Sub-picosecond Z-scan measurements of the nonlinear refractive index of dense materials

We present the results of Z-scan studies on a new setup in the sub-picosecond regime (central wavelength 800 nm) carried out on solid and liquid materials such as pure water and silica. These measurements are made possible thanks to a high sensitivity setting up of our Z-scan method and in-situ characterizations of the spatio-temporal parameters of the beam. Besides, with the use of a newly adapted numerical simulation, only calibration errors of measurement devices are significant. These measurements are then used to separate the different contributions to the nonlinear refractive index from nanosecond scale mechanisms like electrostriction and/or thermal relaxation.