Wavelength Of Incident Radiation Research Articles

ЕФЕКТ АНОМАЛЬНО СИЛЬНОГО ПОГЛИНАННЯ ЕЛЕКТРОМАГНІТНОГО ВИПРОМІНЮВАННЯ ТОНКИМИ ПРОВІДНИКОВИМИ ВОЛОКНАМИ

Subject and Purpose. The effect of abnormally strong interaction of electromagnetic radiation with fine conductive fibers is сonsidered. Metal, semiconductor, or graphite fibers can heavily absorb electromagnetic radiation provided the fiber diameter is several hundred times smaller than the radiation wavelength. For the most effective transfer of radiation energy, a proper ratio of the radiation wavelength, fiber refractive index, and fiber diameter is sought. Methods and Methodology. The diffraction problem of a cylinder whose diameter is much smaller than the incident wavelength is treated. The formulas to compute the radiation absorption efficiency have a series appearance. The series coefficients depend on the diameter of the cylinder, its refractive index, and the wavelength. With the cylinder diameter much smaller than the wavelength, these coefficients can be series expanded in the small parameter, and it should suffice to take into account only the first term. The findings are experimentally verified by measurements of the microwave radiation energy transmitted to a fine graphite fiber. Results. Relationships have been determined of the fiber diameter, fiber conductivity, and wavelength when the effect of the electromagnetic radiation absorption was at its strongest. The experiment showed that even unfocused, an 8 mm wave beam transmitted more than 10% of the energy to a graphite fiber of a 12 μm diameter. The size of the fiber area struck by the beam was 300 times smaller than the beam cross-section. Conclusions. Conductive fibers of a cross-sectional diameter much smaller than the incident radiation wavelength strongly absorb this radiation. The absorption is at its strongest when the radiation wavelength in the fiber substance is approximately 10 times larger than the cross-sectional diameter of the fiber. The effect of the anomalously strong absorption of electromagnetic radiation can be used to transfer the electromagnetic radiation energy to fine-fiber targets no matter whether the radiation beam is focused or not. Also, this effect can be of use for making protective screens in the microwave region.

Усиление угловой дисперсии лазерных гармоник высокого порядка при взаимодействии с плотными плазменными кластерами

Diffraction gratings and photonic crystals are widely used to control light. However, their capabilities are less effective in the case of extreme ultraviolet (XUV) radiation due to the high absorption of the optical material in this frequency range. In this work, we study the possibility of enhancing the angular dispersion of XUV radiation due to scattering by plasma clusters whose dimensions are smaller than the incident radiation wavelength. An analytical model was developed using the plasma Drude dielectric function and the Mie scattering theory in the quasi-static approximation. The resonant parameters of the target for the tenth harmonic of the Ti : Sa-laser are determined, and a significant enhancement of the scattered field in this case compared to the laser one is shown. Under resonance conditions for one cluster, the diffraction of radiation by an array of such clusters is simulated using the CELES code. The results obtained show a significant enhancement of the scattered field in the resonance case for large angles corresponding to the theory of Bragg-Wulf diffraction, which makes it possible to control high harmonics of laser radiation in the XUV range using ionized cluster gas.

Analysis of quality of «Puma» soybean seeds by luminescent and spectroscopic methods

The seed shell of soybeans performs a protective function and participates in the vital processes of the seed. Soybean seeds are characterized by a unique chemical composition. The priority direction in the development of technologies for the production of foodstuffs from soybeans is the control of the quality indicators of their seeds shells. The use of a spectrofluorimeter and an IR-Fourier spectrometer allows you to study the coating material of soybean quickly and without destruction. For the purposes of comparative spectral characterization, studies were carried out on the soybean seed envelope of the untreated and treated modifier mixture. Main characteristics of luminescence excitation spectrum are determined including recording wavelength, excitation spectrum region, excitation wavelength intensity. Parameters glow attenuation are revealed by spectral-kinetic studies of phosphorescence of soybean seeds shell. IR spectroscopic analysis of milled and whole soybean seeds, as well as modifiers, allows us to interpret groupings that have characteristic oscillation frequencies. The main spectral characteristics of the soybean seed shell are determined, including wave numbers, incident radiation wavelength, transmission, and oscillation character. Modifiers adsorbed on surface of soybean seed shell are identified. The type of adsorption of the modifier shell is defined.

Plasmon-Tuned Particles for the Amplification of Surface-Enhanced Raman Scattering from Analytes.

Inelastic scattering from molecules because of vibrational modes produces unique Raman shifts, allowing these analytes to be detected with high specificity. Because Raman scattering is weak, surface-enhanced Raman scattering (SERS) has been used as a label-free technique for the detection of a variety of analytes at low concentrations. Using simple solution-based colloidal processing techniques, we have fabricated gold-coated carbon-black nanoparticles that show enhanced Raman activity. By varying the fabrication conditions, we create particles of different surface morphologies, allowing control over the peak wavelength for localized surface plasmon resonance (LSPR). By matching the LSPR wavelength to the incident laser wavelength, we get the highest signal from two model analytes, 4-nitrobenzenethiol (4-NBT) and Congo Red (CR). Our straightforward room-temperature-solution-based approach for making tunable SERS-active particles expands the range of incident radiation wavelengths that can be used for the detection of analytes using Raman scattering.

Investigation of high temperature thermal insulation performance of fiber-reinforced silica aerogel composites

Silica aerogel has been recognized as a promising material for thermal insulation applications in buildings, cryoengineering, and aerospace due to its ultralow thermal conductivity (0.014–0.020 W/(m·K)) and density (0.01–0.1 g/cm3). However, pure silica aerogel shows a high transmittance at the wavelength range of 2–8 μm, resulting in an ultrahigh radiative thermal conductivity at high temperature (> 600 K). To block thermal radiation at high temperature and to increase the mechanical performance of silica aerogel, ceramic fibers (e.g., SiO2, and SiC) with a diameter comparable to the wavelength of incident thermal radiation are usually introduced into the pure silica aerogel. Here, we developed a theoretical model to investigate the thermal conductivity of fiber-reinforced aerogel composites at high temperature, which considers the inclination angle, diameter and mass fraction of the doped fibers. Our modelling results show that aligning the doped fibers in the direction perpendicular to the incident radiation is the most effective way to reduce the radiative thermal conductivity. The optimal fiber diameter decreases from ∼ 5.0 μm to ∼ 2.5 μm when the temperature increases from 600 K to 1400 K. Owing to the trade-off relationship between the conductive and radiative thermal conductivities, there exists an optimal mass fraction of doped fibers to achieve the minimized thermal conductivity. The work helps to understand heat transfer in aerogel composites and to guide the geometric design of thermal insulation materials for high-temperature applications.

Charge properties and currents in the silicon/nanoparticles of zinc oxide heterostructure irradiated by the solar light

Silicon/zinc oxide heterostructures have shown themselves to be promising for use in photovoltaics. This paper presents the results of modeling the charge properties and currents in a Si/nanosized ZnO particle with different types of conductivity under sunlight irradiation. The simulation was carried out using the Comsol Multiphysics software package. The energy diagrams of the investigated heterostructures were plotted, the charge properties and currents flowing in the structure were investigated, the dependences of the rate of generation of charge carriers on wavelength on the surfaces of silicon, zinc oxide, and at the interface between silicon and zinc oxide, the rate of recombination of charge carriers at various wavelengths of incident radiation was obtained. The regularities of the influence of wavelength of the incident radiation on the charge density and electric potential on the surface of heterostructures have been established. It is shown that the potential on the surface of the p-Si / n-ZnO heterostructure is positive, depends on the wavelength of the incident radiation and reaches the maximum of 0.68 V. For other structures, it is negative and does not depend on the wavelength: n-Si / p-ZnO –0.78 V, p-Si / p-ZnO –0.65 V, n-Si / n-ZnO –0.25 V.

Optical Determination of Solid Fat Content in Fats and Oils: Effects of Wavelength on Estimated Accuracy

AbstractThe melting profile of solid fat content (SFC) is a parameter of primary importance for the food industry since it affects many important product characteristics such as stability, physical appearance, spreadability, and sensation in the mouth. Reference techniques to measure SFC in fats and oils include pulsed nuclear magnetic resonance (pNMR) and differential scanning calorimetry (DSC), which are reliable and accurate, but require expensive instrumentation and trained personnel. Herein, the accuracy of a recently proposed optical technique to measure SFC is investigated in terms of peak wavelength of incident radiation. A sensor system featuring an array of seven LEDs with peak wavelength in the visible and NIR range is built, and the results compared with data from DSC. All the wavelengths investigated have high accuracy in SFC estimation, especially at 590 (yellow) and 880 nm (NIR). Practical applications: Quick and easy determination of solid fat content in fats and oils by a simple experimental setup. The technique is based on optical attenuation measurements during a thermal cycle. The technique can be implemented in a measurement instrument for in‐situ analysis of solid fat content.

Development of lead-free Cu2BiI5 rudorffite thin films for visible light photodetector application

Recently bismuth-based perovskites have gained intense research interest in the scenario of developing lead-free perovskites for optoelectronic applications. In the current work, we report a new rudorffite material, namely Cu2BiI5 as a successful lead replacement material. Cu2BiI5 thin films were fabricated via thermal evaporation of copper onto spin coated BiI3 thin films. Structure and morphology analysis revealed that the films formed were hexagonal Cu2BiI5 with compact surface morphologies. Raman spectra for Cu2BiI5 films showed distinct peaks at 44, 52, 83, and 112 cm−1 are reported for the first time. The films formed at the best condition showed nearly stoichiometric composition. Cu2BiI5 displayed direct bandgap values ranging from 1.53 to 1.74 eV suggest the potential absorption of light in the Vis-NIR region. Photodetector devices were fabricated using the Cu2BiI5 thin films and their visible light sensing was evaluated. The devices displayed stability and reproducibility towards different wavelengths of incident radiation, at a low bias of 0.2 V. The present investigation on the properties of Cu2BiI5 thin films suggests that it is a potential lead-replacement candidate for photodetector applications and solar energy harvesting.

The Umov effect in cosmic dust analogue fluffy aggregates

ABSTRACT We investigate the effect of porosity in the Umov effect for the first time using the aggregate dust model. The Umov effect is an inverse correlation between the reflectivity (or geometric albedo) of an object and the degree of linear polarization of light scattered by it. Three different types of fractal aggregates: ballistic agglomeration (BA), ballistic agglomeration with one migration (BAM1), and ballistic agglomeration with two migrations (BAM2) having porosities 0.87, 0.74, and 0.64, respectively (which have the same characteristic radius ∼1 μm), are considered in our simulations. Using the multisphere T-matrix (mstm) code, maximum positive polarization (Pmax) and geometric albedo (A) are calculated for three different fractal aggregated structures considering amorphous silicate composition. Then Pmax and A are plotted against each other in logarithmic scale that shows a linear inverse correlation and a strong porosity dependence. This study shows that the porosity of the aggregates plays a crucial role in the Umov-law diagram. Further, we explore the effect of aggregate size parameter and the effect of composition in the Umov diagram for particles larger than the wavelength of incident radiation. A systematic study is presented in this paper.

Mie scattering study of dielectric nanoparticles and nanoantennas applications

The development of devices for focusing radiation on desired targets is of great importance in different fields of science and communication technologies as it would allow the creation of more efficient optical instruments. In this study, we explored the dispersion of dielectric spherical nanoparticles using elements from Mie’s theory. There was evidence that the form of dispersed radiation patterns depends on factors such as the size of particles and the wavelength of incident radiation. The knowledge regarding radiation dispersion could be applied in the development of nanoantennas, as well as new nanotechnology devices and arrangements.

The NASA‐JAXA Global Precipitation Measurement mission – part II: New frontiers in precipitation science

The <scp>NASA‐JAXA</scp> Global Precipitation Measurement mission – part <scp>II</scp>: New frontiers in precipitation science

Multiple-graphene layer based p++–n–n−–n++ device on Si/3C-SiC (100) substrate: a highly sensitive visible photo-sensor

The current paper reports the prospects of a multiple-graphene-layer (MGL) based vertically doped p++–n–n––n++ avalanche photo-sensor in visible wavelength region (300 nm–800 nm). High carrier mobility, intrinsic optical and mechanical properties in graphene at room temperature, have made this material promising for various novel applications. The authors have used an indigenously developed and experimentally verified quantum-corrected field maximum classical drift-diffusion (QCFMCDD) mathematical model for studying the optical characteristics of MGL based p++–n–n––n++ avalanche photo-diode sensor. The validity of the simulator is established through a comparative study between the experimental and analytical observations under similar operating (structural/electrical/thermal) conditions. Additionally, the superiority of the QCFMCDD model over the conventional classical drift-diffusion model is established through this comprehensive study. The analysis reveals that the opto-electrical properties of the device-under-test improve significantly as a result of the incorporation of MGL in the low doped active region. The authors have compared the results with those of a Si/4H-SiC super-lattice avalanche photo-sensor at 500 nm wavelength of incident radiation. It is observed that graphene outperforms its Si/4H-SiC counterpart in terms of photo-responsivity (0.820 A W−1 vs. 0.650 A W−1) and quantum efficiency (84% vs. 62%) for optical irradiation with visible laser source. The opto-electrical performance of the 3 × 3 array type graphene photo-sensor is further analyzed and compared with those of its single array counterpart. The photo-responsivity as well as quantum efficiency increases by at least 30% in the case of the 3 × 3 photo-sensor array. In comparison to available photo detectors, reported so far in published literature, the designed photo-sensor shows overall performance betterment in the visible wavelength region. To the best of authors’ knowledge, this is the first report on MGL based 3 × 3 array type ultra fast highly sensitive visible avalanche diode photo-sensor.

Probing dipole and quadrupole resonance mode in non-plasmonic nanowire using Raman spectroscopy

Electric field enhancement in semiconductor nanostructures offers a possibility to find an alternative to the metallic particles which is well known for tuning the light–matter interaction due to its strong polarizability and size-dependent surface plasmon resonance energy. Raman spectroscopy is a powerful technique to monitor the electric field as its scattering depends on the electromagnetic eigenmode of the particle. Here, we observe enhanced polarized Raman scattering from germanium nanowires of different diameters. The incident electromagnetic radiation creates a distribution of the internal electric field inside the naowires which can be enhanced by manipulating the nanowire diameter, the incident electric field and its polarization. Our estimation of the enhancement factor, including its dependence on nanowire diameter, agrees well with the Mie theory for an infinite cylinder. Furthermore, depending on diameter of nanowire and wavelength of incident radiation, polarized Raman study shows dipolar (antenna effect) and quadrupolar resonances, which has never been observed in germanium nanowire. We attempt to understand this polarized Raman behavior using COMSOL Multiphysics simulation, which suggests that the pattern observed is due to photon confinement within the nanowires. Thus, the light scattering direction can be toggled by tuning the polarization of incident excitation and diameter of non plasmonic nanowire.

Talbot effect based tunable setup for the measurement of stepped surfaces: Plane and spherical wavefront illumination

The self-imaging phenomenon, or Talbot effect, consists of the replication of a periodic structure at certain distances along the optical axis when an object is illuminated with spatially and temporary coherent light. In the case of plane wave illumination, the distance between self-images is constant. This distance is directly dependent on the square of the grating period and inversely dependent on the wavelength of incident radiation. Although the Talbot effect has mainly been applied to measure stepped surfaces from the position of the first self-image, this phenomenon is also observed under spherical wavefront illumination. In the latter case, the distance between self-images is not constant, but depends on the radius of curvature of the incident spherical wavefront. Here, we demonstrate that by using the position of the first self-image with spherical illumination and variable period of the grating, we can open new range possibilities to the ones obtained with the Talbot setup with plane wave illumination, by simply removing the collimating lens. Furthermore, we briefly describe how the Talbot measurement technique can be tuned by accounting for the positions of both the first self-image and the pattern observed at half of this distance.

Graphene Based Heterojunction PIN Device as Photo-Sensor

In this paper, we propose to prospects of Multiple-Graphene-Layer (MGL) based vertically doped p ++-n-n - -n ++ Avalanche photo diode-sensor in visible wavelength region (400nm-700nm). At room temperature, the authors have studied the high carrier mobility, intrinsic optical and mechanical properties in Graphene in various novel applications. To study the comparative analysis between the experimental and analytical observation of APD sensor, the authors have design, developed and experimentally verified Quantum-Corrected Field Maximum Classical Drift-Diffusion (QCFMCDD) mathematical model. The authors have compared the results with those of Si/4H- SiC super-lattice avalanche photo-diode sensor at 600 nm wavelength of incident radiation. It is noticed that Graphene performs better than Si/4H-SiC counterpart in terms of photo-responsivity (0.76A/W vs. 0.60A/W) and quantum efficiency (82% vs. 60%) for optical irradiation in visible wavelength region. The optical-electrical performance of 3x3 array type Graphene photo sensor diode is further analyzed and compared with those of its single array counterpart. In published literature, the available photo detector comprises with the designed photo-sensor shows the significant overall better performance in visible wavelength region.

Effect of optical properties on radiative-conductive heat transfer in a system of two semitransparent layers

The paper offers a numerical simulation of the heat state for a two-layer semitransparent medium that imitates a hypothetical snow cover upon an opaque semi-infinite substrate; the layers of cover have different absorption and scattering coefficients. Computations were performed for key parameters typical of winter season. It was shown that, depending on the optical thickness of every layer and proportions of absorption to scattering in the incident radiation, we observe more intense heating of near-surface or deeper zones in the snow-ice medium. The radiation part of problem was solved using a modified average-flux method used to take into account the dependency of optical properties on the wavelength of incident radiation, scattering, and reflectance at the layers boundaries.

On anomalous absorption of electromagnetic radiationby a subwave metal wire

Background: The effect of anomalously strong absorption, scattering and attenuation of microwave electromagnetic radiation by thin conductive wires is considered. The investigated effect can be used in the development of radio-absorbing and radio-masking materials for various purposes. The aim of the work is to clarify the physical nature of the effect. Materials and methods:. On the basis of the generalized Lorentz-Mi theory the mathematical model of diffraction interaction of microwave radiation with a cylindrical object which material is characterized by a complex refractive index is constructed. The case of normal incidence of a plane electromagnetic wave of E- and H-polarizations on a cylinder is considered. Numerical calculations of the field distribution were performed in the MathCard environment. Results: It is shown that for thick cylinders with a diameter greater than the wavelength, characteristic resonant peaks of absorption and scattering of wave energy are observed. For very thin cylinders, the diameter of which is much smaller than the wavelength, there are maxima of absorption and scattering of energy of incident radiation, which cannot be explained by resonant phenomena. Simplified analytical expressions for the efficiency coefficients of attenuation, absorption and scattering of electromagnetic radiation by thin cylinders are obtained. The field distributions inside and outside the dielectric and metal cylinders at different ratios of their diameter and wavelength of incident radiation are calculated. The efficiency of radiation absorption by a thin wire at different ratios of its diameter and skin-layer thickness for wire material has been studied. Conclusion: It was found that the effect of abnormally strong absorption of microwave radiation by very thin metal wires is due to the existence of a skin effect for conductive materials that interact with microwave radiation. It is obtained that the maximum efficiency of radiation absorption is achieved when the diameter of the wire is twice less than the thickness of the skin layer. The observed effect of anomalous absorption is nonresonant.

ИСПОЛЬЗОВАНИЕ МЕТОДА ДИАГРАММНЫХ УРАВНЕНИЙ ДЛЯ АНАЛИЗА ДИФРАКЦИИ НА МАЛЫХ РАССЕИВАТЕЛЯХ

Scattering of electromagnetic waves by small particles is an important key task of diffraction theory. This is due to a wide range of practical applications of the effects associated with the scattering of electromagnetic waves by particles, small in com-parison with the wavelength. From the moment of the appearance of the first papers devoted to this subject and up to the present, the most used mathematical model used in solving the problem of scattering by small bodies is the dipole approximation (Rayleigh approximation). This approach is described in sufficient detail for particular cases of scattering by balls and ellipsoids, when the solution of the auxiliary electrostatic problem can be obtained in explicit form. Note that the solution of the problem in the electrostatic approximation in the general case, in itself, is quite complicated and time-consuming compared with the solution of the original wave problem. Existing methods for solving it have a number of fundamental limitations. In this paper, we developed a technique based on the use of the method of Pattern Equations Method (PEM), first proposed in 1992. In a significant number of publications, it has been clearly demonstrated that PEM have important advantages over many alternative methods and are very effective in solving a wide class of problems. In constructing a new approach to the analysis of scattering by small bodies, we used the high convergence rate of the PEM established in our previous papers. Indeed, as shown in previous works of the authors of this article, to solve the problem of scattering by impedance bodies, whose characteristic size is comparable with the wavelength of the incident field, it suffices to take into account, depending on the polarization of the incident field, one to three terms in the Fourier decomposition of the scattering pattern. This circumstance made it possible to obtain explicit formulas for the integral scattering characteristics applicable to complex-shaped impedance scatterers. In this work, explicit formulas are obtained for the integrated scattering characteristics that are applicable to small, compared with the incident radiation wavelength, scatterers. A review is given of the application of an approximate methodology for calculating the integral scattering characteristics of small diffusers of arbitrary shape, in particular, thin dielectric cylinders, based on the use of PEM. As the above results show, the approximate relations obtained have sufficient accuracy in a wide range of problem parameters.

Засади автоматизованого проектування електромагнітних екранів з урахуванням просторових факторів

The purpose of the work is to develop the principles of designing electromagnetic screens taking into account diffraction phenomena and methodological approaches to the automation of design work. Results. The principal approaches to the design of materials and structures for shielding electromagnetic radiation are considered. It is shown that for shielding radiation with frequencies up to 1 GHz, it is necessary to take into account the diffraction phenomena at the edges of flat structures, which cause the presence of “penumbra”. A convenient mathematical apparatus for determining the size of the penumbra depending on the wavelength of incident electromagnetic radiation is provided. The need to account the reflection of electromagnetic waves from building structures, flat surfaces of technological equipment, and other objects in the design of electromagnetic screens is substantiated. The corresponding computation procedure is offered. Practical significance. The obtained functions allow modelling the propagation of radiation in the protected area and selecting the necessary parameters of the composite shielding material in the automated mode. The main parameters are the content and dispersion of the metal substance and the thickness of the material. They determine the contribution of the reflection and absorption coefficients of electromagnetic waves to the overall shielding coefficient. This makes it possible to optimize the parameters of the shielding design on the principles of reasonable sufficiency.

Surface Plasmon Resonance assisted optical analysis of Strontium Barium Niobate thin films

Preferred c-axis (0 0 1) oriented SrxBa1-xNb2O6 (SBN60) thin films were grown exploiting Pulsed Laser deposition (PLD) technique. For development of an efficient Electro-Optic (EO) modulator based on SBN60 thin film, observation of minutiae change in refractive index is essential. Highly sensitive Surface Plasmon Resonance (SPR) tool is used to examine the optical property of SBN60 film. Significant increase from 1.94 to 2.50 in refractive index values with increasing deposition pressure from 8mTorr to 12mTorr is observed. Refractive index dispersion with the incident radiation wavelength has been also analysed for SBN60 thin films using SPR technique and theoretically fitted with Sellmeier equation.