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.