Ridged Waveguides with Inhomogeneous Dielectric-Slab Loading

The dispersion equation of the ridged waveguide with inhomogeneous dielectric-slab Ioading is derived. Numerical results for the cutoff frequencies of the three lowest order TE/sub m0/ modes are given which substantiate the feasibility of the modal expansion and field-matching technique employed. For a Teflon-slab loaded ridged waveguide, a 40-percent decrease of dominant-mode cutoff frequency, simultaneously providing 20-percent enhanced TE/sub 20/-mode separation compared to an empty ridged waveguide, is demonstrated.     

Analysis of Wave Propagation in Inhomogeneous Dielectric Slab Waveguides

The propagation characteristics of the guided modes in an inhomogeneous dielectric slab waveguide are analyzed by tbe regularized WKBJ method. The corrected propagation constants of the guided modes in a near parabolic index medium are derived in analytic form. The effects of the refractive index profile and the homogeneous cladding on the guided modes can be expressed in terms of the mode indices and evaluated numerically.     

Correction to "Theory of Periodic Dielectric Waveguides" (Letters)

In the above paper, the information given by (10) on page 125 has been incompletely stated and is therefore misleading.     

Comments on "Coupling of Waveguides through Large Aperture" (Letters)

The authors thank Dr. Sangster for his useful comments on their paper. At the time of preparation of the paper it was not known to the authors that there was an unfortunate printing error in reproduction of eq. (34) of [2].     

Comment on "On the Design of Dielectric Loaded Waveguides" (Letters)

In the above paper, the authors show that, by loading a rectangular waveguide with an E-plane dielectric slab, its theoretical power-handling capacity can be significantly increased. Their conclusion may come as a surprise to experimenters designing high-power E-plane devices such as ferrite isolators or phase shifters. It is a well-known fact that such structures tend to exhibit breakdown at power levels well below those of the empty waveguide.     

Propagation, Attenuation, and Dispersion Characteristics of Inhomogeneous Dielectric Slab Waveguides

A numerical method based upon invariant imbedding and the transverse impedahce concept is applied to the problem of calculating various properties of inhomogeneous slab waveguides. The approach appears not only to be rapidly convergent but is also capable of giving arbitrary accuracy for any given mode. In particular, some interesting properties of a class of asymmetric profiles are pointed out, relating to discussions of lossy structures, temporal pulse distortion, and spatial broadening.     

A Variational Theory for Wave Propagation in Inhomogeneous Dielectric Slab Loaded Waveguides

A novel numerical technique based on the variational formulation defined only in the slab is developed to study the loaded rectangular waveguide with an inhomogeneous dielectric slab. The variational equation for the boundary value problem is formulated and solved numerically, using the finite element method with piecewise quadratic trial functions. A comparison of this new technique with the conventional variational ones is presented. Various propagation characteristics, such as the phase constant, useful bandwidth, power handling capacity, and attenuation constants due to conductor and dielectric losses, are investigated for the waveguide centrally loaded with a slab of parabolic dielectric profile. The effects of changes in dielectric profiles are discussed by examining the results for the slabs with constant and parabolic profiles.     

Comments on "Asymmetric Coupled Transmission Lines in an Inhomogeneous Medium" (Letters)

In the above paper, the terminal characteristic parameters for a uniform coupled-line four-port for the general case of an asymmetric, inhomogeneous system are derived, and some of the equivalent circuits are presented.     

Comments on "Radiation from Curved Dielectric Slabs and Fibers" (Letters)

In the above paper, Lewin gave an expression for the bending loss of a dielectric fiber with circular cross section. I have shown that the bending loss of arbitrary optical guides can be obtained in a simple manner when the field of the straight guide is known. The purpose of this letter is to show that the results of the two theories are in agreement, except for a factor of 2.     

Propagation of Cladded Inhomogeneous Dielectric Waveguides

An approximate theory on the propagation of modes in an arbitrarily inhomogeneous optical waveguide embedded in a homogeneous medium is presented. Simple formulas are given, whereby the propagation constants can be determined assuming that the analytic solution is known in the absence of cladding. The results obtained applying the theory to a truncated parabolic-index profile are shown to be in good agreement with those obtained by the rigorous analysis. The theory is also applied to the propagation of TE and TM waves in truncated near-parabolic-index media.     

Comments on "Scattering of Surface Waves at a Dielectric Discontinuity on a Planar Waveguide" (Letters)

An analysis of the problem of scattering of surface waves at a dielectric discontinuity on a planar waveguide has recently appeared in this TRANSACTIONS. (Letters)     

Electromagnetic Wave Propagating in Uniform Waveguides Containing Inhomogeneous Dielectric

Uniform waveguides filled with inhomogeneous dielectric whose permittivity varies along one dimension are studied. Emphasis is given to the modes of propagation and to the calculation of the propagation constants. Exact solutions are given for some special cases. In some of these only asymptotic or polynomial solutions have been available previously. No restriction is placed on the waveguide dimensions so that results developed here apply to the transmission of optical frequency waves as well as to microwaves and millimeter waves. In the waveguide problems of this paper, results obtained cannot be directly found in the existing literature and have been worked out from fundamental theory of differential equations. The theory of the confluent hypergeometric function has been of great help in our treatment of these problems.     

Uniform Asymptotic Technique for Analyzing Wave Propagation in Inhomogeneous Slab Waveguides

The guided modes of inhomogeneous dielectric slab waveguides are analyzed by a uniform asymptotic technique based on the related equation method. This technique gives highly accurate solutions in the sense of asymptotic expansion. The algorithm for calculating the guided modes of slab waveguides with an even polynomial refractive-index medium is presented. As an example, we calculate the third-order approximate solutions for the guided modes in an analytic form. The results show that the WKB solutions for higher order modes are more accurate than for the lower order modes and the correction to the WKB solutions is significant for the lower order modes. The numerical result for eigenvalues and modal fields confirms that the third-order asymptotic solution is accurate for all the guided modes of the near-parabolic profile waveguides and for higher order modes in the case of the quasi-Gaussian profile.