ИСТИНА

The process of non-linear interaction of atomic gas with the two-color laser field of frequencies and is an effective mechanism to produce the terahertz radiation. It is usually assumed that this specific non-linear transformation is mainly due to the plasma nonlinearities. Here we study the process of single argon atom interaction with the pulses of Ti:Sapphire laser at basic frequency (λ=800 nm) and second harmonic. In our computer simulations we have assumed that the intensity of laser field is below the ionization threshold. Nevertheless, the results of our study show that the terahertz radiation is effectively emitted under these conditions. The methods of control of conversion efficiency are discussed. They are based on the variation of relative orientation of polarization vectors of linear polarized laser pulses at frequencies of and , delay time between them, and their relative intensities. In our computer simulations we have used the non-perturbative theory of light-atom interaction based on the exact eigenfunctions of the boundary value problem for the atom in the external field. This approach has been proposed in [1] and later developed for explanation of a number of specific features of high optical harmonic generation effect [2-4]. In the frame of this approach the spectra of atomic electrons in the final state (after action of laser pulse) are calculated analytically, therefore the threshold ionization intensity, which depends on the given values of laser pulse parameters and atomic energy level diagram, can be strongly defined. As a result, the input of the bound and free electrons to the atomic response can be exactly estimated. References [1] A.V. Andreev, “Interaction of an atom with superstrong laser fields”, JETP, 116, №3(9), 793, (1999). [2] A.V. Andreev, O.A. Shoutova, S. Yu. Stremoukhov, “Ionization of a single hydrogen-like atom by laser pulses of near-atomic strength”, Laser Physics, 17(4), pp. 496 (2007). [3] A.V. Andreev, S.Yu. Stremoukhov, O.A.Shoutova, “Atom in electromagnetic field of near-atomic strength”, JRLR, 29 (3), pp. 203 (2008). [4] A.V. Andreev, S.Yu. Stremoukhov, O.A.Shoutova, “Theory of Multilevel Atom Ionization”, AIP Conference Proceedings 1228, pp. 92-111 (2010).