Terahertz-radiation generation in the ionization-free regime of light-atom interaction

Abstract

We present an interpretation of the terahertz (THz) generation in atomic gases interacting with two-color laser fields. Within the presented interpretation the process of the THz generation is associated with purely intra-atomic nonlinearity and the energy of emission is determined by the work (executed by the laser field) on the atomic electron motion in the nonharmonic intra-atomic field. To illustrate the specific features of this generation mechanism we present the results of numerical simulations on an argon atom interaction with a two-color laser field formed by the arbitrary polarized pulses at fundamental frequency and second harmonic of Ti:sapphire laser. The intensity of the laser field has been limited by ${I}_{0}<6.77\ifmmode\times\else\texttimes\fi{}{10}^{12}\frac{W}{{\mathrm{cm}}^{2}}$ (for $\ensuremath{\lambda}=800$ nm) that enables us to model the ionization-free regime of the light-atom interaction. It is demonstrated that the spectrum of the THz emission, integral efficiency of generation, and polarization state of spectral components strongly depend on the angle between the polarization vectors of laser field components. So, the variation of this angle provides the effective method of the THz generation control.