Showing papers on "Coupled mode theory published in 1990"
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01 Dec 1990
TL;DR: In this article, the fundamental field equations of wave propagation in homogeneous and layered media waveguides and cavities have been studied, including the effects of a dipole on the conducting earth, inverse scattering radiometry, and interferometry numerical techniques.
Abstract: Fundamental field equations waves in homogeneous and layered media waveguides and cavities Green's functions radiation from apertures and beam waves periodic structures and coupled mode theory dispersion and anisotropic media antennas, apertures and arrays scattering of waves by conducting and di-electric objects waves in cylindrical structures, spheres and wedges scattering of complex objects geometric theory of diffraction and low fequency techniques planar layers, strip lines, patches and apertures radiation from a dipole on the conducting earth, inverse scattering radiometry, noise temperature and interferometry numerical techniques.
1,050 citations
TL;DR: In this article, a set of coupled linear differential equations is derived for various mode amplitudes in a chirowaveguide, and it is shown that, owing to the handed properties of chiral materials filling the waveguide, energy coupling occurs from one mode to the other.
Abstract: In this paper, electromagnetic wave propagation and mode coupling in a chirowaveguide are treated using the coupled‐mode theory. A chirowaveguide, as defined in our previous work, is a conventional cylindrical waveguide filled with homogeneous chiral materials. A set of coupled linear differential equations is derived for various mode amplitudes in the waveguide. We then show that, in any single chirowaveguide, owing to the handed properties of chiral materials filling the waveguide, energy coupling occurs from one mode to the other. We also demonstrate that in a parallel‐plate chirowaveguide a TE mode can be completely converted into a TM mode and vice versa as they propagate in the guide. Thus a chirowaveguide can indeed be used as a mode converter. Selected results are compared with those reported in the literature. Applications of such mode coupling in the design of novel microwave, millimeter‐wave, and optical devices and components are mentioned.
53 citations
TL;DR: In this article, a nonorthogonal coupled-mode theory for nonparallel waveguides is derived based on the exact local array modes, and closed-form solutions are obtained for the two-guide synchronous tapered coupler.
Abstract: A nonorthogonal coupled-mode theory for nonparallel waveguides is derived. An orthogonal coupled-mode theory is developed based on the exact local array modes. The relation between the two formulations is established. Closed-form solutions are obtained for the two-guide synchronous tapered coupler. The formalism obeys power conservation. >
29 citations
TL;DR: In this article, the second harmonic generation in the form of Cerenkov radiation from a planar waveguide is analyzed in detail by a coupled-mode theory, where a fundamental wave is taken as a guided mode, and a second harmonic wave as a substrate radiation mode.
Abstract: Optical second harmonic generation (SHG) in the form of Cerenkov radiation from a planar waveguide is analyzed in detail by a coupled-mode theory, where a fundamental wave is taken as a guided mode, and a second harmonic wave is taken as a substrate radiation mode. An approximate solution is given which expresses the SHG efficiency in terms of waveguide parameters such as refractive indexes, a waveguiding layer thickness, and the optical nonlinearities of a waveguiding layer and a substrate. Numerical examples are plotted for LiNbO/sub 3/ crystals. Finally, the significant effect of a periodic modulation of the sign of an optical nonlinear d constant is discussed. >
29 citations
TL;DR: A new derivation of the coupled-mode equations and coupling coefficient for the troublesome but important case of the Bragg reflection of TM guided waves in a corrugated, planar optical waveguide is presented.
Abstract: A new derivation of the coupled-mode equations and coupling coefficient for the troublesome but important case of the Bragg reflection of TM guided waves in a corrugated, planar optical waveguide is presented The technique solves the (approximate) wave equation directly and clarifies those features of the analysis that are essential to treat the problem correctly
28 citations
TL;DR: In this paper, it was shown that the slowly-varying approximation usually adopted in the frame of coupled-mode theory is actually unnecessary, and the slowly varying approximation is not necessary.
22 citations
TL;DR: In this article, a variational scalar coupled-mode theory is developed from the variational principle for slab and fiber couplers, where the mode parameters are adjustable subject to the coupling between the guides.
Abstract: A scalar coupled-mode theory is developed from the variational principle. The formulation is variational in the sense that the mode parameters are adjustable and can be optimized subject to the coupling between the guides. The theory is applied to slab and fiber couplers. In comparison with the conventional scalar coupled-mode theory in which only the amplitudes of the modes in the individual guides are adjustable, the variational scalar coupled-mode theory predicts more accurate propagation constants and field patterns of the normal modes of the couplers. >
13 citations
TL;DR: In this paper, the eigenvalue equation for a symmetric system with N coupled slab waveguides is shown to be of the same functional form as that of a single-slab waveguide.
Abstract: Finite periodic structures for multichannel waveguiding are analyzed by self-consistent field matching at the interfaces and matrix formalism for lateral propagation. The characteristic eigenvalue equation for a symmetric system with N coupled slab waveguides is shown to be of the same functional form as that of a single-slab waveguide. The eigenmodes of the system are exactly calculated and compared to the approximate results of coupled mode theory. Basic features of multiwaveguide structures not derivable from the coupled-mode theory (CMT) are uncovered by rigorous formulation and solutions. More complicated structures are solved, and ways of mode shaping and mode filtering are suggested. >
12 citations
TL;DR: This formalism provides a framework for understanding the complicated modal structure of leaky-mode arrays by expressing their modes as linear combinations of the two dimensional modes of the buried-ridge waveguides and the active-region confinement structure.
Abstract: The use of a two-dimensional coupled-mode theory for modeling buried-ridge-waveguide index-guided arrays in general and leaky-mode arrays in particular is described. This formalism provides a framework for understanding the complicated modal structure of leaky-mode arrays by expressing their modes as linear combinations of the two-dimensional modes of the buried-ridge waveguides and the active-region confinement structure. As a result, the inherently large parameter space of these devices may be collapsed dramatically so that the device behavior is describable in terms of only the propagation constant mismatch between the buried-ridge modes and the active-region modes and their coupling coefficient.
10 citations
04 Dec 1990
TL;DR: In this paper, an improved KLM model for medical ultrasound array transducer elements is proposed, which involves the use of the symmetric fundamental Lamb wave modes as the primary mode of operation in all the layers.
Abstract: An improved KLM (Krimholtz-Leedom-Matthaei) model for medical ultrasound array transducer elements is proposed. The proposed approach involves the use of the symmetric fundamental Lamb wave modes as the primary mode of operation in all the layers. The idea is justified by comparing the calculated resonance frequencies of isotropic slabs with those obtained from coupled mode theory. Transducer sensitivities can be predicted within +or-1 dB and transducer center frequencies can be estimated within +or-50 kHz with the proposed modifications. In particular, the effect of kerf depth variations on the transducer characteristics can successfully be explained and predicted. >
6 citations
TL;DR: In this paper, the authors review the various forms of the coupled-mode theory for optical waveguides and compare them with the recently formulated new theory for the two-and three-slab waveguide structures.
Abstract: We review the various forms of the coupled-mode theory for optical waveguides. One subtle distinction between two different formulations of the conventional coupled-mode theory is pointed out. Comparison of accuracy between them and the recently formulated new theory is conducted for the two- and three-slab waveguide structures.
01 Jan 1990
TL;DR: In this article, a set of coupled linear differential equations is derived for various mode amplitudes in a chirowaveguide, and it is shown that, owing to the handed properties of chiral materials filling the waveguide, energy coupling occurs from one mode to the other.
Abstract: In this paper, electromagnetic wave propagation and mode coupling in a chirowaveguide are treated using the coupled-mode theory. A chirowaveguide, as defined in our previous work, is a conventional cylindrical waveguide filled with homogeneous chiral materials. A set of coupled linear differential equations is derived for various mode amplitudes in the waveguide. We then show that, in any single chirowaveguide, owing to the handed properties of chiral materials filling the waveguide, energy coupling occurs from one mode to the other. We also demonstrate that in a parallel-plate chirowaveguide a TE mode can be completely converted into a TM mode and vice versa as they propagate in the guide. Thus a chirowaveguide can indeed be used as a mode converter. Selected results are compared with those reported in the literature. Applications of such mode coupling in the design of novel microwave, millimeterwave, and optical devices and components are mentioned. Comments Reprinted from Journal of Applied Physics, Volume 67, Issue 6, March 1990, pages 2742-2745. Publisher URL: http://dx.doi.org/10.1063/1.345439 This journal article is available at ScholarlyCommons: http://repository.upenn.edu/ese_papers/184
TL;DR: In this paper, a new coupled-mode theory by extending Chuang's theory to include the radiation modes is presented via numerical analysis, and the model for the numerical analysis is that of a symmetrical and asymmetrical optical slab waveguide.
Abstract: This paper presents a new coupled-mode theory by extending Chuang's theory to include the radiation modes. The effectiveness of this theory is demonstrated via numerical analysis.
The coupling equations are derived following a procedure similar to Chuang's and the radiation modes are included in it. The coupling equations are simplified by neglecting the terms which represent the coupling between the radiation modes because their contribution is insignificant.
In the numerical analysis, the radiation modes are treated in isolation and the coupling between them is neglected. The model for the numerical analysis is that of a symmetrical and asymmetrical optical slab waveguide. The light intensity distribution inside the guide is investigated numerically and the results are compared with those by Chuang's theory.
As the result of analysis, it is shown that due to excitation of radiation modes near the input/output end, the coupling length estimated by the present theory is longer than that by Chuang's theory. Moreover, the light intensity distribution has been extended.
01 Nov 1990
TL;DR: In this article, the effect of various device parameters on waveguide behavior is investigated, and design curves to make waveguides with required characteristics are provided, and the ion-exchanged glass channel waveguide is analyzed.
Abstract: Finite difference and finite element methods, and the coupled mode theory are
combined to study in detail the ion-exchanged glass channel waveguides. Ordinary
and grating assisted waveguides are analyzed. The effect of various device
parameters on waveguide behavior is investigated. Design curves to make waveguides
with required characteristics are provided.