Evolution of a femtosecond laser-induced plasma and energy transfer processes in a SiO$_2$ microvolume detected by the third harmonic generation technique

A nonlinear optical method has been proposed for probing the evolution of a plasma and energy transfer processes in the microvolume of a transparent dielectric using the third-harmonic probe signal. The electron self-trapping time has been estimated as t = 150 ± 80 fs. A decrease in the third-harmonic probe signal has been detected at the picosecond time scale; this decrease can be attributed to a change in the third-order susceptibility χ⁽³⁾ of a fused silica sample modified by laser radiation.