Ionization induced plasma grating and its applications in strong-field ionization measurements

TL;DR

This paper introduces a method using plasma gratings formed by intersecting laser pulses to measure ionization degrees and characterize low-density gases, aiding research in dense and low-density plasma physics.

Contribution

It demonstrates a novel application of plasma gratings for absolute electron density measurement and low-density gas characterization in strong-field ionization studies.

Findings

Effective measurement of ionization degree in dense gases.

Characterization of extremely low-density gas jets.

Potential for plasma-based acceleration applications.

Abstract

An ionization-induced plasma grating can be formed by spatially selective ionization of gases by the interference of two intersecting ultra-short laser pulses. The density modulation of a plasma grating can approach unity since the plasma is produced only where the two pulses constructively interfere and ionization does not occur in destructive interference regions. Such a large density modulation leads to efficient Thomson scattering of a second ultra-short probe pulse once the Bragg condition is satisfied. By measuring the scattering efficiency, it is possible to determine the absolute electron density in the plasma grating and thereby deduce the ionization degree for a given neutral gas density. In this paper, we demonstrate the usefulness of this concept by showing two applications: ionization degree measurement of strong-field ionization of atoms and molecules and characterization of extremely low-density gas jets. The former application is of particular interest for ionization physics studies in dense gases where the collision of the ionized electron with neighboring neutrals may become important-sometimes referred to as many-body ionization, and the latter is useful for plasma-based acceleration that requires extremely low-density plasmas.