Attosecond pulse generation by a two-color laser field

We suggest a new method for attosecond electromagnetic pulse generation. The key idea consists in using a two-color laser pump in the technique of "high-order harmonic generation": linearly polarized low-frequency field and circularly polarized high-frequency field. We found conditions and specific parameters of two-color pump, for which the duration of recombination emission can be less than 10 attoseconds. Our numerical simulations show that with pump radiation of relativistic intensity and due to effect of "magnetic" focusing it is possible to get 20 as pulses of recombination radiation