Focusing and negative refraction in anisotropic indefinite permittivity media

Abstract

Materials that exhibit negative refraction demonstrate physical phenomena that may be used for novel applications. This work serves to evaluate the possibility of hyperbolic focusing due to an indefinite anisotropic permittivity tensor. Two single-loop antennas were used to approximately achieve a transverse magnetic (TM) point source and 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 around the center of the sample. A scanning robot allowed for the automatic scanning of the space behind the sample in the x, y, and z directions, to establish the focusing patterns, and to compare the signal amplitudes in the presence and absence of the sample. 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 a symmetric configuration with respect to the sample. These results suggest a method of focusing electromagnetic waves using negative refraction in indefinite materials.

Soft-Focusing in Anisotropic Indefinite Media Through Hyperbolic Dispersion

“…When the elements of the array are very thin straight wires of infinite length, A graph showing the relationship between the frequency and κ is shown in (Figure 3) [18]. This permittivity form is valid only for an electric field polarized parallel to the wires.…”