Large nonlinear optical response of polycrystalline Bi _3.25La_0.75Ti₃O₁₂ ferroelectric thin films on quartz substrates

We measure the nonlinear susceptibility of B_3.25La _0.75Ti₃O₁₂ (BLT) thin films grown on quartz substrates using the Z-scan technique with picosecond laser pulses at a wavelength of 532 nm. The third-order nonlinear refractive index coefficient y and absorption coefficient γ of the BLT thin film are 3.1 × 10 ^-10 cm²/W and 3 × 10^-5 cm/W, respectively, which are much larger than those of most ferroelectric films. The results show that the BLT thin films on quartz substrates are good candidate materials for applications in nonlinear optical devices.