基于SOI的2×2 MMI耦合器的设计

设计了一种可用于阵列波导光栅(AWG)解调集成微系统的绝缘体上硅(SOI)基2×2多模干涉(MMI)耦合器,用光束传播法(BPM)对MMI耦合器进行了模拟。耦合器输入/输出波导采用倒锥形,多模干涉区尺寸为6μm×57μm。在TE偏振中心波长为1.55μm时,器件附加损耗为0.46dB,不均匀性为0.06dB。在1.49～1.59μm波长范围内耦合器的附加损耗小于1.55dB。仿真结果表明所设计的2×2MMI耦合器体积小、附加损耗低、波长响应范围宽、分光均匀,符合片上集成系统的要求。     

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.     

一种紧缩型的SOI3- d B多模干涉耦合器

采用线锥形结构 ,在 silicon- on- insulator(SOI)材料上设计并实现了一种新的紧缩型 3- d B多模干涉耦合器(MMI) .与普通的矩形结构 3- d B MMI耦合器相比 ,该器件长度减少了 4 0 % .耦合器输出均衡度为 1.3d B,过剩损耗为 2 .5 d B.     

MMI阵列波导光栅复用/解复用器的研制

详细分析了基于自镜像效应的 MMI DMUX器件的基本工作原理 ,在此基础上 ,在 SOI材料上完成了对 8信道 MMI DMU X的具体设计 .该器件的输入、输出单模波导采用 Soref的大截面脊形光波导理论进行优化设计 ,最后获得了当输入、输出单模波导宽度为 5 μm,SIE多模波导宽度和长度分别为 72 μm和 6 313.4μm时 ,该器件对8信道波长的隔离度均在 35 d B以上 ,且理论传输损耗 <0 .18d B.     

基于绝缘体上硅脊型纳米线光波导方向耦合器的TE/TM偏振分束器

利用有限元方法和时域有限差分方法,优化设计了一种结构紧凑的基于绝缘体上硅脊型纳米线光波导方向耦合器的TE/TM偏振分束器。考虑到方向耦合器的波导间隙较小时制作工艺较为困难,且模式失配会引入一些损耗,因此波导间隙取约100nm较为合适。通过优化脊型纳米线光波导的几何尺寸(脊高和脊宽)、耦合区波导间隙,使得偏振分束器长度最短。数值计算结果表明经过优化的偏振分束器最短长度大约为17.3μm,偏振分束器的消光比大于15dB时,波导宽度制作容差为-20～10nm,带宽约为50nm。     

新型质子交换扩钛波导TM模偏振器特性分析

提出将质子交换区域做在扩钛LiNbO3光波导两侧邻近区域来获得TM模光波导偏振器的方案.用二维BPM分析计算了质子交换区域的长度、宽度等参数对器件消光比的影响,给出了数值分析结果,并得到了偏振消光比优于51dB的实验结果.     

InP基4×4MMI合波器的设计与仿真

采用空气限制的InP基波导,利用其弯曲半径小的优点,设计了一款紧凑型4×4 MMI(多模干涉)合波器,整个器件的尺寸为3 890 μm×100 μm.在输入/输出波导与多模干涉区域之间引入了锥形波导,有效改善了MMI合波器的性能.并通过广角三维光束传输法对器件进行了模拟仿真,得到优化参量,从而实现了其结构的优化.     

基于光子晶体和纳米线波导的马赫-曾德尔型调制器

提出了一种基于光子晶体和纳米线波导的马赫-曾德尔型调制器.该调制器由硅基光子晶体平板波导、纳米线波导和光子晶体多模干涉耦合器(MMI)构成。在光子晶体与纳米线波导连接处采用了锥型结构,用于减少模式失配造成的损耗。利用时域有限差分法(3D-FDTD)进行仿真分析,结果表明,该调制器在工作波长1 550 nm下的插入损耗为0. 3 dB,消光比为15. 1 dB,器件尺寸仅46μm×8μm×0. 22μm,调制带宽可以达到68 GHz,且工作区域覆盖了以1 551 nm为中心波长20 nm的通信波段。该调制器结构紧凑,易于集成,可应用于高速光通信系统。     

MMI阵列波导光栅复用/解复用器的研制

详细分析了基于自镜像效应的MMI DMUX器件的基本工作原理,在此基础上,在SOI材料上完成了对8信道MMI DMUX的具体设计.该器件的输入、输出单模波导采用Soref的大截面脊形光波导理论进行优化设计,最后获得了当输入、输出单模波导宽度为5μm,SIE多模波导宽度和长度分别为72μm和6313.4μm时,该器件对8信道波长的隔离度均在35dB以上,且理论传输损耗＜0.18dB.     

一种紧缩型的SOI 3-dB多模干涉耦合器

采用线锥形结构,在silicon-on-insulator (SOI)材料上设计并实现了一种新的紧缩型3-dB多模干涉耦合器(MMI).与普通的矩形结构3-dB MMI耦合器相比,该器件长度减少了40%.耦合器输出均衡度为1.3dB,过剩损耗为2.5dB.     

Nonlinear finite-element semivectorial propagation method forthree-dimensional optical waveguides

A nonlinear semivectorial beam propagation method based on the finite element method is presented. It applies to three-dimensional optical waveguides and accounts for polarization effects. To show the usefulness of this approach numerical results regarding both E^x (quasi-TE) and E^y (quasi-TM) waves are presented for directional couplers with nonlinear cores. The limits of scalar formulations are highlighted especially when working near and above the coupler threshold power     

Theoretical Investigation of Polarization-Insensitive Multimode Interference Splitters on Silicon-on-Insulator

An ultracompact polarization-insensitive 1times2 multimode interference (MMI) splitter based on silicon-on-insulator is investigated theoretically. The impact of the insulator index on the size of the MMI and the polarization-dependent performance is analyzed. A polarization-insensitive 1times2 MMI splitter of 4 mum by 16.5 mum is shown as an example. Relaxed tolerances on MMI width (> plusmn100 nm) and length (> plusmn0.7 mum) are obtained for both polarizations while the polarization differential loss is kept in range of 0.1 dB and its excess loss is kept below 0.5 dB. In addition, a wide operation wavelength window of 150 nm is obtained for both polarizations as well.     

Novel approach to design high-performance large-port-count switches in low-index-contrast materials based on cascaded multimode interference couplers

Using a novel design approach, high-performance large-port-count switches based on cascaded multimode interference (MMI) couplers are shown to be feasible in low-index-contrast materials. This approach combines the transfer matrix method, optimization of the MMI dimensions, and mode propagation analysis (MPA) for calculation of phase shifts. 1/spl times/4, 1/spl times/8, 1/spl times/16, and 1/spl times/32 switches are designed, with insertion losses of 1 dB and crosstalk as low as -31.7 dB. Also, it is shown that this approach can balance the losses for different switch states.     

Signal bandwidth of general n×n multimode interferencecouplers

Analytical expression of signal bandwidth of general straight and tapered N×N multimode interference (MMI) couplers is presented. The signal bandwidth is characterized as a function of mode relative energy, mode propagation delay time, and mode pulse broadening in the multimode section of MMI coupler. The model is used to evaluate the signal bandwidth of specific couplers. Results indicate that the signal bandwidth decreases seriously with the increase of channel number and channel guide space. Compared with the straight MMI coupler, the tapered MMI coupler has an improved signal bandwidth     

Ultracompact multimode interference 3-dB coupler with stronglateral confinement by deep dry etching

Extremely short InP-InGaAsP MMI 3-dB couplers (L~15-50 μm) with conventional structure have been successfully fabricated. The significant size reduction was achieved by deep dry etching and tapered access waveguide with large S-bend design. Optical transmission measurements on these devices have been performed. An optical bandwidth about 80 nm with a limit of 2-dB excess loss was obtained for most of the couplers. During the whole tunable wavelength range (λ~1485-1580 nm), the imbalance is within ±0.5 dB. Fabrication tolerance and polarization independence are also investigated and the results demonstrated the applicability of these ultracompact devices in high-density photonic integrated circuit     

Polarization independent, integrated optical, acoustically tunablewavelength filters/switches with tapered acoustical directional coupler

Enhanced sidelobe suppression of the filter characteristics of tunable acousto-optical mode converters in LiNbO₃ has been achieved using for the first time tapered acoustical directional couplers. A sidelobe suppression of more than 15.5 dB could be demonstrated in a single stage device. By combining the mode converter with two integrated optical polarization splitters a polarization independent filter/wavelength selective switch has been fabricated with less than 3 dB intrinsic insertion loss, a polarization dependence of less than 1 dB, and a sidelobe suppression exceeding 14 dB     

PLC-Based Novel Triplexer With a Simple Structure for Optical Transceiver Module Applications

A novel triplexer is introduced for optical communication applications in this letter. The triplexer consists of two cascaded multimode interference (MMI) couplers and can be fabricated by planar lightwave circuit technology. The concept of the extraneous self-imaging phenomenon, which is not generally mentioned in MMI theory, is applied to this triplexer to design a relatively simple and compact device. From the simulation results for wavelengths of 1310, 1490, and 1550 nm, the excess losses were determined to be 1.37, 0.63, and 0.79 dB, respectively, while the extinction ratios were 15.93, 24.28, and 18.44 dB, respectively.     

Design of an ultra-compact 3 dB MMI coupler

The design of an ultra-compact SOI-based 1×2 3 dB multimode interference（MMI） coupler is proposed.The symmetric multimode interference structure and deeply-etched parabolically tapered multimode waveguide are used in the device.The length of the device is reduced by about 87% compared with general multimode interference straight couplers.Based on effective index method（EIM） and two dimensional beam propagation method（2D-BPM）,the structure parameters are optimized and the fabrication tolerances are analyzed.The results indicate that the performance of the coupler is deeply affected by the coupler＇s width,etching depth and photolithography alignment error in perpendicular direction.     

Three-dimensional electromagnetic modeling of fiber-core effects onthe coupling characteristics of weakly fused tapered fiber-opticcouplers

Based on the full-wave formulations, which combine the finite element method add the boundary element technique, and the step-like approximation method, a three-dimensional (3-D) electromagnetic modeling approach is proposed in this work to investigate the fiber-core effects on the coupling characteristics of the weakly fused tapered couplers. We find the fiber cores have significant effects on the mode field patterns, coupling coefficients, and birefringence for the coupler with large normalized frequencies. The influence of the fiber cores on the coupling behavior for the real couplers, such as 3 dB power dividers, polarization beam splitters, and wavelength demultiplexing/multiplexing couplers, are also studied in 3-D view. It is found that the effects of fiber-cores in the weakly fused tapered couplers have to be considered for accurately modelling their coupling behavior, although the model with no core assumption can predict the trend of the coupling characteristics for the real couplers