High-order harmonic generation in atom clusters interacting with an intense linearly polarized laser field is studied by means of numerical simulations of the time-dependent Schrödinger equation for a two-dimensional model cluster in the single-active electron approximation. The well-known first and second cutoffs (in the atomic and molecular cases) are not clear in cluster calculations. In fact, the structure of the spectrum consists of a long plateau that extends far beyond the I<sub>P</sub>+3.17 U<sub>P</sub> limit and a collection of high-order harmonics with decreasing but significant intensities up to extremely high frequencies.
© 2001 Optical Society of America
Javier R. Vázquez de Aldana and Luis Roso, "High-order harmonic generation in atomic clusters with a two-dimensional model," J. Opt. Soc. Am. B 18, 325-330 (2001)