Effect Of Laser Wavelength Research Articles

Effect of Different Laser Wavelengths on Periodontopathogens in Peri-Implantitis: A Review of In Vivo Studies.

Nowadays, many studies are examining the effectiveness of dental lasers in the treatment of peri-implantitis; however, most of them only report periodontal parameter changes. The authors of this review tried to address the question: “What is the effect of different laser wavelengths on oral bacteria that cause peri-implantitis?” An electronic search of PubMed and Cochrane Central Register of Controlled Trials was performed. The following search terms were used: (peri-implantitis OR periimplantitis) OR/AND (microbial OR microbiologic) AND (laser OR Er:YAG OR erbium OR diode OR Nd:YAG OR neodymium-doped OR Er,Cr:YSGG OR chromium-doped). Initially, 212 studies were identified. After screening the titles and abstracts and excluding studies according to predefined inclusion criteria, seven publications were included in the review. Three studies about the effect of aPDT (antimicrobial photodynamic therapy) reported a decrease in the different bacterial strains associated with peri-implantitis, e.g., A. actinomycetemcomitans, P. gingivalis, P. intermedia, T. denticola, T. forsythia, F. nucleatum, and C. rectus. Two studies showed that the high-power diode laser may have some effect on peri-implant pathogens. Two articles about the Er:YAG laser reported a lowering in the count of oral pathogens; however, it was hard to determine if this was due to the use of the laser. aPDT has the ability to decrease the count of peri-implant pathogens, whereas Er:YAG laser application shows no significant effect on oral bacteria in the long term.

Investigation of laser wavelength effect on optical properties of graphene oxide colloidal nanostructures prepared by pulsed laser ablation

In this work we prepared graphene oxide nanostructures (GONE) in a liquid environment using pulsed laser ablation technique. We used for the synthesis Nd: YAG pulsed laser operatating at 1064 nm and 532 nm of wavelength, we study the effect of wavelength of the laser on the optical properties of Nanostructures (NE) synthesized. The aim was determining the optical bandgap and the characteristic peak related by bond transitions using the absorbance UV-Vis spectra. Both samples show high absorption in the ultraviolet region in the UV-Vis spectra. Using Tauc’s plot method we compute the bandgap energy for GONEs assuming indirect bandgap. In addition, we observe characteristic peak formation 1 hour after synthesized NPs at 256 nm for NPs prepared at 1064 nm and for NPs prepared at 532 nm the peak with less intensity is observed at a wavelength of 218 nm. The characteristic peak for both samples increase of intensity 24 hours after preparation.

The Effect of Laser Wavelength on Sensitivity and Accuracy of the Evanescent-Based Blood Glucose Sensor

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Effects of laser wavelength on aluminum plasma in transverse magnetic fields

The influence of the laser wavelength on nanosecond laser-produced Al plasma in a transverse magnetic field is studied and presented. A Q-switch Nd:YAG pulsed laser (FWHM: 6 ns) is used to ablate an aluminum sample at 50 mJ at the fundamental, second, and fourth harmonics of 1064 nm, 532 nm, and 266 nm, respectively. A permanent magnetic trap is used with a nearly uniform magnetic field of 0.8 T to confine plasma expansion, reduce both fast and slow components of plasma velocity, and increase signal intensity. Fast photography is performed using an Intensified Charged Coupled Device camera to study the plume hydrodynamics as it evolves through the induced magnetic field. Optical Emission Spectroscopy is used to determine the effect of the laser wavelength on key ionic and neutral emission lines, as well as to study the enhancement and reduction of certain emission lines in the presence of a magnetic field. Fast photography results confirm that the laser wavelength has a significant effect on plume hydrodynamics, especially as it evolves through the magnetic field. The magnetic field confines both fast and slow components of the plasma as early as ∼45 ns after laser impact for all laser wavelengths used, as well as reducing the velocity of the plasma by about 5×. It is shown that the 266 nm laser wavelength under the magnetic field enhanced both ionic and neutral lines by up to 11×, while 532 nm laser plasma only showed enhancements in ionic lines with reduction in neutral. A laser wavelength of 1064 nm showed a slight enhancement of ionic lines with a significant reduction in neutral lines under the same conditions.

Photoinduced Hysteresis of Graphene Field-Effect Transistors Due to Hydrogen-Complexed Defects in Silicon Dioxide.

Photoinduced hysteresis (PIH) of graphene field-effect transistors (G-FETs) has attracted attention because of its potential in developing photoelectronic or nonvolatile memory devices. In this work, we focused on the role of SiO2 dielectric layer on PIH, where G-FETs have only a SiO2 dielectric layer. Adsorbates are effectively removed before the PIH test. The effects of laser wavelength, laser power density, and temperature on the PIH are systematically investigated. The PIH is significantly enhanced by increasing the hydrogen flow in a hydrogen-atmosphere device thermal annealing. This strongly suggests proton-related defects that play a key role. The pure electronic process for PIH is further ruled out by the significant dependence of the doping rate on the temperature. A mechanism of PIH based on proton generation after hole trapping at [O3≡Si-H] is proposed. The proposed mechanism is well-supported by our experimental data: (1) the observed threshold photon energy for PIH is between 2.76 and 2.34 eV, which is close to the energy barrier for [O3≡Si-H], releasing a proton. (2) No obvious carrier mobility degradation after the PIH process suggests that the bulk defects in SiO2 are the major contributors rather than graphene/SiO2 interface defects. (3) The dependence of the doping rate on the temperature and the laser power density matches a theoretical model based on the random hopping of H+. The results in this work are also valuable for the study of degradation of other oxide dielectric materials in various field-effect transistors.

Laser wavelength and energy effect on optical and structure properties for nano titanium oxide prepared by pulsed laser deposit

Nano TiO2 thin films on glass substrates were prepared at a constant temperature of (373 K) and base vacuum (10-3 mbar), by pulsed laser deposition (PLD) using Nd:YAG laser at 1064 nm wavelength. The effects of different laser energies between (700-1000)mJ on the properties of TiO2 films was investigated. TiO2 thin films were characterized by X-ray diffraction (XRD) measurements have shown that the polycrystalline TiO2 prepared at laser energy 1000 mJ. Preparation also includes optical transmittance and absorption measurements as well as measuring the uniformity of the surface of these films. Optimum parameters have been identified for the growth of high-quality TiO2 films.

Intravenous Laser Wavelength Irradiation Effect on Interleukins: IL-1α, IL-1β, IL6 in Diabetic Rats.

The main purpose of this investigation in Low-Level Laser Therapy (LLLT) on diabetic rats is laser wavelength effect on interleukins: IL-1α, IL-1β, IL6. At first, diabetes was induced in Wistar rats by streptozotocin (STZ) injection. Then, by intravenous laser therapy, the rats were irradiated by four continuous wave lasers: IR (λ = 808 nm), Red (λ = 638 nm), Green (λ = 532 nm) and Blue (λ= 450 nm) to compare the related laser wavelength effect on different interleukins. The inflammatory parameters were measured 2,6 and 24 hours after laser therapy from blood samples and plotted for different laser wavelengths. The results show a decrease in all the above parameters by different laser irradiation in comparison to non-radiated diabetic control ones. More importantly with constant laser energy as the laser wavelength decreases, it affects more efficiently on lowering the above parameters. we can conclude from our data on diabetic rats that in intravenous LLLT, with constant laser energy, shorter wavelengths like Blue (λ= 450 nm) is more effective than longer wavelengths such as Red (λ = 638 nm) and IR (λ = 808 nm) lasers to lower the level of interleukins toward non-diabetic ones.

Laser Wavelength and Argon Ambient Gas Pressure Effects on Metallic Plasma Emission

The effects of laser wavelength and argon ambient gas pressure on ionic and atomic emission from aluminum and copper metal plasmas has been studied. The plasmas were generated using metal targets excited with a Q-switched Nd:YAG laser operating at the first fundamental (1064 nm), second (532 nm), third (355 nm), and fourth harmonics (266 nm) with repetition rate up to 10 Hz. The spectroscopic analysis of the plasma plume emission revealed that the intensities and signal-to-noise (S/N) ratio of various neutral and ion spectral lines, small components, and trace impurities increase sharply when the fourth laser harmonic is used at a wavelength of 266 nm. Based on LTE assumption, the electron excitation temperature (Te) and electron number density (Ne) of the produced plasma have been estimated from the Boltzmann plot using neutral spectral lines of Al I at 256.8, 257.5, 309.3, and 396.15 nm and Cu I at 427.58, 510.59, 570.07, and 578.58 nm and from Stark broadening width profile of Al II at 281.6 nm and Cu I at 324.75 nm, respectively. The variations of Te, Ne, and emission intensities of metals as a function of laser irradiance of different laser wavelengths at 1064, 532, 355, and 266 nm were studied. The effect of the argon ambient gas pressure on the plasma parameters was also studied. The diagnostics of the produced metal plasma was undertaken using laser induced breakdown spectroscopy (LIBS).

Effects of laser polarization and wavelength on hybrid laser wakefield and direct acceleration

We demonstrate that hybrid laser wakefield and direct acceleration can be significantly improved by using two laser pulses with different polarizations or frequencies. The improvement entails higher energy and charge of the accelerated electrons, as well as weaker sensitivity to the time delay between the leading (pump) pulse responsible for generating the wakefield, and the trailing laser pulse responsible for direct laser acceleration (DLA). When the two laser pulses have the same frequency, it is shown that it is advantageous to have their polarization states orthogonal to each other. A specific scenario of a frequency-doubled (λDLA = λpump/2) DLA laser pulse is also considered, and found to be an improvement over the single-frequency (λDLA = λpump) format.

Intense laser filament-solid interactions from near-ultraviolet to mid-infrared.

Studies of high-power ultrashort laser pulse interaction with matter are not only of fundamental scientific interest, but are also highly relevant to applications in the domain of remote sensing. Here, we investigate the effect of laser wavelength on coupling of femtosecond laser filaments to solid targets. Three central wavelengths have been used to produce filaments: 0.4, 0.8, and 2.0 µm. We find that, unlike the case of conventional tight focusing, use of shorter wavelengths does not necessarily produce more efficient ablation. This is explained by increased multi-photon absorption arising in near-UV filamentation. Investigations of filament-induced plasma dynamics and its thermodynamic parameters provide the foundation for unveiling the interplay between wavelength-dependent filament ablation mechanisms. In this way, strategies to increase the sensitivity of material detection via this technique may be better understood, thereby improving the analytical performance in this class of applications.

Effect of Various Laser Wavelengths on Temperature Changes During Periimplantitis Treatment: An in vitro Study.

This study aimed to investigate and compare temperature change during implant decontamination with different laser types (carbon dioxide [Co2]/diode/neodymium-doped yttrium aluminum garnet [Nd:YAG]/erbium-doped yttrium aluminum garnet [Er:YAG]/antimicrobial photodynamic therapy [aPDT]). Sixty implants were inserted into a bone block cut from a sheep's mandible. A 3 × 8 mm vertical lesion was made at the buccal of each implant. The bone block was placed into a 37°C water bath to simulate the in vivo oral condition. A K-type thermocouple was placed in contact with the implant to register temperature changes at 3 points (apical/middle/coronal). In the entire laser irradiations, the mean of temperature changes remains below 10°C. The apical temperature rise was higher than the coronal and middle regions (P < 0.05), and the apical temperature took longer time to reach the initial temperature (37°C) (P < 0.001). Temperature changes over 10°C occurred at the apical point of the implants with the Co2, Nd:YAG, and diode laser irradiations; however, only the Co2 laser reached the statistical significance in this regard (P < 0.05). Our findings indicate the promising results of Er:YAG laser and aPDT in implant decontamination. Precaution should be taken in the application of Nd:YAG, diode, and especially Co2 lasers.

Effect of laser irradiance and wavelength on the analysis of gold- and silver-bearing minerals with laser-induced breakdown spectroscopy

The influence of laser irradiance and wavelength on the analysis of gold and silver in ore and surrogate samples with laser-induced breakdown spectroscopy (LIBS) was evaluated. Gold-doped mineral samples (surrogates) and ore samples containing naturally-occurring gold and silver were analyzed with LIBS using 1064 and 355 nm laser wavelengths at irradiances from 0.36 × 109 to 19.9 × 109 W/cm2 and 0.97 × 109 to 4.3 × 109 W/cm2, respectively. The LIBS net, background and signal-to-background signals were analyzed. For all irradiances, wavelengths, samples and analytes the calibration curves behaved linearly for concentrations from 1 to 9 μg/g gold (surrogate samples) and 0.7 to 47.0 μg/g silver (ore samples). However, it was not possible to prepare calibration curves for gold-bearing ore samples (at any concentration) nor for gold-doped surrogate samples with gold concentrations below 1 μg/g. Calibration curve parameters for gold-doped surrogate samples were statistically invariant at 1064 and 355 nm. Contrary, the Ag-ore analyte showed higher emission intensity at 1064 nm, but the signal-to-background normalization reduced the effect of laser wavelength of silver calibration plots. The gold-doped calibration curve metrics improved at higher laser irradiance, but that did not translate into lower limits of detection. While coefficients of determination (R2) and limits of detection did not vary significantly with laser wavelength, the LIBS repeatability at 355 nm improved up to a 50% with respect to that at 1064 nm. Plasma diagnostics by the Boltzmann and Stark broadening methods showed that the plasma temperature and electron density did not follow a specific trend as the wavelength changed for the delay and gate times used. This research presents supporting evidence that the LIBS discrete sampling features combined with the discrete and random distribution of gold in minerals hinder gold analysis by LIBS in ore samples; however, the use of higher laser irradiances at 1064 nm increased the probability of sampling and detecting naturally-occurring gold.

Effect of laser wavelength and energy on the detecting of trace elements in steel alloy

In order to investigate the effect of laser wavelength and energy on the detection of the trace elements in alloy steel, pulsed laser at 1064 nm and 532 nm wavelength have been employed to generate plasma. The effects of the laser energy of these two laser wavelengths on plasma emission intensity, plasma temperature and electron density were studied. The trace elements of Ni, Al and Cr in the sample were quantitatively analyzed by internal standard method under these two different laser wavelengths with different laser energies. The results have shown that the intensities of the spectral intensities increased with the increasing of laser energy at different wavelengths, and then tended to change gently. The plasma temperature also increased with the increasing of laser energy, and the change of plasma temperature under 532 nm wavelength is slower. The plasma electron density firstly increased with laser energy, and then decreased when the laser energy exceeded the threshold. The quantitative analysis results show that the elements of Ni and Al have lower detection limits at 1064 nm wavelength, while the lower detection limit of Cr corresponding to the 532 nm wavelength. When the sample was ablated at 1064 nm wavelength, the detection limit of the three elements was gradually reduced with the increasing of laser energy.

Effect of Laser Wavelength on AZO Surface Texturing by Direct Laser Processing / Patterning for Thin-Film Silicon Solar Cells Applications

ABSTRACTSurface texturing of transparent conductive oxides is crucial to improve the fraction of incident light trapped in the absorber layer of thin film silicon based solar cells to improve the device performance. In this work, we fabricate and compare periodic, overlapping, and random surface textures and patterns on aluminium doped zinc oxide (AZO) using direct laser processing. The effects of the used laser wavelength, laser operating frequency, and pulse periodicity on the structural, morphological, and optical response of the AZO films were investigated. By optimizing the laser parameters and the associated process conditions, a drastic increase up to 60% in the transmittance haze over the entire solar was achieved.

Nonlinear absorption dynamics simulated in internal modification of glass at 532nm and 1064nm by ultrashort laser pulses

Dynamic ionization process at high pulse repetition rate is analysed based on the model consisting of rate equation for free-electrons, Gaussian beam propagation equation, thermal conduction and thermal ionization, showing the plasma generated near the geometrical focus moves toward the laser source periodically by the contribution of avalanche ionization. The effects of laser wavelength on the ionization process are discussed by comparing the contributions of multiphoton ionization and avalanche ionization. The crack tendency of 532nm and 1064nm is also compared between single pulse and multipulse irradiation.

Tungsten borides layers deposited by a nanosecond laser pulse

Tungsten borides belong to the group of potentially superhard materials which hardness could be compared to cubic boron nitride and diamond. However, difficulty in fabrication of single phase material using conventional methods is the main drawback of this group of ceramics. In order to overcome this problem material can be deposited as a thin layer e.g. in the pulsed laser deposition process. In this paper, the effect of laser wavelength and energy density of nanosecond Nd:YAG laser on the WBx-type layers were analyzed using wavelengths 355 and 1064nm with the energy density of laser beam from 1.7 to 5J/cm2 and from 1.7 to 9.3J/cm2, respectively. The WB2.5 and WB4.5 targets synthesized in Spark Plasma Sintering process were used and the layers were deposited onto Si (100) substrate heated to a temperature of 570°C. Layers' microstructure were analyzed using X-ray Diffraction and scanning electron microscope equipped with energy dispersive X-ray spectrometer. Change of laser wavelength and energy density resulted in variations of the chemical composition and morphology of deposited layers. Finally, W2B-βWB, αWB-WB-WB3 and WB3, and boron layers were deposited wherein WB3 structure is formed in a wide range of laser fluences and at both investigated wavelength. Next, WB3 layers were investigated in the indentation test at a load of 5–30mN and its hardness was up to 50±10GPa.

The effect of laser wavelength on the delay time of laser triggered vacuum switch.

The study on the influence of laser wavelength on the initial plasma properties of laser-triggered vacuum switch (LTVS) is not only beneficial to understanding the trigger mechanism but also to optimizing its design for miniaturization and generalization. In this paper, the one-dimensional heat conduction model of the target was developed and then the effect of laser wavelength on the depth of laser ablation and the quantity of initial plasma were investigated experimentally and theoretically with the laser absorption rate. The theoretical analysis was in good agreement with experimental measurement of the delay time of the LTVS. It is clear that the shorter the wavelength, the shorter the delay time will be after the LTVS is triggered.

Surface microstructure and chemistry of polyimide by single pulse ablation of picosecond laser

Polyimide (PI) surface was ablated by the single pulse of picosecond laser, and the effects of laser wavelength (λ=355nm and 1064nm) and fluence on surface microstructure and chemistry were explored. Scanning electron microscopy (SEM) analysis found that different surface microstructures, i.e., the concave of concentric ring and the convex of porous circular disk, were generated by 355nm and 1064nm picosecond laser ablation, respectively. X-ray photoelectron spectroscopy (XPS) characterization indicated that due to the high peak energy density of picosecond laser, oxygen and nitrogen from the ambient were incorporated into the PI surface mainly in the form of CO and CNC groups. Thus, both of the O/C and N/C atomic content ratios increased, but the increase caused by 1064nm wavelength laser was larger. It inferred that the differences of PI surface microstructures and chemistry resulted from different laser parameters were related to different laser-matter interaction effects. For 355nm picosecond laser, no obvious thermal features were observed and the probable ablation process of PI was mainly governed by photochemical effect; while for 1064nm picosecond laser, obvious thermal feature appeared and photothermal effect was thought to be dominant.

Wavelength and ambient luminance dependence of laser eye dazzle

A series of experiments has been conducted to quantify the effects of laser wavelength and ambient luminance on the severity of laser eye dazzle experienced by human subjects. Eight laser wavelengths in the visible spectrum were used (458-647nm) across a wide range of ambient luminance conditions (0.1-10,000 cd·m-2). Subjects were exposed to laser irradiance levels up to 600 μW·cm-2 and were asked to recognize the orientation of optotypes at varying eccentricities up to 31.6deg of visual angle from the laser axis. More than 40,000 data points were collected from 14 subjects (ages 23-64), and these were consolidated into a series of obscuration angles for comparison to a theoretical model of laser eye dazzle. Scaling functions were derived to allow the model to predict the effects of laser dazzle on vision more accurately by including the effects of ambient luminance and laser wavelength. The updated model provides an improved match to observed laser eye dazzle effects across the full range of conditions assessed. The resulting model will find use in a variety of laser safety applications, including the estimation of maximum dazzle exposure and nominal ocular dazzle distance values.

Two-color laser wavelength effect on intense terahertz generation in air☆☆Project supported by the National Natural Science Foundation of China (Grant Nos. 51132004, 11604205, and 11474096), Science and Technology Commission of Shanghai Municipality, China (Grant No. 14JC1401500), Shanghai Municipal Education Commission, China (Grant No. ZZGCD15066), and Foundation of Fujian Educational Committee, China (Grant No. JAT160412).

Near-IR femtosecond lasers have been proposed to produce high-field terahertz radiation in the air via the laser–plasma interaction, but the physical mechanism still needs to be further explored. In this work, we theoretically investigate the effect of the two-color laser wavelength on the terahertz generation in the air based on a transient photocurrent model. We show that the long wavelength laser excitation can greatly enhance the terahertz amplitude for a given total laser intensity. Furthermore, we utilize a local current model to illustrate the enhancement mechanism. Our analysis shows that the terahertz amplitude is determined by the superposition of contributions from individual ionization events, and for the long wavelength laser excitation, the electron production concentrates in a few ionization events and acquires the larger drift velocities, which results in the stronger terahertz radiation generation. These results will be very helpful for understanding the terahertz generation process and optimizing the terahertz output.