Water window soft x-ray source enabled by 25-W few-cycle mid-IR OPCPA at 100 kHz

TL;DR

This paper reports a high-power, high-repetition-rate mid-IR laser system that enables the generation of coherent soft x-ray sources in the water window at 100 kHz, significantly advancing experimental capabilities.

Contribution

Development of a 25-W, 100-kHz mid-IR OPCPA system that achieves record peak power, facilitating high-repetition-rate soft x-ray generation via high-harmonic generation.

Findings

Achieved 25 W average power at 100 kHz in mid-IR OPCPA

Generated soft x-ray continuum beyond 0.6 keV

Set a new record for peak power in high-repetition-rate mid-IR lasers

Abstract

Coherent soft x-ray (SXR) sources enable fundamental studies in the important water window spectral region. Until now, such sources have been limited to repetition rates of 1 kHz or less, which limits count rates and signal-to-noise ratio for a variety of experiments. SXR generation at high repetition rate has remained challenging because of the missing high-power mid-infrared (mid-IR) laser sources to drive the high-harmonic generation (HHG) process. Here we present a mid-IR optical parametric chirped pulse amplifier (OPCPA) centered at a wavelength of 2.2 {\mu}m and generating 16.5-fs pulses (2.2 oscillation cycles of the carrier wave) with 25 W of average power and a peak power exceeding 14 GW at 100-kHz pulse repetition rate. This corresponds to the highest reported peak power for high-repetition-rate mid-IR laser systems. The output of this 2.2-{\mu}m OPCPA system was used to generate a SXR continuum extending beyond 0.6 keV through HHG in a high-pressure gas cell.