  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.
