A hybrid Ti:Sa CPA/BBO OPCPA system with a XPW filter in between the two has been developed to produce a broadband high contrast seeder of 10 mJ for the two 10 PetaWatt beamlines of ELI NP infrastructure.
A laser system made of two beams of 10 PW each has been designed and is currently built for ELI-NP research infrastructure. Design is presented as well as preliminary results up to the 1PW level amplifier.
Ultra-fast soft x-ray lasers have opened a new area of laser-matter interactions which in most cases differ from the well
understood interaction of UV-vis radiation with solid targets. The photon energy >30eV essentially exceeds the width of
band gap in any known material and excites the electrons from the deep atomic and valence levels directly to the
conduction band. Both thermal and non-thermal phenomena can occur in such a material being caused by electron
thermalization and bond breaking, respectively. We report the first observation of non-thermal single-shot soft x-ray
laser induced desorption occurring below the ablation threshold in a thin layer of poly (methyl methacrylate) - PMMA.
Irradiated by the focused beam from the Free-electron LASer in Hamburg (FLASH) at 21.7nm, the samples have been
investigated by an atomic-force microscope (AFM) enabling the visualization of mild surface modifications caused by
the desorption. A model describing non-thermal desorption and ablation has been developed and used to analyze singleshot
imprints in PMMA. An intermediate regime of materials removal has been found, confirming the model predictions.
We also report below-threshold multiple-shot desorption of PMMA induced by high-order harmonics (HOH) at 32nm as
a proof of an efficient material removal in the desorption regime.
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.
Among X-ray and extreme ultraviolet light sources able to produce shorter and shorter, coherent and intense pulses, High
order harmonics generated in rare gases are currently the unique way to generate attosecond pulses. However, the
manipulation and transport of attosecond pulses require the development of dedicated optics for reaching specific
characteristics in terms of amplitude but also in terms of spectral phase control. We present here a multilayer design for
chirp compensation of attosecond pulses. We also present an application of these multilayers mirrors for attosecond train
pulse holography experiment with high harmonics. This experience took benefit of both temporal and spatial phase
properties of high harmonics. A resolution of 750 nm has been achieved by using a 350 as train pulse for the reference
wave constituted of four consecutive harmonics (λ=28 nm to λ=41 nm). This new method will allow making ultra fast
movies with attosecond resolution of transient phenomena with quasi-3D resolution.