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Interaction of intense ultrashort laser pulse with gases generates a transient spatiotemporal electron density distribution via field ionization, which may lead to the spatiotemporal reshaping of the pulse, viz., its beam profile, pulse width, etc. Here, we present an experimental study on ultrashort laser pulse interaction with argon gas sheath in an ionization saturation intensity regime (∼1015–1017 W/cm2). The present investigation has been performed using a 6 mJ, 1 kHz, and 55−60 fs Ti:Sapphire laser pulse interaction with a ∼2.5 mm long argon sheath. After the laser gas interaction, the laser spatial profile exhibits a multi-ring structure around a central maximum spot. Laser gas interaction parameters, such as laser intensity, gas pressure, etc., affect the ring pattern significantly. Under optimum parameter conditions, the laser pulse has two rings in spatial profile, and the pulse width of the central spot is self-compressed to ∼35 fs. A theoretical calculation reveals that the laser beam's spatiotemporal profile evolves as it propagates inside the gas sheath. The calculation also demonstrates that the gas ionization profile plays a crucial role in the spatiotemporal reshaping and self-compression of the laser beam. The calculation also shows that the generation of concentric ring patterns in the spatial profile is mainly due to the ionization of argon atoms into Ar+, Ar2+, and Ar3+ species in the interaction region. Such self-compressed laser pulses with concentric ring beam profiles may be useful for high-harmonic generation and shorter attosecond pulse trains. [ABSTRACT FROM AUTHOR]

Diode-pumped rare gas lasers (DPRGLs) have the potential for high-energy laser output with high beam quality. The metastable concentration >1014 cm−3 and pump intensity >10 kW/cm2 are required in developing high-power and efficient DPRGLs. However, the kinetics of 1s and 2p levels (Paschen notation) under these conditions is unclear yet, particularly regarding the adverse effects of interference energy levels (e.g., 1s4 and 2p1–2p8). This study addresses this gap by measuring the number densities of 1s and 2p levels in a diode-pumped plasma jet metastable argon laser. The experiment was conducted with a much higher number density of 1014 cm−3 and a higher pump intensity of 12 kW/cm2 than our previous works. The results indicate that the adverse effect of 1s4 accumulation could be partially compensated, and the relative population distribution of 2p energy levels remained unchanged. However, the high gas temperature (>1000 K) caused a significant negative impact of high 2p levels (2p1–2p8), and the air environment weakened the effect of He collision relaxation. [ABSTRACT FROM AUTHOR]

Laser corneal reshaping is a safe and effective technique utilized to treat common vision disorders. An advanced laser delivery system equipped with a pulsed UV laser with specific parameters is used to ablate parts of the cornea surface to correct the existing refractive error. The argon fluoride (ArF) excimer pulsed gas laser at 193 nm is the most employed type in the commercial devices for such treatments. This laser is generated using a mixture of Argon, Fluorine, and a significant amount of Neon gases. However, due to the ongoing Russian‐Ukraine war, the availability of Neon gas is currently very limited, as this region is considered the primary supplier of pure Neon gas. Consequently we suggest replacing the common ArF laser source in the commercial devices with a solid‐state (forth harmonic neodymium‐doped yttrium aluminum garnet laser at 266 nm). This replacement uses the same operation parameters, optics, and scanning algorithm. Parameters from five commercial devices (Zeiss MEL 90, Technolas TENEO 317, Alcon Wave Light EX 500, Schwind Amaris 750 s, OptoSystems MICROSCAN VISUM) were compared with those of the i‐ablation device, a research device that uses a 266 nm laser source. Our goal is to reduce production costs through a simple modification that has a significant impact. Consequently, the present study aims to find an alternative laser source for the current ArF laser without exchanging the complete system's design. This recommendation is based on a numerical simulation study. The thermal effect on a human cornea model was numerically evaluated using finite‐element solutions of Pennes' bioheat equation on the COMSOL platform by applying two laser wavelengths. The results demonstrated that changing the laser source significantly impacts the thermal effect, even with the same laser settings. All studied devices showed a reduction in the thermal effect to below 40°C, compared with nearly 100°C under ordinary conditions. [ABSTRACT FROM AUTHOR]

Laser Chemical Vapor Deposition (LCVD) is a process in which fibers are deposited from a gaseous precursor to a solid phase under a traversing laser focal point. Here, we grow titanium carbide (TiC) fibers and tubes dependent upon a hyperbaric hydrogen-rich, hydrogen-balanced, and hydrogen-lean environment referenced to a titanium tetrachloride and ethylene gas mixture under three different laser intensities. X-ray diffraction confirms the deposition of TiC with energy dispersive spectroscopy noting a radial compositional gradient of titanium and carbon in the diameter of the deposit. Depending on the hydrogen concentration, the TiC encased a core carbon-rich fiber or formed a hollow tube, with these formations explained by thermophoresis. Furthermore, depending on the gas mixture and laser intensity, the carbon-rich interior and TiC outer shell exhibited different morphologies that are discussed in terms of growth rate regimes. The collective outcomes demonstrate the complex processing space in forming ceramic materials by LCVD. [ABSTRACT FROM AUTHOR]

Control of exposed crystal facets in nanostructures is scientifically important, but technically challenging due to the inherent difficulty in manipulating surface energy of crystals. Here, laser‐induced periodic surface structures (LIPSS) induced by femtosecond laser is applied to produce periodic subwavelength 1D nanostructures with high index crystal facets on epitaxial CoFe2O4 surfaces, providing an efficient, maskless, cost‐effective "top‐down" method for nanostructure fabrication. Homogenous 1D LIPSSs (1D‐LIPSSs) with a period of 131 ± 15 nm and a depth of 90 ± 5 nm are obtained. The orientation of LIPSS nanostructures is finely controlled by tuning the polarization of fs laser beam, therefore flexibly producing 1D‐LIPSSs along various crystallographic orientations. Gas sensing performance evaluation shows that the fabrication of 1D‐LIPSSs on CoFe2O4 enlarges its surface area and contributes to enhanced gas sensing response. Compared to CoFe2O4 with LIPSSs faceted along {100} orientation, CoFe2O4 with LIPSSs faceted along high‐index {110} facets exhibits further improved gas sensing performance, suggesting the critical role of high‐index crystal facets in promoting surface reactivity and sensing sensitivity. The development of a laser‐based nanostructure fabrication route with high controllability of exposed crystal facets provides a novel solution for high‐density film‐based gas sensing applications. [ABSTRACT FROM AUTHOR]

This paper presents a preliminary analysis of the plasma dynamic modes of operation of end-type magnetoplasma compressor (MPC) discharges. The characteristic methods used to organize the optical pumping of a photodissociation gas laser using an MPC discharge are briefly described. The kinetic and energy characteristics of photodissociation gas optical quantum generators (OQGs) with optical pumping by an MPC discharge were evaluated. Based on the numerical calculations, an analysis of the radiation–plasma dynamic structures and the spectral brightness characteristics of the MPC discharge in the ohmic mode of plasma heating was carried out. [ABSTRACT FROM AUTHOR]

Since its first application in the 1950s, the laser has become an indispensable tool in scientific research and manufacturing. Laser manufacturing includes traditional methods such as cutting and engraving and emerging methods such as laser‐induced surface modification, laser‐induced materials transfer, and laser ablation synthesis. Laser manufacturing is widely applied in the fabrication of multifunctional sensing systems. Compared with other manufacturing methods such as lithography, vacuum deposition, and etching processes, laser manufacturing technology has several advantages, including maskless patterning, high precision, non‐contact processing, minimum heat affected zone, high throughput, ability to work with multiple materials, and ease of automation and integration. Here, this review aims to present a comprehensive analysis of the applications of laser manufacturing in various components of health and gas monitoring systems. Emphasis is placed on the application of laser manufacturing in various components of biosensors, including microchannels, sensing circuits, and working electrodes. Subsequently, laser manufacturing of physical and gas sensors is introduced. Meanwhile, traditional laser manufacturing methods, laser surface modification, laser‐induced material transfer, and laser ablation synthesis are introduced. Finally, the challenges and prospects of laser manufacturing in sensing systems are discussed. [ABSTRACT FROM AUTHOR]

It is well established that the interaction of light with matter generally imparts mechanical forces and associated torques. Where laser light is involved, such effects can be deployed for the microscale and nanoscale manipulation of matter, giving rise to notable applications in wide areas of physics, chemistry, and the life sciences. The diversity of applications is enriched not only by the complexity of the constitution of matter, but also by the structure of the laser light itself, according to its polarisation, amplitude, and phase. This article reviews in comprehensive terms the origins of laser-based optical forces and their manifestations in a variety of current contexts and applications. [ABSTRACT FROM AUTHOR]

Prospects for the application of orbital lidars for the detection of gas leaks from spacecrafts are investigated. The optical characteristics of the main light-scattering components – molecules and atoms of gases, are estimated at altitudes of 100–600 km from the Earth surface. It is shown that an orbital lidar with modern technical parameters can reliably detect signals from dispersed gas leak components at distances from several tens to one hundred meters from the spacecraft. [ABSTRACT FROM AUTHOR]

The urban lifeline safety project is a major national livelihood project, which ensures the safe operation of urban gas, water, electricity and other systems. Nowadays, the project is confronted with three types of difficulties: Difficulties in mechanism discovery and experimental reproduction; difficulties in risk detection and early identification, and difficulties in accurate early warning and collaborative prevention and control. In order to reveal the mechanism and reproduce the experiments, a full-size urban lifeline multihazard large-scale scientific device is firstly developed in the world, a series of dis-aster modes with 5 categories and 169 kinds of disasters coupled are established, based on which a comprehensive risk dynamic assessment method coupled with underground pipelines and above-ground disaster-bearing body is presented. To improve the risk detection and early identification, highly sensitive gas sensing laser chip as well as detector with active grating and wavelength-biased are invented. We develop an intelligent ball for leakage located in water supply pipe network based on the inertial guidance, force balance, acoustic spectrum and Bei Dou. Bridge overall modal (fingerprint) monitoring technology is break-through. In order to solve the problem of accurate early warning and collaborative prevention and control, an urban lifeline safety risk physical heuristic artificial intelligence early warning technology is presented, based on which a monitoring and early warning system is developed with collaborative sensing, fusion monitoring, targeting early warning, linkage response and other functions. The related studies result in the development of the safety and emergency response industry, followed by the pioneering and substantial contributions to the prevention and control of urban lifeline risks [ABSTRACT FROM AUTHOR]

In diffusion-cooled gas lasers, the laser medium gas is cooled through the discharge tube wall. Empirical findings suggest that, in longitudinally excited CO2 lasers with fast pulsed discharges, the materials of the discharge tube and coolant impact the discharge. This study investigates their effects on fast discharges rather than on cooling. Within a discharge tube with a cooling tube, the discharge tube and coolant create a capacitor, influencing the discharge. The laser output energy varies based on the discharge tube and coolant materials. The primary discharge input energy is influenced by these materials, as is the efficiency of converting it into laser output energy. [ABSTRACT FROM AUTHOR]

Mass diffusion coefficient measurement techniques with high temporal and spatial resolution have become essential for the research and development of leading-edge technology in a wide range of cross-disciplinary fields, but cannot be achieved using conventional methods. We provide a comprehensive review of the state-of-the-art theoretical and experimental investigations on Soret forced Rayleigh scattering (SFRS), a grating excitation technique (GET) for measuring the mass diffusion coefficient of binary liquid mixtures. SFRS utilizes the Soret effect to create micrometer-order periodic spatial concentration modulation in a sample due to the absorption of an optical interference grating generated by two intersecting heating laser beams. The decay of the concentration modulation by the mass diffusion process within several milliseconds is detected by the diffraction of a probing beam. The theoretical considerations regarding deviations from the ideal mass diffusion conditions are the effects of: (1) the Gaussian beam intensity distribution, (2) the light absorbing material and (3) the cell wall. The proper settings for the optical system are also analyzed, e.g., the effect of coherency and polarization of the heating laser and the effect of the z-direction length of the interference region. We also consider the frame of reference, center of gravity invariance and effect of convection, which are particularly important for mass diffusion experiments. Using the correct implementation of the theory, the optimal SFRS apparatus design and its appropriate use are described in detail. Finally, two successful applications of SFRS are demonstrated using visible light laser heating and mid-wavelength infrared gas laser heating. [ABSTRACT FROM AUTHOR]

Based on the Hagena scaling law, the cluster size in a gas jet is dependent on the equivalent diameter of a conical nozzle. In this work, the effect of the equivalent diameter deq of a conical nozzle on cluster size is separated into the individual effects of the throat diameter d and the half-opening angle α by comparing the Rayleigh scattering signals from gas jets. Nine types of conical nozzles with three different throat diameters (0.3, 0.5, and 0.7 mm) and three different half-opening angles (8.5°, 14.0°, and 24.2°) are used to produce argon gas jets at gas backing pressures from 10 up to 80 bar. The experimental results show that the effect of the throat diameter d is almost the same as that expected by the scaling law. However, the scaling law overestimates the effect of the half-opening angle α. The result is helpful for the precise characterization of cluster size and further understanding the interaction between intense laser and gas clusters. [ABSTRACT FROM AUTHOR]

An ablation crater depth estimation model, founded on the concept of an ionizing bleaching wave, has been developed for metal targets irradiated by an extreme ultraviolet (EUV) laser. Two EUV capillary discharge lasers operating at a wavelength of 46.9 nm were focused onto targets of gold, aluminum, and copper using two different experimental setups to maximize the laser fluence range. The experimental ablation craters were measured using an atomic force microscope, and the depths were compared to the ionizing wave model. The model depends on the dominant ion charge of the ablated plasma, which was measured experimentally using the low fluence setup with a time-of-flight mass spectrometer. The measured ablation depths and ion charges at low fluences are in agreement with the model. The ablation crater depths in the higher fluence range confirmed the trends predicted by the model, showing potential to expand its use to other materials and fluence ranges. [ABSTRACT FROM AUTHOR]

To reduce defects in wood laser processing, this study establishes a multi-field coupling model that reflects the coupling relationship between laser energy, auxiliary gas, and slit quality. It reveals the temperature field distribution and heat transfer during this process at a macroscopic level. Using the COMSOL Multiphysics 5.6 software to simulate laser processing with or without helium gas assistance, we show that helium-assisted laser processing positively affects the quality of wood processing. We further researched the influence of different laser powers and spot radii on ablation damage volume and gasification volume, and the results indicate that the adopted model effectively simulates the influence of laser power and auxiliary gas on laser cutting ability, accurately reflecting the impact of different process parameters on cutting depth and kerf width. The accuracy and effectiveness of this model were validated through comparison with experimental data. This research enhances process reliability and economic benefits through numerical simulation and prediction, expands theoretical research and engineering applications in the laser processing field, and optimizes and innovates wood processing technology. It provides a promising method for enhancing the added value of wood products and efficiently using wood resources. [ABSTRACT FROM AUTHOR]

Gas evolution is fundamentally problematic in rechargeable batteries, and may lead to swelling, smoking, and device‐level failure. In laboratories, monitoring gas evolution can help understand dynamic chemical events inside battery cells, such as the formation of solid‐electrolyte interphases, structural change of electrodes, and electrolyte degradation reactions. However, gassing in commercial batteries, discrete or continuous, is not monitored due to a lack of compatible sensing technologies. Here we describe the working principles of four real‐time gas monitoring technologies for lithium‐ion batteries. Gassing mechanisms and reaction pathways of five major gaseous species, namely H2, C2H4, CO, CO2, and O2, are comprehensively summarized. Since pertinent progress has been made on the optical fiber‐based sensing of strain, pressure, and temperature of various battery cells recently, special emphasis has been given to fiber‐based laser spectroscopy for gas detection. The technical details of the fiber‐enhanced photothermal spectroscopy are compared with the four gas sensing technologies, and the commercialization possibilities are discussed. Owing to its small size, flexibility, and robustness, fiber‐based sensing technology can be compatible with almost all kinds of battery cells, showcasing their great potential in various applications. It is envisioned that gas‐event monitoring of rechargeable cells can be unlocked soon by utilizing fiber‐based gas spectroscopy. [ABSTRACT FROM AUTHOR]

Short pulses of millimeter wave (MMW) radiation at 43 GHz create microplasma within a photonic crystal for pressures from 40 to 600 Torr (1.3 × 103–8.0 × 104 Pa). Gas breakdown occurs within a photonic crystal, which acts as an electromagnetic resonator to create a strong initial electric field. The time response of the argon metastable density is experimentally determined during the pulse and in the afterglow using laser absorption. The metastable density overshoots the steady-state condition at the beginning of the pulse and during the afterglow. Modeling is presented to understand these observations. The overproduction of argon 1s5 at the beginning of each pulse is due to a concurrent overshoot in the MMW electric field within the photonic crystal. This field overheats the plasma electrons and enhances the production of excited states. The burst of argon metastables observed in the afterglow is due to the pooled energy of the plasma stored in electrons, ions, and excited states of argon. Understanding metastable production is an important intermediate step to ionization and is also critical in the study of diode-pumped rare gas lasers. [ABSTRACT FROM AUTHOR]

Superconductivity in ultradoped Si1−xGex:B epilayers is demonstrated by nanosecond laser doping, which allows introducing substitutional B concentrations well above the solubility limit and up to 7 at%. A Ge fraction x ranging from 0 to 0.21 is incorporated in Si:B: 1) through a precursor gas, by gas immersion laser doping; 2) by ion implantation, followed by nanosecond laser annealing; and 3) by ultrahigh‐vacuum‐chemical vapor deposition growth of a thin Ge layer, followed by nanosecond laser annealing. The 30 and 75 nm‐thick Si1−xGex:B epilayers display superconducting critical temperatures Tc tuned by B and Ge between 0 and 0.6 K. Within Bardeen Cooper Schrieffer (BCS) weak‐coupling theory, Tc evolves exponentially with both the density of states and the electron–phonon potential. While B doping affects both, through the increase of the carrier density and the tensile strain, Ge incorporation allows addressing independently the lattice deformation influence on superconductivity. To estimate the lattice parameter modulation with B and Ge, Vegard's law is validated for the ternary SiGeB bulk alloy by density functional theory calculations. Its validity is furthermore confirmed experimentally by X‐ray diffraction. A global linear dependence of Tc versus lattice parameter, common for both Si:B and Si1−xGex:B, with δTc/Tc ≈ 50% for δa/a ≈1%, is highlighted. [ABSTRACT FROM AUTHOR]

Experimental study has been made of the ignition of a subcritical microwave discharge at pressures in the range 55–79 Torr with the initiation by pulsed laser radiation (58 mJ in a pulse). A rise of 36% in the critical pressure was obtained to form the discharge with the orientation of the laser beam along the vector of the microwave-field strength. Computer modeling has shown that upon the traversal of a focused laser beam, a highly conductive laser trail can be formed with a peak ionization degree as high as 10%, which, for a period of the order of 1 μs, locally enhances the electric microwave field up to supercritical values. [ABSTRACT FROM AUTHOR]

Laser corneal reshaping is an eye surgery utilizes UV lasers to modify a targeted corneal surface to correct vision disorders such as myopia, hyperopia and astigmatism. The most commonly used laser type in such treatment is a pulsed gas laser namely argon fluoride (ArF) excimer laser (193 nm). A mixture of Argon, Fluorine and high percentage of Neon gas is utilized for producing the required laser. However, the availability of Neon gas is currently very limited due to the existent Russian-Ukraine war as this region is considered the main supplier of pure Neon gas. The present work provides a novel alternative system for the commercially available corneal reshaping eye surgery devices with a special opening for entering the operational laser beam from external sources. The proposed system is a flying spot platform coupled with a solid state laser, that is a forth harmonic of Nd: YAG laser. The aperture in the system's design enables it to take in the generated UV-laser beam (266 nm) from the external Nd: YAG laser source. The beam is then modified and directed at the treatment area. The device was tested for hyperopia laser profile algorithm on different targets. Furthermore, the hyperopia profile procedure was also applied to the ex-vivo rabbit eye to investigate the ablation effect on the corneal tissues. The obtained results showed an appropriate ablation effect for hyperopic correction via a complete corneal reshaping platform. Although, the device's current state may not be appropriate for immediate clinical use. It holds significant value as a training and educational platform. [ABSTRACT FROM AUTHOR]

In this study, a spherical CrCoFeNiMn high-entropy alloy (HEA) powder with uniform size was prepared using gas atomization. High-quality CrCoFeNiMn HEA coatings were then applied to a 316L stainless steel substrate using prepowdered laser cladding. The main focus of the study is on the phase structure composition and stability, microstructure evolution mechanism, mechanical properties, and wear resistance of CrCoFeNiMn HEA coatings. The results show that the CrCoFeNiMn HEA coatings prepared using gas atomization and laser melting techniques have a single FCC phase structure with a stable phase composition. The coatings had significantly higher diffraction peak intensities than the prepared HEA powders. The coating showed an evolution of columnar and equiaxed crystals, as well as twinned dislocation structures. Simultaneously, the microstructure transitions from large-angle grain boundaries to small-angle grain boundaries, resulting in a significant refinement of the grain structure. The CrCoFeNiMn HEA coating exhibits excellent mechanical properties. The microhardness of the coating increased by 66.06% when compared to the substrate, the maximum wear depth was reduced by 65.59%, and the average coefficient of friction decreased by 9.71%. These improvements are mainly attributed to the synergistic effects of grain boundary strengthening, fine grain strengthening, and twinning and dislocation strengthening within the coating. [ABSTRACT FROM AUTHOR]

In the field of ultra-thick plate cutting, thermal cutting using high-temperature heat is used rather than mechanical cutting, and research is being conducted to increase the efficiency of cutting. In this paper, in order to improve cutting efficiency, a hybrid cutting head using both laser and gas cutting was designed, and the optimal cutting conditions were demonstrated through an experiment for cutting ultra-thick plate using the manufactured cutting head. The plate material used 100 t carbon steel, and a multi-axis hybrid method was adopted. As a result of the experiment was confirmed that the cutting speed was improved more than twice as much as when using the single cutting method, and the optimal speed condition in which sludge did not occur was derived. The maximum cutting speed was 600 mm/min, and the optimal cutting speed at which sludge did not occur was confirmed at 550 mm/min. [ABSTRACT FROM AUTHOR]

A low-energy, diode-pumped, solid-state passively Q-switched laser operating at a wavelength of 1535 nm has been demonstrated to trigger gas switches. This technology has the potential to bring significant improvements to the operation and reliability of compact pulsed power drivers. Compact pulsed power drivers are often required to operate for hundreds to thousands of shots without maintenance; thus, the reliable operation of the laser triggered switch is significant for the adoption of this technology. A primary limiter of spark gap lifetime is electrode erosion. In the case of a laser triggered switch where the laser is focused on one electrode, an additional source of erosion is the direct ablation of the electrode material by the laser. The micro-laser used in the previous experiments is very low energy, but over thousands of shots, it does damage directly to the target electrode. This damage could potentially interact with the erosion due to the current discharge and impact the operation of the switch. The focus of this paper is to describe experiments undertaken to assess this damage and quantify its effect on switch operation over many discharges at current and energy levels relevant to compact pulsed power systems. [ABSTRACT FROM AUTHOR]

In this study, femtosecond (FS) laser irradiation with different laser energy densities of 138, 276, and 414 mJ/cm2 is applied to SnO2-nanowire (NW) gas sensors, and the effect of the FS laser irradiation on the gas sensor response toward toluene (C7H8) gas is investigated. The FS laser irradiation causes oxygen deficiency in the SnO2 NWs and forms SnO and SnOx. Moreover, an embossing surface with multiple nano-sized bumps is created on the SnO2 NW surface because of the FS laser irradiation. The FS laser-irradiated SnO2-NW gas sensor exhibits superior sensing performance compared with the pristine SnO2-NW gas sensor. Moreover, the FS laser energy density significantly affects gas-sensing performance, and the highest sensor response is achieved by the gas sensor irradiated at 138 mJ/cm2. The long-term stability test of the laser-irradiated SnO2-NW gas sensor is performed by comparing fresh and 6-month-old gas sensors in different gas concentrations and relative humidity levels. Comparable gas-sensing behaviors are examined between the fresh and 6-month-old gas sensor, and this verifies the robustness of the laser-irradiated SnO2-NW gas sensor. [ABSTRACT FROM AUTHOR]

In this study, we analyzed the laser cutting characteristics of pulse transverse electrical discharge in gas at atmospheric pressure (TEA) CO2 and ultraviolet (UV) pulse laser processing in a multilayer display panels. First, the numerical calculation for was performed to confirm the thermal characteristics of each materials and optical field distribution at the interface of different material layers. Also, processing characteristics were experimentally confirmed by measuring cutting profile and adhesion characteristics of layer interface. Experimental results show that the characteristics of multi layers polymer cutting have different trend from those in a single‐layer because of the optical and thermal properties of each layer. In particular, the interface of layers had a substantial affect due to optical field distributions and thermal characteristic difference. Also, the optical absorbance of layers affect adhesion at the interface. The result suggests proper processing condition to enhance the laser ablation processing quality of multilayer display panel. In conclusion, understanding the characteristics of multilayer laser cutting processing is important for determining the optimal conditions for display panel micromachining and enhancing the quality of laser cutting for the cutting edge technology. [ABSTRACT FROM AUTHOR]

The novel photoswitchable ligand 3,3'‐Azobenz(metPA)2 (1) is used to prepare a [Cu2(1)2](BF4)2 metallocycle (2), whose photoisomerization was characterized using static and time‐resolved spectroscopic methods. Optical studies demonstrate the highly quantitative and reproducible photoinduced cyclic E/Z switching without decay of the complex. Accordingly and best to our knowledge, [Cu2(1)2](BF4)2 constitutes the first reversibly photoswitchable (3d)‐metallocycle based on azobenzene. The photoinduced multiexponential dynamics in the sub‐picosecond to few picosecond time domain of 1 and 2 have been assessed. These ultrafast dynamics as well as the yield of the respective photostationary state (PSSZ = 65 %) resemble the behavior of archetypical azobenzene. Also, the innovative pump‐probe laser technique of gas phase transient photodissociation (τ‐PD) in a mass spectrometric ion trap was used to determine the intrinsic relaxation dynamics for the isolated complex. These results are consistent with the results from femtosecond UV/Vis transient absorption (fs‐TA) in solution, emphasizing the azobenzene‐like dynamics of 2. This unique combination of fs‐TA and τ‐PD enables valuable insights into the prevailing interplay of dynamics and solvation. Both analyses (in solution and gas phase) and quantum chemical calculations reveal a negligible effect of the metal coordination on the switching mechanism and electronic pathway, which suggests a non‐cooperative isomerization process. [ABSTRACT FROM AUTHOR]

In a previous study, we considered that the laser characteristics of longitudinal discharge pumped CO2 lasers with fast pulse discharge were affected by changes in the discharge characteristics due to operations with high repetition rates. However, the discharge form has not been investigated in detail. In this study, the effects of repetition rate and gas pressure on the discharge were investigated by observing the discharge using a Pyrex discharge tube with an inner diameter of 12.6 mm and, length of 470 mm, and a CO2/N2/He gas mixture ratio of 1:1:2. At repetition rates of 150 Hz or lower, the discharge was uniform throughout the inner diameter of the discharge tube, whereas at repetition rates of 200 Hz or higher, the discharge contracted. The contracted discharge is thought to be caused by the residual charged particles generated by the discharge. At a high repetition rate, the discharge current density changes owing to the contraction of the discharge, which affects the optimal gas pressure and laser output energy. These findings are important for establishing the optimal operating conditions for longitudinally excited CO2 lasers pumped by fast pulsed discharges. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate and compare the clinical efficacy of diode laser and ozone gas in the treatment of dentin hypersensitivity (DHS). One hundred thirty-two teeth from 44 patients with moderate DHS were randomized into 3 groups according to a split-mouth design. In the diode laser group, the operator irradiated the superficial dentin exposed with an 808-nm wavelength and incremental power from 0.2 to 0.6 W with a 20-second interval. In the ozone gas group, the operator applied a high dose of ozone (32 g/m3) for 30 seconds using a silicon cup. In the placebo group, no therapy was applied. The dentin sensitivity level was evaluated upon enrollment (T0), immediately after treatment (T1), 3 months post-treatment (T2), and 6 months post-treatment (T3) with a cold air blast challenge and tactile stimuli. The pain severity was quantified according to the visual analogue scale. The Wilcoxon signed rank test was used to scrutinize potential statistical disparities among the treatments. Statistical significance was predetermined at P <.05. A significant decrease of DHS was observed in the ozone gas group and the 'diode laser group immediately after treatment and after 3 and 6 months of the therapy. After 6 months from the therapy, the sensitivity values in the teeth treated with ozone gas remained statistically lower than those treated with diode lasers (P <.05). A laser diode and ozone gas are both efficient as dentin sensitivity treatment. Ozone maintains an invariable effectiveness after 6 months. [ABSTRACT FROM AUTHOR]

We utilized a nonlinear post-compression technique to generate 675-fs, 9.2-µm CO2 laser pulses with a peak power of 1.6 TW. This achievement represents the highest peak power ever attained in the femtosecond pulse format within the long-wave infrared (LWIR) spectral range. The successful implementation of this post-compression technique opens avenues for the development of few-cycle, multi-terawatt 9-10 µm lasers, crucial for applications currently relying on near-infrared solid-state lasers, and which stand to benefit from the scaling of laser wavelengths into the long-wave infrared region. [ABSTRACT FROM AUTHOR]

Hollow-core photonic crystal fibers (HC-PCFs) provide an ideal transmission medium and experimental platform for laser–matter interaction. Here, we report a cascaded all-fiber gas Raman laser based on deuterium (D2)-filled HC-PCFs. D2 is sealed into a gas cavity formed by a 49 m-long HC-PCF and solid-core fibers, and two homemade fiber Bragg gratings (FBGs) with the Raman and pump wavelength, respectively, are further introduced. When pumped by a pulsed fiber amplifier at 1540 nm, the pure rotational stimulated Raman scattering of D2 occurs inside the cavity. The first-order Raman laser at 1645 nm can be obtained, realizing a maximum power of ~0.8 W. An all-fiber cascaded gas Raman laser oscillator is achieved by adding another 1645 nm high-reflectivity FBG at the output end of the cavity, reducing the peak power of the cascaded Raman threshold by 11.4%. The maximum cascaded Raman power of ~0.5 W is obtained when the pump source is at its maximum, and the corresponding conversion efficiency inside the cavity is 21.4%, which is 1.8 times that of the previous configuration. Moreover, the characteristics of the second-order Raman lasers at 1695 nm and 1730 nm are also studied thoroughly. This work provides a significant method for realizing all-fiber cascaded gas Raman lasers, which is beneficial for expanding the output wavelength of fiber gas lasers with a good stability and compactivity. [ABSTRACT FROM AUTHOR]

The article considers the results of studying the emission radiation of Ar, Kr, CO2, CHF3, CF4 and N2 gas jets excited by pulsed laser radiation. The shape of the spectral dependence in the spectral range 2.3‒4.4 nm and the emission intensity of a number of lines in absolute units were studied. To excite the targets, a Nd:YAG laser, λ = 1064 nm, τ = 5.2 ns, Eimp= 0.8 J was used. A supersonic conical nozzle with dcr = 450 μm, 2α = 11°, L = 5 mm was used to form a pulsed gas jet. The pressure at the nozzle inlet was 25 bar, which corresponds to the developed condensation of molecular gases in gas jets. The spectra were deciphered and the ions emitting under the given experimental conditions were determined. [ABSTRACT FROM AUTHOR]

A remarkable large-amplitude density modulation has been observed in ozone-mixed oxygen gas at atmospheric density and temperature conditions following irradiation with a nanosecond pulse of ultraviolet laser radiation. This paper outlines the experimental findings and describes a hydrodynamic simulation that reproduces several quantitative aspects of this phenomenon. It is important to note that these density waves are not simple sound waves; instead, they are combined with another type of density modulation wave. These density modulation wave profiles are expected to have applications for new optical components using a gas medium. [ABSTRACT FROM AUTHOR]

New computational and experimental studies have been carried out for the MgCCH radical in its X2Σ+ state. Coupled cluster theory [CCSD(T)], was used in conjunction with post-CCSD(T) and scalar relativistic additive corrections to compute vibrational quartic force fields for MgCCH and its cation. From the quartic force fields, higher-order spectroscopic properties, including rotational constants, were obtained. In tandem, the five lowest energy rotational transitions for MgCCH, N = 1→0 through N = 5→4, were measured for the first time using Fourier transform microwave/millimetre wave methods in the frequency range 9–50 GHz. The radical was created in the Discharge Assisted Laser Ablation Source (DALAS) developed in the Ziurys group. A combined fit of these data with previous millimetre direct absorption measurements have yielded the most accurate rotational constants for MgCCH to date. The computed principle rotational constant lies within −1.51 to +1.65 MHz of the experimental one, validating the computational approach. High-level theory was then applied to produce rovibrational spectroscopic constants for MgCCH+, including a rotational constant of B0 = 5354.5–5359.5 MHz. These new predictions will further the experimental study of MgCCH+, and aid in the low-temperature characterisation of MgCCH in the interstellar medium. [ABSTRACT FROM AUTHOR]

New computational and experimental studies have been carried out for the MgCCH radical in its X2Σ+ state. Coupled cluster theory [CCSD(T)], was used in conjunction with post-CCSD(T) and scalar relativistic additive corrections to compute vibrational quartic force fields for MgCCH and its cation. From the quartic force fields, higher-order spectroscopic properties, including rotational constants, were obtained. In tandem, the five lowest energy rotational transitions for MgCCH, N = 1→0 through N = 5→4, were measured for the first time using Fourier transform microwave/millimetre wave methods in the frequency range 9–50 GHz. The radical was created in the Discharge Assisted Laser Ablation Source (DALAS) developed in the Ziurys group. A combined fit of these data with previous millimetre direct absorption measurements have yielded the most accurate rotational constants for MgCCH to date. The computed principle rotational constant lies within −1.51 to +1.65 MHz of the experimental one, validating the computational approach. High-level theory was then applied to produce rovibrational spectroscopic constants for MgCCH+, including a rotational constant of B0 = 5354.5–5359.5 MHz. These new predictions will further the experimental study of MgCCH+, and aid in the low-temperature characterisation of MgCCH in the interstellar medium. [ABSTRACT FROM AUTHOR]

A theoretical analysis of a radiation amplifier based on metastable noble gas atoms excited by laser diodes in transverse pumping mode is presented. In the case when the amplified radiation reaches a sufficiently high intensity, the original equations allow a simple analytical solution, from which all the most important characteristics of the amplifier and the optimal parameters of both the working environment and the pump radiation, which ensure the most efficient operation of the amplifier, are easily found. [ABSTRACT FROM AUTHOR]

The possibilities of organizing a repetitively pulsed process with given frequency characteristics in a cavity of constant volume with an external energy supply to the working gas mixture are considered. Modelling of gas-dynamic and thermal processes is carried out using the numerical solution of the conjugate heat transfer problem. The gas medium is described on the basis of a viscous compressible gas model. To find the temperature field in the walls of the structure, the equation of non-stationary heat conduction is solved. The conjugation of temperature fields in a gas and a solid is carried out using an iterative procedure. In the calculations, the geometrical parameters of the cavity, the density of the energy supply, the initial pressure, and the composition of the working mixture are varied. The results of calculations obtained in the framework of the one-dimensional and two-dimensional formulation of the problem under the action of both a single pulse and a series of pulses are compared. The results obtained demonstrate the possibility of implementing the required frequency characteristics of the process for given geometric and energy parameters. [ABSTRACT FROM AUTHOR]

The findings of the study demonstrate the impact of low-intensity laser and quasi-monochromatic light on the biosynthetic activity of the edible medicinal fungus L. edodes during submerged cultivation. An artificial lighting installation based on matrices of light-emitting diodes (LED) emitting light at 470 nm (blue), 530 nm (green), 650 nm (red), and argon gas laser (488 nm) was used. Irradiation with blue and red LED and laser led to a shortening of the lag phase by 2 days and an increase in the mycelial mass. Irradiation with laser light resulted in the highest mycelial mass yield (14.1 g/L) on the 8th day of cultivation. Irradiation in all used wavelength ranges caused an increase in the synthesis of both extracellular and intracellular polysaccharides. Laser light at 488 nm and LED at 470 nm proved to be the most effective. Irradiation with red, green, and blue laser light caused an increase in the total amount of fatty acids in the mycelial mass compared to the control. A significant distinction in qualitative composition was observed: short-chain acids C6‒C12 compounds were produced under red light irradiation, whereas long-chain C20‒C24 were formed under green light irradiation. The most significant changes in the aromatic profile of the mycelial mass and culture liquid were recorded upon irradiation with green light. The content of aromatic components increased 24.6 times in the mycelial mass and 38.5 times in the culture liquid. The results suggest the possibility of using low-intensity quasi-monochromatic light for targeted regulation of L. edodes biosynthetic activity. [ABSTRACT FROM AUTHOR]

• SiC incorporation in a Mg 2 Si matrix for improving wear resistance during additive manufacturing. • Localization of secondary phase along the edge of each melt pool of the primary phase. • Formation of a compositional gradient distribution from the center to the edge of each melt pool of the Mg 2 Si–SiC/nitride hybrid composite. • Yield strength of the aged Mg 2 Si–SiC/nitride hybrid composite after longitudinal additive manufacturing was 559.6 MPa. • Discovery of a new type of hybrid composite with a build-direction-dependent functionally graded structure. The ex-situ incorporation of the secondary SiC reinforcement, along with the in-situ incorporation of the tertiary and quaternary Mg 3 N 2 and Si 3 N 4 phases, in the primary matrix of Mg 2 Si is employed in order to provide ultimate wear resistance based on the laser-irradiation-induced inclusion of N 2 gas during laser powder bed fusion. This is substantialized based on both the thermal diffusion- and chemical reaction-based metallurgy of the Mg 2 Si–SiC/nitride hybrid composite. This study also proposes a functional platform for systematically modulating a functionally graded structure and modeling build-direction-dependent architectonics during additive manufacturing. This strategy enables the development of a compositional gradient from the center to the edge of each melt pool of the Mg 2 Si–SiC/nitride hybrid composite. Consequently, the coefficient of friction of the hybrid composite exhibits a 309.3% decrease to –1.67 compared to –0.54 for the conventional nonreinforced Mg 2 Si structure, while the tensile strength exhibits a 171.3% increase to 831.5 MPa compared to 485.3 MPa for the conventional structure. This outstanding mechanical behavior is due to the (1) the complementary and synergistic reinforcement effects of the SiC and nitride compounds, each of which possesses an intrinsically high hardness, and (2) the strong adhesion of these compounds to the Mg 2 Si matrix despite their small sizes and low concentrations. [ABSTRACT FROM AUTHOR]

He-Ne lasers play a crucial role in ultra-precision measurement and optical sensing across various fields. For many applications based on He-Ne lasers, a higher output power is required to enhance the accuracy and signal-to-noise ratios of the associated optical measurements. However, conventional methods to increase the output power by reducing the diameter of the He-Ne laser discharge capillary inevitably result in higher diffraction losses and constrain the lasing performance. Here, we propose an approach to enhance laser pumping efficiency and output power through optimizing the ratios of He and Ne gasses. The validity of our proposal has been confirmed by both numerical simulations of He-Ne laser plasma discharge processes and experimental demonstrations, showing that the optimal gas ratio increases with the capillary diameter and total gas pressure. [ABSTRACT FROM AUTHOR]

Extreme Ultraviolet (EUV) radiation is a short-wavelength light source that has important applications in many fields, such as optical communication, particle manipulation, and ultrahigh resolution imaging. However, the highly absorptive nature of EUV light makes it challenging to design suitable focusing optics, such as focal splitters, to properly manipulate the energetic light. Here, we propose modified spiral photon sieves to transform EUV laser light into azimuthally splitting focusing. A genetic algorithm was used to design and optimize the azimuthally focal splitters. A capillary discharge EUV laser at 46.9 nm was used to verify the effectiveness of our proposed method, and PMMA targets were used to record the focused laser spot. The profile of the recorded patterns measured by atomic force microscopy shows that the focal spots in the experiment are diffraction-limited and agreed with the theoretical analysis. The proposed technique provides a new way for manipulating EUV light and further extends the applications ranging from EUV to soft x rays. [ABSTRACT FROM AUTHOR]

The gain characteristics of a CO2 laser pumped by a longitudinal pulsed discharge were investigated to develop a compact He-free CO2 laser operating at a high repetition rate. The longitudinal discharge tube had an inner diameter of 0.8 cm and a length of 45 cm. High-voltage pulses with a discharge starting voltage of 13.4–30.2 kV at a rise time of about 321 ns were applied to the discharge tube. CO2/N2 mixture gas with mixing ratios of 1:0, 1:1, 1:2 and 1:3 was used. The small signal gain coefficient was measured by inputting a seed CO2 laser pulse into the longitudinal discharge tube. The small signal gain coefficient depended on the delay time between the start of the discharge in the longitudinal discharge tube and the input of a seed CO2 laser pulse, the gas mixing ratio, the gas pressure, the repetition rate and the input energy to the longitudinal discharge tube. In this work, in He-free gas, the maximum small signal gain coefficient at a repetition rate of 300 Hz was 2.11%/cm with a delay time of 30.4 μs, a CO2/N2 gas mixing ratio of 1:2, a gas pressure of 2.6 kPa and an input energy of 191 mJ. [ABSTRACT FROM AUTHOR]

The velocity distribution of a classical gas of atoms in thermal equilibrium is the normal Maxwell distribution. It is well known that for sub-recoiled laser cooled atoms, Lévy statistics and deviations from usual ergodic behavior come into play. In a recent letter, we showed how tools from infinite ergodic theory describe the cool gas. Here, using the master equation, we derive the scaling function and the infinite invariant density of a stochastic model for the momentum of laser cooled atoms, recapitulating results obtained by Bertin and Bardou [Am. J. Phys. 76, 630 (2008)] using life-time statistics. We focus on the case where the laser trapping is strong, namely, the rate of escape from the velocity trap is R(v) ∝ |v|α for v → 0 and α > 1. We construct a machinery to investigate time averages of physical observables and their relation to ensemble averages. The time averages are given in terms of functionals of the individual stochastic paths, and here we use a generalization of Lévy walks to investigate the ergodic properties of the system. Exploring the energy of the system, we show that when α = 3, it exhibits a transition between phases where it is either an integrable or a non-integrable observable with respect to the infinite invariant measure. This transition corresponds to very different properties of the mean energy and to a discontinuous behavior of fluctuations. While the integrable phase is described by universal statistics and the Darling–Kac law, the more challenging case is the exploration of statistical properties of non-integrable observables. Since previous experimental work showed that both α = 2 and α = 4 are attainable, we believe that both phases could also be explored experimentally. [ABSTRACT FROM AUTHOR]

Diode-pumped metastable rare gas lasers are showing their potential for high-energy laser systems with intensive investigations carried out to understand their lasing characteristics. Here, we demonstrated pulsed lasing of a diode-pumped argon metastable laser based on a pulsed DC glow discharge in argon and helium mixtures for different discharge voltages and pressures. A transient rate equation model was established and solved to explain the cause of the pulsed lasing in our experiment. The insufficient production rate of argon metastable atoms (1s5) and the slow transfer rate out of the 1s4 state in the plasma during the lasing process were found to be the key reasons. This work may shed some light on the future design of plasma sources that have higher metastable atom production rates to achieve highly efficient continuous wave lasing. [ABSTRACT FROM AUTHOR]

To solve such global problems as climate stabilization and reducing greenhouse gas luminescences requires an integrated approach, including a strategic analysis of the problem and the development of criteria for selecting proposed solutions, a natural scientific research on the possibilities and ways to implement the assigned tasks, as well as an economic justification for the feasibility of implementing the developed measures. The present publication is an attempt to apply this approach to the problem of hydrogen energy via proposing the production of hydrogen by pyrolysis of natural gas in laser plasma as one of the ways to its solution. Therewith, the main attention is focused on the chemical processes that occur in laser plasma, as well as on the nature of the transformations that occur in the solid pyrolysis product. [ABSTRACT FROM AUTHOR]

A standoff methane (CH4) sensor with actual hard topographic targets (usually called non-cooperative targets) is essential for natural gas pipeline leakage inspection and many other practical applications. To address this requirement, a miniaturized and low-power-consumption gas sensor was developed based on tunable diode laser absorption spectroscopy for standoff CH4 detection with a non-cooperative target. Wavelength modulation spectroscopy with a 1 f normalized 2 f detection method was employed for calibration-free CH4 measurement. A Kalman filter algorithm was used to improve the precision of the detection. The performance of the standoff CH4 sensor was evaluated comprehensively under various conditions, including different incident angles, different hard topographic targets, and different standoff distances. The results show that the measurement precision is 0.107% and the sensitivity is 4.08 parts per million per meter (ppm·m) with a time resolution of 1 s and a standoff distance of 40 m. The detection limit can achieve 1.24 ppm·m at an optimal integration time of 70 s. This sensor can be easily integrated into mobile platforms, which lays the foundation for intelligent leak inspection. Graphical abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

The active Brownian motion of single dust particles in a three-dimensional DC discharge trap under the action of laser radiation is experimentally studied. Spherical particles of melamine formaldehyde (MF), part of the surface of which had a copper coating (Janus particle) are used in the experiment. Two-dimensional and three-dimensional analysis methods for root-mean-square displacements are compared. The mean kinetic energy of motion of dust particles at different laser irradiation intensities is determined. The energy balance of dust particles and the influence of their rotation on the nature of the motion are estimated. [ABSTRACT FROM AUTHOR]

K403 nickel-base superalloy is widely used in the manufacture of aero-engine turbine blades because of its excellent properties at room temperature and high temperature. In order to solve the problem of turbine blade crack defects caused by long-term service in complex working conditions, in this work, two different processes of (tungsten inert gas, TIG) welding and laser cladding were used to repair the blade cracks, and the microstructure and properties of the repaired region were studied. The influence of TIG welding and laser cladding repairing on microstructure, mechanical properties and failure behavior was analyzed. The results show that the microcracks tend to occur near the repair interface using the TIG welding repairing process, which are mainly caused by carbides and low melting point eutectic structure. The grain and structure of the repaired area by laser cladding repair technology are more uniform, and the microcrack defects can be easier to control. The comprehensive mechanical properties of the samples repaired by laser cladding are obviously higher than those repaired by TIG welding repairing process, and the samples repaired by laser cladding have better process stability. The tensile strengths of the samples using the laser cladding repair process and the TIG welding repair process at room temperature have reached 87.44% and 69.22% of the strength of K403 base material, respectively. According to the failure analysis results, the tensile fracture at room temperature in the repaired region presents mixed fracture characteristics, and the tensile fracture at high temperature presents intergranular fracture characteristics. Microcracks in the repaired area, local liquid phase deficiency defects and carbide structure are the main reasons of failure. The laser cladding technology has the advantages of heat source concentration and smaller heat affected zone, which can effectively restrain the defects and refine the microstructure. Therefore, the laser cladding repair process is used to repair the edge plate crack damage generated during the blade test run. After fluorescence and kerosene-chalk detection, the repairing process meets the relevant reuse requirements. [ABSTRACT FROM AUTHOR]

An atmospheric pressure nanosecond (few tens of ns) repetitively pulsed discharge (NRPD) in a mixture of helium with a small fraction of a heavier rare gas Rg allows producing a large number density of metastable atoms Rg(1s5), required, for example, for optically pumped rare gas lasers. At the repetition rate of hundreds of kilohertz, the memory effect in this type of discharge becomes important because the initial conditions for the discharge pulse are determined by the afterglow kinetics from the previous pulse. In addition, the overall plasma kinetics is strongly dependent on the dynamics of the cathode sheath formation. Therefore, the characterization of an NRPD requires simulation of the discharge plasma together with its decay during the afterglow across the entire discharge gap. In this work, a periodic numerical solution for the NRPD in the 1% Ar in the He mixture at near atmospheric pressure was found within the frame of extended drift-diffusion approximation. Spatial and temporal distributions of discharge parameters were calculated and conditions for production of Ar(1s5) with the number density ∼1013 cm−3 determined. The influence of atmospheric impurities on the Ar(1s5) yield and the specific heat release was assessed. Results of modeling were compared with available experimental results. The sensitivity analysis of the model to the choice of kinetic constants is presented, and the applicability of drift-diffusion approximation is justified. [ABSTRACT FROM AUTHOR]

The influence of post-welding heat treatment on the surface and corrosion properties of the interstitial high-entropy alloy (Fe50Mn30Cr10Co10)99C1 has been examined using gas tungsten arc welding (GTAW) and laser welding. The as-welded and post-weld heat-treated samples were characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Face-centered cubic (FCC) and hexagonal close-packed (HCP) structures were present in the base metal. There was no change in the phases after welding and post-heat treatment. After laser and GTAW, a small reduction in hardness (25 HV) was noticed. Following both laser and GTAW processes, the base metal's corrosion resistance dropped. However, heat treatment applied after the weld brought the resistance back to almost base metal levels (0.002 mm/year). The development of Mn oxides on the surface, which minimizes the micro-segregation of Cr and generates a uniform Cr oxides layer, is primarily responsible for the increased corrosion resistance in the post-welded samples. This layer also exhibits superior passivation and corrosion resistance. The study clearly demonstrates that, in Mn-containing high-entropy alloys, it is important to suppress elemental Mn content on the surface for improved corrosion resistance. [ABSTRACT FROM AUTHOR]

In a short-pulse CO2 laser based on discharge excitation, there is a pulse tail that depends on the device configuration and operating conditions. The pulse tail is longer than the spike pulse and causes thermal effects such as a crack, heat-affected zones (HAZ), and so on. There are various types of glass having different physical constants related to heat, such as the thermal expansion coefficient and the softening point. Even if the same CO2 laser pulse is radiated onto glass, the processing results may differ depending on the glass material. Four types of glass, namely, crown glass, soda-lime glass, borosilicate glass, and synthetic quartz glass were irradiated with two types of short CO2 laser pulses, one with a large pulse tail and one with a small pulse tail, at a repetition rate of 200 Hz and a fluence per pulse of 22 J/cm2. As the processing characteristics, the ratios of the surface hole diameter and the HAZ diameter to the irradiation diameter, as well as the drilling depth, were investigated. The pulse-tail energy of the short CO2 laser pulses did not affect the surface hole diameter. In the glasses with small softening points of 740 °C or less, the pulse-tail energy of short CO2 laser pulses affected the HAZ with a large number of pulse irradiations with a total irradiation fluence of 2000 J/cm2 or more. The short CO2 laser pulses with a small tail produced a smaller HAZ than the short CO2 laser pulses with a large tail. In drilling with a large number of pulse irradiations, the short CO2 laser pulses with a small tail produced deeper drilling than the short CO2 laser pulses with a large tail. The glass material did not affect the surface hole diameter and the drilling depth. The glass material affected the HAZ. [ABSTRACT FROM AUTHOR]