Fabry-Pérot Huygens' metasurfaces: On homogenization of electrically thick composites

Abstract

Realization of the anomalous refraction effects predicted by Huygens' metasurfaces (HMS) have required tedious and timeconsuming trial-and-error numerical full-wave computations. It is shown herein that these requirements can be alleviated for transverse magnetic (TM) propagation by a periodic dielectric-based HMS consisting of an electrically thick array of cascaded Fabry-Pérot etalons. This "Fabry-Pérot HMS" (FP-HMS) is easily designed to mimic the local scattering coefficients of a standard zero-thickness HMS (ZT-HMS) which, according to homogenization theory, should result in the desired anomalous refraction. To probe the characteristics of this practical FP-HMS, a method based on Floquet-Bloch (FB) analysis is derived for predicting the fields scattered from it for arbitrary angles of incidence. This method produces simple closed-form solutions for the FB wave amplitudes and the resulting fields are shown to agree well with full-wave simulations. These predictions and full-wave simulations verify the applicability of homogenization and scattering properties of zero-thickness HMS's to thick structures. They also verify the proposed semi-analytical microscopic design procedure for such structures, offering an effective alternative path to implementation of theoretically envisioned intricate field manipulating devices.

Electrically thick Fabry-Perot omega bianisotropic metasurfaces as virtual antireflective coatings and nonlocal field transformers

“…However, as indicated previously, the HMS generally produces an unwanted specularly reflected wave in addition to the desired transmitted wave [7,10,13]. This is the case both for the zero-thickness implementation of the HMS and for the Fabry-Pérot implementation described in [30].…”

“…In this section, the methodology will be discussed for designing a realistic thick structure that mimics an abstract zero-thickness OBMS. This is accomplished by generalizing the previously-developed FP-HMS structure and design procedure [30] to allow synthesis of the FP-OBMS.…”

“…In previous work, we have tackled this realization problem for HMSs using an original physical structure, based on a periodic array of parallel plate waveguides [30]. A sample structure that is being proposed here for the OBMS is shown in Fig.…”

Multimodal Anti-Reflective Coatings for Perfecting Anomalous Reflection from Arbitrary Periodic Structures

“…This failure was overcome by omega bianisotropic metasurfaces (OBMSs) which introduced an additional magnetoelectric degree of freedom, leading to a metasurface capable of producing perfect anomalous reflection, refraction and beam-splitting [13,[15][16][17]; perfect in the sense that all incident power is transferred to the desired anomalously scattered wave(s). Comparing analytical solutions for both the HMS [18] and the OBMS [19], we recently employed a ray-optics interpretation of the process to demonstrate the equivalence between an OBMS, and a HMS with a virtual anti-reflective coating (ARC) [19,20]. The purpose of the ARC (be it virtual [19] or real [21]) is, of course, to suppress a single, unwanted specularly reflected mode, which is done by ensuring the resulting multiply-reflected waves add up destructively.…”

“…2; it includes evanescent waves as well, which we have found to be essential for the fidelity of the model. For some surfaces, the S pq can be found in closed form [18,19,23,[25][26][27]; otherwise, they are readily provided by full-wave commercial programs as by-products of their solution for scattering from a periodic surface [28]. Hence, we consider them as known for a given BPS, and use them as our starting point for designing the MARC.…”