Anomalies observed in the cut off law of High-order Harmonics Generation. Are spatially inhomogeneous fields the key for this change?

We studied high-order harmonic generation (HHG) through the three-step model, in gaseous phase atoms driven by plasmonic-enhanced fields. We have demonstrated that the spatial inhomogeneous and bounded character of the electric field, modeled by Gaussian-shaped functions, leads to an unexpected relationship between the HHG cutoff and the laser wavelength.