High-order-harmonic generation by Laguerre-Gaussian laser modes: Control of the spectra by manipulating the spatial medium distribution

We study high-order-harmonic generation (HHG) by the incident laser beam in the Laguerre-Gaussian mode with a nonzero topological charge. We find that the harmonic signal in the central spot on the beam axis does not always vanish and depends on the distribution of the medium in the focal region of the incident laser beam. The HHG spectra on the beam axis can be controlled by changing the spatial medium distribution. General theoretical results are confirmed by calculations of HHG in the medium of argon atoms, with the single-atom response obtained by means of the time-dependent density functional theory.