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- anharmonic Bloch oscillations
- coupled mode method
- array of waveguides
- active harmonic filter
- Multifunctional VSC
- unity power factor operation
- power quality improvement
- grid-connected SPV system
- renewable energy sources
- Optoelectronic Information Science and Engineering
- Electrical Engineering and Automation
- Shevchenko Pridnestrovskii State University
- Malaviya National Institute of Technology
- Academy of Sciences of Moldova
- IIITD&M Kancheepuram
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Pb <sub/>2</sub> GaF <sub/>2</sub> (SeO <sub/>3</sub> ) <sub/>2</sub> Cl: Band Engineering Strategy by Aliovalent Substitution for Enlarging Bandgap while Keeping Strong Second Harmonic Generation Response
摘要： Wide bandgap and strong second-order generation (SHG) effect are two crucial but contradictory conditions for practical nonlinear optical (NLO) materials. Herein, a new NLO crystal Pb2GaF2(SeO3)2Cl (I) containing novel functional (GaO3F3)6? octahedra is designed and synthesized by a rational band engineering strategy with aliovalent substitution. Benefiting from the removal of transition metal cations and the introduction of bridged F anions, I exhibits the widest bandgap among all reported phase-matchable NLO selenites. Meanwhile, a strong SHG response more than 4.5 times of KH2PO4 (KDP) is maintained. The dominate role of the (GaO3F3)6? groups to the enlarged bandgap in I are elucidated by first-principles studies.
关键词： aliovalent substitution,second harmonic generation,nonlinear optical materials,selenites,band engineering
更新于2025-09-23 15:21:21
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Attosecond pulse generation via multicolor beam superposition in the over-barrier ionization regime
摘要： Based on coherent superposition of multicolor continuous wave beams, high order harmonics and attosecond pulse generation from a hydrogen molecular ion (HMI), +H ,2 with different internuclear distances, R, are studied. Driving pulse intensity was taken to be 400 TW cm?2, which can ionize an +H2 ion with R?>?Rb?=?2.4 a.u. over the barrier. It is seen that cutoff harmonic with respect to R decreases until the over barrier ionization threshold, Rb, then becomes almost uniform to the end of R?=?10 a.u. whereas it is almost constant with respect to the spectral width of the beams, Δω. Besides attosecond pulse intensity increases versus R, and decreases with respect to Δω so that the most intense attosecond pulses can be generated from HMIs with R???5 a.u. via the pulses by Δω???0.03 a.u. Attosecond pulse durations were insensitive to both Δω and R.
关键词： hydrogen ion molecule,high order harmonic generation,H2,attosecond
更新于2025-09-23 15:21:21
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Coherent Tabletop EUV Ptychography of Nanopatterns
摘要： Coherent diffraction imaging (CDI) or lensless X-ray microscopy has become of great interest for high spatial resolution imaging of, e.g., nanostructures and biological specimens. There is no optics required in between an object and a detector, because the object can be fully recovered from its far-field diffraction pattern with an iterative phase retrieval algorithm. Hence, in principle, a sub-wavelength spatial resolution could be achieved in a high-numerical aperture configuration. With the advances of ultrafast laser technology, high photon flux tabletop Extreme Ultraviolet (EUV) sources based on the high-order harmonic generation (HHG) have become available to small-scale laboratories. In this study, we report on a newly established high photon flux and highly monochromatic 30 nm HHG beamline. Furthermore, we applied ptychography, a scanning CDI version, to probe a nearly periodic nanopattern with the tabletop EUV source. A wide-field view of about 15 × 15 μm was probed with a 2.5 μm?diameter illumination beam at 30 nm. From a set of hundreds of far-field diffraction patterns recorded for different adjacent positions of the object, both the object and the illumination beams were successfully reconstructed with the extended ptychographical iterative engine. By investigating the phase retrieval transfer function, a diffraction-limited resolution of reconstruction of about 32 nm is obtained.
关键词： high-order harmonic generation,ptychography,lensless X-ray microscopy,Extreme Ultraviolet,Coherent diffraction imaging
更新于2025-09-23 15:21:21
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Transfer and approximation of the impedance for time-harmonic Maxwell’s system in a planar domain with thin contrasted multi-layers
摘要： We consider the diffraction of time-harmonic electromagnetic waves by a perfectly conducting planar obstacle, coated by thin contrasted multi-layers of dielectric materials. A partial Fourier transform is used to derive an impedance condition that links the tangential components of the electric and magnetic fields, and transfers the boundary condition from the obstacle’s face to the other face of dielectric multi-layers. We first determine the exact formula and construct approximations of the impedance condition for one dielectric thin layer; after that, we extend the obtained result to multi-layers.
关键词： scattering,thin dielectric layers,Time-harmonic Maxwell’s system,impedance operator
更新于2025-09-23 15:21:21
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Some structural, linear and nonlinear optical characteristics of single KDP crystals influenced by EDTA additive
摘要： Single Potassium Dihydrogen Phosphates (KDP) crystals were successfully grown in pure and 1 mol% Ethylenediaminetetraacetic acid disodium salt (EDTA) added KDP solutions by Sankaranarayanan–Ramasamy method. Their growth was oriented in type I phase-matching direction which is one of two conditions of maximum second harmonic generation efficiency. The elemental compositions of the crystals were determined by EDX analysis. The UV–Vis spectroscopy, FT-IR analysis, X-Ray diffraction, and second harmonic generation studies have been carried out in order to assess the influence of EDTA additive on quality of KDP crystal. EDTA can improve the structural perfection and optical characteristics of the crystal. Especially, this additive helps increase second harmonic generation efficiency of KDP crystal, which is very useful for frequency doublers.
关键词： Second harmonic generation,EDTA,KDP,Nonlinear optics,SR method
更新于2025-09-23 15:21:21
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[IEEE 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Trebic, Czech Republic (2018.9.18-2018.9.20)] 2018 VII. Lighting Conference of the Visegrad Countries (Lumen V4) - Electrical Parameters of Dimmable Luminaire
摘要： Lighting systems are currently one of the main uses of electricity. The most popular option for reducing of electricity consumption is the use of dimming. Dimming is a type of regulation in which we can regulate luminous flux of a lamps and luminaires. This system of regulation is used in the road lighting industry, but also in households. Dimming allows adaptation of the lighting system according to specific requirements and various ambient conditions such as traffic density, daylight, etc. The regulation of the luminous flux depending on the dimming system can affect the electrical parameters of the luminaires such as the power factor. The article deals with the electrical parameters of luminaires with various lamps at different types of dimming.
关键词： LED,total harmonic distortion,Power factor
更新于2025-09-23 15:21:21
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Robust Harmonic Retrieval via Block Successive Upper-Bound Minimization
摘要： Harmonic retrieval (HR) is a problem of significance with numerous applications. Many existing algorithms are explicitly or implicitly developed under Gaussian noise assumption, which, however, are not robust against non-Gaussian noise such as impulsive noise or outliers. In this paper, by employing the (cid:2)p-fitting criterion and block successive upper-bound minimization (BSUM) technique, a variant of the classical RELAX algorithm named as BSUM-RELAX is devised for robust HR. It is revealed that the BSUM-RELAX successively performs alternating optimization along coordinate directions, i.e., it updates one harmonic by fixing the other (K ? 1) components, such that the whole problem is split into K single-tone HR problems, which are then solved by creating a surrogate function that majorizes the objective function of each subproblem. To further refine the frequency component, the Newton’s method that takes linear complexity O(N ) is derived for updating the frequency estimates. We prove that under the single-tone case, BSUM-RELAX converges to a Karush-Kuhn-Tucker point. Furthermore, the BSUM-RELAX is extended to the multidimensional HR case. Numerical results show that the proposed algorithm outperforms the state-of-the-art methods in heavy-tailed noise scenarios.
关键词： robust estimation,impulsive noise/outliers,Harmonic retrieval,RELAX,majorization minimization
更新于2025-09-23 15:21:21
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Synthesis of Pyridazine Derivatives by Suzuki-Miyaura Cross-Coupling Reaction and Evaluation of Their Optical and Electronic Properties through Experimental and Theoretical Studies
摘要： A series of π-conjugated molecules, based on pyridazine and thiophene heterocycles 3a–e, were synthesized using commercially, or readily available, coupling components, through a palladium catalyzed Suzuki-Miyaura cross-coupling reaction. The electron-deficient pyridazine heterocycle was functionalized by a thiophene electron-rich heterocycle at position six, and different (hetero)aromatic moieties (phenyl, thienyl, furanyl) were functionalized with electron acceptor groups at position three. Density Functional Theory (DFT) calculations were carried out to obtain information on the conformation, electronic structure, electron distribution, dipolar moment, and molecular nonlinear response of the synthesized push-pull pyridazine derivatives. Hyper-Rayleigh scattering in 1,4-dioxane solutions, using a fundamental wavelength of 1064 nm, was used to evaluate their second-order nonlinear optical properties. The thienylpyridazine functionalized with the cyano-phenyl moiety exhibited the largest first hyperpolarizability (β = 175 × 10?30 esu, using the T convention) indicating its potential as a second harmonic generation (SHG) chromophore.
关键词： pyridazine,Density Functional Theory (DFT),Nonlinear optics (NLO),Second Harmonic Generators (SHG),Suzuki-Miyaura coupling
更新于2025-09-23 15:21:21
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Ferroelectric Polarization Rotation in Order-Disorder-Type LiNbO3 Thin Films
摘要： The direction of ferroelectric polarization is prescribed by the symmetry of the crystal structure. Therefore, rotation of the polarization direction is largely limited, despite the opportunity it offers in understanding important dielectric phenomena such as piezoelectric response near the morphotropic phase boundaries and practical applications such as ferroelectric memory. In this study, we report the observation of continuous rotation of ferroelectric polarization in order-disorder-type LiNbO3 thin films. The spontaneous polarization could be tilted from an out-of-plane to an in-plane direction in the thin film by controlling the Li vacancy concentration within the hexagonal lattice framework. Partial inclusion of monoclinic-like phase is attributed to the breaking of macroscopic inversion symmetry along different directions and the emergence of ferroelectric polarization along the in-plane direction.
关键词： second harmonic generation,vacancy engineering,spatial inversion symmetry breaking,ferroelectric polarization rotation,LiNbO3 thin films
更新于2025-09-23 15:21:21
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Maturation of the Meniscal Collagen Structure Revealed by Polarization-Resolved and Directional Second Harmonic Generation Microscopy
摘要： We report polarization-resolved Second Harmonic Generation (p-SHG) and directional SHG (forward and backward, F/B) measurements of equine foetal and adult collagen in meniscus, over large field-of-views using sample-scanning. Large differences of collagen structure and fibril orientation with maturation are revealed, validating the potential for this novel methodology to track such changes in meniscal structure. The foetal menisci had a non-organized and more random collagen fibrillar structure when compared with adult using P-SHG. For the latter, clusters of homogeneous fibril orientation (inter-fibrillar areas) were revealed, separated by thick fibers. F/B SHG showed numerous different features in adults notably, in thick fibers compared to interfibrillar areas, unlike foetal menisci that showed similar patterns for both directions. This work confirms previous studies and improves the understanding of meniscal collagen structure and its maturation, and makes f/B and p-SHG good candidates for future studies aiming at revealing structural modifications to meniscus due to pathologies.
关键词： Second Harmonic Generation,meniscus,directional SHG,polarization-resolved,collagen
更新于2025-09-23 15:21:01