Coherent hard x-rays from attosecond pulse train-assisted harmonic generation

TL;DR

This paper demonstrates a method to generate coherent hard x-ray pulses up to 40 keV and 10 attoseconds duration by using attosecond pulse trains to assist high-order harmonic generation in relativistic laser fields.

Contribution

It introduces a novel scheme combining attosecond soft x-ray pulses with relativistic laser fields to overcome relativistic drift and produce coherent hard x-ray pulses.

Findings

Generation of coherent hard x-rays up to 40 keV.

Production of 10 attosecond duration pulses.

Effective compensation of relativistic drift via one-photon ionization.

Abstract

High-order harmonic generation from atomic systems is considered in the crossed fields of a relativistically strong infrared laser and a weak attosecond-pulse train of soft x-rays. Due to one-photon ionization by the x-ray pulse, the ionized electron obtains a starting momentum that compensates the relativistic drift which is induced by the laser magnetic field, and allows the electron to efficiently emit harmonic radiation upon recombination with the atomic core in the relativistic regime. In this way, short pulses of coherent hard x-rays of up to 40 keV energy and 10 as duration can be brought about.