M. G. Ivanov

Formation of Nano-Scale Domain Structures in Lithium Niobate Using High-Intensity Laser Irradiation

The polarization reversal process under pulsed laser irradiation without application of electric field was investigated in single crystalline congruent and MgO doped lithium niobate LiNbO 3 . The nano-domain structures obtained in different experimental conditions were statistically analyzed and characterized in terms of domain growth anisotropy.

Self-similar surface nanodomain structures induced by laser irradiation in lithium niobate

Self-similar surface structures composed of nanodomain rays, which are formed in congruent lithium niobate single crystals under pulsed laser irradiation, are investigated. The computer simulation of the formation of the domain structure is performed using the experimentally revealed rules of ray growth. It is demonstrated that the domain structures formed are fractal objects with a limited range of scaling.

Dynamics and spectroscopy of the laser plume from solid targets

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 yttrium-aluminum oxides with neodymium (YAO:Nd), and single-crystal YAG:Cr are studied. The targets are irradiated in air at room temperature using a repetitively pulsed CO2 laser with a wavelength of 10.6 μm, a peak power of up to 9 kW, a pulse energy of 1.69 J, and a pulse duration of 330 μs 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 (except for the single-crystal YAG:Cr) represent the flows of a weakly nonequilibrium gas plasma with a temperature of 10 kK (graphite) and 3.1–4.7 kK (YSZ and YAO: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 single radical (YO) and the spectral lines of atoms and atomic ions are observed in the YAG:Cr plume. 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.

Luminescence of neodymium-doped yttria

Pulsed cathodoluminescence of Nd3+: Y2O3 nanopowders of the cubic and monoclinic phases and the ceramics synthesized from these nanopowders has been investigated in the spectral range 350–850 nm. It is found that the IR emission band of neodymium ions in the Nd3+: Y2O3 cubic phase is located at λ1 ≈ 825 nm. When there is a monoclinic phase admixture, two additional luminescence bands of Nd3+ arise in the spectrum at λ2 ≈ 750 nm and λ3 ≈ 720 nm. The emission spectrum of all Nd3+: Y2O3 materials also contains a wide intrinsic band of yttrium oxide at λ ≈ 485 nm; however, the presence of neodymium decreases the intensity of this band and increases the its structurization. It is suggested that the structure of this band in Nd3+: Y2O3 materials is mainly determined by local absorption (self-absorption) of neodymium ions.

Nonlinear dynamics of a plasma torch generated by a laser pulse of large width

Experimental data on the nonlinear dynamics of a plasma torch generated by a laser pulse of large width acting upon a graphite target are presented and discussed. The mushroom shape of the luminous region and the duration of emission observed in experiment are explained by the development of the Richtmyer-Meshkov instability at the carbon plasma-air interface and by the formation of nanoparticles in the plasma expanding into the buffer gas.

Fabrication and Properties of Neodymium-Activated Yttrium Oxide Optical Ceramics

About new technology of production of transparent ceramics including laser synthesis of nanopowders, their magnetic pulsed compaction and vacuum sintering is reported. The results of investigations of the synthesized samples of transparent ceramics made from neodymium-activated yttrium oxide are presented. It has been shown that in a 1.1 mm thickness sample with optical loss coefficient α1.07μm = 0.03 cm−1 laser generation at λg ∼ 1.08 μm with a slope efficiency of 15% at laser diode pumping at a wavelength of 807 nm has been obtained.

Study of the luminescence of Nd 3+ :Y 2 O 3 optical ceramic

Pulsed cathodoluminescence of Nd3+:Y2O3 ceramic synthesized from nanopowders obtained by laser evaporation of a solid target has been investigated in the 350-850-nm range. The samples were sintered in vacuum furnaces at temperatures of 1550-2050°C, but with different heating rates: 5K/min (first group) and 0.75K/min (second group). Strong luminescence bands of the Nd3+ ion showed up in the samples of the second group at λ≈425 and 457nm. A wide emission band at λ≈485nm of the intrinsic center predominates in the samples of the first group, while the luminescence bands of neodymium become weaker as the sintering temperature of the samples increases. It is shown that the appearance of the bands at λ≈425 and 457nm is associated with the presence in the ceramic of an impurity, most likely the monoclinic γ-Y2O3 phase, concentrated in micron-size regions along the edges and at the junction points of the crystals.

Radioluminescence Properties of Bulk, Fiber, and Nanosized NaF–U Crystals

The results of comparative investigations into the scintillation and optical properties of bulk, fiber, and nanosized NaF-U crystals are presented. Fiber and nanosized samples of the NaF-U crystals are prepared for the first time and show considerable promise for practical applications in radiation technology.