Understanding the mechanism of pulse cumulative effect on supercontinuum generation from femtosecond laser filament in air

We investigate the influence of pulse cumulative effect on supercontinuum generation from femtosecond laser filaments in air. Based on experimental and numerical insights, a clear physical picture of the pulse cumulative effect on the supercontinuum generation is constructed. The experimental results show that higher repetition rates correlated with supercontinuum extension into shorter wavelengths, attributed to the pulse cumulative effect, which is a consequence of gas dynamics influenced by heating, resulting in a reduced density of gas molecules. The effects on Kerr and plasma-induced self-phase modulation are analyzed in terms of the supercontinuum generation mechanism, and it is concluded that enhanced Kerr-induced self-phase modulation leads to supercontinuum broadening towards shorter wavelengths. This study holds promise not only for better understanding the supercontinuum generation mechanism in the filaments but also for providing guidance on the supercontinuum generation in different repetition rate and their applications.