Spatial aberrations in high-order harmonic generation

TL;DR

This paper studies the spatial patterns in high-order harmonic generation, revealing how beam aberrations cause cross-like patterns and demonstrating correction methods to improve harmonic spatial quality.

Contribution

It introduces an analytical model linking beam astigmatism to harmonic divergence patterns and shows how wavefront correction enhances harmonic spatial quality.

Findings

Cross-like patterns are caused by astigmatism in the driving beam.

Small aberrations significantly affect harmonic divergence.

Wavefront correction improves the spatial profile of harmonics.

Abstract

We investigate the spatial characteristics of high-order harmonic radiation generated in argon, and observe cross-like patterns in the far field. An analytical model describing harmonics from an astigmatic driving beam reveals that these patterns result from the order and generation position dependent divergence of harmonics. Even small amounts of driving field astigmatism may result in cross-like patterns, coming from the superposition of individual harmonics with spatial profiles elongated in different directions. By correcting the aberrations using a deformable mirror, we show that fine-tuning the driving wavefront is essential for optimal spatial quality of the harmonics.