任意形状光栅皱阶光波导的分布反馈耦合系数

根据转移矩阵理论,在弱周期结构近似下获得了任意形状光栅皱阶光波导的TE模分布反馈耦合系数的计算公式,同时给出了几种典型的周期型皱阶光波导耦合系数的简洁解析表达式。     

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.     

具有同轴结构的高功率微波弯曲波导设计

 基于模式耦合理论,在理论推导出弯曲同轴波导TEM模和同轴TE11模之间耦合系数显式表达的基础上,报道了可传输同轴TE11模的弯曲同轴波导的设计方法和计算结果,并进行了实例研究。数值仿真结果表明：设计的具有同轴结构的弯曲波导,利用不同的同轴空间,在P,L,S波段中心频率0.680,1.575和3.75 GHz处TE11模单模传输效率超过了99.5%,单模传输效率超过90%的工作带宽分别为0.60～0.83,1.10～2.42和3.10～4.16 GHz。该结构的功率容量在各频段均达到了GW量级。     

梯形截面硅基水平多槽纳米线定向耦合器全矢量分析

定向耦合器是构成各类光子器件的基础元件. 本文采用一种基于电场分量的全矢量有限元法, 分析由梯形截面硅基水平多槽纳米线构成的定向耦合器. 给出了准TE与准TM偶、奇模有效折射率、耦合长度及模场分布, 揭示了其模式的混合特性及模场分布特点. 分析结果表明, 准TE模与准TM模的耦合长度随波导间距的增大均呈指数增长, 其中准TE模的耦合长度对波导侧壁倾角的变化敏感, 而准TM模的耦合长度对槽厚及槽折射率的变化敏感. 恰当选择结构与材料参数, 可实现两偏振态下相同耦合长度, 定向耦合器在偏振无关条件下工作.     

基于导模共振效应三基色窄带滤光片的研究

为获得性能优良的三基色窄带滤光片,提出了一种基于减反射薄膜波导光栅结构的导模共振滤光片.该滤光片由亚波长光栅结构、波导层和基底组成.采用严格耦合波理论分析了亚波长光栅结构和波导层厚度对导模共振滤光片反射光谱性能的影响.数值分析表明λ/4-λ/2-λ/4结构能有效提高导模共振滤光片的性能.当光栅结构位于基底侧时,红绿蓝三...     

矩形光栅的衍射特性

本文采用严格的一阶耦合波理论,对矩形光栅的衍射特性进行了分析,给出了TE模和TM模同时具有很高的衍射效率时的光栅结构。计算表明:只有在满足Bragg衍射条件时,TE模和TM模才能达到峰值衍射效率。为了验证理论与编制程序的正确性,将计算结果与已有的资料进行了比较.     

L波段全腔提取轴向输出相对论磁控管设计

设计了一种全腔提取轴向输出相对论磁控管。在模工作的N腔磁控管中, 该结构利用磁耦合的方式通过两个相邻谐振腔在一个扇形波导内激励起TE11模, 然后再由N/2个相位相同的扇形波导TE11模沿轴向向外传输。对L波段全腔提取轴向输出磁控管进行了仿真设计, 在600 kV, 6.3 kA的条件下, 获得1.89 GW微波输出, 功率转换效率50%, 微波频率1.57 GHz。该结构在径向方向上仅增加一个扇形波导厚度, 便于实现相对论磁控管的紧凑、高效设计。     

InGaAs/InAlAs多量子阱脊形波导及定向耦合器光波特性准矢量分析

提出了一种基于级数展开的三维准矢量束传播法(SE-QV-BPM)用以分析由InGaAs/InAlAs多量子阱构成的脊形光波导及定向耦合器.结果表明，刻蚀深度相同时，TM模比TE模在水平方向限制强，且TM模的模场在波导角上出现畸变；波导间距相同时，定向耦合器TM波的耦合长度大于TE波的耦合长度，对偏振态敏感.分析获得了浅/深刻脊形光波导承载的准矢量TE/TM基模、定向耦合器承载的TE/TM偶/奇模的模场分布及其有效折射率，模拟了光场在定向耦合器中的传输演变情况.另外，SE-QV-BPM导出矩阵小，计算效率高 关键词： 级数展开 准矢量束传播法 多量子阱 InGaAs/InAlAs     

石墨烯TE模表面等离子体波和表面等离子体波导的特性

基于含石墨烯的双/三层介质结构中的光学色散方程,研究了覆层和基底层材料对石墨烯表面等离子体波横电(TE)模的影响。计算结果表明,近红外波段内,石墨烯表面等离子体波TE模的性质对覆层和基底层介电常数的差值极其敏感。当覆层和基底层介电常数出现微小差异时,TE模可以进行传输。随着两介电常数差值的增大,TE模的有效折射率显著增大,甚至超过覆层折射率,而传播损耗不断减小。对于三层介质结构,相邻两介质分界面间添加单层石墨烯形成了平板波导结构,研究该结构发现,当传导层和基底层介电常数相近时,其夹层的石墨烯对波导TE模的调控尤其显著,这种调控来源于电磁波耦合到石墨烯形成的表面等离子体波TE模。这些结果为设计调制器、检测器和过滤器等石墨烯表面等离子体波导器件提供了理论支持。     

阵列波导光栅中心波长温度稳定性的研究

阵列波导光栅中心波长的温度不稳定性成为限制其应用的主要原因。为了设计温度不敏感阵列波导光栅,结合弹性多层板热应力理论和应力集中效应给出掩埋波导芯层应力的解析解,利用等效折射率法计算阵列波导的有效折射率及其温度系数,考虑波导材料折射率和波导长度随温度的变化得到了硅基二氧化硅阵列波导光栅中心波长的温度系数。并研究了贴有应力板的阵列波导光栅中心波长的温度特性,结果表明在芯片底部贴有0.37 mm厚的铝板时,TE模和TM模中心波长的温度系数分别是5.9 pm/℃和8.0 pm/℃,下降到传统阵列波导光栅中心波长温度系数的一半。     

Theoretical analysis of optical coupling properties of the waveguide grating with novel rectangular structure

For the waveguide grating photocoupler with novel structure [Yu XQ, Zhang X, Wong KS, Xu GB, Xu XG, Ren Y, et al. A fabrication of coupling grating in the polymeric waveguide by using two-photon initiated photopolymerization. Mater Lett 2004;58:3879–83. [1]; Yu XQ, Zhang X, Xu GB, Zhao HP, He W, Shao ZS, et al. Fabrication of grating waveguide and coupling grating using two-photon initiated photopolymerization. Chem J Chin Univ 2004;25(10):1931–3 (in Chinese). [2]], the electric fields of the TE guided wave and the TE radiating wave are obtained by solving the Helmholtz equation in the spatial rectangular coordinates. And then the relations between the loss coefficient and the different structure parameters of the waveguide and grating are analyzed by using the mode coupling theories, and their corresponding numerical simulation results are given. In the end the result obtained for this novel structure and that for conventional rectangle structure are compared, and the difference and the sameness are obtained.     

Polarization-independent grating couplers for silicon-on-insulator nanophotonic waveguides

We propose the use of subwavelength structures in a waveguide grating to achieve polarization-independent coupling of light between an optical fiber and a silicon-on-insulator (SOI) optical waveguide. The subwavelength structure allows the mode effective indices of the TE and TM modes in the grating section to be precisely engineered. We calculate that coupling efficiency of over 64% is possible using the proposed design for polarization-independent coupling between single-mode optical fibers and SOI nanophotonic waveguides.     

矩形栅慢波系统的高频特性分析

 对于矩形栅这一经典的慢波结构，采用场匹配法来分析其慢波特性，进而得到其耦合阻抗。其中对槽区内的场处理，保留其高次项，表示为一无限本征驻波之和的形式。然后通过数值实例具体分析了矩形栅的两种典型结构：浅槽栅和深槽栅。当增大槽深后，色散增强，系统通带变窄，同时耦合阻抗有明显增大，工作点移向前向波区，适合用在放大器的慢波结构上。     

Compact double-layer subwavelength binary blazed grating 1×4 splitter based on silicon-on-insulator

We describe a compact double-layer waveguide grating splitter that not only achieves efficient coupling between single mode fiber and a silicon-on-insulator optical waveguide but also realizes effective splitting. By appropriate choice of waveguide/grating parameters, including thicknesses, periods, height, and fill factor to optimize the mode matching, coupling efficiency is improved and the value of power difference of each output port is also significantly decreased. The maximum of power difference between four output ports is about 6.2%; however, the minimum value is only 0.6% or so. Moreover, the average power difference of four output ports is lower than 10% for TE polarization light over the 10?nm wavelength bandwidth centered at 1.54?μm. In addition, the splitter structure has the best tolerance for grating fabrication with deviations of grating depth 90?nm.     

DIELECTRIC EFFECT ON THE RADIO-FREQUENCY CHARACTERISTICS OF A RECTANGULAR WAVEGUIDE GRATING TRAVELING WAVE TUBE

A new type of partial-dielectric-loaded rectangular waveguide grating slow-wave structure (SWS) for millimeter wave traveling wave tube (TWT) is presented in this paper. The radio-frequency characteristics including the dispersion properties, the longitudinal electric field distribution and the beam-wave coupling impedance of this structure are analyzed. The results show that the dispersion of the rectangular waveguide grating circuit is weakened, the phase velocity is reduced and the position of the maximum E _z is basically invariant after partially filling the dielectric materials in the rectangular waveguide grating SWS. Although the coupling impedance decreases a little, it still keeps above 40 Ω.     

内开槽矩形波导栅慢波电路高频特性的数值分析

 介绍了用德国CST公司提供的MWS 4.2软件模拟计算色散特性和耦合阻抗的理论方法，对内开槽矩形波导栅结构的高频特性进行了数值模拟。结果表明：在传统矩形波导栅结构的基础上，开槽后的矩形波导栅结构比开槽前的相速更低，用作行波管的慢波结构时，可降低工作电压，工艺上容易实现，而且耦合阻抗均在45 W以上，满足毫米波行波管的要求；在内开槽宽度一定的前提下，槽深、栅间距和栅周期的增大对降低系统相速有利。     

矩形波导栅慢波系统的实验研究

 从实验上研究了矩形波导栅慢波系统的色散特性及其耦合装置的驻波系数，用分布加工的方法分别制作了矩形、燕尾形、梯形3种不同槽形的矩形波导栅慢波结构模型和带输入输出结构的矩形波导栅慢波结构实体模型。采用谐振法测量它们的色散特性和驻波系数，实验结果与理论计算值和模拟值吻合良好。     

Modelling of finite-size grating waveguide filters on the basis of a free-space diffraction approach

The field reflection coefficient R of a high strength and short length waveguide grating section is obtained by resorting to a free-space diffraction approach whereby the waveguide grating is excited by means of a virtual high index prism. The effective index of the guided mode, the coupling coefficient between contradirectionally propagating modes of the grating waveguide as well as the modal field are first obtained in the case of an infinite grating by interpreting the results given by an exact diffraction solution by means of a three-wave coupled mode formalism. These results are then introduced in the coupled wave analysis of the structure of finite extent to provide the field at the entrance of the waveguide grating section where the usual overlap integral with the incident field delivers the reflection coefficient. We neglect only the result of radiation mode propagation. This assumption can be made when the grating section is longer than the propagating length of all the leaky modes.     

Modelling of finite-size grating waveguide filters on the basis of a free-space diffraction approach

The field reflection coefficientR of a high strength and short length waveguide grating section is obtained by resorting to a free-space diffraction approach whereby the waveguide grating is excited by means of a virtual high index prism. The effective index of the guided mode, the coupling coefficient between contradirectionally propagating modes of the grating waveguide as well as the modal field are first obtained in the case of an infinite grating by interpreting the results given by an exact diffraction solution by means of a three-wave coupled mode formalism. These results are then introduced in the coupled wave analysis of the structure of finite extent to provide the field at the entrance of the waveguide grating section where the usual overlap integral with the incident field delivers the reflection coefficient. We neglect only the result of radiation mode propagation. This assumption can be made when the grating section is longer than the propagating length of all the leaky modes.     

Optimization of a Waveguide Grating for Normal TM Mode Coupling

The conditions for maximum longitudinal electric field of a TM mode at the surface of a step index slab waveguide, and the value of this maximum are given in a normalized analytical form. They are applied to a grating coupling structure corresponding to a resonant laser mirror or to optical interconnects involving a normally incident free space wave and a singlemode slab waveguide.