Optics-free focusing down to micrometer spot size and spectral filtering of XUV harmonics

TL;DR

This paper demonstrates optics-free focusing of XUV harmonics to micrometer spots and achieves spectral filtering and fundamental beam rejection by characterizing wavefronts during generation.

Contribution

It introduces a method to focus XUV harmonics without optics and to perform spectral filtering by wavefront characterization during generation.

Findings

Focused XUV spots with micrometer size achieved.

Effective spectral filtering of XUV light demonstrated.

Strong rejection of fundamental beam without XUV optics.

Abstract

Controlling the wavefront of an extreme ultraviolet (XUV) high-order harmonic beam during the generation process offers to focus the beam without resorting to any XUV optics. By characterizing the XUV intensity profile and wavefront, we quantitatively retrieve both the size and the position of the waist of each generated harmonics and show that optics-free focusing leads to focused XUV spot with micrometer size. We use this remarkable coherent effect to demonstrate efficient and adjustable spectral filtering of the XUV light, along with a strong rejection of the fundamental beam, without using any XUV optics.