Bright, polarization-tunable high repetition rate extreme ultraviolet beamline for coincidence electron-ion imaging

TL;DR

This paper presents a versatile Ytterbium-based high-harmonic generation setup producing tunable, high-flux extreme ultraviolet radiation for advanced electron-ion imaging, enabling new circular dichroism experiments.

Contribution

It introduces a novel experimental setup with cascaded high-harmonic generation producing high-power, tunable XUV radiation, including circularly polarized light, for coincidence imaging.

Findings

Achieved 1.8 mW average power at 18 eV

Demonstrated circularly polarized XUV generation

Successfully measured photoelectron distributions in xenon

Abstract

After decades of supremacy of the Titanium:Sapphire technology, Ytterbium-based high-order harmonic sources are emerging as an interesting alternative for experiments requiring high flux of ultrashort extreme ultraviolet (XUV) radiation. In this article we describe a versatile experimental setup delivering XUV photons in the 10-50 eV range. The use of cascaded high-harmonic generation enables us to reach 1.8 mW of average power at 18 eV. Several spectral focusing schemes are presented, to select either a single harmonic or group of high-harmonics and thus an attosecond pulse train. In the perspective of circular dichroism experiments, we produce highly elliptical XUV radiation using resonant elliptical high-harmonic generation, and circularly polarized XUV by bichromatic bicircular high-harmonic generation. As a proof of principle experiment, we focus the XUV beam in a coincidence electron-ion imaging spectrometer, where we measure the photoelectron momentum angular distributions of xenon monomers and dimers.