Nonconventional characterization of single-mode planar proton-exchanged LiNbO3 waveguides by Cherenkov second harmonic generation

A nonconventional characterization method for single-mode planar proton-exchanged (PE) LiNbO3 waveguides is presented. The method exploits the dependence of the output angle of Cherenkov second-harmonic radiation-mode on the boundary conditions of the fundamental guided mode, and thus, in particular, on the cover refractive index. The measurement of this angle in the presence of different Liquid covers of known refractive index provides sufficient information to determine both parameters of the waveguide refractive-index profile, i.e., the index change and the optical depth. The experimental results confirm the reliability of the method proposed. (C) 1999 Elsevier Science B.V. All rights reserved.