Hyperbolic metamaterials based on stacked metasurfaces with application to microwave absorber design

Summary form only given. Hyperbolic metamaterials (HMs) have received a paramount interest due to their exotic properties such as enhancing the photonic density of states. This particular phenomena is associated with allowing the otherwise evanescent spatial spectrum of waves (that exists in dielectric materials) to propagate inside such media. This has lead to substantial advancements in super resolution imaging and lifetime engineering of quantum emitters. With various implementation techniques, HM has also evolved to be a novel candidate for designing absorbers thanks to their ability of absorbing near-fields generated at their surface. In this paper we approach absorber design at microwave frequencies as a potential application of HMs. We implement a multilayer HM at microwave frequencies that comprises reactive layers separated by subwavelength dielectric slabs. The multilayer can be regarded as an effective anisotropic material with negative transverse permittivity, as done in [Othman et al, J. Nanophoton. 7(1), 073089, (2013)] for grapheme layers at teraherz frequencies. Thus, the HM can host waves with a large transverse wavenumber, provided that the reactive layers are inductive; which mimics the plasmonic characteristics of metals in HM designs at optical frequencies. Furthermore, a few-layer HM is shown to capture the properties of the semi-infinite multilayered HM. A metasurface cap layer made of scatterers is also designed which enhances coupling between external plane waves and the HM, as well as absorption. We develop analytical formulations and verify their validity through full wave simulations. An important aspect of such HM is that it does not require any resonant properties, hence it is inherently wideband. Moreover, microwave implementation can provide new opportunities of reconfigurable HM via integration with electronics. Application of HM knowledge at microwave absorbers contributes to the understanding of angle- and frequency-dependent abso- ption features and their optimization.