Scaling strong-field interactions towards the classical limit

• Published in: Nature physics Vol. 4; no. 5; pp. 386 - 389
• Main Authors: DiMauro, L. F, Colosimo, P, Doumy, G, Blaga, C. I, Wheeler, J, Hauri, C, Catoire, F, Tate, J, Chirla, R, March, A. M, Paulus, G. G, Muller, H. G, Agostini, P
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.05.2008; Nature Publishing Group
• Subjects: Argon; Atomic; Classical and Continuum Physics; Complex Systems; Condensed Matter Physics; Ionization; Lasers; letter; Light sources; Mathematical and Computational Physics; Molecular; Optical and Plasma Physics; Physics; Physics and Astronomy; Predictions; Theoretical; Theory; Wavelengths
• ISSN: 1745-2473; 1745-2481
• DOI: 10.1038/nphys914

In 1964 Keldysh helped lay the foundations of strong-field physics by introducing a theoretical framework that characterized atomic ionization as a process that evolves with the intensity and wavelength of the fundamental field. Within this context, experiments have examined the intensity-dependent ionization but, except for a few cases, technological limitations have confined the majority to wavelengths below 1 μm. The development of intense, ultrafast laser sources in the mid-infrared (1 μm<λ<5 μm) region enables exploration of the wavelength scaling of the Keldysh picture while enabling new opportunities in strong-field physics, control of electronic motion and attosecond science. Here we report a systematic experimental investigation of the wavelength scaling in this region by concurrently analysing the production of energetic electrons and photons emitted by argon atoms interacting with few-cycle, mid-infrared fields. The results support the implicit predictions contained in Keldysh's work, and pave the way to the realization of brighter and shorter attosecond pulsed light sources using longer-wavelength driving fields.