Imaging the source of high-harmonics generated in atomic gas media

TL;DR

This paper introduces a novel time-gated ion microscopy method to directly image and control the source position of high-harmonics in atomic gases, enhancing experimental precision in attosecond science.

Contribution

It presents a new online imaging technique for harmonic sources, enabling better control and quantitative analysis of harmonic properties in atomic gas media.

Findings

Source position depends on gas medium and IR focus alignment.

Online control of harmonic source position is achieved by translating the gas.

Quantitative info on divergence, coherence, and flux of harmonics is obtained.

Abstract

We report the application of the time gated ion microscopy technique in accessing online the position of the source of harmonics generated in atomic gas media. This is achieved by mapping the spatial extreme-ultraviolet (XUV)-intensity distribution of the harmonic source onto a spatial ion distribution, produced in a separate focal volume of the generated XUV beam through single photon ionization of atoms. It is found that the position of the harmonic source depends on the relative position of the harmonic generation gas medium and the focus of the driving infrared (IR) beam. In particular, by translating the gas medium with respect to the IR beam focus different virtual source positions are obtained online. Access to such online source positioning allows better control and provides increased possibilities in experiments where selection of electron trajectory is important. The present study gives also access to quantitative information which is connected to the divergence, the coherence properties and the photon flux of the harmonics. Finally, it constitutes a precise direct method for providing complementary experimental info to different attosecond metrology techniques.