Power Laser Irradiation Research Articles

The role of temperature in the photoluminescence quantum yield (PLQY) of Ag2S-based nanocrystals.

Highly emissive Ag2S nanocrystals (NCs) passivated with a gradated shell incorporating Se and Zn were synthesized in air, and the temperature dependence of their photoluminescence quantum yield (PLQY) was quantified in both organic and aqueous media at ∼1200 nm. The relevance of this parameter, measured at physiological temperatures, is highlighted for applications that rely on the near infrared (NIR) photoluminescence of NCs, such as deep NIR imaging or luminescence nanothermometry. Hyperspectral NIR imaging shows that Ag2S-based NCs with a PLQY in organic media of about 10% are inefficient for imaging at 40 °C through 20 mm thick tissue with low laser irradiation power densities. In contrast, water-transferred Ag2S-based NCs with an initial PLQY of 2% in water exhibit improved robustness against temperature changes, enabling improved imaging performance.

Analyzing Thermal Processes in Laser Welding of Multi- Component Heat-Resistant Alloy Thin-Walled Butt Joints: A Comprehensive Modeling Approach

Niobium-based alloys are vital in high-temperature environments due to their unique chemical composition, phase structure, high density, and oxidation resistance. These alloys find extensive applications in industries such as medicine, engine manufacturing, and space technology. This study delves into the complexities of modeling laser welding processes, necessitated by the multitude of dynamic parameters specific to each surface configuration. Finite element modeling was conducted using COMSOL Multiphysics to analyze the heat transfer in butt joints between Nb-15W-5Mo-1Zr alloy plates under 400 W laser radiation power. The research employed finite element modeling to analyze heat transfer in Nb-15W-5Mo-1Zr alloy plates, considering non-uniform movement at the start and end of the welding process, Gaussian heat flux distribution along the laser spot radius, and temperature-dependent reflection coefficient. The models accounted for non-uniform movement, Gaussian heat flux distribution, and temperature-dependent reflection coefficient. The study demonstrated that thin plates of Nb-15W-5Mo-1Zr alloy can be effectively welded using specific laser processing modes, leveraging their high initial cooling rate of 1.2-1.3 s. Successful welding of Nb-15W-5Mo-1Zr alloy plates requires careful consideration of laser processing parameters. While the alloy's thermodynamic properties allow for effective welding, ensuring weld quality mandates additional production processes aimed at preventing potential part failure.

Stem cell-derived paracrine factors by modulated reactive oxygen species to enhance cancer immunotherapy

Herein, we present an approach for manipulating paracrine factors and signaling pathways in adipose-derived stem cells (ADSCs) to achieve highly effective tumor immunotherapy. Our method involves precise control of reactive oxygen species concentration using the CD90-maleimide-pluronic F68-chlorin e6 conjugate (CPFC) to create ACPFC, which is then attached to ADSCs through the CD90 receptor-specific interaction. By regulating the irradiated laser power, ACPFC promotes signaling pathways such as cascade-3, VEGFR2, α2β1, C3AR1, CR1–4, and C5AR1, leading to the secretion of various inflammatory cytokines such as IFN-γ, TGF-β, and IL-6, while inhibiting AKT, ERK, NFkB, PAR1, and PAR3/4 signaling pathways to reduce the secretion of cell growth factors like TIMP-1, TIMP-2, VEGF, Ang-2, FGF-2, and HGF. When ACPFC is injected intravenously into a tumor animal model, it autonomously targets and accumulates at the tumor site, and upon laser irradiation, it generates various anti-inflammatory factors while reducing angiogenesis growth factors. The resulting antitumor response recruits CD3+CD8+ cytotoxic T cells and CD3+CD4+ helper T cells into the tumor and spleen, leading to highly effective melanoma and pancreatic tumor treatment in mice. Our technology for regulating stem cell paracrine factors holds significant promise for the treatment of various diseases.

Correlation between 1064 nm laser attack and thermal behavior in STT-MRAM

In this paper, the impact of a 1064 nm laser attack on an STT-MRAM cell is experimentally studied in real-time, for the first time, during reading and writing operations, in order to understand the behavior of a sensing circuit under a temperature variation from 25 °C to 105 °C. This must be considered for the implementation of a hybrid CMOS/MRAM Light-Weight Cryptography circuit, to overcome a laser attack. We highlight a reading current variation during the laser shots, that can impact the sensing circuits. The switching probability between the two states has been measured as well as the impact of the irradiation time, laser power, and cell size. We correlate the results with electrical characterizations in a wide range of temperatures, demonstrating the 1064 nm laser attack thermally affects the STT-MRAM behavior. In conclusion, suitable countermeasures can be adopted.

Effectiveness of Gold Nanorods of Different Sizes in Photothermal Therapy to Eliminate Melanoma and Glioblastoma Cells.

Gold nanorods are the most commonly used nanoparticles in photothermal therapy for cancer treatment due to their high efficiency in converting light into heat. This study aimed to investigate the efficacy of gold nanorods of different sizes (large and small) in eliminating two types of cancer cell: melanoma and glioblastoma cells. After establishing the optimal concentration of nanoparticles and determining the appropriate time and power of laser irradiation, photothermal therapy was applied to melanoma and glioblastoma cells, resulting in the highly efficient elimination of both cell types. The efficiency of the PTT was evaluated using several methods, including biochemical analysis, fluorescence microscopy, and flow cytometry. The dehydrogenase activity, as well as calcein-propidium iodide and Annexin V staining, were employed to determine the cell viability and the type of cell death triggered by the PTT. The melanoma cells exhibited greater resistance to photothermal therapy, but this resistance was overcome by irradiating cells at physiological temperatures. Our findings revealed that the predominant cell-death pathway activated by the photothermal therapy mediated by gold nanorods was apoptosis. This is advantageous as the presence of apoptotic cells can stimulate antitumoral immunity in vivo. Considering the high efficacy of these gold nanorods in photothermal therapy, large nanoparticles could be useful for biofunctionalization purposes. Large nanorods offer a greater surface area for attaching biomolecules, thereby promoting high sensitivity and specificity in recognizing target cancer cells. Additionally, large nanoparticles could also be beneficial for theranostic applications, involving both therapy and diagnosis, due to their superior detection sensitivity.

Magneto-optical and thermo-optical properties of the Ge-Sb-As-S glass

Thermo-optical and magneto-optical properties of high-purity GexAsySbzS100-x-y-z (x = 10–13; y = 20–23; z = 4–6) glasses are studied. Transmission spectra, spectral dependence of the Verdet constant in the 632–1940 nm range, thermally induced depolarization, and thermal lens are investigated. The material parameters responsible for thermally induced depolarization and thermal lens are estimated. The high-purity Ge-As-Sb-S glasses are shown to be promising materials for creating optical elements for Faraday devices operating in high power laser radiation.

Investigation of Non-Metallic Material Laser Processing Modes

One of the relevant problems when processing materials using laser is to provide a certain level of surface roughness of the product. This is especially important for materials of natural origin (wood, leather, plastics, bones, stones, and etc.). One approach to select laser processing modes is to pre-test modes on product samples. This leads to significant time costs, as well as the use of a large number of samples (up to several dozen). The article proposes to process the product sample study results using probabilistic and statistical data processing. The example of using this approach in the wood product processing is given. The results of the products laser treatment with surface roughness assessment of the product using probabilistic processing algorithms of the experimental results are shown. The experiment contained three stages. First, a product sample model is prepared, representing a stepped wedge with different roughness, then the model is installed on a laser and laser processing of the model takes place. At the third stage, surface roughness is measured and statistical processing of experimental results is performed on the computer. The use of this approach accelerates the development of laser processing modes for wood products by 3-4 times in comparison with known approaches. The main algorithms of probabilistic and statistical experiment result processing are presented in the work, diagrams of roughness with respect to various laser processing modes for different materials (wood, glass, and leather) are shown: ablation depth, dispersion of profile irregularities, and relation of dispersion of irregularities on laser radiation power. For the experiment, a Trotec Speedy 300 laser, a microdensitometer, an MII 4 microinterferometer, and a photoelectric glare meter FB-2 were used. For data processing, a regression model was built linking laser processing modes and surface properties of various materials. The article will be useful for students applying laser processing of materials of natural origin.

Investigation of Heat Transfer Regimes in Subsonic Dissociated-Nitrogen Jets of a High-Frequency Induction Plasmatron under Additional Surface Heating by Laser Radiation

The heat transfer to a cylindrical water-cooled copper model was experimentally investigated in an induction VGU-4 high-frequency (HF) plasmatron of the Institute for Problems in Mechanics of the Russian Academy of Sciences. The model, 30 mm in diameter, equipped with a calorimetric transducer with a heat-adsorbing graphite surface, 13.8 mm in diameter, was exposed to the surface heating in the combined regime by nitrogen plasma and laser radiation and in the cases of the heating with only laser radiation or a nitrogen plasma jet. The experiments in the HF-plasmatron jets were performed at the pressure in the setup low-pressure chamber p = 1 × 104 Pa, nitrogen mass flow rate G = 2.4 g/s, and the plasmatron HF-generator anode power Na.p. = 22 kW. It is established that in the chosen experimental regimes the dissociated-nitrogen jet and the high-frequency induction discharge do not produce a considerable effect on the laser beam passing through them. The values of the heat flux density are obtained as functions of the laser radiation power delivered. The subsonic nitrogen plasma flow in the quartz discharge channel and in the low-pressure chamber of the VGU-4 setup is numerically modeled under the experimental conditions basing on the solution of the complete Navier–Stokes equations using the Patankar–Spalding method.

The Laser Influence on the Formation of Ni-Al Compounds in the Nickel Foil Surface Layers Depending on the Laser Radiation Power Density

The Laser Influence on the Formation of Ni-Al Compounds in the Nickel Foil Surface Layers Depending on the Laser Radiation Power Density

An Integrated Temperature-Feedback Photothermal Therapy Platform Based on Dual-Functional Rare Earth-Doped NaSrGd(MoO4)3 Phosphors

Nd3+ doped and Er3+/Yb3+ codoped NaSrGd(MoO4)3 (NSGM) phosphors were synthesized and used to build an integrated temperature-feedback photothermal therapy platform. Intense green upconversion emissions were observed in Er3+/Yb3+-codoped NSGM phosphors and used to construct an all-fiber temperature sensing probe. The temperature dependent fluorescence intensity ratio (FIR) calibration curve was established and the absolute temperature sensitivity Sa reached the maximum value of 0.013 K–1 at 423 K. The photothermal conversion performance of NSGM:Nd3+ phosphors could be easily modified by altering Nd3+ doping concentration and 808 nm laser irradiation power. An integrated all-fiber photothermal temperature measurement platform was built and the temperature measurement error was smaller than ±1 K, which could simultaneously achieve photothermal conversion and temperature measurement in narrow spaces and was expected to be used in local photothermal therapy applications.

COMPARATIVE ANALYSIS OF METHODS FOR MEASURING LASER POWER

The application of lasers in many fields of technology and medicine is constantly increasing. This causes the development of new physical methods and principles for correct measurement of power, energy, and other parameters of laser sources. In most cases, the correct measurement of the laser power is important because the quality of the processes in which laser sources are used depends on it. In the paper, a comparative analysis of the existing methods for measuring the power and energy of laser radiation of diverse types of laser sources is made. This research aims to help users of laser equipment to choose the right measurement method depending on the laser source.

On Possible Mechanism of Enhancement of Absorption of Powerful Laser Radiation by Metals

In this work, it is shown that the dependence of the mass of conductive band electrons in a metal on their energy can be a reason of enhancement of the absorption of powerful laser radiation by the metal. To do this, a problem of response (current) of the electron placed in one-dimension periodic potential (lattice) to an electric field periodic in time (electromagnetic wave) is solved. The solution shows that for sufficiently large amplitude of the wave the dependence of the electron current on the wave amplitude becomes non-linear. Within a certain rangе of parameters, this dependence can be described by a simple formula that corresponds to the dependence of the electron mass on its energy. The formula was used for solving the problem of penetration of electromagnetic wave into a metal with the approach of modified Drude model. The non-linearity results in the enhancement of the wave absorption and generation of wave with frequencies close to those of plasma penetrating deep into the metal. The discussed effects manifest themselves in electric fields about. 1 V/Angstrom. The obtained results can be used in the interpretation of experiments data and in the creation of mathematical modeling of the interaction of powerful laser radiation with metal.

Dynamic Characteristics Determination of the Radiation Power Control System for the Industrial CO2 Laser Excited by а Nonself-Sustained Glow Discharge

In the article, an automatic system for radiation power control of lasers excited by а nonself-sustained glow discharge is studied using industrial lasers of the Lantan series as an example. They are designed for cutting, welding and surface modification of various materials as part of laser machines. The power of laser radiation is one of the most important parameters of a laser that determines its technological capabilities. The radiation power is controlled by changing the ionization pulses frequency of high voltage pulses with duration of 100 ns, given with a frequency of 1-5 kHz. The step response of the laser is experimentally obtained. Laser radiation is fed to a thermoelectric mirror-detector with thermo-EMF anisotropy, which measures its power. After preliminary amplification, the differential signal from the mirror-detector is recorded by a digital oscilloscope. A delay in the change in the laser radiation power relative to the control signal was established. The delay is 1487 ms that is explained by the fact that several ionization pulses are required for the initial exciting of the gas volume before the start of radiation generation. The initial section of the step response and damped oscillations are explained by the presence of a protective choke in the main discharge source connection circuit. The choke slows down the rise in current during the short circuit of discharge, allowing circuit breakers to turn off the power supply. To simulate the transient process, the step response of the oscillating circuit is used. The original signal was filtered to remove noise that does not al[1]low determining the parameters of the step response. To determine the spectrum of the step response, fast Fourier transform is carried out, frequencies introducing noise were cut out, and the inverse fast Fourier transform is performed. According to the step response obtained after filtering, the parameters of the modeling step response are determined. Based on the parameters of the step response, the laser transfer function is calculated. It makes possible to proceed to the calculation of the optimal radiation power controller, which ensures the best quality of the transient process.

Research of Laser Beam Combining in Ring Fiber-Optic Delay Line

At present time widespread use of autonomous laser systems supposes reducing of supply energy, consumed by laser sources that are included in their composition and at the same time increasing of their output energy characteristics. The objective of this work was practical confirmation of possibility of laser beam combining in systems based on a ring delay line.The experimental setup that implements the principle of synchronous laser beam combining scheme on the ring fiber-optic delay line, developed by authors earlier, is made. The schematic diagram of the manufactured setup is presented, its operation principle is described in detail and its composition is considered. It is noted that in order to achieve the objective measurements of electrical signals received from the photodetector of the setup and measurements of the part of laser radiation power removed by the splitter and formed in the fiber-optic path of the setup are performed. Results of measurements are presented as the waveforms of electrical signals from the photodetector and of power values at the output of the splitter. Plots of dependence of the output power and the circulation power on the power of the initial laser beam introduced into the setup are presented.Analysis of results showed that the laser beam combining occurs in the ring fiber-optic delay line. Besides, it was found that the proposed scheme provides an increase in the power of the initial beam by 1.05…1.11 times.

Effect of Continuous Laser Treatment on the Wear Resistance of Hard Alloy WCo8

The hardening of hard alloy WCo8 was performed by continuous laser radiation with a laser beam of 1 mm/min diameter, laser radiation power of 200 W, and different speeds of laser beam movement. After laser treatment of hard alloy WCo8, diamond-abrasive wear tests were performed. Duration of the tests varied: 3–6–9 minutes; then the wear, intensity of wear, wear rate were calculated. The analytical dependences of determining the diamond-abrasive wear of hard alloy WCo8 depending on three parameters (power, laser beam propagation speed and duration of the diamond-abrasive wear process) were evaluated. There are no methodological difficulties in applying those dependencies, therefore we get high reliability of the results obtained in that case and the possibility to further calculate the effect of increasing the power and speed of laser radiation on the diamond-abrasive wear.

Effect of New Design of the Laser Installation and Spraying Method on the Physical and Mechanical Properties the Inner Surface a Small Diameter Coated with 15Cr17Ni12V3F35ZrO2

A unique controlled laser head with an adaptive module was developed to stabilize the trajectory of movement. The scientific and practical problem of developing a technology for restoring the inner surface of a small diameter up to ∅44 mm was solved by the introduction of a laser head. Adhesion was achieved by moving the laser along the vectors, forming a regular pyramid with opening angles at the top. High physical and mechanical properties of the restored pump surface were achieved by the laser technology when spraying powder composition 15Cr17Ni12V3F35ZrO2. The optimal values of the microhardness of the coating of 5000 MPa were achieved due to the optimal transition melting zone of 0.8 ÷ 1.45 mm; the laser radiation power density of 3 × 105 W/cm2; and the diameter of the focus spot of the laser beam of up to 1.3 mm. High corrosion resistance and tribology were achieved by an optimally matched distance of 10 ÷ 15 mm and a surfacing speed of 15 mm/s. Homogeneous spheroidized particles of the material were observed in the martensitic phase of the structure. The stable compression stresses in the phase structure during the laser deposition of zirconium dioxide were fixed at the level of 1.0 ÷ 1.5 N/m2, and the compression stresses were at the level of 0.2 ÷ 0.4 N/m2. A multifactorial experiment established the dependence of the coating hardness on the distance to the focal plane and the energy characteristics of the laser source, providing optimal laser parameters (area, pulse power, and duration).

Engineering J-aggregates for NIR-induced meso-CF3-BODIPY nanoparticles by activated apoptosis mechanism in photothermal therapy

Forming J-aggregates by organic monomer is a fascinating strategy to urge spectroscopic redshift with respect to that of the monomer. Herein, we designed 1,7-diphenyl-substituted meso‑CF3-BDP monomer confirmed by X-ray crystallographic analysis. The low-barrier rotation of the –CF3 group in meso‑CF3-BDP 1 significantly enhances the non-radiative efficiency, and the photothermal conversion efficiency (PCE) of the self-assembled nanoparticles (1-NPs: λabs = 746 nm) by J-aggregates was 82%. 1-NPs could effectively block cell cycle progression, inhibit cancer cell proliferation and trigger cell apoptosis under low power laser irradiation (0.2 W/cm2). This study proposes an alternate molecular design platform by J-aggregates to promote PCE through the insertion of rotating segment and trigger the cancer cells apoptosis in photothermal therapy at low power laser density.

Room Temperature 2-Fold Morphology Porous Silicon Impedance Matching Pesticide Sensor

In this work, an investigation was conducted to study the effect of electrodes’ configuration of the double morphology macPSi on the performance of electrically matched impedance pesticides sensors. The purpose was to develop an efficient electrical sensor for the quantitative detection process of (Chlorpyrifos) pesticide in organic solvents. The effect of electrodes configuration of the front, front-back, and back coplanar electrodes on macPSi as based substrate was tested to select an optimum sensor metallization pathway. The based efficient macPSi layer was fabricated using elevated laser irradiation power density at different periods. Morphological, optical, and electrical properties of the sensors were investigated using field emission scanning electron microscope (FE-SEM), X-ray diffraction (XRD), photoluminescence (PL) spectroscopy, and R-L-C measurement. The sensing method depended on measuring the resonance frequency shift as the organic solvent was exposed to the sensor’s surface. The sensor’s performance at various configurations and concentrations ppm was inspected at room temperature. The current findings revealed extremely low instabilities (less than 0.017 %), higher sensitivity, and a detection limit of 0.004ppm for top coplanar electrode configuration. The fabricated sensor is simple and low-cost for excellent quantitative pesticide detection.

Experimental study on characteristic and mechanism of simulated lunar rock destruction under high energy laser irradiation

The large load and poor heat dissipation of moon rock core drilling leads to the difficulty of rock breaking and low drilling and sampling efficiency. As a new auxiliary rock breaking method, laser rock breaking is expected to be applied to perturbation sampling in lunar rock drilling. Revealing the fracture characteristics and mechanism of rock under laser irradiation is an important basis for realizing laser-assisted lunar rock sampling. Basalt was used as simulated lunar rock sample, and its mechanical response characteristics under laser irradiation were analyzed from macro to micro point of view, and the failure law under different laser power and different irradiation time was explored. The results show that the failure of the sample under laser irradiation is mainly characterized by local rock melting and dynamic crack propagation, and the surface temperature of the sample follows the characteristics of Gaussian distribution. The laser power has a greater influence on the degree of rock weakening than the irradiation time. Laser irradiation of rocks can significantly reduce rock strength, and has obvious effects on improving rock breaking efficiency and reducing in situ disturbance. It is expected to provide theoretical and technical support for assisting lunar rock drilling and sampling in the future.

Исследование оптически индуцированного формирования магнонных зон в структуре ЖИГ | периодический арсенид галлия

The present work is devoted to the study of the optically induced formation of the band structure of a magnon crystal consisting of a ferrite microwave diode loaded with a semiconductor with periodic thickness modulation. Using the Brillouin light scattering method, it is demonstrated that an increase in the power of laser radiation illuminating the semiconductor layer leads to the formation of non-transmission bands in the spectrum of surface magnetostatic waves (PMSW) with a simultaneous increase in the central frequency of these bands. Using the finite element method, we connected the formed non-transmission bands with the Bragg resonances of the periodic structure, and also evaluated the effect of changes in the density of semiconductor electrons on the dispersion dependences and non-reciprocal properties of PMSV in such a structure.