Interferences induced by spatially nonhomogeneous fields in high-harmonic generation

The high-harmonic spectrum simulated in a few-cycle laser pulse with spatially nonhomogeneous field presents two types of interferences, which characterize different plateaus in the spectrum. One of these plateaus is discernible with the nonequidistant peaks due to the interference of short and long trajectories, while another one is distinguished by a periodicity much larger than the laser frequency arising from trajectories modified by the nonhomogeneous field. Beside, the continuum-continuum harmonic generation appears in the spectrogram in the tunneling regime of the laser parameters. These features bear the tracking of classical trajectories and the complete characterization of emission spectrum, when using nanostructures in attoscience.