Non-Linear Compton Scattering of Ultrashort and Ultraintense Laser Pulses

TL;DR

This paper develops a covariant quantum electrodynamics framework to analyze non-linear Compton scattering of ultrashort, ultraintense laser pulses, revealing complex photon spectra and quantum effects beyond classical predictions.

Contribution

It introduces a pulse-shape independent cross section expression and a scaling law linking classical Thomson scattering with quantum results for arbitrary kinematics.

Findings

Broad photon spectra with subpeaks similar to Thomson scattering.

Overlap of peaks at high intensities challenges harmonic interpretation.

Quantum effects significantly modify photon distributions in certain regimes.

Abstract

The scattering of temporally shaped intense laser pulses off electrons is discussed by means of manifestly covariant quantum electrodynamics. We employ a framework based on Volkov states with a time dependent laser envelope in light-cone coordinates within the Furry picture. An expression for the cross section is constructed, which is independent of the considered pulse shape and pulse length. A broad distribution of scatted photons with a rich pattern of subpeaks like that obtained in Thomson scattering is found. These broad peaks may overlap at sufficiently high laser intensity, rendering inappropriate the notion of individual harmonics. The limit of monochromatic plane waves as well as the classical limit of Thomson scattering are discussed. As a main result, a scaling law is presented connecting the Thomson limit with the general result for arbitrary kinematics. In the overlapping regions of the spectral density, the classical and quantum calculations give different results, even in the Thomson limit. Thus, a phase space region is identified where the differential photon distribution is strongly modified by quantum effects.