Influence Of The Cosine Style Of Y Branchparameters On The Transmission Characteristic

Y-branch waveguides are key elements in the realization of various integrated optical systems. Which can be widely used as modulator, power combiner / divider, optical switches, semiconductor and 3-dB in power dividers and couplers of the Mach-Zehnder interferometer type etc. Therefore researched the transmission performances have important meaning. With the development of integrated optics, all kinds of optical waveguide devices with different function and structure have appeared. Designing waveguide completely by experimental method is complicated, while design a waveguide with CAD method can not only overcome such difficulty but also analyze the characters of optical waveguide and thus lead to a quick designation. Then numerical algorithms are used to analyze integrated optical waveguides and beam propagation method(BPM) is a good method which is widely used.This paper researched traits of Y-branch by both optical waveguide theory, BPM and numerical analysis. First of all, we simply introduced the optical waveguide theory: the fluctuation equations of planar wave-guide. Then based on Maxwell equations and in the paraxial limit we deduced the formula needed in calculating FD-BPM. 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 used these conclusions, founded the model of cosine style of Y branch structure, simulate the light field by computer. Based on these, simulate the main parameters (waveguide width, transition length, branch height) versus transmission loss. So that can make a crossed extent, which gets the lowest loss, use the conclusion with the material refractive index can achieve the each optimal value by quantificational analysis.Numerical analysis showed that, the optimal result is waveguide width is 10μm, transition length is 6 mm, branch height is 80μm .and the transmission loss decrease with the waveguide width increasing and transition length decrease with the branch height increasing. for the sake of validate the method is efficiency and preciseness, simply simulate the asymmetric wide angle crossed waveguide of X type, the results were precise as the Y-branch, and furthermore compared the results with those in related papers, the research result showed that it was precise when we used FD-BPM to simulate the apparatus that refractive index value change was small. It was favorable to our further study.