Wire metamaterial based on semiconductor matrices

Abstract

1 Introduction Metal-dielectric nanocomposites (wire metamaterial) based on porous alumina matrices fabricated by electrochemical eatching attract increasing attention for many reasons, ranging from fundamental research problems (study of nonlinear properties [1]) to applications in many different fields (biosensors [2], optical metamaterials [3], nanophotonics [4], etc.). Other materials which have similar structural parameters (e.g. aspect ratio) and optical properties are metallic nanotubes based on dielectric [5] and semiconductors matrices [6,7]. However, as is shown in the theoretical [8] and experimental [9] works, the medium with nanotubes is not a suitable material to realise the properties of wire metamaterials because the latter require the thickness of the tubes to be greater than the skin depth of a metal for proper operation (at least 15-20 nm for operation in the visible domain). The investigation and application of the unique properties of these materials face significant challenges, such as small values of the aspect ratio (less than 100) and low values of electric permittivity, ε, in dielectric matrices. Another material in which porous matrices can be created by an anodic electrochemical etching [10,11] is an A III B V semiconductor. In this case the nanoporous matrices give a unique set of parameters: the aspect ratio greater than 10000, the thickness of porous matrices up to 150 μm and more [12]. Using different orientations of the original semiconductor crystal, etching regimes and types of electrolyte, one can control the param-

Compton-Like Polariton Scattering in Hyperbolic Metamaterials

“…Thus, we should generate an additional population of free electrons in the system, e.g., by using a direct injection with an e gun [17]. An alternative way is to use a heavily doped semiconductor as a matrix for the wire array [18]. Free carriers in the semiconductor matrix can play the role of scattering centers as was shown in a number of studies [19] where the scattering of light from free carriers in semiconductors was experimentally observed.…”

“…For the case of light scattering by an electron gas rather than an isolated free electron, the value of the shift increases with the Fermi wave vector of the gas: δω ∼ ℏ 2 =mk 0 ðk 0 k F þ k 0 =2Þ, k 0 ¼ ω i =c [19]. To isolate the contribution of the modified photonic density of states from the overall shift enhancement, we assume the same electron distributions for the case of dielectric and hyperbolic media which correspond experimentally to the case of a bulk semiconductor and a metallic wire array grown in the same semiconductor matrix [18].…”

Impact of filling ratio on subwavelength optical imaging using metallic nanolens of different geometries

“…Through full wave electromagnetic simulations we have established our findings using infinitesimal silver nanorod array in equilateral triangular or, hexagonal lattice arrangement with two different crosssectional geometries. Nanorod array with cylindrical [15], triangular [16] and square [17] porous matrices for fabrication was realized using different substrate material as shown in Fig. 1 which can be employed for experimental demonstrations in the near future.…”

“…1 which can be employed for experimental demonstrations in the near future. [15]- [17] In our analysis, we have considered filling ratio, f r ≈ (2π/3 √ 3)(r/a) 2 for cylindrical shaped wire array and f r ≈ (1/2)(r/a) 2 for triangular shaped wire array. Here the parameter 'a' is known as periodicity or lattice constant of the array and 'r' is the radius of circular cross-section of cylindrical shape Fig.2(d) and also represents the distance of the polished edged equilateral triangular cross-section Fig.2(e).…”