Denis I. Shevtsov

Nanofaceting of LiNbO3 X-cut surface by high temperature annealing and titanium diffusion

Abstract The topmost surface of crystal during Ti-indiffused LiNbO 3 waveguide preparation was studied using atomic force microscopy and high energy electron diffraction. The formation of the flat terraces with high step ∼0.24 nm as a result of high temperature annealing has been detected. The global changing of surface morphology induced by Ti diffusing was observed. No new phase formation on the surface was detected.

Chemical Etching Technique for Investigations of a Structure of Annealed and Unannealed Proton Exchange Channel LiNbO3 Waveguides

The proton exchanged channel waveguides are actively used for different integrated-optic components. There is a problem of the channel waveguide characterization because the single-mode channel waveguides for infrared region have the cross section about several microns. The wet etching and noncontact profilometry were used to investigate phase composition in proton exchanged channel waveguide. It has been found the known phases of H x Li 1−x NbO 3 have noticeably different etching rates. So, obtained experimental data gives the possibility of phase composition identification for channels with cross-section down to ∼ 2 μm.

Structural properties of silicon oxide prepared by high-power PECVD

The paper presents results of structure analysis of silicon oxide films prepared by plasma enhanced chemical vapor deposition (PECVD) methods with a high power plasma excitation. The films were deposited from hexamethyldisilazane and oxygen mixture. Dependences on deposition parameters are presented.

Use of method for chemical etching for identification of structure of proton exchange channel waveguides fabricated on Z-cut of lithium niobate crystal

It was established by chemical etching that proton exchange on the surface of LN +Z cut in the molten benzoic acid at the temperature of 190°…210°С during 1…4 h causes fabrication of channel waveguides, consisting of 3 proton exchange phases.

Aging effect in proton-exchanged optical waveguides based on lithium niobate crystals

The optical characteristics of planar waveguides produced by proton exchange in lithium niobate crystals in different acids (with and without additives) are unstable with time (“aging” effect). The aging effects in LiNbO3 optical waveguides are investigated at room and elevated (50, 60, or 70°C) temperatures. In all cases, variations in the refractive index of the waveguide layer with time, i.e., for two or three years at room temperature and for several weeks at elevated temperatures, are determined for waveguides prepared in different media. The dependences of the optical characteristics of waveguides on the nature of proton sources and the aging conditions are obtained experimentally.

Deformations in Ti-diffused proton-exchanged X-cut LiNbO3 waveguide layers

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.

Proton sites occupation sequence in crystal lattice of HxLi1-xNbO3 monocrystal layers

The infrared OH absorption band has been studied by Fourier spectroscopy for proton exchanged layers of HxLi 1−xNbO3 and nominally pure congruent LiNbO3. Frequencies of OH band components were associated with a set of structurally nonequivalent proton positions in oxygen plane perpendicular to polar c axis. The model was developed to describe the sequence of proton sites occupation in oxygen plane of HxLi 1−xNbO3 crystal lattice with proton concentration in the range from x < 0.01 to x ≈ 0.63. It has been found that nominally pure LiNbO3 and α-phase layer of HxLi 1−xNbO3 have hydrogen bonds with semi-uniform vibration frequency distribution.

Applying of microwave asymmetrical double-ridged waveguide for measuring of the integrated optical electrodeless electric field sensor sensitivity.

We present a new method for investigation of sensitivity of the integrated optical electrodeless electric field sensor. This method is based on a compact microwave asymmetrical double-ridged waveguide with regular inhomogeneities. Small dimensions of the waveguide along with medium power of the microwave generator produce a strong electric field. The efficiency of the presented experimental unit was verified in the course of testing of the real integrated optical electrodeless electric field sensor (E-sensor).

Short-term DC-drift in integrated optical Mach-Zehnder interferometer

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.

Structure and properties of proton exchange waveguides on Z cut of lithium niobate crystal fabricated in molten benzoic acid with the addition of lithium benzoate

Methods of chemical etching, non-contact profilometry, X-ray analysis and mode spectroscopy enabled to find out that proton exchange channel waveguides formed on Z cut of lithium niobate crystal in the molten benzoic acid with the addition of 3 mol.% of lithium benzoate at the temperature of 225°C were composed of κ2-phase and a thin layer of α-phase. Proton exchange on +Z and -Z faces of the lithium niobate crystal in benzoic acid (with or without the addition of lithium benzoate) occurs at the same rate.