Second-order optical nonlinearities in dilute melt proton exchange waveguides in z-cut LiNbO3

Planar optical waveguides with different refractive indices are made in z-cut LiNbO3 with a dilute proton exchange method using a system of glycerol containing KHSO4 and lithium benzoate. The optical second-order susceptibilities of these waveguides are measured by detecting the 266 nm reflected second-harmonic signal generated by a 532 nm beam directed onto the waveguide surface. It is found for this kind of waveguides that in the waveguide region all the second-order susceptibilities take values of at least 90% of the original LiNbO; values for refractive index changes less than similar to 0.013 at the 632.8 nm wavelength, whereas the susceptibilities are strongly reduced for larger index changes. (C) 1996 American Institute of Physics.