Spectrum and polarization of THz radiation from two-color femtosecond laser breakdown: Theory and experiment

We present a comprehensive experimental and numerical study of spectral, spatial and polarization features of the widely used THz source - plasma of optical breakdown by a two-color femtosecond laser. We show experimentally presence of high-frequency component of THz radiation related to response of neutral gas molecules. Taking into account evolution of phase and polarization of optical pulses propagating through plasma allows to account for the experimentally observed polarization and spectrum of the emitted pulse.