Investigations of Ta and Nb doped KTiOPO_4 derivatives

The non-linear optical material KTiOPO4 (KTP) has been established as an industry standard material for frequency-doubling of Nd:YAG 1#mu#m radiation into the green visible range. Technological requirements for extended frequency-doubling into the visible blue have prompted the pursuit of doped KTP isomorphs which possess the already desirable characteristics of KTP itself, with modified non-linear optical responses to produce novel, useful materials. This thesis is an investigation of the crystal quality of some of these KTP isomorphs and the structural features of one such material. High-resolution x-ray diffraction techniques are used to examine the structural quality of Nb, Ta and Ta/Ga doped KTP. It is demonstrated that differing perfection is found for these materials compared to pure KTP, and each possesses a degree of mosaicity. Single-crystal diffraction is used to carry out a detailed structural refinement for 4% Ta-doped KTP, and demonstrates the similarity of this structure to previously refined structures for Nb-doped KTP. A potential new site for Ta incorporation into the unit cell is suggested. A simulation of the material's refractive indices, based on polarisability volume calculations, is carried out. The significance of the simulation is discussed in the context of improved optical performance of these crystals. White-beam synchrotron radiation topographic studies are carried out for the Ta and Ta/Ga-doped KTP materials, and the presence of significant defect structures and associated domains is reported. The implications for non-linear optical quality are discussed. (author)Available from British Library Document Supply Centre-DSC:DXN030693 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo