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

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