Zeptosecond $\gamma$-ray pulses

TL;DR

This paper proposes a method using high-order harmonic generation in relativistic regimes to produce coherent zeptosecond gamma-ray pulses in the MeV energy range, enabling advanced nuclear spectroscopy.

Contribution

It introduces a novel approach employing counterpropagating laser pulses to generate relativistic harmonics without electron drift issues, enabling zeptosecond gamma-ray pulses.

Findings

Feasible generation of 10 MeV gamma-ray harmonics.

Production of coherent zeptosecond gamma-ray pulses.

Potential applications in time-resolved nuclear spectroscopy.

Abstract

High-order harmonic generation (HHG) in the relativistic regime is employed to obtain zeptosecond pulses of $\gamma$-rays. The harmonics are generated from atomic systems in counterpropagating strong attosecond laser pulse trains of linear polarization. In this setup recollisions of the ionized electrons can be achieved in the highly relativistic regime via a reversal of the commonly deteriorating drift and without instability of the electron dynamics such as in a standing laser wave. As a result, coherent attosecond $\gamma$-rays in the 10 MeV energy range as well as coherent zeptosecond $\gamma$-ray pulses of MeV photon energy for time-resolved nuclear spectroscopy become feasible.