Nondegenerate and degenerate two-photon absorption in cuprous oxide thin film

Abstract

A cuprous oxide (Cu2O) thin film was prepared by radio-frequency (RF) magnetron sputtering. The crystal structure, linear transmission spectrum and film thickness were characterized by X-ray diffraction (XRD), ultraviolet–visible–near infrared (UV–Vis–NIR) absorption spectroscopy and ellipsometry. By performing the pump-probe and [Formula: see text]-scan technique, respectively, nondegenerate and degenerate two-photon absorption (D-TPA) coefficients of the Cu2O thin film at several different excitation wavelengths were experimentally determined. The nondegenerate two-photon absorption (ND-TPA) coefficient always exhibits larger magnitude than the corresponding D-TPA coefficient. In particular, the ND-TPA coefficient shows a maximum value of [Formula: see text][Formula: see text]cm/GW. This study indicates that the cuprous oxide could be a potential material for ultrafast nonlinear photonic devices based on two-photon absorption due to its large ND-TPA coefficient.