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Nonequilibrium Magnetic Oscillation with Cylindrical Vector Beams
摘要： Magnetic oscillation is a generic property of electronic conductors under magnetic fields and widely appreciated as a useful probe of their electronic band structure, i.e. the Fermi surface geometry. However, the usage of the strong static magnetic field makes the measurement insensitive to the magnetic order of the target material. That is, the magnetic order is anyhow turned into a forced ferromagnetic one. Here we theoretically propose an experimental method of measuring the magnetic oscillation in a magnetic-order-resolved way by using the azimuthal cylindrical vector (CV) beam, an example of topological lightwaves. The azimuthal CV beam is unique in that, when focused tightly, it develops a pure longitudinal magnetic field. We argue that this characteristic focusing property and the discrepancy in the relaxation timescale between conduction electrons and localized magnetic moments allow us to develop the nonequilibrium analogue of the magnetic oscillation measurement. Our optical method would be also applicable to metals under the ultra-high pressure of diamond anvil cells.
关键词： Topological lightwaves,Magnetic oscillation,Cylindrical vector beams,Nonequilibrium measurement,Fermi surface geometry
更新于2025-09-23 15:21:21
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Rabi Oscillation Study of Strong Coupling in a Plasmonic Nanocavity
摘要： Strong interaction between emitters and plasmonic nanocavity has various applications in quantum fields at room temperature. As Rabi oscillation gives the direct proof to the energy exchange in strong coupling, it is more intuitive and necessary to analyze the interaction in time domain. In this paper, we give the Rabi oscillation in a high-dissipation plasmonic nanocavity by using full-quantum method and draw a new strong coupling criterion about mode volume which provides a significant guidance in plasmonic nanocavitys nanofabrication. Moreover, we reveal the relation between Rabi oscillation and Rabi splitting, which is beneficial for exploring emitter-plasmon hybrid systems time-domain property through frequency-domain response. An emitter-hexagon hybrid system with ultrasmall mode volume is designed to verify our theory. The numerical simulation shows good agreements with our theoretical results. Our work has applications in quantum information and quantum computing in the future.
关键词： plasmonic nanocavity,quantum information,Rabi oscillation,quantum computing,strong coupling
更新于2025-09-23 15:21:01
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Effect of hydrogen-like impurity on a qubit in quantum pseudodot at finite temperature
摘要： In?uences of temperature on the qubit's properties in a quantum pseudodot (QPD) are studied by using the variational method of Pekar type (VMPT) and quantum statistics theory (QST). The formation of qubit requires two special conditions: One is the strong-coupling between the electron and the bulk longitudinal optical (LO) phonon, and the other is the hydrogen-like impurity (HLI) locating at the center of the QPD. So, we choose strong-coupling RbCl crystal as an example and calculate the electron probability density (EPD) and the oscillating period (OP) of the QPD qubit changing with the temperature and the Coulombic impurity potential (CIP).
关键词： Coulomb impurity potential,Oscillation period,Quantum pseudo dot,Qubit probability density
更新于2025-09-23 15:21:01
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A highly sensitive optofluidic-gas sensor using two dimensional photonic crystals
摘要： Photonic crystals (PCs) are optical structures based on periodic arrays of dielectric materials. These structures enable the manipulation of photons as semiconductors do for electrons. Many optical devices with miniature sizes have been designed based on novel properties of PCs. In this paper, we proposed a new refractive index sensor with high sensitivity and high quality factor, which is implemented in a two dimensional PC with a hexagonal lattice structure. The proposed sensor has been constructed using a PC waveguide surrounded by two rows of ring-shaped holes. The emersion of Fabry-Perot interference pattern within the transmission band and its role in the determination of the features of the proposed refractive index sensor has been investigated. The finite-difference time-domain simulation results indicate that in the case of filling the holes of central waveguide and its surrounding ring-shaped holes by different materials with refractive indices from n = 1 to n = 1.5, a high sensitivity of 575 nm/RIU and a high quality factor of 7070 is achieved, which makes the proposed design applicable for liquid and also gas sensing.
关键词： sensing waveguide,quality factor,sensitivity,Fabry-Perot oscillation,gas sensor,photonic crystal
更新于2025-09-23 15:21:01
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Periodically Poled MgO:LiNbO <sub/>3</sub> , MgO:LiTaO <sub/>3</sub> and KTiOPO <sub/>4</sub> Crystals for Laser Light Frequency Conversion
摘要： We present the recent achievements in periodical poling in MgO doped single crystals of lithium niobate (LN), lithium tantalate (LT) and potassium titanyl phosphate (KTP) based on the experimental study of the domain structure evolution by the complementary high-resolution domain visualization methods [1]. The crystals with tailored periodically poled domain structures (PPLN and PPLT) produced with nano-scale period reproducibility have been used for Second Harmonic Generation (SHG) and Optical Parametric Oscillation (OPO) based on quasi-phase-matched nonlinear optical wavelength conversion. The periodical poling techniques were based on the deep experimental and theoretical study of the mechanisms of domain growth and domain wall motion in these crystals. The wide range of wall velocities with two orders of magnitude difference was observed for switching in a uniform electric field [2,3]. The kinetic maps allowed analyzing the spatial distribution of the wall motion velocities and classifying the walls by velocity ranges. The distinguished slow, fast, and superfast types of domain walls in KTP differed by their orientation. The revealed increase in the wall velocity with deviation from low-index crystallographic planes for slow and fast walls was considered in terms of determined step generation and anisotropic kink motion. It was shown that the polarization reversal in KTP with artificial surface dielectric layer leads to formation and growth of the large number of narrow domain streamers oriented strictly along [010] direction with about ten times higher velocity (6-60 mm/s) than the domain walls (2-5.5 mm/s). Study of the static domain structures demonstrated that the streamers are formed by [100] and [010]-oriented domain walls. The streamer width was about 500 nm and the distance between the neighboring streamers – about 100 nm. The global domain kinetics during the poling process at elevated temperatures has been studied by in situ optical observation which allowed us to reveal the main characteristics of the poling process at elevated temperatures. It has been shown that the periodically poled area propagates from the edges to the middle of the electrode pattern. The interfering effect of essential increasing of the bulk conductivity during poling has been studied and several ways to overcome this problem have been proposed. The static domain images revealed by chemical etching were visualized by optical and scanning probe microscopy. The influence of the spatially nonuniform electric field on the domain kinetics has been studied for finite-size electrodes of various shapes. The key role of the field anomalies at the electrode corners, ends, and edges in the nucleation process has been revealed by computer simulations and confirmed experimentally. Essential acceleration of the switching at the boundaries of the electrode patterns (so called “pattern effect”) has been explained. The optimized design of the electrode pattern was based on experimental results and computer simulation. The fan-out periodical domain structures created in 3-mm-thick MgO:LN wafers allowed us to realize the widely tunable OPO generation with the signal wave from 2.5 to 4.5 μm using the 1.053 μm pump. The possibility of producing the elements with thickness up to 10 mm for high-power application has been discussed. The peridical domain struture with period of 40 μm was created in KTP single crystals for OPO generation at 2.4 μm using the 1.053 μm pump. The abilities and perspectives of producing the elements with submicron periods has been discussed. The optimized periodical poling techniques have been used for creation of ridge waveguides in periodically poled MgOLN single crystals. The high-index contrast of obtained multi-mode waveguides allowed tuning of the SHG wavelength from 510 to 570 nm using the 1.064 μm pump. The deep knowledge of the domain structure evolution at elevated temperatures and relaxation of the high bulk conductivity along the charged domain walls MgO:LN and MgO:LT allowed us to optimize the periodical poling technique and to produce high-fidelity domain patterns.
关键词： domain structure evolution,MgO:LiTaO3,KTiOPO4,Second Harmonic Generation,Optical Parametric Oscillation,MgO:LiNbO3,Periodically Poled
更新于2025-09-23 15:19:57
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A pathway to mitigate macrosegregation of laser-arc hybrid Al-Si welds through beam oscillation
摘要： Macrosegregation is rather serious during laser-arc hybrid welding (LAHW) due to poor arc penetration ability. Here we presented a simple and effective method to improve solute transfer and mitigate macrosegregation by using beam oscillation. When oscillating amplitude A ≥0.8 mm and frequency f ≥ 300 Hz, the macrosegregation of the overall weld cross-section was 300% lower than that of the non-oscillation weld, and the longitudinal section reduced by 220%. The reduction of macrosegregation was attributed to the stirring and vortex suction effect produced by high-frequency oscillating beam, which improved turbulent ?ow and the convection of molten pool to homogenize the alloying elements of hybrid weld.
关键词： Solute transfer,Element distribution,Laser-arc hybrid welding,Beam oscillation,Macrosegregation
更新于2025-09-23 15:19:57
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Ultra-Short-Term Photovoltaic Power Prediction Based on Self-Attention Mechanism and Multi-Task Learning
摘要： This paper deals with methods for parameter estimation of two-mass mechanical systems in electric drives. Estimates of mechanical parameters are needed in the start-up of a drive for automatic tuning of model-based speed and position controllers. A discrete-time output error (OE) model is applied to parameter estimation. The resulting pulse-transfer function is transformed into a continuous-time transfer function, and parameters of the two-mass system model are analytically solved from the coefficients of this transfer function. An open-loop identification setup and two closed-speed-loop identification setups (direct and indirect) are designed and experimentally compared. The experiments are carried out at nonzero speed to reduce the effect of nonlinear friction phenomena on the parameter estimates. According to results, all three identification setups are applicable for the parameter estimation of two-mass mechanical systems.
关键词： resonant mechanical load,Electric drives,parameter estimation,torsional oscillation
更新于2025-09-23 15:19:57
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Development of a New Maximum Power Point Tracking Method for Power Conversion Efficiency Measurement of Metastable Perovskite Solar Cells
摘要： A new algorithm for the maximum power point tracking (MPPT) method has been developed in order to determine the maximum power (Pmax) for slow-responding metastable PV devices such as perovskite solar cells (PSCs). It is well known that such devices often cause significant Pmax oscillation during a standard MPPT measurement. This oscillation was found to occur caused by difference in the current acquired after increasing the voltage and that acquired after decreasing the voltage. The new algorithm developed in this paper has eliminated such oscillation with comparison between the powers at different voltages after changing the voltage in the same direction. Pmax data determined by using this algorithm were found to be reliable by comparing with those determined by the dynamic I-V measurements.
关键词： Maximum Power,MPPT,Oscillation,Perovskite Solar Cell
更新于2025-09-23 15:19:57
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Optimization of the optical fiber with triple sector stress elements
摘要： The stress distribution characteristics of the optical ?ber with triple sector stress elements are studied in detail. The relationship between the stress oscillation amplitude of the optical ?ber and the structural parameters is analyzed. The structural parameters include the distance from the stress element center to the core center and the stress element area. The results show that the stress oscillation amplitude of the optical ?ber with triple sector stress elements will increase rapidly if the stress element is close to the core while the stress element area is ?xed. When the distance from the stress element center to the core center is ?xed, the stress oscillation amplitude increases linearly with the increase of the stress element area under the premise of selecting the optimum stress element expanded angle. Based on the drawn conclusion, the optical ?ber with triple sector stress elements is optimized. The maximum stress oscillation amplitude and the optical ?ber structure with optimal stress distribution are determined to improve the coupling e?ciency of the optical ?ber and better realize the circular polarization state stable transmission.
关键词： Optimization,Stress distribution characteristics,Stress oscillation amplitude
更新于2025-09-19 17:13:59
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Laser oscillation at an intended wavelength from a distributed feedback structure on anisotropic organic crystals
摘要： An organic laser device is constructed as distributed feedback (DFB) type using an anisotropic single crystal of an organic semiconductor oligomer BP3T. The DFB structure is formed on top of the crystal via an interference exposure technique of a positive type photoresist. In the DFB structure, both the phase matching condition and waveguide condition must be fulfilled. Under these conditions, the effective refractive indices can be precisely predicted for a BP3T crystal, and they vary depending upon the crystal thickness. As a result, the device produces a single-mode laser oscillation at an intended wavelength (typically ～569 nm). The present study enables us to design a down-to-earth laser device based on an anisotropic organic semiconductor crystal toward practical use.
关键词： organic laser,single-mode laser oscillation,anisotropic organic crystal,BP3T,distributed feedback
更新于2025-09-19 17:13:59