YAG Pulsed Laser Research Articles

Characterization of Hydroxyapatite Film Obtained by Er:YAG Pulsed Laser Deposition on Sandblasted Titanium: An In Vitro Study.

The surface of titanium (Ti) dental implants must be modified to improve their applicability, owing to the biological inertness of Ti. This study aims to use sandblasting as a pretreatment method and prepare a hydroxyapatite (HA) coating on Ti to improve its biocompatibility and induce bone bonding and osteogenesis. In this paper, sandblasted Ti discs were coated with α-tricalcium phosphate (α-TCP) via Er:YAG pulsed laser deposition (Er:YAG-PLD). An HA coating was then obtained via the hydrothermal treatment of the discs at 90 °C for 10 h. The surface characteristics of the samples were evaluated by SEM, SPM, XPS, XRD, FTIR, and tensile tests. Rat bone marrow mesenchymal stem cells were seeded on the HA-coated discs to determine cellular responses in vitro. The surface characterization results indicated the successful transformation of the HA coating with a nanorod-like morphology, and its surface roughness increased. In vitro experiments revealed increased cell attachment on the HA-coated discs, as did the cell morphology of fluorescence staining and SEM analysis; in contrast, there was no increase in cell proliferation. This study confirms that Er:YAG-PLD could be used as an implant surface-modification technique to prepare HA coatings with a nanorod-like morphology on Ti discs.

A study on sub-bandgap photoexcitation in nitrogen- and boron-doped diamond with interdigitated device structure

Diamond is an ultrawide-bandgap semiconductor suitable for high power devices that require high current carrying capacity, high blocking voltages, and smaller form factors. We investigated various diamond structures for extrinsic photoconductive semiconductor switches, including an insulating high-pressure high-temperature type Ib (highly nitrogen-doped) substrate, a chemical vapor deposited (CVD) type IIa (unintentionally doped) substrate, a CVD grown semiconducting boron-doped epilayer on a type IIa substrate, and boron-implanted type Ib and IIa substrates. Using these samples, we fabricated and characterized planar interdigitated photoconductive switches with 30 μm, electrode gaps. 532 and 1064 nm Nd:YAG laser pulses with energies up to 3.5 mJ/pulse were used to trigger the switches. Photoresponses were measured at bias voltages ranging from 10 to 100 V, corresponding to electric fields of 3.3–33 kV/cm. In this field range, the type Ib device exhibited the highest average on/off-state current ratio, on the order of 1011, when triggered with 0.8 mJ/pulse, 532 nm laser pulses. However, only the CVD grown boron-doped epilayer and boron implanted IIa devices showed decent sensitivity to 1064 nm.

Research of laser ultrasonic defect statistics recognition technology based on radial basis function neural network

In this study, we detected the depth of surface defect at a statistic on rate of 95.8% or more by using the Radial Basis Function Neural Network, a Q-switched and pulsed Nd:YAG laser and optical fiber Fizeau interferometer. In the experiment, Nd:YAG pulsed laser was used for generating ultrasound in a sample, while an optical fiber Fizeau interferometer was used to detect the ultrasound generated by a laser line source. Our results showed that this system has a high sensitivity as well as a high spatial resolution, what is more important is that this system is applicable to practice field.

Laser direct patterning induced the tunable optical properties of indium tin oxide micro-hole arrays films

Here we introduce a facile method to fabricate patterned indium tin oxide (ITO) thin films via selective laser ablation at ambient conditions. By scanning the ITO thin films with focused Nd: YAG pulsed laser, the ITO thin films were selective ablated and patterned without using any conventional chemical etching or photolithography steps. Then we investigated the effects of scanning rate for the structure, morphology and optical properties of patterned ITO thin film. These results indicate that the epsilon-near-zero (ENZ) wavelength of ITO thin films can be tuned from 1100 nm to 1340 nm by adjusting the period of the micro-hole array in microstructure. The nonlinear absorption response of patterned ITO films was about 2.85 time than of the as-deposited ITO thin film. Additionally, the results of the Finite-Difference Time-Domain (FDTD) simulation are in good agreement with those of the experiments.

High-speed imaging of vapor plume in the treatment of dissimilar Aluminum/Titanium interface with Yb:YAG laser pulse

It is ideal to observe the vapor plume to have a better understanding of the keyhole dynamics in dissimilar laser welding. This work is dedicated to the high-speed imaging and spectroscopic analysis of the vapor plume and postmortem analysis of melted zone produced from the interaction of a 6 ms Yb:YAG laser pulse with the aluminum A5754 - titanium T40 interface. These experiments are performed for different offsets of the laser spot from the joint line. The high-speed imaging is performed at two different wavelength (infrared 810 nm and ultraviolet 394 nm) regions. Morphological characteristics such as dimensions and orientation of the plume are studied and compared. The laser spot position affects the angle of inclination. It is observed that the plume inclines towards the aluminum side. The observation of inclination varies with the recording wavelength. The interrelationship between the inclination of the vapor plume and the laser spot position for a chosen observation wavelength is not self-explanatory. postmortem observation and EDX analysis of the melted zone, are correlated with the results from high-speed imaging. Spectroscopic analysis of the vapor plume associated with the Boltzmann linearization for temperature calculation, provides confirmation on the existing correlations between results from high-speed imaging and postmortem analysis.

Effect of laser plasma on Nd:YAG laser drilling of acrylic plate with high optical density

Laser material processing (LMP) is used to replace traditional material processing techniques, such as material cutting, thin plate drilling, and surface processing. When a high-energy laser is projected onto a material, the temperature of the material increases rapidly, changing the characteristics of the material and making the material on the surface vaporize and peel off instantly. In this study, we developed a laser system using a Quantel Brilliant neodymium-doped yttrium aluminum garnet (Nd:YAG) with a wavelength of 1064 nm laser a pulse width of 5–6 ns, a beam diameter of the 6 mm, and 10 repetition rate (Hz) on the energy stability is within 5.60%, an F-theta lens is used to obtain a focused laser beam with a diameter of 0.2 mm. The developed system was employed to drill holes in a 3-mm-thick optical-grade acrylic polymethyl methacrylate (PMMA) plate with high optical density and 7 + safe windows. A laser-safe, flat-window, visible-light-transmitting (VLT) sample was used, and the material to be drilled was a PMMA plate. The laser beam must be focused on the center of the F-theta lens and must be aligned with the distance between the F-theta lens and the linear stage. The working distance was set to 300 mm. Furthermore, the diameter was adjusted to obtain the laser plasma effect; that is, the working distance was fixed. First, the characteristics of the laser plasma and the ability of the laser to penetrate optical-grade acrylic (PMMA) plates samples were studied. By changing the lifting position of the vertical axis and varying the working distance of the acrylic (PMMA) plates, the laser beam was targeted at different positions on the acrylic (PMMA) plates. To determine the optimal parameters for the drilling process, a pulsed laser output of 174.7 mJ/pulse (3000 pulses in 5 min) was focused on the hole. Results showed that the energy was 522.98 J/cm2; a laser energy density of 141.26–275.93 J/cm2 resulted in an acceptable heat-affected zone. The Nd:YAG pulsed laser can produce laser plasma that can increase the hole diameter by up to 50% because of the produced cavity gap. Various exit and entrance hole shapes can be achieved and thus employed for different applications, such as laser beam cutting.

Defect detection of concrete in infrastructure based on Rayleigh wave propagation generated by laser-induced plasma shock waves

Defects in large concrete structures, including critical infrastructure such as bridges and tunnels, are traditionally detected by hammering tests by inspectors. However, the results depend on the inspectors’ skills. Additionally, hammering tests are impractical to thoroughly inspect massive structures in a short time. Herein defect detection in concrete structures is realized by telemetry using shock waves generated by laser-induced plasma (LIP). LIP is generated by irradiating a Nd:YAG pulsed laser near the concrete surface. As LIP spreads to the surrounding area at an ultrafast speed, a spherical shock wave is generated. This shock wave realizes a non-contact, non-destructive impulse excitation force on a concrete structure. The response of the concrete structure is measured with a laser Doppler vibrometer (LDV). Applying this method to detect defects in an artificial concrete specimen can identify the natural frequencies and modes of the defects. By measuring the propagation of the Rayleigh waves generated by the LIP shock waves, defects and the approximate location of the boundary between the defective part and the defect-free part are detected.

Laser shock wave loading of the vanadium and titanium

Measurements of the plastic wave attenuation in the material is very important for understanding Laser Shock Peening (LSP) surface treatment (Seddik et al. (2022)) mechanisms. We have tested thin disk-shaped specimens from titanium VT6 and vanadium VnP-1. Specimens were loaded by Beamtech SGR-Extra-10 Nd:YAG pulse laser. To increase the wave amplitude the front surface was covered by a thin water layer. The water layer should be thin because of the absorption of the IR radiation in the water. At provided laser energy density we did not observe any spallation. We did not observe grain fragmentation and other signs of severe plastic deformation.

The investigation of keyhole behavior in dissimilar aluminum/titanium interface

The in-situ investigation of keyhole behavior is essential for the comprehension of laser beam interaction with dissimilar joint. In the present study, the keyhole behavior at the interface between titanium T40 and aluminum A5754 under a Yb:YAG laser pulse was characterized by high-speed imaging through the quartz plate and by SEM-EDX. The effect of beam offset from the joint line on keyhole geometry and drilling rate, as well as on the elemental mapping and composition of the melted zones was investigated. The SEM-EDX analysis of the deposits left by vapor plume on the quartz plate above the keyhole opening was performed. A strong synergetic effect between the joined materials was observed: the keyhole tended to shift on A5754 having lower vaporization temperature due to the heat transfer from highly absorbing T40. The evolution of keyhole and melted zone features with beam offset was consistent with previously reported behavior of the plume.

Structural and nonlinear optical absorption studies of Mn doped PbWO4 nanoparticles

Manganese (Mn) -doped PbWO4 nanostructures with different concentration of Mn have been synthesized by chemical precipitation method followed by thermal annealing. The influence of Mn on the structural, optical and morphological properties was systematically investigated by various spectral-analytical techniques. X-ray diffraction (XRD) study reveals the successful incorporation of Mn into PbWO4 lattice without any secondary phase formation. From the UV–Vis spectra, it is clear that the dopant has shifted the absorption towards higher wavelength. Photoluminescence measurements showed a broad blue-green emission band with a maximum emission peak centered at 490 nm. The magnetic investigation further evidences the transport of dia to paramagnetism of Mn-doped PbWO4 and weak contribution of ferromagnetism at low magnetic field. It can be due to the effect of Mn clusters in host lattice and led to the changes in the magnetic properties. Typical third order nonlinearity of the proposed Mn-doped PbWO4 nanostructures has been investigated by an open aperture Z-scan technique using 10 ns Nd:YAG laser pulses operating at 532 nm. The nonlinear absorption data suggests that two photon absorption as the dominant nonlinear mechanism. A good nonlinear optical absorption is observed for both pure and doped nanostructures and the nonlinearity increases linearly with increase in Mn concentration.

(Noble Gas)n -NC+ Molecular Ions in Noble Gas Matrices: Matrix Infrared Spectra and Electronic Structure Calculations.

An investigation of pulsed‐laser‐ablated Zn, Cd and Hg metal atom reactions with HCN under excess argon during co‐deposition with laser‐ablated Hg atoms from a dental amalgam target also provided Hg emissions capable of photoionization of the CN photo‐dissociation product. A new band at 1933.4 cm−1 in the region of the CN and CN+ gas‐phase fundamental absorptions that appeared upon annealing the matrix to 20 K after sample deposition, and disappeared upon UV photolysis is assigned to (Ar) n CN+, our key finding. It is not possible to determine the n coefficient exactly, but structure calculations suggest that one, two, three or four argon atoms can solvate the CN+ cation in an argon matrix with C−N absorptions calculated (B3LYP) to be between 2317.2 and 2319.8 cm−1. Similar bands were observed in solid krypton at 1920.5, in solid xenon at 1935.4 and in solid neon at 1947.8 cm−1. H13CN reagent gave an 1892.3 absorption with shift instead, and a 12/13 isotopic frequency ratio–nearly the same as found for 13CN+ itself in the gas phase and in the argon matrix. The CN+ molecular ion serves as a useful infrared probe to examine Ng clusters. The following ion reactions are believed to occur here: the first step upon sample deposition is assisted by a focused pulsed YAG laser, and the second step occurs on sample annealing: (Ar)2 ++CN→Ar+CN+→(Ar) n CN+.

The influence of Nd: YAG pulsed laser treatment on the structure, morphology and hardness of e.max ceram dental material

The use of ceramics in dentistry is increasing day by day owing to their more aesthetic look, better mechanical properties, and easy-to-fit approach. The material used in the study is IPS e.max Ceram by Ivoclar Vivadent which has been widely adopted as the ceramic of choice by many dentists as it is ideally suitable for the veneering of more opaque substructures. The study aims to elucidate the result of Nd: YAG pulsed laser irradiation at different numbers of pulses on structure, surface morphology, and hardness of e.max Ceram dental material. XRD shows the amorphous nature of the material before the laser irradiation, whereas the crystallinity in the material is slightly induced after the exposure of e.max Ceram with 150 laser shots. The surface morphology and hardness degradation are attributed to the swelling potential of the material and induced increase of the residual micro-stresses during laser irradiation. This technique could provide more ease for bonding and de-bonding of orthodontic brackets and might be used as a chairside tool.

Optical Emission Spectroscopic Analysis of Plasma Parameters in Cadmium by Nd: YAG laser Technique

In this work, optical emission spectroscopy (OES) was used to estimate the parameters of plasma electron temperature (Te), electron density (ne), plasma frequency (fp), Debye length (λD), and Debye number (ND). Understanding how an energy pulsed laser affects these variables is also important. Irradiation of pure cadmium using an Nd: YAG laser pulse with a wavelength(1064)nm and energy ranging from (200-600)millijoules, of frequency (6) Hz. The spectrum of laser-induced plasma was detected under atmospheric pressure. It was discovered that when the energy of the laser pulse rises, the intensity of the CdI and CdII lines increases.

Search for sub-eV axion-like resonance states via stimulated quasi-parallel laser collisions with the parameterization including fully asymmetric collisional geometry

We have searched for axion-like resonance states by colliding optical photons in a focused laser field (creation beam) by adding another laser field (inducing beam) for stimulation of the resonance decays, where frequency-converted signal photons can be created as a result of stimulated photon-photon scattering via exchanges of axion-like resonances. A quasi-parallel collision system (QPS) in such a focused field allows access to the sub-eV mass range of resonance particles. In past searches in QPS, for simplicity, we interpreted the scattering rate based on an analytically calculable symmetric collision geometry in both incident angles and incident energies by partially implementing the asymmetric nature to meet the actual experimental conditions. In this paper, we present new search results based on a complete parameterization including fully asymmetric collisional geometries. In particular, we combined a linearly polarized creation laser and a circularly polarized inducing laser to match the new parameterization. A 0.10 mJ/31 fs Ti:sapphire laser pulse and a 0.20 mJ/9 ns Nd:YAG laser pulse were spatiotemporally synchronized by sharing a common optical axis and focused into the vacuum system. Under a condition in which atomic background processes were completely negligible, no significant scattering signal was observed at the vacuum pressure of 2.6 × 10−5 Pa, thereby providing upper bounds on the coupling-mass relation by assuming exchanges of scalar and pseudoscalar fields at a 95% confidence level in the sub-eV mass range.

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.

Influence of substrate temperature on graphene oxide thin films synthesis by laser ablation technique

In this paper, we studied the influence of the substrate temperature (Ts) on the deposition of carbon thin films by the pulsed laser deposition technique. Thin films were synthesized using a highly oriented pyrolytic graphite target, which was irradiated by the fundamental harmonic (1064 nm) of a Nd:YAG pulsed laser. In the experimental conditions, the Ts varied from room temperature to 500 °C, the gas pressure (oxygen, 50 mTorr) remained the same for all samples, and the ablation time was 5 min for each thin film. The samples were characterized by x-ray diffraction (XRD), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy in conjunction with energy dispersive x-ray spectroscopy, atomic force microscopy, and contact angle measurement. The characterization results allowed us to determine that the thin films deposited on silicon substrates at 400 and 500 °C (samples S1 and S2) were multilayers graphene oxide. From XRD, Raman spectroscopy, and FTIR results, we concluded that the degree of oxidation and graphitization of the carbon thin films were influenced by the Ts. Additionally, the contact angle measurement showed that for samples S1 and S2, the contact angle was greater than 94°, and for samples S3 and S4 (amorphous carbon), it was less than 62°.

Cascade Er:YAG pulsed lasers at room temperature.

Cascaded mid-infrared (MIR) pulsed laser output in Er:YAG crystals at room temperature is achieved experimentally. The existence of a cascade at room temperature in Er:YAG crystals is confirmed. Furthermore, the effect of the cascade on MIR laser performance is studied. With the assistance of the cascade, the thresholds are reduced by 13.3% and 12.5%, and the slope efficiencies are increased by 3.2% and 12.3% compared to a non-cascade configuration in 10 and 15 at.% Er:YAG, respectively. The excited-state absorption is considered to be the mechanism responsible for the laser performance optimization. This Letter should be helpful for the improvement of erbium-doped 3 µm laser output energy.

Superior nonlinear optical and optical limiting properties of cross-linked and thermally stable HiPCO-SWCNTs@PVA films

We present non-linear optical (NLO) and optical limiting (OL) properties of high pressure catalytic CO single-walled carbon nanotubes (HiPCO-SWCNTs) immobilized inside cross-linked poly vinyl alcohol (PVA) using 1 wt% sodium dodecylbenzene sulfonate (SDBS) as surfactant and plasticizer. The content of HiPCO-SWCNTs was changed to be 0.05, 0.1, 0.2 and 0.3 wt%. The NLO properties were investigated using open aperture Z-scan method with nanosecond Nd:YAG pulsed laser at 532 nm and 1064 nm in Q-switched mode. The nonlinear absorption coefficient β and third order nonlinear susceptibility χ3 were calculated. The results show that all HiPCO-SWCNTs@PVA film exhibit reverse saturable absorption (RSA) at both 532 and 1064 nm laser excitations, expect the 0.05 wt% HiPCO-SWCNTs@PVA at 1064 nm showed saturable absorption (SA) behavior. The 0.3 wt% HiPCO-SWCNTs@PVA film showed lower OL threshold than other films at both 532 nm and 1064 nm and increased the critical value of laser fluence damage for a commercial CCD camera ≈10 times. The remarkable OL enhancement was attributed the enhanced thermal conductivity and thermal stability of the 0.3 wt% HiPCO-SWCNTs@PVA film.

Multifunctional Optical Device with a Continuous Tunability over 500 nm Spectral Range Using Polymerized Cholesteric Liquid Crystals.

We report that polymerization makes a robust, practically applicable multifunctional optical device with a continuous wavelength tunable over 500 nm spectral range using UV-polymerizable cholesteric liquid crystals (CLCs). It can be used as a circular polarizer generating an extremely high degree of circularly polarized light with |g| = 1.85~2.00. It can also be used for optical notch filters, bandwidth-variable (from ~28 nm to ~93 nm) bandpass filters, mirrors, and intensity-variable beam splitters. Furthermore, this CLC device shows excellent stability owing to the polymerization of CLC cells. Its performance remains constant for a long time (~2 years) after a high-temperature exposure (170 °C for 1 h) and an extremely high laser beam intensity exposure (~143 W/cm2 of CW 532 nm diode laser and ~2.98 MW/cm2 of Nd: YAG pulse laser operation for two hours, respectively). The optical properties of polymerized CLC were theoretically analyzed by Berreman’s 4 × 4 matrix method. The characteristics of this device were significantly improved by introducing an anti-reflection layer on the device. This wavelength-tunable and multifunctional device could dramatically increase optical research efficiency in various spectroscopic works. It could be applied to many instruments using visible and near-infrared wavelengths.

Calculation of the Coupling Coefficient of Electrons in Laser Induced Plasma for Samples of Writing Ink Elements Using LIBS Technique

The technique of laser breakdown spectroscopy (LIBS) was employed for samples of writing inks under the influence of a Nd:YAG laser pulse 1064 nm with a pulse duration of 10 ns on different targets of writing ink models. The plasma parameters were also calculated, which are the temperature and density of electrons, assuming local thermodynamic equilibrium conditions (LTE) and using a spectral detector model (View spectra 2100) for the spectral range (200nm - 900nm). The results showed differences in the values of the pairing coefficient of electrons in the plasma. Produced due to the laser pulse used as well as in the plasma parameters mentioned, which can be applied in plasma spectroscopy for forensic sciences in detecting forgery in documents and tracking the performance and phenomena of the plasma formed due to the laser pulse.