Optical characteristics of asymmetrical hyperbolic metamaterials

Background and Objectives: Metamaterials, which are artificial structures with specified properties, keep the interest to nest investigations and creation of new types of them due to their unusual properties. One of the promising variant of the metamaterials is hyperbolic metamaterials (HMM) which exhibit the hyperbolic-type dispersion in the space of wave-vectors and are described by the diagonal extremely anisotropic permittivity tensor. Here we investigated optical properties of asymmetrical hyperbolic metamaterial (AHMM) consisting of periodically arranged layers (or wires) in a host media, titled relatively to the outer boundary. The most important feature of AHMM is the possibility to excite a very slow wave in AHMM by a plane wave, incoming from free space, while a minimal reflection may be achieved. We calculated spectral characteristics of the AHMM at different values of parameters of the structure. Methods: We have used the algorithm for solving of the Maxwell 130 equation based on the Berreman 4x4 matrix which is convenient for the investigation of the propagation of polarized light in anisotropic media. We have adopted this method for the system when active atoms or ions are embedded into the medium for the calculations of light propagation in AHMM slabs which is infinite in the x and y-direction and has a finite-thickness in the z direction. Anisotropy of the hyperbolic media slab was taken into account. We use the effective medium model. Results: The transmittance and reflectance were calculated for different orientation of optical axis, angles of incidence and THz field frequencies in the AHMM with graphene layers. Spectral characteristics of reflection and transmission are presented. We have shown that huge resonances in transmittance and reflectance observed near 5 THz for different values of the incident angles which characterized a huge amplification in the AHMM. The effects of changing in the structure parameters have been demonstrated.