Radial focusing of electron wave packets using linearly chirped intense pulses

We present a theoretical study of the properties of an electron wave packet created by a linearly chirped pulse in the strong-field regime. Radial focusing of the wave packet at macroscopic distances which occurs in the case of a weak laser pulse is still possible but at different time and position. Two different situations are reported. (1) The case of a weakly chirped pulse, for which power broadening of the energy distribution occurs. The electron wave packet focuses to less than the inverse of the pulse spectrum bandwidth. (2) The case of highly chirped pulses, for which a new regime is highlighted where power narrowing of the energy distribution occurs. Saturation effects are shown in this case to improve the quality of focusing by reducing the temporal distortions of the wave packet at the focus point