Macroscopic HHG spectra of Ne calculated by the QRS model. (a) Two-color (800 + 2126 nm) waveform in the current scheme is compared with the two-color waveform (mid-infrared laser and its 3rd harmonic) in Fig. 2. One-color results are shown for reference. The parameters are indicated in the figures, I₀ is in the units of 10¹⁴ W/cm². (b) Comparison of the harmonic spectra by optimized two-(800 + 2126 nm) and three-color (800 + 2356 + 400 nm) waveforms. Adapted from Ref. [100].