Search Results (545)

Harmonic-assisted phase amplification was investigated in a 300-µm-thick Nd:GdVO₄ laser with coated end mirrors in the self-mixing interference scheme. The key event is the self-induced hybrid skew cosh Gaussian (abbreviated as skew ch-G)-type transverse mode oscillation in a thin-slice solid-state laser with wide-aperture laser-diode pumping. The present hybrid skew-chG mode was proved to be formed by the locking of nearly frequency-degenerate TEM₀₀ and annular fields. The resultant modal-interference-induced gain modulation at the beat frequency between the two modal fields, which is far above the relaxation oscillation frequency, increased the experimental self-mixing modulation bandwidth accordingly. Fifty-fold phase amplification was achieved in a strong optical feedback regime. Full article

The laser-directed energy deposition (L-DED) technique, with its excellent environmental adaptability and superior repair capability, shows great potential for the repair of damaged X70 pipeline steel. In this work, the microstructure and mechanical properties of L-DED repaired X70 steel were systematically investigated. The deposited material exhibited inhomogeneity along the building direction. From the bottom to the top, the grains gradually coarsened, and the proportion of polygonal ferrite increased. This was mainly attributed to increasing thermal accumulation with deposition height, which reduced the cooling rate and promoted solid-state transformations at higher temperatures. Meanwhile, the heat accumulation and intrinsic heat treatment reduced the dislocation density and promoted Fe₃C precipitation within grains and along boundaries. Microhardness was highest in the bottom region and decreased along the building direction due to the gradual coarsening of microstructure and decreasing in dislocation density. The L-DED X70 showed lower yield strength (435 MPa) and ultimate tensile strength (513 MPa) compared to the base material and API 5L requirements. The elongation of the L-DED X70 was 42.9%, which was 58% higher than that of the base material, indicating excellent ductility. These results revealed a thermal history-dependent strength–ductility trade-off in the L-DED repaired X70 steel. Therefore, more efforts are needed to control the L-DED thermal process, tailor the microstructure, enhance strength, and meet the service requirements of harsh environments. Full article

The growing generation of solid waste, driven by urbanization and industrialization, represents one of today’s greatest environmental challenges. The construction industry can play a key role in this scenario by incorporating recycling and waste reuse practices. Glass, a fully recyclable material, is still largely disposed of in landfills. A promising alternative is the use of ground glass in cementitious materials, partially or completely replacing cement or aggregates. Thus, in this paper, the effect of partially replacing Portland cement with ground glass of different colors including green, blue, transparent, amber, and colorful (all colors used mixed) in proportions of 15 and 35% in mortars was evaluated. The ground glasses were characterized by laser granulometry and chemical analysis. The properties of the mortars were then evaluated in the fresh and hardened state (apparent specific gravity, mechanical strength, water absorption, and open porosity). Regarding workability, the highest improvement observed was 6.8% for the 35% colored glass series compared to the reference series. In terms of entrapped air, there was an increase of up to 18.8% in the 35% green glass series. At 28 days of hydration, the 15% colored glass series obtained a 33% increase in flexural strength compared to the REF series. In the microstructure, it was found that a 15% glass presence was sufficient to reduce the portlandite index from 16.04 to 13.53, while a 35% glass presence was sufficient to reduce it to 7.51% portlandite, equivalent to a 54% reduction, suggesting significant potential for the reaction of the finer glass fractions with portlandite. This study suggests that the use of glass waste in a cementitious matrix can provide an environmentally appropriate alternative for recycling this material, contributing to a sustainable application and increased recycling rates of glass waste. Full article

Additively manufactured maraging steel components often require surface engineering to achieve superior wear resistance for demanding industrial applications. This study investigates 18Ni300 maraging steel manufactured by Laser Powder Bed Fusion (L-PBF), comparing non-aged and pre-aged (480 °C × 6 h) specimens to systematically analyze the effects of nitriding duration (0 h, 24 h, 48 h, 60 h) on nitride layer microstructure, hardness, and wear resistance. Results show that the non-aged specimen, with its supersaturated solid solution matrix, exhibits slower nitride layer growth; a thin, dense nitride layer formed after 24 h of nitriding minimizes the wear depth (−9.043 μm) for optimal friction reduction. In the pre-aged specimen, matrix refinement, through intermetallic compound precipitation, enables a 211 μm nitride layer to form after 48 h of nitriding, elevating surface hardness to 650 HV, and creating a gradient structure (“high-hardness surface + strengthened matrix”), which yields the narrowest and shallowest wear scars and superior wear resistance. The experiments demonstrate that nitriding processes must align with matrix states; 24 h nitriding suits non-aged steel, while 48 h is optimal for aged steel, providing critical guidance for optimizing surface strengthening in additively manufactured 18Ni300 steel. Full article

A high-power single-frequency continuous-wave wideband continuously tunable dual-wavelength laser at 1064/532 nm is presented in this paper. Firstly, a thermally insensitive cavity containing a type-I phase-matching LiB₃O₅ crystal and an uncoated quartz etalon was specially designed, which provided the fundamental condition for the generation of a high-power single-frequency 1064 nm and 532 nm laser. By carefully optimizing the mode matching, the maximal output powers of 13.3 W at 1064 nm and 12.5 W at 532 nm were achieved when the pump power was 63.7 W, and the total optical–optical efficiency of 40.5% was achieved. After the transmission peak of etalon was locked to the oscillating frequency of the resonator, the continuous frequency tuning ranges of the achieved laser were as wide as 26.75 GHz at 1064 nm and 53.5 GHz at 532 nm. Full article

This paper presents a comprehensive comparative analysis of high-voltage, high-frequency pulse generation techniques for Pockels cell drivers. These drivers are critical in electro-optic systems for laser modulation, where nanosecond-scale voltage pulses with amplitudes of several kilovolts are required. The study reviews key design challenges, with particular emphasis on thermal management strategies, including air, liquid, solid-state, and phase-change cooling methods. Different high-voltage, high-frequency pulse generation architectures including vacuum tubes, voltage multipliers, Marx generators, Blumlein structures, pulse-forming networks, Tesla transformers, switching-mode power supplies, solid-state switches, and high-voltage operational amplifiers are systematically evaluated with respect to cost, complexity, stability, and their suitability for driving capacitive loads. The analysis highlights hybrid approaches that integrate solid-state switching with modular multipliers or pulse-forming circuits as offering the best balance of efficiency, compactness, and reliability. The findings provide practical guidelines for developing next-generation high-performance Pockels cell drivers optimized for advanced optical and laser applications. Full article

Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains a global health problem. One of the characteristic features of mycobacteria is their exceptional resistance to environmental factors and their slow growth rate, both of which significantly prolong microbiological diagnostics. Due to the mortality rate and the rising prevalence of multidrug-resistant (MDR-TB) and extensively drug-resistant tuberculosis (XDR-TB), early detection and prompt initiation of treatment are extremely important. Traditional diagnostic methods, such as microscopic examination and culture on solid and liquid media, are still important, but are time-consuming and resource-intensive. However, the dynamic development of nucleic acid amplification techniques (NAATs), genotyping assays, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) has accelerated the identification of mycobacteria and the detection of drug resistance. Early and precise diagnosis is essential for effective disease control and improved treatment outcomes. This paper reviews the current state of knowledge on tuberculosis; including biological and structural characteristics of mycobacteria; the epidemiology of the disease; and the role of the main diagnostic methods; with a particular focus on molecular methods and MALDI-TOF MS. This paper highlights their advantages and limitations and discusses their implications for the future of TB diagnosis and control Full article

This study develops a low-energy, high-precision nanoporous silicon process technology combining electrochemical etching with multi-wavelength laser irradiation and ultrasonic vibration to precisely control the size, porosity, and distribution of the nanoporous silicon structure and examines its potential applications in next-generation optoelectronic devices. This approach overcomes the challenges of poor pore uniformity and structural stability in conventional processes. The effects of different laser parameters, electrochemical conditions, and plasma bonding on the morphology are systematically analyzed. Additionally, the luminescence of the nanoporous silicon layer and its effectiveness in porous silicon diode devices were evaluated. Under 633 nm laser irradiation at 20 mW, the porosity reached 31.24%, exceeding that obtained with longer-wavelength lasers. The PS diode devices exhibited stable electroluminescence with a clear negative differential resistance (NDR) effect at 0~5.6 V. This technique is expected to significantly reduce energy consumption and simplify the manufacturing of silicon-based light-emitting devices. It also offers a scalable solution for next-generation silicon-based optoelectronic devices and advances the development of solid-state lighting and optoelectronics research. Full article

This work presents a non-destructive methodology to estimate the residual porosity and mechanical properties of titanium foams produced via Hot Isostatic Pressing (HIP) followed by solid-state foaming (SSF). Pulsed laser-spot thermography was employed to measure thermal diffusivity in compact and foamed Ti6Al4V-ELI samples derived from powders of different granulometries. A power-law correlation between thermal diffusivity and porosity was used to estimate post-foaming porosity, which was then used to predict elastic modulus, yield strength, and ultimate tensile strength. Results highlight the potential of thermal diffusivity as a reliable indicator of structural performance, offering a rapid and fully non-destructive route for evaluating metallic foams in biomedical and aerospace applications. Full article

Aluminum spot welding is extensively applied in automotive, aerospace, and rail sectors due to its favorable strength-to-weight ratio. While resistance spot welding (RSW) has been the traditional method, its high residual stresses, electrode wear, and limited performance with high-strength aluminum alloys have driven interest toward alternative techniques. Friction stir spot welding (FSSW) offers significant advantages over RSW, linear friction welding (LFW), and hybrid processes, including solid-state joining that minimizes porosity, lower energy consumption, and the elimination of consumable electrodes. Compared to LFW, FSSW requires simpler fixturing and is more adaptable for localized repairs, while offering superior joint surface quality over hybrid laser-assisted methods. Despite these advantages, gaps remain in understanding the influence of process parameters on heat generation, microstructural evolution, and mechanical performance. This review consolidates advancements in tool design, thermal characterization, and weld property for aluminum alloys. It presents comparative insights into temperature distribution, weld strength, hardness variation, and metallurgical transformations reported across studies. By critically synthesizing the earlier works, this work identifies knowledge gaps and potential design improvements, aiming to support the development of more efficient and robust FSSW processes for industrial application. Full article

Using a 3D microscope imaging technique that we pioneered for alpha-track imaging of Solid-State Nuclear Track Detectors (SSNTDs), here, we present results from imaging of neutron-induced recoil proton tracks formed by exposing CR39-based detectors to an ²⁴¹Am(Be) neutron source. Detectors were arranged at zero, thirty, and sixty degrees to the source to assess any variation in the tracks according to source orientation. An Olympus (Olympus Corporation Japan) LEXT laser scanning confocal microscope was used to image the SSNTDs. Depth and cross-sectional size measurements were made on nine tracks, with a median (range) of 3.07 μm in depth (min 0.98 μm to max 8.34 μm), width in plan view of 7.49 μm (min 4.00 μm to 14.89 μm max), and breadth in plan view of 8.41 μm (min 4.17 μm to max 11.80 μm). In this study, we have shown our confocal microscopy approach can successfully image the 3D surface of neutron-induced tracks in SSNTDs; the imaging method thus enables the measurement of track cross-sectional dimensions and depth, as well as the identification of angled tracks. Full article

To investigate the effect of laser cleaning on the chromium plating of steel tyre moulds, a solid-state laser with an average power of 500 W was used as the cleaning light source. By varying the energy density and the number of pulses applied to the exact location, the changes in the macro- and micro-morphology of the mould surface, surface element content, and chromium plating thickness before and after laser cleaning were studied. The results show that as the laser energy density increases, the cleaning effect improves significantly. However, when the energy density exceeds $1.02\times {10}^4$ mJ/cm², cracks appear in the chrome-plated layer. By changing the number of pulses applied to a specific location, it was found that cracks also appear in the chrome-plated layer when the number of pulses exceeds three. These results provide a reference for the practical application of laser cleaning in the cleaning of chrome-plated steel tyre moulds. Full article

Background: Clinical diagnostics, food industries, and biotechnological processes typically use an enzyme called alpha-amylase to metabolize carbohydrates. Objective: The aim of this study is to investigate how low-level laser irradiation (LLLI) affects alpha-amylase activity towards determining the usability of LLLI in non-invasive enzymatic modulation. Methods: Enzyme solutions were irradiated at 10, 20, 30, and 40 J/cm² utilizing 589 nm and 532 nm diode-pumped solid-state lasers. The iodine–starch colorimetric method was used to quantify post-irradiation enzymatic activity, with inverse correlations found between absorbance and activity levels. Modulation was determined by the wavelength and dosage. Results: Enzymatic activity significantly improved when utilizing 589 nm irradiation at lower doses, maximizing at 120% at 20 J/cm² (p < 0.01). Neutral or inhibitory effects were revealed when higher doses were applied. Enzymatic activity showed progressive inhibition when 532 nm irradiation was applied, declining to 75% at 40 J/cm² (p < 0.01). Conclusions: These outcomes indicate that conformational flexibility and catalytic efficiency occur when applying lower-energy photons at 589 nm, whilst oxidative stress and impaired enzymatic function are induced by higher-energy photons at 532 nm. This is consistent with the biphasic dose–response characteristic of photobiomodulation. Full article

Although corn germ meal is a rich source of dietary fiber, it contains a relatively low proportion of soluble dietary fiber (SDF) and is frequently contaminated with high levels of zearalenone (ZEN). Solid-state fermentation has the dual effects of modifying dietary fiber (DF) and degrading mycotoxins. This study optimized the solid-state fermentation process of corn germ meal using Bacillus subtilis K6 through response surface methodology (RSM) to enhance SDF yield while efficiently degrading ZEN. Results indicated that fermentation solid-to-liquid ratio and time had greater impacts on SDF yield and ZEN degradation rate than fermentation temperature. The optimal conditions were determined as temperature 36.5 °C, time 65 h, and solid-to-liquid ratio 1:0.82 (w/v). Under these conditions, the ZEN degradation rate reached 96.27 ± 0.53%, while the SDF yield increased from 9.47 ± 0.68% to 20.11 ± 1.87% (optimizing the SDF/DF ratio from 1:7 to 1:3). Scanning electron microscopy (SEM) and confocal laser scanning microscope (CLSM) revealed the structural transformation of dietary fiber from smooth to loose and porous forms. This structural modification resulted in a significant improvement in the physicochemical properties of dietary fiber, with water-holding capacity (WHC), oil-holding capacity (OHC), and water-swelling capacity (WSC) increasing by 34.8%, 16.4%, and 15.2%, respectively. Additionally, the protein and total phenolic contents increased by 23.0% and 82.61%, respectively. This research has achieved efficient detoxification and dietary fiber modification of corn germ meal, significantly enhancing the resource utilization rate of corn by-products and providing technical and theoretical support for industrial production applications. Full article

To address the poor thermal performance and low output efficiency of conventional solid-state microchip lasers, this study proposes and implements a bonded Nd:YAG/Cr⁴⁺:YAG laser based on fiber splitter pumping. Experimental results demonstrate that at a 4.02 mJ pump pulse energy and a 100 Hz repetition rate, the system achieves four linearly polarized output beams with an average pulse energy of 0.964 mJ, a repetition rate of 100 Hz, and an optical-to-optical conversion efficiency of 23.98%. The energy distribution ratios for the upper-left, lower-left, upper-right, and lower-right beams are 22.61%, 24.46%, 25.50%, and 27.43%, with pulse widths of 2.184 ns, 2.193 ns, 2.205 ns, and 2.211 ns, respectively. As the optical axis distance increases, the far-field spot pattern transitions from a single circular profile to four fully separated spots, where the lower-right beam exhibits beam quality factors of M_x² = 1.181 and M_y² = 1.289. Simulations at a 293.15 K coolant temperature and a 4.02 mJ pump energy reveal that split pumping reduces the volume-averaged temperature rise in Nd:YAG by 28.81% compared to single-beam pumping (2.57 K vs. 3.61 K), decreases the peak temperature rise by 66.15% (6.97 K vs. 20.59 K), and suppresses peak-to-peak temperature variation by 78.6% (1.34 K vs. 6.26 K). Compared with existing multi-beam generation methods, the fiber splitter approach offers integrated advantages—including compact size, low cost, high energy utilization, superior beam quality, and elevated damage thresholds—and thus shows promising potential for automotive multi-point ignition, multi-beam single-photon counting LiDAR, and laser-induced breakdown spectroscopy (LIBS) online analysis. Full article