Focusing Properties of High-Order Harmonics

Maria Hoflund (1) , Jasper Peschel (1) , Marius Plach (1) , Hugo Dacasa (1) , Kévin Veyrinas (2) , Eric Constant (3) , Peter Smorenburg (4) , Hampus Wikmark (1) , Sylvain Maclot (1) , Chen Guo (1) , Cord Arnold (1) , Anne L'Huillier (1) , Per Eng-Johnsson (1)

1 Skane University Hospital [Lund]
2 CELIA - Centre d'Etudes Lasers Intenses et Applications
3 iLM - DYNAMO - iLM - Structure et dynamique multi-échelle des édifices moléculaires
4 ASML Netherlands B.V.

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.

Domaines: Physique [physics]

Maria Hoflund, Jasper Peschel, Marius Plach, Hugo Dacasa, Kévin Veyrinas, et al.. Focusing Properties of High-Order Harmonics. Virtual Journal of Ultrafast Science / Atomic and Molecular Sciences, 2021, 2021, pp.1-8. ⟨10.34133/2021/9797453⟩. ⟨hal-03330944⟩