We have succeeded for the first time to simulate dynamic phase transition from metal to vapor. This success is due to the CIP method that can treat solid, liquid and gas together and can trace a sharp interface with almost one grid. We report here the application to laser-induced evaporation for nanosecond and femtosecond lasers. In both cases, aluminum is evaporated well after the laser beam ended. In the nanosecond laser, evaporation occurs with a large angle to the target normal causing filamentary structure. In the femtosecond laser, evaporation front is formed and shows discontinuous solution that continues over a long time.

The construction ofmonitoring systems for a process of laser welding with deep penetration requires a choice from all possible signals, bearing information about the process [1], those, which is the most complete satisfy to the technological requirements, as essence ofthe control process. There are: 1 . Presence ofthe clear and physical -adequate connection between parameters ofthe signal measured and behavior ofthe welding bath; 2. Possibility to "recalculate" the signal measured in technologically significant parameters: a depth and width of the welding seam, and perhaps its mechanical properties, during a time, acceptable for the technologists; 3. Possibility to monitor the appearance ofdefects ofthe weld seam, such as pores, root peaks and etc. by the measured signal; 4. Convenience ofmeasurement and processing and protection from external interference. It has to note, that the acoustic signal so far have not physically clear connection with behavior of the welding bath, in spite ofthe fact that a lot of works are devoted to study ofthem in a number of years. Experimental researches ofprocess ofacoustic emission at laser welding [2]togetherwith results of frequent analysis have shown dependence ofthe signal level on intensity ofthe laser radiation and processing regime. Correlation ofthe acoustic emission signal with radiation power, welding speed and level ofradiation focusing are established by the authors ofthe [3]. The similar results are described in a number ofworks [4,5].Itis established specifically, that the acoustic signal bears in selfthe information about presence ofthe through or partial penetration [5,6],however to understand the acoustic emission nature, there are used as a rule either phenomenological reasons [7] or the models which far from reality, for example [8]. The authors of [9] basing on [10] connect the acoustic signal with time derivative of the evaporation mass flux but thus they completely neglect a real physical picture of generation ofthe sound in the active zone. The purpose of given investigation is to establish the connection and decide a question about usefulness ofthe acoustic emission to monitor the process of laser welding. Let's begin from description ofthe phenomenon and formulation of the investigation problems. The cavity is a source of sound oscillations at laser welding with deep penetration. By evaporation from the cavity surface a vapor flow running into surrounding space is formed. Self-oscillations oftemperature of the cavity walls, described in [1 1], result in oscillation ofthe evaporation mass ratio, and oscillating walls of the cavity modulate a vapor jet in addition. By virtue of connection described by gas-dynamic equations the velocity and temperature oscillations ofthe vapor jet lead to those ofpressure, i.e. to appearance of the sound oscillations. When acoustic frequencies observed in experiments on laser welding (f-i 0 -I0000 lIz) are typical, length of the acoustic wave "A" is much more than the cavity depth and especially than its radius. Since for the surrounding space the outlet section ofthe cavity is a point source ofthe acoustic oscillations. Power ofthis source and its frequent spectrum are defined by nature ofthe radiation process of the sound fluctuations from the cavity into the surrounding space. It is necessary to take into account, that the gas temperature and hence the sound velocity inside the cavity and in the surrounding space are essentially distinguished. The size of the transitive area above the cavity, where the sound velocity changes from value which is typical for the cavity up to the value corresponding to the room temperature, is a lot of less than length of the acoustic wave. Therefore we can neglect its sizes and require on some border (coinciding with the metal surface), in order that the solution ofthe problem about internal acoustics of the cavity coincides with the solution of the external problem about spreading of the oscillations in the surrounding space

A 2D gas-dynamic model of laser ablation an ambient gas atmosphere is proposed. To obtain the boundary conditions at the evaporated target surface, a nonlinear heat transfer problem in the target including the dynamics of the melt and evaporation fronts is considered. Back condensation of the vapor at the target is taken into account. At later stages, compete absorption of the vapor and back condensation thereof with a local sound speed are assumed. The gas- dynamic problem in divided into the initial 1D and final 2D stages. The 1D stage describes the ablation plume formation under the action of laser pulse. The 2D stage is responsible for the formation of the energy and angular distributions of the ablated material. A considerable compression of the ambient gas around the expanding plume of the laser- evaporated material and a shock front propagating through the undisturbed ambient one. Once the laser pulse is over, the vapor pressure eventually drops down to the value comparable to the compressed ambient gas pressure. From this time on, the gas considerably suppresses the vapor expansion. There is a noticeable difference between the vapor distribution in vacuum and the one in the ambient atmosphere: the vapor fills the entire plume volume in vacuum while in the presence of ambient atmosphere it is accumulated near the plume boundary and tends to form a thin shell. The angular and energy distributions of the ablated material are especially sensitive to the nature and pressure of the ambient gas. Both the kinetic energy of the ablated atoms and the width of their angular distribution decrease with the ambient pressure.

The results of mathematical modeling are presented to the two qualitatively different stages of evolution of the laser-induced plasma.

We produced a totally conservative finite-volume scheme for modeling of Al₂O₃-TiC ceramics processing with excimer laser radiation. Evolution of a cylindrical TiC grain at the surface of an alumina matrix is traced for a few nanaoseconds. Its melting causes a small surface swelling - a possible nucleator for the experimentally observed TiC globules.

Special techniques of non-contact optical diagnostics under actual industrial conditions is required for accurate temperature monitoring and control in a wide range of laser applications. The set of pyrometers was developed and applied for surface temperature monitoring in pulsed periodic Nd:YAG laser welding and surface treatment, deep penetration welding by CO₂ and Nd:YAG lasers, and electron beam; laser assisted machining; laser cladding, etc.

Cavitation bubbles generated in water by Tm:YAG laser pulses were studied. Timer-resolved photography was applied to determine volume change with time and surface velocities of expanding and collapsing cavitation bubbles. A new method of determining vapor densities inside bubbles based on reflection changes of a fiber probe placed inside the cavitation bubble has been developed. Density distribution changes with time were measured spatially at 17 points within the bubble. Maximum bubble diameter was about 4.5 mm. Densities measured were compared to the growth of the bubble as shown by ultra fast imaging. Temporal and spatial pressure and temperature distribution will be computed from density distributions based on equilibrium values at maximum bubble extension.

Crystal 4—< liquid phase transitions induced in monocrystalline silicon surface layers by pulsed irradiation of a ruby laser have been studied using in situ methods and also by numerical modeling the laser - induced thermal processes. Hydrodynamic phenomena and convective heat transfer from the liquid surface absorbing laser radiation to the melt-crystal interface are possible at the melting stage. During epitaxial crystallization, the undercooling of liquid Si at <1 1 1< crystal growth direction is '-15 K more than the same for <100< and <1 10< directions. Two kinetics regimes characterize the epitaxial process to various directions. This regimes differ not only in undercooling, but also in morphology of the liquidsolid interface which can be atomically smooth or rough.

The paper considers a number of principle algorithms to control feedback systems in submillisecond pulsed lasers designed for biological tissue treatment and having absorption coefficient within 0.1 cm^-1 - 100cm^-1. Feedback for those laser systems is based upon an analysis of amplitude and frequency characteristics of a thermo optical signal going along with a treatment of a tissue. Herewith some samples of thermo optical feedback algorithm realization for medical laser systems are presented. For the first time the paper demonstrates a must of a proportional change of laser radiation energy to a first variable of thermo optical signal amplitude signal amplitude in feedback systems at stabilized laser wound parameters.

In the paper the researches on development of informational - measuring channels of quality indexes monitoring of laser cutting process with use of acoustic and optical signals of a different range are submitted. The estimations of their information significance and efficiency of use of acoustic and optical signals of a different range are submitted. The estimation of their information significance and efficiency of use are reduced. The structure of the informational - measuring research stand including the basic measuring channels for definition critical by criteria of quality and productivity of process parameters is offered. The carried out researches are aimed to system engineering of monitoring and the quality control of laser cutting processing of materials in real-time mode.

Today the laser technologies are widely used in the processing of materials, including also the precise microshaping. Deep UV lasers have very good prospects in the lithograph, used for fabrication of chips, while the femtosecond pulsed lasers open the new horizons for the micro- and submicroprofiling. But these are the field of the future prospects. As for today's state-of-the-art, contribution to the application of lasers for these purposes are the numerous advantages of the laser techniques over the traditional methods, such as: wide variety of material to be treated, possibility of achieving narrow cuts and practically waste-free separation, small heat-affected zone, minimal mechanical effect and minimum thermal deformations, possibility of microshaping along a complex profile in two, or even three dimensions, possibility of fast and precise process switch-on and -off and to include in the processing feedback on the treated parameters.

The controlled laser microstructuring of solid surfaces improves their wear properties: microholes induced on a friction surface can act like lubricant reservoirs and as traps for debris particles. In generating such microstructures, the laser has the advantage of its great versatility, since it can be used in various environments and it can be adapted to a wide range of desired structures. In this work metallic surfaces where precisely and reproducibly patterned on a micrometer scale by an industrial, Q-switch-operated Nd:YAG laser. The duration of the pulses was 100 ns FWHM. For laser ablation in this pulse length range local melting and vaporing govern the mechanisms of materials expulsion and the melt ejection occurs through the vapor pressure gradient, yielding the formation of resolidified droplets and rims on the target surface.

For the last decade processing application with the Nd:YAG laser operating int eh UV, visible and IR region has taken a new dynamic turn in the micro technology. It has covered a wide range of applications in microelectronics, semiconductors and screen printing as well as in the medical industries. From laser ablation to marking and from precision cutting to micro welding, it has opened a new horizon of industrial needs in micro technology. Of these, processing with the UV radiations have a unique characteristics of ablation and allow the production of small micrometers order microstructures, but their industrial application has yet to be established. On the contrary, processing with the IR radiations usually considered as thermal processing covers mainly precision cutting of stencil mask for screen printing technology, micro processing of metallic stents for medical therapy and various other microstructuring applications. In all these processes, due to different scale length of the beam interaction time with the material, various physical phenomenon are encountered that ultimately affect the quality of the end product. The present paper elaborates a few of these basic processes and explores the possibilities of current and new application areas.

In the paper the results of an image application non materials method researches by a laser marking are established with use of acoustically-optically modulated radiation of laser technological installations on the basis of Nd-YAG solid state lasers EVERMARK-8070, MLS-132, Alpha- 201, Kvant-60, LTU-16, BETAMARK-2000. The experimental technique of an estimation of a quality image ona surface of materials by criterion of contrast and sharpness of the application image is offered.

The laser perforator of passports have been developed and created. Besides its direct purpose the equipment can be also used for engraving of a paper, tree, plastic. The computer management allows to put any figures, number etc., that also can be used for documents protection.

In the emerging field of micro robotics and micro- electromechanical systems, the requirement of complex mechanical parts is gaining much importance. On one hand, the overall size and shape of the product is becoming continuously smaller and more complex, whereas the new product demand/offer is increasing manifold. In order to overcome this problem, the new organizational structure of the compete process for the product development as well as the new technology is necessary. This paper highlights the various processes viz. Micro-stereolithography of polymer resin, selective laser sintering of metallic powder as well as melting processes using lasers for the rapid prototyping of 3D parts in micro domain.

This paper deals with the development of simple and practical methods for fabrication of micro parts using laser induced photopolymerization. Mask pattern transfer method is used for high aspect ratio parts. Focused laser beam writing method is used for both high aspect ratio parts and 3D parts. The accuracy of the solidified polymer when using these methods is examined. Various shapes of micro polymer structures are produced using these methods.

New materials and schematic decisions targeted for functional prototyping are offered. All materials and schemes were experimentally proven, test-models obtained and checked. Main factors which takes an effect on accuracy and productivity of considered RP processes are considered.

Laser processing is quite attractive for micromachining, microstructuring, and modification of materials. Conventional laser processing using IR, visible, or UV lasers, however, cannot realize precision microfabrication of advanced materials such as fused silica, quartz, sapphire, diamond, SiC, GaN, etc. Novel laser processing is recent topics for microprocessing of these materials. In this paper, such novel approaches are reviewed.

Optically transparent materials such as fused silica, quartz crystal, calcium fluoride, and fluorocarbon polymer were etched upon irradiation of organic solution containing pyrene with a conventional KrF or XeCl excimer laser. Threshold fluences for etching were 240 mJ/cm² for fused silica, 330 mJ/cm² for quartz crystal, 740 mJ/cm² for calcium fluoride, and 45 mJ/cm² for fluorocarbon polymer. These threshold values were remarkably low compared with those of direct ablation by using conventional lasers. Their etch rates remarkably depended on a concentration of pyrene: the etch rate became higher as the pyrene concentration increased. It means that pyrene molecules play an important role in this process. The mechanisms for this process is discussed by cyclic multiphotonic absorption of pyrene in the excited states, thermal relaxation, and formation of super-heated solution. As the results suggest, the process is based on the combination of two physical processes in the interface between the transparent materials and the liquid: one is a heating process by a super-heated liquid and the other is an attacking process by a high temperature and pressure vapor. The mechanism is also referred to thermal properties of materials.

The laser-assisted method of the near-field optical probes shaping-laser-assisted drawing-out-is discussed. The experimental set-up for the NOP fabrication is suggested with its peculiarities discussed as well. And the consequences of the kinetic and integrated experiments for the investigation of the drawing-out processing of the NOP are presented, as well as the theoretical analysis.

Micropipettes mathematical modeling and fabrication are presented. New approaches to treatment of modeling light passing through narrow glass tubes and calculation of intensity distribution in the vicinity of a tube are shown. This method is based on a layer-to-layer Fourier transform procedure which is an alternative to waveguide technique. Laser technique to produce micropipettes and to control the shape of them are described and experimental results are considered. Perspectives of medical and optical applications are discussed.

Perspective of using the optoelectronic methods for remote monitoring of the quality of products surfaces is connected first of all with the possibility of their functioning in the real time. The fact, in its turn, allows one to use the information from such devices in the feedback channels of process control system when there is a need to receive surfaces with the given properties.

Laser micro processing technology has been applied to industries in a number of aspects: (1) laser cleaning, laser deflash and plasma-assisted laser micro processing, (2) laser texturing, laser bumping and related technologies, (3) real-time monitoring of laser surface processing, (4) laser- induced controllable periodic structures and (5) laser nano- etching and nano lithography by tip-enhanced laser irradiation.

Liquid-solid phase transitions induced in monocrystalline GaAs by two laser beam irradiation have been studied by a numerical modeling. The modeling was carried out on the basis of solving the Stefan problem in 1D approximation by a finite difference method. Two variants of combined irradiation by Q-switched ruby and CW Nd:YAG lasers were considered. In the first variant nanosecond radiation from a ruby laser induced the surface melting of a GaAs wafer and 'switches on' the absorption of additional CW intensive radiation directed from the back side of the wafer through its volume. Two laser beams are directed from one side in the second variant of combined irradiation. As it follows from the data obtained, the motion of the liquid-solid interface can be controlled by changing the intensity of CW radiation. Because of strong temperature dependence of optical absorption in solid GaAs at (lambda) equals 1064 nm, a heat wave moving toward Nd:YAG laser radiation can arise near the liquid-solid interface in opposite geometry and screen the melt from the CW laser beam. In the case of one- sided geometry the time dependence of melting depth has a nonmonotone character; the crystallization process can be terminated and the melting develops again.

In this work the kinetics of heterogeneous precipitation of silicon oxide in silicon is investigated. Laser induced centers act as nuclei for precipitates. Laser induced centers were formed in a near surface layer during pulsed laser annealing by double frequency of a Nd⁺³:YAG laser without introduction of any additional impurities. It is shown, that the process of formation and growth of precipitates in the presence of laser induced centers differs from the case of homogeneous. The dependence of the concentration of oxidation stacking faults on thermal treatment duration is given. The thickness of the layer with inhomogeneous distribution of oxidation stacking faults grows with thermal treatment duration in an inert ambient. This growth can be explained by the drift of oxygen atoms in the direction of the gradient of tensile internal stresses, which increases in silicon during the growth of silicon oxide precipitates.

X-ray diffraction patterns reflected from the laser treated crystalline CoSi₂ layer, the measurements of surface electrical resistance and atomic force microscopy micrographs confirm the 'generation-diffusion-deformational instabilities' model of formation of defect ordered structures of various types. The CO₂ laser induced decrease of the thermal coefficient of resistance to zero in Co-Ti-Si films is realized. X-ray diffraction studies of the treated films confirm that the obtained (alpha) changes with number of laser pulses are caused due to solid phase reaction Co + 2Si equals CoSi₂ and 5Ti + 3Si equals Ti₅Si₃.

In this work there is described the improved construction of laser cavity which makes possible to form submicron periodic structures on the surface of such perspective but not high- reflective materials as semiconductor single-crystals. The experimental investigation of the intracavity processing of the pure single-crystalline surface of germanium and silicon by means of 1.06-micrometer radiation of neodymium glass laser shows that 0.3-micrometer width periodic structures may be formed even on the surfaces with the reflection coefficient lower than 40 percent.

It is shown that for integrating control of thickness of uniform metal films along surface samples it is possible to use low frequencies of modulation of heating radiation and relatively large sizes of laser beams, that permits to simplify registration, to reduce the requirements to accuracy of optical adjustment and to simplify mechanical stabilization of all installation to vibrations.

Pulsed-laser deposition (PLD) is a unique technique that has been employed for thin film growth of a broad variety of materials. In this contribution, PLD of high-temperature superconducting films of YBA₂Cu₃O_7-(delta ), Bi₂Sr₂CaCu₂O_8+(delta ) and (Hg,Re)Ba₂CaCu₂O_6+(delta ) is reported. Emphasis is put on the optimization of deposition parameters and the growth of so-called tilted films on vicinal cut substrates. Such films offer the unique possibility to measure in-plane and out-of- plane transport properties which is especially important for materials not available as single crystals. Experiments on photodoping and on vortex string channeling are presented. The electrical properties and the microstructure of the vicinal films are investigated with respect to the tilt angle and the film thickness.

12 A review of results of a last few years investigation in the field of laser light induced liquid phase metal deposition on different substrates is presented. The role of liquid phase chemical deposition techniques represents a certain interest for contemporary micro technology because of its technical and economical advantages compared to other technics e.g. chemical vapor phase deposition. The methods do not require harmful precursors, complicated vacuum tools, and it is cost effective.

Synthesis of carbon nitride has been an important topic in materials science since 1993. Ion-assisted pulsed laser deposition is proven to be a good method to deposit carbon nitride thin films. Both amorphous and crystal (beta) -C₃N₄ layers can be deposited on many substrates. A standard experimental set-up comprises a pulsed KrF excimer laser that is used to ablate the graphite target and a nitrogen ion beam bombarding simultaneously on the substrate. A variety of experimental derivatives have been developed based on pulsed laser deposition. The deposited thin films have been characterized by Auger Electron Spectroscope, X-ray photoelectron spectroscopy, mass time of flight spectrum, optical emission spectrum, Rutherford backscattering, high energy backscattering, Raman spectroscopy, Fourier transform IR spectroscopy, Ellipsometry, electron diffraction, scanning tunneling microscope and atomic force microscope. Investigations are carried out to identify the binding structure, nitrogen content, electronic properties, optical properties and crystal structures of the deposited thin films.

Results of experimental investigations and numerical simulations of thin films and multilayers of Fe-Al and Co-Cu binary systems synthesized by PLD are presented. The influence of specific features of PLF on the structure of thin metal and alloy films is discussed. Examples of non- conventional microstructure formation are given.

In the present work iron discilicides were synthesized in tow phases: metal and semiconductor under the action of YAG:Nd⁺³-laser radiation on pure iron thin film to have been sputtered on Si substrate surface. Temperature dependencies of specific conductivity for samples with iron discilicides layers revealed the presence of semiconductor and metal phase in the formed alloy owing to the rapid solidification of the molten phases after finishing of laser pulse. There is decreasing of (sigma) equals (0.40 divided by 0.08)(Omega) ^-1 cm^-1 while decreasing the sample temperature in the range (333 divided by 77)K. For all samples one can see decreasing of bandgap while increasing of laser power density. Electrical resistance as a function of relative mechanical deformation was measured on obtained samples. While changing of relative resistance in the range (0 divided by 1.6) X 10^-2 meaning of (epsilon) was being changed in the range (0 divided by 1.6) X 10^-4.

Recent advances in hybrid technologies combining pulsed laser ablation with non-pulsed plasma sources are discussed. One was a deposition of multi phase materials made of nanocrystalline TiC, WC, WS₂, and amorphous diamond-like carbon by a hybrid of laser ablation and magnetron sputtering. These phases were combined into layered and grain/matrix nano-composite materials, using the laser ablated plasma for low temperature synthesis of crystalline materials. Another was the production of AlON film by the laser ablation of Al₂O₃ accompanied by a nitrogen ion beam, where synergistic interaction between the two plasma sources provided the generation of chemically active NO molecules critical for the growth of AlON films. In both hybrid process, the high energy, excitation level, and short duration of the laser ablated plasma were the key factors that enabled production of material with composition, structure, and properties unobtainable by other deposition.

High power diode lasers form a few Watts up to several Kilowatts have entered industrial manufacturing environment for materials processing applications. The technology has proven to show unique features, e.g. high efficiency, small size, low energy consumption and high reliability. This paper provides a description of high power diode laser technology and applications and evaluates the benefits and restrictions of this laser technology. As an outlook an ambitious research project, the five year National German 'MDS'-project is shortly described. New developments in the opto-semiconductor technology itself, but also in micro- optics and precision mounting technology will help to increase the beam quality by about one order of magnitude, so that the beam quality of today's lamp pumped high power Nd:YAG lasers can be reached. New type of laser applications are supported by the modular concept of the diode lasers.

The systems of pulse-periodical pumping of the solid-state lasers with adjustable time-amplitude and frequency parameters of pulses of pumping currency, as well as laser radiation pulses, intended for power supply of the lasers, operating in the mode of free generation, are presented.

The laser systems with passive Q-switching by LiF:F₂ crystals for precision technology are submitted. It is shown, that the application of laser system of the combined radiation allow to increase the processing productivity, and laser systems with the combined Q-switching-the processing quality.

A spherical concave diffraction grating was chosen as the dispersing element for a number of spectroscopic deices. More recent application of these grating is designing of multiplexers/demultiplexers for wavelength routed optical networks. Concave grating acts as the focusing element and can be the sole optical element of a device, which simplifies its adjustment and increases the transmittance. However, it possesses aberrations. Conventional method of concave diffraction grating recording using interference of two spherical waves formed using dividing an depending of laser beam, gives possibility to minimize three main types of aberrations, the defocusing, the meridional coma and the first order astigmatism. For the wide range of spectrometers these gratings can be used with rather good results. However, if we want to design spectrometer with increased aperture, wide spectral region or extremely high resolving power, we have to take into consideration per limit more than two aberrations - the sagittal coma and the spherical aberration. We also have this problem in designing of wavelength routers, where aberration geometric size of image should be not more than the optical fiber diameter. We can resolve this problem using aspheric wavefront recording systems. Since refraction optics is not good for holographic recording because of scattering, this system can include mirrors or other diffraction gratings. In present work different recording systems are discussed from the point of view of geometric theory of grating and from the point of view of reality of experimental installing and using of these systems as well.