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This article discusses the generation of a watt-level continuous wave deep ultraviolet (UV) laser at 261 nm through efficient frequency doubling of a blue-diode-pumped Pr: YLF laser at 522 nm. The researchers achieved an output power of 2.53 W with perfect beam quality, making it the first report of a watt-level Pr: YLF laser operating at 261 nm. The deep UV laser has potential applications in optical storage, spectral analysis, and industrial settings. The article provides details on the experimental setup and results, including the laser's output power, stability, and beam profile. [Extracted from the article]

Synthesis and characterization of a Dy3+-activated calcium yttrium oxide (CaY2O4) phosphor are reported. The CaY2O4:Dy3+ (1.5 mol%) phosphor is synthesized using a modified solid-state reaction technique for calcination and sintering. The cubic structure is revealed by the X-ray diffraction technique. The morphology and particle size distribution of the prepared phosphor are investigated by the FEGSEM technique. The chemical bonds and functional group analysis are confirmed by the FTIR. A photoluminescence analysis of the CaY2O4:Dy3+ phosphor shows dual excitation wavelengths at 285 and 348 nm, especially in the ultraviolet region. At 383 nm, three distinct emission peaks are found at the wavelengths 238, 485, and 571 nm. The spectroscopic parameters are calculated using the CIE chromaticity coordinates. The CIE coordinates of the Dysprosium ion-activated CaY2O4 phosphor (1.5 mol%) show an emission near the white light region of the chromaticity diagram, suggesting that it is suitable for W-LED applications. [ABSTRACT FROM AUTHOR]

Laser corneal reshaping is an eye surgery utilizes UV lasers to modify a targeted corneal surface to correct vision disorders such as myopia, hyperopia and astigmatism. The most commonly used laser type in such treatment is a pulsed gas laser namely argon fluoride (ArF) excimer laser (193 nm). A mixture of Argon, Fluorine and high percentage of Neon gas is utilized for producing the required laser. However, the availability of Neon gas is currently very limited due to the existent Russian-Ukraine war as this region is considered the main supplier of pure Neon gas. The present work provides a novel alternative system for the commercially available corneal reshaping eye surgery devices with a special opening for entering the operational laser beam from external sources. The proposed system is a flying spot platform coupled with a solid state laser, that is a forth harmonic of Nd: YAG laser. The aperture in the system's design enables it to take in the generated UV-laser beam (266 nm) from the external Nd: YAG laser source. The beam is then modified and directed at the treatment area. The device was tested for hyperopia laser profile algorithm on different targets. Furthermore, the hyperopia profile procedure was also applied to the ex-vivo rabbit eye to investigate the ablation effect on the corneal tissues. The obtained results showed an appropriate ablation effect for hyperopic correction via a complete corneal reshaping platform. Although, the device's current state may not be appropriate for immediate clinical use. It holds significant value as a training and educational platform. [ABSTRACT FROM AUTHOR]

Lead in any food is harmful even at low concentrations. In this study, a direct and highly sensitive lead analysis technique was developed for wheat flour using laser-induced fluorescence combined with laser-induced breakdown spectroscopy. Wheat flour was pressed into small pellets and ablated by a low-energy ultraviolet 266-nm laser. A tunable dye laser constructed in our laboratory was used to resonantly excite the lead. The optimized interpulse time delay was 400 ns. A calibration curve was constructed and the detection limit for lead was 73.8 ppb. This method could be used to directly and sensitively analyze wheat flour for trace concentrations of lead. [ABSTRACT FROM AUTHOR]

The paper presents experimental data on the absolute values of the radiation intensity in the wavelength range of 6.6–32 nm for a stainless steel target excited by a Nd:YAG laser with parameters λ = 1064 nm, Epulse = 0.45 J, τ = 4 ns, = 10 Hz. The results are of interest for various applications using laboratory laser-plasma sources of soft X-ray and extreme ultraviolet radiation. [ABSTRACT FROM AUTHOR]

The article considers broadband multilayer X-ray mirrors based on Mo/Be and Mo/Si structures with a transmission band coinciding with the Si Lα (13.5 nm) and Sn (13.5 nm) emission lines. The described structures are of great interest for the currently developed liquid source of EUV radiation, since they make it possible to increase the efficiency of the source-X-ray optical system due to the "complete" capture of emission lines. [ABSTRACT FROM AUTHOR]

This study presents a two-step methodology, integrating support vector machine (SVM) and non-dominated sorting genetic algorithm II (NSGA-II) to model and optimize machining characteristics in laser-machined sapphire. In the first step, SVM was employed to predict the machined depth and surface roughness of sapphire substrates exposed to ultraviolet (UV) nanosecond laser pulses. A set of 27 systematic experiments, covering various levels of laser pulse energy, scanning speed, and hatching distance, was conducted to train SVM models. Both established SVM models showed remarkably low error values for the prediction of machined depth and surface roughness. An additional set of five experiments underscored the reliability of these SVM models. The laser machining outputs were extended by using the proposed SVM models to unveil the profound impact of processing parameters on machining characteristics. In the second step, the validated SVM models from the previous step were utilized as objective functions within the NSGA-II algorithm to maximize machined depth and minimize surface roughness simultaneously. This approach yielded a range of optimal solutions tailored to specific design requirements. It is found that by leveraging SVM in the first step to predict machined depth and surface roughness with exceptional accuracy, followed by the integration of NSGA-II for multi-objective optimization in the second step, the proposed approach offers a pioneering solution to unravel the intricate interplay of processing parameters and optimizing laser machining outcomes. These findings underscore the remarkable potential of the proposed two-step SVM–NSGA-II method in addressing a diverse array of engineering challenges. [ABSTRACT FROM AUTHOR]

Among all the nuclei, Thorium-229 has the lowest excited level at approximately 8.3 eV. This level is an isomeric state with a long radiative lifetime. Therefore, 229 Th can be excited to the isomeric state using a vacuum ultraviolet laser and is expected to have applications such as in frequency standards. Our group has been conducting experiments to excite 229 Th to the isomeric state via the second excited state using the high-intensity X-ray beam available at the SPring-8 facility. To detect vacuum ultraviolet photons from the isomeric state of 229 Th, a dedicated apparatus was constructed. We employed 229 Th-doped CaF 2 crystals as the irradiation target. Because these targets emit numerous scintillation photons due to nuclear decay and X-ray beam irradiation, detectors are required to significantly reduce these background events. To achieve this, we adopted dichroic mirrors and a photomultiplier tube for detecting scintillation photons by nuclear decay, in addition to a solar-blind photomultiplier tube for detecting decay photons from the isomeric state of 229 Th. In this proceedings paper, we describe the experimental apparatus used in the beamtime in 2023. [ABSTRACT FROM AUTHOR]

For the first time, a detailed comprehensive study is conducted of the dry etching of dislocation and dislocation-free samples of germanium on planes {111}, {110}, and {100}. Etching is performed by exposure to pulses of nanosecond ultraviolet (UV) laser radiation of the subthreshold intensity (wavelength, 355 nm; duration, ~10 ns; energy density, ~0.5–1.3 J/cm2; pulse repetition rate, 100 Hz; and divergence, 1–2 mrad). Before and after the laser heat treatment of the surface, the samples are examined using a Zygo optical profilometer and a scanning electron microscope. Features of the nature of the damage to the surfaces corresponding to different crystallographic planes of single crystals of industrial dislocation germanium are revealed. They are compared with the data on the subthreshold damage of typical dislocation-free crystals. It is shown that in dislocation samples of germanium on the {111} plane, it is possible to create a regime of exposure to radiation, leading to the formation of etch pits, which is outwardly identical to the dislocation pits detected during selective chemical etching. Their concentration corresponds in order of magnitude to the density of dislocations. On the {100} plane of dislocation samples, etching results are also found, which clearly have a crystallographic nature. At the energy density of the acting radiation ≥0.4 J/cm2 on the surfaces of dislocation (plane {100}) and dislocation-free germanium (planes {111}, {100}, {110}), only individual spots of ~50 µm and individual microcraters of ~0.1–1 µm having crystallographic features are recorded. The possibility of the environmentally friendly detection of dislocations in germanium without the use of chemical reagents is shown. [ABSTRACT FROM AUTHOR]

The prethreshold processes on the surface of copper and its alloys are investigated. In the absence of obvious traces of melting, while preserving the metal in a condensed state, under a nanosecond ultraviolet laser radiation energy density of 0.1–1.0 J/cm2, manifestations of high-temperature plastic deformation were observed. These are sliding and cracking along grain boundaries, within which crystallographic slipping was observed. A microprotrusion was formed on the surface of the irradiated zone, which was outwardly similar the distribution of laser radiation in the spot. The height of the microprotrusion reached 1 μm, and sometimes even more. An increase in the number of impacting impulses led to the accumulation of damage. The data obtained are in many ways similar to the acoustoplastic, electroplastic, and magnetoplastic effects. By analogy, we consider it possible to call the discovered effect optoplastic. [ABSTRACT FROM AUTHOR]

This work reports the microstructuring of cobalt (Co) thin films by high-energy UV pulsed laser irradiation. The parameters responsible for the efficient formation of such microstructures include laser fluence and film parameters. Cracks and island formations were observed for Co thin films deposited by RF sputtering. Such rough films rendered to produce inefficient microstructuring. To overcome this limitation, Co thin films were deposited by vacuum evaporation resulting in a smooth thin film compatible for laser-induced microstructuring. Two stages of conical patterning are discussed in terms of localized melting and abrupt condensation of the melted Co film owing to laser irradiation. An efficiency of 90% for laser-based microstructuring suggests that it is an efficient and non-invasive technique for fabricating nanostructures. [ABSTRACT FROM AUTHOR]

The charge exchange (CE) reaction is an effective probe to study the structure of atomic nuclei in the isospin dimension, which has been studied for decades. To expand the range of nuclei studied by CE reactions to a wider range and research the structure characteristics of unstable nuclei, including the isospin symmetry, spin-isospin excitation, and nuclear symmetry energy, a semi-cylindrical time projection chamber (scTPC) prototype was designed and constructed to probe ( 3 He,t) CE reactions in inverse kinematics. The 266 nm UV laser was used to achieve electron-drift-velocity calibration. The scTPC has an energy resolution (FWHM) of 5.6% for α particles emitted by 241 Am radioactive source. The position resolution of scTPC is described by the residual method. The spatial resolution on the pad plane is 409 μ m. And the position resolution in the drift direction is 326 μ m, equivalent to an angular resolution of 0.4 ∘ . These performances suggest that the scTPC can measure Δ E and particle tracks precisely. The successful development of the scTPC prototype provides better conditions for the next step of experimental data analysis and processing. [ABSTRACT FROM AUTHOR]

In the current study, SnO2 nanoparticles were fabricated using laser ablation in water and characterized using ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The XRD results showed that the fabricated nanoparticles had a tetragonal crystal structure. TEM micrographs revealed that the nanoparticles were spherical, with average sizes ranging from 10 to 50 nm, depending on the laser energy used. The band gap energy of the SnO2 nanoparticles was found to increase with decreasing particle size. The antibacterial activity of the SnO2 nanoparticles was tested against Staphylococcus aureus and Escherichia coli, and the results showed that the nanoparticles were more effective against S. aureus. In addition, the anticancer activity of the SnO2 nanoparticles was tested against the lung cancer cell line A549 cells, and the findings suggest that the nanoparticles can act as an anti-proliferative agent against A549 cells. This study reveals that SnO2 nanoparticles that are synthesized by laser ablation in water could be a future strategy for other biomedical applications such as antifungal, antiviral, and immune modulators. [ABSTRACT FROM AUTHOR]

An ultra-low pump intensity and high photon flux have been long pursuits of high harmonic generation (HHG) in solids. However, there is lack of a criterion to identify a pristine solid material exhibiting such characteristics. Here, we report systematic investigation into HHG from a cadmium telluride (CdTe) bulk crystal with a flat band dispersion near the Fermi level which leads to a large density of states. The measured pump intensity for the 31st harmonics (229 nm) is only 75 GW/cm2, one order of magnitude lower than that of other pristine crystals including two-dimensional materials reported so far. A comparative measurement shows CdTe has two-to-three orders of magnitude stronger HHG than silicon does, and high HHG yields in the ultraviolet region compared to GaSe. A high photon flux of ~ 6 × 1012 photons/s (5th−8th) with a robust long-time sustainability is obtained. This work offers a route towards compact vacuum ultraviolet laser sources. Efficient high harmonic generation (HHG) in solids is instrumental for devising applications in XUV spectroscopy, attosecond science and coherent diffraction imaging. Through a systematic experimental comparison, the authors individuate CdTe as the ideal candidate for generating high harmonics with ultra-low pump intensity and high photon flux. [ABSTRACT FROM AUTHOR]

High (15–25) harmonic generation in the vacuum ultraviolet spectral range (83–50 nm) has been realized by focused (NA = 0.033) near-infrared femtosecond laser radiation (wavelength λ = 1.24 μm) with a vacuum intensity of ~7.5 × 1014 W/cm2 irradiating a dense gas jet. It has been shown experimentally that the use of such a high-numerical aperture focusing requires high (up to 10 bar) gas jet pressures to optimize phase matching. The use of the dense gas jet results in a noticeable manifestation of nonlinear propagation effects for generating radiation, which affect the generation process through the change in the phase matching conditions. Furthermore, it has been shown that the prechirping of the generating pulse makes it possible to compensate a chirp appearing due to self-phase modulation and to increase the harmonic generation efficiency because of the nonlinear compression of the generating pulse. This approach has allowed 17th (73 nm) harmonic generation with an energy of 2 pJ in a pulse and a generation efficiency of 5.4 × 10–9. The estimates obtained have shown that this radiation can be used for single-pulse maskless photolithography in the extreme ultraviolet range. [ABSTRACT FROM AUTHOR]

UV-induced processes are commonly studied in acetylacetone analogues. In this contribution, we revisit the existing work on the photoisomerization process in some of the fluorinated analogues of acetylacetone, i.e., trifluoroacetylacetone (F3-acac) and hexafluoroacetylacetone (F6-acac). We performed selective UV laser excitation of these molecules trapped in soft cryogenic matrices, namely neon and para-hydrogen, and probed by vibrational spectroscopy. Clear spectroscopy of 3 isomers of F6-acac and 6 isomers of F3-acac is obtained, including the first characterization of a second open enol isomer of hexafluoroacetylacetone. In addition, we present the electronic absorption spectra of both molecules in cryogenic matrices before and after specific UV irradiations, giving new data on the electronic transitions of photoproducts. Vibrational and electronic experimental results are analyzed and discussed within comparisons with DFT and TD-DFT calculations. Our findings contribute to a deeper understanding of the photoisomerization process in these molecules after electronic excitation in gas and condensed phase. [ABSTRACT FROM AUTHOR]

Photocatalytic degradation of bisphenol A (BPA) was investigated using commercial TiO2 P25 nanoparticles supported on natural zeolite clinoptilolite (Cli). Employing ultrasound assisted solid-state dispersion method hybrid photocatalyst containing 20 wt% of TiO2, marked TCli-20, was prepared. The structural, morphological and surface properties, and particle size distribution of TCli-20 were studied by X-ray powder diffraction, Fourier transform infrared spectroscopy, ultraviolet–visible diffuse reflectance spectroscopy, scanning electron microscopy with energy dispersive spectroscopy, atomic force microscopy, Brunner-Emmet-Teller method and laser diffraction. The results revealed a successful loading of TiO2 P25 nanoparticles on Cli surface and the preservation of both zeolitic structure and optical properties of TiO2. The influence of catalyst dose, pH value and the addition of hydrogen peroxide (H2O2) was evaluated. The optimal reaction conditions were 2 g/L of catalyst at near-neutral conditions (pH = 6.4) for complete BPA (5 mg/L) photodegradation after 180 min of exposure to simulated solar light. The addition of H2O2 was beneficial for the degradation process and led to the removal of BPA after 120 min of irradiation. BPA removal (60% for 180 min of irradiation) was reduced when TCli-20 was tested in bottled drinking water due to the presence of bicarbonate ions which acted as scavengers for hydroxyl radicals. Even though the photocatalytic activity of TCli-20 decreased after several cycles of usage, 70% of BPA was still successfully degraded during the fourth cycle. The reusability study showed easy separation, stability and good photocatalytic ability of investigated cost-effective hybrid photocatalyst. [ABSTRACT FROM AUTHOR]

The kinetics of photooxidation of tetrahydrobiopterin was investigated, the quantum yields of the formation of dihydropterin dimers were calculated when using a xenon lamp, a tunable UV laser and a UV LED as UV radiation sources. A comparative analysis of the effectiveness of these sources for the photooxidation process of tetrahydrobiopterin allowed us to conclude that the most effective for the purposes of vitiligo phototherapy are, apparently, UV LED sources with emission maxima in the region of 325 nm. [ABSTRACT FROM AUTHOR]

The authors previously discovered a new optoplastic effect and observed it under the action of a nanosecond UV laser pulse irradiation of subcritical intensity. In this paper it is shown that under this effect no micropores arise in the subsurface layer of metal. This proves the statement that swelling of metal under laser impact of moderate (subcritical) intensity occurs due to interstitial atoms migrating to the surface and not due to melting with formation of bubbles. At a abrupt cooling (for ~20 μs) interstitial atoms migrate to the surface by the Schottky mechanism due to abnormal mass transfer and the less mobile vacancies have no time to coagulate with formation of micropores in the time of the process. [ABSTRACT FROM AUTHOR]

We laser-ablated sub-wavelength structures (SWS) on 200 mm diameter birefringent sapphire disks to produce broadband anti-reflection coating (ARC). The disks were assembled into a stack of five plates making an achromatic half-wave plate (AHWP) suitable for operation between 40 and 140 GHz. We report on the SWS fabrication and transmission measurements of the stack at room temperature. From the measurements, we compute a band average transmission and modulation efficiency for nine spectral bands that correspond to the frequency coverage of the LiteBIRD Low-Frequency Telescope (LFT). We also assess the level of instrumental polarization the AHWP exhibits. We discuss paths for further development to minimize the instrumental polarization from the AHWP. This work is a development milestone toward the implementation of an AHWP for the LiteBIRD satellite. [ABSTRACT FROM AUTHOR]

Surface-emitting (SE) semiconductor lasers have changed our everyday life in various ways such as communication and sensing. Expanding the operation wavelength of SE semiconductor lasers to shorter ultraviolet (UV) wavelength range further broadens the applications to disinfection, medical diagnostics, phototherapy, and so on. Nonetheless, realizing SE lasers in the UV range has remained to be a challenge. Despite of the recent breakthrough in UV SE lasers with aluminum gallium nitride (AlGaN), the electrically injected AlGaN nanowire UV lasers are based on random optical cavities, whereas AlGaN UV vertical-cavity SE lasers (VCSELs) are all through optical pumping and are all with large lasing threshold power densities in the range of several hundred kW/cm2 to MW/cm2. Herein, we report ultralow threshold, SE lasing in the UV spectral range with GaN-based epitaxial nanowire photonic crystals. Lasing at 367 nm is measured, with a threshold of only around 7 kW/cm2 (~ 49 μJ/cm2), a factor of 100× reduction compared to the previously reported conventional AlGaN UV VCSELs at similar lasing wavelengths. This is also the first achievement of nanowire photonic crystal SE lasers in the UV range. Further given the excellent electrical doping that has already been established in III-nitride nanowires, this work offers a viable path for the development of the long-sought-after semiconductor UV SE lasers. [ABSTRACT FROM AUTHOR]

Fabrication of a through hole in a polyimide film (PI) was demonstrated by holographic ultraviolet (UV) nanosecond laser processing with a computer-generated hologram displayed on a phase-only spatial light modulator (SLM). The UV laser was directly modulated into a Bessel beam by a diffractive axicon displayed on the SLM. The direct modulation contributed to improved light-utilization efficiency of the UV laser and a simplified optical setup compared to the conventional method based on a combination of an SLM and harmonic generation using a nonlinear optical crystal. The Bessel beam reduced the number of pulse shots required for through-hole fabrication to 1/5 compared to the Gaussian beam near the ablation threshold energy of the PI film. Furthermore, adaptive optics was implemented in holographic laser processing to compensate for aberrations in the optical setup. The aberration was reduced to 1/5 compared with before the compensation. The proposed method is suitable for improving the throughput and accuracy of drilling, cutting, and additive manufacturing using UV lasers with industrial requirements. [ABSTRACT FROM AUTHOR]

A novel technology for the precise fabrication of quartz resonators for MEMS applications is introduced. This approach is based on the laser-induced chemical etching of quartz. The main processing steps include femtosecond UV laser treatment of a Cr-Au-coated Z-cut alpha quartz wafer, followed by wet etching. The laser-patterned Cr-Au coating serves as an etch mask and is used to form electrodes for piezoelectric actuation. This fabrication approach does not alter the quartz's crystalline structure or its piezo-electric properties. The formation of defects, which is common in laser micromachined quartz, is prevented by optimized process parameters and by controlling the temporal behavior of the laser-matter interactions. The process does not involve any lithography and allows for high geometric design flexibility. Several configurations of piezoelectrically actuated beam-type resonators were fabricated using relatively mild wet etching conditions, and their functionality was experimentally demonstrated. The devices are distinguished from prior efforts by the reduced surface roughness and improved wall profiles of the fabricated quartz structures. [ABSTRACT FROM AUTHOR]

The major goal of the paper is to provide empirical proof of view that innovative stochastic dynamic mass spectrometric equation D″SD = 2.6388·10−17·(< I2 > − < I > 2) determines the exact analyte concentration in solution via quantifying experimental variable intensity (I) of an analyte ion per any short span of scan time of any measurement, which also appears applicable to quantify laser-induced ultraviolet photofragmentation and high energy collision dissociation mass spectrometric processes. Triadimenol (1) and sucralose (2) using positive and negative polarity are examined. Laser irradiation energy λex = 213 nm is utilized. The issue is of central importance for monitoring organic micro-pollutants in surface, ground, and drinking water as well as tasks of risk assessment for environment and human health from contamination with organics. Despite the significant importance of the topic, answering the question of functional kinetic relations of such processes is by no means straightforward, so far, due to a lack of in-depth knowledge of mechanistic aspects of fragment paths of analytes in environment and foods as well as kinetics of processes under ultraviolet laser irradiation. Although there is truth in the classical theory of first-order reaction kinetics, it does not describe all kinetic data on analytes (1) and (2). A new damped sine wave functional response to a large amount of kinetics is presented. High-resolution mass spectrometric data and chemometrics are used. The study provides empirical evidence for claim that temporal behavior of mass spectrometric variable intensity under negative polarity obeys a certain scientific law written by means of equation above. It is the same for positive and negative soft-ionization mass spectrometric conditions. [ABSTRACT FROM AUTHOR]

Complete and highly selective nitration of tyrosine (Tyr) as a residue-specific modification in peptides was found without side reactions, using ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI) with a nitroaromatic reagent 3, 5-dinitrosalicylic acid (3,5-DNSA). The tyrosine nitration supported two propositions, namely, the UV-induced. NO2 attack reaction mechanism by Long et al. and the C–NO2 homolysis as a thermal process by Wiik et al. and Furman et al. With the UV-MALDI of peptides, a residue-specific reaction was observed in glycine (Gly) residue, i.e., an oxidation of the alpha-carbon of Gly due to attack of hydroxyl radical (.OH). [ABSTRACT FROM AUTHOR]

This report is about a continuous wave (CW) deep ultraviolet laser operation at 273 nm by intracavity frequency doubling of laser diode pumped Pr3+ doped LiYF4 lasers. We use two 3 W InGaN laser diodes, one 3 mm long Pr3+:LiYF4 (Pr:YLF) crystal and one 5 mm long beta-barium-borate (BBO) crystal, coherent radiation with an output power of 128 mW at 273 nm was obtained with a 2.9% optical to optical conversion efficiency. To the best of our knowledge, this is the first report detailing a Pr:YLF laser that emits light at 273 nm. [ABSTRACT FROM AUTHOR]

1-Pyrenylboronic acid (1-PBA) is a type of a reactive matrix useful for the analysis of polyfunctional compounds by MALDI mass spectrometry. It exhibits conventional matrix properties (absorption and transfer of laser radiation energy) and acts as a derivatizing reagent capable of interacting with vicinal functional groups under mild conditions and forming covalent adducts. Pyrenyl group in its structure, which has high ability to absorb UV laser quanta, ensures the detection of analyte derivatives containing a 1-PBA residue as radical cations, which is untypical for MALDI. The effectiveness of its use was earlier proved for compounds containing 1,2-diol fragments. This work presents additional cases of using this reactive matrix in the analysis of practically significant compounds of this type, demonstrating that 1-PBA can also react with distant OH groups. Many examples show its applicability to the study of various α-hydroxy acids and vicinal aminols and capability of forming cyclic covalent adducts with 1,2-diamines. [ABSTRACT FROM AUTHOR]

Epitaxial La0.7Sr0.3MnO3 thin films on SrTiO3 (001) single-crystal substrates were successfully prepared by a chemical solution deposition usage of an ultraviolet laser (KrF, λ = 248 nm)-assisted annealing at 400 °C. It was observed that the prepared thin films were amorphous when the laser energy density was below 50 mJ/cm2, and epitaxial La0.7Sr0.3MnO3 thin films were successfully obtained when the laser energy density was higher than 60 mJ/cm2. The epitaxial relationship is of La0.7Sr0.3MnO3(001)||SrTiO3(001) and La0.7Sr0.3MnO3[110]||SrTiO3[110]. With the enhancement of laser energy density, the temperatures of metal–insulator transition and magnetic transition are increased, and the resistivity is decreased. The results will provide a facile method to deposit epitaxial La0.7Sr0.3MnO3 thin films at low temperatures. [ABSTRACT FROM AUTHOR]

The small dimensions of superconducting tunnel junction (STJ) radiation detectors have motivated the development of STJ arrays to increase detection efficiency and statistical accuracy. We have used a pulsed UV laser and X-rays to characterize and understand non-uniformities in the response of different pixels in Ta-based STJ arrays. To separate the contributions of the detector and the readout electronics, we have also injected the pulses from an arbitrary waveform generator into the array's amplifier chain. We discuss the magnitude and the sources of the non-uniformity and approaches to reduce it. [ABSTRACT FROM AUTHOR]

Soft robotic hands can facilitate human–robot interaction by allowing robots to grasp a wide range of objects safely and gently. However, their performance has been hampered by a lack of suitable sensing systems. We present a flexible and stretchable multi-modal sensor network integrated with a soft robotic hand. The design of wired sensors on a flexible metalized film was embodied through a manufacturing approach that uses both UV laser metal ablation and plastic cutting simultaneously to create sensor electrode and stretchable conductive wires in a Kirigami pattern into a single network. We evaluated the interconnects and sensors by measuring an impedance change to each external stimulus and showed that are not substantially affected by stretching the network. With the sensor sheet wrapped around a soft robotic gripper, we demonstrated several interaction scenarios, including a warm burrito for food handling, and a warm baby doll for medical applications. [ABSTRACT FROM AUTHOR]

Disinfection eliminates pathogenic microorganisms and ensures a biosafe environment for human beings. The rapid spread of COVID-19 is challenging traditional disinfection methods in terms of reducing harmful side effects and conducting faster processes. Spraying large-scale chemical disinfectants is harmful to individuals and the environment, while UV lamp and light-emitting diode (LED) disinfection still requires a long exposure time due to the low irradiance and highly divergent beam characteristics. Given that a laser maintains a high irradiance over a long distance, we studied the effectiveness of lasers as a new disinfection method, and the results show the capability for ultrafast inactivation of SARS-CoV-2 virus with a 266 nm laser. This work confirms UV lasers as a good candidate for disinfection. [ABSTRACT FROM AUTHOR]

An electron blocking layer (EBL) is often utilized in the p-type region of AlGaN-based deep ultraviolet laser diodes (DUV LDs) to control electron overflow. However, Al-rich semiconductor DUV LD EBLs can be difficult to p-doping and have a highly-complicated structure. Furthermore, the composition of Al in quantum barriers (QBs) of multiple quantum wells (MQWs) affects the performance of AlGaN-based DUV laser diodes. Omitting the EBL and reducing the Al content of the QBs can enhance the optical confinement and optical output power. Observing the performance parameters, such as the optical confinement factor (OCF), emitted power, band diagram, carrier concentration, and stimulated recombination, may be an effective way to monitor these changes. In this paper, using the crosslight software LASTIP, we simulate and compare three DUV LD devices with a nominal wavelength of 267.5 nm. In contrast to the reference DUV LD with a p-type EBL, the proposed EBL-free DUV LD with reduced Al-composition QBs is applied in MQWs; this results in a 21% improvement in the OCF and an increase in the output power. [ABSTRACT FROM AUTHOR]

Ferrite composites composed of brittle ferrite ceramic, soft polymers and rubber pose a challenge for low-damage cutting. In this paper, nanosecond UV (Ultra Violet) laser was used to cut the ferrite composite flake with thickness of 0.3 mm. The HAZ (Heat Affected Zone) of nanosecond UV laser cutting composite sheet is studied, and an improved "Scanning-Cooling" strategy for reducing HAZ width is proposed. The results demonstrate that the improved scanning strategy suppresses the expansion of HAZ significantly, and its width is only 147.6 µm (reduced by 7.15 times). Furthermore, parameters are optimized on the basis of the improved strategy, and the narrowest HAZ width of 45.3 µm is obtained under high-laser frequency (120 kHz) and scanning speed (1400 mm/s). Improved scanning strategy and optimized parameters are used to cut and pattern the surface of the electromagnetic shielding patch, with edges of low thermal damage and uniform depth. [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]

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]

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]

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]

Gallium oxide (Ga2O3)-based photodetectors are attracting more and more attention for their wide range of applications in optical imaging, spatial communication, etc. In this work, solar-blind deep-ultraviolet thin-film transistors (TFTs) based on polycrystalline β-Ga2O3 thin film were constructed by pulsed laser deposition. The photoelectric performance of β-Ga2O3 TFT is effectively improved by a Si-doping method. The turn-on voltage (Von) of Si-doped β-Ga2O3 TFT is negatively shifted by 20 V, exhibiting enhancement-mode (E-mode) operation. The optimized Si-doped Ga2O3 TFT photodetector shows a high on/off ratio of ~ 105, a turn-off current (Ioff) of ~ 10−11 A at drain voltage (VD) = + 20 V, responsivity (R) of 3.23 A/W, detectivity (D*) of 4.41 × 1013 Jones, and a photocurrent/dark current (Ilight/Idark) of ~ 104 at gate voltage (VG) = − 5 V, VD = + 20 V under 254 nm light. The obtained results suggest that the Si-doping method can effectively modulate the Von of β-Ga2O3 TFT and promote photoelectric performance. [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]

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]

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]

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]

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 compact coastal-mounted sensor for detection of ultraviolet-induced fluorescence from oil slicks in coastal aquatic environments was constructed. By combining filters and a lens, the designed optical structures ensure that the sensor can effectively emit an ultraviolet laser by a xenon flash lamp and accurately capture and measure fluorescence emitted by oil slicks. Laboratory measurements of six oil samples were performed, and field recordings of natural seawater and oil slicks fluorescence were conducted. The data change rate recorded by the sensor can be used as a warning indicator for oil spills. Long-term measurement results obtained by deploying the proposed sensor in PetroChina-owned ports in Dalian, China indicate that the proposed sensor and detection method can be employed as a rapid detection system for oil spills on seawater surfaces. [ABSTRACT FROM AUTHOR]

The inorganic single crystal of potassium chromium sulphate (PCS) was grown by slow evaporation solution technique at room temperature. The grown crystal has been characterized by using UV, FTIR, photoluminescence technique, SHG and Vickers microhardness test and the detailed results have been reported for the first time. The grown PCS crystal was found to be crystallizing in centrosymmetric cubic structure. EDAX analysis affirms the elements present in the sample and substantiate the purity of the grown crystal. Functional groups of the PCS crystal were corroborated by FTIR spectral analysis. The UV–Visible spectrum was examined to determine the optical band gap. Additionally, the linear optical parameters such as extinction coefficient, reflectance, refractive index, dielectric constant, optical conductivity and electrical conductivity were determined. Thermal analysis, in the temperature range of 40–730 K, shows two endothermic peaks at 90 and 170 K. The PL spectrum recorded shows an intense blue emission at 490 nm indicating that the grown crystal can be beneficial for fluorescence in blue LED applications. The microhardness study reveals that the PCS crystal has a high mechanical strength, implying that it can endure significant stress without permanent deformation. The grown crystal was also subjected to second harmonic generation and the results of which has been discussed. PCS crystal could be used for third-order nonlinear optical applications and hence it is a third harmonic generator to produce UV laser light. [ABSTRACT FROM AUTHOR]

The effect of infrared, green, and ultraviolet laser radiation on the electrical resistance of the Ba0.8Sr0.2TiO3/LaMnO3 heterostructure is studied. Illumination increases the resistance in the temperature range of 80–200 K with a characteristic time of ~4–15 s. The negative effect of the photoconductivity is detected under irradiation by infrared, green, and ultraviolet radiation. [ABSTRACT FROM AUTHOR]

The modification of the polished {111} surface of single-crystal germanium (n-type of conductivity, resistivity 47 Ohm cm) as a result of exposure to focused frequency-pulse radiation of nanosecond ultraviolet Nd : YaG laser are studied by optical profilometry, as well as scanning electron and probe microscopy. It is revealed that the threshold of the plasma formation with the formation of a crater on the surface arises at the energy density of laser radiation E ~ 1.2–1.3 J/cm2. When the sample is stationary at E ~ 0.1 J/cm2 irreversible damage to the surface occurred. When scanning a surface with radiation at E ~ 0.50–1.15 J/cm2, in the absence of noticeable traces of crater formation, the formation of etching pits is observed with a regular triangular shape, the concentration of which is (3–5) × 105 cm–2. The shapes resemble dislocation etching pits obtained by selective chemical etching. Dislocations are detected by ablation as a result of exposure to laser radiation. The centers of ablation nucleation are dislocations emerging on the crystal surface. The transverse size of the etching pits is ~5–10 μm, and their overlap results in an alternating pattern of trihedral pyramids formed by the {111} planes. The rounded edges and tops of the pyramids are observed and the height of the profile of the figures is ~1–2 microns. The linear dimensions of the pits indicate a rapid course of the process. The rate of the formation of flat faces in the pits, which is ~0.1–0.3 m s–1, which is several orders of magnitude higher than the rate of formation of the same faces during the crystal growth is set based on the total time of exposure to radiation on the surface of ∼200 ns. The depth of the surface layer in which the structure was formed is ∼15 μm. [ABSTRACT FROM AUTHOR]

3D WLCSP with via last TSV and UV laser releasable temporary bonding technologies is an ideal scheme to meet the increasing high performance, low cost and small-form-factor requirements. In present paper, we demonstrate a thin 3D WLCSP process using 8 inch wafers, and a number of critical process technologies were developed to realize the final 3D assembly. For example, higher deposition temperature PECVD with single frequency was applied for the passivation layer growth owing to the good quality temporary bonding film with high temperature and chemical resistance properties. A new suspension litho coating method was successfully developed to complete redistribution layer and bump formation.Automated optical inspection (AOI) results show a good bump height and coplanarity with the yield of 99.1%. In favor of 355 nm UV laser, the carrier glass was easily debonded and the device wafer was completely cleaned. Finally, chip to chip stacking process was carried out to accomplish the final 3D stacking package. [ABSTRACT FROM AUTHOR]