Bulletin of the Russian Academy of Sciences: Physics最新文献

The angular velocity of microparticles moving along a vortex light ring in an optothermal trap was experimentally demonstrated to be higher than that in an optical trap with the same trap parameters. It was shown that this velocity can be controlled without increasing radiation power on the light ring. The data obtained were analyzed based on the results of numerical simulation for the distribution of temperature and convection flow velocity over the sample area.

Results are presented from studying the optical characteristics of nanostructured surfaces obtained via electrochemical deposition in pores of track-etched membranes. Such structures display a pronounced effect of enhancing Raman scattering from the molecules adsorbed on their surface. Rhodamine 6G and Malachite Green dyes are used as model compounds to estimate the efficiency of enhancement. The dependence between the parameters of synthesis of nanowires and the degree of signal enhancement is established experimentally, allowing the optimum conditions for obtaining SERS-active substrates to be determined.

A model of scattering in disperse media has been developed considering secondary scattering. It has been found that the main reasons for the disturbance of monotonicity are the existence of optical inhomogeneities in the medium and the fact that the light scattered primarily by optical inhomogeneities of the medium undergoes secondary scattering by the dispersed phase.

The authors study the behavior of the Raman spectra of titanium foils after they come into contact with a fluorine–gas mixture. It is shown that the bands at 905, 1795, and 2680 cm⁻¹ correspond to fluorine under a titanium oxide nanofilm. The contact between such a foil and humid air reduces the intensity of these bands, while those of titanium oxynitrides and oxyfluorides emerge and grow brighter.

Nanophotonic (photonic crystal) cavities with high Q factor and low mode volume are promising for research in the field of on-chip nonlinear and quantum optics on a crystal. In this paper, the Q factor, mode area, mode volume, and Purcell factor of a nanophotonic cavity based on silicon and silicon nitride are calculated to generate high-Q resonant states.

The electron paramagnetic resonance spectra of Mn²⁺ and Gd³⁺ ions in crystals of the narrow-gap semiconductor Pb_0.996Cu_0.003Mn_xGd_yS (x ( approx ) 6 × 10^–4, y ( approx ) 4 × 10^–4) were discovered to demonstrate an unusually strong dependence of the spin relaxation processes of these ions on temperature and power of X-band microwave radiation acting on the crystal sample in a magnetic field. The observed effect manifests itself as sharp dependences of the line shape parameters of the EPR spectra of Mn²⁺ and Gd³ ions on temperature and microwave power. The results of the experimental study indicate a high efficiency of the exchange interaction between these ions via free charge carriers.

In BaF₂, a crystal of the fluorite structure group, in a helium atmosphere with small additions of fluorine and oxygen, paramagnetic complexes [NiF₄F₄O_int]^6–(C_4v) were synthesized by diffusion from the surface. These complexes are stable associates of a trivalent nickel ion with an interstitial oxygen ion ({text{O}}_{{{text{int}}}}^{ - }). The molecular structure of the synthesized complexes was studied by the electron paramagnetic resonance method at frequencies of 9.65, 34.35, and 94–265 GHz in the temperature range from 4.2 to 120 K. It was shown that the studied complex is formed by Ni³⁺(3d⁷, ⁴F, S = 3/2) and O^–(2p⁵, ²P, S = 1/2) ions. The Ni³⁺ ion replaces the Ba²⁺ lattice cation in the crystal, and the O^– ion is located in the adjacent interstitial site in one of the crystallographic directions (leftlangle {001} rightrangle .) It was determined that, in the synthesized complexes, the ferromagnetic exchange interaction between the Ni³⁺ and O^– ions occurs.

A study of the effect of nanosecond pulsed magnetic fields on the behavior of a photon echo in Y(Lu)LiF₄:Er³⁺ samples determined that the action of a pulsed field leads to nonreciprocity and an asymmetric amplification of the photon echo signal. The effect strongly depends on the orientation of the crystals in the external magnetic field and on the orientation of the pulsed magnetic field relative to the direction of the laser pulses.

The paper studies the spectral and kinetic characteristics of hydroxyapatite samples doped with Eu³⁺ in different molar concentrations (1 and 10%) at an excitation wavelength of 266 nm. For the sample with 1% Eu³⁺, the luminescence decay lifetime was measured at temperatures from 80 to 300 K; the temperature dependence of the luminescence decay lifetime is well approximated by a linear function. The absolute temperature sensitivity for the sample with 1% europium is 0.23 μs/K.

A prototype is proposed and experimentally tested for an optical thermal sensor made of a ground optical fiber with a rough surface, which electrically modulates the phonon–photon interaction and imitates the effect of the Bragg grating. The prototype has an improved detection performance due to the increased surface area and the electromodulation of the active sensor part. The possibilities of applying the scheme in noise-immune temperature monitoring and combining the sensor with light cell technologies in quantum information science are discussed.