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High-speed x-ray imaging system for the investigation of laser welding processes
摘要： A high-speed x-ray imaging system was built to investigate the fundamentals of laser material processing, such as laser welding. The system allows visualizing and analyzing the laser-induced process dynamics occurring also inside optically nontransparent workpieces. The details of the setup are presented together with the resulting performance with regard to edge sharpness, contrast, contrast transfer, and spatial as well as temporal noise. For voids with a depth (in respect to the x-ray radiation) of 100–500 μm, which is a typical range for focal diameters used in laser beam welding, a maximum contrast of 3%–19%, respectively, can be achieved. Due to the edge blurring, caused by the imaging system, the contrast is further decreased by 20% for voids with a lateral size of 100 μm and less than 10% for voids with a lateral size of 500 μm, when a magnification of 5.4 is used. The image intensifier, needed to increase the number of photons to saturate the camera, induces a noise floor of +15% in respect to the mean gray value and results in a maximum achievable signal to noise ratio for a 100 μm step of 1.2.
关键词： optical devices,x-ray imaging,materials synthesis and processing,scintillators,welding,electronic noise,vacuum tubes,noise floor,covariance and correlation,lasers
更新于2025-09-12 10:27:22
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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) - The Role of Detector Position in Quantum Ghost Diffraction
摘要： Quantum ghost diffraction enables the measurement of the spatial diffraction pattern of an object without measuring the spatial distribution of the photons that actually interacted with the object [1]. It uses photon pairs generated e.g. by spontaneous parametric down conversion (SPDC) in a nonlinear optical crystal, and relies on the correlation of the generated signal and idler photons in their spatial and temporal degrees of freedom. This measurement scheme is sketched in Fig. 1 (a). After the source, the two photons are separated into two different paths. The object, here we consider a grating, is located only in the signal path and thus interacts only with the signal photons. To measure the diffraction pattern, two detectors of small cross sections are used in the signal and idler arms. The signal detector is usually at a fixed position, collecting photons that interacted with the object. The idler detector can have varying positions, allowing to spatially resolve the collected photons that never interacted with the object. Through measuring the two-photon coincidence counting rate (cid:1842), there exists the potential for recovering the diffraction pattern of the object, which allows to retrieve the grating period.
关键词： Quantum ghost diffraction,diffraction pattern,spatial correlation,photon pairs
更新于2025-09-12 10:27:22
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[IEEE 2018 International CET Conference on Control, Communication, and Computing (IC4) - Thiruvananthapuram, India (2018.7.5-2018.7.7)] 2018 International CET Conference on Control, Communication, and Computing (IC4) - Simulation of MIMO System with 2-D and 3-D Optical Orthogonal Codes Using MATLAB and OptiSystem
摘要： An Optical Orthogonal Code (OOC) is a family of binary codes involving 0s and 1s which is having prede?ned auto correlation function (ACF) and cross correlation functions (CCF). The study of OOCs has an immense application in a ?ber optic code division multiple access (FO-CDMA/ OCDMA). Two dimensional optical orthogonal codes (2-D OOCs) spreads over time and wavelength co-ordinates, while three dimensional optical orthogonal codes (3-D OOCs) spreads over time, wavelength and space co-ordinates, which obviously shows improved performance over 1-D and 2-D OOCs. For a 1-D OOC, if we opt for maintaining good correlation function values, the code length must be a large value as the number of users in the system is more. By adding more dimensions, we can increase the performance parameters, by allowing codewords to be formed with restrictions applied on the occurrence of pulses in each row, resulting in the autocorrelation value (λa) to become zero. This paper aims to simulate the study of 2-D and 3-D OOCs using MATLAB and OptiSystem tools, for implementing a MIMO communication system over ?bre optic channel.
关键词： Auto-correlation function (ACF),2-D OOC,OptiSystem,Optical Orthogonal Codes,Space-Time Codes,Cross-correlation function (CCF),3-D OOC
更新于2025-09-11 14:15:04
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Controlling Surface Chemical Heterogeneities of Ultrasmall Fluorescent Core–Shell Silica Nanoparticles as Revealed by High-Performance Liquid Chromatography
摘要： Ultrasmall (diameter below 10 nm) fluorescent core?shell silica nanoparticles have garnered increasing attention in recent years as a result of their high brightness and favorable biodistribution properties important for applications including bioimaging and nanomedicine. Here, we present an in-depth study that provides new insights into the physical parameters that govern full covalent fluorescent dye encapsulation within the silica core of poly(ethylene glycol)-coated core?shell silica nanoparticles referred to as Cornell prime dots (C′ dots). We use a combination of high-performance liquid chromatography (HPLC), gel-permeation chromatography, and fluorescence correlation spectroscopy to monitor the result of ammonia concentration in the synthesis of C′ dots from negatively and positively charged versions of near-infrared dyes Cy5 and Cy5.5. HPLC, in particular, allows the distinction between cases of full versus partial dye encapsulation in the silica particle core leading to surface chemical heterogeneities in the form of hydrophobic surface patches, which, in turn, modulate biological response in ferroptotic cell death experiments. Our results demonstrate that there is a complex interplay between dye?dye and dye?silica cluster interactions originally formed in the sol?gel synthesis governing optimal dye encapsulation. We expect that the reduced surface chemical heterogeneities will make the resulting nanoparticles attractive for a number of applications in biology and medicine.
关键词： gel-permeation chromatography,ferroptotic cell death,high-performance liquid chromatography,fluorescent core?shell silica nanoparticles,fluorescence correlation spectroscopy
更新于2025-09-11 14:15:04
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Experimental test of error-tradeoff uncertainty relation using a continuous-variable entangled state
摘要： Heisenberg’s original uncertainty relation is related to measurement effect, which is different from the preparation uncertainty relation. However, it has been shown that Heisenberg’s error disturbance uncertainty relation is not valid in some cases. We experimentally test the error-tradeoff uncertainty relation by using a continuous-variable Gaussian Einstein–Podolsky–Rosen (EPR)-entangled state. Based on the quantum correlation between the two entangled optical beams, the errors on amplitude and phase quadratures of one EPR optical beam coming from joint measurement are estimated, respectively, which are used to verify the error–tradeoff relation. Especially, the error–tradeoff relation for error-free measurement of one observable is veri?ed in our experiment. We also verify the error–tradeoff relations for nonzero errors and mixed state by introducing loss on one EPR beam. Our experimental results demonstrate that Heisenberg’s error–tradeoff relation is violated in some cases for a continuous-variable system, while the Ozawa’s and Branciard’s relations are valid.
关键词： continuous-variable Gaussian Einstein–Podolsky–Rosen (EPR)-entangled state,error-tradeoff uncertainty relation,quantum correlation,Heisenberg’s uncertainty relation,joint measurement
更新于2025-09-11 14:15:04
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Simulation of 1D Topological Phases in Driven Quantum Dot Arrays
摘要： We propose a driving protocol which allows us to use quantum dot arrays as quantum simulators for 1D topological phases. We show that by driving the system out of equilibrium, one can imprint bond order in the lattice (producing structures such as dimers, trimers, etc.) and selectively modify the hopping amplitudes at will. Our driving protocol also allows for the simultaneous suppression of all the undesired hopping processes and the enhancement of the necessary ones, enforcing certain key symmetries which provide topological protection. In addition, we have discussed its implementation in a 12-QD array with two interacting electrons and found correlation effects in their dynamics, when configurations with different number of edge states are considered.
关键词： hopping amplitudes,topological protection,quantum dot arrays,correlation effects,1D topological phases,driving protocol,bond order
更新于2025-09-11 14:15:04
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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) - Statistical Properties of Phase and Eigenvalues of Nonlinear Fourier Transform of Second Order Solitons
摘要： Due to the inherently nonlinear nature of optical fibres, the increased demand for transmission capacity means that fibre optic communication systems will reach a limit, known as the Linear Capacity Limit. A radically new solution has received significant attention in the past few years, which is based on Nonlinear Fourier Transform (NFT). Under NFT a signal q(t) in time domain transforms into a continuous, qc(λ), and a discrete, qd(λk), complex spectral part, with continuous and discrete eigenvalues λ, and λk, respectively. Considering only multisolitons (a class of optical signals that have discrete NFT eigenvalues), it is well-known that 1) complex eigenvalues λk are invariant, and 2) the spectral part propagates as: (cid:3031)((cid:1878)) = |(cid:1869)(cid:3038) (cid:1869)(cid:3038) (cid:3031)(0)|(cid:1857)(cid:3037)(cid:2957)((cid:3053)); Φ((cid:1852)) = ∠(cid:1869)(cid:3038) (cid:3031)(0) ? 4(cid:2019)(cid:3038) (cid:2870) (cid:1878), where |(cid:1869)(cid:3038) (cid:3031)(0)| and ∠(cid:1869)(cid:3038) (cid:3031)(0) are the initial spectral amplitude and phase associated with the eigenvalue λk, respectively. In the discrete NFT domain, QPSK modulation has been proposed to encode data on the phase of the NFT spectral components qd(λk). For efficient encoding/decoding of the proposed modulation schemes, it is crucial to have knowledge of NFT noise perturbation on spectral phases and eigenvalues. There are limited reports on correlations among eigenvalues in multi-soliton systems and correlation between eigenvalues and their corresponding phases. However, there is no report with detailed analysis of correlation properties among NFT parameters of multi-soliton signals as a function of initial signal parameters. Here, we investigate correlations of the discrete spectra components in a two-eigenvalue system related to their relative NFT phase differences and distinguish a correlation pattern, which reaches extreme values at a NFT phase difference of π. We show this pattern to be unrelated to the choice of eigenvalues nor their spectral amplitude or constant phase offsets. We show that not only the eigenvalues but also the phases of signals in NFT domain are correlated, approaching a maxima at a NFT phase differences of π. We consider second-order solitons with different eigenvalue pairs, where for each of them, 129 symbols have been defined in the NFT domain with varying initial NFT phase differences Φ1,2=∠qd 2 between 0 and 2π, representing Φ1,2 on discrete positions of propagation over z. For every symbol, 1500 copies have been produced and exposed to white Gaussian noise. Using a combination of the fast inverse NFT algorithm and bidirectional NFT algorithm, each signal is translated into time domain, introduced to Gaussian noise, and translated back into NFT domain. The resulting scattering data has been used to estimate the eigenvalues λ1,2 and corresponding spectral components qd 1,2. The ellipticity (defined as the relative difference of principal axes of the scattering cloud) as a function of phase difference for a range of eigenvalue pairs, Fig.1 a,b, shows almost an ellipse at a phase difference of π and a circle at π/2. While both (Im((cid:79)1),Im((cid:79)2)) and (∠qd 2) are highly correlated at the phase difference of π, |Correlation coefficient|≈1, they are negative of each other, where its reason is under investigation. These correlation properties help to gain deeper physical insight of noise properties of signals in NFT domain, which is crucial for developing efficient NFT communication schemes.
关键词： phase,eigenvalues,Nonlinear Fourier Transform,correlation,solitons
更新于2025-09-11 14:15:04
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[IEEE 2018 2nd IEEE Conference on Energy Internet and Energy System Integration (EI2) - Beijing (2018.10.20-2018.10.22)] 2018 2nd IEEE Conference on Energy Internet and Energy System Integration (EI2) - Photovoltaic-load model based-on load and power supply correlation
摘要： Photovoltaic power generation has become a non-negligible part of hybrid power generation in regions with sufficient solar energy or countries. Aiming at the correlation of light intensity and load fluctuations, this paper proposes a new photovoltaic-load model method for building correlations. The non-parametric kernel density estimation method was used to analyze the probability distribution of light intensity and node load, and the corresponding bandwidth was obtained. The correlation between light intensity and node load was analyzed by using Kendall rank correlation coefficient. The load nodes were divided into strong light intensity related nodes and illumination. There are two types of weakly correlated nodes; for the node with strong light intensity, the Copula function is used to establish the photovoltaic-load correlation model. For the weakly correlated nodes of light intensity, the Latin hypercube sampling method was used to establish the load fluctuation model. Finally, the 220kV system in B city is taken as an example to verify the practicability and effectiveness of the proposed model.
关键词： Photovoltaic power generation，Node load，Kendall rank correlation coefficient，Copula function
更新于2025-09-11 14:15:04
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Spatial and temporal resolution in entangled ghost imaging
摘要： We show that, when the integration time of the single photon detectors is longer than the correlation time of the biphoton, the attainable spatial resolution in ghost imaging with entangled signal-idler pairs generated in type II spontaneous parametric down conversion is limited by the angular spread of single-frequency-signal-idler pairs. If, however, the detector integration time is shorter than the biphoton correlation time, the transverse k-vectors of different spectral components combine coherently in the image, improving the spatial resolution.
关键词： ghost imaging,spontaneous parametric downconversion,entangled photons,nonclassical correlation,single photon,phase matching
更新于2025-09-11 14:15:04
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RMT: R-matrix with time-dependence. Solving the semi-relativistic, time-dependent Schr?dinger equation for general, multielectron atoms and molecules in intense, ultrashort, arbitrarily polarized laser pulses
摘要： RMT is a program which solves the time-dependent Schr?dinger equation for general, multielectron atoms, ions and molecules interacting with laser light. As such it can be used to model ionization (single-photon, multiphoton and strong-field), recollision (high-harmonic generation, strong-field rescattering) and, more generally, absorption or scattering processes with a full account of the multielectron correlation effects in a time-dependent manner. Calculations can be performed for targets interacting with ultrashort, intense laser pulses of long wavelength and arbitrary polarization. Calculations for atoms can optionally include the Breit-Pauli correction terms for the description of relativistic (in particular, spin-orbit) effects.
关键词： electron correlation,R-matrix,ionization,strong-field physics,ultrafast physics,Attosecond physics
更新于2025-09-11 14:15:04