ИСТИНА

Interactions of laser radiation with gas cluster targets have been investigated in the past two decades. Cluster jet, obtained by the adiabatic condensation of gas flow, has pronounced nonlinear optical properties and combines the advantages of solidstate and gas target. Cluster inherits high local density and this implies high value of nonlinear response: generation of X-ray radiation, generation of optical harmonics, self-focusing, Stimulated Raman Scattering. In some recent publications, intense THz generation in cluster beam excited by ultrashort laser pulses was reported. At the present moment there is no clear theoretical interpretation of the experimental results and complete understanding of the mechanism of low-frequency emission in cluster plasma. It seems reasonable to carry out further study of terahertz generation in a clustered plasma, and examine this process in both ways: as a fundamental issue of laser-matter interaction on the way to solving a problem of the dynamics of laser-cluster interaction, and as a practical goal of obtaining an effective source of pulsed THz radiation. In addition, there is possible to apply two-color excitation scheme, which has been successfully used in the past to increase the efficiency of the optical to terahertz conversion in laser-induced plasma of gas media. Two-color scheme allows to increase THz yield by Ϯ͙ϯ ŽƌĚĞƌƐ ŽĨ ŵĂŐŶŝƚƵĚĞ ĂŶĚ ŶŽǁĂĚĂLJƐ ƚŚŝƐ ƐĐŚĞŵĞ ŝƐ ǁŝĚĞůLJ ƵƐĞĚ ĨŽƌ d,nj generation in gaseous media. In this paper we present the results of experimental and theoretical studies of generation of terahertz emission in the laser-induced clustered plasma. We have performed experiments using both single-color and two-color excitation schemes. Simultaneously with the control of terahertz emission of clustered plasma we measured the power of accompanying X-ray radiation, which is an important source of information about the processes that occur in a cluster plasma. In the theoretical section we made an attempt to explain the experimental results.