Breaking of the Axial Symmetry of Terahertz Radiation from Single-Color Filament Plasma

Two-dimensional distribution patterns of terahertz radiation generated in a laser single-color filament plasma are measured at several frequencies. In the low-frequency region (0.1–0.5 THz), the radiation propagates in a cone with a minimum on the axis. At higher frequencies, the terahertz radiation pattern depends significantly on the laser pulse polarization. In the case of linear polarization, the axial symmetry is broken: terahertz radiation propagates into two maxima located along the axis perpendicular to the laser polarization. In the case of circular polarization, the axial symmetry of the terahertz radiation distribution is restored.