Formation of spiraling infrared emission patterns by controlled interaction of optical filaments.

We analyzed the formation of mid-infrared conical emission patterns possessing spiral and half-ring shaped wavelength contours from a beam of a few optical filaments. The complex patterns were generated and modified experimentally by adaptive wavefront shaping of the femtosecond laser pulse. Mutual interactions between co-propagating filaments can induce curvature in their paths, and the spiral and half-ring emissions were shown to be a direct consequence of this angular deflection. Based on our experimental and computational results, the spirals form in the far-field due to self-interference of conical emission from a helically moving filament. The presented findings will advance the tailoring of spatial conical emission patterns potentially beneficial for spectroscopic applications and terahertz generation.