Two-dimensional Diffraction Research Articles

Controllable two-dimensional asymmetric diffraction grating via vortex light in semiconductor double quantum wells system

Abstract We present a theoretical scheme to realize two-dimensional (2D) asymmetric diffraction grating in a five-level inverted Y-type
asymmetric double semiconductor quantum wells (SQWs) structure with resonant tunneling. The SQW structure interacts with a weak probe laser field, a spatially independent 2D standing-wave (SW) field, and a Laguerre-Gaussian (LG) vortex field respectively. The results indicate that the diffraction patterns are high sensitive to amplitude modulation and phase modulation. Because of the existence
of vortex light, it is possible to realize asymmetric high-order diffraction in the SQW structure, and then a 2D asymmetric grating
is established. By adjusting the detunings of the probe field, vortex field and SW field, as well as the interaction length, diffraction intensity and direction of the 2D asymmetric electromagnetically induced grating (EIG) can be controlled effectively. In addition, the
number of orbital angular momentum (OAM) and beam waist parameter can be used to modulate the diffraction intensity and energy
transfer of the probe light in different regions. High-order diffraction intensity is enhanced and high efficiency 2D asymmetric diffraction grating with different diffraction patterns are obtained in the scheme. Such 2D asymmetric diffraction grating may be beneficial to the research of optical communication and innovative semiconductor quantum devices.

Polarization beam splitter empowered by two-dimensional diffraction metagrating

Polarization beam splitter empowered by two-dimensional diffraction metagrating

All-optical switch based on two-dimensional asymmetric electromagnetically induced grating in nanohybrid systems.

This study investigates (EIG) in a nanohybrid configuration involving a semiconductor quantum dot (SQD) and a core-shell bimetallic nanoparticle coated with graphene. The goal is to optimize interactions between plasmons and excitons. This is achieved by utilizing nanoparticles covered with graphene, which enhances control over surface plasmons. These interactions decrease light absorption by quantum dots. At the same time, they enhance the presence of coherent states and quantum interference. The innovative aspect of this model lies in its ability to produce a two-dimensional asymmetric diffraction grating. This is accomplished by modulating the phase within a closed-loop structure and utilizing the nonlinear multi-wave mixing phenomenon, without needing to adjust other system parameters. More specifically, altering the phase of the incident fields produces an asymmetric diffraction grating with an efficiency exceeding 50%. Similarly, varying the frequency of the probing field results in an asymmetric diffraction grating with efficiencies exceeding 40%. This technology has the potential to enhance optical systems, such as all-optical switches in communications, by simplifying the alteration of laser beam phases and probe field frequencies.

Polar coordinate-based background removal algorithm for 2D x-ray scattering data.

During the data collection of x-ray diffraction experiments with various detectors, background signals are often unavoidable along with the sample signal. Addressing the background during post-data analysis is not a straightforward task. In this work, we introduced an algorithm specifically designed to handle centrally symmetric two-dimensional x-ray diffraction data and processed the data using the Python programming language. The two-dimensional data are first transformed from Cartesian coordinates to polar coordinates. Second, utilizing existing background processing algorithms, one-dimensional background curves are identified for each azimuth angle. These background data are then merged to generate two-dimensional background data. Finally, by subtracting the background from the original data, we obtain the clear diffraction signal. The algorithm can effectively remove the background from x-ray diffraction data and exhibits the ability to handle backgrounds with high intensity and irregular shapes, and the discernibility of the weak signal is significantly enhanced. Moreover, researchers have the flexibility to choose whether to preserve or eliminate the signals from additional amorphous components based on their needs. This algorithm will provide researchers with the possibility for further data analysis.

Investigation on solidification crack susceptibility for weld metals of GH3539 alloy with Trans-Varestraint test

In this work, the welding solidification crack susceptibility of GH3539 alloy was investigated under different strains using a trans-varestraint test. The results indicate that the saturation strain of GH3539 alloy reaches a bending strain of 1 %. High-angle grain boundaries in the weld metal are fragile areas where welding solidification cracks are formed due to element segregation and stress concentration, which are essential factors causing crack initiation and propagation. Furthermore, the surface residual stress of the crack tip was calculated by two-dimensional synchronous micro X-ray diffraction analysis of the partial Debye ring, which was deduced as the major factor for the cracking. The element Si in the alloy tends to segregate at grain boundaries, forming low-melting liquid films with elements such as Mo, Cr, and Mn during the final solidification stage. These liquid films reduce the interfacial bonding strength at the grain boundaries. The failure of the liquid films to accommodate local stress, resulting in subsequent interface separation, serves as the other catalyst for initiating solidification cracks in welding.

Crystal Modulation of Mn-Based Layered Oxide toward Long-Enduring Anionic Redox with Fast Kinetics for Sodium-Ion Batteries.

Mn-based layered oxide cathodes for sodium-ion batteries with anionic redox reactions hold great potential for energy storage applications due to their ultra-high capacity and cost effectiveness. However, achieving high capacity requires overcoming challenges such as oxygen-redox failure, sluggish kinetics, and structural degradation. Herein, we employ an innovative crystal modulation strategy, using Mn-based Na0.72Li0.24Mn0.76O2 as a representative cathode material, which shows that the highly exposed {010} active facets enable an enhanced rate capability (119.6 mAh g-1 at 10 C) with fast kinetics. Meanwhile, the reinforced Mn-O bond inhibits excessive oxidation of lattice oxygen and O-O cohesion loss, stabilizing and maintaining a long-enduring reversible oxygen-redox activity (100 % high capacity retention after 100 cycles at 0.5 C and 84.28 % retention after 300 cycles at 5 C). Time-resolved operando two-dimensional X-ray diffraction reveals the robust structural stability, zero-strain behavior, and suppressed phase transition with ultra-low volume variation during cycling at different rates (0.1 C: 1.75 %, 1 C: 0.31 %, 5 C: 0.04 %). Additionally, the full cell coupled with hard carbon achieves a high energy density of approximately 211 Wh kg-1 with superior performance. This work highlights the significance of crystal modulation and presents a universal approach in developing Mn-based oxide cathodes with stable anionic redox for high-performance sodium-ion batteries.

Two-Dimensional X-Ray Diffraction (2D-XRD) and Micro-Computed Tomography (Micro-CT) Characterization of Additively Manufactured 316L Stainless Steel

In-depth quality assessment of 3D-printed parts is vital in determining their overall characteristics. This study focuses on the use of 2D X-Ray diffraction (2D-XRD) and X-Ray micro-computed tomography (micro-CT) techniques to evaluate the crystallography and internal defects of 316L SS parts fabricated by the powder-based direct energy deposition (DED) technique. The test samples were printed in a controlled argon environment with variable laser power and print speeds, using a customized deposition pattern to achieve a high-density print (>99%). Multiple features, including hardness, elastic modulus, porosity, crystallographic orientation, and grain morphology and size were evaluated as a function of print parameters. Micro-CT was used for in-depth internal defect analysis, revealing lack-of-fusion and gas-induced (keyhole) pores and no observable micro-cracks or inclusions in most of the printed body. Some porosity was found mostly concentrated in the initial layers of print and decreased along the build direction. 2D-XRD was used for phase analysis and grain size determination. The phase analysis revealed single phase γ-austenitic FCC phase without any detectable presence of the δ-ferrite phase. A close correlation was found between Electron Backscatter Diffraction (EBSD) and 2D-XRD results on the average size distribution and the crystallographic orientation of grains in the sample. This work demonstrates the fast and reliable as-printed crystallography analysis using 2D-XRD compared to the EBSD technique, with potential for in-line integration.

Two-dimensional distribution experiment of ‘lattice diffraction’ using ultrasound in an educational laboratory

Abstract A device that can study the two-dimensional distribution of ultrasonic diffraction on lattice structures was developed for educational laboratories, enabling students to design the size, shape and dimension of diffraction obstacles independently. In this experiment, metal balls were used to simulate atomic lattice structures, and the two-dimensional diffraction distribution data of simple cubic, body-centered cubic, and hexagonal close-packed structure were collected. The results were compared with the sound field simulation of COMSOL, and a good consistency was found. By observing the diffraction results of complex structures, students can gain a better understanding of the concept of diffraction.

Применение модифицированного метода дискретных источников в задаче дифракции импульсной волны на подповерхностном импедансном цилиндре

In contrast to the classical method of auxiliary sources (MAS) with the location of discrete sources (DS) on a closed additional contour, this article investigates the use of a complete system of functions for describing DS fields localized on an open curve in a modified MAS (MMAS). The MMAS was applied to solve a two-dimensional diffraction problem of a broadband electromagnetic impulse on an impedance cylinder located in free space and in the subsurface. The electric thread was a source of external current, excited by an impulse of 1.6 ns duration with a spectrum width from 122 MHz to 726 MHz (at the level of -6 dB). In various combinations, fresh water, thawed and frozen soil, air, and ice were used as the filling medium of the cylinder and the dielectric half-space. The complete system of functions for describing the fields of DS was constructed based on the Hankel functions of the first kind of zero order, the corresponding Green's function for the layered medium problem, and their derivatives in the direction of normal to the curve on which the DS was placed. When compared with the finite difference time domain method (FDTD), it is shown that the MMAS, using Leontovich impedance boundary conditions, can describe impulse fields, scattered by a dielectric cylinder with practically significant accuracy. It has been established that in the case of an elliptical cylinder, the MMAS requires approximately half as many auxiliary DSs compared to the classical MAS while achieving the same accuracy of the solution. In general, this article confirms the possibility of using a complete system of functions to describe the fields of DSs, localized on an open curve for the solving of impulse diffraction problems on subsurface impedance cylinders.

Texture and lattice strain evolution in a pearlitic steel during shear deformation: An in situ synchrotron X-ray diffraction study

In-situ synchrotron X-ray diffraction experiments were conducted on the pearlitic steel sample with a carbon content of 0.74% by weight. Specimens were subjected to uniaxial loading that induced shear deformation and two-dimensional diffraction patterns were acquired. The evolution of the lattice microstrain and the strain-resolved crystallographic texture development of both ferrite (α-BCC) and cementite (θ-orthorhombic) phases were followed. The analysis revealed that the texture changed from {110}<113>α to {113}<121>α component and then, stabilized at {013}<uvw>α orientations. The θ phase exhibited a weak texture in the {100, 010, and 001}θ family planes. Additionally, it was revealed that the nucleation of interfacial defects at the α/θ interface promotes the amorphization of cementite and the activation of slip systems in less densely packed {310}α planes. The influence of microstructural changes on mechanical properties is discussed.

High-efficiency polarization-selective two-dimensional diffraction gratings based on silver cuboid arrays

A two-dimensional (2D) diffraction grating based on silver cuboid arrays is demonstrated. With the structural optimization by three-dimensional (3D) finite-difference time-domain method, the proposed grating exhibits favorable polarization selectivity. At wavelength 1550 nm, high diffraction efficiency and polarization correlation can be realized in the case of two-port output ((0, ±1) or (±1, 0)) under TE polarization, as well as five-port output ((0, 0), (0, ±1) and (±1, 0)) under TM polarization. Under the two-port output state, the diffraction efficiency is nearly 48% with the extinction ratio of 16.44 dB and insertion loss of 0.20 dB. Under the five-port output status, the efficiency is larger than 19% for each diffraction order, meanwhile, the total efficiency and uniformity are 97% and 0.58%, respectively. The proposed grating with positive implications has good potentials in polarization multiplexing and polarization-correlated grating interferometry.

Design of bipolar transport D-A discotic liquid crystals based on triphenylene and perylene cores: Effect of the chain length of ester groups

A series of novel discotic liquid-crystalline donor–acceptor dyads (D-A) adjusted by changing the chain length of diester groups on perylene were synthesized based on triphenylene and perylene units which linked by a flexible linkage of 9-nonyloxy-1-amine. The mesomorphism properties and their self-assembly behaviors were studied by differential scanning calorimetry, polarized optical microscopy, one-dimensional wide-angle X-ray diffraction, small angle X-ray scattering and two-dimensional wide-angle X-ray diffraction. Charge carrier mobilities were measured by Time-of-flight device. These discotic liquid crystalline compounds exhibited highly efficient ambipolar charge-transport properties and the charge carrier mobility can reach the order of 10−4 cm2 v−1 s−1 by segregated donor–acceptor columns, providing potential utility of the strategy in organic optoelectronic applications.

Two-dimensional diffraction and radiation problems of a floating body in varying bathymetry

In this study, a coupling method of the higher order boundary element method and the eigenfunction expansion method is applied to investigate the diffraction and radiation problems of a floating body over an uneven seabed under the assumption of linear small-amplitude wave theory. The wave exciting forces and hydrodynamic coefficients are calculated for a floating rectangular box. It is found that the curves of the wave exciting forces and hydrodynamic coefficients versus frequency become fluctuating as the horizontal length L and vertical height D of the sloping seabed gradually increase. The period of the fluctuations decreases with the increase of L, and the magnitude of the fluctuations increases with the increase of D. The mechanism of the fluctuation phenomenon is then examined, and found that it is associated with the wave reflection from the slope seabed. With increasing horizontal scale L and vertical scale D of the sloping seabed, the amplitude and phase of the reflection wave change, which leads to the combined action of the incident, scattering and reflection waves fluctuating with the wave frequency.

Local structural modelling and local pair distribution function analysis for Zr–Pt metallic glass

In disordered glass structures, the structural modelling and analyses based on local experimental data are not yet established. Here we investigate the icosahedral short-range order (SRO) in a Zr–Pt metallic glass using local structural modelling, which is a reverse Monte Carlo simulation dedicated to two-dimensional angstrom-beam electron diffraction (ABED) patterns, and local pair distribution function (PDF) analysis. The local structural modelling invariably leads to the icosahedral SRO atomic configurations that are similarly distorted by starting from some different initial configurations. Furthermore, the SRO configurations with 11–13 coordination numbers reproduce almost identical ABED patterns, indicating that these SRO structures are similar to each other. Further local PDF analysis explicitly indicates the presence of the wide distribution of atomic bond distances, which is comparable to the global PDF profile, even at the SRO level. The SRO models based on the conventional MD simulation can be strengthened by comparison with those obtained by the present local structural modelling and local PDF analysis based on the ABED data.

Asymmetric two-dimensional diffraction grating via a vortex field in an inverted-Y-type atomic system

We propose a theoretical scheme to realize a two-dimensional (2D) diffraction grating in a four-level inverted-Y-type atomic system coupled by a standing-wave (SW) field and a Laguerre–Gaussian (LG) vortex field. Owing to asymmetric spatial modulation of the LG vortex field, the incident probe field can be lopsidedly diffracted into four domains and an asymmetric 2D electromagnetically induced grating is created. By adjusting the detunings of the probe field and the LG vortex field, the intensities of the LG vortex field and the coherent SW field, as well as the interaction length, the diffraction properties and efficiency, can be effectively manipulated. In addition, the effect of the azimuthal parameter on the Fraunhofer diffraction of the probe field is also discussed. This asymmetric 2D diffraction grating scheme may provide a versatile platform for designing quantum devices that require asymmetric light transmission.

IRing: a program for two-dimensional powder diffraction image integration with automatic calibration

iRing is a processing program developed for the more convenient processing of two-dimensional diffraction images collected by image detectors. During the calibration process, iRing uses the Hough transform to achieve automatic peak finding and calibration. The speed of calibration is greatly improved and the difficulty of calibration is reduced. iRing also provides many supporting functions to help process data.

2D asymmetric diffraction grating controlled by vortex light in double-Λ-type atomic system

A two-dimensional (2D) asymmetric diffraction grating controlled by vortex light in a double-Λ-type atomic system is studied. Such an atomic system is driven by a weak traveling-wave probe field and a signal field, a position-dependent strong standing-wave (SW) control field, and a Laguerre–Gaussian (LG) vortex field. Due to the asymmetric properties of the LG vortex field, the probe photons can be asymmetrically diffracted into four different domains after passing through the atomic media. The Diffraction patterns and intensities of the 2D asymmetric diffraction grating can be manipulated by the detuning of the probe field, the interaction length, and the intensity of SW control field. In addition, the relative phase and the azimuth parameter which is closely related to the vortex light also can be used to regulate the asymmetric diffraction grating effectively. This work may provide useful reference for optical information processing, especially for the design of optical beam dividers with desired intensities and novel quantum devices requiring asymmetric optical transmission.

Voltage-controlled two-dimensional Fresnel diffraction pattern in quantum dot molecules

This study explores the influence of inter-dot tunneling effects within a quantum dot molecule on the Fresnel diffraction phenomenon. Our findings indicate that the Fresnel diffraction of the output probe Gaussian field can be manipulated by adjusting the inter-dot tunneling parameter’s strength and the characteristics of the coupling field. The inter-dot tunneling effect establishes a closed-loop system, setting conditions for the interference of the applied fields. We specifically examine a Laguerre–Gaussian (LG) coupling field, investigating how its properties-such as strength, value, and sign of the orbital angular momentum (OAM)-impact the Fresnel diffraction of the output probe field. Increasing the inter-dot tunneling parameter and the coupling LG field’s strength allows for control over the spatial distribution of the Fresnel diffraction pattern. Notably, the inter-dot tunneling parameter can disturb the symmetry of the diffraction patterns. Additionally, considering a negative OAM for the coupling LG field transforms the diffraction pattern into its inverse shape. This suggests that, in the presence of the inter-dot tunneling effect, the Fresnel diffraction pattern is contingent on the direction of rotation of the helical phase front of the coupling LG field. Our results offer insights into quantum control of Fresnel diffraction patterns and the identification of OAM in LG beams, presenting potential applications in quantum technologies.

Role of customized scan strategies and dwell time on microstructure and properties of additively manufactured 316L stainless steel

Direct energy deposition (DED)-based additive manufacturing facilitates fabrication of medium-to-large functional parts. This study assesses the role of varying scan strategies and dwell time between each layer to control the cooling rate of 316L stainless steel produced by the laser-engineered net shaping-DED method. Customized print patterns were designed, keeping other optimized print parameters constant to obtain printed parts with better dimensional tolerance. The parts, which were &gt;99% dense, were fabricated in a controlled argon environment. A heterogeneous microstructure consisting of a cellular columnar and equiaxed substructure was obtained. Two-dimensional X-ray diffraction revealed the presence of a single-phase &amp;gamma;-austenitic FCC phase. A refined microstructure with less elemental segregation was noticed with an increase in dwell time between the print layers. Internal defect analysis using X-ray micro-computed tomography revealed low lack-of-fusion voids along the build direction without any micro-cracks, which is attributed to higher cooling rates between subsequent print layers. As demonstrated in a mechanical performance evaluation of tensile and micro-hardness properties, better performance can be achieved by controlling the cooling rate and customizing deposition patterns.

Solution of a Scalar Two-Dimensional Nonlinear Diffraction Problem for Objects of Arbitrary Shape

In this study, the development, design, and software implementation of the methods for solving the nonlinear diffraction problem were performed. The influence of nonlinear medium defined by the Kerr law on the propagation of a wave passing through an object was examined. The differential and integral formulations of the problem and the nonlinear integral equation were considered. The problem was solved for different bodies with the use of various computational grids. Convergence graphs of the iterative processes were generated. The obtained graphical results were presented. The explicit and implicit methods for solving the integral equation were compared.