In this article authors present the developed optoelectronic set for controlled, repeatable exposure by electromagnetic radiation of biological structures in the spectral band of tissue transmission window 600-1000 nm. The set allows for an objective selection and control of exposure parameters and comparison of results for variable energetic, spectral and polarization parameters of radiation beam. Possibility of objective diagnostics of tissue state during laser treatment was provided in the presented optoelectronic set.

Background: The main purpose of this study was to analyze the influence of power intensity and wavelength of Low Level Laser Therapy (LLLT) and HILT (High Intensity Laser Therapy) on endothelial cell proliferation.
Material and methods: The tests were done on human umbilical vein endothelial cells (HUVEC). Cultures were exposed to laser irradiation of 660 nm and 670 nm at different dosages, power output was 10 – 40 mW as well as 820 nm with power 100 mW and 808 nm with power 1500 mW. Energy density was from 0.28 to 11,43 J/cm². Cell proliferation of a control and tested culture was evaluated with a colorimetric device to detect live cells. The tests were repeated 8 times.
Results: We observed good effects of LLLT on live isolated ECs and no effects in experiments on previous deep-frozen cultures. Also HILT stimulated the proliferation of HUVEC.
Conclusion: Endothelial cells play a key role in vascular homeostasis in humans. We observed the stimulatory effect of LLLT and HILT on proliferation of HUVEC. Many factors influence the proliferation of EC, so is it necessary to continue the experiment with different doses, intensity and cell concentration.

The pulsed dermatologic laser for photothermolysis is constructed basing on technology of 975 nm diode lasers developed for fiber-laser excitation. In near future these lasers can replace ND:YAG ones for dermatologic applications, especially therapy of deep skin diseases.

Fluorescence analysis of dry samples of biological origin like pollens, fungi, flours and proteins was presented. In the laboratory study presentenced here two fluorescence methods using semiconductor light sources were applied. Firstly, laser induced fluorescence emission (LIF) spectra of the samples were recorded under 266 and 375 nm excitation. The second technique covered fluorescence decay (FD) at 280 and 340 nm excitation. Hierarchical Cluster Analysis (HCA) of acquired spectra and decays was performed. Both LIF and FD showed that single wavelength excitation 266 and 280 nm, respectively allow distinguishing of pollens from other samples. Combining data of both excitation wavelengths, for LIF and FD, respectively, resulted in substantial improvement of data classification for groups according to the samples origin.

Photocoagulators are one of the most popular laser devices in medicine. Due to different kind of interaction of particular wavelength range of laser light with live tissues, sources of laser radiation which can cover as much as possible of visible spectrum are still very wanted (see [1,2]). In last years it also can be observed the intensive developing works on new photocoagulation technique called “micropulse coagulation” [3,4]. The most critical feature of lasers for micropulse coagulation is the possibility of fast switching between two selected laser power values. It seems that the good proposal for these applications can be ion laser filled with argon-krypton mixture. Authors previously have indicated the possibility of improvement of generation conditions in this type of laser in presence of buffer gases [5,6] and with use developed by authors pulse supply regime [7,8]. These improvements allow to obtain output power values of most important argon and krypton laser lines in laser filled with mixture of both gases, similar to values available in laser filled with pure gases. Presented in this paper the following researches are concerned on verification of possibilities of use of the developed laser system in photocoagulation with possibility of use of the laser system in micropulse coagulation technique.

This paper concerns the fundamentals, construction and operation of low-cost devices for treatment of superficial skin injuries by blue-violet light irradiation. The biophysical background of therapeutic properties of blue-violet light is described and technical aspects of construction of devices for the phototherapy are discussed. Prototypes of two variants of the device are presented: portable, for individual users in random locations, and stationary, for clinical applications.

In applications of high power hand lasers, as addition to the standard eyes protection, it is suggested to use protective garment to avoid skin burns. Fabrics used for this kind of garment have to pass respective qualification tests. One of test procedures is optical characterization of the fabric - measurement of its reflectance, transmittance and angular characteristics of reflection of laser radiation. In this article a method for simplified measurement of these features is presented, which uses light reflection models called BRDF (Bidirectional Reflection Distribution Function) and function fitting with numerical optimization. It allows for quantitative estimation of mentioned optical properties with lower effort and shorter time than with classical methods.

The article describes application of cavity enhanced absorption spectroscopy (CEAS) for detection of nitrogen oxides and vapours of explosives. The oxides are important greenhouse gases that are of large influence on environment, living organisms and human health. These compounds are also markers of some human diseases as well as they are emitted by commonly used explosives. Therefore sensitive nitrogen oxides sensors are of great importance for many applications, e. g. for environment protection (air monitoring), for medicine investigation (analyzing of exhaled air) and finally for explosives detection. In the Institute of Optoelectronics MUT different types of optoelectronic sensors employing CEAS were developed. They were designed to measure trace concentration of nitrogen dioxide, nitric oxide, and nitrous oxide. The sensors provide opportunity for simultaneous measurement of these gases concentration at ppb level. Their sensitivity is comparable with sensitivities of instruments based on other methods, e.g. gas chromatography or mass spectrometry. Our sensors were used for some explosives detection as well. The experiment showed that the sensors provide possibility to detect explosive devices consisting of nitroglycerine, ammonium nitrate, TNT, PETN, RDX and HMX.

For limitation of the noise in environment, the necessity occurs of determining and location of sources of sounds emitted from surfaces of many machines and devices, assuring in effect the possibility of suitable constructional changes implementation, targeted at decreasing of their nuisance. In the paper, the results of tests and calculations are presented for plane surface sources emitting acoustic waves. The tests were realized with the use of scanning laser vibrometer which enabled remote registration and the spectral analysis of the surfaces vibrations. The known hybrid digital method developed for determination of sound wave emission from such surfaces divided into small finite elements was slightly modified by distinguishing the phase correlations between such vibrating elements. The final method being developed may find use in wide range of applications for different forms of vibrations of plane surfaces.

In presented work the analysis of liquid fuels with use of optical spectroscopy was performed. The fuels were examined with the use of two fluorescence techniques: steady-state fluorescence and time-resolved fluorescence. Recorded excitation-emission matrices (EEMs), with the use of steady-state fluorescence, allowed for estimation of the absorption and emission maxima, classification of the fuels was partially possible. Time-resolved fluorescence allowed for classification of the fuels into four groups. Among examined fuels the longest time of fluorescence decay was observed in diesel, petrol Pb98 and Pb95, in descending order.

For the last few years we were elaborating the laser-fiber vibrometer working at 1550 nm. Our main stress was directed towards different aspects of research: analysis of scattered light, efficient photodetection, optimization of the fiber-free space interfaces and signal processing. As a consequence we proposed the idea of a multichannel fiber vibrometer based on well developed telecommunication technique – Wavelength Division Multiplexing (WDM). One of the most important parts of a fiber-laser vibrometer is demodulation electronic section. The distortion, nonlinearity, offset and added noise of measured signal come from electronic circuits and they have direct influence on finale measuring results. We present the results of finished project “Developing novel laser-fiber monitoring technologies to prevent environmental hazards from vibrating objects” where we have constructed a 4-channel WDM laser-fiber vibrometer.

The paper discusses the experimental results pointing to the efficient channel of the CO vibrational to the C₂ electronic energy-transfer. The radiation spectra D¹Σ_u - X¹Σ_g , known as Mulliken bands, are investigated and the relation of their kinetics to a vibrational excitation of CO molecules in the He-CO-O₂ plasma is discussed. The rate constant for VE process ( CO(v ≥ 25) + C₂ → CO(v - 25) + C₂(D¹Σ_u) ) is estimated, kVE ~ 10^-14 см³/с.

Hazardous chemicals detection systems based on cascade lasers are wider and wider used for monitoring the earth atmosphere pollution, as well as in the safety apparatus installed in buildings of public services. The main feature of these systems is a high sensitivity that for the most advanced set ups allows detecting chemical substances at the level of single ppt (part per trillion). In this paper, we present a measuring system dedicated to detecting hazardous chemical substances in which a semiconductor cascade laser has been implemented for the generation of IR radiation. The system operation and potentialities are exemplified by its application to detecting and monitoring the ammonia concentration in the air.

The paper presents results of direct micromachining and direct interference lithography using high power laser. The technology allows one step (direct) manufacturing of surface structures in micro- and submicro-scale with well defined long-range arrangement. Construction of the two-channel laser system creates arms of the Mach-Zehnder interferometer, which allows fast and easy change of the interference pattern parameters as well as control of energy density in the interfering laser beams.

This paper presents the analysis of the impact of selected process parameters on the resulting laser color marking. The study was conducted for AISI 304 multipurpose stainless steel using a commercially available industrial fiber laser. It was determined how various process parameters, such as laser power, scanning speed of the laser beam, temperature of the material, location of the sample relative to the focal plane, affect the repeatability of the colors obtained. For objective assessment of color changes, an optical spectrometer and the CIE color difference parameter ΔE_ab * were used.

In modern machines for realization of goals like lubrication intesyfication, heat flow intensyfiacation, microflow simulation; more and more often surface texturing is used. It became possible due to develepment of technologies that use sources of concentrated energy stream like microlasers. The paper shows results of experimental investigation on seal rings made of silicon carbide. Experiments were conducted using seal rings without surface modifications and a seal rings with a geometrical surface textures made with Nd:Yag laser.

In cooperation with the Institute of Optoelectronics MUT, the Institute of Ceramics and Building Materials conducts work on laser decoration of ceramic products. Two methods are under development: laser activation and laser sintering. The activation method is based on change of color of specially prepared ceramic material due only to illumination by laser beam. Laser sintering is a deposition welding process in which a layer of ceramic powder is deposited on the substrate material, and the two ceramic materials are fused through the application of laser beam, in turn creating any desired color pattern. The paper describes the influence of some physical phenomena on the progress of the laser process as well as sample experimental results.

Absorptance is the base parameter that is determining the energy coupling of a laser radiation into workpiece during its laser treatment. The absorptance for AlSi12/SiC_p composites along with their temperature’s dependence for the AlSi12 alloy matrix and for wavelengths that correspond to DL, Nd:YAG and CO₂ lasers were investigated. Based on the absorptance, the characteristic laser energy densities at which the surface of the metal matrix composite reaches melting temperature were estimated. This estimation was crucial in order to find the bottom level of energy densities, i.e. operational parameter window for AlSi12/SiC_p laser melting. Using higher energy densities than the characteristic the surfaces of the AlSi12/SiC_p were remelted. In this process the industrial Diode and Nd:YAG lasers were used. Laser remelted composites were subjected to methods of XRD, hardness and residual stress tests. The tests showed that the control of the laser energy density during the laser treatment of the AlSi12/SiC_p allowed to obtain a refine structure of the composite matrix. This refine structure is advantageous for the improvements in hardness and corrosion-resistant of the investigated AlSi12/SiC_p composite surface.

In this work formation of highly wear resistant metal matrix composites (MMC) surface layers on the titanium-based Ti- 6Al-4V alloy by means of laser dispersing of SiC powder is investigated. In the process, the substrate surface is locally melted to the depths up to about several hundreds μm by the slightly defocused high power laser beam. Simultaneously, SiC powder particles of irregular shape and average size of about 80 μm are injected into the molten material and single traces are produced. The optimal process parameter windows for the laser dispersing of SiC particles in Ti-6Al-4V substrate are searched for high power cw CO₂ and disk lasers. The results for both laser sources are compared and the applicability of the CO₂ laser in the treatment of Ti alloy is confirmed.

This paper presents another technique of manufacturing the unit cells of spiral-shaped resonators - SR on the aluminium nitride (AlN) ceramics. In this technique the AlN plane surface is irradiated by the Nd:YAG (1.06 μm). As a result of the supplied energy, the rupture of aluminium and nitrogen bonds occurs. Consequently, on the dielectric surface the conductive aluminium "paths" are formed. Obtaining the low-ohm conductive structures allows deploying this method to manufacture SR structures which can be used in antennas in order to reduce their coupling. An advantage of the demonstrated method is a possibility of selective and direct metallization of the AlN ceramics surface without a mask as it is required in photolithography process, which greatly reduces the implementation time of the projected metamaterials structures.

The photocatalytic activity of TiO₂ layer modified by laser radiation is discussed in the paper. Commercially available nanopowder P25(Degussa) was used, which consists of a mixture of anatase and rutile - two crystallographic forms of TiO₂ . The spin-coating technique was applied to produce thin layers on glass. After drying and calcination the layer was thermally modified using a pulsed (6 ns) Nd:YAG laser (FHG 266 nm). This caused a clearly visible surface darkening effect. The XRD spectra show that phase change transition (from anatase to rutile) took place partially. This was also confirmed by Raman spectra. The main peak of Raman-spectra shifts from 142,84 to 145,22 cm^-1, probably due to decreasing size of TiO₂ nanoparticles or more probably due to a defects generation in nanocrystallite structure. Defects have been reported in the literature as surface oxygen depletion and generation valance states Ti³⁺ and Ti⁴⁺. Eventually, kinetics of methylene-blue decay and CO₂ to methane conversion were examined. In both cases an increase of catalytic activity was observed.

Set of different physical processes has crucial influence on the required precision in case of shaping of elements with dimensions less than tenths millimeter by means of a laser beam, both in terms of the 3D geometry and the structure of the material in micro-volume. Many issues in the field of micrometer scale materials can be solved and used in practice by modeling processes. This article presents some selected examples of accomplished laser microtechnologies, using beam of nanosecond pulses of fiber laser, successfully supported by computer modeling. Using a pulsed fiber laser beam in the process of a thermal ablation spatial structures of micro elements in ceramic and semiconductor materials were produced. Optimum range of process parameters to ensure efficient removal of material, and acceptable quality of a surface of made elements was set by modeling. In micro-technologies, where structures with submillimeter dimensions are formed, modeling of the process with the phase transition phenomena requires taking into account the energy coupling of a beam – material, nonlinear thermal phenomena and the difficult to modeling problems associated with moving phase boundary as well as latent heat of phase transition.

We investigated the dynamics of laser generated ablation plasma plume expanding in ambient air and dynamics of the sound wave generated by the expanding plasma. The ablation plasma plume was generated during nanosecond laser micromachining of the thin metal foil. The time-resolved images of the expanding plasma plume and sound wave were captured at several nanosecond intervals. Using captured images the expansion rate of the plasma plume was determined. The initial velocity of the plasma was found to vary from 6.0•10³ m/s ± 0.3•10³ m/s to 7.3•10³ m/s ± 0.3•10³ m/s depending on the laser fluence. The initial velocity of the sound wave generated by the expending plasma plume also varies with laser fluence. We also investigated sound wave using acoustic microphone. Based on obtained results we proposed a method for automatic focusing of the laser beam before laser micromachining that involves sound wave acoustic signal analysis.

The study reported here is part of a larger research project on laser-beam welding conducted at the Centre for Laser Technologies of Metals. The primary objectives were to compare laser-beam welding with a conventional process when used for longitudinal seams in street lamp posts, to select the process parameters for girth welds in cylindrical high-strength steel machine elements, and to assess whether laser-beam welding can be used for magnesium alloys. The paper includes recommendations for the selection of welding parameters.

The study of laser bead-on-plate welding of nickel based superalloy Rene 77 using single mode high power fiber laser has been undertaken to determine the effect of process parameters, such as laser power, welding speed and laser beam defocusing, on the weld geometry and quality. Non-porous and crack-free welds can be achieved for a relatively wide range of fiber laser welding parameters. The welding speed has a major effect on the weld aspect ratio. The laser beam defocusing significantly affects the weld bead geometry, the stability of the keyhole and pore formation. The transition from keyhole mode to conduction mode welding occurs between focal point position +2.0 mm and +4.0 mm. The high porosity was observed at the focal point position of +2.0 mm. The heat input higher than18 J/mm results to hot cracking in the heat affected zone (HAZ). Moreover, it was found that the welds with the weld aspect ratio higher than 1.5 contain cracks, which propagate from the HAZ into the weld metal.

The paper describes the application of single mode high power fiber laser (HPFL) for the welding of nickel based superalloy Inconel 625. Butt joints of Inconel 625 sheets 0,8 mm thick were laser welded without an additional material. The influence of laser welding parameters on weld quality and mechanical properties of test joints was studied. The quality and mechanical properties of the joints were determined by means of tensile and bending tests, and micro hardness tests, and also metallographic examinations. The results showed that a proper selection of laser welding parameters provides non-porous, fully-penetrated welds with the aspect ratio up to 2.0. The minimum heat input required to achieve full penetration butt welded joints with no defect was found to be 6 J/mm. The yield strength and ultimate tensile strength of the joints are essentially equivalent to that for the base material.

The following article describes results of investigations on influence of laser welding parameters on the weld shape, quality and mechanical properties of 2.5 mm thick butt joints of thermo-mechanically rolled, high yield strength steel for cold forming S420MC (according to EN 10149 - 3 and 060XLK according to ASTM) welded with high power diode laser HPDL ROFIN SINAR DL 020 with rectangular laser beam spot and 2.2 kW output power, and 808 nm wavelength. The investigations at the initial stage were focused on detailed analysis of influence of the basic laser welding parameters such as laser power and welding speed on the shape and quality of single bead produced during bead-on-plate welding. Then the optimal parameters were chosen for laser welding of 2.5 mm thick butt joints of the thermo-mechanically rolled, high yield strength steel sheets for cold forming S420MC. The test joints were prepared as single square groove and one-side laser welded without an additional material, at a flat position. Edges of steel sheets were melted in argon atmosphere by the laser beam focused on the top joint surface. The test welded joints were investigated by visual inspection, metallographic examinations, mechanical tests such as tensile tests and bending tests. It was found that the high power diode laser may be applied successfully for one-side welding of the S420MC steel butt joints. Additionally it was found that in the optimal range of laser welding parameters the high quality joint were produced.

The following article describes results of investigations on influence of laser welding parameters on the weld shape, quality and mechanical properties of 2.0 mm thick butt joints of titanium alloy Ti6Al4V (Grade 5 according to ASTM B265) welded with a new generation disk laser TRUMPF TRUDISK 3302, emitting at 1030 nm, with maximum output power 3300 W at circular laser beam spot, characterized by laser beam divergence 8.0 mm•mrad. The test butt joints of Ti6Al4V titanium alloy sheets were prepared as single square groove (I-type joint) and one-side laser welded without an additional material, at a flat position, using a specially designed system for shielding gas (purity 99.999%). The investigations at the initial stage were focused on detailed analysis of influence of the basic laser welding parameters such as laser power and welding speed on the shape and quality of single bead produced during bead-on-plate welding. Then the optimal parameters were chosen for laser welding of 2.0 mm thick butt joints of the titanium alloy Ti6Al4V. Edges of the titanium alloy sheets were melted in argon atmosphere by the laser beam focused on the top surface of butt joints. The test welded joints were investigated by visual inspection, metallographic examinations, hardness and micro-hardness measurements and mechanical tests such as tensile tests and bending tests. It was found that the welding mode is a keyhole welding and providing high quality of joints requires a special techniques and conditions of laser welding, as well as special gas shielding nozzles is required.

In the paper are presented new analytical modeling of deep penetration laser welding and its experimental verification. The model is an extension of analytical model of 1973. The model allows the derivation of penetration and width of melting zone caused by moving laser beam. As a result there was derived dependences of penetration length, width of the melting zone and aspect ratio of the zone as a function of welding speed and laser power. The theoretical results was compared with experimental data. The results allows the determination of optimal conditions for keyhole effect. Results of the modelling are expressed in non dimensional parameters therefore can be applied to any metals and alloys for design of laser welding parameters.