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Author(s): M. Garg [1]; M. Zhan [1]; T. T. Luu [1]; H. Lakhotia [1]; T. Klostermann [1]; A. Guggenmos [1]; E. Goulielmakis (corresponding author) [1] The frequency of electric currents [...]

The time it takes a bound electron to respond to the electromagnetic force of light sets a fundamental speed limit on the dynamic control of matter and electromagnetic signal processing. Time-integrated measurements of the nonlinear refractive index (1) of matter indicate that the nonlinear response of bound electrons to optical fields is not instantaneous; however, a complete spectral characterization of the nonlinear susceptibility tensors (2)--which is essential to deduce the temporal response of a medium to arbitrary driving forces using spectral measurements--has not yet been achieved. With the establishment of attosecond chronoscopy (3-5), the impulsive response of positive-energy electrons to electromagnetic fields has been explored through ionization of atoms (6) and solids (7) by an extreme-ultraviolet attosecond pulse (8) or by strong near-infrared fields (9-11). However, none of the attosecond studies carried out so far have provided direct access to the nonlinear response of bound electrons. Here we demonstrate that intense optical attosecond pulses synthesized in the visible and nearby spectral ranges allow subfemtosecond control and metrology of bound-electron dynamics. Vacuum ultraviolet spectra emanating from krypton atoms, exposed to intense waveform-controlled optical attosecond pulses, reveal a finite nonlinear response time of bound electrons of up to 115 attoseconds, which is sensitive to and controllable by the superoctave optical field. Our study could enable new spectroscopies of bound electrons in atomic, molecular or lattice potentials of solids (12), as well as light-based electronics operating on sub-femtosecond timescales and at petahertz rates (13-15)., Intramolecular atomic motion dynamically distorts the interatomic electron cloud and thereby gives rise to a transient electronic polarizability (16) and a finite nonlinear response of matter to light fields. Timeresolved [...]

Intense light interacting with a thin film of silicon dioxide is used to generate broadband extreme ultraviolet radiation; the spectra reveal detailed information on the energy dispersion of the conduction band of silicon dioxide, which is at present inaccessible by conventional photoemission spectroscopy. Solid-state EUV spectroscopy Laser-based generation of extreme ultraviolet (EUV) radiation in gases, leading to the generation of light with frequencies that are high-order harmonics of the fundamental laser frequency, is widely used as a spectroscopy and imaging tool. High harmonics are also generated in bulk crystals, although the underlying emission mechanisms are under debate. Here Eleftherios Goulielmakis and colleagues extend the technique to generate broadband EUV radiation in thin films of silicon dioxide. The spectra reveal detailed information on the energy dispersion of the conduction band of silicon dioxide, which is at present inaccessible by conventional photoemission spectroscopy. This work is an important step in the development of the emerging field of solid-state EUV photonics. Extreme ultraviolet (EUV) high-harmonic radiation.sup.1,2 emerging from laser-driven atoms, molecules or plasmas underlies powerful attosecond spectroscopy techniques.sup.3,4,5 and provides insight into fundamental structural and dynamic properties of matter.sup.6,7. The advancement of these spectroscopy techniques to study strong-field electron dynamics in condensed matter calls for the generation and manipulation of EUV radiation in bulk solids, but this capability has remained beyond the reach of optical sciences. Recent experiments.sup.8,9 and theoretical predictions.sup.10,11,12 paved the way to strong-field physics in solids by demonstrating the generation and optical control of deep ultraviolet radiation.sup.8 in bulk semiconductors, driven by femtosecond mid-infrared fields or the coherent up-conversion of terahertz fields to multi-octave spectra in the mid-infrared and optical frequencies.sup.9. Here we demonstrate that thin films of SiO.sub.2 exposed to intense, few-cycle to sub-cycle pulses give rise to wideband coherent EUV radiation extending in energy to about 40 electronvolts. Our study indicates the association of the emitted EUV radiation with intraband currents of multi-petahertz frequency, induced in the lowest conduction band of SiO.sub.2. To demonstrate the applicability of high-harmonic spectroscopy to solids, we exploit the EUV spectra to gain access to fine details of the energy dispersion profile of the conduction band that are as yet inaccessible by photoemission spectroscopy in wide-bandgap dielectrics. In addition, we use the EUV spectra to trace the attosecond control of the intraband electron motion induced by synthesized optical transients. Our work advances lightwave electronics.sup.5,13,14,15 in condensed matter into the realm of multi-petahertz frequencies and their attosecond control, and marks the advent of solid-state EUV photonics., Author(s): T. T. Luu [sup.1] , M. Garg [sup.1] , S. Yu. Kruchinin [sup.1] , A. Moulet [sup.1] , M. Th. Hassan [sup.1] , E. Goulielmakis [sup.1] Author Affiliations: (1) [...]

Author(s): R. Kienberger [1, 5]; E. Goulielmakis [1, 5]; M. Uiberacker [1, 5]; A. Baltuska [1]; V. Yakovlev [1]; F. Bammer [2]; A. Scrinzi [1]; Th. Westerwalbesloh [3]; U. Kleineberg [...]

Author(s): A. Baltuška [1]; Th. Udem [2]; M. Uiberacker [1]; M. Hentschel [1]; E. Goulielmakis [1]; Ch. Gohle [2]; R. Holzwarth [2]; V. S. Yakovlev [1]; A. Scrinzi [1]; T. [...]