Numerical Simulation For Embranchment Optical Waveguide

With the development of integrated optics, all kinds of optical wave-guide devices with different function and structure have appeared. Designing wave-guide completely by experimental method is complicated, while design a wave-guide with CAD method can not only overcome such difficulty but also analyze the characters of optical wave-guide and thus lead to a quick designation. Then numerical algorithms are used to analyze integrated optical wave-guide and beam propagation method is a good method which is widely used.This paper build a theoretical model based on two dimensional FD-BPM. On this basis, we analyzed the trait of optical field in optical wave-guide and factors influencing the propagation, and furthermore compared the results with those in related papers.First, we simply introduced the optical wave-guide theory: the fluctuation equations of planar wave-guide and the preparation of embranchment wave-guide . Then based on Maxwell equations and in the paraxial limit we deduced the formula needed in calculating FD-BPM. The refractive index section was n(x,y). Because the space we simulated has its boundary, we needed to found a man-made condition to simulate the space that has no boundary. Here we introduced the Transparent Boundary Condition(TBC). Then we found the theory model when we study the embranchment wave-guide using FD-BPM. And we simulated the optical field's propagation of the ridge wave-guide, Y-type embranchment wave-guide, more embranchment wave-guide and X-type embranchment wave-guide. After this we studied the factors influencing the propagation of optical field and the precision of calculating BPM. For example, we studied the influence of angle to the propagation efficiency of Y-type embranchment and influence of calculation window size, selection of reference refractive index, the interval between dots, the difference of refractive index to the calculation of BPM.The result showed that it was precise when we used FD-BPM to simulate the apparatus that the refractive index value change was small. It was favorable to our further study.