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High-index LiTaO3 optical waveguides with controlling birefringence prepared by nonisovalent ion exchange

Optical waveguides in lithium tantalate crystals prepared by nonisovalent ion exchange have been characterized. We found that the waveguides can be formed by ion exchange reactions Me2+ yields 2Li+ (Me: Ni, Mn, Fe, Co) in the salt melts at the temperatures below the Curie point of lithium tantalate. The fabrication and properties of optical waveguides formed in LiTaO3 by simultaneous processing of nonisovalent and proton exchange have been also described. A surface increase of the refractive index up to 0.14 was observed for the extraordinary polarization and up to 0.11 for the ordinary polarization. The birefringence and index change of such waveguides can be controlled by varying the melt concentrations. The dynamics of the process is discussed. Rare-earth doping of LiTaO3 by ion exchange reactions Er3+ yields 3Li+ and Nd3+ yields 3Li+ have been obtain at the temperature below the Curie point.