Bulletin of the Lebedev Physics Institute最新文献

The present work reported the preparation of Sm-doped zinc oxide (ZnO:Sm) nanoparticles using a chemical precipitation method. Particle size, morphology, luminescence and optical properties are studied. The role of doping concentration on the antibacterial and photocatalytic properties is explored. The atomic doping concentration of Sm is chosen as 0, 1, 3, and 5%. The uniformity and grain sizes of the prepared nanoparticles are effectively controlled by doping. Violet, blue and greenish yellow emissions are observed in the photoluminescence spectrum. The band gap of the material ranges from 3.322 to 3.143 eV as the doping concentration of Sm changes from 0 to 5%. The electron and hole concentrations are examined. The prepared nanoparticles have a high refractive index and are examined using various models. Antibacterial studies against the bacteria that cause the disease septicemia have been reported. The enhanced photocatalytic performance is observed. A maximum of 94% of the degradation of methylene blue is obtained using ZnO:Sm (5%) nanoparticles.

After achieving thermonuclear ignition in inertial confinement fusion (ICF), a new stage of research began, the ultimate goal of which is creation of an industrial ICF reactor for generating electric energy. This work is devoted to radiation stability of the optical components of ICF reactor chamber and a promising KrF laser driver as one of the unsolved problems along this path. The adaptation of a ten-megaelectronvolt pulsed linear electron accelerator with an average power of 15 kW for testing a number of optical materials transparent to UV radiation of KrF laser is described. With a peak electron beam power of 4 MW and a repetition rate of 8-μs pulses of 50 Hz, the accelerator provided a maximum dose rate of electron irradiation of materials of 2.5 kGy/s at controlled temperature of optical samples under conditions close to the operation of KrF laser driver windows. The results of current and dosimetric measurements are in good agreement with Monte Carlo calculations.

We report efficient (∼10^–4) generation of terahertz (THz) radiation under relativistic laser irradiation of nitrogen and oxygen gas-cluster targets. The relationship between the THz radiation yield and the process of laser-plasma generation of a megaelectronvolt electron beam, the divergence of which depends on the target density, has been studied. For a femtosecond laser beam intensity of ∼10¹⁹ W/cm², an energy of 20 μJ is recorded in the frequency range from 0.1 to 3 THz at an accelerated electron bunch charge of nanocoulomb units. Directionality and polarization of the THz pulse, as well as the dependence of its energy on the gas type, pressure, power, and duration of the pump pulse, are measured.

The paper examines conditions for obtaining a precursor of polymer microcapsules of binary emulsion droplets with specified geometric parameters and acceptable droplet dispersion symmetry in coaxial capillary systems. The conditions for generating droplets of a given size and the factors affecting the droplet symmetry during dispersion are analyzed. The flows of droplet-forming phases and a dispersed medium necessary for obtaining emulsion droplets with specified parameters are estimated. The ways of improving the model determining the flow rate of dispersion and dispersed phases in the process of coaxial dispersion are shown. Alternative processes of droplet splitting are analyzed from the point of view of generating droplets with acceptable symmetry. It is shown that the compositions of droplet-forming phases can be optimized by using the capillary number of the spinning regime.

We discuss the key principles of laser diffraction imaging of plasma microchannels with a high degree of ionization, arising during a pulsed nanosecond gas discharge and registered at a wavelength of 1064 nm. The direct problem of laser radiation diffraction on a model plasma microchannel is solved numerically, and the propagation of diffracted radiation in an optical lens system up to the image plane of the object is described. Important properties of diffraction patterns of plasma microchannels obtained in the optical lens system are demonstrated, which can be used for their processing and subsequent accurate reconstruction of the plasma permittivity distributions. The results can be of wide interest for the development of new precision methods for optical imaging of rapidly evolving phase micro-objects.

The results of experiments on the synthesis of laser-induced graphene (LIG) on the surface of polyimide film via pyrolysis induced by radiation from commercial pulsed diode lasers with a wavelength of 450 nm, operating in either line-by-line or raster regime, are presented. To better understand the unique aspects of LIG synthesis using diode lasers, an investigation was conducted into the operations of three distinct models of laser heads. It is demonstrated that the surface morphology, thickness, and hydrophilicity of LIG film structures synthesized in either a line-by-line or raster regime differ significantly from one another. The thickness of LIG films synthesized in the raster regime is not uniform over the area, with a variation reaching ±60% of the average value. In the line-by-line regime, LIG films about 130 μm thick have been produced with a scatter of ±20%. Regardless of the incident fluence, the LIG synthesized in the raster regime is hydrophobic. In the line-by-line regime, both hydrophilic and hydrophobic LIG films can be produced depending on fluence.

This paper describes a high-power, multichannel solid-state laser setup. The characteristics of adaptive system elements within an eight-channel laser module are presented. A wavefront correction method at the output of the laser module’s amplifying path, using Zernicke polynomials, is described, investigated, and tested. The results of correcting 'thermal' aberrations in the amplification path caused by the heating of active elements were obtained experimentally. The amplitude of the wavefront, PV = 0.71 μm and its mean-square deviation from planar RMS = 0.11 μm. The results of testing the correction method for the remaining channels of the module are presented.

We report a detailed study of characteristics of vortex light fields formed using a sector spiral plate based on the DHF effect in liquid crystal ferroelectrics with a subwavelength helix pitch. In contrast to conventional nematic liquid crystal spatial light modulators, this crystal provides a switching frequency of up to 3 kHz. However, the process of crystal reorientation leads to a change in the polarization state of the modulated light. The issues of light field formation under these conditions are considered. It is shown that a change in the light polarization state does not significantly affect the formation of vortex fields. The experimentally measured values of the topological charge are in good agreement with the calculated ones.

Within the framework of the geometric optics model, an algorithm is developed for numerical calculation of the oblique ray trajectory in a highly multimode tapered optical fiber with a rectilinear generatrix. The algorithm makes it possible to simulate 3D trajectories of oblique rays in a tapered fiber with larger and smaller core diameters D/d = 400/200 μm/μm, length l_t = 10 cm, and a nominal numerical aperture NA = 0.42. Aperture properties of such fiber and regimes of ray propagation along the taper are studied; “resonant” types of trajectories are identified. Experiments are performed to excite oblique rays in a taper with core diameters D/d = 2000/400 μm/μm, l_t = 30 cm, and a nominal numerical aperture NA = 0.22 upon illumination from a larger diameter, qualitatively confirming the results of numerical simulation.