Semi-analytical model of the optical properties of a metasurface composed of nanofins

We propose a method to evaluate the optical propagation properties of a dielectric non-resonant metasurface composed of rectangular nanofins. Our approach is based on a semi-analytical assessment of the effective indices to perform guided vectorial propagation inside the nanostructure. The proposed model is an extension of the commonly used Pancharatnam–Berry model where the effect of the incidence angle can be satisfactorily accounted for. The model shows good agreement with numerical simulations, and it can be inverted to give the nanofin rotation angle for a given output phase function. We show that the far-field distribution of a metalens predicted by our model is in good agreement with data from a simulation code.