We present an optical system based on two toroidal mirrors in a Wolter configuration to focus broadband XUV high harmonic radiation generated by the non-linear interaction of a fs, 10 Hz laser with neutral gas. The experiment was carried out at Lund University in collaboration with Laboratoire d’Optique Appliquée, ELI-ALPS and Imagine Optic. Optimization of the focusing optics alignment is carried out with the aid of an XUV Hartmann wavefront sensor commercialized by Imagine Optic.
Back-propagation of the optimized wavefront to the focus yields a focal spot of 3.6 * 4.0 µm2 full width at half maximum, which is consistent with ray-tracing simulations that predict a minimum size of 3.0 *3.2 µm2.
We will show also how the optimization of the high harmonic beam by the use of an infrared adaptive optic may help for compensating the residual aberrations of the Wolter, leading to a clear improvement of the focal spot.