Propagation Theory of Nonlinear Optical Waveguides and Simulation of Optical Soliton Propagation

本文的研究结果如下：1。研究了采用非对称非线性光纤耦合器的全光逻辑门的三阶色散、激波效应和溶液自频移等高阶效应，发现三阶色散严重影响逻辑器件的工作。为了减小信号的衰减，引入了限频放大。通过在有限增益带宽内只捕获孤子分量，可以改进逻辑函数。提出了一种分析非线性光纤的三维光束传播方法。提出了由光纤和非线性薄膜组成的实用的三维几何结构的全光逻辑门，并对其布尔运算进行了论证。针对TB波和TM波在非线性光波导中的传播，提出了一种基于渐隐近似的广角有限元光束传播方法。为了避免计算窗口边缘的非物理反射，引入了透明边界条件和完美匹配层，并在每一步自适应更新有限元网格和参考折射率以提高数值精度。

The results of this research are as follows :1. Higher order effects such as third-order dispersion, shock effect, and soltion self-frequency shift on all-optical logic gates that use asymmetric nonlinear optical fiber couplers were investigated, and it was found that third-order dispersion seriously affects the operations of logic devices. In order to diminish the degradation, the bandwidth limited amplification was introduced. The logic functions can be improved by trapping only the soliton components in the finite gain-bandwidth.2. A three-dimensional beam propagation method was developed for the analysis of nonlinear optical fibers. All-optical logic gates with practical, three-dimensional geometry consisting of optical fibers and a nonlinear film were proposed, and their operations of Boolean arithmetric were demonstrated.3. A wide-angle finite element beam propagation method based on the Fade approximation was developed for both TB and TM waves propagating in nonlinear optical waveguides. In order to avoid nonphysical reflections from computational window edges, the transparent boundary condition and the perfectly matched layer were introduced, and to improve numerical accuracy, the finite element mesh and the reference refractive index were adaptively renewed at each propagation step.