Showing papers on "Coupled mode theory published in 1981"
TL;DR: In this article, the effects of boundary condition approximations that arise whenever the coupled mode theories of A. D. Pierce and D. M. Milder are applied to propagation problems involving range dependent boundaries are examined.
Abstract: This article examines the effects of boundary condition approximations that arise whenever the coupled mode theories of A. D. Pierce [J. Acoust. Soc. Am. 37, 19–27 (1965)] and D. M. Milder [J. Acoust. Soc. Am. 46, 1259–1263 (1969)], are applied to propagation problems involving range dependent boundaries. This boundary condition approximation requires that the depth derivative, rather than the normal derivative of the field, be continuous across a sloping interface. The approximation is necessary in order to carry out the partial separation of depth and range variables effected in the mathematical formulation of the theory. This article will show that a consequence of this approximation is that conventional coupled mode theory applied to dissipationless media with nonhorizontal boundaries does not conserve energy. It is shown that a correction to coupled mode theory can be derived such that the proper boundary conditions are satisfied and energy is conserved to first order in the local bottom slope. Moreover, the corrections are not prohibitive in terms of added computational complexity. Numerical examples are presented which illustrate the nonconservation of energy effect and the corrections to the theory.
64 citations
TL;DR: In this article, a coupled-mode theory for dielectric waveguide structures containing a gyrotropic layer is developed. And the feasibility of such structures as the new type of non-reciprocal devices for millimeter-wave applications is studied.
Abstract: A general coupled-mode theory is developed for dielectric waveguide structured containing a gyrotropic layer. The theory applied is to several specific structures. Based on qualitative and numerical analysis, we studied the feasibility of such structures as the new type of nonreciprocal devices for millimeter-wave applications. A number of considerations for practical design are included.
48 citations
TL;DR: The formalism of coupled-mode theory is adopted for describing nonlinear pulse propagation in optical fibers, the coupling being induced by the nonlinear part of the refractive index.
Abstract: The formalism of coupled-mode theory is adopted for describing nonlinear pulse propagation in optical fibers, the coupling being induced by the nonlinear part of the refractive index. This approach describes in a natural way the influence of the waveguide, and in principle allows of the possibility of investigating soliton propagation when more than one mode is excited.
34 citations
TL;DR: In this paper, the propagation constants and eigenfunctions for the normal modes of the coupled systems were derived for a variety of coupled waveguide pairs: identical slab waveguides, identical and non-identical single-mode optical fibers, and identical fewmode optical fiber.
Abstract: Evanescent field coupling between parallel optical waveguides is treated by the propagating beam method This method utilizes Fourier analysis to generate the modal properties of optical waveguides from numerical solutions to the paraxial-wave equation Previous applications have been for single waveguides Detailed results are presented here for a variety of coupled waveguide pairs: identical slab waveguides, identical and nonidentical single-mode optical fibers, and identical few-mode optical fibers Results include propagation constants and eigenfunctions for the normal modes of the coupled systems The difference between the propagation constants of the corresponding normal modes determines the coupling length for the mode pair, whereas the eigenfunctions determine the extent of power transfer The results obtained establish the applicability of the propagating beam method to the study of coupling in a general class of practical waveguides
27 citations
TL;DR: In this article, a Debye type relaxation mode at a frequency of 50 kHz has been identified for a tungsten bronze group ferroelectric Ba0.4 Sr0.6 Nb2 O6, up to 3.5 k-bar and across the c-axis.
Abstract: The pressure and temperature dependence of the dielectric properties of a tungsten bronze group ferroelectric Ba0.4 Sr0.6 Nb2 O6, have been measured up to the pressure of 3.5 k-bar and across the c-axis. In a pressure induced paraelectric state, a Debye type relaxation mode at a frequency of 50 kHz has been identified. We associate this mode to the structural instability of the lattice and to the localised mode of the Burn's Coupled Mode Theory. The structural instability also accounts for the large relative permittivities observed for the tungsten bronze ferroelectrics.
14 citations
TL;DR: The study shows that coupled-mode theory indeed leads to very good results for weak coupling but may lead to quite inaccurate results for sufficiently strong coupling.
Abstract: An exact scalar wave analysis of a directional coupler obtained by coupling two identical graded-index wave-guides having exponential profiles is given. This analysis has been used to study the validity of the widely used coupled-mode theory for studying such problems. The study shows that coupled-mode theory indeed leads to very good results for weak coupling but may lead to quite inaccurate results for sufficiently strong coupling.
9 citations
TL;DR: In this article, the coupling of a plane wave and a cylindrical wave, expressed by a Hankel function, in optical waveguide Bragg grating lenses is theoretically treated in two dimensions.
Abstract: The coupling of a plane wave and a cylindrical wave, as expressed by a Hankel function, in optical waveguide Bragg grating lenses is theoretically treated in two dimensions. Analytical solutions of the coupled-mode equations are derived, and numerical examples for lenses with rectangular corrugations are shown for both the TE and the TM modes. The results are also compared with those obtained by treatment in one dimension.
7 citations
TL;DR: A proper choice of material constants and waveguide structure is discussed to build a high-efficiency light intensity modulator using guided-to-radiation mode coupling through the electrooptic effect.
Abstract: A proper choice of material constants and waveguide structure is discussed to build a high-efficiency light intensity modulator using guided-to-radiation mode coupling through the electrooptic effect. The preferred structure is a 2-D light waveguide such as a LiNbO3 thin film deposited on a LiTaO3 substrate, with two planar modulation electrodes.
6 citations
TL;DR: In this paper, the coupledmode theory of sea surface scattering is shown to be identical to the small-wave height theory for the case of a deep isovelocity ocean where the modal spectrum forms a continuum.
Abstract: The coupled‐mode theory of sea‐surface scattering is shown to be identical to the small‐waveheight theory for the case of a deep isovelocity ocean where the modal spectrum forms a continuum. Numerical calculations demonstrate that the same results are also obtained for a shallow‐water example where the modal spectrum is discrete.
5 citations
TL;DR: In this article, a coupled mode set of eigenfunctions is obtained for investigations of the quantum theory of surface enhanced Raman scattering by a physiadsorbed molecule on a metal surface.
Abstract: A ‘coupled mode’ set of eigenfunctions is obtained for investigations of the quantum theory of surface enhanced Raman scattering by a physiadsorbed molecule on a metal surface. The enhancement ratio R(ω) for scattering cross-section of adsorbed to free molecules is calculated. The theory is applied to the pyridine on silver system. In the classical limit, using a geometry with flat silver surface, the ‘image enhancement’ model is recovered, and a large enhancement can be forced if unrealistic values of parameters are used. In the correct quantum theory a sharply peaked enhancement of about 10−3 of that reported can be obtained at laser energy about 3.7 eV. The conventional image model is thus not supported by the quantum theory. Surface roughness needs to be incorporated into this coupled mode theory.
2 citations
15 Jun 1981
TL;DR: In this article, a coupled dielectric-ferrite waveguide is analyzed by a coupledmode theory, and numerical studies are performed for designing new distributed non-reciprocal devices for millimeter-waves.
Abstract: A coupled dielectric-ferrite waveguide is analyzed by a coupled-mode theory, and numerical studies are performed for designing new distributed nonreciprocal devices for millimeter-waves A number of practical considerations are included
TL;DR: In this article, the impulse response of optical components such as contradirectional couplers and corrugated waveguide filters is analyzed based on the coupled mode theory which utilizes the main forward and backward modes in the absence of higher harmonics.
Abstract: This paper discusses the impulse response of optical components such as contradirectional couplers and corrugated waveguide filters. The analysis is based on the coupled mode theory which utilizes the main forward and backward modes in the absence of higher harmonics.
The impulse response of the forward and backward modes is derived in a form corresponding to repeated reflections at two ends of the system. As for the backward modes, the behavior of reflected waves is related to the coupling length. The impulse responses of transmitted and reflected waves are derived and their pulse responses are analyzed by the convolution integral.