Quantum theory of terahertz emission due to ultrashort pulse ionization of gases

摘要

A microscopic model is developed to analyze terahertz (THz) emission after ultrashort one- and two-colornlaser-pulse excitations of an atomic gas. Optical Bloch equations are derived to describe the pulse-inducednionization in the many-atom system including the Coulombic scattering of the ionized electrons. The modelncaptures the continuous transition between the tunneling and the multiphoton ionization regimes. Numericalnevaluations for a wide range of pulse configurations identify optimized excitation conditions for strong THznemission.