High-intensity Laser Research Articles

High-velocity laser accelerated deposition (HVLAD): An experimental study

A versatile solid-state cladding technique named high-velocity laser accelerated deposition (HVLAD), which is capable of creating highly uniform coverage on various surfaces, is reported here. The method is a non-thermally driven, mechanically based process that relies on laser peening (LP) technology which has been used for commercial applications for decades. In HVLAD, a high-intensity laser is used to accelerate, propel, and deposit small areas of a thin film in a controlled step-by-step manner onto a substrate. This process can be repeated until a desired thickness of material is deposited onto the substrate. This technique does not generate any large variations in temperature between the thin film and the substrate material. Instead, it employs intense laser pulses with energies up to 50 J for a duration of 8–50 ns to create a plasma generated pressure wave which accelerates the thin film in the order of a few hundred meters per second into the substrate material. Two cladding methods were evaluated in this study including the confined method, which incorporates a confining water media and a vinyl tape overlay, and the unconfined method which does not. High speed and thermal imaging cameras showed no macrolevel melting or significant temperature increase in the clad or substrate material during the cladding process, however signs of microlevel melting and re-solidification were observed at the interface primarily in specimens cladded using the unconfined method. Grain structures in adjacent areas to the clad location remained preserved using both methods, and no signs of any phase or alloy composition changes, except for at the interface, were observed. The effects of a confining media (water) and vinyl tape in the process were studied both analytically and experimentally and a change in the deposition mechanism was observed. With further research and development this technique has the ability to be used to deposit a variety of coatings without any limitations dictated by their strength on complex geometries in a cost-effective manner. The HVLAD process can be implemented to deposit corrosion, wear, thermal, and even impact-resistant coatings with strong bonding on a wide range of substrates.

Characterization of a platform for the gas transport, collection, and identification of fission products in the high-intensity laser environment

Recent progress in the production of laser accelerated high flux proton beams opens new possibilities for the study of fission in unique environments. To this end, we are currently pursuing the development of a platform for the swift gas transport, collection, and identification of fission products. Fission is induced in targets fixed inside a sealed chamber through which a carrier gas flows, transporting fission products to a carbon filter for collection and online spectroscopy. This has been recently demonstrated using target normal sheath accelerated protons at the PHELIX laser facility. There were large discrepancies between measured rates and those expected based on established fission yields and measured beam parameters. These discrepancies prompted a large number of tests at the Idaho Accelerator Center (IAC), where fission in uranium is induced by bremsstrahlung photons generated by 21 MeV electrons from a linear electron accelerator. The results are compared to a series of models that account for the slowing of energetic fission fragments in the carrier gas and the fluid dynamics of the gas flow that transports fission products to the collection filter. Characterization of the apparatus reveals a few mechanisms that together account for a portion of the previously observed discrepancies at the PHELIX laser facility. However, additional research is necessary before high-accuracy experiments can be performed with the apparatus. Work performed under the auspices of the U.S. Department of Energy by LLNL under contract DE-AC52-07NA27344.

High-intensity laser pulse interaction with a counter propagating electron beam for terahertz field generation in magnetized plasmas

High-intensity laser pulse interaction with a counter propagating electron beam for terahertz field generation in magnetized plasmas

Nonlinear Optical Response of Dispersed Medium Based on Conjugates Single-Walled Carbon Nanotubes with Phthalocyanines

Nanosecond lasers have recently been widely involved in human activity. However, high-intensity laser radiation can cause severe damage to organs of vision and expensive photonic devices. Radiation in the near UV range is especially dangerous for human eyes, since it is strongly absorbed by biological media and is also invisible, i.e., the reaction time of the eye to such radiation is much lower than that of visible light. Passive limiters have high transmission (>70%) at a low light intensity and begin to “darken” only when the threshold value of the laser radiation intensity is reached. In this work, we studied liquid nanodispersed nonlinear optical limiters based on hybrids of single-walled carbon nanotubes (SWCNTs) with metal-free tetra(hydroxy)phthalocyanine (OH)4PcHH). The value of the hydrodynamic radius of separate particles after (OH)4PcHH binding increased from 288 ± 55 nm to 350 ± 60 nm, which confirms the attachment of phthalocyanine complexes to nanotubes. The third harmonic of a Nd:YAG nanosecond laser (355 nm, 20 ns) was used to study the nonlinear optical response. Based on a Z-scan with open-aperture and input-output dependence curves, third-order nonlinear optical absorption coefficients of 149, 236, and 229 cm/GW were obtained for dispersions of composites of SWCNTs and (OH)4PcHH in water, dimethylformamide (DMF), and dimethylsulfoxide (DMSO), respectively. Threshold values did not exceed 100 mJ/cm2. The Z-scan showed a gradual decrease in the duration of the laser pulse by 53%; however, near the focus, there was a sharp increase in the duration of the transmitted pulse, reaching a value of 29 ns in z = 0. This phenomenon confirms the occurrence of reverse saturable absorption in the investigated media and can be used in photonic devices to control the temporal characteristics of the signal. Thus, the possibility of protection of sensitive photonic devices and human eyes from nanosecond laser pulses in the near UV range by nanodispersed liquid media based on composites of SWCNTs with (OH)4PcHH has been discussed in this paper.

Branching of High-Current Relativistic Electron Beam in Porous Materials.

Propagation of high-current relativistic electron beam (REB) in plasma is relevant to many high-energy astrophysical phenomena as well as applications based on high-intensity lasers and charged-particle beams. Here, we report a new regime of beam-plasma interaction arising from REB propagation in medium with fine structures. In this regime, the REB cascades into thin branches with local density a hundred times the initial value and deposits its energy 2 orders of magnitude more efficiently than that in homogeneous plasma, where REB branching does not occur, of similar average density. Such beam branching can be attributed to successive weak scatterings of the beam electrons by the unevenly distributed magnetic fields induced by the local return currents in the skeletons of the porous medium. Results from a model for the excitation conditions and location of the first branching point with respect to the medium and beam parameters agree well with that from pore-resolved particle-in-cell simulations.

16Cr3Al-Hf ODS steel: Surface effects of high laser intensity of 1015 W/cm2 in ambiences of air, helium and vacuum

Behavior of ODS steel under high energy fluxes is important as it is one of the most promising fusion reactor materials. The addition of hafnium provides improved microstructure and therefore better mechanical properties at high temperatures, and the goal here was to investigate the effects induced on Hf-containing ODS steel by the action of high-intensity ∼1015 W/cm2 radiation obtained by ultrashort pulsed laser. Morphological and chemical parametric study of the surface was conducted at different work ambiences. New data were obtained on damage parameters, threshold fluences and chemical changes. Measured damage depths were ∼7.5 μm (air), ∼14 μm (helium), ∼48 μm (vacuum), which is somewhat lower compared to ODS steel without the addition of hafnium.

Monte Carlo simulations for the evaluation of oligomerization data in TOCCSL experiments

The interplay and communication between cells build the foundation of life. Many signaling processes at the cell surface and inside the cell, as well as the cellular function itself, depend on protein-protein interactions and the oligomerization of proteins. In the past, we presented an approach to single out interactions of fluorescently labeled membrane proteins by combining photobleaching and single-molecule microscopy. With this approach, termed “thinning out clusters while conserving the stoichiometry of labeling” (TOCCSL), oligomerization can be detected even at physiologically high surface densities of fluorescently labeled proteins. In TOCCSL, an aperture-restricted region of the plasma membrane is irreversibly photobleached by applying a high-intensity laser pulse. During a recovery time, in which illumination is turned off, nonphotobleached molecules from the nonilluminated area of the plasma membrane re-populate the aperture-restricted region. At the onset of this recovery process, these molecules can be detected as well-separated, diffraction-limited signals and their oligomerization state can be quantified. Here, we used extensive Monte Carlo simulations to provide a theoretical framework for quantitative interpretation of TOCCSL measurements. We determined the influence of experimental parameters and intrinsic characteristics of the investigated system on the outcome of a TOCCSL experiment. We identified the diffraction-affected laser intensity profile and the diffusion of molecules at the aperture edges during photobleaching as major sources of generating partially photobleached oligomers. They are falsely detected as lower-order oligomers and, hence, higher-order oligomers might be prevented from detection. The amount of partially photobleached oligomers that are analyzed depends on the photobleaching and the recovery time, on the mobility of molecules and—for mixed populations of oligomers—on mobility differences between different kinds of oligomers. Moreover, we quantified random colocalizations of molecules after recovery, which are falsely detected as higher-order oligomers.

Damage effects of high-intensity laser pulse on W for fusion applications: modelling and experiments

In future nuclear fusion reactors plasma-facing materials (PFMs) will be exposed to transient high energy events such as disruptions, edge localized modes (ELMs) and vertical displacement events (VDEs) which may cause melting and vaporization leading to component damage and plasma contamination. The interaction between plasma and refractory metals, namely bulk tungsten (W) and W deposited by plasma spraying (PS-W), has been simulated through a single laser pulse of high energy (≈ 4 J) and short duration (≈ 15 ns). The morphology of the zone affected by laser pulse has been then examined by scanning electron microscopy (SEM) and 3D optical surface profilometry. Both an analytical and a numerical thermal model of the phenomenon based on the specific conditions of heat transfer from the laser spot into each irradiated material were developed. The attention has been focused on the erosion occurring on the material surface because this is the primary cause of damage of PFMs and plasma contamination. Numerical, analytical, and experimental results were found in good agreement.

Multi-field coupling characteristics of the thermophotovoltaic cell under high-intensity laser beam radiation

Improving energy conversion efficiency is a crucial challenge in the development of thermophotovoltaic (TPV) technology, particularly under high-intensity radiation, where enhancing energy reuse can have significant environmental benefits. The current study aims to address this challenge by constructing an optical-thermal-electric coupled conversion model of a single thermophotovoltaic (TPV) cell under high-intensity laser beam radiation. The primary connection parameter in the coupling model is a spectral response (SR). Therefore, the SR experimental platform has been established to obtain accurate parameter values. A fitting formula between SR, temperature, and wavelength was established and validated by testing. Based on the suitable fitting formula, the finite element method (FEM) has been used to study the energy distribution of incident optical and thermal heat transfer, as well as the electric characteristics of the TPV cell. The performance of a thermophotovoltaic (TPV) cell can be characterized by its I-V curve, which is influenced by various factors such as temperature, incident radiation, and spot size. In particular, it was found that when the incident radiation energy is the same as the spot size increases from 4 to 7 cm, the change in current is not proportional to the spot diameter. The results showed that the maximum power output could be achieved when the spot diameter was 6 cm. However, the temperature is the decisive factor affecting the conversion performance of the cell. The energy conversion efficiency can rise by 40.54% if the convective heat transfer coefficient is doubled. Therefore, it is important to maintain the TPV cell at a low temperature to achieve optimal electric conversion efficiency.

A Literature Review on High Intensity Laser Therapy in Patients with Chronic Low Back Pain

A Literature Review on High Intensity Laser Therapy in Patients with Chronic Low Back Pain

Effectiveness of High-Intensity Laser Therapy in Patients with Lateral Epicondylitis on the Level of Disability, Pain, Grip Strength and Quality of Life: A Systematic Review and Meta-Analysis

The systematic review and meta-analysis aim to evaluate the clinical effectiveness of High-Intensity Laser Therapy (HILT) in managing Lateral Epicondylitis (LE). The electronic databases (Pubmed, Europepmc, NCBI-NIH, Medline, Science direct, and google scholar) were searched. Studies that meet the following criteria are included in the review: 1) experimental studies, 2) participants were diagnosed with LE, 3) at least one of the treatment groups included HILT, and 4) at least one research outcome was on level of disability of elbow, level of perceived pain, handgrip strength, or quality of life. The last search was conducted in May 2021. Six studies (n=321) were included in the review. Overall, HILT significantly reduced pain comparing with the active controls (weighted mean difference: -0.65; 95% CI-0.98 to -0.33; p=0). Also, effect of HILT on improving participants’ quality of life in physical domain was significantly better than that of the active controls. (Standardized mean difference: 0.486; 95% CI=0.066 to 0.906; p=0.023). Though all included studies revealed that HILT had a higher therapeutic effect than the comparators in aspects of grip strength and level of disability, no significant difference was detected. These outcomes show a “weak” strength of evidence in quality assessment. In conclusion, although HILT showed a positive impact on LE, the number of studies on HILT was limited and the risk of selection, performance and detection bias was revealed. Therefore, further well-designed studies are warranted

SiC Measurements of Electron Energy by fs Laser Irradiation of Thin Foils.

SiC detectors based on a Schottky junction represent useful devices to characterize fast laser-generated plasmas. High-intensity fs lasers have been used to irradiate thin foils and to characterize the produced accelerated electrons and ions in the target normal sheath acceleration (TNSA) regime, detecting their emission in the forward direction and at different angles with respect to the normal to the target surface. The electrons' energies have been measured using relativistic relationships applied to their velocity measured by SiC detectors in the time-of-flight (TOF) approach. In view of their high energy resolution, high energy gap, low leakage current, and high response velocity, SiC detectors reveal UV and X-rays, electrons, and ions emitted from the generated laser plasma. The electron and ion emissions can be characterized by energy through the measure of the particle velocities with a limitation at electron relativistic energies since they proceed at a velocity near that of the speed of light and overlap the plasma photon detection. The crucial discrimination between electrons and protons, which are the fastest ions emitted from the plasma, can be well resolved using SiC diodes. Such detectors enable the monitoring of the high ion acceleration obtained using high laser contrast and the absence of ion acceleration using low laser contrast, as presented and discussed.

Laser wakefield acceleration of electrons using Bessel–Gauss doughnut beams for accelerating beam guiding

A high-intensity laser pulse propagating through a gas target disturbs the uniform plasma distribution. Plasma density structures, created by high-order Bessel–Gauss beams for guiding the accelerating Gaussian beam and laser wakefield acceleration of electrons, are analysed using Wake-T and Fourier–Bessel particle-in-cell (FBPIC) simulation tools. The use of Bessel–Gauss doughnut beams increases the acceleration distance and energy of accelerated electrons up to 2.3 times at a 2 mm distance relative to the Gaussian beam of the same intensity.

Short-term Effectiveness of High-intensity Laser Therapy in De Quervain Tenosynovitis: A Prospective, Randomized, Controlled Study.

The effectiveness of high-intensity laser therapy (HILT) has been demonstrated in some musculoskeletal repetitive strain injury disorders. This study aimed to determine the short-term effectiveness of HILT in de Quervain tenosynovitis (DQT). Sixty-four patients with DQT diagnosis (32 males, 32 females; 18-65 years) were randomly divided into two groups. A short opponens splint was applied to both groups and HILT to the treatment group and sham HILT to the control group once a day, on alternate days, 3 days a week, for 5 weeks. Pre- and post-treatment evaluations were made using a visual analog scale (VAS); Quick Disabilities of the Arm, Shoulder, and Hand questionnaire; Short Form-36 Health Survey; and hand grip strength test. The demographic results (age, gender, duration of complaint, body mass index, occupational group) of both groups were similar (p>0.05). The pre-treatment measured values were similar in both groups (p>0.05). After a 5-week treatment, a significant improvement was observed in all parameters in both groups. Post-treatment, hand grip strength levels were statistically higher in the HILT group than in the sham therapy group, and VAS levels were significantly lower (p<0.001). HILT is a non-invasive and reliable method that increases grip strength and decreases pain in DQT.

Effect of nonlinear saturation of electromagnetic instability on the viscosity of the inertial fusion fuel

One of the interesting topics of recent research is the study of the Weibel electromagnetic instability growth rate in the interaction of high-intensity lasers with the dense plasma of fusion fuel pellets. In this paper, the effect of stresses caused by laser ponderomotive force on the growth rate of Weibel instability in the nonlinear phase is investigated. The growth of the nonlinear phase of Weibel instability growth rate, which is the saturation phase of Weibel instability, in the presence of stress leads to viscosity turbulence. The results show that the coefficient of reduction of fuel viscosity in the presence of the stress flow is about 0.0014 due to the anomalous transfer mechanism caused by the nonlinear growth of the Weibel instability.

Gamma Photons and electron-pairs Generation estimation for collision of PW-class Laser and electron beams

After the proposal of the concept of CPA techniques, the laser intensity has boosted dramatically since then. As the focusing intensity of the laser beam reaches the order above 1023 W/cm2 for multiple PW laser facilities, the laser material interaction enters the QED regime, where the gamma photons generation and electrons-positron pairs generation can be realized. This paper provides an overview of the current research in the field of electrodynamics about laser intensities and electron generation. Basic theories of the generation of e and e- pair and photons are introduced. The history of the development of major laser facilities with high-laser intensities is introduced, and the laser facilities are compared and discuss in terms of the electron generations. The results are further compared with the PIC simulation and typical generation scenarios are demonstrated. Potential limits are mentioned as the drawbacks of the models. Overall, these results shed light on guiding further exploration of laser-plasma interactions in the extremely strong intensity laser beam.

High-quality micro/nano structures of 4H-SiC patterning by vector femtosecond laser

High-intensity femtosecond laser processing of hard and brittle materials such as silicon carbide (SiC) has poor surface quality and is prone to micro-cracks, making it difficult to meet the application requirements of silicon carbide microdevices. In this study, a method for fabricating high-quality micro-nanostructures of 4H-SiC using vector polarized light was proposed. The influences of linear polarization and vector polarization on the quality and surface morphology of processed SiC microgrooves were studied, and the micromachined size rule of microgrooves machined under different pulse numbers was summarized. The damage distribution of microstructures machined by linearly polarized light and vector polarized light were characterized by confocal Raman mapping. The study had shown that using vector beam, especially azimuthal polarization beam, can ensure the uniformity of the processing area, effectively reduce micro-cracks and chipping in the processing of hard and brittle materials, and obtain better processing quality. In addition, the vector polarized light can avoid the large microgroove taper during the processing, and ensure good structure size. Finally, a high-quality multi-ring structure was fabricated by an azimuthal polarization beam, which provides an accurate method for preparing microstructures with excellent performance.

Laser-induced topological spin switching in a 2D van der Waals magnet

Two-dimensional (2D) van der Waals (vdW) magnets represent one of the most promising horizons for energy-efficient spintronic applications because their broad range of electronic, magnetic and topological properties. However, little is known about the interplay between light and spin properties in vdW layers. Here we show that ultrafast laser excitation can not only generate different type of spin textures in CrGeTe3 vdW magnets but also induce a reversible transformation between them in a topological toggle switch mechanism. Our atomistic spin dynamics simulations and wide-field Kerr microscopy measurements show that different textures can be generated via high-intense laser pulses within the picosecond regime. The phase transformation between the different topological spin textures is obtained as additional laser pulses are applied to the system where the polarisation and final state of the spins can be controlled by external magnetic fields. Our results indicate laser-driven spin textures on 2D magnets as a pathway towards reconfigurable topological architectures at the atomistic level.

A photonic resonator interferometric scattering microscope for label-free detection of nanometer-scale objects with digital precision in point-of-use environments

Label-free detection and digital counting of nanometer-scaled objects such as nanoparticles, viruses, extracellular vesicles, and protein molecules enable a wide range of applications in cancer diagnostics, pathogen detection, and life science research. Here, we report the design, implementation, and characterization of a compact Photonic Resonator Interferometric Scattering Microscope (PRISM) designed for point-of-use environments and applications. The contrast of interferometric scattering microscopy is amplified through a photonic crystal surface, upon which scattered light from an object combines with illumination from a monochromatic source. The use of a photonic crystal substrate for interferemetric scattering microscopy results in reduced requirements for high-intensity lasers or oil-immersion objectives, thus opening a pathway toward instruments that are more suitable for environments outside the optics laboratory. The instrument incorporates two innovative elements that facilitate operation on a desktop in ordinary laboratory environments by users that do not have optics expertise. First, because scattering microscopes are extremely sensitive to vibration, we incorporated an inexpensive but effective solution of suspending the instrument’s main components from a rigid metal framework using elastic bands, resulting in an average of 28.7 dBV reduction in vibration amplitude compared to an office desk. Second, an automated focusing module based on the principle of total internal reflection maintains the stability of image contrast over time and spatial position. In this work, we characterize the system's performance by measuring the contrast from gold nanoparticles with diameters in the 10–40 nm range and by observing various biological analytes, including HIV virus, SARS-CoV-2 virus, exosome, and ferritin protein.

Theoretical Simulation of the High–Order Harmonic Generated from Neon Atom Irradiated by the Intense Laser Pulse

Based on the strong field approximation theory and numerical solution of Maxwell’s propagation equations, the high–order harmonic is generated from a neon (Ne) atom irradiated by a high–intensity laser pulse whose central wavelength is 800 nm. In the harmonic spectrum, it is found that in addition to the odd harmonics of the driving laser, a new frequency peak appeared. By examining the time–dependent behavior of the driving laser, it is found that the symmetry of the laser field is broken. We demonstrated that these new spectrum peaks are caused by the intensity reduction and frequency blue shift of the high–intensity laser during propagation. Our results reveal that it is feasible to modulate the harmonics of the specific energy to produce high–intensity harmonic emission by changing the gas density and the position of the gas medium interacting with the laser pulse.