Manipulation of femtosecond laser multi-filament array by spatiotemporal phase modulation

Unstable random multi-filament distribution by free propagation of high power femtosecond laser in transparent medium is unfavorable to the filamentation applications and controllable regular multi-filament array is desired. Here, we present a novel method to modulate the spatial distribution of multi-filament by a phase plate-assisted interference of two delayable femtosecond laser pulses. The experimental results show that regular femtosecond laser multifilament array can be realized and the array can be conveniently converted from one patten to another with the varying of the delay of the two laser pulses. It is found that the spatiotemporal phase variation of the interference beam is responsible for this control process. This work provides a new way to regulate the spatial distribution of multi-filament by simply varying relative phase of the two laser beams and holds a great flexibility for a filament array in many applications.