Efficiency Of Nd Research Articles

Influence of welding speed on the melting efficiency of Nd:YAG laser welding

A B S T R A C T A R T I C L E I N F O Melting efficiency is one of the more important measurable parameters in laser welding when assessing the performance of a process. This paper aims to study the effects of speed on the melting efficiency and energy transfer efficiency of Nd:YAG laser welding process. The weld bead on a 304L austenitic stainless steel sheet is created by varying the welding speed. The weld samples are cut in the transverse direction by using electric discharge machining, and the cross-section is prepared for metallographic inspection. The cross-sectional dimensions and beads length are measured by using an optical microscope and image analyzer. A methodology is proposed for estimating the weld pool volume from experimental data and a generalised equation for predicting the melting efficiency and energy transfer efficiency is developed. The results obtained by the proposed method have reasonably good agreement with the models proposed by various researchers. The outcome of the result shows the significant influence of welding speed on melting efficiency and energy transfer efficiency in welding of austenitic stainless steel thin sheets. It will be seen from results that one can select appropriate welding speed and processing conditions to obtain desired melting efficiency.

Electrochemical Co-Reduction Extraction of Neodymium in LiCl-KCl-ZnCl<sub>2</sub> Molten Salt System

This work focused on the electrochemical behavior of Nd(III) and the formation of Zn-Nd alloys on Mo electrodes in LiCl-KCl-ZnCl2 molten salt system at 773 K. Cyclic voltammetry, open-circuit chronopotentiometry, and square-wave voltammetry were used. The results showed that the underpotential deposition of Nd on a predeposited Zn cathode gave three types of Zn-Nd intermetallic compounds in LiCl-KCl-ZnCl2 solutions. Based on the electrochemical results, square-wave voltammetry was used to determine the concentration changes of Nd during potentiostatic electrolysis. The extraction efficiency of Nd was evaluated based on the concentration changes after electrolysis. The results indicated that the concentration of Nd(III) was close to zero, and the extraction efficiency was 99.67% after potentiostatic electrolysis at-1.84 V for 50 h. The extraction of Nd and preparation of Zn-Nd alloys were performed by galvanostatic electrolysis at 973 K. The phase compositions and 1674

Evaluation of Nd: YAG Laser Welding Efficiencies for 304L Stainless Steel

The laser material interaction, controlling of process parameters and their effect on melting, solidification and process efficiency are critical to understand the behavior of the weld joints. This paper aims to study the effect of welding speed on different process efficiencies in 304L Stainless Steel. The bead on 304L austenitic stainless steel plate is created by varying welding speed. A novel semi-empirical method based on weld pool volume measured from experimental results is used to predict the melting efficiency of Nd: YAG laser welding process. The dimensionless parameter models are used to estimate various types of measurable controlling parameters. These parameters have good agreement with the various available models in literature.

Endoscopic lithotripsy for gastric bezoars by Nd:YAG laser-ignited mini-explosive technique

Until now, there still has no standard treatment option to deal with gastric bezoars. This respective study was conducted to evaluate the safety and efficiency of Nd:YAG laser-ignited mini-explosive technique for the treatment of gastric bezoars. Two hundred sixty patients with 285 gastric bezoars were treated by endoscopic lithotripsy with Nd:YAG laser-ignited mini-explosive technique. Among the 260 patients, the 284 gastric bezoars of the 259 patients completely disappeared, with the cure rate of 99.6% after 1-2 treatments at 2-4 weeks follow-up. Only one patient, who was cured by surgery, had gastric perforation during the explosion. No intraoperative or delayed complications was found in the other 259 patients. The endoscopic lithotripsy with Nd:YAG laser-ignited mini-explosive technique is an effective, safe, and promising alternative for gastric bezoars.

Effects of crystal parameters on power and efficiency of Nd : YVO4 laser in-band pumped by 914 nm laser

To overcome the main drawback of poor pump absorption of Nd : YVO4 lasers in-band pumped at 914 nm, three possible methods of higher temperature, longer crystal length and higher doping concentration were experimentally studied. A Nd : YVO4 laser operating at 914 nm was used as high beam quality, narrow line-width pump source to make the measurement of pump absorption accurate. Four different Nd : YVO4 crystals were used as gain mediums to investigate the effects of crystal parameters. We found that heating the crystal effects differently on output power and overall efficiency when crystal doping concentration changed. To improve the pump absorption and meanwhile achieve high efficiency, longer crystal with proper doping concentration and pump feedback should be adopted instead of highly doped crystal.

Quantum efficiency of Nd 3+-doped glasses under sunlight excitation

The internal quantum efficiencies under sunlight and laser excitation were measured directly by an integrating sphere method for tellurite, borosilicate and fluoride glasses. The radiative quantum efficiency was also obtained by Judd–Ofelt analysis. The radiative quantum efficiency was almost 100% for tellurite and fluoride glasses and 50% for borosilicate glasses. The quantum efficiency under laser excitation was 86%, 34% and 88% for tellurite, borosilicate and fluoride glasses at a low Nd 3+ content and decreased by concentration quenching. The quantum efficiency under sunlight excitation was up to 33%, 21% and 70% for tellurite, borosilicate and fluoride glasses. Nd 3+-doped fluoride glass is a promising candidate for solar pumped laser applications since it has the high quantum efficiency under sunlight excitation.

A Light‐Harvesting Antenna Resulting from the Self‐Assembly of Five Luminescent Components: A Dendrimer, Two Clips, and Two Lanthanide Ions

We have investigated the self-assembly of three luminescent species in CH(3)CN/CH(2)Cl(2), namely: 1) a polylysin dendrimer (D) composed of 21 aliphatic amide units and 24 green luminescent dansyl chromophores at the periphery, 2) a molecular clip (C) with two blue luminescent anthracene sidewalls and a benzene bridging unit that bears two sulfate groups in the para position, and 3) a near infrared (NIR)-emitting Nd(3+) ion. For purposes of comparison, analogous systems have also been investigated in which Gd(3+) replaced Nd(3+). The dendrimer and the clip can bind Nd(3+) ions with formation of [D.2Nd(3+)] and [C.Nd(3+)] complexes, in which energy transfer from dansyl and, respectively, anthracene to Nd(3+) ion takes place with 65 and 8% efficiency, in air-equilibrated solution. In the case of [C.Nd(3+)], the energy-transfer efficiency is quenched by dioxygen, thereby showing that the energy donor is the lowest triplet excited state of anthracene. In [D.2Nd(3+)] the intrinsic emission efficiency of Nd(3+) is much higher (ca. 5 times) than in [C.Nd(3+)] because of a better protection of the excited lanthanide ion towards nonradiative deactivation caused by interaction with solvent molecules. By mixing solutions of D, Nd(3+), and C with proper concentrations, a supramolecular structure with five components of three different species, [D.2Nd(3+).2C], is formed. The excitation light absorbed by the clips is transferred with 100% efficiency to the dansyl units of the dendrimer and then to the Nd(3+) ions with 65% efficiency either in the presence or absence of dioxygen. These results show that the [D.2Nd(3+).2C] complex is able to efficiently harvest UV light by the 24 dansyl units of the dendrimer and the four anthracene chromophores of the two clips, and efficiently transfer it to the encapsulated Nd(3+) ions that emit in the NIR spectral region.

Extraction of rare earth elements from their oxides using organophosphorus reagent complexes with HNO 3 and H 2O in supercritical CO 2

Direct extraction of metals from solids with complexing agents in supercritical CO 2 (SC-CO 2) has recently attracted interests in separation, purification, recovery, and analysis of metals. In the present study, the static/dynamic extraction of rare earth elements (Nd, Ce) from their oxides (Nd 2O 3, CeO 2) with organophosphorus complexes with HNO 3 and H 2O in SC-CO 2 was investigated. The static extraction efficiency of Nd from Nd 2O 3 with the tri- n-butylphosphate (TBP)-HNO 3 complex could reach 95% under optimized experimental conditions. However, the static extraction efficiency of Nd from Nd 2O 3 with the trilkyl phosphine oxide (TRPO)-HNO 3 complex was less than 10%, and the static extraction efficiency of Ce from CeO 2 with the TBP-HNO 3 complex was less than 1%. The dynamic extraction efficiency of Nd from Nd 2O 3 with the TBP-HNO 3 complex could reach more than 97%. Effects of parameters were evaluated on the extraction efficiency to ascertain the optimum conditions. This study illustrated the extraction process using the TBP-HNO 3 complex in SC-CO 2 would be feasible for separation, purification, recovery, and analysis of some rare earth elements from various oxide mixtures.

Continuous-wave and passively Q-switched laser performance of LD-end-pumped 1062 nm Nd:GAGG laser

Continuous-wave (CW) and passively Q-switched operations of LD-end-pumped Nd:Gd(3)Al(x)Ga(5-x)O(12) (Nd:GAGG) laser at 1062 nm were reported. The highest CW output power of 5.7 W was obtained, corresponding to an optical conversion efficiency and slope efficiency of 51.0% and 54.5%, respectively. The CW output efficiency of Nd:GAGG laser is comparable and even better than that of Nd:GGG. The passively Q-switched output was realized for the first time to our knowledge. In addition, a maximum output power of 1.12 W, a maximum pulse repetition rate of 39 kHz and a minimum pulse width of 6 ns were obtained by using Cr(4+):YAG as the saturable absorber.

CRYSTAL GROWTH, THERMAL, OPTICAL, AND DIELECTRIC PROPERTIES OF L-LYSINE DOPED KDP CRYSTALS

Single crystals of pure and various amount of L-lysine doped KDP crystals were grown from aqueous solution. The doping of L-lysine was confirmed by CHN analysis and FT-IR spectroscopy. Powder XRD was carried out to assess the single phase nature of the samples. The effect of doping on thermal stability of the crystals was carried out by TGA and the kinetic and thermodynamic parameters of dehydration were evaluated. It was found that as the amount of doping of amino acid, L-lysine, increased the thermal stability of the grown crystals decreased. However, the second-harmonic generation (SHG) efficiency of Nd :YAG laser and UV-vis spectroscopy studies indicated that as the L-lysine doping increased in KDP crystals the SHG efficiency and optical transmission percentage increased. The dielectric constant and the dielectric loss of L-lysine doped KDP crystals are lower than the pure KDP crystals. Hence L-lysine doped KDP crystals are found to be more beneficial from an application point of view as compared to pure KDP crystals. The results are discussed.

Quasi-continuously pumped passively mode-locked operation of a Nd:GdVO4 and Nd:YVO4 laser in a bounce geometry

The comparative study of pulsed diode pumped Nd:GdVO4 and Nd:YVO4 slab lasers in a bounce geometry in a free running and a passively mode-locked regime was performed. The better efficiency of Nd:GdVO4 in both regimes was obtained. In the free running regime the efficiency of 39% was achieved from Nd:GdVO4 comparing with 28% from Nd:YVO4. Passive mode-locking of both lasers using a semiconductor saturable absorber in the transmission mode was demonstrated. Trains containing 6 pulses were generated in both cases but the pump energy for Nd:GdVO4 was 50% lower. The single pulse extraction using cavity dumping was demonstrated with contrast better than 10−3.

Clinical review of Nd:YAG laser in treatment of the anterior fibrinous membrane of intraocular lens

目的 评价Nd:YAG激光治疗白内障术后人工晶状体前膜的疗效.方法 回顾性总结Nd:YAG激光治疗白内障术后人工晶状体前膜42例(45眼).激光参数:单次脉冲能量0.6～3.8 mJ,击发次数平均42次(16～150次).结果 所有患眼应用Nd:YAG激光均成功切除人工晶状体前膜.其中32例(33眼)术后视力有不同程度的提高,5眼无变化.并发症包括虹膜出血、晶状体表而细小损伤、短暂性眼压升高、前房炎性反应,对术后视力无影响.结论 应用Nd:YAG激光可有效、安全的切除人工晶状体前膜。

Nd:YAG Laser-aided ceramic brackets debonding: Effects on shear bond strength and enamel surface

In order to evaluate the efficiency of Nd:YAG laser-aided ceramic brackets debonding technique, both ceramic brackets and metallic brackets were bonded with orthodontic adhesive to 30 freshly extracted premolars. The specimens were divided into three groups, 10 in each, according to the brackets employed and the debonding techniques used: (1) metallic brackets with shear debonding force, (2) ceramic brackets with shear debonding force, and (3) ceramic brackets with Nd:YAG laser irradiation. The result showed that laser irradiation could diminish shear bond strength (SBS) significantly and produce the most desired ARI scores. Moreover, scanning electron microscopy investigation displayed that laser-aided technique induced little enamel scratch or loss. It was concluded that Nd:YAG laser could facilitate the debonding of ceramic brackets and diminish the amount of remnant adhesive without damaging enamel structure.

Thermal lens and Auger upconversion losses' effect on the efficiency of Nd^3+-doped lead lanthanum zirconate titanate transparent ceramics

A thorough investigation of optical losses for the 1064nm emission in Nd3+-doped lead lanthanum zirconate titanate (PLZT) transparent ceramics is presented. Thermal lens experiments were carried out to evaluate thermo-optical properties and the fluorescence quantum efficiency of the emitting level 4F3/2. Excited-state absorption losses were measured in the emitting wavelength region, and the Auger upconversion energy transfer parameter γ was calculated. By using γ, the pump-intensity dependence of the optical gain at 1064nm, the fluorescence quantum efficiency, and the generation of heat in the ceramic were simulated for a high 803nm pump-power regime. Since the radiative and nonradiative losses in Nd:PLZT were verified to be considerably lower than in various commercial laser crystals and glasses, it is suggested that this material might become an interesting alternative for high-power laser emission.

Doubling the optical efficiency of a chiral liquid crystal laser using a reflector

A simple method for doubling the laser emission efficiency of Nd:yttrium-aluminum-garnet pumped cholesteric liquid crystal (CLC) photonic band edge lasers is demonstrated. By adding a mirror or a CLC reflector behind the dye-doped CLC cell, the lasing intensity is nearly doubled. For the mirror reflector, due to the mixing of right-handed and left-handed circular polarizations, the output laser is basically unpolarized. However, for the CLC reflector, a partially coherent laser can be built in which either right-handed or left-handed circularly polarized laser could dominate the output, depending on the handedness of the cholesteric structure.

Growth of large-sized Nd:NY(WO 4) 2 crystal and its spectral properties

This paper reports the growth of Nd 3+:NY(WO 4) 2 crystal with high optical quality and large size. Nd 3+:NY(WO 4) 2 crystal with the dimension Φ30×75 mm 2 and optical homogeneity 4×10 −5 was grown by Czhchoralski method: the seed used was [1 0 0] orientation, the pulling rate and rotating rate were 0.5–1.25 mm/h and 15 rpm, respectively. The growing processes and characteristics of Nd 3+:NY(WO 4) 2 crystal was discussed. Its unpolarized absorption spectra and emission spectra were measured. The absorption cross-section and emission cross-section were presented. Based on the Judd–Ofelt theory, we obtained the three intensity parameters: Ω 2 = 5.8 × 1 0 - 20 , Ω 4 = 5.74 × 1 0 - 20 , and Ω 6 = 4.32 × 1 0 - 20 cm 2 . The radiative probabilities, radiative lifetimes, branch ratios and quantum efficiency of Nd 3+:NY(WO 4) 2 were calculated too.

Comparative study on the spectroscopic properties of Nd:GdVO/sub 4/ and Nd:YVO/sub 4/ with hybrid process

We have proposed a hybrid procedure for determining spectroscopic parameters for uniaxial solid-state laser crystals. Using our procedure, the spectroscopic properties of Nd:GdVO/sub 4/ were evaluated and compared to those of Nd:YVO/sub 4/. As a result, the peaks of absorption and stimulated emission cross sections of Nd:GdVO/sub 4/ in /spl pi/-polarization were determined to be 2.6 and 10.3/spl times/10/sup -19/ cm/sup 2/, respectively, and were smaller than those of Nd:YVO/sub 4/. On the other hand, the fluorescence lifetime of 1 at% Nd:GdVO/sub 4/ was evaluated to be 83.4 /spl mu/s, and was similar to 84.1 /spl mu/s of 1 at% Nd:YVO/sub 4/. Therefore, the product of stimulated emission cross section and fluorescence lifetime (/spl sigma//sub em//spl tau//sub f/ product) of Nd:GdVO/sub 4/ was smaller than that of Nd:YVO/sub 4/ under 1 at% of Nd/sup 3+/ doping concentration. The radiative lifetime of spontaneous emission of Nd:GdVO/sub 4/ was 168 /spl mu/s and was 1.9 times longer than that of Nd:YVO/sub 4/. Because of the low value of radiative quantum efficiency of Nd:GdVO/sub 4/ (50%), careful cavity design is required for creating a well performing solid-state laser with Nd:GdVO/sub 4/, based on the larger /spl sigma//sub em//spl tau//sub f/ product rather than the /spl sigma//sub em//spl tau//sub f/ product of Nd:YAG.

Compositionally tuned lasers for remote sensing

NASA needs lasers that are capable of generating a specific preselected wavelength, have a small but useful tuning range, and are highly efficient. NASA Langley responded to this need by developing 2 compositionally tuned Nd laser materials that operate at a preselected wavelength, 0.94411 μm in this case. Although Nd:YAG was known to operate at 0.946 pm, it could not be tuned to 0.944 μm. In addition, the efficiency of Nd:YAG flash lamp pumped lasers operating at this wavelength was low. NASA Langley overcame these problems by analyzing and then utilizing nonstoichiometric garnet laser materials to compositionally tune the laser wavelength and a laser design to increase the efficiency. Implementing these ideas led to 2 compositionally tuned laser materials that operate at 0.94411 μm and a diode pumped, 0.946 μm Nd:YAG laser that operates in the TEM 00 mode with a normal mode, optical to optical slope efficiency of 0.28.

Threshold and slope efficiency of Nd 0.5La 0.5Al 3(BO 3) 4 ceramic random laser: effect of the pumped spot size

We have experimentally found that in a random laser based on Nd 0.5La 0.5Al 3(BO 3) 4 scattering ceramic, the threshold pumping density decreases and the output slope efficiency increases with the increase of the diameter of the pumped spot. The experimental behavior is explained in terms of random photon's walk in an amplifying medium.

Self-quenching of Nd3+ emission in laser garnet crystals

Abstract The emission self-quenching mechanism in Nd 3+ :YAG at low pump intensities is identified as a cross-relaxation on intermediate levels inside the system of active ions. Up to 1.5 at.% Nd 3+ this down-conversion process is a direct donor–acceptor process, without important contribution from migration and is induced by a multiple interaction picture consisting of superexchange and dipole–dipole contributions. The parameters measured from non-selectively excited global decay under 532 nm excitation at room temperature are verified by this consistent explanation of the characteristics of decay of the first-, second- and third-order Nd 3+ ion pairs that induce resolved spectral satellites at low temperatures. A further check is provided by the agreement of the experimental data on emission quantum efficiency or on fractional thermal load with those calculated by using the characteristic parameters of the energy transfer determined in this work. It is thus shown that self-quenching of emission is a limiting factor for the quantum efficiency of Nd 3+ :YAG. The extension of the theoretical formalism based on a discrete, random and equiprobable occupation of crystallographic sites by Nd 3+ ions, used in the analysis of down-conversion to the case when up-conversion is also present is discussed.