[Studies on characteristics of proton-exchanged LiNbO3 optical waveguides by X-ray diffraction and infrared...

The characteristics of proton-exchanged and annealed proton-exchanged LiNbO3 optical waveguides were studied by X-ray diffraction and infrared absorption spectroscopy. The X-ray diffraction experiments show that there are diffraction peaks of Lil-x, HxNbO3 on the left of the main peak of the LiNbO3 crystal substrate. This result means that the crystal lattice constant of the layer Li1-x, Hx NbO3 is little larger than that of the LiNbO3 crystal substrate, resulting in a stress. After annealing, the X-ray diffraction peaks of the waveguide layer move towards the main peak of the LiNbO3 crystal substrate, and the stress decreases. The infrared absorption spectroscopy experiments show that there are absorption peaks of OH- at 3 500 and 3 300 cm(-1), and after annealing, the intensity of the absorption peak at 3 300 cm(-1) decreases or disappears, while the intensity of the absorption at 3 500 cm(-1) remains almost invariable. Experiments also show that the integral area of the absorption at 3 500 cm(-1) is proportional to square root te.