光波导端面耦合自动调芯仪研制

设计了两种适用于光波导高精度对接耦合的自动调芯方案,这两种方案从原理上克服了常规调芯过程依赖于对微变信号精确测试的困难.提出了实现自动调芯的结构,完成了调芯系统的光机电一体化、相应的控制程序以及与计算机的接口界面.采用通信用单模光纤作为标准光波导做了端面耦合试验,自动调芯结果显示,在1310nm波长上,平均耦合损耗为0.075dB,标准误差为0.0099dB;在1550nm波长上,平均耦合损耗为0.062dB,标准误差为0.0066dB.自动调芯过程在2min内完成.     

玻璃基片上双层多模光波导的制备

在光学玻璃基片上制作了双层掩埋式多模光波导芯片,这种芯片中的上、下两层光波导均通过熔盐离子交换和电场辅助离子迁移形成。对光波导的横截面以及输出光斑进行了观察,并进行了损耗和串扰测试。研究结果表明:双层多模光波导芯片中上、下两层光波导芯部横截面尺寸分别为29 m19 m和31 m20 m;两层波导的输出光斑尺寸相互匹配;两层波导传输损耗分别为1.000.32 dB/cm和0.780.35 dB/cm;两层光波导之间的串扰在17.7dB左右。这种玻璃基片上的双层多模光波导可以使板级光互连的互连密度增大一倍,提高EOCB的性能。     

光纤耦合声光Ti:LiNbO3波导器件的研究

波导型声光调制器作为高功率全光纤调Q激光器中的调制器件,光纤与器件对接耦合损耗大是影响其性能的主要因素。通过分析波导端面的Ti条半宽度与光波导模场分布的关系,计算出Ti∶LiNbO3锥形光波导与光纤耦合损耗最小时对应的最佳Ti条半宽度。分析得到Ti∶LiNbO3波导端面的Ti条半宽度对耦合损耗的影响,以及光波导的不同切型对最佳Ti条半宽度的影响。     

高功率光纤放大器中光纤端面处理分析

光纤端而进行斜而抛光一直是高功率光纤放大器中抑制ASE和自激振荡的关键技术.根据放大器结构建立了光纤端面信号光注入、信号激光输出以及泵浦光耦合的物理模型,数值模拟了不同光纤斜端面角度下信号光、泵浦光的耦合效率,纤芯端而的回波损耗.结果表明信号光注入端而斜面处理会导致耦合效率降低,输出端面斜角处理可有效减小端面反射率,而微小斜角对泵浦激光进入光纤内包层的耦合效率影响不大;根据不同的光纤参数选择合理的斜角处理可以有效提高放大器性能.     

新型低损耗1×3光分路器的优化设计

针对传统Y分支光分路器损耗较大的缺陷，采用直锥形波导代替传统的直波导来减小器件的尺寸，并且采用激模波导结构设计1×3分支波导。设计中，利用辐射模和本征基模的叠加来修正光波场，通过改善模匹配来降低分支耦合损耗，并通过对对称输出弯曲分支波导的优化来降低弯曲损耗，最后在1×3光分路器中的两弯曲波导的输入端加入过渡锥形波导来降低损耗和优化分路器的输出均匀性，并用有限差分光束传播法对该1×3分支波导进行数值模拟。模拟结果表明，该结构具有均匀性好、器件尺寸小、损耗小和结构简单等优点，有利于器件的进一步集成。     

基于压电陶瓷的光开关结构设计与实验研究

提出一种新型的基于压电陶瓷以及微流控技术的阵列光开关,重点研究了该光开关波导层的光功率损耗.运用Opti-FIBER软件对波导层波导的耦合损耗进行了分析与仿真,实验测量了不同情况下光开关的耦合损耗.仿真及实验研究表明,该光开关理论最低插入损耗值为0.042 524 dB,光开关速度为100 μs.该光开关具有结构简单、...     

新型低损耗1×3光分路器的优化设计

针对传统Y分支光分路器损耗较大的缺陷,采用直锥形波导代替传统的直波导来减小器件的尺寸,并且采用激模波导结构设计1×3分支波导.设计中,利用辐射模和本征基模的叠加来修正光波场,通过改善模匹配来降低分支耦合损耗,并通过对对称输出弯曲分支波导的优化来降低弯曲损耗,最后在1×3光分路器中的两弯曲波导的输入端加入过渡锥形波导来降低损耗和优化分路器的输出均匀性,并用有限差分光束传播法对该1×3分支波导进行数值模拟.模拟结果表明,该结构具有均匀性好、器件尺寸小、损耗小和结构简单等优点,有利于器件的进一步集成.     

端面抽运双包层Nd:YAG平面波导激光放大器设计

设计了一种高效率、结构紧凑的高功率激光放大器。采用解析方法分析了对称结构Nd:YAG双包层平面波导增益介质的内部热应力,获得了其可承受的最大抽运光强。针对不同厚度的内包层结构,采用Trace Pro软件模拟分析得到了最佳的抽运源结构和耦合系统。为了便于进行激光模式控制,掺杂区厚度取为100μm。内包层和外包层分别为纯YAG和蓝宝石,整个波导尺寸为60 mm×10 mm×2 mm。半导体激光器阵列输出的抽运光从波导的两个端面进入,两个大面和铜热沉焊接来获得良好的散热条件。种子光从一个端面注入,单通放大输出。通过模拟计算,在3384 W的抽运功率下,进入波导芯层的种子光功率为0.1 W,放大输出功率可以到达1322 W,光光效率约为39%。     

光波导传输损耗测量新方法

详细介绍了一种测量光波导传输损耗的匹配液测量法.通过将波导插入折射率高于波导芯层的液体将光线耦合出波导,获得波导传输线上各点实际通过的光强,拟合出光强传输衰减曲线.与传统测量方法相比,本方法可对波导进行重复性测量,尤其适用于传输损耗低于0.1 dB/cm光波导的测量.     

聚合物波导光栅耦合器的衍射场仿真

为了实现横截面尺寸为50 m50 m的聚硅氧烷聚合物光波导的耦合转向问题,设计了一种表面覆盖高折射率包层的多层蚀刻光栅耦合器。首先,分析了影响聚合物波导光栅耦合器耦合效率的结构因素;然后,采用在光栅表面蚀刻高折射率层的方法,提高了聚合物波导光栅耦合器的耦合效率;接着,对不同的周期（范围:100~4 000 nm）和不同的蚀刻深度（范围:0~50 000 nm）进行排列组合,形成不同的光栅结构,基于时域有限差分法编写程序,遍历所有情况,得到不同光栅结构下的光场情况以及其耦合效率,找到使耦合效率最大的周期以及蚀刻深度。最后,设计了多层蚀刻的光栅耦合器,进一步提高耦合效率。当蚀刻深度为5 000 nm,光栅周期为2 600 nm时,带高折射率层的聚硅氧烷聚合物光波导均匀光栅耦合器的耦合效率达到最大,为17.2%。采用多层蚀刻的方式,对结构进行优化,其耦合效率能达到37.4%。为聚硅氧烷聚合物光波导在光互连中的实际应用提供了理论依据。     

Low‐Loss Compact Arrayed Waveguide Grating with Spot‐Size Converter Fabricated by a Shadow‐Mask Etching Technique

This paper describes a low‐loss, compact, 40‐channel arrayed waveguide grating (AWG) which utilizes a monolithically integrated spot‐size converter (SSC) for lowering the coupling loss between silica waveguides and standard single‐mode fibers. The SSC is a simple waveguide structure that is tapered in both the vertical and horizontal directions. The vertically tapered structure was realized using a shadow‐mask etching technique. By employing this technique, the fabricated, 40‐channel, 100 GHz‐spaced AWG with silica waveguides of 1.5% relative index‐contrast showed an insertion‐loss figure of 2.8 dB without degrading other optical performance.     

Design of a single-mode tapered waveguide for low-losschip-to-fiber coupling

The novel waveguide structures described in this paper have nonlinearly tapered shapes that result in low radiation losses despite their relatively short lengths. The core at the waveguide endface connected with the fiber has a very small cross section and an expanded mode field with a non-Gaussian shape. The taper structures are analyzed by using an improved step-transition method. This method is a based on the theory of enclosing a waveguide within electrical walls and that can therefore treat the radiation modes in a tapered waveguide as discrete mode spectra. Analyzing the relationships between the lengths and shapes of the tapers and the radiation loss due to the tapers show that appropriately tapered semiconductor waveguides operating at an optical wavelength of 1.55 μm and having a taper length of less than 0.7 mm can have a radiation loss of only 0.1 dB and a coupling loss with a conventional single-mode fiber of less than 0.5 dB     

Optical spot-size converters for low-loss coupling between fibersand optoelectronic semiconductor devices

Structures of spot size converters that allow low loss and easy coupling between an optical semiconductor device and a fiber are proposed and designed theoretically. These spot-size converters have a tapered small core for expanding the mode field. They also have a double cladding region which consists of an n⁺-doped InP substrate as the outer cladding and a p-doped or nondoped InP layer as the inner cladding with a ridge structure. This double cladding utilizes the plasma effect of a carrier which makes the refractive index of highly doped n-InP lower than that of p-doped or nondoped InP. The double-cladding structure can tightly confine an expanded mode field in the inner cladding, and results in low radiation loss at the tapered waveguide, in addition, this structure reforms the mode field shape into a Gaussian-like shape and achieves a low loss coupling of less than 1 dB with a large misalignment tolerance for fiber coupling. These spot-size converters are easily fabricated and applicable to all types of optical semiconductor devices     

A simple laterally tapered waveguide for low-loss coupling tosingle-mode fibers

Low-loss coupling between semiconductor photonic devices and single-mode fibers is achieved using a simple InP/InGaAsP tapered waveguide. The proposed simple structure has a small and nearly square guiding core at its output facet. In this structure, the output field has a non-Gaussian profile, but low-pass filter coupling can be achieved by optimizing the design of the guiding core sizes. The waveguide is composed of a laterally tapered InGaAsP guiding layer and an InP cladding region on an InP substrate, facilitating integration of the waveguide with active devices using conventional processes. The waveguide is shown to have a total insertion loss of 2.6 dB, including a coupling loss of 0.9 dB and large ±2.5-μm misalignment tolerance in lateral and vertical directions with single-mode filters     

Compact and low-loss arrayed waveguide grating module with tolerance-relaxed spot-size converter

A compact, low-loss arrayed waveguide grating (AWG) module was achieved by adopting a novel optical spot-size converter (SSC) to planar lightwave circuits (PLCs). The SSC is a laterally tapered waveguide that can be fabricated simply by the conventional fabrication process. The structure is composed of a core width converting region where the spot-size is converted efficiently, and a core width fine-tuning region where the cut-position tolerance is relaxed. We have applied this structure to a 1.5%-/spl Delta/ silica-based waveguides and reduced the single-mode fiber coupling loss to less than 0.5 dB/point. The SSC provides a large cut-position tolerance that enables angle polishing of the PLC endfaces to prevent reflection and low-loss connection of pigtail fibers. The center channel insertion loss of the AWG module was reduced from 4.2 to 2.2 dB, and the reflection was less than -60 dB.     

Tapered polymer single-mode waveguides for mode transformation

This paper presents a tapered polymer waveguide structure for coupling light between optical waveguides with differing geometries. Optical fibers, lasers, and other photonic integrated circuit components can be coupled with tapered waveguides. The polymer waveguide performs a mode transformation between different mode shapes and sizes. For example, the mode transformation can be from an elliptical laser diode mode to that of a circular optical fiber mode. The input and output of a tapered waveguide structure are analyzed, for the case of laser to fiber coupling, in order to determine the effect of misalignments on the coupling efficiency. Adiabaticity in waveguide propagation is discussed. The fabrication of our polymer waveguides is also described     

Index-and-dimensional taper and its application to photonic devices

A mode-field-converting optical channel waveguide with tapered refractive index and cross-sectional dimensions is proposed. In this waveguide, both the refractive index and cross-sectional dimensions of a core are adiabatically varied along a propagation direction in such a way that the normalized frequency V of the waveguide may be kept constant. Since radiation loss caused by waveguide imperfections is strongly dependent on the V value, the waveguide has good mode-field-converting capability without causing high radiation loss. Layer thickness and index of a core of a silica waveguide were tapered by modulating a raw material gas flow in a flame hydrolysis deposition method, and a channel width taper was formed by a photolithographical technique. In order to confirm the usefulness, taper waveguides have been used (1) to achieve good field matching between a fiber and a guided-wave optical switch, and (2) to fabricate a fiber-compatible monolithic 32×32 star coupler in a small chip     

Analysis of optical properties of fundamental-mode in waveguide tapered fibers

An analysis of optical properties of fundamental-mode in waveguide tapered fibers is theoretically investigated and realized in this paper. The waveguide device is tapering an SMF-28 fiber to few tens of micrometers of diameter. For discussing the cladding size of waveguide structure affects the fundamental-mode cutoff (FMC) and the optical characteristics of the devices, to etch outer cladding to reduce the pure-silica cladding diameter proceeded and to compare optical properties of FMC with non-etched cladding tapered fibers. Numerical results show the cutoff wavelength of FMC is mainly dominated by the size of squeezed core and slope of FMC could be influenced by the size of pure-silica cladding.     

Analysis of the coupling characteristics of a tapered coupledwaveguide system

Optical coupling characteristics between one uniform waveguide and one tapered waveguide are discussed. This coupling structure is analyzed by utilizing coupled-mode theory and system step approximation. Based on numerical investigation, various coupling characteristics are presented. It is shown that the proposed structure can be used as a waveguide-type optical power divider by selecting an appropriate taper slope for the tapered waveguide or by separating the coupled waveguides properly for a desired power-dividing ratio     

阵列集成光波导应用于光学相控阵中的理论分析

基于光学相控阵理论和钛扩散铌酸锂光波导的导模特性,提出了一种新型阵列集成光波导应用于光学相控。根据光束传输法（BPM）,并结合现有半导体工艺水平及参数,对该阵列波导的导光特性,损耗特性以及耦合特性进行了仿真计算,最终给出了相控阵的结构设计参数。结果表明,应用该集成阵列波导的光学相控阵结构可实现光束连续精确定向偏转,偏转角度可达4.5,相位控制半波电压小于6 V,其系统光学控制单元损耗低且响应速度快。