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1、上海交通大学 博士学位论文 基于铌酸锂光学超晶格的非线性光学效应及其应用研究 姓名：曾祥龙 申请学位级别：博士 专业：光学 指导教师：夏宇兴;陈险峰 20040426 摘 要 - I - 基于铌酸锂光学超晶格的非线性光学效应及其应用研究 摘 要 本论文对基于铌酸锂光学超晶格的非线性光学效应及其应用进 行了理论分析和实验研究对质子交换铌酸锂波导进行实验表征和 在高压脉冲电场极化研究的基础上 制备了基于周期性极化铌酸锂波 导实验上观测到了波导中倍频光的产生并实现了基于准位相匹配 级联效应的 1.5m通信波段的全光波长转换 理论上引入了两种不同 构造方式的非周期光学超晶格实现了多波长二次谐波和宽带倍
2、频 把准位相匹配原理的应用推广到了非周期超晶格结构 最后分析了光 学超晶格的电光效应在相位调制中的应用 提出了一种利用非周期光 学超晶格结构实现高频位相调制的方法 本文首先从实验上研究了质子交换波导的制备 建立了质子交换 和退火过程中波导制备参数(交换时间和退火时间)与波导参数间的关 系实验结果表明制备波导的重复性较好我们利用变分法对质子交 换波导进行了数值分析 结合周期性极化铌酸锂(PPLN)光栅周期的设 计 在理论上预测了 1.5m通信波段基于波导的光栅周期和光栅周期 与波导制备参数间的关系 根据理论预测和质子交换波导实验制备的 基础上得到了基于周期性极化铌酸锂的波导器件在实验中我们 观察
3、到了基波波长在 1531.8nm 的倍频光输出利用 1.5m波段半导 摘 要 - II - 体可调谐激光器作为泵浦光源 实现了 1.55m通信波段的基于PPLN 波导级联效应的全光波长转换 归一化转换效率为 12 90%Wcm 在超 过 60nm 范围内实现了多波长转换我们对这种波长转换器的转换性 能和局限性进行了分析提出了利用非周期光学超晶格, 克服了周期 性极化铌酸锂波导中对泵浦光的窄带宽限制实现了可变输入可变 输出的可调谐波长转换 对非周期光学超晶格在非线性光学过程中的宽带倍频和多波长 倍频进行了分析和研究提出两种不同构造方式的非周期光学超晶 格一是基于超结构光栅的非周期光学超晶格另一种
4、是基于等长度 基元的非周期光学超晶格 利用遗传模拟退火算法优化每个基元的 自发极化方向 通过非周期超晶格提供的大量空间倒格矢补偿作用光 波矢间的位相失配 这种非周期光学超晶格的构造方式和优化方法不 仅能够得到宽带的倍频响应 克服了非线性过程中泵浦光带宽很窄的 限制而且为实现可调谐的准位相匹配提供了一种途径 利用光学超晶格的光电系数的空间调制特性 我们对非周期畴反 转行波电极进行了理论分析 选取具有代表性的相位调制器作为分析 对象从理论上得到了微波调制的中心频率为 200GHz带通分别为 10GHz 和 20GHz 的高频通带位相调制频率响应曲线为进一步利用 准速度匹配技术在光学超晶格中的应用提
5、供了一种新的思路 关键词周期性极化铌酸锂, 光学超晶格, 全光波长转换器, 遗传- 模拟退火法, 位相调制 摘 要 - III - I N V E S T I G A T I O N O F N O N L I N E A R O P T I C A L E F F E C T A N D A P P L I C A T I O N S B A S E D O N L I T H I U M N I O B A T E O P T I C A L S U P E R L A T T I C E ABSTRACT The thesis investigates the nonlinear opt
6、ical effect based on lithium niobate optical superlattice (LNOS) and its applications theoretically and experimentally. In the first part, proton exchange (PE) waveguide and annealing process are studied experimentally to obtain the characterization of annealing proton exchange (APE) wavegiude. The
7、domain reversal in lithium niobate crystal by the room-temperature high-voltage-pulse electrical poling process is described. The all-optical wavelength converter is successfully made based on periodically poled LiNbO3 (PPLN), which takes advantage of QPM (Quasi-Phase-Matching) technology to realize
8、 the frequency shift and succeed to convert wavelengths within 1.5m optical communication band. Two kind of aperiodic optical superlattices in different constitution way are investigated in theory and used to realize the second harmonic generation (SHG) of multi-wavelength and broadened fundamental
9、wavelengths. The theory of QPM is extended to aperiodic optical superlattice. And the application of optical superlattice in phase modulation is also studied. We investigate the fabrication process and set up the characterization of annealing proton exchange (APE) wavegiude and study the relationshi
10、p between the fabrication condition (exchange time and annealing time) and waveguide parameters. The results turn out that the productivity of the APE waveguide is good. In theory we predict the relationship between the domain reversal period and the fabrication parameters of 1.5m-wavelength band in
11、 APE waveguide by the numerically variable analysis method of two-dimensional waveguide as well as the design of the grating period of 摘 要 - IV - PPLN. We experimentally demonstrate multi-channel wavelength conversion through the cascaded second-order nonlinear processes in periodically poled lithiu
12、m niobate waveguide in the optical communication wavelength band. The normalized conversion efficiency as high as 12 90%Wcm is obtained. Wavelength conversion over a broad wavelength range of 60 nm has been confirmed. Some fruitful and guidable results are put forward. And the principle of the tunab
13、le wavelength conversion by use of variable pump wavelengths in aperiodic optical superlattice (AOS) is also suggested. The theoretical analysis of the broadened bandwidth for the fundamental waves in aperiodic optical superlattice (AOS) is reported. One kind of AOS, similar with the super-structure
14、 grating, is shown. And another is constituted by the cell domain with equal length. The sequences and the polarization direction of each domain are optimized to realize the pre-designed wide bandwidth by the Genetic-Simulated Annealing (GSA) method in the quasi-phase-matched (QPM) second-harmonic g
15、eneration. This kind of AOS can provide plenty of reciprocal vectors to compensate for the wavevector mismatch between the interactive waves. About 3 nm prescribed flattop bandwidth as the full width at maximum 95% with 25% reduction of the nonlinear coefficient relative to that of a perfectly perio
16、dic QPM grating are obtained. Thus it may be expected that spectral components can continuously expand in a wide range of the wavevectors. These new structures offer greater design flexibility in the pre-designed broad bandwidths of second harmonic generation. This method is not only useful in achieving the broad acceptance bandwidth of SHG by overcoming the narrower acceptance bandwidths for the fundam
