Unified framework for terahertz radiation from a single- or two-color plasma filament

The plasma filament induced by photo-ionization in transparent media (e.g., air) is a competitive terahertz (THz) source, whose mechanism has been widely studied in two separate schemes, i.e., the one- or two-color femtosecond laser filamentation. However, the physical commonality of these two schemes is less explored currently, and a common theory is in urgent need. Here, we proposed the traveling-wave antenna (TWA) model applicable to both single- and dual-color laser fields, which successfully reproduced the reported far-field THz angular distribution/dispersion from different filament lengths with either a constant or a varied plasma density. This work paves the way toward a deeper understanding of the important laser-filament-based THz sources within the same theoretical framework.