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Over the last decades, remarkable efforts have been made to improve the resolution in photon-based microscopes. The employment of compact sources based on table-top laser-produced soft X-ray (SXR) in the “water window” spectral range (λ = 2.3–4.4 nm) and extreme ultraviolet (EUV) plasma allowed to overcome the limitations imposed by large facilities, such as synchrotrons and X-ray free electron lasers (XFEL), because of their high complexity, costs, and limited user access. A laser-plasma double stream gas-puff target source represents a powerful tool for microscopy operating in transmission mode, significantly improving the spatial resolution into the nanometric scale, comparing to the traditional visible light (optical) microscopes. Such an approach allows generating the plasma efficiently, without debris, providing a high flux of EUV and SXR photons. In this review, we present the development and optimization of desktop imaging systems: a EUV and an SXR full field microscope, allowing to achieve a sub-50 nm spatial resolution with short exposure time and an SXR contact microscope, capable to resolve internal structures in a thin layer of sensitive photoresist. Details about the source, as well as imaging results for biological applications, will be presented and discussed.

We present a near edge X-ray fine structure (NEXAFS) spectromicroscopy, that was developed based on a compact laboratory laser-plasma soft X-ray light source. The presented approach to spectromicroscopy is different from the usual synchrotron-based one when the series of full-field microscopy images are obtained at different energies. Herein, spatially localized NEXAFS spectra are obtained using a broad-band SXR emission, and the microscopic image is obtained by a raster scanning. The plasma is formed by the interaction of nanosecond laser pulses with a double stream gas puff target. The laser plasma source was optimized for efficient soft X-ray emission from a krypton plasma in the range ~2 nm to 5 nm wavelength radiation (energy of ~250 eV – 620 eV). This emission is used to acquire simultaneously emission and absorption spectra of soft X-ray light from the source and from the investigated sample. The spectra were acquired from a small area of PET polymer ~30 × 30 μm2 in size. A raster scanning was implemented to obtain 2-D elemental composition maps. A chemical (elemental) composition of EUV-irradiated PET was investigated. The data are in agreement with the reference measurements and the theoretical values. EUV irradiated PET spectra are showing hydrogen decrease in the PET structure due to the EUV irradiation. In the paper, a detailed information about the source, the system, the spectral measurements and the results are presented and discussed.

We present optical coherence tomography (OCT) with 2 nm axial resolution using broadband soft X-ray radiation (SXR) from a compact laser plasma light source. The laser plasma was formed by the interaction of nanosecond laser pulses with a gaseous target in a double stream gas puff target approach. The source was optimized for efficient SXR emission from the krypton/helium gas puff target in the 2 to 5 nm spectral range, encompassing the entire “water-window” spectral range from 2.3 nm to 4.4 nm wavelength. The coherence parameters of the SXR radiation allowed for the OCT measurements of a bulk multilayer structure with 10 nm period and 40% bottom layer thickness to period ratio, with an axial resolution of about 2 nm and detect multilayer interfaces up to a depth of about 100 nm. The experimental data are in agreement with OCT simulations performed on ideal multilayer structure. In the paper, detailed information about the source, its optimization, the optical system, OCT measurements and the results are presented and discussed.

In this paper, we present the application of partially spatially coherent extreme ultraviolet (EUV) radiation from xenon plasma from a laser-plasma source, based on a double stream gas puff target, in coherent imaging. The radiation at the wavelength of 13.5 ± 0.5 nm was employed to record Gabor-type holograms. An iterative algorithm, based on a phase retrieval technique, was developed and used to remove the twin image from the reconstructed EUV image of test objects. Using partially coherent radiation from a compact, laser-plasma source based on a double stream gas puff target, which is intrinsically incoherent, a Gabor EUV holography was successfully demonstrated.

Characterization of Xe emission in the spectral range between 1 and 1.5 keV is presented in the case when the laser-plasma is generated by nanosecond laser pulse irradiation of a double stream Xe/He gas-puff target. Gas target density was estimated using extreme ultraviolet (EUV) radiography. Emission spectral characteristics in the wavelength range from 0.8 to 5.2 nm were determined by using a flat field SXR spectrometer. Significant emission was recorded in two high-energy bands, the first one at wavelengths 0.8–1.6 nm (photon energy range 0.78–1.5 keV) and the second one at 1.6–2.5 nm (0.5–0.78 keV). Both plasma size and photon yield in each band were measured separately to individually assess radiation and source characteristics. Moreover, a proof-of-principle experiment for near-edge X-ray absorption fine structure spectroscopy of metallic sample near the L2,3 absorption edge was performed to show one of the applicability areas of such a compact source.

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.

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.

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.

We report on a very compact desk-top transmission extreme ultraviolet (EUV) microscope based on a laser-plasma source with a double stream gas-puff target, capable of acquiring magnified images of objects with a spatial (half-pitch) resolution of sub-50 nm. A multilayer ellipsoidal condenser is used to focus and spectrally narrow the radiation from the plasma, producing a quasi-monochromatic EUV radiation (λ = 13.8 nm) illuminating the object, whereas a Fresnel zone plate objective forms the image. Design details, development, characterization and optimization of the EUV source and the microscope are described and discussed. Test object and other samples were imaged to demonstrate superior resolution compared to visible light microscopy.

We present a few examples of imaging experiments, which were possible using a compact laser-plasma extreme ultraviolet (EUV) and soft X-ray (SXR) source, based on a double stream gas puff target. This debris-free source was used in full-field EUV imaging to obtain magnified images of test samples, ZnO nanofibers and images of the membranes coated with salt crystals. The source was also employed for SXR microscopy in the “water-window” spectral range using grazing incidence Wolter type-I objective to image test samples and to perform the initial studies of biological objects. Gas puff target EUV source, spectrally tuned for 13.5 nm wavelength with multilayer mirror and thin film filters, was also used in variety of shadowgraphy experiments to study the density of newly developed modulated density gas puff targets. Finally, the source was also employed in EUV tomography experiments of low density objects with the goal to measure and optimize the density of the targets dedicated to high harmonic generation.

We present a 2-D mapping of a sample thickness with nanometer accuracy employing a compact arrangement of near-edge X-ray absorption fine structure (NEXAFS) technique. A NEXAFS spectrum coupled with a scanning system was used to generate a 2-D thickness map of the TiO2 sample (anatase form) deposited on the top of a SiN membrane. The thickness values were retrieved from the experimental data by applying different methods of data processing. In the paper, the detailed analysis of the data processing methods and the identified sources of the errors show that the proposed procedure based on averaging two imperfect estimates reduces the error caused by the uncontrolled bias of the measured signals. This procedure was termed as the average one. The estimates from the proposed average approach and the standard absorption-jump ratio in the absorption edge vicinity were compared with the direct results obtained by applying scanning electron microscopy (SEM). The experimental arrangement of the NEXAFS spectroscopy system, the data acquisition method, as well as the possible error sources, are presented and discussed in detail.

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

We present a proof of principle experiment on single-shot near edge soft X-ray fine structure (NEXAFS) spectroscopy with the use of a laboratory laser-plasma light source. The source is based on a plasma created as a result of the interaction of a nanosecond laser pulse with a double stream gas puff target. The laser-plasma source was optimized for efficient soft X-ray (SXR) emission from the krypton/helium target in the wavelength range from 2 nm to 5 nm. This emission was used to acquire simultaneously emission and absorption spectra of soft X-ray light from the source and from the investigated sample using a grazing incidence grating spectrometer. NEXAFS measurements in a transmission mode revealed the spectral features near the carbon K-&alpha, absorption edge of thin polyethylene terephthalate (PET) film and L-ascorbic acid in a single-shot. From these features, the composition of the PET sample was successfully obtained. The NEXAFS spectrum of the L-ascorbic acid obtained in a single-shot exposure was also compared to the spectrum obtained a multi-shot exposure and to numerical simulations showing good agreement. In the paper, the detailed information about the source, the spectroscopy system, the absorption spectra measurements and the results of the studies are presented and discussed.

A laser-plasma double stream gas-puff target source coupled with Fresnel zone plate (FZP) optics, operating at He-like nitrogen spectral line λ=2.88nm, is capable of acquire complementary information in respect to optical and electron microscopy, allowing to obtain high resolution imaging, compared to the traditional visible light microscopes, with an exposition time of a few seconds. The compact size and versatility of the microscope offers the possibility to perform imaging experiments in the university laboratories, previously restricted to large-scale photon facilities. Source and microscope optimization, and examples of applications will be presented and discussed.

Application of a compact laser plasma source of soft X-rays and extreme ultraviolet (EUV) in imaging with nanometer resolution is demonstrated. The source is based on a gas puff target irradiated with nanosecond laser pulses from a small commercial Nd:YAG laser. Soft X-ray radiation in the ‘water window’ spectral range and EUV near 10 nm are generated efficiently without production of target debris. Nanoscale imaging of biological samples as well as micro- and nanostructures using transmission soft X-ray and EUV microscopy based on Fresnel optics and soft X-ray contact microscopy is demonstrated.

Short illumination wavelength allows an extension of the diffraction limit toward nanometer scale; thus, improving spatial resolution in optical systems. Soft X-ray (SXR) radiation, from “water window” spectral range, λ=2.3–4.4 nm wavelength, which is particularly suitable for biological imaging due to natural optical contrast provides better spatial resolution than one obtained with visible light microscopes. The high contrast in the “water window” is obtained because of selective radiation absorption by carbon and water, which are constituents of the biological samples. The development of SXR microscopes permits the visualization of features on the nanometer scale, but often with a tradeoff, which can be seen between the exposure time and the size and complexity of the microscopes. Thus, herein, we present a desk-top system, which overcomes the already mentioned limitations and is capable of resolving 60 nm features with very short exposure time. Even though the system is in its initial stage of development, we present different applications of the system for biology and nanotechnology. Construction of the microscope with recently acquired images of various samples will be presented and discussed. Such a high resolution imaging system represents an interesting solution for biomedical, material science, and nanotechnology applications.

The results of formation of elongated krypton/helium plasma channels are presented. Two laser pulses were used: one to produce plasma channels and the second one for conversion to soft X rays. The soft X-ray radiation was in turn used for backlighting the channels and their visualization. The study of their formation and uniformity was performed using a combination of soft X-ray shadowgraphy and pinhole camera imaging. The plasma channels, with various lengths and various densities, were visualized and the results of their characterization are presented. Using moderate laser pulse energy quite uniform channels, up to 9 mm in length, were demonstrated.

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 compact, desktop size microscope, based on laser-plasma source and equipped with reflective condenser and diffractive Fresnel zone plate objective, operating in the extreme ultraviolet (EUV) region at the wavelength of 13.8 nm, was developed. The microscope is capable of capturing magnified images of objects with 95-nm full-pitch spatial resolution (48 nm 25–75% KE) and exposure time as low as a few seconds, combining reasonable acquisition conditions with stand-alone desktop footprint. Such EUV microscope can be regarded as a complementary imaging tool to already existing, well-established ones. Details about the microscope, characterization, resolution estimation and real sample images are presented and discussed.

A compact microscope based on nitrogen double stream gas puff target soft X-ray source, which emits radiation in the water-window spectral range, at the wavelength of λ = 2.88 nm, is presented. The microscope, employing ellipsoidal grazing incidence condenser and a Fresnel zone plate objective, is capable of capturing images with a 60 nm spatial resolution and exposure time as low as a few seconds. Examples of different applications of the SXR microscopy, and its applicability for various fields of science, are presented and discussed.

We present our recent results, related to nanoscale imaging in the extreme ultraviolet (EUV) and soft X-ray (SXR) spectral ranges and demonstrate three novel imaging systems recently developed for the purpose of obtaining high spatial resolution images of nanoscale objects with the EUV and SXR radiations. All the systems are based on laser-plasma EUV and SXR sources, employing a double stream gas puff target. The EUV and SXR full field microscopes—operating at 13.8 nm and 2.88 nm wavelengths, respectively—are currently capable of imaging nanostructures with a sub-50 nm spatial resolution with relatively short (seconds) exposure times. The third system is a SXR contact microscope, operating in the “water-window” spectral range (2.3–4.4 nm wavelength), to produce an imprint of the internal structure of the investigated object in a thin surface layer of SXR light sensitive poly(methyl methacrylate) photoresist. The development of such compact imaging systems is essential to the new research related to biological science, material science, and nanotechnology applications in the near future. Applications of all the microscopes for studies of biological samples including carcinoma cells, diatoms, and neurons are presented. Details about the sources, the microscopes, as well as the imaging results for various objects will be shown and discussed.

In the last 30 years much effort was made in order to develop compact laser-produced plasma sources emitting short wavelength radiation, from the soft X-ray (SXR, λ = 0.1–10 nm), especially in the so-called “water window” (λ = 2.3–4.4 nm) and in the extreme ultraviolet (EUV, λ = 10–120 nm) spectral ranges. Investigations in the nanometer scale, employing short wavelengths, drive the need for developing table-top microscopes, to overpass the limitations imposed by large facilities, such as their high complexity, maintenance costs and the limited user access. In this paper we present our recent results related to nanoscale imaging using such table-top and desk-top EUV/SXR microscopes. Their construction is based on a double stream gas puff target laser plasma source. The double stream gas puff target EUV and SXR sources, coupled with Fresnel zone plates (FZPs) represent a suitable platform for microscopy experiments in transmission mode, employing SXR and EUV radiation. It represents a possible complementary technique to synchrotrons and free-electron laser facilities. The sources, which are very easy to be used by a single user, allow for efficient generation of plasma radiation with high SXR/EUV flux. Presented herein compact microscopes, based on that source, allow one to capture SXR and EUV images of various samples, with 50–60 nm half-pitch spatial resolution (corresponding to a Rayleigh resolution of 100–120 nm) and exposure time of the order of few seconds. Thus, herein, we would like to present our recent developments and progress in compact desk-top SXR/EUV microscopy employing laser plasma gas puff target sources, showing examples of acquired images and possible applications.

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.

We present a possibility of reaching higher energy absorption edges of organic materials, beyond the carbon K-edge, in the near edge X-ray absorption fine structure (NEXAFS) spectroscopy technique using a compact laser-produced plasma soft X-ray (SXR) source based on a double-stream gas puff target. The source was optimized for emission in the SXR spectral range from 1.5 to 5 nm wavelength using the krypton/helium target. The emission spectrum of the source and the absorption spectrum of the investigated sample were measured simultaneously by means of a grazing incidence spectrometer, equipped with a single, large aperture diffractive element. Based on both spectra, the optical density was computed for the silicon nitride membranes in a transmission mode, to reveal the NEXAFS features near the nitrogen K-edge. Moreover, due to spectral narrowing of the SXR emission by the use of titanium filter, reaching the titanium L-edge was also possible. Multiple SXR pulse data were compared to single SXR pulse (single-shot) data as well as to the numerical simulations. In this paper, the detailed information about the source, spectroscopy system, and the results of NEXAFS measurements is presented and discussed.

We report for the first time on a compact, desk-top size, laboratory-type microscopy setup, based on nitrogen gas puff target soft X-ray source, which emits radiation in “water-window” spectral range. The microscope employs Wolter type-I objective and allows capturing magnified images of objects with 850 nm spatial resolution and exposure time as low as a few seconds. Details about the source and the microscope as well as imaging results for test and biological objects are presented and discussed.

Using a table-top size soft X-ray (SXR) microscope, based on a laser plasma source with a double stream gas-puff target and a Fresnel zone plate objective, series of images of test samples were acquired. Characterization and optimization of the acquisition parameters were studied and evaluated in terms of signal to noise ratio (SNR). Conclusions for the optimization of SXR imaging were reached. Similar SNR measurements might be performed to characterize other SXR imaging systems as well. Software enabling live calculation of the SNR during the image acquisition might be introduced in future in the compact imaging systems for optimal image acquisition or for benchmarking purposes.

Laser-produced plasma sources of short-wavelength radiation offer an interesting alternative to synchrotron and free-electron laser installations. Recently, we reported on a newly developed desktop EUV microscope based on plasma generated from a gas-puff target and diffractive optics. The half-pitch resolution of the microscope approached 50 nm. Compared to analogous microscopes based on synchrotron sources, our system is compact and cost-effective. In this paper, we present the results of imaging experiments on a thin polycrystalline object that was carried out in order to further examine the applicability of the microscope. We have demonstrated here that EUV microscopy can provide structural information that cannot be accessed by conventional optical microscopy or SEM.

A slit-shaped elongated nozzle, capable of forming an extended gas density profile, is presented and studied in detail. Argon and xenon target density backlighting measurements revealed the elongated density profiles with gas density that can be tuned by changing valve backing pressure and valve timing. Two dimensional density maps for Ar and Xe targets, obtained at soft X-ray wavelengths around 7 A, are shown and spatially characterized. Moreover the influence of valve backing pressure and valve timing on gas puff target density is studied. This geometry of the nozzle has potential applications in high harmonic generation for an efficient conversion of femto-second duration, intense infrared pulses to extreme ultraviolet (EUV) region.

Various imaging methods and techniques capable of reaching a nanometer spatial resolution are currentlyunder development. One of them is an extreme ultraviolet microscopy, based on the Fresnel zone plates. Inthis paper a compact, high-repetition, laser-plasma EUV source, with a gas puff target, capable of emittingquasi-monochromatic radiation at 13.8 nm wavelength was used in the first demonstration of a desk-top EUVtransmissionmicroscopywithaspatial(half-pitch)resolutionof50nm. EUVmicroscopyimagesofobjectswithvariousthicknessesandthespatialresolutionmeasurementsusingtheknife-edgetestarepresented.PACS:52.38.Ph,52.50.Dg,41.50.+h,42.30.Va,42.79.Ci

Imaging systems with nanometer resolution are instrumental to the development of the fast evolving field of nanoscience and nanotechnology. Decreasing the wavelength of illumination is a direct way to improve the spatial resolution in photon-based imaging systems and motivated a strong interest in short wavelength imaging techniques in the extreme ultraviolet (EUV) region. In this review paper, various EUV imaging techniques, such as 2D and 3D holography, EUV microscopy using Fresnel zone plates, EUV reconstruction of computer generated hologram (CGH) and generalized Talbot self-imaging will be presented utilizing both coherent and incoherent compact laboratory EUV sources. Some of the results lead to the imaging with spatial resolution reaching 50 nm in a very short exposure time. These techniques can be used in a variety of applications from actinic mask inspection in the EUV lithography, biological imaging to mask-less lithographic processes in nanofabrication.

In this work, a 10 Hz laser-plasma extreme ultraviolet (EUV) source built for surface processing of polymers is presented. The source is based on a double-stream gas puff target created in a vacuum chamber synchronously with the pumping laser pulse. The target is formed by pulsed injection of Kr, Xe or a KrXe gas mixture into a hollow stream of helium. The EUV radiation is focused using a grazing incidence gold-plated ellipsoidal collector. Spectrum of the reflected radiation consists of a narrow feature with intensity maximum at 10–11 nm wavelength and a long-wavelength spectral tail up to 70 nm. The exact spectral distribution depends on a gas applied for plasma creation. To avoid strong absorption of the EUV radiation in a residual gas present in the chamber during the source operation a two step differential pumping system was employed. The system allows for polymer processing under relatively high vacuum conditions (10−5 mbar) or in a reactive gas atmosphere. Polymer samples can be irradiated in a focal plane of the EUV collector or at some distance downstream the focal plane. This way fluence of the EUV beam at the polymer surface can be regulated.

We have developed compact, high repetition, table-top soft-X-ray sources, based on a gas puff target, emitting in “water window” spectral range at λ = 2.88 nm from nitrogen gas target or, in 2–4 nm range of wavelengths, from argon gas target. Double stream gas puff target was pumped optically by commercial Nd:YAG laser, energy 0.74 J, pulse time duration 4 ns. Spatial distribution of laser-produced plasma was imaged using a pinhole camera. Using transmission grating spectrometer, argon and nitrogen emission spectra were obtained, showing strong emission in the “water window” spectral range. Using AXUV100 detector the flux measurements of the soft-X-ray pulses were carried out and are presented. These debris free sources are table-top alternative for free electron lasers and synchrotron installations. They can be successfully employed in microscopy, spectroscopy and metrology experiments among others.

Extreme ultraviolet (EUV) radiation is the electromagnetic radiation ranging from vacuum ultraviolet to soft X-rays. A single EUV photon carries enough energy to ionize any atom or molecule. The penetration depth of the radiation in any material is very short, ranging from tens to hundreds nanometers. Intense EUV pulses can remove material from the surface or modify its morphology or/and chemical structure. In this work, the radiation from a laser-plasma EUV source based on a double-stream gas-puff target was used for surface modification of polyethylene terephthalate (PET). The PET samples were irradiated with the EUV pulses emitted from krypton plasma and focused with a gold-plated ellipsoidal collector. The spectrum of the focused radiation covered the wavelength range from 9 to 70 nm. The PET samples were irradiated for 1 s–2 min at a 10-Hz repetition rate. Surface morphology of polymer samples after irradiation was investigated using a scanning electron microscope. Changes in chemical surface structure of the irradiated samples were investigated using an X-ray photoelectron spectroscopy. Different kinds of surface microstructures were obtained depending on the EUV fluence in a single pulse and the total EUV fluence. XPS measurements also revealed a modification of the chemical structure.

Extreme ultraviolet (EUV) covers wavelength range from about 5 nm to 50 nm. That is why EUV isespeciallyapplicableforimagingandpatterningonnanometerscalelength. Inthepaperperiodicnanopatterningrealized by interference lithography and high resolution holographic nanoimaging performed in a Gabor in-lineschemearepresented. IntheexperimentsacompacttabletopEUVlaserwasused. PreliminarystudiesonusingalaserplasmaEUVsourcefornanoimagingarepresentedaswell.PACSnumbers:42.25.Hz,42.40.Ht,42.40.

In this work we present three experimental, compact desk-top imaging systems: SXR and EUV full field microscopes and the SXR contact microscope. The systems are based on laser-plasma EUV and SXR sources based on a double stream gas puff target. The EUV and SXR full field microscopes, operating at 13.8 nm and 2.88 nm wavelengths are capable of imaging nanostructures with a sub-50 nm spatial resolution and short (seconds) exposure times. The SXR contact microscope operates in the “water-window” spectral range and produces an imprint of the internal structure of the imaged sample in a thin layer of SXR sensitive photoresist. Applications of such desk-top EUV and SXR microscopes, mostly for biological samples (CT26 fibroblast cells and Keratinocytes) are also presented. Details about the sources, the microscopes as well as the imaging results for various objects will be presented and discussed. The development of such compact imaging systems may be important to the new research related to biological, material science and nanotechnology applications.

Surface modification of PMMA and FEP polymers using extreme ultraviolet (EUV) in two spectral ranges was investigated. A laser-plasma EUV source based on a double stream gas puff target equipped with an Au coated ellipsoidal collector was used for the experiment. The spectrum of the focused radiation from Kr plasma consisted of a narrow feature with a maximum at 10 nm and a long-wavelength tail up to 70 nm. Al and Zr filters were employed for the selection of radiation from these two spectral regions. The radiation fluences in the two cases were comparable. Polymer samples were mounted in the focal plane of the EUV collector and irradiated for 1–2 min with a 10 Hz repetition rate. Weak ablation accompanied by creation of micro- and nanostructures of different kinds was obtained in both cases. Significant differences in the surface structures after irradiation of PMMA and FEP in these two spectral regions were revealed.

Extreme ultraviolet (EUV) radiation is absorbed in a thin surface layer of any material. Irradiation of material samples with intense EUV pulses may cause different surface changes. Some of them, especially connected with material desorption, can be clearly visible using an optical or electron microscope. Other changes concerning crystal structure or chemical composition may not be visible under the microscope. They can however be detected using the EUV radiation itself. In this paper a new method of measurement of surface changes by irradiation with a laser-plasma EUV source is presented. The radiation was collected and focused on a material surface using a specially designed multifoil collector. Radiation scattered or excited in the material was detected with the use of a Wolter-type mirror coupled to a back-illuminated CCD camera. Depending on material samples, images with different intensity distributions were registered. For some samples, the intensity distributions of the images obtained before and after irradiation were slightly different. The intensity differences in such cases allowed us to obtain differential images. The appearance of such images was assumed to be evidence of surface changes.

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.

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.

In this work a review of investigations concerning interaction of intense extreme ultraviolet (EUV) and soft X-ray (SXR) pulses with matter is presented. The investigations were performed using laser-produced plasma (LPP) EUV/SXR sources based on a double stream gas puff target. The sources are equipped with dedicated collectors allowing for efficient focusing of the EUV/SXR radiation pulses. Intense radiation in a wide spectral range, as well as a quasi-monochromatic radiation can be produced. In the paper different kinds of LPP EUV/SXR sources developed in the Institute of Optoelectronics, Military University of Technology are described.Radiation intensities delivered by the sources are sufficient for different kinds of interaction experiments including EUV/SXR induced ablation, surface treatment, EUV fluorescence or photoionized plasma creation. A brief review of the main results concerning this kind of experiments performed by author of the paper are presented. However, since the LPP sources cannot compete with large scale X-ray sources like synchrotrons, free electron lasers or high energy density plasma sources, it was indicated that some investigations not requiring extreme irradiation parameters can be performed using the small scale installations. Some results, especially concerning low temperature photoionized plasmas are very unique and could be hardly obtained using the large facilities.

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.