A Z-Scan Study of LiNbO₃ Thin Films

Poly-crystal LiNbO₃ films on a fused SiO₂ substrate are prepared by the rf sputtering technique. The third-order optical nonlinearity of the LiNbO₃ films has been investigated by using Z-scan method with picosecond laser pulses at the wavelength of 532 nm. The nonlinear refractive index γ and nonlinear absorption coefficient β are determined to be -7.2 x 10^-9cm²/W and 0.39cm/kW, respectively. The third-order optical nonlinearity x⁽³⁾ of the LiNbO₃ film is about 9.1 x 10^-7 esu, which is considerably large than the reported value for Z-cut pure LiNbO₃ crystals.