Experimental Study of a Slot Antenna Excited by a TE011 Mode Coaxial Cavity

A slot antenna is developed to excite the high harmonic waveguide mode for generating large-area plasmas. This antenna consists of a TE₀₁₁ mode coaxial cavity with the axial slots positioned on equal interval on the inner wall. The waves radiated from those slots can excite the high harmonic mode in the central area. With the azimuthal symmetric wave field of the TE₀₁₁ mode, the number of the slots can be chosen to match the field pattern of the high harmonic mode. In this report, the dispersion relation of the coaxial waveguide, the coupling scheme and the mode competition of the cavity are studied. A method has been successfully developed to suppress the TE₁₂₁ mode which is the most competing mode to the TE₀₁₁ mode.     

The dispersion relations for surface plasmon in a nonlinear-metal-nonlinear dielectric structure

In the asymmetric and symmetric nonlinear-metal-nonlinear dielectric structures, this paper studies the analytic dispersion relation for surface plasmon in a system consisting of a thin metallic film covered on two sides media of intensity-dependent refractive indexes by applying a generalised first integral approach. Especially in the symmetric waveguide structure, two possible modes can exist: the odd mode and the even mode. The dispersion relations of the two modes are obtained. Due to the nonlinear dielectric, the squared magnitude of the electric field at the interface appears and alters the dispersion relations. Numerical results are compared to those from a certain approximate treatment.     

多孔微结构光纤中飞秒激光脉冲超连续谱的产生

报道了利用800nm飞秒激光脉冲在多孔微结构光纤中产生超连续谱展宽的现象，连续谱展宽范围为440—890nm.基于标量波近似理论对微结构光纤包层的有效折射率和基模的有效面积以及光纤的色散特性进行了计算，发现微结构光纤具有特殊的控制色散和波导特性的能力，对超连续谱展宽的机理进行了初步解释.本文的理论分析和实验结果有较好的一致性，认为即使包层由无序填充气线组成的多孔微结构光纤也可以出现超连续谱展宽效应. 关键词： 多孔微结构光纤 超连续谱 有效折射率 色散     

Dispersion relation for surface plasmon polaritons in metal/nonlinear-dielectric/metal slot waveguides

We present the first (to our knowledge) exact dispersion relation for the transverse-magnetic surface plasmon polariton (SPP) modes of a plasmonic slot waveguide, which is formed by a nonlinear Kerr medium sandwiched between two metallic slabs. The obtained relation is then simplified to the case of small field intensities, while retaining nonlinear terms, to derive approximate dispersion equations for the symmetric and antisymmetric SPP modes.     

Anomalous dispersion and group velocity properties in subwavelength uniaxial metamaterial waveguide with metal cladding

We investigate propagation behavior of electromagnetic waves in a slab uniaxial metamaterial waveguide with metal cladding and discuss the dispersion relation, group velocity and energy flux distribution of transverse electric guided modes in two kinds of uniaxial metamaterial waveguides with different orientations of optical axis in detail. The numerical results show that there exist anomalous dispersion properties such as backward modes existing in low-frequency range, and the group velocity can be negative or approach zero. If the orientation of optical axis is selected properly, each guided mode has two dispersion curves—one is normal dispersion and another belongs to anomalous dispersion and shows a transition from a backward mode to a forward one with the angular frequency increasing. In addition, the condition of the existence of cutoff frequency is clarified. These properties may have potential applications in optical information storage, optical communication, integrated optics and nanophotonic devices.     

光子晶体光纤色散的无量纲化计算方法

关键词：     

Mode analysis of realistic optical waveguide structures and microstructured holey fibers by modal field evolution

In this article, we describe a useful technique for calculating modes of practical optical waveguides having two-dimensional arbitrary transverse refractive index profile. The method uses a finite difference platform for evaluating Helmholtz's equation in scalar and semivectorial forms through a field evolution algorithm. The method is straightforward, easy to handle and does not involve any complex analysis or matrix formulation. We tested the accuracy of our analysis approach by applying it on a large number of realistic waveguide problems having known results or results available in the literature. The formulation has facilitated us to study the modal properties, viz., field distribution, birefringence, dispersion and mode effective area, of a variety of practical two-dimensional structures namely, planar structure, coupler, semiconductor optical waveguides, optical fibers and arbitrary profile microstructured fibers which are uniquely important in photonics and guided-wave devices. The algorithm will therefore be very useful in designing and studying any arbitrary-structure waveguides, and to explore new geometry and properties.     

新型光学聚合物——Topas环烯烃共聚物微结构光纤的设计及特性分析

以新型光学聚合物Topas 环烯烃共聚物（折射率为1.53）为基质,设计了四种微结构聚合物光纤.应用有限元方法对各种光纤在波长0.5—2.0 μm范围内的基模有效折射率、模场面积和数值孔径进行了计算.研究了结构参数对模场分布、单模特性和色散特性的影响.得出了具有极大/小模场面积、无限单模传输和平坦近零色散的光纤结构参数.与石英、聚甲基丙烯酸甲酯基质的微结构光纤相比,该光纤具有更大的数值孔径和较宽的平坦近零色散范围.为光纤的制备提供了理论指导. 关键词： 微结构聚合物光纤 有限元方法 传输特性 Topas 环烯烃共聚物     

Influence of a holey cladding structure on spectral characteristics of side-polished endlessly single-mode photonic crystal fibers

We experimentally investigate the spectral characteristics of side-polished endlessly single-mode photonic crystal fibers of different polishing depths and radii of curvature that are important to mode field diameter, evanescent coupling, waveguide losses, higher-order mode excitation, and dispersion slopes of photonic crystal fiber components. A polished photonic crystal fiber with a greater polishing depth or a larger radius of curvature shows a more dispersive characteristic. In contrast to conventional single-mode fibers, in photonic crystal fibers the evanescent field is more strongly localized, and the propagating light can be more efficiently guided within the deformed core.     

Analysis of circular fibers with an arbitrary index profile by the Galerkin method

We propose a full-vectorial Galerkin method for the analysis of circular symmetric fibers with arbitrary index profiles. A set of orthogonal Laguerre-Gauss functions is used to calculate the dispersion relation and mode fields of TE and TM modes. Examples are given for both standard step-index fibers and Bragg fibers. For standard step-index fiber with low or high index contrast, the Galerkin method agrees well with the analytical results. In the case of the TE mode of a Bragg fiber it agrees well with the asymptotic results.     

Comparative study of asymmetric versus symmetric planar slab dielectric optical waveguides

In this paper we have studied the asymmetric versus symmetric planar waveguide in terms of their usefulness in optical fiber communication systems. We have explored the thin waveguide versus thick waveguide first. Later on usefulness of asymmetric versus symmetric waveguide is carried out to target for WDM optical network application. All kinds of optical network components are fabricated on Si substrate with the point of view of their application. Here asymmetric planar structure may be more useful compared to symmetric waveguide in terms of their non-uniform power confinement properties. However, the symmetric waveguide structure may be more useful for their high power confinement properties. It is well known that the thin symmetric waveguide supports at least one mode. However the thick waveguide may support many even as well as odd modes. We study the power confinement properties for symmetric as well as asymmetric waveguide structure. We conclude that higher order modes show the nonlinear power variations. Mode field profile for various cases is discussed as well. Comparative study between asymmetric versus symmetric waveguide has a lot of significance in optical network area. It has been shown through analysis that in asymmetric waveguide, the power flows more through film region in the case of fundamental mode. Power confinement properties for asymmetric waveguide versus symmetric waveguide have been studied.     

未磁化等离子体介质切连科夫脉塞的线性理论

利用线性自洽场理论，讨论了电子在扰动场作用下的三维扰动．在此基础上，对常用的薄环形相对论电子环束在填充未磁化等离子体的介质筒慢波波导中激励的切连科夫辐射进行了详细的分析，导出了此电子环束与慢波系统中任意波导模互作用的色散方程和波增长率，并对其进行了详细的分析和讨论．分析表明切连科夫辐射是由其波导模与电子注模耦合所致．最后详细计算和分析了等离子体密度对色散特性和波增长率的影响 关键词：     

基于双芯光子晶体光纤的低非线性宽带色散补偿光纤的设计

采用矢量光束传输法数值模拟了基于模式耦合的双芯光子晶体光纤的色散和非线性与其结构的关系。结果表明:通过在包层中移除一层空气孔以形成外纤芯并调整内外纤芯之间的距离及包层空气孔的占空比,内外纤芯间的模式耦合可以在宽带范围内发生,导致产生大负色散。同时,由于光场分布在两个纤芯内,增大了模场面积,产生低非线性,可以实现低非线性宽带色散补偿。     

Tailoring the dispersion properties of photonic crystal fibers

Photonic crystal fibers (PCFs) have had a substantial impact on nonlinear fiber optics and shortpulsed fiber laser systems due to their novel dispersion properties. The large normal or anomalous waveguide dispersion available in such fibers opens up a number of new opportunities not accessible with standard fiber technology. In this contribution, the fundamentals of PCF dispersion are briefly reviewed along with earlier results. In addition, some of our recent work on dispersion tailoring to facilitate nonlinear processes, and dispersion control in lasers will be presented.     

Optical modes in a plasmonic waveguide with electrically anisotropic metamaterial

We study the optical modes in a plasmonic waveguide with electrically anisotropic metamaterial and dielectric, including symmetric (anti-symmetric) photonic mode and symmetric (anti-symmetric) plasmonic mode. The dispersion curves for these modes are derived, and a graphical method is used to calculate the solution of symmetric photonic mode and anti-symmetric plasmonic mode. By simulation results the conditions of the existence for these modes are deduced in each case.     

含间隔层的增益导引-折射率反导引平面波导激光器中高阶模式抑制研究

为了抑制高功率波导激光器中的高阶模式,改善其光束质量,基于增益导引-折射率反导引理论,在对称分层波导结构中添加了一层间隔层,进一步加大了高阶模式与基模之间阈值增益系数的差异,利用这种模式竞争抑制高阶模式.同时从波动方程出发,推导出各模式的本征方程,并给出了基模和高阶模的场分布.引入间隔层之后的高低阶模式损耗计算结果表明,通过合理地选择间隔层参数,可以有效地抑制高阶模式.     

含左手材料对称五层平面波导模场特性

对芯层为左手材料而内外包层都是普通材料的对称五层平面波导进行了探讨.得到了两类TE振荡模的色散方程,且在考虑材料色散的条件下,画出了相关模式的色散曲线.随着模阶数的增加,模色散曲线左移,它们的截止频率变小.其次,发现零阶TE振荡模的存在.除此以外,TE振荡模有三类色散特性：正常色散;反常色散;双模简并.     

含左手材料对称五层平面波导模场特性(英文)

对芯层为左手材料而内外包层都是普通材料的对称五层平面波导进行了探讨.得到了两类TE振荡模的色散方程,且在考虑材料色散的条件下,画出了相关模式的色散曲线.随着模阶数的增加,模色散曲线左移,它们的截止频率变小.其次,发现零阶TE振荡模的存在.除此以外,TE振荡模有三类色散特性:正常色散;反常色散;双模简并.     

Anomalous behaviour in a Bragg reflection waveguide

A novel asymmetric Bragg reflection waveguide (BRW) showing anomalous dispersion characteristic is presented. The abnormal behaviour of increase of modal effective index with wavelength is primarily caused by the changes taking place in the imaginary part of the Bloch wavevector, in the periodic stratified cladding. The phase velocity and the group velocity dispersion characteristics for the waveguide have also been analyzed. Such an anomalous behaviour can find applications in the design of integrated optical devices.     

有机高聚物PPQ薄膜的反常群速色散

通过对ＰＰＱ薄膜的吸收光学谱的计算分析，由Ｋｒａｍｅｒｓ－Ｋｒｏｎｉｇ关系得到ＰＰＱ膜在５５０ｎｍ～７００ｎｍ左右波段存在负群速色散区，并且色散量对相对较小，│β２│〉１．２ｐｓ＾２／ｍ，这使得对飞秒激光脉冲在ＰＰＱ平面光波导中的传输的传输的描述可以忽略色散顶，根据这一间化，仅考虑自相位调制（ＳＰＭ）效应，由于飞秒对撞锁激光脉冲的光谱展宽民计算的ＰＰＱ的非线性折射率系数ｎ２，与报道的结果吻合很好。