Phase space evaluation of distributed-index branching waveguides

In this paper, we propose a new evaluation concept for characterizing multimode optical branching waveguides. In a ray tracing to simulate multimode branching waveguides, we introduce a phase space expression with the ray position and slope in order to describe the modal distribution of guided light. We have applied this technique for branching waveguides, which have a parabolic distributed-index, and clarified branching characteristics. Experimental results obtained for diffused branching waveguides are compared with theory.