Experimental investigations of nonlinear optical properties of soda-lime glasses and theoretical study of self-compression of fs laser pulses

Nonlinear optical properties of soda-lime glasses irradiated by 100 fs laser pulses with intensities ranging from 80 to 182 GW/cm2 and wavelengths from 780 to 870 nm were investigated by the Z-scan technique. Saturated three photon absorption (3PA) was observed and the dependence of the 3PA coefficient on the intensity and the irradiation wavelengths. The measured value of the nonlinear refractive index was found to be intensity dependent and wavelength independent. The estimated nonlinear optical properties were in good agreement with the experimental results. The self-compression of femtosecond laser pulses in a soda-lime glass was evaluated numerically taken into account the interplay between group velocity dispersion (GVD) and self-phase modulation (SPM) in the soda-lime. A numerical simulation of the transmission of a 200 fs laser pulse through soda-lime glass of 1.2 cm thickness showed that the interplay between anomalous GVD and SPM lead to a significant compression of the pulse to 8.5 fs i.e. by a factor of 23.