Third-order Nonlinear Optical Properties of TiO_2 Films

Anatase TiO2 films were fabricated on fused quartz by pulsed laser deposition(PLD) technique and the single-phase anatase films were obtained under the optimal conditions.The X-ray diffraction and atomic force microscope were used to investigate the structure and surface characters of the film.The third-order optical nonlinearities of the films were measured by Z-scan technique using a femtosecond laser(50fs) of 800nm.From the transmission spectra,the optical band-gap and linear refractive index of the TiO2 film are determined to be 3.18eV and 2.1,respectively.The nonlinear Absorption coefficient and nonlinear refractive index are determined to be-6.2×10-11m/W and-6.32×10-17m2/W,respectively.The real and imaginary parts of third-order nonlinear susceptibility χ(3) are determined to be-7.1×10-11esu and-4.42×10-12esu,respectively.And the following figure of merit T=βλ/n2 is calculated to be 0.8 for the film,indicating that the anatase TiO2 films have great potential applications to nonlinear optical devices.