Eur. Phys. J. D 48, 459-463 (2008)
https://doi.org/10.1140/epjd/e2008-00123-2

Optimization of the wave front of high order harmonics

¹ Laboratoire d'Optique Appliquée, École Nationale Supérieure de Technique Avancées, École Polytechnique, CNRS UMR7639, Chemin de la Hunière, 91761 Palaiseau Cedex, France
² Synchrotron SOLEIL, 91192 Gif-sur-Yvette Cedex, France
³ Imagine Optic, 18 rue Charles de Gaulle, 91400 Orsay, France
⁴ Instituto de Plasmas e Fusão Nuclear, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal
⁵ Commissariat à l'Énergie Atomique, Service des Photons, Atomes et Molécules, Bâtiment 522, Centre d'Étude de Saclay, 91191 Gif-sur-Yvette, France

Corresponding author: ^a julien.gautier@ensta.fr

Received: 15 January 2008
Revised: 17 March 2008
Published online: 18 June 2008

Abstract

We present a full optimization of the high harmonics wave front owing to the use of a soft X-ray Hartmann sensor. The sensor was calibrated using a high harmonic source with an accuracy of λ/50 root-mean-square (rms) with λ around 30 nm. We observed a high harmonic wave front of λ/7 rms, which is two times the diffraction-limit, astigmatism being the dominant aberration for every condition of generation. By clipping slightly the unfocused high harmonic beam, it is possible to produce a diffraction-limited beam containing approximately 90% of the incident energy.