Periodically poled Cs-exchangedRbTiOAsO4optical waveguides: High-resolution x-ray diffraction, scattering, and topography study

Abstract

A crystal of periodically poled ${\mathrm{RbTiOAsO}}_{4},$ in which optical channel waveguides have been produced by Cs ion exchange, has been studied using combined optical and x-ray diffraction imaging, reciprocal-space mapping, and diffuse scattering. The lattice strains which result from the uptake of Cs in periodically poled ${\mathrm{RbTiOAsO}}_{4}$ are determined and are found to be $\ensuremath{\Delta}c/c=+0.02%--0.04%$ for different orientations of the sample in the (001\ifmmode\bar\else\textasciimacron\fi{}) plane, $\ensuremath{\Delta}b/b=\ensuremath{-}0.02%$ and $\ensuremath{\Delta}a/a\ensuremath{\cong}0%,$ to within the resolution of reciprocal-space measurement. The detailed microstructural features of the periodically domain-inverted structure and the modulation of the Cs uptake in the ion-exchanged regions are shown directly in x-ray diffraction images from the (001\ifmmode\bar\else\textasciimacron\fi{}) surface. Evidence of defect clusters, formed during the ion-exchange processing and of size approximately 180 nm, is presented from analysis of the x-ray diffuse scattering around the Bragg peaks from the ion-exchanged layer and substrate. Discussions of the domain-inversion and ion-exchange processing and the consequences for the microstructure of the waveguiding layer and its properties are given in terms of our observations.