Intense Laser Beam Research Articles

Relativistic cross-focusing of Gaussian laser beams in thermal quantum plasma

Recent work focuses on propagating two intense Gaussian laser beams in thermal quantum plasma considering the relativistic regime. The presence of a second beam affects the focus of another beam in plasma and cross-focusing occurs. Considering the dependence of plasma nonlinearity on the intensity of both beams, an expression for the nonlinear dielectric constant of plasma has been estimated. Nonlinear partial differential coupled equations governing the dynamics of two beams in the thermal plasma are obtained by assuming a quantum hydrodynamic model. The obtained equations are solved numerically using the paraxial ray approximation and the fourth-order Runge-Kutta method. The numerical results show that the second beam strengthens the relativistic factor. Furthermore, variations of the beam width parameter and the laser intensity are investigated with and without the cross-focusing mechanism. This study presents that the cross-focusing enhances laser focusing. The results could be useful in understanding the mechanism of the laser propagation in the quantum plasma that is important in the fast ignition of modern ICF experiments, where deuterium-tritium plasma is compressed by intense laser beams and the quantum effects are dominant.

Transient opto-thermal simulation analysis and experimental validation of LERP systems

Abstract Solid-state technology has revolutionized the lighting industry. However, efficiency-droop-limited LEDs introduce constraints to the luminances achieved, and as a result, laser diodes (LDs) are replacing them in the remote phosphor setup. This introduces a new family of lighting solutions, laser-excited remote phosphor (LERP) systems, which can outperform cutting-edge LEDs. LERP systems however have not yet reached their full potential as the high intensity laser beam induces high temperatures within the phosphor material whose emission characteristics heavily depend on temperature. For this reason, a simulation framework has been developed that combines optical and thermal analysis in order to study and optimize these systems and derive their temperature thresholds for sustainable long-term usage. The focus here is on transient analysis, where the interplay between optical and thermal effects can be accounted for and the time dynamics of the system can be investigated. This enables the study of operation points near or at the thermal quenching regime. Furthermore, advanced material models have been developed in order to incorporate the temperature-dependence. The experimental validation of the model has shown that experimental and simulated results are in good agreement.

Influence of intensity distributions on the process dynamics during laser deep penetration welding of pure nickel with a flexible ring mode laser source

Current research results demonstrate the potential of spatter reduction in laser deep penetration welding by using adapted laser beam intensity distributions between a ring and a core intensity. The spatter-reducing effect, resulting from the additional ring intensity, is often attributed to an enlarged keyhole opening. However, it remains a matter of debate how exactly an additional ring intensity influences the process. This study, therefore, investigates the effect of an increasing ring intensity on process dynamics and the spatter formation regime. Laser beam welding experiments were carried out on 2.4068 nickel hidden T-joints at different welding speeds of up to 16 m/min, as well as different intensity distributions, while maintaining a constant weld depth. The tests were evaluated by using two high-speed cameras from different angles to analyze spatter and their formation mechanisms as well as the keyhole opening. Metallographic analyses and x-ray images were used to determine influences on the seam shape and porosity. It was shown that a change in intensity distribution has a significant influence on the melt flow, the resulting amount of spatter, and the porosity, which is comparable across the investigated welding speeds. While a core-based power distribution leads to spatter formation on the rear of the keyhole opening, it was shown that a ring-based power distribution leads to spatter formation on both sides of the keyhole. With an optimal power distribution, spatter formation could be largely prevented. Based on these findings, the single wave regime, a stabilized regime, and a lateral spatter regime were identified.

EFFECT OF SALINITY CONCENTRATION AND WATER TEMPERATURE ON THE RAYLEIGH WING ACCORDING TO FOUR-PHOTON POLARIZED SPECTROSCOPY DATA

Objective: The purpose of this study is to examine how the temperature of the water and the concentration of NaCl affect the Rayleigh wing line, with an emphasis on how supersonic lattice modulation contributes to the narrowing of the Rayleigh wing and the creation of maxima. Method: To examine the nonlinear optical characteristics of water and aqueous solutions, the study uses four-photon polarization spectroscopy under pre-threshold Brillouin scattering circumstances. The modification of nonlinear cubic susceptibility and its effect on anisotropic scattering were investigated under controlled experimental settings, such as varied salt concentrations and laser beam intensities. Result: The results show that higher water temperatures and NaCl concentrations improve adiabatic compressibility, which in turn raises the Brillouin scattering threshold and decreases the degree of nonlinear cubic susceptibility modulation. Novelty: This study provides new insights into the interplay between the anisotropy of Brillouin scattering, hypersound lattice modulation, and the structural changes in water induced by NaCl concentration and temperature variations, offering a deeper understanding of the microscopic mechanisms influencing water's scattering properties.

Gas flows generated by pulse-periodic optical breakdown and quiet optical discharge

Quiet optical discharge in high-pressure xenon is visually stable pre-breakdown stage of optical discharge supported by pulse-periodic short-wavelength infrared laser radiation with intensity of the order of 109 W/cm2. Increasing the laser intensity leads to the transition of the quiet discharge into a pulse-periodic optical breakdown. In this study, quasi-stationary directional flows generated by both the quiet discharge and the optical breakdown are observed. The flows and their initial stages under limited number of discharge pulses are visualized by shadow imaging method using a point-like laser-plasma radiation source. It is shown that the gas streams outflow points in a quiet discharge correspond to the positions of the laser radiation intensity local maxima in the focal beam waist with astigmatism complicated by defocusing effect of thermal lens arising in the discharge zone. The pulse-periodic optical breakdown emits a turbulent gas flow toward the laser beam. The beam refraction on density gradients in the turbulent flow causes the breakdown instability from pulse to pulse. It was found that time-average absorption of laser radiation in a quiet discharge is about 3% (also in a pulse), while that in optical breakdown is 15% and higher (from 70% to 100% in a pulse). Laser beam intensity for quiet discharge at pulse repetition rate νp = 20 kHz ranges from 1.3 × 109 to 1.5 × 109 W/cm2. At intensities above 4 × 109 W/cm2 and repetition rates νp > 50–55 kHz, laser breakdowns are observed in each laser pulse with the focal ratio f/d ≤ 7. At f/d = 10.6 and νp > 28 kHz, the quiet discharge does not transit to laser breakdown due to defocusing by the thermal lens induced.

A semi-analytical method based on the Green's function for the laser melting process of the metal materials

Thermal responses of the metal materials subjected to intense laser irradiation are complicated due to the phase change in the melting process. In order to simplify this problem, previous studies usually ignored the liquid phase or took the usage of finite element method, which limited the achievement of theoretical breakthroughs. In the present study, a one-dimensional heat transfer model with consideration of phase change was established to describe the melting process of the metal materials caused by a constant intense laser beam. The governing equations with three domains were constructed in the piecewise form: the liquid phase region (melted already), the solid phase region (unmelted yet) and the melting region. The limited discretization method was employed to describe the moving of the soli-liquid interface and the energy exchange. The piecewise governing equations in liquid and solid region were solved separately and analytically by means of the Green's function method, and the calculation result was verified by the finite element simulation. The results of the analytical model were in good agreement with those of the finite element simulation, and the maximal prediction errors of the temperature field prediction between the theoretical model and FE simulation is limited to 2.8 %. In addition, the influences of heat source intensity, material heat conductivity, latent heat on the melting process were discussed in detail. The analytical and simulation results reveal that the semi-analytical solution in piecewise for 1-D laser melting process can be successfully used to reflect the dynamic temperature response of the metal materials and the movement of the solid-liquid interface. This work is of guiding significance for the analytical solution of the multi-dimensional melting process of the metal materials under the fixed and continuous laser beams.

Cumulant method for identifying spatial distributions of laser beam intensity

The article considers the identification of spatial distributions of laser beam intensity, which is of significant practical importance for laser developers when certifying radiation sources. As an identification parameter, a measure of similarity of the measured axisymmetric distributions of laser radiation intensity with a given Gaussian distribution is proposed and investigated. To determine this measure, it is not necessary to first find the beam width at the waist. A mathematical apparatus for identification based on the use of cumulants of spatial intensity distributions is developed. A feature of the method is a limited number of cumulants of the Gaussian distribution, which makes it attractive for practical application. A comparative analysis of a number of two-dimensional distributions with a Gaussian distribution is carried out and it is shown that even with a small number of measured cumulants, high sensitivity of the method to the shapes of intensity distributions is ensured. A similarity measure for continuous one- dimensional intensity distributions of arbitrary shape is presented. The asymmetry measure of two-dimensional spatial distributions of laser beam intensity based on the ratio of moments and cumulants of the fourth and second orders is considered. The proposed measure of similarity of the measured axisymmetric intensity distributions with the Gaussian distribution is an alternative to the well-known propagation coefficient M 2 and can be used together with this coefficient.

Analysis of an induced Langmuir wave by ponderomotive forces and its applicability for plasma diagnostics

We present a numerical study on the electron and ion density perturbation in low-temperature plasmas driven by the frequency detuning of two intense laser beams. Our study is performed in the hydrodynamic regime, which becomes applicable when the plasma grating period induced by the beating of the laser beams is greater than the Debye length and collective processes such as plasma oscillations can be excited. Our findings show a resonance in electron density perturbation as the frequency detuning approaches a value consistent with the Bohm–Gross dispersion relation in low- and high-pressure plasmas. We discuss the potential of this resonance as a diagnostic tool for precisely measuring electron temperature and density in low-temperature plasmas through coherent scattering.

A new method to recycle Li-ion batteries with laser materials processing technology

Efficient and cost-effective recycling of spent lithium-ion batteries is essential for the sustainable growth of the clean energy sector, conserves critical mineral resources, and contribute to environmental sustainability. The pyrometallurgy process, involving high-temperature smelting and solid-state reduction, plays a key role in the industrial-scale recycling of these batteries. Traditional smelting methods, however, face criticism for their substantial energy requirements and the loss of lithium in slag. In this study, an innovative laser-based in-situ pyrometallurgical process, hereinafter referred to as laser recycling, was developed to recycle Li-ion batterie materials without using slag, enabling the simultaneous recovery of Co, Ni, Mn, and Li. Lab-scale experiments were carried out to investigate the influences of laser power density and duration on the carbothermic reduction behavior of battery materials. The results showed that the maximum temperature reached approximately 1850 °C with a laser power between 1500 and 2000 W focused to an area of 20 mm in diameter within a few seconds. The laser recycling facilitates concurrent smelting and solid-state reduction, with carbothermic reduction completed in just 30 s due to rapid reaction kinetics, ultra-high temperatures, and the enhanced contact area resulting from surface tension-driven molten material flow under intense laser beam exposure. This laser recycling process reduced LiCoO2 and LiNi0.33Mn0.33Co0.33O2 to metallic Co or Co-Ni-Mn alloy, respectively, while Li was recovered as Li2CO3. The new process allowed for the near-total recovery of Co, Ni, and Mn in the alloy and virtually 100% Li recovery in the form of Li2CO3 by a vapor phase capture system. Additionally, continuous laser recycling in the battery material powder bed showed potentials to scale up for industry battery recycling. A mechanism for the laser recycling process was proposed. A preliminary discussion on the techno-economic implications of laser recycling was also provided.

Memory Response of Refined GN Models on a Rotating Fiber-Reinforced Magneto-Thermoelastic Medium Due to Pulsed Laser and Inclined Load

With the aid of the Caputo fractional derivative, this study constructs a novel mathematical model of magneto-thermoelasticity to investigate the transient phenomena for a fiber-reinforced rotating half-space under the influence of pulsed laser as heat source and inclined load in the context of refined three-phase-lag (TPL) Green–Naghdi (GN) models of generalized thermoelasticity, which is defined in an integral form of a common derivative on a slipping interval by incorporating the memory-dependent heat transfer. Together with the temperature gradient (Seebeck effect) and charge density influence, the generalized magneto-thermoelasticity model’s equations now include the modified Ohm’s law. An intense non-Gaussian laser beam heats the bounding plane’s surface. By using the normal mode analysis, the analytical expressions of the thermophysical quantities are produced in the physical domain. All physical quantities have been graphically depicted for different GN models (refined GN-II and GN-III models) to indicate the effect of memory-dependent derivative, Seebeck parameter, rotation and reinforcement of the medium under the influence of inclined load and pulsed laser.

Experimental study of the solutions of the Lippmann–Schwinger equation for an elliptical billiard with an intense laser beam

This work presents an experimental study to emulate solutions of Lippmann-Schwinger equations for scattering by an elliptical billiard. The probability density patterns are recovered in the intensity of a laser beam scattered by a Spatial Light Modulator (SLM). This result opens an interesting perspective to explore scattering solutions, mainly when physical distributions with specific properties are required. Optical simulations performed by experiments with intense laser beams have been applied for many quantum systems and in this work, we expand this application.

Various exact solutions to the time-fractional nonlinear Schrödinger equation via the new modified Sardar sub-equation method

We aim to investigates the nonlinear Schrödinger equation including time-fractional derivative in (3+1)-dimensions by considering cubic and quantic terms The modified Sardar sub-equation method is used that lead to the discovery of a unique class of optical solutions. To transform the suggested nonlinear equation into an ordinary differential equation, we applied wave transformations, resulting in a set of nonlinear equations that offer diverse solution scenarios. The derived solutions encompass dark, wave, bright, mixed dark-bright, bell-shape, kink-shape, and singular soliton solutions. To enhance our understanding of the dynamic behavior exhibited by these solitons under varying time parameter values, visual simulations through a variety of graphs is presented. Furthermore, a comprehensive comparison is conducted, exploring a range of values for the conformable fractional order parameter. This comparison aims to highlight on the influence of fractional order variations on the solutions, contributing valuable insights into the nuanced dynamics of the system. Overall, this study serves to advance our understanding of nonlinear processes, and its potential applications in real-life phenomena. In the field of nonlinear optics, this equation can describe the propagation of optical pulses in nonlinear media. It helps in understanding the behavior of intense laser beams as they propagate through materials exhibiting nonlinear optical effects such as self-focusing, self-phase modulation, and optical solitons.

Mitigation of laser plasma filamentation by rotating beam smoothing scheme

The propagation of intense laser beams in plasma inevitably gives rise to laser plasma instabilities, which have a significant impact on the illumination uniformity of the focused spot on the target in inertial confinement fusion (ICF) facilities. Here we propose an ultrafast smoothing scheme using a rotating beam (RB) to mitigate the laser plasma filamentation. Using the propagation model of the rotating beam in plasma for the laser-plasma self-focusing (SF) and filamentation, the filamentation characteristics of laser spots were analyzed. The results indicate that the rotating beam smoothing scheme, operating at picosecond timescale, exhibits superior mitigation effect of laser plasma filamentation.

Generation of Isolated Subfemtosecond Electron Bunches by the Diffraction of a Polarization-Tailored Intense Laser Beam.

We propose utilizing a polarization-tailored high-power laser pulse to extract and accelerate electrons from the edge of a solid foil target to produce isolated subfemtosecond electron bunches. The laser pulse consists of two orthogonally polarized components with a time delay comparable to the pulse duration, such that the polarization in the middle of the pulse rapidly rotates over 90° within few optical cycles. Three-dimensional particle-in-cell simulations show that when such a light pulse diffracts at the edge of a plasma foil, a series of isolated relativistic electron bunches are emitted into separated azimuthal angles determined by the varying polarization. In comparison with most other methods that require an ultrashort drive laser, we show the proposed scheme works well with typical multicycle (∼30 fs) pulses from high-power laser facilities. The generated electron bunches have typical durations of a few hundred attoseconds and charges of tens of picocoulombs.

High-performance silicon photonic single-sideband modulators for cold-atom interferometry.

The laser system is the most complex component of a light-pulse atom interferometer (LPAI), controlling frequencies and intensities of multiple laser beams to configure quantum gravity and inertial sensors. Its main functions include cold-atom generation, state preparation, state-selective detection, and generating a coherent two-photon process for the light-pulse sequence. To achieve substantial miniaturization and ruggedization, we integrate key laser system functions onto a photonic integrated circuit. Our study focuses on a high-performance silicon photonic suppressed-carrier single-sideband (SC-SSB) modulator at 1560 nanometers, capable of dynamic frequency shifting within the LPAI. By independently controlling radio frequency (RF) channels, we achieve 30-decibel carrier suppression and unprecedented 47.8-decibel sideband suppression at peak conversion efficiency of -6.846 decibels (20.7%). We investigate imbalances in both amplitudes and phases between the RF signals. Using this modulator, we demonstrate cold-atom generation, state-selective detection, and atom interferometer fringes to estimate gravitational acceleration, g ≈ 9.77 ± 0.01 meters per second squared, in a rubidium (87Rb) atom system.

Self‐Excited Free‐Standing VO2 Film for Infrared Optical Limiter

AbstractEffective optical limiters (OLs) are necessary devices for the protection of various sensitive photo‐detectors, cameras, infrared sensors, or even the human eyes once encountering unexpected high‐intensity illumination or laser blinding attacks. Vanadium dioxide (VO2) shows pronounced infrared switching behavior across the phase transition, which is considered as an idea optical limiter for broad‐band infrared laser protection. However, the self‐adapting optical limiter function based on VO2 is quite difficult to realize since the open‐state absorptance of the VO2 layer is always very low, which makes the laser irradiation cannot trigger the phase transition quickly. In the current study, a self‐excited VO2 infrared optical limiter is proposed, which is integrated by a transferred VO2 layer, InGaAs micro/nano wires, and a local heater. Based on the“optical response–electric heating” strategy, the phase transition of VO2 layer can be quickly triggered once the incident laser beam intensity exceeds the pre‐set threshold value. In addition, this integrated device has an excellent switching ratio, flexible controllability, and stability. This work achieves a practical VO2 optical limiter device and provides a promising strategy for developing VO2‐based integrated multifunctional devices in the future.

Analyzing the time-fractional (3 + 1)-dimensional nonlinear Schrödinger equation: a new Kudryashov approach and optical solutions

The paper focuses on investigating the time-fractional (3 + 1)-dimensional cubic and quantic nonlinear Schrödinger equation. We adopt the novel Kudryashov method to generate a distinct class of optical solutions for the current conformable fractional derivative problem. Our method explores various solution forms, including dark, wave, mixed dark-bright, and singular solutions. The soliton solutions we construct are visually represented to illustrate the influence of the fractional order derivative. Further, we elucidate the influence of solution parameters on the wave envelope, providing clear interpretations through 2D graphics presentations. The results underscore the efficacy of our approach in discovering exact solutions for nonlinear partial differential equations, especially in cases where alternative methods prove ineffective. The significance of the present paper lies in its contribution to advancing the understanding of the behavior of optical solutions in nonlinear systems, providing valuable insights for both theoretical and practical applications. In the field of nonlinear optics, this equation can describe the propagation of optical pulses in nonlinear media. It helps in understanding the behavior of intense laser beams as they propagate through materials exhibiting nonlinear optical effects such as self-focusing, self-phase modulation, and optical solitons.

Searching for axion resonances in vacuum birefringence with three-beam collisions

We consider birefringent (i.e., polarization changing) scattering of x-ray photons at the superposition of two optical laser beams of ultrahigh intensity and study the resonant contributions of axions or axionlike particles, which could also be short lived. Applying the specifications of the Helmholtz International Beamline for Extreme Fields (HIBEF), we find that this setup can be more sensitive than previous light-by-light scattering (birefringence) or light-shining-through-wall experiments in a certain domain of parameter space. By changing the pump and probe laser orientations and frequencies, one can even scan different axion masses, i.e., chart the axion propagator. Published by the American Physical Society 2024

Analytical modeling of the spray amplification of a spatially smoothed laser beam

Spatial amplification of the near-forward Brillouin scattering (FSBS) produced by a laser beam smoothed with a random phase plate (RPP) is considered by using a novel technique based on the central limit theorem [C. Ruyer et al., Phys. Rev. E 107, 035208 (2023)]. It is demonstrated that FSBS amplification proceeds over a length much larger than the longitudinal speckle correlation length and, under certain conditions, scales as a square of the average gain coefficient. Analytical expressions for the spatial gain are successfully compared with paraxial electromagnetic simulations, demonstrating that the beamlet correlation through ion-acoustic waves dominates the spatial growth for intense enough laser beams. The scattered wave aperture increases with the gain and can extend beyond the small angle scattering limit. These results open the way for developing reduced modeling of beam spray amplification in radiation hydrodynamics codes.

Effect of mutual interaction of two cosh-Gaussian laser beams on upper hybrid wave excitation and subsequent electron acceleration

This paper presents the excitation of an upper hybrid wave by resonant excitation of two intense cosh-Gaussian laser beams of frequencies ω 1 and ω 2 in a collisionless plasma. The excited upper hybrid wave is used for electron acceleration which accelerates the electrons towards higher energy. The acceleration of electrons through an excited upper hybrid wave has also been studied. This study has been analysed using the Wentzel Kramers Brillouin (WKB) and paraxial-ray approximation, where relativistic and ponderomotive nonlinearities are employed together. Analytical expressions for the beam width/intensity of the cosh-Gaussian laser beams, the electric field/power of the excited upper hybrid wave and the electron acceleration have been derived, which have been solved numerically for an established set of laser and plasma parameters. The results are also compared to relativistic nonlinearity. It has been observed that the mutual interaction of two cosh-Gaussian laser beams at a difference frequency significantly affects the self-focusing of each beam, leading to an increase in the amplitude/power of the upper hybrid wave as well as energy gain by the electrons. The effect of the magnetic field (ωc) and decentered parameter (b) on the power of the excited upper hybrid wave and the energy gain by the electrons are also explored. The results show that the power of upper hybrid wave and the energy gain by the electrons increase at higher values ​​of b and ω c.