Interaction Of Laser Beam Research Articles

CO2 laser interactions with wood tissues during single pulse laser-incision

Incising is a technique used to improve fluid flow in impermeable woods during wood treatment processes. Previous studies relating to the laser-incision of wood have neglected many aspects such as detailed analysis of the anatomy of the wood, including consideration of tangential/radial faces and earlywood/latewood interactions with the laser beam. By considering wood anatomy, a complete investigation of the CO2 laser-incision processes is presented that yields new knowledge of laser beam interaction with growth rings when incising into tangential/radial faces, and the low-density earlywood and higher density latewood within the growth ring. Southern Yellow Pine, Radiata Pine, European Redwood and Beech, each having different bulk densities, were laser-incised using a 2 kW ROFIN CO2 laser with radiation in the far-infrared regime (10.6 μm). Microstructural characterisations were carried out to better understand the effect of CO2 laser-incision and its parameters on the depth, diameter and quality of the incised holes. The laser-incised hole shapes were found to be uniform in depth, however, the hole circularity was significantly affected by the presence of earlywood and latewood tissues. Maximum and minimum diameters of incised holes were measured in the Radiata Pine (~1.3 mm) and in the Beech (~0.7 mm), respectively. Similarly, for equal laser powers used, the maximum and minimum depths of laser-incised holes were measured in the European Redwood (~33 mm) and in the Beech (~25 mm), respectively, with the laser incident on the radial face of the samples. CO2 laser pulse duration had a greater effect on diameter and depth of incised holes when compared to laser power and showed that the CO2 laser pulse duration is a dominant parameter when designing CO2 laser-incision processes.

Experimental determination of scattering processes in the interaction of laser radiation with polyamide 12 powder

Energy density, scanning strategy and laser spot size are some of the parameters influencing the optical energy input during laser-based powder bed fusion of polymers. For newly developed polymer powders, such parameters must still be determined empirically. Understanding the complex mechanisms underlying the beam-matter interaction, including absorption characteristics or multiple scattering behavior, is crucial to predict material processability and to improve interlayer fusion for enhanced final part properties.A measurement system based on two integrating spheres is employed to analyze the scattering processes during the interaction of a CO2 laser beam with polymeric powder materials. The setup is used to measure total reflection from the sample surface as well as unscattered and diffuse transmission through the sample. The resulting optical properties of polyamide 12 powder are evaluated and compared to those of thin films of the same base material. Thus, the influence of particle interfaces on the energy deposition characteristics can be analyzed qualitatively.

Nanoplasma properties in metallic clusters driven by a Gaussian laser beam in the presence of helical magnetic undulator

The motivation of present paper is the investigation of effective permittivity and absorption cross section of cluster nanoplasmas in the interaction of a Gaussian laser beam with a cluster of metallic nanoparticles, in the presence of a helical magnetic undulator. The static magnetic field of the undulator couples with the field of the laser wave, and forms a nonlinear force in the interaction region. As a result, the nonlinear force varies the plasmonic oscillations of the electron of nanoplasmas that leads to electron density modulation, which modifies absorption cross section and effective permittivity of nanoparticles. Using a perturbative method, we analytically derived the nonlinear dispersion waves and dielectric constant of metallic nanoparticles lattice (gold, silver, and copper) in the presence of a helical magnetic undulator. Numerical results indicate that with increasing the undulator magnetic field strength, absorption cross section of cluster nanoplasmas increases and absorption phenomenon occurs at frequencies close to the effective plasma frequency. Besides, with decreasing distance of nanoparticles in the cluster (and with increasing the nanoparticles radius), absorption cross section increases. We also found that the dielectric constant of the cluster nanoplasma medium increases with enhancing undulator magnetic field strength only near the effective plasmonic frequency. This concept opens a path toward new properties of cluster nanoplasmas as quantum dots, diagnostics, and sensors based on magnetic undulator structures.

The Impact of Laser Radiation on Polypropylene Molded Pieces Depending on Their Surface Conditions

The article presents an analysis of the impact of a laser beam interaction (Nd: YVO4) with selected operational parameters on the quality of graphical marks obtained on the surfaces of polypropylene-molded pieces with different surface textures (variable parameters of the surface layer). Polypropylene test specimens were produced by injection using the original injection mold, which allowed for the obtainment of products with variable surface finish parameters determined by the surface condition of the forming cavity. The presented relationship between the parameters of laser performance, the texture of a molded piece surface, the molded piece’s color, and types of masterbatches supporting the marking process allows for the assessment of the efficiency of graphic symbol application by laser marking. The original evaluation criteria for the conducted process were adopted.

Simulation of the interaction of a high energy laser beam with the sea surface in the short wavelength infrared

The knowledge of the interaction of a high energy laser beam with a dynamic sea surface is of great practical interest in maritime environments. The components transmitted into the sea and reflected at the sea surface have to be considered. The calculation of energy transfer into the sea is fundamental to the prediction of upper-ocean heating and temperature-dependent optical properties of the sea, which in turn influence its reflectance characteristics. In addition, the spatial energy (or power) distribution of the laser beam reflected at the dynamic sea surface is also of high significance. For the estimation of the laser light energy reflected into a specific spatial direction, several parameters need to be considered, e.g., wind speed, wind direction, and fetch. The calculated amount of light energy reflected into a specific direction varies statistically and depends largely on the dynamics of the wavy sea surface. A 3D simulation of a dynamic sea surface is presented interacting with a high energy laser beam in the short wavelength infrared spectral band. The simulation computes the upper-ocean heating, the temperature-dependent Fresnel reflectances, and the absorption in seawater considering the laser geometric configuration. For the reflectance calculations, a bistatic configuration of the laser source and receiver is regarded, where the receiver positions are on a virtual hemisphere having the laser spot center as the center point. The specular reflection of the laser beam at the sea surface is modeled by an analytical statistical bidirectional reflectance distribution function of the sea surface. The simulation is restricted to sea surfaces heated to the boiling point to avoid complex phase transition effects between water and gas. For a high energy laser beam focused on a small laser spot on the evolving wavy sea surface, the maximum expected reflected laser power is calculated for the specular forward- and back-reflection direction for glints. The probability of occurrence and temporal occurrence of those glint events is estimated for both directions.

Coupling effects and ultrafast third-order nonlinear optical behavior in ion-implanted silicon quantum dots and platinum nanoclusters

Third-order nonlinear optical properties exhibited by ion-implanted hybrid systems integrated by Silicon quantum dots and Platinum nanoclusters embedded in a Silica host matrix are reported. Femto-, pico- and nano-second pulses were employed as optical sources with excitation wavelengths at 830 nm, 355 nm and 532 nm, respectively. Transmission electron microscopy studies revealed sizes between 3 and 7 nm for Si quantum dots and 0.5–4 nm for Pt nanoclusters. Quantum confinement effects in this nanoscale seem to dominate the physical properties of the nanostructures and they must be taken into account to describe the interaction of intense laser beams with the hybrid nanocomposites. Femtosecond Z-scan studies showed a strong nonlinearity provided by the Si quantum dots influence, with no important contribution from the Pt nanoparticles to the nonlinear absorption and positive refractive index exhibited by the sample at 830 nm wavelength. Picosecond two-wave mixing experiments with self-diffraction indicate an enhancement close to one order of magnitude at 355 nm compared to the 532 nm wavelength of excitation. The picosecond results can be explained from the active participation of Pt nanoclusters together with Si quantum dots which can be efficiently excited at shorter wavelengths to reach higher electronic states above their energy band gaps. This selectable behavior by changing wavelength and pulse duration of excitation can be useful for tuning multifunctional operations performed by all-optical nanodevices.

Obliquely incident laser and electron beam interaction in an undulator

The angular drift of a laser beam is of particular concern in applications such as seeded free-electron lasers. A systematical study of the obliquely incident laser and electron beam interaction in an undulator is presented in this paper. Theoretical analysis and numerical simulations demonstrate that the interaction would imprint energy and angular modulations on the electron beam simultaneously. Compared with the normally incident pattern, the obliquely incident laser-electron interaction leads to reductions in the bunching factors of HGHG and EEHG. In the meanwhile, proactive applications of this multi-dimensional modulation technique may bring vitality to the field of laser-electron manipulation

Space and time resolved measurement of surface magnetic field in high intensity short pulse laser matter interactions

Magnetic fields produced by the interaction of intense laser beams on the surface of flat solid targets have been characterized. Laser probe polarimetry diagnosed the spatial and temporal evolution of the magnetic field by measuring the changes in the probe beam polarization due to Cotton-Mouton and Faraday effects at different times with respect to a pump laser pulse. The results show that 1 ps after the interaction of the pump laser with the target, a magnetic field of the order of a few MG is already present over a region ≈150 μm in diameter centered around the interaction spot. From the spatial and temporal evolutions of the magnetic field, we infer information on the resistivity of the material, showing evidence of a strongly magnetized resistivity.

Extending the constraint for axion-like particles as resonances at the LHC and laser beam experiments

We study the discovery potential of axion-like particles (ALP), pseudo-scalars weakly coupled to Standard Model fields, at the Large Hadron Collider (LHC). Our focus is on ALPs coupled to the electromagnetic field, which would induce anomalous scattering of light-by-light. This can be directly probed in central exclusive production of photon pairs in ultra-peripheral collisions at the LHC in proton and heavy-ion collisions. We consider non-standard collision modes of the LHC, such as argon-argon collisions at sNN=7 TeV and proton-lead collisions at sNN=8.16 TeV, to access regions in the parameter space complementary to the ones previously considered for lead-lead and proton-proton collisions. In addition, we show that, using laser beam interactions, we can constrain ALPs as resonant deviations in the refractive index induced by anomalous light-by-light scattering effects. If we combine the aforementioned approaches, ALPs can be probed in a wide range of masses from the eV scale up to the TeV scale.

Modulation instability and soliton formation in the interaction of X-ray laser beam with relativistic quantum plasma

In this theoretical study, based on a nonlinear wave equation describing the interaction of fields of an X-ray laser beam with relativistic quantum plasma, modulation instability and formation of solitary waves are investigated. Analytical expressions are derived for the growth rate of modulation instability and electromagnetic envelope solitons. The frequency interval of instability and the dependence of the growth rate on some physical parameters such as the initial laser beam amplitude and frequency are considered. Additionally, the effect of the laser amplitude on the solitary waves is studied. It is shown that quantum effects lead to the reduction of nonlinearity of plasma.

Laser absorption behavior of randomly packed powder-bed during selective laser melting of SiC and TiB2 reinforced Al matrix composites

In this paper, a randomly packed powder-bed model by sequential addition method was established mathematically and physically to simulate the condition of the interaction between the laser beam and powder particles. The ray-tracing calculation was used to analyze laser absorptivity and irradiance distribution occurring on powder particle surface as well as the influence of reinforcements on the laser energy absorption during selective laser melting additive manufacturing of pure AlSi10Mg, SiC/AlSi10Mg and TiB2/AlSi10Mg materials. The simulation results reveal that addition of reinforcements enhanced the interactions of laser beam with powder particles, which were illustrated by an increase of laser ray track spots on the particles surface. A respective absorptivity fluctuated from 0.37 to 0.59 and from 0.34 to 0.49 for the randomly packed SiC/AlSi10Mg and TiB2/AlSi10Mg, both of which were significantly enhanced with respective to that of AlSi10Mg powder. The addition of ceramic reinforcement particles can significantly improve the absorption irradiance of laser for powder-bed of pure AlSi10Mg, while the SiC reinforcement was more effective in enhancing this effect than TiB2. The influence of different absorption irradiance on the melt pool dimensions and surface morphologies were studied experimentally to verify the reliability of this simulation.

Scanning Velocity Measurement of an Acousto-Optic Deflector

Beside a demonstrated theoretical formula that describes the variation of diffracted order angle as a function of time, another formula about the scanning velocity of an acousto-optic deflector is successfully demonstrated with experimental results very close to the theoretical formula. This deflector is obtained using laser beam interaction with frequency modulated ultrasonic sinusoidal wave in water. The particular attention that devoted to select the best experimental method of measuring scanning velocity has enabled us to find promising results; the scanning velocity of each diffracted order varies linearly according to modulating signal frequency as well as frequency excursion and sinusoidally as a function of time. Furthermore, the scanning maximum velocity of the pth diffracted order is p times the first diffracted order.

Identification of Coupling Mechanisms between Ultraintense Laser Light and Dense Plasmas

The interaction of intense laser beams with plasmas created on solid targets involves a rich non-linear physics. Because such dense plasmas are reflective for laser light, the coupling with the incident beam occurs within a thin layer at the interface between plasma and vacuum. One of the main paradigms used to understand this coupling, known as Brunel mechanism, is expected to be valid only for very steep plasma surfaces. Despite innumerable studies, its validity range remains uncertain, and the physics involved for smoother plasma-vacuum interfaces is unclear, especially for ultrahigh laser intensities. We report the first comprehensive experimental and numerical study of the laser-plasma coupling mechanisms as a function of the plasma interface steepness, in the relativistic interaction regime. Our results reveal a clear transition from the temporally-periodic Brunel mechanism to a chaotic dynamic associated to stochastic heating. By revealing the key signatures of these two distinct regimes on experimental observables, we provide an important landmark for the interpretation of future experiments.

Acceleration of carbon ions to high energies by a multi-PW laser

Extreme Light Infrastructure (ELI) is a large-scale European project, still in the development stage, offering parameters of laser drivers required for multiple applications (femtosecond pulse duration, ultra-relativistic laser intensities ∼ 1022 - 1023 W/cm2), however studies of ion acceleration in the given intensity regime are still in the very early stages and require a deeper understanding of the processes occurring during laser-matter interactions to maximize the efficiency of ion acceleration. The purpose of this work is a numerical examination of the properties of carbon ion beams produced during the interaction of an ultra-intense laser beams (of intensities ∼ 1021 – 1023 W/cm2 and pulse duration order of femtoseconds, predicted to be available at ELI-NP, Romania) with C12 target. The dependence of ion beam parameters, such as intensity, energy spectrum, maximum and average ion energy and spatial distribution of ion charge density, on laser pulse parameters (mainly intensity) and the target thickness is investigated. The possibility of generation of high intensity, GeV energy ion beams in the foregoing conditions is demonstrated. The obtained results can be useful for research in high energy-density physics, nuclear physics or medical applications of ion beams.

Scanning velocity measurement of an acousto-optic deflector-=SUP=-*-=/SUP=-

Beside a demonstrated theoretical formula that describes the variation of diffracted order angle as a function of time, another formula about the scanning velocity of an acousto-optic deflector is successfully demonstrated with experimental results very close to the theoretical formula. This deflector is obtained using laser beam interaction with frequency modulated ultrasonic sinusoidal wave in water. The particular attention that devoted to select the best experiment method of measuring scanning velocity has enabled us to find promising results; the scanning velocity of each diffracted order varies linearly according to modulating signal frequency as well as frequency excursion and sinusoidally as a function of time. Furthermore, the scanning maximum velocity of the pth diffracted order is p times the first diffracted order.

Relationship Between Parasitic Infections in Diabetic Patients and the Importance of Raman Spectroscopy in Determining Parasites at Molecular Level

<i>Diabetes mellitus</i> (DM) is a metabolic disorder of protein, carbohydrate and fat. Insulin secretion, insulin action, or both cause to diabetes mellitus. According to the World Health Organization, the number of diabetic patients in the world is around 200 million and it is stated that this number will reach 300 million in 2025. Parasitic diseases are widespread all over the world and are a major public health problem, especially in underdeveloped or developing countries. It ranks first among the diseases that should be controlled by the World Health Organization. Among the factors causing parasitic diseases include protozoa, helminths and arthropods. In certain geographical areas where parasitic infections are common, many autoimmune diseases such as asthma, rheumatoid arthritis (RA), type1diabetes (T1DM), multiple sclerosis (MS), and inflammatory bowel diseases (IBD) are reported to have a lower incidence. The relationship between helminth infections on the onset and development of T1DM, one of the multigenetic diseases affected by environmental factors, is remarkable. It is not clear how helminth infections prevent T1DM development. In diabetic patients, it is known that there is a decrease in immune system functions, especially cellular immunity, and in these patients CD8 and CD16 values for suppressor T cells and NK cells are decreased compared to normal individuals. Therefore, it does not prevent the development of diabetes and can be seen more in patients with diabetes. Raman Spectroscopy (RS) is a vibrational technique due to inelastic scattering that occurs during the interaction of monochromatic laser beams with molecules. It is preferred in biomedical examinations because RS does not damage the sample and can be obtained quickly by non-invasive method. DM and different parasitic diseases can be determined by analyzing the spectra obtained in RS examinations. The obtained Raman spectra of different molecular systems are different and each system has its own fingerprint.

Plasma solenoid driven by a laser beam carrying an orbital angular momentum

A tens of Tesla quasi-static axial magnetic field can be produced in the interaction of a short intense laser beam carrying an Orbital Angular Momentum with an underdense plasma. Three-dimensional "Particle In Cell" simulations and analytical model demonstrate that orbital angular momentum is transfered from a tightly focused radially polarized laser beam to electrons without any dissipative effect. A theoretical model describing the balistic interaction of electrons with laser shows that particles gain angular velocity during their radial and longitudinal drift in the laser field. The agreement between PIC simulations and the simplified model identifies routes to increase the intensity of the solenoidal magnetic field by controlling the orbital angular momentum and/or the energy of the laser beam.

Nanoscale investigation by TEM and STEM-EELS of the laser induced yellowing

Nd-YAG QS laser cleaning of soiled stone at 1064 nm can sometimes result in a more yellow appearance compared to other cleaning techniques. Especially in France, this yellowing effect is still considered as a major aesthetic issue by the architects and conservators. One explanation states that the yellowing is linked to the formation of iron-rich nanophase(s) through the laser beam interaction with black crusts that would re-deposit on the cleaned substrate after irradiation. To characterize these nanophases, a model crust containing hematite was elaborated and laser irradiated using a Nd-YAG QS laser. The color of the sample shifted instantaneously from red to a bright yellow and numerous particles were ablated in a visible smoke. Transmission electron microscopy (TEM) was used to examine the morphology and the crystallinity of the neo-formed compounds, both on the surface of the samples and in the ablated materials. In addition, an investigation of the chemical and structural properties of the nanophases was conducted by X-ray dispersive energy (EDX) and electron energy loss (EELS) spectroscopies. It was found that both the surface of the sample and the ablated materials are covered by crystallized nano-spheres and nano-residues, all containing iron and oxygen, sometimes along with calcium and sulfur. In particular an interfacial area containing the four elements was evidenced between some nanostructures and the substrate. Magnetite Fe3O4 was also identified at the nanoscale. This study demonstrates that the laser yellowing of a model crust is linked to the presence of iron-rich nanophases including CaxFeySzOδ nanostructures and magnetite Fe3O4 at the surface after irradiation.

THE MORPHOLOGY FEATURES OF NANOSTRUCTURE OF ZIRCONIUM, MOLYBDENUM AND WOLFRAM OXIDES SYNTHESISED BY LASER ABLATION OF METALS IN WATER

The paper gives the investigation results of composition and morphology of oxide nanostructures of transition metals – zirconium, molybdenum and wolfram synthesized by laser ablation pure metals in water. High temperatures and pressures in zone of interaction of the pulse laser beam with the surface of metal in water contribute to the intensive synthesis of oxides in the form of clusters of particles with size about 1−2 nanometres. This is characteristic for metals with high ionization potential. As it follows from the data of X-ray diffraction analysis and scanning electron microscopy, specifically, the clusters are amorphous building material for nanostructures of the oxides of the metals enumerated above. The paper demonstrates the general pattern of their structure, namely, the stratification of the material from which the foam formations, thin-walled hollow round particles, plates, filaments, and other forms of nanostructures are composed. The research of morphological features of the nanostructures of zirconium, molybdenum and wolfram oxides obtained by the authors indicates that their use as substrates will achieve high gain values of Raman scattering ~ 10 4 −10 8 . In this range, there are the gain data previously obtained by the authors in the experiments on the synthesis of zirconium nano-oxides when using them as a substrate. This indicates that the nanostructures of molybdenum and wolfram nano-oxides also can serve as the effective substrates and can be used as a sensor in the high sensitive composition of substances analyzers based on surface enhanced Raman scattering.

Laser Sintering of Abrasive Layers with Inclusions of Cubic Boron Nitride Grains

One of the mainstream technologies for industrial tools manufacturing is the high-speed local heating technique that drastically increases the productivity of tools manufacturing. With further optimization of sintering processes, it is possible to manufacture industrial processing tools with high density and relatively small grain size. The use of a focused laser beam as a heating source also contributes significantly to the increase in productivity of tool manufacturing and broadens the range of bonding materials that could be used to form the Cubic boron nitride (CBN) containing abrasive layers. The research is mainly focused on the irradiation of CBN grains with lasers of two different wavelengths - λ = 1.06 μm and λ = 10.6 μm. Technological parameters of laser processing were as follows: Laser power P – 200 - 700 W, focal spot diameter d – 3 mm, processing speed V – 0.01 - 2.0 m/min. The density of CBN grains was measured before and after laser irradiation using DA-2 measuring unit according to standard procedure. Bronze and Nickel powders (BrО10 and PS-12 N-WC) were used as a bonding material. They were mixed with CBN grains and were applied onto the steel base plates followed by laser irradiation of the prepacked layer. Scanning electron microscopy (SEM) was used to investigate the microstructure of samples along with local and integral X-ray element analysis. Microhardness of irradiated samples was measured as well. The interaction of laser beam and CBN grains was studied in detail and relationships between key technological parameters and quality of composites (grains durability, wear resistance and bonding strength) was established.