Characterisation of single-mode channel waveguides from far field measurements

A method for the experimental characterisation of single mode channel waveguides using their far field radiation pattern is proposed. It is shown that if the substrate and cover refractive indices are known (which is true in most cases) then the core refractive index and the core dimensions, and hence the aspect ratio can be predicted by the far field patterns of the fundamental modes. The present method should find application in the characterisation of elliptical core fibers and in predicting the carrier induced index changes in diode-lasers.