Emission of spiral patterns from filaments in the infrared.

We investigated the spectral and spatial properties of the supercontinuum emission of single filaments in air in the infrared (1.5 µm-5.3 µm). The infrared emission of the filament was controlled by modulating the spatial phase of the femtosecond driver pulse with a deformable mirror. Filaments with a characteristic spiral emission pattern in the infrared were generated for a variety of different wavefront profiles of the femtosecond pulse. The properties of this novel class of emission were analyzed more closely. Further understanding of the corresponding emission dynamics of the filament will help to refine current models of filament propagation.