Second Harmonic Generation in Quasi-Phase-Matching Waveguides

The purpose of this study is to see how low-power red laser helium-neon and diode lasers with wavelengths of 632.8 nm and 650 nm, respectively, affect some human blood sample factors like viscosity HCT, Platelets PLT, White blood cells WBC, white blood lymphocytes LYM, neutrophilic white blood cells NEUT, red blood cells RBC, and Erythrocyte Sedimentation Rate ESR. Blood samples were collected from healthy people and placed in EDTA-contained tubes, blood tests were performed on control samples in a blood analyzer, and the samples were divided into two parts and split into two equal tubes to be irradiated with diode and helium-neon lasers for 15 minutes. Using a blood analyzer, measurements were taken immediately after irradiation. The results of this analysis indicated a decrease in the number of white blood cells (WBC), red blood cells (RBC), and blood viscosity (HCT), as well as a significant rise in the number of neutrophils (NEUT) and platelets (PLT) and increase in the Erythrocyte Sedimentation Rate ESR after exposure to both helium-neon and diode lasers. This suggests that It is possible to make recommendations, a low-power laser could be used to stimulate blood cells so a laser could be used to treat blood viscosity. Because of the increasing concentrations of free intracellular Calcium ions and the action of laser on the plasma composition, it is acceptable to suggest that laser irradiation can lower the number of white blood cells (WBC), red blood cells (RBC), and the reason of that is because of a mechanical change in the blood such as a change in the pores of the surfaces and their fixation.

Subject and purpose. Currently, gas, solid-state, and fiber lasers are used to process materials in the aviation industry. For the thermal treatment of steels, gas CO2 lasers with a capacity of more than 1 kW used, which are reliable in operation but have high cost and low efficiency. There are no results on the use of low-power (up to 20 W) pulsed-mode lasers for surface hardening of steel products. The purpose of this work is to determine the modes of surface hardening of products from carbon and alloy steels using low-power solid-state pulsed YAG lasers. Methodology. For laser hardening, a 5 W solid-state YAG laser was used (diode pumping, radiation wavelength λ = 1,064 μm, pulse mode). The use of a nonlinear crystal made it possible to obtain UV radiation with λ = 0,355 μm (third harmonic). The following modes were investigated: processing with single pulses (duration 0,1...0,4 ms) and multi-pulse processing with short (30...70 ms) pulses. The scanning speed was 8...2 mm/s. The energy in the pulse was determined by the photoelectric method. Thermal hardening was performed on the following steels: У12, P6M5. The possibility of UV radiation hardening was evaluated on steel 20, 45, У12, and ШХ15. Findings. The optimum values of pulse duration for maximum hardness in laser hardening of the investigated steels. With multi-pulse treatment of steels, the pulse duration is shorter than with single-pulse treatment, the hardening intensity is higher, and the quality of the processed surface is better. Single-pulse and multi-pulse processing are accompanied by partial melting of the surface of steel products, which does not allow it to be used in cases where a high quality of the surface is required. Laser hardening of steel by ultraviolet radiation is not accompanied by melting. Conclusion. For surface hardening of products, where partial melting of the surface is possible, low-power lasers in pulse mode can be used. Laser hardening by ultraviolet radiation is a promising direction for thermal hardening of steels, which allows maintaining the original quality of the surface layer. Thermal hardening with low-power lasers can be effective for small-sized areas of the processed parts of the fuel equipment of aircraft engines, friction elements, and, especially, the tool is small.

We demonstrate a passively Q-switched Tm3+-doped all-fiber laser (TDFL) at around 2 μm with a graphene-based saturable absorber (SA). The graphene is prepared by the reduction of graphite oxide (GO), deposited on the fiber core and inserted into a linear cavity as the passive Q-switch. A 793 nm laser diode (LD) is used as the pump source, with a maximum power of 200 mW. A maximum output power of ∼33.5 mW is obtained at a pump power of 200 mW, with a high optical conversion efficiency of about 17%. The corresponding single pulse energy is 260 nJ and the repetition rate is 128 kHz.

Solar Cell Capacitance Simulator in 1 Dimension (SCAPS-1D) is used to investigate the possibility of realizing ultrathin CdTe based solar cells with high and stable conversion efficiency. In the first step, we modified the conventional cell structure by substituting the CdS window layer with a CdS:O film having a wide band gap ranging from 2.42 to 3.17 eV. Thereafter, we simulated the quantum efficiency, as well as the parameters ofJ-Vcharacteristics, and showed how the thickness of CdS:O layer influences output parameters of Glass/SnO2/ZTO/CdS:O/CdTe1-xSx/CdTe/Ni reference cell. High conversion efficiency of 17.30% has been found using CdTe1-xSx(x=0.12) and CdTe layers of thickness 15 nm and 4 μm, respectively. Secondly, we introduced a BSR layer between the absorber layer and back metal contact, which led to Glass/SnO2/ZTO/CdS:O/CdTe1-xSx/CdTe/BSR/Ni configuration. We found that a few nanometers (about 5 nm) of CdTe1-xSxlayer is sufficient to obtain high conversion efficiency. For BSR layer, different materials with large band gap, such as ZnTe, Cu2Te, and p+-CdTe, have been used in order to reduce minority carrier recombination at the back contact. When ZnTe is used, high conversion efficiency of 21.65% and better stability are obtained, compared to other BSR.

Journal of Medicine and Medical Sciences Vol. 8(5) 069.-076, August 2017 DOI: http:/dx.doi.org/10.14303/jmms.2017.038 Available online http://www.interesjournals.org/JMM S Copyright © 2017 International Research Journals Full Length Research Paper Role of 810 nm and 980 nm diode laser in treatment of dentinal hypersensitivity: A literature review 1* Mohammed Abdelfattah 2 Ahmed samy 3 Mostafa Aboellil Via Zanardi, 40131 Bologna, Italy *Corresponding Author’s Email:m_foxa@hotmail.com Abstract Laser therapy was first introduced as a potential m ethod for treating dentinal hypersensitivity (DH) i n the mid-1980s Various types of laser used in treatm ent like low power lasers He-Ne (632.5 nm), diode lasers with various wavelengths 810, 940,980 nm and medium power lasers as Nd:YAG (1064nm), CO2 10600 Er:YAG (2940nm) and Er,Cr:YSGG (2780nm). He-N e (632.5 nm) and diode lasers have analgic effect. Objectives: To appraise the efficiency of d ifferent techniques by using diode lasers 810 and 9 80 nm alone or in a combination with different desensi tizing agents in management and treatment of dentinal hypersensitivity Data:138 articles are inc luded then according to exclusion criteria, 46 arti cles are included, after specific exclusion criteria a nd evaluation of the articles, they become 35 artic les, from the 35 articles there were 5 systematic review articles 22 in vivo study and 8 in vitro study. Sources: A thorough search of Literature was perfor med through Pubmed databases. Words used in the search: diode lasers and hypersensitivity, diod e lasers in treatment dental hypersensitivity, dent inal hypersensitivity, and low power lasers. Conclusions : 810 and 980 diode lasers are effective in treatment of dentinal hypersensitivity, diode lasers with dif ferent wavelengths alone or with desensitizing materials are efficient

We demonstrate, for the first time to the best of our knowledge, four wave mixing (FWM) process in a 900 nm wavelength region. A 54 m highly nonlinear photonic crystal fiber (HN-PCF) is used as nonlinear medium, and continuous wave laser diodes at near 975 nm are selected as pump sources. By simultaneously injecting two pump sources into the HN-PCF, FWM is observed with wavelength spacing of 0.4 nm and 2 nm, respectively. Compared with FWM in conventional highly nonlinear fibers, HN-PCF one possesses much higher conversion efficiency. These FWMs introduce an opportunity to extend the wavelength coverage of fiber lasers and amplifiers in 900 nm waveband, and also indicate that HN-PCFs can have great potential for FWM applications towards short wavelength regions.

The aim of the study was to investigate the biochemical and molecular changes in the process of epidermal healing of burn injuries after therapeutic treatment with low-power laser (LPL) and light-emitting diode (LED). Rats were divided into six groups: skin without injury (Sham), burn wounds (BWs), BW + 660-nm LPL, BW + 904-nm LPL, BW + 632-nm LED, and BW + 850-nm LED. The burn wound model was performed using a 100°C copper plate, with 10s of contact in the skin. The irradiations started 24h after the lesion and were performed daily for 7days. The burn wound groups showed an increase in the superoxide production, dichlorofluorescein, nitrites, and high protein oxidative damage. The activities of glutathione peroxidase and catalase were also increased, and a significant reduction in glutathione levels was observed compared to the control group. However, treatments with 660-nm LPL and 850-nm LED promoted protection against to oxidative stress, and similar results were also observed in the IL-6 and pERK1/2 expression. Taken together, these results suggest that LPL 660nm and LED 850nm appear reduced in the inflammatory response and oxidative stress parameters, thus decreasing dermal necrosis and increasing granulation tissue formation, in fact accelerating the repair of burn wounds.

Robust high-efficiency LuAG: Ce phosphor-in-silica glass (PiSG) for high-brightness laser lighting

One of the key developments in the renaissance in solid-state laser technology has been the rapid improvement of diode laser pump sources.1–3 Some of the advantages of diode-pumping relative to lamp-pumping of solid-state lasers include higher overall efficiency, reduced thermal loading of the gain medium, higher reliability, and reduced size. In addition, there are other important differences between these two types of pump sources. For example, diode lasers have higher spectral and spatial brightness, in other words, the diode laser output is narrowband spectrally, and it is directional. The consequence is that much higher volumetric pumping density can be achieved using diode-laser pumps even with low power single-stripe diode lasers relative to high-power lamps. The high pump densities has led to the demonstration of good laser performance at room temperature of several transitions that performed only poorly or not at all at room temperature under lamp pumping. These transitions in rare-earth ions include the 4F3/2- 4I9/2 near 0.94 µm in Nd3+,4–6 the 5I7 - 5I8 near 2.1 µm in Ho3+,7–10 the 3F4 -3H6 near 2.0 µm in Tm3+,11–13 the 4I13/2 - 4I15/2 near 1.5 µm in Er3+,13,14 and the 2F5/2 - 2F7/2 near 1.0 µm in Yb3+ (refs. 15, 16) as shown in Fig. 1. The common element in these laser transitions is that the lower laser levels are in the ground-state multiplet which means that the lower laser levels are only a few hundred cm-1 above the ground state. Thus the lower levels have significant population in thermal equilibrium at room temperature since kT is 207 cm-1 at 300 K. This is in contrast to the common four-level Nd3+ transition near 1.06 µm which has a lower level about 10kT above the ground-state at 300 K thus can be considered unpopulated in thermal equilibruim, or ruby in which the lower laser level is the ground-state. With lamp-pumping, these lasers with lower levels in the ground-state manifold were typically operated at cryogenic temperatures to reduce the lower-level population in thermal equilibruim; at sufficiently low temperature these lasers become four-level lasers and efficient, low threshold performance was obtained.

Vascular restenosis after injury of blood vessel has been implicated in various responses including apoptosis, migration, and proliferation in vascular smooth muscle cells (VSMCs) stimulated by diverse growth factors underlying platelet-derived growth factor (PDGF). Previous studies evaluated the effects of low-power laser (LPL) irradiation over various wavelength ranges on VSMC events in normal and pathologic states. However, whether VSMC responses are affected by LPL irradiation remains unclear. The purpose of this study is to explore the effects of LPL (green diode laser 532-nm pulsed wave of 300mW at a spot diameter of 1mm) irradiation on the responses, apoptosis, migration, and proliferation of VSMCs. The effect of LPL irradiation was tested on VSMCs through cytotoxicity, proliferation, migration, and apoptotic assays. Aortic ring assay was used to assess the effect of LPL irradiation on aortic sprout outgrowth. Protein expression levels were determined by western blotting. LPL irradiation did not affect VSMC viability but slightly attenuated PDGF-BB-induced proliferation in VSMCs. In addition, LPL irradiation inhibited PDGF-BB-evoked migration of VSMCs. Aortic sprout outgrowth in response to PDGF-BB was diminished in cells treated with LPL. In contrast, LPL irradiation evoked apoptosis in VSMCs in the presence of PDGF-BB. Similarly, activation of caspase-3 and Bax, as well as p38 mitogen-activated protein kinase (MAPK), in VSMCs treated with PDGF-BB was enhanced by exposure to LPL. These findings indicate that LPL irradiation induces vascular apoptosis via p38 MAPK activation and simultaneously inhibits VSMC proliferation and migration in response to PDGF-BB.

Dye-sensitized solar cells (DSSCs) have aroused intense interest and been regarded as one of the most prospective solar cells, due to low-cost, flexibility, simple device fabrication and high conversion efficiency under weak light, in comparison to the conventional photovoltaic devices. Very recently, G2E in Swiss and G24i in UK including Korean and Japan companies have demonstrated commercial and prototyped components based on DSSC technology with liquid electrolytes. However, the unit costs, long-term device stability and power conversion efficiency must be further improved for real-life applications. For this purpose, considerable efforts have been devoted to the search for low cost Pt-free catalysts that exhibit high electrochemical activity and fast electron transfer kinetics, while a platinum (Pt) catalyst is still the most efficient and widely used counter electrode (CE) in DSSCs, but it has some problems that make it unsatisfactory, such as its high manufacturing cost, due to scarcity, and poor long-term stability for the iodide/triiodide redox couple in a DSSC. As a result, significant efforts have been devoted to finding possible alternatives to Pt, including carbon blacks, carbon nanotubes, functionalized graphene, and heteroatom-doped GnPs as efficient metal-free electrocatalysts. One of the most promising candidates as CE materials is non-metallic heteroatom-doped graphene nanoplatelets (GnPs). Heteroatom-doped GnPs gave high power conversion efficiency (PCE) of DSSCs employing cobalt electrolytes. However, they are not sufficiently active in iodidde electrolytes, which are more common and desirable electrolytes. Thus, the better elcetrocatalytical ability and electrochemical stability of carbon-basedmaterials toward the redox couples still need to be significantly improved for the practical applicationof DSSCs. Very recently, a series of edge-fuctionalized heteroatom-doped and metalliod-doped graphene nanoplatelets (GnPs) have been prepared through a simple mechanochemical ball-milling process. In this presentation, comparative study of edge-functionalized heteroatom-doped and metalloid-doped graphene nanoplatelets as metal-free counter electrodes for highly efficient dye-sensitized solar cells employong bothe redox shuttles will be described to understand and establish the structure-property relationship between sort of fuctionalization and cell performance with regard to the present GnPs through the same fabrication process under the same experimental condition.

Performance and reliability of solid state laser diodes in the IR region exceeds those in the visible and UV part of the light spectrum. Single frequency visible and UV laser diodes with higher than 500 mW power are not available commercially. However we successfully stabilized a multi-longitudinal mode IR laser to 860 mW single frequency. This means high efficiency harmonic generation using this laser can produce visible and UV laser light not available otherwise. In this study we examined three major leading nonlinear crystals: PPMgO:SLN, PPKTP and PPMgO:SLT to generate blue light by second harmonic generation. We achieved record high net conversion efficiencies 81.3% using PPMgO:SLT (~500 mW out), and 81.1% using PPKTP (~700 mW out). In both these cases an external resonance buildup cavity was used. We also studied a less complicated single pass waveguide configuration (guided waist size of ~ 5 um compared to ~60 um) to generate blue. With PPMgO:SLN we obtained net 40.4% and using PPKT net 6.8% (110mW and 10.1 mW respectively).

Oscillators based on Raman gain, known in the literature as Raman lasers, have until now necessitated an external optical pump. A powerful multi-watt fundamental laser radiation is usually required to offset a small value of the Raman gain coefficient, typically several 10-9cm/W in most Raman-active media. For example, these limitations in solid-state Raman lasers which employ scattering off a vibrational (phonon) resonance in a crystal or fiber have led to high thresholds and small conversion efficiencies. If these could be overcome such lasers would find important applications as compact light sources due to their spectral agility and could extend the range of semiconductor lasers. An important step in this direction was the recent demonstration of near infrared Raman lasers, in which ultralow threshold was achieved thanks to the use of high quality-factor dielectric microsphere resonators. Here we demonstrate a compact injection Raman laser operating in the mid-infrared, in which low threshold and high conversion efficiency are achieved by integrating within the active region of a quantum cascade region a Raman section designed to resonantly enhance the Raman gain by many orders of magnitude.

III‐nitride laser diodes (LDs) are an interesting light source for solid‐state lighting (SSL). Modelling of LDs is performed to reveal the potential advantages over traditionally used light‐emitting diodes (LEDs). The first, and most notable, advantage is LDs have higher efficiency at higher currents when compared to LEDs. This is because Auger recombination that causes efficiency droop can no longer grow after laser threshold. Second, the same phosphor‐converted methods used with LEDs can also be used with LDs to produce white light with similar color rendering and color temperature. Third, producing white light from color mixed emitters is equally challenging for both LEDs and LDs, with neither source having a direct advantage. Fourth, the LD emission is directional and can be more readily captured and focused, leading to the possibility of novel and more compact luminaires. Finally, the smaller area and higher current density operation of LDs provides them with a potential cost advantage over LEDs. These advantages make LDs a compelling source for future SSL.

High-power, broad-area, semiconductor lasers are attractive sources for material processing, aerospace, and laser pumping. The design of the active region is crucial to achieve the required high power and electro-optical conversion efficiency, since the temperature significantly affects the performance of the quantum well, including the internal quantum efficiency and mode gain. In this work, the temperature effects on the active region of a 808 nm high-power semiconductor laser were investigated theoretically and experimentally. The simulations were performed with a Quasi-3D model, which involved complete steady-state semiconductor and carrier confinement efficiency combined with a new mathematical method. The critical aluminum content of the quantum barrier was proposed and the relationship between temperature and various loss sources was disclosed in the temperature range of 213 to 333 K, which provides a reliable reference for the design of epitaxial structures of high-power semiconductor lasers in different operating conditions. Subsequently, the optimized epitaxial structure was determined and used to fabricate standard laser bar chips with a cavity length of 2 mm. The experimental electro-optical conversion efficiency of 71% was demonstrated with a slope efficiency of 1.34 W/A and an injection current of 600 A at the heatsink temperature of 223 K. A record high electro-optical conversion efficiency of 73.5% was reached at the injection current of 400 A, while the carrier confinement efficiency was as high as 98%.