三个非平行波导间的耦合

提出一种分析非平行波导的简明方法…耦合系数推广法,把非平行波导几何图形的变化直接转化成波导耦合系数中波导间距的变化．即对耦合系数进行了巧妙的推广．把波导间距的变化以指数的形式潜人到耦合微分方程中,建立了非平行三波导系统的耦合方程。这些耦合方程包含了非平行波导传输的全部信息,即非平行波导输出光的振幅和相位,非平行传输波导的长度及其夹角．非平行波导输人端口的间距,能量转换与波导参量的关系等。对这些微分方程作巧妙的数学变换,得到非平行三波导耦合系统输出光的完整分析解,分析和讨论了对称和不对称输人初始条件下三个非平行波导的耦合情况。由此可以优化非平行波导的设计参量。     

两个非平行波导间的能量转换

提出一种分析非平行波导间耦合的简明方法-耦合系数推广法.利用这种方法,导出一种新的非平行双波导的耦合方程,由此得到一组非平行波导耦合的完美的分析解,依据这些分析解可以优化非平行波导的传输距离、输入／输出端口波导间距和夹角.     

互易波导模式耦合理论

波导中模式耦合是一种普遍的现象.在光纤通信中不同导模之间的耦合会引起串扰,导模和辐射模的耦合会降低导模的功率.另一方面,利用模式耦合现象能设计出具有特定功能的耦合器和分束器等光学器件.模式耦合在光纤通信和光纤传感中也具有广泛应用.因此,分析研究波导模式如何耦合具有重要的应用价值.模式耦合理论是研究波导中模式耦合的常用方法,不仅提供了一种直观的物理图景来描述光学模式如何杂化,而且还对相关模式如何杂化给出定量评估.近年来,以宇称时间对称性结构为代表的非厄米波导成为研究热点,但传统模式耦合理论在这种情况下不再适用.本文简述了模式耦合理论的发展历史,详细介绍了构造互易波导模式耦合理论的关键概念和方法,进一步回顾了在波导模式耦合理论方面的一系列代表性工作,尤其是手征对称模式耦合理论以及广义模式耦合理论,总结了这些模式耦合理论和传统模式耦合理论之间的联系,最后简单介绍了它们在宇称时间对称波导及各向异性波导中的应用.     

光栅作用下双波导间的反向耦合

本文根据非正交模理论导出了描述光栅作用下双波导间反向耦合的耦合模方程组.通过数值计算对这种结构的反向耦合特性进行了初探,并同光栅作用下单波导反向耦合特性作了比较.     

平板波导谐振腔耦合损失的衍射理论

计算了一板波导谐振腔的耦合损失，给出了平板波导中ＥＨ１１模的耦合损失与球镜的曲率及位置的关系。计算结果表明存在两种特定的结构使耦合损失最小。     

半径渐变同轴波导模式耦合系数研究

 为了用耦合波理论研究一些同轴结构的高频特性，推导了半径渐变同轴波导内模式耦合系数的计算公式，发现半径渐变圆波导模式耦合系数只是同轴波导模式耦合系数的特例。对同轴波导中的模式及其本征方程根的特点进行了讨论，通过建立同轴波导模式和矩形波导模式之间的对应关系，给出了同轴波导模式本征方程根的快速计算方法。对所给模式耦合系数公式进行了验证，耦合波理论计算结果与有限元方法计算结果吻合良好。     

半径渐变同轴波导模式耦合系数研究

为了用耦合波理论研究一些同轴结构的高频特性,推导了半径渐变同轴波导内模式耦合系数的计算公式,发现半径渐变圆波导模式耦合系数只是同轴波导模式耦合系数的特例。对同轴波导中的模式及其本征方程根的特点进行了讨论,通过建立同轴波导模式和矩形波导模式之间的对应关系,给出了同轴波导模式本征方程根的快速计算方法。对所给模式耦合系数公式进行了验证,耦合波理论计算结果与有限元方法计算结果吻合良好。     

平行耦合腔波导对半导体激光器谱线宽度的控制作用

本文详细分析了平行耦合腔波导对谱线增宽因子的作用,得出在弱耦合和两腔内涨落互不相关的条件下,可以调节波导参数使增宽因子趋于零,从而使谱线宽度降低一个数量级以上,并讨论了耦合腔波导结构的近场和远场分布以及同相和反相模式的选择过程. 关键词：     

仅有相邻波导耦合的定向耦合器的一般解法

应用切比雪夫多项式 ,求得了仅有相邻波导耦合的 (N +1)× (N +1)定向耦合器在弱耦合、无损耗和忽略正交偏振模场分量间耦合的情形下波导耦合方程的通解。列出线形排列 2× 2 ,3× 3,4× 4定向耦合器的解的表达式 ,并对环形排列 3× 3定向耦合器的解作了较详细的分析     

利用耦合波导列提高光子晶体波导辐射

将耦合波导列应用于光子晶体单模波导,提出一种提高光辐射的光子晶体结构. 基于时域有限差分方法的理论研究表明,当将耦合波导列附加到单模光子晶体波导出口端的适当位置,使出射光分成若干强弱不一的光束,这些光束在传播空间通过干涉形成一定程度的汇聚,大大提高了光子晶体波导在水平方向的光辐射效率. 另外,当耦合波导列的行数大于某固定值(2N=8)时,辐射质量基本保持不变,由此可获得最紧凑的器件结构. 这种类型光子晶体在近场光学和集成光学等诸多方面有潜在的应用价值. 关键词： 光子晶体波导 光辐射 波导列 耦合波导     

TE mode coupling between end separated buried waveguides: expressions and calculations

In this paper the power coupling expression between two identical axially aligned and spatially separated waveguides is presented. Calculations using the coupling expression for a Gaussian mode profile in the input waveguide produce results that are in excellent agreement with experimental observations.     

Experimental mode coupling analysis in optical waveguides for sensor and component optimization

A computer controlled mode coupling analyser is conceived and described in detail to characterize and to analyse mode coupling in all known kinds of cylindrical, multimode, step index, optical waveguides (CMSIOWs) by experimental measurement. These waveguides can be present in many ways like simple fibres, multimode fibre-optic sensors (MFOS) or other optical components like couplers or modulators. The computer processed results of measurements lead to transfer matrices and modulation transfer matrices. The transfer matrices describe the light distribution in the far field of these waveguides depending on the direction and power of the light that is injected into it. By visualizing the modulation transfer matrices in the form of mesh diagrams, the influence of external physical parameters, like a measured variable, on the mode coupling mechanisms inside CMSIOWs can be shown directly. The computer controlled mode coupling analyser will make the optimization of MFOS more efficient and, moreover, it will ease modelling of CMSIOWs and define their properties. The potential field of applications for the mode coupling analyser will be in engineering and optimization of intrinsic multimode fibre-optic sensors and their components.     

Contra-directional coupling between two-dimensional photonic crystal waveguides

The contra-directional coupling between two photonic crystal (PC) waveguides is studied, using the finite-difference time-domain (FDTD) method. A design of contra-directional coupler is presented and its transmission properties are investigated. The device can be used as an add/drop filter. It is also shown that the coupled mode theory is suitable to study the photonic crystal waveguide coupler.     

Excitation of anti-symmetric coupled spoof SPPs in 3D SIS waveguides based on coupling

According to the electromagnetic field distributions, there exist two kinds of coupled spoof surface plasmon polaritons(SSPPs), the symmetric and anti-symmetric modes, in the three-dimensional(3D) subwavelength spoof–insulator–spoof(SIS) waveguide. We study the dispersion and excitation of the two kinds of coupled SSPPs supported by the 3D SIS waveguide. The evolution of the dispersion with the thickness and gap width of the waveguide is numerically investigated,and we give a theoretical analysis according to the coupling mechanism. Specially, based on the coupling mechanism,we design a zipper structure, through which the excitation and propagation of the anti-symmetric coupled modes can be realized effectively.     

Characteristics of vertical bent coupling between straight and curved rectangular optical waveguides

In terms of the coupled mode theory (CMT) and the transfer matrix method, we present a technique and relative formulas including the bent coupling coefficient, amplitude coupling ratio, amplitude transmission ratio and propagation power for analyzing the vertical bent coupling between a curved rectangular waveguide and a straight one. Investigations show that the bent coupling appears in an effective coupling region by both sides of the central coupling point. Beyond this effective coupling region, however, the bent coupling is very weak, and the propagation power in the waveguide is closer to a constant. As the bent radius increases, or the thickness of the coupling layer between these two waveguides decreases, this effective coupling region becomes wider, in which the coupling behavior becomes stronger.     

一种分析三维楔脊形光波导与光纤耦合的方法

和直波导的不同在于，三维楔脊形波导中的光场都是不稳定的.分别对波导-光纤耦合、光纤-波导耦合两种情况，将三维楔脊形波导等效为多段短的直波导，利用束传播法同时对三维楔脊形波导内不稳定的入射、反射场，及它们在传播方向上的偏导进行处理，再用自由空间辐射模法计算透射率和反射率.以SOI楔脊形波导和光纤的耦合为例，验证了该方法的可行性. 关键词： 自由空间辐射模法 束传播法 耦合 透射 楔脊形光波导 绝缘体上硅(SOI)     

加入增益介质的表面等离子体激元耦合共振波导传输特性理论研究

将增益介质加入金属环构成的表面等离子体激元耦合共振波导,利用传输矩阵及时域有限差分方法研究了不同增益系数下该耦合共振波导的透射谱线、色散关系以及群折射率.结果表明,增益介质共振频率附近的反常色散及正常色散变化能有效影响由共振波导几何结构决定的色散关系曲线,且具有相反的效果,分别使其变得平坦和陡峭,从而放大和缩小由共振波导几何结构决定的群折射率.另外,增益系数随外加抽运光改变的特点使得加入增益介质的耦合共振波导具有传输性能可灵活调节特性.文章的研究对促进耦合共振波导在高密度光学集成中的广泛应用具有积极意义. 关键词： 增益介质 耦合共振波导 表面等离子体激元 群折射率     

双光束耦合增益振荡的理论研究

本文从双光束增益振荡的动态方程组出发,给出一般情况下双光束光折变振荡稳态时的普遍结果,解释了文献[1,2]中理论不完全符合实验规律的原因,表明文献[1,2]中的理论只适合于光折变效应为纯扩散机制的特殊情况。     

Realization of a broadband terahertz wavelength-selective coupling based on five-core fibers

We propose a novel kind of wavelength-selective coupling for the terahertz range based on solid five-core fiber(FCF).The performances of coupling, propagation characteristics, and confinement loss properties are numerically investigated by using a full vector beam propagation method(BPM). Simulation results show that it is possible to realize a broadband wavelength-selective coupling. The coupling length can reach 1.913 cm, and the confinement loss is better than1.965×10-4cm-1. Furthermore, a parameter, the power difference, is defined, and it numerically demonstrates the working performance of the wavelength-selective coupler; that is, when the power difference is better than-15 dB, the frequency located in the range of 0.76 THz–1.00 THz is separated relatively well from the frequency of 0.3 THz. Finally, the effect of the structural parameter on the working performance of the coupler is also investigated. We show that the performance optimization is possible by appropriately tuning the core diameter, and the tunabilities of frequency and bandwidth are possible by appropriately tuning the pitch. The wavelength-selective coupler is of potential application for optical fiber sensing and communication in terahertz wavelength division multiplexer fields.     

Modal approach to waveguide coupling when gaps, offsets and rotations of one waveguide with respect to the other are present

In this paper, optical power coupling when waveguide separations, translations and rotations are present is addressed using a modal expansion technique. Numerical results are presented and discussed for Hermite-Gaussian input and output guided-mode profiles.