Finite Element Beam Propagation Method (FE-BPM)

目的

FE-BPM is able to analyze optical propagatong behavior in longitudinally slowly varying optical waveguide.

概要

As shown in the follwing figure, light propagting behavior is successively analyzed from input end to output end. In the standard FE-BPM, the backward reflective wave is ignored. However, some approaches to treat the reflectied wave have benn also reported. In this study, finite element method (FEM) is employed to discretize in transverse direction and, in the longitudinal direction, Crank-Nicholson scheme is employed to successively obtain propagating field. In our approach, finite element mesh is upated subject to the change of cross-sectional field distribution during the light propagation.

The propagation field in Y-branch is shown in the following figure. The radiated waves toward the upper and lower directions are absorbed without reflection and the artificial infinite comuplational region is assumed.

The simple simulator for demo use is placed here.

Numerical Example

Y-branch waveguide

Y-branch equally dvides inputted optical power into two output waveguides. In the follwing analysis results, straight waveguides are placed after the output end and the peaks of optical power is osscillating by the interference effect between the fundamental and higher order modes in the straight waveguides.