Analytical expression for femtosecond-pulsed z scans on instantaneous nonlinearity

Abstract

By employing the Gaussian decomposition method, the analytical formulas of the Gaussian-beam Z-scan traces have been derived for an optically thin material exhibiting both refractive and absorptive parts of third-order nonlinearity, with Gaussian or hyperbolic secant squared laser pulses of femtosecond duration. The formulas have been verified experimentally with femtosecond-pulsed Z scans on a carbon disulfide and acetone solution of a chalcone derivative (0.95C 18H17ClO4 ·0.05C17H 14Cl2O3). An efficient yet accurate analytical technique has been demonstrated for extracting both the nonlinear refraction coefficient and the nonlinear absorption coefficient from a single closed-aperture Z-scan trace. © 2008 Optical Society of America.