Vt. Platonenko et Vv. Strelkov, SPATIOTEMPORAL STRUCTURE OF THE COMBINED FIELD OF HIGH-ORDER HARMONICS AND GENERATION OF ATTOSECOND PULSES, Quantum electronics, 27(9), 1997, pp. 779-784
An investigation is made of the feasibility of separating a train of a
ttosecond short-wavelength pulses from a combined field of high-order
harmonics. Semiclassical and quantum-mechanical theories of the genera
tion of high-order harmonics are used to consider the problem of minim
um duration of a pulse which can be generated by summing the fields of
several adjacent harmonics near a harmonic-generating gas layer. A st
udy is made of the spatial structure of the field of harmonics generat
ed in a thin layer subjected by a Gaussian laser beam. It is shown tha
t harmonics of different orders have different divergences and that th
ey focus at different distances when generated in a converging beam. T
his effect may be utilised to separate harmonics of specific orders, p
articularly in the generation of attosecond pulses. High-intensity fun
damental-frequency and third-harmonic radiations should be suppressed
by other methods. Calculations predict that pulses of duration down to
90 as and of intensity comparable with that of the third harmonic can
be generated.