Ray-Tracing Simulation on Filamentation of Prefocused and Freely Propagated Laser Pulses in Air

The filamentation mechanisms of prefocused and freely propagated femtosecond laser pulses are compared using the ray-tracing method. The dynamic spatial replenishment mechanism takes place in the filaments with high electron density, which is generally formed by prefocused laser pulses. The mechanism of long-range filamentation over 100m distance is analyzed to be the spatiotemporal moving focus.