4. Conclusion

In this article, we have tried to give an overview of the (rapidly expanding) universe of metasurfaces, both in microwave and optical applications. This article cannot be exhaustive, as the number of articles published on the subject currently stands at several thousand. Its main aim is to give an idea of the variety of studies and applications that have been published to date.

We first looked at the basic physical principles of these metasurfaces. As these principles show, metasurfaces operate quite differently from metamaterials. Whereas metamaterials are based on the effective material principle, with electromagnetic properties translated into concepts of effective permittivity and permeability, isotropic or anisotropic, or polarization-dependent, metasurfaces use coefficients of reflection and refraction, and polarization transformation. These properties are...