Formation of multiple laser filaments assisted by laser-induced diffraction gratings in air

The manipulation of the filaments formed by two dual-color laser pulses in air in parallel arrangement is investigated experimentally. When the two pulses interfere with each other, a spatially periodic distribution of the light intensity is produced, thereby altering the refractive index of the air through the nonlinear Kerr effect and forming a series of diffraction gratings across the entire optical path. The co-propagating 400-nm laser components could be deflected by these interference gratings and form a new filament in the middle of two filaments excited by two pumps at 800 nm. This grating diffraction model is validated by the reasonably good agreement with experimental observations. This study proposes a practical method for the manipulation of laser plasma filaments in an all-optical manner based on the laser-induced diffractive gratings, which will enrich the applications of multiple filaments in many aspects, such as terahertz radiation, waveguide writing, and remote sensing detection.