超薄金属膜V-型槽等离子波导的定向耦合研究

分析了在 1 550 nm 波长下超薄金属膜(金膜厚t=10 nm)V-型槽等离子波导间长程沟道等离激元导模的定向耦合。通过计算不同波导间距下的模式分布,得出了定向耦合器中奇、偶模有效折射率实部和传播长度随波导间距的变化情况,并进一步计算了相邻波导间的耦合长度、最大串扰与波导间距的关系曲线。计算结果表明:在波导间距较小时,耦合长度小于各模式的传播长度,随着波导间距的增加,耦合长度随之增加,最大串扰随之减小。对超薄金属膜V-型槽等离子波导的定向耦研究在集成光路的实际应用中具有重要的价值。     

声表面波技术讲座 第五讲 多条耦合器及其应用

多条耦合器(Multistrip coupler)是应用于声表面波的定向耦合器。它由在压电基片上的平行金属条阵列组成。它的特殊性能是耦合在单晶基片上的非波导声波。这是与波导耦合器以及邻接媒质耦合器大不相同的。     

一种人工表面等离激元的小型化毫米波天线

设计了一款基于人工表面等离子体激元(Spoof Surface Plasma Polariton,SSPP)的小型化高效率定向辐射天线.在介质基板表面印刷了共面波导(CPW)、波矢匹配结构和SSPP传输线三种结构,其中波矢匹配结构与共面波导部分相结合,更好地完成阻抗匹配.此外,因人工表面等离子体激元可以将电场约束在天线...     

一种光集成定向耦合器的优化

本文研究的定向耦合器是由两条平行的光波导组成,每个波导具有三个折射率台阶。折射率分布与工作波长约为λ=1.3μm四元的InGaAsl'/InP装置相符合。在2C—150λ范围内给定一个耦合器长度,为了获得最高耦合效率,对各层的折射率和厚度进行了优化。     

新型波导的开关设计及特性分析

通过SPP(表面等离子体激元)的优越特性分析了楔形波导SPP的透射特性,设计了嵌有光栅的楔形等离子体波导结构。对SPP激发的分析采用衍射光栅耦合的方式,通过改变金属薄膜厚度以及入射光角度得出其结构特性。结果表明:金属薄膜厚度的减少会导致透射带宽迅速降低,透射率也随之下降;而入射光角度的改变会导致透射光效率的变化。模拟了楔形波导结构的表面等离子体,得到了薄膜厚度的变化透射曲线和入射光角度透射率,得出了透射率变化图。研究结果对半导体设备的纳米等离子激元耦合具有一定的意义。     

梯形截面硅基垂直多槽纳米线定向耦合器全矢量分析

采用一种基于三电场分量的全矢量有限元法,其中引入了完善匹配层(PML)吸收边界条件,分析由梯形截面硅基垂直多槽纳米线构成的平行定向耦合器.考虑了波导侧壁倾角、耦合波导间距、槽宽及槽折射率的变化对定向耦合器性能的影响.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,恰当选择结构参数及材料参数,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T型腔结构的表面等离子体波导滤波器

表面等离子体激元(surface plasmon polaritons,SPPs)能将光场束缚在亚波长量级,可以突破衍射极限,被认为是有希望实现纳米集成光学器件的载体之一。设计了一种T型腔结构的表面等离子体波导滤波器,并且利用时域有限差分(FDTD)法对其滤波特性进行了分析。结果表明,改变T型腔的长度和宽度可以改变透射谱的中心波长,而改变腔与耦合波导之间的间距,则可以调节腔的Q值。     

日本研制成功硅纳米线定向耦合器

日本NEC公司和日本光电子工业与技术发展协会及东京大学的科学家们第一个成功研制出Si纳米线定向耦合器。该Si纳米线定向耦合器比传统的用玻璃光纤、基于半导体SiO2或铌酸锂波导制作的定向耦合器尺寸小得多。与传统定向耦合器的几个mm的长度相比较,Si纳米线定向耦合器的总长度≤50μm。由于Si芯与SiO2包层之间的折射率差很大,Si纳米线波导的S形弯曲的曲率半径小得多,所以弯曲损耗小。此外,传统的定向耦合器的典型耦合长度为几百μm或甚至为几个mm,而Si纳米线定向耦合器的耦合长度≤10μm。该Si纳米线定向耦合器采用一间隔为0.3μm的矩…     

光纤定向耦合器的开关特性研究

基于耦合非线性薛定谔(NLS)方程组,利用分步傅里叶法(SSFM),研究了二阶色散长度与线性耦合系数的乘积LDκ、三阶色散长度与线性耦合系数的乘积L′Dκ以及模间色散(IMD)对双芯非线性光纤定向耦合器开关特性的影响。研究表明,在光纤正常色散区,当入射功率大于阈值功率时,从波导1到波导2有明显的能量转移,耦合器的开关性能差;而在光纤反常色散区,当LDκ1时,非线性定向耦合器(NLDC)能够表现出良好的开关特性。且阈值功率随着LDκ的增大而减小。当|IMD|≤0.01,IMD对NLDC开关特性的影响可以忽略。当|IMD|=0.2,且LDκ的值较小时,在入射功率大于阈值功率的条件下,IMD对开关特性的影响不明显;而在入射功率小于阈值功率时,耦合器的开关特性下降。此外,三阶色散(TOD)效应对NLDC的影响通常可以忽略。     

二维光子晶体波导和微腔缺陷态研究

利用二维三角晶格及正方晶格介质柱光子晶体TE偏振的禁带与介质柱半径的变化关系,分析了二维光子晶体缺陷态的分布.根据光子晶体波导间的耦合作用,计算其耦合长度设计合理的定向耦合器.通过分析波导与微腔的耦合特性,选取不同的传输方向,可以设计多种基于光子晶体波导与微腔耦合的波分复用系统.     

Effect of transition waveguides on dielectric waveguide directionalcouplers

The coupling of energy between two curved dielectric waveguides is investigated by the staircase approximation method, which combines the building-block approach of multimode network theory with a rigorous mode-matching procedure. Particular attention is directed toward two major effects of transition waveguides on the performance of directional couplers composed of dielectric waveguides: one is the change in the coupling length, the other is the radiation loss. The coupling problem is analyzed in terms of the scattering of an incident guided mode by the coupler structure as a whole. Numerical results are given to illustrate the coupling characteristics of various structures and to establish useful guidelines for the design of directional couplers     

Crystalline organic semiconductor optical directional couplers andswitches using an index-matching layer

A directional coupler using crystalline organic semiconductor waveguides grown by the vacuum process of organic molecular beam deposition is demonstrated. An index-matching layer placed between two coupled waveguides separated by a 1 μm gap greatly increases the coupling coefficient, significantly decreasing the coupling length and making the device very compact. Switching of 1.06 μm wavelength light from one guide to another in the coupler has been observed by pumping the surface of one guide in the coupling region with 0.514 μm     

Ultrashort 2-D photonic crystal directional couplers

A novel approach to reduce the coupling length and to increase the coupling coefficient in waveguide directional couplers implemented on two-dimensional (2-D) photonic crystals (PhC) is proposed. To increase the coupling coefficient of a 2-D PhC directional coupler, which is composed of two parallel PhC waveguides separated by one or several rows of rods, the radius of the rods between both waveguides is reduced. The application of this feature to ultrasmall channel interleavers and wavelength demultiplexers is addressed.     

Numerical analysis of three-parallel embedded optical waveguides

Three parallel embedded dielectric waveguides are investigated numerically. The mode-matching method that matches the boundary conditions in the sense of least squares is applied to this problem, using the hybrid-modal representation. Precise numerical results for the dispersion relations and field distributions are presented for the lowest three modes near the cutoff. The frequency range in which only the three modes can propagate and the differences in their propagation constants are discussed at length, in order to highlight the available frequency range and the coupling length of the configuration with respect to its use as a directional coupler     

Combined directional and contradirectional coupling in athree-waveguide configuration

A three-waveguide coupler, combining directional and contradirectional coupling between the central and side waveguides, respectively, is discussed. Coupled-mode formalism is used to examine the superposed processes both in synchronism and near synchronism. The nature of the solution is shown to depend on the relative coupling strengths of the individual processes. For stronger contradirectional coupling, the power is divided among the three output ports, at ratios closely related to the ratio of the coupling coefficients, and with a nonperiodic, slowly varying length dependence. The coupler can thus be used as a power divider without the need for a precisely special case where the directional and contradirectional coupling coefficients are equal     

The Bragg reflection waveguide directional coupler

A directional coupler formed by two Bragg reflection waveguides (BRWs) with a common finite periodic region between them is analyzed. The coupling coefficient is a sensitive function of the index difference in the periodic coupling section. This feature can lead to a novel kind of electrooptic switch. In addition, the BRW directional coupler exhibits dispersion properties characteristic of the periodic bounding media, which can be used to implement a narrowband wavelength filter and a TE polarizer     

近红外波长下COMSOL软件实现新型耦合器的设计

一直以来条状表面等离子波导被认为是实现高集成光路的有效器件,首先采用经典的Drude模型对条状波导中SPP激发与传播特性完成了分析。针对可见光到近红外入射波长的条件完成了条状SPP波导的模场分布的研究,得出,当金属的厚度不变宽度越大,电磁场分布就越集中在条状波导的两侧;当金属条状的宽度不变,厚度越大时电磁场分布会越集中在金属内;入射波长越长会使得金属条状周围电场的集中越小,且还会导致信道间的干扰。利用得到的条状波导特性进而设计了一种新型的耦合器,器件设计结果表明:条状SPP波导在有限传输距离上能量完全转移只发生一次;波长较长时,场的集中度减小,耦合增强;条状SPP波导耦合器可以实现1310 nm和1550 nm的光波分复用。这一研究对光子器件的发展有一定的理论和实际意义。     

Microstrip Spiral Directional Coupler

A new microwave directional coupler with a spiral-shaped construction is described. This coupler is named the spiral coupler and is formed by coiling two edge-coupled lines. Therefore, the size of the coupler can be greatly miniaturized. Furthermore, this coupler can achieve tight coupling much easier than the conventional coupler with edge-coupled lines on account of the multiconductor structure. The spiral couplers with a total length of a quarter-wave were fabricated on alumina ceramic substrates and resulted in 3.5-dB maximum conpling for a 40-mu m strip spacing. The size of the coupler was about one-sixth of the conventional one. The spiral coupler with a total length of three quarter-waves theoretically showed 2.5-dB coupling for a 95-mu m strip spacing on an alumina substrate. The achieved coupling is due to the skillful construction of the spiral. An experimental coupler fabricated on a Teflon substrate confirmed the usefulness of this approach.     

Cladding layer thickness-controlled directional coupler opticalswitch

The AlGaAs/GaAs cladding layer thickness-controlled directional coupler optical switch (CTC-SW) is discussed. To increase the efficiency of coupling between two waveguides, the CTC-SW was designed with a thin i-AlGaAs cladding layer h between the two waveguides. The coupling length L_c can be reduced, without reduction of the extinction ratio and increase of the switching voltage. For instance, L_c of CTC-SW (h=0.07) can be reduced 40% more than that of a conventional directional coupler switch (h=0). The extinction ratio is near 20 dB, both for the crossover (applied voltage V=0 V) and straight-through (V =19 V) states. A technique for adjusting L_c to the device length was developed