Semiclassical approaches to below-threshold harmonics
We study the generation of below-threshold harmonics in a model atom by extending the three-step semiclassical model of harmonic generation to include effects of the atomic potential. We explore the generalization of semiclassical trajectories of the electron in the presence of the combined laser-atom potential and calculate the intensity-dependent dipole phase associated with these trajectories. Our results are in good agreement with fully quantum mechanical calculations, as well as with recent experimental observations. We show that the so-called long trajectory readily generalizes to below-threshold harmonic generation and is relatively insensitive to the choice of initial conditions. We also find that the short trajectory can only lead to low-energy harmonics for electrons that have been released close to the ion core in a process that is closer to multiphoton than to tunnel ionization. © 2010 The American Physical Society.
Publication Source (Journal or Book title)
Physical Review A - Atomic, Molecular, and Optical Physics
Hostetter, J., Tate, J., Schafer, K., & Gaarde, M. (2010). Semiclassical approaches to below-threshold harmonics. Physical Review A - Atomic, Molecular, and Optical Physics, 82 (2) https://doi.org/10.1103/PhysRevA.82.023401