Pulsed Laser Research Articles

Experimental study of picosecond laser-assisted grinding of GH4169 nickel-based superalloy

The nickel-based superalloy GH4169 exhibits excellent thermal stability and fatigue resistance, making it widely utilized in the aerospace and marine manufacturing industries. However, the high mechanical strength of the nickel-based superalloy GH4169 leads to issues such as high grinding forces during grinding and poor surface morphology of the material after grinding. To improve the processing quality of GH4169, this study employs ultrafast pulse laser texturing to create two distinct biomimetic structures on its surface. The study explores the impact of laser parameters on both the recast layer and surface hardness. Subsequently, grinding experiments are conducted on both structured and non-structured workpieces. The grinding forces and surface roughness during grinding are analyzed, and the surface morphology of the workpiece after grinding and the corrosion resistance of the material are also tested. According to the test results, the grinding forces of the fishbone-like and nacre-like structure workpieces are reduced compared with those of the non-structured workpieces, and the maximum tangential grinding forces are reduced by 38.54 % and 35.98 %, and the maximum normal grinding forces are reduced by 30.24 % and 29.6 %, respectively. In addition, the corrosion resistance of the surface of the structured workpieces after grinding is better compared to the non-structured workpieces, and the best corrosion resistance is obtained for the fishbone-like structure.

Mn-inlaid antiphase boundaries in perovskite structure

Improvements in the polarization of environmentally-friendly perovskite ferroelectrics have proved to be a challenging task in order to replace the toxic Pb-based counterparts. In contrast to common methods by complex chemical composition designs, we have formed Mn-inlaid antiphase boundaries in Mn-doped (K,Na)NbO3 thin films using pulsed laser deposition method. Here, we observed that mono- or bi-atomic layer of Mn has been identified to inlay along the antiphase boundaries to balance the charges originated from the deficiency of alkali ions and to induce the strain in the KNN films. Thus, rectangular saturated polarization-electric field hysteresis loops have been achieved, with a significantly improved twice remanent polarization of 114 μC/cm2 with an applied electric field of 606 kV/cm, which can be comparable to that of the typical Pb-based thin films. Moreover, we directly see the Mn occupation at the A-site of KNN perovskite structure using atomic-scale microstructure and composition analysis. The Mn-inlaid antiphase boundary can further enrich the understanding of perovskite crystal structure and give more possibilities for the design and optimization of perovskite materials.

Posterior staphyloma-induced serous maculopathy: Evolution and successful treatment with subthreshold micro pulse Laser.

To describe the evolution of posterior staphyloma-induced serous maculopathy (PSISM) in a patient with myopic tilted disc syndrome and its treatment with subthreshold micro pulse laser (SMPL) therapy. A 38-year-old male, diagnosed previously with classical features of myopic tilted disc syndrome presented to the retina clinic after 5 years from the initial presentation with blurred vision in the right eye for 6 months, visual acuity of 6/15 and findings of serous macular detachment (SMD) and subretinal precipitates at the upper margin of the posterior staphyloma. Retinal imaging ruled out other causes of SMD such as chronic central serous chorioretinopathy, myopic macular neovascularisation and dome shaped macula. A diagnosis of PSISM was confirmed. The left eye fundus and macula was normal. Confluent SMPL burns were applied across the SMD. The serous maculopathy resolved over a period of 2 months and visual acuity improved to 6/9. No recurrence of SMD was noted even after 14 months post SMPL. PSISM develops gradually in eyes with myopic titled disc syndrome. SMPL is a viable therapeutic option in the management of PSISM and should be considered early in the treatment options.

Random phase plate designed by the genetic algorithm for decoherence in energy homogenization units of a photolithography illumination system

The microlens array (MLA) is used in the flexible pupil shaping module of lithography illumination system for energy balance. However, the coherence of the light source can lead to interference patterns. Most of the decoherence methods are restricted for the pulse laser and the scanning exposure application. To solve this issue, a specific random phase plate (RPP) is designed to eliminate the interference patterns caused by the coherence of the light source. The model of partially coherent light propagation in the MLAs homogeneous system is established based on the mutual intensity theory, and the genetic algorithm is introduced to design a high-performance RPP. The corresponding measurement device is constructed, and the intensity of the image plane light field is measured. Experiment results indicate that the intensity integral non-uniformity is 32.14% in the x-direction and 66.04% in the y-direction without the RPP, and the intensity integral non-uniformity is 22.95% in the x-direction and 19.18% in the y-direction with the RPP, which verifies the feasibility of the proposed method.

Low Gilbert Damping in Bi/In-Doped YIG Thin Films with Giant Faraday Effect

Abstract Magnetic films with low Gilbert damping are crucial for magnonic devices, which provide a promising platform for realizing ultralow-energy devices. In this paper, low Gilbert damping and coercive field were observed in Bi/In-doped Yttrium Iron Garnet (BiIn:YIG) thin films. The BiIn:YIG (444) films were deposited onto different substrates using pulsed laser deposition. Low coercivity (＜1 Oe) with saturation magnetization of 125.09 emu/cc was achieved along the in-plane direction of BiIn:YIG film. The values of Gilbert damping and inhomogeneous broadening of ferromagnetic resonance in BiIn:YIG films were obtained to be as low as 4.05×10-4 and 5.62 Oe, respectively. In addition to low damping, the giant Faraday rotation angles (up to 2.9×104 deg/cm) were also observed in BiIn:YIG film. By modifying the magnetic structure and coupling effect between Bi3+ and Fe3+ of Bi: YIG, doped In3+ plays a key role on variation of the magnetic properties. The low damping and giant Faraday effect made the BiIn:YIG film an appealing candidate for magnonic and magneto-optical devices.

Structural changes in Ge1−xSnx and Si1−x−yGeySnx thin films on SOI substrates treated by pulse laser annealing

Ge1−xSnx and Si1−x−yGeySnx alloys are promising materials for future opto- and nanoelectronics applications. These alloys enable effective bandgap engineering, broad adjustability of their lattice parameter, exhibit much higher carrier mobility than pure Si, and are compatible with the complementary metal-oxide-semiconductor technology. Unfortunately, the equilibrium solid solubility of Sn in Si1−xGex is less than 1% and the pseudomorphic growth of Si1−x−yGeySnx on Ge or Si can cause in-plane compressive strain in the grown layer, degrading the superior properties of these alloys. Therefore, post-growth strain engineering by ultrafast non-equilibrium thermal treatments like pulse laser annealing (PLA) is needed to improve the layer quality. In this article, Ge0.94Sn0.06 and Si0.14Ge0.8Sn0.06 thin films grown on silicon-on-insulator substrates by molecular beam epitaxy were post-growth thermally treated by PLA. The material is analyzed before and after the thermal treatments by transmission electron microscopy, x-ray diffraction (XRD), Rutherford backscattering spectrometry, secondary ion mass spectrometry, and Hall-effect measurements. It is shown that after annealing, the material is single-crystalline with improved crystallinity than the as-grown layer. This is reflected in a significantly increased XRD reflection intensity, well-ordered atomic pillars, and increased active carrier concentrations up to 4 × 1019 cm−3.

Laser irradiation-induced surface-enhanced Raman scattering of Sn@SnO composite films

In this work, Sn@SnO composite films were obtained by Nd:YAG fiber pulsed laser ablation at room temperature. The effects of laser ablation on the microstructure, optical properties, and Raman scattering properties of the films were investigated. Tunable Localized Surface Plasmon resonance(LSPR)of Sn nanoparticles was realized in the wavelength range of 380–450 nm by varying the scanning rate to modulate the degree of oxidation of Sn nanoparticles. Surface enhanced Raman scattering (SERS) was also observed in the composite structure, which was demonstrated excellent stability and SERS sensitivity with the detectable concentration of methylene blue (MB) as low as 10−9 M and an enhancement factor of 1.75 × 105 as well as a good uniformity. Finally, the electric field distribution of the samples before and after the laser treatment is simulated by the finite difference in time domain (FDTD) method, and the results are consistent with those of experimental ones.

Laser surface structuring of diamond-like carbon films for tribology

The paper overviews experimental findings of the direct laser processing and surface microstructuring (texturing) of various diamond-like carbon films (a-C:H, ta-C, DLN, metal-doped DLN), aimed at improvements of their tribological and nanotribological properties. The nanosecond UV and femtosecond IR/visible pulsed lasers were applied in microprocessing of the films, focusing on high precision surface structuring with fs-laser pulses. The studies were concentrated on the following tasks: (i) surface graphitization in laser microstructuring of the films under different irradiation conditions, (ii) lubricated friction performance of DLN films micropatterned with UV ns and visible fs pulsed lasers, and (iii) nanoscale friction of laser-structured DLN and metal-doped DLN films examined with contact-mode atomic force microscopy. The important findings of our studies are related to fabrication of highly-precise microgroove/microcrater patterns on DLN films and improvements of frictional properties of the laser-structured films at the macro, micro and nanoscale. The surface microstructures improved the film properties under oil-lubricated sliding in dependence on their geometrical parameters (size, depth, period) and ambient temperature. The nanoscale friction behavior of laser-structured films was shown to be controlled by the surface graphitization, nanoscale roughness, capillary forces and wear of AFM tips during friction force imaging.

Atmospheric chemistry of CF3CHFCF2OCH3 (HFE-356mec3) and CHF2CHFOCF3 (HFE-236ea1) initiated by OH and Cl and their contribution to global warming.

The kinetic study of the gas-phase reactions of hydroxyl (OH) radicals and chlorine (Cl) atoms with CF3CHFCF2OCH3 (HFE-356mec3) and CHF2CHFOCF3 (HFE-236ea1) was performed by the pulsed laser photolysis/laser-induced fluorescence technique and a relative method by using Fourier Transform infrared (FTIR) spectroscopy as detection technique. The temperature dependences of the OH-rate coefficients (kOH(T) in cm3s-1) between 263 and 353K are well described by the following expressions: 9.93 × 10-13exp{-(988 ± 35)/T}for HFE-356mec3 and 4.75 × 10-13exp{-(1285 ± 22)/T} for HFE-236ea1. Under NOx-free conditions, the rate coefficients kCl at 298K and 1013mbar (760Torr) of air were determined to be (2.30 ± 1.08) × 10-13 cm3s-1and (1.19 ± 0.10) × 10-15 cm3s-1, for HFE-356mec3 and HFE-236ea1, respectively. Additionally, the relative kinetic study of the Cl + CH2ClCHCl2 reaction was investigated at 298K, as it was used as a reference reaction in the kinetic study of the Cl-reaction with HFE-356mec3 and discrepant rate coefficients were found in the literature. The global atmospheric lifetimes were estimated relative to CH3CCl3 at the tropospheric mean temperature (272K) as 1.4 and 8.6years for HFE-356mec3 and HFE-236ea1, respectively. These values combined with the radiative efficiencies for HFE-356mec3 and HFE-236ea1 derived from the measured IR absorption cross sections(0.27 and 0.41 W m-2 ppv-1) yield global warming potentials at a 100-yrs time horizon of 143 and 1473, respectively. The contribution of HFE-356mec3 and HFE-236ea1 to global warming of the atmosphere would be large if they become widespread increasing their atmospheric concentration.

Wafer-scale mesoporous GaN distributed bragg reflectors with enhanced luminescence for Eu doped β-Ga2O3 thin films

Wafer-scale Mesoporous GaN (MP-GaN) distributed Bragg reflectors (DBRs) with high reflectivity (>99 %) are prepared by electrochemical etching, and then are used as the substrate in growth of large-area europium (Eu) doped Ga2O3 thin films via the pulsed laser deposition (PLD) technology. X-ray diffraction analysis shows that all Ga2O3 thin films with different doping concentration have monoclinic β-Ga2O3 structures with [−201] orientation. The angle of β-Ga2O3 (−201) peak decreases as Eu contents increases, which is due to the fact that Eu3+ substituting for Ga3+ rises the lattice constant of β-Ga2O3. With the increase of Eu doping, the photoluminescence (PL) of the Ga2O3 thin film is enhanced. The epitaxial relationship is β-Ga2O3 (−201) || GaN (0001) with β-Ga2O3 [010] || GaN [-12-10]. Compared to the sample without DBRs, wafer-scale Ga2O3 thin films with MP-GaN DBRs exhibit a markedly increased PL intensity, which is attributed to improved internal quantum efficiency (IQE) of Ga2O3 thin films and enhanced light extraction efficiency (LEE) related to the light reflection effect of MP-GaN DBRs.

Effects of Er,Cr:YSGG Laser Surface Treatments and Composites with Different Viscosities on the Repair Bond Strength of CAD/CAM Resin Nanoceramic

This study aims to evaluate the repair micro-shear bond strength of the CAD/CAM resin nanoceramic block treated using four different surface treatments and composite resins of different viscosities. For the current study, 96 samples with dimensions of 14 × 12 × 2 mm were obtained from a CAD/CAM resin nanoceramic block (Cerasmart) with a low-speed precision cutting saw under water cooling. The relevant samples were randomly divided into four groups according to the surface treatment processes: grinding with diamond bur, aluminum oxide airborne-particle abrasion, long-pulse laser, and short-pulse laser. Following silane application, universal adhesive was applied to all surface-treated samples and cured with an LED for 10 s. The samples prepared for the repair procedure were divided into two subgroups (microhybrid composite and injectable composite) according to the viscosity of the repair material to be used (n = 12). After the repair procedure, care was taken to keep the samples in distilled water in an incubator at 37 °C for 24 h. The repair micro-shear bond strength values (μSBSs) of CAD/CAM resin nanoceramic-composite resin complexes were tested. In addition, randomly selected samples from each group were examined with a scanning electron microscope to evaluate the surface topography after both surface treatments and the micro-shear bond strength test. Data were analyzed by two-way ANOVA and Bonferroni test. It was determined that the surface treatment preferred in the repair protocol significantly affected the μSBS value (p < 0.001). While the highest μSBS value was obtained with the short-pulse laser airradiation group, the lowest μSBS values were found in samples with long pulse laser irradiation. However, samples grinded with a bur and airborne-particle abrasion showed similar μSBS values (p > 0.05). The preferred composite viscosity in the repair procedure has a significant effect on the μSBS value (p < 0.001). However, the interaction between the surface treatment and the viscosity of the repair composite does not affect the μSBS values in a statistically significant way (p = 0.193). It may be recommended to clinicians to repair CAD/CAM resin nanoceramic restoration surfaces with injectable composites or after treatment with short-pulse lasers.

Improving pulsed laser induced fluorescence distribution function analysis through matched filter signal processing.

Laser induced fluorescence is used to measure argon ion heating during magnetic reconnection in the PHase Space MApping experiment (PHASMA). Sufficient signal-to-noise ratio (SNR) of the processed signal with pulsed laser injection is a delicate balance between saturation of the absorption line and injecting enough laser power to overcome the spontaneous emission of the plasma at the fluorescence wavelength. Averaging over many laser pulses and integrating over the fluorescence lifetime improves the SNR of the processed signal (processed SNR) when the SNR of the laser pulse time series is small (pulse SNR), but for laser powers small enough to avoid saturation, averaging over hundreds of pulses is needed to obtain an appreciable processed SNR over the entire Doppler-broadened absorption line. Here, we describe a matched filter processing method that significantly improves the SNR of the final measurement with fewer shots averaged. Investigation of simulated measurements validated by experimental results suggests that the matched filter method provides up to a 20% improvement in the processed SNR, resulting in less uncertainty in distribution function fits.

Study on the processing characteristics of carbon fiber-reinforced plastics by ultra-short pulse laser

Study on the processing characteristics of carbon fiber-reinforced plastics by ultra-short pulse laser

XFEL Beamline Optical Instrumentation for Ultrafast Science.

Free electron lasers operating in the soft and hard X-ray regime provide capabilities for ultrafast science in many areas, including X-ray spectroscopy, diffractive imaging, solution and material scattering, and X-ray crystallography. Ultrafast time-resolved applications in the picosecond, femtosecond, and attosecond regimes are often possible using single-shot experimental configurations. Aside from X-ray pump and X-ray probe measurements, all other types of ultrafast experiments require the synchronized operation of pulsed laser excitation for resonant or nonresonant pumping. This Perspective focuses on the opportunities for the optical control of structural dynamics by applying techniques from nonlinear spectroscopy to ultrafast X-ray experiments. This typically requires the synthesis of two or more optical pulses with full control of pulse and interpulse parameters. To this end, full characterization of the femtosecond optical pulses is also highly desirable. It has recently been shown that two-color and two-pulse femtosecond excitation of fluorescent protein crystals allowed a Tannor-Rice coherent control experiment, performed under characterized conditions. Pulse shaping and the ability to synthesize multicolor and multipulse conditions are highly desirable and would enable XFEL facilities to offer capabilities for structural dynamics. This Perspective will give a summary of examples of the types of experiments that could be achieved, and it will additionally summarize the laser, pulse shaping, and characterization that would be recommended as standard equipment for time-resolved XFEL beamlines, with an emphasis on ultrafast time-resolved serial femtosecond crystallography.

Fabrication of rGO-bridged TiO2/g-C3N4 Z-scheme Nanocomposites via Pulsed Laser Ablation for Efficient Photocatalytic CO2 Reduction.

Highly efficient photocatalysts can be fabricated using favorable charge transfer nanocomposite channel structures. This study adopted pulsed laser ablation in liquid (PLAL) to obtain rGO-bridged TiO2/g-C3N4 (rGO-TiO2/g-C3N4) photocatalytic Z-scheme without the need for noble metals. In addition to evaluating the resulting nanocomposite's (comprising rGO nanosheets, TiO2 nanotubes, and g-C3N4 nanosheets) CO2 reduction effectiveness, its chemical, morphological, structural, and optical characteristics were examined using various analytical techniques. The findings revealed a synergistic interaction between g-C3N4 and TiO2, suggesting the presence of unique interfacial bonding, as well as enhanced visible light absorption. Notably, the ternary rGO-TiO2/g-C3N4 Z-scheme exhibits an excellent photocatalytic performance by photocatalytically converting CO2 into CO and CH4, with 81% selectivity towards the CO and 1.91% apparent quantum efficiency at 420 nm. Thus, the findings can pave the way for various Z-scheme systems in wide photocatalytic applications.

EXPRESS: Feasibility of a Fiber-Dispersive Raman Spectrometer for Biomarker Detection.

Raman spectroscopy is among the top analytical techniques for ultra-low-dense organic matter, crucial to the search for life and analysis of celestial body surfaces in space exploration missions. Achieving the ultimate sensitivity in in situ Raman spectroscopy necessitates a breakthrough in detecting inelastically scattered light. Single-photon detectors (SPD) operating in photon counting mode, which can differentiate between Raman and luminescence responses, are promising candidates for the challenging scientific requirements. Since large SPD arrays are not yet commercially available, a dispersive element can be adapted to a single-pixel detector. By exploiting chromatic dispersion in optical fibers and picosecond-pulsed excitation, we delay the arrivals of different spectral components onto a single-pixel SPD. This method also separates weak Raman signals from stronger luminescence through correlated time-domain measurements. We study the impact of fiber properties and the excitation wavelength of a pulsed laser on the spectral resolution of the fiber-dispersive Raman spectrometer (FDRS). Additionally, we demonstrate the FDRS's potential for studying biomarkers and discuss its feasibility for analyzing inclusions in ice matrices.

Pulsed Laser-Modified Zinc Anode with Improved Dendrite and Corrosion Resistance for Sustainable High Performance Zinc Ion Hybrid Supercapacitors

This research explores the development and evaluation of zinc ion hybrid supercapacitors (ZIHSCs) with a focus on the enhanced performance and low corrosion attributes of pulsed laser-modified zinc anodes compared to their non-modified counterparts. These anodes, paired with cathodes crafted from activated carbon derived from jute sticks on graphite foil, were immersed in a 2 M zinc sulfate electrolyte. A pivotal aspect of the study is improving the electrochemical properties and corrosion resistance of zinc anodes achieved through precise pulsed laser modification. Extensive electrochemical testing was conducted to assess the capacitive behavior, energy storage capabilities, and durability of the supercapacitors during prolonged cycling. Hence, using the laser modified anode, we attain remarkable stability in Zn||Zn symmetric cells for 1000 hours at high current density of 10 mA cm-2 with a capacity of 1 mAh cm-2, and ZIHSCs achieving specific capicitance up to 287 F/g at a current density of 0.1 A/g, and reaching an energy density of 102 Wh/kg while sustaining a power density of 80 W/kg. After 10,000 galvanostatic charge-discharge cycles, these supercapacitors maintained high capacitance values, underscoring their resilience. Notably, charge transfer resistance reduction, improved ion diffusion and enhanced corrosion resistance contributes to the supercapacitors' longevity and efficiency, which can be attributed to these anodes laser-induced surface alterations. This study highlights the crucial role of pulsed laser-modified zinc anodes in advancing ZIHSCs performance, marking a significant step towards achieving efficient and sustainable energy storage solutions.

Ambient dosimetry in pulsed neutron fields with LINrem detectors

The status of the LINrem project is presented, focusing on the development of innovative neutron dosimeters with enhanced energy sensitivity, time resolution, and portability. Designed to meet the technical demands of radiation protection in modern particle and nuclear facilities, these dosimeters are discussed in detail. Results from experimental campaigns showcasing their efficacy in pulsed fields generated by fusion plasmas and high-intensity pulsed lasers are presented. Additionally, prospects and future plans for the LINrem project are outlined.

In-plane and out-of-plane anisotropy in the optical and dielectric properties of YBa2Cu3O7-x superconducting film

YBa2Cu3O7-x (YBCO) is a crucial aspect of research in the field of superconducting applications, where its high anisotropy is generally undesirable in strong power transmission. However, from a dialectical perspective, a thorough investigation of material anisotropy can offer an additional degree of freedom to tune potential properties and design innovative devices. This work employed pulsed laser deposition to fabricate a high-quality YBCO thin film (Tc = 89 K) and used the Mueller matrix spectroscopic ellipsometer (MMSE) to determine the complete dielectric tensor of the YBCO film across the ultraviolet to near-infrared spectrum (245–1000 nm), enabling a comprehensive, quantitative study of the optical anisotropy of YBCO. It provided optical constants and dielectric function spectra for different axes. We found that YBCO exhibits birefringence and dichroism both in-plane and out-of-plane. By combining standard critical point (SCP) analysis and first-principles calculations, we identified specific interband transitions related to SCP in the YBCO dielectric spectra, revealing the physical essence of anisotropic optical transitions from a quantum mechanical standpoint. Temperature-dependent studies of the transitions and optical constants were conducted. The work fills a partial void in the optical parameters of the anisotropy of YBCO and holds relevance for understanding the origins of copper-based high-temperature superconductivity.

The role of thickness on the structural and luminescence properties of Y2O3:Ho3+, Yb3+ upconversion films

The structural, surface, and upconversion (UC) luminescence properties of Y2O3:Ho3+,Yb3+ films grown by pulsed laser deposition, for different numbers of laser pulses, were studied. The crystallinity, surface, and UC luminescence properties of the thin films were found to be highly dependent on the number of laser pulses. The X-ray powder diffraction analysis revealed that Y2O3:Ho3+,Yb3+ films were formed in a cubic structure phase with an Ia 3¯\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\overline{3 }$$\\end{document} space group. The thicknesses of the films were estimated by using cross-sectional scanning electron microscopy, depth profiles using X-ray photoelectron spectroscopy (XPS), and the Swanepoel method. The high-resolution XPS was used to determine the chemical composition and oxidation states of the prepared films. The UC emissions were observed at 538, 550, 666, and 756 nm, assigned to the 5F4 → 5I8, 5S2 → 5I8, 5F5 → 5I8, and 5S2 → 5I7 transitions of the Ho3+ ions. The power dependence measurements confirmed the involvement of a two-photon process in the UC process. The color purity estimated from the Commission International de I’Eclairage coordinates confirmed strong green UC emission. The results suggested that the Y2O3:Ho3+,Yb3+ UC transparent films are good candidates for various applications, including solar cell applications.