We have developed a novel method for efficient structuring of the surface of materials by applying femtosecond near
infrared laser pulses simultaneously with a weak extreme ultraviolet beam, which leads to a very strong radiation-matter
interaction and brings a dramatic increase of the surface processing speed. We present our recent experimental results on
surface nanostructuring of thin films of amorphous carbon and polymethyl methacrylate deposited on bulk substrates and
discuss the underlying physical mechanisms. In the case of amorphous carbon, large areas of laser-induced periodic
surface structures with a spatial period of 550 nm were created, having their origin in laser-induced convective currents.
Our method provides a powerful tool for fast modification of tribological properties of the irradiated sample.
We demonstrate a novel experimental method for improvement of efficiency of structural surface modification of
various solids (PMMA, amorphous carbon) achieved by simultaneous action of XUV (21.6 nm), obtained from high-order
harmonic generation (HHG), and VIS-NIR (410/820 nm) laser pulses. Although the fluence of each individual
pulse was far below the surface ablation threshold, very efficient and specific material modification was observed after
irradiation by a single or a few shots of mixed XUV/VIS-NIR radiation.
We also report results on comprehensive characterization of ultrafast coherent X-ray beamline at Prague Asterix
Laser System (PALS). The beamline is based on 1 kHz, table-top, high-order harmonic generation source capable to
deliver fully coherent beam in the 30 nm spectral range. Ti:sapphire (810 nm, 1 kHz) laser pulses with a duration of 35 fs
and energy 1.2 mJ have been focused into gas cell containing conversion medium (Ar). To achieve highly efficient HHG
we will apply the technique of guided laser pulses. Source parameters were investigated.
We demonstrate a novel experimental method for efficient structural surface modification of various solids (PMMA,
amorphous carbon) achieved by simultaneous action of XUV (21.6 nm), obtained from High-order Harmonic Generation
(HHG), and Vis-NIR (410/820 nm) laser pulses. Although the fluence of each individual pulse was far below the surface
ablation threshold, very efficient and specific material modification was observed after irradiation even by a single shot
of mixed XUV/Vis-NIR radiation.
The desktop capillary-discharge Ne-like Ar laser (CDL) providing 10-μJ nanosecond pulses of coherent 46.9-nm
radiation with a repetition rate up to 12 Hz was developed and built at the Colorado State University in Fort Collins and
then installed in Prague. The beam of the laser was focused by a spherical mirror covered with Si/Sc multilayer coating
onto the surface of poly(methyl methacrylate) - PMMA. Interaction parameters vary by changing the distance between
sample surface and beam focus. The samples were exposed to various numbers of shots. Analysis of damaged PMMA by
atomic force (AFM) and Nomarski (DIC - differential interference contrast) microscopes allows not only to determine
the key characteristics of the focused beam (e.g. Rayleigh's parameter, focal spot diameter, tight focus position, etc.) but
also to investigate mechanisms of the radiation-induced erosion processes.
We report on the development of ultrafast coherent soft X-ray beamline at the Prague Asterix Laser System (PALS)
Research Center intended for interdisciplinary applications such as ablation and controlled surface modification of solid
materials for a micro/nano-patterning, soft X-ray interferometry and holography for surface probing with nanometric
resolution, and improvement of focusing optics for soft X-ray beams. The beamline is based on 1 kHz, table-top, highorder
harmonic generation (HHG) source capable of delivering fully coherent beam, tunable in the 13 - 40 nm spectral
range. The Ti:sapphire (810 nm) laser pulses with a duration of 35 fs and energy 1.1 mJ are focused into a static gas cell
containing conversion medium (Ar). To achieve highly efficient HHG at 30 nm we apply the technique of guided laser
pulses. Experimental results on HHG source characterization, optimization, and spectral tunability are presented.
Achievements on the implementation of so called two-color HHG using gas cell have been reported for the first time.
The complete beamline will consist of a tandem of two vacuum chambers: one for the HHG source and its diagnostics,
and second intended for the application experiments. The access to this new soft X-ray installation will be opened to
external users since 2009.
We present a review of recent development and applications of soft x-ray lasers, undertaken at the PALS Centre. The applications benefit from up to 10-mJ pulses at the wavelength of 21.2 nm. We describe the pumping regimes used to produce this soft x-ray laser, and outline its emission characteristics. A significant fraction of applications carried out using this device includes probing of dense plasmas produced by IR laser pulses and high-energy-density-in-matter experiments. Results obtained in these experiments are reviewed, including x-ray laser probing of dense plasmas, measurements of transmission of focused soft x-ray radiation at intensities of up to 1012 Wcm-2, measurements of IR laser ablation rates of thin foils, and probing high density plasmas by x-ray laser Thomson scattering
We report on the development of ultrafast coherent soft X-ray beamline at the Prague Asterix Laser System
(PALS) Research Center intended for interdisciplinary applications such as ablation and controlled surface modification
of solid materials for a micro/nano-pattering, soft X-ray interferometry and holography for surface probing with
nanometric resolution, and improvement of focusing optics for soft
X-ray beams. The beamline is based on 1 kHz, tabletop,
high-order harmonic generation (HHG) source capable to deliver fully coherent, tunable beam in the 13 - 40 nm
spectral range. Ti:sapphire (810 nm, 1 kHz) laser pulses with a duration of 35 fs and energy 1.5 mJ have been focused
into a gas jet or gas cell containing conversion medium (Ar). To achieve highly efficient HHG we will apply the
technique of guided laser pulses and the two-color laser field. Results on the optimization of HHG near 21 nm are
presented. The beamline consists of a tandem of two vacuum chambers: one for the HHG source and its diagnostics, and
second for the application experiments. After completion, access to this new installation will be opened to external users.
This table-top system will be complementary to the existing, high energy (~10 mJ) Ne-like Zn soft X-ray laser at 21.2
nm developed at PALS. We will also present the first experimental results on the structural surface modifications of
various solid materials (i.e., PMMA - poly(methyl methacrylate); amorphous carbon) caused by a few shot exposure to
the focused HHG beam at 21.6 nm.
Results on micro- and nanoprocessing of organic polymers with extreme ultraviolet (EUV) radiation from a compact
laser plasma EUV source based on a gas puff target are presented in the paper. Processing of polymers is connected with
non-thermal ablation under the influence of energetic EUV photons. The process can be useful for practical applications
as it makes possible to produce structures with sub-micron spatial resolution that is not possible using the thermal
ablation. The new technology will be used for production of photonic microstructures and for modification of polymer
surfaces for biomedical applications.
Results on micro- and nanoprocessing of organic polymers using X-rays and extreme ultraviolet (EUV) generated from
laser-plasma radiation sources are presented in the paper. The sources used in the studies are based on the gas puff target
approach developed at the Institute of Optoelectronics, Warsaw. Processing of polymers is connected with non-thermal
ablation under the influence of energetic photons of X-ray and EUV radiation. The process can be useful for practical
applications as it makes possible to produce structures with sub-micron spatial resolution that is not possible using the
thermal ablation. The new technology will be used for production of photonic microstructures and for modification of
polymer surfaces for biomedical applications.
We present the recent progress in high intensity micro focused EUV beam generation. Ellipsoidal thin glass foils were used in Multi-foil optical systems for focusing radiation in 50 eV to 150 eV energy band from gas-puff laser plasma source. Multifoil optic (MFO) condenser was designed and tested for applications with Xe laser plasma gas-puff source. High intensity EUV beam focal spot was recorded, analyzed and compared with theoretical results from computer ray-tracing. Direct EUV lithography using radiation induced decomposition and ablation of TEFLON was studied.
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