High-resolution X-ray characterization of periodically domain-inverted nonlinear optical crystals

A high-resolution triple-axis diffractometer has been used for the structural characterization of periodically domain-inverted nonlinear optical crystals of KTiOPO 4 and LiNbO 3 . Striations have been revealed in high-strain-sensitivity multiple-crystal topographs of the domain-inverted regions of both these samples and these are dominated by orientation contrast. The combination of high-resolution reciprocal-space mapping and topography has shown that the extended diffraction streak in the q (210) direction for the domain-inverted LiNbO 3 originates from the 'minutely misoriented structure' which is related to the original configuration of dislocations. The reason for the generation of the structural imperfections via the domain-inversion processing is interpreted in terms of the converse piezoelectric effect.