全光纤激光相干合成实验研究

设计了由两支光纤激光器组成的迈克尔逊型全光纤激光器阵列.通过实验,分析输出光束的耦合相干性,分析两泵浦激光器泵浦功率比对耦合效率、泵浦效率及输出功率的影响,分析所设计的光纤激光器阵列的稳定性.结果表明:激光器阵列的输出功率等于子光纤激光器输出功率的相干合成,耦合效率相对稳定;未达到增益饱和的情况下,泵浦效率和输出功率均与泵浦功率比成递减关系.     

空间光-光纤阵列耦合自动对准实验研究

为了使空间光-光纤耦合结构具有一定的抗抖动能力,采用自聚焦透镜和多模光纤耦合阵列结构结合模拟退火算法对光纤阵列实行2维控制,自动搜寻空间光-光纤耦合最佳视轴对准姿态。对光纤阵列和模拟退火算法进行了理论分析实验验证,取得了耦合效率变化的相关数据。结果表明,通过模拟退火算法可以实现空间光-光纤视轴对准,且光斑中心在耦合端面中心抖动小于2.5mm时,耦合功率波动小于35%,满足无线激光通信系统的要求。     

光纤阵列中纤芯间距的检测系统

在光通讯器件中,由光纤阵列和光波导封装而成的光波导分路器芯片,有着广泛的应用.光纤阵列与光波导封装的关键技术在于实现光纤阵列与光波导的低损耗耦合.然而,光纤阵列中纤芯分布的均匀性将会直接影响到耦合的性能,因此,需要对光纤阵列的纤芯分布进行检测,以选择分布均匀的阵列用于和光波导的耦合.系统利用显微视觉和纳米微驱动平台搭建...     

半导体激光二极管的光纤耦合技术

将半导体激光二级管（LD）发出的光更高效地注入到光纤中是光纤激光器与光纤放大器研究的先决条件.半导体激光二级管包括二极管单管、条形巴、二维堆栈和二极管阵列等,其各自的耦合技术之间有联系也有区别.分析介绍了有代表性的柱状楔形法、V型槽法、微透镜法等二极管单管与光纤的耦合技术;光纤束耦合法、光束整形法等二极管条形巴与光纤的耦合技术;以及二极管二维堆栈和二极管阵列与光纤的耦合技术等各种光纤耦合技术,比较了这些方法之间的共通点,供今后的研究人员选择和参考.     

大功率半导体激光器二维阵列光纤耦合技术

介绍了大功率半导体激光器二维阵列的光纤耦合技术,其中有整形耦合法、偏振合束法和波长合束法.用光线追迹法进行了二维阵列的光纤耦合模拟,对结果进行了分析,提出了改进办法,为进一步开展二维阵列的光纤耦合工作提供了有益的借鉴.     

与光纤阵列耦合的微透镜阵列设计与损耗分析

设计了2种不同冠高的圆形微透镜阵列，将平行光耦合进16路单模光纤阵列和多模光纤阵列。每种微透镜阵列均由16个直径为120pm的平凸微透镜排成一行组成，相邻微透镜间距为127μm。模拟其成像特性知，2种微透镜可以将平行光会聚成在其像平面直径分别为8．0μm和32．5μm的光斑。分析了微透镜与光纤存在横向、纵向和角向误差3种位置失配时的耦合损耗，并得出对耦合损耗影响最大的因素是角向误差，由此得出：在微透镜与光纤耦合对准过程中，要注意减小角向误差。     

大气湍流中透镜阵列的空间光耦合效率研究

比较研究了基于Von Karman折射率谱下大气湍流中单透镜和与单透镜直径相同的透镜阵列的空间光到单模光纤耦合效率,并给出了相应表达式。设计了小口径透镜阵列的空间光-单模光纤耦合结构,证明采用阵列中每个透镜直径是空间相干半径2~3倍的结构具有最好的耦合效果。理论分析和实验结果表明:当通信距离足够远时,透镜阵列的耦合效果优于等口径耦合效果单透镜。     

微结构空心POF与单模石英光纤的耦合

为了解决包层为蜘蛛网结构的空心塑料光纤(POF)与单模石英光纤的耦合同题,采用了在两根光纤间插入倒锥透镜型光纤端头的方法,分析了光线在该光纤端头中的传播过程,并对其进行了数值仿真,计算出了耦合效率.给出了光纤端头的最佳耦合长度.     

基于微透镜阵列的高效率光纤耦合系统设计

光纤耦合是半导体激光器集成光源进一步改善输出光束质量和远距离传输的重要手段。然而,由于半导体激光器单管体积和散热的限制,合成后激光光源的输出光束光参量积仍较大,不利于与单根多模光纤的耦合;直接与光纤束耦合又受到光纤束填充比的限制。针对多个半导体激光器单管集成的光源,采用倒置前端光学放大系统,对合成光束直径进行压缩;并采用六方排列的微透镜阵列作为耦合元件,使其光瞳成像在光纤端面,从而实现微透镜与光纤的一对一耦合,得到理论无损耗的高效光纤耦合系统。为了改善光场边缘像差影响,采用空心光管进一步匀化光场分布,且减小了边缘光线的发散角,提高了边缘光线的成像质量,优化后的系统耦合效率达98%。这一系统利用微透镜阵列将光束分束、成像,克服了集成光源输出光束光参量积较大不易与单根光纤耦合的缺点;通过使微透镜的入瞳成像在光纤端面,且光纤束的排列与微透镜阵列排列相同,提高了光束与光纤束的耦合效率。     

980nm InGaAs应变量子阱激光器及组合件

利用分子束外延技术研制出了高质量InGsAs/GaAs应变量子阱材料及量子阱激光器.脊形波导窄条形量子阱激光器的阈值电流和微分量子效率分别为15mA和0.8 W/A,线性输出功率大于150mW,基横模输出功率可达100mW.InGaAs应变量子阱激光器和单模光纤进行了耦合,其组合件出纤光功率典型值为40mW,最大值可达60mW.显示出了高的基横模输出功率和高的耦合效率.其组合件在40～60mW下,中心发射波长在977nm.满足了对掺铒光纤高效率泵浦的波长要求,成功地研制出适于掺铒光纤放大器用的应变量子阱激光器.     

Mode Converters for Coupling to High Aspect Ratio Silicon-on-Insulator Channel Waveguides

The design, simulation, and experimental performance of mode converters for coupling from single-mode silicon-on-insulator ridge waveguides to high aspect ratio channel waveguides are described. The converters consist of a two-level adiabatic taper structure. The final channel waveguide is 1.5 mum high by 0.8 mum wide. Simulations predict that for total coupler lengths longer than 20 mum, the coupling loss from the fundamental ridge mode to the slit mode is better than -0.2 dB. The couplers and waveguides were fabricated using a two-step self-aligned process. The measured coupling loss for fabricated mode converters is -0.4 dB     

A compact two-dimensional grating coupler used as a polarization splitter

We demonstrate a novel polarization splitter based on a two-dimensional grating etched in a silicon-on-insulator waveguide. The device couples orthogonal modes from a single-mode optical fiber into identical modes of two planar ridge waveguides. The extinction ratio is better than 18 dB in the wavelength range of 1530-1560 nm and the coupling efficiency is approximately 20%. The device is very compact and couples light only to transverse-electric modes of the planar waveguides. Therefore, it may be used in a polarization diversity configuration to implement a polarization insensitive photonic integrated circuit based on photonic crystal waveguides.     

Milled-groove method for fiber-to-waveguide couplers

We report a simple milled-groove process integrated with a two-step ion-diffused waveguide fabrication for efficient coupling between single-mode fibers and integrated optical waveguides andY- branches. We demonstrate such a coupling technique using a) a multimode transition to single-mode waveguide coupler, and b) an integrated optical 3-dB branching waveguide coupler from a single-mode fiber to silver/sodium ion-enchanged waveguide components. The coupling loss was about 1-2 dB over a propagation length of 2 cm at an operating wavelength of 633 nm.     

Efficient single-mode fiber to titanium diffused lithium niobate waveguide coupling for λ = 1.32 µm

We report detailed results on the achievement of very high optical throughput for titanium diffused lithium niobate waveguides coupled between input and output single-mode fibers. By determining appropriate diffusion parameters to obtain excellent dimensional match between the fiber and waveguide modes and simultaneously low propagation loss, we have achieved total measured fiber-waveguide-fiber insertion loss as low as 1 dB for a 1 cm long waveguide atlambda = 1.32 mum. The relative contributions of coupling and propagation loss are determined. Very good correlation is found between the coupling loss and the match between the fiber and waveguide mode dimensions. Design data for diffusion parameters to obtain good mode match for arbitrary fiber dimension are presented.     

基于有限元法分析设计双奇异脊波导

本文应用电磁场有限元法分析了双奇异脊波导的传输特性,编程分析计算了不同横截面的双奇异脊波导的主模工作带宽。并比较了脊的尺寸和间距不同时,其主模截止波长和单模带宽的变化规律,得到了相应的数值解。讨论了网格划分对计算结果的精确度的影响。为双奇异脊波导的设计和研究提供了参考。     

Size influence on the propagation loss induced by sidewall roughness in ultrasmall SOI waveguides

Silicon-on-insulator (SOI) optical waveguides with high electromagnetic field confinement suffer from sidewall roughness which is responsible for strong scattering effects. This letter reports a numerical investigation on the size influence of ultrasmall SOI waveguides on the propagation loss due to sidewall roughness. It is shown that for a size smaller than 260 /spl times/ 260 nm the roughness-induced propagation loss decreases. As the optical mode confinement is reduced, a very low loss light coupling from and to a single-mode fiber can be achieved with propagation loss as low as 0.5 dB/cm for a 150 /spl times/ 150 nm cross-sectional waveguide.     

Optical directional coupler using deposited silica waveguides (DS guides)

A new optical directional coupler using embedded single-mode glass waveguides is presented. The glass waveguides, called deposited silica waveguides (DS guides), were fabricated by depositing doped glass on a silica substrate after forming grooves by reactive sputter etching. Waveguide transmission loss was measured to be 1.3 dB/cm, and fiber-to-waveguide coupling loss was 0.1 dB. Using a tunable monochromatic light source, 96 percent power transfer or 14 dB isolation was measured. The DS guide directional coupler is compatible with single-mode fiber and is expected to be a useful component for future wavelength division multiplexing transmission systems.     

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     

Eigenmodes of sectoral coaxial ridged waveguides

The results of numerical investigation of sectoral coaxial ridged waveguides eigenmodes of two configurations (with a ridge on inner or outer wall) for different cross-section dimensions are presented. In particular, dependences of cutoff wave numbers on geometrical dimensions ratios for first four modes are investigated, electric field components distributions for these modes have been obtained and the optimization of sectoral coaxial ridged waveguides has been carried out to provide maximal single-mode operation frequency band. Two optimal configurations of waveguides with single-mode operation bandwidth ratio 5.6:1 are obtained. It is shown that smaller cross-section dimensions at the fixed single-mode operation frequency band has the waveguide with the ridge at the inner round wall. The size of the gap between the ridge and the round wall of optimal waveguide is identical for both configurations and is determined by the required ratio of cutoff frequencies of two lower TE modes. Calculations are conducted utilizing the mathematical model obtained in [1] by the integral equation technique with the correct account of singular behavior of the field at the ridge.     

Two-mode interference photonic waveguide switch

Based on the two-mode interference principle and the free-carrier plasma dispersion effect, a two-mode interference (TMI) photonic waveguide switch with double carrier injection has been designed and fabricated for application in fiber-optic communications. It consists of an input Y-branch with single-mode ridge waveguides, a TMI waveguide coupling section, and an output Y-branch with single-mode ridge waveguides. The single-mode waveguides and the two-mode waveguide are composed of a SiGe waveguide layer on a Si substrate. The width of the TMI region of the switch is two times that of the single-mode waveguide. On the top of the TMI region and one side of the TMI region, two abrupt p-n junctions are made to inject the carriers into the optical modulation region; on the other side of the TMI region, an abrupt carrier collection region is made to collect the carriers when they are forward biased, so that the double carrier injection photonic waveguide switch has the lowest injection current density. The waveguide layers are made of SiGe/Si material, and the rib waveguides are realized by reactive ion etching. The carrier injection regions and the carrier collection region are formed by ion implantation. The input and output facets of the waveguides were ground and polished by a mechanical method. The switch was characterized by using a 1310-nm InGaAsP/InP heterostructure laser diode. Its insertion loss and ON-state crosstalk were measured to be 2.74 and -15.5 dB, respectively, at a total switching current of 110 mA. The switching time is 180 ns, and the fastest switching time is up to 30 ns.