Optical properties of rough, inhomogeneous lithium fluoride films with colour centres

Lithium fluoride (LiF) films containing colour centres (CCs) are interesting because of their potential applications in the field of integrated optics as passive and active waveguides. Four LiF films, about 3 μm thick, were grown by thermal evaporation. After deposition, the films were irradiated with γ-rays (doses up to 106 Gy) so that primary and aggregate CCs would be generated in them. The optical properties of the films with CCs were studied by means of spectrophotometry. Absorption bands ascribable to primary and aggregate CCs were detected in the two films irradiated at higher doses. The measured photometric spectra were best-fitted with a unified model and the concentrations of the main CCs were estimated.