Caustic structures in the spectrum of x-ray Compton scattering off electrons driven by a short intense laser pulse

TL;DR

This paper investigates how short intense laser pulses influence the spectrum of x-ray Compton scattering off electrons, revealing sharp spectral caustics sensitive to pulse shape through semiclassical analysis.

Contribution

It introduces a detailed analysis of caustic structures in the x-ray Compton spectrum caused by laser pulse shape effects, using semiclassical methods.

Findings

Sharp spectral caustics depend on laser pulse shape

Spectral plateau features are shaped by nonlinear photon mixing

Semiclassical analysis explains caustic formation in spectra

Abstract

We study the Compton scattering of x-rays off electrons that are driven by a relativistically intense short optical laser pulse. The frequency spectrum of the laser-assisted Compton radiation shows a broad plateau in the vicinity of the laser-free Compton line due to a nonlinear mixing between x-ray and laser photons. Special emphasis is placed on how the shape of the short assisting laser pulse affects the spectrum of the scattered x-rays. In particular, we observe sharp peak structures in the plateau region, whose number and locations are highly sensitive to the laser pulse shape. These structures are interpreted as spectral caustics by using a semiclassical analysis of the laser-assisted QED matrix element.