Z-scan analyses for PbO-containing glass with large optical nonlinearity.

In order to evaluate the large third-order optical nonlinearity of materials accurately, the influence of the irradiance (I[sub 0]) and sample thickness (L) on the Z-scan transmittance of PbO-containing glass as a representative material was investigated using simple and conventional Z-scan experiments and analyses. The transmittance difference between the peak and valley (ΔT[sub p–v]) in the Z-scan curve resulting from nonlinear refraction and the difference between the baseline (1.0) and valley (ΔT[sub 1-v]) due to nonlinear absorption deviated from a linear relationship at increased I[sub 0] and L. It was found that an analysis based on the linear relationship at large I[sub 0] and L underestimated the third-order optical nonlinearity due to saturation. Taking into consideration the saturation of ΔT[sub p-v] and ΔT[sub 1-v] with L under moderate irradiance, the intrinsic nonlinear refractive index (γ) and nonlinear absorption coefficient (β) of the present glass were calculated to be 1.58×10[sup -17] m[sup 2] W[sup -1] and 7.75 cm GW[sup -1], respectively. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]