Structural phase diagram of Hx/Li1-xNbO3 waveguides: The correlation between optical and structural properties

We show that proton exchanged H
_x
/Li
_1-x
NbO
₃
single-crystalline solid solutions exhibit very complex structural chemistry, which is different from those known for powders. Seven crystallographic phases have been identified in H
_x
/Li
_1-x
NbO
₃
layers. Correlation between the crystal structure and the ordinary and extraordinary refractive indices has been experimentally determined which allows us to explain some of the observed optical phenomena and to predict the characteristics of the great variety of proton exchanged waveguides.