Peaks separation of the nonlinear refraction and nonlinear absorption induced by external electric field

To investigate the relation between the nonlinear susceptibility and the wavelength, Ag : BaTiO 3 composite films were synthesized on MgO ( 100 ) substrates under different external electric fields using pulsed laser deposition. The nonlinear optical properties of the films were measured by z -scan in the wavelength of 355- 650 nm . It is found that with increasing the electric field, the peak of the nonlinear refraction index shifts to longer wavelength (redshift) and is separated from the peak of the nonlinear absorption. With the separation, the values of ∣ Re χ ( 3 ) ∕ Im χ ( 3 ) ∣ can be enhanced obviously.