数值方法和计算参数对束传播方法精度影响的研究

The Effect of the Numerical Method and Parameters on the BPM

本文以聚合物方向耦合器为对象，研究了二维ＢＰＭ 和三维ＢＭＰ在模拟精度方面的差别以及剖分点数、传播步长、初始有效折射率等计算参数对模拟精度的影响。在研究过程中，利用有效折射率的方法，把三维波导转化为二维波导，分别采用三维ＢＰＭ 和二维ＢＰＭ 进行了模拟，并对模拟结果进行了比较，发现二者符合很好，表明二维ＢＰＭ 具有很高的精度。研究还表明初始有效折射率、传播步长的取值对模拟结果影响不明显。

Basing on a directional coupler we study the differences in simulation accuracy between 2 D BPM and 3 D BPM and the effect of calculating parameters size and initial effective refractive index.on simulation accuracy that include the number of the grid points,propagation step.During simulating,the method of effective refractive index is employed to transform 3 D waveguide to 2 D waveguide.The results show that the 2 D BPM agrees with 3 D BPM.Our study indicates that 2 D BPM is also accurate and propagation step size or initial effective refractive index doesn't affect the simulation results evidently,but the number of the grid points can lead to great influence.