Mid-infrared (mid-IR) photodetectors play a crucial role in various applications, including the development of biomimetic vision systems that emulate neuronal function. In this work, we demonstrate a new infrared photodetector based on graphene/boron nitride/graphene tunneling heterostructure combining perception and memory functions. The detection principle is based on the shift of the N-shaped tunneling resonant feature in the I-V–curve upon infrared illumination. In the current-biased mode, such a shift results in a strong voltage “jump” (0.05−1 V) to another branch of the I-V–characteristic that persists after switching the radiation off. As a result, the structure can be considered as a visual neuron that combines perception and memory functions. More interestingly, the direction of voltage switching depends on laser beam position, adding extra recognition functionality to our perception device. The observed phenomena are explained within the theory of selective light-induced heating of electrons in the graphene layers, and the tunneling of hot carriers.

2D materials offering ultrafast photoresponse suffer from low intrinsic absorbance, especially in the mid‐infrared wavelength range. Challenges in 2d material doping further complicate the creation of light‐sensitive p − n junctions. Here, a graphene‐based infrared detector is experimentally demonstrated with simultaneously enhanced absorption and strong structural asymmetry enabling zero‐bias photocurrent. A key element for those properties is an asymmetric singular metasurface (ASMS) atop graphene with keen metal wedges providing singular enhancement of local absorbance. The ASMS geometry predefines extra device functionalities. The structures with connected metallic wedges demonstrate polarization ratios up to 200 in a broad range of carrier densities at a wavelength of 8.6 µm. The structures with isolated wedges display gate‐controlled switching between polarization‐discerning and polarization‐stable photoresponse, a highly desirable yet scarce property for polarized imaging.

The paper presents an experimental study of the process of methane hydrate formation from stabilized water foam. In all cases, the hydrate formation front started from the region inside the foam. Upon reaching the foam-solution boundary, it initiated the formation of polycrystalline conical conglomerates at this boundary - hydrate needles oriented deep into the solution. A mechanism for their formation and subsequent spontaneous shortening of some of them is proposed.

Magnetic microcombs are necessary in microrobotics, MEMS technologies, actuator and magnetic flow analyzer industries. Usually, magnetic microcombs are artificial linear magnets of periodic shape. We propose another type of microcombs based of microwires, where periodicity of magnetization is caused by equidistant alternation of natural domains. We have demonstrated the presence of quasi-periodic radial magnetization and the effect of temperature and magnetic field on magnetic relief in PrDyFeCoB microwires. Accurate analysis of chemical, phase and structural composition of the microwires allowed us to reveal necessary conditions for the creation of periodical magnetic relief. Annealing affects magnetic relief and changes structure of initially amorphous microwires. Crystal structure of inclusions enriched with Fe and Co instead of Dy and Pr is body-centered cubic (BCC), while the bulk of the microwire has tetragonal structure. We have found laser stimulated amorphization of surface of PrDy-FeCo-B microwires. Partial restoration of the amorphous structure in polycrystalline microwires under single laser pulse of irradiation of 1mJ power and 120 ns duration has been found in 1-2 mu m depth.

Graphene/hBN/graphene tunnel devices offer promise as sensitive mid-infrared photodetectors but the microscopic origin underlying the photoresponse in them remains elusive. In this work, we investigated the photocurrent generation in graphene/hBN/graphene tunnel structures with localized defect states under mid-IR illumination. We demonstrate that the photocurrent in these devices is proportional to the second derivative of the tunnel current with respect to the bias voltage, peaking during tunneling through the hBN impurity level. We revealed that the origin of the photocurrent generation lies in the change of the tunneling probability upon radiation-induced electron heating in graphene layers, in agreement with the theoretical model that we developed. Finally, we show that at a finite bias voltage, the photocurrent is proportional to either of the graphene layers heating under the illumination, while at zero bias, it is proportional to the heating difference. Thus, the photocurrent in such devices can be used for accurate measurements of the electronic temperature, providing a convenient alternative to Johnson noise thermometry.

Improvement of firefighting means and methods for measuring their effectiveness are important tasks in the field of fire safety. The paper presents the results of experimental measurements of the minimum extinguishing concentration of powder mixtures that can be applied as effective explosion-suppressing barriers. Measurements of the minimum extinguishing concentration of the investigated powders were carried out using a laboratory method with their pulsed delivery to a microfire of class B using compressed air. In order to justify and assess possible errors of the mentioned laboratory method for measuring extinguishing efficiency, numerical 3D modeling of the interaction of a multiphase flow with a model combustion focus was performed. The analysis of the numerical modeling results has shown that, for the applied laboratory method, almost the entire portion of the investigated powder enters the combustion zone. Additionally, the numerical calculations indicate that under the specified experimental conditions, the particle size of the powder has no noticeable effect on their loss into the surrounding flame space. Thus, these results justified the use of the mentioned laboratory method for he comparative evaluation of fire-extinguishing powders with a wide range of dispersity. The application of this laboratory method for assessing the effectiveness of the fire-extinguishing powder allowed for the development of an optimal powder composition for explosion suppression, incorporating inert mineral particles as the main component and an additive of a chemically active potassium-containing combustion inhibitor.

In this work, the process of dissociation of methane hydrate obtained under laboratory conditions in the form of a loose shapeless mass and in a pressed granular form, placed on a warm surface and on a surface covered with a thin layer of water, including the initiation of combustion of the gas released during the dissociation process, was experimentally studied. The rate of dissociation, the characteristic time of complete decomposition, and the proportion of water evaporating over a given time were determined for all cases considered. Based on the analysis of the dynamics of temperature ranges, as well as data illustrating the rate of mass loss by the sample, it was assumed that the process of dissociation of granular hydrate, both in the case without combustion and in the case of combustion, is accompanied by the phenomenon of self-preservation, which is not observed for loose hydrate.

We report the experimental observation of multiple standing spin modes in a three-dimensional (3D) optomagnonic nanocavity formed by a nanometer-sized iron-garnet nanocylinder. We show that launching of the standing spin modes is achieved due to a high confinement of the optically generated effective magnetic field caused by the localized optical resonance. Quantization and spin-wave mode inhomogeneity are achieved in each of the three spatial dimensions. The presented approach opens horizons for 3D optomagnonics by combining nanophotonic and magnonic functionalities within a single nanocavity.

Preparation of single-walled carbon nanotubes (SWNTs) with diameters ranging from 1.2 to 1.5 nm has been highly demanded for field-effect transistors with superior properties. In the work, we report the chemical vapor deposition synthesis of SWNTs with an average diameter of 1.2 nm from a rationally designed nickel catalyst supported by magnesia. The high metal dispersion, the suitable reaction temperature, and the use of a methane carbon source co-determine the SWNT diameter distribution. Furthermore, through the synergistic application of poly(9,9-dioctylfluorene-2,7-diylalt-pyridine-2,6-diyl) wrapping and ultracentrifugation, SWNTs with enriched (10,8) species of 1.24 nm are successfully extracted, which is attributed to the selective interaction between the polymer molecules and the targeted SWNTs. This work not only sheds light on the growth of SWNTs with relatively large diameter, but also paves the way towards the preparation of high purity (n,m) species that could meet the requirements of advanced high-tech applications.

Interaction between single molecule magnets (SMMs) and metal surface is a hot topic promising controllable deposition of SMMs, programmable frequency of magnetic relaxation and addressed reading of information. In this paper, we develop strategy of the Er3+ based SMM functionalization by its penetration inside the arrays of Ferromagnetic Micro Particles (FMPs). We show that predictable residual magnetic field of the FMPs arrays is an effective tool for regulation of the frequency maximum of imaginary magnetic susceptibility. We analyzed color of magnetic noise in respect to physical origin of magnetic relaxation. An additional channel for control over spin noise is formation of chemical bonds between SMM and the FMPs surface. Oxidation of an Er complex transforms 20 +/- 5 % of the initial 10 -coordinated SMM complex to the 9 -coordinated complex with reduced relaxation time. Memorized residual magnetization of the composite material allows one to set desirable relaxation frequency in the individual micronized cells to create a sound frequency register. The proposed compaction of SMMs of different types in ferromagnetic composites provides engineering of the chemically designed spin interface on ferromagnetic surface for spintronics and quantum computing.

We demonstrate optical nonthermal excitation of exchange dominated spin waves of different orders in a magnetophotonic crystal. The magnetophotonic structure consists of a thin magnetic film and a Bragg stack of nonmagnetic layers to provide a proper nonuniform interference pattern of the inverse Faraday effect induced by light in the magnetic layer. We found a phenomenon of the pronounced phase slippage of the inverse Faraday effect distribution when the pump wavelength is within the photonic band gap of the structure. It allows to tune the interference pattern by a slight variation of light wavelength which results in the modification of excitation efficiency of the different order spin waves. The approach can be applied for different magnetic dielectrics expanding their application horizons for spin-wave based devices.

The control of light through all-optical means is a fundamental challenge in nanophotonics and a key effect in optical switching and logic. The optical bistability effect enables this control and can be observed in various planar photonic systems such as microdisk and photonic crystal cavities and waveguides. However, the recent advancements in flat optics with wavelength-thin optical elements require nonlinear elements based on metastructures and metasurfaces. The performance of these systems can be enhanced with high-Q bound states in the continuum (BIC), which leads to intense harmonic generation, improved light-matter coupling, and pushes forward sensing limits. In this study, we report on the enhanced thermo-optical nonlinearity and the observation of optical bistability in an all-dielectric metasurface membrane with BICs. Unlike many other nanophotonic platforms, metasurfaces allow for fine control of the quality factor of the BIC resonance by managing the radiative losses. This provides an opportunity to control the parameters of the observed hysteresis loop and even switch from bistability to optical discrimination by varying the angle of incidence. Additionally, we propose a mechanism of nonlinear critical coupling that establishes the conditions for maximal hysteresis width and minimal switching power, which has not been reported before. Our work suggests that all-dielectric metasurfaces supporting BICs can serve as a flat-optics platform for optical switching and modulation based on strong thermo-optical nonlinearity.

The 2D materials are the fundamental building blocks for modern optoelectronics and photonics. Optically anisotropic monolayers give even more flexibility in device design and performance. However, the random orientation of optical axes in the large‐scale samples prevents anisotropic monolayers from widespread use. The alternative structure is a monolayer of aligned single‐walled carbon nanotubes (SWCNTs) with an anisotropic dielectric tensor. Herein, aligned SWCNTs monolayer anisotropic optical constants in a broad spectral range (250–1700 nm) are measured for the first time. It is discovered that it has a large birefringence of Δ n ≈ 0.2 and a high dichroism of Δ k ≈ 0.4. Moreover, it is demonstrated that aligned SWCNTs monolayer optical response can be described by an effective medium approximation using the graphene dielectric function. In addition, it gives a universal approach for a determination of carbon concentration in nanotubes structures. It also applies for other types of carbon nanotubes, such as multi‐walled and randomly oriented carbon nanotubes arrays. Hence, in the results, aligned SWCNTs monolayer optical constants are added to the optical anisotropy database, which facilitates the longstanding challenge of using 1D structures in two dimensions, and a rapid characterization method for carbon nanotubes is provided.

The lattice geometry of natural materials and the structural geometry of artificial materials are crucial factors determining their physical properties. Most materials have predetermined geometries that lead to fixed physical characteristics. Here, the demonstration of a carbon nanotube network serves as an example of a system with controllable orientation achieving on-demand optical properties. Such a network allows programming their optical response depending on the orientation of the constituent carbon nanotubes and leads to the switching of its dielectric tensor from isotropic to anisotropic. Furthermore, it also allows for the achievement of wavelength-dispersion for their principal optical axes - a recently discovered phenomenon in van der Waals triclinic crystals. The results originate from two unique carbon nanotubes features: uniaxial anisotropy from the well-defined cylindrical geometry and the intersection interaction among individual carbon nanotubes. The findings demonstrate that shaping the relative orientations of carbon nanotubes or other quasi-one-dimensional materials of cylindrical symmetry within a network paves the way to a universal method for the creation of systems with desired optical properties.

Dynamics of gas bubble growth in a highly viscous gas-saturated liquid (magmatic melt) subjected to decompression is investigated. A mathematical model of the process, which is a joint dynamic and diffusion problem, is proposed. An approximate semi-analytical solution is found based on the existence of a quasi-stationary state for the bubble growth process. The influence of certain factors on the process under consideration at all its stages is shown. In particular, a significant dependence of the bubble growth rate on the decompression rate is illustrated. It is shown that, at long times, bubble growth has a self-similar character and occurs only as a result of gas desorption from the surrounding liquid.

The discovery of new methods of purely optical ultrafast excitation of spin waves led to the creation of the first optomagnonic gate XNOR. However, with the help of XNOR alone, it is not possible to perform all types of logical operations. In this work we demonstrate the way to realize an optomagnonic NOR gate. Micromagnetic simulations are used to estimate the requirements for such type of logic gates. The resulting NOR gate forms a complete set of logic gates and has the same advantages as XNOR while not much more complicated than its predecessor.

This paper first presents particle image velocimetry measurements of the chemical time scales versus equivalence ratio and the concentration of the inhibitor trimethyl phosphate for premixed methane–air and dimethyl ether–air flames at atmospheric pressure. Comparison of the experimental results with theoretical estimates based on the Zel’dovich–Barenblatt hypothesis shows their qualitative agreement. Within the accuracy of the experiment, the chemical time scale depends only on the burning rate, rapidly decreasing as it increases. At fuel–air flame speeds close to and above 0.6 m/s, the results of the experiments show the high accuracy of theoretical estimates based on the Zel’dovich–Barenblatt hypothesis.

Cs 2 MoO 4 and Li 1.9 Cs 0.1 MoO 4 crystals were grown from melt by the low-thermal-gradient Czochralski technique. The standard formation enthalpy of cesium molybdate Cs 2 MoO 4 was measured by solution calorimetry. The heat capacity of Li 1.9 Cs 0.1 MoO 4 was measured by differential scanning calorimetry (DSC) in the temperature range 320–710 K. The lattice enthalpy of Cs 2 MoO 4 was calculated using the Born-Haber cycle. Cesium molybdate was shown to be thermodynamically stable to decomposition into constituent simple oxides (Cs 2 O and MoO 3 ), which made it promising for application. Li 1.9 Cs 0.1 MoO 4 experienced no phase transitions in the temperature range 320–710 K.

We report the first experimental observation of multiple standing spin modes in 3D optomagnonic nanocavity formed by nanometer-sized iron-garnet nanocylinder. We show that launching of standing spin modes is achieved due to a high confinement of the optically generated effective magnetic field caused by the localized optical resonance. Quantization and spin-wave mode inhomogeneity is achieved in each of the three spatial dimensions. The presented approach opens new horizons of 3D optomagnonics by combining nanophotonic and magnonic functionalities within a single nanocavity.

The discovery of new methods of purely optical ultrafast excitation of spin waves led to the creation of the first optomagnonic gate XNOR. However, with the help of XNOR alone, it is not possible to perform all types of logical operations. In this work, we demonstrate the way to realize two optomagnonic gates—NOR and majority gate. Micromagnetic simulations are used to estimate the requirements for such types of logic gates. Each of the resulting gates forms a complete set of logic gates and possesses the same advantages as XNOR, giving more versatility for further ultrafast light-modulated application of logic gates.