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X-ray free electron laser (XFEL) sources coupled to high-power laser systems offer an avenue to study the structural dynamics of materials at extreme pressures and temperatures. The recent commissioning of the DiPOLE 100-X laser on the high energy density (HED) instrument at the European XFEL represents the state-of-the-art in combining x-ray diffraction with laser compression, allowing for compressed materials to be probed in unprecedented detail. Here, we report quantitative structural measurements of molten Sn compressed to 85(5) GPa and ∼ 3500 K. The capabilities of the HED instrument enable liquid density measurements with an uncertainty of ∼ 1 % at conditions which are extremely challenging to reach via static compression methods. We discuss best practices for conducting liquid diffraction dynamic compression experiments and the necessary intensity corrections which allow for accurate quantitative analysis. We also provide a polyimide ablation pressure vs input laser energy for the DiPOLE 100-X drive laser which will serve future users of the HED instrument. [ABSTRACT FROM AUTHOR]

When a diamagnetic graphite plate is placed on top of a magnet, it is subject to both magnetic levitation and gravitational forces. Computational modeling is used to demonstrate that these forces can balance each other to allow a stable tilt angle θ to be attained when the graphite plate pivots on the magnet surface. θ depends on the magnetic susceptibility χmag, which can be controlled by using laser irradiation to change the temperature of the graphite. Over a limited temperature range, there is a linear relation between the angle change Δθ and the temperature change ΔT. This predicted behavior is confirmed experimentally using a graphite plate (5 × 5 × 0.83 mm) placed on top of a 7.5 cm diameter neodymium iron boride magnet with a surface field strength of ∼5000 G. Using a 532 nm laser, θ could be continuously tuned from 52° to 26° by varying the laser power between 20 and 800 mW. The response time was about 15 s at all powers. Higher laser powers were observed to lead to a complete loss of levitation, followed by recovery and oscillation in and out of the laser beam. The linear dependence of Δθ on power suggests that photothermal tilting of the graphite plate in a magnetic field provides a fatigue resistant way to achieve large angular deviations using an external light source. This effect can be harnessed to function as a laser-controlled beam steering device. [ABSTRACT FROM AUTHOR]

Nitrogen-incorporated ultrananocrystalline diamond [(N)UNCD] pyramid tip cathode has been considered as a next-generation high peak current electron source for dielectric laser accelerators as well as other high peak current particle accelerator applications. In this work, we study non-linear photoemission from an (N)UNCD pyramid tip cathode using an ultrafast laser with the pulse length of 150 fs with the central wavelength of 800 nm in the peak intensity range of 10 9 – 10 10 W / cm 2. We demonstrated that as the incident laser intensity increases, the current emitted from the nano-tip first increases as a power function with an exponent of about 5 and then starts to roll over to an exponent of 3. This roll over is attributed to the Coulomb interaction between electrons emitted from the tip also known as the space charge. We also measured the photoemission electron energy spectra that show electrons with energies as high as ∼ 10 eV. Based on the shape of the electron energy spectra, we conclude that the high-energy electrons are thermally emitted electrons due to ultrafast laser heating at the tip of the (N)UNCD pyramid tip cathode. [ABSTRACT FROM AUTHOR]

Inspired by the emerging field of twistronics, moiré photonic structures have attracted great interest. In this paper, we introduce the concept of the moiré Kagome lattice (MKL), which arises from the overlapping of a Kagome lattice at a commensurable angle of 38.211°. MKL exhibits a significantly broader main photonic bandgap (PBG) when compared to the traditional Kagome lattice. Through numerical simulations, we delved into the adjustable properties of the PBG of MKL by varying lattice parameters, including filling factors and materials. Meanwhile, we also observed the presence of photonic flatbands within the MKL structure. Specifically, the emergence of a super flat isolated flatband aids in achieving single-mode omnidirectional lasers and enhancing the omnidirectional electromagnetic interaction of materials, thereby expanding the applications of moiré photonic crystals. [ABSTRACT FROM AUTHOR]

Antiferromagnetic materials have recently been proposed as new types of terahertz (THz) range spintronic devices owing to their ultrafast spin dynamics. Manipulating their spin dynamics expediently, however, remains a key challenge. Here, we demonstrate the laser excitation of magnons in a prototypical antiferromagnet NiO via spin–phonon coupling. The terahertz time-domain spectrum revealed the frequencies of antiferromagnetic magnons near 1 THz. Laser excitations in the visible spectrum caused a noticeable softening of the magnons. Raman spectroscopy results established the presence of optical phonons. The laser heating effect was excluded by finite-element analysis and variable-temperature measurements. The temperature- and power-dependent properties suggest an optical phonon–magnon coupling mechanism. Laser excitation raises the optical phonon temperature, linked with the magnon temperature, via the magnon–phonon interaction. Consequently, the magnon temperature rises, and the magnon mode frequency softens. Our findings shed light on spin–phonon coupling in antiferromagnetic insulators and open a route for creating rapid opto-spintronic devices that utilize antiferromagnetic materials. [ABSTRACT FROM AUTHOR]

In the current work, laser thermal treatment of the FeSiB amorphous foil with a single linear laser track was carried out. The resultant microstructure and phase evolution were examined with the aid of x-ray diffraction, differential scanning calorimetry, and site-specific transmission electron microscopy. The laser power was kept constant at 100 W, whereas, laser beam scanning speeds were varied in the range of 500–235 mm/s, generating corresponding laser fluences of 0.42–0.91 J/mm 2 on the sample surface. Laser fluences of up to 0.48 J/mm 2 structurally relaxed the FeSiB foil, retaining the amorphous structure. Laser fluences of higher than 0.48 J/mm 2 led to partial crystallization of FeSiB amorphous foils. The crystallite sizes were in the range of 11–31 nm (laser fluence of 0.49–0.91 J/mm 2). α -FeSi formed as a major phase of partial crystallization while its quantity steadily increased from 3.6 to 46 vol. % with laser fluence (laser fluence 0.49–0.91 J/mm 2). Fe 2 B formed in recognizable quantities (≥ 2%) for laser fluences ≥ 0.53 J/mm 2. Laser fluences leading to structural relaxation and evolution of predominantly α -FeSi phase exerted minimal effects on ratios of intrinsic coercivities to saturation compared to the as-cast FeSiB amorphous foil. On the contrary, formation of Fe 2 B in significant quantities (≥ 2 %) led to the steady increase in intrinsic coercivities and remanence to saturation ratios as a function of laser fluence indicating a loss in soft magnetic characteristics. Nonetheless, continuous increase in fractions of α -FeSi with laser fluence led to a steady improvement in saturation magnetostriction of the FeSiB foil. [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]

Here, we analyzed the effect of a donor molecule (Rh6G) on the random laser emission of an acceptor molecule (Rh640 perchlorate) coated on the surface of a polymer optical fiber. Due to the energy transfer mechanism, the random lasing threshold of Rh640 perchlorate was found to be reduced in the presence of Rh6G. Also, the emission spectrum of Rh640 perchlorate was blue-shifted with the addition of Rh6G. Meanwhile, there is an enhancement in the lasing threshold of Rh6G in the presence of Rh640 perchlorate. The present study demonstrates that by properly adjusting the concentrations of both donor and acceptor molecules, we can obtain a dual-color random laser emission from polymer optical fiber. [ABSTRACT FROM AUTHOR]

In this work, low-temperature photoluminescence spectroscopy was employed to investigate the N3 optical color center in natural type Ia diamond. The optical properties of the N3 center with regular changes in testing temperature and laser power were studied, and the energy level transition was also discussed. The results showed that the PL intensity of the N3 center enhanced sub-linearly with laser power increased, indicating that the electron transition of the N3 center was mainly radiative recombination with weak Auger recombination participation. In addition, the physical model was employed to analyze the change in the zero phonon line with the increase in the test temperature; it obtained thermal quenching activation energy (25.2 meV), bond softening, and strong interaction with acoustical phonons of the N3 center. The theoretical analysis of the broadening parameters revealed that the longitudinal optical phonon energy was 55.1 meV, and the electron–optic phonon coupling strength was 2.3 meV. [ABSTRACT FROM AUTHOR]

We report on InGaAs/GaAs quantum dot injection microdisk lasers laterally connected with a bus waveguide fabricated by planar technology from the same epi-structure. Various coupling schemes of microlaser with waveguide are studied including a microlaser attached to a waveguide (zero gap), a 100 nm gap for evanescence light outcoupling, and with a waveguide surrounding the resonator. The modes outcoupling and microlaser's loss (Q-factor) are analyzed by simulation of the lasers. A strong decrease in the number of the microdisk resonance lines associated with an increase in loss in the resonator due to the coupling with waveguide is observed in modeling and experimentally. We study the spectral and lasing parameters of the microdisk lasers, as well as characteristics of the outcoupled emission, and demonstrate efficient light outcoupling for 30 and 40 μm diameter continuous wave operating microdisk laser up to 96 °C. [ABSTRACT FROM AUTHOR]

A pulse-shaping technique in the mid-infrared spectral range based on pulses with a super-Gaussian temporal profile is considered for laser control. We show a realistic and efficient path to the population of a dark rovibrational state in acetylene (C2H2). The laser-induced dynamics in C2H2 are simulated using fully experimental structural parameters. Indeed, the rotation–vibration energy structure, including anharmonicities, is defined by the global spectroscopic Hamiltonian for the ground electronic state of C2H2 built from the extensive high-resolution spectroscopy studies on the molecule, transition dipole moments from intensities, and the effects of the (inelastic) collisions that are parameterized from line broadenings using the relaxation matrix [A. Aerts, J. Vander Auwera, and N. Vaeck, J. Chem. Phys. 154, 144308 (2021)]. The approach, based on an effective Hamiltonian, outperforms today's ab initio computations both in terms of accuracy and computational cost for this class of molecules. With such accuracy, the Hamiltonian permits studying the inner mechanism of theoretical pulse shaping [A. Aerts et al., J. Chem. Phys. 156, 084302 (2022)] for laser quantum control. Here, the generated control pulse presents a number of interferences that take advantage of the control mechanism to populate the dark state. An experimental setup is proposed for in-laboratory investigation. [ABSTRACT FROM AUTHOR]

Numerical calculations and experimental approaches are used to examine the slip characteristics of 1064 nm laser ablated single crystal germanium. The ablation and cooling processes are used to investigate the influence of laser power density on the creation of the slip process. A 1064 nm continuous laser and a nanosecond laser were used to ablate single-crystal germanium samples, and the damage to the surface was seen using an optical microscope. The results demonstrate that raising the laser power density to 107 W/cm2 efficiently suppresses slip production during laser processing. [ABSTRACT FROM AUTHOR]

Control of the charge state of the nitrogen-vacancy (NV) center is crucial because of its instability and its transitions between the negative (NV–) and neutral (NV0) NV charge states under laser irradiation In this study, we fabricated an n-i-n junction, with an i-layer sandwiched between two phosphorus-doped n-layers; then, we measured the charge state of NV centers under steady state and laser irradiation in a known band structure where the Fermi energy changes gradually. The steady-state charge state measured by a nondestructive single shot exhibited stable NV– and NV0 signals when the Fermi level was even slightly above and below the transition level, respectively. This result indicates that the charge state can be significantly stabilized through band engineering. Both charge-state populations were observed only when the Fermi level was close to the transition level. Under continuous green laser irradiation, the ratio of NV– measured by the photoluminescence spectra changed gradually with the Fermi level in the depletion layer because of the balance between excitation from the laser and the supply of charge from the band. This outcome agrees reasonably with the calculated bands. Furthermore, we measured the PL spectra of the ensemble NV centers and discovered that their charge state can be well-controlled, as in the single NV center. The charge state of the i-layer at the interface can be stabilized by depositing a thin n-layer on the surface. These results would contribute significantly to improve sensor performance. [ABSTRACT FROM AUTHOR]

Atomic stabilization is a universal phenomenon that occurs when atoms interact with intense and high-frequency laser fields. In this work, we systematically study the influence of the ponderomotive (PM) force, present around the laser focus, on atomic stabilization. We show that the PM force could induce tunneling and even over-barrier ionization to the otherwise stabilized atoms. Such effect may overweigh the typical multiphoton ionization under moderate laser intensities. Our work highlights the importance of an improved treatment of atomic stabilization that includes the influence of the PM force. [ABSTRACT FROM AUTHOR]

To realize fully integrated silicon photonics (Si photonics), reliable III–V light sources that can be efficiently coupled with Si/SiN waveguides are essential. Here, based on a monolithic InP/silicon-on-insulator (SOI) platform, we developed a selective regrowth scheme and constructed a regrowth platform for on-chip lasers that can be efficiently coupled with Si/SiN waveguides. InP and InGaAs/InP multi-quantum wells (MQWs) were regrown on the regrowth template on SOI as well as patterned commercial InP wafers in the same growth run for comparison. A flat (001) top surface after regrowth with a low roughness of 0.38 nm was obtained on SOI. Benefitting from the high quality of MQWs regrowth, strong photoluminescence emission at telecom band can be obtained on both growth templates. Also, multi-wavelength emission on the same chip can be potentially achieved by designing various regrowth openings. Furthermore, the large material volume with vertical stacking structure and intimate placement of MQWs and the Si layer of SOI allow for the potential demonstration of electrically pumped lasers and efficient light coupling between them and Si/SiN waveguides. Therefore, the demonstrated regrowth method provides a promising solution for the monolithic integration of III–V on-chip lasers on Si. [ABSTRACT FROM AUTHOR]

Rationale: Solvent‐free sample preparation offers some advantages over solvent‐based techniques, such as improved accuracy, reproducibility and sensitivity, for matrix‐assisted laser desorption/ionization (MALDI) analysis. However, little or no information is available on the application of solvent‐free techniques for the MALDI analysis of polymer blends. Methods: Solvent‐free sample preparation by ball milling was applied with varying sample‐to‐matrix ratios for MALDI time‐of‐flight mass spectrometry analysis of various polymers, including polystyrenes, poly(methyl methacrylate)s and poly(ethylene glycol)s. The peak intensity ratios were compared with those obtained after using the conventional dried droplet sample preparation method. In addition, solvent‐assisted milling was also applied to improve sample homogeneities. Results: Depending on the sample preparation method used, different peak intensity ratios were found, showing varying degrees of suppression of the signal intensities of higher mass polymers. Ball milling for up to 30 min was required to achieve constant intensity ratios indicating homogeneous mixtures. The use of wet‐assisted grinding to improve the homogeneity of the blends was found to be disadvantageous as it caused partial degradation and mass‐dependent segregation of the polymers in the vials. Conclusions: The results clearly show that solvent‐free sample preparation must be carefully considered when applied to synthetic polymer blends, as it may cause additional problems with regard to homogeneity and stability of the blends. [ABSTRACT FROM AUTHOR]

Although the hydroxyapatite (HA) coating implant prepared by laser cladding exhibits good biological activity due to its chemical composition similar to biological bone, the original surface roughness of the laser-clad coating is high, which is unfavorable for long-term cell adhesion and proliferation. In order to improve the biological activity of HA coating implants and increase the adhesion and proliferation rate of osteoblasts on their surface, microtextures with different length-diameter ratios and depth gradients were prepared on the HA coating surface by nanosecond laser with reference to the microscopic morphology characteristics of the biological bone surface. By investigating the effects of microtexture aspect ratio and depth gradient on osteoblast adhesion characteristics, it was found that bone-like microtextures better controlled and simulated cell-material surface interactions. The geometric morphology of microtextured bone with a wide front end and narrow rear end and a depth gradient from front to back was an important signal for osteoblast proliferation. When the aspect ratio of bone microtexture was 2.5:1 and the maximum depth gradient was 15.7 μm, osteoblasts within the microtexture showed optimal growth, proliferation, and adhesion. Additionally, due to induction by microtexture contour shape and depth gradient morphology, cell morphology showed varying adhesion morphology from the front to the back of the microtexture. The results demonstrated that HA coatings with bone-like microtextures had superior osteoblast proliferation and adhesion properties compared to the original cladded coating surface, beneficial for enhancing the application of HA-coated bone implants in large segment bone repair. [ABSTRACT FROM AUTHOR]

The damage mechanisms of Ti 3 AlC 2 ceramics during laser processing in air and water were studied using the pulsed laser. The focused high-energy laser induced the melting of surface of Ti 3 AlC 2 ceramics, causing the decomposition of Ti 3 AlC 2 into TiC and Al with Al rapidly evaporating. During the laser processing in the air, oxygen diffused inward to form a solid solution of TiC x O y , and the rapidly heating and cooling of resolidified layer generated high thermal tensile stresses to result in a large amount of microcracks. When processing in the water, the thermal stresses were greatly weakened, and the outward diffusion of Al steam resulted in the voids on the sample surface. Additionally, it is determined that after treating in the air and water, the residual flexural strengths of Ti 3 AlC 2 ceramics could retain the high values of 292 MPa and 484 MPa, and the Weibull moduli were kept at 7.2 and 16.0, respectively, exhibiting the excellent damage tolerance and high reliability. [ABSTRACT FROM AUTHOR]

Phosphors in glass films (PiFs) is considered ideal conversion materials for laser lighting, but heat dissipation issue is the main challenge limiting its development. Therefore, it is urgent to find more excellent heat dissipation materials. Herein, we proposed to use AlN with high thermal conductivity as the substrate, and innovatively introduced TiO 2 coating to improve the interface reflection ability and solve the possible problems of shedding and cracking. After a series of optimizations, the LSN PiG-TiO 2 -AlN (PTA) color converter obtained a high thermal conductivity of 29W m−1k−1 and a low surface temperature. At an input power of 5.2W, the luminous efficiency can reach 175 lm/W and the relative initial intensity can still be maintained by 95.3% at 200 °C. Benefiting from the extremely strong heat dissipation capacity of the AlN substrate, the LSN PTA color converter maintains its relative luminous intensity at 95 % of the initial intensity after 24 h of continuous illumination, which is the best value recorded so far. In addition, LSN PTA is combined with CaAlSiN 3 :Eu2+ phosphor to achieve high-quality white light with a CRI of 82.5. The above results indicate that LSN PiG-TiO 2 -AlN color converters have a promising research prospect in the field of laser lighting. [ABSTRACT FROM AUTHOR]

Semiconductor nanowire (NW) quantum devices offer a promising path for the pursuit and investigation of topologically-protected quantum states, and superconducting and spin-based qubits that can be controlled using electric fields. Theoretical investigations into the impact of disorder on the attainment of dependable topological states in semiconducting nanowires with large spin–orbit coupling and g -factor highlight the critical need for improvements in both growth processes and nanofabrication techniques. In this work, we used a hybrid lithography tool for both the high-resolution thermal scanning probe lithography and high-throughput direct laser writing of quantum devices based on thin InSb nanowires with contact spacing of 200 nm. Electrical characterization demonstrates quasi-ballistic transport. The methodology outlined in this study has the potential to reduce the impact of disorder caused by fabrication processes in quantum devices based on 1D semiconductors. [ABSTRACT FROM AUTHOR]

Silicon carbide fiber reinforced silicon carbide ceramic matrix composite (CMC SiC f /SiC) has the advantages of high temperature resistance, corrosion resistance, high strength, low density, and oxidation resistance. It is a high-performance advanced material in aerospace, energy and other fields. However, due to its high hardness, brittleness and anisotropy of fiber structure, the research on application-oriented high-quality processing technology has become a hot issue. In this paper, a new process of rotational thirteen-beam coupling nanosecond laser processing of CMC-SiC f /SiC was studied. The rotational thirteen-beam coupling ablation experiments were carried out on CMC-SiC f /SiC workpiece. A laser beam is divided into thirteen beams and rotated around the beam center by using a beam splitter element. The morphology, structure and composition of ablation holes at different speeds were observed and analyzed by laser confocal microscope, scanning electron microscope, and X-ray energy dispersive spectrometer. It is found that the characteristics of rotational beam coupling have a significant effect on the laser ablation morphologies. The results show that the ablation region of CMC-SiC f /SiC is elliptical due to the fast heat transfer of fibers. The energy density distribution of the waist section of the Gaussian like beam after beam coupling is similar to the "W" shape, and the central energy is lower than the surrounding energy, and the ablation holes also show a similar "W" shape. With the increase of rotational speed, the hole depth first decreased and then increased, the hole diameter and roundness first increased and then decreased, and the hole section was "W" shaped. The ablation area can be divided into five parts: the white granular SiO 2 solid coverage area, the recast layer, the lower recast layer, the molten layer, and the heat affected zone. The rotational characteristics will make the reaction intensity of the whole ablation area more uniform in the circumferential direction. The formation mechanism and element distribution of each part were explored. The research work in this paper will provide a new technical way for the high-performance application of CMC-SiC f /SiC. [ABSTRACT FROM AUTHOR]

Objectives: Third generation lasers with longer wavelengths (>1900 nm) have been introduced, in recent years, for the treatment of varicose veins. The possible advantage of the new generation lasers is that they allow complete damage to the vein wall using a lower Power in Watts (W: J/sec) and a lower linear energy density (LEED: J/cm). The aim of this work is to evaluate the results present in the literature regarding efficacy and safeness of the new generation lasers for the treatment of varicose veins. Methods: Published articles were searched on PubMed database and on Cochrane Library, entering the keywords "1940 nm or 1920 nm laser AND varicose veins laser thermoablation (EVLA)." The primary endpoint of the study was to value rate of occlusion and adverse events at the short term follow-up. The search yielded a total of 14 studies. In the end, only six studies were judge eligibility. Results: The studies were heterogenous in their documentation, EVLA, duplex ultrasound protocol and result reporting. A total of 540 limbs of 377 patients were treated with endovenous laser ablation (EVLA) with laser 1920–1940 nm. The treated veins had a mean diameter of 0.74 ± 0.17 cm and a mean length of 27.87 ± 20.63 cm. The pooled estimates of immediate occlusion rate was of 99.8% (95% CI: 97.9% to 100.0) with high heterogeneity (I2 = 60%; 95% PI: 89.7% to 100%), while at short-term follow-up was of 98.2% (95% CI: 94.0% to 100.0%) with higher heterogeneity (I2:79%; 95% PI: 77.1% to 100.0%). EHIT occurred in 7 cases (pooled estimate: 0.7%). The other adverse events rate reported were 1% of hyperpigmentation, 2.8% of neurological complications, 0.6% thrombophlebitis and 1.9% of bruising/hematoma. The pooled mean estimates of LEED was equal to 38.2 J/cm (95% CI: 26.3 to 50.1 J/cm) although with a very large heterogeneity (I2 = 100%). Conclusions: The overall success rate of EVLA was high. The analysis of these studies suggests that using lower parameters (Power and linear administered energy) may have no effect on the treatment success rate. Short-term results demonstrate comparable occlusion rates respect the second-generation lasers. Instead, data suggest a low complication rates. Short-term results demonstrate comparable complications rates respect the second-generation lasers (1300-1470 nm). Randomized studies with longer follow-up are required to evaluate the EVLA 1900 nm procedure further. [ABSTRACT FROM AUTHOR]

Narrowband laser sources are used in applications that require high-precision or stable optical frequency. Such applications include high-resolution spectroscopy, long-distance measurement, and coherent optical communication. The linewidth of a laser is a direct measure of the laser's stability; therefore, characterization of laser linewidth is essential. In practice, however, determining a laser's linewidth is not a trivial task and typically requires expensive equipment or a complex experimental arrangement. This paper presents a straightforward, low-cost method based on unbalanced interferometry, which allows us to determine the visibility of fringe patterns as a function of the optical path difference and, consequently, the linewidth of the laser. As a test laser, we use a tunable external cavity laser source at around 780 nm, where an interference filter is employed for wavelength selection. Data obtained by applying the interferometric technique to this laser and the analysis of these data, along with the resulting linewidth value, are presented. Given that the described measurement setup is inexpensive, straightforward, and pedagogically accessible, it is well-suited for an instructional physics laboratory experiment and will also be of interest to laboratory researchers. Editor's Note: This paper presents a low-cost interferometric technique for measuring the linewidth of a laser. The author first provides context for the interferometric technique by giving a comprehensive, clear, and detailed description of other techniques that can be used to measure a laser's linewidth, including the benefits and drawbacks of each. The principle behind the interferometric method is then presented, and the required experimental setup is explained. Data obtained by applying the interferometric technique to an external cavity laser are presented, and the analysis of these data, along with the resulting linewidth value, are given. This work provides a well-suited experiment for an advanced instructional physics laboratory or optics/laser course. It will also hold appeal as a cost-effective tool for laser linewidth measurement in laboratory research. [ABSTRACT FROM AUTHOR]

Background: Pulsed dye lasers (PDL) are currently the first‐line treatment of port‐wine birthmarks (PWB). Due to high maintenance costs and instable technology, alternative methods are needed. Objectives: To compare clinical outcomes of a variable‐sequenced, long‐pulsed 532‐nm potassium titanyl‐phosphate (KTP) laser and PDL on treating PWB. Methods: A prospective, randomized, split‐side study. Patients were treated with a KTP laser and PDL with 1 to 5 sessions at intervals of 6–8 weeks. A follow‐up visit was scheduled 6 weeks post‐treatment. Efficacy was evaluated through colorimetric analysis, area reduction measurements and clinical evaluations by two blinded investigators based on photo documentation. Subjects provided rating of pain intensity during treatment, post‐treatment reactions and satisfaction. Safety was measured by adverse events. Maintenance issues of the laser systems were documented. Results: A total of 35 patients (mean age 42.1 years) were enrolled. 63% were female. Patients received 2.4 (SD 1.4; 1–5) treatment sessions. Colorimetric analysis indicated a comparable clearance effect in PWB of both KTP laser and PDL. Independent investigators rated clinical appearance to be significantly improved compared to baseline. No significant difference was observed between both laser systems. Regarding post‐treatment reactions, the KTP laser caused less swelling, purpura and crusts. 96% would recommend both treatment modalities. Patients were satisfied with both laser systems. During the study, PDL systems malfunctioned for 6.6 months in total. For the KTP laser, we did not observe any system failures. Conclusion: Our data indicate that the KTP laser of the latest generation with large‐spot sizes, subpulse technology and cryogen cooling has a comparable efficacy to the PDL in treating PWB. In addition, KTP laser is associated with greater tolerability, fewer technical failures and lower repair costs. Further prospective studies are required to determine the true effectiveness of the KTP laser in PWB treatment. This study was preregistered in Clinicaltrials.gov (NCT05771298). [ABSTRACT FROM AUTHOR]

Objective: Compare ventilation pressures of 2 endotracheal tube designs used in laser airway surgery in clinical practice and with a benchtop model to elucidate differences and understand the design elements that impact airflow dynamics. Methods: Ventilatory and aerodynamic characteristics of the laser resistant stainless-steel endotracheal tube (LRSS-ET) design and the laser resistant aluminum-wrapped silicone endotracheal tube (LRAS-ET) design were compared. Ventilatory parameters were collected for 32 patients undergoing laser-assisted airway surgery through retrospective chart review. An in vitro benchtop simulation measured average resistance and centerline turbulence intensity of both designs at various diameters and physiological frequencies. Results: Baseline patient characteristics did not differ between the 2 groups. Clinically, the median LRAS-ET peak inspiratory pressure (PIP; 21.00 cm H2O) was significantly decreased compared to LRSS-ET PIP (34.67 cm H2O). In benchtop simulation, the average PIP of the LRAS-ET was significantly lower at all sizes and frequencies. The LRSS-ET consistently demonstrated an increased resistance, although no patterns were observed in turbulence intensity data between both designs. Conclusion: The benchtop model demonstrated increased resistance in the LRSS-ET compared to the LRAS-ET at all comparable sizes. This finding is supported by retrospective ventilatory pressures during laser airway surgery, which show significantly increased PIPs when comparing identically sized inner diameters. Given the equivocal turbulence intensity data, these differences in resistance and pressures are likely caused by wall roughness and intraluminal presence of tubing, not inlet or outlet geometries. The decreased PIPs of the LRAS-ET should assist in following lung protective ventilator management strategies and reduce risk of pulmonary injury and hemodynamic instability to the patient. [ABSTRACT FROM AUTHOR]

Background: Striae distensae (SD) is a challenging cosmetic condition. Ablative fractional laser (AFL) is an effective method for treating SD. Recently, fractional radiofrequency (FRF) has been shown to be a promising treatment for SD; however, few studies have shown the differences between FRF and AFL in the treatment of SD. Aims: This study aimed to evaluate and compare the clinical efficacy and safety of bipolar FRF with 2940‐nm erbium yttrium aluminum garnet (Er:YAG) AFL in the treatment of SD. Patients/Methods: Twenty volunteers with abdominal SD were enrolled in this study. One half of the abdomen was treated with 2940‐nm Er:YAG AFL, whereas the other half was treated with bipolar FRF, with three sessions at 4‐week intervals. Photographic evaluations of clinical improvement were conducted by two independent investigators before and after treatment, and the patients provided self‐assessments. Two participants underwent three punch biopsies, one before treatment and two obtained from bilateral representative skin lesions on the abdomen 3 months following the final treatment. Results: Clinical improvements were observed in SD on both sides of the abdomen after the two treatments. Post‐treatment skin biopsies revealed increased thickness in the epidermis and dermis, and higher collagen and elastin density compared to those at the baseline. No statistically significant differences were observed in the clinical outcomes between the two treatment approaches. Conclusions: The efficacy and safety of bipolar FRF treatment are comparable to those of 2940‐nm Er:YAG AFL treatment, providing an alternative and effective treatment for SD. [ABSTRACT FROM AUTHOR]

Background: Acne vulgaris is a common inflammatory disease associated with various sequelae after skin lesion remission. Acne erythema has been considered simple erythema or a vascular lesion; however, because the understanding of this disease has improved, acne erythema is currently considered an early scar with erythematous components. Aims: This study evaluated the efficacy of using both a 595‐nm pulsed dye laser (PDL) and 1565‐nm nonablative fractional laser (NAFL) for the treatment of erythematous scars caused by acne. Methods: Ninety patients with acne scars were equally randomized to two groups. Group A (n = 45) received treatment with the NAFL. Group B (n = 45) received treatment with the PDL and NAFL. Each patient underwent one treatment session and 4 weeks of follow‐up. Results: Qualitative (χ2 = 12.415; p < 0.05) and quantitative (t = 2.675; p < 0.05) scores of Groups A and B were determined using a global scarring grading system and exhibited statistically significant differences. The quantitative score of Group A was higher than that of Group B (6.67 ± 3.46 vs. 4.98 ± 2.44). The erythema areas of the groups differed significantly after treatment, with Group B exhibiting more notable score improvements (5.00 [3.10, 7.10] vs. 2.80 [1.65, 4.60]; Z = 3.072; p < 0.05). The erythema regression rate of Group B (88.9%) was significantly higher than that of Group A (66.7%) (χ2 = 20.295; p < 0.001). Adverse events, including redness and swelling (86.6%), scabbing (78.8%), and purpura (36.6%), occurred within 7 days for 86.6% of patients. Conclusions: The combined use of the PDL and NAFL is safe and effective for erythematous acne scars. [ABSTRACT FROM AUTHOR]

Background: Keratoacanthomas (KAs) following laser treatment are a rare, but well‐described entity. Aim: Herein, we describe a case of eruptive keratoacanthoma (KA) following laser resurfacing treatment and aim to better characterize laser‐associated KAs. Methods: A literature search was performed on PubMed reviewing laser‐associated KAs including various characteristics: epidemiology, history of skin cancer, location, and number, type of laser, as well as the management and outcome. Results: Fractional ablative was the most common type of laser triggering KAs, and most cases presented within the first month following treatment. The majority of cases of laser‐induced KA had a prior history of a malignant or premalignant skin neoplasm. Laser‐induced KAs were treated using modalities similar to KAs arising in other contexts. Conclusion: Clinicians need to be knowledgeable and prepared to understand, and manage complications following laser treatments, as rare as they may be, including KAs. [ABSTRACT FROM AUTHOR]

Parallel laser photogrammetry (PLP), which consists of attaching two or three parallel laser beams at a known inter‐beam distance to a camera, can be used to collect morphological measurements of organisms noninvasively. The lasers project onto the photo being taken, and because the inter‐beam distance is known, they act as a scale for image analysis programs like ImageJ. Traditionally, this method has been used to measure larger morphological traits (e.g., limb length, crown‐rump length) to serve as proxies for overall body size, whereas applications to smaller anatomical features remain limited. To that end, we used PLP to measure the testes of 18 free‐living mantled howler monkeys (Alouatta palliata) at La Selva Biological Station, Costa Rica. We tested whether this method could reliably measure this relatively small and globular morphology, and whether it could detect differences among individuals. We tested reliability in three ways: within‐photo (coefficient of variation [CV] = 4.7%), between‐photo (CV = 5.5%), and interobserver (intraclass correlation = 0.92). We found an average volume of 36.2 cm3 and a range of 16.4–54.4 cm3, indicating variation in testes size between individuals. Furthermore, these sizes are consistent with a previous study that collected measurements by hand, suggesting that PLP is a useful method for making noninvasive measurements of testes. Research Highlights: Testes measurements are a critical data type that can elucidate key questions related to sperm competition and endocrine disruption, and deriving the measurements noninvasively is a great benefit to conservation effortsWe collected and measured photos of 18 individual adult mantled howler monkeys (Alouatta palliata) from La Selva, Costa Rica via parallel laser photogrammetryWe used three tests of repeatability to provide evidence that parallel laser photogrammetry can be used to measure the testes of a large‐bodied nonhuman primate noninvasively while being precise and accurate [ABSTRACT FROM AUTHOR]

In this study, auxiliary laser irradiation was introduced into MAO processing (L-MAO), and its influence on the microstructure and properties of MAO coating was investigated. The results show that laser irradiation causes a reduction in the breakdown and working voltage of MAO processing while the number and brightness of discharge channels increase. Generating more discharge channels promotes a uniform energy distribution on each discharge channel and avoids the formation of high-intensity discharges. Therefore, after introducing laser irradiation, the obtained coating improves in terms of homogeneity, density, thickness, and bonding strength. Compared with MAO processing, the thickness of coating prepared by L-MAO processing increases by 33.8%, while the porosity decreases from 11.94% to 9.77%. The compositions and phase of coating are also impacted after introducing laser irradiation. More electrolyte ions (SiO 3 2−) enter the coating under laser irradiation, raising the Si content from 18.804 to 21.309 at. %. Besides, more rutile TiO 2 phases are detected in L-MAO coating. Based on the above microstructural improvements by laser irradiation, the wear and corrosion resistance of the resultant coating are enhanced correspondingly relative to the MAO processing without laser irradiation. [ABSTRACT FROM AUTHOR]

Fabricating and introducing new materials with new features is one of the most important goals for many scientific groups. Today, additive manufacturing (AM) is known as one of the new production methods, which can create an excellent opportunity for achieving this goal. As one of the ongoing production processes, the laser AM (LAM) methods have the proper capacity for producing new advanced materials like carbide, nitride, and boride‐based materials. Hence, this work aims to review carbide‐based materials produced by LAM techniques with the composite viewpoint. These materials can act as a matrix, reinforcement, or tertiary component in advanced composites. With this viewpoint, these composite materials were introduced in eight separate sections, which are tungsten carbide, titanium carbide, silicon carbide, niobium carbide, chrome carbide, vanadium carbide, and boron carbide, as well as high entropy alloy composites. [ABSTRACT FROM AUTHOR]

Tungsten carbide was manufactured by picosecond laser in this study. Shapes of the ablated craters evolved from parabolic‐like (less than 10 pulses) to Gaussian‐like (more than 500 pulses) as the pulse number increased. The shape changes were closely associated with the discontinuous diameter expansion of ablated crater. To explain these phenomena, two thresholds were identified: an upper threshold of 0.129 J/cm2 and a lower threshold of 0.099 J/cm2. When the laser energy exceeded the upper threshold, ablation occurred under the laser‐energy‐dominated mode. When the laser energy fell between the upper and lower thresholds, ablation occurred under the cumulative‐effect‐dominated mode. The transition of ablation mode contributed to the diameter expansion and shape change. In addition, elemental composition varied significantly at the ablated crater and heat‐affected zone (HAZ), which were related to the degrees of reactions that occurred at different distances from the laser. Finally, surface hardness decreased from base material (32.52 GPa) to edge of crater (11.59 GPa) due to the escape of unpaired interstitial C atoms from the grain boundaries. [ABSTRACT FROM AUTHOR]

Highly transparent 10 at.% Yb:GdxY3−xAl5O12 (x = 0.3, 0.5, and 0.7) ceramics were successfully fabricated by vacuum solid‐state reactive sintering at 1800°C for 20 h combined with hot isostatic pressing posttreatment at 1700°C for 3 h under 176 MPa pressure in Ar atmosphere. The in‐line transmittances of these ceramics with the thickness of 2.5 mm are 84.4%, 84.0%, and 83.5% at 1100 nm for x = 0.3, 0.5, and 0.7, respectively. The relationships of the Gd3+ content among the phase, microstructures, spectral, and laser properties of the Yb:GdxY3−xAl5O12 ceramics were elucidated in detail. The introduction of Gd3+ has a little influence on the crystal field strength of the Yb3+ sites in GdxY3−xAl5O12. The absorption, emission spectra, and fluorescence lifetime of the Yb3+ in these ceramics are similar, close to 10 at.% Yb:YAG ceramics. Quasi‐continuous wave laser outputs of the ceramics were also achieved. The maximum laser output powers are 7.8, 7.7, and 6.6 W with the corresponding slope efficiency as 46.2%, 44.7%, and 39.2% for x = 0.3, 0.5, and 0.7, respectively. The 7.8 W laser output power is the highest value achieved so far for the Yb:GdYAG ceramics, to the best of our knowledge. The previous discussions show that not all the mixed garnets could enhance full width at half maximum of absorption and emission peaks for the active ions; however, the Yb:GdYAG ceramics are still excellent laser gain media. [ABSTRACT FROM AUTHOR]

In this work, ultrafast Yb-doped fiber laser was realized using multi-layer palladium diselenide (PdSe2) film as the saturable absorber, which was prepared by simple selenization of palladium film deposited by magnetron sputtering method. The prepared polycrystalline PdSe2 film has a thickness of about 12 nm. At a pump power of 180 mW, the obtained mode-locked fiber laser based on the PdSe2 film has a central wavelength of 1063.75 nm, a pulse width of 615 ps, a repetition rate of 17.66 MHz, and an output power of 4.43 mW, respectively. These results indicate that PdSe2 has great potential in applications of ultrafast lasers. [ABSTRACT FROM AUTHOR]

Here we report a novel quadrilayer structure glass/ceramic with multicolor emission, which has a great potential to be used as a light converter for laser lighting with low blue light and high color rendering index. The multilayer glass/ceramic was prepared by controlling the crystallization of the double-layer Sr 1.07 Eu 0.03 Al 2.2 Si 1.8 O 8 /Sr 1.09 Sm 0.01 Al 2.2 Si 1.8 O 8 glass. The outer layers of the glass/ceramic are the ceramic layers and the inner layers are the glass layers. Hexagonal Sr 1.1 Al 2.2 Si 1.8 O 8 is the only crystal phase precipitated during the crystallization process and these crystals are highly oriented in growth. The Ra and CRI values of the white light-emitting LD prepared by employing the multi-layer glass/ceramic as the light converter and a 405 nm LD as the pump source are both more than 90. This work provides a novel and enlightening idea for the design and preparation of the multilayer glass/ceramic with multicolor emission. [ABSTRACT FROM AUTHOR]

Photothermal therapy (PTT) has garnered considerable attention as an attractive treatment tool for cancer due to precisely selective treatment and minimal side effects. The primary challenge of PTT, which hinders its widespread application, is the limited therapeutic depth. This limitation arises from optical scattering in biological tissues, causing inadequate heat distribution within the deep tissue. To overcome this challenge, ultrasound‐assisted PTT (ULTRA‐PTT) is proposed that leverages the temporary formation of gas bubbles induced by ultrasound within the light propagation path. These bubbles act as optical clearing agents, effectively reducing optical scattering in biological tissues. To facilitate ULTRA‐PTT, a dedicated handpiece consisting of a ring‐shaped ultrasound transducer and a laser delivery module is developed. In‐vivo experiments show that ULTRA‐PTT statistically outperforms conventional PTT in melanoma treatment, mostly due to its ability to deliver sufficient laser energy to deep‐seated cancer cells. These findings underscore the potential of ULTRA‐PTT to expand the clinical applications of PTT beyond local tumors occurring in superficial tissue. [ABSTRACT FROM AUTHOR]

In recent years, there has been a dramatically increasing demand for high-performance narrow-linewidth lasers for optical atomic clock and quantum applications. In this paper, we report on a single-frequency distributed Bragg reflector fiber laser operating at 871 nm that can be used to produce a 435.5 nm narrow-linewidth laser for a Yb+ clock via second-harmonic generation. Linearly polarized single-longitudinal-mode laser output with a power of 6.7 mW and a polarization extinction ratio of 29 dB was obtained by using a 3-cm long 1 wt. % neodymium (Nd3+)-doped phosphate fiber as the gain fiber. [ABSTRACT FROM AUTHOR]

As a new functional material, metal halide perovskites provide new possibilities for preparing gain media for nanosemiconductor lasers. This paper reviews the fabrication results of nanosemiconductor lasers based on metal halide perovskite materials. Firstly, three standard metal halide perovskite-based nanosemiconductor lasers are described: thin-film, nanowire, and quantum dot lasers. Under the corresponding gain structure of each laser, the appropriate gain dielectric material is discussed, and its application in the fabrication of nanosemiconductor lasers is discussed. On this basis, the effects of these gain structures and metal halide perovskite materials on the performance of nanosemiconductor lasers and related application progress are analyzed. Finally, the challenges and opportunities of nanosemiconductor lasers based on metal halide perovskite materials are summarized and the future development trend was discussed. [ABSTRACT FROM AUTHOR]

Heritage buildings represent history and act as vessels of human civilisation. The significance of these architectural phenomena increases as society increases, which renders their preservation and ethical use increasingly crucial. Hence, preserving heritage buildings is necessary for societal benefit. The accuracy of three-dimensional (3D) point cloud models of heritage buildings is important to their digital conservation. Traditional mapping methods typically require more time and human resources. Furthermore, the outcome is subject to measurement omissions, errors, and other issues, which are contrary to the protection of the object measured. The complex elements of ancient Chinese architecture render it challenging for traditional measuring techniques to accurately capture spatial structural information. The 3D laser scanning technology is a novel technology to obtain 3D data rapidly. In this paper, the Great Achievement Palace of the Confucian Temple in Yuci District, Jinzhong City, Shanxi Province, was used as an example to examine the application of 3D laser scanning technology to acquire point cloud models of heritage buildings. Field data collection for architectural heritage using 3D laser scanning technology requires measuring station setting analysis to ensure effect accuracy while considering the elements of target location and quantity. For the 3D point cloud model of the Great Achievement Palace, error analysis and accuracy assessment were conducted on the quality elements of alignment accuracy between scanning stations, point cloud model reliability, point cloud data noise condition, and whether the point cloud data were stratified. The findings demonstrated that the improved method quickly and accurately acquired 3D point cloud model data and obtained realistic spatial data models of the heritage building. [ABSTRACT FROM AUTHOR]

The influence of various trivalent lanthanides was investigated in the silica phosphate multi-component glass matrix, synthesized by the sol-gel method. The prepared glasses were analyzed to explore the degree of bandwidth amplification for telecommunication systems, and the potentiality of lasing media and smart glass films. Alkaline earth metal ions of Ca2+ were effectuated as a glass modifier, mediating the formation of non-bridging oxygen with the glass formers, and imputing favorable structural attributes to the glasses for versatile applications. The bonding parameter derived from the average nephelauxetic ratio implies covalency around the rare earth ion sites in the Er3+ and Nd3+ doped systems, while the Sm3+ doped glass exhibits ionicity. In the silica-based glass matrix singly doped with Yb3+, the coexistence of Yb3+/Yb2+ ions was evidenced. Transitions across 4f14 and 4f135d levels of Yb2+, with an experimental lifetime of 45.8 ns would provide prospective pulsed yellow lasers, for non-invasive therapeutics. Er3+ doped glass evinced a large bandwidth of 93.775 nm at 1477 nm and a high quantum efficiency of 97%, favorable for O + E + S-band telecommunication networks. The transition corresponding to 4 G 5 / 2 → 6 H 7 / 2 of Sm3+ and 2 G 7 / 2 → 4 I 9 / 2 of Nd3+ is suggestive that the respective doped glasses could be devised into solid-state red and green laser sources. Novel near-infrared emission at 1476 nm was also evidenced in the Sm3+ and Nd3+ doped systems. Prominent absorption at 280 nm and complete transparency in the visible region observed in the Ce3+ mono-doped system make it ideal for smart glasses as UVB and UVC shielding films. [ABSTRACT FROM AUTHOR]

In this paper, a comprehensive study of the mechanical properties of selective laser sintered polyamide components is presented, for various different process parameters as well as environmental testing conditions. For the optimization of the static and dynamic mechanical load behavior, different process parameters, e.g., laser power, scan speed, and build temperature, were varied, defining an optimal parameter combination. First, the influence of the different process parameters was tested, leading to a constant energy density for different combinations. Due to similarities in mechanical load behavior, the energy density was identified as a decisive factor, mostly independent of the input parameters. Thus, secondly, the energy density was varied by the different parameters, exhibiting large differences for all levels of fatigue behavior. An optimal parameter combination of 18 W for the laser power and a scan speed of 2666 mm/s was determined, as a higher energy density led to the best results in static and dynamic testing. According to this, the variation in build temperature was investigated, leading to improvements in tensile strength and fatigue strength at higher build temperatures. Furthermore, different ambient temperatures during testing were evaluated, as the temperature-dependent behavior of polymers is of high importance for industrial applications. An increased ambient temperature as well as active cooling during testing was examined, having a significant impact on the high cycle fatigue regime and on the endurance limit. [ABSTRACT FROM AUTHOR]

Laser trackers (LTs) are dimensional measurement instruments commonly employed in the manufacture and assembly of large structures. Terrestrial laser scanners (TLSs) are a related class of dimensional measurement instruments more commonly employed in surveying, reverse engineering, and forensics. Commercially available LTs typically have measurement ranges of up to 80 m. The measurement ranges of TLSs vary from about 50 m to several hundred meters, with some extending as far as several kilometers. It is difficult, if not impossible, to construct long reference lengths to evaluate the ranging performances of these instruments over that distance. In this context, we explore the use of stitching errors (i.e., stacking errors in adjoining or overlapping short lengths) and stitching lengths (i.e., constructing long reference lengths from multiple positions of a reference instrument by registration) to evaluate these instruments. Through experimental data and a discussion on uncertainty, we show that stitching is indeed a viable option to evaluate the ranging performances of LTs and TLSs. [ABSTRACT FROM AUTHOR]

Laser bending is a kind of cumulative forming technology and bending efficiency is one of its most important indexes. This study investigates the bending behavior and the microstructure of DP980 steel plates under different laser scanning strategies, using an IPG laser system. Two sets of experiments varied the accumulated line energy density (AED) by altering the laser scanning velocity and number of scans. The results show that, for the single laser scanning process, the bending angle of the plate increases with AED, due to a larger temperature gradient through the thickness direction; however, this relationship is nonlinear. A higher AED led to a sharper initial increase in bending angle, which then plateaued. Under the same AED conditions, the bending angle of the plate undergoing multiple laser scans increases by at least 26% compared to the single one, due to the microstructure changes. It is revealed that the bending efficiency is affected by both the AED and the resultant microstructure evolution in the DP980 steel. Higher AED values and appropriate peak temperatures facilitate better bending behavior due to the formation of uniform martensite and grain refinement. Conversely, excessive peak temperatures can hinder bending due to grain growth. [ABSTRACT FROM AUTHOR]

In this study, a pulsed laser operating at a wavelength of 1064 nm and with a pulse width of 100 ns was utilized for the removal of paint from the surface of a 2024 aluminum alloy. The experimental investigation was conducted to analyze the influence of laser parameters on the efficacy of paint layer removal from the aircraft skin's surface and the subsequent evolution in the microstructure of the laser-treated aluminum alloy substrate. The mechanism underlying laser cleaning was explored through simulation. The findings revealed that power density and scanning speed significantly affected the quality of cleaning. Notably, there were discernible damage thresholds and optimal cleaning parameters in repetitive frequency, with a power density of 178.25 MW/cm2, scanning speed of 500 mm/s, and repetitive frequency of 40 kHz identified as the primary optimal settings for achieving the desired cleaning effect. Thermal ablation and thermal vibration were identified as the principal mechanisms of cleaning. Moreover, laser processing induced surface dislocations and concentrated stress, accompanied by grain refinement, on the aluminum substrate. [ABSTRACT FROM AUTHOR]

This work presents results on laser-induced surface structuring of AlN ceramic and its application in Surface-Enhanced Raman Spectroscopy (SERS). The laser processing is performed by nanosecond pulses in air and vacuum. Depending on the processing conditions, different surface morphology can be obtained. The ablation process is realized by ceramic decomposition as the formation of an aluminium layer is detected. The efficiency of the fabricated structures as active substrates in SERS is estimated by the ability of the detection of ammonium nitrate (NH4NO3). It is conducted for Raman spectrometer systems that operate at wavelengths of 514 and 785 nm where the most common commercial systems work. The obtained structures contribute to enhancement of the Raman signal at both wavelengths, as the efficiency is higher for excitation at 514 nm. The limit of detection (LOD) of ammonium nitrate is estimated to be below the maximum allowed value in drinking water. The analysis of the obtained results was based on the calculations of the near field enhancement at different conditions based on Finite Difference Time Domain simulation and the extinction spectra calculations based on Generalized Mie scattering theory. The structures considered in these simulations were taken from the SEM images of the real samples. The oxidation issue of the ablated surface was studied by X-ray photoelectron spectroscopy. The presented results indicated that laser structuring of AlN ceramics is a way for fabrication of Al structures with specific near-field properties that can be used for the detection of substances with high social impact. [ABSTRACT FROM AUTHOR]

The use of mobile laser scanning for mapping forests has scarcely been studied in difficult forest conditions. In this paper, we compare the accuracy of retrieving tree attributes, particularly diameter at breast height (DBH), stem curve, stem volume, and tree height, using six different laser scanning systems in a managed natural boreal forest. These compared systems operated both under the forest canopy on handheld and unmanned aerial vehicle (UAV) platforms and above the canopy from a helicopter. The complexity of the studied forest sites ranged from easy to difficult, and thus, this is the first study to compare the performance of several laser scanning systems for the direct measurement of stem curve in difficult forest conditions. To automatically detect tree stems and to calculate their attributes, we utilized our previously developed algorithm integrated with a novel bias compensation method to reduce the overestimation of stem diameter arising from finite laser beam divergence. The bias compensation method reduced the absolute value of the diameter bias by 55–99%. The most accurate laser scanning systems were equipped with a Velodyne VLP-16 sensor, which has a relatively low beam divergence, on a handheld or UAV platform. In easy plots, these systems found a root-mean-square error (RMSE) of below 10% for DBH and stem curve estimates and approximately 10% for stem volume. With the handheld system in difficult plots, the DBH and stem curve estimates had an RMSE under 10%, and the stem volume RMSE was below 20%. Even though bias compensation reduced the difference in bias and RMSE between laser scanners with high and low beam divergence, the RMSE remained higher for systems with a high beam divergence. The airborne laser scanner operating above the forest canopy provided tree attribute estimates close to the accuracy of the under-canopy laser scanners, but with a significantly lower completeness rate for stem detection, especially in difficult forest conditions. [ABSTRACT FROM AUTHOR]

Objective Materials and Methods Results Conclusions Clinical Significance This study aimed to examine the shear bond strength (SBS) of repair material to conventionally, subtractive‐, and additive‐manufactured denture bases after different surface treatments.Disk‐shaped test specimens (N = 300) were prepared from denture base materials produced by one conventional (Procryla), one subtractive (Yamahachi), and one additive (Curo Denture) method. The test specimens were randomly divided into five groups (n = 10) and exposed to a variety of surface treatments—Group A: no surface treatment; Group B: grinding with silicon carbide paper; Group C: sandblasting; Group D: erbium: yttrium‐aluminum‐garnet laser; and Group E: plasma. Repair was performed with autopolymerizing acrylic resin (Meliodent). Surface roughness analyses were performed with a profilometer. Scanning electron microscopy was used to examine one specimen from each subgroup. SBS was evaluated on a universal testing machine. Failure types were observed under a stereomicroscope.Surface roughness values were significantly higher in all test materials in Group D than in the other groups (p < 0.001). For conventional resin, the SBS values were higher in Group C than in Groups A, D, and E (p < 0.001). For CAD/CAM material, Groups B and C had significantly greater SBS increases compared with Group E (p < 0.001). For 3D material, Group D showed higher SBS than all groups except Group C (p < 0.001).For SBS, sandblasting was most effective in the conventional group, whereas laser treatment was the most effective in the additive‐manufactured group. For the subtractive group, surface treatments other than plasma exhibited similar SBS.In repairing fractured prostheses, any degree of roughening suitable for the material content may provide an SBS benefit. [ABSTRACT FROM AUTHOR]