-optical properties under the influence of an external magnetic field is important. However, in the THz range there are no materials that have the ability to influence the state of radiation polarization in a non-reciprocal manner. The magneto-optical activity of nanosystems with combined magnetic and plasmonic functions can be significantly increased by enhancing the electromagnetic field associated with plasmon resonance, and magnetic functionality allows controlling plasmonic properties using an external magnetic field. Excitation of surface magnetoplasmons-polaritons in graphene and graphene structures dramatically changes the magneto-optical response, and this makes graphene a unique platform for magneto-optical phenomena controlled by surface magnetoplasmons-polaritons. Aim. The purpose of this work is to develop new methods for efficient control of THz radiation characteristics and numerical study of the influence of gyrotropy and excitation of surface magnetoplasmons-polaritons on the parameters (polarization) of the scattering field on magnetoplasmonic graphene gratings in the THz frequency range. Methods. This important scientific problem related to modeling the scattering of THz waves on magnetoplasmonic graphene gratings and investigation of the characteristics of the scattered THz radiation can be solved by automated modeling tools using the CST MWS software package based on the solution (by the finite element method in the frequency domain) of the electrodynamic diffraction problem. Results. Magnetoplasmonic gratings of graphene nanoribbons in a perpendicular external magnetic field were selected as the object of analysis, their models were developed in the CST MWS software package, and the possibility of resonant frequency tuning was shown. The results of modeling 3D e-Field scattering patterns of normally and at an angle of 30° incident plane wave of p- or s-polarization on the cell of the magnetoplasmonic graphene nanoribbone grating, as well as the calculation of the ratio of the amplitudes of the horizontal and vertical components Ex/Ey of the scattered field and the axial ratio AR at the cross-section points (φ = 0°) of the main lobe of 3D e-Field scattering patterns at resonant frequencies are obtained. Methods of magnetic control of the polarization of scattered THz radiation based on the selection of operating frequencies corresponding to the magnetoplasmons-polaritons resonances are revealed, and the possibility of transforming the linear polarization of the incident wave, depending on the magnitude of the external magnetic field, is shown, while the transmitted wave can have elliptical polarization (the polarization ellipse is elongated), the reflected wave can have elliptical polarization close to circular. Conclusion. The possibility of magnetic control of the polarization of scattered THz radiation on magnetoplasmonic graphene gratings makes it possible to create integrated photonic devices for telecommunications, THz communications and visualization, biomedical technologies, sensors, including biosensors, and optoelectronics.