Structural and optical properties of proton-exchanged lithium tantalate waveguides

A method to determine the lattice parameters of proton-exchanged (PE) lithium tantalate solid solutions by examining the PE processes on rotated (Okl)LiTa03 cuts is proposed. It has been shown that, depending on exchange and annealing conditions and crystal cuts, the five phases a-, ~-, 7-, o- and ~-HxLi1-xTaQ3 can exist in single crystal H:LiTa03 layers. The relationships between the lattice parameters and the index change in a-, ~-, ~- and o - unstrained HxLi1-xTaQ3 solid solutions has been experimentally determined. The regularities of proton exchange in lithium tantalate crystals under different exchange and annealing conditions are studied and various specific features are explained.