Optimal wavelength for two-color filamentation-induced terahertz sources.

We theoretically study the generation of terahertz (THz) radiation by two-color filamentation of ultrashort laser pulses with different wavelengths. We consider wavelengths in the range from 0.6 to 10.6 μm, thus covering the whole range of existing and future powerful laser sources in the near, mid and far-infrared. We show how different parameters of two-color filaments and generated THz pulses depend on the laser wavelength. We demonstrate that there is an optimal laser wavelength for two-color filamentation that provides the highest THz conversion efficiency and results in generation of extremely intense single cycle THz fields.