Search

The separation and detection of isomers remains a challenge for many areas of mass spectrometry. This article highlights laser photodissociation and ion mobility strategies that have been recently deployed to meet this challenge with focus on small molecule isomers including protonation isomers, structural isomers, conformation isomers and new studies emerging on chiral isomers. Laser techniques span UV and visible laser photodissociation, time-resolved pump–probe schemes and application of laser hole-burning arrangements to assign isomers within selected ion populations. Also surveyed are applications of ion mobility strategies to separate isomers followed by laser spectroscopic techniques to assign the separated ions. Ultimately, with ongoing refinement in hardware and methods, there are clear pathways forward for laser and mass spectrometry techniques to make decisive breakthroughs in understanding how isomeric details affect biological processes, physiology and disease. [ABSTRACT FROM AUTHOR]

Adhesive bonding of CFRP is one major approach to join this class of compound materials with other components, e.g., metals. The necessity to clean CFRP parts after fabrication and generate a bond-ready interface without damaging the implemented fibers demands a gentle and highly reproducible surface treatment. Lasers operating in the UV region are one promising technique for that topic. Yet, the factors influencing the adhesion properties of laser-treated CFRP are not sufficiently understood. The present paper describes the influence of nanosecond-pulsed laser parameters on CFRP treatment effects in context of adhesive bonding properties. A special focus was given on the distribution and avoidance of re-deposition effects by laser parameter selection. Furthermore, the effect of laser-induced fiber exposure was analyzed. Re-deposition and fiber exposure were complementarily discussed with chemical analyses of the surface composition after laser treatment in the context of bond strength studies under Mode I loading. It was found that both effects, i.e., re-deposition on the treated surface and laser-induced fiber exposure by overtreatment, result in lower strength values compared to an "optimized" treatment exhibiting none of the descripted conditions. [ABSTRACT FROM AUTHOR]

There exists an extensive research interest in the performance improvement of AlGaN-based deep-ultraviolet (DUV) laser diodes (LDs). Herein, to reduce the carrier leakage problem of LDs, we propose a convex waveguide (WG) layer for improving the optoelectronic properties. Numerical analyses are carried out to compare the proposed convex WG layer with traditional and stepped WG layers. For LDs with seven different WG layers, parameters used for comparison are P – I and V – I characteristic curves, carrier concentrations, stimulated recombination rates, slope efficiencies, and electro-optical conversion efficiencies. We show that the application of the convex WG layer considerably enhances the carrier confinement ability of LDs and reduces carrier leakage, improving the performance of the LDs. The overall performance of LDs with only a convex lower WG (LWG) layer or a stepped LWG layer is stronger than that of LDs with only a convex upper WG (UWG) layer or a stepped UWG layer. [ABSTRACT FROM AUTHOR]

Extreme ultraviolet laser ablation and ionization time-of-flight mass spectrometry (EUV TOF), using a laser that operates at a wavelength of 46.9 nm (26.4 eV photon energy), is a relatively new analytical technique with many unexplored performance characteristics. In this work, we use the EUV TOF to directly measure the 206Pb/238U and 232Th/238U isotope ratios in different geological materials to investigate if the EUV laser is a good candidate for reducing matrix effects in geological analyses. We use the EUV TOF to analyze synthetic glasses of silicate, basalt, and phosphate as well as mineral samples ranging from iron manganese to zircons and monazites to uraninites and a thorite at a spatial scale of approximately 8 μm and at depths ≤500 nm. The results show that the EUV TOF measures 206Pb/238U ratios that have a systematically low bias in glass, iron manganese, zircon, and monazite matrices. This bias can be calibrated using NIST 610 as a non-matrix matched external calibration sample, resulting in 206Pb/238U ratios that are within analytical uncertainty (±2σ) of the expected values. Unlike 206Pb/238U, the 232Th/238U ratios measured in the glass, zircon, and monazite matrices do not show a systematic bias and are within ±2σ of the expected values from direct measurements. The 206Pb/238U and 232Th/238U ratios measured in the uraninite and thorite samples are not within analytical uncertainty of the expected values. The uncertainty in the uraninite and thorite measurements are likely a result of the high amounts of Pb, Th, and U in these samples relative to the other analyzed samples and their effect on the instrument's performance. Overall, this study shows that the EUV ionization mechanisms for Pb, Th, and U are similar in glass, iron manganese, zircon, and monazite matrices, resulting in inter-element ratios that are within analytical uncertainty. EUV laser ablation and ionization is therefore a good candidate for directly measuring the isotopic content in select geological materials at spatial scales of <10 μm. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) lasers with dynamic wavelength‐tunability and high monochromaticity are crucial in a multitude of practical applications yet still remarkable challenges. Here, we show wide wavelength‐tuning of single‐mode UV lasing based on lanthanide‐doped upconversion nanoparticles (UCNPs). The rationally designed Yb3+/Er3+/Tm3+/Gd3+/Ce3+ co‐doped multilayer UCNPs, which exhibits a broad gain spectrum with the full width of half maximum of around 57 nm in the UV regime, are developed. More importantly, by taking advantages of a diffraction grating as the tuning component, stable single‐mode emission can be achieved in the UCNPs‐based external‐cavity‐extended Fabry–Pérot laser at room temperature. Specifically, the lasing threshold is around 137 µJ cm–2, which is two orders of magnitude lower than that in the previously reported articles. Precise wavelength‐tuning from 310 to 363 nm can be realized by adjusting the Littrow angle. This achievement highlights a portable alternative to continuously wideband‐tunable UV lasers and opens up new opportunities for constructing compact solid‐state UV photon sources. [ABSTRACT FROM AUTHOR]

The CO2 methanation is an important component of the "power to gas" strategy, and the Ru‐Al2O3 catalyst is considered to be a state‐of‐the‐art catalyst for this reaction. Conventional Ru‐Al2O3 is prepared by wet impregnation. Due to weak interactions between Ru and the Al2O3, construction of a controllable interface between the metal and the substrate is still challenging. In this work, a UV pulse laser is used to controllably construct ultra‐small Ru nanoparticles on defects‐rich Al2O3‐x‐L in situ grown on Al foil (Ru‐Al2O3‐x‐L) for effective photothermal CO2 methanation. The catkin‐like fluff Al2O3‐x‐L efficiently traps light to ensure the light adsorption of Ru‐Al2O3‐x‐L. The defects in Al2O3‐x‐L efficiently anchors Ru. A Strong‐Metal‐Support‐Interaction (SMSI) effect is constructed between the ultra‐small Ru nanoparticles and the Al2O3‐x‐L. The Ru‐Al2O3‐x‐L exhibits remarkable photothermal catalytic performance (CH4 yield of 12.35 mol gRu−1 h−1) in the closed batch system. Then an innovative flow reactor is established based on the one‐piece Ru‐Al2O3‐x‐L microchannel catalyst. Thanks to local pressure on the edge of the microchannels, the CH4 yield is further enhanced to 14.04 mol gRu−1 h−1. Finally, an outdoor setup demonstrates the feasibility of photothermal CO2 methanation (CH4 yield of 18.00 mmol min−1). This work provides novel perspectives for the construction of multi‐level micro/nanostructures integrated catalysts for photothermal CO2 methanation. [ABSTRACT FROM AUTHOR]

Single cell RNA sequencing has the potential to elucidate transcriptional programs underlying key cellular phenotypes and behaviors. However, many cell phenotypes are incompatible with indiscriminate single cell sequencing because they are rare, transient, or can only be identified by imaging. Existing methods for isolating cells based on imaging for single cell sequencing are technically challenging, time-consuming, and prone to loss because of the need to physically transport single cells. Here, we developed See-N-Seq, a method to rapidly screen cells in microwell plates in order to isolate RNA from specific single cells without needing to physically extract each cell. Our approach involves encapsulating the cell sample in a micropatterned hydrogel with spatially varying porosity to selectively expose specific cells for targeted RNA extraction. Extracted RNA can then be captured, barcoded, reverse transcribed, amplified, and sequenced at high-depth. We used See-N-Seq to isolate and sequence RNA from cell-cell conjugates forming an immunological synapse between T-cells and antigen presenting cells. In the hours after synapsing, we found time-dependent bifurcation of single cell transcriptomic profiles towards Type 1 and Type 2 helper T-cells lineages. Our results demonstrate how See-N-Seq can be used to associate transcriptomic data with specific functions and behaviors in single cells. A selective sequencing method, termed SeeN-Seq, is presented to link morphological phenotypes to single-cell RNAseq using UV laser patterning of hydrogel porosity. [ABSTRACT FROM AUTHOR]

This Letter describes the development and implementation of an ultraviolet and broadband ultrafast-laser-absorption-imaging (UV-ULAI) diagnostic for one dimensional (1D) imaging of temperature and CN via its B 2 Σ + ← X 2 Σ + absorption bands near 385 nm. The diagnostic was demonstrated by acquiring single-shot measurements of 1D temperature and CN profiles in HMX flames at a repetition rate of 25 Hz. Ultrashort pulses (55 fs) at 800 nm were generated using a Ti:Sapphire oscillator and then amplification and wavelength conversion to the ultraviolet were carried out using an optical parametric amplifier and frequency doubling crystals. The broadband pulses were spectrally resolved using a 1200 l/mm grating and imaged on an EMCCD camera to obtain CN absorbance spectra with a resolution of ≈ 0.065 nm and a bandwidth of ≈ 4 nm (i.e., 260 cm–1). Simulated absorbance spectra of CN were fit to the measured absorbance spectra using non-linear curve fitting to determine the gas properties. The spatial evolution of gas temperature and CN concentration near the burning surface of an HMX flame was measured with a spatial resolution of ≈ 10 μm. 1D profiles of temperature and CN concentration were obtained with a 1-σ spatial precision of 49.3 K and 4 ppm. This work demonstrates the ability of UV-ULAI to acquire high-precision, spatially resolved absorption measurements with unprecedented temporal and spatial resolution. Furthermore, this work lays the foundation for ultraviolet imaging of numerous atomic and molecular species with ultrafast time resolution. [ABSTRACT FROM AUTHOR]

Cesium lead halide perovskite nanocrystals (NCs) have gained enormous attention as promising light‐emitting and light‐converting materials. Most of their applications require embedding NCs in various matrices, which is a challenging task due to their low stability, especially in the case of red‐emitting CsPbI3 NCs. In this work, a new approach is proposed allowing the formation of red‐emitting perovskite NCs by anion exchange induced directly inside a solid polymer matrix using green‐emitting CsPbBr3 NCs as templates and iodododecane as an iodine source. Moreover, a simple and efficient route to photo‐assisted termination of the anion exchange reaction in the polymer composite after reaching desired optical properties is demonstrated. The findings allow the authors to pattern a thin composite film with an ultrashort UV laser resulting in a selective generation of green‐ and red‐emitting features with a 15 µm resolution. [ABSTRACT FROM AUTHOR]

Due to low penetration ability of ultraviolet (UV) light, UV‐induced free radical reactions of polymers are limited to the preparation of thin‐layer materials such as coatings and inks. Although upconversion (UC) nanomaterials that can be excited by near‐infrared (NIR) light and emit UV light which is used to achieve polymerization or curing of monomers or prepolymers, low quantum efficiency and high excitation threshold limit their applications. Here, triplet‐triplet annihilation up‐conversion luminescent (TTA‐UCL) chromophores of platinum (II) octaethylporphyrin (PtOEP) and 9,10‐diphenylanthracene (DPA) are used to realize TTA‐UCL‐assisted photoinitiated polymerization of butyl acrylate (BA) and ethoxylated trimethylolpropane triacrylate (ETPTA) as well as photo curing of polyurethane acrylates (PUA) using visible light at 520 nm. The effects of chromophores concentrations and incident light power density on double‐bond conversion rate are investigated. The results show that a mediate TTA‐UCL chromophore concentration of 0.02% is beneficial for polymerization of ETPTA‐co‐BA with thickness of 25 mm within 15 min. Satisfied adhesion of colored plastic substrates using PUA prepolymers can be achieved after irradiation for 30 s when chromophore concentration of 0.1% is used. TTA‐UCL assisted photoinitiated reactions show great potential in engineering aspects including quick repair of leaking tubes and photocuring of adhesives underwater. [ABSTRACT FROM AUTHOR]

We report on the laser ablation of cyclic olefin copolymer using an amplified ultrashort pulsed laser in the ultraviolet spectral range. In addition to a high ablation depth per laser-structured layer up to 74 μ m at a fluence of 22 J cm − 2 , an excellent mean roughness R a of laser-patterned surfaces down to 0.5 μ m is demonstrated. Furthermore, with increasing fluence, increasing ablation efficiencies up to 2.5 mm3 W−1 min−1 are determined. Regarding the quality of the ablation, we observed steep ablation flanks and low debris formation, though for fluences above 10.5 J cm − 2 the formation of troughs was observed, being attributed to multiple reflections on the ablation flanks. For comparison, laser ablation was performed under identical conditions with an infrared laser wavelength. The results highlight that UV ablation exhibits significant advantages in terms of ablation efficiency, surface roughness and quality. Moreover, our results show that a larger UV focus spot accelerates the ablation process with comparable quality, paving the way for high-power UV ultrashort pulsed lasers towards an efficient and qualitative tool for the laser machining of cyclic olefin copolymer. The production of complex microfluidics further underlines the suitability of this type of laser. [ABSTRACT FROM AUTHOR]

We report on the development of a novel direct-detection Doppler wind lidar (DD-DWL) within the strong requirements of an aeronautic feed-forward control application for gust load alleviation (GLA). This DD-DWL is based on fringe imaging of the Doppler-shifted backscatter of ultraviolet laser pulses in a field-widened Michelson interferometer (FW-FIMI) using a fast linear photodetector. The double approach of detailed simulation and demonstrator development is validated by field measurements with reference wind sensing instrumentation. These experiments allow us to establish wind determination precision at a high repeat rate, short range resolution and close distance of approximately 0.5 m/s, which is in accordance with the dedicated simulations. These findings lead us to the conclusion that this FW-FIMI-based Doppler wind lidar is a pertinent development meeting the special requirements of this aeronautics application. Second, the developed simulators are well suited (given their validation) to be used in the overall and full analysis as well as the optimization of the lidar-based GLA control scheme. [ABSTRACT FROM AUTHOR]

Ultraviolet (UV) irradiation-based methods used for viral inactivation have provided an important avenue targeting severe acute respiratory-syndrome coronavirus-2 (SARS-CoV-2) virus. A major problem with state-of-the-art UV inactivation technology is that it is based on UV lamps, which have limited efficiency, require high power, large doses, and long irradiation times. These drawbacks limit the use of UV lamps in air filtering systems and other applications. To address these limitations, herein we report on the fabrication of a device comprising a pulsed nanosecond 266 nm UV laser coupled to an integrating cavity (LIC) composed of a UV reflective material, polytetrafluoroethylene. Previous UV lamp inactivation cavities were based on polished walls with specular reflections, but the diffuse reflective UV ICs were not thoroughly explored for virus inactivation. Our results show that LIC device can inactivate several respiratory viruses including SARS-CoV-2, at ~ 1 ms effective irradiation time, with > 2 orders of magnitude higher efficiency compared to UV lamps. The demonstrated 3 orders of magnitude cavity enhancement relative to direct exposure is crucial for the development of efficient real-time UV air and water purification systems. To the best of our knowledge this is the first demonstration of LIC application for broad viral inactivation with high efficiency. [ABSTRACT FROM AUTHOR]

Nonlinear optical processes are intrinsically dominated by the phase relationships among the relevant electromagnetic fields, including the phase of nonlinear polarization produced in them. If one can arbitrarily manipulate these phase relationships at a variety of desired interaction lengths, direct and highly designable manipulations for the nonlinear optical phenomenon could be achieved. Here, we report a proof-of-principle experiment in which a high-order Raman-resonant four-wave-mixing process is used as a representative nonlinear optical process and is tailored to a variety of targets by implementing such arbitrary manipulations of the phase relationships in the nonlinear optical process. We show that the output energy is accumulated to a specific, intentionally selected Raman mode on demand; and at the opposite extreme, we can also distribute the output energy equally over broad high-order Raman modes in the form of a frequency comb. This concept in nonlinear optical processes enables an attractive optical technology: a single-frequency tunable laser broadly covering the vacuum ultraviolet region, which will pave the way to frontiers in atomic-molecular-optical physics in the vacuum ultraviolet region. Adaptive optics permits control of linear and nonlinear optical phenomena in order to achieve the desired output signal. Here, arbitrary manipulation of phase relations are used to engineer nonlinear interactions in a higher-order Raman-resonant four-wave-mixing platform. [ABSTRACT FROM AUTHOR]

To improve the carrier confinement capability and optimize the performance of deep ultraviolet laser diodes (DUV-LDs), we propose the graded rectangular superlattice (GRSL) electron blocking layer (EBL) and the graded trapezoidal superlattice (GTSL) hole blocking layer (HBL) in this paper. Crosslight software is used to simulate and compare the DUV-LDs with rectangular superlattice (RSL) EBL and RSL HBL, GRSL EBL and GRSL HBL, and GRSL EBL and GTSL HBL. The simulation results indicate that GRSL EBL and GTSL HBL increase the carrier concentration in the quantum wells, reduce the electron leakage in the p-type region and the hole leakage in the n-type region, increase the radiation recombination rate, reduce the threshold voltage and threshold current, and increase the electro-optical conversion efficiency and output power of DUV-LDs more effectively. [ABSTRACT FROM AUTHOR]

Laser‐induced graphene (LIG) produced by irradiation of paper (paper‐LIG)holds substantial promise for flexible devices. This article presents paper‐LIG humidity and temperature sensors fabricated by single‐step irradiation of common filter paper with a pulsed UV laser (355 nm). The influence of the process parameters on the conversion of cellulose fibers into LIG is discussed based on the resulting morphology, structure, conductivity, and chemical composition, revealing a distinct barrier to transformation and a propagation behavior not seen under CO2 laser irradiation. The obtained material is constituted by a porous, electrically conductive network of fibers. The paper‐LIG relative humidity (RH) and temperature sensors with sensitivities of up to 1.3 × 10−3%RH−1 and ‐ 2.8 × 10−3 °C−1, respectively, are examined in terms of their linearity, reproducibility, and response time. A detailed discussion on the response mechanism is presented in the context of literature, pointing towards the absorption of water molecules in the interlayer spacing of graphene as the main reason for the increase in resistance with RH. Additionally, a contribution from variable range hopping along the ab plane of graphene at high RH is suggested. These results demonstrate the potential of paper‐LIG for low‐cost, sustainable, and environmentally friendly sensing. [ABSTRACT FROM AUTHOR]

The central processes driving biological phenomena are based on the conduction of ions and electrons in biomaterials, implying the possibility of achieving a fully biomaterial‐based electronic skin. However, finding the appropriate biomaterials for electronic skins is still challenging. Here, a photoresponsive, self‐healable, and biomaterial‐based optoelectronic skin (OE‐skin) fabricated with melanin nanoparticles and silk protein is proposed and the electronic properties and their mechanisms in the artificially generated OE‐skin are reported. Not only does silk protein hydrogel provide a transparent and skin‐compatible platform for use as OE‐skin but it also provides the appropriate environment for melanin to demonstrate high electrical conductivity. The OE‐skin can be considered a p‐type semiconducting material showing high conductivity of up to 6 mS cm−1 in addition to a 40% enhancement in the conductivity by green laser and ultraviolet light emitting diode illuminations. Additionally, the OE‐skin autonomously heals itself from multiple cuts, allowing the restoration of its electrical properties. These material properties enable applications for strain‐sensors, humidity sensors, and ultraviolet light sensors, as well as image pixels to convert light‐lettering into electrical signals. The proposed fully biomaterial‐based OE material platform offers a new way for next‐generation electronic skins to achieve a seamless interface with the human body. [ABSTRACT FROM AUTHOR]

With the arrival of the "von Neumann bottleneck," neuromorphic systems are receiving a lot of attention from scholars as an innovative technology by mimicking the massive parallelism and low‐power operation of the human brain. Herein, a floating‐gate‐like device constructed by the InSe/hBN/O2‐hBN van der Waals heterostructure, where the defective O2‐hBN plays the central role to trap charges, is proposed. This well‐designed device is proved to realize the synaptic functions under UV laser irradiation, such as short‐term plasticity (STP), long‐term plasticity (LTP), paired‐pulse facilitation (PPF), and long‐term potentiation/long‐term depression (LTP/LTD). Especially, the synaptic weight of excitatory postsynaptic current (EPSC) reaches as high as 104%, it reaches the highest standard of this kind of device in recent years, and remains above 300% synaptic weight after 200 s, thus successfully imitating the LTP in biological synapses. The key factors of LTP/LTD curves are overall excellent and can be optimized with input pulses: nonlinearity value can reach 3.32/2.35, and Gmax/Gmin above 10 is achieved. The InSe floating‐gate‐like device with O2‐hBN layer provides an alternative for better and more practical synaptic performances in the field of neuromorphic architectures based on 2D materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • La-doped BiCuSeO TTE detector exhibits good linearity, long-term stability, ultra-broad spectral detection ability ranging from UV to FIR as well as the excellent thermal detection performance. • The detection sensitivity of La-doped BiCuSeO TTE detector is much higher than that of commercial Gordon gauge. • La-doped BiCuSeO films have a great prospect and potential application in self-powered high-performance photo and thermal detectors. Transverse thermoelectric (TTE) effect of the inclined thin films has attracted great attention owing to the application in self-powered photo and thermal detectors. Here, we report the significant enhancement of TTE performance of the inclined BiCuSeO thin films via La doping. The maximum voltage sensitivity of the La-doped BiCuSeO TTE detector reaches about 15.7 V/mJ under the ultraviolet pulsed laser irradiation, which is more than 17 times larger than that of the intrinsic BiCuSeO thin film. Besides, the detector also exhibits good linearity, long-term stability, ultra-broad spectral detection ability as well as the excellent thermal detection performance, with the voltage sensitivity is much higher than that of commercial Gordon gauge. The results show that La doping can effectively improve the TTE performance of the inclined BiCuSeO thin films, which has a prospect and potential application in self-powered high-performance photo and thermal detectors. [ABSTRACT FROM AUTHOR]

Efficient ultraviolet (UV) laser diodes (LD) emitting in the 260–270 nm range have been proposed numerically in this work. Using engineered quaternary waveguides (QWGs) in place of conventional ternary waveguides, in the p-region, results in much higher output power as well as internal quantum efficiency (IQE) and lower the lasing threshold. The electron outflow is reduced and the injection of holes is enhanced which results in high efficiency and high light power output. • We have employed engineered quaternary waveguides (QWGs) instead of conventional AlGaN waveguides in the p-region of AlGaN-based ultraviolet laser diode to improve laser power. • We believe that our proposed design may substantially improve the laser diode performance in the ultraviolet range, which is of keen interest to the community. • Detailed optoelectronic analysis of the device performance is presented. [ABSTRACT FROM AUTHOR]

Ultraviolet laser with controllable spatial coherence is essential for a wide range of applications. In this study, we developed a pulsed, partially spatial coherence laser source operating in the ultraviolet (UV) range through extra-cavity frequency tripling of a solid-state Nd:glass degenerate laser. The oscillating modes of the laser can be flexibly controlled by size of the spatial filter inside the laser cavity, thus modulating the spatial coherence of the UV laser. The beam pattern and focusing, speckle suppression and imaging, coherence property of the partially coherent UV laser is investigated in detail. The third-harmonic generation (THG) supports many more transverse modes than the fundamental generation and the second-harmonic generation (SHG). Compared with high coherent UV laser, low spatial coherent UV laser has better speckle suppression effect and smoother focused spot intensity distribution. The high brightness, good monochromaticity and low spatial coherence make the UV degenerate laser an attractive illumination source for inertial confinement fusion, lithography, laser processing and others. • We have achieved a partially coherent laser in the ultraviolet band. • We found that ultraviolet partially coherent laser has significant advantages in suppressing speckle, improving imaging quality, and enhancing the uniformity of focal spot irradiation. • We explained why the number of third-harmonic generation transverse modes was more than that of fundamental and second-harmonic generation transverse modes. [ABSTRACT FROM AUTHOR]

Laser Induced Reverse Transfer (LIRT) is a versatile technique as a single-step deposition method allowing the localized transfer of a variety of different metals and polymers on transparent, ultra-thin and stretchable substrates. Also referred to as laser induced backward transfer (LIBT), the process can be manipulated to transfer material from bulk materials to transparent targets, providing a direct method potentially sustainable to generate microelectronic circuitry. In this work, a fs-pulsed UV laser (343 nm) was employed for the first time to transfer electrically conductive copper tracks and layers from bulk Cu in the form of sheet metal onto ultra-clear soda lime glass slides with sub-micrometric thickness. The process development started from the selection of the materials for adequate energy transfer between the beam source and the donor/receiver combination. In the single-track study, the effect of donor/receiver gap was analyzed while tracks ranges with 5 to 233 nm thickness and 7 to 41 μm average width were produced. Based on the results, multi-track layer deposition was assessed by varying the overlap between the tracks. Functional demonstrator cases were produced. The work confirms the suitability of LIRT as a direct approach to create microelectric circuitry by using readily available and sustainable bulk Cu material. [Display omitted] • Laser induced reverse transfer system based on fs-pulsed UV laser was developed. • Ultrashort pulses were used to transfer nm-thick tracks from bulk Cu donors. • Influence of pulse energy, speed, and donor gap evaluated. • Overlapping between adjacent tracks was studied to determine deposited surface quality. • Electrically conductive deposits in cm-scale were produced with fine details. [ABSTRACT FROM AUTHOR]

[Display omitted] • An experimental study of a ultra-violet (UV) photodetector was performed to get its improved performances. • The photo-response and switching ability of the present UV photodetector was evaluated. • An enhanced photo-detection performance is due to improved opto-electronic properties of MoS 2 & GNR heterostructure. • The performance of the photodetector was compared with the previous one and found to be much better. The integration of graphene nanoribbons (GNR) with nanostructured chalcogenides like MoS 2 is yielding remarkable results in the realm of opto-electronics. This collaboration enhances light-matter interactions and promotes efficient charge transfer pathways by modifying GNR's bandgap and defect levels. To exploit these advantages, we are synthesizing MoS 2 and GNR heterostructures with varying ratios using a chemical route. Extensive characterizations involving XRD and SEM analysis are validating the successful creation of these heterostructures. Furthermore, we are assessing their optical properties through UV, PL, Raman, and FTIR analyses, with absorbance peaks and Raman modes being used to determine the number of MoS 2 layers in each composition. Our primary focus is to develop a photodetector based on MoS 2 and GNR heterostructures to enhance its performance. Fabricated through chemical process, the MoS 2 and GNR heterostructures are being deposited between silver electrodes on a Si/SiO 2 substrate. The resulting photodetector is expected to exhibit substantially improved photo-response and switching capabilities compared to individual nanomaterials. We anticipate that the optimized photodetection performance will feature remarkable attributes, including photo-responsivity of 18.81 mAW−1, detectivity of 46.5 × 107 jones, external quantum efficiency of 19.91, and swift response and recovery times. We expect these notable results, particularly for GNR: MoS 2 ratios of 3:1 and 2:1 under 390 nm UV laser illumination, to underscore the immense practical potential of high-performance photodetectors. [ABSTRACT FROM AUTHOR]

• Local electric field enhancement (LEFE) for NPs aggregate in oxide glass was obtained. • Approach to LEF analysis reproduces Er3+ luminescence enhancement by Ag NPs aggregate. • Optimal parameters of Ag NPs aggregate which maximize LEFE were estimated. • LEFE is largest for aggregates of Ag, less for Rb, lowest for aggregates of Au NPs. • Rb containing bimetallic NPs enable to tune LSPR-LEF characteristics in wide ranges. Local electric field (LEF) distribution near Ag, Au, AgAu NPs synthesized by UV laser or temperature treatments, and near simulated Rb, AgRb, AuRb NPs in oxide glasses, was studied considering aggregates of 10–15 particles - necessary condition for description of optical extinction spectra. For efficient analysis of LEF spatial distributions under different sizes, components, agglomerations of NPs in these aggregates, approach was proposed that enables to obtain dependence of averaged LEF enhancement upon the distance from the nearest particles in aggregate. This approach reproduced enhancement of Er3+ luminescence intensity in zinc-tellurite glass after formation of Ag NPs and showed that average LEF enhancement per hypothetical Rare Earth ion (REI) is largest for aggregates of Ag, less for Rb, lowest for Au NPs. The optimal Ag NPs aggregate was estimated for best LEF enhancement per hypothetical REI. Simulated aggregates of Rb containing NPs demonstrated strong LEF, shifted in a wide range. [Display omitted] [ABSTRACT FROM AUTHOR]

Some of the most famous diamonds of historical significance display beautiful and rare colors such as pink, blue and green. Many have been recut one or more times, either in attempts to improve their appearances, or to disguise their provenance. Given the major advances in instrumentation for characterizing diamonds in the past two decades, we pose the question: can one devise a methodology to create an analytical fingerprint of a diamond to identify it even after recutting, or to identify two polished diamonds of unknown provenance as having been cut from the same rough or polished diamond? To determine if this is feasible, we carried out an in-depth study of two pairs of polished diamonds colored mainly by the GR1 absorption, one pair known to have been cut from the same rough crystal, and one pair of diamonds of unknown provenance for which it was possible to prove that they originated from the same piece of rough. The data obtained by a combination of absorption spectroscopy from the UV to the mid-infrared, photoluminescence spectroscopy with various lasers from the UV to the NIR and luminescence imaging with a range of excitations was found to establish, beyond any doubt, that each of the two diamond pairs shared a common progenitor. Nevertheless, for each of the diamond pairs only one diamond was identified as naturally colored while for the other one the color origin was given as "undetermined" by a prominent gem testing laboratory. The methodologies described herein can prevent such inconsistencies regarding diamonds of previously unknown provenance; they show spectroscopically how and why the color of some natural color origin green diamonds is enhanced by polishing, especially when removing surface radiation "stains"; further, such methodologies will identify "diamond twins separated at birth". [Display omitted] • A method of creating a unique data set for diamond is presented – a data fingerprint. • Based on the unique combination of growth structures and defects of every diamond • Characterization through imaging – including luminescence – and spectroscopy • Can be used to determine whether several diamonds originate from the same rough • May be used to prove that diamonds are of identical color origin [ABSTRACT FROM AUTHOR]

The rapid developments in orbital-angular-momentum-carrying Laguerre–Gaussian (LG) modes in recent years have facilitated progress in optical communication and quantum information. However, it is still challenging to efficiently generate the high-fidelity LG laser modes. We propose a scheme to generate the high-fidelity ultraviolet (UV) LG mode via four-wave mixing (FWM) in a five-level atomic system. It is found that the output FWM field transferred from a probe beam carrying orbital angular momentum (OAM) can be efficiently controlled. Interestingly, by appropriate choices of the system parameters, the FWM field can be significantly enhanced and the maximum FWM conversion efficiency is more than 60%, which is several orders of magnitude larger than many previous investigations. More importantly, the fidelity of the output FWM field is studied and find that the generated LG laser mode has the fidelity approximately 100%. As we known, any light beam can be decomposed as a linear combination of LG beams and we can expand the theoretical approach to the case of an arbitrary LG probe beam. Thus, our work may be exploited for generation of the high-fidelity UV LG mode in a compact, efficient, and robust way. [ABSTRACT FROM AUTHOR]

Laser-induced forward transfer (LIFT) has emerged as a versatile technique for printing high-resolution metal microstructures. However, a common drawback of this method is the inadequate coalescence of the deposited metal microdroplets, which results in inferior electrical and mechanical properties. This paper proposes a novel approach for fabricating high-performance metal micropillars using a single-pulsed laser to alternately deposit and remelt metal microdroplets. Specifically, an ultraviolet nanosecond laser was used to induce the deposition of copper microdroplets, forming a patterned powder bed with high resolution. Subsequently, a laser pulse train was applied to fuse the patterned powder bed. The results showed that voids and microdroplet delamination were eliminated in the printed copper micropillars, whose yield strength and elastic modulus increased threefold, approaching 63% of those of the bulk metal. The remelting behavior of the deposited microdroplets was elucidated by modelling and analysing the thermal accumulation effects of a laser pulse train. A remelting map was proposed, including the non-melting, remelting, and vaporizing regimes. According to the depth of melt pool, the evolutions of morphology and microstructure in the depositing and remelting process were elucidated. Hence, this study advances the LIFT process for fabricating high-performance metal microstructures. [Display omitted] • Alternate deposition and remelting microdroplets was proposed to eliminate voids and delamination suffered by LIFT. • The yield strength and elastic modulus of printed micropillars were measured to augment threefold, approaching 63% of the bulk metal. • Laser remelting regime was elucidated, including the non-melting, remelting, and vaporizing regions. • The morphology and microstructure of printed micropillar were governed by remelting depth. [ABSTRACT FROM AUTHOR]

• Innovative introduction of UV-ns laser for paint removal from resin matrix composites. • The paint layer on the surface of resin matrix composites is safely removed under reasonable parameters. • The mechanism of paint removal by UV nanoseconds and the matrix damage mechanism of resin matrix composites are discussed. Laser cleaning shows exciting promise for removing paint from aircraft skins. This paper focuses on the application of a 355 nm (UV) nanosecond pulsed laser for paint removal from aircraft skin composites. First, the effects of process parameters on laser paint removal are analyzed, and mapping relationships between these parameters and the depth and roughness of paint removal are established. After that, the micromorphology and dynamic behavior of the samples are observed and characterized with the help of SEM, EDS and high-speed photography. Finally, the paint cleaning mechanism and damage mechanism of the 355 nm laser are discussed. The results show that the removal of paint is a combined result of photothermal and photochemical effects, while the damage of carbon fiber is caused by thermo-mechanical forces. When the laser repetition frequency is 50 kHz, the scanning speed is 1100 mm/s, and three cleanings are performed, the paint on the CFRP surface can be completely removed while maintaining the integrity of the carbon fiber. [ABSTRACT FROM AUTHOR]

• A mulit-feed method is proposed for the manufacture of diamond structures with high aspect ratios. • Deeply controllable processing of diamond microstructures and joining methods for different structures are realized. • Successful fabrication of a high aspect ratio diamond straight microchannel heat sink with practical significance. The high heat flux density of modern chips presents a major challenge to their development. Single-phase or two-phase flow heat dissipation techniques using high thermal conductivity materials are seen as a potential solution. However, creating microfluidic channels from ultra-high thermal conductivity diamond materials is a significant challenge. In this paper, we present an experimental study on the fabrication of diamond heat sinks with high aspect ratio microchannels using a UV-nanosecond laser processing system, along with two multi-feed processing techniques for the collecting grooves and microchannels. We used a 1 μm spacing grid path combined with a polished multi-feed process to fabricate a 1600 μm deep collecting groove with a smooth bottom morphology. We also proposed a multi-area multi-feed fabrication technique for microchannels with an aspect ratio of 8:1 and a depth of 1600 μm. Finally, we have successfully fabricated a diamond straight microchannels heat sink, featuring a high aspect ratio and low phase change damage. [ABSTRACT FROM AUTHOR]

• The electronic responses of single-crystal silicon irradiated by different wavelengths (800, 400 and 46.9 nm) are compared. • Tunneling ionization in silicon is difficult to happen under EUV irradiation due to the high laser frequency. • The impact ionization rate of 46.9 nm is greater than 800 and 400 nm. • The 46.9 nm laser may be a promising approach to removing atomic layers without destroying the surface lattice. The phenomenon of laser-induced electronic evolution in semiconductors is an essential issue in laser fabrication, which has been extensively investigated within the near-infrared and visible spectral ranges. However, electronic evolution at short wavelength laser has neither been systematically investigated. In this paper, time-dependent density functional theory is employed to investigate the response in silicon under laser irradiation of different wavelengths. The result shows that shorter wavelength induces the excitation of electrons to higher energy levels, consequently leading to increased impact ionization rates. Such a moderate excitation of energetic electrons even at low-medium intensity is considered as a distinctive feature of extreme ultraviolet light laser, which is expected to further enhance the quality of laser processing. [ABSTRACT FROM AUTHOR]

• Optical fiber sensor for pH measurement as low-cost solution. • pH sensitive material as polyaniline using synthetic oxidative polymerization on optical fiber surface. • Transition between protonated and deprotonated polyaniline increasing RI of the layer as the pH increases. • FBGs inscribed by UV laser in tapering fiber and D-shaped fiber as optical solution. • Sensors with good reproducibility and repeatability with excelent sensitivities for tapers and D-shape fibers. Optical fiber sensors show potential for monitoring multiple parameters essential to the growth and health of fish, particularly the pH value of the aquaculture medium. Two types of optical fiber sensors, using tapered silica single mode fibers with a Bragg grating inscribed and D-shaped plastic optical fibers (home-made and reused) were produced. A pH-sensitive layer made of polyaniline (PANI) was deposited on the optical fibers' surface. The sensors demonstrated reproducibility and repeatability with a sensitivity of −0.22 ± 0.02 dB/pH, −472 ± 9 Counts/pH, and −(26 ± 2) × 102 Counts/pH for tapers, D-shape home-made, and reused, respectively, but only for increasing pH. Stabilization time tests indicated that a minimum of 60 s is required for a stable response, with no significant cross-sensitivities regarding temperature and ionic strength. [ABSTRACT FROM AUTHOR]

In this paper, we have grown a large NaSr 3 Be 3 B 3 O 9 F 4 (NSBBF) crystal with a top-seeded solution method and generated a continuous-wave (cw) laser radiation at 266 nm with a Brewster-cut NSBBF. With a high-power cw 532 nm and a frequency doubling stage, up to 120 mW cw UV laser was generated at 266 nm. A high stability at 50 mW was obtained more than 10 h. This cw UV laser source is applicable for self-calibrating solar irradiators. • We have grown a NSBBF crystal with size of 45 × 30 × 25 mm3. • A continuous-wavelaser at 266 nm was realized using a Brewster-cut NSBBF with120 mW. • A stability of 50 mW was obtained for more than 10 h. [ABSTRACT FROM AUTHOR]

Due to the widespread emergence of COVID-19, face masks have become a common tool for reducing transmission risk between people, increasing the need for sterilization methods against mask-contaminated microorganisms. In this study, we measured the efficacy of ultraviolet (UV) laser irradiation (266 nm) as a sterilization technique against Bacillus atrophaeus spores and Escherichia coli on three different types of face mask. The UV laser source demonstrated high penetration of inner mask layers, inactivating microorganisms in a short time while maintaining the particle filtration efficiency of the masks. This study demonstrates that UV laser irradiation is an efficient sterilization method for removing pathogens from face masks. [ABSTRACT FROM AUTHOR]

Perovskite solar cells (PSCs) are currently attracting a great deal of attention for their excellent photovoltaic properties, with a maximum photoelectric conversion efficiency (PCE) of 25.5%, comparable to that of silicon-based solar cells. However, PSCs suffer from energy level mismatch, a large number of defects in perovskite films, and easy decomposition under ultraviolet (UV) light, which greatly limit the industrial application of PSCs. Currently, quantum dot (QD) materials are widely used in PSCs due to their properties, such as quantum size effect and multi-exciton effect. In this review, we detail the application of QDs as an interfacial layer to PSCs to optimize the energy level alignment between two adjacent layers, facilitate charge and hole transport, and also effectively assist in the crystallization of perovskite films and passivate defects on the film surface. [ABSTRACT FROM AUTHOR]

Flow control is a highly relevant topic for micromanipulation of colloidal particles in microfluidic applications. Here, we report on a system that combines two-surface bound flows emanating from thermo-osmotic and diffusio-osmotic mechanisms. These opposing flows are generated at a gold surface immersed into an aqueous solution containing a photo-sensitive surfactant, which is irradiated by a focused UV laser beam. At low power of incoming light, diffusio-osmotic flow due to local photo-isomerization of the surfactant dominates, resulting in a flow pattern oriented away from the irradiated area. In contrast, thermo-osmotic flow takes over due to local heating of the gold surface at larger power, consequently inducing a flow pointing toward the hotspot. In this way, this system allows one to reversibly switch from outward to inward liquid flow with an intermittent range of zero flow at which tracer particles undergo thermal motion by just tuning the laser intensity only. Our work, thus, demonstrates an optofluidic system for flow generation with a high degree of controllability that is necessary to transport particles precisely to desired locations, thereby opening innovative possibilities to generate advanced microfluidic applications. [ABSTRACT FROM AUTHOR]

The optical resonances of nanoparticles have drawn considerable attention in academia and industry; however, the formation of uniform nanoparticles has been challenging, hindering their application. Herein, we propose that reflective-type color filters can be achieved using the optical resonance effect arising from Si nanoparticles created on an amorphous Si thin film via laser irradiation. Multiple equally spaced irradiations of an amorphous-Si surface by a Gaussian laser beam created Si nanoparticles with sizes of 100–200 nm at laser fluences in the range of 150–200 mJ/cm2. Furthermore, we demonstrated that the resonance colors could be tuned to red, green, and blue by adjusting the laser fluence and scan speed. The optical properties of the nanoparticles were analyzed using dark-field microscopy, scanning electron microscopy, and transmission electron microscopy. According to the measured nanoparticle geometries and spectral data, the Si nanoparticles are spheroidal shapes embedded in the Si layer, and simulations indicate that the resonance colors originate from electric and magnetic dipoles inside the Si nanoparticles. The results could inform the fabrication of color filters in reflective display device or sensor applications through a simple laser scanning process. [ABSTRACT FROM AUTHOR]

This study investigated ultraviolet-laser-induced graphene (ULIG) through the far-infrared irradiation (FIR) of polyimide films for constructing flexible electric heaters. Graphene, which has a uniform micro-scale porous structure with high electrical conductivity, was formed along the laser-induced paths through photothermal and photochemical reactions. Raman spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were used to measure the microstructure, elemental composition, and chemical states of the ULIG films and thereby investigate their graphenization and defect level. Moreover, the surface morphology and electrical properties of the ULIG films were evaluated using a field-emission scanning electron microscope and source measurement unit, respectively. Finally, optimal processing parameters, namely a surface laser fluence of 48 J/cm2, a pulse repetition rate of 100 kHz, and a scan pitch of 0.01 mm, were used to fabricate ULIG heaters with triangular and honeycomb electrode structures. The ULIG films with FIR exhibited a high-quality and high-integrity porous structure, a low electrical resistance of 2.55 Ω, and a low sheet resistance of 14.34 ± 2.04 Ω/sq. Furthermore, the ULIG heaters exhibited ultrafast heating and cooling rates (90.93 and 89.37 ℃/s, respectively) as well as excellent heating stability and flexibility. [ABSTRACT FROM AUTHOR]

Following indirect-drive experiments which demonstrated promising performance for low convergence ratios (below 17), previous direct-drive simulations identified a fusion-relevant regime which is expected to be robust to hydrodynamic instability growth. This paper expands these results with simulated implosions at lower energies of 100 and 270 kJ, and 'hydrodynamic equivalent' capsules which demonstrate comparable convergence ratio, implosion velocity and in-flight aspect ratio without the need for cryogenic cooling, which would allow the assumptions of one-dimensional-like performance to be tested on current facilities. A range of techniques to improve performance within this regime are then investigated, including the use of two-colour and deep ultraviolet laser pulses. Finally, further simulations demonstrate that the deposition of electron energy into the hotspot of a low convergence ratio implosion through auxiliary heating also leads to significant increases in yield. Results include break even for 1.1 MJ of total energy input (including an estimated 370 kJ of short-pulse laser energy to produce electron beams for the auxiliary heating), but are found to be highly dependent upon the efficiency with which electron beams can be created and transported to the hotspot to drive the heating mechanism. [ABSTRACT FROM AUTHOR]

Many important biological processes such as protein folding and ligand binding are too fast to be fully resolved using conventional stopped-flow techniques. Although advances in mixer design and detection methods have provided access to the microsecond time regime, there is room for improvement in terms of temporal resolution and sensitivity. To address this need, we developed a continuous-flow mixing instrument with a dead time of 12 to 27 µs (depending on solution viscosity) and enhanced sensitivity, sufficient for monitoring tryptophan or tyrosine fluorescence changes at fluorophore concentrations as low as 1 µM. Relying on commercially available laser microfabrication services, we obtained an integrated mixer/flow-cell assembly on a quartz chip, based on a cross-channel configuration with channel dimensions and geometry designed to minimize backpressure. By gradually increasing the width of the observation channel downstream from the mixing region, we are able to monitor a reaction progress time window ranging from ~10 µs out to ~3 ms. By combining a solid-state UV laser with a Galvano-mirror scanning strategy, we achieved highly efficient and uniform fluorescence excitation along the flow channel. Examples of applications, including refolding of acid-denatured cytochrome c triggered by a pH jump and binding of a peptide ligand to a PDZ domain, demonstrate the capability of the technique to resolve fluorescence changes down to the 10 µs time regime on modest amounts of reagents. [ABSTRACT FROM AUTHOR]

We studied the tolerance of one species of quinoa achenes from ecotype RQ252 to simulated extraplanetary conditions in a vacuum chamber (high low-pressure 10–2 to 10-7 Torr, UV laser simulated plasma radiation, and cryogenic temperature). The selection of this ecotype of quinoa achenes was a condition to previous studies, where RQ252 shows evidence of high efficacy in grow adaptation in the South America Puna between 3800–4500 m asl subjected to low oxygen and increased UV radiation exposition. After extraplanetary experiment exposure, we evaluated quinoa tolerance to experimental conditions through germination and early growth responses under a controlled laboratory standard atmosphere. Rate and final germination subjected to high low-pressure treatments during 4 h, 8 h, and 16 h were not different to control. Laser plasma application accelerated the germination rates. Final germination always reaches values up to 90%. SEM-EDS analysis showed structural changes on the pericarp surface, especially in high low-pressure and high low pressure + plasma treatments. EDS revealed that the quinoa pericarp subjected to different treatments showed changes in mineral content. Potassium ions decreased under high low-pressure and high low pressure + laser plasma irradiation (between 32 and 42%) but increased in a prolonged vacuum (35%) and more when plasma was added (96%). Early growth was affected by the different treatments, being the radicle length the most affected parameter. Our results suggest that quinoa achene ecotype RQ252 viability has excellent tolerance to extraplanetary conditions. • Quinoa viability has a great tolerance to extraplanetary conditions. • Quinoa achenes are viable after high low-pressure and laser irradiation conditions. • Quinoa sprouts seem to be a good fresh food alternative for long term space missions. [ABSTRACT FROM AUTHOR]

This Letter reports a femtosecond ultraviolet laser absorption spectroscopy (fs-UV-LAS) for simultaneous in situ measurements of temperature and species. This fs-UV-LAS technique was demonstrated based on X2Π-A2Σ+ transitions of OH radicals near 308 nm generated in low temperature plasmas and flames. The fs-UV-LAS technique has revealed three major diagnostic benefits. First, a series of absorption features within a spectral bandwidth of ∼3.2 nm near 308 nm were simultaneously measured and then enabled simultaneous multi-parameter measurements with enhanced accuracy. The results show that the temperature and OH concentration could be measured with accuracy enhanced by 29–88% and 58–91%, respectively, compared to those obtained with past two-narrow-line absorption methods. Second, an ultrafast time resolution of ∼120 picoseconds was accomplished for the measurements. Third, due to the large OH X2Π-A2Σ+ transitions in the UV range, a simple single-pass absorption with a 3-cm path length was allowed for measurements in plasmas with low OH number density down to ∼2 × 1013 cm−3. Also due to the large OH UV transitions, single-shot fs absorption measurements were accomplished in flames, which was expected to offer more insights into chemically reactive flow dynamics. [ABSTRACT FROM AUTHOR]

The performance of deep ultraviolet (DUV) laser diodes (LDs) may be affected by structural variations in the composition of AlGaN devices. In this work, we investigate the impact of structural variations in three AlGaN-based DUV-LDs, namely, the traditional DUV-LD (D1), traditional device structure with stepped-doped lower waveguide (LWG) (D2), and Mg-doped p-cladded D2 (D3). In this study, we closely analyze the performance dependence of different structural variations on the traditional DUV-LD. The stepped-doped LWG method utilized in D2 has proven to be an improvement factor among the three DUV-LDs. Moreover, the threshold current decreases when the LWG doping concentration increases. An adequately constructed stepped-doped LWG layer replaces the homogeneously and heavily doped LWG layer in D1, which decreases the electron leakage current and increases the hole injection current. The performance gains of AlGaN-based ultraviolet laser diodes are demonstrated using the simulation software LASTIP. The deep wavelength of all the DUV-LDs is 269 – 280 nm, with D1, D2, and D3 exhibiting an operating threshold voltage of 2.64, 4.24, and 4.24 V, respectively, and a lasing threshold current of 0.4, 0.002, and 0.002 A, respectively. Overall, D2 is considered as the preferred LD, because it achieves the best reduction in total optical loss, thereby resulting in 40% optical confinement. [ABSTRACT FROM AUTHOR]

We demonstrate a 294.2 nm all-solid-state Q-switched laser, with 241.4 mW average output power, produced by frequency doubling of a 588.4 nm laser. The 588.4 nm laser is obtained by intracavity sum-frequency generation of a 1064 nm laser and a 1319 nm laser. By synchronizing the fundamental lasers and adjusting the focal length of the focusing lens, average output powers of 10.2 W at 588.4 nm and 241.4 mW at 294.2 nm with 297 ns pulse width are obtained at 6 kHz frequency. The 294.2 nm laser beam quality M X 2 = 1.18 and M Y 2 = 1.26 for the X and Y directions, respectively. To the best of our knowledge, this is the highest power of all-solid-state Q-switched laser at 294.2 nm. [ABSTRACT FROM AUTHOR]

Attempts were made over the years to achieve economic and easy methods for water purification. This could well save time, cost, and earn a good process quality for many countries. This study aims to enhance the purification process parameters for Congo red dye polluted water and introduce a developed methodology with an impact on many associated parameters such as the time for water purification process. The research proposes a method to achieve this time reduction by mixing gold nanoparticle (AuNPs) (prepared by chemical reduction method) with Titanium dioxide nanoparticles (TiO2NPs) (prepared by sol-gel techniques). The resulting mixture is incorporated into PVA host to synthesize a hard disk used as a purification disk to treat the pollutant water. The pollutant solution was exposed to different light sources to complete the photocatalyst process. In this respect, sunlight, UV ligh, green laser, blue laser, and combined UV light and green laser were used as a photocatalysis sources. Experimental work was conducted to adjust the right mixture and the right combination of light sources. Results were recorded accordingly and showed a significant reduction in the purification time with less than half the standard period when the conventional purification process is used. [ABSTRACT FROM AUTHOR]

The paper investigates the possibility of improving the technology of diffusion welding, which can be used both for joining dissimilar materials for the manufacture of complex devices in the aerospace industry on the ground, and for repair and design in outer space. A laser treatment by nanosecond laser pulses of the ultraviolet range was carried out for surface modification of industry alloys (CrNi55CuВZn, steel AISI 316, Cu–Cr bronze) used in space technology due to high values of thermal and electrical conductivity. It was shown that the preliminary laser treatment leads to an improvement in the properties of the weld: an increase in tensile strength by more than 10%, and tensile strain by more than 20% for certain joints of materials. Also, laser pre-processing can improve the productivity of the welding process, in particular, reduce the temperature and shorten the welding time. • Preliminary laser treatment of alloy samples for diffusion welding was studied. • A method of direct micro- and nanostructuring was used for surface modification. • Laser treatment improves mechanical properties of welded joints used in space and aviation technologies. • Tensile strength increases by more than 10% for joints with treated samples. • Laser pre-processing can reduce the welding temperature and shorten the welding time. [ABSTRACT FROM AUTHOR]

In connection with the possible use of laser technological equipment in space the impact of nanosecond UV laser on copper and its alloys was investigated. At the pre-threshold mode, in the absence of obvious traces of melting, at an energy density of E = 0.1–1.0 J/cm2, the metal in the irradiated zone swelled up and traces of plastic deformation were found. The uplift arised as a result of the formation of an excessive number of point defects. With an increase of the number of impacting pulses, accumulation of damage occurred, despite the fact that the surface completely cools down during the time between pulses. The height of the resulting uplift reached 1 μm, and sometimes even slightly more. Sliding and cracking along grain boundaries occurred, as well as crystallographic slipping. The discovered effect of the impact of laser pulse on the metal surface, associated with the occurrence of uplift and the presence of plastic deformation, is similar to the well-known acoustoplastic, electroplastic, and magnetoplastic effects. The discovered effect was called optoplastic. Exceeding the laser damage threshold (E ∼ 1.0 J/cm2) leads to melting and evaporation of the metal with the formation of a crater. This is oppositely directed process, which suppresses the manifestations of the optoplastic effect. • Copper surface modification due to nanosecond laser pulses impact was investigated. • An optoplastic effect was found. • It is of interest for the preparation of a metal surface for diffusion welding. [ABSTRACT FROM AUTHOR]

The properties of graphene oxide foils were modified by excimer laser irradiation at different fluences and times. The irradiations were performed in air and in vacuum using a pulsed UV laser operating at 248‐nm wavelength and 23‐ns pulse duration. Measurements of ablation yield, microscope surface morphology and Raman spectroscopy were performed. The residual surface shows a significant oxygen reduction due to the removing of functional oxygen groups, a thickness reduction due to the removal of graphene layers depending on the used laser shots and a presence of defects in the graphene sheets as evident by the Raman spectroscopy investigation. [ABSTRACT FROM AUTHOR]

Chemical vapor deposition ( CVD) technology has enabled synthetic diamonds to be applied in many fields, in which the excellent comprehensiveness of diamond has been fully developed, and may lead to a leap-forward development. The color center makes the diamond quantum accelerator initially show the feasibility of great power. Various scenarios, including the application of UV laser writing technology windows, maximize the comprehensive advantages of diamond windows in terms of optics, electricity, heat and mechanics. Ultra-wide bandgap diamond semiconductor applications will soon be realized, and diamond heat dissipation applications are constantly expanding. By summarizing the preparation methods and characteristics of CVD diamond, according to the intrinsic characteristics of diamond, CVD diamond is classified into quantum grade, electronic grade, optical grade, thermal grade and mechanical grade. The current status of research and application of CVD diamond are reviewed in detail, which is of great significance for judging the future development trend of CVD diamond. [ABSTRACT FROM AUTHOR]

Surface ion traps are among the most promising technologies for scaling up quantum computing machines, but their complicated multi-electrode geometry can make some tasks, including compensation for stray electric fields, challenging both at the level of modeling and of practical implementation. Here we demonstrate the compensation of stray electric fields using a gradient descent algorithm and a machine learning technique, which trained a deep learning network. We show automated dynamical compensation tested against induced electric charging from UV laser light hitting the chip trap surface. The results show improvement in compensation using gradient descent and the machine learner over manual compensation. This improvement is inferred from an increase of the fluorescence rate of 78% and 96% respectively, for a trapped 171 Yb + ion driven by a laser tuned to - 7.8 MHz of the 2 S 1 / 2 ↔ 2 P 1 / 2 Doppler cooling transition at 369.5 nm. [ABSTRACT FROM AUTHOR]

A significant area of study and upgrading for increasing sensitivity and general performances of matrix-assisted laser-desorption ionization (MALDI) mass spectrometry (MS) is related to matrix design. Several efforts have been made to address the challenge of low-mass-region interference-free for metabolomics analysis and specifically for lipidomics. To this aim, rationally designed matrices as 4-chloro-α-cyanocinnamic acid (ClCCA) were introduced and reported to provide enhanced analytical performances. We have taken this rational design one step further by developing and optimizing new MALDI matrices with a range of modifications on the CHCA core, involving different functionalities and substituents. Of particular interest was the understanding of the electron-withdrawing (e.g., nitro-) or donating (e.g., methoxy-) effects along with the extent of conjugation on the ionization efficiency. In the present work, ten matrices were designed on a reasonable basis, synthesized, and characterized by NMR and UV spectroscopies and laser desorption ionization. With the assistance of these putative MALDI matrices, samples containing phospholipids (PL), and neutral di-/tri-acylglycerols (DAG, TAG) were investigated using milk, fish, blood, and human plasma extracts. In comparison with CHCA and ClCCA, four of them, viz. [(2E,4E)-2-cyano-5-(4-methoxyphenyl)penta-2,4-dienoic acid] (1), [(2E,4E)-2-cyano-5-(4-nitrophenyl)penta-2,4-dienoic acid] (2), [(E)-2-cyano-3-(6-methoxynaphthalen-2-yl)acrylic acid] (6) and [(E)-2-cyano-3-(naphthalen-2-yl)acrylic acid] (7) displayed good to even excellent performances as MALDI matrices in terms of ionization capability, interference-free spectra, S/N ratio, and reproducibility. Especially compound 7 (cyano naphthyl acrylic acid, CNAA) was the election matrix for PL analysis and matrix 2 (cyano nitrophenyl dienoic acid, CNDA) for neutral lipids such as DAG and TAG in positive ion mode. [ABSTRACT FROM AUTHOR]