Increasing Laser Energy Research Articles

Enhancing UV photodetection sensitivity via pulsed laser optimization in SnO2: WO3/Si nanostructures

Abstract This manuscript investigates the deposition of tin oxide (SnO2) doped tungsten trioxide (WO3) films on silicon (Si) substrate using pulsed laser deposition technique (PLD) for ultraviolet (UV) photodetection. The structural, optical, morphological, electric, and photodetector properties of SnO2 doped WO3 films were extensively investigated. The optical characteristics, using UV-Vis spectroscopy, reveals a tunable optical band gap ranging from 2.85 eV to 2.25 eV with increasing laser energy, which is consistent with the findings obtained from photoluminescence (PL) analysis. Raman spectroscopy demonstrates three vibration modes at 319.80, 603.30, and 866.20 cm-1. Field emission scanning electron microscopy (FESEM) images displayed spherical nanoparticles with average diameters of 43.90, 47.55, and 62.20 nm for 140, 180, and 220 mJ, respectively. Atomic force microscopy (AFM) measurements indicate an increase in the thin film grain size, roughness surface, and root mean square at higher laser energies (140, 180 and 220 mJ). Under illumination condition, the photodetector gives a considerable photocurrent amount (0.5 mA), which increases with higher laser energies. The proposed geometry demonstrates an excellent photo-response within the wavelength range of 350 to 550 nm, mainly at 420 nm. The optimized device illuminated with laser energy of 220 mJ exhibits a response and recovery time of 352 ms and 737 ms, respectively, highlighting its potential for efficient and responsive applications.

Effect of IR Laser Energy on Several Polymers Using LIBS Analysis

ABSTRACTThe focus of this research is to use the thermal ablation properties of a Nd:YAG infrared laser to highlight the thermal damage caused by the extinction of the plasma, which leads to the disappearance of the spectra of certain polymers as the laser energy increases. The study involved testing five commonly used polymers: polytetrafluoroethylene (PTFE) also known as Teflon, polyoxymethylene (POM), polyvinyl chloride (PVC), Bakelite, and polyamide. Laser induced breakdown spectroscopy (LIBS) analysis was used to qualitatively analyze the plasma generated from the polymer samples, identifying the excited species present in each of the five polymers. Wavelength dispersive X‐ray fluorescence (WDXRF) analysis of the polymer samples further confirmed the identification of these excited species. The results obtained from the spectra recorded at different laser energies in an air environment showed that the saturation observed in the plasma, induced by increasing laser energy, is not consistently observed for all polymers. This plasma extinction phenomenon in certain polymers is attributed to thermal effects when using an infrared (IR) laser as a heating source.

Tailored porosity in additive manufacturing of 7075 aluminum alloy for crack suppression and high strength

Laser-directed energy deposition (LDED) additive manufacturing of 7075 aluminum (Al) alloy is highly challenging due to the inherent poor printability and high cracking tendency. Here, we disclose a new approach to suppress cracking in LDED-processed 7075 Al alloy by engineered porosity (about 1.14 %). The crack-free 7075 Al alloy was achieved by slightly sacrificing the densification. Further increasing the density of the material by increasing laser energy input leads to cracking. The mechanisms of minor pores in alleviating cracks are mainly reflected in three aspects: (i) pores disrupt the epitaxial growth of columnar grains; (ii) free-form surfaces surrounding pores could release the accumulated residual stress, and (iii) more dislocations near pore drive nucleation of near equiaxed grains. The LDED-processed crack-free 7075 Al alloy after heat treatment shows an ultimate tensile strength of 464 ± 12 MPa and break elongation of 9.7 ± 1.2 %, attaining a good strength-ductility synergy among many additively manufactured 7075 Al alloys in the current literature. Unlike the mainstream additive manufacturing of metallic materials, which pursues high densification to attain high-performance components, this work demonstrates the positive roles of pores in the additive manufacturing of cracking-sensitive materials. The findings of this work highlight new insights regarding the balance between pores and cracks for better manufacturability and higher mechanical performance of materials.

Unlocking high photosensitivity direct laser writing and observing atomic clustering in glass

The direct laser writing (DLW) of photoluminescent metal clusters is inspiring intensive research in functional glasses. However, understanding the influence of the host structure on cluster formation and visualizing DLW-induced clusters at the atomic scale remains challenging. In this work, we develop a highly photosensitive fluorophosphate glass through fluorine incorporation. The addition of fluorine establishes a conducive environment for Ag+ ions before DLW and enhances the availability of reducing agents and diffusion pathways during DLW. These advantages facilitate the formation of Ag clusters under low-energy single-pulsed DLW. Increasing laser energy results in a combination of Ag clusters and glasses defect, forming a dot + ring photoluminescent pattern. Atom probe tomography (APT), a technique capable of mapping the elemental spatial distribution and identifying clustering, is employed to gain more information on laser-induced clusters. Comparison of APT results between samples without and with DLW reveals the formation of Ag clusters after laser writing. The design concept and characterization enrich the understanding of Ag cluster behavior in glasses. This knowledge opens the possibility of rational design of clusters confined in glasses and inspires their synthesis for various applications.

Epitaxial growth and characterization of copper gallate (CuGa2O4) thin films by pulsed laser deposition

High-quality crystalline copper gallate (CuGa2O4) thin films were grown on c-plane sapphire substrates using the pulsed laser deposition (PLD) technique by optimizing the growth parameters (i.e., temperature, oxygen chamber pressure, and laser energy density). The obtained XRD patterns validated that the preferred orientation of the crystalline CuGa2O4 thin film is along the [111] direction, and the crystallinity of the films improved with increasing substrate temperature while maintaining a constant O2 pressure, as assessed by measuring the full width at half maximum (FWHM) of the prominent (222) plane. Reducing the oxygen pressure leads to the emergence of β-Ga2O3 peaks rather than the CuGa2O4 peaks due to the incomplete oxidation of copper (Cu). Subsequent XRD phi (φ) scans revealed a sixfold rotational symmetry of CuGa2O4 and a 30° epitaxial relationship between the film and the sapphire substrate. X-ray photoelectron spectroscopy (XPS) spectra confirmed the presence of Cu1+, Cu2+, and Ga3+ oxidation states in the films. Increasing laser energy density resulted in the complete oxidation of Cu and an increase in the film thickness from 51.8 nm to 183.4 nm. The direct bandgap of CuGa2O4 films was determined to be approximately 4.50 eV by analyzing the UV–Vis absorbance spectra using the Tauc equation. The refractive index was found to be approximately 2.05 ± 0.01 based on the spectroscopic ellipsometry data. While the impact of increasing laser energy density was negligible on the parameters such as crystal structure, rotational symmetry, oxidation states of gallium (Ga), oxygen (O), bandgap, and refractive index of CuGa2O4 thin film, notable alterations in the oxidation state of Cu and film thickness were observed. The surface roughness (Rrms) measured from AFM images showed a strong correlation with the values derived from ellipsometry analysis.

Effect of laser energy on the fretting wear resistance of femtosecond laser shock peened Ti6Al4V

Femtosecond laser shock peening (FsLSP) is performed on engineering alloys to improve their wear resistance in dry and oil-lubricated sliding conditions. In this study, the influence of FsLSP on the fretting wear behavior of Ti6Al4V alloy is studied. For this purpose, FsLSP treatment, with laser energies of 50, 100, 150, and 200 μJ, is performed on a Ti6Al4V sample which mainly consists of α-phase. Topographical investigations using white light interferometry reveal that with increase in the laser energy, the coverage area of laser-induced periodic surface structures (LIPSSs) decreases, and the extent of surface pitting damage increases, leading to higher surface roughness. While surface hardness also initially increases with increasing laser energy, it remains invariant when the energy is increased beyond 150 μJ. Sub-surface microstructural investigations and kernel average misorientation maps obtained from electron backscatter diffraction reveal that FsLSP treatment leads to the formation of severely deformed and mildly deformed layers along the depth of the alloy surface. Surface hardening due to FsLSP is attributed to the activation of prismatic <a>, basal <a> slip systems, and 101¯2, 112¯3 tensile twins in the severely deformed zone along with grain refinement, which is an outcome of dynamic recrystallization. Fretting wear tests indicate that the coefficient of friction (CoF) of FsLSP treated alloys is consistently lesser than that of its as-received counterpart, whose CoF is 0.38. In contrast, the wear resistance, quantified by the wear rate, wear volume and wear depth, is highest in the sample treated with laser energy of 100 μJ but lower for the as-received as well as 150 and 200 μJ laser treated samples. These results are explained on the basis of the differences in the contact area, formation of surface hardening layer and the size and integrity of asperities on the surface, which in turn influences the dominant fretting wear mechanism.

Microstructure and mechanical properties of wire and arc additive manufactured 2319 aluminum alloy treated by laser shock peening

The components manufactured by Wire and Arc Additive Manufacturing (WAAM) have some problems to be solved urgently, such as uneven microstructure, numerous pore defects, and residual tensile stress. Laser Shock Peening (LSP) is an innovative and advanced surface modification technology that improves mechanical characteristics by inducing significant plastic deformation and high compressive residual stress on metal surfaces. Therefore, combining LSP with WAAM is expected to solve its existing problems. In this work, LSP with different energy parameters was used to post-process the WAAM 2319 aluminum alloy. The results indicated that LSP could improve the microstructure, eliminate near-surface pores, harden the surface layer, and induce a residual compressive stress layer, and the effect was more effective with the increase of laser energy applied. The yield strength of the peened specimens significantly increased by 60.73 %, and the ultimate tensile strength also increased by 16.03 %. The hole fatigue life of the peened specimens was significantly improved, increasing by 179.8 % and 261.7 %, respectively, applying laser energies of 5 J and 10 J. Therefore, the engineering industry may benefit from a combination of LSP and WAAM technology.

Ni4Ti3 precipitates formed in NiTi alloy modulated by powder bed fusion and their effects on mechanical and electrical deformation

In this study, NiTi alloys featuring different distributions and morphologies of Ni4Ti3 precipitates were developed via powder bed fusion (PBF) technology. The effects of these Ni4Ti3 precipitates on the mechanical, resistive, and electrical deformational properties of the alloys were also studied. With increasing laser energy density, a coarsening behavior of the semi-coherent Ni4Ti3 precipitates was observed, with these precipitates transitioning from needle-like to disk-like structures. Consequently, their coherence with the B2 matrix diminished, thus weakening the surrounding strain field. The presence of dislocations and uniformly dispersed Ni4Ti3 precipitates, endowed the NiTi alloy with enhanced resistivity (7.294 μΩ·m) and stable tensile recovery strain (2–4 %) during stress-controlled loading and unloading. Employing PBF, a NiTi spring actuator was produced, capable of lifting loads over 145 times its weight, with a shape-memory recovery efficiency of 76.80 % at a current of 3.0 A. This study demonstrated the versatility of PBF technology in tailoring the microstructure of NiTi alloys by adjusting the laser energy density, providing a laboratory reference for advanced applications in electrically induced deformation.

Experimental and numerical investigation on residual stress of 316L SS treated by different laser shock peening parameters

316 L stainless steel has excellent mechanical properties, but fracture occurs when working in some extreme environments for a long time. As one of the important surface treatment technologies, laser shock peening (LSP) can improve the mechanical properties by inducing compressive residual stress (CRS) within the material, and has been widely used in a variety of fields due to its outstanding capabilities. Since LSP produces significant CRS, the influence of different laser parameters on the residual stress distribution of 316 L stainless steel was studied by numerical simulation, and verified by experiments. The results reveals that with the increase of laser energy, the residual stress in the surface and depth direction of the material increases firstly and then decreases gradually; three LSP cycles were performed on the same material, and it was found that the surface CRS within material had only a slight increase with three LSP cycles compared to the one with two LSP cycles, indicating that the CRS had reached the saturation; the effect of LSP on the residual stress of materials under different spot shapes was also studied, which indicates that the square spot can achieve better strengthening effect for multi-point LSP. Furthermore, the reasons for the improvement of mechanical properties were analyzed through microstructure observation.

Effect of laser energy density on cracking susceptibility and wear resistance of laser-clad tribaloy T-800 coatings on DD5 single-crystal alloys

In order to enhance the wear resistance of DD5 single-crystal alloys, Tribaloy T-800 wear-resistant coatings were prepared on their surfaces using laser-cladding technology. This study examines the effect of laser energy density on the cracking susceptibility and wear resistance of laser-clad Tribaloy T-800 coatings on DD5 single-crystal alloys. Three distinct laser energy densities (η1=33 J/mm², η2=50 J/mm², η3=60 J/mm²) were applied to create the coatings. The results show that the microstructures of the T-800 laser-clad coatings mainly consist of primary, coarsened, and spheroidized Laves phases, as well as Co-based solid solution and eutectic structures. The phases include Co3Mo2Si phase (Laves phase) and face-centered cubic Co-based solid solution. However, increasing laser energy density enhanced elemental diffusion at the heterogeneous joining interface of the DD5 substrate/T-800 coating, leading to higher Ni content in the coating. This resulted in a reduction in the tendency and content of Mo-rich Laves phase formation respective contents of 53.2 %, 49.2 %, and 47.5 %. Moreover, the decrease in the difference between laser cladding temperature and initial temperature, ∆T, led to reduced thermal stress at the interface, σ, contributing to a decrease in cracking susceptibility (a), with corresponding values of 0.16184, 0.00034, and 0.00022. Thermal expansion coefficients of materials in the cracked region near the interface, measured according to the CALPHAD method, Jmatpro software, and average EDS elemental content data at the crack edge, surpassed those of the corresponding DD5 substrate. Consequently, cracks in the coatings originated from stretching at the interface, with paths tending to cross Laves phase particles in a cleavage mode. The average microhardness of the coatings decreased due to reduced Laves phase content, with values of 783.4 HV0.5, 741.7 HV0.5, and 708.2 HV0.5, respectively, while the fatigue wear of T-800 coatings increased due to exacerbated wear damage from cracking defects. Specifically, average COFs were 0.659, 0.583, and 0.506, with corresponding mass losses of 7.1 mg, 3.4 mg, and 2.9 mg, respectively. The wear mechanisms observed encompassed fatigue wear, abrasive wear, and oxidative wear.

Optical Investigation of In2O3/ Quartz Nano-films Deposited at Different Laser Energies

The study conducted in this research focuses on the deposition of In2O3 thin films onto quartz substrates using the pulsed laser deposition technique (PLD). The importance of this study lies in the exploration of the optical properties of these thin films under varying laser energies (1200 mJ, 1400mJ, 1600mJ, 1800 mJ, and 2000 mJ), and the subsequent determination of their energy band gaps. In the pursuit of enhancing our understanding of In2O3 thin films, this research exhibits a direct relationship between the laser energy and laser band gap. It was discovered that the energy band gap of thin In2O3 films increased due to the increase in laser energy. This phenomenon resulted in an overall blue shift from the fundamental energy gap of In2O3 thin films. The significance of this study extends to potential applications in various fields. In2O3 thin films with tunable energy band gaps can find applications in optoelectronics, photovoltaic and other emerging technologies. This research not only contributes to the fundamental understandings of thin film properties but also offers a pathway for tailoring their characteristics for specific applications, thus advancing the field of materials science and engineering.

Mechanical and surface characteristics in laser-assisted machining of NiFeCr alloy: An atomic-scale understanding

This investigation explores mechanical characteristics and subsurface damage of NiFeCr alloy in laser-assisted machining through molecular dynamics simulation. The results of machining force, friction coefficient, local strain/stress, temperature distribution, subsurface damage, surface morphology, and worn volume are comprehensively explored, thereby revealing the mechanism of laser-assisted machining under different working conditions. Compared to conventional processing, average machining force, shear strain, subsurface damage, and dislocated length are all reduced in laser-assisted machining, which improves surface finish quality. Amorphization of removed chips in laser-assisted machining enhances the material removal efficiency. Analysis of various laser powers shows a decreased machining force with increasing laser power. However, residual stress and temperature rise, potentially impacting surface integrity. The subsurface damage depth exhibits nonlinearity with increasing laser energy, highlighting the competition between mechanical stress and thermal effect. The surface morphology and atomic flow demonstrate effective material removal with increasing laser power. The average machining force, friction coefficient, and subsurface damage depth show nonlinear relationships with cutting speed. The number of worn atoms is proportional to machining length and cutting speed, indicating enhanced material removal during high-speed machining.

Multiscale simulation combined with experimental investigation on residual stress and microstructure of TC6 titanium alloy treated by laser shock peening

The evolution behavior of residual stress and microstructure of TC6 titanium alloy under laser shock peening (LSP) were investigated using finite element (FE) and molecular dynamics (MD) simulations combined with experiments. The propagation process of laser-induced stress wave and plastic deformation behavior of TC6 titanium alloy model were studied using FE software with ABAQUS. The FE simulation results showed that increasing laser energy and impact time could increase the amplitude of compressive residual stress (CRS) to a certain extent, while a higher overlapping rate improved the CRS uniformity. The experimental results of residual stress testing based on XRD technology were consistent with the FE simulation results. Based on the piston shock method, the microstructural evolution process of α phase of titanium alloy under different shock velocities was simulated using MD software with LAMMPS. Laser shock wave promoted the transformation of hexagonal close-packed (HCP) structure to body-centered cubic (BCC) and face-centered cubic (FCC) structures in titanium alloy, and the generated dislocation density increased with increasing shock velocity. The severe plastic deformation caused by laser shock wave induced the formation of mechanical twin, subgrain and stacking fault, which was consistent with the (transmission electron microscope) TEM characterization results.

Influence of double-side symmetric oblique laser shock peening on shape deviation, surface integrity, and fatigue properties of the blades in small-sized blisk

Double-sided symmetric oblique laser shock peening (DSOLSP) was adopted to experiment on a small-sized blisk with restricted space. The influences of different laser energies on the shape deviation, surface roughness, microhardness, and residual stress of the blades were studied. The optimum process parameters were selected based on the shape deviation results of the blades and the microstructural evolution of the surface layers was investigated. The strengthening effect of DSOLSP treatment on notched blades was evaluated by vibration fatigue tests. It was found that DSOLSP can effectively cover the fatigue vulnerable regions without interference. Two-way bending deformation was formed after DSOLSP, and the shape deviation of the blades could be controlled within ±0.02 mm. With the increase of laser energy, the surface roughness and the depth of work-hardened layer increased. The full-thickness compressive residual stress (CRS) field was induced. A gradient microstructure was generated on the surface of the blade, and the size of average nanograins on the topmost surface is approximately 36.5 nm. The fatigue strength of the DSOLSP treated blades with notches was increased by 25.9 %. The enhancement can be attributed to the synergistic strengthening of CRS and gradient microstructure.

Laser weeding of common weed species

The massive use of herbicides since the 1950s has resulted in increasing problems with herbicideresistant weeds and pollution of the environment, including food, feed, and water. These side effects have resulted in political pressures to reduce herbicide application. The European Commission aims to reduce the use and risk of chemicals and more hazardous pesticides in the EU. Therefore, new weed control methods are in demand. Laser weeding might be an alternative to replace or supplement herbicides and other weed control methods in an Integrated Weed Management (IPM) strategy. This work aimed to investigate how increasing laser energy affected common weeds when the apical meristem was exposed to irradiation at the early stages of development. A 50 W thulium-doped fibre laser with a diameter of 2 mm and a wavelength of 2 µm was used. The highest efficacy of laser irradiation was achieved when the grass weed (Alopecurus myosuroides) had one leaf and the dicot species were at the cotyledon stage. There was a large difference between the species’ susceptibility to irradiation probably caused by differences in morphology and growth habit. At the 4-leaf stage, most of the species regrew after irradiation. Laser weeding may be a solution to replace or supplement other weed control methods in some crops, but in general the weeds must be irradiated when they are at the cotyledon to 2-leaf stage to avoid regrowth.

Experimental Study of Laser-Induced Cavitation Bubbles near Wall: Plasma Shielding Observation

To investigate the plasma shielding of laser-induced cavitation bubbles near a wall, a pulsed laser with different energies was selected to induce cavitation bubbles on the surface of 7050-T7451 aluminum alloy. A high-speed camera captured the evolution of the cavitation bubble, while a fiber-optic hydrophone system collected the acoustic signals during the evolution. Finally, a confocal microscope was used to view and analyze the surface morphology of 7050 aluminum alloy. The experimental results indicate that as the laser energy increases, the diameter, the evolution time, the pressure of the bubble, and both the pit diameter and depth all increase. Beyond an energy level of 1.4 J, the maximum diameter and the evolution time of the laser-induced cavitation bubble begin to decrease; the maximum diameter decreases by 2.04%, and the first evolution time decreases by 3.26%. Plasma shielding was observed in this experiment. Considering that the essence of a laser-induced cavitation bubble is the interaction between a high-energy laser and a liquid medium, the abnormal decrease in the maximum diameter, evolution time, and sound pressure epitomizes the manifestation of plasma shielding.

Influence of pulse laser energy on the Nickel plasma characteristics that produced in laser-induced plasma system

تُستخدم تقنية قياس طيف الانبعاث البصري ( OES) لتحليل البلازما المتولدة من هدف (النيكل) المضاء باستخدام ليزر Q- Switched (Nd: YAG) بطاقات مختلفة في الهواء. تم استخدام طريقة التوسيع Boltzmann-Plot و Stark لحساب معاملات البلازما بما في ذلك كثافة الإلكترون (ne) ودرجة حرارة الإلكترون (Te) وتردد البلازما (fp) وطول ديباي (λD). يتضح أن قيم (ne) و (Te) و (λD) و (fp) تزداد بزيادة طاقة الليزر مع قيم درجة حرارة الإلكترون المحسوبة التي تتراوح بين (0.934 - 1.479) الكترون - فولت.

The ablation behavior and modification mechanism of SiC under different laser energy

The laser modification pretreatment method is an effective way to address the machining difficulties of silicon carbide (SiC), a typical hard-to-machine material. Therefore, the ablation behavior and modification mechanism of SiC under different laser energy were explored in this paper. A new multi-scale model of laser irradiation SiC that couples heat transfer and fluid motion is first established. Then, a series of experiments is carried out to evaluate the model's accuracy, and the interaction between laser and SiC is discussed in detail. The results show that the dominant modification mechanism changes from coulomb explosion to multiphoton absorption, incubation effect, and heat accumulation with the laser energy increase. This leads the surface topography of SiC to transition from nanoparticle formation to disorder to a melting state. In ablative state, micro/nano porous and humps are formed at the edge of ablation groove due to surface tension, generation and rupture of bubbles, respectively. Furthermore, the surface roughness is not proportional to the laser energy due to the plasma shielding effect, and the surface roughness can be reduced by enhancing the flow of the molten material. Amorphous Si–O–C, Si and spherical SiO2 exist in deposition area, leading to SiC elastic modulus decreases from 347 GPa to 103.82 GPa, and the shear strength decreases from 20.9 GPa to 17.25 GPa. The results of this study can provide references for parameters selection and theoretical support for improving the machinability of SiC.

On the role of target mass in extreme ultraviolet light generation from CO2-driven tin plasmas for nanolithography

Target conditioning is a crucial ingredient of high-power extreme ultraviolet (EUV) source operation in state-of-the-art nanolithography. It involves deforming tin microdroplets into tens of nanometer-thin sheets, sheets which are subsequently irradiated by intense CO2 laser radiation to form a hot, EUV-emitting plasma. Recent experiments have found that a substantial fraction of the initial droplet mass is lost in the deformation phase through fragmentation. The goal of the present study is to investigate, using radiation-hydrodynamic modeling, how variations in the sheet mass affect EUV source power and the laser-to-in-band conversion efficiency (CE). It is found that high-mass sheets can “feed” the plasma with sufficient mass to sustain the production of in-band-emitting charge states over the course of laser irradiation. Low-mass sheets, on the contrary, cannot supply enough mass to sustain this production over the pulse, thus leading to a reduction in in-band power and CE. The dependence of CE on laser energy and target thickness is quantified, and a rather weak reduction of CE with increasing laser energy for high-mass sheets is identified.

Effect of nanosecond laser pulse width and energy on damage characteristics in carbon fibre reinforced plastic (CFRP) laminates

AbstractThis study explores the effects of laser pulse width and energy on CFRP laminates damage in laser bond inspection technology. Three testing programs were used, including varying laser energy while keeping pulse width constant, altering pulse width while maintaining constant power density, and modifying pulse width while keeping energy constant. The results show that when the pulse width remains constant, increased laser energy has a minimal effect on the initial damage location but leads to gradual interlayer delamination and fiber fracture propagation toward the impact surface. With constant laser energy, a specific threshold for pulse width is observed. When the laser pulse width is below this threshold, it exhibits a positive correlation with the damage characteristics of CFRP laminates, whereas when it exceeds this threshold, it shows a negative correlation. Power density correlates with damage when pulse width is constant, but there is no direct correlation when pulse width varies.Highlights CFRP laminates underwent laser shock tests with varying pulse widths. Power density is positively correlated with damage under specific conditions. There exists a specific threshold for laser pulse width. In single‐sided laser shock, initial damage spreads within a specified range.