A method to resolve thermal and electronic contributions to the nolinear optical response.

This paper presents the study and implementation of a modified Z-scan technique using a chopper to change the thermal load of the sample, while keeping the input peak irradiance constant. It was verified numerically and experimentally that by changing the frequency of the chopper and keeping the power of the laser beam constant, it is possible to vary the thermal load on the sample. This technique is illustrated under the study of the nonlinear optical (NLO) properties of nucleated Au–Pt metallic nanoparticles (NPs) by ion implantation. The nonlinear optical response was studied using the Z-scan. technique using a Ti:Sapphire laser with femtosecond pulses at a wavelength of 800 nm and a repetition rate of 76 MHz. By scanning the sample using the Z-scan technique it was It is possible to determine the refractive and absorbing contributions to the nonlinear response, in this case as a consequence of a high pulse repetition rate, cumulative pulse-to-pulse thermal effects occurred. Because of this, a modification of the Z-scan technique allowed to separate the resolution of the electronic and thermal contributions on the sample. • We present a technique that allows the determination of the electronic and thermal contributions to the third-order nonlinear optical response of a material, through the use of a variable frequency optical chopper in the z-scan technique. • We present a complete calculation of the heating produced in a sample by a femtosecond pulse train of finite duration. • The technique is illustrated by a study of the nonlinear response of a dual system of metallic nanoparticles (NPs) consisting of Au and Pt NP distributions embedded at different depths in a glass substrate, which was produced by ion implantation, using a femtosecond laser oscillator. • The technique allowed us to extract the thermal and electronic contributions to the nonlinearity of the sample studied, together with some thermal parameters. [ABSTRACT FROM AUTHOR]