The paper reports the results of initial research on the creating of a new laser active element based on manganese aluminate spinel. A technique for preparing iron-doped manganese aluminate spinel is described. Nanopowders with different Al/Mn ratios were obtained by laser ablation followed by vapor condensation in a carrier gas flow. It was found that the particles had an average size of 16.5 nm and a narrow (about 40 nm) size distribution. The compacts prepared from these nanopowders with a diameter of 14 mm and a thickness of 2 mm had a density of 50% of the theoretical one. The compacts were sintered in a vacuum at a temperature of 1300 °C for 3 hours. It is shown that to obtain a single-phase spinel, the molar ratio of Al/Mn cations in the nanopowder should be 1.2–1.75. The transmission spectra of the samples were measured and a transmission range of 2–8 μm and 5 absorption bands were found and the diagram of the lower levels of Fe2+ was plotted.
Vladimir Osipov, Nickolay Il’ichev, Vladislav Shitov, Pavel Pashinin, Vladimir Solomonov, Andrey Sidorin, Konstantin Lukyashin, Roman Maksimov, Viktor Tumorin, Egor Tikhonov, Elmira Gulyamova
In this work we report on the results of synthesis and investigation of Fe2+:MgAl2O4ceramic samples. Nanopowders with small average particle size of ~ 18 nm were used for the preparation of the samples. It has allowed to synthesize the ceramics with an average grain size of 300–400 nm at a temperature as low as ~ 1200 °С. It was shown that the Fe ions occupy tetrahedral sites of lattice with a mandatory valence equaled to 2 when the content of iron in the samples of magnesium aluminate spinel is higher than 1 wt.%. Transmission of radiation in the samples increased with an increase in wavelength due to the reduction of Rayleigh scattering caused by pores. It was determined that the transmission of radiation in the samples at strong and weak laser radiation remains constant in a temperature range from -164 °С to+22°C.
The paper reports about the results of researches of nanopowder production with a help powerful repetitively pulsed
CO2 laser "LAERT" which generated radiation with pulse energy of ≈1 J, peak power of ≈8 kW and mean power of
500 W. Laser radiation affected and evaporated the target. The target material vapor condensed into nanoparticles as a
result of intermixing vapor with a flow of cold gas. In basic the air of atmospheric pressure was used as the carrier gas.
However in some experiments were used He and Ar and the gas pressure also was changed. In our experiments we
produced nanopowders of such materials as: YSZ, YSZ:Al2O3, Al2O3, CeO2:Gd2O3, 0.5%Nd:Y2O3, 1%Nd:YAG, Fe3O4and carbon with a middle size 10÷30 nm. Received nanopowders were also weakly agglomerated. We carried out 3D
numerical modeling of thermo-hydrodynamic processes occurred during the laser evaporation of a target. Results of
calculations have cleared up many details of target evaporation. In particular, influence of liquid melt movement on
stoichiometry of evaporation of a target from oxide mixes is found out. Results of calculations are in a good agreement
with experimental data.
S. Bagayev, V. Osipov, M. Ivanov, V. Solomonov, V. Platonov, A. Orlov, A. Rasuleva, V. Ivanov, A. Kaygorodov, V. Khrustov, S. Vatnik, I. Vedin, A. Mayorov, E. Pestryakov, A. Shestakov, A. Salkov
The results of investigations of mechanical, optical and laser characteristics of ceramics made from neodymiumactivated
yttrium oxide are presented. The ceramics was fabricated with the use of a new technology including Laser
synthesis of nanopowders and their magnetic pulsed compaction (LSN&MPC). The fracture toughness ΚIC = 0,9 -
1,4 MPa•m1/2) and microhardness (HV = 11,8 GPa) of the ceramics have been determined. It has been found that ceramic
samples sintered in the temperature range from 1550 to 2050°C have (1 - 150) vol. ppm porosity and optical loss
coefficient α1,07 μm = 0,03 - 2,1 cm-1. It has been shown that pore content in this range did not influence on the optical
loss coefficient. Laser generation at λg ≈ 1,08 μm with a slope efficiency of 15 % at laser diode pumping has been
obtained in 1.1 mm thickness sample with α1,07 μm = 0,03 cm-1.
The dynamics and the spectral kinetic characteristics of the plume emerging in the vicinity of graphite targets, pressed
pellets consisting of zirconium oxide powder stabilized with yttrium (YSZ) and of garnet stock with neodymium
(YAG:Nd) are studied. The targets are irradiated in air at room temperature using a repetitively pulsed CO2 laser with a
wavelength of 10.6mm, a peak power of up to 9 kW, a pulse energy of up to 1.69 J, and a pulse duration of 330ms at a
level of 0.1. The plume propagates normally to the target surface at an angle of 45° relative to the laser radiation. The
spectral kinetic characteristics of the plume luminescence are discretely measured along the entire length. It is
demonstrated that the plumes of all targets represent the "ows of a weakly nonequilibrium gas plasma with a temperature
of 10 kK (graphite) and 3.1...4.7 kK (YSZ and YAG:Nd pressed pellets). The plume size is determined by the peak
power of the laser pulse. The luminescence of the two-atom radicals (C2 in graphite; ZrO and YO in YSZ; and YO, AlO,
and NdO in YAO:Nd) dominates in all of the plumes. A relatively high temperature of the graphite plume is maintained
owing to the energy of the exothermic reaction involving the association of carbon atoms and the energy of the
vibrationally excited molecules resulting from this reaction. The dynamics of plasma plume was studied by luminescence
imaging and shadowgraphy.
This report deals with the production and characteristics of Y2O3 -stabilized ZrO2 (YSZ), A12O3+YSZ, GDC, Nd:Y2O3 and Nd:YAG nanopowders prepared by evaporation of the materials with the help of a pulse-repetitive CO2 laser. The design of a setup for the nanopowders production, scheme and characteristics of the original CO2 laser excited by a pulse-periodic combined discharge are reported. For YSZ; Al2O3+YSZ, Nd:Y2O3, Nd:YAG the output rate was 15-25 g/h, for GDC ~ 50-75 g/hour, the energy consumption 30-40 (W*h)/g and 8-15 (W*h)/g, respectively. Data for the nanopowders specific surface, size distribution, the results of X-ray phase and structure analysis, as well as the results of luminescence analysis are discussed. The analysis of the obtained results showed that two main factors that determine the output rate of the nanopowders synthesis are the type of material evaporated and the mean laser radiation power. The mean size of the nanoparticles doesn't depend on the type of material.
The design and characteristics of a setup for producing oxide nanopowders are reported. Y2O3-stabilized Zr02 (YSZ), Al2O3+YSZ and CeGdO nanopowders are prepared by target evaporation with a pulse-periodic C02-laser. Average laser radiation power is 600 W, pulse power ~10 kW. The output rates of YSZ and Al2O3+YSZ nanopowders are 15-20g/h, and CeGdO nanopowder-55-6Og/h. The grain mean size in the powders is l5nm. Data for the powder characteristics, as well as results of X-ray phase and structure analysis, are reported. The results of investigation of unstable behavior of plasma plume produced by the long-pulse laser irradiation of the targets are reported as well. The mushroom-like shape of the glowing area is believed to be determined by the Richtmyer-Meshkov instability of the plasma-air interface and formation of nanoparticles in the plasma expanding into the buffer gas.
The paper reports about a new pulse-repetitive high-efficient technological CO2-laser and its applications. An original method of active medium excitation was used for laser pumping. Efficiency of the laser constructed on the basis of this method reached 12%, average radiation power 600 W, pulse power ~ 10 kW. The laser was used for YSZ powders production by successive evaporation and crystallization in the gas stream. The output rate was 15-20g/h, specific surface of the powder was up to 70m2/g. Evaporation of materials by CO2 laser was also used for ZrO2 and Al2O3 thin films deposition on stainless steel plates. The average thickness of the film was ~500nm, the deposition rate was ~10nm on the area ~1cm2 per pulse. The deposited films have high adhesion properties.
The ability of middle pressure room temperature combined discharge pumped CO-laser development is investigated in this paper. The active media optimal parameters (pressure, specific energy input, E/p relation for different mixtures) are obtained. The efficiency approximately equals 14% is calculated at this optimal parameters for mixture CO:He equals 1:3. The influence of the N2 and Xe addition also is investigated.
Our paper reports about YSZ powders by successive evaporation and crystallization in the gas stream. In the laser applied the original method of active medium excitation was used. Efficiency of the laser constructed on the basis of this method reached 22 percent and specific power output at approximately 1 W/cm3. Pulsed regime is proved to be more efficient for active medium excitation and target evaporation than continuous one. Targets made from coarse YSZ powder with Y2O3 content of 10.15 mol. percent were evaporated and crystallized in a stream of cleaned air. Cubic-structure YSZ particles were obtained which had a shape close to spherical. Particle size distribution was close to a lognormal distribution with dg equals 10 nm and (sigma) equals 1.75. Specific surface of the powder was up to 70 m2/g, while the Y2O3 content reduced to 9.8 mol. percent.
The development of high-efficient and scaleable CO2- lasers is important both for technology and for large-scale laser systems engineering. Our paper reports about original method of active medium excitation with no limits for its volume. Efficiency of the laser constructed on the basis of this method reached 22% and specific power output -1 W/cm3. Pulse regime is proved to be more efficient for active medium excitation then continuous one. Pulsed radiation is also more suitable for material processing.
Works on creating a series of lasers 'IGIA' have been completed at our institute. The series consists of the lasers of different modifications, input characteristics of them following energy in the radiation pulse 0,02-2J, pulse repetition rate 1-200 Hz, pulse duration at the half height 26-36 microsecond(s) , middle power is 0,1-200 W. The main results obtained during this long experimental cycle are presented. It is necessary to note that some of them have been published earlier.
The work is devoted to the pulsed cathodoluminescence (PCL) of solids that occurs upon irradiating them later by high-current pulsed e-beams. The parameters of e-beams that cause no irreversible disintegration in the material under investigation are given. The conclusion has been made that PCL can be used in a spectral-emission analysis of solids being single-piece structures, thereby offering a new field of application of electron beams.
The solution of the problem of a vacuum diodes development for a ribbon e-beams of nanosecond and subnanosecond time duration production meets some obstacles. They are defined both by electrotechnical problems and by difficulties arisen from e-beam formation. This paper is devoted to the investigation of the main causes of a current amplitude limitation of the short-time e-beams.
Experimental and theoretical results are presented of photosensitive semiconductor structures as well as the main developments of modern semiconductor photoresistors, photodiodes, including injection ones, based on polycrystalline and monocrystalline materials, multilayer structures and superlattices for the visual-far infrared spectral range. Performance of multielement photodetectors based on lead chalcogenides, germanium and silicon, AIIIBV compounds, and CMT structures is described.
Experimental and theoretical results of photosensitive semiconductor structures as well as the main developments of modern semiconductor photoresistors, photodiodes, including injection ones, based on polycrystalline and monocrystalline materials, multilayer structures and superlattices for visual far infrared spectral range are presented. Performance of multielement photodetectors based on lead chalcogenides, germanium and silicon, AIIIBV compounds, and CMT structures are described.
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