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Atom driven by superstrong laser fields as a source of ultrashort-pulse XUV radiation

Recent progress in the technique of generation and amplification of ultrashort laser pulses has resulted in the production of pulse duration of the order of or even shorter than 10 fs [1,2]. The use of Ti:Sa active crystals and broad-band optical elements, perfect compensation of wave dispersion in laser cavities and thorough comprehension of mode locking at self-focusing nonlinearity (Kerr-lens-mode-locking) have provided pulses having only few (∼3) optical cycles. Application of such a remarkable instrument opens up new prospects for experimental research on the interaction of ultrashort pulses with matter. It is also evident that a time has come for a serious theoretical analysis of these interaction models. Our report addresses the problem on nonlinear spectrum conversion of high intensity ultrashort laser pulses during the process of rapid optically-induced gas ionization.