High-Order Harmonic Radiation of a Single Helium Atom Driven by a Strong Laser Pulse
Attosecond light pulses have revolutionized our view of fundamental atomic, molecular and solid state processes in the attosecond - femtosecond time domain [1]. The availability of such pulses is based on high-order harmonic generation (HHG) in noble gas samples by a femtosecond laser pulse of suitably high intensity. At the heart of this HHG process, the tunnel ionization of a single atom happens, followed by the return of the just liberated electron to its parent ion due to the strong oscillating electric field of the laser pulse. The resulting recombination enables the emission of high-frequency radiation. Recent developments in attosecond physics revealed that the accurate description of this single-atom emission is more important than ever before [2].
In this contribution, we present simulation results of the electromagnetic radiation emitted by a helium atom which is driven by a linearly polarized few-cycle near-infrared laser pulse.
The quantum mechanical part of the simulation is provided by our own algorithm and computer program [3].
We use COMSOL Multiphysics® and the RF Module to perform the computation of the emitted electromagnetic radiation which belongs to the extreme ultraviolet spectral range. Our COMSOL Multiphysics® model is based on the axial symmetric (2D) formulation of the electromagnetic wave equation in the frequency domain.
We expect that our results contribute to the deeper understanding of the HHG emission process.
References
[1] F. Krausz and M. Ivanov, Rev. Mod. Phys. 81, 163 (2009).
[2] A. N. Pfeiffer, C. Cirelli, A. S. Landsman, M. Smolarski, D. Dimitrovski, L. B. Madsen, and U. Keller, Phys. Rev. Lett. 109, 083002 (2012)
[3] S. Majorosi and A. Czirjak, Comput. Phys. Commun. 208, 9 (2016).
