Semi-Analytical finite-difference technique for steady-state field characterization of space-time modulated huygens' metasurfaces

A simple semi-analytical technique to compute the steady-state field profile of new harmonic frequencies generated at the output of a space-time modulated Huygens' metasurface is proposed and numerically demonstrated. For a given monochromatic excitation, the metasurface output fields are first computed using a finite-difference routine taking into account the Generalized Sheet Transition Conditions (GSTCs) and the Lorentzian surface susceptibilities. The field profiles in the surrounding region of the metasurface are then obtained by computing the temporal Fourier transforms of metasurface outputs and applying the analytical Fourier propagation to each of its harmonic components.