Impact Of Laser Irradiation Research Articles

Evidence of oxygenated species in laser-irradiated carbon particles

Combustion-generated carbon nanoparticles exhibit a variety of optical and physicochemical properties. Therefore, when applying laser diagnostic tools for monitoring purpose, it is important to consider the different response of the particles with varying properties as well as the impact of laser irradiation on these properties. In this work, we analyze the possible modification of particle optical and physicochemical properties by coupling extinction measurements with FT-IR and Raman spectroscopy. The aim is to retrieve optical, chemical, and structural properties of the particles under analysis. To our knowledge, the approach proposed in this work has not yet been performed on irradiated particles. Particles are sampled from a premixed flame at two heights above the burner, representing two different aging stages. While extinction measurements are carried out in-flow, FT-IR and Raman spectroscopy are performed on particles collected for ex-situ analysis. Moreover, the analysis is conducted on both pristine and irradiated nanoparticles with one and ten laser shots. While nascent particles do not exhibit relevant modification under laser irradiation, heating mature particles with one or more laser pulses of relatively high energy density is observed to significantly affect absorption properties, particle structures and specific surface functionalities. The presence of oxygenated species in mature particles and in particular the structures spectroscopically correlated with graphene oxide indicates that specific chemical reaction pathways can occur under laser irradiation, likely promoted in the ambient condition under analysis.

Effect of Picosecond Laser Irradiation on the Properties of Nanostructured Zinc Oxide Thin Films

In this article, a picosecond laser source was employed to irradiate the nanostructured ZnO thin film prepared by the sol-gel method. The impact of laser irradiation on the characteristics of a nanostructured ZnO thin film was investigated. Analysis using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy confirmed a significant influence on the structure of the ZnO thin film. As the duration of laser irradiation (the number of laser pulses) increased, there was a remarkable decrease in both the electronic and photoluminescence intensities of the nanostructured film. Tauc's plot indicates a noticeable change in the optical band gaps of the thin film with the increase in irradiation time. The morphological image suggests that the laser irradiation energy induces both degradation and modification of the film surface, consequently causing changes in the structural, absorption, and photoluminescence properties of nanostructured ZnO. The observed effects are attributed to alterations in the crystal structure and size of the nanostructured ZnO film, as confirmed by XRD. The reduction in photoluminescence intensity observed over the laser irradiation times may be a result of potential degradation in the crystalline structure of the nanostructured ZnO film.

Influence of time dependent laser-irradiation for tuning the linear-nonlinear optical response of quaternary Ag10In15S15Se60 films for optoelectronic applications.

The impact of laser irradiation on thin films results in multiple beneficial modifications of their structural, morphological, nonlinear-linear properties for optoelectronics applications. This work deals with the thermally evaporated Ag10In15S15Se60 films and post-laser irradiation to study the variations in structural and optical properties. The current investigation was carried out for different laser irradiation time durations such as 0, 10, 20, 30, and 60 minutes by 532 nm laser (2.34 eV). According to the X-ray diffraction analysis, all thin films have polycrystalline character. The change in the surface morphology after being exposed to the laser has been checked by FESEM, whereas the presence of constitutional elements has been verified by the EDX study. The related changes with laser irradiation in the optical properties, including both linear and nonlinear, were studied using UV-Vis spectroscopy data. The irradiation caused an enhancement in the transmission, and the absorption edge moved towards a lower wavelength, increasing the bandgap energy from 1.71 eV to 1.88 eV. The refractive index reduced as a result of the film's altered structure. The behaviour of the refractive index satisfies Moss's rule (E g n 4 = const). The nonlinear refractive index, first-order and 3rd order nonlinear susceptibility, is found to be decreased with laser irradiation. The dielectric parameters are also observed to be decreased with irradiation. Considering all the alterations in its properties caused by irradiation, the Ag10In15S15Se60 sample could be a favourable material for various photonic devices.

Study of Crack Growth of Transparent Materials Subjected to Laser Irradiation by Digital Holography

The crack growth of transparent materials after laser wavelength irradiation was studied. It is known that laser irradiation is used in many applications for the ablation of undesired material and/or coatings. The impact of laser irradiation on cracks was studied using the digital holography (DH) technique. Transparent samples were irradiated using near-ultraviolet, visible, near-infrared, and infrared light. The DH system is able to detect cracks and crack growth of the transparent samples irradiated by a range of laser wavelengths. Results also show that light with infrared to near-infrared wavelengths has a great effect on crack growth. High-resolution photomechanical effects of laser irradiation on material expansion or/and generation of defects due to specific wavelengths are also illustrated. The DH system with a multispectral laser has practical applications for laser cleaning of painted artworks.

Impact of laser irradiation on microstructure and phase development of tungsten carbide - cobalt

Previous studies on Laser Powder Bed Fusion of tungsten carbide-cobalt (WC-Co) revealed several defects in the laser molten microstructures. To analyze the defect formation mechanisms and the fundamental impact of laser energy input on phase development and microstructure of WC- Co, single-pulse and single-track analogy experiments are conducted. Conventional WC-Co is used as substrate. Variations in cobalt content and processing conditions are investigated. It is found that a single laser exposure can be enough to induce decomposition of microstructure, WC grain growth, formation of non-equilibrium phases and thermal cracking. Based on the results, defect formation mechanisms and countermeasures are discussed.

In vitro impact of laser irradiation on platelet aggregation.

The review of blood optical and rheological parameters plays an important role in many medical routine diagnosis and therapeutic applications and is the best way to understand the mechanism of action of low-level laser irradiation on biological tissues. The aim of this study was to investigate the in vitro effect of laser radiation on platelet count and aggregation. Blood samples were obtained from 30 healthy volunteers; each sample was divided into four aliquots, one of them was considered as a control while the other three were exposed to three different laser doses. A wavelength of 532nm and a low power of 100mW were used for irradiation with a 4-mm-diameter beam spot. The irradiation times were 1.8, 3.7, and 6.2s giving doses of irradiation 1.5, 3, and 5J/cm2, respectively. Microsoft Excel was used for statistical analysis. Low laser irradiation induced significant changes in platelet aggregation in the presence of weak agonists such as adenosine diphosphate (ADP) (P ≤ 0.05) and epinephrine (P ≤ 0.01). Low-level laser therapy has no influence on platelet count; however, it promotes platelet aggregation in response to weak agonists, specifically ADP and epinephrine.

Вплив лазерної терапії та діадинамофорезу на мікрофлору ясен дітей із хронічним катаральним гінгівітом

Вплив лазерної терапії та діадинамофорезу на мікрофлору ясен дітей із хронічним катаральним гінгівітом

Development of a Skin Burn Predictive Model adapted to Laser Irradiation

Laser technology is increasingly used, and it is crucial for both safety and medical reasons that the impact of laser irradiation on human skin can be accurately predicted. This study is mainly focused on laser–skin interactions and potential lesions (burns). A mathematical model dedicated to heat transfers in skin exposed to infrared laser radiations has been developed. The model is validated by studying heat transfers in human skin and simultaneously performing experimentations an animal model (pig). For all experimental tests, pig’s skin surface temperature is recorded. Three laser wavelengths have been tested: 808 nm, 1940 nm and 10 600 nm. The first is a diode laser producing radiation absorbed deep within the skin. The second wavelength has a more superficial effect. For the third wavelength, skin is an opaque material. The validity of the developed models is verified by comparison with experimental results (in vivo tests) and the results of previous studies reported in the literature. The comparison shows that the models accurately predict the burn degree caused by laser radiation over a wide range of conditions. The results show that the important parameter for burn prediction is the extinction coefficient. For the 1940 nm wavelength especially, significant differences between modeling results and literature have been observed, mainly due to this coefficient’s value. This new model can be used as a predictive tool in order to estimate the amount of injury induced by several types (couple power-time) of laser aggressions on the arm, the face and on the palm of the hand.

Laser Effects on Volta Potential Transients Recorded by a Kelvin Probe

A laser beam focused beneath a Kelvin probe needle allows for evaluation of laser-induced Volta potential shifts that can be used to identify (ir)reversible structural rearrangements at the sample surface. This work investigates the impact of laser irradiation on different substrate materials and the influence of laser power and wavelength to explore possible additional areas of analytical applications. Complete and instantaneous potential recovery was achieved with a 785 nm beam, whereas inverse and less meaningful potential shifts result for highly reflective Si wafers. Moreover, similarities to photovoltage transients recorded on solar cell devices are discussed.

The impact of laser irradiation on global stability in patients with vertebrobasilar insufficiency: A clinical report

SummaryBackgroundThe purpose of our experiment was to determine whether laser stimulation can improve microcirculation in the posterior regions of the brain in patients with vertebrobasilar insufficiency (VBI).Material/MethodsWe studied 25 patients (20 female, 5 male, mean age 64) diagnosed with chronic VBI. All were evaluated using the De Klyn test, followed by qualitative assessment of stability using a Berg Balance Scale and evaluation of global stability using an electronic balance platform. A CTL-1100 low power laser was used with standard parameters. We established a protocol for laser irradiation at 5 points along the vertebral artery in the cervical region bilaterally. Irradiation was performed 10 times over two weeks.ResultsSignificant improvement occurred after therapy in headache (p=0.0005), vertigo (p<0.0000), and tinnitus (p=0.0387). No significant differences were observed in nausea or nystagmus caused by head rotation. The Berg Balance Scale results showed significant differences in almost all features. There was a tendency towards improved stability in all parameters, and statistically significant differences in the total surface of support and the spread surface of support for the left foot.ConclusionsLaser stimulation as applied in this study can be useful in the treatment of patients with VBI. The main reason for improvement in global stability, balance, and other VBI symptoms is better blood perfusion.

Impact of Laser Irradiation on Brain Resistance to Postresuscitative Emotional Stresses (Experimental Study)

The paper shows how to solve the urgent problem of posthypoxic rat brain resistance to emotional stress. An hour hypovolemic hypotension (mean blood pressure 45 mm Hg) served as a model of a terminal condition. The integra-tive activity of the rat brain was evaluated by the elevated cross labyrinth test. Emotional stress was induced by confrontation between the falsely operated and antihypertensive rats within 30 postischemic days. Laser irradiation was carried out an hour after blood reinfusion. Laser irradiation used before emotional stress was shown to increase the resistance of the posthypoxic rat brain to emotional stress and to prevent the development of depression-like states in the late periods after resuscitation. Key words: blood loss, postresuscitative period, emotional stress, laser irradiation.

Lethal and sub‐lethal impacts of pulsed laser irradiations on the larvae of the fouling barnacle Balanus amphitrite

Laboratory experiments were conducted to study the impact of laser irradiation on the larvae of the fouling barnacle Balanus amphitrite. Research pertaining to fouling invertebrate larvae‐laser interaction is sparse and, hence, data on this aspect were thought significant in order to consider pulsed low power laser irradiations as a possible future antifouling tool. Lethal and sub‐lethal impacts of four very low laser fluences, viz. 0.013, 0.025, 0.05 and 0.1 J cm‐2 for three different durations, viz. 2, 10 and 30 s were investigated. Three growth stages of barnacle larvae, viz. nauplii stage II, nauplii stage IV and cyprids were exposed to the mentioned laser fluences for different durations. While lethal impact was assessed immediately after and 1 d after irradiation, sub‐lethal impacts were studied by monitoring the success rate of the irradiated nauplii in reaching the cyprid stage. In addition, the swimming speed of VIth stage nauplii after irradiation was studied. In the case of cyprids, in addition to the mortality measurement immediately after and 1 d after irradiation, the settlement rate was investigated. In all the above experiments, non‐irradiated larvae served as controls. The results showed an increase in mortality with increasing laser fluence and duration of irradiation. Irradiation for 2 s resulted in significant mortality in nauplii, while it was less in the case of cyprids. In IInd stage nauplii, the mortality immediately after irradiation for 2 s varied from 14.8±2.12 to 97.1±4.1% for laser fluences of 0.013 and 0.1 J cm‐2, respectively. However, in cyprids, the mortality immediately after irradiation for 2 s varied from 12.2±3 to 13.4±1.2% for fluences of 0.013 and 0.1 J cm‐2, respectively. The mortality in IVth stage nauplii was less than that for IInd stage nauplii but more than that for cyprids. There was a significant increase in mortality with time after irradiation. The formation of cyprids from the irradiated larvae was significantly less than that observed for non‐irradiated larvae. Also, the irradiated larvae showed a significantly slower swimming speed compared to the control samples. The settlement rate in cyprids was reduced significantly by the laser irradiation. This was true even for the lowest fluence and shortest period of irradiation tested. Thus, the results of the experiment showed that even a low power pulsed laser irradiation of 0.013 J cm‐2 for 2 s can cause significant damage to fouling barnacle larvae.