Properties of proton exchanged optical waveguiding layers in LiNbO3 and LiTaO3

Abstract

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-.

Formation of Ion Exchanged Cu:LiTaO3 Waveguides and Their Investigations

“…Thus, the exchange process in this case is essentially different from proton exchange, where the lattice deformations grow in a discrete way [8]. The optical quality of Iand 11-structures of Cu : LiTaO, is much higher than that of Cu : LiNbO, waveguides obtained under similar conditions, in which, beginning at a certain value of doping time, colloidal impurities appear on the surface [2].…”

Analysis of Quasi-Periodic Structural Defects in H:LiNbO3 Layers

“…Nevertheless, the formation of PE layers without surface destruction at LN crystal Y-cut was explained by such partial compensation in Ref. [11]. Apparently, the main reason for structural defects absence in hybrid layers is that titanium ions create their own partial lattice in LN area of PE layer.…”

“…Seven single crystal phases were revealed in PE waveguide layers by X-ray diffraction and optical microscopic methods, and the concentration ranges of their existence were determined [3]. For better understanding of physics of the processes occurring during protonation it is necessary to clarify the cause of waveguide layer surface destruction during PE in neat acids [4]. This phenomenon doesn't allow creation of optical waveguides with higher than ∼0.1 gain of refractive index at the waveguide surface.…”

Raman spectroscopic study of proton-exchanged LiTaO3 crystals

“…According to our experimental results, the changes of the internal strain are closely related to the proton concentration and its distribution in the sample. The proton exchange is an order-disorder process which is accompanied by various complicated phase transitions [6 to 8,191. The disorder has two reasons.…”