| Abstract [eng] |
The goal of this study was to investigate residual excitation in air induced by high repetition rate laser filamentation and to evaluate its influence on subsequent laser pulses. Two different femtosecond laser systems were used in the work. Filament-assisted X-ray generation from a metallic target was studied using Yb-based laser system at 1030 nm, while residual excitation and thermal channel formation in the air were investigated using a Ti:Sapphire laser system at 800 nm. The results showed that increasing the repetition rate alone does not ensure a proportional increase in X-ray yield, because cumulative thermal effects in air can disturb beam propagation and filament stability. Pump-probe phase imaging measurements showed that the thermal channel formed after the laser pulse remains observable for up to approximately 1 ms. This indicates that at repetition rates of 1 kHz and above, subsequent pulses can propagate through air that has not fully returned to its initial state. It was also estimated that airflow velocities of the order of several meters per second (0,58 m/s – 2,84 m/s range) are sufficient to displace the thermal channel from the interaction region. Therefore, forced airflow can be considered a practical method for reducing cumulative thermal effects and improving the stability of high repetition rate filamentation experiments. |
