N. Iqbal

Scattering from silver metal cylinder due to L-nihility coated with conducting sheath helix embedded dielectric medium

In this article, scattering from silver metal cylinder due to L-nihility, coated with dielectric material that encapsulates perfectly electric conducting sheath helix structure, is presented. The orientation of helix can be altered, and the cases of both the parallel (TM) and the perpendicular (TE) polarizations of electromagnetic (EM) waves are analyzed. Co- and cross-polarized fields for different values of pitch angle are formulated under oblique angle of incidence. The bi-static echo width of the scatterer is investigated as a function of at the L-nihility frequency which lies within the optical frequency range. The results are compared with those obtained for perfect electric conductor (PEC) at different values of the angle of incidence. It is observed that the considered guiding structure behaves identically with the simple PEC cylinder under the situation when the helix structure is oriented parallel to the axial direction of the guide. However, for the other forms of the helix orientation, the structure behaves differently – thereby confirming the validity of the analytical approach for the aforementioned complex structured guide presented in the article.

Tailoring of group velocity dispersion in dual-core chiral nihility waveguide

The article focuses on an approach to overcome the dispersion present in optical communication systems. The group velocity dispersion (GVD) remains an important issue in this context. The approach presented in this paper is based on the use of chiral nihility mediums with different chirality parameters in dual-core planar optical waveguide. It is found that the two cores can be resonantly coupled in the guide, and also, the waveguide would yield high GVD by choosing suitable design parameters. For the analytical investigation, transfer matrix method is used and the dispersion relation is derived by implementing appropriate boundary conditions. Excitation of supermodes in the guide may be achieved through the coupling of two particular core modes, which would ultimately result in giant GVD. This essentially demonstrates that the structure may find applications in dispersion compensating systems.

On the power distributions in elliptical and circular helically designed chiral nihility core optical fibers

Abstract. The structural designs of nonmagnetic chiral nihility-based optical fibers of elliptical and circular cross-sections, embedded with conducting sheath helix structure at the core–cladding interface, are investigated. Emphasis is given to the power confinement patterns while considering the hybrid EH01, EH11, and EH21 modes in the fiber and their comparative features. Variations in fiber dimensions are considered, and the corresponding effects on the power confinements under different orientations of sheath helix structure are reported. It has been found that the chiral nihility-based fiber structure results in the enhancement of the confined power, particularly in the case of an elliptic fiber. Apart from these, keeping in mind the possible lossy nature of chiral nihility mediums, the dispersive characteristic of material is also considered for both kinds of cross-sectional geometry, and the results are compared with situations when the mediums are lossless. The results essentially indicate less confinement of power in the case of lossy mediums.

On the Chiroferrite Medium-Based Waveguide Dispersion Compensator

The letter investigates a kind of dispersion compensator composed of dual-core planar waveguide separated by isotropic dielectric medium. Both the resonantly coupled cores are comprised of anisotropic chiroferrite materials. A dielectric clad layer of silicon dioxide is combined adjacent to one of the core sections. Supermodes are generated through mode-coupling at the resonance frequency that lead to the investigation of the group velocity dispersion (GVD) feature of the structure. The chiroferrite material parameters, particularly the chiral admittance and gyrotropy of the cores, play vital roles in achieving high GVDs. A fine tuning of resonance is achieved through proper choice of the core material parameters, and the results would be useful to devise dispersion compensator for usage in communication systems.

Current density distribution along conducting sheath helix encapsulated silver metal cylinder coated with dielectric material under L-nihility and upon oblique incidence

Abstract This communication is aimed at investigating the electromagnetic (EM) characteristics of silver metal cylinder coated with homogeneous dielectric material, which is loaded with tightly wound perfectly electrical conducting sheath helix (outside of the dielectric layer) structure of different angles of orientation. Considering the L-nihility kind of behavior of silver metal at a particular frequency, the current density distributions are discussed corresponding to the parallel polarization (transverse magnetic) of the incident EM wave. The investigations are made taking into account the different values of oblique incidence, and also, the orientation angle of sheath helix structure. It is found that the current density, and hence the scattering of radiation, greatly depends on these parameters, and its magnitude increases with the increase in helix pitch as well as the angle of incidence.

Scattering response of featured uniaxial anisotropic chiral medium-coated twisted PEC cylinder

Abstract Scattering of electromagnetic waves from a perfectly electrical conducting (PEC) cylinder of circular cross-section, coated with uniaxial non-magnetic chiral anisotropic medium, was discussed. A conducting sheath helix structure with adjustable pitch angle exists over the outer surface of coated cylinder, which is interfaced with the free-space. Under the uniform parallel polarized plane wave with fixed oblique incidence angle, the echo widths were determined emphasizing the other relevant scattering-related parameters (e.g. scattering/extinction efficiency etc.), taking into account different pitch angle values (of the sheath helix) and the kinds of coating mediums. The results revealed that the coating of negative uniaxial chiral medium causes enhancement in scattering efficiency (of the scatterer). Also, the scattering efficiency was found to be the same as the extinction efficiency, thereby yielding vanishing absorption of the medium. The obtained results were also compared with the situation of vanishing chirality of coating medium over the PEC cylinder; the echo width and scattering efficiency both decrease in this case.

Scattering of waves by chiral medium-coated dielectric elliptical/circular cylinders with PEC sheath helix loading

Abstract The paper reports scattering of plane waves by elliptical/circular homogenous, isotropic, and non-magnetic dielectric cylinders coated with chiral medium and surrounded by a perfectly electrical conducting sheath helix structure. The effect of pitch angle on the echo width under the assumption of parallel polarization is discussed, and the results are compared taking into account dielectric cylinders of different dimensions. The introduction of negative refraction in chiral mediums, and its effects on both the elliptical- and circular-shaped scattering objects are evaluated. The results indicate significant impact of the used chiral medium coating as well as the embedded sheath helix structure to alter the bi-scattering echo width of the object.

Impact of conducting sheath helix on waves in chirofiber with chiral nihility core

Using Maxwell’s equations, distributions of fields and/or power in optical fiber having helically designed conducting sheath helix introduced at the core-clad interface are analyzed theoretically. In the fiber structure, the core section falls in the category of chiral nihility, whereas the clad region is composed of chiral material. Dispersion relation is derived by applying suitable boundary conditions for the aforesaid complex fiber medium, and the expressions of transmitted power in the core and the clad regions are derived, followed by their further analyses corresponding to low-order propagating mode under the situation of varying pitch angle and fiber dimension.