A method for the generation of attosecond electromagnetic pulses is suggested. The key idea of the method consists in using a two-color laser pump for high-order harmonic generation composed of a low-frequency linearly polarized field and a high-frequency elliptically polarized field. Such a two-color pump can provide for the return of photoelectrons (after atom ionization) to the vicinity of the parent ion with high kinetic energy and their recombination for only specific ionization moments t<sub>0</sub>. The range of these moments, δt<sub>0</sub>, is defined by the velocity of electron wave-packet spreading and the time that the photoelectron spent in the continuum (before the recombination). Conditions were found that minimize the range δt<sub>0</sub>. For the specific parameters of a two-color pump, the duration of recombination emission, τ<sub>g</sub>, can be in the range of 1–10 as. With an increase of pump intensity, the duration τ<sub>g</sub> decreases and can be reduced to the subattosecond scale.
© 2004 Optical Society of America
(190.4160) Nonlinear optics : Multiharmonic generation
(190.4180) Nonlinear optics : Multiphoton processes
(270.4180) Quantum optics : Multiphoton processes
(270.6620) Quantum optics : Strong-field processes
Vladimir D. Taranukhin, "Attosecond pulse generation by a two-color field," J. Opt. Soc. Am. B 21, 419-424 (2004)