【作者】 吴维庆；

【导师】 林旭升；

【作者基本信息】 汕头大学 ， 材料物理与化学， 2006， 硕士

【摘要】 本文采用理论分析和数字模拟相结合的方法研究了光子晶体光纤的色散特性，含有缺陷结构的非线性光子晶体波导的单向透射性，以及它们在器件设计上的应用。 首先利用平面波展开法，系统地研究了一种具有混合纤芯结构的光子晶体光纤的色散特性。数值计算结果表明，通过优化结构参数，这种新型结构的光子晶体光纤在通信窗口1.55μm附近可以获得带宽超过800nm的超平坦色散区域(色散曲线的变化范围不超过±0.6ps·km^-1·nm^-1)。在此基础上，我们提出了一种全新结构的双芯光子晶体光纤偏振束分裂器。不同于其它设计，这里我们采用了椭圆形空气孔的结构，能够大大地加强光纤本身的双折射特性。数值模拟结果表明，在通信波长1.55μm处，这种偏振束分裂器具有较短的分裂长度（1.651mm）和较高消光率（-20dB）的优点。在此通信窗口附近，消光率高于-12dB的带宽可以达到50nm。进一步的研究发现，对纤芯区域的掺杂能进一步缩短器件的长度，这对实现器件的高容量和超小型化具有重要意义。 其次，我们利用时间耦合模理论，研究了含有缺陷结构的非线性光子晶体波导的单向透射性，重点放在通过缺陷耦合提高单向透射的对比度上。虽然全光器件的单向透射性的物理本质来源于结构的非对称性和光学非线性效应，但我们的研究表明，基于光子晶体缺陷结构的器件最大透射对比度主要依赖于缺陷的线性耦合效应，如：耦合导致的频率分裂、频率失谐量的最高阶次数等。理论分析和数值模拟实验均显示，通过光子晶体缺陷耦合能大大提高单向透射性，这对今后基于光子晶体的全光二极管的开发、设计具有重要的参考价值。更多还原

【Abstract】 We investigate the dispersive properties of photonic crystal fibers （PCFs）, the unidirectional transmission of slab waveguides containing photonic crystal defects, and their application in the design of optical devices by theoretical analysis and numerical simulation.Firstly, the dispersion properties of PCFs with hybrid core are systematically investigated by using the plane-wave expansion method. It shows that an ultraflattened dispersion range of more than 800 nm in which the variation of dispersion is less than ±0.6 ps·km^-1·nm^-1 can be achieved at ～1.55μm by optimizing the structure configuration. Also, the coupling characteristics of the dual-core PCFs with elliptical air holes are utilized to realize the polarization splitters. By using the full-vector beam propagation method, we find that a polarization splitter with an extinction ratio better than -20 dB at 1.55 μm and a total length of only 1.651 mm can be developed. The length of the splitters can be further reduced by properly doping the core region of the PCFs.Secondly, we investigate the unidirectional transmission behavior of slab waveguides containing photonic crystal defects with nonlinearity by using the coupled mode theory, focusing on how to enhance the transmission contrast. Although the unidirectional transmission originates from the asymmetric configuration and nonlinear property of the structure, it is revealed that the maximum transmission contrast depends mainly on two linear factors. For two coupled defects, they are the highest order of the frequency detuning appearing in the transmission formula and the frequency splitting due to the coupling. Our analyses are supported by the numerical simulations based on the finite-difference time-domain technique. An enhancement of the maximum transmission contrast by an order of magnitude is achieved in the structure consisting of two coupled defects.更多还原