Laser Action Research Articles

ПРО ОСЕРЕДКИ ЗАРОДЖЕННЯ КОРОЗІЇ В СТАЛЯХ, ЩО ПІДДАНІ ЛАЗЕРНІЙ ДІЇ

The effect of laser action on the initiation and development of corrosion damages in steels near non-metallic inclusions has been investigated. It has been established that laser treatment enhances the corrosion resistance in low-cycle fatigue of steels containing various inclusions. It is shown that the effect of laser treatment on increasing the resistance of steels to the formation of corrosion damages is associated with a change in the state of the inclusion-matrix interphase boundaries, which contributes to a decrease in their permeability for corrosive elements and an increase in the cohesive strength of these boundaries in active media.

Regulation of molten pool in borosilicate glass welding with picosecond laser based on multifocal shaping

Glass welding based on ultrafast laser is an effective method to achieve glass packaging. However, there are some problems in ultrafast laser glass welding, such as laser energy loss caused by the fact that the molten material generated by part of the laser energy cannot enter the gap to participate in welding, and microcracks. In this paper, borosilicate glass welding was conducted with high uniformity horizontal multi-focus based on an improved Gerchberg-Saxton (GS) algorithm proposed for the first time, which can effectively improve uniformity from 74 % to 99.8 %. By compressing the energy distribution of the beam propagation direction and increasing the energy distribution perpendicular to it, the formation of the molten pool can be regulated to prevent excessive longitudinal expansion of the laser action zone, resulting in a 75 % increase in weld width. Moreover, stress distribution can be reshaped to suppress the generation of microcracks. These advantages have a significant driving effect on the engineering application of this technology.

The molecular structure and spectroscopic properties of formaldoxime (CH2NOH)

Formaldoxime (CH2NOH) belongs to the possible interstellar molecules. Its isomerization, spectroscopic properties as well as the potential for pumped laser action has long received a lot of attention. Herein, the benchmark database of the spectroscopic constants and anharmonic force fields has been achieved for trans- and cis- formaldoxime. Evaluation is done by using the coupled-cluster theory [CCSD(T)] and density functional theory (B3LYP and B2PLYP), and different basis sets [cc-pVTZ, aug-cc-pVTZ, 6-311+G**, 6-311++G (3df,3pd)] are utilized. The calculated spectroscopic constants commendably reproduce previous experimental results. Besides, a series of vital anharmonic parameters such as vibration-rotation interaction constants, etc, has been provided, which is used for the in-depth study of high-resolution rovibronic spectrum of formaldoxime.

Influence of Different Surface Treatments on the Bond Strength of Yttria-Stabilized Tetragonal Zirconia Ceramic.

Objective: This in vitro study evaluates the shear bond strength (SBS) of yttria-stabilized tetragonal zirconia (Y-TZP) and resin cement after different surface treatments. Materials and methods: Forty-eight ceramic cubes were divided into four groups (n = 12): G1 (control) sandblasting with Al2O3; G2-sandblasting with silica-coated Al2O3 (Rocatec); G3-Rocatec + CO2 laser; and G4-CO2 laser + Rocatec. A metallic primer was applied to the pretreated ceramic. A rubber ring was adapted on the central area, and then, the resin cement was inserted into the matrix and photoactivated. The samples were evaluated regarding surface roughness (Ra), SBS, failure type, and qualitatively with scanning electron microscopy (SEM). The data were analyzed by one-way analysis of variance followed by Tukey's test (p < 0.05). Results: The mean values of Ra (μm) were as follows: G1-4.52a, G2-4.24a,b, G3-4.10a,b, and G4-2.90b and the mean values of SBS (MPa) were as follows: G1-7.84a , G2-4.41b , G3-4.61b and G4-6.14a,b. SEM analyses showed superficial irregularities for all groups, being more prominent for G1. The presence of silica deposits was observed for G2, G3, and G4, but in the last two groups there were some linear areas, promoted by the fusion of silica, due to the thermomechanical action of the CO2 laser. Conclusions: The surface treatment with CO2 laser + Rocatec, using one MDP-based cement, can be an alternative protocol for the adhesion cementation of Y-TZP ceramic since it was as effective as the conventional pretreatment with aluminum oxide sandblasting.

Bioinspired photonic crystal structures from Papilio Ulysses butterfly wings for versatile laser applications

Photonic crystals found within the wing of a Papilio Ulysses butterfly have demonstrated their efficacy in facilitating laser processes, particularly as a scattering material for imaging and illumination applications. This study delves into the investigation of the photonic crystal's band gap within the butterfly's wing, aiming to realize blue band-edge lasing using a newly developed gain medium comprising diphenylaminofluorene-based chromophores featuring a donor-acceptor-donor (D-A-D) motif. The versatility of the fabricated sample is highlighted, as it can function as both a single-mode laser and a random laser, with the operational mode determined by adjusting the excitation power and the direction of the pump source. Specifically, it exhibits a threshold of 2.5 μJ for random laser operation and 7.6 μJ for single-mode laser operation. The unique architectural elements found in the butterfly's wing, including the ridges on the wing scale and the photonic crystal within the scales, play distinct roles in enabling random laser and single-mode laser actions, respectively. This distinctive butterfly wing architecture holds promise for inspiring the development of future photoelectronic circuits requiring a hybrid design that incorporates both single-mode and comb-mode laser functionalities.

Experimental modelling of heating and local field enhancement by iron oxide nanoparticles upon laser excitation

SignificanceLocal determination of the iron oxide nanoparticles (IONPs) temperature during laser heating is important in the aspect of laser phototherapy. ApproachWe have carried out theoretical modeling of local EM field enhancement and heating under the laser action near individual IONPs and ensembles of NPs with different sizes of the magnetic core and different content of iron oxide in them. To experimental determine the temperature of IONPs water colloids, we used fluorescence thermometry based on rhodamine B (RhB) fluorescence lifetime. ResultsLocal EM field enhancement and heating strongly depend on the NPs shape and distance between them. In the case of anisotropic NPs, a significant change in the spatial distribution of the EM field near the NPs surface was observed. The local heating of NPs in an ensemble reaches sufficiently higher values, the relative change was about 35°С for Fe2O3 NPs. Nevertheless, all the studied IONPs water colloids showed heating by no more than 15°C. ConclusionsSignificant enhancement of the local field occurs in IONP pairs and ensembles. The heating temperature of the ensemble depends on the thermal conductivity of the medium, in which the heat dissipation depends.

Физика залечивания нанопор в конденсированном веществе в условиях воздействия лазерного излучения и высокотемпературной плазмы

The paper theoretically and experimentally investigates the influence of laser radiation and high-temperature plasma on changes in the physical properties of amorphous-nanocrystalline materials with nanopores in a thin surface layer. At present, the possibility of simultaneous increase of hardness and resistance to cracking of the material surface because of selective laser action has been experimentally established. Experimental results can be explained based on the model of selective impact of laser radiation on individual nanopores. The physics of laser selective initiation of healing processes of inhomogeneous/defective areas at the nanoscale has been investigated. Using the proposed physical model, the specificity of selective heating of areas near nanopores, as well as the influence of nanoscale defects in the structure on the specificity of isotherm propagation has also been revealed. The process of healing of nanopores located in the inhomogeneously heated surface layer of the material under the action of shock loading is considered. Theoretical results are compared with experimental data. It is shown that as a result of selective laser treatment it is possible to increase microhardness by three-four times, with simultaneous growth of resistance to cracking under conditions of local loading by the Vickers pyramid. The results obtained can be explained within the framework of ideas about selective laser healing of nano- and micro-sized defects located in the surface layer of the material. Thus, the physical and mechanical properties of the surface of condensed materials in an extreme state caused by strong compression under conditions of simultaneous short-term heating to high temperatures have been studied theoretically and experimentally.

Оптимизация режимов селективного лазерного плавления порошковой композиции системы AlSiMg

Introduction. New aluminum-based powder systems are currently being developed for additive manufacturing. The scientists' work is aimed at comprehensive studies of powder production, optimization of conditions for alloy production and formation of three-dimensional specimens with minimal porosity and absence of cracking during selective laser melting. The purpose of this work is the synthesis of an almost spherical Al-Si-Mg composite powder (91 wt. % Al, 8 wt. % Si, 1 wt. % Mg) from aluminum powder PA-4 (GOST 6058-22), silicon powder (GOST 2169-69) and magnesium powder MPF-4 (GOST 6001-79), which were not originally intended for selective laser melting technology. The work also provides for the optimization of selective laser melting modes to obtain an alloy and form three-dimensional specimens with minimal porosity and no cracking. To create a powder composition, powders ranging in size from 20 to 64 μm were selected by sieve analysis and subjected to mechanical mixing in a ball mill in a protective argon medium for one hour. The research methods are methods of X-ray diffraction and X-ray phase analysis, transmission electron microscopy, mechanical tests of microhardness. Studies of the powder composition after mechanical mixing showed that the mixed powder of aluminum, silicon and magnesium is a conglomerate of particles of spherical, oval and irregular shape. Results and discussions. The optimal modes for obtaining a specimen with a minimum porosity of 0.03 % and a microhardness of 1,291 MPa are selective laser melting modes: P = 90 W, V = 225 mm/s, S = 0.08 mm, h = 0.025 mm. The conducted research shows the possibility of synthesizing products from metal powders that are not adapted to processing by selective laser melting and obtaining an alloy with new mechanical properties during laser action.

Influence of Intravascular Laser Irradiation of Blood (ILIB) on inflammatory cytokines and nitric oxide in vivo: a systematic review.

The use of Intravascular Laser Irradiation of Blood (ILIB) as a treatment or adjunct tool has been used around the world since the 1980s. So that more professionals can deliver benefits to their patients in different areas of health, it is necessary to understand in depth the mechanisms of laser action at the molecular level, for correct indication and success in the treatment.To analyze works that evaluated the influence of ILIB on inflammatory cytokines and nitric oxide (NO) in animals and humans. The literature search was carried out between February and April 2023 in Pubmed, Medline, Web of Science, SciELO, Lilacs database. The risk of bias was assessed using the bias table where the authors performed the analyzes of all articles with the risk of bias domains. The methodology was defined following the PRISMA guidelines (Preferred Systematic Reviews and MetaAnalysis Report). The search retrieved 135 possibly relevant articles. After removing duplicates, according to the eligibility criteria, evaluation of titles and review of abstracts, in the end, 6 articles were included.An increase in anti-inflammatory cytokines, a decrease in pro-inflammatory cytokines and an increase in NO can be observed. The wavelengths used ranged from 660 to 808nm when using a low intensity laser and when using a VIP light source 480-3400nm, they also differed in terms of the light emission pattern.ILIB may be a complementary treatment option for patients who have comorbidities that lead to systemic inflammation.

On the Behavioral Reachability of a Confined Molecule Under Laser Action

On the Behavioral Reachability of a Confined Molecule Under Laser Action

Influence of boundary conditions on non-equilibrium heat transport under ultrafast laser action based on the lattice Boltzmann method

Based on the lattice Boltzmann method, this paper simulated the non-equilibrium heat transfer process in nano-silicon thin film under ultrafast laser irradiation. The influence of boundary conditions on heat transport was investigated. Results show that under rebound and diffuse boundary conditions, the energy distribution within the film is non-uniform due to interface effects. However, the specular boundary condition is equivalent to eliminating the interface, resulting in a smooth energy distribution. Under convective boundary conditions, the thermal wave phenomenon disappears owing to the open interface. When the energy tends to be stable, the energy density under convective boundary conditions is reduced to 50% of that under adiabatic boundary conditions. As the film size decreases, the differences between boundary conditions become more significant. Particularly when the film size is smaller than the phonon mean free path, the influence of boundary conditions cannot be neglected. Therefore, boundary conditions and size effects are important for the design of nanodevices. Furthermore, compared with the results obtained by the Cattaneo-Vernotte model, it is found that at smaller Knudsen numbers, the Cattaneo-Vernotte model has a better match with the lattice Boltzmann method.

IMPROVEMENT OF THE METHODOLOGY FOR OPTIMIZING THE PARAMETERS OF COMPLEX SYSTEMS UNDER THE INFLUENCE OF THERMAL LOAD SOURCES

The article investigates some aspects of solving the problem of constructing mathematical models for optimizing the parameters of local laser action on multilayer microbiological systems. The constraints on the desired laser parameters and on the temperature field in the material subject to laser fission are set. Verification of compliance with the restrictions on not exceeding the maximum value of the temperature field requires multiple calculations of the corresponding temperature field in the microbiological material. Control over the temperature field limits ensures the viability of its parts during the biotechnological process of laser fission. To construct adequate optimization mathematical models, the author substantiates the adequacy of the computational mathematical models describing the state of a microbiological system under the action of laser radiation sources. A multi-point boundary value problem with a system of inhomogeneous differential heat conduction equations for a multilayer microbiological medium is investigated and the correctness of this problem is substantiated for minor perturbations of the right-hand side of the differential equation. The results obtained in the article guarantee the adequacy of applied optimization mathematical models for finding rational values of technical parameters of laser emitters. In order to improve the accuracy of optimization of the technical parameters of laser emitters, the article presents a mathematical modeling of the preparatory stage of embryo defrosting. The presented mathematical models and methods of their implementation are necessary to improve the quality of embryo defrosting. Improvement of the methodology for solving applied biotechnological problems will certainly lead to the complication of mathematical models, but it will increase the accuracy of calculation and optimization of technical parameters of the biotechnological process of laser embryo division.

Manipulating random lasing correlations in doped liquid crystals.

Random lasers are highly configurable light sources that are promising for imaging and photonic integration. In this study, random lasing action was generated by optically pumping N-(4-methoxybenzylidene)-4-butylaniline (MBBA) liquid crystals infiltrated with gold nanoparticles and a laser dye (pyrromethene 597 (PM597)). By varying the pump energy near a lasing threshold, we show that it is possible to control intensity correlations between random lasing modes. The correlations in the system were phenomenologically characterized using the Levy statistics of the emission spectrum survival function. We also find that correlations and persistence of lasing action are correlated. These results demonstrate the possibility to dynamically control a key physical feature of random lasers, which may find applications in biomedical settings and network communications.

The Origin of Threshold Reduction in Random Lasers Based on MoS2/Au NPs: Charge Transfer

Random lasers have attracted much attention in recent years owing to their advantages of a simple fabrication process, low processing cost, and material flexibility for any lasing wavelengths. They provide a roadmap for the design of ultra-bright lighting, displays, etc. However, the threshold reduction in random nanolasers remains a challenge in practical applications. In this work, lower-threshold random laser action from monolayer molybdenum disulfide film-encapsulated Au nanoparticles (MoS2/Au NPs) is demonstrated. The observed laser action of the MoS2/Au NPs shows a lower threshold of about 0.564 µJ/mm2, which is about 46.2% lower than the threshold of random lasers based on Au NPs. We proposed that the charge transfer between MoS2 and the gain material is the main reason for the reduction in the random laser threshold. The finite-difference time-domain (FDTD) method was used to calculate the lasing action of these two nanostructures. When charge transfer is taken into account, the theoretically calculated threshold of the MoS2/Au NPs is reduced by 46.8% compared to Au NP samples, which is consistent with the experimental results. This study provides a new mechanism to achieve low-threshold and high-quality random lasers, which has the potential to facilitate the application of random lasers and the development of high-performance optoelectronic devices.

Controllable nonreciprocal phonon laser in a hybrid photonic molecule based on directional quantum squeezing.

Here, a scheme for a controllable nonreciprocal phonon laser is proposed in a hybrid photonic molecule system consisting of a whispering-gallery mode (WGM) optomechanical resonator and a χ(2)-nonlinear WGM resonator, by directionally quantum squeezing one of two coupled resonator modes. The directional quantum squeezing results in a chiral photon interaction between the resonators and a frequency shift of the squeezed resonator mode with respect to the unsqueezed bare mode. We show that the directional quantum squeezing can modify the effective optomechanical coupling in the optomechanical resonator, and analyze the impacts of driving direction and squeezing extent on the phonon laser action in detail. Our analytical and numerical results indicate that the controllable nonreciprocal phonon laser action can be effectively realized in this system. The proposed scheme uses an all-optical and chip-compatible approach without spinning resonators, which may be more beneficial for integrating and packaging of the system on a chip. Our proposal may provide a new route to realize integratable phonon devices for on-chip nonreciprocal phonon manipulations, which may be used in chiral quantum acoustics, topological phononics, and acoustical information processing.

Formation Mechanism of Nano Silver Film by Laser Action on Particle-Free Complexed Silver Ion Ink

Formation Mechanism of Nano Silver Film by Laser Action on Particle-Free Complexed Silver Ion Ink

Dissociation dynamic study of H&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; in time-delayed two-color femtosecond lasers

In recent years, the rapid development of ultrashort pulse laser technology has made it possible to regulate the ionization and dissociation dynamics of atoms and molecules. Among them, the microscopic dynamics of molecular dissociation have always been a hot topic. The phenomenon of molecular dissociation caused by the interaction between femtosecond intense laser fields and H&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; molecules has attracted widespread attention. Previous theoretical studies on the dissociation of H&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; molecules mainly focused on studying its dissociation dynamics through numerical calculations, while there were relatively few theoretical models. This paper aims to establish a simple classical model to describe the dissociation dynamics. Firstly, this paper calculates the joint distribution of nuclear and electronic energies during the dissociation process of H&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; molecules under the action of pump lasers by numerically solving the Schrödinger equation, and proves that H&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; molecules initially in the ground state dissociate into H&lt;sup&gt;+&lt;/sup&gt; + H&lt;sup&gt;*&lt;/sup&gt; after absorbing a pump photon in the pump light field. Next, this paper studies the dissociation dynamics of H&lt;sub&gt;2&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt; molecules in time-delayed two-color femtosecond lasers and finds that it closely depends on the specific forms of the pump light and the probe light. By utilizing the dependence of the dissociation kinetic energy release (KER) spectrum on the time delay of the two-color femtosecond lasers, we have retrieved the sub-attosecond microscopic dynamic behaviors of electrons and atomic nuclei during the dissociation process, and established a classical model based on the conservation of energy and momentum to describe the dissociation dynamics. This model can qualitatively predict the ion dissociation KER spectrum depending on the time delay of the two-color femtosecond lasers. In addition, by taking advantage of the dependence of the ion kinetic energy spectrum on the frequency of the probe laser (that is, the electronic resonant transition between the molecular ground state and the first excited state caused by the probe light will affect the ion kinetic energy spectrum during the dissociation process), we propose a scheme to reconstruct the evolution of the internuclear distance over time. Our reconstruction results can qualitatively predict the trend of the numerical simulation results, and this scheme may provide some theoretical guidance for experiments.

Topical issues of countering modern autonomous unmanned aerial vehicles and FPV drones

The high level of development of unmanned aviation has predetermined the possibility of its use to solve a wide range of tasks. At the same time, it should be noted that achievements in this area are not always used for peaceful purposes. The results of the analysis of the practice of using unmanned aerial vehicles (UAVs) in modern military conflicts and information about terrorist acts with their use allow us to conclude that the most difficult targets resistant to various methods of influence are modern autonomous UAVs and FPV drones with explosive devices. Therefore, the search for effective ways to counteract them seems to be an urgent area of research. The aim of the work is to develop the means for effective counteraction to modern autonomous UAVs and FPV drones by electromagnetic, laser and mechanical ways. The methods of system analysis are used in the work. The article notes the increasing level of threats associated with the mass use of autonomous UAVs and FPV drones, presents the results of the "revision" and critical analysis of the main methods of countering modern UAVs, reflecting their characteristics, advantages and disadvantages. Based on the results obtained, a comparative analysis of methods of countering autonomous UAVs and FPV drones was carried out. It is concluded that the most effective of them are the methods of electromagnetic, laser and mechanical action. The required parameters for the effective application of these types of impacts on modern autonomous UAVs and FPV drones are presented. The results of the research can be used as initial data for the creation of new and improvement of existing means of countering UAVs as part of physical protection systems (SFZ). The scientific novelty of the work consists in the development of a scientific and methodological apparatus for substantiating the SFZ of objects in terms of taking into account the functioning features and vulnerabilities of modern autonomous UAVs and FPV drones, as well as determining ways to improve systems to counter them based on the use of electromagnetic, laser and mechanical means.

Controlling the random lasing action from GaAs/AlGaAs axial heterostructure nanowire arrays.

Controlling the random lasing action from disordered media is important to obtain customizable lasers with unprecedented properties. In this paper, systematic investigations of random scattering based on GaAs/AlGaAs axial heterostructure nanowire (NW) arrays are presented. By manipulating the diameter and density of GaAs/AlGaAs axial heterostructure NWs during growth, different types of random lasers (Anderson localized and delocalized random lasers) have been successfully realized. The threshold, Q factor, and spatial coherence of these two types of lasers are experimentally discussed and analyzed. Finally, a proof-of-concept demonstration of speckle-free imaging based on the NW lasers has been conducted. This research enables the tunability of random lasers with exceptional performance and lays the foundation for achieving random lasing control.

Treatment of plasma coatings by laser remelting

The article analyzes the effect of reflow and thermal cycling by laser beam on the structure and properties of plasma eutectic coatings. The facts of carbon diffusion into the solid phase at a distance of 150-200 microns with a laser pulse duration of 4 ms have been established. This is due to the high deformation rates that occur in the zone of thermal influence under pulsed laser action. This effect is aimed at increasing both the surface and volumetric strength of the sprayed coatings.