Near-infrared third-order optical nonlinearity in CaCu₃Ti₄O12 thin films

Abstract

We investigate the optical nonlinearity of CaCu 3 Ti 4 O[Formula: see text] (CCTO) thin films on MgO substrates using Z-scan technique at a near-infrared wavelength of 1064[Formula: see text]nm with 25[Formula: see text]ps duration pulses. The near-infrared nonlinear saturable absorption coefficient [Formula: see text] and the nonlinear refraction coefficient [Formula: see text] of the values [Formula: see text][Formula: see text]cm/GW and 0.66[Formula: see text]cm 2 /GW, respectively, were deduced from the study of the nonlinear response at different excitation intensities. The three-level model is proposed to interpret the large optical nonlinearity in CCTO films in near-infrared spectrum, by considering the intermediate energy levels due to the defects or grain boundaries. The large optical nonlinearity and fast response at picosecond time-domain indicate that CaCu 3 Ti 4 O[Formula: see text] thin films are promising candidates for applications in near-infrared nonlinear photonics devices.