Giant optical nonlinearity of a Bi2Nd2Ti3O12 ferroelectric thin film

We investigate the optical nonlinearity of a Bi2Nd2Ti3O4 ferroelectric thin film using the top-hat Z scan technique at a wavelength of 532 nm with 35 ps duration pulses. The film exhibits the fast and giant optical nonlinearities having the two-photon absorption coefficient of 3.1x10(4) cm/GW and the nonlinear refraction coefficient of 0.7 cm(2)/GW, respectively. The mechanism of the optical nonlinearity is discussed in detail. In particular, we also give two important formulas for the top-hat Z scan, which are very valuable and helpful for estimating the nonlinear optical coefficients when the material possesses the simultaneous nonlinear absorption and nonlinear refraction. (C) 2004 American Institute of Physics.