Effect of hot electron kinetics on self-reflectivity of warm dense gold irradiated with femtosecond laser pulses

Above the damage threshold of Au nanofoil, experimental and theoretical investigations of the fluence-dependent self-reflection of intense femtosecond laser pulses are presented. Measured reflectance shows not only the fluence-dependency, but also the laser pulse duration dependency, which is barely described by the calculation of dielectric function of high-temperature Au, based on the traditional two-temperature model. A simple hot electron kinetic model, which contains a nonthermalized electronic subsystem cooperated with the two-temperature model, is considered to determine transient electron densities and temperature to calculate the dielectric functions and self-reflection of femtosecond laser pulses. Comparison to experimental data shows the effect of hot electrons with a relaxation time of a few hundreds of femtoseconds on the transient optical properties of gold under a strong excitation.

Automated summary

This study presents experimental and theoretical investigations on the self-reflection of intense femtosecond laser pulses on gold nanofoils beyond the damage threshold. The reflectance is found to be dependent on both fluence and pulse duration, which cannot be fully explained by the traditional two-temperature model. A kinetic model incorporating hot electrons with a relaxation time of a few hundreds of femtoseconds is used to determine transient electron densities and temperatures, leading to calculations of dielectric functions and self-reflection properties of femtosecond laser pulses on gold.Comparisons to experimental data indicate the significant impact of hot electrons on the transient optical properties of gold under strong excitation.