Virtual hyperbolic metamaterials for manipulating radar signals in air

Abstract

Microwave beam transmission and manipulation in the atmosphere is an important but difficult task. One of the major challenges in transmitting and routing microwaves in air is unavoidable divergence because of diffraction. Here we introduce and design virtual hyperbolic metamaterials (VHMMs) formed by an array of plasma channels in air as a result of self-focusing of an intense laser pulse, and show that such structure can be used to manipulate microwave beams in air. Hyperbolic, or indefinite, metamaterials are photonic structures that possess permittivity and/or permeability tensor elements of opposite sign with respect to one another along principal axes, resulting in a strong anisotropy. Our proofof-concept results confirm that the proposed virtual hyperbolic metamaterial structure can be used for efficient beam collimation and for guiding radar signals around obstacles, opening a new paradigm for electromagnetic wave manipulation in air.

Coherence-Driven Topological Transition in Quantum Metamaterials

“…eral configurations, such as in arrays of metallic nanowire embedded in a dielectric host [29], multilayered metal-dielectric structure [30,31], plasma [32,33], metasurface [34], to name a few. These hyperbolic metamaterials have been harnessed for sub-diffraction imaging [35,36], negative-refraction [30,31], photon density of states engineering [37][38][39], heat transfer [40], and so forth.…”

Negative refraction and self-collimation in the far infrared with aligned carbon nanotube films

“…Pendry and collaborators were early pioneers in designing electromagnetic metamaterials using patterned sub-wavelength standing cylindrical structures [12,13]. Since then, these studies have inspired numerous researchers to realize nanoscale structural analogs, such as silver nanowires [14], doped silicon nanowires [15], and other metallic nanorods [16,17]. The optical anisotropy in such nanowire arrays was identified as a mechanism for negative refraction [18,19].…”

Free-space components for microwave transmission

“…Previously, it was shown that a rectangular or circular array of plasma filaments can also exhibit anisotropic behavior as above, in which case the mixing rule equations used to determine the permittivity components of the material take the form [17] …”

“…Here, f is the fill fraction of plasma channels in the filament array given as f = d pl /a pl , where d pl ≈ 50 − 120 m is the diameter of each filament and a pl ≈ 450 − 650 m is the average distance between filaments in the two dimensional case, ε d is the permittivity of the background dielectric material, which is air in this case [17]. The parameter ε fil is the permittivity of each filament, which can be described by the Drude model as…”

“…Finally, the plasma frequency of each plasma channel is a function of the free electron density N e , which is governed by the different interaction processes between the components of partially ionized plasma filament. This fact is taken into account by solving the system of rate equations to determine temporal dynamics of positive (N + ), negative (N − ) and free electron densities [17]: Table 1. As it was discussed above, when the two tensor components ε || and ε ⊥ in Eq.…”