光纤耦合波导器件中光波导深度的研究

声光波导光开关可以作为高速光通信网络中的开关器件,其中光纤-器件对接耦合损耗大是影响其性能的主要因素.从光波导模场椭圆度和不对称度对模场失配引起的耦合损耗出发,计算Ti:LiNbO3波导与光纤耦合损耗最小时对应的最佳Ti离子扩散深度.分析得到不同切型的Ti:LiNbO3,波导中扩散深度、光纤模场半径对耦合损耗的影响.结果表明,y切Ti:LiNbO3波导耦合损耗约为z切波导的3倍.研究结果为共面型声光波导调制器中光波导制作参数的设计提供帮助.     

光致折变Taper光纤耦合器的耦合波分析

研究利用光纤中光致折变效应研制的光纤波导折射率沿轴向渐变的Ｔａｐｅｒ器件的模式耦合特性．在标量场近似下，用本地模表示的方法分析在阶梯折射率分布光纤和平方律折射率光纤的轴向折射率渐变过渡结构中传输的基模向反向散射模和高价模的耦合。对阶梯折射李光纤两种不同折射率Ｔａｒｅｒ结构的数值计算结果表明：在折射率变化相对缓慢情况下，这种折射率Ｔａｐｅｒ耦合器的基模反向散射和向高阶模的耦合都很小；基模能够自适应地调节以适应波导折射率的渐变，具有优良的传输性能．     

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。     

部分填充双各向异性介质的圆柱形波导中混合模特性研究

本文首先引入一种新型双各向异性波导结构;给出了这类复杂波导中横向场分量的纵向场表示式以及纵向场分量满足的一组耦合模方程;重点分析了具有不同电磁参数的双各向异性介质中心加载时,金属圆柱形波导中混合模的分裂效应,色散特性和场分布。结果表明,由于多个电磁参数的引入,双各向异性波导具有一般各向异性和双各向同性波导结构所没有的新奇特性。     

微纳纤芯/包层结构大模场单模聚合物光纤设计

提出了一种微纳纤芯/包层结构大模场单模聚合物 光纤。建立了光纤结构模型,在非 弱导近似条件下,根据波导理论,分析了微纳光纤的单模和波导特性;讨论了微纳纤芯直径 、 芯/包层折射率差以及包层直径等结构参数对微纳纤芯/包层结构聚合物光纤的模场分布、有 效 模场直径等导波特性的影响。结果表明,在传输波长λ＝650nm、微纳纤芯直径Dcore＝172μm、包层 直径Dclad＝250μm和芯/ 包层折射率差δn=0.128时,可获得有效模场直径达126.56μm和芯内能流比为10.66% 的大模场单模聚合物光纤。     

应用于Ⅲ-Ⅴ族半导体光调制器的模斑变换器设计

半导体光调制器波导的输出模斑通常是直径为2～3μm的椭圆形,与光纤进行耦合时会因模斑不匹配而产生严重的耦合损耗,并影响对准容差.为降低光纤与调制器波导的耦合损耗,同时改善对准容差,设计了两种应用于光调制器中的模斑变换器(Spot-size Converter),通过仿真对其传输损耗和模场耦合效率进行了比较,其中采用混合结构的模斑变换器具有更优的性能.     

部分填充各向异性介质的圆柱形波导中混合模特性研究

本文首先引入一种新型双向向异性波导结构；给出了这类复杂波导中横向场分量的纵向场表示式以及纵向场分量满足的一组耦合模方程；重点分析了具有不同电磁参数的双各向异性介质中心加载时，金属圆柱形波导中混合模的分裂效应，色散特性和场分布。结果表明，由于多个电磁参数的引入，双各向异性波具有一般各向异性和双各向同性波导结构所没有的新奇特性。     

平面光波导与光纤的低损耗耦合

文章提出一种新型的波导结构,该结构通过改变波导芯在宽度和长度方向的截面形状和大小,借此来改变波导中光束的模场分布,有效地降低了波导与光纤间的耦合损耗,提高了产品性能。此外,该波导结构生产制造相对简单,易于大规模生产。     

超辐射LD与带类球透镜保偏光纤的耦合技术

采用高斯模场近似和模场匹配方法,对超辐射激光二极管与带类球透镜单模熊猫型保 偏光纤的耦合,进行了仿真计算和实验研究。分析了耦合效率与光源激发的光模场、光纤结构及光纤头部形状、耦合工作参数等因素的关系。通过改进耦合技术获得了较高的耦合效率。     

双折射波导偏振耦合的短相干干涉测量

保偏光纤内部具有的高双折射,使其在内部传播的主模和耦合模之间存在一定的光程差。研究了高双折射波导中连续偏振耦合分布和分立点耦合的白光干涉测量法,推导出一种简明使用的公式,求出双折射波导的保偏参数,并且根据调制解调相关原理精确测量耦合点的强度和位置。实验测量了国产类矩形保偏光纤以及光纤偏振器。该方法最突出的优点是采用非破坏性方法测出保偏波导的每个局部的保偏参数,可用于检测集成波导器件和保偏光纤的质量、双折射波导之间的主轴对准、分布式光纤应变传感器等领域,并且可作为保偏光纤生产和使用的一种有效检测方法,大大提高集成波导器件及相关传感器的性能。     

Theoretical study of annealed proton-exchanged Nd:LiNbO3channel waveguide lasers with variational method

The controllable fabrication parameters, including anneal time, initial exchange time, channel width, dependences of TM₀₀ mode size, corresponding effective refractive index, effective pump area, and coupling efficiency between pump and laser modes in z-cut annealed proton-exchanged (APE) Nd:LiNbO₃ channel waveguide lasers were studied by using variational method. The effect of channel width on the surface index increment and the waveguide depth was taken into account. The features of mode size and effective refractive index were summarized, discussed, and compared with previously published experimental results. The effective pump area, which is directly proportional to threshold pump power, increases strongly, slightly, and very slightly with the increase of anneal time, channel width, and initial exchange time, respectively. However, the coupling efficiency, which is directly proportional to slope efficiency, remains constant (around 0.82) no matter what changes made to these parameters. The variation of the coupling loss between an APE channel waveguide and a fiber with these parameters for both laser (1085 nm) and pump (815 nm) wavelengths was also calculated. The calculated results indicate that the coupling loss decreases rapidly, slightly and very slightly with the increase of anneal time, channel width and initial exchange time, respectively     

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.     

缓冲质子源LiNbO3波导折射率计算及实验

为实现铌酸锂退火质子交换(APE)波导折射率分布的准确计算,选择含苯甲酸锂的苯甲酸缓冲液作为质子交换质子源,高温退火制作了波导样本.针对该工艺过程建立退火质子交换波导模型,包括非线性扩散模块和光学数值仿真模块,分别计算APE波导折射率及其模式有效折射率.以测得的样本波导模式有效折射率和计算的有效折射率差的均方根构建评价函数(FOM),结合遗传算法提取该工艺条件下质子扩散参数,实现了不同交换深度和退火时间波导折射率分布及其光学特性的一体化计算.实验表明:FOM小于0.001,计算折射率分布同IWKB方法测得结果吻合较好,最大偏差约0.002.     

Characterization of annealed proton exchanged LiNbO3waveguides for nonlinear frequency conversion

A thorough and detailed characterization of annealed proton-exchanged (APE) waveguides in Z-cut LiNbO₃ is described. The mode index measurements in planar waveguides as a function of wavelength and annealing time are reported, including useful analytical relations for the refractive index change, its dispersion, and the depth profile as a function of annealing parameters. Analytical expressions for the mode propagation characteristics are presented and experimentally verified with reasonable accuracy. It is shown that the planar waveguide characterization results can be used to model the channel waveguide characteristics accurately. The model provides closed-form expressions for the mode index and the mode field profile, and the theoretical results are in excellent agreement with the measured data. The technique is used to accurately predict the phase mismatch between the fundamental and second harmonic modes in frequency-doubling experiments using APE channel waveguides. An optimum waveguide geometry for which the phase mismatch is relatively insensitive to the waveguide nonuniformity was predicted and verified experimentally     

不同切型质子交换弯曲波导的弯曲损耗研究

退火质子交换铌酸锂光波导是一类重要的光波导。对2种不同切型的3种常用S形弯曲质子交换光波导,利用宽角有限差分光束传播法进行了分析。结果表明,3种弯曲波导的弯曲损耗,随波导结构参数的变化基本上是相同的,而在相同的波导结构参数下,X切型的质子交换光波导的弯曲损耗总体上都要小于Z切型的质子交换光波导。数值计算结果为相应波导器件的设计和制备提供了一定的参考。     

新型的可调谐微环谐振器的设计

为了改进微机电系统中的传感器应用范围和特性参数,采用微纳光纤制作了环形谐振腔结构,设计的结构具有尺寸小、损耗低,品质因素高等优点。理论上分析了微纳光纤的光传输模式特性,通过电场的传数矩阵推导了谐振腔中的速度变化与光强变化间的关系,得到了加速度作用下微环谐振腔的谐振波长、周长、有效折射率的变化值间的函数关系。仿真结果分析表明:设计的微环波导电场波动明显,耦合效率较好;光谱强度和3 dB带宽变化较小,Q值达到104;在质量块每增加10 g时,输出光谱图约向右漂移3 nm;加速度与谐振波长漂移量基本呈线性关系,可以通过谐振波长的漂移量来实现对加速度的测量。研究结果能够为全光网络和微机电系统提供实现多种功能的光波导器件。     

硅包层质子交换条形光波导的频率响应

退火质子交换工艺已成为一种制备低损耗铌酸锂光波导的重要技术.但目前对该类光波导传输特性的研究还不多.利用半矢量光束传播法,对硅包层X切退火质子交换铌酸锂条形光波导的频率响应特性进行了数值分析.给出了几种波导结构参数下的计算结果.结果表明,波导传输模式的衰减特性与波长相关.波导的衰减特性,可以通过调整波导表面中心处折射率增量,硅包层厚度,及缓冲层的折射率和厚度来控制.硅包层光波导可以用来制作光频滤波器.     

Non-polarization and high-coupling-efficiency coupler using multilevel grating structure

A multilevel grating coupler based on silicon-on-insulator (SOI) material structure is proposed to realize the coupling between waveguide and waveguide or waveguide and fiber. This coupler is compatible with the current fabrication facilities for complementary metal oxide semiconductor (CMOS) technology with vertical coupling. This structure can realize coupling when the beams with transverse electric (TE) polarization and transverse magnetic (TM) polarization are incident at the same time. The influences of the grating coupler parameters including wavelength, the thickness of waveguide layer, the thickness of SiO₂ layer and the number of steps on the TE mode and TM mode coupling efficiencies are discussed. Theory researches and simulation results indicate that the wavelength range is from 1533 nm to 1580 nm when the TE mode and TM mode coupling efficiencies are both more than 40% as the grating period is 0.99 μm. The coupling efficiencies of the incident TE and TM modes are 49.9% and 49.5% at the wavelength of 1565 nm, respectively, and the difference between them is only 0.4%.     

Observation of externally controlled mode coupling in optical waveguides

Externally controlled mode coupling was observed in a 0.7-km optical waveguide fiber resulting in a significant pulse narrowing. The method of mode coupling generation requires that care be exercised in any mode coupling measurement. Observations on a 3-km waveguide failed to show evidence of mode coupling, allowing the possibility of practical external control.     

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