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Waveguides in LiNbO3 are realized by a soft proton exchange (SPE) process with use of a melt of stearic acid highly diluted by lithium stearate. No phase transitions are formed when alpha-phase waveguides are obtained by SPE. The alpha-phase presents the same crystalline structure as that of pure LiNbO3 crystal, and it maintains the excellent nonlinear and electro-optical properties of the bulk material. The kinetics of the SPE method is studied by the use of secondary-ion mass spectrometry and prism-coupling techniques. The hydrogen effective diffusion coefficient as well as the self-diffusion coefficients of H+ and Li+ ions are determined as a function of the proton-exchange temperature for X-cut LiNbO3.

Complex studies of proton exchange doping of LiNbO, and LiTaO, single crystals are carried out to investigate the regularities and specific features of structural changes and optical parameters of waveguiding layers. I n fact, depending on doping melt type and crystalline cut H:LiNbO, waveguides can involve two to six and H : LiTaO, up to three layers with different properties.A qualitative description of the proton exchange mechanism is suggested. Mi% dem Ziel der Untersuchung von GesetzmliSigkeiten und Besonderheiten vonStrukturumwandlungen und Eigenschaften planarer Lichtleiter werden Komplexuntersuchungen zum Protonen-Lithium-Austausch an LiNbO, und LiTaO, Kristallen durchgefuhrt. Es wird gezeigt, daD in Abhangigkeit vom Schmelsentyp und der kristallographischen Orientierung der Plattenoberflache H:LiNbO,-Lichtleiter aus zwei bis sechs und bei H:LiTaO, aus bis zu drei Schichten mit verschiedenen Eigenschaften bestehen konnen. Es wird eine qualitative Beschreibung des Protonen-Lithium-Austausch gegeben. PE Waveguides in LiNbO3Ag+, T1+, Cu+, and K+ ions can take part in the I E process forming waveguides in LN [6 to 81, and also protons [9]. A considerable number of works on PE has been published. The analysis of all known doping melts indicates that they can be classified into two types. Melts of type 1 (1-melts) are those that facilitate H:LiNbO, waveguide formation with Y-cut crystals featuring more than one mode, and without surface destruction. On the other hand, stongly acidic melts with a high intensity of PE are of type 2 (2-melts). Direct Y-cut waveguide formation in 2-melts is impossible because of high H+ saturation of the surface and its destruction. ') SU-103498 MOSCOW, USSR-.

Copper-doped LiNbO 3 waveguides were prepared by Cu-Li ion-exchange process. Compositional, structural, and optical analyses were performed by secondary ion mass spectrometry, x-ray diffraction, and m-line spectroscopy, respectively. The chemical state of Cu 2+ ions was studied by electron paramagnetic resonance, and the results were correlated with structural modification of the LiNbO 3 matrix. Copper incorporation in the crystal took place under different regimes, and it induced a lattice rearrangement with the formation of new crystalline phases. Cu 2+ ions were surrounded by tetragonally compressed octahedra with rhombic distortions. Cu:LiNbO 3 optical waveguides were formed supporting two optical modes.

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