The influence to filamentation of femtosecond by atmospheric turbulence at wavelength of 400 nm has been studied numerically. Simulations show that the distance of filamentation at 400 nm is advanced, the number of filaments increases, and the energy of filaments decreases with the addition of turbulent screen. Compared with the filaments formed by the 800 nm femtosecond laser, the nonlinear propagation of 400 nm laser has a longer filamentation distance in the turbulent atmosphere, and the clamping light intensity of the filaments is higher, but the number of filaments has reduced. With the increase of propagation distance, the multifilament structure disappears and the beam gradually converges into a stable monofilament structure. The position of the monofilament structure at 400 nm is closer than the 800 nm. Therefore, stable filament structure can be obtained more easily with a femtosecond laser at 400 nm.
We numerically investigated the nonlinear propagation of femtosecond positive temporal Airy pulses in air. Effects of background energy distribution of the laser pulses on the characteristics of filamentation are studied by changing the confinement parameter of the temporal Airy pulses. The simulation results indicate that the on-axis intensity and electron density increase with the confinement parameter decreases. More defocusing-refocusing cycles have been observed during the propagation of Airy pulses with smaller confinement parameter. More temporal distortions occur in the trailing edge of Airy pulses than Gaussian pulse. The temporal Airy pulses can form longer filament than the Gaussian pulse when fixing the initial intensity.
Characteristics of energy deposition during filamentation are numerically investigated to understand the formation of different mass of snow with femtosecond laser pulses in a cloud chamber. The results show that the evolution of maximum airflow velocity and mass of snow is closely related to the amount of deposited energy. For the same input energy, the deposited energy is higher for laser pulse externally focused by an f=30 cm lens than an f=50 cm lens, which is in accordance with the higher airflow velocity and mass of snow in experiments with the former lens.