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

This paper deals with the detection of molecules in a solution using luminescent nanoparticles. Plasmonic nanoparticles change their photoluminescence due to the Purcell and Förster effects, the latter leading to luminescence quenching. Modeling these effects in colloidal solution allows us to determine the conditions of amplification and quenching, which opens the way to improving the sensitivity of sensors based on photoluminescence.

A theoretical model was developed to describe the interaction of a photonic crystal of semiconductor carbon nanotubes and a three-dimensional extremely short laser pulse in the presence of an external magnetic field. Numerical modeling was used to construct the patterns of the time evolution of current density in a medium containing a multilevel impurity. The dependences of the shape of the current density on the external magnetic field and on the hopping integrals between impurity levels were determined.

NaYF₄:Yb³⁺/Er³⁺/Tm³⁺ particles are synthesized in the form of rods with dimensions of 0.21 × 0.77 μm. They exhibit upconversion luminescence in the visible and near-infrared spectral ranges when irradiated at a wavelength of 980 nm. The possibility of using them as multimodal luminescent sensors with temperatures in the range of 250–350 K is shown ratiometrically, based on the emergence of spectral bands at wavelengths of 525, 545, 655, 700, and 805 nm, of particular interest for biological applications.

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.

The transformation of the Raman spectra from titanium foils after their fluorination in gas mixtures was experimentally studied. It was found that fluorination leads to a strong increase in the intensity of scattering bands from the initial components of the nanocoating of titanium foils. A new strong band at 905 ± 5 cm^–1 and a wide continuum with a maximum at ~1700 cm^–1 also appear and increase in intensity after fluorination.

Studies of the effect of nanosecond pulsed magnetic fields have on the behavior of photon echoes in samples of YLiF₄:Er³⁺ and LuLiF₄:Er³⁺ show they depend strongly on the magnitude and direction of a change in the constant magnetic field. An unexpected increase in the intensity of the photon echo is observed when two identical magnetic pulses are switched on, one after the first laser pulse and the second after the second laser pulse.

Algorithms for modeling the spatial dispersion in epsilon-near-zero media are needed in designing compact nonlinear-optical devices. Improved finite-difference time-domain modeling of a metallic thin film shows that spatial dispersion increases the group velocity of the surface mode at an epsilon-near-zero frequency.

Photonic integrated circuits with improved optical input are used to obtain high-performance data transmission and processing systems. Transmitance spectra are studied for 3D microstructures fabricated via two-photon polymerization for inputting radiation in the range of 1480 to 1640 nm into photonic integrated circuits. Results were compared to transmittance of diffraction gratings.

The study of exchange-coupled [Fe⁺–Fe²⁺] pairs that we previously found in X-ray–irradiated BaF₂:Fe crystals was continued by the EPR method. It was confirmed that the ground state of the studied pairs is the electron spin multiplet S = 7/2 split by the anisotropic part of the exchange interaction and by the crystal field so that the ground state turned out to be the Kramers doublet (left| { pm 1{text{/}}2} rightrangle ). It was found that the energy interval to the next spin doublet is 125 GHz. It was established that the nearest ligands of iron ions in the exchange-coupled [Fe⁺–Fe²⁺] pair are eight fluorine ions detected in the EPR spectra as structurally equivalent. The parameters of the superhyperfine interaction with the magnetic moments of the nuclei of these ligand ions were determined. It was shown that the observed experimental facts clearly indicate that the exchange between iron ions in the studied pairs occurs mainly by Zener’s double exchange mechanism.

The scattering of extremely short optical pulses propagating in a medium with carbon nanotubes containing a metallic inhomogeneity was studied. The behavior of a 3D pulse depending on three spatial coordinates and one temporal coordinate was examined. The electromagnetic field was considered based on Maxwell’s equations supplemented with a term that takes onto account the multiphoton absorption of carbon nanotubes. Features of the interaction of the pulse with a metal wire in the nonlinear medium under study were identified.