Nonlinear TE waves in an optically nonlinear curved waveguide andpulse compression

The propagation properties of the TE₀ mode in an optically nonlinear curved waveguide are examined in detail. As the input power increases, the self-focusing effect of the nonlinear core is found to largely reduce the radiation loss and to moderately reduce the mode-conversion loss. It is made clear from detailed examinations of the power transmissivity that the nonlinear curved guide can be used as a threshold device for a logical AND gate or an optical amplifier, and that the device property improves with the bend length and curvature radius. The optical pulse compression using the curved guide is also considered. It is shown that larger values of the bend length and peak input power are preferable for shorter output-pulse widths and lower power losses, respectively     

Pulse propagation in a nonlinear dielectric slab waveguide

The evolution of an optical pulse in a single-mode, step index dielectric slab waveguide which is characterized by an intensity dependent dielectric function in the core and cladding regions is treated by means of differential equation techniques. A cubic order non-linearity is considered. The electromagnetic field distribution in the slab waveguide region satisfies a non-linear wave equation. This field can be represented in terms of even TE guided modes with a slowly varying envelope amplitude function. Then using the well known approximation, based on the slowly varying character of the amplitude function, a non linear partial differential equation is obtained for the amplitude function. As the coefficients of this equation depend on the distance across the transverse direction X, an averaging technique over x is applied to reduce the nonlinear partial differential equation into a form that is easily transformed to the so-called non-linear Scroedinger differential equation. This equation is then attacked by means of the well known Inverse Scattering method in the case of reflection less potentials. The single and double soliton solutions are obtained explicitly for a single-mode slab waveguide. Finally numerical results are presented in the time domain.     

Reflection of millimeter waves by a corrugated dielectric slab waveguide

The TM wave propagation in a corrugated dielectric slab has been studied using a singular boundary perturbation procedure, which is supported subsequently by experiments in the millimeter-wave region.     

Slow propagation of electromagnetic waves in a dielectric slab waveguide with a left-handed material substrate

The dispersion properties of the guided modes propagating along a dielectric slab waveguide with a left-handed material substrate are studied. It is shown that both the oscillating and surface modes can propagate very slowly along such a waveguide if the thickness of the core layer is chosen appropriately. The propagation speed of the guided waves can even approach zero and this slow propagation is illustrated with an finite-difference time-domain simulation in a tapered waveguide. The influence of the material loss on the slow propagation is also discussed.     

Explicit formulas for cutoff values of TE modes on symmetric dielectric slab waveguide with Kerr-like permittivity

Based on the perturbation method, very simple expressions are derived which give accurate approximations for the cutoff values of TE modes in the symmetric slab waveguide with a Kerr-like nonlinear thin film.<>     

Diffraction of guided waves by the end face of a dielectric slab waveguide terminated with a finite conductive strip

The diffraction of guided waves by the end face of a dielectric slab waveguide short circuited with a finite conductive strip is analyzed. An integral equation technique is employed to formulate the corresponding boundary problem. The unknown term in this integral equations is the electric field E(x) on the terminal plane of the waveguide. The homogeneous term is determined from the incident guided wave. A method of moments technique is employed to compute approximately the electric field E(x) by using Laguerre functions as describing and testing functions. The reflection coefficients of the guided waves are computed by using the approximate expression of the E(x) field. Numerical results are given for several guide and conductor plate dimensions.     

Propagation of electromagnetic TE waves in a nonlinear medium with saturation

Propagation of electromagnetic TE waves in a nonlinear dielectric layer with saturation is considered. The layer is located between two isotropic nonmagnetic semi-infinite media with constant electromagnetic parameters. A nonlinear boundary-value problem for the eigenvalues of a second-order ordinary differential equation is studied. The dispersion equation for the eigenvalues of the problem (propagation constants) is derived. Dispersion curves are calculated.     

Loss reduction in curved dielectric optical slab waveguide

Formulas of the pure bending loss and the transition loss valid for TM modes in dielectric optical slab waveguides are presented. The characteristic of the total transmission loss of a step-index slab waveguide containing a circular bend having an asymmetric waveguide structure are analysed numerically by applying derived loss formulas. It is found that the features of the total transmission loss of TM modes are closely analogous to those of TE modes except for small discrepancies in the numerical values.     

Design of slot arrays in waveguide partially filled with dielectric slab

The Elliot procedure for the design of a waveguide slot array is extended to the case of partially filled radiating waveguides. The dielectric slab lies on the top of the radiating waveguide, i.e. on the slotted wall. The proposed solution prevents some of the most common drawbacks of waveguide slot arrays. Results are validated against a commercial FEM software.     

Propagation of soliton waves in nonlinear dielectric slab waveguides of parabolic index of refraction

The pulse propagation in a non-linear slab waveguide of parabolic index of refraction is treated by using differential equation techniques. A graded index dielectric slab waveguide free of material dispersion with a cubic order non-linearity is considered. The electromagnetic wave inside the waveguide is described in terms of a non-linear equation. Slowly varying envelope function representation is employed to develop a non-linear partial differential equation for the unknown envelope function of the electric field. An averaging method over the transverse direction is applied to reduce the unknown envelope function non-linear differential equation into a form resembling the well known non-linear Schrödinger differential equation. This equation is solved by applying the Inverse Scattering Method. The N-soliton solution is developed and presented explicitly for the practical case of the single mode dielectric slab waveguide. Numerical results presenting single and double soliton propagation are also given.     

Investigating nonlinear propagation in dielectric slab waveguides

A numerical method is employed to analyze the TE-wave propagation in Kerr-like nonlinear dielectric waveguides in which a nonlinear film is sandwiched between two linear media. The dispersion curves dependent on the magnitude of the electric field are obtained. All the results can be used in future investigations of devices composed of nonlinear dielectric slab structures     

Approximate solution for step discontinuity in dielectric slab waveguide

A simple method is presented for obtaining approximate expressions for the power reflection and transmission coefficients of surface waves scattered by a step discontinuity in a dielectric slab waveguide. The approximation is compared with Rozzi's exact solution. Agreement is quite good for a wide range of the relevant parameters.     

A novel wide-angle low-loss dielectric slab waveguide Y-branch

A new Y-branch structure for dielectric waveguides is proposed and analysed using simple geometrical optics and beam propagation methods. It is shown both qualitatively and quantitatively that the proposed structure has larger branching angles but lower radiation loss than those associated with either conventional Y-branches or structures with antenna coupled and phase front accelerators. The optimal design parameters calculated by numerical simulations are in very good agreement with those found from the geometrical optics. The simulations also reveal that the performance is fairly insensitive to fabrication errors     

Reflection of millimeter waves by a corrugated ferrite slab waveguide

The electromagnetic wave interactions in a corrugated ferrite slab have been investigated using a singular boundary perturbation procedure, which are supported subsequently by experiments in the millimeter-wave region.     

New rigorous analysis of the step discontinuity in a slab dielectric waveguide

The scattering of the even TE guided modes incident on a step discontinuity in a planner dielectric waveguide is analysed by means of a novel integral formulation. An accurate numerical solution is obtained from an iterative procedure needing a successive order of approximation in the scattering mechanism.     

Tube-contacted slab waveguide for millimetre and submillimetre waves

A new type of dielectric waveguide, which we call a tube-contacted slab waveguide, is proposed for millimetre and sub-millimetre waves. Transverse sizes of the waveguide can be made much larger than the wavelength. Dispersion characteristics and field distributions of the guided modes are calculated using the method of effective dielectric constant.     

Scattering and mode conversion by a screen-like inhomogeneityinside a dielectric slab waveguide

In this paper, the interaction of surface guided waves with a perfectly conducting scatterer shaped as a part of a circular screen and placed into a dielectric slab waveguide is investigated in mathematically correct manner. Due to the geometry of screen the original boundary value problem is reduced to dual series equations treated further by means of the Riemann-Hilbert Problem technique. Based on this approach, the numerical solution can be obtained, theoretically, with any desired accuracy. The reflection, transmission, and radiated-field quantities are computed for both single-mode and multimode slab guides containing cavity-shaped and strip-shaped scatterers     

Surface waves on a grounded dielectric slab covered by a resistivesheet

Surface wave propagation in a grounded dielectric slab covered with a resistive sheet is examined. Transcendental equations are derived for each polarization and are solved using iterative techniques. Attenuation and phase velocity are shown for a representative geometry. The results are applicable to both a grounded slab covered with a resistive sheet and an ungrounded slab covered on each side with a resistive sheet     

TE wave properties of slab dielectric guide bounded by nonlinearnon-Kerr-like media

TE wave properties of slab dielectric waveguides with nonlinear non-Kerr-like substrate and cladding are presented. The guide can support even- and odd-symmetric modes in asymmetrical substrate and asymmetrical modes in completely symmetrical substrate. Dispersion relations and electric field profiles are illustrated and analytically discussed in detail     

Reflection and transmission of radio waves at a dielectric slab with variable permittivity

Expressions for the reflection and the transmission power coefficients are derived for the case where a plane wave is obliquely incident on a dielectric slab in which the relative permittivity decreases symmetrically according to a1/z^{2}law from a given maximum value at the plane of symmetry and tends towards unity at the two faces of the slab. The effect of the curvature and other parameters governing the inverse square profile on the transparency property of the material at radar frequencies has been studied within a larged/lambdarange wheredis the half-slab thickness andlambdathe wavelength of the incident wave.