YAG Laser Source Research Articles

Reducing Feature Size in Laser Implantation Texturing.

Embossing rolls are used in a variety of sectors to transfer surface textures to a product. Textures on the rolls are typically achieved by material-removal techniques, resulting in craters in the surface of the roll. The wear resistance of the surfaces is improved by additional coating technologies. A novel process offering improved surface design freedom and which negates the need for post-coating techniques is the embedding of micro-meter-sized ceramic particles in the surface of the roll. This can be achieved through micro-additive processing. This work presents and discusses experimental results of surface texturing through locally derived laser-induced melt pools in which ceramic particles are dissolved. This process is termed laser implantation, or laser dispersing. Using this technology, dome-shaped surface structures with significantly increased hardness compared to the bare steel can be achieved. Reported results in the literature focus on implantations with diameters ranging from 150 μm to 400 μm and heights ranging from 10 μm to 30 μm. However, features with smaller diameters and heights are desired for technology adoption to permit a wider range of surface roughness. This paper presents and discusses the experimental results of implantations with a diameter smaller than 150 µm, with heights between 1 μm and 15 μm. For that purpose, a Nd:YAG laser source (focal diameter 70 μm, pulse durations from 3 to 15 ms, pulse power from 20 to 50 W average) was used to induce a melt pool driving the particle embedding.

A modified flying-spot laser eye-surgery platform for hyperopic correction

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.

The role of silver nanoparticles effects in the homeostasis of metals in soybean cultivation through qualitative and quantitative laser ablation bioimaging

BackgroundNanoparticles (NPs) are currently found in the world in the form of natural colloids and volcanic ash, as well as in anthropogenic sources, such as nanofertilizers; however, in the literature, there is still a lack of toxicological evidence, risk assessment, and regulations about the use and environmental impact of NPs in the agroindustrial system. Therefore, the aim of this work was to evaluate alterations caused by the presence of AgNPs during the development of soybean plants. MethodsThe BRS232 non-transgenic (NT) soybean plant and 8473RR (TRR) and INTACTA RR2 PRO (TIntacta) transgenic soybean plants were irrigated for 18 days under controlled conditions with deionized water (control), AgNPs, and AgNO3. The isotopes 107Ag+, 55Mn+, 57Fe+, 63Cu+, and 64Zn+ were mapped in leaves, using 13C+ as an internal standard (IS), and carried out using a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) technique with a Nd:YAG (213 nm) laser source in the imagagin mode using the LA-iMageS software and also Mathlab. ResultsLeaf images showed a low Ag translocation, indicated by the basal signal of this ion. Additionally, the presence of Ag in the ionic form and as NPs altered the homeostasis of 112Cd+, 64Zn+, 55Mn+, 63Cu+, and 57Fe+ in different ways. Quantitative image analysis was performed for Cu. ConclusionThe behavior of TRR and TIntacta plants was different in the presence of ionic silver or AgNPs, confirming that the metabolism of these two plants, despite both being transgenic, are different. Through the images, it was observed that the response of plants was different in the face of the same stress conditions during their development.

Vibrational Spectroscopic Studies of Amino acid p-toluenesulfonic acid NLO Crystals

In the present work, a comparative study on the vibrational spectrums recorded on some newly synthesized amino acid p- toluenesulfonic acid NLO crystals are discussed. Infrared spectral measurements of all the grown crystals were made in the range of 4000–400 cm-1 using Jasco Spectrometer FT-Raman spectra of the grown crystals were recorded in the BRUKER RFS 27, Stand alone FT-Raman Spectrometer in the range of 4000 – 400 cm-1 The Nd: YAG laser source was operated at 1064 nm. FT-IR and FT-Raman spectral analyses shows the different functional groups present in the studied compounds. Its intensities and positions are analyzed. The high intensity vibrational bands observed around 2950 cm-1 which is assigned to N- H...O vibrations shows the influence of hydrogen bonds in the analyzed compounds. Keywords: NLO crystal, Organic single crystal, FTIR, FTRAMAN.

Nd:YAG infrared laser as a viable alternative to excimer laser: YBCO case study

We report on the growth and characterization of epitaxial YBa_{2}Cu_{3}O_{7-delta } (YBCO) complex oxide thin films and related heterostructures exclusively by Pulsed Laser Deposition (PLD) and using first harmonic Nd:Y_{3}Al_{5}O_{12} (Nd:YAG) pulsed laser source (lambda = 1064 nm). High-quality epitaxial YBCO thin film heterostructures display superconducting properties with transition temperature sim 80 K. Compared with the excimer lasers, when using Nd:YAG lasers, the optimal growth conditions are achieved at a large target-to-substrate distance d. These results clearly demonstrate the potential use of the first harmonic Nd:YAG laser source as an alternative to the excimer lasers for the PLD thin film community. Its compactness as well as the absence of any safety issues related to poisonous gas represent a major breakthrough in the deposition of complex multi-element compounds in form of thin films.

Chemometrics and Spectroscopic Analyses of Peganum harmala Plant’s Seeds by Laser-Induced Breakdown Spectroscopy

In the present work, the rapid identification of elements and their relative chemical composition in various Peganum harmala seed samples were investigated using a calibration-free laser-induced breakdown spectroscopy technique (CF-LIBS). A pulsed Nd:YAG laser-source with a 5 ns pulse-duration, and 10 Hz pulse repetition rates providing 400 and 200 mJ energy at 1064 and 532 nm wavelength, respectively, was focused on the Peganum harmala seed samples for ablation. A LIBS 2000+ spectrometer within the wavelength range (200 to 720 nm), emission-spectra were recorded. The measured spectra of the Peganum harmala sample gives spectral lines of Carbon (C), Magnesium (Mg), Lithium (Li), Sodium (Na), Calcium (Ca), Silicon (Si), Iron (Fe), Strontium (Sr), Copper (Cu), Potassium (K), and Lead (Pb). A CF-LIBS technique has been employed for the compositional study of the elements exist in the Peganum harmala seed samples. The measured results demonstrate that C, Mg, and Ca are found to be major elements in the Peganum harmala seed samples with compositions of ~36.64%, ~24.09%, and ~19.03%, respectively. Along with the major elements, the elements including Li, Na, Si, K, Fe, and Sr were identified as minor elements with compositions of ~2.87%, ~2.33%, ~3.72%, ~7.17%, ~2.83%, and ~1.14%, respectively. Besides Cu (~8.07 μg/g), and Pb (~1.10 μg/g) elements were observed as trace elements exist in the Peganum harmala seed samples. Furthermore, the electron number density including the plasma excitation-temperature were calculated using the stark-broadening line profile method and the Saha–Boltzmann plot method, respectively. The plasma parameters versus laser-irradiance and the distance from the sample were further investigated. Moreover, a principal component analysis (PCA) method was also utilized to the spectral data obtained by using LIBS to discriminate various seed samples with four classes, namely, α, β, γ, and Δ. Three principal-components (PCs) calculated from eigenvalues of score matrix described 87.6%, 4.6%, and 2.5% of total variance for PC1, PC2, and PC3, respectively. The LIBS spectral data variance covered by the initial 3 PCS was found as ~94.7% of total variance. The PCA results have successfully demonstrated the different classes of the Peganum harmala seed samples based on the different doping compositional ratios of the Zn element. This study confirmed the feasibility and ability of LIBS and PCA for the rapid analysis of Peganum harmala seed samples. Finally, the results achieved using CF-LIBS were incorporated with those obtained from the XRF and EDX analytical techniques.

Laser-assisted hydrothermal synthesis of MoS2 nanosheets under different laser energies and potential application in nonlinear optics

The main aim of this work is the investigation and evaluation of the structural, morphological, molecular structural, chemical-bond, dielectric, linear, and nonlinear optical behavior of MoS2 nanosheets synthesized using a laser-assisted hydrothermal method when irradiated at different laser energies. The successful formation of the hexagonal phase of MoS2 was confirmed by using XRD analysis. The calculations of the optical constants and dielectric coefficients of MoS2 nanosheets were performed by FTIR measurements using Kramers-Kronig relations. MoS2 nanosheets were pumped using a continuous-wave Nd:YAG laser source operating at 532 nm to consider the optical absorptive and refractive nonlinearity through the open and closed-aperture Z-scan technique, respectively. A negative nonlinearity and a third-order nonlinear optical susceptibility of the order of 10−5 esu were obtained for MoS2 nanosheets. An increase in all nonlinear optical parameters was observed when MoS2 nanosheets were irradiated with higher laser energy during the synthesis process. The findings of the current research open a new path to improving two-dimensional nanomaterials leading to the development of nanophotonic devices.

The usage of Nd:YAG laser in SMAS lifting of the middle and lower third of the face

The purpose of the work is to improve the quality of vertical face lifting by introducing into surgical practice a laser system of the Fotona SP Spectro model with a Nd:YAG laser source. The technique of intraoperative exposure of the Fotona SP Spectro laser system with an Nd:YAG laser source to the superficial muscular-aponeurotic system (SMAS) of the middle and lower third of the face is proposed. The authors conclude that the use of Nd:YAG laser in a single procedure shortens the rehabilitation period and significantly increases the rejuvenation effect in cases with hypermobile and thinned SMAS.

Laser ablation of a solid target in liquid medium for beryllium nanoparticles synthesis

In this paper, we describe a method to synthesize beryllium (Be) nanoparticles (NPs) by laser ablation of a solid target immersed in a liquid medium. Beryllium dust was successfully synthesized following the irradiation of a Be bulk target, which was immersed in water, acetone or heavy water, respectively, using the first and second harmonic (1064 and 532 nm) of a Nd: YAG laser source providing ns pulses, with a repetition rate of 10 Hz. The laser fluences used for Be target ablation were 8 and 15 J/cm2. In order to argue the successful obtaining of Be dust, scanning electron microscopy (SEM) was used for surface analysis. Colloidal solutions analysis by dynamic light scattering (DLS) supports the SEM analysis in terms of NPs size, whereas chemical analysis by X-ray photoelectron spectroscopy (XPS) was used in order to investigate the chemical composition. Moreover, thermal desorption spectroscopy (TDS) was performed on Be dust synthesized in heavy water to study the retention of deuterium (D). The key parameters for obtaining much sharper and regular size distribution were identified as being the liquid medium, laser fluence, and wavelength.

Underwater laser ablation process using an Yb:YAG laser source for the weakening of mild steel sheets for the deflagration of hazardous substances

With an estimated amount of about 1.6 metric million tons, unexploded ordnances (UXO) in the German North and Baltic Sea pose a serious threat to the environment due to increasing corrosion. One way to allow safe salvage of the objects from the sea is to weaken them and then disarm them by low order detonation. This paper deals with the weakening by laser ablation, aiming for the introduction of ablation gaps with a depth of 2/3 the material thickness in 4 and 10 mm thick mild steel samples. An Yb:YAG laser source is used with a laser power of up to 2 kW in combination with a coaxial gas jet supplying the process zone with nitrogen to ensure a controllability of the process and the depth of the gap. The study is thus focused on achieving constant and predictable gap depths.

Effect of energy, temperature, and Cu-doped coatings on crystallinity of Hydroxyapatite thin films obtained by pulsed laser deposition

In this work, a pulsed laser deposition (PLD) technique with an Nd:YAG laser source was used to produce pure Hydroxyapatite (HA) and Cu-substituted HA (Cu-HA) coatings on stainless steel substrates in vacuum at room temperature. It is observed that the combined effects of percentages of Cu dopants and laser energy as well as annealing temperature significantly modify the crystallinity of the films. The morphology and structural properties of the deposited HA films were analyzed by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Raman spectroscopy. FESEM images displayed various shapes of nanoparticles with high-surface density throughout the area of the substrate and with typical sizes around 26–208 nm. XRD analysis confirmed that post-deposition annealing is essential to achieve the desired crystallinity and uniformity of coatings. The Raman spectrum of HA has peaks at 958.22, 437.48, and 587.05 cm[Formula: see text] attributed to the [Formula: see text] PO[Formula: see text], [Formula: see text] PO[Formula: see text], and [Formula: see text] PO[Formula: see text], respectively. The synthesized HA and Cu-HA crystalline films are nanostructures with dense and compact microstructures. Finally, irregular surface and crystalline structure of fabricated films lead to the extension of the surface and enhance the cell’s proliferation in medical uses and biomedical applications.

Statistical modelling and optimization of nanosecond Nd:YAG Q-switched laser scarfing of carbon fiber reinforced polymer

This paper explores the effects of laser scarfing on a CFRP tape consisting of unidirectional carbon fiber with a layup of [(45/0/-45/90)4] sym with a total laminate dimension of 5.952 mm. The laser system used in the experimental investigations consisted of a nanosecond Nd: YAG laser source with an average maximum power of 20 W in a pulsed mode. The material was a with a total laminate of 5.952 mm. The laser process aims to investigate the surface modification by laser ablation. In more details, the effects of scanning speed (550 ÷ 650 mm/s) and frequency (23 ÷ 27 kHz) for three different scanning strategies on the scarfing depth, specimen dimensions (in x and y direction) and surface conditions were studied by full factorial experimental plan. By scarfing, the fibers were either oxidized, partially stripped, stripped and excessively stripped. After the statistical analysis, the best results in terms of surface conditions were achieved with the x-parallel laser scanning strategy, where the presence of excessively stripped fibers was not noticed. The mixed-hatching (MH) mode was the strategy that produced the worst results for the scarfing depth, which can negatively affect the ablation rate, even if it turns out to be the most stable strategy. The best results in terms of scarfing depth and x-y dimensions were achieved with MH mode, and with a scanning speed of 600 mm/s and a frequency of 27 kHz.

Investigation of the blast pressure following laser ablation at a solid–fluid interface using shock waves dynamics in air and in water

Simple and universal relations between the laser pulse energy of the third harmonic of a Nd:YAG laser source (5 ns) and the pressure at the ablation point are investigated for the ablation of a solid target in air and in water. Shockwaves propagation are reconstructed using time-resolved shadowgraph imaging. The propagation in air is well-described by Taylor–von Neumann–Sedov’s theory for over-pressure at the shock front larger than ten times the atmospheric pressure, but the energy distribution appears to be anisotropic and mostly directed in the normal direction to the target’s surface. We compare the pressure at the shock front deduced from its velocity using Rankine–Hugoniot’s relation with the pressure deduced from Taylor’s model only related to the laser pulse energy. Rankine–Hugoniot’s relation appears more appropriate to evaluate the early pressure in the plasma plume. The shockwaves velocity in water is hyper-sonic during 50 ns and then reaches the sound velocity. Pressure values at the shock front are compared using two different approaches accounting for different state’s equations, namely the Rice and Walsh’s equation and Tait’s equation. In both cases, the ablation pressure is found out to reach several GPa and increases as the square root of the laser intensity.

In situ growth of an ethyl p-hydroxybenzoate single crystal by the vertical Bridgman technique: a potential nonlinear optical material for third-harmonic generation

Optically transparent single crystals of ethyl p-hydroxybenzoate (EPHB) were successfully grown by the vertical Bridgman technique. The crystalline phase and unit-cell dimensions were obtained from powder X-ray diffraction using Rietveld analysis. The presence of defects and grain boundaries was investigated by high-resolution X-ray diffraction. The optical quality of the grown single crystal was assessed by UV–Vis and photoluminescent spectroscopies. A blue emission, with a bi-exponential decay time, was obtained from time-resolved photoluminescence upon laser excitation at 266 nm. The mechanical strength of the EPHB single crystal was studied by Vickers hardness testing. A decrease in the laser-damage threshold was observed with a nanosecond Nd:YAG laser source for increased pulse repetition rates. The third-order nonlinearity, nonlinear absorption coefficient and nonlinear refractive index were measured using the Z-scan technique with a femtosecond Ti:sapphire laser. The third-order nonlinear coefficient values for the grown crystal were compared with those of a potassium dihydrogen phosphate single crystal.

Optical coherence tomography-surveilled laser ablation using multifunctional catheter and 355-nm optical pulses

An optical coherence tomography (OCT)-monitored laser ablation system is presented in this study. The laser ablation subsystem is constructed using the third harmonic output of a Nd:YAG laser source operating at a 355-nm optical wavelength with a single pulse energy greater than 160 mJ and a 1–10 Hz tunable repetition rate. The imaging subsystem is a typical M-mode swept-source OCT system. Moreover, a type of all-fiber multifunctional integrated catheter is demonstrated. The ablation catheter consists of a fiber bundle including 41 multi-mode fibers with an outer diameter of 0.9 mm. A forward-viewing OCT imaging probe is inserted into the ablation catheter for M-mode imaging. The performance of the system is demonstrated by OCT surveillance of the laser ablation process using expanded polystyrene foam as the sample. The OCT system can be used to record the ablation process and simultaneously count the laser ablation duration. This study proposes an effective potential technique to surveil material laser ablation processes, especially in situations where bulky optics are prohibited and all-fiber devices are required.

Pulsed high-repetition rate diode-pumped Nd:YAG laser source with advanced ring Q-switch modulator

It has been experimentally shown that incorporation of the λ/4 phase plate into a cavity of the solid-state laser with the ring Q-switch modulator leads to an enhancement of the maximum achievable energy Emax of the output lasing pulses over a wide interval of the pulse repetition rate f. This is achieved by an improvement of the spatial phase distribution for two orthogonal polarization components formed in the laser cavity by the ring Q-switch modulator. These components transform into each other during every round trip of the laser cavity, thus forming the polarization ring cavity without appreciable hole burning effects. For the transversally diode pumped Nd:YAG laser source with the ring Q-switch modulator and λ/4 phase plate the output pulses with Emax ≈ 584–600 mJ were obtained in the range of f ~ 30–100 Hz at the excitation energy of 2.0–2.2 J.

Spring-to-summer observations of the aerosol load over Sofia-city using near-horizontal lidar sensing

Using lidar and contact facilities, the relation is investigated experimentally between the extinction coefficient and the mass concentration of near-ground aerosol pollution over some districts in Sofia City. The extinction coefficient profiles of the aerosol ensembles along the lidar line of sight (LOS) are measured at the lidar wavelengths of 510.6 nm (CuBr-vapor laser source) and 1064 nm and 532 nm (Nd:YAG laser source). The particulate mass concentration is determined using data obtained concurrently by air-quality measuring sensors close to the LOS. Thus, the results obtained of the aerosol mass concentration-to-extinction calibration constant of the lidar concern mainly the sites around the nearest stations. To help the interpretation of the results, the accompanying weather conditions are also described. The experiments are conducted in the spring and the summer and the results obtained reflect the ecological peculiarities of the corresponding city regions of interest. The values found of the calibration constant are consistent with those obtained earlier in the same seasons.

Determination of As, Hg, S, and Se in liquid jets by laser-based optical diagnostic technique

Laser-induced breakdown spectroscopy (LIBS) has been evaluated for measurement of As, Hg, S, and Se in aqueous samples. Single pulse (SP) and double pulse (DP) LIBS, with a 1064 nm Nd: YAG laser source, were utilized to generate micro plasma from the surface of a liquid jet containing these elements. Plasma emission was collected at a 45° angle with the laser beam for As and Se detection in UV wavelength range. However, the confocal mode was used to collect the atomic emission for Hg and S detection in visible and near IR range, respectively. Atomic emission lines 228.81 nm for As, 546.07 nm for Hg, 921.2 nm for S, and 196.09, 203.98 and 206.32 nm for Se were detected in the LIBS spectra. Calibration curves were developed to estimate the limit of detection for each analyte and found to be 2, 16, 16, and 29 ppm for As, Hg, S, and Se, respectively, with SP LIBS and 0.4, 8, 8 and 11 ppm, respectively, with DP LIBS. The study has implications in monitoring of these pollutants in flue gas desulfurization (FGD) wastewater.

Machine Learning-Based Optoacoustic Tissue Classification Method for Laser Osteotomes Using an Air-Coupled Transducer.

Using lasers instead of mechanical tools for bone cutting holds many advantages, including functional cuts, contactless interaction, and faster wound healing. To fully exploit the benefits of lasers over conventional mechanical tools, a real-time feedback to classify tissue is proposed. In this paper, we simultaneously classified five tissue types-hard and soft bone, muscle, fat, and skin from five proximal and distal fresh porcine femurs-based on the laser-induced acoustic shock waves (ASWs) generated. For laser ablation, a nanosecond frequency-doubled Nd:YAG laser source at 532 nm and a microsecond Er:YAG laser source at 2940 nm were used to create 10 craters on the surface of each proximal and distal femur. Depending on the application, the Nd:YAG or Er:YAG can be used for bone cutting. For ASW recording, an air-coupled transducer was placed 5 cm away from the ablated spot. For tissue classification, we analyzed the measured acoustics by looking at the amplitude-frequency band of 0.11-0.27 and 0.27-0.53 MHz, which provided the least average classification error for Er:YAG and Nd:YAG, respectively. For data reduction, we used the amplitude-frequency band as an input of the principal component analysis (PCA). On the basis of PCA scores, we compared the performance of the artificial neural network (ANN), the quadratic- and Gaussian-support vector machine (SVM) to classify tissue types. A set of 14,400 data points, measured from 10 craters in four proximal and distal femurs, was used as training data, while a set of 3,600 data points from 10 craters in the remaining proximal and distal femur was considered as testing data, for each laser. The ANN performed best for both lasers, with an average classification error for all tissues of 5.01 ± 5.06% and 9.12 ± 3.39%, using the Nd:YAG and Er:YAG lasers, respectively. Then, the Gaussian-SVM performed better than the quadratic SVM during the cutting with both lasers. The Gaussian-SVM yielded average classification errors of 15.17 ± 13.12% and 16.85 ± 7.59%, using the Nd:YAG and Er:YAG lasers, respectively. The worst performance was achieved with the quadratic-SVM with a classification error of 50.34 ± 35.04% and 69.96 ± 25.49%, using the Nd:YAG and Er:YAG lasers. We foresee using the ANN to differentiate tissues in real-time during laser osteotomy. Lasers Surg. Med. © 2020 Wiley Periodicals LLC.

Microstructural characterization and tensile behavior of Nd:YAG laser beam welded thin high strength low alloy steel sheets

Laser beam welding (LBW) has many advantages to join high strength low alloy (HSLA) steels compared with conventional fusion welding processes. The present work is focused on joining HSLA plates of 2 mm thickness efficiently through the application of Nd:YAG laser source. Only one process variable i.e. the welding speed was operated between 70 mm/s to 120 mm/s while the rest of the variables were maintained constant. The microstructure evolution of the fusion zone was recorded through optical, scanning and transmission electron microscopy. The fusion zone was observed to be wider but no major defects were present. Fusion zone experienced a change in morphology of ferrite and pearlite depending upon the rate of cooling and exposure time. Fusion zone showcased various ferrites such as acicular ferrite, widmanstatten ferrite, and grain boundary ferrite. Advancement in the welding speed helped in the formation of acicular ferrite. EBSD results presented a descending tendency of prior austenite grain size against increasing welding speed. TEM micrographs affirmed the ferrite transformation and showed the presence of dense dislocations. The changes in hardness and tensile behavior under the experimental conditions were further reported.