Manipulating permittivity and permeability Negative-index metamaterial

refraction of light @ interface between 2 media of different refractive indices, n2 > n1. since velocity lower in second medium (v2 < v1), angle of refraction θ2 less angle of incidence θ1; is, ray in higher-index medium closer normal.

to describe electromagnetic properties of given material such optical lens, 2 significant parameters should noted. these permittivity, ε, , permeability, μ, allow accurate prediction of light waves traveling within materials, , electromagnetic phenomena occur @ surface between 2 materials (interface).

for example, refractive index electromagnetic phenomenon occurs @ surface (or interface) between 2 materials. snell s law states relationship between radiated angle of incidence, , resulting refracted angle of transmission, rests on refractive index, n, of 2 media (materials). mathematics provides visualization




n
=
±


ϵ
μ





{\displaystyle \scriptstyle n=\pm {\sqrt {\epsilon \mu }}}

. hence, can seen behavior of refractive index dependent on association of these 2 parameters, quantitative values. therefore, if designed or arbitrarily modified values can inputs ε, and, μ behavior of propagating electromagnetic waves inside material can manipulated @ will. ability allows intentional determination of refractive index.

video representing negative refraction of light @ uniform planar interface.

for example, in 1967, victor veselago analytically determined light refract in reverse direction (negatively) @ interface between material negative refractive index , material exhibiting conventional refractive index. extraordinary material realized on paper simultaneous negative values ε, and, μ, , therefore termed double negative material. however, in veselago s day material exhibits double negative parameters simultaneously seemed impossible because no natural materials exist can produce effect. therefore, work ignored 3 decades.

in general physical properties of natural materials cause limitations. dielectrics have positive permittivities, ε > 0 . metals exhibit negative permittivity, ε < 0 @ optical frequencies, , plasmas exhibit negative permittivity values in frequency bands. pendry et al. demonstrated plasma frequency can made occur in lower microwave frequencies metals material made of metal rods replaces bulk metal. however, in each of these cases permeability remains positive. @ microwave frequencies possible negative μ occur in ferromagnetic materials. inherent drawback difficult find above terahertz frequencies. in case, natural material can achieve negative values permittivity , permeability simultaneously has not been found or discovered. hence, of has led constructing artificial composite materials known metamaterials in order achieve desired results.