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Laser plasma sources of soft X-rays and extreme ultraviolet (EUV) have been developed for application in various fields of science and technology. The sources are based on a gas puff target irradiated with a nanosecond laser pulse. The targets are created using an electromagnetic valve system equipped with a double-nozzle. The valve system, which is supplied with two different gases, produces a double-stream gas puff target which consists of an elongated stream of high-Z gas surrounded by a stream of low-Z gas. The double-stream gas puff target approach secures high conversion efficiency of laser energy into soft X-ray and EUV energy without degradation of the nozzle. The targets are irradiated with laser pulses produced by commercial Nd:YAG lasers (EKSPLA) with a duration of 1 ns to 10 ns, energy in the pulse from 0.5 J to 10 J with a repetition of 10 Hz. The sources have been applied in various fields, including metrology, processing of materials, nanoimaging, radiography and tomography, photoionized plasma studies, and radiobiology. In this paper the recent results on application of the sources in X-ray absorption spectroscopy and optical coherence tomography (OCT) are presented. The use of the source in laboratory systems for the near-edge X-ray absorption fine structure (NEXAFS) spectroscopy is demonstrated. The NEXAFS system was applied for 2-D elemental mapping of EUV-modified polymer samples. A single-shot exposure NEXAFS spectroscopy is presented. Application of the source in X-ray optical coherence tomography (XCT) has been also demonstrated. The preliminary results on XCT imaging of Mo/Si multilayers with 2 nm axial resolution, using broad-band soft X-ray emission, are presented.

New instruments and methods for nanoimaging with the use of a compact laser plasma soft X-ray source are presented. The source is based on a double-stream gas puff target irradiated with nanosecond laser pulses from a Nd:YAG laser. Three imaging instruments, operating in the soft X-ray ‘water window’ range, namely two soft X-ray transmission microscopes and a soft X-ray contact microscope, have been developed. The transmission microscopes are based on grazing incidence Wolter type or diffractive Fresnel type optics. Application of these instruments for nanoimaging of hydrated and dry biological samples is presented. A new method for X-ray nanoimaging based on optical coherence tomography (OCT) technique using broad-band soft X-ray emission from the laser plasma source is also demonstrated.

In the paper recently developed microscopes operating in the soft X-rays and extreme ultraviolet (EUV) spectral regions are presented. Soft X-rays and EUV were generated using laser plasma light sources with a double-stream gas puff target. Compact Nd:YAG lasers, generating 4 ns pulses with energy up to 0.8 J at 10 Hz repetition rate, were used to irradiate the targets. Two full-field microscopes based on Fresnel optics have been developed with the use of these sources. The EUV microscope was operating at the wavelength of 13.8 nm and used for imaging of nanostructures with sub-100 nm spatial resolution. The soft X-ray microscope was operating at the wavelength of 2.8 nm and was used for imaging of dry and hydrated biological samples with spatial resolution below 100 nm. The third microscope is based on soft X-ray contact microscopy (SXCM) approach. The new microscopes and their application for imaging at the nanoscale are presented and discussed.

The optical coherence tomography (OCT), typically used in the visible wavelength range, due to relatively long wavelength is limited by the axial resolution to approximately a few hundreds of nanometers to a micron. Visible light is also incapable of resolving multilayered structures of tens of nanometers periods. Thus, the extension of the OCT to shorter wavelengths, such as the extreme ultraviolet (EUV) and soft X-ray (SXR), in the so-called X-ray coherence tomography (XCT), allows mitigating those problems. We present a nanometer resolution XCT using broadband SXR radiation with 2 nm axial resolution using a compact laser plasma soft X-ray source. The laser-produced Kr/He plasma was formed by the interaction of nanosecond laser pulses with a gaseous target in a double stream gas puff target approach, emitting 2 to 5 nm wavelength broadband radiation. The coherence parameters of the SXR radiation allowed for the OCT measurements of a bulk multilayer structure composed of Mo/Si multilayers with 10 nm period, with an axial resolution of about 2 nm, the interface position accuracy of sub-nm and detection of multilayer interfaces up to a depth of about 100 nm. The experimental data were compared to the OCT simulations.

In this work investigations concerning interaction of intense, nanosecond EUV pulses with matter were performed. Various laser-produced plasma radiation sources were employed for creation of the driving EUV pulses. The sources were based on two different laser systems with pulse energies ranging from 0.8 J to 10J and pulse duration 4 ÷ 10 ns. They were equipped with the EUV collectors for focusing of the radiation. This way radiation fluence up to 0.5 J/cm2 in the interaction region was obtained. In our experiments solid material samples or gases injected into the vacuum chamber synchronously with the EUV pulses were irradiated. Irradiation of the gases resulted in ionization and excitation of atoms and molecules forming low temperature plasmas with a relatively high electron density. Emission spectra obtained from these plasmas, contained spectral lines corresponding to radiative transitions in atoms, molecules, atomic or molecular ions. For analysis of the EUV spectra numerical simulations were performed, using a collisional-radiative PrismSPECT code. For computer simulations of the molecular spectra measured in the UV/VIS range a LIFBASE and Specair codes were employed. This way ionization states together with various thermodynamic parameters were deduced. Irradiation of solid samples resulted in melting of a thin near-surface layer or, in some cases its ablation or even conversion to a low temperature plasma. It depended on physico-chemical properties of the material and its thickness. In case of organic polymers, usually ablation connected with fragmentation of the polymer molecules, took place. In case of thick samples of inorganic solids, a thin near surface layer was heated up to a high temperature exceeding melting or even boiling point. In most cases different kinds of micro- or nanostructures were created, modifying the surface morphology. Except the EUV interaction with solid materials, simultaneous EUV and the EUV induced plasma treatment was investigated. Plasmas were created in gases injected close to the exposed surface. Part of the EUV radiation was absorbed in the injected gas forming the low temperature plasma near the surface, while the other part of radiation, that was not absorbed, interacted with the surface material. This way additional atoms could be incorporated into the molecular structure of the exposed material, or reactive etching took place. Especially interesting results were obtained using molecular gases for creation the reactive plasmas.

We present a brief review of radiography technique (shadowgraphy) and its extension to tomography. We used both techniques to characterize i.e. multi-jet gas puff target for different gases with a variable number of jets for various applications. The characterization measurements have been performed with the use of EUV shadowgraphy at 13.5 nm wavelength. Pulses of the EUV radiation were produced with a laser plasma EUV source based on a double-stream gas puff target. The shadowgrams of the characterized gas puff targets were registered using a back-illuminated CCD camera, sensitive to the EUV radiation. The gas density maps were calculated based on 2D transmission map and an atomic photoabsorption cross-section. To obtain 3D tomography reconstruction of multi-jet gas puff target we acquired projections at different viewing angles and performed the reconstruction numerically. This unique technique based on a compact laser-produced plasma source allows imaging 2D and 3D objects having a density 3 orders of magnitude smaller than the density of water.

Tomography is a 3-D imaging method, which allows producing 3-D images by image stacking and numerical refocusing, a spatially localized probing or by sample rotation. Usually, those methods are employed at visible range wavelengths of electromagnetic radiation. It is the simplest, most developed and most common approach since visible light is the part of electromagnetic radiation, which is the closest to humans. There are, however, certain limitations to the visible light methods, such as diffraction limit in the range of hundreds of nanometers, the incapability of direct imaging low-density objects, such as gasses, or the objects being completely opaque to the visible light radiation. Thus, the extension of those methods to the extreme ultraviolet (EUV) and soft X-ray (SXR) spectral ranges allows mitigating those problems. A few examples of such tomographic 3-D imaging experiments employing EUV and SXR compact, tabletop laser plasma sources will be presented and discussed.

A desktop tomography system, based on laser-interaction with a gas puff target, which results in efficient plasma formation emitting in the soft X-ray (SXR, λ = 0.1 - 10 nm) region, was developed at IOE-WAT (Warsaw, Poland). The system, coupled with an ellipsoidal condenser and a Fresnel zone-plate and working in the "water window" spectral range (λ = 2.3 - 4.4 nm) at the quasi-monochromatic He-like nitrogen spectral line (λ=2.88nm), allows acquiring images approaching a resolution of few microns. The development of such setup offers the possibility to obtain a reconstruction of three-dimensional images in a laboratory environment, without the involvement of large "photon facilities". Details about the system and its optimization as well as some imaged samples will be presented and discussed.

Low temperature plasmas induced by irradiation of molecular gases with extreme ultraviolet (EUV) pulses were studied. The EUV pulsed beams of high intensity, were formed using laser-produced plasma (LPP) sources, based on Nd:YAG laser systems and a double-stream Xe/He gas-puff target. The EUV beams were used for irradiation of small portions of gases, injected into a vacuum chamber synchronously with the radiation pulses. Low temperature plasmas produced this way in oxygen, nitrogen or sulfur hexafluoride gas emitted radiation in a wide spectral range. The corresponding EUV spectra were dominated by emission lines originating from singly charged, atomic ions. In case of spectra recorded in an optical range, emission lines, corresponding to radiative transitions in atomic or molecular species, were detected. Taking into account a Stark broadening of F I emission lines an electron density was estimated. Its value exceeded 1017cm-3, which is a few orders of magnitude higher comparing to plasmas produced in standard generators. Employing the SF6 – based plasmas an experiment concerning plasma treatment of a silicon surface was performed. A possibility to create different kinds of nanostructures was demonstrated.

In this work, a near edge X-ray fine structure spectroscopy (NEXAFS) based on a laser-plasma compact soft X-ray (SXR) source is presented. The NEXAFS spectrum was acquired simultaneously for all energies near the absorption edge, using a broadband emission from krypton plasma, in contrary to the existing, synchrotron-based spectroscopic systems. In such SXR source, a plasma is produced by an interaction of a laser beam with a double stream gas puff target. The plasma efficiently emits SXR radiation from 2-5 nm wavelength (250-620 eV photon energy). Such broadband emission allows acquiring simultaneously a sample and a reference spectra, to obtain optical density spectrum of the sample near C-Kα absorption edge, due to a special construction of the SXR spectrometer. The NEXAFS spectra were obtained using PET polymer test sample, from both, the large area and spatially localized to ~30×30 μm2 area. The spatially localized spectra were used to construct 2-D spectromicroscopic maps of sample constituents. Single-shot spectra were also acquired with laser pulse energies of ~10 times larger than in the case of multiple exposures. A short overview of those NEXAFS experiments will be presented.

In the paper new experimental techniques for nano-imaging and nano-spectroscopy operating with electromagnetic radiation in the nanometer wavelength range (soft X-rays - SXR and extreme ultraviolet – EUV) are presented. SXR and EUV radiation is generated using laser plasma sources in which a laser plasma is produced by irradiation of a gas puff target with nanosecond laser pulses at intensities of about 1011-1012 Wcm-2 in the interaction region. Commercially available Nd:YAG lasers (EXPLA) generating 4 ns pulses with energy up to 0.8 J at 10 Hz repetition rate are used to irradiate the targets that are formed by pulsed injection of working gas (Xe, Kr, Ar, N2) in an additional annular stream of He gas under high-pressure using a double-nozzle set up (a double-stream gas puff target approach [1]). Laboratory microscopy systems with the use of compact laser plasma sources of soft X-rays and EUV, operating in the ‘water window’ spectral range (wavelength: 2.3–4.4 nm; photon energy: 280–560 eV) or the EUV range at the wavelength of 13.8 nm have been developed [2]. Application of these microscopes for nano-imaging of hydrated and dry biological samples with spatial resolution from 50 nm to 100 nm and relatively short exposition time is presented. Moreover, a recently developed laboratory system for the near-edge X-ray absorption fine structure (NEXAFS) spectroscopy [3] is also presented. The new NEXAFS system has been used for elemental composition analysis of polymer samples. [1] H. Fiedorowicz et al. Appl. Phys. B 70 (2000) 305 [2] P. Wachulak et al. Appl. Sci. 7 (2017) 548 [3] P. Wachulak et al. (2018) - submitted

In this work different kinds of reflective optical systems were used for creation and investigation of low temperature, photoionized plasmas. The plasmas were created in gases, irradiated with a focused beam of extreme ultraviolet (EUV) or soft X-ray (SXR) radiation, from laser-plasma sources employing 10 Hz Nd:YAG laser systems (0.8 J/ 4 ns and 10 J/ 1-10 ns). In both cases, the EUV radiation was focused using a gold-plated grazing incidence ellipsoidal collector in the wavelength range λ = 9÷70 nm or a gold-plated grazing incidence multifoil collector in the wavelength range λ = 5 ÷ 70 nm. Additionally, in case of the 10 J Nd:YAG laser with the pulse duration 1 ns, a paraboloidal collector optimized for the wavelength range λ ≥ 1 nm was employed. Different gases were injected into the vacuum chamber, perpendicularly to an optical axis of the irradiation system at the focal region, using an auxillary gas puff valve. Irradiation of the gases resulted in ionization and excitation of atoms/molecules. Spectra in SXR/EUV range were measured using a grazing incidence, flat-field spectrometer (McPherson Model 251), equipped with a 450 lines/mm toroidal grating or a home-made spectrograph based on the 5000 l/mm transmission grating. Optical spectra were recorded using the Echelle Spectra Analyzer ESA 4000. In all cases the most intense emission lines were assigned to singly charged ions, however, lines corresponding to ions with higher charge were also recorded. Based on spectral lines originating from ions electron temperature was estimated.

A comparative study of photoionized plasmas created by soft X-ray (SXR) and extreme ultraviolet (EUV) laser plasma sources was performed. The sources, employing high or low energy laser systems, utilized double-stream Xe/He gas-puff targets irradiated with laser pulses of different parameters. The SXR/EUV beams were used for irradiation of a gas stream, injected into a vacuum chamber synchronously with the radiation pulse. Photoionized plasmas produced this way in Ne gas emitted radiation in the SXR/EUV range. The corresponding spectra were dominated by emission lines originating from singly charged ions. Significant differences between spectra obtained in different experimental conditions concern specific transitions in Ne II ions. Creation of photoionized plasmas by SXR or EUV irradiation resulted in K-shell or L-shell emissions respectively. In case of the low energy system absorption spectra were measured additionally. In case of the high energy system, the electron density measurements were performed by laser interferometry, employing a femtosecond laser system. A maximum electron density reached the value of 2·1018cm-3. For the low energy system, a detection limit was too high for the interferometric measurements, thus only an upper estimation for electron density could be made.

A compact size microscope based on nitrogen double stream gas puff target soft X-ray source, which emits radiation in water-window spectral range at the wavelength of λ = 2.88 nm is presented. The microscope employs ellipsoidal grazing incidence condenser mirror for sample illumination and silicon nitride Fresnel zone plate objective for object magnification and imaging. The microscope is capable of capturing water-window images of objects with 60 nm spatial resolution and exposure time as low as a few seconds. Details about the microscopy system as well as some examples of different applications from various fields of science, are presented and discussed.

The detail characteristics of a compact laser-plasma X-ray source, dedicated for application in soft X-ray contact microscopy is presented in the paper. The source is based on a double-stream gas puff target, irradiated with nanosecond laser pulses from a commercial Nd:YAG laser. The use of the gas puff target makes possible to produce soft X-ray radiation in the “water window” region without target debris production. Details of the characterization measurements and optimization of the source are presented and discussed.

An investigation on short-wavelength ablation mechanism of poly(1,4-phenylene ether ether-sulfune) PPEESand poly (1-hexadecene-sulfone) PHDS (Figure 9-10) by EUV radiation is presented. The goal of this work is to evaluate the ablation behavior with respect to the influence of wavelength, fluence and quantum efficiency. Because there is no yet a general EUV ablation theory, data are analyzed in order to underline regularity of the process which can be used in future to detect the scaling laws of the process. The differences with longer wavelengths ablation and EUV one are pointed out and possible applications of EUV ablation are proposed.

In this work photoionized plasmas were created by irradiation of atomic and molecular gases by soft X-ray and extreme ultraviolet intense radiation pulses. Two different laser-produced plasma sources, employing a low energy Nd:YAG laser system (NL 129) and a high energy iodine laser system (PALS), were used for creation of photoionized plasmas. In both cases the SXR/EUV beam irradiated the gas stream, injected into a vacuum chamber synchronously with the radiation pulse. Radiation spectra, measured for photoionized plasmas produced in Ne and Ar gases, are dominated by L-shell emission lines except the Ne plasma produced using the high energy system where K-shell emission dominates. Additionally electron density measurements were performed by laser interferometry employing a femtosecond laser system synchronized with the irradiating system. Maximum electron density for Ne plasma, induced using the high energy system, reached 2·1018cm-3. In case of employing the low energy system a detection limit was too high for interferometric measurements, thus only an upper estimation for electron density could be made.

Laser plasma sources of soft x-rays an d extreme ultraviolet (EUV) developed in our laboratory for application in various areas of technology and science are presented. The sources are based on a laser-irradiated gas puff target approach. The targets formed by pulsed injection of gas under high-pressure are irradiated with nanosecond laser pulses from Nd:YAG lasers. We use commercial lasers generating pulses with time duration from 1ns to 10ns and energies from 0.5J to 10J at 10Hz repetition rate. The gas puff targets are produced using a double valve system equipped with a special nozzle to form a double-stream gas puff target which secures high conversion efficiency without degradation of the nozzle. The use of a gas puff target instead of a solid target makes generation of laser plasmas emitting soft x-rays and EUV possible without target debris production. The sources are equipped with various optical systems, including grazing incidence axisymmetric ellipsoidal mirrors, a “lobster eye” type grazing incidence multi-foil mirror, and an ellipsoidal mirror with Mo/Si multilayer coating, to collect so ft x-ray and EUV radiation and form the radiation beams. In this paper new applications of these sources in various fields, including soft x-ray and EUV imaging in nanoscale, EUV radiography and tomography, EUV materials processing and modification of polymer surfaces, EUV photoionization of gases, radiobiology and soft x-ray contact microscopy are reviewed. Keywords: laser plasmas, soft x-rays, extreme ultraviolet (EUV), laser plasma soft x-ray and EUV sources, soft x-ray microscopy, EUV radiography and tomography, EUV processing materials, radiobiology, soft x-ray contact microscopy, EUV photo-ionized plasmas

Radiation with shorter illumination wavelength allows for extension of the diffraction limit towards nanometer scale, which is a straightforward way to significantly improve a spatial resolution in photon based microscopes. Soft X-ray (SXR) radiation, from the so called ”water window” spectral range, λ=2.3-4.4 nm, which is particularly suitable for biological imaging due to natural optical contrast, providing much better spatial resolution than one obtained with visible light microscopes. The high contrast is obtained because of selective absorption of radiation by carbon and water, being constituents of the biological samples. We present a desk-top system, capable of resolving 60 nm features in few seconds exposure time. We exploit the advantages of a compact, laser-plasma SXR source, based on a double stream nitrogen gas puff target, developed at the Institute of Optoelectronics, Military University of Technology. The source, emitting quasi-monochromatic, incoherent radiation, in the “water widow” spectral range at λ = 2.88 nm, is coupled with ellipsoidal, grazing incidence condenser and Fresnel zone plate objective. The construction of the microscope with some recent images of test and real samples will be presented and discussed.

The wavelength diffraction limit, described by the Rayleigh criterion, can be overcome if short wavelength radiations are employed, thus it is possible to resolve smaller features by the use of radiation in the extreme ultraviolet (EUV) and soft X-ray (SXR) spectral ranges. In particular way, radiation from the “water window” spectral range, which extends between K-absorption edges of carbon and oxygen (280÷540 eV), could be used in order to obtain high-contrast biological imaging. Laser-plasma double stream gas puff target source is suitable for SXR microscopy in the “water window” spectral range, which recently allowed to develop a system, operating at He-like nitrogen spectral line λ=2.88 nm, which permits to obtain images with half-pitch spatial resolution of ∼ 60 nm, exposure time as low as a few seconds and represents an important alternative for high resolution imaging for biomedical applications, material science and nanotechnology using a very compact laser source. The goal of measurements, presented herein, is to show SXR images of various biological samples, proving high contrast in the “water window” and characterize in more detail such compact microscopy system, based on a laser plasma source with a double stream gas puff target and a Fresnel zone plate (FZP) objective. The influence of various acquisition parameters on the quality of the obtained SXR images, expressed in terms of a signal-to-noise (SNR) will be demonstrated. Moreover, because the measurements are performed on SXR images, similar measurements might be performed as a benchmark in order to characterize different imaging systems as well.

In this work soft X-ray (SXR) and extreme ultraviolet (EUV) laser-produced plasma (LPP) sources employing Nd:YAG laser systems of different parameters are presented. First of them is a 10-Hz EUV source, based on a double-stream gaspuff target, irradiated with the 3-ns/0.8J laser pulse. In the second one a 10 ns/10 J/10 Hz laser system is employed and the third one utilizes the laser system with the pulse shorten to approximately 1 ns. Using various gases in the gas puff targets it is possible to obtain intense radiation in different wavelength ranges. This way intense continuous radiation in a wide spectral range as well as quasi-monochromatic radiation was produced. To obtain high EUV or SXR fluence the radiation was focused using three types of grazing incidence collectors and a multilayer Mo/Si collector. First of them is a multfoil gold plated collector consisted of two orthogonal stacks of ellipsoidal mirrors forming a double-focusing device. The second one is the ellipsoidal collector being part of the axisymmetrical ellipsoidal surface. Third of the collectors is composed of two aligned axisymmetrical paraboloidal mirrors optimized for focusing of SXR radiation. The last collector is an off-axis ellipsoidal multilayer Mo/Si mirror allowing for efficient focusing of the radiation in the spectral region centered at λ = 13.5 ± 0.5 nm. In this paper spectra of unaltered EUV or SXR radiation produced in different LPP source configurations together with spectra and fluence values of focused radiation are presented. Specific configurations of the sources were assigned to various applications.

Extreme ultraviolet (EUV) is an ionizing radiation strongly absorbed in any kind of mater. In case of polymers absorption depth is of the order of 100 nm. Interaction of EUV photons with polymer chains results in chain scission and formation of low weight fractions. In this work interaction of intense EUV pulses with poly(vinylidene fluoride) (PVDF) was investigated. Mass spectroscopy was employed to investigate the ablation products indicating emission of numerous molecular species of C-containing fragments of the polymer chain. Chemical surface changes after irradiation were investigated using X-ray photoelectron spectroscopy (XPS). The XPS spectra obtained for PVDF, samples irradiated with low and high EUV fluence, indicate significant differences between chemical structures in near-surface layers. It was shown that irradiation with low fluence results in defluorination and thus carbon enrichment in near-surface layer. In contrary, irradiation with high fluence leads to intense material ablation and hardly modifies the chemical structure of the remaining material. Additionally chemical modification of the PVDF surface by EUV irradiation in a presence of ionized nitrogen was investigated. The nitrogen gas, injected into an interaction region, was ionized and excited by the EUV radiation from a laser-plasma source. An ionization degree and excited states of nitrogen were investigated using an EUV spectrometry and the corresponding spectra are presented. Chemical modification of the polymer after combined EUV and ionized nitrogen treatment was investigated using an X-ray photoelectron spectroscopy. Significant contribution of the nitrogen atoms in the polymer near-surface layer after the treatment was demonstrated.

Photon-based (bosonic-type) imaging at short wavelength vs. electron, or recently neutron, imaging has additional advantages due to different interaction of photons with matter and thus high resolution photon-based imaging is still of high interest to the scientific community. In this work we try to combine the advantages of employing compact, laboratory type laser-plasma short wavelength source, based on Ar/He gas puff target, emitting incoherent radiation, with the “water-window” spectral range. This unique combination is highly suitable for biological imaging, and allows developing a small size microscopy setup, which might be used in various fields of science and technology. Thus, in this paper we report on recent advances in “water-window” desk-top microscopy setup employing a laser-plasma SXR source based on a double stream gas puff target and Wolter type-I objective. The system allows capturing magnified images of the objects with ~1 μm spatial resolution up to ~40 μm thickness and single SXR pulse exposure time as low as 3 ns. For the SXR microscope Ar plasma was produced by focusing of the pumping laser pulses, from Nd:YAG laser (Eksma), by a lens onto a gas puff target. EUV radiation from the plasma was collected and focused by an ellipsoidal, axi-symmetrical nickel coated condenser mirror, developed by Rigaku, Inc. The condenser is a broad-band optic, capable of efficiently reflecting radiation from the EUV range down to SXR region with energy cut-off of ~800 eV. To spectrally narrow the emission from argon plasma a free-standing titanium filter (Lebow) was used. Spectrally filtered radiation illuminates the sample. Then the sample was imaged onto a SXR sensitive back-illuminated, CCD camera (Andor) by a Wolter type-I reflective objective. A characterization and optimization of both the source and the microscope setups are presented and discussed.

In this work photoionized plasmas were created by irradiation of He, Ne and Ar gases with a focused EUV beam from one of two laser-plasma sources employing Nd:YAG laser systems of different parameters. First of them was a 10-Hz laser-plasma EUV source, based on a double-stream gas-puff target, irradiated with the 3-ns/0.8J laser pulse. EUV radiation in this case was focused using a gold-plated grazing incidence ellipsoidal collector in the wavelength range λ = 9÷70 nm. The most intense emission was in the relatively narrow spectral region centred at λ = 11 ± 1 nm. The second source was based on a 10 ns/10 J/10 Hz laser system. In this case EUV radiation was focused using a gold-plated grazing incidence multifoil collector or a Mo-coated ellipsoidal collector. The most intense emission in this case was in the 5 ÷ 15 nm spectral region. Radiation fluence ranged from 60 mJ/cm 2 to 400 mJ/cm 2 . Different gases were injected into the interaction region, perpendicularly to an optical axis of the irradiation system, using an auxiliary gas puff valve. Irradiation of the gases resulted in ionization and excitation of atoms and ions. Spectra in EUV range were measured using a grazing incidence, flat-field spectrometer (McPherson Model 251), equipped with a 450 lines/mm toroidal grating. In all cases the most intense emission lines were assigned to singly charged ions. The other emission lines belong to atoms or doubly charged ions. The spectra were excited in low density gases of the order of 1 ÷ 10% atmospheric density.

In this chapter we report a desk-top microscopy reaching 50nm spatial resolution in very compact setup using a gas-puff laser plasma EUV source. We present the study of source bandwidth influence on the extreme ultraviolet (EUV) microscope spatial resolution. EUV images of object obtained by illumination with variable bandwidth EUV radiation were compared in terms of knife-edge spatial resolution to study the wide bandwidth parasitic influence on spatial resolution in the EUV microscopy.

In this work results of investigations concerning ablation and surface modification of polymers and some other solids using a laser-plasma EUV source are presented. The plasma radiation was produced using a gas puff target and was focused with a gold-plated grazing incidence ellipsoidal collector. The ablation process was investigated using a scanning electron microscope (SEM) and a quadrupole mass spectrometer (QMS). The chemical changes were investigated by X-ray photoelectron spectroscopy (XPS). Different kinds of micro- and nanostructures created in nearsurface layers of the materials were obtained. Forms of the structures depend on a particular material and the EUV exposure. In case of some polymers even a single shot was sufficient for creation of the visible changes in surface morphology. In case of inorganic solids visible changes required usually the exposure with tens or hundreds of EUV pulses. XPS investigations revealed chemical changes in near surface layers of polymers. Significant differences were revealed in the XPS spectra acquired for irradiated and not-irradiated polymers. Significant decrease of functional groups containing oxygen was indicated. Analysis of QMS spectra indicate emission of different kinds of fragments of the polymer chains including the repeating structural units. In case of some polymers only fragments of the repeating unit were detected.

Decreasing the illumination wavelength provides the potential to improve the spatial resolution in all imaging techniques. Hence there is currently high interest in imaging using laboratory short wavelength sources. This chapter describes approaches to EUV imaging utilizing a compact table-top capillary discharge EUV laser. Various coherent imaging techniques, such as two and three dimensional holography, computer generated holograms (CGHs), EUV reconstruction and generalized Talbot self-imaging will be presented.

The recent advancements in technology of compact laser plasma EUV sources based on a gas puff target are presented in the paper. The sources have been developed for application in processing materials using EUV radiation in the wavelength range from about 5 nm to about 50 nm that is efficiently produced in result of irradiation a double-stream gas puff target with high-intensity laser pulses from a Nd:YAG laser (0.8 J/4 ns/10 Hz). The sources can be equipped with two various grazing incidence optical systems to focus EUV radiation: an axisymmetrical ellipsoidal mirror or a multifoil mirror system of the "lobster eye" type. A new design of the laser plasma EUV source dedicated for micro- and nanoprocessing polymers and modification of polymer surfaces is presented for the first time.

We report on the application of a compact laser plasma EUV source for processing of polymer materials. The EUV radiation in the wavelength of about 5 to 50 nm was produced by irradiation of xenon or krypton gas puff target with Nd:YAG laser operating at 10 Hz and delivering 4 ns pulses of energy up to 0.8 J per pulse. The source was equipped with a grazing incidence axisymmetrical ellipsoidal mirror to focus EUV radiation in the relatively broad spectral range with the maximum near 10 nm. The size of the focal spot was about 0.5 mm with the maximum fluence of 70 mJ/cm2 in a single pulse. Nanostructuring of polymer materials was achieved, primarily due to direct photo-etching with EUV photons. The results of the studies should be applicable in biomedical engineering.

Extreme ultraviolet (EUV) is strongly absorbed in any materi al and can be transmitted only through very thin foils. The material surface after irradiation can remain unchanged or becomes modified in some way depending on radiation fluence and material properties. In so me materials the surface changes may aris e due to fast melting or boiling followed by solidification. In other cases photochemical or photothermal ablation can occur. It requires relatively high radiation fluence of the order of tens mJ/cm 2 . A laser-plasma EUV source based on a gas pu ff target equipped with a proper optic can deliver such conditions. In this work EUV radiation coming from xenon or krypton plasma was focused using an ellipsoidal grazing incidence collector. Different kind of material samples were irradiated in the focal plane or at some distance behind the focal plane. This way different intensitie s were applied for irradiation of the samples. Irradiation was performed with 10 Hz repetition rate and different time duration varying from 1s to 2 min. Surface morphology after irradiation was investigated using a scanni ng electron microscope. In a case of so me materials EUV intensity in the focal plane was sufficient for ablation. In other cases material ablation was not possible but surface structure was modified. Forms of the structures for a certain material depend both on EUV fluence in a single shot and the number of shots. Keywords: laser-plasma, EUV, gas puff target , photo-etching, surface modification

In this paper some results of investigations concerning interaction of EUV radiation with inorganic and organic materials were presented. Samples of different materials were irradiated with a 10 Hz laser - plasma EUV source based on a gas puff target. The source was equipped with grazing incidence and multilayer collecting mirrors. The grazing incidence collector was used in experiments concerning surface modification and micromachining of different materials. The micromachining experiments were performed for different polymers that were irradiated through a fine metal grid as a contact mask. For fluoropolymers, EUV radiation with fluence of 10 mJ/cm 2 was enough for efficient photo-etching. The photo-etching speed was maximal for polytetrafluoroethylene (PTFE) reaching 30nm per shot. It was shown that using such a method microstructures with high aspect ratio could be produced. Experiments connected with surface modification were performed either with organic or inorganic materials. Different kinds of surface structures were obtained depending on irradiated materials and irradiation parameters. The Mo/Si collector together with argon plasma was used for obtaining a quasi-monochromatic radiation for EUV microscopy and some metrological applications.

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.

A single photon of EUV radiation carries enough energy to break any chemical bond or excite electrons from inner atomic shells. It means that the radiation regardless of its intensity can modify chemical structure of molecules. It is the reason that the radiation even with low intensity can cause fragmentation of long chains of organic materials and desorption of small parts from their surface. In this work interaction of EUV radiation with inorganic materials was investigated. Different inorganic samples were irradiated with a 10 Hz laser - plasma EUV source based on a gas puff target. The radiation was focused on a sample surface using a lobster eye collector. Radiation fluence at the surface reached 30 mJ/cm 2 within a wavelength range 7 - 20 nm. In most cases there was no surface damage even after several minutes of irradiation. In some cases there could be noticed discolouration of an irradiated surface or evidences of thermal effects. In most cases however luminescent and scattered radiation was observed. The luminescent radiation was emitted in different wavelength ranges. It was recorded in a visible range of radiation and also in a wide wavelength range including UV, VUV and EUV. The radiation was especially intense in a case of non-metallic chemical compounds.

Organic polymers (PMMA, PTFE, PET, and PI) are considered as the important materials in microengineering, especially for biological and medical applications. Micromachining of such materials is possible with the use of different techniques that involve electromagnetic radiation or charged particle beams. Another possibility of high aspect ratio micromachining of PTFE is direct photo-etching using synchrotron radiation. X-ray and ultraviolet radiation from other sources, for micromachining of materials by direct photo-etching can be also applied. In this paper we present the results of investigation of a wide band soft X-ray source and its application for direct photo-etching of organic polymers. X-ray radiation in the wavelength range from about 3 nm to 20 nm was produced as a result of irradiation of a double-stream gas puff target with laser pulses of energy 0.8 J and time duration of about 3 ns. The spectra, plasma size and absolute energies of soft X-ray pulses for different gas puff targets were measured. Photo-etching process of polymers irradiated with the use of the soft X-ray radiation was analyzed and investigated. Samples of organic polymers were placed inside a vacuum chamber of the x-ray source, close to the gas puff target at the distance of about 2 cm from plasmas created by focused laser pulses. A fine metal grid placed in front of the samples was used as a mask to form structures by x-ray ablation. The results of photo-etching process for several minutes exposition with l0Hz repetition rate were presented. High ablation efficiency was obtained with the use of the gas puff target containing xenon surrounded by helium.

Single ≤1 kJ pulses from a high-power laser are focused into molecular gases to create large laser sparks. This provides a unique way to mimic the chemical effects of high-energy-density events in planetary atmospheres (cometary impact, lightning) matching the natural energy-density, its spatio-temporal evolution and plasma-volume scaling of such events in a fully-controlled laboratory environment. Some chemical reactions initiated by laser-induced dielectric breakdown (LIDB) in both pure molecular gases and mixtures related to the chemical evolution of the Earth's early atmosphere were studied. Most of the experiments were carried out in a static gas cell. However, an initial series of experiments was also performed with a gas-puff target placed within a vacuum interaction chamber. Under these dynamic conditions the hot core of a laser spark can be directly investigated.

A new high-density gas puff target for experiments on laser-driven X-ray lasers is presented. The target is based on a double-stream gas puff target approach, which makes possible to form an elongated gas sheet with steep density gradient and high density of gas in the interaction region. In the paper the valve system to produce the gas puff targets and the results of the target characterization measurements performed using X-ray backlighting technique are presented.

A pulse-train Nd:YAG laser system consisting of repetitively Q-switched Nd:YAG oscillator with Cr 4+ :YAG saturable absorber, double pass Nd:YAG amplifier and stimulated Brillouin scattering (SBS) pulse compressor has been demonstrated. Number and energy of the laser pulses were controlled by adjusting width and amplitude of the flash lamp pumping pulses. Efficient SBS compression of Nd:YAG laser pulses was obtained using single-cell compressor.

Experiments on direct photo-etching of organic polymers induced by high-intensity nanosecond pulses of soft X-ray radiation from a laser plasma X-ray source based on a gas puff target are presented. X-rays in the wavelength range from about 1 nm to 8 nm were produced by irradiation of the xenon/helium double-stream gas puff target with laser pulses from the Prague Asterix Laser System (PALS). The resulting X-ray pulses were used to irradiate samples from organic polymers and form microstructures. The results show relatively high efficiency of X-ray direct photo-etching that could be useful for micromachining of organic polymers.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

For conventional wavelength (UV-Vis-IR) lasers delivering radiation energy to the surface of materials, ablation thresholds, ablation (etch) rates, and the quality of ablated structures often differ dramatically between short (typically nanosecond) and ultrashort (typically femtosecond) pulses. Various short-wavelength (l < 100 nm) lasers emitting pulses with durations ranging from ~ 10 fs to ~ 1 ns have recently been put into a routine operation. This makes it possible to investigate how the ablation characteristics depend on the pulse duration in the XUV spectral region. 1.2-ns pulses of 46.9-nm radiation delivered from a capillary-discharge Ne-like Ar laser (Colorado State University, Fort Collins), focused by a spherical Sc/Si multilayer-coated mirror were used for an ablation of organic polymers and silicon. Various materials were irradiated with ellipsoidal-mirror-focused XUV radiation (λ = 86 nm, τ = 30-100 fs) generated by the free-electron laser (FEL) operated at the TESLA Test Facility (TTF1 FEL) in Hamburg. The beam of the Ne-like Zn XUV laser (λ = 21.2 nm, τ < 100 ps) driven by the Prague Asterix Laser System (PALS) was also successfully focused by a spherical Si/Mo multilayer-coated mirror to ablate various materials. Based on the results of the experiments, the etch rates for three different pulse durations are compared using the XUV-ABLATOR code to compensate for the wavelength difference. Comparing the values of etch rates calculated for short pulses with those measured for ultrashort pulses, we can study the influence of pulse duration on XUV ablation efficiency. Ablation efficiencies measured with short pulses at various wavelengths (i.e. 86/46.9/21.2 nm from the above-mentioned lasers and ~ 1 nm from the double stream gas-puff Xe plasma source driven by PALS) show that the wavelength influences the etch rate mainly through the different attenuation lengths.

In the paper a newly developed compact laser plasma EUV source is presented. The source is based on the double-stream gas puff target approach. The targets are formed by pulsed injection of high-Z gas (xenon) into a hollow stream of low-Z gas (helium) using the valve system composed of two electromagnetic valves and equipped with the double-nozzle setup. The outer stream of gas confines the inner stream improving the gas puff target characteristics (higher density of high-Z gas at longer distance from the nozzle output). It causes efficient absorption of laser energy in a plasma and strong EUV production. The source has been developed in the frame of the EUV sources development project under the MEDEA+ program.

Spectral measurements of a laser-produced soft x-ray and EUV source based on a double-stream gas puff target are described. The target was irradiated with a Nd:glass laser producing 1 ns pulses with energy up to 10 J. Production in the wavelength range up to 20 nm (x-ray and EUV emissions) have been measured from xenon, krypton, argon, and nitrogen targets using the transmission grating spectrometer with the back-illuminated CCD. Spectral characteristics of x-ray and EUV emissions are presented.

In this work we report our numerical modeling results of laser-generated transient inversion and capillary discharge X-ray lasers. In the search for more efficient X-ray lasers we look closely at other approaches in conjunction with experiments at LLNL. In the search for improved X-ray lasers we perform modeling and experimental investigations of low density targets including gas puff targets. We have found the importance of plasma kinetics in transient X-ray lasers by expanding the physical model beyond hydrodynamics approach with Particle In Cell (PIC) and Fokker-Planck codes. The evidence of the Langdon effect was inferred from the recent experimental data obtained with the Ni-like Pd X-ray laser. We continue modeling different kinds of capillary discharge plasma configurations directed toward shorter wavelength X-ray lasers, plasma diagnostics and other applications.

The development of the transient collisional excitation x-ray laser scheme using tabletop laser systems with multiple pulse capability has progressed rapidly in the last three years. The high small-signal gain and strong x-ray output have been demonstrated for laser drive energies of typically less than 10 J. We report recent x-ray laser experiments on the Lawrence Livermore National Laboratory (LLNL) Compact Multipulse Terawatt (COMET) tabletop facility using this technique. In particular, the saturated output from the Ni-like Pd ion 4d - 4p x-ray laser at 146.8 angstrom has been well characterized and has potential towards a useable x-ray source in a number of applications. One important application of a short wavelength x-ray laser beam with picosecond pulse duration is the study of a high density laser-produced plasma. We report the implementation of a Mach-Zehnder type interferometer using diffraction grating optics as beam splitters designed for the Ni-like Pd laser and show results from probing a 600 ps heated plasma. In addition, gas puff targets are investigated as an x-ray laser gain medium and we report results of strong lasing on the n equals 3 - 3 transitions of Ne-like Ar.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

In this work we demonstrate a soft x-ray laser with neon-like argon ions using a gas puff target irradiated with acombination of long 600 ps and short 6 ps high-power laser pulses with a total of 10 J energy. The gas puff target was formed by pulsed injection of gas from a high-pressure solenoid valve through a nozzle in the form of a narrow slit. Thetarget was irradiated in a travelling-wave excitation geometry. Lasing was observed on the 3p 'So —f 3s 1P1 transition at 46.9 nm and the 3d 1P1 — 3p 1P transition at 45. 1 nm. Gain of 1 1 cm' was measured on these transitions for targets upto 0.9 cm long.Keywords: x-ray lasers, laser-produced plasmas, x-ray optics, gas puff target 1. INTRODUCTION Significant progress towards the realization of a laser-driven tabletop x-ray laser has been achieved during the last few years using different variants of the prepulse technique.15 In this technique a solid target is irradiated with several laserpulses. The first pulse is used to create a large-scale length plasma, which has the appropriate density range for gain andsufficiently small density gradients for laser propagation. The subsequent pulses can be absorbed more efficiently and heatthe preformed plasma to lasing conditions. Efficient, high-brightness soft x-ray lasers with neon-like and nickel-like ions

Measurements of soft x-ray emission from a nitrogen/helium double-stream gas puff target irradiated with the Prague Asterix Laser System (PALS) have been performed. The aim of the studies was to measure the absolute yields of soft x-ray radiation in the water window from a gas puff laser plasma source and to verify the possibilities of using of this source in x-ray imaging microscopy.

Characterization measurements of a laser-produced x-ray source based on a double-stream ga puff target are presented. The target was irradiated with a Nd:glass laser producing 1 ns pulses with energy up to 10 J. Production in the wavelength range up to 200 nm have been measured form xenon, krypton, argon, and nitrogen targets using the transmission grating spectrometer with the back-illuminated CCD and the absolutely calibrated silicon photodiodes. Spectral characteristics of x-ray and EUV emissions are presented.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Generation of x-ray and extreme ultraviolet (EUV) radiation from laser-produced source with a new double-stream gas puff target has been investigated. The target was formed by pulsed injection of heavy gas (argon, or xenon) into a hollow gas stream from helium by using a double-nozzle setup. This new approach allows to form a high-density gaseous target at a relatively large distance from the nozzle output. X-ray emission was produced by irradiation of the argon/helium target with pulses of 1 ns time duration with energy up to 20 J from a Nd:glass laser. Strong x-ray emission at the wavelength near 0.4 nm from the argon target, similar to the emission from the solid sulphur target irradiated in the same conditions, have been observed. These new results may be useful to develop a laser-produced radiation source for x-ray lithography. To generate EUV radiation the xenon/helium target was irradiated using a Nd:YAG laser producing pulses of 10 ns and 0.7 J or energy. Efficient production near 11 nm from the xenon target exceeding emissions from solid targets was observed that should be useful for EUV lithography.