Figure 7: Experimental comparison between conventional phase matching with a 2.2-µm driver and unconventional phase matching with a 0.8-µm driver

Experimental HHG spectra with a 0.8 µm and a 2.2 µm driver in helium and neon. The different generation parameters are summarized in Table 1. All spectra are recorded with the same grating (2400 g/mm), except the 2×10^(15) W/cm^2 case, recorded with a 1200 g/mm grating. For the latter, the diffraction efficiency above 260 eV was determined experimentally by recording the same spectrum with both gratings and using the 2400 g/mm diffraction efficiency as a reference.