High performance nanoscale imaging with table-top high harmonic sources

Todays high harmonic sources provide high photon flux, short wavelengths and excellent coherence. We will present a number of experiments, including record-13 nm resolution imaging, which have been performed with fiber laser driven XUV sources. Lensless Coherent diffractive imaging (CDI) is a technique where a sample is imaged by recording the far field intensity diffraction pattern and subsequently phase retrieval by iterative computer algorithms. It nowadays enables imaging with only a few-nanometers resolution by employing X-ray radiation usually provided either by free-electron lasers or synchrotrons. Table-top coherent XUV sources using high-order harmonic generation (HHG) have seen enormous progress during the recent years. Nowadays, they can provide high photon flux combined with excellent coherence and femtosecond pulse durations, which makes them highly attractive for high-resolution imaging. In this contribution, we present CDI experiments performed with a 68.6 eV XUV source, driven by a 1mm wavelength, 0.66 mJ, 33 fs, 30 kHz high-average power femtosecond fiber laser system. A high photon flux of ~1×1010 photons/sec was generated at 68.6 eV and focused onto the CDI sample by a pair of multilayer mirrors. Excellent coherence and beam quality have been observed. The intensity and phase of the illuminating beam has been characterized by CDI of a uniform array of 100 nm diameter holes as shown in fig. 1. The transmitted intensity samples the beam profile and indicates a round Gaussian-like beam profile with ~ 4 mm width (1/e2).