Many applications of the extreme ultraviolet(XUV)radiation obtained by high-order harmonic generation(HHG)in gases require a small focus area in order to enable attosecond pulses to reach a high intensity.Here,high-or...Many applications of the extreme ultraviolet(XUV)radiation obtained by high-order harmonic generation(HHG)in gases require a small focus area in order to enable attosecond pulses to reach a high intensity.Here,high-order harmonics generated in Ar with a multiterawatt laser system in a loose focusing geometry are focused to a few micrometers using two toroidal mirrors in a Wolter configuration with a high demagnification factor.Using a knife-edge measurement technique,we determine the position and size of the XUV foci as a function of harmonic order.We show that the focus properties vary with harmonic order and the generation conditions.Simulations,based on a classical description of the harmonic dipole phase and assuming that the individual harmonics can be described as Gaussian beams,reproduce the experimental behavior.We discuss how the generation geometry affects the intensity and duration of the focused attosecond pulses.展开更多
基金support from the Swedish Research Council,the European Research Council(advanced grant QPAP)the Knut and Alice Wallenberg Foundation,and the Crafoord Foundation.The research leading to these results has received funding from LASERLAB-EUROPE(grant agreement no.654148,European Union’s Horizon 2020 research and innovation programme)+1 种基金S.M.acknowledges financial support from the COST Action CA18212-Molecular Dynamics in the GAS phase(MD-GAS)supported by COST(European Cooperation in Science and Technology).
文摘Many applications of the extreme ultraviolet(XUV)radiation obtained by high-order harmonic generation(HHG)in gases require a small focus area in order to enable attosecond pulses to reach a high intensity.Here,high-order harmonics generated in Ar with a multiterawatt laser system in a loose focusing geometry are focused to a few micrometers using two toroidal mirrors in a Wolter configuration with a high demagnification factor.Using a knife-edge measurement technique,we determine the position and size of the XUV foci as a function of harmonic order.We show that the focus properties vary with harmonic order and the generation conditions.Simulations,based on a classical description of the harmonic dipole phase and assuming that the individual harmonics can be described as Gaussian beams,reproduce the experimental behavior.We discuss how the generation geometry affects the intensity and duration of the focused attosecond pulses.
