High order harmonics wavefront measurement and optimization

Abstract

We present a full optimization of the high harmonics wave-front thanks to the use of a soft x-ray Hartmann sensor. The sensor was calibrated using high harmonics source with a λ/50 accuracy. We observed relatively good high harmonics wave-front, two times the diffraction-limit, with astigmatism as the dominant aberration for any interaction parameters. By slightly clipping the unfocused beam, it is possible to produce a diffraction-limited beam containing about 90% of the incident energy. The influence of high harmonic generation parameters was also studied in particularly the influence of the infra-red wave-front. In particular we studied the correlation between the infrared wave-front use to create high harmonics and the high harmonic wave-front. We also report wave-front measurements of a high order harmonic beam into an x-ray laser plasma amplifier at 32.8 nm.