This PDF file contains the front matter associated with SPIE Proceedings Volume 6985, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Polarization-dependent ripples were formed at silicon surfaces under femtosecond laser irradiation. Proposed theoretical model describes changes in optical response of semiconductor surface, induced by generation of nonequilibrium electron-hole plasma, and explains mechanism of surface polaritons and waveguide modes exciatation during femtosecond laser pulse action.

Various structures can be produced at the focal point inside a transparent material by using pulsed laser operating at the non-resonant wavelength with pulse widths of the order of femtoseconds. We have succeeded in the three-dimensional structural-phase transformation from diamond to amorphous structures which have high electrically conductive properties by the femtosecond laser pulses irradiation. The spatially periodic conductive structures indicate photonic crystal properties in terahertz region. We have also demonstrated the three-dimensional nanostructuring inside a glass material by the single femtosecond laser beam irradiation. The self-organized sub-wavelength periodic nanostructures are created by a pattern of interference between the incident light field and the electric field of the bulk electron plasma wave excited via two plasmon parametric decay. More recently, we have observed metallic Cu nanowires with a length of 1.0 μm and a diameter of 85 nm which were successfully photo-converted from commercial scale-like Cu particles, dispersed in a methanol solution, by using femtosecond laser irradiation. The growth mechanism of Cu nanowires under laser irradiation was suggested to be a nucleation growth process.

This report deals with self-focusing of axial symmetric laser beam in Kerr medium with the temporal dispersion of nonlinear response. Laser beam propagation is described by so-called generalized nonlinear Schrödinger equation in 3D case. The essential feature of this equation is a term, which contains a time derivation from nonlinear response. As a re-sult, a group velocity of wave packet depends on laser pulse intensity. On the other hand, as well known, self-focusing of an axial symmetric laser beam results in unlimited growth of its intensity for the picoseconds diapason of pulse duration. Action of both factors gives a new quality of laser beam propagation. Its main feature is a possibility to control of self-action for chirped laser pulse. Under certain conditions, we can easy to change regime of self-focusing to opposite one. Temporal dispersion of nonlinear response can be the main nonlinear response of medium under the laser light propagation.

Laser assisted direct manufacturing and in particular Selective Laser Melting (SLM) becomes a promising manufacturing technique. Recent progress makes it possible to create fully functional parts directly from metal powder without using any intermediate binders or any additional processing steps after laser melting. At present only a few studies were carried out to monitor and to on-line control SLM process. In this paper, the optical diagnostic tools as infra-red camera and pyrometer are applied for SLM process visualization and control : surface temperature evolution, phenomena in laser-powder interaction zone, dynamics of droplets emitted from the molten pool.

Interference coating for infrared spectral region required the transparent optical films with different refraction indexes and minimal an absorption factor. It is well known, that chalcogenide materials based on sulfide and selenide are the perspective film's forming materials for manufacturing of the interference coating. Among the known materials, the minimal absorption factors have arsenic chalcogenide films. It allows using them for manufacturing of the high quality optics in wide optical region, including optics for CO₂ powerful lasers.¹ Despite of good operational characteristics and the small optical losses, many of known chalcogenide materials have not received a wide distribution. One of the reasons of that is the absence of the data of their film's optical constants (OC) of these substances, which strongly depend on a way and conditions of manufacturing and are different from OC of initial monocrystals. In this paper the optical constants of the chalcogenide films various composition were described. Investigated films were manufacturing on fused quartz substrates by vacuum deposition. Initial substances As₂Se₃, AsSe₄, AsS₄ and AsS_16.2Se_16.2 were evaporated from molybdenum hull in vacuum 3•10^-5 Pa. Refractive index and extinction coefficient dispersion in 0.5-2.5 μm spectral range were determined by method is based on analysis of the interference transmission spectra.

A multifunctional laser technological system for processing large-scale (3 × 3 × 0,6 m³) articles with free surface shape is presented. It is established that the error of laser head displacement is below 10 mm in any region of the working space. Engineering solutions ensure efficiency of the system without deterioration of its performance characteristics at a temperature varying from 18°C up to 30°C. This system can be used for 3D inspection of objects with arbitrary topology.

Effect of temperature on the optical parameters of the molecules in the homologous series of 10 dicarbocyanine polymethine dyes was studied. The thermally and photostimulated reversible changes in the isomer compositions and optical properties of solutions and molecular layers were investigated experimentally. The effect of temperature on the optical density, absorption spectra, fluorescence intensity, fluorescence quantum yield, photoisomerization quantum yield, and kinetics of changes in the isomer composition of the solutions was studied in the range (-60÷+60)°C. It was shown that the thermal sensitivity of the optical parameters of the polymethine molecules depends on the electrondonating ability of end groups. The reversible relative changes in the optical density of the solution with temperature are (0.4-1.4) % /deg. The range of relative changes of the fluorescence intensity is (1-2.3) % /deg. The new method of direct transformation of a thermal image into visible image with the aid of three-level molecular systems was proposed involving optical excitation from the low state into the intermediate fluorescent state and the thermally stimulated transitions from this state into the nearby upper state. The visible image can be observed by the optical methods, either by measuring the fluorescence intensity or as a change in the optical density of a screen of the detector in the region where the thermal image is formed.. The bolometric matrix-receiving medium was polymethine dye, which undergoes isomerization, i.e., changes structure under the action of thermal and optical radiation.

A femtosecond laser machining has been utilized to fabricate various optical devices inside transparent material. To elucidate the mechanism of the femtosecond laser induced structural change inside a glass, we have observed the dynamics of the structural change and detected pressure wave propagation by a Transient Lens (TrL) method. Although the pressure wave generation has been already observed in our previous study, the analysis to obtain the temporal evolution of the refractive index distribution change was rather complex. In this study, we show alternative analysis method for TrL signals of bulk modification inside glass by femtosecond laser. From the analysis, the dynamics of the structural change including refractive index change at the center and shape of pressure wave becomes clear.

A 3D numerical model for the surface hardening process simulation carried out by means of a CO2 laser source is presented. The model is able to predict the extension of the treated area into the workpiece, the type of the resulting micro-structure and the optimal laser path strategy in order to minimize the micro-structural softening due to the tempering effect. The Fourier equation is solved using the Finite Difference Method (FDM) applied on a generical grid obtained by means of the domain discretization. The resulting time dependent temperature distribution into the workpiece is used for the evaluation of the induced heating cycle. By calculating the cooling velocity, the micro-structure transformation is determined together with the hardness in every point of the domain. The hardness reduction due to the tempering effect is also predictible. The computational times are small and the software is very suitable in industrial environment in the early stage of the process planning when several simulation runs must be performed. The modeling activity was developed by considering the class of the hypo-eutectoid steel. The experimental tests were realized on a C43 steel plate. The good agreement between the theoretical and experimental results is shown.

Use of the self-adaptive Nd:YAG laser with dynamically adjustable passive Q-switch allowed to drill high-aspect-ratio holes deeper than 7 mm in steel, aluminium, Ni-based alloy, and ceramics Al₂O₃, AlN, SiC at the average drilling rate exceeding 1 mm per laser pulse, which is close to the initial drilling rates.

Waves of optical bleaching in glass-ceramic under cw Nd:YAG laser action are discovered. This phenomenon is compared with the effect of CO₂ laser radiation on the same glass-ceramic. Transparency and temperature changes of glass-ceramic ST-50-1 during the Nd:YAG laser action was investigated. Mathematical model of these periodic transparency and phase-structure oscillations is offered.

Physical processes occurring by laser cleaning of metal surfaces from soiling particles, coatings and near-surface oxide or corroded layer are considered. Unconventional methods of laser cleaning which promote increasing the quality and effectiveness of cleaning and solving of the problem of soiling substance gathering are proposed. Applications of these methods in a number of novel fields, such as pinholes cleaning, coatings removal, radioactive contaminated layers removal, cleaning of objects of historic and cultural heritage are considered.

It is generally known that every commercial glass has its own crystallization ability it means that a certain temperature interval exists and glasses can crystallize in this interval. We have to know the crystallization ability and crystallization speed to choose the proper regime for glass melting, manufacturing of different articles and for thermal processing in glass-ceramics manufacture. Crystallization character depends on relation between crystallization centers formation rate, crystal growing rate from this centers and viscosity. The larger the interval between peak rates of crystal growth and formation of crystallization centers, and lower the rates themselves, the lower the tendency of glass to crystallization. Crystallization of glass materials depends on several factors: chemical composition and viscosity of glass, basic material, mutual solubility of every component, duration of exposure on proper temperatures, existence of crystallization catalysts and conditions of thermal processing of glass. To get crystallization conditions one have to provide slow passing through the temperature interval 1000-1200°C. Earlier the possibility of glass-ceramic crystallization under that CO₂ laser action was experimentally shown. But even now it is not clear enough how crystallization centers can form and grow in such a small period of time (several seconds) and what role do impurity materials play (i.e. Au, Ag, etc.). It is known that their atoms play role of crystallization centers in conventional regimes of glass-ceramic crystallization. So, to make a step forward in understanding the laser crystallization process of different glasses we decided to check the assumption of vacancy model that any glass can be crystallized during several seconds regardless of above mentioned impurity materials presence. We decided to choose a glass material for our experiment with large crystallization temperature interval and without any impurity materials like Au, Ag or Ti: Li₂O•₂SiO₂ glass. In this paper we'd like to show the results of our investigation.

Thin film of permanent magnetic material is very important for different electronics application^1,2 We present here preliminary results on SmCo thin film grown on steel substrate. X-Ray diffraction data Magnetic Scanning SQUID (Superconducting Quantum Interference Device) and Vibrating Sample Magnetometer (VSM) analyses have been performed with the aim to study the functional magnetic properties of the deposited thin film.

Thermal and hydrodynamic processes in layer of metals on exposure to pulsed heating by laser radiation ensemble of pores, gas filling of which occur due to the desorption of gas layers, covering the porous wall are considered. The temperature, stress and plastic strain fields dynamics inside the samples were investigated. Shown that for materials with melt temperature T_melt> 2000 K the pore structure explosion is quite possible at solid state with particles release.

We report on the potentiality of the Matrix-Assisted Pulsed Laser Evaporation (MAPLE) technique for the deposition of thin films of colloidal nanoparticles to be used for gas sensors based on electrical transduction mechanisms. The MAPLE technique seems very promising, since it permits a good thickness control even on rough substrates, generally used to enhance the active surface for gas adsorption. TiO₂ (with a capping layer of benzyl alcohol) and SnO₂ (with a capping layer of trioctylphosphine) colloidal nanoparticles were diluted in suitable solvents (0.2% concentration), frozen at liquid nitrogen temperature and ablated with a ArF (λ=193 nm) or KrF (248 nm) excimer laser. The nanoparticle thin films were deposited on silica, interdigitated alumina and <100> Si substrates and submitted to morphological (SEM-FEG), structural (XRD, FTIR), optical (UV-Vis transmission) and electrical (sensing tests) characterizations. A uniform distribution of TiO₂ nanoparticles, with an average size of ~10 nm, was obtained on flat and rough substrates. The deposited TiO₂ nanoparticles preserved the anatase crystalline structure, as evidenced by the XRD spectra. FTIR analysis showed that the SnO₂ nanoparticles maintained the capping layer after the laser-assisted transfer process. This protective layer was removed after annealing at 400 °C. The starting nanoparticle dimensions were preserved also in this case. Electrical tests, performed on TiO₂ nanoparticle films, in controlled atmosphere in presence of ethanol and acetone vapors, evidenced a high value of the sensor response even at very low concentrations (20-200 ppm in dry air). In contrast, in the case of SnO₂ nanoparticle films, electrical tests to ethanol vapor presence showed poor gas sensing properties probably due to the small nanoparticle sizes and interconnections.

The fast growing market for micro technical products requires parts with increasing complexity. While sheet metal forming enables low cost mass production with short cycle times, it is limited by the maximum degree of deformation and the quality of the cut edge. The technology of warm forming partially eliminates these deficiencies. This operation takes place at elevated temperatures before structural transformation is initiated. It combines characteristic advantages of traditional cold and hot forming processes. Lasers as heat sources provide a high, selective and controllable energy input. The general difficulty of a uniform temperature distribution during the heating process can be reached by using an Axicon which generates an annulus on the sheet metal surface. The temperature of the workpiece, measured by a pyrometer, is tuned by a PI-Controller. A tool incorporating a multistage operation die is used for the manufacturing of up to three parts at the same time. The tool is integrated into a hydraulical press. A gearwheel made of the magnesium alloy AZ31 is chosen as metal demonstrator. The quality of these punched parts could be significantly improved at elevated temperatures

Two methods were used for the deposition of thin films and layers: pulsed laser deposition (PLD) and laser-induced film transfer (LIFT). The first one was based on using KrF laser radiation. Thin films and layers were deposited by KrF laser ablation of CrSi₂ and β-FeSi₂ targets with the aim to obtain silicide layers with narrow band gap for sensor applications. The CrSi₂-based films display both semiconductor and metal properties, depending on the deposition parameters. Thus, the film d ≅ 40 nm thick, deposited on Si at 740 K, presents a band gap E_g ≅ 0.18 eV, a thermo e.m.f. coefficient α ≅ 1.0-1.4 mV/K for 300≤T≤340 K and a coefficient of tensosensitivity (R-R₀)/R_0ε) ≅ 5. The film with the same thickness, but deposited on SiO₂ at 740 K, presents a metal behavior in the range 125≤T≤296 K and a semiconductor one for 77≤T≤125 K. Its α coefficient changes in the range 5.0 - 7.5 μV/K for 300≤T≤340 K. The 750 nm thick film deposited on SiO₂ at 740 K displays only semiconductor behavior in the range 296-77 K with E_g ≅ 0.013 eV and α ≅ 10-15 μV/K for 293≤T≤340 K. The coefficient of tensosensitivity for these films is changing in the range 2-5. The β-FeSi₂-based films deposited on SiO₂ at 295≤T≤740 K show only semiconductor behavior. The thicker the film, the higher E_g: d ≅ 150 nm, E_g ≅ 0.032 eV; d ≅ 70 nm, E_g ≅ 0.027 eV; d ≅ 60 nm, E_g ≅ 0.023 eV. The thermo e.m.f coefficient α ≅ 10 μV/K for the 150 nm thick film and α 8 μV/K for the 60 nm thick film at 293≤T≤340 K. The coefficient of tensosensitivity for these films varies in the range 2.3-4.7. The second one was based on LIFT of CrSi₂ and β-FeSi₂ targets, using a Q-switched Nd: YAG laser. The α coefficient for the deposited layer from β-FeSi₂ is about 2.2 μV/K with E_g ≅ 0.05 eV. While decreasing the average power density of the Q-switched Nd: YAG laser, the band gap decreases down to 0.005 eV. For this film we found α ≅ 2.0 μV/K. The α coefficient for the deposited layer from CrSi₂ is about 36 μV/K with E_g ≅ 0.09 eV. Coefficient of thermo e.m.f. for layers obtained by LIFT method was measured at 300≤T≤350 K. The coefficient of tensosensitivity for layers obtained by LIFT varied in the range 1.5-4.2. The higher the semiconductor phase content in the deposited films and layers obtained by PLD and LIFT methods, the higher are the values of α and (R-R₀)/R_0ε.

The silicon clusters formation processes under vapor expansion from a suddenly switched on spherical source into a vacuum and an ambient inert gas are considered. To describe vapor expansion and clusterization processes the direct simulation Monte Carlo method is used. The clusterization model includes description of processes of clusters growth and decay, as well as heat exchange processes accompanying the specified processes. The given model and obtained results are of essential interest for applications concerned with evaporation of rapidly heated small particles.

Processes of metal nanoclusters formation under pulsed laser ablation (PLA) of a flat target in vacuum and deposition of ablation products on a flat surface have been studied. The general PLA model consists of three parts: a model which describes absorption of laser radiation and evaporation of the target, a model for description of vapor dynamics and processes of clusters formation and a model of atoms and clusters deposition on the substrate. A heat model based on unsteady one-dimensional heat conduction equation with volumetric heat source has been used to describe laser radiation absorption and heating of the target. An analogous heat model has been used to describe heating of the substrate. The direct simulation Monte-Carlo method has been used to describe vapor expansion and formation of clusters. The process of ablation products (atoms and clusters) transport from the target to the substrate under conditions typical for production of thin films (nanosecond pulses, moderate radiation intensities) has been considered on the example of laser ablation of niobium. Performed numerical investigations allow to establish general correlations between parameters of vapor flow (including clusters parameters) and deposited film properties.

To optimize laser processing of some materials, it is necessary to ensure high-speed displacement of the focused laser beam ~1 m/s with a great power density. A required speed can be attained owing to scanning systems based on galvanometer deflectors, but the writing field of such scanning systems is restricted to a size of less than 1 dm² for the lasers with λ=1-10 micron. In many laser microprocessing applications a field that must be larger by one order of magnitude required.It is possible to solve such problems using complementary scanners. We developed several devices with use of complementary scanning principle for microprocessing with micron resolution by high power lasers (50-400 W). The developed systems contain the "fast" scanning unit consisting of precision galvanometer scanners and F-Theta lens that, in its turn, can be displaced by "slow" drives over the entire writing field. This paper will describe problems arising in creating the systems based on complementary scanner devices, namely, correct image partitioning into small writing zones, "joining" of writing elements occurred in adjacent zones, and also consideration of geometric distortions in the optical system of the scanning head and its orientation. Furthermore, in order to obtain the maximal writing speed with minimal errors over the entire field, we have to ensure effective four-drive system control. Experimental results of microprocessing of the dielectric specimens, obtained by means of created complementary scanners system, will be pesent.

In the submitted work the diffractive model of radiation scattering on a rough surface representing spatial structure of the scattered field as a result of radiation diffraction on the area of a spot on the rough surface is discussed. Roughness parameters obtained from angular dependence of intensity of the scattered radiation and spatial spectrum of intensity fluctuations.

Method of guided termocleavage of glass, was developed in 80-th⁽¹⁾ and found wide expansion in precession breaking of glass for displays, that is proved with appropriate equipment and a wide variety of publications^(1-2). There are few advantages of this method: high speed of cutting; high accuracy in processing; low power intensity of process; high purity of process, cause of wastelessness of cutting process; zero width of cut. Feature of this method is that cutting of glass is executed due to making of separating split under the voltage of straining, caused of the heating of material with laser radiation and next freezing of zone of heat using refrigerating medium^(1-2). The existing termocleavage technologies by means of infra-red (IR) lasers - CO₂ and Nd have some insuperable constraints such as: the problem of intersection of through-the-thickness crack across previously made by laser, the problem of guided thermocrack drift from linearity upon laser emission input and output into glass samples and others problems. We offer to use other laser radiation sources for overcoming these problems. Preview analyze showed, that the most optimal laser sources are lasers with the spectrum in the field of translucency of glasses (2-7 micron).

Expansion of the laser plume into surrounding gas is considered in the range of ambient gas pressure from 0.1 bar to 1 bar using a kinetic approach. Plume is generated by a nanosecond laser pulse irradiating a silicon wafer. Absorption of laser radiation by the silicon wafer, its heating and melting are described by a two-dimensional thermal model. Axisymmetric flow in the laser plume is calculated by the Direct Simulation Monte Carlo method. Collisions between molecules are described by the hard spheres - Larsen-Borgnakke model. Ablation rate is found from the Hertz-Knudsen equation with taking into account of the back flux of atoms re-deposited at the surface from the plume. The purpose of the work is to study the influence of surrounding gas pressure and its chemical composition on the flow patterns and mixture process in the ablation plume and deposition of the ablated material back to the irradiated surface.

Many materials have already been investigated for laser micro sintering. Nearly all technical metals can be processed with this rapid prototyping technology. A new field of investigation is the sintering of ceramics. For industrial and also for medical, especially dental, application silicon dioxide is a multiply applicable material. One of its interesting features is that the properties of the resulting material can be varied between ceramic on the one and vitreous on the other side, depending on the extent of crystalline or amorphous character of the nano-scale structure. A special problem with laser micro sintering of ceramics is the poor absorption of Nd:YAG laser radiation by most of the materials. Besides that, laser micro sintering of ceramics, in contrary to the process with metals, is not merely a series of aggregational transitions. A solution for the micro part generation of SiO₂ is reported. Typical laser sintering results from this material are presented. Material specific behaviors during laser micro sintering are discussed.

The paper is devoted to R&D of novel experimental technique - laser-driven shock tube (LST) for modeling of Rayleigh-Taylor (R-T) and Richtmyer-Meshkov (R-M) hydrodynamic instabilities development at the contact surface of two immiscible liquids under a shock wave (SW) passage. 100-J, 100-ns KrF laser facility GARPUN has been used to irradiate some opaque liquids. A homogenizing focusing system combined multi-element prism raster and a lens to provide non-uniformity less then few percents across a square 7*7-mm spot, laser intensities being varied in the range of q = 0.004 - 2 GW/cm². Surface plasma blow off produced a planar SW propagated into the liquid. SW amplitudes as high as 0.8 GPa weakly damping with increasing thickness were measured in dibutyl-phthalate (DBP), which strongly absorbed UV laser light. Test bench experiments were performed to produce standing acoustic waves as initial perturbations at the interface between two immiscible liquids.

Developments of laser plants with different purpose, the starting of which was in the middle sixties, are being successfully made in Laser Physics Research Institute (LPRI). Investigations of physical fundamentals of the lasers operation, nonlinear optics and properties of high-temperature dense plasma that is formed under the action of intensive laser emission on a matter are realized at these plants.