YAG Nanosecond Laser Pulses Research Articles

Pulsed laser ablation production of Ni/NiO nano electrocatalysts for oxygen evolution reaction

Efficient and sustainable materials are requested to overcome the actual major issues related to green energy production. Ni/NiO nanoparticles (NPs, 2–4 nm in size) produced by Pulsed Laser Ablation in Liquid (PLAL) are reported as highly efficient and stable electrocatalysts for oxygen evolution reaction (OER) in water splitting applications. Ni/NiO NPs dispersions are obtained by ablating a Ni target immersed in deionized water with an Nd:YAG nanosecond pulsed laser. NPs size and density were driven by laser energy fluence (ranging from 8 to 10 J cm−2) and shown to have an impact on OER performance. Ni/NiO NPs were characterized by scanning and transmission electron microscopy, x-ray diffraction, photoemission spectroscopy, and Rutherford back-scattering spectrometry. By drop-casting onto graphene paper, anode electrodes were fabricated for electrochemical water splitting in alkaline electrolytes. The extrinsic and intrinsic catalytic performances for OER have been quantified, achieving an overpotential of 308 mV (at a current density of 10 mA cm−2) and unprecedented mass activity of more than 16 A mg−1, using NPs synthesized with the highest and lowest laser energy fluence, respectively. The impact of NPs’ size and density on OER performances has been clarified, opening the way for PLAL synthesis as a promising technique for highly efficient nano-electrocatalysts production.

A Comparative Study on the Effect of Peri-Implant Infection Management Lasers (1064-nm Q-Switch Nd:YAG, 1064-nm Nd:YAG and 980-nm Diode) on Titanium Grade 4 Surface

Over the past 10 years, the number of dental implants has grown significantly. This increase has consequently led to an elevation of the statistics related to cases of peri-implantitis. Laser therapy has conquered a place among the therapies of excellence to treat peri-implantitis. However, the laser device used could influence the therapy’s success. The aim of this comparative experimental work was to highlight the differences in the work on grade 4 titanium surfaces of the most commonly used laser lights in this field, taking into consideration any structural damage that lasers could cause to implant surfaces. The lasers examined were a 980 nm diode laser; a 1064 nm Nd:YAG laser; and a new generation of 1064 nm Nd:YAG Q-switch nano pulsed laser. We evaluated the titanium temperature increase, the pre- and post-treatment two-dimensional surface appearance observed under the scanning electron microscope; finally, the three-dimensional pre- and post-treatment topographic analysis was assessed using atomic force microscopy. We showed that the 1064-nm Q-switch Nd:YAG nanosecond pulsed laser appears to be more suitable for the preservation of implant morphology because of the absence of the induction of metal damage.

Vibration fatigue life and fracture analysis of 2024-T351 aluminum alloy treated by cryogenic laser peening.

A Nd:YAG nanosecond pulsed laser was used to carry out laser peening and cryogenic laser peening (CLP) experiments at room temperature (25°C) and cryogenic temperature (-100∘C), respectively, on the vibration fatigue life of 2024-T351 aluminum alloy. It was found that CLP induced a higher amplitude of compressive residual stress and improved the nano-hardness and the elastic modulus. Compared to the LP-ed samples, the fatigue life of the CLP-ed specimens was higher, and the initiation and propagation of fatigue cracks were more effectively inhibited. Therefore, CLP can effectively improve the fatigue performance of aluminum alloys.

Histological analysis of tattoo removal by water cavitation bubbles and jet formation using Nd: YAG and nanosecond laser pulses

Background: For efficient laser tattoo removal, photodisruption of tissue can ensure a very powerful means to shutter ink granules. At very high laser intensity level, photodisruption dominates and selective photothermolysis will have secondary effect in clearing the tattoo ink. Lower laser fluence is all what to trigger non-linear photons absorption and the generation of exploding cavitation bubbles that can tremendously hammer the ink granules.Subjects, materials, and methods: Three domestic white rabbits; each received simultaneous injections of a color pigment tattoo under general anesthesia, followed by a single session of (1064) Q.S Nd: YAG nanosecond laser pulses for tattoo removal.Results and Discussion: Spectroscopic properties of black, dark brown and red tattoo inks were studied. Near threshold laser fluence was selected to select the optimum conditions for obtaining scar-free treatment. Histological images of the biopsies, taken after thirty days of laser treatment of black, dark brown and red tattoos showed a marked reduction in pigment granules size with no appearance of hyperplasia or inflammatory cells. Coexistence of macrophages was suggested to be responsible for actively phagocytizing the laser-dispersed tattoo fragments.Conclusion: skin biopsies have demonstrated ink granules local redistribution. Photodisruption at 1064nm laser effectively targeted black and dark brown tattoo pigments by the generation of cavitation bubbles. The weaker laser light absorption of red pigments at 1064nm only showed tattoo clearance when using 532nm wavelength.

Experimental investigation of deep-hole micro-drilling of glass using LIPAA process

ABSTRACT This paper aims to study the mechanism of glass deep-hole micro-drilling by the Laser-Induced Plasma-Assisted Ablation (LIPAA) process. The Micro-drilling of glass was studied under various laser intensities. Nd:YAG nanosecond pulsed laser with 12 ns pulse duration was used as the laser light source. Copper was used as the metal target for the experiments. It is shown that laser glass micro-drilling is divided into two ablation stages. In the first stage, ablation is done by the brittle failure of glass caused by the collision of plasma plume with the glass surface. Exertion of mechanical pressure is also an important factor in the first few laser shots. Due to mechanical failure, glass microstructure changes in the focal spot. Second stage ablation is directly conducted by the thermal mechanism through absorption of laser by the glass. The hole produced on the glass by thermal mechanism is free of cracks. Cylindricity and roundness of the hole are very desirable. Laser intensity plays a vital role in material removal rate, hole depth and diameter. The process can be used for high-speed deep-hole micro-drilling of transparent materials to laser with good surface integrity and high-aspect ratio.

Modifications of Hydroxyapatite properties by nanosecond Nd: YAG laser pulses

Lasers unique characteristics can be utilized to enhance hydroxyapatite (HAp) properties by modifying its surface features; namely microhardness and morphology. Laser treatment is a promising route to enhance surface properties of HAp coatings and HAp components. Hydroxyapatite pressed pellets were laser-treated by Q-Switched Nd: YAG nanosecond laser pulses with different laser fluences to alter their surface specifications. A significant increase in laser-treated microhardness was observed compared to the control sample. The use of lasers demonstrated clear improvement of the HAP surface against demineralization. Digital Micro Vickers hardness tester, Atomic Force Microscope, and Scanning Electron Microscope were employed to investigate structural changes and laser-treated depth. New aspects for delaying HAp surface abrasion were explored; showing reduced wear after laser treatment.

Nd:YAG纳秒脉冲激光水下烧蚀锗靶研究

Laser ablation in liquid can modify the target morphology, as well as fabricate micro-nano materials in the solution. Many researchers were attracted by this method, because it was chemically clean, low cost and simple operation. Here, germanium particles with micron and submicron scale were prepared by Nd: YAG nanosecond pulsed laser ablation in water. The characteristics of germanium particles were studied by ultraviolet-visible absorption spectrum (uv-vis), X-ray diffraction (XRD) and scanning electron microscope (SEM). Then, studied the target morphology and ablation quality were studued after laser ablation of the germanium target. It was found that the ablation quality increases with the number of laser pulses, but the increase rate decreases, which means the ablation efficiency decreases. Finally, the reasons for the decrease of ablation efficiency were discussed to provide theoretical reference and feasible strategy for improving the preparation rate of materials fabricated by laser ablation in liquid.

Laser cleaning of slots of chrome-plated die

Removal of rubber contaminants from chrome-plated die with slots was studied using an acousto-optic Q-switched Nd:YAG nanosecond pulsed laser with an average power of 100 W. The contaminants deposited non-uniformly on the die can be distinguished as rubber particles with a nominal diameter of 10 μm, located mainly in the plane region (PR), while a thick rubber layer up to 50 μm can be discovered in the slot region (SR). Results show that, by positive defocusing the laser with single pulse energy density of 0.97 J/cm2 and adding the argon gas, single-scan high-efficiency cleaning of the slots could be achieved, and the net cracks on the chromium layer could be cleaned too. The optical microscopy (OM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and atomic force microscopy (AFM) were used to investigate the surface of the die before and after cleaning.

Solid state ASE from an oligomer (HOTF) in polymethyl methacrylate

Solid state laser material based on oligomer 9,9,9′,9′,9″,9″-hexakis(octyl)-2,7′,2′,7″-trifluorene (HOTF) doped poly methyl methacrylate (PMMA) was fabricated. The absorption spectrum showed only one band at 355 nm with different concentration ratios (7–12 mM); thus the broad absorption band could be attributed to the α-phase formation. In addition, there was no new band detected at the end of the spectrum as the concentration increased. This indicates the absence of the β-phase formation for all concentrations used. On the other hand, HOTF exhibited two distinct emission bands at 420 and 470 nm for 7 mM concentration. When the concentration was increased to 9 mM, the intensity of the band 470 nm increased. Further increase the concentration to 12 mM, the intensity of the band at 420 nm totally vanished and there was only one band at 470 nm. Therefore, the band at 470 could be attributed to excimer state. However, the results revealed that there is a strong correlation between quantum yield of fluorescence and fluorescence life-time, absorption cross section, and emission cross section. Under pulsed laser excitation. The ASE spectrum of HOTF has been obtained using a transverse cavity configuration where the conjugated HOTF was pumped by the third-harmonic of Nd:YAG nanosecond pulsed laser (λex = 355 nm). We demonstrate that HOTF in the solid state could produce an ASE peak at 420 nm. The obtained results were compared with the HOTF and a conducting polymer poly (9,9-dioctylfluorene) (PFO)in the liquid state.

Effect of lens focusing distance on laser-induced silicon plasmas at different sample temperatures

We investigated the dependence of laser-induced breakdown spectral intensity on the focusing position of a lens at different sample temperatures (room temperature to 300 °C) in atmosphere. A Q-switched Nd:YAG nanosecond pulsed laser with 1064 nm wavelength and 10 ns pulse width was used to ablate silicon to produce plasma. It was confirmed that the increase in the sample’s initial temperature could improve spectral line intensity. In addition, when the distance from the target surface to the focal point increased, the intensity firstly rose, and then dropped. The trend of change with distance was more obvious at higher sample temperatures. By observing the distribution of the normalized ratio of Si atomic spectral line intensity and Si ionic spectral line intensity as functions of distance and temperature, the maximum value of normalized ratio appeared at the longer distance as the initial temperature was higher, while the maximum ratio appeared at the shorter distance as the sample temperature was lower.

A self-consistent first order analytical model of plasma jets: A two fluids approach

Laser ablation processes have applications from thin film deposition to isotope separation, through plasma plume generation, which suggests mass and charge separation of species as the plume evolves. However, they do not have a theoretical model that takes into account equilibrium configurations. The present work is dedicated to build a simplified non-neutral self-consistent two fluid model, based on a few parameters for the first and fast analysis of morphological and statistical features for typical experimental plasma plumes. The velocity field, density profiles, and normalized histograms for the velocity module associated with the species were determined. The electrostatic potential field was also depicted. The model was validated for laser-ablated plasma plumes and found to be in good agreement with the experimental molybdenum plasma jet generated by the interaction of the Nd:YAG nanosecond pulsed laser with the solid target expanding in air at atmospheric pressure.

Ultra-pure silicon nanofluid by laser ablation: thermal diffusivity studies using thermal lens technique

Ultra-pure silicon nanoparticles were synthesized through pulsed laser ablation (PLA) in ethanol medium using a Q-switched Nd:YAG nanosecond pulsed laser. Concentration dependence of thermal diffusivity of the silicon nanofluid was studied using dual beam thermal lens technique at room temperature. The thermal diffusivity was found to be decreased with increase in concentration of silicon nanoparticles. This property of nanofluids can be used for thermal trapping and insulating applications.

Comparative study on Cu, Al and Cu-Al alloy nanoparticles synthesized through underwater laser ablation technique

In this work, we have done a comparative study on Cu, Al and Cu-Al alloy nanoparticles synthesized through underwater pulsed laser ablation technique. Second harmonic of Nd: YAG nanosecond pulsed laser with 50 J/cm2 fluence was used to ablate the Cu (99.99%), Al (99.99%) and Cu-45% Al alloy targets. However, the laser synthesis of Cu-Al alloy nanoparticles is not yet investigated best of our knowledge. Thus, it is the first time we have synthesized alloy nanoparticles through underwater laser ablation in a chemical free environment. Moreover, we have used abundant earth metals to synthesize the nanoparticles. The particles morphology, shape and size were analysed through SEM and DLS analysis where we have observed that the average size of alloy nanoparticle was much smaller than its monometallic counterparts. The crystallinity and elemental analysis of synthesized nanoparticles were studied through XRD and EDS respectively. The alloy formation of nanoparticles was evident from such structural investigations. Further a comparative study on optical properties of alloy and monometallic particles were investigated through UV-Vis absorption spectroscopy. Alloy particle shows a remarkable improvement in optical absorption in comparison to its parent materials.

High level active n+ doping of strained germanium through co-implantation and nanosecond pulsed laser melting

Obtaining high level active n+ carrier concentrations in germanium (Ge) has been a significant challenge for further development of Ge devices. By ion implanting phosphorus (P) and fluorine (F) into Ge and restoring crystallinity using Nd:YAG nanosecond pulsed laser melting (PLM), we demonstrate 1020 cm−3 n+ carrier concentration in tensile-strained epitaxial germanium-on-silicon. Scanning electron microscopy shows that after laser treatment, samples implanted with P have an ablated surface, whereas P + F co-implanted samples have good crystallinity and a smooth surface topography. We characterize P and F concentration depth profiles using secondary ion mass spectrometry and spreading resistance profiling. The peak carrier concentration, 1020 cm−3 at 80 nm below the surface, coincides with the peak F concentration, illustrating the key role of F in increasing donor activation. Cross-sectional transmission electron microscopy of the co-implanted sample shows that the Ge epilayer region damaged during implantation is a single crystal after PLM. High-resolution X-ray diffraction and Raman spectroscopy measurements both indicate that the as-grown epitaxial layer strain is preserved after PLM. These results demonstrate that co-implantation and PLM can achieve the combination of n+ carrier concentration and strain in Ge epilayers necessary for next-generation, high-performance Ge-on-Si devices.

Thermal annealing performance of sulfur-hyperdoped black silicon fabricated using a Nd:YAG nanosecond-pulsed laser

Compared to femtosecond-pulsed laser and ion implantation with chemical texturing methods, the nanosecond (ns)-pulsed laser method is inexpensive and efficient for fabricating a microstructured and hyperdoped crystalline silicon surface (usually known as black Si), facilitating the industrial manufacturing of optoelectronic devices. However, the ns-pulsed laser method has been rarely studied in material post-processing and device manufacturing. In this study, a microstructured and sulfur-hyperdoped p-type Si〈100〉 wafer surface was fabricated using a neodymium-doped yttrium aluminum garnet (Nd:YAG) ns-pulsed laser irradiation in sulfur hexafluoride gas. The effects of thermal annealing on the morphological, optical (visible and infrared (IR) spectra), and electrical properties of black Si samples were evaluated. The results show that the small particles and protrusions, overlying conical structures of the samples, decreased after the annealing. The light reflectance of the samples in the wavelength range 400–1000nm decreased by ∼2%, and a high IR absorptance (λ=1100–2400nm) was observed. The IR absorptance decreased slowly from 86% to 60% with an annealing time of 30 (or 60) min and temperature increase from 575K to 800K (corresponding to the increase in diffusion length of S-dopant from 0.09nm to 68.63nm). Furthermore, sheet carrier concentration and resistivity of the black Si samples increased and decreased with increasing S-dopant diffusion length, respectively. The improvements in electrical property indicate that thermal annealing can enhance the activation of S-dopant and electrical rectification of the samples. These are important for developing Si-based broad-spectrum solar cells and IR detectors.

A Rapid and Cost-Effective Laser Based Synthesis of High Purity Cadmium Selenide Quantum Dots.

A rapid and cost effective method is developed to synthesize high purity cadmium Selenide (CdSe) quantum dots in acetone medium using second harmonic of Nd:YAG nanosecond pulsed laser of 532 nm wavelength. The thermal agglomeration due the nanosecond pulse duration of the laser was successfully eliminated by using unfocussed laser beam and thereby providing a favorable conditions for the synthesis of quantum dots having the grain size of 3 nm. The morphological and optical characterizations like XRD, HRTEM, optical absorption of the synthesized CdSe quantum dots, reveal that the material possesses the similar characteristics of the one synthesized through cumbersome wet chemical methods. Relative to the CdSe bulk material, the synthesized CdSe quantum dots showed a blue shift in the measured band gap energy from near infrared spectral region to visible region, making this material very attractive for many solar energy harvesting applications like photo-catalysis and solar cells.

Experimental evidence of temporal and spatial incoherencies of Q-switched Nd:YAG nanosecond laser pulses

Seeded nanosecond Q-switched Nd:YAG lasers working with an unstable resonator and a variable reflectivity mirror are widely used, for they represent useful sources for stable and repeatable light–matter interaction experiments. Moreover, in most setups, the fundamental wavelength is converted to higher harmonics. When the injection seeder is turned off, random longitudinal mode beating occurs in the cavity, resulting in strong variations of the temporal profile of the pulses. The generated spikes can then be ten times higher than the maximum of equivalent seeded pulses. This strong temporal incoherence is shown to engender spatial incoherence in the focal plane of such unseeded pulses leading to an instantaneous angular displacement of tens of µrad. This effect is even more pronounced after frequency conversion.

Quadrupole distribution generated by a laser induced plasma (LIP) in air in earliest instants using pulses of 532 or 355 nm

The self-generated electric and magnetic fields in laser induced plasmas (LIPs) in air during the first 40 ns are experimentally investigated using different electric, magnetic and optical techniques. To produce LIPs we used the second and third harmonics (532 and 355 nm) of a Nd:YAG nanosecond pulsed laser with a range of irradiance from to W . The variation in time of the electric field was detected using the tip of a coaxial cable, and the spontaneous magnetic field (SMF) was measured using a probe. The spatial and temporal evolution of the plasma was studied using shadowgraphy and fast photography. It was observed that produced LIPs using pulses of 532 and 355 nm, generate plasmas of double core over the laser axis, while we observed that produced LIPs by pulses of 1064 nm are composed of a single core plasma. We found that the double-core plasmas have a quadrupole distribution of the charge, consisting of two oppositely directed dipoles which in turn correspond to each plasma core. The magnetic diagnostic showed an oscillating magnetic field azimuthal to the main axis of the double-plasma.

Effectiveness and harmful effects of removal sulphated black crust from granite using Nd:YAG nanosecond pulsed laser

Sulphated black crust is a common form of deterioration affecting stone used in monuments, usually occurs in contaminated atmospheres or urban environments. Its origin and cleaning have been studied extensively, for decades, in the case of carbonate rocks. Recent studies show that this form of alteration also affects granites. Scientific research on laser removal effectiveness of gypsum-rich black crust on granites needs to be scientifically addressed considering the inexistent references.This paper assesses the removal by laser of sulphate-rich black crusts on granite using the different harmonics of a Nd:YAG nanosecond pulsed laser (266nm, 355nm, 532nm and 1064nm). Effectiveness was evaluated using Scanning Electron Microscopy with Energy Dispersive X-ray Spectrometry (SEM–EDS), X-Ray Diffraction (XRD) and Attenuated Total Reflection-Fourier Infrared Transform Spectroscopy (ATR-FTIR). We also evaluated the effect of the radiation on granite-forming minerals and on the colour of the stone using Scanning Electron Microscopy and spectrophotometry colour measurements respectively.SEM–EDS, XRD and ATR-FTIR analyses show that the higher the wavelength, the more efficient the cleaning, so samples cleaned using 1064nm pulsed laser recovered its original colour. Nevertheless, the Nd:YAG laser did not completely eliminate the crust, and gypsum crystals remaining on the rock surface are observed, even at the most effective wavelength.

HIGH RESOLUTION OPTICAL EXPERIMENTAL TECHNIQUE FOR COMPUTING PULSED LASER-INDUCED CAVITATION BUBBLE DYNAMICS IN A SINGLE SHOT

The experiments conducted in this study consisted of a series of plasma generated cavitation bubbles in water, obtained by focusing a 532-nm Q-switched Nd:YAG nanosecond-pulsed laser. For the purpose of detection of such cavitation bubbles, a novel direct light transmission technique is used, referred to as spatial transmission modulation (STM), consisting of a nearly collimated beam of light passing through the sample at the point where the cavitation bubble is formed. The presence of the cavitation bubble modifies the direct light transmission, which is detected with a photodiode located at the opposite end. This is observed as an electrical signal response with an oscilloscope. A 1-megapixel high-speed video camera simultaneously records the cavitation event. The video was taken in an orthogonal direction with respect to the STM optical axis and was triggered simultaneously with an oscilloscope using the electronic synchronization signal from the pulsed laser. Data from the highspeed video was used to show that a computational spatial energetic analysis from the continuous laser probe beam is a valid method to directly obtain the cavitation bubble evolution from a single shot pulse. © 2013 by Begell House, Inc.