Analysis of radiation mechanism and polarizing properties of metamaterials

Abstract

(cont.) isotropic permeability. The characteristics used as a basis for comparison are: 1. Leakage of light (transmittance) through a pair of crossed-polarizers, and 2. Fresnel coefficients of a single polarizer. The expressions for the transmittance and the Fresnel coefficients are obtained analytically using the kDB method. A novel procedure to determine the angles of transmission of the ordinary and extraordinary waves through a uniaxial slab is developed, along with the procedures for validation. The viability of enhancing the performance of polarizers by using metamaterial media is investigated.

Metamaterials are media have a negative permittivity (epsilon) or a negative permeability (mu) or both. Metamaterials promise tremendous advances in lensing applications, antenna technologies and the like. In the present research, the radiation mechanism of metamaterial composites made up of pairs of S-shaped structures (also known as S-rings) is studied in detail. Numerical simulations using the Ansoft HFSS [TM] software package, lead to an understanding of the currents induced on a single S-ring due to a plane wave excitation. The current density observed along a single ring is expressed as a periodic function of the distance along it, and the vector current moment is determined. The far field radiation for a pair of S-rings is determined using this vector current moment. The refraction of a plane wave travelling from a prism made up of S-rings into free-space is studied. In order to determine the far field radiation due to a prism made up of S-rings, the array factor specific to the prism structure is determined first. This array factor coupled with the radiation pattern due to a single ring gives the pattern due to the prism. The radiation pattern of a prism of S-rings, which shows the refraction direction, is determined for two cases with prism angles of 28⁰ and 39⁰. Metamaterials with negative uniaxial permittivities, and positive isotropic permeabilities, display unusual polarizing capabilities. The polarizing capabilities of such metamaterials are also studied in the present work. The performance characteristics of a metamaterial polarizer are compared to those of existing O-type and E-type polarizers. The proposed metamaterial polarizer has a uniaxial permittivity tensor with a negative permittivity along the optic axis and a positive