Experimental observation of longer trajectories than previously observed in high-order harmonic generation

Abstract

We experimentally observe longer than long trajectory influence in high-order harmonic generation (HHG) by varying the peak intensity of the driving laser field either through direct attenuation or by chirping the laser pulse. Using a theoretical Gaussian beam model to simulate spatial interference resulting from quantum path interference, we show that the measured interference patterns cannot be solely explained by the well-established short and long trajectories. The structure change is most prominent for the more divergent, off-axis components of the lower plateau harmonic region, affecting the direction and amplitude of the extreme ultraviolet light emitted, and is thus of importance for understanding and controlling the fundamentals of the HHG process.