Nanosecond Laser Research Articles

Optimization of Laser-Patterned Superhydrophilic–Superhydrophobic Surfaces on 304 Stainless Steel for Enhanced Fog Water Collection

This study focuses on creating micro-nano structures on the surface of 304 stainless steel using nanosecond lasers to achieve superhydrophobicity for fog water collection experiments in a fog chamber. By adjusting pattern parameters, an uneven wettability surface was processed, and six samples were placed at different positions in the chamber to study water collection efficiency from various surfaces. The experimental results indicate that the water collection efficiency of the patterned superhydrophobic surface is superior to that of the original surface, with the front sample collecting 0.4524 ± 0.005 g of water, representing a 90.38% improvement. As the kinetic energy of the fog flow gradually diminishes, a total of 1.1913 ± 0.005 g of water was collected, achieving a 60.25% improvement. The study also investigates the durability and optimal temperature conditions for fog water collection, ultimately achieving 1.4781 ± 0.005 g of water collection in a 5 °C fog environment, resulting in a 98.83% enhancement.

Room-temperature ferromagnetic MnGa nanoparticles in dilute magnetic semiconductor (Ga, Mn)As thin film: preparation and characterization

The GaAs based diluted magnetic semiconductor, (Ga, Mn)As, with the unique advantage of manipulating the spin and charge was widely investigated in the scientific community and considered as a potential material for the spintronic devices. However, its Curie temperature (Tc), which is limited to around 200 K, hinders the research progress of diluted magnetic semiconductors for potential device applications. Herein, we propose an approach to prepare the MnGa nanoparticles embedded in (Ga, Mn)As matrix using the magnetron sputtering deposition of Mn on GaAs surface, followed by the nano-second pulsed laser annealing (PLA), which gives aTcabove 400 K. We demonstrate that the MnGa nanoparticles are only formed in (Ga, Mn) As thin film during the nano-second PLA under a critical range of energy density (0.4-0.5 J cm-2). The highest achieved coercivity, saturation magnetization and remanent magnetization are 760 Oe, 11.3 emu cm-3and 9.6 emu cm-3, respectively. This method for preparing the hybrid system of ferromagnetic metal/dilute magnetic semiconductor builds a platform for exploring the interesting spin transport phenomenon and is promising for the application of spintronic devices.

Mo2TiAlC2 as a Saturable Absorber for a Passively Q-Switched Tm:YAlO3 Laser.

Owing to their remarkable characteristics, two-dimensional (2D) layered, MAX phase materials have garnered significant attention in the field of optoelectronics in recent years. Herein, a novel MAX phase ceramic material (Mo2TiAlC2) was prepared into a saturable absorber (SA) by the spin-coating method for passively Q-switching (PQS), and its nonlinear optical absorption properties were characterized with a Tm:YAlO3 (Tm:YAP) nanosecond laser. The structure characteristics and composition analysis revealed that the Mo2TiAlC2 material exhibits a well-defined and stable structure, with a uniform thin film successfully obtained through spin coating. In this study of a PQS laser by employing a Mo2TiAlC2-based SA, an average output power of 292 mW was achieved when the absorbed pump power was approximately 4.59 W, corresponding to a central output wavelength of 1931.2 nm. Meanwhile, a stable pulse with a duration down to 242.9 ns was observed at a repetition frequency of 47.07 kHz, which is the narrowest pulse width recorded among PQS solid-state lasers using MAX phase materials as SAs. Our findings indicate that the Mo2TiAlC2 MAX phase ceramic material is an excellent modulator and has promising potential for ultrafast nonlinear photonic applications.

Magneto‐Optical Control of Ordering Kinetics and Vacancy Behavior in Fe–Al Thin Films Quenched by Laser

One of the issues arising in materials science is the behavior of nonequilibrium point defects in the atomic lattice, which defines the rates of chemical reactions and relaxation processes as well as affects the physical properties of solids. It is previously theoretically predicted that melting and rapid solidification of metals and alloys provide a vacancy concentration in the quenched material, which can be comparable to that quantity at the point of melting. Here, the vacancy behavior is studied experimentally in thin films of the near equiatomic Fe–Al alloy subjected to nanosecond laser annealing with intensities up to film ablation. The effects of laser irradiation are studied by monitoring magneto‐optically the ordering kinetics in the alloy at the very ablation edge, within a narrow (micron‐scale) ring‐shaped region around the ablation zone. Quantitatively, the vacancy supersaturation in the quenched alloy has been estimated by fitting a simulated temporal evolution of the long‐range chemical order to the obtained experimental data. Laser quenching (LQ) of alloys and single‐element materials will be a tool for obtaining novel phase states within a small volume of the crystal.

Tunable optical limiting in silver nanoparticle-naphthophenanthridine hybrids

Incorporation of functional nanoparticles into liquid crystals has emerged as a promising approach to create liquid crystal nanocomposites with superior opto-electronic properties. The properties of self-assembled supramolecular structures change remarkably upon the dispersion of a minute amount of metal nanoparticles in them. The effect of dispersing alkyl thiol-functionalized silver nanoparticles (Ag NP) in Naphthophenanthridine discotic liquid crystals on the nonlinear optical (NLO) properties is discussed in this work. Discotic liquid crystals (DLC) are synthesized via N-annulation of hexabutoxytriphenylene-1-amine with heptanaldehyde through the Pictet–Spengler reaction. A uniform dispersion of about 1–3 wt% Ag NPs in the columnar matrix enhances the nonlinear optical absorption, when measured under excitation by nanosecond laser pulses at 532 nm. By changing the amount of Ag NP loading, the nonlinear response of the hybrid can be tuned. These results indicate that the Ag-DLC hybrids are potential candidates for applications in NLO devices such as tunable optical limiters.

A green approach to improve antibacterial properties of PVC/PVDF film doped by silver nanoparticles via nanosecond laser ablation for wound healing application

Nanocomposite films of (30% PVC/70% PVDF) blend containing silver nanoparticles were synthesized via pulsed laser ablation route (PLA). Changes in physical characterization of PVC/PVDF blend before and after the incorporation of AgNPs have been studied. FTIR results confirms the interaction between AgNPs and PVC/PVDF. XRD results obtain the existence of peak at 38.42̊ in sample PVC/PVDF/Ag4 which confirm the embedded AgNPs in the high concentration. SEM photos confirm the distribution of silver nanoparticles on the surface of the sample in spherical shape which approved the dispersion of silver nanoparticles in PVC/PVDF blend. The inhibitory zone diameters observed for PVC/PVDF/Ag4 against Escherichia coli, Klebsiella pneumonia, Staphylococcus aureus, and Bacillus cereus were recorded as 11 ± 1, 10 ± 1, 15.7 ± 0.6, and 17.7 ± 0.6, respectively. PVC/PVDF/AgNPs nanocomposite film could be suggested for biomedical applications such as wound healing products.

Nanosecond Laser Passivation and Corrosion Resistance Mechanism on the Surface of 2205 Duplex Stainless Steel

In addressing issues related to defects in laser quenching technologies, this study undertakes surface passivation treatment on 2205 duplex stainless steel. The investigation explores the impact of different laser parameters on the corrosion resistance of the passive film on the steel surface. The findings may provide theoretical references for the laser passivation treatment and corrosion resistance mechanism of steel surfaces.

Simultaneous laser polishing and N-doping of niobium

Superconducting niobium is the base material for many modern particle accelerators. The high cleanliness requirements in all radio frequency superconductor technology have led to the development of complex cleaning processes in recent decades. High-pressure rinsing, heating processes under vacuum and gas atmospheres as well as chemical and electrochemical polishing are commonly applied procedures, that are required to obtain the properties needed for their application. In order to optimize the surface finish of Nb materials in a more environment-compatible way, i.e., with less energy consumption and avoiding hazardous liquids, we report on a combination of simultaneous N-doping and laser polishing here. A nanosecond laser was employed, and the prepared Nb surfaces were investigated with a combination of electron microscopy, x-ray fluorescence spectroscopy (EDX), optical profilometry, and x-ray absorption spectroscopy (EXAFS) to show the effect of different N2-pressures during the laser polishing procedure in an ultrahigh vacuum chamber. The results show that for N2-pressures above ca. 10−3 mbar, traces of nitrogen can be observed by both EDX and EXAFS. In parallel, a smoothing of the surfaces occur, with slightly different roughnesses and microstructures of the polycrystalline Nb surfaces depending on the N2-pressure.

Intelligent multi-parameter control of a rectangular pulse in a passively mode-locked fiber laser

Rectangular pulses with tunable width and intensity in fiber lasers are critical for the study of nonlinear pulse dynamics and applications of nanosecond laser sources. However, due to the complex nonlinear dynamics within the laser cavity, precisely controlling multiple parameters of the rectangular pulses in fiber lasers remains challenging. Here, we propose an approach for intelligently controlling the intensity and width of rectangular pulse using an improved particle swarm optimization (PSO) algorithm in a passively mode-locked fiber laser with a nonlinear polarization rotation (NPR) technique. By automatically adjusting the electronic polarization controller (EPC) and pump power, multiple parameters of the output rectangular pulse can be effectively tailored, and thus, to desirable ones. This enables the flexible setting of the intensity and width of the rectangular pulse within the permissible range in a passively mode-locked fiber laser. Our approach provides a promising way to meet the diverse demands of seed laser source in scientific and engineering fields.

Nanosecond laser interference ablation of fluorine-free aluminum alloy surfaces for dynamic adhesion and static wettability synergistically modulating water collection

Water collection from mist is a potential solution to water scarcity, which is a critical issue worldwide. In this paper, laser interference ablation assisted with stearic acid immersion has been used to achieve synergistic modulation of dynamic adhesion and static wettability for water collection on fluorine-free aluminum alloy surface. The research demonstrates that there is an optimal balance point between dynamic adhesion and static wettability for water collection. This optimal point shifts toward low dynamic adhesion at the high misting rate due to the flooding on metastable surfaces with high dynamic adhesion. In addition, wetting transition induced by tilting is observed on metastable surfaces. The good stability of the proposed fluorine-free surface has been demonstrated by the long-term water collection and long periods of immersion in water. This work can provide theoretical inspiration and a scalable preparation method for green and stable water collection strategies.

Conductive Biocomposite Made by Two-Photon Polymerization of Hydrogels Based on BSA and Carbon Nanotubes with Eosin-Y.

Currently, tissue engineering technologies are promising for the restoration of damaged organs and tissues. For regeneration of electrically conductive tissues or neural interfaces, it is necessary to provide electrical conductivity for the transmission of electrophysiological signals. The developed biocomposite structures presented in this article possess such properties. Their composition includes bovine serum albumin (BSA), gelatin, eosin-Y and single-walled carbon nanotubes (SWCNTs). For the first time, a biocomposite structure was formed from the proposed hydrogel using a nanosecond laser, and a two-photon absorption cross section value of 580 GM was achieved. Increased viscosity over 3 mPa∙s and self-focusing with a nonlinear refractive index of 42 × 10-12 cm2/W make it possible to create a biocomposite structure over the entire specified area. The obtained electrical conductivity value was 19 mS∙cm-1, due to the formation of effective electrically conductive networks. For a biocomposite with a concentration of gelatin 3 wt. %, formed by low-energy near-IR pulses, the survival of Neuro 2A nerve tissue cells was confirmed. The obtained results are important for the creation of new tissue engineering structures and neural interfaces from a biopolymer hydrogel based on the organic dye eosin-Y and carbon nanotubes by two-photon polymerization.

Dynamic characterization of plasma and combustion wave interactions during millisecond-nanosecond combined laser-induced enhanced damage on fused silica

Fused silica, which is widely used in optical systems, limits the load capacity of the optical system when it is damaged by laser irradiation. In this paper, a combined millisecond-nanosecond pulsed laser induced triple combustion wave dynamics model for fused silica generation is developed. The relationship between pulse delay and the dynamic propagation of plasma and combustion waves induced by combined laser-induced fused silica was studied from three aspects: theory, simulation, and experiment. The results show that the energy deposition of the nanosecond laser injects energy into the dilute plasma, which increases the speed of the double-burning wave to form a triple-burning wave. In addition, it was found that the combined effect of viscous shear between the plasma plume and the air exacerbates the degree of imbalance in the Knudsen layer instantaneously releasing pressure and increasing the complexity of plasma and combustion wave propagation, recoil pressure produces a more complex crack network on the fused silica surface. The results provide a better understanding of the propagation properties of plasma and triple-burning waves during combined millisecond-nanosecond induced fused silica damage.

Patchy Dermal Melanocytosis: Differential Diagnosis and Management.

Nevus of Ito and Mongolian spots are distinct clinical presentations of patchy dermal melanocytosis, characterized by similar dermatological manifestations that can pose diagnostic difficulties for clinicians. This review aims to consolidate current understanding and research advancements on these conditions to facilitate clinical diagnosis, differential diagnosis, and management. A comprehensive search of databases including PubMed and Google Scholar was conducted, along with an analysis of pertinent literature retrieved from reference lists spanning nearly four decades. Epidemiological, clinical, and pathological profiles exhibit nuanced differences between the two conditions, with unique expressions under electron microscopy and the regression possibility. It is noteworthy that most Mongolian spots naturally fade with advancing age, in contrast to nevus of Ito, which persist and may potentially evolve into malignant lesions. While picosecond laser treatment has shown greater efficacy than nanosecond lasers, the lower-energy approach holds particular promise in pediatric cases. The therapeutic landscape for patchy dermal melanocytosis is evolving, shifting from selective photothermal action to photomechanical or subcellular photothermal modalities. This review underscores the importance of meticulous clinical assessment and the potential of innovative therapeutic approaches in managing these conditions.

An improved laser photo-detachment diagnostic for negative ion density measurement

A photo-detachment Langmuir probe is a crucial tool because it gives a point measurement of negative ion density. The detection circuitry of a photo-detachment diagnostic with nanosecond laser pulses is critical for the accuracy of the results. Applying the electromagnetic theory to the design of the photo-detachment system has allowed it to stabilize its frequency response up to ~445 MHz, providing a significantly higher time resolution than in a common photo-detachment circuit setup. A systematic design rule is given in this paper to standardize the proper circuit. The new standard allows comparison between laboratories without concern for electronic parameter differences. The high-time resolution result shows three different peaks in the photo-detached electron current. This paper identified that the first peak is the most correlated to negative-ion density information, and the second and third peaks are related to background electrons interacting with build-up potential.

Blue lasers using low-toxicity colloidal quantum dots.

Blue lasers play a pivotal role in laser-based display, printing, manufacturing, data recording and medical technologies. Colloidal quantum dots (QDs) are solution-grown materials with strong, tunable emission covering the whole visible spectrum, but the development of QD lasers has largely relied on Cd-containing red-emitting QDs, with technologically viable blue QD lasers remaining out of reach. Here we report on the realization of tunable and robust lasing using low-toxicity blue-emitting ZnSe-ZnS core-shell QDs that are compact in size yet still feature suppressed Auger recombination and long optical gain lifetime approaching 1 ns. These characteristics allow us to handle the blue QDs like laser dyes for liquid-state amplified spontaneous emission and lasing. The blue QD laser is operated under quasi-continuous-wave excitation by solid-state nanosecond lasers. A Littrow-configuration cavity enables narrow linewidth (<0.2 nm), wavelength-tunable, coherent and stable laser outputs without circulating the solution. These results indicate the promise of ZnSe-ZnS QDs to fill the 'blue gap' of QD lasers and to replace less stable blue laser dyes for a multitude of applications.

Facile fabrication of foldable electrospun nanofiber electrodes for electrodes for electronic biosensing

This study presents a rapid, sensitive and selective sensor based on electrospun nanofibers on laser-patterned electrodes, in which the laser micromachining process can directly fabricate the graphene electrode device for the electronical detection of glucose molecule. The layer of graphene film was formed on the glass substrate by a screen printing technique, and then the graphene electrodes can be fabricated by the ultraviolet (UV) nanosecond laser process with the wavelength of 355 nm. Based on the controlled the laser fluence and pulses, the electrode gap of 60 μm within the device can be fabricated. The polyvinyl alcohol (PVA) and glucose oxidase (GOD) composite nanofiber with weight percentage of 8% can be used by the electrospun process with used Glutaraldehyde(GA) steam for cross linking process. After that, it is blended with the conductivity of poly(3,4-ethylenedioxythiophene): poly (styrene sulfonate) (PEDOT:PSS), and the foldable nanofiber structures was made by electrospun process on the graphene electrode device. Finally, the electrical detection of graphene electrode device with the nanofibers at different concentrations of glucose can be measured, resulting in the linear variation is detecting the glucose concentration ranging form 0.01 to 3.12 mM. This work indicated that the low concentration and highly sensitive can be used for electronic biosensors

Enhanced stability and durability of Cassie-Baxter state in aluminum-based superhydrophobic surfaces fabricated via nanosecond laser ablation

The stability of the Cassie-Baxter (CB) state plays a crucial role in the application of metallic superhydrophobic surfaces, especially in low-temperature and high-humidity environments. Despite the extensive research on superhydrophobic properties achieved through various micro/nanostructures, the instability of the CB state remains a significant obstacle to commercializing these surfaces. In this study, we present a hybrid method combining nanosecond laser ablation and chemical modification to fabricate superhydrophobic aluminum surfaces. Three distinct micro/nanostructures are prepared and their CB state stability is evaluated through evaporation and underwater pressure tests. The results show that surfaces with conical microstructures exhibit the most stable CB state. Additionally, these structures can spontaneously transition from the Wenzel to CB state during icing/melting cycles, maintaining their superhydrophobicity after 15 cycles. This scalable, cost-effective method produces surfaces with excellent CB state stability and durability, making them promising for various industrial applications.

Nanostructured Gd2O3:Yb Micropowder for Antibacterial Hyperthermia

A method has been proposed for photoinduced hyperthermia of pathogenic Gram-negative bacteria P. aeruginosa using Gd2O3:Yb micropowder. It is based on the possibility of laser excitation of anti-Stokes luminescence on ytterbium ions in the gadolinium oxide micropowder, which allows us, on the one hand, to heat the powder to the required temperature and, on the other hand, to accurately control the powder temperature using remote luminescent thermometry. It has been demonstrated that the long-term irradiation of the Gd2O3:Yb micropowder with 1035-nm nanosecond laser radiation changes the shape of anti-Stokes luminescence spectra associated with micropowder heating in the range from 27 to 63°C. The application of the proposed photoinduced hyperthermia method to a mixture of solutions of the Gd2O3:Yb micropowder and P. aeruginosa bacteria demonstrates a decrease in the bacterial population by 90%.

Mechanism of UV photodegradation of fluoroquinolone antibiotic ciprofloxacin in aqueous solutions

Mechanism of direct UV photolysis of the zwitterionic and anionic forms of the quinolone antibiotic ciprofloxacin (CIP) was revealed by combination of nanosecond laser flash photolysis, steady-state photolysis coupled with high resolution LC-MS and DFT quantum-chemical calculations. For both forms, the main intermediate is a dissociative triplet state, which loses a fluorine ion to form a triplet carbocation; subsequent solvent attack of the latter leads to the formation of products of hydroxylation both the aromatic ring and the piperazyl substituent. Correspondingly, the quantum yield of photolysis of both CIP forms does not depend on the excitation wavelength, but depends on the concentration of dissolved oxygen. Secondary photolysis leads to a number of products of oxidation of the aromatic system, as well as oxidation, opening and full destruction of the piperazinyl substituent. The results obtained may be important for understanding the fate of quinolone antibiotics in UVC disinfection processes and in natural waters under the action of sunlight.

Micro/Nano Hierarchical Dumbbell-like and Micropapillae Structure Improves Light Absorption and Facilitates Anti-icing/Deicing Performance.

The emergence of ice formation and accretion presents significant challenges, catalyzing an urgent need for clean and efficient anti-icing solutions. Solar energy, a powerful and sustainable resource, can be integrated with the micronano-structured superhydrophobic surface to enhance anti-icing and deicing performance through the solar photothermal effect, overcoming the limitations of a traditional superhydrophobic surface. Herein, inspired by bamboo and lotus leaves, a synergetic photothermal anti-icing superhydrophobic surface (PASS) has been developed. This was achieved through nanosecond laser ablation and chemical modification, resulting in a surface with remarkable superhydrophobic low adhesion (water contact angle >167°, rolling angle < 2°). The PASS notably extends the freezing time of water droplets to 1056 s and delays frost formation to 47 min at 60% humidity. Moreover, the surface retains its superhydrophobic properties after enduring several rigorous tests. Additionally, the photothermal conversion efficiency reaches up to 67.31%, and the temperature increases to 95.6 °C under 1.5 sun illumination for 600 s in ambient conditions (Tr = 7 °C). The ice melting time is only 120 s under 1 sun illumination at -15 °C. Consequently, the PASS sample stands as a preeminent strategy for anti-icing and deicing pursuits owing to its exceptional photothermal proficiency, superhydrophobicity, and enduring robustness.