Vol 89, No 12 (2025)

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

Visualization of glass- water and glass- air interfaces by second harmonic generation microscopy has been carried out. The possibility of recovering the value of the electrostatic surface potential from the recorded signal intensity from the glass surface in contact with solutions with different pH is shown. Comparison of images of glass in contact with air and solution at pH 2 indicates the similarity in the molecular structure of these interfaces.

Based on numerical modeling, the process of generating broadband terahertz radiation by an optical pulse in a nonlinear uniaxial crystal was investigated. It was shown that the generation process is accompanied by the formation of a stable optical-terahertz soliton, as well as a broadband terahertz signal additional to the soliton.

We studied the dynamics of propagation of electromagnetic pulses consisting of a single field oscillation in a composite system of carbon nanotubes integrated into a polymer matrix. We considered nanotubes with an impurity energetically isolated from the zone structure of nanotubes. The influence of the composite parameters on the processes of propagation of ultra-short pulses is revealed, which opens up new possibilities for controlling their characteristics in such hybrid systems.

The ability of a mesogenic europium(III) beta-diketonate complex fixed on a quartz substrate by drying a highly concentrated solution of the complex in carbon tetrachloride to reduce the luminescence brightness of Eu3+ ions during prolonged UV laser irradiation and to spontaneously restore the initial luminescence parameters when kept in the dark for at least 22 hours at room temperature has been experimentally established.

An optical quantum memory protocol was implemented in the revival of silenced echo scheme in the 167Er3+:Y2SiO5 crystal at the telecommunication wavelength. The signal pulse recovery efficiency was 13% for a storage time of 60 μs for the optimal intensity of rephasing laser pulses. With a further increase in the laser pulse intensity, a superradiance pulse appears, causing a decrease in the signal pulse recovery efficiency. Methods for increasing the quantum memory efficiency by further increasing the pulse area of rephasing pulses are discussed.

We investigated a quantum memory scheme for three optical resonators that form a photonic molecule with a programmable spectrum topology. The dependence of the spectrum on the tuning parameters is analyzed to implement effective signal transfer to memory. The dynamics of the field in individual resonators is calculated for use in processing.

The behavior of Raman spectra of titanium foils after their fluorination was studied. It is shown that the bands at 905, 1795 and 2680 cm−1 belong to fluorine located under the titanium oxide nanofilm. Contact of fluorinated foils with humid air leads to a decrease in the intensity of these bands. At the same time, the bands of titanium oxynitrides and oxyfluorides appear and increase.

We presented the results of a numerical analysis of frequency entanglement in the context of generating multidimensional polarization-entangled states of biphotons, proposed by the authors earlier. The results presented will be useful for researchers in the field of quantum optics to understand the internal structure of entanglement of hybrid two-photon states of light and the possibility of controlling these states.

In a crystal of the fluorite structural group, BaF₂, 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, which represent a stable associate of a trivalent nickel ion with an interstitial oxygen ion, O_int ^- . The study of the molecular structure of the synthesized complexes was carried out by the electron paramagnetic resonance method at frequencies of 9.65, 34.35 and 94- 265 GHz, and in the temperature range from 5 to 120K . 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 001 crystallographic directions. It was established that in the synthesized complexes between Ni³⁺ and O^- ions, a ferromagnetic exchange interaction was realized.

In the electron paramagnetic resonance spectra of crystals of narrow-gap semiconductor Pb_(1-x)Gd_xS (3,2 · 10⁻⁴ ≤ x ≤ 9,5 · 10⁻³), unusual changes in the shape of the lines of Gd³⁺ (4f⁷, S = 7/2) centers were detected, associated with a change in the concentration of impurity gadolinium. In the studied crystals with increased gadolinium concentrations, weaker additional lines of two types of new gadolinium centers with cubic symmetry of magnetic properties and with effective electron spins of S = 7/2 and S = 5/2 were also observed. Two possible explanations for the observed properties of the discovered paramagnetic centers are proposed.

We presented the results of a study of the optical properties of nanostructured surfaces obtained by electrodeposition in the pores of track membranes on copper substrates. Such structures demonstrate a pronounced effect of enhancing Raman scattering from molecules adsorbed on their surface. Rhodamine 6G and malachite green dyes were used as model compounds to assess the amplification efficiency. The dependence of and the degree of signal amplification on parameters of nanowire synthesis was experimentally established, which made it possible to determine the optimal conditions for obtaining SERS- active substrates.