Session 17 – ATTOSECOND PROCESSES IN CONDENSED MATTER II

Chair: Caterina Vozzi, CNR, Milano, Italy

#78, 10:30 – 11:00 High order harmonic generation in solid argon, GEORGES NDABASHIMIYE, DAVID A. REIS, AND SHAMBHU GHIMIRE, We report on comparisons of high-order harmonic generation in solid argon with the atomic response in a dilute argon gas. The harmonic spectrum in the solid exhibits a secondary plateau and a subsequent cut-off extending beyond the gas phase cut-off at the peak intensity of 1.8x1013W/cm2. These observations point to solid-state effects beyond single-band coherent Bloch oscillations in strongly-driven periodic media.

#79, 11:00 – 11:15 Linking high harmonics from gases and solids, G. VAMPA, T. J. HAMMOND, N. THIRÉ, B. E. SCHMIDT, F. LÉGARÉ, C. R. MCDONALD, T. BRABEC, AND P. B. CORKUM, In the generation of high harmonics from a ZnO crystal we find a “generalized recollision” between the electron and the hole to dominate the emission. Further, we report on high harmonic generation from GaN, quartz and silicon. The generation process is extremely sensitive to perturbing fields and we suggest using this sensitivity to image time-dependent fields in circuits and nanoplasmonic devices. Finally, we develop a method to reconstruct the material’s momentum-dependent bandgap by decoding this information from the spectral phase of the harmonics. This all-optical method can be applied when photoelectrons are not accessible, such as in high-pressure physics experiments.

#80, 11:15 – 11:30 High harmonic generation from Bloch electrons in solids, MENGXI WU, SHAMBHU GHIMIRE, DAVID A. REIS, KENNETH J. SCHAFER, AND METTE B. GAARDE, We study the generation of high harmonic radiation by Bloch electrons in a model transparent solid driven by a strong mid-infrared (MIR) laser field. We solve the single-electron time-dependent Schrödinger equation (TDSE) using a velocity-gauge method. The resulting harmonic spectrum exhibits a primary plateau, due to the coupling of the valence band to the first conduction band, with a cutoff energy that scales linearly with field strength and laser wavelength.

#81, 11:30 – 11:45 Ultrafast semi-metallization transition in quartz and sapphire induced by strong few-cycle optical field, OJOON KWON, TIM PAASCH-COLBERG, VADYM APALKOV, FERENC KRAUSZ, MARK I. STOCKMAN, AND D. KIM, We demonstrate that quartz and sapphire undergo an ultrafast semi-metallization transition induced by strong few-cycle optical pulses, allowing current to flow within a femtosecond time interval. The similarity in response of both materials, despite the significant differences in their physical properties, confirms a physical picture of formation of localized Wannier-Stark states. This study suggests that optical-field-induced semi-metallization offers a means of ultrafast control of dielectric media and currents in them, opening up the doors to further developments.