Emissions from single filaments in air triggered by tailored background energy flows.

We investigated emission patterns from single or few filaments in air created by femtosecond laser pulses with spatially modulated wavefronts. For 800 nm filaments, spiral emissions can be obtained in the infrared. Time-resolved analysis of the corresponding dynamics of the energy surrounding the filament reveals stable energy flows with angular momentum that interact with the filament and with each other. Changing this energy distribution by modulation of the wavefront of the initial laser pulse directly affects the emission behavior of the filament.