Action Of Nd Research Articles

Capabilities of remote laser homeostasis of the conjunctiva and sclera

During some eye surgeries, a need for hemostasis can arise in order to prevent bleeding. To determine the optimal settings for remote laser action of Nd:YAG laser with a wavelength of 1.44 µm on the conjunctival and episcleral vessels of the eye to stop bleeding, as well as for preemptive anemisation of tissue prior to performing a surgical incision. The characteristics of the laser impact on vessels of the conjunctiva and sclera were studied clinically while conducting surgeries on 36 patients for cataract, glaucoma and excision of pterygium. The best mode of operation of Nd:YAG laser for remote laser anaemisation of the area of planned cut were 1.44 µm wavelength with 5 Hz frequency and energy of 100 mJ. Remote hemostasis can be achieved with the following settings for energy parameters: for pulse frequency of 5 Hz - pulse energy from 150 to 200 mJ; for pulse frequency of 10 Hz and 15 Hz - energy from 100 to 150 mJ; for pulse frequency of 25 Hz - energy not exceeding 100 mJ. No scar remained after the action of 1.44-µm Nd:YAG laser, and recanalization of individual vessels was possible.

Special Features of AgIn5S8 Luminescence and Photoconductivity Under the Action of Laser Radiation

Luminescence spectra and relaxation curves of nonequilibrium photoconductivity of AgIn5S8 single crystals under the action of Nd:YAG-laser radiation are experimentally investigated. It is shown that depending on the nature of excitation (one- or two-photon excitation), the emission lines of a free exciton with its phonon repetition and the emission caused by structural defects are observed in the luminescence spectrum. Investigation of the nonequilibrium photoconductivity relaxation curves shows the presence of two recombination channels with times τ ~ 2.7·10–7 s and ~2·10–6 s.

Luminescence properties of heavily doped AlxGa1-xN/AlN films grown on sapphire substrate

Luminescent properties of the AlxGa1-xN films with Si dopant concentration more than 1020 cm−3 grown by molecular beam epitaxy on sapphire substrates with AlN buffer film were investigate at room temperature. Time-resolved photoluminescence spectroscopy was employed to study the donor-acceptor pair transitions in the AlxGa1-xN/AlN/Al2O3 structures with Al mole fraction x from 0.47 to 1 under action of Nd:YAG (λ = 266 nm) laser radiation. The radiation inside planar waveguide consists of spontaneous emission and amplified spontaneous emission. The spontaneous emission spectra demonstrated inhomogeneous broadening with FWHM of 0.58 eV covers full visible range and propagate randomly in all directions. The amplified spontaneous emission propagate at near the critical angle of incidence along zigzag path under total internal reflection conditions at the interfaces of the waveguide. Its spectrum consists of several TEm and TMm modes, which have mutually orthogonal polarizations. The optical measured gains are equals to g ≈ 58 cm−1 for Al0.65Ga0.35N at 510 nm and g ≈ 20 cm−1 for Al0.74Ga0.26N films at λ = 528 nm. The measured values of quantum yields of spontaneous emission for AlxGa1-xN films grow monotonically from 0.11 to 0.79 with increasing x from 0.47 to 0.74. Estimated emission cross-sections for the donor-acceptor pair transitions are more than 10−18 cm2.

Effect of Nd:YAG laser combined with fluoride on the prevention of primary tooth enamel demineralization

Most studies dealing with the caries preventive action of Nd:YAG laser have been done in permanent teeth and studies on primary teeth are still lacking. The aim of this study was to evaluate in vitro the effect of Nd:YAG laser combined or not with fluoride sources on the acid resistance of primary tooth enamel after artificial caries induction by assessing longitudinal microhardness and demineralization depth. Sixty enamel blocks obtained from the buccal/lingual surface of exfoliated human primary molars were coated with nail polish/wax, leaving only a 9 mm² area exposed on the outer enamel surface, and randomly assigned to 6 groups (n=10) according to the type of treatment: C-control (no treatment); APF: 1.23% acidulated phosphate fluoride gel; FV: 5% fluoride varnish; L: Nd:YAG laser 0.5 W/10 Hz in contact mode; APFL: fluoride gel + laser; FVL: fluoride varnish + laser. After treatment, the specimens were subjected to a des-remineralization cycle for induction of artificial caries lesions. Longitudinal microhardness data (%LMC) were analyzed by the Kruskal-Wallis test and demineralization depth data were analyzed by oneway ANOVA and Fisher's LSD test (á=0.05). APFL and APF groups presented the lowest percentage of microhardness change (p<0.05). Demineralization depth was smaller in all treated groups compared with the untreated control. In conclusion, Nd:YAG laser combined or not with fluoride gel/varnish was not more effective than fluoride alone to prevent enamel demineralization within the experimental period.

Crystal growth, spectral and laser properties of Nd:LSAT single crystal

Nd:(La, Sr)(Al, Ta)O3 (Nd:LSAT) crystal was grown by the Czochralski method. The absorption and fluorescence spectra of Nd:LSAT crystal at room temperature were investigated. With a fiber-coupled diode laser as pump source, the continuous-wave (CW) laser action of Nd:LSAT crystal was demonstrated. The result of diode-pumped laser operation of Nd:LSAT crystal single crystal is reported for what is to our knowledge the first time. The maximum output power at 1064 nm was obtained to be 165 mW under the incident pump power of 3 W, with the slope efficiency 10.9%.

Continuous-wave diode-pumped laser action of Nd^3+-doped photo-thermo-refractive glass

Laser action of the photo-thermo-refractive (PTR) glass, which is the photosensitive material for holographic recording of volume Bragg gratings (VBGs), was demonstrated for the first time by introducing Nd³⁺. Nd:PTR glass has a bandwidth of 27.8 nm and 16.0 nm for luminescence and absorption, respectively. An uncoated 2 mm thick Nd:PTR element generated cw laser output of 124 mW, with a slope efficiency of 25%, by laser diode pumping. This Nd:PTR glass also performed wide bandwidth laser action at 1053.9-1063.3 nm, where the decrease of the pump-absorption efficiency was held off below 30%, even under a 3.5 nm shift of pump wavelength from its absorption center.

Nanostructural modification of an Al–C–Ti coating on alloy AZ91D under the multipulse action of Nd:YAG and Ng-glass lasers

Experimental results on the nanostructural modification of an Al–C–Ti coating on magnesium alloy AZ91D under the multipulse action of Nd:YAG lasers (λ = 1064 nm, τ = 20 ns, and E = 200 mJ) and Nd-glass lasers (λ = 1060 nm, τ = 85 ns, and E = 2 J) are given. It is shown that the formation of the found nanocrystalline coating structure with a grain size of 35 to 400 nm involves the process of background deposition of ablated particles and condensed clusters formed in the plasma plume.

Conditions defining the mechanisms of the formation of light gas ions in multicomponent laser-produced plasmas

Using the mass-spectrometric method we study the charge, energy and spatial characteristics of ions in multicomponent plasma, generated under the action of Nd : YAG laser radiation on the surface of solid targets. We focus on the effect of the entry form of light gas atoms on the parameters of ions in such laser-produced plasmas. We found that the presence of light gas atoms considerably affects the parameters (e.g. the intensity and the charge multiplicity) of the heavier ions.

Surface temperature evolution in pulsed laser action of millisecond range

An originally developed multi-wavelength pyrometer (12 wavelengths in the range 1.001–1.573 μm, 50 μs acquisition time for each photodiode, 800 μm spatial resolution, 900–3500 °C brightness temperature range) is used to measure brightness temperature under the pulsed action of Nd:YAG laser (HAAS–HL62P) on stainless steel (INOX 304L) substrates. Specially developed “notch” filters (10−6 transparency at 1.06 μm wavelength) are applied to avoid the influence of laser radiation on temperature measurements. The true temperature is restored on the basis of method of multi-colour pyrometry. The accuracy of brightness temperature measurements is examined by comparing the temperature evolution for pulses with different durations but with the same value of energy density flux. The influence of the following parameters is studied keeping the remaining ones constant: pulse duration (6–20 ms, rectangular pulse shape), energy per pulse (10–33 J, rectangular pulse shape), pulse shape (three types of triangulars and one rectangular). Finally the evolution of surface temperature for pulses with more complex shapes but with the same pulse duration and energy per pulse is compared.

Improvement of Hydrogen Storage Properties of Mg-Ni Alloys by Rare-Earth Addition

A simple and efficient method has been employed to prepare a Mg-rich Mg-Ni-Nd alloy which exhibits a substantially large hydrogen storage capacity with excellent absorption/desorption kinetics at moderate temperatures. This method consists of fully melting raw materials in a sealed steel crucible filled with Ar and subsequent quenching into cold water. It overcomes the difficulties in the melting process of the materials due to large differences in the melting points, specific weights, oxidizability and evaporativity of the raw materials at high temperatures. Initial activation processes, hydriding/dehydriding rates, and presure-composition isotherm (PCT) characteristics of the alloy have been examined and the results are compared with those of a Mg-rich Mg-Ni alloy prepared with the same technique. The Mg-Ni-Nd ternary alloy can absorb ∼5.0 mass%H (H/M∼1.6) at excellent speeds between 573 and 373 K, and can desorb it at moderate speeds between 573 and 473 K. This attractive property of the alloy can be explained by the catalytic action of Nd as well as the unrelaxed multiphase structure formed in the preparation process.

Damage to the surface of silicon in the solid phase by the action of Nd:YAG laser pulses

An investigation was made of solid-phase damage to the surface of silicon by Nd:YAG laser pulses. The results made it possible to postulate particle emission when the surface of silicon was subjected to laser pulses with the threshold power density Imelt corresponding to the onset of surface melting. Such emission was attributed to the formation of surface microcracks as a result of condensation of nonequilibrium defects under the action of elastic stresses.

Structural and transport properties of La 1.85−xNd xSr 0.15CuO 4F y solid solutions

Simultaneous action of Nd 3+, Sr 2+ and F species on La 2CuO 4 phase was investigated. While the neodymium ions distort structure and deteriorate the transport properties, fluorine species oppose to these tendencies.

Laser action of Nd:YAlO3 at 1300 nm

From our measured value of the stimulated emission cross section for 4F3/2–4I13/2 transition of Nd3+ ion in YAlO3 crystal as well as the results of continuous wave (cw) and pulsed 1341.4 nm Nd:YAP lasers, it can be seen that Nd:YAP is an excellent 1300 nm laser crystal. In our laboratory cw output power of 195.8 W at 1341.4 nm with an overall efficiency of 1.43% and pulsed output energy of 5.1 J at 1341.4 nm with an overall efficiency of 2.02% have been achieved by using this kind of crystal.