Ultrafast Polarization-Tunable Monochromatic Extreme Ultraviolet Source at High-Repetition-Rate

TL;DR

This paper presents a high-repetition-rate, polarization-tunable monochromatic extreme ultraviolet source based on high-order harmonic generation, enabling advanced spectroscopic techniques with high brightness and controllable polarization.

Contribution

The authors developed a novel HHG-based EUV source with spatial separation of laser and XUV beams, allowing polarization control at high repetition rates, which was not previously achievable.

Findings

Achieved 5.7×10^12 photons/s brightness at 21.6 eV

Demonstrated polarization tunability with ellipticities up to 90%

Operates at 250 kHz repetition rate

Abstract

We report on the development of a high-order harmonic generation (HHG)-based ultrafast high-repetition-rate (250 kHz) monochromatic extreme ultraviolet (21.6 eV) source with polarization tunability, specifically designed for multi-modal dichroism in time- and angle-resolved photoemission spectroscopy. Driving HHG using an annular beam allows us to spatially separate the high-power 515 nm driving laser from the XUV beamlet while preserving the linear polarization axis angle tunability. This enables controlling the polarization state of the XUV radiation with a fixed all-reflective phase-shifter. This scheme leads to a source brightness of 5.7$\times$10$^{12}$ photons/s at 21.6 eV (up to 4$\times$10$^{11}$ photons/s on target) with ellipticities as high as 90$\%$.