Reference Wave Research Articles

Steady state oscillations of circular currents in concentric polariton condensates

Concentric ring exciton polariton condensates emerging under non-resonant laser pump in an annular trapping potential support persistent circular currents of polaritons. The trapping potential is formed by a cylindrical micropillar etched in a semiconductor microcavity with embedded quantum wells and a repulsive cloud of optically excited excitons under the pump spot. The symmetry of the potential is subject to external control via manipulation by its pump-induced component. In the manuscript, we demonstrate excitation of concentric ring polariton current states with predetermined vorticity which we trace using interferometry measurements with a spherical reference wave. We also observe the polariton condensate dynamically changing its vorticity during observation, which results in pairs of fork-like dislocations on the time-averaged interferogram coexisting with azimuthally homogeneous photoluminescence distribution in the micropillar.

Kylin 1.0: An ab-initio density matrix renormalization group quantum chemistry program.

The accurate evaluation of electron correlations is highly necessary for the proper descriptions of the electronic structures in strongly correlated molecules, ranging from bond-dissociating molecules, polyradicals, to large conjugated molecules and transition metal complexes. For this purpose, in this paper, a new ab-initio quantum chemistry program Kylin 1.0 for electron correlation calculations at various quantum many-body levels, including configuration interaction (CI), perturbation theory (PT), and density matrix renormalization group (DMRG), is presented. Furthermore, fundamental quantum chemistry methods such as Hartree-Fock self-consistent field (HF-SCF) and the complete active space SCF (CASSCF) are also implemented. The Kylin 1.0 program possesses the following features: (1) a matrix product operator (MPO) formulation-based efficient DMRG implementation for describing static electron correlation within a large active space composed of more than 100 orbitals, supporting both and symmetries; (2) an efficient second-order DMRG-self-consistent field (SCF) implementation; (3) an externally contracted multi-reference CI (MRCI) and Epstein-Nesbet PT with DMRG reference wave functions for including the remaining dynamic electron correlation outside the large active spaces. In this paper, we introduce the capabilities and numerical benchmark examples of the Kylin 1.0 program.

Intelligent optoelectronic processor for orbital angular momentum spectrum measurement

Orbital angular momentum (OAM) detection underpins almost all aspects of vortex beams’ advances such as communication and quantum analogy. Conventional schemes are frustrated by low speed, complicated system, limited detection range. Here, we devise an intelligent processor composed of photonic and electronic neurons for OAM spectrum measurement in a fast, accurate and direct manner. Specifically, optical layers extract invisible topological charge information from incoming light and a shallow electronic layer predicts the exact spectrum. The integration of optical-computing promises us a compact single-shot system with high speed and energy efficiency (optical operations / electronic operations ~{10}^{3}), neither necessitating reference wave nor repetitive steps. Importantly, our processor is endowed with salient generalization ability and robustness against diverse structured light and adverse effects (mean squared error ~10^{(-5)}). We further raise a universal model interpretation paradigm to reveal the underlying physical mechanisms in the hybrid processor, as distinct from conventional ‘black-box’ networks. Such interpretation algorithm can improve the detection efficiency up to 25-fold. We also complete the theory of optoelectronic network enabling its efficient training. This work not only contributes to the explorations on OAM physics and applications, and also broadly inspires the advanced links between intelligent computing and physical effects.

Identification of wave profiles encountered by a ship with no forward speed using Kalman filter technique and validation by tank tests - long-crested irregular wave case -

This paper addresses a Kalman filter (KF) technique for identifying wave profiles encountered by a ship with no forward speed from measured ship responses. The KF technique has been applied to a series of tank test results for long-crested irregular head and oblique waves. In the test, an acrylic resin ship model is used. The method is validated by comparing the identified wave profile with reference wave measurement. It is shown that the accuracy of the wave identification can be improved by selecting more appropriate input, and further by combining two input signals. It is also used to estimate non-measured ship responses and its effectiveness is investigated. Finally, it is extensively applied to the future prediction of the wave profile and shown to be effective in predicting the wave profile a few cycles ahead.

N-Electron Valence Perturbation Theory with Reference Wave Functions from Quantum Computing: Application to the Relative Stability of Hydroxide Anion and Hydroxyl Radical

Quantum simulations of the hydroxide anion and hydroxyl radical are reported, employing variational quantum algorithms for near-term quantum devices. The energy of each species is calculated along the dissociation curve, to obtain information about the stability of the molecular species being investigated. It is shown that simulations restricted to valence spaces incorrectly predict the hydroxyl radical to be more stable than the hydroxide anion. Inclusion of dynamical electron correlation from nonvalence orbitals is demonstrated, through the integration of the variational quantum eigensolver and quantum subspace expansion methods in the workflow of N-electron valence perturbation theory, and shown to correctly predict the hydroxide anion to be more stable than the hydroxyl radical, provided that basis sets with diffuse orbitals are also employed. Finally, we calculate the electron affinity of the hydroxyl radical using an aug-cc-pVQZ basis on IBM's quantum devices.

Modulating Wave-Based Timing Calculation for a Multilevel 24-Sided Polygonal Voltage Space Vector Structure With Similar Triangles

This article proposes a multilevel 24-sided polygonal voltage space vector structure (VSVS), eliminating lower order harmonics up to 19th order and suppressing higher order harmonics in motor phase voltage throughout the modulation range. Unlike switched average vectors in literature, the proposed scheme generates real active vectors that have the advantage of less switching frequency operation. The proposed VSVS consists of two concentric polygons divided into similar triangles resulting in a simple modulation algorithm. Instantaneous error in phase voltage reduces due to the multilevel property of the proposed VSVS. The proposed scheme extends the dc bus utilization and linear range of operation. The proposed scheme is implemented on an open-end winding induction motor fed with primary and secondary inverters from either end. This article also presents a modulating wave-based method to compute nearest vector timings using sampled reference waves only. Unlike conventional methods, the proposed timing calculation method does not require trigonometric operations, sorting algorithms, and iterative search algorithms. Experimental verification of the proposed scheme is performed to validate the concept. Switching loss and Fourier analysis comparison with some existing schemes is also presented.

Theoretical and experimental study of inversion of spectral absorption function using experimental data of laser absorption spectrum with slow scanning and fast modulation of wavelength

Based on the tested data of laser absorption spectra, a matrix slicing method is proposed to invert the absorption function of spectral lines by using the two parameters of laser modulation frequency and laser scanning range as well as transmitted wave signal and reference wave signal under the condition of slow uniform scanning wavelength and fast periodic modulation wavelength. When the modulation is single frequency sinusoidal modulation, an accurate contour of the spectral line absorption function can be obtained by using the matrix data consisting of the values of the transmitted wave signal by the reference wave signal through the minimum value of two slice integrals with the interval of half modulation period, and the amplitude of modulation can be estimated. When the fast modulation of the wavelength is distorted to the multi-frequency superposition modulation, the absorption function is also formed by using the complementarity of multiple slices. The method above is utilized for investigating a real absorption function inversion process involving multiple overlapping absorption lines in the range of the scanning wavelengths. Moreover, the scanning range of laser wavelength can be calibrated by the interval parameters of several spectral lines in the scanning wavelength range. The absorption function of CO at 4300.700 cm<sup>–1</sup> and CO<sub>2</sub> at 6336 cm<sup>–1</sup> are successfully obtained by using this matrix slice method for experimental verification.

Взаимная трансформация световых волн при встречном взаимодействии на отражательной голографической решетке в кристалле Bi-=SUB=-12-=/SUB=-SiO-=SUB=-20-=/SUB=- среза (001)

The features of energy exchange during the contra-directional mixing of two linearly polarized light waves in a cubic photorefractive Bi12SiO20 piezocrystal of (001)-cut are analyzed. The dependences of the relative intensity of the signal wave on the azimuth of its polarization at the entrance to the crystal during mixing with the reference wave polarized in the plane of incidence are theoretically studied for various crystal orientation angles. The dependence of the relative intensity of the signal wave on the azimuth of its polarization is experimentally studied for the cases when the vector amplitudes of light waves propagating in the crystal are parallel and perpendicular to each other. The calculation is based on the numerical solution of the coupled waves equations with and without taking into account the self-diffraction of the light waves by the reflection holographic grating recorded in the crystal. Based on a comparison of theoretical and experimental data, the influence of self-diffraction on the mutual transformation of light waves during their contra-directional mixing is analyzed. The limits of applicability of the static grating and the dynamic grating approximations for solution of the coupled waves equations are determined.

Mutual transformation of the light waves by contra-directional mixing on reflection holographic grating in Bi-=SUB=-12-=/SUB=-SiO-=SUB=-20-=/SUB=- crystal of (001)-cut

The features of energy exchange during the contra-directional mixing of two linearly polarized light waves in a cubic photorefractive Bi 12 SiO 20 piezocrystal of (001)-cut are analyzed. The dependences of the relative intensity of the signal wave on the azimuth of its polarization at the entrance to the crystal during mixing with the reference wave polarized in the plane of incidence are theoretically studied for various crystal orientation angles. The dependence of the relative intensity of the signal wave on the azimuth of its polarization is experimentally studied for the cases when the vector amplitudes of light waves propagating in the crystal are parallel and perpendicular to each other. The calculation is based on the numerical solution of the coupled waves equations with and without taking into account the self-diffraction of the light waves by the reflection holographic grating recorded in the crystal. Based on a comparison of theoretical and experimental data, the influence of self-diffraction on the mutual transformation of light waves during their contra-directional mixing is analyzed. The limits of applicability of the static grating and the dynamic grating approximations for solution of the coupled waves equations are determined. Keywords: Photorefractive crystal, reflection holographic grating, coupled wave equations, self-diffraction.

Complex wave and phase retrieval from a single off-axis interferogram.

Single-frame off-axis holographic reconstruction is promising for quantitative phase imaging. However, reconstruction accuracy and contrast are degraded by noise, frequency spectrum overlap of the interferogram, severe phase distortion, etc. In this work, we propose an iterative single-frame complex wave retrieval based on an explicit model of object and reference waves. We also develop a phase restoration algorithm that does not resort to phase unwrapping. Both simulation and real experiments demonstrate higher accuracy and robustness compared to state-of-the-art methods, for both complex wave estimation and phase reconstruction. Importantly, the allowed bandwidth for the object wave is significantly improved in realistic experimental conditions (similar amplitudes for object and reference waves), which makes it attractive for large field-of-view and high-resolution imaging applications.

Dual‐view holographic AR display based on Bragg mismatched reconstruction of the holographic optical element

AbstractA method for dual‐view holographic display based on Bragg mismatched reconstruction of holographic optical element (HOE) is proposed. Under the Bragg mismatched condition, the reconstructed images are guided into two separated viewing zones to realize dual‐view holographic display. Meanwhile, the viewing angle of each perspective is increased to 11.2°, which is almost 2.5 times as large as the traditional holographic display system. The design process of HOE is simple only by interference of plane reference wave and converging spherical signal wave, which has high practicability. Furthermore, the HOE can mix the virtual 3D image with real‐world scenes, which could implement augmented reality (AR) display. Experiments validate that the proposed system can achieve dual‐view holographic AR three‐dimensional (3D) display with accommodation effect.

Fast Near-Field Frequency-Diverse Computational Imaging Based on End-to-End Deep-Learning Network.

The ability to sculpt complex reference waves and probe diverse radiation field patterns have facilitated the rise of metasurface antennas, while there is still a compromise between the required wide operation band and the non-overlapping characteristic of radiation field patterns. Specifically, the current computational image formation process with a classic matched filter and other sparsity-driven algorithms would inevitably face the challenge of a relatively confined scene information sampling ratio and high computational complexity. In this paper, we marry the concepts of a deep convolutional neural network with computational imaging literature. Compared with the current matched filter and compressed sensing reconstruction technique, our proposal could handle a relatively high correlation of measurement modes and low scene sampling ratio. With the delicately trained reconstruction network, point-size objects and more complicated targets can both be quickly and accurately reconstructed. In addition, the unavoidable heavy computation burden and essential large operation frequency band can be effectively mitigated. The simulated experiments with measured radiation field data verify the effectiveness of the proposed method.

Effective seismic force retrieval from surface measurement for SH-wave reconstruction

We present a new method to obtain dynamic body force at virtual interfaces to reconstruct shear wave motions induced by a source outside a truncated computational domain. Specifically, a partial differential equation (PDE)-constrained optimization method is used to minimize the misfit between measured motions at a limited number of sensors on the ground surface and their counterparts reconstructed from optimized forces. Numerical results show that the optimized forces accurately reconstruct the targeted ground motions in the surface and the interior of the domain. The proposed optimization framework yields a particular force vector among other valid solutions allowed by the domain reduction method (DRM). Per this optimized or inverted force vector, the reconstructed wave field is identical to its reference counterpart in the domain of interest but may differ in the exterior domain from the reference one. However, we remark that the inverted solution is valid and introduce a simple post-process that can modify the solution to achieve an alternative force vector corresponding to the reference wave field. We also study the desired sensor spacing to accurately reconstruct the wave responses for a given dominant frequency of interest. We remark that the presented method is omnidirectionally applicable in terms of the incident angle of an incoming wave and is effective for any given material heterogeneity and geometry of layering of a reduced domain. The presented inversion method requires information on the wave speeds and dimensions of only a reduced domain. Namely, it does not need any information on the geophysical profile of an enlarged domain or a seismic source profile outside a reduced domain. Thus, the computational cost of the method is compact even though it leads to the high-fidelity reconstruction of wave response in the reduced domain, allowing for studying and predicting ground and structural responses using real seismic measurements.

Pulse recording of dynamic holograms in bismuth silicate crystal in a broad wavelength range

The formation of dynamic holograms in a photorefractive bismuth silicate crystal by nanosecond laser pulses with a change in the radiation wavelength is studied. An original scheme for recording holograms is proposed to preserve the grating period when operating at different wavelengths. The method of pulsed recording of dynamic gratings based on the proposed optical scheme is applied, which ensures the fulfillment of the Bragg condition for probing radiation. The originality of the scheme lies in the use of the first orders of diffraction of a transmitting diffraction grating as the reference and signal waves, as well as a telescopic system used to fix the period of the recorded grating, regardless of the wavelength used. Kinetic dependences of the diffraction efficiency of dynamic holograms in a photorefractive bismuth silicate crystal are obtained with a change in the wavelength of recording radiation in the actual spectral range (from 450 nm to 600 nm). The effect of the manifestation of competing recording mechanisms of short-lived (hundreds of microseconds) and long-lived (seconds) gratings, the contribution of which depends on the wavelength of the radiation recording the hologram, has been established. The optimal wavelength for obtaining the highest diffraction efficiency of holograms is determined. It is shown that radiation in the blue-green region of the spectrum leads to the predominant recording of a short-lived grating, while long-lived gratings dominate in the red region of the spectrum. The need to study photorefractive crystals of the sillenite family is determined by their use for multiplex recording of dynamic holograms and the implementation of the adaptive interferometry method to track changes in objects in real time.

In-Line and Off-Axis Hybrid Digital Holographic Imaging Method Based on Off-Axis Hologram Constraints

We put forward a novel hybrid iterative algorithm to improve the imaging quality of digital holography. An off-axis hologram is added to the iteration process via interference and inverse interference process and becomes part of the constraints. A frequency domain filter varying with the number of iterations is used to improve the competitive advantage of low frequency information in the early iterations, while retaining the high frequency information. In practical applications, an additional iterative process is used after averaging filtering to suppress the influence of the imperfect consistency between the reconstructed reference wave and the actual reference wave. Numerical simulations and experiments show that image reconstruction may be significantly improved compared to the conventional method.

Binocular holographic display based on the holographic optical element.

Due to the limited pixel pitch of the spatial light modulator (SLM), the field of view (FOV) is insufficient to meet binocular observation needs. Here, an optimized controlling light method of a binocular holographic three-dimensional (3D) display system based on the holographic optical element (HOE) is proposed. The synthetic phase-only hologram uploaded onto the SLM is generated with the layer-based angular spectrum diffraction theory, and two different reference waves are introduced to separate the left view and the right view of the 3D scene. The HOE with directional controlling light parameters is employed to guide binocular information into the left-eye and the right-eye viewing zones simultaneously. Optical experiments verify that the proposed system can achieve binocular holographic augmented reality 3D effect successfully with real physical depth, which can eliminate the accommodation-vergence conflict and visual fatigue problem. For each perspective, the FOV is 8.7° when the focal length of the HOE is 10 cm. The width of the viewing zone is 2.3 cm when the viewing distance is 25 cm.

Hysteresis Based Quasi Fixed Frequency Current Control of Single Phase Full Bridge Grid Integrated Voltage Source Inverter

The traditional Fixed Band Hysteresis Current Control (FB-HCC) though being widely used for the current control of grid integrated voltage source inverter (GI-VSI), has the drawback of variable switching frequency. To overcome this drawback, Complex Programmable Logic Device (CPLD) based switching scheme is proposed in this paper. The proposed method calls for a single reference wave and the control concept is to terminate the rising and falling inductor current (iL) either by the comparator or by the CPLD, based on the nature of its slope. Termination of the iL with steeper slope by the comparator ensures lower current ripple, whereas the CPLD ensures constant switching frequency (fsw). However, the iL obtained with the proposed logic has a DC offset, which is corrected by modifying the reference. The basic concept, switching logic, and reference correction are thoroughly detailed. MATLAB/Simulink results are included to verify the proposed concept. The constant frequency operation of the proposed method is also validated in a 2 kW, 230 V, 50 Hz GI-VSI prototype.

Peristaltic Transport Of Casson Fluid In A Vertical Permeable Channel With Suction And Injection By Numerical Technique

The peristaltic transport of a Casson fluid in a vertical permeable channel with suction and injection by Galerkin method is studied.. The mathematical modeling is realized with an approximation of the extended wave length and a low Reynolds number. The mathematical solution is obtained for the velocity field, pressure gradient, frictional force within the reference wave system over one wavelength. The results of various parameters on pressure rise characteristics and frictional forces are discussed graphically. It is observed that the pressure rise decreases because the slip parameters and suction/injection parameter increases and increases because the amplitude increases.

Association of the Expiration of Child Tax Credit Advance Payments With Food Insufficiency in US Households

Advance Child Tax Credit (CTC) monthly payments administered to more than 35 million households with children in the US between July and December 2021 were associated with a substantial decrease in food insufficiency. These monthly payments expired in January 2022 after Congress failed to extend the policy, and the subsequent impact on food insufficiency is currently unknown. To assess whether the expiration of monthly CTC payments in January 2022 was associated with changes in food insufficiency in US households with children. This study used repeated cross-sectional, nationally representative data from multiple waves of the Household Pulse Survey, conducted by the US Census Bureau. Online data collection occurred from July 21, 2021, to July 11, 2022, and data analysis was performed in July 2022. The first missed advance CTC payment on January 15, 2022. The main outcome was unadjusted prevalence of household food insufficiency. Event study specification was used to estimate the association between the expiration of the CTC payments and household food insufficiency with the exposure of being in a household with children present. The sample (592 044 respondents, representing households with and without children, for a weighted population size of 123 350 770 individuals) was majority female (362 286 individuals [51.3%]) and non-Hispanic White (425 497 individuals [62.2%]), and a plurality of respondents (248 828 [48.3%]) were aged 25 to 44 years at the time of the survey. During the survey wave just before CTC expiration (reference wave, December 29, 2021, to January 10, 2022), unadjusted household food insufficiency was 12.7% among households with children. In late January and early February 2022, following the first missed CTC monthly payment, 13.6% of households with children reported food insufficiency, increasing to 16.0% by late June and early July 2022. The event study specification estimated a 3.2 percentage point increase (95% CI, 1.4-5.0 percentage points; P < .001) in food insufficiency by the most recent wave available after the first missed CTC payment (June 29 to July 11, 2022) among households with children compared with the reference wave, a 25% increase. The findings of this study suggest that there was an increase in food insufficiency among households with children after they stopped receiving monthly CTC payments. Given the well-documented associations between inability to afford food and poor health outcomes across the life span, Congress should consider swift action to reinstate this policy.

UAV-Mounted GPR for Object Detection Based on Cross-Correlation Background Subtraction Method

Unmanned aerial vehicle (UAV) ground-penetrating radar (GPR) is an important research topic for target detection in many fields. In this paper, we develop a UAV-mounted GPR system with a frequency band at 150 MHz–309 MHz. However, the received signal in the complex background is covered by various clutter and interference, leading to the serious obscuring of the target. To meet this challenge, a cross-correlation-based background subtraction (CCBS) method and an interference suppression technique are adopted in combination for more accurate detection. The CCBS method processes the raw echo by establishing a background-removal model and using the similarity between each A−Scan and a reference wave. In addition, a Butterworth filter is adopted to get rid of the active electromagnetic interference beyond the working frequencies of the system; then, a lateral Doppler filtering (LDF) technique is introduced to suppress the passive interference generated by the rotation of the UAV rotor itself. Moreover, a practical method for estimating the dielectric constant is introduced by the calibration process of the measured radar echo. Numerical simulations and experimental results by our UAV-GPR system demonstrate that the proposed method has presented a better performance than the traditional methods, and the system has great potential in detecting deeply buried targets.