Femtosecond Third-Order Optical Nonlinearity ofAu:Bi2O3 Nanocomposite Films

Abstract

Ultrafast third-order optical nonlinearities of the as-deposited andannealed Au:Bi2O3 nanocomposite films deposited bymagnetron cosputtering are investigated by using femtosecondtime-resolved optical Kerr effect (OKE) and pump–probe techniques. Thethird-order optical nonlinear susceptibility is estimated to be2.6×10−10 esu and 1.8×10−9 esu at wavelength of800 nm, for the as-deposited and the annealed film, respectively. TheOKE signal of the as-deposited film is nearly temporally symmetricalwith a peak centred at zero delay time, which indicates the dominantcontribution from intraband transition of conduction electrons. For theannealed film, the existence of a decay process in OKE signal impliesthe important contribution of hot electrons. These characteristics arein agreement with the hot electron dynamics observed in pump–probemeasurement.