Today's ultrafast lasers operate at the physical limits of optical materials to reach extreme performances. Amplification of single-cycle laser pulses with their corresponding octavespanning spectra still remains a formidable challenge since the universal dilemma of gain narrowing sets limits for both real level pumped amplifiers as well as parametric amplifiers. We demonstrate that employing parametric amplification in the frequency domain rather than in time domain opens up new design opportunities for ultrafast laser science, with the potential to generate single-cycle multi-terawatt pulses. Fundamental restrictions arising from phase mismatch and damage threshold of nonlinear laser crystals are not only circumvented but also exploited to produce a synergy between increased seed spectrum and increased pump energy. This concept was successfully demonstrated by generating carrier envelope phase stable, 1.43 mJ two-cycle pulses at 1.8 mm wavelength.

An intuitive and complete understanding of the underlying processes in high harmonic generation (HHG) in solids will enable the development and optimization of experimental techniques for attosecond measurement of dynamical and structural properties of solids. Here we introduce the Wannier quasi-classical (WQC) theory, which allows the characterization of HHG in terms of classical trajectories. The WQC approach completes the single-body picture for HHG in semiconductors, as it is in quantitative agreement with quantum calculations. The importance of WQC theory extends beyond HHG; it enables modeling of dynamic processes in solids with classical trajectories, such as for coherent control and transport processes, potentially providing better scalability and a more intuitive understanding.

Experiments and simulations in solid-state high harmonic generation often make use of the distinction between interband and intraband currents. These two contributions to the total current have been associated with qualitatively different processes, as well as physically measurable signatures, for example in the spectral phase of harmonic emission. However, it was recently argued [P. Földi, Phys. Rev. B 96, 035112 (2017)] that these quantities can depend on the gauge employed in calculations. Since physical quantities are expected to have gauge-independent values, this raises the question of whether the decomposition of the total current into interband and intraband contributions is physically meaningful, or merely a feature of a particular mathematical representation of nature. In this article, we explore this apparent ambiguity. We show that a closely related issue arises when calculating instantaneous band populations. In both the case of inter/intraband currents and in the case of instantaneous band populations, we propose definitions which are gauge-invariant, and thus allow these quantities to be calculated consistently in any gauge. arXiv:1808.09288v1 [cond-mat.mes-hall]

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=0705740e-13f4-45d7-8247-0a83b36c8ac2 http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=0705740e-13f4-45d7-8247-0a83b36c8ac2 2.5 TW, two-cycle IR laser pulses via frequency domain optical parametric amplification V . GRUSON, 1,2 Abstract: Broadband optical parametric amplification in the IR region has reached a new milestone through the use of a non-collinear Frequency domain Optical Parametric Amplification system. We report a laser source delivering 11.6 fs pulses with 30 mJ of energy at a central wavelength of 1.8 µm at 10 Hz repetition rate corresponding to a peak power of 2.5 TW. The peak power scaling is accompanied by a pulse shortening of about 20% upon amplification due to the spectral reshaping with higher gain in the spectral wings. This source paves the way for high flux soft X-ray pulses and IR-driven laser wakefield acceleration.