Large third-order optical nonlinearity in PdO thin films

Abstract

We report on a study of the absorption spectra and third-order nonlinear optical properties of crystalline PdO thin films, grown by oxidation of thin palladium films deposited on a substrate. The spectra reveal an absorption peak at [Formula: see text][Formula: see text]nm, which grows and narrows significantly as the temperature is lowered to [Formula: see text][Formula: see text]K. This behavior suggests an exciton nature of the peak. According to the position of the long wavelength absorption edge in the spectra, the bandgap of the material is [Formula: see text][Formula: see text]eV. Utilizing the techniques of degenerate four-wave mixing and Z-scan, using a pulsed laser radiation with a wavelength [Formula: see text][Formula: see text]nm and a pulse duration of [Formula: see text][Formula: see text]ns, we determined the real part of the third-order nonlinear susceptibility of Re[Formula: see text][Formula: see text]esu. Possible nature of this high refractive nonlinearity is discussed.