Propagation time and nondipole contributions to intraband high-harmonic generation.

Properties of intraband high-harmonic generation (HHG) are investigated within the semiclassical model. We identify two connected effects that must be included for a complete description of such HHG: (1) Propagation time from the point of emission at the source to the point of detection, (2) Beyond electric dipole corrections to the light-matter interaction. These effects are responsible for specific features in the spectra including even-ordered harmonics in systems with space- and time-inversion symmetry and features associated with the nondipole dynamics in the laser propagation direction.