Functional metasurfaces: Do we need normal polarizations?

TL;DR

This paper investigates whether normal polarizations are necessary in reciprocal metasurfaces for shaping reflection and transmission, concluding they do not provide additional degrees of freedom.

Contribution

It demonstrates that normal polarization components do not enhance the design flexibility of metasurfaces and compares volumetric and planar realizations of their properties.

Findings

Normal polarizations do not add extra degrees of freedom.

Equivalent volumetric and planar metasurface realizations have distinct advantages.

Normal components are not essential for metasurface design flexibility.

Abstract

We consider reciprocal metasurfaces with engineered reflection and transmission coefficients and study the role of normal (with respect to the metasurface plane) electric and magnetic polarizations on the possibilities to shape the reflection and transmission responses. We demonstrate in general and on a representative example that the presence of normal components of the polarization vectors does not add extra degrees of freedom in engineering the reflection and transmission characteristics of metasurfaces. Furthermore, we discuss advantages and disadvantages of equivalent volumetric and fully planar realizations of the same properties of functional metasurfaces.