Showing papers on "Coupled mode theory published in 1998"
TL;DR: It is shown that optical Bloch oscillations can emerge in waveguide arrays with linearly varying propagation constants and the existence of localized modes (Wannier-Stark states) with equidistant wave-number spacing that do not undergo diffraction is analytically proved.
Abstract: We show that optical Bloch oscillations can emerge in waveguide arrays with linearly varying propagation constants. The existence of localized modes (Wannier-Stark states) with equidistant wave-number spacing (Wannier-Stark ladder) that do not undergo diffraction is analytically proved. The evolution of arbitrary initial excitations is described, and potential applications are suggested.
291 citations
TL;DR: In this article, a transfer matrix analysis is presented that can describe the general class of grating-guided waveguides with either finite and/or infinite grating boundaries, and the theory is applied to describe the new angled-grating distributed feedback laser (/spl alpha/-DFB), predicting a broad near-Gaussian near field and a collimated diffraction-limited far field.
Abstract: Angled-distributed-feedback semiconductor lasers have demonstrated 1-W diffraction-limited collimated output from a broad-area aperture. We present the first theoretical analysis of the modes of these devices, explaining their principle of operation and the reasons for their high spatial mode quality. A transfer matrix analysis is presented that can describe the general class of grating-guided waveguides with either finite and/or infinite grating boundaries. Lateral grating-confined broad-area waveguides are shown to have extremely high spatial mode selectivity. The theory is applied to describe the new angled-grating distributed feedback laser (/spl alpha/-DFB), predicting a broad near-Gaussian near field and a collimated diffraction-limited far field, in good agreement with experiment.
122 citations
TL;DR: Using coupled-mode theory, a theoretical model shows that PMD can be reduced effectively by use of frequency-modulated spin profiles.
Abstract: Using coupled-mode theory, we develop a theoretical model to analyze the effects of fiber spin profiles on polarization mode dispersion (PMD). Constant, sinusoidal, and frequency-modulated spin profiles are examined, and phase-matching conditions are analyzed. Our analysis shows that PMD can be reduced effectively by use of frequency-modulated spin profiles.
105 citations
TL;DR: In this article, a theoretical model for the bending waveguide polarization rotator has been developed based on the full vectorial wave equations and the coupledmode theory, which is found to agree favorably with measurement data reported in literature.
Abstract: A theoretical model for the bending waveguide polarization rotator has been developed based on the full-vectorial wave equations and the coupled-mode theory. Calculation results from this model are found to agree favorably with measurement data reported in literature. It is found that the polarization conversion efficiency of this device hinges on the degree of asymmetry of the cross-sectional field profile with respect to both the x- and y-axes. Sensitivity analysis, furthermore, revealed that the device characteristics are strongly dependent on the waveguide geometry, in particular, the sidewall tilt angle and the amount of over-etch of the ridge waveguide. Finally, it is also found that the bending waveguide polarization rotator is virtually wavelength independent, making it suitable for wavelength division multiplexing (WDM) applications.
92 citations
TL;DR: In this paper, the design of an optical switch based on a directional coupler with tapered velocity and tapered coupling is investigated, and the physical principle is based on power transfer by the evolution of a single normal mode.
Abstract: The design of an optical switch based on a directional coupler with tapered velocity and tapered coupling is investigated. The physical principle is based on power transfer by the evolution of a single normal mode. We consider cases where the coupling coefficient and guide mismatch variation are determined by optimized shape functions related to rectangle, raised cosine, Hamming, and Blackman window functions. Following simplified analysis by coupled mode theory, the physical parameters of the device are determined and the predicted performance is verified by the method of lines. Significant improvement in sidelobe levels and coupling length ran be obtained by careful design.
49 citations
TL;DR: Based on coupled mode theory for the vectorial modes of rectangular isotropic waveguides, the authors numerically simulate the performance of such devices in an experimental isolator setup, including birefringence and optical absorption.
41 citations
TL;DR: In this article, the nonlinear propagation of coupled Langmuin and dust acoustic waves in a multi-component dusty plasma is considered, and exact analytical solutions for the coupled waves having single-, double-and triple-hump structures for the Langmuir field intensity are also derived, and are solved approximately.
Abstract: The nonlinear propagation of coupled Langmuin and dust acoustic waves in a multi-component dusty plasma is considered. The coupled mode propagation is deseribed by a Schrodinger Boussinesq system, which reduces to the Schrodinger -KdV system for unidirectional wave propagation. For stationary propagation, the coupled waves are governed by a generic Hamiltonian that is integrable in both sub- and the supersonic regimes of Mach number. Depending on the parameter regimes, exact analytical solutions for the coupled waves having single-, double- and triple-hump structures for the Langmuir field intensity are obtained. The exact governing equations for large-amplitude waves are also derived, and are solved approximately. The existence conditions for large-amplitude localized solutions in the quasineutral limit are discussed.
33 citations
TL;DR: A self-consistent Green's function technique is developed to calculate the full photonic band structure for guided modes in slab waveguides that have been textured in one dimension with a thin surface grating and yields the correct TM-TM coupling coefficient at oblique incidence.
Abstract: We develop a self-consistent Green’s function technique to calculate the full photonic band structure for guided modes in slab waveguides that have been textured in one dimension with a thin surface grating. The technique is conceptually simple and can easily be reduced to an eigenvalue problem by use of approximations similar to those used in conventional coupled-mode theories. We show that this approach yields the correct TM–TM coupling coefficient at oblique incidence and provides a transparent interpretation for its vanishing at a critical angle.
20 citations
TL;DR: In this paper, the authors observed light coupling between dual-core dye-doped polymer optical fibers, which is consistent with the standard coupled-mode theory for single-mode-single-mode coupling between step-index waveguides.
Abstract: We have observed light coupling between dual-core dye-doped polymer optical fibers. The experimentally observed coupling length is consistent with the standard coupled-mode theory for single-mode–single-mode coupling between step-index waveguides [ P. D. McIntyre A. W. Snyder , J. Opt. Soc. Am.63, 1518–1527 (1973)]. We also show that a graded refractive-index profile of such dual-core fibers can be made by controlled dye diffusion. The concentration, as measured by optical absorption, shows a graded profile that matches the refractive-index profile, confirming that dye concentration determines the refractive index.
14 citations
TL;DR: A vectorial coupled mode theory was used to analyze sol-gel ridge waveguides with UV-light-imprinted Bragg gratings in this paper, and it was shown that 100% reflectivity for both TE and TM modes can be achieved using short (1 to 2 mm) gratings.
Abstract: A vectorial coupled mode theory is used to analyze sol-gel ridge waveguides with UV-light-imprinted Bragg gratings. The effect of device parameters on the grating reflectivity is investigated. It is shown that 100% reflectivity for both TE and TM modes can be achieved using short (1 to 2 mm) gratings. The measured reflectivity in a ridge waveguide with a grating agrees with the theoretical predictions for TE and TM modes.
12 citations
TL;DR: In this article, the long-period fiber Bragg grating (LPFBG) coherence spectrum was investigated using mode selection rule and coupling equations, in which the coupling between the forward propagating core-bounded mode and multicladding-based modes was taken into consideration in modeling based upon their contribution to the spectrum.
Abstract: The long-period fiber Bragg grating (LPFBG) coherence spectrum was investigated using mode selection rule and coupling equations. The coupling between the forward propagating core-bounded mode and multicladding-bounded modes was taken into consideration in modeling based upon their contribution to the spectrum. Modes involved in the coupling process were ranked into a converging series. This makes the modeling procedures described practical. The grating coherence spectrum under assumed testing conditions was modeled and simulated.
TL;DR: In this paper, the localization properties of a disordered multi-waveguide system composed of randomly different cores are presented, and the average extent of the localized mode depends only on the single parameter δβ / κ where δ β is the fluctuation of the propagation constants of modes and κ is the mode coupling coefficient between neighboring cores.
TL;DR: In this article, a numerical code is developed by applying the invariant imbedding technique to the coupled mode theory for acoustic/elastic wave propagation in shallow water to examine the effects of lateral heterogeneities and transverse isotropy on mode coupling and signals.
Abstract: Coupled mode theory is applied to acoustic/elastic wave propagation in shallow water to examine the effects of lateral heterogeneities and transverse isotropy on mode coupling and signals. A numerical code is developed by applying the invariant imbedding technique to the coupled mode theory. From the code, the reflection and transmission matrices and the forward/backward-propagating wave fields in the frequency domain are generated for a range-dependent medium. The effect of transverse isotropy of bottom sediment layers is also considered. Time domain signals are synthesized with a 2-Hz bandwidth between 10 Hz and 12 Hz for the excitation by a unit line force and for an incident fundamental mode. The generation of higher overtones and the decay of the fundamental mode propagating in a range-dependent medium are clearly shown.
TL;DR: In this paper, a corrugated dielectric waveguide with silicon overlay has been analyzed by coupled mode theory to study the variation of Bragg reflection characteristics at the millimeter-wave band.
Abstract: A corrugated dielectric waveguide with silicon overlay has been analyzed by coupled mode theory to study the variation of Bragg reflection characteristics. By optical illumination, the plasma-induced semiconductor exhibits an interesting behavior on the propagation characteristics of a corrugated dielectric waveguide. To validate theoretical estimations, experiments have been carried out at Q-band. The results could be used for optically controlled filters and switches at millimeter-wave band. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 17: 352–357, 1998.
TL;DR: In this paper, the first electrically injected coupled resonator vertical-cavity laser diode was presented, and a coupled mode theory was used to model the output modulation of the coupled-resonator vertical cavity laser.
Abstract: The monolithic integration of coupled resonators within a vertical cavity laser opens up new possibilities due to the unique ability to tailor the interaction between the cavities. The authors report the first electrically injected coupled resonator vertical-cavity laser diode and demonstrate novel characteristics arising from the cavity coupling, including methods for external modulation of the laser. A coupled mode theory is used model the output modulation of the coupled resonator vertical cavity laser.
07 Jun 1998
TL;DR: In this paper, a twenty-element microstrip array that emits twenty coupled leaky modes is analyzed and validated by a novel, generic technique combing the full-wave integral equation method and coupled mode theory.
Abstract: A twenty-element microstrip array that emits twenty coupled leaky modes is analyzed and validated by a novel, generic technique combing the full-wave integral equation method and coupled mode theory. The new method enables fast, accurate assessment of coupled leaky modes and gives physical insight on how the large array may excite the leaky modes considering the mode-coupling effects.
TL;DR: The derivation of the coupled-mode equations for thickness-longitudinal vibrations of piezoelectric plate resonators is given and the behavior of the resonator in the vicinity of primary resonance is discussed.
Abstract: Coupled-mode equations were developed for thickness-longitudinal vibrations of piezoelectric plate resonators. The equations describe the resonator as a parametrically excited nonlinear vibrational system with two degrees of freedom. Thus one can examine the behavior of piezoelectric resonators from a nonlinear dynamic point of view. In the present paper the derivation of the equations is given. As an example of the application of the equations, the behavior of the resonator in the vicinity of primary resonance is discussed. The method of multiple scales is used to solve the coupled-mode equations. An experiment which verises the amplitude-driving voltage relation predicted by the theory is conducted for LiNbO/sub 3/ resonators.
TL;DR: In this article, an antiresonant reflecting optical waveguide (ARROW) type vertical coupler filter exhibiting low sidelobe charateristics is demonstrated, where the sidelobe level of the filter has been suppressed by using an X-crossing arrangement to provide strength apodization along the device.
Abstract: An antiresonant reflecting optical waveguide (ARROW) type vertical coupler filter exhibiting low sidelobe charateristics is demonstrated. The sidelobe level of the filter has been suppressed by using an X-crossing arrangement to provide strength apodization along the device. The main sidelobe of the fabricated filter is measured to be less than -17 dB with the central wavelength in the 1.55 µm region. An analysis procedure which combines the coupled mode theory with the finite difference mode solver is also presented to efficiently calculate the vertical coupler filter response.
TL;DR: In this article, the mode coupling in a helical fiber with a circular cross-section undergoing perturbations is investigated in the Serret-Frenet frame and coupled-mode equations have been derived and compared with the conventional ones.
Abstract: The mode coupling in a helical fibre with a circular cross-section undergoing perturbations is investigated in the Serret-Frenet frame. The coupled-mode equations have been derived and are compared with the conventional ones. Applying the coupled-mode equations to a helical fibre with an elliptical core deformation, we obtained, for the first time, a rigorous analysis of the transmission characteristics of the fibre. The numerical examples show that the mode ellipticity and elliptical birefringence increase as the core ellipticity increases and also vary as the pitch or the core offset change.
TL;DR: In this article, the four-wave coupled-mode theory (CMT) was proposed to account for the simultaneous interaction among plane waves, obliquely incident on a grating with infinitely long grooves.
Abstract: Diffraction of plane waves, obliquely incident on a (waveguide) grating with infinitely long grooves, is analyzed with the four-wave coupled-mode theory (CMT). Unlike the ordinary analysis that considers only coupling between pairs (i.e., TE+↔TE-,TE+↔TM-,TM+↔TE-, or TM+↔TM-), the simultaneous interaction among these waves is properly accounted for. The field variation along the grating and the impulse response representation of the grating (reflectivity and transmission as functions of the plane-wave incidence angle) are calculated. Significant differences between the ordinary (two-wave) CMT and the four-wave CMT are observed over a wide range of incident angles.
TL;DR: In this article, the modified switching conditions of directional coupler optical switches, in the presence of parasitic couplings in bending sections, are discussed by means of the coupled mode theory, and it is shown that a parallel section's length needs to be adjusted by less than the coupling length lc (=pi/2kappa0), depending on the amount of parasitic coupling.
Abstract: The modified switching conditions of directional coupler optical switches, in the presence of parasitic couplings in bending sections, are discussed by means of the coupled mode theory. As expected, a parallel section's length needs to be adjusted by less than the coupling length lc (=pi/2kappa0), depending on the amount of parasitic coupling. For weak parasitic coupling, however, the switching voltage does not need to be altered but maintains the same value as without parasitic coupling.
TL;DR: In this paper, a vectorial coupled mode theory is used to analyze sol-gel ridge waveguides with UV-light imprinted Bragg grating and the effect of device parameters on grating reflectivity is investigated.
Abstract: A vectorial coupled mode theory is used to analyze sol-gel ridge waveguides with UV-light imprinted Bragg grating. The effect of device parameters on grating reflectivity is investigated. It is shown that 100% reflectivity for both TE and TM modes can be achieved using short (1 - 2 mm) gratings. The measured reflectivity in a ridge waveguide with grating agrees with the theoretical predictions for TE and TM modes.
TL;DR: In this article, a theoretical model for investigating AlGaAs-GaAs quantum-well (QW) vertical cavity waveguides defined by impurity-induced disordering is presented.
Abstract: A theoretical model is presented for investigating AlGaAs-GaAs quantum-well (QW) vertical cavity waveguides defined by impurity-induced disordering This model is based on a two-dimensional (2-D) description of the implantation profile to produce quantum-well intermixing The modal propagation constant, power, and field evolution along the nonuniform circular waveguide is analyzed in terms of the coupled-mode equation The influence of varying the mask dimension and length of cavity on the fundamental mode operation is studied In a long cavity, guided mode can be supported by using higher implantation energy, however, a larger mask diameter should be used to maintain strong guiding Result shows that optical lateral confinement is accomplished, with more than 70% of the power gathered in the cavity The fraction of power confined in the waveguide is shown to improve by 30% after annealing In addition, waveguide loss is estimated to be less than 40 cm/sup -1/ which results in less than 1 dB for our structure
TL;DR: A novel photonic switch structure is described in which the coupling of light between two fiber waveguides is controlled by the resonant interference of a third waveguide.
Abstract: A novel photonic switch structure is described in which the coupling of light between two fiber waveguides is controlled by the resonant interference of a third waveguide. The switching action is controlled by a small variation of the index of refraction of the control waveguide by the application of either photo-optical (Kerr) techniques or electro-optical (Pockels) techniques. The control waveguide can be either a fiber waveguide or a slab waveguide. The equations for the waveguide coupling were obtained by analytical approximations from coupled-mode theory. A beam-propagation simulation was also used. The results of the two models were compared. Multiple resonant interferences were observed in the case of a slab waveguide.
30 Mar 1998
TL;DR: In this article, filters are needed to separate wavelengths at the two channels of 1.3 and 1.55 μm in the subscriber WDM system, and the two wavelengths at 1.5 and 2.5 µm are separated.
Abstract: In the subscriber WDM system, filters are needed to separate wavelengths at the two channels of 1.3 and 1.55 μm.
TL;DR: In this paper, a coupled-mode formulation for parallel cavities of a laser array is presented, where the interaction between neighboring elements is via diffraction resulting from perturbation of the boundary conditions.
Abstract: A coupled-mode formulation is presented for parallel cavities of a laser array. The interaction between neighboring elements is via diffraction resulting from perturbation of the boundary conditions. Each high-reflectivity cavity mirror is surrounded by a much-lower-reflectivity background, which, for practical purposes, is considered to be zero. The formulation applies both to ordinary laser arrays and to vertical-cavity laser arrays with high-contrast laterally patterned mirrors. Some examples are considered and compared against exact numerical calculations.
30 Mar 1998
TL;DR: In this paper, integrated optoelectronic devices are critical components in optical communications systems due to enhanced performance and cost-efficient production, and they are used for optical communication systems.
Abstract: Integrated optoelectronic devices are critical components in optical communications systems due to enhanced performance and cost-efficient production.
18 Aug 1998
TL;DR: In this article, a full-wave coupled-mode formulation for the line parameters of multilayered and multiconductor transmission lines is presented, where the elements of the impedance matrix for a coupled-line four-port derived from the coupledmode equations are of the same form as those obtained by the quasi-static approach.
Abstract: We have presented a full-wave coupled-mode formulation for the line parameters of multilayered and multiconductor transmission lines. It is shown that the elements of the impedance matrix for a coupled-line four-port derived from the coupled-mode equations are of the same form as those obtained by the quasi-static approach. This fact suggests that the design technique for microwave integrated circuits developed by using the impedance matrix for coupled TEM lines is also applicable in the full-wave approach. However, it should be noted that the characteristic mode impedances, the current ratios, and the voltage ratios in the present full-wave approach are obtained using the electromagnetic coupling coefficients, whereas those of the TEM lines are derived in terms of a quasi-static capacitance matrix. When the coupled conductor lines are microstrips with a negligible thickness, the electromagnetic coupling coefficients are easily evaluated by making use of the Galerkin's moment method solutions in the spectral domain for the single microstrips in isolation. The extension of the present formulation to the multi-port system is straightforward.
TL;DR: In this paper, a curved waveguide structure is translated into an equivalent straight waveguide with a modified asymmetric index profile, and the wave propagation through this structure is described by coupled-mode formalism with ideal mode expansion.
Abstract: Coupled-mode analysis of uniformly bent slab waveguides with finite claddings is demonstrated. Using the method of conformal transformation, a curved waveguide structure is translated into an equivalent straight waveguide with a modified asymmetric index profile. The wave propagation through this structure is described by coupled-mode formalism with ideal mode expansion. The step-index profiles as well as graded-index profiles are considered. The numerical results of transmitted power, wave propagation along the bend and pure bend loss are presented for TE0-mode excitation.
TL;DR: Diffraction of obliquely incident Gaussian beams on waveguide gratings with infinitely long grooves is described, based on the angular spectrum of the beam and on the grating response derived from the four-wave coupled-mode theory.
Abstract: Diffraction of obliquely incident Gaussian beams on waveguide gratings with infinitely long grooves is described. The analysis is based on the angular spectrum of the beam and on the grating response derived from the four-wave coupled-mode theory, which simultaneously considers all four (approximately) synchronous waves. Results concerning the shapes of the emerging beams and their directions, the power content, and the possibility of beam splitting could differ significantly from those obtained by means of two-wave coupling. The analysis method is general and can be performed on many kinds of realistic beam shapes and applications.