物理与天体物理最新文献

Films consisting of arrays of MoS₂ crystallites (nanowalls), which are oriented perpendicular to the substrate, attract the attention of researchers as a promising material for creating photonic, optoelectronic, and sensor devices. The additional ordering of the structure of such layers by orientating nanowalls along a certain direction in the substrate plane allows creation of materials with unique characteristics. For their formation, we use the method of selective laser ablation of MoS₂ films formed via deposition from the vapor phase and consisting of nanowalls on the surfaces of silicon substrates. The parameters of a laser pulse, which lead to the emergence of the maximum degree of ordering of nanowalls in the film, are determined. The photoluminescence (PL) and Raman scattering (RS) have been studied. In particular, the degree of polarization of PL and RS signals was determined as a function of the angle between a selected direction in the film plane and the polarization of exciting radiation. It was revealed that exactly nanowalls are responsible for the optical properties of such films but not the underlying film. The possible applications of the materials obtained using the selective ablation method in photonics are discussed.

This paper presents an analysis of spring atmospheric blockings (SAB) in the Northern Hemisphere (NH) for the period 1992–2023. The results of the analysis indicate a significant increase in blocking activity in the NH atmosphere in recent decades. This trend is observed against the background of a general increase in near-surface temperature in the NH during the spring seasons. The following SAB parameters were used in the study: quantity, average duration, total duration, intensity, and size. Statistically significant increases were obtained for the total duration, quantity, and size of SAB, associated with an increase in the average spring near-surface temperature in the NH.

Within the framework of parameterized post-Maxwellian vacuum electrodynamics, the propagation of an X-ray and gamma radiation pulse through the electromagnetic field of a relativistically rotating pulsar is investigated. Expressions are obtained for the trajectory of this pulse and for the law of its motion from the point (mathbf{r}_{s}={x_{s},y_{s},z_{s}},) where at the moment of time (t=t_{s}) an X-ray or gamma-ray burst occurs, to the point (mathbf{r}_{d}={x_{s},y_{s},z_{d}},) where the detector of this radiation is located. In the case when the post-Maxwellian parameters of the theory differ, (eta_{1}neqeta_{2}), the time of nonlinear electrodynamic delay of electromagnetic signals carried by different normal modes is calculated. The change in the polarization state of the X-ray or gamma radiation pulse after passing through the electromagnetic field of a relativistically rotating pulsar is analyzed. The possibilities of observing the nonlinear effect of the electromagnetic field of a relativistically rotating pulsar on X-ray and gamma-ray pulses are discussed.

The paper examines the influence of the delivery scheme and spectral characteristics of remote optically pumped amplifiers (ROPA) on the maximum length of unrepeatered communication lines. It is established that in the backward ROPA (BROPA) scheme, signal amplification due to stimulated Raman scattering (SRS) in the working telecommunication fiber causes a small shift (~5 nm) of optimal pump wavelength toward shorter wavelengths relative to the maximum gain-to-noise ratio of the erbium-doped fiber (max[Gain_EDF(λ_pump)/NF_EDF(λ_pump)]). The pump delivery through the working fiber in the case of BROPA has been found to increase the transmission distance due to additional signal amplification caused by SRS and the absence of significant depletion of pump power delivered to the erbium-doped fiber. Conversely, when the signal and pump propagate forward (FROPA) along the working fiber, the pump power decays due to SRS, which makes its delivery via an additional fiber more efficient. It has been determined that for a pump spectral width exceeding 4 GHz, the effect of the Mandelstam-Brillouin stimulated scattering on pump power can be disregarded. Approximate formulas are derived for calculating the dependence of the BROPA gain on the microparameters of the erbium-doped fiber, the signal spectrum, and on the delivered power and pump spectrum subject to the amplified spontaneous emission.