arXiv subjects
Publications and source records attributed to Akhlesh Lakhtakia.
Whereas Cantor multilayers made of an isotropic dielectric-magnetic material with positive refractive index will show power-law characteristics, low-order Cantor multilayers made of materials with negative refractive index will not exhibit the power-law nature. A reason for this anomalous behavior is presented.
Several issues relating to oppositely directed phase velocity and power flow are reviewed. A necessary condition for the occurrence of this phenomenon in isotropic dielectric-magnetic mediums is presented. Ramifications for aberration-free lenses, homogenization approaches, and complex mediums are discussed.
The Bragg regime shifts when conventional materials in a multilayer distributed Bragg reflector (DBR) are replaced by artificial materials with the so-called negative index of refraction. This provides an avenue for characterizing the latter class of materials.
Negative real parts of the permittivity and permeability lead an isotropic chiral medium to exhibit circular dichroism that is reversed with respect to that exhibited by an identical medium but the real parts of whose permittivity and permeability are positive.
A structurally right/left-handed ferrocholesteric slab with negative real permittivities and permeabilities is theoretically shown to display the Bragg phenomenon on axial excitation as if it were a structurally left/right-handed ferrocholesteric slab with positive real permittivities and positive real permeabilities. In addition to the promise of isotropic homogeneous materials with negative real permittivities and permeabilities for unexpected applications, the presented results underscore the similar potential of anisotropic nonhomogeneous materials with analogous characteristics.
The reflection of a normally incident wideband pulse by a half-space whose permittivity and permeability obey the one-resonance Lorentz model is calculated. The results are compared with those from frequency-domain reflection analysis. In the spectral regime wherein the real parts of the permittivity and the permeability are negative, as well as in small adjacent neighborhoods of that regime, the time-domain analysis validates the conclusion that it is sufficient to ensure that the imaginary part of the refractive index is positive - regardless of the sign of the real part of the refractive index.
Sculptured thin films (STFs) are nano-engineered materials whose columnar morphology is tailored to elicit desired optical responses upon excitation. Two canonical forms of STFs have been identified. Linear constitutive relations for general STFs as unidirectionally nonhomogeneous (continuously or piecewise uniformly) and locally bianisotropic continuums are presented, along with a 4$\times$4 matrix ordinary differential equation for wave propagation therein. A nominal model for the macroscopic properties of linear STFs is devised from nanoscopic considerations. The accomplished implementation of STFs as circular polarization filters and spectral hole filters is discussed, as also are emerging applications such as bioluminescence sensors and optical interconnects.
The canonical problem of a perfect lens with linear bianisotropic materials is formulated. Its solution is shown to be directly connected with the concept of nihility, the electromagnetic nilpotent. Perfect lenses as well as nihility remain unrealizable.
An electromagnetic trinity comprising vacuum, anti--vacuum, and nihility is postulated -- after making use of materials with "negative permittivity" and "negative permeability" -- to illuminate the structure of electromagnetic theory, at least insofar as the relationship of phase velocity with Poynting vector is concerned.