The absorption edge of thin-film GaAs on glass has been investigated with the standard constant photocurrent method (s-CPM) method and photocurrent analysis. The films have been formed by pulsed-laser deposition (PLD) employing the 532 nm emission of a YAG:Nd laser (6 ns, 10 Hz). Notably, the films have been deposited without heating the substrate. Fitting the measured absorption data with the crystalline density of states and the Urbach tail a very good agreement has been found. X-ray analysis showed that the films are predominately oriented towards the (111) plane. The function used to fit the absorption data describes the photocurrent data at different biases as well. Annealing of the samples up to 400 K did not cause notable changes in the absorption edge and overall photocurrent spectra. The presented results reveal that "cold" PLD, i.e., without substrate heating, forms high-quality oriented photosensitive thin-film GaAs on glass, which hardly alters its optoelectronic features under thermal treatment. Under this prospect and due to the relative ease to form the films, PLD GaAs might be of interest for applications in optoelectronics and photovoltaics.

Co and Fe-based alloy films were deposited and studied as perspective materials for the development of fast magnetic sensors. Pulsed laser ablation deposition (PLD) was used as an appropriate technique to fabricate thin films preserving the stoichiomeUy ofthe complex bulk materials. Co₆₇Cr₇Fe₄SiB₁₄, Fe₇₅Nb₃Cu₁Si₁₂B₉, Fe₄₀Ni₄₀B₂₀ and Fe_xNi_1-x (x=22, 36, 50) amorphous ribbons and metallic foils were ablated to deposit 10-120 nm thick films onto oxidized Si wafers using a KrF (λ= 248 urn) laser with 30 ns pulses at fluence from 2 to 7 Jcm^-2. The films were analyzed by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), Rutherford backscattering spewometiy (RBS), x-ray diffraction (XRD) and reflectivity (XRR), and ferromagnetic resonance (FMR). The structural and magnetic characteristics of the films strongly depend on the laser fluence. Stoichiometry is well preserved at low laser fluences. At higher fluences lighter elements (Si, B) are partly lost. Unwanted crystallization of films is also observed at the high fluence. Magnetic characteristics are closely related to the corresponding source materials, unless the light elements are partly lost. When this happens increased magnetization of film is observed. The relaxation process in films was characterized by FMR linewidth. They are typically very narrow (110-250 G) for Fe-based alloys, indicating low values of magnetization motion damping (down to 6.06x10⁷ radius) and therefore pointing to a perspective use of these materials for fast sensors.

Photoluminescence properties of Er-doped nanocrystalline Si/ Si0₂ structures have been investigated under strong optical excitation. The energy of optical excitation of Si nanocrystals was shown to be almost completely transferred to Er³⁺ ions in surrounding Si0₂. It was found that at high pump intensity the energy transfer process competes successfully with nonradiative Auger-recombination in Si nanocrystals. At high excitation level the population inversion of Er³⁺ ions was achieved and a decrease of the decay time of the photoluminescence at 1.5 μm was observed. Possible mechanisms of the shortening of the Er³⁺ ion lifetime are discussed.

The synthesis of silicon nanocrystals (Si-NC) has attracted a great deal of interest due to their size-dependent optical properties. The appearance of a strong visible photoluminescence (PL) even at room temperature makes this kind of material very interesting for applications in optoelectronics and photonics. In this work, we report on the possibility to control the optical properties of silicon nanostructures by fine tuning of both preparation and processing parameters. Large amount of Si-based nano-powders were prepared by cw CO₂ laser pyrolysis of gasphase precursors followed by annealing at different temperatures, in controlled atmosphere. After the heat treatment, the structural and optical analyses revealed the presence of size-controlled optical properties, characterized by the typical Si-NC red-IR emission with lifetime ranging from a hundred of μs to some ms. Next step was the nano-powder dispersion by several methodologies and their incorporation into a silica sol-gel matrix. The realization of a glassy material that preserves the powder luminescence opens the way to a wide range of applications. To this purpose we focused our attention on the study of the influence of the sol-gel processing steps on the optical properties of Si-nano-powders. Moreover, a study of 1.54 micron Er emission sensitizing effect from Si-based nanostructures in sol-gel glasses was performed and is presented here.

Laser techniques have demonstrated very promising applications for diagnostic and restoration purposes in art conservation. Nevertheless only in the last decade a growing interest in Europe has brought this innovative approach to be tested and validated on various important tasks: laser cleaning of stone, metals, paintings, paper etc; structural laser diagnostics of frescoes and art objects; compositional laser diagnostics of materials; environmental laser monitoring etc. Many programs funded by the European Commission have contributed to the development of new laser instruments and techniques. Presently the COST Action G7 is pursuing the main task of monitoring the advancements achieved in the development of new instrumentation, accumulating validation of laser based techniques with case studies, extending the use of laser for conservation in Europe and other countries, selecting best practices and preparing safety guidelines.

The pulsed laser ablation and deposition of Sr₂FeMoO₆ films having good magnetic performances is strongly affected by the adopted deposition parameters, which require precise choices. Among them, the laser energy density seems to be the basic factor governing the achievement of the correct material phase during film growth. Optical emission spectroscopy of the plasma plume, produced by the laser interaction with stoichiometric targets, in different ablation and ambient conditions, can outline the plasma dynamics and consequently sustain hypothesis about the film formation mechanism. In order to follow the plasma dynamics during Nd:Yag laser (2=532 nm) ablation of Sr₂FeMoO₆ targets, time- and space-resolved optical emission spectroscopy measurements in the range 350 -500 nm have been performed. The integral intensities of spectral lines were measured as a function of distance from the target surface and laser power density in the presence of 02 partial pressure. The intensity ratio of ionic and atomic Strontium emission spectral line and their time-of-flights were measured as a function of laser energy density. On the basis of the obtained results it is shown how different plasma species kinetics can play a key role in determining the magnetic film properties.

The effects of energy and pulse duration in laser ablation experiments have been investigated in the case of copper based alloys. Experiments were carried out near 530nm by using two laser sources with different widths (8 ns and 250 fs). The craters generated by lasers were examined and their characteristics were related to different mechanisms involved in the ablation by laser pulses acting on different timescales. The optical emission of plasma produced was analyzed by LIPS, acquiring time resolved line intensities of the major elements contained in the samples, and determining plasma characteristics (temperature, electron density). Experiments demonstrated that fs and ns laser pulse must be modeled by different ablation regimes, the onset of which can be used to decrease the effect of fractionation on brasses and bronzes.

Post-processing of crystalline and glass materials after the exposure to femtosecond pulses was carried out by wet etching in water solutions of hydrofluoric acid. Crystalline sapphire and quartz showed high (larger than 100) anisotropy of etching, which allowed to develop high-aspect-ratio three-dimensional structures in the volume of those dielectrics. In silicate glasses the anisotropy of wet etching can be achieved by a proper selection of the overlap of adjacent pulses during recording, their energy, and focusing. Three-dimensional structures in silica glass (viosil with OH concentration below 1200 ppm) with a high aspect ratio of 100 were achieved. The mechanism of anisotropy in wet etching is discussed. Surface irradiation of sapphire at irradiance close to that of surface ablation recorded structural modifications resembling the ripples. Those structures were made observable only after wet etching. Period of the ripples can be explained by the recently presented theory (Y. Shimotsuma et al., Phys. Rev. Lett. 91 247405-1 (2003)). Submicrometer structuring of surface is demonstrated. Electron temperature at the moment of structure recording can be estimated from the period of ripples (for sapphire T_e≈ 11 keV was found).

The generative process of selective laser sintering of powders such as Titanium, Platinum alloys and steel can in comparison to cw radiation significantly be improved by using pulsed radiation. With an appropriate energy deposition in the metallic powder layer, the material properties of the selective laser sintered parts can locally be tailored to the requirements of the finished work piece. By adapting the laser parameters of a Q-switched Nd:YAG laser, notably pulse duration and local intensity, the degree of porosity, density and even the crystalline microstructure can be controlled. Pulsed interaction allows minimizing the average power needed for consolidation of the metallic powder, and leads to less residual thermal stresses. With laser post processing, the surface can achieve bulk-like density. Furthermore, we present the possibility of forming metallic glass components by sintering amorphous metallic powders.

Laser ablation of porous silicon as a function of laser wavelength and width of silicon nanowires was studied in our experiments. The time-resolved evolution of the cloud of the porous silicon particles produced by laser ablation is studied by the analysis of the kinetics of photoluminescence (PL) signal. The laser ablation of porous silicon produced by pulses of 532 nm or 337 nm radiation with addition of synchronized power pulses of 1064 nm radiation. The cloud of the nanometer-sized silicon crystallites had the high enhancement of luminescence quantum efficiency in the red region of spectra. The slow PL kinetics component, which is due to the localized carriers, decays on a millisecond time scale. The mechanism of destruction of the strongly correlated nanostructures was considered. Experimental results were analyzed from the point of view of theoretical models of laser interaction with nanostructures and the theory "Lattinger liquid" proposed by P.W. Anderson (1) for low dimensional nanosystems.

Hollow photonic-crystal fibers (PCFs) with large core diameters are shown to allow waveguide nonlinear-optical interactions to be scaled to higher pulse peak powers. Phase-matched four-wave mixing is demonstrated for millijoule nanosecond pulses guided by photonic band gaps of hollow fibers with a two-dimensionally periodic cladding and a core diameter of about 50 tm. Such hollow PCFs provide interesting nonlinear-optical waveguide transmission regimes for 10-MW femtosecond Cr: forsterite laser pulses, allowing dispersion pulse spreading to be substantially reduced through nonlinear-optical refractive-index modulation.

The formation of periodic ripples is reported under exposure in air of several solids (Ge, GaAs, W, steel, etc.) to a scanning beam of a femtosecond Ti:sapphire laser operating at wavelength λ = 810 nm. Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM) characterization shows that the period of ripples at normal incidence of laser radiation lies in a sub-λ domain and depends on the nature of the solid. Ripples are oriented perpendicular to the plane of polarization of the laser beam. Their period is different under ablation of a solid in a liquid environment at otherwise equal conditions. The results are interpreted as an interference of the incident laser radiation with a surface electromagnetic wave induced in the solid. The examples are presented of sub-μm structures generated by intersection of several ripple arrays.

Laser ignition of internal combustion engines reveals a number of advantages. High-pressure chamber experiments with lean hydrogen-methane-air mixtures were successfully performed and monitored by optical Schlieren diagnostics. Multipoint ignition was tested for 2 and 3 ignition points with different separations. In this way, relevant ignition parameters were acquired allowing estimate future laser ignition systems. Transportation of high intensity 6-ns Nd:YAG laser pulses via photonic bandgap fibers with hollow core was investigated. Evacuation of the core for the first time allowed to increase the peak intensity of the propagating pulses far beyond the breakdown limit of silica yielding 600 μJ fiber output with single mode characteristics.

The paper proposes an approach to classification of different types of laser-induced surface micro-structures. The approach is based on the relation between different ranges of laser pulse duration and determinant mechanisms of micro-structuring including thermo-mechanical, optical and electrical effects. Detailed analysis of kinetics of silicon surface micro-structuring in millisecond range and consideration of polariton mechanism of microstructuring in nanosecond range resulted in assumption, that inhomogeneous electrical field must be the determinant factor for micro-structuring in femtosecond range.

Radical ions are open-shell elusive species of paramount importance in many organic reactions and in biological processes. Oxidative bond breaking and forming involving radical ions are common process taking place in asymmetric enzyme cavities. Side-chain C_α-C_Β bond fragmentation in the radical cations of aromatic alcohols is a common process in solution [1-3], whose efficiency is enhanced in polar solvents such as water. Hydrogen-bonding between the ion and the solvent in the relevant transition structure is thought as responsible of the rate acceleration [4]. Effects of achiral and chiral microsolvation on the radical cation of R-(+)-l-phenyl-l-propanol, have been investigated. The energy thresholds of the homolytic Cα-Cβ bond breaking of R-(+)-1-phenyl-1-propanol radical cation, its mono-hydrated cluster, and its clusters with (2R,3R)-(-)-2,3-butanediol and (2S,3S)-(+)-2,3-butanediol have been studied through two color Resonant Two Photon Ionization, Photodissociation and Mass Spectrometry. The barrier of the Cα-Cβ fragmentation is appreciably higher for the unsolvated molecular ion than for its adducts with solvent molecules. Moreover, marked differences in the ethyl loss fragmentation energy are observed for the clusters with water and with the two diols. In particular the homochiral cluster with (2R, 3R)-(-)-2,3-butanediol exhibits a fragmentation barrier higher than that of the corresponding heterochiral adduct with (25, 35)-(+)-2,3-butanediol.

The paper underlines the importance of breath tests in medicine and the potential of laser techniques to measure in-vivo and in real time human biomarkers. The presence of trace amounts of gases or the metabolites of a precursor in exhaled air could be linked to kidney or liver malfunction, asthma, diabetes, cancer, ulcers or neurological disorders. The measurement of some human biomarkers (ethylene, ammonia), based on laser photoacoustic spectroscopy methods, insure very high sensitivity and selectivity. The technical characteristics of this instrument were measured to determine the detection limits (sub-ppb for ethylene). The results of ethylene release following lipid peroxidation initiated by X-ray irradiation or ingestion of radioactive compounds are presented. The possibility to extend this technique for measurement of breath ammonia levels in patients with end-stage renal disease while they are undergoing hemodialysis is discussed.

In this work we present a theoretical study concerning the Laser Induced Breakdown Spectroscopy (LIBS) in water. A 1D Euler code has been developed and coupled with a complete kinetic model. This study has been applied to the evaporation of a titanium target in water. The strong influence of chemical processes on the fluid dynamic expansion has been shown. Moreover the introduction of two pulses, which is a typically experimental approach in water, has been simulated. The effect of the second pulse on the macroscopic quantities has been deeply discussed.

Micro-Raman spectroscopy has been widely applied to the investigation of heterogeneous materials for it enables a not destructive way for the microscopic identification of the various chemical components. However it may not ever answer the question of how these species are distributed on a specific area. Global Raman imaging represents in this sense the ideal solution, for it combines Raman spectroscopy and digital imaging to provide molecular images that detail material morphology, composition and structure. By filtering a given Raman band over a wide sample area, the correspondent intensity distribution is immediately constructed in a bidimensional map which allows the user to easily and visually determine the location of even complex components in the irradiated sample area. An example of how a distribution map may be obtained by global Raman imaging is here reported for a fresco cross-sectioned sample.

Balanced heterodyne technique for registration of backscattered Cr:forsterite femtosecond radiation from strongly scattering material has been developed. It was found that the dependence of response signal for strongly scattering media on time delay has long 'tail'. The tail is the result of multiple scattering processes. The exponential index is defined by photon lifetime in strongly scattering media. Dynamics of vaporization of ethanol from random porous material (paper) was investigated and velocity of evolution of liquid-vapor interface was measured V=0,08m/s. Laser induced sintering process in polystyrene powder was investigated and velocity of sintered zone increasing was measured V≈100μm/s.

The emission of ethylene from climacteric fruit banana (Musa x paradisiaca L.) and non climacteric fruits lemon (Citrus limon Burm. F.) at different stages of ripening (from a few days after setting to full maturity stage) by the Laser Photoacoustic Spectroscopy System, developed in ENEA Frascati, was measured. A high ethylene production rate from mature banana fruit was found, as expected for climacteric fruit. Significant differences between ethylene emitted by the lemon after setting stage and by the young fruit were observed. Also ethylene emission from lemon fruits at different ripening stages (from light green to turning and full ripe) was detected. Depending on the ripening stage, differences in ethylene emission rates were found, although the emissions were low as expected for non-climacteric fruit.

A high performance Amplitude Modulated Laser Rangefinder (AM-LR) is presented, aimed at accurately reconstructing 3D digital models of real targets, either single objects or complex scenes. The scanning system enables to sweep the sounding beam either linearly across the object or circularly around it, by placing the object on a controlled rotating platform. Both phase shift and amplitude of the modulating wave of back-scattered light are collected and processed, resulting respectively in an accurate range image and a shade-free, high resolution, photographic-like intensity image. The best performances obtained in terms of range resolution are ~100 μm. Resolution itself can be made to depend mainly on the laser modulation frequency, provided that the power of the backscattered light reaching the detector is at least a few nW. 3D models are reconstructed from sampled points by using specifically developed software tools, optimized so as to take advantage of the system peculiarities. Special procedures have also been implemented to perform precise matching of data acquired independently with different sensors (LIF laser sensors, thermographic cameras, etc.) onto the 3D models generated using the AM-LR. The system has been used to scan different types of real surfaces (stone, wood, alloys, bones) and ca be applied in various fields, ranging from industrial machining to medical diagnostics, vision in hostile environments cultural heritage conservation and restoration. The relevance of this technology in cultural heritage applications is discussed in special detail, by providing results obtained in different campaigns with an emphasis on the system's multi-sensor data integration capabilities.

We established a master equation for a system of fermions coupled by electric dipol interaction with the free electromagnetic field. This equation has a Lindblad equation form, with a hamiltonian part corresponding to the shell model and a dissipative part with microscopic coefficients depending on physical constants, matrix elements, and temperature. The dependence on the transition energy of the dissipative coefficients satisfies asymptothycal conditions for the energy transfer in full agreement with the principle of the detailed balance.

The LIPS technique has been applied to tree trunk samples taken at the Tunguska site (Siberia-Russia), analyzed in order to identify the most relevant chemical elements absorbed by the trees owing to the event of the 30th of June 1908. Preliminary results of the investigation are reported.

Theoretical and experimental investigations on image quality are extremely important in optical imaging in order to better define the role of optical techniques in medical diagnostics. Today time-resolved laser transillumination can be considered a good candidate as an alternative and/or auxiliary technique in medical diagnostic field. The intrinsic quality of an image is related to the concepts of spatial resolution, noise and contrast. A common method to measure these parameters is by using Edge Response Function measurements with a black mask. We investigated these parameters using an experimental apparatus mainly composed by a picosecond solid-state laser and a time-correlated single photon-counting system. The investigated samples were suspensions of Intralipid 10% with distilled water in which a black mask was inserted and bidimensional scanning were performed. The experimental data were analyzed in order to get information on the above-mentioned image quality parameters. For spatial resolution a comparison with random walk predictions has been attempted. The results of this study can be particularly useful in identifying the best working conditions and in improving teh performance of image reconstruction algorithms since the clinical prototypes of optical mammogrpahers nowadays under pre-clinical investigation adopt time-correlated single photon-counting technique.

A modern trend in the development of laser based analytical instruments is to integrate more functions in a single device. This approach could be useful for two purposes. The elimination of redundancies could reduce the global cost of the instruments and reduce the maintenance and operators training cost. Besides, the avalaibility of different analytical tools in a single instrument could simplify the application in situ of the methods and could improve the accuracy in the identification of different components, thanks to the possible cross-correlation of the results of different spectral markers.

A new laser spectrofluorometric apparatus has been recently developed and assembled in the mobile laboratory ENVILAB of at ENEA Research Center of Frascati. The instrumentation was utilized from October 20 to 25,2003 in the measurement campaign carried on in Sicily within the activities of the "RIADE project" (Integrated Research for the Application of Innovative Technologies and Processes for the Struggle Against Desertification) in order to monitor waters in areas at risk of desertification. During the campaign, the concentrations of dissolved (proteins and humic acids) and suspended (algae) organic substances have been measured in natural waters of Sicilian sites (near Syracuse and Licata).

A compact scanning lidar fluorosensor apparatus has been realized at the ENEA Research Center of Frascati and employed in the diagnosis of stone samples and wall frescos relevant to the preservation and valorization of the Southern Italy cultural heritage in the framework of the TECSIS project. A detailed spectroscopic investigation was performed in our laboratory on different cleaned and dirty stones before the participation to the Advanced On-Site Laboratory for European Antique Heritage Restoration, held in Constanta (Romania), April 24-26, 2004. Scanned images at different spectral channels and their suitable combination, showing the occurrence of biodegradation from different microorganisms, are presented.

The cubic susceptibility tensor properties in (100) porous silicon with strong in-plane birefringence caused by form anisotropy is considered. Polarization-sensitive third-harmonic generation in such media reveals a modification in the cubic susceptibility tensor.

It will be shown that experimental data, obtained by pump-probe measurements in HTSC compounds, can be interpreted in terms of long-living meta-stable non-equilibrium states with specific energy gap and rather high (up to 600 K) electronic temperature.

A new ultra-fast (increasing the calculation rate about 9 orders and more) calculation scheme, enabling one to solve small-angle multi-scattering problems for large (size about 100 scattering lengths and more) objects is described.

In this paper, experimental data are presented on the synthesis and properties of nanocrystalline diamond (NCD) films grown by a dc plasma CVD technique from various gas mixtures (CH₄-H₂, CH₄-H₂-Ar, CH₄-Ar, CH₄-H₂-N₂, CH₄-Ar- N₂). The interrelation between the CVD conditions, the film microstructure and film properties is established using Raman spectroscopy, XRD, XPS, AES, SEM, TEM, AFM/STM, spectroscopic ellipsometry and optical transmission spectroscopy techniques. Experimental methods for laser assisted fabrication of ultrathin and highly smooth NCD films are described. Effects of the deposition parameters (substrate temperature, CH₄ content, addition of Ar gas to CH/H₂ gas mixtures) on the grain size, surface roughness and optical properties of NCD films are discussed. Results of nitrogen doping of nanocrystalline diamond films are presented and discussed.

The design and characteristics of a setup for producing oxide nanopowders are reported. Y₂O₃-stabilized Zr0₂ (YSZ), Al₂O₃+YSZ and CeGdO nanopowders are prepared by target evaporation with a pulse-periodic C0₂-laser. Average laser radiation power is 600 W, pulse power ~10 kW. The output rates of YSZ and Al₂O₃+YSZ nanopowders are 15-20g/h, and CeGdO nanopowder-55-6Og/h. The grain mean size in the powders is l5nm. Data for the powder characteristics, as well as results of X-ray phase and structure analysis, are reported. The results of investigation of unstable behavior of plasma plume produced by the long-pulse laser irradiation of the targets are reported as well. The mushroom-like shape of the glowing area is believed to be determined by the Richtmyer-Meshkov instability of the plasma-air interface and formation of nanoparticles in the plasma expanding into the buffer gas.

The review of results on nanoparticles formation is presented under laser ablation of Ag, Au, and Cu-containing solid targets in liquid environments (H₂O, C₂H₅OH, C₂H₄Cl₂, etc.). X-ray diffractometry (XRD), UV-Vis optical transmission spectrometry, and High Resolution Transmission Electron Microscopy (HRTEM) characterize the nanoparticles. The morphology of nanoparticles is studied as the function of both laser fluence and nature of the liquid. The possibility to control the shape of nanoparticles by ablation of an Au target by an interference pattern of two laser beams is demonstrated. Formation of alloyed Au-Ag and Ag-Cu nanoparticles is reported under laser exposure of a mixture of individual nanoparticles. Self-influence of the beam of a femtosecond laser is discussed under ablation of the Ag target in liquids under Ti:sapphire laser. The factors are discussed that determine the distribution function of particles size under laser ablation. The influence of laser parameters as well as the nature on the liquid on the properties of nanoparticles is elucidated.

The micropatteming of multilayer gratings (MLG) using ultraviolet sub-ps laser pulses is described. A micromachining system operating with a 0.5 ps KrF laser (248 nm) was used. Grating structures with a groove width in sub-pm region were created in Mo/Si, Si/Mo, W/Si and Si/W multilayers (MLs) with 5 (in one case 10) periods, each 7-10 nm thick. Grating area was up to 900 x 900 μm². Laser fluence on the samples varied between 60 and 710 mJcm^-2. Atomic force microscopy, scanning electron microscopy, X-ray reflectivity and X-ray diffraction were used to characterize multilayers and gratings. MIs were locally ablated up to the Si, oxidized Si or glass substrate, or deeper, using from 1 to 5 pulses. The roughness on the surface of lines and in grooves of MLG increased with the depth of ablation. It was caused first of all by debris. The ω-scans around the 1st Bragg maximum show symmetric satellites up to the 2nd or 3rd order, giving the evidence that the ML in MLG is preserved.

Laser ablation and ionization is investigated as a technique suitable to the fabrication of nanowire interconnects and of biological and organic molecule monolayer immbilization. The technique can be exploited both as an unconventional source of material in conventional top-down lithographic approaches and in bottom up approaches based on the use of scanning probe instruments. Recent results demonstrating maintenance of integrity of thin layers of immobilized aromatic molecules and functionality of nanopatterned biomolecular monolayers are shown. Also, ultrathin and uniform metallic layers suitable for the fabrication of nanowire interconnects are obtained. Finally, first results on the bottom up fabrication of nanoscopic metallic features are shown.

The wafers of thickness 60μm÷100μm were made at compression of nanocrystalline silicon (nc-Si) powders in a range of pressures from 10⁸ up to 10⁹ Pa. Optical and electrical properties ofthese wafers have been investigated by means of registration of IR transmission spectra and dark conductivities. Analysis of IR absorption spectra of wafers shows that structures Si-H, Si-CH_x and O_x-Si-H_y (x,y=1÷3) are formed at a pressing of nc-Si powder. We believe that these structures are formed at pressing of powder after break of links in network of a silicon atoms and consequent saturation of Si-dangling bonds by hydrogen, carbon or oxygen atoms which are located on free surfaces of silicon particles. It is found that dark conductivity of a wafer is depending on temperature of buffer gas in which original powder is formed. Wafers which have been made of the powders created at higher temperatures of a buffer gas flow had more pronounced hydrogen microstructure and higher dark conductivity. Analysis of dark conductivity vs. temperature T of the wafer shows that at the temperatures higher than approximately 270K the conductivity follows Arrhenius behavior with single activation energy, and at lower ones, conductivity is depending on T as: σ=(A/T^1/2)-exp(-B/T^1/4). Last equation allows asserting that variable-range hopping is mechanism oftransport in nc-Si wafers at temperatures T<270K.

Nowadays there is an acute problem to protect human skin against harmful influence of violet and ultraviolet solar radiation. The aim of this research is to evaluate, how optical properties of the horny layer of human skin can be changed by imbedding the titanium dioxide (TiO₂) fine particles in order to achieve the maximal attenuation of the UV solar radiation. In-depth distribution in the skin of TiO₂ particles typically achieved with the sunscreens is determined experimentally by the tape-stripping technique. Computer code implementing the Monte Carlo method is used to simulate photon migration within 2O-m thick horny layer partially filled with nano-sized TiO₂ spheres. Dependencies of absorbed by and reflected from, as well as transmitted through the horny layer UV radiation of two wavelengths (290.5 and 400 nm) on the concentration of TiO₂ particles are obtained and analyzed.

A new laser technology, based on spatiallyl non-uniform illumination of ultra-thin ferromagnetic films by short trains of ultra-short laser pulses and enabling to create the regular domain structures, is presented.

Experimental results are presented on laser ablation of brass in liquid environment (e.g., ethanol and water) by radiation of either a copper vapor laser (wavelength of 0.51 μm) or a pulsed Nd:YAG laser (1.06 μm). In a certain range of laser parameters (fluence and number of laser shots) the surface consists of regular micro-cones. The period of micro-cones is about 30 μm and depends on the laser fluence. The composition of micro-cones (Cu/Zn ratio) differs from that of the initial surface. The ablated material is ejected into surrounding liquid in the form of nanoparticles with average size of 20 nm. The composition of nanoparticles depends on the nature of the liquid. For instance, ablation in ethanol results in formation of core-shell nanoparticles. The results are discussed on the basis on phase diagram of brass.

The permanently development of microelectronics production by continuously increasing of devices densities meantime with corresponding decreasing of processing line till further submicronic range. The processing of huge diversity of materials as metals, polymers, ceramics, silicon, germanium, other materials III-Vs, glass, diamond, hard metal oxides, composites is need. On this paper will be presented our advanced studies and of experiments realized with very good results for a full range of those materials by micro and nanoprocessing for to realize the best accuracy, according with microelectronics technical requirements specified as below: 1. The microdrilling for microvias used for MCM's, MEMS and MOEMS application. 2. The high precision microcutting and scribing used for individual chips separation Isingulation on processed wafers of micro and optoelectronics applications 3. 2D I3D processing for microlens, microlens array and microalveoles fabrication 4. Microengraving of KOP (Potasium dihydrogen phosphate) crystal by laser microablation 5. Micro and nano cleaning of thin and ultrathin layers need for production of microelectronics devices production.

The continuously shrinking of the photonic structures has stimulated the research and development of low-dimensionality photoluminescent patterns based on visible-emitting color centers (CCs) in thin films. In particular, Lithium Fluoride (LiF) treated with ionizing radiation by using versatile lithographic techniques, represents a very promising candidate for the realization of innovative photonic devices. Permanent tluorescent patterns based on CCs have been realized in LiF films by direct writing with a X ray microprobe -of the ESCA Microscopy beamline at ELETTRA synchrotron in different configuration. Luminescent nanostructures, written by scanning the LW specimen with respect to the X-ray beam, have been investigated by near-field optical microscope and a sub-wavelength spatial resolution is demonstrated.

Optical properties and third order optical nonlinearity of liquid metal colloids prepared by laser ablation in water and ethanol are investigated. It was found out that water colloids took stable state after partial sedimentation with changing of ONL sign during sedimentation process. The optical absorption spectra are interpreted within the framework of Drude model for metallic particles with taking into account the effect of nanoparticles sizes on optical properties. Stable state is explained by colloid of small Ag particles with presumable oxide shell. The sizes of small Ag particles were calculated and nonlinear optical absorption parameters were measured by z-scan technique.

To date, a great number of investigations have been devoted to studying the physical properties of carbon structures and technological processes providing the basis for their formation. This is connected with the wide variety and unique properties of carbon compounds, which have determined their widespread practical use in areas from nanoelectronics to spacecrafts. However, the preparation of various carbon modifications within a unified technology is a complicated problem, which remains still unsolved [1]. Previously [2], the authors have shown that the periodic potential built-in the structure by alternation of layers with different hand gap can affect the crystalline modification the substance crystallized. The prepared superlattices are also characterized by the existence of built-in periodic potential, which can control the formation of a specific carbon modification.

Adsorbed metal on the semiconductor surface change strongly the optical properties of the interface due to the charge distribution. This effect is more important for nanoparticles. In this paper we present the experimental results and analysis of amorphous silicon nanoparticles (a-n-Si) covered by the different metal layers. The optical properties of individual particles of a-n-Si dressed by the silver, copper and iron and imbedded in water have been studied. In spite of the thickness of metal films was more less than 1 nm for the nanoparticles diameter more than 20 nanometers the optical absorption spectra for each nanocomposites measured in the spectral range from 300 to 900nm differs much one from another. The reason is it depends on the surrounding media, mainly, but not on the particles microstructure. This character of optical absorption in the visible range is defined by the double charge layer near the surface inside of the particles. The mechanism of the optical absorption is the composition of absorption by the surface electrons plasma waves and valence electron in strong static electric field created by double charge layer.

The techniques for synchronizing ultra fast lasers to external radio frequency reference sources are well established and characterized in the literature. However, there is little data on the actual light-to-light jitter that can be achieved in different synchrotron operation modes when an external laser is locked to the storage ring master clock. Here we present first results of the synchronization of an ultra fast Cr:LiSAF laser with synchrotron radiation generated by the ELETTRA storage ring in different filling modes. In addition, data on the synchronization of the same laser with the ELETTRA FEL pulses, both in free running and Q-switching regimes, are reported. In our experiments, laser-to-RF locking was continuously monitored using built-in phase detection. The laser light to storage ring light locking was characterized by simultaneous acquisition of the two/three pulse trains by a streak camera. In addition, pulse jitter was determined by processing of the signal of fast photodiodes monitoring the different light beams.

Laser medical device "Maria" on the basis of KrF excimer laser with the wavelength 248 nm was made for fiber-cavernous lung tuberculosis and bronchia tuberculosis treatment. This very spectral range has maximum efficiency due to the peak of micro bacteria destruction. The main difficulty in the operation with 248 nm radiations arises in the transportation of the radiation from the laser into a tuberculosis cavern along a fiber light guide. The necessity to obtain the desirable mean power of the radiation with a low frequency of pulses it is necessary to increase the peak power in the pulse, which leads us to the destruction of the light guide. In order to bypass this restriction a unique excimer laser was developed. In this laser generation was exited with a discharge propagate along the surface of the dielectric, namely the sliding discharge. High pulse repetition rate was obtained by the thick plasma layer (thickness about 1-1.5 mm) formation by the sliding discharge, which actually use as the pumping source. The sliding discharge plasma propagates along the sapphire plate placed on massive metallic electrode. This provides the optimum conditions for electrode cooling and gives us the increase of the generation repetition rate. The sliding discharge used as pumping source for excimer KrF laser gives us the possibility to obtain the repetition rate up to 2000 Hz without replacing the gaseous mixture. At this condition and the mean power of the generation about 20 mW (pulse duration about 10ns) the peak power was about 1 kW. This gives us the possibility to transport the UV radiation into the cavern without wave-guide destruction. This excimer laser was able to work continuously during 3 hours without replacing the gaseous mixture. This opens wide possibilities to apply excimer lasers into the medical practice.

In this work we present some laser experimental achievements obtained with the Ce:LiCaA1F₆ (Ce:LiCAF) active medium. The Ce:LiCAF belongs to the family of fluorides Ce³⁺ activated, which emit in the near UV with tunable emission. In particular it emits in the band 280-315 nm. The laser action was obtained by pumping Ce:LiCAF with frequency quadrupled Nd:YLF and Nd:YAG lasers. We developed a multi-kHz tunable laser with high quality beam, tunable in the range 280-315 nm and with an average power exceeding hundred of mW, pumping with a pulsed Nd:YLF laser. Due to the high quality of Ce:LiCAF crystal we grew, we were able to obtain the highest ever reported slope efficiency. We achieved also the highest ever reported energy of 26 mJ for a Ce:LiCAF tunable oscillator pumping with a single low repetition rate Nd:YAG IVth harmonic laser. The wavelength coverage is further extended in the range 225-230 nm by means of nonlinear frequency mixing of the Ce:LiCAF output with the residual emission of the fundamental wavelength of the Nd:YAG laser.

In this work we present an accurate experimental study of Xenon filled flash-lamps developed to achieve a fast submicrosecond light pulse with high emission in the ultraviolet (UV) spectral range. This study has been initiated to obtain an efficient pump for solid state lasers with Ce³⁺ activated crystal as active medium. For Ce³⁺ doped fluorides the absorption bands lie in the UV spectrum, in the region between 248 and 288nm. Due to the very short lifetime (-4Ons) of the upper level ofthe laser transition (5d->4f), Cerium activated hosts must be pumped with a fast rising light pulse. To our best knowledge, no direct ultraviolet laser action from a Ce³⁺ activated host with incoherent pumping has been reported. To achieve a threshold population inversion, an unusually fast lamp pulse is required making necessary the development of a lamp system opposite to what it is usually required in terms of duration and stability. We present here a detailed characterization of the lamp and ofthe discharge circuit parameters. Furthermore we discuss the opportunity to use an excimer mixture or a Silicon-Xenon based gas mixture to optimize the spectral coupling of lamp emission to the active medium adsorption.

Nowadays communications require a continuous increase of data rates and, as far as the single customer is concerned, there is a severe bottleneck in the last kilometer of the transmission line. The only viable solution to this problem is the Fiber to the Home (FTTH) system, which requires an amplification of the incoming signal in the optical fiber. However, the device of election, the Erbium Doped Fiber Amplifier (EDFA), is still very expensive, so that new optical waveguide amplifiers based on Lithium Fluoride (LiF) thin layers containing color centers have been recently proposed. Such electronic defects are characterized by broad absorption bands in the visible and near ultra-violet (UV) spectral range and by efficient, broad-band emissions extending from the visible to the near-infrared (NIR). One of the important properties of these light emitters arises from the short lifetime, several nanoseconds, which is a fundamental feature for high gain laser media. Several basic and technical aspects of novel solid-state amplifier configurations based on active waveguides in LiF will be presented and discussed.

We shows that the phase of a backward stimulated Brillouin scattering (SBS) wave can be controlled, which is necessary for a beam combination laser using SBS phase conjugate mirrors. The phase control is achieved by a self-generated density modulation without seeding the Stokes beam. Theoretical analysis shows that the phase fluctuation is mainly due to the pump energy fluctuation and is inversely proportional to the pump energy. We have achieved that the relative phase difference between two SBS waves is smaller than λ/4 for all the pump pulses.

The scheme of intracavity four-wave mixing is used to measure the spectrum of turbulent pulsation of velocity of ative-medium flow in fast-axial flow CO₂ laser. The coefficient of transverse turbulent diffusion and viscous size of turbulent pulsations are also obtained.