Prism-waveguide coupling efficiency for waveguides with an arbitrary refractive-index profile

Abstract

Using the WKB approximation, we generalize Ulrich’s solution to the optimum coupling efficiency of a prism‐waveguide coupler, so that it can be applied to a waveguide with an arbitrary refractive‐index profile. As an example, we give an analytic solution to a waveguide having an exponential refractive‐index profile.