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

2012; American Association for the Advancement of Science; Volume: 336; Issue: 6086 Linguagem: Inglês

10.1126/science.1218497

1095-9203

Tenio Popmintchev, Ming-Chang Chen, Dimitar Popmintchev, P. Arpin, Susannah Brown, S. Ališauskas, G. Andriukaitis, Tadas Balčiūnas, Oliver D. Mücke, A. Pugžlys, Andrius Baltuška, Bonggu Shim, Samuel E. Schrauth, Alexander L. Gaeta, Carlos Hernández-García, Luis Plaja, Andreas Becker, Agnieszka Jaroń-Becker, Margaret M. Murnane, Henry C. Kapteyn,

Laser-Plasma Interactions and Diagnostics

High-harmonic generation (HHG) 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 greater than 5000, that emerge as a bright supercontinuum that spans the entire electromagnetic spectrum from the ultraviolet to more than 1.6 kilo-electron volts, allowing, in principle, the generation of pulses as short as 2.5 attoseconds. The multiatmosphere gas pressures required for bright, phase-matched emission also support 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 HHG encounter other atoms during the emission process.