Femtosecond Z-scan measurement of third-order optical nonlinearities in anatase TiO2 thin films

Anatase phase TiO2 films have been grown on fused silica substrate by pulsed laser deposition technique at substrate temperature of 750 °C under the oxygen pressure of 5 Pa. From the transmission spectra, the optical band gap and linear refractive index of the TiO2 films were determined. The third-order optical nonlinearities of the films were measured by Z-scan method using a femtosecond laser (50 fs) at the wavelength of 800 nm. The real and imaginary parts of third-order nonlinear susceptibility χ(3) were determined to be −7.1 × 10−11esu and −4.42 × 10−12esu, respectively. The figure of merit, T  , defined by T=βλ/n2T=βλ/n2, was calculated to be 0.8, which meets the requirement of all-optical switching devices. The results show that the anatase TiO2 films have great potential applications for nonlinear optical devices.