共查询到20条相似文献,搜索用时 125 毫秒
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本文用自由空间模简化及近似表示弱导多层介质光波导的辐射模.只要辐射方向与介质界面的角度不是很小,近似程度很好.将其应用于求解光栅耦合器的辐射损耗问题,使计算公式简化,用自由空间模计算的结果与用辐射模计算的结果比较接近,也与其它近似方法进行了比较. 相似文献
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左手介质椭圆光波导基模传播特性 总被引:1,自引:0,他引:1
在椭圆柱坐标系中,采用分离变量方法,得出了左手介质椭圆光波导本征方程的近似解,通过数值计算,分析了椭圆波导偏心率、左手介质的电容率、磁导率对椭圆光波导基模传播特性的影响,并将左介质光波导与右手介质光波导基模特性进行对比,得出左手介质光波导的基模特性与右手介质光波导基模特性差别不大的结论. 相似文献
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本文讨论了大半径空芯圆柱形介质波导中存在的线偏振模EH_(1m)和LP_(nm)(n≥1)的场合分布,后者是一对简并模的线性组合.然后,我们计算了自由空间高斯-拉盖尔模TEM_(np)与这些线偏振模的耦合系数,得到的结果与已发表的实验资料符合得很好.我们还讨论了较小输入孔半径对光泵远红外激光器输出功率的影响. 相似文献
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Fermi折射率分布光波导的模方程 总被引:3,自引:0,他引:3
对Fermi折射率分布的特性进行了分析,用光线理论推导出Fermi折射率平面光波导的近似超越模方程.理论分析和实验结果比较表明,Fermi折射率分布函数能较好地描述准阶跃渐变折射率.得到的近似模方程相当精确地决定了这类波导的模式特性,比阶跃折射率近似精确. 相似文献
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一维光子晶体掺杂缺陷模研究 总被引:57,自引:9,他引:48
用特征矩阵法计算了光波在包含多种掺杂缺陷的一维光子晶体中的传播规律,与不包含缺陷的结构相比较,在禁带中形成缺陷模。缺陷模的位置、数目和强度不仅和缺陷的产生方式有关,还和缺陷位置处的光学厚度及折射率的变化有关。当掺杂缺陷的位置呈等间距时,相应缺陷模也呈等间距排列。随着掺杂缺陷光学厚度的变化,缺陷模的位置、数目也随之变化。保持掺杂缺陷光学厚度不变,掺杂缺陷折射率的变化将会引起缺陷模强度的变化,并存在一个最大值。缺陷模的出现一般使带隙加宽,尤其是掺杂介质的折射率与周期介质的折射率差别较大时更加明显。掺杂空气介质时可使缺陷模的透射率近似为1。 相似文献
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A. V. Vinogradov A. N. Mitrofanov A. V. Popov M. A. Fedin 《Journal of Russian Laser Research》2007,28(6):576-593
This paper considers a planar Bragg waveguide. The guided modes and their dissipation due to the fundamental absorption are
described. In the interacting-wave approximation, an analytical relation between the characteristics of the modes and parameters
of the Bragg-waveguide geometry was established. Absorption losses in hollow Bragg waveguides were shown to be significantly
lower than in a regular waveguide fabricated from the same material. Quantitative estimates of the fundamental and radiation
losses in Bragg waveguides are given for materials used at wavelengths of 1.55, 10.6, and 0.245 μm. 相似文献
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J. P. Crenn C. Charollais 《International Journal of Infrared and Millimeter Waves》1996,17(9):1475-1506
The field distributions and propagation constants of the circular electric, circular magnetic and hybrid modes of oversized waveguides are expressed, taking the effects of walls into account. These effects are described by wall functions which depend on surface impedances of the wall, and are determined for different types of guides. The near and far field patterns are derived in the case of real wall functions. It is shown that, for very oversized waveguides, the terms containing wall functions can be ignored in the calculations, and it results that the expressions of fields and propagation constants become independent of the types of waveguides. An application to corrugated waveguides for Electron Cyclotron Resonance Heating experiments shows the variations of the radiation characteristics versus geometric parameters of the corrugations and determines the ranges of interest for these parameters. 相似文献
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Ideal Bragg reflection waveguides (BRWs) are assumed to have an infinitely extended periodic cladding whereas in practice, the cladding of BRWs is of a finite extent. Bloch theorem is widely used to analyze the propagation characteristics of the BRWs. Since Bloch theorem is ideally valid only for an infinitely extended periodic medium, its application to study such BRWs is an approximation. We present a matrix method for a more accurate analysis of finite-clad BRWs and estimate the extent of errors involved in the values of the propagation constant obtained by the Bloch wave formalism. The proposed method can be used to obtain the mode effective indices as well as the radiation loss of a finite-clad BRW without resorting to solving any complex transcendental equation. In addition, since the method does not inherently assume a periodic cladding, it can also be used to analyze symmetric multi-channel BRWs, chirped structures and directional couplers. 相似文献
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Wave propagation through curved bends in integrated optical waveguides is governed by the evanescent field and the radiation loss of the eigenmodes. Since these parameters are influenced by the refractive index of the surrounding medium, circular bends in rib waveguides have been successfully employed as chemical sensors for liquids and gases. In this paper the electromagnetic field, the refractive index and the radiation loss of the eigenmodes are precisely determined by a fully vectorial approach based on the method of lines. An axial discretization and Bessel functions of complex order are employed for the rigorous computation of the evanescent field. The intensity distributions of the first modes in a rib waveguide are presented. The influence of the rib height on the sensitivity of the modal index to the refractive index of the surrounding medium is investigated. The results are useful for the optimization of the sensor design. 相似文献
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This paper gives, in brief the theoretical and computational investigation of a new light guide having a curvilinear triangular core cross-section. This structure is here introduced for the first time and may be conceived as a distortion of a rectangular core cross-section. Using Goell's point matching method under weak guidance approximation, the modal characteristics equations for the lowest order mode have been derived in two cases. In one case, all the sides of the proposed light guide are bounded by dielectric material. In other case we will consider all the sides bounded by conducting materials. From these equations the modal dispersion curves are obtained and compared. It is seen that the dielectric light guide supports more modes than the metallic light guide. Thus, metallic light guide may be used as a mode filter. 相似文献
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The graphene-based double-barrier waveguides induced by electric field have been investigated. The guided modes can only exist in the case of Klein tunneling, and the fundamental mode is absent. The guided modes in the single-barrier waveguide split into symmetric and antisymmetric modes with different incident angles in the double-barrier waveguide.The phase difference between electron states and hole states is also discussed. The phase difference for the two splitting modes is close to each other and increases with the order of guided modes. These phenomena can be helpful for the potential applications in graphene-based optoelectronic devices. 相似文献
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k 《Photonics and Nanostructures》2003,1(1):43-53
When describing localized electromagnetic modes in dielectric waveguides by the planewave method, a supercell geometry must necessarily be adopted. We demonstrate in the present work that the convergence of the calculations with respect to supercell size depends strongly on the choice of the transverse Bloch wave vector, k. We describe a method to derive k-points that minimize the coupling between repeated images of the guided modes in real space. Calculations have been done for a quadratic and a triangular photonic crystal fiber structure. With the new coupling reducing (CR) k-points, the convergence of the eigenfrequencies for both the fundamental and second order modes with respect to supercell size is considerably improved. The general approach outlined may also be applied in the case of three-dimensional photonic crystal structures. 相似文献
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S. T. Surzhikov 《Doklady Physics》2012,57(3):119-124
The calculation data on convective and radiation heating of the Pathfinder space vehicle (SV) during entry into the Martian
atmosphere at an angle of attack are presented. Comparison with the results of calculations of convective heating of the frontal
surface of the Pathfinder SV in the axisymmetric statement is carried out. The data on the radiation heating of the Pathfinder
SV entering the Martian atmosphere at an angle of attack have been obtained for the first time. The analysis of the spectral
composition of the thermal radiation reaching the surface of the space vehicle is carried out; this makes it possible to mark
the change of modes of the radiation heating. 相似文献
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V. P. Petukhov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2012,6(2):287-291
X-ray ion radiation, caused by resonant coherent excitation (RCE) in a crystal, arises at the crystal-vacuum interface and
propagates along the surface, generating a so-called surface wave. The dependence between the surface-wave intensity and the
departure angle of characteristic X-ray radiation upon RCE is investigated in a kinematic approximation of diffraction theory.
It has been shown that the angular dependence for the intensity of this radiation leaving the crystal surface differs substantially
from the radiation intensity inherent to the decay of ion states excited by RCE. 相似文献