Conducting Sheath Helix Research Articles

Scattering due to uniaxial anisotropic chiral medium-coated PEC cylinder with conducting helix loading

ABSTRACT A perfect electrically conducting (PEC) cylinder (having a circular cross-section) encapsulated with uniaxial anisotropic chiral medium was studied emphasizing the features of scattering. A conducting sheath helix structure having a varying orientation with respect to the optical axis (or pitch angle) was assumed to be at the outermost surface. This allows alterations in scattering patterns. The echo width of the structure was evaluated under the assumption of parallel polarized oblique incidence of waves. The effect on scattering was evaluated under varying chirality and permittivity of the coating medium along with the variations in the helix pitch angle. The obtained results are compared with those achieved by replacing the chiral coating with a simple anisotropic kind of medium (without chirality).

Complex-structured liquid crystal clad elliptical guides – the cases of with and without conducting sheath helix loadings

Electromagnetic (EM) wave propagation through three-layer liquid crystal clad elliptical optical guides was investigated under the situations when those were loaded with and without conducting sheath helix structures. Due to exceptional features of liquid crystals, such as durable electro-optic behaviour as well as optical anisotropy, the presence of these greatly affects wave propagation, thereby controlling the confinement of power in guides. The present work was aimed to investigate the comparison between three-layer elliptical optical guide having radially anisotropic liquid crystal as its outer clad, and loaded with and without conducting sheath helix structure at the core-inner (dielectric) clad interface. The results reveal prudent use of the former kind (of guide) over the latter one owing to its having on-demand control over the propagation of power, and also, enhanced confinement in the outermost section for the guide. These features allow such sheath helix-loaded guides to be useful in optical sensing applications.

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

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.

Effects of admittance and gyrotropy on the scattering due to chiro-ferrite medium coated microstructured PMC cylinder

The paper deals with scattering of electromagnetic (EM) waves by perfectly magnetic conducting (PMC) cylinder coated with chiro-ferrite medium under the assumption of oblique angle of incidence wave with perpendicular polarization (transverse electric; TE). An on-demand (in respect of orientation) kind of conducting sheath helix structure is assumed to exist at the outer surface of cylinder. The effects of sheath helix orientation, along with the material parameters, such as chirality admittance and gyrotropy, on the echo width as well as the magnitude and phase of the electric and magnetic fields are investigated. Control on the anisotropic property remains greatly useful in obtaining the required optical response from the scatterer — the feature which would find fabulous sensing related applications.

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

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.

Scattering due to twisted PEC cylinder coated with chiral/chiroferrite mediums

Scattering of electromagnetic waves by perfectly electrical conducting (PEC) cylinder, coated with chiroferrite medium, is investigated under the oblique angle of incident. The coated PEC cylinder is wrapped with perfectly conducting sheath helix structure. For this structural configuration, the bi- and the mono-scattering echo widths are computed numerically while assuming the incident wave with parallel polarization. The roles of pitch angle (of sheath helix structure) and the material parameters on the echo width are analyzed. The obtained results for scattering echo widths are compared with those achieved when the PEC cylinder is coated with simply chiral material. It is found that the chiro-ferrite coating causes larger scattering of waves than the situation when the PEC cylinder is coated with simply chiral medium. Furthermore, a parallel orientation of the helix structure results in larger echo width.

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

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.

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

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 Fast-Waves in Dispersive Core-Twisted Clad Waveguides

The propagation of fast-waves through twisted clad waveguide is reported, taking into account the group velocity of wave through the guide. Twists are considered in the form of conducting sheath helix structure loaded at the core–clad interface of the guide. The dispersion behavior is evaluated through developing the eigenvalue relation for guiding structure under suitable boundary conditions. Results indicate that the group velocity can be tailored, and it gets enhanced by taking into account dispersive double-negative medium in the core section. Apart from this, the condition close to mode degeneracy is also achieved. It is suggested that the guiding structure under consideration would find potential applications in dual-mode filtering purpose.

On the conducting sheath double-helix loaded liquid crystal optical fibers

This work presents analysis of wave propagation in a rather new type of three-layer optical fiber wherein the outermost region being composed of radially anisotropic liquid crystal, and conducting sheath helix loadings exist at the core–inner clad as well as the inner clad–outer liquid crystal clad interfaces. The fiber structure offers two-way control on wave propagation through it. Focus is, however, made on the wave confinements in fiber due to the helix structures, as characterized by the respective pitch angles. Specific values of helix pitch angles at the two layer interfaces are taken into account, and the confinement patterns are analyzed. The dominant property of sheath helix structure over confinement patterns is quite an obvious fact. Clearly, the helix pitch angle greatly controls over the power confinement characteristics, which can be altered upon suitable adjustments of helical windings. Treatments have been made to illustrate the power patterns in all possible scenarios for critical pitch variations in each layer interface.

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.

Conducting tape helix loaded radially anisotropic liquid crystal clad optical fiber

The paper reports investigation of a rather new type of optical fiber composed of three layers with the outermost region being radially anisotropic liquid crystal material, and the inner two regions as linear, homogeneous, and isotropic dielectrics. As such, the anisotropy remains in the outermost section of fiber. The core–clad interface of the inner dielectric regions is assumed to be loaded with conducting tape helix structure. It has been found that the width of the tape as well as the helix pitch angle are the effective parameters to govern the dispersion characteristics. Taking into account the zero-order guided modes, the effects on confinements due to the amalgamation of birefringence (optical property of liquid crystal) and tape helix pitch (geometrical/structural property of perfect conductor) are reported. The obtained results are compared with the case of a conducting sheath helix loaded liquid crystal fiber structure, and it has been found that the conducting tape helix loadings would be more useful than the sheath helix loaded fibers.

Dispersion Features of Conducting Sheath Helix Embedded Elliptical and Circular Fibers with Chiral Nihility Core

Discussions have been made of the electromagnetic wave propagation through optical fibers of elliptical and circular cross‐sections with the loadings of conducting sheath helix at the core‐clad interface with particular orientations. In both geometrical situations, the core section of fiber is assumed to be composed of chiral nihility medium, and the clad remains linear, homogeneous, isotropic, and nonmagnetic dielectric. Dispersion relations are deduced for both fiber structures, followed by the analysis of dispersion features considering a few low‐order EH modes. Furthermore, the effects of conducting helix pitch angle on the features of wave propagation are also discussed.

Transmission characteristics of circular and elliptical helically cladded optical fibers – A comparative analysis

Lightwave propagation through complex structured optical fibers, viz. twisted clad fibers with circular as well as elliptical cross-sections, are taken into account. Twists in the fiber are considered in the form of conducting sheath helix structures introduced at the core–clad interface. Wave propagation in such fibers can be controlled by suitably adjusting the helix pitch angle – the prime motivation of this work, which is tuned to emphasize on the power confinement patterns (or the fractional modal power) of these on a comparative platform. Taking into account a few low-order hybrid modes, variations of confinement are studied for the aforesaid two fiber types in respect of changes in the helix pitch angle. The obtained results indicate profound impact of introducing the helical structure – the feature that would find potential technological applications. Furthermore, helical clad elliptical fibers are found to be more responsive than the circular ones in terms of the variations in pitch angle.

On the control of optical confinement in sheath helix-loaded elliptical dielectric guide

An investigation has been made of the propagation of electromagnetic waves through dielectric optical guide loaded with conducting sheath helix at the core–clad interface. The guide structure falls into the category of complex media, wherein it has been assumed that the helix sheath remains continuous in nature along with each of the turns being isolated from the adjacent ones. Power confinement factors in the two regions of guide under consideration have been evaluated under the situation of varying values of helix pitch angle – from its orientation being parallel to the optical axis to the perpendicular orientation. Two different illustrative values of guide dimensions have been taken into account, and the effect on the propagation of power have been demonstrated under the variations in helix pitch angle.

Twisted clad microstructured optical fibers: revisited

The paper discusses confinements corresponding to low-order sustained hybrid modes in twisted clad microstructured optical fiber with twists in the form of conducting sheath helix structure introduced at the core–clad interface and inclined at certain angles. Dispersion relations for such fiber structures are deduced under strict electromagnetic boundary conditions. Varying the angle of pitch (of the introduced conducting sheath helix), investigations in respect of the dependence of power confinements due to the existing low-order hybrid modes have been carried out. The obtained results indicate the usefulness of such microstructured fibers for attenuation or amplification of power in the guide.

Propagation through complex structured liquid crystal optical fibers

Wave propagation in optical mediums greatly depends on the materials of which the guides are composed. Among the other forms of optical mediums, liquid crystals are both inhomogeneous and optically anisotropic in nature, and exhibit strong electro-optic behavior, which allows alternation in their optical properties under the influence of external electrical fields. These features make optical fibers containing liquid crystals greatly useful for fabricating many optical devices for practical applications. As such, the analytical investigation of wave propagation through liquid crystal optical fibers, particularly a three-layer fiber with radially anisotropic liquid crystal material in the outermost clad section, remains interesting. The power confinement in the liquid crystal section of such fibers can be enhanced for these to be efficiently used in optical coupling and/or sensing applications. Furthermore, a control over the dispersion characteristics, and, hence, the confinement of power, in such fibers may be imposed by making the guide even more complex in the form of introducing a conducting sheath helix structure at the core-inner clad interface.

Waves in Microstructured Conducting Sheath Helix Embedded Optical Guides with Chiral Nihility and Chiral Materials

The paper deals with the sustainment of electromagnetic waves in circularly cylindrical optical guide with chiral nihility and chiral materials in the core and the clad sections, respectively. A perfectly conducting tightly wound helix is introduced at the core‐clad interface. The eigenvalue relation for such a complex optical microstructured guide is deduced by applying suitable boundary conditions at the core‐clad interface, and the dispersion behavior is analyzed by varying the pitch angle of helix. The sustainment of energy flux density in such optical guides is estimated under various structural conditions, and the density patterns in core‐clad sections are anatomized analytically.

CONDUCTING SHEATH HELICAL WINDING ON THE CORE-CLADDING INTERFACE OF A LIGHTGUIDE HAVING A PIET HEIN SUPER ELLIPTICAL CORE CROSS-SECTION AND A STANDARD OPTICAL FIBER OF CIRCULAR CROSS-SECTION-A COMPARATIVE MODAL ANALYSIS

In this article, a theoretical and computational analysis has been made to obtain the modal dispersion characteristics of an unconventional optical waveguide with a Piet Hein core cross section having a conducting sheath helix winding on its core-cladding boundary. A simple analytical method using the vector boundary conditions has been utilized to get the modal eigen value equation. From this equation dispersion curves are obtained and plotted for some particular values of the pitch angles of the winding. Next, these predicted results are compared with those of a new optical fiber having a conducting sheath helix winding on its core-cladding boundary. It is seen that the cutoff values are somewhat lower for the Piet Hein lightguide than those for the circular guide. This is not unexpected since the Piet Hein curve approaches the shape of a square. The

An Optical Waveguide with a Hypocycloidal Core Cross-Section having a Conducting Sheath Helical Winding on the Core-Cladding Boundary — A Comparative Modal Dispersion study vis-a-vis a Standard Fiber with a Sheath Winding

A simple analytical method using vector boundary conditions is proposed for the theoretical derivation of the modal characteristics equation for an unconventional optical waveguide having a hypocycloidal core cross-section with a conducting sheath helix winding on its core-cladding interface. Using this equation modal dispersion curves have been obtained for some particular values of pitch angles of the winding. Further, these obtained results are compared with those of a standard optical fiber loaded with a conducting sheath helix winding on its core-cladding interface. It is found that the cutoff values are somewhat lower for the hypocycloidal waveguide than those for the standard fiber. This is due to the fact that when a hypocycloid is distended from the inner side we get a circle and when a square is compressed from outside we get a hypocycloid. We also see that when a conducting sheath helical winding is added to the waveguides, their modal properties are modified. Among many new features, it is found that the hypocycloidal guide with a conducting helical winding supports fewer mode than the circular waveguide with a conducting helical winding, and this is relevant in the case of practical application.