Coupling Efficiency of Gaussian Beams Into Step-Index Waveguides—An Improved Ray-Optical Approach

The coupling efficiency of Gaussian beams into multimodal waveguides is calculated with the intention of validating ray-optical approaches, that can be used for a simulation tool for optical interconnections. A full-wave analysis using the mode matching technique serves as reference method. Therefore, waveguides with known mode spectra, the circular fiber, and the planar slab waveguide, have been considered. Detailed results especially for the fiber are presented for different geometry and material parameters and varying parameters of the incident Gaussian beam. It is shown that a ray-optical approach regarding a simplified Goos-Haenchen Shift gives accurate results.