Soft-Focusing in Anisotropic Indefinite Media Through Hyperbolic Dispersion

Abstract

Abstract-Materials that exhibit negative refraction may have many novel applications. We seek to evaluate the possibility of soft-focusing of microwave signals using a medium with an indefinite (hyperbolic) anisotropic permittivity tensor. We fabricated a 147 mm thick and 220 mm wide Styrofoam sample with an embedded array of 12-gauge brass wires of 6.35 mm lattice spacing. Two single-loop antennas were used to approximately generate a transverse magnetic (TM) point source and the associated detector. Using an Agilent 8510C Vector Network Analyzer (VNA), the frequency spectrum was scanned between 7 and 9 GHz. Relative gain or loss measurements were taken at equal spatial steps behind the sample. A scanning robot was used for automatic scanning in the x, y, and z directions, in order to establish the focusing patterns. The signal amplitudes measured in the presence and absence of the sample were compared. The robot was controlled using LabVIEW † , which also collected the data from the VNA and passed it to MATLAB ‡ for processing. A soft focusing spot was observed when the antennas were placed in two different symmetric configurations with respect to the sample. These results suggest a method for focusing electromagnetic waves using negative refraction in indefinite (hyperbolic) anisotropic materials.

Three‐dimensional imaging of an object behind an anisotropic wall

“…The conductivity and permittivity parameters of these media are tensors. Electromagnetic forward scattering of anisotropic structures has been studied in [22][23][24][25][26]. Considering the anisotropic media in the inverse three-dimensional (3D) problems is still challenging.…”

Wave Propagation and Fresnel Coefficients for Three Layered Uniaxially Anisotropic Media With Arbitrarily Oriented Optic Axes

“…Composite and layered structures involving anisotropic materials have been commonly employed in electromagnetic problems including scattering and radiation [4][5][6][7][8][9][10][11][12][13]. The better device performance is obtained if the electromagnetic properties of the medium are known.…”

Plane Wave Beam Produced by an Exclusive Medium

“…In the family of anisotropic media, indefinite medium is a rising star due to its negative refraction property and the capability of transferring an evanescent wave into a propagation mode [1][2][3][4][5][6][7][8]. The term indefinite implies that the principle items in the permittivity or permeability tensor have different signs, which results in a strong anisotropy and a hyperbolic EFC (equifrequency contour) in an indefinite medium [9].…”