Quasi planar spot-size transformer for efficient coupling between acleaved fibre and an InP/InGaAsP rib waveguide

A spot-size transformer structure is proposed for InP/InGaAsP double-heterostructure (DH) rib waveguide. Vertical expansion of a factor of 7 is achieved with 3 dB internal loss. Coupling from standard cleaved fibre (11 μm diameter mode) to a DH rib waveguide (5.8×0.8 μm large mode), is achieved with 4.5 dB polarisation independent loss. Coupling tolerances are highly relaxed. The fabrication method uses a thin cladding layer which ends up to a quasi-planar structure suitable with further integration process     

有双包层结构的楔变脊型光斑转换器的设计

为了提高硅基上单模波导器件与单模光纤的耦合效率和工艺容差,设计了一种实用新型光斑转换器,它由水平和垂直双向楔变的波导芯区和双内包层构成.分析了内包层折射率与其厚度对耦合效率的影响,发现通过优化内包层的参数可以加强对扩展光场的限制.针对在硅基上制作垂直楔变结构的波导还很困难的情况,提出了一种低成本、简单可行的制作方法.     

Monolithic integration of DFB laser with spot-size transformer forhighly efficient laser fibre coupling

The monolithic integration of a mushroom type InGaAs-InGaAsP MQW DFB laser with a spot-size transformer based on a two-layer lateral taper is reported. Highly efficient coupling to a butt-joined dispersion shifted singlemode fibre with a coupling loss down to 0.9 dB and large alignment tolerances was achieved, maintaining the good spectral characteristics of an isolated DFB-laser structure     

Polymeric buried core adiabatic optical spot-size transformer

Design, fabrication and characterisation of a polymeric optical spot-size transformer formed by a laterally tapered, buried core is described. Only standard photolithography and dry etching have been used to fabricate this transformer. A fibre to waveguide insertion loss of 0.7 dB has been measured, compared to 2.5 dB without the transformer     

Low-loss spot-size transformer by dual tapered waveguides (DTW-SST)

The reduction of the insertion loss of a spot-size transformer based on dual tapered waveguides (DTW-SST) by controlling the shape of the tapered portion is discussed. The transformer is easily fabricated using a shadow mask sputtering method. A method is described for controlling independently the parameters of the tapered portion, such as the maximum taper angle, and length, and the position of tapered portion with respect to the edge of the shadow mask. A large transformation ratio (5 and 1/5) and a low insertion loss (0.7 dB) have been obtained     

Low-loss fibre-chip coupling by buried laterally tapered InP/InGaAsP waveguide structure

A passive InP/InGaAsP spot-size transformer for low-loss coupling of semiconductor optoelectronic devices to single-mode fibres has been fabricated entirely on InP. Using a buried two-layer laterally tapered section, spot-size transformation is demonstrated from below 2 mu m up to 8 mu m, the spot size of a dispersion-shifted fibre at 1550 nm. For a chip without antireflection coating a total insertion loss of 2.7 dB was achieved at a taper length of approximately 600 mu m.<>     

Rib waveguide spot-size transformers: modal properties

Efficient spot-size convertors are an essential component of modern integrated optoelectronics, providing a simple and reliable interface with fibers. One recently proposed design functions by forcing the field from a small spot rib waveguide into a large spot one by using a taper. Accurate models of these structures, and a clear understanding of the coupling mechanisms they rely upon, are essential if optimized designs are to be produced. Furthermore, it is necessary to develop analysis techniques which are accurate yet not computationally intensive, suitable for use within an iterative design environment. Here, the well known and proven spectral index method is extended to efficiently analyze this class of vertically coupled rib waveguide spot-size transformer, providing both the guided modes and for the first time, the substrate radiation modes of the structure. These modes can then subsequently be used to design and determine the performance of the full tapered structure     

多功能2×2 GaAs/GaAlAs多模干涉型光开关分析

提出了一种基于深刻蚀脊形光波导带模斑转换器的多功能2×2 GaAs/GaAlAs多模干涉型光开关,并用变量变换级数展开法及三维有限差分束传播法对其进行了模拟分析与优化设计.结果表明,通过控制多模波导中央的两段Schottky电极,器件可实现交叉态、直通态及3dB耦合器功能,并有较大的制作容差、较宽的工作带宽,只须一个多模波导,器件结构紧凑.采用深刻蚀脊形光波导能够满足多模干涉型器件的精确自镜像要求,并使输入/输出光波导在单模工作下有较大的横截面,较低的弯曲损耗及较小的耦合串扰.通道末端引入的模斑转换器可方便地与单模光纤连接耦合.     

1.55-/spl mu/m spot-size converter integrated laser diode with conventional buried-heterostructure laser process

A 1.55-/spl mu/m spot-size converter integrated laser diode is demonstrated with conventional buried-heterostructure laser process. For the spot-size converter, we employed a double-waveguide structure in which a ridge-based passive waveguide was incorporated. The passive waveguide was optically combined with a laterally tapered active waveguide to control mode size. The threshold current was measured to be 5 mA together with high slope efficiency of 0.45 W/A. The beam divergence angles in the horizontal and vertical directions were as small as 9.0/spl deg/ and 7.8/spl deg/, respectively.     

使用传统工艺实现1.55μm激光器与模斑转换器的单片集成

采用传统的光刻和湿法腐蚀工艺制作了1.55μm波长的新型半导体激光器和模斑转换器的单片集成器件.其中激光器采用脊型双波导,模斑转换器采用掩埋双波导结构,水平楔型的有源波导和宽而薄的无源波导同时控制光斑模式大小.实验测得器件的阈值电流为40mA,斜率效率为0.35W/A,水平和垂直方向的远场发散角分别为14.89°和18.18°,与单模光纤的耦合损耗为3dB.     

Multiquantum-well lasers with tapered active stripe for direct coupling to single-mode fiber

We demonstrate narrow beam divergence in 1.3-/spl mu/m wavelength multiquantum-well (MQW) lasers with an active stripe horizontally tapered over the whole cavity, for direct coupling to single mode-fibers. The lasers have reduced output beam divergence in a simple structure which does not contain an additional spot-size transformer. The fabricated laser shows narrow beam divergence of /spl sim/12/spl deg/, while a low-threshold current of 6.9 mA and a high efficiency of 0.62 mW/mA are realized. Furthermore, a direct-coupling efficiency to a single-mode fiber is -4.0-dB and -3-dB alignment tolerance is /spl plusmn/2.5 /spl mu/m.     

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     

基于电流纹波率反激式变压器导通模式的分析

提出了利用电流纹波率设计反激式变压器和判别其导通模式的方法,用该方法导出了反激式变压器从CCM进入DCM模式的数学式,用MATLAB计算并分析了输入电压、负载电流及反射电压对导通模式的影响。设计了一款反激式开关稳压电源,测量了变压器的电流波形。实验表明,测量结果与推导的数学式相符,用电流纹波率设计反激式变压器比传统的波形系数更直观和便于测量。     

Optimization design of an electroabsorption modulator integrated with spot-size converter

In the recent years ,the electroabsorption modulator(EAM) is attractive as anexternal modulator because ofits many features ,such as low power consumption,lowdrive voltage,small size,large bandwidth,polarization-intensity and potential for monolithic integration withother components[1-3].An optical device integrated witha spot-size converter(SSC) has been paid more attentionfor its direct couplingto an optical fiber without using amicro-lens or tapered fiber[4].EAMintegrated with anSSC(EA…     

半导体激光器电吸收调制器和双波导模斑转换器的单片集成

报道了1.6μm的半导体激光器和电吸收调制器以及双波导模斑转换器的单片集成器件.该器件具有良好的单横模特性和准单纵模特性(边模抑制比达25.6dB),3dB调制带宽为15GHz,直流消光比为16.2dB,远场发散角为7.3°×18.0°,和单模光纤的耦合效率达3.0dB.     

Direct method of determining equivalent-step-index profiles for monomode fibres

A new technique for measuring equivalent-step-index profiles of monomode fibres is presented which involves measuring the mode spot-size directly as a function of wavelength, and compares favourably with measured profiles. Since characterisation of the fibre is derived from easily measured optical properties, knowledge of the actual profile and the modelling of the propagation characteristics from it is unnecessary.     

硅基波导用楔形模斑变换器的研究进展

楔形模斑变换器在利用硅基光子集成技术实现芯片间光互连中有着广泛的应用.文章概述了国内外楔形模斑变换器的最新研究进展.介绍了几种新型模斑变换器的结构及制作的工艺流程,并对其性能及影响楔形模斑变换器耦合效率的几个因素进行了分析比较,进而讨论了这几种模斑变换器存在的问题及进一步提高耦合效率的可能性.     

Tolerance Requirements for Dispersion Free Single-Mode Fiber Design: Influence of Geometrical Parameters, Dopant Diffusion, and Axial Dip

The dispersion sensitivity to small changes in index-differences, radius, and wavelength is investigated in the case of dispersion free single-mode fibers. If a minimum bandwidth is required, tolerances on the various parameters can then be deduced: singly- and doubly-clad structures are compared. Constant reference is made to the HE/sub 11/ mode spot-size to relate dispersion properties and attenuation. A nonzero fundamental mode cutoff is shown to induce an enhanced sensitivity to a change in fiber geometrical characteristics. The effect of dopant diffusion and axial dip on dispersion is then considered and conclusions are drawn concerning the use of profiles measured on preforms to predict fiber propagation properties.     

Fully Symmetrical Monolithic Transformer (True 1 : 1) for Silicon RFIC

A novel on-chip transformer configuration that gives an identical inductor pair, a higher individual coil self-resonant frequency (SRF), and excellent area efficiency are presented. This technique involves the unique way of inter-crossing the transformer's primary and secondary coils using multiple metallization layers. Truly symmetrical transformer configuration (100%) is demonstrated using minimum die size. Thus, a true 1 : 1 transformer has been realized on silicon. The effects of the parasitic within the transformer are represented by an equivalent-circuit model. Accurate semiempirical expressions describing the circuit components are provided based on the various layout parameters. Of all the transformer structures presented, the two designs occupying the minimum silicon area by a factor of > 2× have been selected for performance evaluation of the SRF, coupling coefficient, input impedance, quality factor, and inductance. The transmission line transformer mode has also been studied to examine the designs' performance in the differential mode. The second proposed design reported in this paper, with enhancements in S21 and k performance, is created by adding a unique routing technique onto the first proposed structure. The method presented is fully compatible with the standard foundry CMOS processes. The silicon data reported in this study are based on chartered semiconductor manufacturing's 0.13-mum RF CMOS technology node.     

Analyzing the polarization dependence in optical spot-sizeconverter by using a semivectorial finite-element beam propagationmethod

This paper describes a semivectorial wide-angle finite-element beam propagation method (FE-BPM) that uses the Pade approximation and that can allow efficient and accurate analyzes of the polarization dependence in arbitrary step-index optical waveguide devices. It also reports the use of this method to analyze the polarization dependence of coupling loss between a semiconductor tapered-waveguide spot-size converter and a single-mode optical fiber. It is shown that semiconductor spot-size converters having cores with a small cross-section provide low-loss and polarization-insensitive coupling to flat-end fibers. A low-loss (far less than 1 dB) and completely polarization-insensitive spot-size converter can be made using a lightly n-doped InP substrate for the tapered waveguide. These spot-size converters are consequently potentially useful for making polarization-insensitive semiconductor optical devices such as optical amplifier gate switches