Accurate determination of the ordinary index profile of proton-exchanged waveguides

A new method for an accurate characterization of the ordinary refractive index profile of proton-exchanged waveguides is presented and discussed, The method is based on the measurement of the power coupled into radiation modes of the waveguide as a function of the corresponding effective indexes, and allows the determination of the depth and of the film refractive index of the ordinary profile by a least squares fitting of the experimental points. The:depth and the film refractive index have been experimentally obtained with an accuracy of 0.005 mu m and 0.0001, respectively.