【作者】 袁菁；

【导师】 罗风光；

【作者基本信息】 华中科技大学 ， 物理电子学， 2007， 博士

【摘要】 随着PLC工艺的成熟和成本的降低,集成光器件日益取代原有的分立器件,无论从技术还是从市场角度来看,都是大势所趋。在众多PLC技术中,离子交换工艺因折射率及模场分布与光纤匹配良好、传输损耗小、光损伤小、制作工艺简单、成本低等优点,而成为研究的热点。特别是用于制备光功分器,因FTTH的广泛应用而受到关注。本论文的研究重点即为离子交换技术及光功分器。本论文以离子交换光波导的特性及MMI型光功分器设计为研究对象,研究内容主要包括渐变型光波导折射率分布的求解、离子交换扩散理论模型及工艺、混和盐离子交换、基于离子交换光波导的多模干涉型光功分器的设计及优化。具体内容如下:针对反WKB在模式数小于3时无法求解折射率分布的应用限制,总结了偏振态法、测试波长法和外部折射率法等三种改进方法,并从常见函数折射率分布及实际应用等方面进行了数学验证。结果表明不仅可应用于模式数小于3的渐变折射率光波导折射率分布求解问题,对模式数大于3的情况可进一步提高拟合精度。扼要介绍了离子交换的基本原理及扩散理论。提出了一种采用基于粒子群优化的离子交换神经网络模型来构造工艺参数与光波导特征参数之间关系的新方法,有效解决了常规扩散理论中因扩散系数难于精确确定而使得分析结果强烈受其影响的弊端。该模型具有计算简单、便捷,可靠性高,精度高,速度快等特点。针对常用交换离子源Ag+和K+具有的优缺点,提出采用AgNO3和KNO3的混和盐作为交换离子源,这样可既具有Ag+ (大的折射率变化)和K+(小的传输损耗)的优势,又可克服它们的缺点(高传输损耗和低交换速度),还可降低熔盐的熔点。摸索总结了离子交换光波导的制备工艺流程,对实验样品分别进行了成分及折射率分布测试,重点分析了样品的均匀性、双折射性、纯K+及AgNO3:KNO3混和盐离子交换特性、交换时间、折射率分布形态以及不同基底玻璃性能对比等多个方面的特点,给出了工艺参数选择的推荐条件。扼要介绍了多模干涉的基本原理,分别用导模传输法和光束传播法进行了分析。针对波导设计中的多目标参数优化,提出了基于遗传算法的优化设计方法,并将优化结果与传统结果对比,结果表明该方法可以在器件设计时有效提供最优解。总结了多模干涉型光功分器的基本设计流程。分别设计优化了工作在0.85μm的1×8MMI和工作在1.55μm的1×16MMI光功分器。在此基础上,提出了级联多模干涉结构的大分路数光功分器结构,可以有效优化器件性能,降低设计难度,缩小器件尺寸。更多还原

【Abstract】 With the developing of PLC and cutting down of cost, it is possible that integratedoptical devices based on PLC replace traditional discrete ones. Ion exchange has becomethe research focus for its main advantages of similar refractive index profile with fiber, littletransmission loss, simple manufacturing technology and low cost over other PLC technolo-gies, especially for applied in optical power splitter in FTTH.This dissertation mainly researches on performance of ion-exchanged optical waveg-uide and design of MMI optical power splitter, which mostly includes solution of indexprofile of grade-index optical waveguide, diffusion theory and technique of ion-exchangedoptical waveguide, mixed salt ion exchange, design of MMI splitter based on ion-exchangedwaveguide. It has been carried out as the followings:Three improved methods of TE/TM, measuring wavelength and external refractive in-dex are addressed and discussed, both of which can satisfy the limitation that IWKB methodis useless when mode number is less than 3. Computing results are implemented from usualfunction refractive index and experiment data. It also showed that these methods couldimprove fitting accuracy when mode number is more than 3.Basic principle of ion exchange and diffusion theory are introduced. Ion exchangeNeural Network based on Particle Swarm Optimization algorithm was proposed to predictcharacters of ion-exchanged waveguide at any arbitrary experiment condition more easilyand quickly, because it overcame the limitation of the conventional theories in which theconclusion had error caused by uncertain diffusion coefficient. This model has the advan-tages of reliability, accuracy, and time saving, which are identified by simulation.Ion exchange of Ag + /K + mixed salts is considered for absorbing the advantages ofAg + (big index change) and K + (small transport loss), avoiding the disadvantages of Ag +(big loss) and K + (slow exchange speed), and dropping exchange temperature.The results of experiments, which are focused on uniformity, birefringence, characterof K+ and K+-Ag+ mixed salt ion exchange, ion exchange time, index profile and differentsubtract glass are discussed and analyzed by the measures of ingredient and refractive indexchange.Principle of multimode is introduced summarily and analyzed by mode transportmethod and beam propagating method. Optimizing design based on GA is brought forward,design result of which shows ability of affording efficient optimized solution.Basic components of waveguide splitter and design ?ow are analyzed in detail.Parameters optimization and technics errors of 1×8 optical splitter at 0.85μm and 1×16 optical splitter at 1.55μm are researched. Cascaded structure of multimode interference isput forward, which shows several advantages to parameters of optical splitter, such as insertloss, uniformity, size, et al.更多还原