Nonlinear Compton scattering in ultra-short laser pulses

TL;DR

This paper investigates photon emission spectra during nonlinear Compton scattering of electrons in ultra-short laser pulses, revealing broad emission lines and no electron mass dressing at high intensities, using strong-field QED.

Contribution

It provides a detailed analysis of emission spectra in ultra-short laser pulses, emphasizing nonperturbative effects at high intensities with exact laser field treatment.

Findings

Emission lines are broader in ultra-short pulses.

No electron mass dressing observed at high intensities.

Spectra differ significantly from long pulse or monochromatic cases.

Abstract

A detailed analysis of the photon emission spectra of an electron scattered by a laser pulse containing only very few cycles of the carrying electromagnetic field is presented. The analysis is performed in the framework of strong-field quantum electrodynamics, with the laser field taken into account exactly in the calculations. We consider different emission regimes depending on the laser intensity, placing special emphasis on the regime of one-cycle beams and of high laser intensities, where the emission spectra depend nonperturbatively on the laser intensity. In this regime we in particular present an accurate stationary phase analysis of the integrals that are shown to determine the computed emission spectra. The emission spectra show significant differences with respect to those in a long pulsed or monochromatic laser field: the emission lines obtained here are much broader and, more important, no dressing of the electron mass is observed.