A method to efficiently and rapidly approximate the vectorial fields generated by large area metasurfaces

In order to calculate the electromagnetic fields that are produced after light passes through a metasurface, simulation methods such as the Finite-Difference Time-Domain method are often employed. While these provide a good approximation to the fields, the level of detail at which the volume of space that the light is propagating in needs to be modelled and the time for which simulations need to run, mean that as the area of the metasurface is increased these simulations rapidly become unwieldy. In this paper we show how the result of a FDTD simulation of a unit cell can be used to generate a good approximation of the vectorial field that large area metasurfaces will generate, but using a fraction of the computational resources. This approach can provide an intermediate design step, allowing potentially interesting designs to be rapidly identified or discarded.