Fig. 4.

Interference through multiple temporal slits. (A) The interference of two EWPs separated by half of a laser cycle with a $\pi$ phase difference (Left, 1) leads to a modulation in the energy (frequency) domain, with maxima at the energies corresponding to excitation by odd harmonics (Right, 1, blue curve). A phase change, $\phi$, of one EWP shifts the interference fringes (1, green curve). A momentum-dependent phase change, $2{\eta }_p$ (2), leads to an energy-dependent shift of the interference fringes, as well as to a temporal shift ($\delta t$) of one EWP relative to the other. (B) The interference of three EWPs separated by half of a laser cycle with a $\pi$ phase difference (Left, 1) leads to interferences with maxima at the energies corresponding to excitation by odd harmonics, and weak “secondary” maxima at the SB position (Right, 1, blue curve). A phase change between the side and central EWPs ($\phi$) enhances the SB relative to the main peak (1, green curve). A momentum-dependent phase change ($2{\eta }_p$) leads to energy-dependent sideband amplitudes, but no energy shift (Right, 2). The spectral phase difference between consecutive attosecond pulses ($s$) enhances (yellow curve) or reduces (red curve) this effect depending on the direction of emission (3).