Guided modes of a width-reduced photonic-crystal slab line-defect waveguide with asymmetric cladding

The authors fabricated GaAs-based width-reduced photonic-crystal (PC) slab line-defect waveguides with asymmetric cladding, characterized optically by broadband transmission spectral results. These waveguides were vertically sandwiched between air and oxide claddings. Transmission peaks originating from the guided mode located within the bandgap were observed, thereby showing the presence of a bandgap effect for the transverse-electric (TE)-like guided mode even with the coexistence of a fundamental transverse-magnetic (TM)-like mode. Propagation loss spectra were derived from transmission spectra for both TE and TM polarization inputs. Comparing the obtained spectra to band diagrams, the authors detected a mini-stopband effect in the transmission spectra arising from a folding of the fundamental TM-like mode at the Brillouin zone boundary. The coupling coefficient was then estimated to be /spl sim/0.01 [a/sup -1/] (with a being a lattice constant). Dips in spectral intensity were also observed and were attributed to TE-TM mode conversion based on a comparison to the band diagram.     

Radiation modes of a five-layer symmetric slab waveguide

The radiation modes of a five-layered symmetric slab waveguide are treated in detail. Since the slab is assumed to be infinitely extended in the yz plane, all field quantities are considered to be independent of y. The analysis is based on modal expansion formulation and the modes can be classified as TE and TM as well as even and odd ones. Applying the boundary conditions at interfaces, the expansion coefficients of the field components are easily calculated. In addition, the normalization factors and the orthogonality properties are determined by deriving appropriate integrals over the cross section of the waveguide. Finally, the validity of the orthogonality relations between the radiation modes and the guided ones, which propagate in such a waveguide, is proved explicitly.     

对称单负材料平面波导的波导模

基于经典电磁理论建立了芯层为单负材料的对称三层平板波导的导波方程,采用图解法研究了该波导中的TE和TM波导模,分析了TE波导模和TM波导模会受波导参数μ1/μ2和R的影响,给出TE模和TM模解的横向场分布图.结果显示,在单负材料的对称三层平板波导中只存在慢波导模,TE慢波模只能在磁负材料中传播,TM慢波模只能在电负材料...     

Guided modes in a rectangular waveguide with semiconductor metamaterial

The dispersion equations of bulk modes and surface modes in a rectangular waveguide of semiconductor metamaterial are derived by a modified "Marcatili's method".The cutoff frequencies of the lowest TM bulk mode are discussed,and the Brillouin diagrams of different bulk modes are drawn.They demonstrate that different heights correspond to different guidance frequency ranges which have no superposition with each other and a waveguide with a larger height possesses a wider passband of light.In addition,tendencies of degeneracy for different modes are observed.Finally,the existence of surface modes is verified by a graphical method.     

含半导体超常媒质的矩形波导的导模研究

采用改进后的马可梯里方法推导出了半导体超常媒质矩形波导中体模和表面模的色散方程,讨论了最低阶TM模的截止频率并画出了布里渊图。结果显示不同的波导高度具有不同的导模频带,波导高度大的对应的导模频带较宽,并且彼此之间没有重叠。除此之外,不同模式还存在着简并的趋势。最后采用作图法验证了表面模的存在性。     

Guided modes of a four-layer optical waveguide with a metal buffer

A 4-layer optical waveguide with a metal buffer layer of varying thickness has been examined theoretically and solutions of the dispersion relation have been found numerically. Particular attention has been paid to the electric-field distributions and the losses in the waveguide.     

Oscillating guided modes in a symmetric five-layer slab waveguide with anisotropic-dispersive left-handed material

A symmetric five-layer slab waveguide with anisotropic and dispersive left-handed material (LHM) in the core and righthanded material (RHM) in other layers is investigated. Through Maxwell’s equations and a transfer matrix method, the dispersion equations for the TE oscillating guided modes are obtained. Under consideration of two extremely anisotropic cases, some mode dispersion curves are plotted. The zero-order TE oscillating guided mode exists. Meanwhile, with the increase of mode number, their dispersion curves move to left or right, corresponding to positive or negative dielectric permittivity and magnetic permeability in the longitudinal direction. Besides, as the core thickness increases, mode dispersion properties change and three propagation properties appear: positive group velocity, negative group velocity and zero group velocity. The negative group velocity indicates the characteristics of the left-handed materials, and the zero group velocity implies that electromagnetic waves are trapped in the waveguide completely.     

Analysis of wave modes in slab waveguide with truncated parabolic index

The exact wave equation for a lenslike dielectric medium derived from Maxwell's equations contains the term of gradient of permittivity ε. The purpose of this correspondence is to clarify the effect of thebigtriangledown epsilonterm on the propagation constants of the modes. We find that the propagation constants of the lower order modes suffer significant modification by taking thebigtriangledown epsilonterm into account, while for the higher order modes the effects are small enough to be disregarded.     

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.     

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.<>     

High-order modes in a square coaxial waveguide

The normalized cutoff wavelengths for the first six higher order modes in a square waveguide with a circular inner conductor are presented. Some of these results are compared with those obtained recently by Laura et al.     

Isoform modes in a ferrite filled waveguide

The conditions governing the propagation of electromagnetic fields in a ferrite filled waveguide when the longitudinal electric and the longitudinal magnetic fields have the same transverse behavior, i.e., are isoform, are discussed. In particular an exact solution for a rectangular waveguide is obtained.     

Cutoff frequencies of a parabolic-core W-type fibre

The cutoff frequencies of guided modes in a weakly guiding W-type fibre with parabolic core profile have been obtained. It is found that the cutoff frequency of the TE01-mode in such a fibre is much higher than for a homogeneous-core W-type fibre. This should allow greater ease in splicing.     

片状固体激光器的基模

片状固体激光器片内的光束在上下表面产生全内反射,按之字形路径传输,提高了激活介质的利用率,从而可获得较高的能量输出.更重要的是,与传统的棒状固体激光器相比,它能补偿激光介质内部因温度不均匀而造成的光学畸变,因而引起了人们的广泛注意.本文试图用矩阵光学来分析它的补偿性.同时对这种结构的基模进行分析.由于片状固体激光器的菲涅耳数N(?)1,因而适于用矩阵光学来进行分析.     

Leaky-wave dispersion behavior on a grounded ferrite slab waveguide

In this letter, leaky-wave dispersion behavior is studied for a grounded biased-ferrite slab waveguide. The full-wave analysis encompasses space-wave leaky modes, surface waves, and magnetostatic modes supported by a ferrite slab as the magnetic bias field varies in strength. In particular, as the bias field increases from a value the TE leaky-wave cutoff frequencies of the isotropic slab split into two cutoff frequencies, resulting in complicated dispersion behavior of the corresponding forward and backward leaky waves. TM modes are unaffected by variation in the strength of the bias field for this orientation.     

Fundamental modes of a nonsymmetric planar metamaterial waveguide

The properties of fundamental (lower) guided wave modes propagating in a nonsymmetric planar metamaterial waveguide are considered. A graphical approach is applied for the analysis of their dispersion characteristics oriented toward the determination of the waveguide’s parameters ensuring the propagation of these waves in the waveguide. It is shown that, a nonsymmetric waveguide, as a symmetric one, can support both forward and backward wave modes.     

In-situ investigation of coupling between a fibre and a slab waveguide

The mode coupling between a fibre and a slab waveguide was experimentally investigated during the formation of the slab. A thin film has been deposited on a polished fibre close to the core-clad interface. By monitoring the optical transmittance of the fibre during the film deposition the coupling efficiency between the formed slab and the fibre has been studied as a function of the film thickness. Strong attenuation in the fibre output has been observed for thickness values at which the propagation constants of the optical mode in the fibre match those of the slab waveguide.<>     

Analysis of a line-defect waveguide on a silicon-on-insulator two-dimensional photonic-Crystal slab

This paper describes the investigation of the waveguide properties of a silicon-on-insulator (SOI)-based two-dimensional photonic-crystal slab. It is found that coupling between transverse-electric (TE)-like defect modes and transverse-magnetic (TM)-like slab modes occurs in some frequency range due to structural asymmetries in the vertical direction. This TE-TM coupling, together with the smaller refractive-index contrast between the slab and dielectric cladding, results in propagation losses for a line-defect waveguide in an SOI structure. The paper also presents optimization methods for obtaining a wide lossless propagation band using such a line defect.     

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.     

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.