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Broadband spectral splitting of white light via 2D diffractive optical elements
摘要： An effective way of increasing the efficiency of solar cells is to spectrally split sunlight into several frequencies and absorb each frequency using appropriate photovoltaic materials. In this study, we establish a method to show spectral splitting of broadband solar light via iteratively optimized diffractive optical elements. We develop an algorithm in order to calculate 2D holographic patterns that focus two different frequencies to designated positions.
关键词： diffraction,Spectral splitting,solar cells
更新于2025-09-04 15:30:14
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Rapid classification of micron-sized particles of sphere, cylinders and ellipsoids by diffraction image parameters combined with scattered light intensity
摘要： Spatial distributions of light scattered by single particles correlate closely with their morphologies in terms of refractive index (RI) distribution. Diffraction imaging of scattered light under coherent excitation presents a unique approach to acquire and extract feature parameters for particle classification. A validated method has been applied in this study to accurately simulate diffraction imaging of light scattered by homogeneous particles and obtain calculated diffraction image (DI) data. The feature parameters of DI data have been extracted by the gray-level co-occurrence matrix (GLCM) algorithm. We have developed an unsupervised machine learning algorithm based on Gaussian mixture model (GMM) to classify 1965 particles made of single and double spheres, cylinders and ellipsoids with varied RI values in parameter space. It has been shown that selected GLCM parameters combined with integrated forward scatter intensity can provide effective markers for accurate and morphology based classification. For 1791 particles of the same RI, the mean accuracy values of classifying particles into 3 particle types range from 82.6% to 97.2%. These results demonstrate the strong potential of diffraction imaging method for rapid analysis and classification of nonspherical and homogeneous particles by the GMM classifiers that is very challenging in comparison to distinguishing biological cell types.
关键词： Image analysis,Nonspherical particle analysis,Diffraction imaging,Single light scattering
更新于2025-09-04 15:30:14
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Synthesis of (BiSe) <sub/> 1+ <i>δ</i> </sub> (Bi <sub/>2</sub> Se <sub/>3</sub> ) <sub/> 1+ <i>γ</i> </sub> (BiSe) <sub/> 1+ <i>δ</i> </sub> TiSe <sub/>2</sub> by Directed Self-Assembly of a Designed Precursor
摘要： The synthesis, structure and properties of a new three constituent heterostructure containing BiSe, Bi2Se3, and TiSe2 layers, each with a different structural motif, is reported. (BiSe)1+δ(Bi2Se3)1+γ(BiSe)1+δTiSe2, where δ and γ are the misfit parameters representing the differences in the in-plane packing density of the constituents, forms via a self-assembly process during low-temperature annealing from precursors with a range of compositions and repeat period thicknesses. This indicates that the compound exists in a relatively broad and deep free-energy minima in the energy landscape. The formation was followed as a function of annealing temperature using X-ray diffraction to determine optimum annealing temperatures and stability range. High-resolution electron microscopy images revealed the layering sequence of the constituents and a supercell within the BiSe layers created by periodic anti-phase boundaries. Temperature dependent electrical transport measurements show unexpected changes in carrier mobility and concentration relative to (BiSe)1.15TiSe2. This study suggests that new ternary and multinary phases containing fragments of known binary phases can be synthesized via precursors that mimic the desired product and that the properties of these new phases with ultrathin constituent thicknesses will probably be different from that expected based on composite behavior.
关键词： X-ray diffraction,electron microscopy,heterostructure,BiSe,self-assembly,TiSe2,Bi2Se3,electrical transport
更新于2025-09-04 15:30:14
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Single-crystal investigation of the proposed type-II Weyl semimetal CeAlGe
摘要： We present details of materials synthesis, crystal structure, and anisotropic magnetic properties of single crystals of CeAlGe, a proposed type-II Weyl semimetal. Single-crystal x-ray diffraction con?rms that CeAlGe forms in a noncentrosymmetric I 41md space group, in line with predictions of nontrivial topology. Magnetization, speci?c heat, and electrical transport measurements were used to con?rm antiferromagnetic order below 5 K, with an estimated magnon excitation gap of (cid:2) = 9.11 K from heat capacity and hole-like carrier density of 1.4 × 1020 cm?3 from Hall effect measurements. The easy magnetic axis is along the [100] crystallographic direction, indicating that the moment lies in the tetragonal ab plane below 7 K. A spin-?op transition to less than 1 μB /Ce is observed to occur below 30 kOe at 1.8 K in the M (H ) (H(cid:2)a) data. Small magnetic ?elds of 3 and 30 kOe are suf?cient to suppress magnetic order when applied along the a and c axes, respectively, resulting in a complex T –H phase diagram for H(cid:2)a and a simpler one for H(cid:2)c.
关键词： Weyl semimetal,CeAlGe,electrical transport measurements,single-crystal x-ray diffraction,antiferromagnetic order,magnetization,specific heat
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE International Conference on Mechatronics and Automation (ICMA) - Changchun (2018.8.5-2018.8.8)] 2018 IEEE International Conference on Mechatronics and Automation (ICMA) - Status and Trends of the Large Aperture Space Optical Remote Sensor
摘要： Aiming at catching up with the leading countries, this paper gives the right development direction of large aperture optical remote sensor in China. Firstly, we introduced the current situation of large aperture remote sensors using traditional and new imaging systems. Then we summarized the monolithic and deployable remote sensors with full range spectra and high spectrum resolution are the future main development trends. Furthermore, we discussed the key technologies include large aperture lightweight monolithic reflective mirror, active support, precise deployment, co-phasing in orbit, fabrication of large aperture membrane diffractive optics element (DOE) and high performance imaging processing technology of interferometric imaging system. Finally, we conclude China should give more attention to the large aperture monolithic and deployable optical remote sensors, and tackle the key technology in 1.5m~3m aperture monolithic remote sensors at first step and 4m aperture monolithic and the deployable remote sensors next.
关键词： large aperture space optical remote sensor,interference imaging,optical synthetic aperture diffraction imaging,imaging,space deployable segmented imaging
更新于2025-09-04 15:30:14
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Synthesis, Growth and Characterization of Nonlinear Optical Ce-Doped L-Prolinium Picrate Single Crystals
摘要： A non-linear optical material L-prolinium picrate and cerium doped L-prolinium picrate were synthesized and grown as single crystals by slow evaporation method. The grown crystals were subjected to structural, elemental, thermal, optical and dielectric studies. The structural analysis reveals that pure L-prolinium picrate and Ce doped L-prolinium picrate belongs to the monoclinic crystallographic system with space group P21. Optical transparency of the grown crystals was investigated by UV-visible-NIR spectrum. The thermal analyses reveal that Ce doped L-prolinium picrate is thermally stable up to 162 °C. The dielectric constant and dielectric loss of the crystals were studied as a function of frequency. The non-linear optical property of the doped crystal was confirmed by the Kurtz-powder second harmonic generation test and the result is compared with pure L-prolinium picrate. Mechanical strength of the crystals was also carried out by Vicker's micro hardness test.
关键词： X-ray diffraction,Micro hardness,Growth from solution,Semi organic compound,Non-linear optical crystal
更新于2025-09-04 15:30:14
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Design Study of Time-Preserving Grating Monochromators for Ultrashort Pulses in the Extreme-Ultraviolet and Soft X-Rays
摘要： The design of grating-based instruments to handle and condition coherent ultrafast pulses in the extreme-ultraviolet is discussed. The main application of such instruments is the monochromatization of high-order laser harmonics and free-electron-laser pulses in the femtosecond time scale. Broad-band monochromators require the use of diffraction gratings at grazing incidence. A grating can be used for the spectral selection of ultrashort pulses without altering the pulse duration in a significant way, provided that the number of illuminated grooves is equal to the resolution. We discuss here the design conditions to be fulfilled by a grating monochromator that does not increase the pulse duration significantly longer than the Fourier limit.
关键词： monochromators,diffraction gratings,ultrafast optics
更新于2025-09-04 15:30:14
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Structural, optical, and dielectric studies of LaFe1?xMoxO3 (x?=?0.0, 0.5) perovskite materials
摘要： The structural, optical, and dielectric properties of LaFe1?xMoxO3 (x = 0.0, 0.5) synthesized by the sol–gel method were investigated by X-ray diffraction (XRD), Raman scattering, and impedance spectroscopy. XRD analysis revealed that the x = 0.5 compound is single-phase and orthorhombic, with space group Pbnm, similar to the parent x = 0.0 compound but with larger lattice parameters and/or a larger unit-cell volume. The Raman scattering spectra revealed local lattice distortions in the x = 0.5 compound and spin–phonon coupling related to the magnetic transition (Néel) temperature. The impedance data were well fitted with an R(R1-CPE1)//(R2-CPE2) equivalent electrical circuit, demonstrating the contributions of both grains and grain boundaries. The temperature (300–500 K) and frequency (100 Hz–1 MHz) dependences of the dielectric properties showed that Mo substitution adversely affected the dielectric parameters.
关键词： X-ray diffraction,LaFe1?xMoxO3,impedance spectroscopy,Raman scattering,sol–gel method,dielectric properties
更新于2025-09-04 15:30:14
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Studies on growth and characterization of (E)-N′-[4-(dimethylamino) benzylidene]-4-hydroxybenzohydrazide hemihydrate: a nonlinear optical material
摘要： Hydrazone compound (E)-N′-[4-(dimethylamino) benzylidene]-4-hydroxybenzohydrazide hemihydrate (DMABHBH) was synthesized and single crystals of DMABHBH were grown by solvent evaporation method at room temperature. Molecular structure of DMABHBH compound was confirmed by 1H and 13C nuclear magnetic resonance techniques. The presence of functional groups was confirmed by Fourier transform infrared and FT Raman spectral analyses. The X-ray crystal structure was elucidated at 173 K by single crystal X-ray diffraction and the results were compared with the corresponding values obtained at 298 K. The compound crystallizes in the chiral monoclinic space group P21. Mechanical stability of the grown crystals was estimated from the Vicker’s microhardness test. Powder second harmonic generation efficiency of DMABHBH is about 1.1 times that of potassium dihydrogen phosphate. DMABHBH is found to show optical limiting behavior at high input light intensities, the third order nonlinear optical absorption coefficient measured using open aperture Z-scan studies, is 0.95 × 10?11 m/W. Anti-bacterial activity was studied using the well and disc diffusion methods.
关键词： X-ray diffraction,Mechanical properties,Nonlinear optical material,Thermal analysis,Antibacterial activity,Hydrazone,Crystal growth
更新于2025-09-04 15:30:14
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Point defect chemistry of donor-doped bismuth titanate ceramic
摘要： This communication reports on the defect chemistry at room temperature of barium (Ba) doped bismuth titanate (Bi4Ti3O12), emphasizing the influence of the point defects on its electrical properties. Pure and Ba doped Bi4Ti3O12 were prepared by a conventional solid-phase reaction technique. The addition of Ba into the crystal structure of Bi4Ti3O12 was monitored by X-ray diffraction measurements combined with Rietveld refinement studies where it was determined that Ba occupies the bismuth (Bi) lattice sites as well as the presence of oxygen vacancies (V??O). The characterization of the point defects was carried out using impedance and electron spin resonance spectroscopies where the results support the models of compensation mechanisms dominated by electrical positive charges (h?) and oxygen vacancies (V??O).
关键词： defect chemistry,X-ray diffraction,Rietveld refinement,impedance spectroscopy,solid-phase reaction,barium doped bismuth titanate,electron spin resonance spectroscopy,electrical properties,oxygen vacancies
更新于2025-09-04 15:30:14