INVESTIGATION OF OPTICAL LOSS MECHANISMS IN OXIDE THIN-FILMS

KNbO3, K(Ta,Nb)O-3, KTaO3, and Ta2O5 thin films have been grown by ion -beam sputter deposition. KNbO3 has excellent nonlinear properties for second harmonic generation; however, high optical losses are still ch aracteristic of these films. Several loss mechanisms, such as, high an gle grain boundaries, twin domains, interface and surface scattering, and oxygen vacancies can all contribute to the high losses. In order t o isolate the various mechanisms, amorphous Ta2O5 films, epitaxial cub ic KTaO3 and tetragonal K(Ta,Nb)O-3 films were grown on MgO and Al2O3 substrates subjected to post-deposition annealing treatments and vario us oxygen pressure conditions. The optical losses and refractive indic es were observed to differ depending on the substrate surface and anne aling treatments. Resonant scattering experiments were performed to an alyze the oxygen composition. The optical properties of these oxide th in film systems are reported and the breakdown of the loss mechanisms is addressed.