Scaling and Saturation of High-Power Terahertz Radiation Generation in Two-Color Laser Filamentation

Broadband terahertz generation via two-color femtosecond laser filamentation is studied with laser input energies up to 60 mJ. In the small f-number focusing regime, the output THz energy strongly saturates, which is attributed to ionization-induced laser defocusing in filamentation. This saturation effect can be minimized by elongating the plasma filament with weak focusing. A conversion efficiency of >10⁻⁴ is achieved in elongated filamentation.