Vol 88, No 12 (2024)

Diffraction optical elements, made by contact printing on a bichrome gelatin and direct laser recording using photoresist, have been studied in order to modify the point-scattering function for the implementation of 3D ultrahigh-resolution fluorescence microscopy. It has been shown that these elements produce two-lobed, rotating light fields that can be used for 3D nanoscopy. Results of 3D subdiffractive localization of fluorescent labels, with an assessment of the accuracy of coordinate restoration, have also been presented.

The numerical algorithm for calculating the transmission function was implemented based on the numerical method of searching for energy levels and eigenwave functions of stationary states for Schrödinger particles. The program has been tested on well-known analytical and numerical solutions. Nanoribbon and chiral liquid crystal considered as two-dimension nanostructures. Results can be used to generalize on waveguide: the problem of calculating the eigenfunctions and propagation constants of guided modes.

Using numerical modeling, the possibility of forming (2D+1) short-period (3—5 oscillations under the envelope) light bullets in non-centrosymmetric media with the second harmonic at the presence of phase and group velocities mismatches is shown. It is demonstrated that cubic nonlinearity does not prevent the formation of space-time solitons only up to certain intensity values.

We studied the scattering of extremely short optical pulses propagating in a medium with carbon nanotubes containing metallic inhomogeneity. The behavior of a 3D pulse depending on three spatial coordinates and one time coordinate is investigated. The electromagnetic field is considered based on Maxwell’s equations, supplemented with a term that considers multiphoton absorption of carbon nanotubes. The peculiarities of the interaction of the pulse with a metal wire in the nonlinear medium under study have been established.

The study of exchange-coupled [Fe⁺ - Fe²⁺] pairs found by authors of the work [1] in X-ray irradiated BaF₂:Fe crystals is continued by the EPR method. It is confirmed that the electron spin multiplet S = 7/2 corresponds to the basic state of the studied pairs, split by the anisotropic part of the exchange interaction and the crystal field so that the Kramers doublet turned out to be the ground one. It was found that the energy interval to the next spin doublet corresponds approximately to 125 GHz. It was found that the nearest ligands of iron ions in an exchange-coupled pair [Fe⁺ - Fe²⁺] are eight fluorine ions registered in the EPR spectra as structurally equivalent. The parameters of the superhyperfine interaction with the magnetic moments of the nuclei of these ligand ions have been determined. It is shown that the observed experimental facts clearly indicate that the exchange between iron ions in the studied pairs is realized mainly by the mechanism of double Zener exchange.

In a crystals of the narrow-band semiconductor Pb_1-x-yGd_xCu_yS (x = 1.1·10^–3, y = 2.5·10^–3) at temperatures T = 5—300 K, unusual dependences of the shape of the lines of the EPR spectra of paramagnetic centers Gd³⁺ on the temperature and microwave power level in the resonator of EPR-spectrometer were discovered by the electron paramagnetic resonance method. Based on the results of the analysis of the shape parameters of the resonance lines recorded in the X-range, it was concluded that one of the reasons for the unusual changes in the observed EPR spectra of Gd³⁺ centers is the uneven distribution of the acceptor impurity of copper with the formation of regions with different concentrations of free charge carriers. Apparently, in these regions, resonant transitions between the spin states of Gd³⁺ centers have different effects on the values of the kinetic characteristics of free charge carriers, which lead to different contributions to the quasi-resonant absorption of microwave power.

The interaction of luminescent nanoparticles with plasmonic nanoparticles changes their luminescence, which is associated with the appearance of Förster and Purcell effects. To enhance luminescence, it is important to reduce the effect of the Foerster effect. The finite difference method in the time domain made it possible to determine the conditions for the predominance of the Purcell effect and to develop a technique for analyzing the amplification of transitions, which increases the sensitivity of sensors based on fluorescent nanoparticles.

We presented numerical estimates of the degree of quantum entanglement based on Schmidt mode analysis for ultra-broadband biphotonic states generated in a photonic crystal fiber. We show that these states have a high degree of quantum entanglement even when the source is pumped broadband by femtosecond laser pulses.

We studied the possibility of using upconversion fluoride nanoparticles NaYF₄ doped with Yb³⁺ and Er³⁺ ions as ordered non-invasive hidden labels. The synthesized upconversion fluoride nanoparticles were first deposited from suspension onto the surface of the substrate with labels used as large-scale markers, and then, using a scanning probe microscope, small conglomerates of upconversion nanoparticles were transferred over macroscopically significant distances and controlled deposited onto a clean surface, thereby imprinting nanoobjects. The process of transfer and deposition was monitored using a conventional optical microscope. Luminescent signals from orderly located labels were recorded in an optical confocal microscope.

Studying the influence of nanosecond pulsed magnetic fields on the behavior of the photon echo in YLiF₄: Er³⁺ and LuLiF₄: Er³⁺ samples, it was found that the effect of the pulsed field strongly depends on the magnitude and direction of change of the constant magnetic field. An unexpected increase in the intensity of the photon echo is observed when two identical magnetic pulses are turned on, one after the first laser pulse, the second after the second laser pulse.

NaYF₄: Yb³⁺ /Er³⁺ /TM³⁺ particles were synthesized in the form of rods with dimensions of 0.21×0.77 μm². They exhibit upconversion luminescence in the visible and near-infrared spectral ranges when irradiated at a wavelength of 980 nm. The possibility of their use as multimodal luminescent sensors with temperatures in the range of 250—350 K is shown based on the appearance of spectral bands at wavelengths of 525, 545, 655, 700 and 805 nm by the ratiometric method, which is of particular interest for biological applications.

A methodology and a system for complex remote diagnostics of insulation elements of high-voltage equipment of substations and power transmission lines, including support, suspended and through-pass insulators, have been developed. The developed system is based on the principle of simultaneous measurement and subsequent analysis of a set of characteristics of partial discharges by high-frequency (400—800 MHz) and acoustic (30 kHz) sensors. Using this system, more than 50 specimens of polymer (LC70/35) and porcelain (IOS110/400) insulators were examined during their operating mode. As a result, the amplitude-phase diagrams of partial discharge parameters were obtained, which can be used to determine the type and degree of influence of the defect on the insulation object. The features of defects for 35 and 110 kV electrical networks have been studied.