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Compensation of electron wave packet spreading with linearly chirped pulses : theoretical analysis

We investigate in this paper the properties of electron wavepackets created in the continuum by ultrashort pulses, linearly chirped. We consider alkali atoms, where complete quantum calculations can be carried out. The spreading of the wavepacket is radial and mainly due to free propagation, except for very low kinetic energy where Coulomb interaction has to be considered. We show that the wavepacket can be focused into a position located at macroscopic distances far from the ion core. Distances as large as several centimetres are obtained for standard values of laser parameters. Moreover, we derive the conditions where the wavepacket is temporally optimally focused. Finally, we study several characteristics of the wavepacket, such as the temporal divergence (in ps cm-1) and the temporal profile, when the focusing is not maximum.


Voir en ligne : J. Phys. B 35, 1819-1830 (2002)