Infrared-to-visible upconversion in a variety of rare-earth compounds leads to strong fluorescence and also to laser emission in the visible upon excitation of the media by an appropriate infrared beam. Usually, a diode laser operating at a wavelength of about 800 nm is used as a pumping source. Efficiency of the upconversion process strongly depends on temperature. The best results were obtained at liquid nitrogen or lower temperatures. The reason for lowering temperatures is to depopulate the ground state manifold and to reduce the quenching of fluorescence by phonons. Upconversion based fluorescence and laser emission in rare-earth doped crystals (mainly in erbium doped materials) as well as in stoichiometric erbium pentaphosphate are described.

Ultra violet and blue wavelengths emission has been observed and studied in Tm³⁺ doped YAG crystals. Laser, selectively excited fluorescence from ¹I₆, ¹D₂ and ¹G₄ manifolds of Tm³⁺ ions was observed at cryogenic temperature. These results, together with the decay dynamics and upconversion fluorescence studies, were considered against the possibility of a blue laser.

In this lecture several topics relating to the short wavelength solid state lasers are discussed, these include: self doubling crystals, tunable UV and visible lasers, mechanisms of upconversion excitation, upconversion lasing in bulk materials and optical fibers.

Ultrashort-pulse lasers inspire increasing researcher interest because of their wide possibilities of application in various branches of science and technology. Rapid development of such lasers during the last decade made it possible to obtain pulses of duration in the femtosecond range and to increase their energy and power by several orders of magnitude. Considerable development was attained in improvement of operation stability, increase of repetition frequency, and enhancement of tunability of femtosecond lasers, which made them indispensable research tools applied in many laboratories. The paper describes principal ideas concerning generation of femtosecond pulses and reviews important achievements in femtosecond laser investigations. Ultrashort-pulse formation mechanisms in passively mode- locked lasers and the role of dispersion and self-phase modulation in techniques for generation of such pulses are discussed. Principal methods for generation of femtosecond pulses in dye lasers and solid-state lasers are characterized, techniques for ultrashort-pulse generation within the ultraviolet with the use of excimer lasers are described, and typical construction layouts of femtosecond lasers are presented.

A possibility of generation and compression of ultrashort pulses in excimer systems with saturable absorbers was investigated numerically. It is shown that using fast pulse periodic Q- switching millijoule pulses of duration in the 1 - 10 ps range are attainable from KrF oscillator with acridine dye as an absorber. Then the pulses can be compressed to subpicosecond range in an excimer amplifying system containing saturable absorbers. The proposed technique makes it possible to construct all-excimer pico- and subpicosecond high-power systems considerably less complex and less expensive than hybrid systems used at present.

Ti:sapphire femtosecond laser pulse duration is limited by the group-velocity dispersion (GVD) of the laser cavity with the main contribution coming from the laser rod itself. The GVD of Ti:sapphire crystal is positive throughout its tuning range thus, in order to minimize the effect, one has to include into the laser cavity a negative GVD delay line. Several designs based on Brewster cut prisms made out of different materials have been reported so far. In this paper we consider delay lines consisting of two- and four-prisms sequences, both in double pass configuration. The four prism sequence is an attractive solution since use of two pairs of prisms made from different materials gives one more control over the dispersive properties of the delay line. We use the method of the ray tracing to estimate wavelength dependent group velocity delay for two- and four-prism sequences. Results of our computer calculations indicate clearly that a four-prism delay line is superior to that of a two-prism, providing very similar cancellation of third-order dispersion, as two prism sequence has considerably longer interprism separation.

The description of new gas laser generation, known as multi-waveguide lasers, is introduced. These devices are prime candidates to benefit from advances in phase-locking technologies. Included in this treatment are the properties of rectangular optical waveguide and resonator structures. Basic parameters of rf excited waveguide lasers are described inclusive of their power and mode-frequency characteristics.

The effects of the gain saturation of the active medium and spatial hole burning, and system parameters such as loss coefficient, coupling coefficient, and waveguide geometry on the 3-dB modulation bandwidth in planar and fiber distributed feedback lasers is discussed for various transverse laser modes. Additionally, the effect of the amplitude and phase of the end reflectivity on the modulation bandwidth is analyzed for both structures. The characteristics revealing competition between the Fabry-Perot resonator and the distributed feedback resonator are presented.

An approximate analysis of the nonlinear operation of the DFB laser with complex coupling coefficient is presented. An expression relating the small signal gain to the output power and structure parameters including the spatial hole burning effect is obtained. The effect of the gain grating, the loss grating, and the coupling via the higher Bragg order grating is discussed. It is shown that the effect of the `negative' gain is possible. This effect depends on the output power level, the distributed loss level, and the spatial hole burning effect.

We discuss the nonorthogonality of the longitudinal modes of the distributed feedback (DFB) lasers. The excess-noise factors in real DFB structure with end reflectivity are shown. Moreover, the effect of complex coupling coefficient on the excess-noise factor in partly gain coupled DFB lasers is analyzed.

Some ion doped crystals of the transient group of metals have a broad band of luminescence in the VIS/IR spectral region, and thus they are suitable for the design of tunable lasers free from a series of disadvantages of tunable dye lasers. Physical properties and advantages of solid state lasers using the Ti-doped sapphire and Cr-doped forsterite crystals are reviewed.

The results of laser action in Cr, Tm, Ho doped YSAG and YAG are presented in this paper. Output characteristics of these holmium lasers acting in different conditions (a few laser cavities, resonator optics, pumping pulse energy, and pulse duration) are shown. One interesting result has been obtained -- optimal pump pulse duration strongly depends on the kind of laser medium host (for YAG it is equal to 500 - 600 microsecond(s) ).

The transverse radio-frequency discharge, the features of which resemble those of the hollow- cathode discharge plasma, is very efficient and suitable for excitation of the ionic transitions in the He-metal vapor mixtures. This is due to the relatively high number of the high-energy electrons capable of exciting the atoms and ions to the energetically high-lying states. The other advantages of the transverse radio-frequency discharge are: longitudinal homogeneity of the discharge, efficient transforming of the input power into the energy of fast electrons, simplicity of the discharge tube design, absence of the arc formation at higher input powers, and external electrodes enabling it to operate with the substances of high chemical activity. The He-metal vapor ion lasers excited by the transverse radio-frequency discharge also exhibit some negative features: discharge tube overheating due to the high input power and deterioration of the inner walls of the discharge tube by the ion bombardment.

A continuous-wave He-Kr⁺ laser with capacitively coupled transverse radio- frequency excitation is presented for the first time. The laser oscillations were obtained in a simple alumina oxide discharge tube (40 cm active length, 4.9 mm inner diameter) closed in a fused silica tube envelope. The laser discharge tube was filled with a He-Kr mixture at optimum He:Kr ratio 1000:1. The operating gas pressure ranged from 4 kPa to 16 kPa. The rf power was capacitively coupled into the discharge with 40 cm long and 4 mm wide transverse nickel electrodes mounted along the discharge tube. The discharge was maintained by an rf generator operating at 13.56 MHz with an output power up to 400 W. Transformation of the laser discharge tube impedance to the 50 ohms output resistance of the rf source and symmetrization of the rf voltage were performed by a special matching network. Continuous- wave laser oscillations were obtained at 469.4 nm, 438.7 nm, and 431.8 nm lines of Kr⁺ ion. The laser output powers were 6.2 mW, 0.14 mW, and 1.27 mW, respectively. The laser action at the 438.7 nm line occurred only when the other laser lines were suppressed with a birefringent filter. The rms noise to signal ratio of the laser output power did not exceed 0.8%.

In this paper, on the basis of literature and the author's own works there has been made a review of various configurations of laser resonators, optical and electro-optical elements, leading to an enlargement of TEM₀₀ mode volume and to a smoothing of its transverse distribution of irradiance, both in a near and a far field. Special attention has been paid to an unstable resonator, `p-branch' type, as well as to an output mirror with a radially variable reflection coefficient. Thus, there has been carried out some kind of review of methods of putting out a laser beam out of resonators. Moreover, in the paper there are summarized advantages and disadvantages of designs of the discussed resonators, causing the smoothing of a transversal distribution of irradiation in a laser beam.

Continuous progress observed in performance of semiconductor lasers is to a great extent owed to implementation of quantum well heterostructures. Quantum confinement of carriers in such structures leads to lower threshold current density, higher quantum efficiency and output power, and to many more improvements of laser parameters. Most of them can be further developed when strained layer quantum well heterostructures are used. Application of quantum wires and dots are promising further advantages in the future.

One of the main disadvantages of free-running semiconductor lasers in spectroscopy is gaps in their tuning ranges. Due to these gaps only part (about 30%) of the spectrum can be covered in a typical temperature tuning. A method of avoiding such gaps in a multiple quantum well type STC LT50A-03U laser is reported in this contribution. One can expect that the results may be extended to the whole class of MQW lasers. In other types of diode lasers spectrum coverage of about 45% (instead of typical 30%) can be obtained in the proposed way. Furthermore, a qualitative relationship between wavelengths available this way and parameters of a laser junction can be derived within a simple model of mode-hopping behavior.

Multimode, asymmetric, and astigmatic light beam generated by laser diodes and laser diode arrays are the subject of this paper. The exact description of propagation of this type of beams is very important in several applications as: diode pumped solid state lasers, laser diode range finders, laser printers, etc. Developed in this paper is a quasi-geometrical method of transformation of these beams in real, generally asymmetric, optical systems. The inherent property of the asymmetric beam is the appearance of the pair of astigmatic foci after passing through a focusing lens. This effect can be corrected for single mode beam, but in the case of multimode beam generated by laser diode array it becomes the main drawback difficult to remove. A few examples are presented of transformation of these beams in real optical systems including spot diagrams of astigmatic foci for typical cases.

An approximate analysis of an output power in two-mirror lasers and distributed feedback lasers is presented. The approach is based on the semiclassical theory. It includes gain saturation effects, non-linear dispersion effect, and spatial hole burning effect. The spatial field dependence of the laser modes is taken into account. Using energy theorem and the threshold field approximation an expression relating the small signal gain to the output power and system parameters is obtained. The laser characteristics obtained reveal an optimal coupling strength providing maximal power efficiency of the systems as a function of the structure parameters. The results obtained are found to be in good agreement with the exact solutions and experiment.

The work deals with phenomena affecting propagation and amplification of radiation in a high power laser system. The studies were performed by means of numerical modeling. The parabolic equation is used to describe the laser beam propagation. The equation includes diffraction, amplification with saturation, self-focusing and thermo-optical effects. The code also includes apodization, relaying, and spatial filtration. Cylindrical symmetry is assumed. The influence of aberration of a soft dielectric diaphragm on intensity distribution is described. Some phenomena caused by self-focusing are investigated. It is shown that, first of all, the self-focusing but not amplification saturation limits pulse energy which may be delivered from the laser under consideration.

Methods and means for measurements of radiation power, energy, and spatial parameters of lasers are reviewed. Russian technological lasers such as optically pumped Nd-glass or Nd:YAG lasers and diffusion or convectively cooled gas-discharge CO₂ lasers are primarily discussed.

The role of laser methods in molecular photophysics and molecular spectroscopy is briefly discussed. In particular, the application of laser technology in investigation of such phenomena and processes as various radiative transitions, internal conversion, intersystem crossing, intermolecular energy transfer, photochemical reactions and aggregation by both absorption and emission spectroscopic methods is considered. The most important techniques of time resolved molecular spectroscopy permitting dynamic studies in the pico- and subpicosecond time range are discussed in more detail. Particularly, applications of time-correlated single- photon counting, the frequency domain measurements, pulse-probe methods for transient absorption spectroscopy and emission studies by frequency conversion and other indirect techniques are presented.

The initial stage of fluorescence quenching (the transient quenching) has been studied for the S₂-xantanione/3,3-diethylpentane/perfluoro-1,3-dimethylcyclohexane (as a donor/quencher/solvent, respectively) system. A picosecond time-correlated single photon counting system with a proximity type microchannel plate photomultiplier tube was used in dynamic studies of a strong time dependence of the transient quenching of S₂-xanthione fluorescence. A satisfactory description of the data within the Smoluchowski-Collins-Kimball model has been obtained, permitting the determination of realistic values of the encounter radius, the sum of diffusion coefficients, and the intrinsic rate coefficient.

The Raman and IR spectra of the C-X stretching modes (X equals Cl, Br, I) in the axial and the equatorial positions of cyclohexyl halides and 4-chloro-oxacyclohexane have been measured at room temperature. The mechanism and the differences in the rate of vibrational dephasing of the axial and the equatorial conformers has been discussed.

Time-resolved laser induced fluorescence spectroscopy has been used to study complexation of Eu(III) ion with nitrilotriacetic acid (NTA). An experimental setup consisting of the nitrogen laser pumped tunable dye laser and two different detection devices has been built and extensively tested. Using this apparatus, the lifetimes of the 5D₀ level of Eu(III) ion in complexes with NTA in water solution for 2:1, 1:1, 1:2 Eu:NTA molar ratios over the wide pH range have been measured.

The roughness of the silver electrode was changed by variation of parameters of oxidation- reduction procedure. Investigations of SERS intensity as a function of parameters of ORC procedure and roughness sizes have been performed. The experimentally found relationship between the roughness size and observed SERS signal is compared with the predictions of the classical electromagnetic enhancement (CEME) model.

In the paper an extinction of the laser radiation at 1.06 and 10.6 micrometers wavelengths in aerosol clouds generated by burning of pyrotechnic mixtures is investigated. The results of transmission measurements and evaluated values of volume attenuation coefficient are presented for a few kinds of chloro-organometallic smoke-producing agents. An estimation of the laser ranging diminution by the pyrotechnic-derived smoke was carried out.

The new design of three-frame interferometer is proposed. The optical system of the interferometer, though very simple, has some advantages in comparison with classical interferometers (e.g., Mach-Zehnder interferometer). For registration and analysis of interferograms the CCD cameras and multichannel image acquisition system are used. The interferometer has been tested in a laser-matter experiment. Some results of plasma investigation are presented.

Sodium clusters were produced in the stainless steel cell containing sodium vapors and helium, with the aid of the laser light resonant with the Na² particles. The clusters formation was investigated. Data on the cluster size and dynamics were obtained. The theoretical model of clusters evolution based on the thermodynamics of the vapor-liquid transition was developed. The scattering of light on sodium clusters was studied and the theoretical formulas were fitted to the experimental data.

Oscillatory features of light scattering characteristics must be taken into consideration in the construction of particles' size meters because they represent one of the sources of errors. Despite this it was revealed that these oscillations themselves can provide information about particles' physical properties, especially about their size. However, one has to observe light scattered by an individual particle. Such conditions are fulfilled when the scattering particle takes part in the spectacular phenomenon called optical levitation.

The investigation of phase transition in butanediol-1,4 dimethacrylate (BDM) using Brillouin light scattering has been performed. Using this method we have studied the temperature behavior of the hypersonic velocity of BDM in the range of 290 - 323 K. The above temperature dependence displays a characteristic discontinuity in the vicinity of 298 K.

One of the nonlinear optics phenomena, discovered after lasers have been put to use, is birefringence of transparent media induced by a laser beam, known as optical Kerr effect. The report presents the development of the technique of optical Kerr effect and a review of the theories of this effect including fundamental formulas and dependencies used for interpretation of experimental data. Recent experimental techniques: nanosecond, picosecond, and femtosecond are discussed and schematic diagrams of most frequently used two- and four- component systems are given and compared. A method, developed by the author, permitting considerable improvement of sensitivity of measuring equipment is described. The application of this method enabled observation of optical Kerr effect in vapors and gases and thus systematic investigation of Kerr effect versus gas pressure and temperature. The exemplary results of optical Kerr effect measurements in liquid and gas media are given as a function of temperature, solution concentration, or gas pressure with particular emphasis put on their cognitive value. Practical applications of Kerr effect are specified. The results of OKE investigation of molecule conformation and local structure of organic liquids, water, and water solution of optically active substances which are a simple model of biological media are presented. Perspectives of further studies of optically induced birefringence of the media using the femtosecond technique are also outlined.

A study of the temperature dependence of optical Kerr effect in butanediol-1,4 dimethacrylate has been performed. The obtained results indicate the presence of a phase transition near 298 K with temperature hysteresis of Kerr effect.

Application of lasers in chemical studies and instrumental analysis has been discussed. Particular attention has been paid to the stationary and dynamic photochemical and photophysical measurements whose performance was made possible thanks to the unique properties of laser radiation, like measurement of very low quantum yield of photochemical and emission processes, dynamics of dissociation reaction, isotope separation, determination of the properties of molecules in electronic-excited states, or short-lived chemical intermediates as well as analytical use of lasers. The results presented in this work are an illustration of the progress made in spectral, photophysical, and photochemical studies thanks to the use of laser radiation.

Structure changes in laser modified surface layers of aluminum alloys -- Al-Zn,Al-Fe,Al-Fe- Ni -- and steels -- DIN X45CrSi93,C50 -- as well as high speed steel (HSS) AISI M2 (DIN 6- 5-2) were studied after laser remelting and laser alloying by means of carbide (VC) and borides (CrB, VB₂). The significant structure refinement and formation of characteristic precipitates for rapidly quenched microstructures were stated in aluminum based alloys. Fine microstructure with martensite was observed in constructional steels. Laser alloying of HSS resulted in microstructure variation and appearance of new types of precipitates enriched with W, Cr, and V, respectively. The microstructural features were discussed in relation to the stated increase of hardness in all the cases of laser modification and to the results of wear tests.

Surface laser treatment of metals comprises a number of diversified technological operations out of which the following can be considered the most common: oxidation and rendering surfaces amorphous, surface hardening of steel, modification of selected physical properties of metal surface layers. In the paper basic results of laser treatment of a group of metals used as base materials for electric contacts have been presented. The aim of the study was to test the usability of laser treatment from the viewpoint of requirements imposed on materials for electric contacts. The results presented in the paper refer to two different surface treatment technologies: (1) modification of infusible metal surface layer: tungsten and molybdenum through laser fusing of their surface layer and its crystallization, and (2) modification of surface layer properties of other metals through laser doping of their surface layer with foreign elements. In the paper a number of results of experimental investigations obtained by the team under the author's supervision are presented.

Modern methods of treatment of the surface layer allow improvement in mechanical properties of metals (an increase in the life and resistance to wear of mechanical elements as well as other properties, e.g., electrical ones). Owing to the very large temperature gradients (approximately 10⁸ K/m) and great rates of crystallization obtained, the laser treatment method is the most efficient of them all. The range of changes in mechanical properties obtained through such treatment cannot be achieved by other methods. The method of laser doping of metal surface layers offers especially distinct advantages. This is related to obtaining various and atypical heterogeneous systems in these layers. In the paper the results have been discussed of the treatment of the surface layer using a Nd-YAG pulsed laser. Studies have been carried out for metals of significance in electrical engineering: Ag, W, Mo -- as base metals and Sn, Ni, Pd and Au -- as a doping material. Special attention has been paid to changes in the microhardness of the layers obtained compared with the properties of base metals and doping metals. The results point to strong possibilities of modification of microhardness through laser doping.

This paper presents selected results of investigations on the process transport of mass within the field of laser thermic initiation for a simplified diffusivity configuration, i.e., for a configuration with an undirectional character of thermodynamic coercions. This field is characterized by a considerable thermal gradient which in a substantial way bears an influence on a resulting distribution of the concentration of the element diffusing inside the saturation zone. This influence has been observed in the case of iron saturation with chromium and carbon.

An analysis has been carried out of the time characteristics of the laser cutting process resulting from the solution of heat conductivity equation inside the steel sheet on heat sources (laser beam) inside that sheet. It is assumed that laser beam has a Gaussian spatial shape. The heat conductivity equation and boundary conditions have been derived for a 3D sheet which moves with a constant velocity v towards x direction. Results obtained were compared to solutions of quasistationary equation referring to the same problem.

In the paper a conception of deep fusion laser welding using laser pulses of complex time characteristics has been discussed. The technology of generating pulses of such a shape has already been developed on an industrial scale. The pulse envelope q(t) assumed in the analysis has a `stepwise' shape and two time intervals of different power, q'((tau) '-(tau) ') and q'((tau) '''-(tau) '), can be distinguished in it. In the first interval, the pulse power q ensures the fusion on the metal and formation of a vapor-gaseous passage. At the beginning of the second interval, a stepwise increase in the pulse power to the value q' occurs, which leads to intensive evaporation of the metal in the front part on the vapor-gaseous passage and to an increase in the pressure of metal vapors in the vapor-gaseous passage. The vapor pressure causes `extrusion' on the liquid metal from the front to the rear passage wall. The whole process is of cyclic character. In the paper, energetic process in the first and the second part of one fusion welding cycle have been analyzed. An algorithm of procedure for determining proper welding conditions has been proposed. Finally, an example of calculating technological conditions of steel-welding has been presented.

The alloying of the metal surface layer using a pulsed laser is a rather complex process. It is necessary to develop technological conditions for each pair of metals: base-alloying material. The paper presents the results of investigations into this problem for silver as a base metal and for nickel and tin as alloying materials. Studies on the laser alloying of the surface layer of Ag aim at improving its functional qualities from the viewpoint of use of Ag as a material for electrical contacts. This defines desirable properties of the modified surface layer: a uniform depth of about 100 micrometers and structural homogeneity at a set percentage variable of alloying material content. The results of previous studies allowed determination of a set of technological parameters necessary for producing a layer of an appropriate, uniform depth (duration and energy of a pulse and coefficient of coverage characterizing the degree of overlapping of successive areas of action). The two remaining requirements can be satisfied owing to the use of special methods--multiple treatment of the sole layer or multiple pulse action on particular areas of the surface under treatment.

Samples of 38HMJ steel predestined for nitriding under an eutectoid point have been laser- processed in a flow of Ar:N₂ mixture with and without the continuous optical discharge sustained over the sample surface. The resulting increase of microhardness is smaller than that observed for carbon steel samples under similar conditions. A model of the plasma in the vicinity of metal surface and results of temperature field calculations are also presented.

The upper surface of tool steel has been enriched with SiC by the laser melting method. Before the laser treatment a layer of glass-water having a suspension of SiC powder was applied on the steel surface. Melting of the surface was done with the help of YAG Nd³⁺ pulsed laser. Metallographic and x-ray analyses have been done and their results are compared with changes of microhardness.

Laser ablative acceleration method is a very useful method to study the hypervelocity impact problem (HVI), i.e., impact of accelerated foil on solid target, crater formation, and other accompanying effects. The essential problem of these investigations is to check the influence of experimental conditions (laser energy, pulse time duration, material and configuration of the target, etc.) on the velocity of the accelerated foil. In this paper, the dependence of accelerated foil velocity on the heavy layers (Ag, Au) covering Al foils was considered. Conversion of the laser energy into x-ray radiation in the heavy material layer can cause an additional acceleration of the foil due to the rise of the ablation pressure. Results obtained show that craters are smaller and more irregular compared to the results of our earlier investigations when foils without heavy cover were used. It means that the acceleration process is now less effective. These results are rather unexpected ones. Some reasons for this situation are pointed out.

The influence of laser remelting on the structure and properties of Al₂O₃ - Ni and ZrO₂ - Ni oxide layers plasma sprayed upon the Ni-base alloys has been examined. It has been stated that in the process of laser remelting there is a disappearance of open and close porosity, glazing, and formation of differentiated layer structure from the sample surface to the place of fusion with the substrate. It causes the decrease in the oxide layer thickness and increase in its adherence to the substrate, and its high temperature corrosion resistance in sodium sulphate, especially after additional diffusion chromoaluminizing.

Laser radiation action on the surface of metals allows modification of material surface layer properties. One of the latest methods of such a treatment is the laser doping of the surface layer of metals with foreign atoms. Depending on the selection of the doping material as well as on the selection of the treatment parameters one can affect changes in certain properties of the surface layer of the material under treatment (micro hardness, resistance to abrasion and corrosion, electrical properties and others). In the article a study has been presented of changes in the laser doped surface layer of conducting materials used, among other things, for electric contacts. A comparative analysis of the resistivity of based materials (W, Ag, Ni) prior to treatment has been carried out. The optimization of doping conditions from the viewpoint of obtaining lasers of set parameters has been made.

A laser method of segregation of impurities or interstitial mercury atoms (IMA) in solid phase of Hg_0.8Cd_0.2Te (MCT) is presented. A theoretical model for this process also has been proposed. Equation for diffusion of impurities or IMA was completed by a term describing the influence of phonon flux on diffusion processes. Computer simulations of the laser annealing process point out possibilities of obtaining a sharp maximum of Hg concentration for appropriately chosen parameters of laser pulse. This was experimentally verified with MCT specimens annealed by a YAG:Nd³⁺ laser.

The light scattered from the `rough' surface of a porous body illuminated by a narrow laser beam is carrying the information on geometrical micro structure of this surface. It is possible that the water vapor and water droplets in pores will cause changes in scattered light too. The aim of this paper is to present the results of the experimental investigations of the intensity of a helium-neon laser light reflected by a porous and moist gypsum slurry surface. Experiments show that the scattered light intensity increases with the decrease of the moisture content in porous material.

The vaporization of porous materials (especially internal vaporization of skeleton) has been largely ignored in studies of laser heating and processing of materials. The loss of energy associated with the vaporization process would keep the internal temperature of material from rising. In this paper the author presents the results of the computation of the heat losses for two different models of porous media: the sand and the pores' tree model. In his calculation the author uses the thermophysical parameters of gypsum slurry. In the first step a numerical simulation is carried out for the vaporization of solid skeleton and mass transport of vapor (without the viscosity of vapor), only. Then the water on the pore's wall was taken into account.

Yttrium aluminum garnets doped by Cr, Tm, and Ho have been obtained by Czochralski method using iridium crucible and HF heating. Assumed concentrations of dopants are n(Cr) equals 2.3 X 10²⁰ cm^-3, n(Tm) equals 7.9 X 10²⁰ cm^-3 and n(Ho) equals 5 X 10¹⁹ cm^-3, respectively. Moreover, the distribution coefficients for chromium (Cr), thulium (Tm), and holmium (Ho) are 2.4, 1.2, and 1, respectively. Thus, the concentrations of Cr and Tm dopants change along the crystal. Monocrystals having 28% of the initial mass of the crucible ingot and 75 mm long have been obtained. The concentrations of dopants calculated with the help of the normal freeze equation at the end of the crystal are n(Cr) equals 1.45 X 10²⁰ cm^-3, n(Tm) equals 7.4 X 10²⁰ cm^-3, respectively. The absorptive, luminescence as well as energetic properties of laser rods, having 4 mm diameter and the length equal 63 divided by 67 mm, have been investigated. It is shown that the energetic characteristics of the obtained crystals depend strongly on the annealing in the oxidizing atmosphere.

Comparative research works on spectral characteristics of monocrystals of Y₃Al₅O₁₂ doped with ions of rare-earth elements Pr³⁺, Nd³⁺, Eu³⁺, Ho³⁺, Er³⁺, Tm³⁺, monocrystals SrLaGa₃O₇ and SrLaAlO₄, doped with Nd³⁺, and LiNbO₃ doped with Er³⁺ obtained by the Czochralski method have been realized. Absorption spectra of these monocrystals have been determined in the range 200 nm divided by 20 micrometers and spectra of excitation and emission in the range 200 divided by 800 nm. Research works enabled us to estimate spectroscopic properties of these materials as active media on solid. Except for YAG:Eu⁺³ and LiNbO₃:Er⁺³ in all other materials an appearance of strong absorption bands in the range 780 divided by 840 nm has been stated as what enabled us to carry out an efficiency analysis of selective pumping with the use of laser diodes GaAlAs.

This paper presents research results on color centers induced by radiation of a xenon lamp in non doped crystals of yttrium aluminum garnet Y₃Al₅O₁₂ (YAG), strontium- lanthanum aluminate SrLaAlO₄ (SLAO), strontium-lanthanum gallate SrLaGa₃O₇ (SLGO), and in doped crystals: Nd:YAG, Cr, Tm, Ho:YAG (CTH:YAG), Nd:SLAO and Nd:SLGO. In all these investigated crystals under the influence of intensive exposure by xenon lamp radiation additional bands connected with centers O^-2, O₂ and centers F came up near the short-wave absorption edge. In the case of doped crystals the observed processes are much more complicated. In crystals CTH:YAG the greatest perturbations in relation to basic state are present at the short-wave absorption edge, as well as on areas of absorption bands of ions Cr⁺³ and Tm⁺³ conditioning the sensibilization process of ions Ho⁺³. These spectral structure disturbances essentially influence the efficiency of this process, as proven during generating investigations. In the case of SrLaGa₃O₇:Nd⁺³ under the influence of exposure substantial changes of absorption spectrum occurred on spectral areas 346 divided by 368 nm, 429 divided by 441 nm and 450 divided by 490 nm. Those changes have an irreversible character. They disappear not before the plate is being held at oxidizing atmosphere. Investigations of laser rods Nd:SLGO, CTH:YAG, and Nd:YAG in a free generation demonstrated that the color centers of these crystals are induced by pomp radiation from the spectral area up to 450 nm.

Czochralski-grown Nd-doped SrLaGa₃O₇:Nd (SLGO) crystals have been investigated for their lasing and spectral properties. Absorption spectra in the range of 180 - 8000 nm and the luminescence spectra in the range of 200 - 800 nm were measured. Differential changes of the absorption coefficient were investigated throughout the whole spectrum. Optical transitions corresponding to this effect have been indicated.

The properties of mixtures of cholesteric liquid crystals (CLC) have been studied from the point of view of application in the domain of laser engineering, particular attention being paid to optical properties, namely those of selective reflection of light from a cholesteric liquid crystal layer and circular dichroism. The properties enable us to polarize circularly laser radiation during transmission through a material layer and constitute a basis for functioning of an optical isolator. Models of a liquid crystal polarizer, isolator, and soft aperture have been designed and made.

Theoretical considerations have been realized by using a matrix method and by investigating a magneto-optical crystal under simultaneous influence of two magnetic fields: the first one, parallel to the direction of the light propagation (Faraday configuration); and the second one orthogonal (Cotton-Mouton configuration). An experiment confirms theoretical expectations, namely the possibility of extending the isolation magnitude by parallel arrangement of transmission axis of the input polarizer to the birefringence axis.

Design procedures of variable reflectance mirrors for laser output couplers are proposed. A thin-film technique has been used for vacuum fabrication of mirrors. By properly choosing both the geometry of the substrate and the masking system, one can obtain quasi-Gaussian or super-Gaussian reflectivity profiles. Such devices have been proposed and successfully tested earlier in our Nd:YAG laser oscillators.

In this paper some solutions of anti-laser absorption-interference filters are presented, satisfying demands of increased transmission in the visible range, enlarged resistance, and improved work comfort at longer usage. In order to increase the total transmission the anti- reflecting coatings were used on the glass surface. Besides the contrast increase the work comfort is improved. The anti-reflecting layers are necessary in case of using the large power lasers due to the possibility of reflection of large intensity radiation from the filter surface. A selective reflection of light by thin-layer interference pile was used in construction of anti-laser filters for several wavelengths. The absorption-interference filter was elaborated for I and II YAG:Nd laser harmonics. By depositing the cut-off type thin-layer filter onto the infrared and NIR filters virtually brightened image, very apparent rising of contrast, and a final green color well accepted by the eye were obtained.

The paper presents Fabry-Perot type interference metallic filters with double separator layers, which enables good visibility and blocks thermal radiation. Elimination of UV radiation below 320 nm is obtained by glass substratum. The UV radiation interlocking up to 400 nm can be achieved by an additional interference coating.

The major drawback of IR photodetectors is the need for cooling to suppress thermal generation of free carriers resulting in noise. New ways to improve the performance of infrared photodetectors operated without cryogenical cooling are discussed including the optimum design of the devices, the use of optical immersion of photodetectors to high refraction index lenses and optical resonant cavity. Another and very promising way, however, is the suppression of thermal generation which is governed by Auger mechanism by depletion of semiconductor in charge carriers. The combination of various methods would eventually enable achievement near-BLIP performance of IR detectors without cooling.

A brief description of construction, as well as investigation of properties of the multispectral non-cooled infrared detector, is being presented below. The detector's construction enables its sensitivity control in a wide spectrum range from 0.6 up to 11 micrometers .

A system with tunable cw-single-frequency master-YAG-laser and two Q-switched-slave lasers has been investigated. A thin-film absorbing selector has been used in the master laser. A computer-controlled piezo-ceramic driver provided tuning over 11 longitudinal modes, over 3 transverse modes, and frequency stability about 1 MHz per second. The minimum step in the back-loop system was 0.4 pm per 20 msec. A theory of active spherical cavity with thin-film selector has been developed. A optimum cavity configuration has been found.

Results of a self-injection locked, passively switched Ti:sapphire laser investigation are presented in this paper. Shortening and stabilization of pulse duration have been achieved using the SBS cell inside of the laser cavity. The main advantages of this laser and its features are shown.

Results concerning a Nd:YAG laser pumped by a diode laser array are reported. To calculate the laser output versus input power the laser rate equations for the population densities and for the total number of photons in the cavity were used.

Miniature solid state lasers were built using new active crystals (Nd:SrLaGa₃O₇, Cr, Tm, Ho:YAG, Er:YAG). Output power is equal to 30 - 40 mJ and threshold pump power of 60 - 70 J has been obtained for Cr, Tm, Ho:YAG and Er:YAG lasers.

A novel construction of grazing incidence pulsed dye laser is presented. In this laser light beam passes two times through diffraction grating. Due to that the output laser spectrum is characterized by a narrow line and a very low background caused by amplified spontaneous emission.

A method for the generation of short, single-mode CO₂ laser pulses by applying two voltage gates to an electro-optic Q-switch placed in a three-mirror cavity is proposed. The results of experimental and numerical tests of the method for a TEA CO₂ laser are presented. It is shown that the method enables the user to obtain single megawatt pulses of duration in the 1 - 10 ns range.

A longitudinal excited slow flow laser is presented. In this cooling system a head pump is used. Optical coupled two unstable resonator assembly is used. A multi electrode system in each segment of the discharge tube secured discharge stability in continuous or impulse work. A very simple electrical system is controlled by computer and can be synchronized with plasmatron or plasma gun work.

The paper presents the construction and results of investigations of a new waveguide CO₂ laser in which the synchronization of beams arising from four independent waveguide channels was realized. Thanks to that, the unitary output power of more than 1 W/cm of length, a value which is greater than that in conventional, sealed-off CO₂ lasers, has been obtained. The development of transverse, rf discharge, has increased the efficiency and reliability of the laser head and has decreased the power supply dimensions.

Experimental output characteristics of 1.2 kW cw CO₂ laser are analyzed in order to estimate the small signal gain and saturation intensity parameter. Results obtained from approximate expressions for output power under homogeneous broadening conditions of a non-flow laser are compared with measured ones. Satisfactory agreement is obtained for gain coefficient in the linear range of the laser output characteristics. The results concerning saturation intensity seem to be overestimated due to the flow effect.

Focusing conditions of the cw CO₂ laser radiation beam emitted from the stable semi- spherical resonator have been investigated theoretically and experimentally. The laser beam behavior with the distance to the resonator output has been analyzed for two cases of the beam output coupling; through the flat and through the concave-convex partial reflector. The latter forms a meniscus lens of a long focal length. The meniscus outcoupler reduces divergence of the beam leaving the resonator and also allows for higher beam diameter in the plane of the focusing lens. It results in the smaller dimensions of the focus spot and in the higher values of the radiation power density which are required for some applications.

The results of the numerical, diffraction type analysis performed for an unstable resonator designed for the high power cw CO₂ laser are presented in the paper. The analysis has been performed in order to investigate the possibility of improving the laser energy extraction efficiency and the output beam quality by applying new designs for the laser optical system.

Introducing the quasi-homogenous axial magnetic field from permanent magnets to metal- ceramic argon discharge tube it is possible to increase considerably the output power of laser. This power is approximately close to the output power of laser with a classical magnet coil. The use of permanent magnets allows it to apply an air cooling system. The cw power of air cooled argon laser with active medium length 320 mm is about 2 W and increases to 3.5 W in pulsing excitation.

Application of an axial magnetic field in ion argon lasers causes rotation of the polarization plane of output radiation. This fact increases the optical losses of the resonator. This effect can be reduced remarkably by using the crystal quartz Brewster windows instead of the fused silica ones. A Faraday effect can be calculated with the help of Jones matrix formalism. It has been shown that by using crystal quartz windows we can decrease the optical losses 10 times in comparison with the fused silica windows. This effect has been confirmed experimentally.

This paper presents an application of piezoceramic controller for stabilization of radiation frequency of the He-Ne laser using the selection and stabilization systems. There is also shown the principle of a system operation which is based on the continuous compensation of a resonator length, at the maximum of a single mode power. The structure and the principle of an operation of its particular elements are described. Moreover, the results of the controller investigations are presented, as well as other possibilities of its applications.

In this paper the requirements for single-frequency helium-neon lasers are characterized. The system of single-frequency He-Ne laser is presented with the thin-layer CWA selector operating with the stabilization of power output. In the stabilization loop the computer has been applied, co-working with the specially made for this purpose digital system of piezoceramics control. The principle of operation of computer stabilization loop of the power of single-frequency laser is described, as well as some results of investigations.

High power continuous wave semiconductor lasers (P > W) on the market give a great possibility for use in many fields of technology as well as in medical applications. Due to high price and vulnerability, these sources of radiation require especially detailed elaboration of supply, control, and protection systems. This work presents supply, control, and protection systems of the high power cw laser for medical application. The methods of control and supplying of protection for semiconductor cw laser and thermoelectric cooler were particularly described.

This paper presents a miniaturized power supply of the pulse semiconductor laser. A double- tact transistorized voltage converter is used for charging the storage capacity in the system of laser diode supply. Its parameters and construction ensure a safe and efficient working of lasers used in medical devices.

A new method has been developed for direct measurements of unsaturated and saturated gain in lasing media as well as optical losses in laser resonators. The saturation parameter can be determined if single-frequency laser performance is achieved. This method has been successfully applied to measure and compare lasing features of the media created in sputtered hollow cathode discharge (HCD) copper ion lasers operating on 780.8 nm transition.

Lasing properties of active media in hollow cathode discharge (HCD) He-Cu lasers operating on 780.8 nm line have been investigated for different kinds of hollow cathode geometries. Direct measurements of unsaturated and saturated gain, optical losses in the laser cavity and laser output power vs. resonator coupling carried over the wide range of excitation and filling conditions enable us to compare different laser media. The highest small-signal gains equal to 40%/m for a 2.5 X 6 mm rectangular slot cathode and 43%/m for a 3 mm I.D. helical cathode have been found within the pressure range where the most efficient hollow cathode effect occurs. From gain vs. oscillator intensity dependence, the saturation intensities have been calculated for a homogeneously broadened line. They increase linearly with helium pressure, hence more efficient laser operation can be obtained at higher pressures than required for the highest gain.

The paper describes an application of the GPIB system for measurement automation of the laser beam and laser devices parameters. The setup of the measurement system and examples of the obtained results, as well as methods of verification of measurements accuracy, are described. Acquisition rates obtained in our system are also given.

In this paper the authors present the results of the research that has been carried out hitherto in selected parameters of laser diode. Statistical equation of slotted line processing was defined as well as empirical ratios of the equation, which is useful to analyze metrological properties of the semiconductor laser. The above workings tend to examine the reliability of semiconductor laser processing of current input on optical radiation.

The meter of average energy of holmium laser radiation is a digital measuring instrument, made on the basis of a pyroelectric detector and single-system microprocessor from the MCS- 51 family. This device enables a measurement of a defined number of light pulses, total energy of n-laser pulses as well as the number of pulses received by a detector. The frequency of sampling signal is 25 Hz, the accuracy of measurement is 5%. This meter also enables introducing the defined transmission coefficient (measurement at the back mirror of the laser resonator) to the measurement results as well as control of operation of the output diaphragm of the laser (TTL levels).

This contribution deals with a pyroelectric device used for the measurement of laser radiation energy. Standardization method and its results obtained by using the RkP-300 type energy meter are reported.

On 3 April 1993 the Seym of the Republic of Poland passed the following acts: (1) The law on measures; (2) The law on creation of a Head Office of Measures; and (3) Polish Standard PN- 91/T-06700 Safety at radiation emitted by laser devices. Equipment qualification. Demands and directions for the user. These acts impose a necessity of metrological checking of measuring instruments used in laser technology and are of importance for life safety, health, and environment protection. Metrological checking is a test, statement and certification that the measuring instrument fulfills conditions settled in rules, standards, international recommendations and other adequate documents and its indications have been related to national standards of measure units and are consistent with them within the limits of specified measurement errors. Increasing requirements for precise dosage of laser radiation stimulates a necessity of developing a measurement base of high accuracy and requires production of devices enabling metrological checking of laser radiation measurement instruments. Special attention is paid to automation of measuring systems. In fact, the basis of metrological protection of laser technology does not exist in Poland, that is why basic tasks are presented in the paper. These problems should create an elementary basis of metrological protection of laser technology in the future.

The thirty year period of formation of laser technology has resulted in the production of many devices including lasers of various power and energy of cw or pulsed operation, working from the ultraviolet to the far infrared range of the spectrum. Such a rapid development of laser technology forces the necessity of creation of the basis of metrological protection for this technology. Considering a peculiarity of measurements, the parameters and characteristics of laser radiation can be divided into two groups: (1) energy characteristics; (2) spectral/frequency characteristics. The main interest is directed to energy characteristics and that's why a necessity of metrological protection of measurements of laser energy appears.

This paper presents the project of a laboratory model of a field-glasses range-finger. The optical transmitter of the device contains a commercial pulse semiconductor laser which generates IR wavelength around 905 nm. Some of the technical parameters of this device are: a maximum range of up to 3 km; an accuracy of +/- 5 m, divergence of a laser beam of 1 mrad; a repetition rate of 1 kHz. Dichroic elements of the receiver ensure a capability of an optimization of a field of view, without the worsening of luminance and size of an observation field.

The paper describes some of the results of a research series of the elements of the laser oscillator which are included in the set of a laser designator-rangefinder. The choice of optimized construction of a pump cavity and proper configuration of elements in a laser resonator was the subject of the investigations.

The triangulation method of range and displacement measurements using position sensitive detectors (PSD) is discussed in this paper. The laboratory model of laser triangulation range and displacement sensor built in the Institute of Optoelectronics has been examined and compared with theoretical predictions. The range and resolution of measurements of this sensor dependent on geometrical parameters of the sensor head can be varied in this model. The resolution of 0.5 micrometers of displacement measurement was achieved experimentally in laboratory conditions. The influence of light and electrical noises on linearity and resolution of measurements is discussed.

The paper presents the diagnostic measuring system of overhead cranes used in the CIM. The diagnostic measuring system is based on laser and visual techniques and computer image analysis.

The two frequency laser interferometer, using frequency stabilized HeNe laser 0.63 micrometers , is presented in this paper. The system consists of a laser head, meteo station, and measurement display. The laser system fundamentally measures linear displacement (distance) but can also measure velocity and angle. The resolution and the accuracy of measurements are comparable with parameters of lasers systems produced by Hewlett-Packard 5526A and Spindler & Hoyer ZLI 150.

A laser Doppler velocimeter (LDV) using a multi-fiber optic pickup was designed. A single fiber directs the beam to the moving surface. The back scattered signals were received by ten optical fibers. A multi-fiber laser Doppler velocimeter is (MFLDV) capable of determining the value of velocity as high as 10 mm/sec and as low as 0.031 mm/sec. A good linearity is obtained between Doppler shifted frequency (Delta) f and the velocity of a moving surface with a correlation factor of 0.999. LDV using fiber optics has important advantages over conventional systems, it is simpler, easier to align, and non-invasive i.e., the surface does not need to be touched or physically contacted.

A digital laser anemometer (DLA) built in the Institute of Optoelectronics is destined to examine Doppler signal generated in laser anemometry experiments in laboratory and semi- industrial conditions. The DLA consists of a beam forming/detection head and IBM PC equipped in oscilloscope card to digitally process the Doppler signal. The preliminary results of Doppler signal measurements for He-Ne laser and laser diode beam in the velocity range 2 - 20 m/s are presented. The rms error of measurements was about 0.5%.

A new experimental double beam system for dynamic studies of absorption transitions from initially populated excited states is described. In this system a high power picosecond YAG:Nd³⁺ laser (Quantel YG 570 C) equipped with generators of second, third, and fourth harmonics serves as an excitation source. The fundamental ((lambda) equals 1064 nm) beam is used for generation of the picosecond continuum which serves as an analyzing light. The temporal relation between incident beams is determined using both variable and fixed delay lines. A M-532.22 translation stage (POLYTEC) is used for micropositioning of a movable cube-corner prism in the optical delay line. A photomultiplier or an OMA detector are applied for measurements of the transient absorption dynamics. A PC 286 microcomputer controls the sequence of operation of all elements of the system and also processes the experimental data. The results of initial tests of this system are presented.

The aim of this device is a quantitative analysis of NO₂, SO₂, (or any NO_x, SO_x) content and concentration in the air. It works as an optical spectral correlator and can use either dispersed sunlight (on board version) or any active light, for example, incandescence lamps.

The LMM-1 laser microanalyzer realizes for the first time a patented device which permits a quantitative analysis of the composition of both metals and materials of the non-metal group, including thin metal and dielectric coatings (from 0.2 to 2 micrometers). This analyzer has the following main parameters: analyzed elements, from Li (No. 3) to U (No. 92); dynamic range of concentration measurements (depending on the number of analyzed elements), (10^-3 - 10^-2) to 100%; maximum concentration measurement error, 1%; measurement time, 1 min. The LMM-1 microanalyzer has been created with the aim of developing an automated microanalyzer on the basis of the latest achievements of laser engineering and metrology, spectral and computing engineering, as well as systems software in the form of a single bank of spectrochemical parameters of materials and substances to ensure new qualities of the majority of materials, especially of semiconducting materials and crystals, to meet the demands of microelectronics and other allied branches of the industry.

A model of transmissometer based on a visible diode laser light source is described. The instrument is mainly destined for visibility measurements in foggy and polluted air. It features an integrated construction of transmitter and receiver. The emitted laser beam is reversed to the unit by a remote prism assembly that can be placed several meters away from the instrument. To compensate the instability of both the light source and the detector an internal compensating light path as well as other means were applied. The description of the model has been preceded by the analysis of visibility measurement accuracy.

In the paper the influence of noise on automated detection and analysis of splices in long optical telecommunication lines is discussed.

The paper presents a measuring method of radiation absorbed by biological tissues during the biostimulative intervention. The proposed set is useful for an analysis of absorption changes as well as enabling us to define a radiation dose. The measurements are performed indirectly by analysis of the beam reflected from tissues. The elaborated device can work within the range of radiation 600 divided by 1500 nm, especially radiation obtained from semiconductor lasers (cw and pulse).

The author points out major dust particle size ranges and the scope of their noxious effect on human environment. Also, a dependence of the shape of scattering indicatrix on the size dust particle and the relation of the former to light wavelength are shown. This writer introduces his own design of a measuring head used in the research on the scattered light energy distribution in small solid angles. Examples are given of trial measurements of laser light affecting monofractional dusts with diameter ranges of interest within the study. An attempt has been made to determine the non-discrimination range of dust particles with slightly different radii. Finally, the author points out the further direction of the continued research.

The aim of this work is to present the limits of application of some often-applied criterions of evaluating frequency bandwidths, and to compared the results obtained with those of the so- called informational criterion of frequency bandwidths. Forty-two coefficients of bandwidths were given calculated for seven typical signals according to six definitions of spectral bandwidths applied. it was demonstrated that the problem of evaluating changes of spectral bandwidths cannot be solved by applying any definition of frequency bandwidth separately considered, as cases are possible where patented systems for contracting spectral bandwidths of frequency for some signals could, by other criterions of spectral evaluation, operate as systems of widening the spectral bandwidths. Attention was called to the utility of continuing further investigations on limits of application of the informational criterion of spectral bandwidths W₀ for a wider range of signals, also on its connections with internationally adopted energetic criterions of evaluating the frequency bandwidths for different signals.

Initial stages of digital analysis require proper preprocessing operations in order to prepare images to appropriate processing. The article concerns software tools used for projection of initial image preprocessing operations package by the user.

Genetic algorithm (GA) has been developed to solve the optimal filtering problem over the class of adaptive neural filters. Computational experiments confirm the applicability of GA technique to adaptive nonlinear filtering for one-dimensional (1-D) signals.

Kinoform is a phase modulating computer-generated hologram. Most often, algorithms for nonparaxial kinoform synthesis use discrete propagation operators and solution is given in a discrete form. Kinoform is obtained by interpolation from these discrete samples in its plane. This paper gives the relationship between the continuous reconstruction of that kinoform and the discrete synthesis solution in the image plane. The relationship allows us to describe complex amplitude distribution in diffraction orders, predicts the possibility of speckle-like reconstruction, and is a basis for an efficient method of zero-order image calculation. Spatial frequency filtering properties of discrete algorithms are analyzed and criteria for algorithm sampling parameters are derived.

The use of pulsed laser (e.g., Nd-YAG) in the treatment of the surface layer of metals requires focusing radiation to achieve a desirable value of the surface power density. In the paper a comparison of the laser surface treatment of different metals using radiation pulses focused by means of a spherical and cylindrical optical system has been presented. Different conditions of the technological process and effects obtained in both cases have been analyzed. Objectives containing spherical lenses are in common use, which ensures circular symmetry and exact mapping of the distribution of power density in the beam focused on the surface under treatment. This symmetry also simplifies the analysis of temperature fields caused by energy pulse absorbed. In this case, the boundary surface of the fused zone has approximately a spherical shape. The fusion area structure shows a radial symmetry corresponding to the temperature distribution during solidification. Shaping a beam by means of cylindrical lenses of different focal lengths causes the beam to have a shape in the focus that can be approximated with an ellipse or a rectangle. The surface distribution of power density results in diversified conditions of melting. The shape of boundary surface of the fused zone and the structure orientation in the fused area change. In some cases this manner of focusing a laser beam provides better conditions for obtaining a modified surface layer of the metal.

One of the ways of using laser in industry is its usage in loss treatment of wood and composite wood products. In the furniture industry the above mentioned machining is used in such technological processes in which tool machining (sawing, molding) is not economical or even possible. These processes are mainly curvilinear cutting of layer materials like veneers, plywood, and face layers and thicker materials like particleboards, fiberboards, and lumber- core panels. Wide usage has also been achieved in heat treatment in wood for decoration. It can be calcinating designs, engraving them, blackening of parts of surfaces, or changing of anatomic characteristics of wood tissue. Nevertheless laser usage in recliner cutting seems at present causeless.

To cut inlay from a stack of glued veneer a CO₂ HEBAR-1A laser was used. For setting optimal working parameters of the set used in industrial production of inlay the following elements were defined: the shape and dimensions of the cutting fissure, the dependence between the width of the cutting fissure and the speed with which the laser beam moves and the total thickness of the stack of veneer sheets, the application of the laser for cutting various patterns. Computer aided designing and computer steering of the laser beam enables fast and precise production of large numbers of inlay elements not only from wood but also from other materials like glass, stone, metal, etc. Taking into consideration the high running cost of such a laser set and its very big production only few factories or even one factory in the given area could produce inlay ready for gluing. Further investigation should be carried out on this field particularly considering the lowering of costs not only in inlay production but generally where cutting of wood is concerned.

A system for laser beam deflection and its particular application described in this paper can be treated as a technical aid for contemporary art and visual enhancement of electronic music equipment. The device for special art effects produced by `Optocyfronika' was ordered by disco-clubs. The equipment was designed to enhance light effects with images obtained by means of laser light. One of the results of this work is the device for drawing of simple images by means of the laser beam.