Dependences of the refractive indices on the proton concentration in H : LiNbO3 waveguides

Proton-exchanged optical waveguides in lithium niobate crystals exhibit a r ich variety of structures and phases. It is established that seven HxLi1-xN bO3 crystalline phases with a lithium niobate structure may form under vari ous conditions of proton exchange and post-exchange annealing. A method is proposed to determine the proton concentration in the various phases identi fied. Relationships are established between the structural parameters, the proton concentration, and the ordinary and extraordinary refractive indices of various HxLi1-xNbO3 crystalline phases. The results can explain various optical phenomena observed in proton-exchanged waveguides and permit predi ction of the characteristics of light-guide structures. (C) 1999 American I nstitute of Physics. [S1063-7842(99)00903-4].