Picosecond nonlinear optical transmission measurement on anatase TiO ₂ thin films

A TiO₂ optical thin film is fabricated by use of a sol-gel method. The structure of the TiO₂ thin film is examined by using an X-ray diffraction measurement, which shows that the gelation process at 500 °C results in an anatase phase. A nonlinear optical transmission measurement is performed by pumping near the energy gap edge of the TiO₂ thin film. The nonlinear optical responses of the d- and the sp-orbitals are found to be responsible for the large optical Kerr nonlinearity in the anatase TiO ₂ thin film.