Investigation on third-order nonlinear optical properties of undoped LiNbO3 by modified Z-scan technique

A new method for measuring third-order nonlinear optical properties of photo refractive materials based on modified Z-scan technique in which employing focus-tunable lens was proposed. By this method, the nonlinear refractive index and the nonlinear absorption coefficient of an undoped \({\text{LiNb}}{{\text{O}}_{\text{3}}}\) crystal were investigated \(\gamma = - 1.48 \times {10^{ - 12}}\;{{\text{m}}^{\text{2}}}{\text{/W}}\) and \(\beta = 0.33\;{\text{mm/W}}\), respectively. The investigation suggests that the calculated results keep agreement with the traditional Z-scan technique in the order of magnitude.