Search Results (4,371)

The effect of nanosecond laser modification on X165CrMoV12 tool steel before and after heat treatment was investigated. Three laser texturing modes were applied to the studied material, with the variables being the frequency used and the pulse energy: 50 kHz/pulse energy 0.9 mJ, 100 kHz/pulse energy 0.45 mJ, and 150 kHz/pulse energy 0.3 mJ. The other parameters of laser texturing were power—90%; speed—500 mm/s; hatching angle—0° (horizontal), +60°/−60° (or equivalent 120°), and +30°/−30° (or equivalent 150°); and Hatching Distance—0.02 mm. The surface laser modification process aims to obtain a homogeneous and adaptive surface relief optimizing the operational properties of the working surfaces of the parts under dry contact friction conditions. The influence of the used laser modification modes on the roughness class of the obtained surfaces, the structure of the formed modified surface and the friction coefficient was studied. The comparative analysis showed that the lowest roughness class (Ra—4.123 µm) was obtained when using an operating frequency of 50 kHz. The obtained friction coefficient values were lowest in the following sequence of processes: laser texturing and subsequent thermal treatment. The lowest friction coefficient (µ = 0.0041) was registered in the test bodies processed with a mode in which the operating frequency was 50 kHz and the pulse energy was 0.9 mJ, after which they were subjected to thermal treatment according to the used cycle. In this processing sequence, no diffusion-related defects (decarburization) were observed on the surface layer of the tested steel. Full article

The formation and size evolution of gas-phase nanoparticles (NPs) in laser ablation inductively coupled plasma mass spectrometry critically influence aerosol transport, plasma ionization efficiency, and ultimately analytical accuracy. Nevertheless, burst-mode laser ablation, as an efficient and versatile strategy for controlling gas-phase NP size, remains insufficiently explored. Here, we combine experimental investigations and theoretical analysis to elucidate the mechanisms of gas-phase nanoparticle formation and size control by tuning the interpulse interval in burst-mode femtosecond (fs) laser ablation. The mean nanoparticle size exhibits a non-monotonic dependence on interpulse spacing, decreasing with a narrowing size distribution as the interval increases from 0 to 300 ps, and then increasing with distribution broadening at longer delays up to 1000 ps, closely correlating with ablation-crater depth. A characteristic transition at ~300 ps is identified, where both nanoparticle size and crater depth reach a minimum, revealing a critical timescale in pulse–plume–surface interactions. Simulations show that the interpulse interval governs the redistribution of laser energy between the surface and plume, driving a transition from surface-dominated ablation to plume-dominated absorption and partial recovery of surface coupling. This delay-dependent framework provides a unified explanation for nanoparticle formation, where particle size is determined by the competition between plume-mediated fragmentation and surface-driven material supply, and offers a basis for tailoring NP size distributions via temporal pulse shaping. Full article

Ultrafast fiber lasers operating near 2 μm have emerged as a critical platform for advancing mid-infrared photonics due to their narrow pulse durations, high peak powers, and broad tunability. These sources exploit the rich energy-level structures of Tm³⁺ and Ho³⁺ doped fibers and reside within an atmospheric transmission window, enabling applications spanning nonlinear microscopy, precision micromachining, optical frequency metrology, biophotonics, and free-space optical communication. Recent progress in low-loss fiber fabrication, dispersion-engineered cavity design, and mode-locking technologies has significantly expanded the performance boundaries of 2 μm ultrafast fiber lasers. This review systematically examines the underlying pulse-formation mechanisms and categorizes state-of-the-art mode-locking approaches. Representative laser architectures are compared with respect to pulse duration, energy scalability, repetition-rate enhancement, spectral characteristics, and environmental stability. Key application pathways in high-resolution spectroscopy, biomedical diagnostics, and mid-IR supercontinuum generation are highlighted. Finally, the remaining challenges and prospective research directions are discussed to inform the development of next-generation ultrafast photonic sources in the 2 μm band. Full article

To suppress the Secondary Electron Yield (SEY) of Al₂O₃ ceramic surfaces for accelerator ceramic windows, a synergistic strategy integrating TiN film deposition and laser surface texturing was developed. TiN films were first deposited on Al₂O₃ substrates by pulsed DC magnetron sputtering, and the sputtering power was optimized through systematic characterization of the film morphology and chemical states, with 300 W identified as the optimal deposition condition. Laser surface texturing was then introduced to construct micro-structured Al₂O₃ surfaces with different geometrical features. Among the investigated laser powers, the 12 W-treated surface exhibited the most developed surface morphology and the highest roughness, indicating the most favorable topography for electron trapping. SEY measurements showed that the maximum SEY decreased from 8.2 for the as-received Al₂O₃ to 5.5 after deposition of a 10 nm TiN film, and was further reduced to 2.1, 1.0, and 1.7 for the textured TiN/Al₂O₃ surfaces prepared at 6, 12, and 18 W, respectively, with the best suppression for the 12 W textured TiN/Al₂O₃. The enhanced performance is attributed to the synergistic effect of low-SEY TiN surface chemistry and geometrical electron trapping induced by laser texturing. This work provides an effective route for constructing low-SEY Al₂O₃ ceramic surfaces for beam-window-related applications. Full article

Arsenopyrite (FeAsS) is an important sulfide that holds gold in orogenic systems. Its arsenic content is often used as a proxy for gold fertility. However, arsenopyrite from the Um Rus gold deposit in Egypt’s Central Eastern Desert shows a complicated gold distribution that makes simple Au-As correlations hard to make. Integrated electron microprobe analysis (EMPA), laser ablation ICP-MS, and principal component analysis (PCA) reveal three unique textural and geochemical domains. Fine-grained arsenopyrite inclusions within pyrite aggregates (28–31 at% As) are devoid of detectable gold; PCA elucidates 84% of their variance through Fe–S versus Co-As substitution (PC1: 61.8%) and Pb-decoupled variability (PC2: 22.2%), suggesting crystallization from a Co-rich, Au-poor fluid. On the other hand, coarse oscillatory-zoned arsenopyrite can hold up to 6154 ppm of invisible gold. This is because of a moderate Au-As substitution (R = 0.41063, p = 0.08074) that was overprinted by a separate Au-Ag-Sb-Te hydrothermal pulse (Au–Ag: R = 0.97762; Au–Sb: R = 0.97608). PCA finds four parts (72.8% variance): Ag-Cu-As associations (PC1: 25.1%), Te versus Bi-Au signatures (PC2: 17.8%), Fe–S stoichiometry (PC3: 17.1%), and an Au versus Pb-decoupled event (PC4: 12.9%). This shows that minerals formed in more than one stage. Irregular As-rich overgrowths, containing ≤950 ppm gold and lacking significant Au–As correlation (R = −0.14011, p = 0.56726), show PCA (74.3% variance) that highlights S-As contrasts (PC1: 25.2%), Co-Ni enrichment (PC2: 18.8%), Cu-Fe-Ni associations (PC3: 16.2%), and a late Au-decoupled event (PC4: 14.2%), indicating barren recrystallization. These results show that just adding arsenic is not a good way to tell if gold is fertile. The highest amounts of invisible gold, on the other hand, are found in oscillatory-zoned domains with Ag-Sb-Te signatures. This research highlights the importance of combining PCA, geochemistry, and microtextures to differentiate auriferous from barren arsenopyrite, thereby enhancing exploration methodologies for structurally intricate orogenic gold systems. Full article

Diode-pumped alkali vapor lasers (DPALs) offer high quantum efficiency, low thermal loading, excellent beam quality, and emission wavelengths matched to important application scenarios. Extending DPALs toward pulsed regimes is of particular interest for applications such as lidar, free-space optical communication, and precision material processing, where high peak power and flexible temporal control are required. This review surveys the key technologies underlying DPAL systems and summarizes the progress in pulsed-generation approaches. The pulsed techniques reported to date are systematically reviewed, including pump modulation, intracavity modulation, cavity dumping, and mode-locking, together with a comparison of their performance. The current status indicates that pulsed DPALs remain at an early stage, with limitations in parameter space exploration and performance scaling. Future developments are expected along several directions, including further exploration of mode-locked DPALs, burst-mode pulse generation for structured temporal output, power scaling through MOPA architectures, and spectral extension via nonlinear frequency conversion. These directions collectively define the pathway toward high-performance pulsed DPAL systems. Full article

This study elucidates the critical role of pulse repetition frequency (PRF) in optimizing laser inhibition of Microcystis aeruginosa. Using a 355 nm laser (20 ns pulse width, 5 W average power) at 20–65 kHz, 50 kHz is identified as the optimal parameter, achieving 70.6% growth suppression by day 6 (p < 0.001) and reducing cell viability to 28.0 ± 1.6% by day 5 (p < 0.001). Photosynthetic analysis reveals severe PSII dysfunction with Fᵥ/Fₘ of 0.028, representing 91% inhibition (p < 0.001). Biochemical assays demonstrate peak reactive oxygen species generation at 1.59 (p < 0.001) and progressive lipid peroxidation with MDA of 45 nmol/L protein. Transmission electron microscopy and Evans Blue staining corroborate the complete thylakoid disintegration in abundant cells after laser treatment at 50 kHz. These findings establish PRF-dependent photothermal–photomechanical synergy as a deterministic mechanism for efficient, chemical-free algal control. Full article

Bone tissue plays a vital role in the human body and possesses intrinsic self-repair mechanisms; however, large defects or pathological fractures may exceed its natural healing capacity. Bone tissue engineering provides promising strategies to restore bone integrity through the use of scaffolds, growth factors, and stem cells. While calcium phosphate (CaP)-based ceramics, such as hydroxyapatite (HAp) and tricalcium phosphate (TCP), represent the current benchmark, their limitations, including slow degradation (HAp) and limited osteoinductivity (TCP), have driven the development of alternative biomaterials. In this context, magnesium phosphate (MgP)-based materials have gained increasing attention due to their tunable resorption rate, improved biodegradability, and ability to stimulate osteogenesis and angiogenesis through the release of magnesium (Mg²⁺) ions. This study reports on composite scaffolds based on electrospun poly(ε-caprolactone) (PCL) fibres coated with MgP layers doped with lithium (Li) and zinc (Zn), designed to mimic the nanofibrous architecture of the extracellular matrix. Lithium and zinc were selected due to their known ability to modulate cellular response, with lithium promoting osteogenic activity and zinc contributing to improved cell proliferation and antibacterial potential. The phosphate phases obtained by coprecipitation were deposited onto the PCL fibres using Matrix-Assisted Pulsed Laser Evaporation (MAPLE), enabling controlled surface functionalization. Following thermal treatment, the formation of the crystalline magnesium pyrophosphate (Mg₂P₂O₇) phase was confirmed by chemical and structural characterization. The combination of a slowly degrading PCL matrix, providing sustained structural support, and a bioactive MgP coating, enabling rapid and controlled ion release, results in improved scaffold performance in terms of biocompatibility, biodegradability, and bioactivity. While the slow degradation rate of PCL ensures mechanical stability over an extended period, the surface-deposited MgP phase allows immediate interaction with the biological environment, facilitating faster ion release and enhancing cell–material interactions. These findings highlight the potential of the developed composites as promising candidates for trabecular bone regeneration and as viable alternatives to conventional CaP-based scaffolds in regenerative medicine. Full article

To remove the oxide layer of TC1 titanium alloys in an environmentally friendly and efficient manner, this study conducted experiments using a nanosecond pulsed laser to systematically investigate the influence of different laser energy densities on the cleaning effect. The results showed that the oxide layer could be completely removed at an energy density of 6.37 J/cm², with the surface oxygen element content reduced to 4.87%. The macroscopic surface presented a silvery metallic luster. Moreover, the roughness decreased significantly with the increase in energy density. At 6.37 J/cm², the surface roughness dropped to 0.37 µm. The mechanism of removing the oxide layer of TC1 titanium alloy mainly includes laser ablation and plasma impact. At energy densities ranging from 2.55 J/cm² to 6.37 J/cm², the cleaning mechanism was mainly laser ablation. When the energy density exceeded 6.37 J/cm², the cleaning mechanism gradually shifted from laser ablation to plasma impact as the dominant factor. Meanwhile, the microhardness of the samples after laser cleaning was basically consistent with that of the samples subjected to mechanical grinding, which provides a basis for a nanosecond pulsed laser to replace traditional methods for oxide layer cleaning. Full article

Vertical-External-Cavity Surface-Emitting Lasers (VECSELs) have gained significant attention over the past two decades due to their versatility in a wide range of photonic applications. This review focuses on VECSEL configurations for dual-wavelength emission, highlighting their use in high-resolution spectroscopy, terahertz (THz) generation, and advanced optical communication. We explore recent developments in VECSEL designs, including systems utilizing birefringent crystals for polarization-based frequency separation and configurations with dual-VECSEL chips or dual-gain regions within a single cavity. These two-wavelength VECSELs enable diverse operation modes, including narrow-linewidth, pulsed, multimode, and frequency-converted emission, with high-brightness output, excellent beam quality, and tunable wavelengths. Additionally, the review discusses advancements in dual-frequency VECSELs, with applications in LIDAR systems for environmental monitoring, highly stable optical clocks, and fiber sensors. We examine improvements in cavity design, semiconductor structures, and power stabilization, which have enhanced frequency stability and spectral purity, making VECSELs suitable for precision metrology and sensing applications. Full article

Glass preheating prior to laser scanning is expected to enhance internal modification morphology; however, its effect on weld seam topology and welding strength have not been investigated. In the current work, the effects of preheating on ultrafast laser (184 fs and 10 ps) internal modification and welding strength of borosilicate glass slides are investigated. For the internal modification experiments, pulse energy of 30–100 µJ and repetition rate of 10 kHz are used by focusing a laser beam at the interface of optically contacted slides at room temperature (RT ≈ 23 °C), 150 and 200 °C. Welding is conducted by a pulse energy of 4.5–18 µJ and repetition rate of 200 kHz using pre-clamped glass slides with a scanning speed of 10 mm/s at RT and 150 °C. Also, for welding, the optimum number of scans and hatching spacing are identified. Filamentation experiments show that discoloration is not significant when preheat temperature reaches 200 °C. Compared to 10 ps, pulse duration of 184 fs can produce a 19% narrower plasma-modified region at both RT and 150 °C and a 13% wider heat-affected zone at 150 °C. Welding using optimum conditions of 5 scans and 200 µm hatch, and “crack-free” laser parameters produces an average strength of: 50 ± 3.2 MPa at RT and 40 ± 2 MPa at 150 °C for 184 fs compared to 35 MPa at RT and 32 MPa at 150 °C for 10 ps, using 10 replicates each. However, the welding strength upon preheating to 150 °C using 184 fs is still 25% higher compared to average reported laser welding bonding strength, while the 10 ps strength is within the reported average. The enhanced welding strength for 184 fs can be attributed to reduced microcracking, especially when “crack free” combinations are utilized. Full article

Chirped fiber Bragg gratings (CFBGs) are robust diagnostic sensors that are widely used to track detonation-driven and shock wave propagation. CFBGs are inscribed with a linearly chirped periodic index of refraction changes that alter the Bragg wavelength along the length of the probe. The light return of each individual Bragg element is captured by a detector at a unique time to map the full reflected spectrum. The CFBG spectrum is measured with a dispersive Fourier transform of the reflected light that temporally stretches the spectrum to increase spatial resolution and make a one-to-one map of the wavelength on a time axis. Here, we propose an improvement of CFBG temporal resolution by incorporating two co-linear laser pulses with orthogonal polarization states and a 5 ns time offset. The two separate signals were split and tracked by two separate detectors. An oscilloscope captured good separation in the signals, and two separate spectrograms were generated and interleaved in the post-processing of the data. This novel technique doubled the CFBG temporal resolution and led to a doubled location resolution. As a proof-of-concept of this technique, the resolution improvement was compared between standard CFBG measurements and the two polarization states method on a position-sensitive CFBG sensor. CFBG resolution doubling will advance sensor capabilities and will have a direct impact on improving capture and analysis in dynamic, high-explosive experiments. Full article

Femtosecond laser processing has become a powerful approach for high-precision micro- and nanofabrication in transparent materials, owing to its ultrashort pulse duration and minimized thermal effects. However, the limited predictability of processing depth remains a major obstacle to practical applications. Here, we present a morphology prediction framework for femtosecond Bessel laser processing of ZnS that integrates plasma physics modeling with deep learning. Through combined experimental measurements and plasma physics simulations, the influence of laser pulse energy on electron density evolution and material removal depth is systematically investigated. The results reveal the dominant roles of multiphoton ionization, avalanche ionization, and free-electron dynamics in deep-volume processing, and demonstrate the strong sensitivity of the processing morphology to the plasma distribution. Conventional plasma models can accurately reproduce the ablation diameter, yet exhibit significant limitations in predicting the processing depth. We propose a physics data-based framework for femtosecond Bessel beam processing, which integrates a depth-residual regression network conditioned on the peak electron density distribution to effectively learn and compensate for systematic modeling errors in plasma-based simulations. This strategy leads to excellent agreement between predicted and experimental processing depths and three-dimensional morphologies under various energy conditions. The model achieves a mean absolute error (MAE) of 4.9 nm at the pixel level for 3D crater reconstruction. Under rigorous crater-grouped cross-validation with Leave-One-Group-Out evaluation, the model achieves a mean R² of 0.74 across 8 independent craters, demonstrating reliable generalization to unseen energy conditions. These results demonstrate that incorporating physical priors into data-driven learning provides an effective pathway to overcoming accuracy limitations in modeling complex laser–matter interactions. This approach offers a reliable tool for quantitative prediction and parameter optimization in deep femtosecond laser processing of transparent materials and enabling highly controllable and reproducible micro- and nanofabrication for advanced photonic and three-dimensional optical applications. Full article

Achieving selective cleavage of specific chemical bonds using ultrafast laser pulses remains a central challenge in ultrafast strong-field molecular physics. Here, we theoretically investigate the coherent control of strong-field dissociation of the heteronuclear molecular ion HD⁺ initially prepared in vibrationally excited states driven by an ultrashort pulse with a quadratic spectral phase. Our results reveal a pronounced sensitivity of both the total dissociation probability and the branching ratio (H⁺ + D vs. H + D⁺) to the chirp rate of the laser pulse. To uncover the underlying physical mechanism, we analyze the population dynamics in the coupled $1s\sigma$ and $2p\sigma$ electronic states and identify pronounced Rabi oscillations arising from the coherent interplay between multiphoton excitation and field-induced stimulated emission. By tuning the laser chirp rate, these oscillations can be suppressed via quantum interference, thereby reshaping the dissociation dynamics and significantly enhancing the dissociation probability of the H + D⁺ channel. These findings demonstrate that spectral-phase engineering provides a robust and versatile strategy for selective control of branching ratios in strong-field molecular dissociation. Full article

Laser shock peening (LSP) is a surface treatment technique focused on improving the mechanical performance of metal components by inducing compressive residual stresses. This research evaluated the effects of LSP on a Ti-6Al-4V alloy, an α + β titanium alloy manufactured by wrought and additive manufacturing used in biomedical and aerospace applications. Samples manufactured by conventional processes and additive manufacturing were treated under the following conditions: Pulse width of 6 ns, wavelength of 1064 nm, scan density of 2500 pulses/cm², pulse energy of 0.750 J, and repetition frequency of 10 Hz. The mechanical response was evaluated in terms of residual stress, microhardness, and microstructure before and after treatment. The results showed significant improvements, reaching compressive residual stress fields of up to −800 MPa and a 22% increase in microhardness, and grain refinement from 18.16 μm to 5.54 μm. These results confirm the effectiveness of LSP in improving the surface integrity and mechanical behavior of Ti64 components, regardless of their manufacturing method. Full article