Analytical and experimental study of waveguide optical polarizationsplitter with Langmuir-Blodgett cladding layer

The waveguide-type optical polarization splitter, which utilizes birefringence of a Langmuir-Blodgett cladding layer, is studied theoretically and experimentally. By means of the beam propagation method based on Galerkin's principle, characteristics of the polarization splitter are analyzed. Results of the numerical calculation predict excellent polarization splitting properties with a crosstalk of -30 dB and an insertion loss of less than 0.1 dB for both TE and TM polarization. Successful operation of the polarization splitter was demonstrated in an experimental device     

ARROW-B type polarization splitter with asymmetric Y-branchfabricated by a self-alignment process

We have proposed and demonstrated a polarization splitter based on an ARROW-B type waveguide. This device has an asymmetric Y-branch configuration, connecting a waveguide with a large modal birefringence to a low-birefringent waveguide which is channeled by a stripe lateral confinement structure. The device can achieve a high extinction ratio without precise mask alignment, since these two waveguides are connected by a self-alignment process. In addition, a low insertion loss is achieved because of adiabatic Y-branching. We designed this device at the wavelength of 1.55 μm and fabricated it using RF sputtering. As a result, high extinction ratios of -19.4 dB for TE mode and -19.0 dB for TM mode were achieved     

Polymeric waveguide polarization splitter with a buriedbirefringent polymer

A waveguide polarization splitter is demonstrated based on a low-loss polymer waveguide and a birefringent polyimide. Crosslinkable fluorinated polymers with an excellent stability and a low absorption loss are utilized for the device. The polyimide is buried under one branch of the Y-branch waveguide to enhance the birefringence between the TE and TM modes. By the adiabatic mode evolution, the TE mode is coupled to the branch with the polyimide strip, while the TM mode propagates through the other branch without the polyimide. For the device with a branch angle of 1/400 rad, we obtained a crosstalk less than -20 dB and a fiber-to-fiber insertion loss of 3.8 dB     

短长度的双椭圆纤芯光子晶体光纤偏振分束器

基于双折射效应设计了一种新型的双椭圆纤芯光子晶体光纤(PCF)偏振分束器,通过在每个纤芯处引入一对大空气孔和一对小空气孔来构成椭圆纤芯。采用全矢量有限元法(FEM)和半矢量光束传播法数值模拟偏振分束器的性能,结果表明,在工作波长1.55μm处,光纤长度为544μm时,X、Y方向偏振光可实现分离,且消光比达到-43.75dB,消光比小于-10dB的带宽为80nm。这为设计具有高消光比和极短长度的双芯光子晶体光纤偏振分束器提供了一种新的结构。     

硅基槽波导级联多模干涉耦合器型偏振分束器

提出了一种基于硅基槽波导的级联多模干涉(MMI)耦合器型偏振分束器,由锥形及矩形结构MMI耦合器构成.级联结构使器件长度无需为两偏振模自镜像长度的公倍数,不仅能有效减小器件尺寸,而且提高设计灵活性.同时,利用槽波导的高双折射特性及MMI耦合器的锥形结构,可进一步缩短器件尺寸.分析结果表明,所提器件能够有效实现偏振束分离,两级MMI工作区总长度仅为42μm,准TE与准TM模的偏振消光比分别为29.8和31.4d B,1.55μm波长下的插入损耗分别为0.395和0.699 d B,偏振消光比大于20 d B时光带宽为43 nm,覆盖整个C波段.最后,详细分析了器件关键参数的制造误差对器件性能的影响.     

高双折射双芯光子晶体光纤偏振分束器

设计了一种基于双折射效应的新型矩形纤芯光子晶体光纤偏振分束器,通过在矩形晶格结构的光子晶体光纤的每个纤芯中引入一对椭圆来增加结构的双折射。应用全矢量有限元法（FEM）分析了双芯光子晶体光纤中结构参数对双折射和耦合长度特性的影响,数值模拟了该偏振分束器的性能。结果表明:增大椭圆率可以在增大结构的双折射的同时减小耦合长度,并且该分束器在工作波长为1.55 m、传输长度为282 m 的光纤中能够实现偏振状态的隔离,消光比达到最小值-45.42 dB,并且在1.507~1.596 m、带宽为89 nm 的范围内消光比小于-10 dB。     

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.     

A short polarization splitter without metal overlays on InGaAsP-InP

A new and very short polarization splitter on InGaAsP-InP is designed and realized for the first time. The component contains a ridge waveguide directional coupler of 0.4 mm length and an output section of 0.7 mm. It uses the large waveguide birefringence of the first-order TE and TM modes to obtain polarization selective directional coupling. In this way, additional metal layers on the waveguides to create birefringence are avoided and fabrication becomes very simple. Components are realized, which show splitting ratios close to -20 dB. Excess losses are below 1 dB. The polarization splitting is investigated in the wavelength region of 1525-1560 nm and found to be better than -9 dB.     

Short Polarization Filter in Pillar-Based Photonic Crystals

The strong polarization dependence of two- dimensional photonic crystals is exploited for polarization filtering. The device with a length of 3.9 mum is integrated in a photonic integrated circuit based on InP waveguide technology. The average transmissions in the wavelength range from 1530 to 1570 nm are -8.7 dB for transverse-magnetic polarization and -26.5 dB for transverse-electric polarization.     

Proposal and analysis of an ultrashort directional-couplerpolarization splitter with an NLC coupling layer

We propose a novel, high-performance directional-coupler polarization splitter using a nematic liquid crystal (NLC) as the coupling layer. The beam propagation method is used to investigate the propagation characteristics of the device under various conditions. Results of numerical calculations relevant to the design conditions are presented. Because of the large birefringence of NLC, a very short device length of 140 μm is achievable at a high extinction ratio of 28 dB     

Design and performance evaluation of 1-by-64 multimode interferencepower splitter for optical communications

A 1-by-64 multimode interference power splitter in SiO₂ has been designed for use in fiber-optics communication systems. The splitter exhibits a minimum loss of 0.5 db and a uniformity of 1.7 dB at a wavelength of 1.55 μm. The polarization sensitivity is below 0.14 dB, the reflection level below -55 dB, and the optical bandwidth 30 nm. The fabrication tolerances are ±0.1 mm on the length and ±3.5 μm on the width of the multimode section of the splitter. In comparison with a branching-type splitter it is found that the designed device is approximately 30% shorter than the branching-type device for comparable losses     

交叉型TE/TM模分离器的研制

采用光束传播法（ＢＰＭ）计算了交叉型ＴＥ／ＴＭ模分离器的偏振串音（ｃｒｏｓｔａｌｋ）。通过结构参数的优化，理论计算的偏振串音为－２３．７ｄＢ（ＴＭ）和－２２．８ｄＢ（ＴＥ）。同时制成相应的器件，测试结果表明，理论计算与实验是一致的     

A 1.3 μm directional coupler polarization splitter by ionexchange

A glass waveguide polarization splitter for operation in the 1.3 μm wavelength region is reported. The device, which has a symmetric directional coupler configuration, exploits the stress-induced birefringence in K⁺-Na⁺, ion-exchanged waveguides, giving rise to an adequate difference in the coupling lengths for the two polarizations. Starting from the measured potassium concentration (refractive index) profile of the structure and utilizing a combination of the multilayer stack theory and the effective-index method, the normal mode propagation constants and mode field profiles are calculated to determine the polarization splitting length and the extinction ratio, and the results are compared with the experimental data. It is shown that in a given coupler, the splitting occurs at several wavelengths in the 1.0-1.45 μm range. A 25 mm-long coupler, fabricated by thermal diffusion of K⁺ ions in BK7 glass, exhibits an extinction ratio of 18.2 dB at 1.32 μm, in excellent agreement with the simulation results     

金属修饰的微结构光纤偏振分束器

提出了一种金属修饰的微结构光纤偏振分束器,并且利用全矢量有限元法仿真分析了该偏振分束器的长度与其结构参数的关系,进而得出了该偏振分束器长度随孔间距、占空比变化的一般规律。研究结果表明:当其他结构参数一定时,该偏振分束器长度会随着孔间距的减小而减短;占空比减小,偏振分束器长度也会随之减短。最终综合考虑其性能与金属材料带来的损耗的影响,设计出一种结构简单的微结构光纤偏振分束器。该偏振分束器长度为3.523 mm,在其工作波长1。55 m处消光比高达74.9 dB,消光比高于20 dB的波长范围为1.53~1.57 m之间的40 nm范围,覆盖了整个光通信的C波段范围。并且该偏振分束器有着较好的冗余特性,在偏振分束器长度存在5%的误差时,仍能保持较好的性能。     

Tunable Mach-Zehnder polarization splitter using height-tapered Y-branches

A tunable TE/TM polarization splitter, based on a Mach-Zehnder interferometer with an electrooptic switch, is demonstrated in GaAs-AlGaAs. Symmetric and asymmetric Y-branches employing height-tapered waveguides are used to achieve power splitting and mode sorting, respectively, in the interferometer. The device has an extinction ratio of /spl sim/20 dB and an excess loss less than 1.5 dB for both TE and TM polarized light. The device can be reconfigured by tuning the switching voltage for operation at both 1.3- and 1.55-pm wavelengths.     

双矩形纤芯光子晶体光纤偏振分束器

基于双折射效应设计了一种新颖的纤芯为椭圆空气孔,包层为圆形空气孔的矩形双芯光子晶体光纤偏振分束器。用半矢量光束传播法(BPM)数值模拟了基模情形下该偏振分束器的性能,结果表明:在工作波长为1.55μm,光纤长度为1659μm时,两个纤芯在X、Y方向偏振光的隔离度分别达到了-41.3 dB和-39.1 dB,隔离度小于-10 dB的带宽超过了80 nm,达到了良好的偏振分束性能。同时,模拟了实际加工误差对所设计的偏振分束器的影响,得出在1.55μm的工作波长下,误差达到±7%时,隔离度仍能小于-10 dB,具有较高的实际应用价值。     

双芯光纤的偏振分束特性研究

偏振分束器是光学中的重要器件,它将入射光按其偏振特性进行分离,它主要应用于需要对偏振态进行有效控制的光学系统中。微型化光波导偏振分束器已成为光通信领域的研究趋势。双芯光纤偏振分束器承接了双芯的特殊优势,是一类基于模式干涉的偏振分束器,根据耦合长度的不同将两种偏振态分离开来,这一类的分束器具有设计灵活、体型小、价格低廉、应用广泛等优点。本文基于椭圆芯双芯光纤,先从理论方面介绍了偏振分束的原理,再利用Rsoft软件模拟分析了x、y方向的耦合长度及其x、y方向的耦合长度差值随纤芯长短轴比例、入射光波长、纤芯包层折射率差、纤芯间归一化距离的变化趋势。最后,通过优化设计,获得了长度为22.29cm、消光比可以达到20dB以上的偏振分束器。     

超短双芯光子晶体光纤偏光分束器

提出了一种基于椭圆双芯光子晶体光纤的偏振分束器,并利用全矢量有限元法分析了偏振分束器长度与结构参数的关系,由此得出了偏振分束器长度随孔间距、占空比和桥路变化的一般规律。研究表明,当椭圆双芯光子晶体光纤偏振分束器结构参数一定时,孔间距越小,桥路宽度越宽,则分束器长度越短;占空比变化对长度影响不明显,但对消光比的影响较明显。进而,通过结构参数的优化,设计出一种超短的椭圆双芯光子晶体光纤偏振分束器,在工作波长1 550 nm处,该分束器的长度仅为0.775 mm,消光比高达50 dB,消光比大于20 dB的带宽覆盖了从1 535~1 565 nm之间30 nm的波长范围,即通信C波段范围。     

A novel waveguided polarization mode splitter using refractiveindex changes induced by superlattice disordering

The operating principle of our polarization mode splitter is based on the polarization-dependent refractive index changes induced by disordering InGaAs/InP superlattices. We disordered superlattices by the Si₃N₄ cap-annealing method and measured the near-field patterns to confirm that the device functioned properly at a wavelength of 1.52 μm. The crosstalk was about -10 dB. We should be able to improve the characteristics of this device by optimizing its structure. This device requires no electrical control and will be very suitable for semiconductor monolithic integrated circuits     

集成光学TM/TE模分离器的研制

用光束传播方法 (BPM )对集成光学无间隙指向耦合器型TM/TE模分离器的理论模型进行了仔细的分析 ,通过结构参数的优化 ,设计了一种模分离器 ,理论计算TM模和TE模分离比优于 40dB。同时制作了相应的器件 ,测试结果表明 :TM模和TE模分离比分别达到 2 8dB和 2 5dB。