paper

Bright Coherent Ultrahigh Harmonics in the keV X-Ray Regime from Mid-Infrared Femtosecond Lasers

arXiv:2403.19535 · doi:10.1126/science.1218497

Abstract

High harmonic generation traditionally combines ~100 near-infrared laser photons, to generate bright, phase matched, extreme ultraviolet beams when the emission from many atoms adds constructively. Here we show that by guiding a mid-infrared femtosecond laser in a high pressure gas, ultrahigh harmonics can be generated up to orders > 5000, that emerge as a bright supercontinuum that spans the entire electromagnetic spectrum from the ultraviolet to > 1.6 keV, allowing in-principle the generation of pulses as short as 2.5 attoseconds. The multi-atmosphere gas pressures required for bright, phase matched emission also supports laser beam self-confinement, further enhancing the x-ray yield. Finally, the x-ray beam exhibits high spatial coherence, even though at high gas density, the recolliding electrons responsible for high harmonic generation encounter other atoms during the emission process.

32 pages, 9 figures (4 in main text, 5 in supplemental materials)

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