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Direct Observation of Multiple Photon Absorption by Free Electrons in a Wide Band-Gap Insulator under Strong Laser Irradiation

1994; American Physical Society; Volume: 73; Issue: 17 Linguagem: Inglês

10.1103/physrevlett.73.2352

1092-0145

Ph. Daguzan, S. Guizard, K. Krastev, P. Martín, G. Petite, Laurent El Kaïm, A. Antonetti,

Advanced Electron Microscopy Techniques and Applications

We measure the kinetic energy of photoelectrons emitted from an $\ensuremath{\alpha}$-quartz surface irradiated by short (100 fs) and intense laser pulses. In the high intensity regime (above 100 GW/${\mathrm{cm}}^{2}$), we observe a high-energy tail in the photoemission spectra at 620 and 560 nm. This effect disappears for the doubled frequencies. These observations give direct evidence of free-electron multiple photon absorption in the conduction band, in keeping with recent Monte Carlo simulation results.