Filamentation of interacting femtosecond laser pulses in air

The filamentation of two co-propagated femtosecond (fs) laser pulses in air is studied by numerical simulation. Depending on the different initial separation distances, relative phase shift and crossing angles, simulations show attraction, fusion, repulsion and collision of the two pulses. A long plasma channel can be formed by two in-phase pulses with small separation distance and cross angle. The coupling of two laser beam becomes weaker when the separation distance or cross angle between two beams is larger. In this case, the filamentation of each pulse develops independently. Our simulation results will be helpful for understanding the effect of the initial amplitude and phase modulation of laser pulse on the filamentation characteristics.