A FAR-FIELD METHOD FOR CHARACTERIZING THIN PLANAR OPTICAL WAVE-GUIDES

A modified far-field method for characterizing optical waveguides is p roposed and demonstrated. The method is based on the formation of an i ntermediate near-field image which is spatially filtered to obtain a f inal far-field image with a much higher signal to noise ratio. This re presents an important improvement when the out-coming guided light is blurred by a high level of spurious light as is frequent in many thin planar guides. The method is demonstrated with a h-thick proton exchan ged waveguide, whose thickness and refractive index are determined wit hin a 10% error using the simple slab approximation.