Bright coherent ultrahigh harmonics in the keV x-ray regime from mid-infrared femtosecond lasers.
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.
JILA, University of Colorado at Boulder, Boulder, CO 80309, USA. popmintchev@jila.colorado.edu
Tenio
T
Popmintchev
Ming-Chang
MC
Chen
Dimitar
D
Popmintchev
Paul
P
Arpin
Susannah
S
Brown
Skirmantas
S
Alisauskas
Giedrius
G
Andriukaitis
Tadas
T
Balciunas
Oliver D
OD
Mücke
Audrius
A
Pugzlys
Andrius
A
Baltuska
Bonggu
B
Shim
Samuel E
SE
Schrauth
Alexander
A
Gaeta
Carlos
C
Hernández-García
Luis
L
Plaja
Andreas
A
Becker
Agnieszka
A
Jaron-Becker
Margaret M
MM
Murnane
Henry C
HC
Kapteyn