矩量法研究平面波导点缺陷引起的散射损耗

对平面波导工艺过程里出现的点缺陷，如气泡、灰尘颗粒等对平面波导内光场造成的散射提供了一种简单而又实用的计算方法。计算基于格林函数方法，并利用矩量法求解积分方程，采用分块矩阵优化算法，使得算法的计算时间直接与点缺陷大小相关，提高了效率。证明了一定大小的点缺陷在特定的波长处会产生很大的散射损耗，证明点缺陷的散射损耗依赖于缺陷大小和光学性质而与其在波导中的位置无直接关系。以二氧化硅平面波导为例，分析了对中心波长1．55μm的入射光场，分别存在气泡和灰尘颗粒两种点缺陷时，散射损耗随点缺陷大小的关系特性，指出工艺过程特别应该避免某些孔径的点缺陷。

Moment Method Study for the Scattering Loss Caused by a Point Defect in a Planar Waveguide

simple and effective method for calculating the scattering from a point defect (like an air bubble or a dust grain) in a planar waveguide is presented. The method is based on the theory of Green′s function. To improve the calculation efficiency,the corresponding integral equation is converted into a matrix equation by using the method of moment and the method of blocked matrix is also used. A silica planar waveguide is considered as an example;the scattering loss as a function of the size of the point defect is analyzed for both an air bubble and a dust grain. The results indicate that the scattering loss depends on the size of the defect and optical property rather than its situation in the waveguide. It is also shown that a point defect of a certain size may cause some strong resonances at some special wavelengths and will result in a large scattering loss. For the same reason, point defects with some special sizes should be avoided in the fabrication in order to reduce the scattering loss at an optical communication wavelength windows