Third-order optical nonlinearity of (Ba0.7Sr0.3)TiO3 ferroelectric thin films fabricated by soft solution processing

(Ba_0.7Sr_0.3)TiO₃ (BST) ferroelectric thin films with perovskite crystal structure were fabricated by soft solution processing on a quartz substrate. The third-order nonlinear optical properties were investigated by using Z-scan technique. Positive nonlinear refractive index and nonlinear absorption coefficient were determined to be 4×10⁻⁷ esu and 1.2×10⁻⁶ m/w, respectively. The real part and imaginary part of third-order optical nonlinear susceptibility were calculated and the values were 6.43×10⁻⁸ and 5.14×10⁻⁸ esu, respectively. All of these results show ferroelectric BST thin film is promising for applications in nonlinear optical devices.