A. N. Orlov

Dynamic light scattering by charged silicon nanoparticles in colloid

The experimental results of diameter measurament silicon nanoparticles with using dynamic light scattering method are presented in this article. Colloids of nanosilicon in acetone, in methanol and in water were studied. The measurements were taken with nanotrak device (“Photocor complex,” dynamic light scattering instrument, produced by Photocor Instruments Inc.) during regular time intervals (about several minutes). The results from each solution were compared with the results in other solutions and the stable ones were examined. Results obtained in water appeared to be nonrecurrent. Electrical double layer of nanosilicon particles in liquid had been measured for all samples. It was established that the reason of such behavior of n-Si in water solution was double charge layer which changed hydrodynamical parameters of water.

Effect of pulses from a high-power ytterbium fiber laser on a material with a nonuniform refractive index. I. Irradiation of yttrium oxide targets

The irradiation of Nd:Y2O3 targets with an absorption coefficient of 13–1.7 × 103 cm−1 using laser pulses with a duration of 0.1–3.5 ms and peak power of 200–700 W at a power density of (0.2–1.3) × 106 W/cm2 is studied. A relatively large spread of the delay times of laser plume, spike emission of the laser plume, cleavage of the front surface of the target, and greater ejection of substance from the crater in comparison with the effect of the CO2-laser radiation with almost the same power are demonstrated. A numerical model of the effect of radiation on a target with a nonuniform refractive index is proposed to interpret the destruction of dielectric material (cleavage of the front surface) and the large spread of the delay times of the plume.

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.

Effect of pulses from a high-power ytterbium fiber laser on a material with a nonuniform refractive index. II. Production and parameters of Nd:Y2O3 nanopowders

The laser ablation of the Nd:Y2O3 target with substantially nonuniform refractive index leads to the formation of a needle-shaped surface with a needle height of 6–8 mm. An increase in the displacement velocity of the laser beam on the surface to 80 cm/s and an increase in the diameter of the laser spot at the central part of the beam waist to 430 μm lead to a more uniform relief of the target surface and an increase in the nanopowder yield and production rate to 22% and 23 g/h, respectively. In addition, an excess of the mole content of the low-melting Nd2O3 in the powder decreases from 174 to 11% in comparison with the target. At an air pressure in the evaporation chamber of 0.8 bar, the mean sizes of nanoparticles (13–14 nm) are virtually independent of the displacement velocity of the beam on the surface (7–81 cm/s) and the rate of air flow above the target (13–70 m/s) in spite of significantly different nanopowder production rates.

Divalent ytterbium ions in yttrium aluminum garnet and yttrium oxide ceramics

Laser ceramics based on ytterbium-doped yttrium aluminum garnet and yttrium oxide are synthesized. The transmission, pulsed cathodoluminescence, and electron-spin resonance spectra of these ceramics at room temperature are measured and analyzed. It is shown that all the samples contain Yb2+ ions with the 4f136s electronic configuration of the ground state, which manifest themselves in the form of relatively weak bands in the IR region of the optical spectra in addition to the bands of Yb3+ ions.

A Setup for Measuring the Refractive Index of a Plane-Parallel Ceramic Plate Using the Optical Beam Shift Method

A setup for measuring the refractive indices of transparent solid samples of optical ceramics using shifts of a beam by a plane-parallel plate in a wavelength range of 400–1200 nm was developed. The minimum cross-sectional sizes of the investigated objects are 5–12 mm, and their thicknesses are 0.3–1.0 mm. A standard sample and a precise system for forming and recording optical signals equipped with a stepping motor with a step discreteness of <1 μm were used to improve the measurement accuracy of the refractive index. The cross-sectional size of the measuring beam is ≪1 mm. The accuracy in determining the refractive index is ±0.004.

The energy structure of a neodymium ion in monoclinic yttria

We present an energy level diagram of a Nd3+ ion in monoclinic γ-phase of yttria reconstructed from transmission spectra of Y2O3:Nd3+ nanopowders.

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.