阵列波导光栅平坦化的研究

阵列波导光栅的平坦化在实际应用中有很重要的意义.本文系统地研究了阵列波导光栅的平坦化.在输入波导、输出波导、阵列波导输入端与输出端上分别引入了指数型锥形波导.通过改变锥形波导的形状和尺寸来实现平坦化的优化.本文首先从理论上论述了引入指数型锥形波导的输出光谱特性,给出了结构参量的关系表达式,阐明了输入波导处的锥形波导是影响输出光谱平坦化的主要因素,阵列波导和输出波导处的锥形波导对输出光谱的平坦化有一定的影响.其次采用数值模拟的方法模拟了输出光谱,优化了结构参量,总结出了指数型锥形波导对平坦化影响的趋势和规律.模拟结果显示,输出光谱1 dB带宽大于通道间隔的50％,插入损耗从5.2 dB减小到了4.0 dB,串扰小于-30 dB.最后,本文给出了实验结果,插入损耗减小了0.87 dB,串扰减小了3.67 dB,1 dB带宽增加0.1 nm,增加了54.7％.实验结果表明引入指数型锥形波导提高了阵列波导光栅器件的光谱性能.     

阵列波导光栅平坦化的研究

阵列波导光栅的平坦化在实际应用中有很重要的意义.本文系统地研究了阵列波导光栅的平坦化.在输入波导、输出波导、阵列波导输入端与输出端上分别引入了指数型锥形波导.通过改变锥形波导的形状和尺寸来实现平坦化的优化.本文首先从理论上论述了引入指数型锥形波导的输出光谱特性,给出了结构参量的关系表达式,阐明了输入波导处的锥形波导是影响输出光谱平坦化的主要因素,阵列波导和输出波导处的锥形波导对输出光谱的平坦化有一定的影响.其次采用数值模拟的方法模拟了输出光谱,优化了结构参量,总结出了指数型锥形波导对平坦化影响的趋势和规律.模拟结果显示,输出光谱1 dB带宽大于通道间隔的50%,插入损耗从5.2 dB减小到了4.0 dB,串扰小于-30 dB.最后,本文给出了实验结果,插入损耗减小了0.87 dB,串扰减小了3.67 dB,1 dB带宽增加0.1 nm,增加了54.7%.实验结果表明引入指数型锥形波导提高了阵列波导光栅器件的光谱性能.     

一种高功率微波金属片波导移相器设计与特性分析

设计了一种高功率微波矩形波导移相器,在矩形波导中平行于电场放置金属片,沿波导宽边移动金属片,实现波导内的可变相移。通过优化设计波导和金属片的结构尺寸可实现0~360°相移,通过优化设计金属片过渡匹配结构可实现较低的插损。设计波导内为全金属结构,不存在介质材料,采用真空绝缘可以承受较高的功率传输。设计了中心频率为9.4GHz的金属片波导移相器,移相器最大插损小于0.2dB,功率容量设计达到64 MW。实验测试,移相器最大插损小于0.5dB,相频曲线呈线性关系。     

电光聚合物波导中的锥形结构

提出并设计了一种基于电光聚合物的锥形波导,可用于单模光纤与电光聚合物波导器件之间的连接.锥形波导中采用了宽度锥形和折射率锥形结构.宽度锥形采用劈形形状,通过宽度和折射率的缓慢变化实现模场转换.劈形形状的宽度锥形具有较小的损耗且易于制作,折射率锥形可采用灰度掩膜光刻技术制作.研究了锥形波导的传输损耗与锥形波导的长度、波导宽度和厚度、材料吸收损耗等参数的关系及其优化,分析了锥形波导中的功率传输、模场分布与模式转换效率.结果显示锥形波导的传输损耗小于0.37 dB,光纤-波导-光纤的连接损耗优于1.62 dB,对插入损耗的改善达到8.78 dB,模场转换效率达到了83.7%.     

基于平板波导的小型红外光栅光谱仪光学设计

为实现红外光谱仪器的小型化,通过分析现有小型光谱仪,提出了一种基于平板波导的小型红外光栅光谱仪的设计方法。平板波导光谱仪的小型化原理与一般的微小型光谱仪不同。在平板波导光谱仪中,光束被限制在一层薄薄的平板波导介质中传播,看起来像是整个光学系统被压扁了。在垂直于平板波导的方向上光学元件的尺寸可以做到很小,从而显著减小光学系统的尺寸。该系统的设计可分为Czerny-Turner结构设计、波导结构设计。先根据像差理论设计Czerny-Turner结构,目标是保证光谱分辨率及校正像差;然后根据几何光学理论设计波导结构,包括平板波导和两个柱面透镜,目标是压缩光束并校正像散;最后将它们输入Zemax软件中进行综合优化,以获得最优的光学系统。据此方法设计了一个平板波导红外光栅光谱仪,工作波段为8~12 μm,数值孔径为0.22,采用线阵探测器。通过Zemax软件对结果进行分析和评价,表明仪器光学系统的尺寸为130 mm×125 mm×20 mm,工作波段内光谱分辨率达到80 nm,满足设计指标要求。证明了该优化设计方法是可行的,所得系统尺寸小、性能高。     

全息波导显示系统的实现与优化

在全息波导近眼显示系统中,微像源发出的载像光波经过准直后,被输入耦合光栅耦合入平板波导,进一步在平板波导上下表面内进行全反射传播,到达输出端后通过输出耦合光栅衍射出波导,最终到达人眼。以真实的图像传输为目标,对全息波导光栅的效率、视场角等方面进行理论分析和优化设计,通过激光干涉曝光实验制作了光栅周期为197nm、光栅矢量与介质表面法线方向夹角为26°、厚度为7.5μm的全息光栅,光栅峰值效率大于80%。结合波导光学设计,进一步实现了图像的传输。     

硅基槽式纳米线多模干涉型模阶数转换器全矢量分析

提出了一种基于硅基槽式纳米线结构的紧凑式1×2多模干涉器型模阶数转换器,其中输入/输出通道为槽式直波导,经线性锥形过渡器连接居于中心的二次锥形槽式多模波导.采用全矢量频域有限差分法详细分析了垂直槽波导的模式特性,选取电场主分量E_y得到增强的quasi-TM模作为转换器的光信号模式.对比分析了矩形结构与二次锥形结构中的周期自镜像效应,发现二次锥形结构尺寸更短、损耗更低的特点.根据自镜像效应中一阶模成像位置设计多模干涉区域长度,经线性锥形过渡器从较宽输出端口输出一阶模,从较窄输出端口输出基模,从而实现模阶数转换功能.采用三维有限时域差分法详细分析了该转换器的光波传输特性,详细讨论了器件关键结构参数的制作容差.参数优化结果表明,该转换器的多模干涉区域的尺寸为3×5μm~2时,在1.55μm工作波长下,quasi-TM基模在输出quasi-TM一阶模端口的插入损耗约为0.35 dB,输出波导间的串扰约为-16.9 dB.另外,给出了输入模场主分量在器件中的传输演变情况.     

AWG结构的优化设计

通过分析AWG中心波导倾角特性,优化焦点间距,提出了两个结构约束方程,得出了结构紧凑的AWG设计方法.根据这一方法,可以由一定损耗条件下的最小弯曲半径和接口参数—接口处输入/输出波导间距和最短直波导长度,优化并完全确定其它结构参数,从而得到最小面积的AWG波导结构.最后给出了优化设计实例.     

阵列波导光栅梳状带通滤波器的传输效率

在光波导模场分布高斯近似条件下,根据星形光波导耦合器的耦合特性,推导出了基于累加运算和卷积运算近似表达的阵列波导光栅梳状带通滤波器光谱响应效率的函数表达式。给出了阵列波导光栅梳状带通滤波器光谱响应效率曲线的半最大值全宽度和阵列波导光栅梳状带通滤波器的通道中心波长的光谱响应度与器件参数的关系。在输入信号光谱分布高斯近似条件下,给出了阵列波导光栅梳状带通滤波器信号通道传输效率的计算表达式和输入信号光谱宽度对阵列波导光栅梳状带通滤波器信号通道输出特性的影响。给出了物理意义明确的函数表达式,它们可为快速分析阵列波导光栅梳状带通滤波器的特性提供理论基础。     

平面波导型对称星型耦合器的优化设计

通过有限差分波束传播法(FD-BPM)研究了N×N平面波导型星型耦合器的优化设计思想和方法,并通过17×17星型耦合器的模拟设计证明了它的可行性.给出了在输出端引入辅助波导的方法,以提高输出波导阵列的均匀性.并通过模拟计算,分析了圆心缩入程度和锥形区的形状对输出结果的影响.此法也同样适合于N值更大的星型耦合器.     

A Flattened AWG Demultiplexer with Low Chromatic Dispersion

A design method is introduced to obtain a flat-top arrayed-waveguide grating (AWG) demultiplexer with low chromatic dispersion. A multimode interference (MMI) section is connected at the end of the input waveguide, and a tapered waveguide is connected at the entrance of each output waveguide of the AWG demultiplexer. The design procedure is presented. A design example is given and shown to have a much better performance than the conventional flat-top design using only an MMI section. The insertion loss of the designed AWG demultiplexer is also reduced.     

A concise design of 16 × 16 polymer AWG with low insertion loss and crosstalk

In this paper, a 16-channel arrayed waveguide grating multiplexer (AWG) has been designed using polymer materials with 1.5% refractive index difference. Certain important parameters are optimized using the coupling mode theory and Beam Propagation Method. The factors that affect the insertion loss and the crosstalk are analyzed in this paper. In our design we introduced the parabolic taper structure and evaluated the suitable number of the arrayed waveguide, obtaining a total insertion loss of 2.19 dB. For obtaining a low crosstalk we evaluate the pitches of adjacent input/output waveguides ΔX and arrayed waveguides d as different values. We chose the value of ΔX about 2.5 times of d by enlarging the pitches of adjacent input/output waveguides. The crosstalk of the designed AWG is lower than −40 dB.     

A flat-topped etched diffraction grating demultiplexer with low polarization-dependent loss using a tapered MMI structure

A flat-topped etched diffraction grating(EDG)demultiplexer with a low polarization-dependent loss(PDL)is designed.A design and simulation method based on the method of moment(MoM)is proposed.A 65-channel EDG demultiplexer with channel spacing of 100 GHz is considered as a design example.A tapered multi-mode interferometer(MMI)is used to flatten the passband of the EDG demultiplexer.The numerical results show that the exit width of the tapered waveguide impacts the loss of the TE case more than that of the TM case.Based on this fact,the exit width of the taper is optimized to obtain the lowest PDL.The tapering angle is also optimized where the minimal ripple is obtained.The designed EDG demultiplexer has an excellent flat-topped spectral response and a very low PDL.     

Tapered hollow waveguide for focusing infrared laser beams

A tapered hollow waveguide that can focus a laser beam into a small beam spot is proposed for medical and dental applications. We fabricated hollow tapered optics by using a traveling torch, and the shape was formed as a precise linear taper. For a hollow taper tip with input and output diameters of 700 and 200 microm, respectively, the insertion loss is as small as 0.7 dB in a 10 mm long taper. The hollow taper optic producing a 200 microm spot withstands input energy of 100 mJ. Because a focusing lens is unnecessary at the output end, the laser beam can be introduced into a deep and narrow spot with these tapered optics.     

Optimal design for a flat-top AWG demultiplexer by using a fast calculation method based on a Gaussian beam approximation

Passband broadening of an AWG (array waveguide grating) demultiplexer with an MMI (multimode interference) coupler connected at the end of a tapered input waveguide is considered. An explicit formula based on the field propagation of an approximate Hermit-Gaussian beam is used to calculate quickly and reliably the spectral response of the AWG demultiplexer. The widths of the input waveguide, the output waveguides and the MMI coupler are optimized. The optimal design is verified with the experimental measurement.     

降低AWG插入损耗和串扰设计新方法

在AWG器件的设计中引入了抛物线型的楔形波导结构,根据过渡区理论优化了引入的抛物线型楔形结构的形状和尺寸.采用抛物线型楔形结构代替直线型楔形结构,AWG的插入损耗降低了2 dB左右.在优化参数时使输出/输入波导间距与阵列波导间距取不同的值,并使输出/输入波导间距适当增大,而阵列波导间距取较小值,这样使得串扰降至－30 dB以下且插入损耗保持在低水平.运用光束传播方法给出器件的输出光谱并证实了理论上预想的结果.     

A Passband-Flattened EDG Demultiplexer with an Air-Trenched Taper

A novel passband flattening method for a planar waveguide demultiplexer based on an etched diffraction grating is presented. A strongly confined taper is formed by etching air trenches at both sides of the input waveguide. The geometric parameters of the taper are optimized by considering the figure of merit, ripple, and loss. Numerical simulation for a design example is given to illustrate the passband flattening method.     

A Passband-Flattened EDG Demultiplexer with an Air-Trenched Taper

A novel passband flattening method for a planar waveguide demultiplexer based on an etched diffraction grating is presented. A strongly confined taper is formed by etching air trenches at both sides of the input waveguide. The geometric parameters of the taper are optimized by considering the figure of merit, ripple, and loss. Numerical simulation for a design example is given to illustrate the passband flattening method.     

650 nm聚合物阵列波导光栅波分复用器设计

选择在可见光波段具有较低吸收损耗的聚甲基丙烯酸甲酯-甲基丙烯酸环氧丙酯 共聚物作为波导包层材料,使用双酚A型环氧树脂作为折射率调节剂,根据材料的折射率设计了单模波导截面尺寸;然后,采用束传播法优化设计出16信道阵列波导光栅(AWG)器件的版图结构。利用Optiwave软件模拟了AWG器件的光传输特性,结果显示,器件的信道间隔为0.845 01 nm,插入损耗小于14 dB,串扰小于-25 dB。