Extension of inverse WKB method for refractive-index profiling of single-mode graded-index planar waveguides

It is of fundamental importance to determine the refractive-index profile of a graded-index planar waveguide, as the profile can give useful information about the waveguide fabrication process and the transmission characteristics of the waveguide. The most popular method for refractive-index profiling of planar waveguides appears is the inverse WKB method. In this paper, we propose a technique of combining effective indices measured with different external refractive indices. The technique is simple to implement and allows accurate profiling of single-mode waveguides at a fixed wavelength.