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▪ RESUMO Introdução: Cicatrizes hipertróficas e queloides causam dano estético e funcional e são de difícil tratamento. O objetivo desta revisão foi identificar estudos prospectivos do tratamento com o laser fracionado de CO2, mostrando as alterações clínicas e histológicas e a metodologia utilizada para a avaliação das cicatrizes antes e após intervenção. Métodos: Foi realizada uma revisão eletrônica (LILACS, Medline e SciELO) de estudos publicados entre janeiro de 2004 e dezembro de 2017, com os termos “keloid/queloide”, “hypertrophic scar/cicatriz hipertrófica” e “laser CO2”, de acordo com o PRISMA Statement, sendo selecionados os estudos que comparassem as cicatrizes antes e depois de tratamento isolado com laser fracionado de CO2. Os dados foram analisados por dois revisores independentes. Resultados: Foram analisados 102 artigos, sendo que 7 cumpriam os critérios estabelecidos. Destes, os 7 analisaram cicatrizes hipertróficas, 2 deles também analisaram queloides, e 3 estudaram alterações histológicas. Houve diferença estatística entre os escores clínicos medidos antes e após tratamento de cicatrizes hipertróficas na maioria dos estudos, com melhora nos sintomas, na flexibilidade e altura da cicatriz. Entre os 2 estudos que analisaram os queloides, 1 deles demonstrou diferença clínica após tratamento. Nas alterações histológicas, houve diferença na orientação e densidade das fibras de colágeno e na espessura da epiderme. Conclusão: O laser fracionado de CO2 deve ser considerado como opção promissora no tratamento de cicatrizes patológicas, visto que melhora os sinais e sintomas clínicos como cor, espessura e prurido. ▪ ABSTRACT Introduction: Hypertrophic scars and keloids cause aesthetic and functional damages, and are difficult to treat. This review aimed to identify prospective studies on fractional CO2 laser to present the clinical and histological changes and the methodology used for the evaluation of scars before and after intervention. Methods: We conducted an electronic review (LILACS, Medline, and SciELO) of studies published between January 2004 and December 2017, using the search terms “keloid/queloide,” “hypertrophic scar/cicatriz hipertrófica,” and “CO laser, ” according to the PRISMA Statement. Studies that compared scars before and after isolated treatment with fractional CO2 laser were selected. Two independent reviewers analyzed the data. Results: One hundred two articles were analyzed, of which 7 met the inclusion criteria. Of the 7 articles, all analyzed hypertrophic scars, 2 analyzed keloids in addition to hypertrophic scars, and 3 analyzed histological changes. Most studies showed a statistically significant difference in clinical scores between before and after treatment of hypertrophic scars, with improvement in symptoms, flexibility, and scar height. Between the 2 studies that analyzed keloids, 1 reported a clinical difference after treatment. The histological changes showed significant differences in the orientation and density of the collagen fibers, and in the thickness of the epidermis. Conclusion: The use of fractional CO2 laser should be considered as a promising treatment option for pathological scars, as it improves clinical signs and symptoms such as color, thickness, and pruritus.

Spectra of meteor plasma, their dynamics and dominant spectral features are usually a subject of mathematical modelling and computations. In our study, on the other hand, we describe and evaluate the advantages and limitations of the experimental techniques employed for meteor spectra simulations. The experiments are performed by ablating meteorite samples using a series of laser sources, i.e. a large terawatt−class gas laser infrastructure PALS, a high-power Ti:Sapphire femtosecond laser, and laboratory Nd:YAG and ArF excimer lasers. We demonstrate that, notwithstanding the importance of theoretical spectra computation, laboratory experiments may remarkably enhance the qualitative and quantitative evaluation of the meteor emission spectra measured, as well as the assignment of important spectral features therein. We also perform completing experiments to compare the laser-target interaction observed with the expected dynamics of evaporation and disintegration of a real meteoroid body.

The results of experimental studies are presented and the experience of operating the power supply of a continuous gas laser, which is based on a lithium–polymer storage battery without an intermediate voltage converter, is analyzed. The long-term (more than 4-year) operation of a high-voltage battery power supply as a component of a laser system with an open-circuit voltage of 7.76 kV, a load voltage of 6.1 kV, a load current of up to 250 A, a power higher than 1.5 MVA, and a stored energy of 550 MJ is demonstrated. The response time of the switch for disconnecting the load in the case of breakdowns in the discharge chamber did not exceed 120 μs. The results of measurements of the internal resistance of the batteries and its changes during operation are presented.

Based on a previously developed mathematical model describing the behavior of the window of a multi-kilowatt laser with an unstable cavity, the case of a two-component output window is considered. The two-component window consists of a transparent annular polycrystalline diamond and a central opaque area, separated by a plastic vacuum gasket. To reduce the heat load, the central opaque part is equipped with a cooler. Numerical calculations of thermomechanical processes for such windows used in high-power CO2 lasers are carried out. The mathematical model used for the calculations consists of three parts: thermophysical, mechanical, and optical. The advantages of the two-component design with a cooler being used with a multi-kilowatt gas laser are demonstrated. The dependences of the maximum admissible output radiation power, temperature distribution, and mechanical stresses on the window thickness are obtained. Conditions under which such an output window should not only successfully withstand the extreme radiation loads, but also ensure the minimum possible divergence of the outgoing radiation are considered.

The prospects of hybrid laser-plasma cutting of metals have been justified, a design of an integrated plasmatron for hybrid cutting was proposed and the results of laser-plasma cutting of carbon sheet structural steels using such an integrated plasmatron were forecasted. It was shown that in order to minimize losses of laser radiation and obtain maximum penetration, it is advisable to assemble the integrated plasmatron according to a coaxial scheme with an axial arrangement of laser radiation and a minimum inclination of non-consumable electrodes (one or more), the distance from the working end of which to the axis of the laser beam should lie in the range of 2...3mm. The diameter of the plasma-forming nozzle should lie within 2–5mm and depth of focus under the surface of the cut sheet during hybrid cutting should be 1–2mm. To simulate the processes of laser, plasma, and hybrid cutting, the SYSWELD software package was used which became possible due to taking into account the characteristic for cutting effect of removing sections of molten material in the cutting zone, performed by replacing the maximum overheating temperature during the calculation with the initial temperature (20°C). The main parameters of the regimes of laser-plasma cutting were established which has made it possible to obtain minimum HAZ size with cut quality approaching that of the laser cut. At the same time, hybrid cutting requires an energy input of approximately half that of the air-plasma one. An increase in the speed of hybrid cutting by increasing the pressure and consumption of working gases makes it possible to compare energy input with the same indicator of gas laser cutting with more than a three-fold increase in the productivity of the process

A new automated control system is developed for the In-Gas Laser Ionization and Spectroscopy (IGLIS) laboratory at KU Leuven. The IGLIS Control System is capable of stabilizing a narrowband single-mode tunable diode laser with a standard deviation of 1.14 MHz. Furthermore, the system controls and synchronizes all data acquisition for multiple techniques from resonant laser spectroscopy in gas cell or in gas jet to atomic Planar-Laser Induced Fluorescence (PLIF) spectroscopy of copper atoms seeded in a supersonic gas jet. The IGLIS Control System is validated by measuring the hyperfine splitting parameters of the ground state transition at 327 nm in 63Cu. A new automated control system is developed for the In-Gas Laser Ionization and Spectroscopy (IGLIS) laboratory at KU Leuven. The IGLIS Control System is capable of stabilizing a narrowband single-mode tunable diode laser with a standard deviation of 1.14 MHz. Furthermore, the system controls and synchronizes all data acquisition for multiple techniques from resonant laser spectroscopy in gas cell or in gas jet to atomic Planar-Laser Induced Fluorescence (PLIF) spectroscopy of copper atoms seeded in a supersonic gas jet. The IGLIS Control System is validated by measuring the hyperfine splitting parameters of the ground state transition at 327 nm in 63Cu. ispartof: Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms vol:463 pages:297-301 ispartof: location:SWITZERLAND, CERN, Geneva status: published

© 2019 Elsevier B.V. Radio-frequency (RF) ion guides, also known as Linear Paul Traps, are powerful devices to efficiently transport ion beams from high to low pressure regions while keeping good ion optical properties. A set of ion guides comprising three different RF quadrupole (RFQ) structures has been designed using ion-trajectory simulations to improve the performance of the In-Gas Laser Ionizations and Spectroscopy (IGLIS) technique currently under development at KU Leuven. Results of the commissioning tests for the total transport efficiency and transient time through the ion guides as well as the longitudinal energy spread and transverse emittance are found to be in agreement with ion trajectory simulations considering a realistic ion-atom interaction potential. ispartof: Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms vol:463 pages:148-153 ispartof: location:SWITZERLAND, CERN, Geneva status: published

The realization of output of the controllable transverse mode in a laser resonator has always been the key problem in applications of lasers. At present, the theory of optical resonators for passive resonators is relatively mature, but the non-uniformity of gain media greatly affects the output of the laser transverse mode for astigmatic resonators in operation; especially for gas lasers, controllable high-order modes have not been studied. To realize the theory of an astigmatic passive resonator of a gas laser as a good approximation of an active resonator, this paper develops the theory of selecting the laser eigenmode through an astigmatic resonator, and verifies that the two-dimensional tilt of the cavity mirror can break the axial symmetry. Controllable output of the laser mode is realized in real time and conveniently for the first time, to the best of our knowledge. This scheme is not only common to all kinds of lasers, but also has important research significance for the high-order modes required for real-time and rapid regulation of gas lasers under operating conditions.

The rate constant for the CH3 + C2H6 → CH4 + C2H5 reaction was studied behind reflected shock waves at temperatures between 1369 and 1626 K and pressures from 8.6 to 47.4 atm in mixtures of methane, ethane, and argon. Ethylene time histories were measured using laser absorption of radiation from a carbon dioxide gas laser near 10.532 μm. The resulting rate constant data can be represented by the Arrhenius equation k (T) = 3.90 × 1013 exp(-16670 cal/mol/RT) cm3 mol-1 s-1. We believe this is the first study to extend experimental data for this rate constant to temperatures above 1400 K. The overall 2σ uncertainty of the current data is +18%/-21% resulting primarily from uncertainties associated with the influence of secondary reactions and the fitting of rapidly changing species time histories at the higher temperatures.

Research on laser resonators has been a hot research to improve various laser performances, but there are few studies on the special spot of the external resonant gas laser. In this paper, the special full-resonant modulated gas laser resonant is experimentally studied. With the quantitative change of the tilt angle of the tuned laser resonant in different directions, the shape of the laser spot emitted by the laser resonant is special and the law is different. When a copper wire is added to the resonant, the shape of the laser spot changes greatly, and the shape of the spot is extremely rare.

We treat numerical simulations to investigate how the tube wall thickness affects the confinement loss, power fraction ratio and bandwidth of terahertz (THz) negative curvature fibers at the frequency of 2.52 THz. The frequency of 2.52 THz is chosen to research since the generation from CH3OH based THz gas laser pumped by CO2 laser demonstrates the huge application prospects. We also calculate the confinement loss of bend fiber and find it is insensitive to the bend radius. The negative curvature fibers can be used as the reaction cell of THz or mid-infrared gas lasers since their superior performance characteristics.

V diplomski nalogi je prikazana primerjava laserskega razreza kovinskih in nekovinskih materialov. Glavni razlog je širša uporaba laserja v industriji in s tem rezanja več različnih materialov na enakem laserskem sistemu. Eksperiment smo izvedli na vzorcih iz najbolj pogosto uporabljenih kovinskih in nekovinskih materialov. Kakovost reza smo opravljali z vizualno analizo in na vsakem vzorcu izmerili hrapavost. Ugotovili smo, da na kvaliteto reza vpliva pet ključnih parametrov, ki so med seboj odvisni. Ob pregledovanju kvalitete reza smo ugotovili, da se parametri popolnoma razlikujejo, kakor tudi kakovost in spremembe na materialu. S pridobljenimi rezultati smo podali okvirne smernice primerjave in razumevanje laserskega rezanja kovin ter nekovin. The thesis provides a comparison of laser cutting of metallic and non-metallic materials. The main reason is a broader use of lasers in the industry and thus cutting of different materials with the same laser system. The experiment on samples of the most commonly used metallic and non-metallic materials were performed. The cut quality with a visual analysis and measuring the roughness on each sample was done. It was found that the cutting quality is affected by five interdependent parameters. During the cutting quality assessment, it was found that the parameters are completely different, as well as the quality and changes on the material. With the obtained results, a framework guidelines for comparing and understanding the laser cutting of metals and non-metals was provided.

Infrared spectroscopy is a powerful tool for identification and quantification of functional molecular groups. Molecular gas lasers have long been used for such purposes due to their early development and mature manufacturing technology. Over the past few decades, Quantum Cascade Lasers (QCLs) have popularized due to their continuously tunable wavelength, climbing peak power, and steadily improving manufacturing economics. However, for many applications in the longwave infrared (LWIR) spectral region, carbon dioxide (CO2) lasers retain a clear advantage over QCLs by providing higher power, greater spectral purity and extended coherence length. This combination allows for detection of volatile organic compounds indicative of many diseases such as early-stage lung cancer, an advanced prognosis of which can increase the 5-year survival rate by 37.5%. In addition to medical applications, CO2 lasers also retain their niche in environmental sensing by providing a robust photoacoustic airborne measurement platform for air quality and climate research. Furthermore, recent advances in thermally balanced gas laser architectures have enabled reliable mobile leak monitoring of the insulation gas Sulfur Hexafluoride (SF6) used in medium to ultra-high-voltage electricity transmission lines. With the installed base of SF6 expected to grow 75% by 2030 due to the increase of green energy infrastructure via solar panels and wind turbines – both of which rely on electrical connections, switches, and circuit breakers – this task has gained new urgency due to an upper leak estimate of 15% over the full life cycle of the insulation gas.

The paper presents a study of the diffraction efficiency of polarization holographic gratings recorded in thin films of the azopolymer PAZO (poly[1-[4-(3-carboxy-4-hydroxyphenylazo) benzenesulfonamido]-1,2-ethanediyl, sodium salt]) doped with Cu(II) 3-amino-5,5′-dimethylhydantoin (CLP) and Ni(II) 3-amino-5,5′-dimethylhydantoin (NLP) at three different concentrations, namely 1, 2 and 5 wt.%. The influence of the dopants composition and concentration on the parameters of the polarization holographic gratings recorded in the thin composite films has been discussed. The gratings are recorded with a He-Cd gas laser with wavelength 442 nm. The polarization of the recording beams was left and right circular and the recording angle was 20°. Along with the anisotropic grating in the volume of the media, surface relief is also formed. The diffraction efficiency kinetics is probed at 635 nm and the height of the relief gratings is determined by AFM. Diffraction efficiency (η) higher than 30 % was achieved for the hybrid samples, as well as 585 nm surface relief height.

The results of experimental studies of the effect of narrow-band seeding radiation of a gas laser on the spectral width of the oscillation line of an optical parametric oscillator (OPO), which is based on a fan-out structure of a periodically poled lithium niobate (PPLN) crystal, are presented. The use of a seeding He–Ne laser made it possible to reduce the generation threshold for the OPO by a factor of 1.53, from 120 μJ (29.5 mJ/cm2) to 78 μJ (19 mJ/cm2). When the modes of the He–Ne laser were optimally matched in the OPO cavity, the width of the spectral line of the signal wave decreased by a factor of 4.65 and equaled 0.481 nm.

A large sample has been employed to obtain total reaction cross sections and product state distributions (translational, vibrational and rotational) for the title reaction. Quasi-Classical Trajectory (QCT) calculations and the Gaussian Binning (GB) methodology have been used on Wu-Schatz-Lendvay-Fang-Harding (WSLFH) and Neural Networks (NN) potential energy surfaces. After a first selection, Vibrational-Gaussian Binning (V-GB), (vHO’, vHOD’, vOD’), and a second selection, Rotational-Gaussian Binning (R-GB), although the preference observed (odd or even J') is not exactly followed by each vibrational excitation of HOD, there is a similar behavior to the physical laser phenomenon observed in another triatomic molecule utilized in the gas laser of CO2. The dynamics of polyatomic chemical reactions (e.g., OH + D2 → HOD* + D and its isotopic variants), of relevance in the excitation/emission processes of current and future chemical lasers, could be studied theoretically from the results obtained in this article.

Данная научная статья посвящена определению форм-фактора газового лазера расчетным методом. Результатом работы является типовой алгоритм определения уравнения спектральной линии лазерного излучения для режима развитой генерации с приведенным примером решения задачи по определению форм-фактора газового лазера на примере гелий-неонового лазера. Приведенный в статье алгоритм может быть положен в основу методик определения расчетным методом спектральной плотности лазерного излучения при проектировании газовых лазеров. В статье показано, что для газового лазера в режиме развитой генерации, когда число фотонов в моде резонатора достаточно велико, а амплитудные и фазовые флуктуации являются независимыми, при этом изменения фазы носят случайный характер и имеют нормальное распределение, уравнение огибающей спектра излучения представляет собой результат прямого преобразования Фурье двумерной корреляционной функции сигнальной составляющей излучения, амплитуда которого определяется суммарной амплитудой фотонов в моде резонатора., This scientific article is devoted to the determination of the form factor of a gas laser by the calculation method. The result of the work is a typical algorithm for determining the equation of the spectral line of laser radiation for the developed generation mode with the given example of solving the problem of determining the form factor of a gas laser on the example of a helium-neon laser. The algorithm given in the article can be used as the basis for methods for determining the spectral density of laser radiation by the calculation method when designing gas lasers. The article shows that for a gas laser in the advanced generation mode, when the number of photons in the resonator mode is sufficiently large, and the amplitude and phase fluctuations are independent, while the phase changes are random and have a normal distribution, the equation of the envelope of the radiation spectrum is the result of a direct Fourier transform of the two-dimensional correlation function of the signal component of radiation, the amplitude of which is determined by the total amplitude of photons in the resonator mode., Промышленные АСУ и контроллеры, Выпуск 11 2021

A nitrogen laser is a gas laser operating in the ultraviolet range (typically 337.1 nm) using molecular nitrogen as its gain medium, pumped by an electrical discharge. It is efficient sources for laser-induced fluorescence and photochemistry and general spectroscopy. There is a model for a single-pass, discharge type standoff nitrogen laser initiated by a femtosecond filament in nitrogen gas. A Nitrogen gas laser filament plasma kinetic system is described by the set of plasma kinetic equations which associated with rate equations for the population of the lasing levels and number of emitted photons. The change of concentration of different neural and ionic atomic and molecular species in the filament plasma is described by set of rate equation, Ns is the density of species of type - s, and Gs, Ls are the relevant generation and loss rates. T, Te, and Tvibr are gas, electronic, and vibrational temperatures, respectively. The concentration of system gas is not balanced and Te≈ Tvibr. T parameters transform to N, Ω R. We discuss the system stability and stability switching for different values of TE and Ω parameter. There is a practical guideline that combines graphical information with analytical work to effectively study the local stability of models involving dependent parameters. The stability of a given steady state is determined by the graphs of some function of TE and Ω parameters.

The measuring complex of the submillimeter range, implemented on the basis of a gas laser, is described. The technique of measuring the characteristics of dielectrics and the results are presented. It is concluded that it is possible to use the proposed method for validating the results of determining the dielectric characteristics of materials.

A tunable terahertz gas laser is demonstrated with a germanium ealton served as the spectrum splitter. The germanium ealton is 1.2-mm thick and anti-reflection coated at 10.17 μm, giving good dichroic performance for infrared and far-infrared radiation. By tuning the incident angle of the germanium ealton, the transmittance of 95% at 9– 11 μm wavelengths and the reflectance of more than 70% at 180 – 500 μm wavelengths can be achieved simultaneously. Based on the germanium ealton, a tunable CH3F gas laser is presented when pumped by a transversely excited atmospheric CO2 laser. By tuning the pump lines and the incident angles, four THz laser wavelengths are obtained including 181 μm, 261 μm, 360 μm and 496 μm. The energy conversion efficiency is in the order of 10–3, which is comparable to those of typical efficient CH3F molecule lasers. The germanium ealton is anticipated to be an efficient dichroic element for terahertz gas lasers with different wavelengths.