The paper proposed a method for determining wavefront distortions from the intensity distribution in two planes of laser pulse waist: in focus and out of focus. For the wavefront reconstruction task, we propose to use deep convolutional neural networks. To train the models, we used numerically generated data using Zernike modes. The method has shown good efficiency and can significantly speed up and improve the quality of calibration of an adaptive optical system.

Weibel instability was observed experimentally in plasma generated after irradiation a solid target with a 250 TW ultrashort laser pulse at the PEARL petawatt laser facility. The influence of laser radiation intensity and an external magnetic field on generation of the Weibel instability has been investigated.

We performed an experiment on the acceleration of electrons in the laser peeler regime during the interaction of a focused subpetawatt laser pulses with solid-state targets. Electrons with energies up to 70 MeV were produced, and their directional pattern was determined. The use of serrated targets led to an increase in the maximum energies and the number of accelerated electrons. A numerical study conducted using particle-in-cell simulation showed good agreement with the experimental results.

– We have established a set of technologies for the deposition and annealing of magneto-optic garnets for use in photonic crystals. Devices for sensing magnetic fields and polarisation control using reconfigurable photonic crystals are being developed.

We present the first experimental results obtained with a setup created on the basis of the PEARL laser facility for studying the processes of generating terahertz radiation from laser wake fields which are formed during the propagation of a high-power femtosecond laser pulse in a rarefied plasma. In particular, the occurrence of terahertz generation in the case where the laser–plasma interaction region is located between a pair of dielectric prisms of total internal reflection is demonstrated. The dependence of the terahertz radiation energy on the energy of a femtosecond laser pulse and on the plasma density is studied.

A generator of high-voltage bipolar pulses with adjustable values of the switching frequency (0–2000 Hz) and the output-voltage amplitude (300–3600 V) with the same magnitude for pulses of different polarities has been developed. The rise time of the output voltage pulses when operating into a capacitive load of 400 pF is no more than 3 μs. The asymmetry of the effective values of the pulse voltages of different polarities at switching frequencies of 0–200 Hz is no more than 0.02%. The generator provides synchronization of the moments of switching a high voltage with the operation of the video camera of a magnetograph and other devices. The generator can be used in various fields of experimental physics related to polarization measurements.

We present the results of studying experimentally the expansion of laser plasma in a strong external magnetic field (with a magnetic flux density of 13.5 T) at various sizes of the region of plasma formation on the surface of a solid-state target. It is shown that when the size of the plasma formation region is smaller than the classical plasma braking radius, a nearly identical topology of plasma flows is observed, which is characterized by the formation of a thin plasma sheet directed along the external magnetic field. If the width of the plasma formation region is comparable with the classical plasma braking radius, an additional plasma sheet starts to be formed.

We report on the experimental observation of excitation and detection of parametric spin waves and spin currents in the bulk acoustic wave resonator. The hybrid resonator consists of a ZnO piezoelectric film, yttrium iron garnet (YIG) films on a gallium gadolinium garnet substrate, and a heavy metal Pt layer. Shear bulk acoustic waves are electrically excited in the ZnO layer due to piezoeffect at the resonant frequencies of the resonator. The magnetoelastic interaction in the YIG film emerges magnons (spin waves) excitation by acoustic waves either on resonator's eigenfrequencies or the half-value frequencies at supercritical power. We investigate the acoustic pumping of magnons at the half-value frequencies and acoustic spin pumping from parametric magnons, using the inverse spin Hall effect in the Pt layer. The constant electric voltage in the Pt layer, depending on the frequency, the magnetic field, and the pump power, was systematically studied. We explain the low threshold obtained (∼0.4 mW) by the high efficiency of electric power transmission into the acoustic wave in the resonator.

Magneto-optic (MO) imaging and sensing are at present the most developed practical applications of thin-film MO garnet materials. However, in order to improve sensitivity for a range of established and forward-looking applications, the technology and component-related advances are still necessary. These improvements are expected to originate from new material system development. We propose a set of technological modifications for the RF-magnetron sputtering deposition and crystallization annealing of magneto-optic bismuth-substituted iron-garnet films and investigate the improved material properties. Results show that standard crystallization annealing for the as-deposited ultrathin (sputtered 10 nm thick, amorphous phase) films resulted in more than a factor of two loss in the magneto-optical activity of the films in the visible spectral region, compared to the liquid-phase grown epitaxial films. Results also show that an additional 10 nm-thick metal-oxide (Bi2O3) protective layer above the amorphous film results in ~2.7 times increase in the magneto-optical quality of crystallized iron-garnet films. On the other hand, the effects of post-deposition oxygen (O2) plasma treatment on the magneto-optical (MO) properties of Bismuth substituted iron garnet thin film materials are investigated. Results show that in the visible part of the electromagnetic spectrum (at 532 nm), the O2 treated (up to 3 min) garnet films retain higher specific Faraday rotation and figures of merit compared to non-treated garnet films.

The article analyzes the method of pointing a high-spatial-resolution solar telescope with an angular field of view smaller than the angular size of the solar disk using an auxiliary guide telescope with the field of view covering the entire disk of the Sun and its surroundings. The requirements for the resolution of the telescope, pointing modes, and the structural diagram of the pointing are considered.

The results of experiments with an initiator of lithium and graphite, whose mass was 10% of the mass of the projectile, are presented. Similar initiators produce plasma with a high speed of sound and provide the initial speed of the projectile of ∼0.5 km/s. The droplet-shaped damage on the insulating wall of the accelerator channel are described. The link between the appearance of these damages and the sharp deceleration of the plasma piston (PP) is noted. A hypothesis relating the occurrence of damages to the resonant deformation of the channel under the action of a moving high-pressure front is discussed. It is shown that the hypothesis about the resonant deformation of the channel qualitatively explains the known features of the accelerator operation.

The results of experiments with the initiator of lithium and graphite, the mass of which was ~ 10% by weight of the projectile, are presented. Such initiators create plasma with a high sound velocity value and provide the initial projectile speed of ~0.5 km/s. The drop-like damages on the insulating wall of the launcher barrel are described. There is a link between the appearance of these damages and sudden braking of the plasma piston. A hypothesis is discussed that relates the occurrence of these damages to the resonant deformation of the channel under the action of a moving high-pressure front. It is shown that the hypothesis of the resonant deformation of the barrel at a qualitative level explains the known features of the launcher operation.

We report on the first observation of microvolt-scale inverse spin Hall effect (ISHE) dc voltage driven by an acoustic spin pumping (ASP) in a bulk acoustic wave (BAW) resonator formed by a Al-ZnO-Al-YIG(1)-GGG-YIG(2)-Pt structure. When 2 mW power is applied to an Al-ZnO-Al transducer, the voltage VISHE ∼ 4 μV in the Pt film is observed as a result of resonant ASP from YIG(2) to Pt in the area ∼ 170 μm. The results of frequency and magnetic field mapping of VISHE(f,H) together with reflectivity of the resonator show an obvious agreement between the positions of the voltage maxima and BAW resonance frequencies fn(H) on the (f, H) plane. At the same time a significant asymmetry of the VISHE(fn(H)) value in reference to the magnetoelastic resonance (MER) line fMER(H) position is revealed, which is explained by asymmetry of the magnetoelastic waves dispersion law.

The design of a microwave oscillator based on a microstrip log-periodic antenna integrated with a field effect transistor and a waveguide built in a dielectric substrate has been developed and analyzed. The waveguide geometry provides the possibility of propagation and radiation at both the fundamental frequency of the log-periodic antenna and harmonics. Computer simulation of the oscillator design in a frequency range near resonance frequencies of the log-periodic antenna is conducted. The possibility of summation of powers of several antenna–oscillators arranged ias a linear phased array is investigated.

A study of the initial stages of crystallization in RF magnetron-sputtered ferrite garnet films is reported, in which a series of ultrathin Bi(2)Dy(1)Fe(4)Ga(1)O(12 )layers is fabricated and characterized. The spectral and temperature dependencies of magnetic circular dichroism (MCD) of these films are studied in the temperature range from 300 K down to 8 K. Measured magneto-optical properties are reported in the spectral range between 300 and 600 nm. In ultrathin garnets at temperatures below 160 K, we found that between 360 and 520 nm, the spectral MCD dependencies were typical of bismuth-substituted garnets with high levels of gallium dilution in the tetrahedral sublattice. The MCD signal strength measured at its 440 nm peak grows linearly with reducing temperature between 160 K and 8 K. This observed temperature dependency of MCD differed dramatically from these measured in thicker (3.7 nm) nanocrystalline garnet films. The peak MCD signal at 440 nm in these 3.7 nm-thick samples grows linearly from 215 K down to 100 K, resembling the same dependency seen in 1.7 nm films. In thinnest layers of thickness 0.6 nm, no MCD signals were observed at any temperature in the range between 8 and 300 K.

Aim of this work - to show the possibility of oscillation chaotization at the effect of low-frequency (0.1...3.0 MHz) noise signal both on feed circuit of IMPATT diode in one-frequency IMPATT diode oscillator (IMPATT-DO) and on feed circuit of transistor in one-frequency transistor oscillator. It supposed to confirm the assumption, said early, that this effect, found by us in first time for one-frequency IMPATT-DO, can take place for any semiconductor oscillators with p-n-transition, more exactly, it's nonlinear current-voltage characteristic. Method. The microwave Colpitts oscillator with a simplified structure was created for decision of this problem. The Si-Ge p-n-p-transistor was used in the oscillator as an active element. The same (0.1...3.0 MHz) noise signal oscillator was used for the effect on it's feed circuit as in experiment with IMPATT-DO.The deterministic oscillation regimes (one-frequency and two-frequencies) of the microwave Colpitts oscillator were investigated. Subsequently the low-frequency noise signal effect on the feed circuit of transistor was investigated and the spectra comparison of the microwave generation was leaded without an effect and with it. This comparison has shown in first time the deterministic oscillation spectra has transformed to chaotic oscillation spectra in microwave Colpitts oscillator at the low-frequency noise signal effect on the transistor feed circuit. Result has full confirmed our assumption. Therefore this effect can take place for any semiconductor oscillators with an active element, which has p-n-transition, more exactly, it's nonlinear current-voltage characteristic.

The change in the oscillation spectrum of an oscillator based on an impact avalanche and transit-time (IMPATT) diode of the 7-mm range under the action of a low-frequency harmonic oscillation (3 MHz) in the supply circuit of the diode is studied experimentally. It is demonstrated that, if the low-frequency oscillation amplitude exceeds the trigger negative voltage and the working point in the diode volt–ampere characteristic is located either near the trigger current (trigger negative voltage) or far from it, pulsed oscillation mode is established and, consequently, oscillations are chaotized.

Разработана и исследована конструкция генератора СВЧ-излучения на основе микрополосковой антенны логопериодического типа, интегрированной с полевым транзистором, и волноводом, встроенным в диэлектрическую подложку; геометрия волновода обеспечивает возможность распространения и выхода излучения, как на основной частоте логопериодической антенны, так и на гармониках. Проведено компьютерное моделирование конструкции генератора в частотном диапазоне вблизи резонансных частот логопериодической антенны. Исследована возможность сложения мощностей нескольких антенн-генераторов, расположенных в виде линейной фазированной решетки.