Functional metasurfaces: Do we need normal polarizations?

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.

Angular Scattering Properties of Metasurfaces

“…3) The Huygens principle stipulates that an electromagnetic field can always be expressed in terms of its tangential components. Therefore, a metasurface with both normal and tangential susceptibility components can be transformed into an equivalent metasurface with only tangential susceptibility components such that both metasurfaces exhibit the same scattering response [16], [17], as depicted in Fig. 1(a) and (b).…”

“…376-385]. The legitimate question of whether normal polarizations are useful in bringing new functionalities to metasurfaces, or could they be simply ignored and replaced by purely tangential polarizations, was then raised [16], [17]. As will be succinctly explained thereafter, normal polarizations may indeed be ignored if a metasurface is always excited with the same illumination conditions, e.g., same incidence angle.…”

Optically and radio frequency (RF) transparent meta-glass

“…It is worth noting here that the effect of induced normal and tangential components of electric and magnetic polarization moments on the metasurface boundary conditions has been studied extensively [34][35][36][37]. It has been established that the normal components of EM properties are redundant to the design of far-field responses of a metasurface structure.…”

“…The quasi-optical microwave apparatus consisted of a Vector Network Analyzer (VNA), two k-band antennas, and confocal lenses optimized to operate at (25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38) GHz (Figure 8b). The Gaussian beam-waist (beam width of 4 cm) is located at the centre, where the sample is positioned, and is designed to cover 10 hexagonal unit cells and is small enough so as to avoid any spillover of the incident wave on the 10 × 10 cm sample [38] (Figure 8b).…”