线性剖面克尔材料分层板波导中光波的传播

对三层板波导中光波传播问题进行了讨论.芯材料是克尔型介质,其折射率平方(n²)剖面分布随x作线性变化.此时芯区的亥姆霍兹方程约化为Painleve方程,利用Laurant级数可得到其近似解.     

里兹方法在光波导理论中的应用

本文讨论了在三层平板介质波导中TE波的传播问题.三层平板的芯区由Kerr介质构成,其折射率平方(n²)的剖面分布随x作抛物分布变化.本文将应用变分法中的里兹方法,求出亥姆霍兹方程的第一级近似的解析解.     

非对称金属包覆左手介质平板波导的微扰分析

基于微扰方法分析非对称金属包覆左手介质平板波导的特性,给出了该波导的复有效折射率的一级近似解,并对波导的传输特性和损耗特性进行了数值模拟.结果表明：非对称金属包覆左手介质平板波导没有零阶模式|TE1模传播系数随波导厚度的增加迅速减小,损耗系数随波导厚度的增加快速增加,达到最大值后又迅速减小|非对称金属包覆左手介质平板波导传输特性相对于左手介质三层平板波导传输特性发生了很大改变,TM1模,TM2和 TE2模式以及更高阶模式在截止厚度附近出现双值现象|特别在二阶及高阶模式中,TE模式相对于TM模式具有高传输低损耗的特性,而以右手介质为芯层的金属包覆波导不具有这一特性.     

各向异性非线性介质平板波导中的TM波

本文讨论了在三层平板介质波导中TM₀模的传播问题.三层介质的芯区是一层各向异性的Kerr型介质,上下两层则是线性介质.本文将利用E_x² >> E_x²这一性质,求解非线性方程组,给出零级近似和1级近似的解析解.     

非线性薄膜波导TE模色散特性的多层分割法计算

对于芯区为非线性介质、衬底及包层为线性介质的平板波导、提出用多层分割法分析芯区的模场,采用递推公式（等效于推广的传递矩阵法）求解传播常数与光功率间的依赖关系,该法适用地克尔型或非克尔型介质及芯区折射率非均匀的一般情形,实例计算结果与已有的精确数值计算结果十分符合。     

光波导理论中的伽辽金方法

本文讨论了在三层平板介质波导中横电波的传播问题.三层平板的芯区是Kerr介质,其折射率平方n²的剖面分布随x作抛物分布.本文将应用伽辽金方法,求出赫姆方程的第1次和第2次近似的解析解.     

非线性包层光纤中TE0模的传播特性分析

本文对具有Kerr非线性包层和线性匀芯的光纤在不同光功率下的传播特性进行了理论分析和数值计算.结果表明,在适当光功率下,当模折射率N等于芯折射率n_f时,芯场变得相当均匀,而包层场迅速衰减.对于自聚焦包层,当从N<n_f逐渐变到N>n_f时,芯场剖面越过N=n_f从凸变凹.在拐点,芯场成为均匀的.论文给出了模场分布和光功率与模折射率的关系.指出纤芯出现匀场预期会在光纤器件、光电子器件、光子器件中得到应用.     

非线性介质光波导中的传输功率和光学双稳态

本文对结构为非线性包层/线性芯层/非线性衬底的非线性介质光波导的传输特性进行了深入的分析,给出了模场分布函数,色散关系和传输功率的一组形式统一的公式,并对其传输功率的光学双稳态特性进行了讨论.     

溶胶-凝胶法制备SiO2-TiO2平板光波导工艺研究

采用溶胶-凝胶法制备了SiO₂-TiO₂平板光波导,计算了平板光波导通光条件,分析了硅/钛溶胶-凝胶材料的热性能,观测了平板光波导的结构形貌,并测试了其通光损耗。结果表明：经过200℃,30 min干燥处理的凝胶薄膜呈疏松多孔状态,对于非对称平板波导,存在芯层通光截止厚度,而且当SiO₂-TiO₂芯层厚度为0.5 μm时,SiO₂下包层厚度至少有6 μm才能防止1550 nm波长光泄露入单晶硅衬底中。制备的光波导对于1550 nm波长光传输损耗最小值为0.34 dB/cm。     

InGaAsP SBH激光器光束质量的非傍轴分析

计算了InGaAsPSBH激光器的TE₀₀模,并利用非傍轴矢量矩理论,分析了平行于p-n结方向上的光学质量因子M_y²在以往有关M²的计算中,往往忽略了包层中光场的贡献,因此得出M²小于1的结论当半导体激光器的激活层的尺寸远小于发射波长时,大部分光场将渗透到包层中,因此,包层的光场是不能忽略的考虑到激活层和包层中的光场对M²的影响,给出了非傍轴半导体激光M²的精确表达式结果表明,M_y大于1.     

Thermal stresses in optical waveguides

Birefringence of optical waveguides is closely related to the anisotropy of thermal stresses in the core. Closed-form solutions for estimating the thermal stresses in the cladding layers and in the core of an embedded channel waveguide are presented. The solutions are verified by finite-element simulation. It is found that the thermal stress in the core in the direction perpendicular to the wafer cannot be ignored, and one can tune the core stress anisotropy in the plane normal to the light-propagation direction by varying the thermal-expansion mismatch between the upper cladding and the substrate.     

Simultaneous Measurement of Temperature and Refractive Index of Liquid Using Cladding-Etched Double-Core Fiber Bragg Grating

Abstract

This study proposed and demonstrated a fiber Bragg grating sensor for simultaneous detection of the temperature and refractive index of a liquid. The fiber Bragg grating is composed of three index layers: an inner core, an outer core, and a cladding. The cladding was etched for evanescent wave coupling between the outer core mode and an external liquid. The Bragg wavelength of the inner core mode is used for obtaining temperature data, while the refractive index for the liquid was determined by using the difference between the Bragg wavelength of the inner core mode and that of outer core mode.     

用转移矩阵法研究LNN型非线性平面光波导

用转移矩阵法数值分析了芯区和衬底为非线性介质、覆盖层为线性介质结构平面光波导的传播特性,包括TM的模场分布和功率与有效折射率之间关系的分析.解析地表达了模式本征方程和功率分布,对非线性介质中电场强度与介质非线性系数的关系进行了研究.计算结果表明,TM的模场分布和功率与有效折射率及介质的非线性系数有关.     

光纤纤芯及包层模有效折射率计算及仿真

光纤结构设计、模间色散求解、光纤光栅模式耦合等问题的研究, 都需要对光纤纤芯及包层模的有效折射率进行精确计算. 本文以光纤三层结构模型为基础, 结合该模型下的模式本征方程, 使用截弦法求解了纤芯模有效折射率, 并将计算结果与COMSOL软件模拟的对应纤芯模的传输光场进行对比, 验证了计算结果正确.使用区间遍历算法对包层模有效折射率进行了求解, 与已有的传统方法相比, 该方法可以有效防止求解过程中根的遗漏、避免特征方程产生的奇点, 并能保证模式的正规性.本文采用Mathematica软件对求解过程进行仿真, 获得了纤芯模和包层模有效折射率与波长关系曲线. 关键词： 光纤传输模式 有效折射率 截弦法 区间遍历算法     

The effect of an inhomogeneous cladding of a gradient optical waveguide on the mode and envelope characteristics of a soliton pulse

The nonlinear dynamics of a short pulse in a gradient waveguide layer is studied analytically taking into account the occurrence of a cladding layer and the longitudinal inhomogeneity of the two layers. The class of functions is presented in terms of which the transverse profiles of the refractive indices of both the gradient and the cladding layers can be represented, and, at the same time, the mode structure of the pulse can be explicitly described in terms of a hypergeometric equation. Expressions are presented that describe the variations of the propagation constant and transverse distribution of the wave field under the action of the longitudinal inhomogeneities of the gradient and cladding layers. It is shown that the envelope of the pulse satisfies the generalized nonlinear Schrödinger equation the coefficients of which are functions of the longitudinal coordinate and are expressed via the refractive indices of the waveguide layer and cladding.     

单模手征光纤研究

对圆芯和内外包层都为手征介质构成的双包层手征光纤（W型）进行了解求解,导出了模式场解及模式特征方程,然后用数值计算的方法研究了手征参数对模式的色散曲线和截止频率的影响,结果发现在双包层光纤的纤芯中引入手征或在单包层光纤的包层中引入手征,都可以实现单模工作。     

The cladded parabolic-index profile waveguide: analysis and application to stripe-geometry lasers

A two-dimensional real waveguide having a parabolic distribution of dielectric permittivity in the core region, flanked by cladding layers of constant refractive index is proposed as a model for a class of stripe-geometry injection lasers. The model is analysed by a series-solution method and results are given in terms of plots of normalized propagation constant, near-field filling factor, and far-field half-angle, all versus normalized frequency. These results are compared with those for the alternative models of (a) a homogeneous core waveguide, and (b) a medium whose dielectric permittivity varies quadratically with position throughout the whole of space.Apart from the series-solution method which was employed, a survey is included of other techniques available for analysing this waveguide model. These include perturbation theory, variational analysis, an exact solution of the scalar wave equation, and the WKB approximation.     

Characteristics of the transmission spectrum of the long period fiber gratings based on the coupling of core mode to the higher order cladding modes

The characteristics of the transmission spectrum of the Long-period fiber gratings (LPFGs) based on the coupling of core mode to a higher order cladding mode (HE mode) are investigated using the coupled mode theory. This kind of LPFGs is different from that based on the coupling of core mode to a lower order cladding mode because of the effect of the coupling of core mode to EH cladding mode. When the cladding mode order is higher, the coupling coefficients of core mode to HE and EH cladding modes are comparable and both of the propagation constants of HE and EH cladding modes approach, so the spectrum has an additional loss peak. The bandwidth of LPFG based on the coupling of core mode to different cladding mode differs greatly. With the change of the mode orders from lower to higher, the transmission spectrum changes from narrow to wide and more narrow.     

Nonlinear planar waveguides with gracled-index core: power series solution

Abstact Solutions are presented for a class of nonlinear, planar waveguides with graded-index linear film and nonlinear cladding and/or substrate. The solutions are based on a powerseries expansion for the field in the core and, for several interesting examples, can be expressed explicitly - without the need to solve any eigenvalue equation. For more general problems, the solution can be described in a form that is directly analogous to that for the asymmetric step-index waveguide. Some interesting differences between the mocles of the step-and graded-index waveguides are illustrated.     

Fiber Modal Index Measurements Based on Fiber Gratings

A novel method based on fiber gratings for measuring the effective indices of fiber modes is proposed. The effective index difference between the core mode and a cladding mode was obtained by analyzing the interference fringe of a pair of cascaded long-period fiber gratings. In order to extract the core mode index from the measured index difference, an index matching oil immersion method is proposed. By analyzing the interaction between the cladding mode and the oil applied on the cladding surface, the mode order and the effective index of the involved cladding mode might be calculated. Experimental results about the interference fringe shifts induced by the oil index and the oil-applied length are also presented.