Experimental observation of trajectories beyond the long in high order harmonic generation

TL;DR

This paper experimentally investigates the influence of longer-than-long trajectories in high order harmonic generation, revealing complex interference effects that impact the emitted EUV light's direction and amplitude, crucial for controlling HHG processes.

Contribution

It demonstrates the experimental observation of extended trajectory effects in HHG and introduces a theoretical model explaining complex interference patterns beyond traditional short and long trajectories.

Findings

Interference patterns cannot be fully explained by known trajectories.

Off-axis harmonic components show significant structure changes.

Trajectory effects influence the direction and amplitude of emitted EUV light.

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 through either 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.