Single attosecond soft-x-ray pulse generated with a limited laser beam

The problem of obtaining a single attosecond pulse with high-order harmonic s generation is considered. A method for producing an exciting light pulse with a time-dependent degree of ellipticity from a one-frequency linearly p olarized laser pulse by means of linear optics is suggested. The whole of t he field generated with a limited beam of this light in a gas target is cal culated in the far zone. For this calculation we use an original method bas ed on the time approach of a theory of high-order harmonic generation. Cont rasted and intense (focused) single attosecond soft-x-ray pulses are calcul ated by suppression of the low-frequency part of the field to as many as 11 harmonics of exciting frequency. The possibility of suppressing the low-fr equency part of the field with pinholes is shown. (C) 1999 Optical Society of America [S0740-3224(99)02002-0] OCIS codes: 190.4160, 190.4180, 190.7110 , 320.2250, 320.5550.