The dynamics of a one-dimensional atom driven by three-laser fields is investigated. The total electric field is made up of a fundamental laser field of intensity I = 2 × 1014W cm-2 and wavelength γ = 820 nm and two weak lasers with larger wavelengths. The intensity of the two weak fields is with k2I k = 0.25. The frequencies of the weak fields are 2ωL/3 + ΔωL and 2ωL/3 - δωL/ωL = 2π/λ. The three lasers have a Gaussian envelope of 72 fs FWHM. It is shown, by numerical computation and using the semiclassical theory of high-harmonic generation, that the atom interacting with this combined field is able to emit an isolated attosecond burst of radiation.
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