High harmonic radiation from the scattering of an electron with a focused few-cycle laser pulse

Abstract

We have investigated the radiation property of a relativistic electron counter propagating in an intense focused few-cycle laser pulse. The radiation in this process is very similar to high harmonic generation in the atomic strong-field process, which is strongly dependent on the carrier-envelope (CE) phase and the peak intensity of the driving laser pulse. Dependent on the CE phase, high harmonic spectra in the cutoff region are either well resolved or not resolved. The cutoff of radiation spectra is linearly dependent on the laser intensity with the relation of 32a (here, a is the normalized laser intensity and is given by eE0/mcω0, where e is the electron charge, m is the electron mass, c is the light speed in vacuum, E0 and ω0 are the light field and the light frequency respectively). Using this high nonlinear process, we discuss a potential method to characterize an intense few-cycle laser pulse, e.g., the peak intensity, the pulse duration and the CE phase, and to generate an ultrashort x-ray pulse for extensive applications.