Effect Of Different Laser Wavelengths Research Articles

Fabrication of UV photodetector based on GaN/ Psi heterojunction using pulse laser deposition method: Effect of different laser wavelengths

In this study, GaN/pSi heterojunction photodetectors were fabricated via pulsed laser deposition method (PLD). Photoelectrochemical etching method (PECE) with laser aid prepared a pSi substrate. Different laser wavelengths were tested on GaN and pSi films' structural, spectroscopic, electrical, and performance characteristics. XRD showed that GaN/pSi heterojunction photodetectors were polycrystalline and hexagonal. PL measurements showed two emission peaks attributable to GaN films (374, 364, 359 nm) and the pSi substrate (730, 729, 729 nm). Shorter laser wavelengths raised the GaN/pSi heterojunction's optical energy gap from 3.271 to 3.3415 eV. FESEM pictures showed that the average size of the manufactured samples was 51.88, 36.12, and 22.76 nm for spherical nanoparticles and a cauliflower-like shape. Atomic force microscopy (AFM) results show the root mean square of the surface roughness of prepared samples to be 4.83, 8.87, and 14.51 nm, respectively, as the laser wavelength became shorter with full coverage of all pores of prepared pSi. GaN/pSi heterojunction photodetectors had rectification in their dark I–V characteristics, and the heterojunction made at 355 nm had the best junction characteristics. The spectral responsivity of GaN/pSi photodetectors shows that the maximum responsivity was 29.01 A/W at 370 nm for a photodetector prepared at 355 nm. High detectivity and external quantum efficiency were 8.02×10+12 Jones and 359.73% at 370 nm, respectively. The photodetector fabricated using 355 nm showed a fast rise time of 328μsec and a fall time of 617μsec.

The Impact of Laser Thermal Effect on Histological Evaluation of Oral Soft Tissue Biopsy: Systematic Review

The aim of the study is to review the literature to observe studies that evaluate the extent of the thermal effect of different laser wavelengths on the histological evaluation of oral soft tissue biopsies. An electronic search for published studies was performed on the PubMed and Scopus databases between July 2020 and November 2022. After the selection process, all the included studies were subjected to quality assessment and data extraction processes. A total of 28 studies met the eligibility criteria. The most studied laser was the carbon dioxide (CO2) laser, followed by the diode laser 940 nm-980 nm. Six studies were focused on each of the Erbium-doped Yttrium Aluminium Garnet (Er:YAG), Neodymium-doped Yttrium Aluminum Garnet (Nd:YAG) lasers, and diode lasers of 808 nm and 445 nm. Three studies were for the Potassium Titanyl Phosphate (KTP) laser, and four studies were for the Erbium, Chromium-doped Yttrium, Scandium, Gallium, and Garnet (Er,Cr:YSGG) laser. The quality and bias assessment revealed that almost all the animal studies were at a low risk of bias (RoB) in the considered domains of the used assessment tool except the allocation concealment domain in the selection bias and the blinding domain in the performance bias, where these domains were awarded an unclear or high score in almost all the included animal studies. For clinical studies, the range of the total RoB score in the comparative studies was 14 to 23, while in the non-comparative studies, it was 11 to 15. Almost all the studies concluded that the thermal effect of different laser wavelengths did not hinder the histological diagnosis. This literature review showed some observations. The thermal effect occurred with different wavelengths and parameters and what should be done is to minimize it by better adjusting the laser parameters. The extension of margins during the collection of laser oral biopsies and the use of laser only in non-suspicious lesions are recommended because of the difficulty of the histopathologist to assess the extension and grade of dysplasia at the surgical margins. The comparison of the thermal effect between different studies was impossible due to the presence of methodological heterogeneity.

Effect of different laser wavelengths on laser cladding of pure copper

The blue laser provides a fresh direction for the laser cladding of pure copper materials which have high reflectivity to the infrared laser. Herein, the laser cladding of pure copper is carried out on 316 stainless steel substrates using blue laser and infrared laser. Specifically, the cladding spatters, macroscopic morphology, microstructure, and microhardness were studied by comparing the cladding under these two lasers. The laser absorption of copper does not change sharply with temperature and is higher under blue laser, which is proved to be more conducive to the stability of the molten pool during the cladding process and enables the preparation of coatings with fewer defects at lower energy densities. Also, it is found that the average hardness of the coatings prepared under an infrared laser (166.2 HV0.1) is higher than that prepared under a blue laser (133 HV0.1). This is because the keyhole tendency under an infrared laser enhances the Marangoni convection and leads to a more pronounced diffusion between elements and more Fe-rich phases in the coatings. Overall, this work deepens the understanding of pure copper materials cladding at different-wavelength lasers and provides a reference for blue laser cladding on highly reflective materials.

Laser safety eyewear

The use of Lasers in aesthetic dermatology increased the efficacy and decreased the downtime for various dermatological procedures. In addition to the knowledge of different indications for lasers, knowledge regarding the safety precautions, and effects of lasers on human tissue is essential for the dermatologist. The safety precautions to be taken especially for eye protection need emphasis as the damage induced can be permanent. The current article deals with the effects of different laser wavelengths on eye tissue, the variety of Laser safety eyewear (LSE) available in the market, and how to read the LSE label on protective eyewear. Various LASER textbooks, UK & US national health and safety guidelines, and online LASER physics articles have been referred.

Laser Irradiation Effects at Different Wavelengths on Phenology and Yield Components of Pretreated Maize Seed

This study aims to compare the effects of different laser wavelengths, exposure times, and low-power-intensity laser irradiation on maize seeds. Seeds were exposed to He–Ne (632.8 nm) red laser, Nd:YAG second-harmonic-generation (532 nm) green laser, and diode (410 nm) blue laser. Four different exposure times (45, 65, 85, and 105 s) with different intensity (2 and 4 mW/cm2), for each laser were tested. Phenology and yield components (plant height, leaf area, number of rows per ear, seed yield, harvest index, yield efficiency, and grain weight) were determined. The experiment was conducted in a randomized complete block design with three replications. Plant height was found comparatively high in blue laser light—211 cm at 85 s. Blue and green laser lights showed significant increases in the number of rows per ear to 39.1 at 85 s and 45 at 65 s, respectively, compared to the control of 36 rows/ear. The order of seed yield was blue (7003.4 kg/ha) > green (6667.8 kg/ha) > red (6568.01 t/ha) based on different exposure times of 85 s, 85 s, and 105 s, respectively, compared to the control of 6.9 kg/ha. The findings indicate the possibility of using blue laser light to manipulate the growth and yield of maize.

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.

Laser-induced plasma electron number density: Stark broadening method versus the Saha–Boltzmann equation

We report spectroscopic studies on plasma electron number density of laser-induced plasma produced by ns–Nd:YAG laser light pulses on an aluminum sample in air at atmospheric pressure. The effect of different laser energy and the effect of different laser wavelengths were compared. The experimentally observed line profiles of neutral aluminum have been used to extract the excitation temperature using the Boltzmann plot method, whereas the electron number density has been determined from the Stark broadened as well as using the Saha–Boltzmann equation (SBE). Each approach was also carried out by using the Al emission line and Mg emission lines. It was observed that the SBE method generated a little higher electron number density value than the Stark broadening method, but within the experimental uncertainty range. Comparisons of Ne determined by the two methods show the presence of a linear relation which is independent of laser energy or laser wavelength. These results show the applicability of the SBE method for Ne determination, especially when the system does not have any pure emission lines whose electron impact factor is known. Also use of Mg lines gives superior results than Al lines.

Laser cleaning of diagnostic mirrors from tungsten–oxygen tokamak-like contaminants

This paper presents a laboratory-scale experimental investigation about the laser cleaning of diagnostic first mirrors from tokamak-like contaminants, made of oxidized tungsten compounds with different properties and morphology. The re-deposition of contaminants sputtered from a tokamak first wall onto first mirrors’ surfaces could dramatically decrease their reflectivity in an unacceptable way for the proper functioning of plasma diagnostic systems. The laser cleaning technique has been proposed as a solution to tackle this issue. In this work, pulsed laser deposition was exploited to produce rhodium films functional as first mirrors and to deposit onto them contaminants designed to be realistic in reproducing materials expected to be re-deposited on first mirrors in a tokamak environment. The same laser system was also used to perform laser cleaning experiments, exploiting a sample handling procedure that allows one to clean some cm2 in a few minutes. Cleaning effectiveness was evaluated in terms of specular reflectance recovery and mirror surface integrity. The effect of different laser wavelengths (, 266 nm) on the cleaning process was also addressed, as well as the impact of multiple contamination/cleaning cycles on the process outcome. A satisfactory recovery of pristine mirror reflectance (⩾90%) was obtained in the vis–NIR spectral range, avoiding at the same time mirror damaging. The results here presented show the potential of the laser cleaning technique as an attractive solution for the cleaning of diagnostic first mirrors.

Laser irradiation on growth of trichophyton rubrum: an in vitro study.

Trichophyton rubrum is one of the most common species of dermatophytes which affects superficial keratinous tissue. It is not especially virulent but it can be responsible for considerable morbidity. Although there are different therapeutic modalities to treat fungal infections, clinicians are searching for alternative treatment because of the various side effects of the present therapeutic methods. As a new procedure, Laser therapy has brought on many advantages in clinical management of dermatophytes. Possible inhibitory potential of laser irradiation on fungal colonies was investigated invitro in this study. A total of 240 fungal plates of standard size of trichophyton rubrum colonies that had been cultured from the lesions of different patients at the mycology laboratory, were selected. Each fungal plate was assigned as control or experimental group. Experimental plates were irradiated by a laser system (low power laser or different wavelength of high power laser). The effects of different laser wavelengths and energies on isolated colonies were assessed. After laser irradiation, final size of colonies was measured on the first, the 7th and the 14th day after laser irradiation. Although low power laser irradiation did not have any inhibitory effect on fungal growth, the Q-Switched Neodymium-Doped Yttrium Aluminium Garnet (Nd:YAG) laser 532nm at 8j/cm(2), Q-Switched Nd:YAG laser 1064nm at 4j/cm(2) to 8j/cm(2) and Pulsed dye laser 595nm at 8j/cm(2) to 14j/cm(2) significantly inhibited growth of trichophyton rubrum in vitro. Q-Switched Nd:YAG 532nm at 8j/cm(2), Q-Switched Nd:YAG laser 1064nm at 4j/cm(2) to 8j/cm(2) and pulsed dye laser (PDL) 595nm at 8j/cm(2) to 14j/cm(2) can be effective to suppress trichophyton rubrum growth.

Laser cleaning of diagnostic mirrors from tokamak-like carbon contaminants

This paper presents a laboratory-scale experimental investigation of laser cleaning of diagnostic First Mirrors (FMs). Redeposition of contaminants sputtered from tokamak first wall onto FMs surface could dramatically decrease their reflectivity in an unacceptable way for the functioning of the plasma diagnostic systems. Laser cleaning is a promising solution to tackle this issue. In this work, pulsed laser deposition was exploited to produce rhodium films functional as FMs and to deposit onto them carbon contaminants with tailored features, resembling those found in tokamaks. The same laser system was also used to perform laser cleaning experiments by means of a sample handling procedure that allows to clean some cm2 in few minutes. The cleaning effectiveness was evaluated in terms of specular reflectivity recovery and mirror surface integrity. The effect of different laser wavelengths (λ=1064, 266nm) on the cleaning process is also addressed.

Fungicidal response of a novel natural photosensitizer (Beta vulgaris) on Candida albicans with low-power laser radiation

We report the efficacy of an aqueous extract of Beta vulgaris as a novel, natural photosensitizer for use in photodynamic therapy against Candidiasis disease. This study evaluates the effect of different laser wavelengths (He–Ne: 633 nm, Nd-YAG: 532 nm), power (17, 27 mW) and duration of exposure (5, 10, 15 min) in combination with the Beta vulgaris natural photosensitizer on the viability of Candida albicans causing Candidiasis disease. Although inhibition was observed in all cases, a maximum of 51.91% inhibition takes place with the combination of Beta vulgaris exposed to 532 nm at 27 mW for 15 min by the Agar well diffusion method. The study is important in optimizing different parameters and designing a low-power, compact, non-invasive and portable device for treatment.

Comparison of the Effects of Different Laser Wavelengths on Implants Surfaces

Lasers have been long introduced in dentistry. Today lasers are been used for Endodontics, Periodontics, Oral Surgery as well as restorative procedures. Here, we describe the effect of different wavelengths on the implant surface.

The effects of different laser wavelengths on the embryo biopsy procedure and embryo development to the blastocysts stage

OBJECTIVE: A laser is used to remove a cell for preimplantation genetic screening (PGS). The laser uses intense heat and this heat might disrupt embryo development. Therefore, it is the goal of this study to test the effects of different laser wavelengths (and consequently heat) on the biopsy procedure and embryo development.

Interstitial laser photocoagulation: Evaluation of a 1320 nm Nd-YAG and an 805 nm diode laser: the significance of charring and the value of precharring the fibre tip

Interstitial laser photocoagulation (ILP) is a new percutaneous technique of thermal destruction (necrosis) of deep-seated tumours, using low power laser energy. Our purpose was to investigate: (i) the effects of different laser wavelengths on the extent of thermal damage produced; and (ii) the role of charring around the fibre tip during ILP. Forty-five normal Wistar rats (250–300 g) had ILP to their liver (exposed at laparotomy) by inserting a 400 μm optical fibre into the liver, and activating the laser at 1, 2 or 3W. This was performed at three laser wavelengths (1064 nm Nd-YAG, 1320 nm Nd-YAG, 805 nm diode) using a clean plane-cleaved fibre, and at two wavelengths (1064 nm and 1320 nm Nd-YAG) using a fibre with pre-charring at its tip. The 805 nm and 1320 nm laser wavelengths produced significantly greater necrosis than the 1064 nm, using a clean fibre tip (mean diameters at 2 W were 21.7 mm, 18.3 mm, 8 mm respectively). Pre-charring the fibre significantly increased the necrotic lesion size at 1064 nm (mean diameter at 2 W was 14.7 mm). Using more strongly absorbed wavelengths (805 nm and 1320 nm) and pre-charring the fibre tip give greater thermal damage during ILP, contrary to previously held views that the optimal wavelength for ILP was 1064 nm in the absence of charring.