Problem of short-term operating point dc-drift of an asymmetric waveguide topology X-cut integrated optical Mach-
Zehnder interferometer has been considered. A magnitude of dc-drift was estimated with optical intensity change after
voltage switching. It was shown, that short-term dc-drift depends on initial operating point position. Two types of shortterm
dc-drift were detected and described.
In this study the analysis of deformation and mode refractive index measurements of H:Ti:LiNbO3 layers have been investigated. The variations of the lattice parameter in doped layer have been controlled by high-resolution X-ray diffraction measurements. It has been shown that the presence of Ti greatly impacts on crystal lattice deformation induced by subsequent doping by hydrogen. The stability of H:Ti:LiNbO3 waveguides has been investigated by the high temperature phase freezing by quenching and relaxation to equilibrium phase at room temperature. The variation of the lattice parameter in H:Ti:LiNbO3 layer appears to be smaller then that in H:LiNbO3 layer formed at the same conditions.
The structural defects had been found on the surface of high-doped H:LiNbO3 waveguide layers produced on X-cut
LiNbO3 substrates in pure benzoic acid at T ≥ 185°C during t>1 h. The defects are similar to "scratches" but oriented
definitely in reference to Z crystal axis. Measured 3D and 2D profiles show the defects outspreading above the substrate
surface at a height ~4.4-9.0 nm, having width a half height ~1.7 μm and length from ~2 μm up to 100-300 rim. Areas, where the density of these defects is increased, as a rule, are limited by scratch traces from lapping and polishing. Preliminary annealing of the substrates or Ti in-diffusion at temperature ~1000 °C before PE avoid the defect formation and the substrate roughness is not changed by proton exchange.
The topmost surface of crystal after all stages of proton-exchanged Ti-indiffused LiNbO3 waveguide preparation was studied using atomic force microscopy and high energy electron diffraction. The formation of the flat terraces with minimal height step ~0.24 nm as a result of high temperature annealing has been detected. The global changing of crystal surface morphology induced by Ti diffusing was observed. Ion exchange has no influence upon surface microrelief. No new phase formation on the surface was detected. The stability of refractive index was investigated.