Spectral measurement of the film-substrate index difference in proton-exchanged LiNbO3 waveguides

We report the spectral characterization of proton-exchanged Lithium niobate (PE:LiNbO3) waveguides in terms of the variation of the refractive-index difference between the waveguiding layer and the substrate. The dispersion of the extraordinary refractive-index increase (delta n(e)) is measured from 405 to 1319 nm with several light sources. Two types of proton-exchanged waveguide, prepared under different conditions, are studied. These measurements should be of use in the optimization of PE:LiNbO3 waveguides for nonlinear optical applications, particularly in second-harmonic generation in the blue-green wavelength region. (C) 1998 Optical Society of America.