Effects of delayed Kerr nonlinearity on the propagation of femtosecond annular Gaussian filaments in air

Abstract

The effects of the delayed Kerr nonlinearity on the annular Gaussian filaments nearby the characteristic time of the molecular rotational respond are numerically investigated. The simulated results show that the delayed Kerr nonlinearity leads to the advancement of the filament onset distance when the pulse duration is fixed. Moreover, in the presence of the delayed Kerr nonlinearity, the length of the filament is obviously extended, and the peak plasma density appears the great oscillations that makes the filament become unstable and nonuniform. These results are mainly induced by the redistribution of the fluence and the modulation of the speed of the total energy loss in the presence of the delayed Kerr nonlinearity. Moreover, the delayed Kerr nonlinearity enhances the self-focusing of the trailing edge and leads further to the extension of the optical filament. This research is of great significance to deeply understand the long-distance transmission characteristics of the annular Gaussian filaments.

Numerical investigation on the heat deposition characteristics of femtosecond laser pulses undergoing multiple filaments

“…In order to adequately understand the influences of input pulse energy on the characteristics of laser filaments, figure 7 shows the simulated dependence of various filamentation parameters including length of filament (L f ), maximum electron density (ρ max ), peak fluence (F max ), total deposited energy (ΔE), maximum energy deposition rate ( / ¶D ¶ E z), and maximum local temperature variation (ΔT) as a function of input energy. Here, we define the filament length as the length from the onset distance to the value of the peak plasma density less than 10 14 cm −3 at the last beam collapse [37]. As shown in figure 7(a), the increase of filament length is limited by the formation of multiple filaments with the growth of the pulse energy.…”