Electrically Thick Fabry-P\'erot Omega Bianisotropic Metasurfaces as Virtual Anti-Reflective Coatings and Non-Local Field Transformers

TL;DR

This paper introduces a novel, practical design for omega bianisotropic metasurfaces using cascaded Fabry-Perot etalons, enabling advanced wave control like virtual anti-reflective coatings and non-local field transformations.

Contribution

Proposes an easily designed, electrically thick FP-OBMS structure that replicates ideal OBMS functionalities, advancing practical realization of complex wave manipulation.

Findings

Enhanced wave control capabilities demonstrated

Achieved virtual anti-reflective coating effect

Enabled non-local surface wave excitation

Abstract

Omega bianisotropic metasurfaces (OBMS) provide wave-control capabilities not previously available with Huygens' metasurfaces (HMS). These enhanced capabilities derive from the additional degree of freedom provided by OBMS, and are based on analyses of zero-thickness surfaces with abstract surface impedance properties. However, the design of practical metasurfaces has proven tedious. Herein, we propose a novel, easily designed structure to realize OBMSs. Extending our previous work, we show that an asymmetrical cascade of two judiciously engineered Fabry-Perot (FP) etalons could form an OBMS meta-atom to provide desired wave control capabilities. Implementing this FP-OBMS for anomalous refraction, we show that bianisotropy effectively produces a virtual anti-reflective coating over a HMS, leading to the OBMS efficiency enhancement. This intriguing observation, backed by an approximate closed-form solution, provides an original physical interpretation of the mechanism underlying perfect anomalous refraction, and is used to explain for the first time differences in the angular response of OBMS in comparison to HMS. Implementing the FP-OBMS for the more intricate functionality of beam-splitting, we show that the FP-OBMS are capable of non-local excitation of surface waves required to this end, despite being electrically thick. These results, verified via full-wave computations, demonstrate the ability of the proposed configuration to meticulously reproduce the scattering properties of ideal (abstract) zero-thickness OBMS, thereby paving the path to practical realization of wave transmission with exotic functionalities, some of which have never before been associated with a physical structure.