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-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 (DeltaT(p-v)) in the Z-scan curve resulting from nonlinear refraction and the difference between the baseline (1.0) and valley (DeltaT(1-v)) due to nonlinear absorption deviated from a linear relationship at increased I-0 and L. It was found that an analysis based on the linear relationship at large I-0 and L underestimated the third-order optical nonlinearity due to saturation. Taking into consideration the saturation of DeltaT(p-v) and DeltaT(1-v) with L under moderate irradiance, the intrinsic nonlinear refractive index (gamma) and nonlinear absorption coefficient (beta) of the present glass were calculated to be 1.58x10(-17) m(2) W-1 and 7.75 cm GW(-1), respectively. (C) 2001 American Institute of Physics.