Intensity Distribution of the Three-Wave Diffraction from Dislocation Epitaxial Layers in the Reciprocal Space

The three-wave X-ray diffraction in strongly disordered epitaxial layers of GaN and ZnO is experimentally investigated. The charts of the intensity distribution in the reciprocal space are plotted in coordinates q_θ and q_? for the most intensive three-wave combination (1010)/(1011) by means of subsequent θ- and ?-scanning. A nontrivial shape of the θ-sections of these contours at a distance from the ? center of reflection is revealed; it is different for different samples. For the θ-curves at the center of reflection, we observed a common peak that may be approximated by the Voigt function with a power-low decrease in the intensity at the wings; the decrease law (from–4.5 to–5.0) is found to be considerably greater than that for the similar curves of two-wave diffraction and not depending on the dislocation density and distribution in layers. In some films we observed a coarse-block structure; in addition, it follows from the distribution in the reciprocal space that these blocks are turned with respect to each other around a normal to the surface, which allows us to suggest the existence of low-angle boundaries between them, consisting exclusively of edge dislocations.     

Formation of Spectral Valleys in the Hard X-Ray Spectrum by Diffraction Band Reject Filtering

JETP Letters - The possibility of forming deep spectral valleys in the polychromatic spectrum of X rays with an energy of E ≥ 15 keV using diffraction band rejection is demonstrated....     

Dynamical Theory of X-Ray Diffraction in a Crystal with a Surface Grating of Another Material

Journal of Experimental and Theoretical Physics - A general theory is developed for dynamical X-ray diffraction in a crystal on the surface of which a lateral periodic structure of thin-film lines...     

Spectral and Angular Dependences of the Efficiency of Three-Layer Relief-Phase Diffraction Elements of the IR Range

Within the framework of the scalar and rigorous diffraction theory based on solving a system of Maxwell equations, saw-tooth relief-phase three-layer microstructures designed for the work with polychromatic radiation of the mid-IR range (3 ≤ λ ≤ 5 μm) are studied. The series of effective microstructures composed of different optical materials is extended, and the depths of their reliefs are minimized. The series is extended, in particular, owing to microstructures in which Fresnel losses for reflection from both reliefs do not exceed 10%. This factor, in combination with the relatively low total relief depth, can turn out to be decisive when choosing one or another microstructure for solving a specific scientific or technological problem.     

The Complexity Classes of Angular Diagrams of the Metal Conductivity in Strong Magnetic Fields

Journal of Experimental and Theoretical Physics - We consider angular diagrams describing the dependence of the magnetic conductivity of metals on the direction of the magnetic field in rather...     

Spectral and diffraction properties of microchannel plates in the long-wavelength X-Ray range

The spatial distribution of the intensity and spectra of X rays at the output of microchannel plates is studied both experimentally and theoretically. A model of planar antenna array is used for radiation transmitted through an ordered system of through hollow microchannels for the energy range of 90–2000 eV. The results of the calculations are in good agreement with experimental data obtained with the parallel beams of monochromatic synchrotron radiation. The energy characteristics of the output radiation whose fine spectral structure corresponds to the reflection and fluorescence spectra near the Si L- and Si K-absorption edges are presented.     

Instability of Solution of Phase Retrieval in Direct Diffraction Phase-Contrast Imaging with Partially Coherent X-Ray Source

The theoretical model of direct diffraction phase-contrast imaging with partially coherent x-ray source is expressed by an operator of multiple integral. It is presented that the integral operator is linear. The problem of its phase retrieval is described by solving an operator equation of multiple integral. It is demonstrated that the solution of the phase retrieval is unstable. The numerical simulation is performed and the result validates that the solution of the phase retrieval is unstable.     

Diffraction Fields in the Focal Space of Symmetrical Hyperbolic Focusing Lens

The fields refracted by circular symmetric hyperbolic lens illuminated by a linearly polarized plane wave are calculated from the induced surface currents. It is shown that the fields in the axial region approximate to the fields in the aperture of corrugated horn under balanced hybrid condition. The image structures for different focal ratio are compared with the classical Airy pattern, deduced by scalar analysis, of optical focusing systems. The coupling between the lens and a corrugated horn at different position on focal plane are presented. The lens resolution and pix numbers are evaluated.     

Demonstration of Mo Soft X-Ray Lasers with a Grazing Incidence Pumping Scheme in the XL-II Facility

A Ni-like Mo soft x-ray laser （SXRLs） operating at 18.9nm has been demonstrated by employing a grazing incidence pumping scheme with 120m^3 in the 200ps pre-pulse and 140mJ in the 200fs main pulse. The SXRL gain is estimated to be 1.5-3cm^-1 when a grazing incidence angle of 14° is applied. Numerical simulations are also performed to investigate the dynamics of the ion distribution. It is found that a high intensity at 2.4× 10^14 W/cm^2 of the 200fs main pulse could heat the pre-plasma rapidly to an appropriate temperature for population inversion, and could compensate for the shortage of the total pump energy to a certain extent.     

On the Transparency of Alkali-Halide Crystal in the Terahertz Spectral Range

Optics and Spectroscopy - The transmission of THz (to 3000 μm) radiation by alkali halide single crystals of sodium chloride (NaCl), potassium chloride (KCl), potassium bromide (KBr), and...     

Direct Numerical Simulation of the Rayleigh-Taylor Instability with the Spectral Element Method

A novel method is proposed to simulate Rayleigh-Taylor instabilities using a specially-developed unsteady three-dimensional high-order spectral element method code. The numerical model used consists of Navier-Stokes equations and a transport-diffusive equation. The code is first validated with the results of linear stability perturbation theory. Then several characteristics of the Rayleigh-Taylor instabilities are studied using this three-dimensional unsteady code, including instantaneous turbulent structures and statistical turbulent mixing heights under different initial wave numbers. These results indicate that turbulent structures of Rayleigh-Taylor instabilities are strongly dependent on the initial conditions. The results also suggest that a high-order numerical method should provide the capability of simulating small scale fluctuations of Rayleigh-Taylor instabilities of turbulent flows.     

On the Spectral Theory of Operator Pencils in a Hilbert Space

Abstract

Consider the operator pencil L _λ = A ? λB ? λ ² C, where A, B, and C are linear, in general unbounded and nonsymmetric, operators densely defined in a Hilbert space H. Sufficient conditions for the existence of the eigenvalues of L _λ are investigated in the case when A, B and C are K-positive and K-symmetric operators in H, and a method to bracket the eigenvalues of L _λ is developed by using a variational characterization of the problem (i) L _λ u = 0. The method generates a sequence of lower and upper bounds converging to the eigenvalues of L _λ and can be considered an extension of the Temple-Lehman method to quadratic eigenvalue problems (i).     

Combined Diffraction Grating in the Scheme of Grazing Incidence: Calculation and Parameter Optimization

The method of parameter optimization of combined structures, which consist of a dielectric grating and a metallic or multilayer dielectric mirror, was proposed. It is based on the use of the waveguide properties of the combined diffraction grating. Its main advantage lies in the possibility of determining the optimum parameters of the combined grating without solving the diffraction problem.     

Angular Dependences of the Intensity of the Raman Light Scattering on Polaritons in a Gallium Phosphide Crystal

Optics and Spectroscopy - Raman light scattering on phonons and polaritons is measured in a gallium phosphide sample. An unfocused beam of a 532-nm single-mode laser was used for excitation. A...     

Neutron Spin Rotation at Laue Diffraction in a Weakly Deformed Transparent Crystal with No Center of Symmetry

Journal of Experimental and Theoretical Physics - The effect of neutron spin rotation at Laue diffraction in a weakly deformed neutron-transparent noncentrosymmetric crystal has been described...     

Suppression of Distortions in the X-Ray Fourier-Transform Holography Scheme Based on the Two-Block Fresnel Zone Plate Interferometer with Common Optical Axis

Strict requirements were imposed on the sizes of testing sample in the previously suggested scheme of hard X-ray Fourier-transform holography based on a two-block Fresnel zone plate interferometer with common optical axis. The failure of these requirements leads to appearance of distortions in the reconstructed image. In this work, the mechanism of distortion formation, as well as possibility of its suppression are considered.     

On Change in the Silicon Crystal Structure Implanted with Hydrogen Ions during Annealing Based on Three-Crystal X-Ray Diffractometry Data

Physics of the Solid State - In this paper, we present the results of a three-crystal X-ray diffractometry (XRD) study of the state of a disturbed layer formed in silicon crystals by implantation...     

光轴方向任意时光折变晶体中体全息光栅的衍射性质

利用坐标旋转方法和Kogelnik耦合波理论,建立了光轴方向任意时单轴晶体中体光栅布拉格衍射的耦合波方程,分析了Li NbO3晶体的光轴方向对光折变体全息光栅的各向同性和各向异性布拉格衍射性质的影响。模拟计算表明,在给定光栅的结构参量时,通过适当选择光轴方向角可以使得光折变体光栅的各向同性和各向异性布拉格衍射的衍射效率达到最大,给出了相应类型的衍射效率取得最大值时晶体光轴的大致方向。这些理论分析为光折变体全息光学器件的优化设计和进一步广泛应用提供了很好的理论参考依据。