Efficient Tunable THz Frequency Convertors Based on Multilayer Graphene Metasurfaces

Abstract

A numerical approach for modeling of nonlinear THz frequency conversion effect in the multilayer graphene nanoribbon metasurfaces was developed to solve the nonlinear diffraction problem for Maxwell's equations, together with a model of the nonlinear graphene surface conductivity of third order nonlinearity. By using developed computational algorithm, the numerical modelling of performances of THz converters based on the multilayer graphene ribbon metasurfaces depending on the chemical potential and the incident angle of signal and pump waves was performed. The numerical analysis shows an efficient nonlinear THz frequency conversion mechanism in the condition of resonance when the frequencies f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> , f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> of the incident pump and signal waves and generated wave at the combination frequency f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> =2 f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sub> - f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> are selected near the resonant frequency f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">res</sub> of the surface plasmon-polariton modes in multilayer graphene metasurfaces. It is demonstrated a significant tunability of performances of THz converters, namely increase in the efficiency of the THz frequency conversion upon decreasing the value of chemical potential (the external bias electric field) and its insensitivity to the incident angles of the pump and signal waves over a wide range of angles.