Phase Shift Research Articles

A semiempirical model for low energy electron-atom transport cross sections: The case of noble gases

A semiempirical approach to describe low energy electron-atom transport cross sections of easy implementation and reproduction is presented. The heart of the model is an energy independent two-parameter potential that was adjusted to reproduce the accurate total cross sections for He, Ne, Ar and Kr, measured with a threshold photoelectron source technique from meV up to 20 eV. Once the potential was conceived, the model was validated by comparing the values obtained for the calculated scattering lengths and phase shifts with the respective quantities previously reported in the literature. We close the article by presenting the momentum transfer and viscosity cross sections. Good agreement is found when compared to the similar data obtained from swarm experiments, from phase shifts according to differential cross section measurements and to the cross sections reported by sophisticated ab initio relativistic many-body calculations. Tables for the phase shifts and cross sections are provided for direct use and applications.

Direct observation of a few-photon phase shift induced by a single quantum emitter in a waveguide.

Realizing a sensitive photon-number-dependent phase shift on a light beam is required both in classical and quantum photonics. It may lead to new applications for classical and quantum photonics machine learning or pave the way for realizing photon-photon gate operations. Nonlinear phase-shifts require efficient light-matter interaction, and recently quantum dots coupled to nanophotonic devices have enabled near-deterministic single-photon coupling. We experimentally realize an optical phase shift of 0.19π±0.03 radians (≈34 degrees) using a weak coherent state interacting with a single quantum dot in a planar nanophotonic waveguide. The phase shift is probed by interferometric measurements of the light scattered from the quantum dot in the waveguide. The process is nonlinear in power, the saturation at the single-photon level and compatible with scalable photonic integrated circuitry. The work may open new prospects for realizing high-efficiency optical switching or be applied for proof-of-concept quantum machine learning or quantum simulation demonstrations.

Controllable helical collapse caused by a nonlinearity-related Gouy phase shift

Controllable helical collapse caused by a nonlinearity-related Gouy phase shift

Experimental Verification of the Gouy Phase for Higher-Order Hermite-Gaussian Beams

The Gouy phase is related to the axial phase shift experienced by any focused light beam with respect to a reference plane wave when passing through its focus. Generally, the Gouy phase ΦG for a higher-order Hermite-Gaussian (HG) beam is this for the fundamental Gaussian beam multiplied by a factor, which is the sum of the mode indices of the HG beam plus unity. Although this result is a paradigm in optics, we are not aware of its experimental verification. In this paper, we present experimental results obtained with a single-lens interferometer for higher-order HG modes generated using spatial light modulator. The retrieved Gouy phase ΦG is found in a very good quantitative agreement with the mentioned theoretical result.

Reflux Power Optimization of a Dual-Active Hybrid Full-Bridge Converter Based on Active Disturbance Rejection Control

The dual-active hybrid full-bridge (H-FDAB) DC–DC converter has great potential in medium-voltage high-power photovoltaic power station applications by introducing a three-level bridge arm to increase the output voltage range. However, its mathematical model and optimum modulation schemes have not been fully explored. Under the traditional PI control, the H-FDAB DC–DC converter will produce significant reflux power, which will lead to a decrease in converter efficiency and output voltage fluctuation. On this basis, this paper proposes a reflux power optimization strategy for an H-FDAB DC-DC converter based on active disturbance rejection control (ADRC). Firstly, the structure and power characteristics of the H-FDAB DC–DC converter are analyzed, and the relationship among the reflux power, the transmission power, and the phase shift angle is derived. Secondly, to reduce the complexity of the control calculation, upon the foundation of dual phase-shifting modulation, the Karush–Kuhn–Tucker (KKT) condition is used to solve for the phase shift angle that corresponds to the minimum reflux power. Simultaneously, we develop an ADRC loop utilizing an extended state observer (ESO) for the real-time estimation of system states. We also consider the sudden changes in input voltage, load switching, and transmission power fluctuations caused by reflux power optimization strategies as system disturbances and compensate for them accordingly. Finally, the experiments conclusively validate the designed control strategy’s correctness and feasibility.

Ultra-Broadband Mode (De)Multiplexer on Thin-Film Lithium Niobate Platform Adopting Phase Control Theory

Mode (de)multiplexers (MDMs) serve as critical foundational elements within systems for facilitating high-capacity communication, relying on mode conversions achieved through directional coupler (DC) structures. However, DC structures are challenged by dispersion issues for broadband mode coupling, particularly for high-order modes. In this work, based on the principles of phase control theory, we have devised an approach to mitigate the dispersion challenges, focusing on a thin-film lithium niobate-on-onsulator (LNOI) platform. This solution involves integrating a customized inverse-dispersion section into the device architecture, offsetting minor phase shifts encountered during the mode coupling process. By employing this approach, we have achieved broadband mode conversion from TE0 to TE1 and TE0 to TE2 within a 300 nm wavelength range, and the maximum deviations were maintained below −0.68 dB and −0.78 dB, respectively. Furthermore, the device exhibited remarkably low crosstalk, reaching down to −26 dB.

Research on flexible and fast tunable laser in coherent optical communications

A flexible and fast tunable laser based on hybrid integration is proposed, which can realize single and multi-wavelength reconfigurable output by controlling the on or off of semiconductor optical amplifiers (SOAs) array in combination with a tunable arrayed waveguide grating (AWG). The wavelength switching time achieves <0.8 ns. The stable output power of the tunable laser is >16 dBm with >70 dB side mode suppression ratio (SMSR) and 6.4 nm tunability. The designed laser exhibits narrow linewidths down to 1 kHz and longitudinal mode spacing of 0.8 nm, which is suitable for ITU-T standards and the output power meets the requirements of coherent optical communications. A broadened spot-size converter (SSC) for bi-directional transmission is designed and implemented with a power coupling efficiency about 0.93 and an optical bandwidth of more than 200 nm. Demonstration of the 100 Gb/s quadrature phase shift keying (QPSK) self-homodyne coherent optical transmission based on designed laser is achieved.

Polarized APSK modulation system with polymorphic SC signals

AbstractThis paper discusses a new symbol modulation scheme known as polarized amplitude and phase shift keying, (‐APSK) modulation with four rings in its basic form. The new scheme maps power‐polarized symbol pairs on its constellation in order to increase the number of data symbols. ‐APSK exploits a symbol mapper based on a conjugate power splitting algorithm. Product modulation is applied, where a voltage signal of a specified amplitude and phase is multiplied by another current signal of a specified amplitude and phase, thus forming polymorphic signals in the product constellation. At the receiver, an isolated detection is performed, where the voltage signal is detected independently of the received current signal. A selection combining scheme is then used. The results depict unity peak‐to‐average power ratio and low average symbol energy, which is desirable for Green communications in 5G networks. It presents lower bit error rates when compared with the state‐of‐the art ‐ary quadrature amplitude modulation, with a signal‐to‐noise ratio gap of at least . The proposed analytical framework closely matches the simulations for bit error rates under .

Ultrasound enabled simultaneous measurement of coating wear depth and lubricant film thickness in a sliding bearing

Sliding bearings, serving as critical supporting components in rotating machinery, often work by riding on an ultra-thin oil film. The rupture of this oil film can cause wear of the soft coating on the bearing and even lead to catastrophic failures. This paper introduces a novel ultrasonic reflection-based approach to simultaneously measure both lubricant film thickness and coating wear depth. Through an analysis of the ultrasonic wave propagation in a worn bearing, it is observed that the echo waveform remains independent of wear depth but correlates with changes in the time of flight back to the transducer. Given this, the captured time or phase shift between the reflected and incident waves, together with the reduction in the wave amplitude, enables a simultaneous calculation of both oil film thickness and coating wear depth. The efficacy of the proposed method is validated through acoustic simulations and experiments with varied coating roughness.

Edge-wave phase shifts versus normal-mode phase tilts in an Eady problem with a sloping boundary

One mechanistic interpretation of baroclinic instability is that of mutual constructive interference of Rossby edge waves. The suppression of baroclinic instability over slopes has been widely established, where previous research argues that a sloping boundary modifies the properties of these Rossby edge waves, but does not provide a mechanistic explanation for the suppression that is valid over all parameter space. In the context of an Eady problem modified by the presence of a sloping boundary, we provide a mechanistic rationalization for baroclinic instability in the presence of slopes that is valid over all parameter space, via an equivalent formulation explicitly in terms of Rossby edge waves. We also highlight the differences between edge-wave phase shifts and normal-mode phase tilts, showing that the edge-wave phase shifts should be the ones that are mechanistically relevant, and normal-mode phase tilt is a potentially misleading quantity to use. Further, we present evidence that the edge-wave phase shifts but not normal-mode phase tilts are well correlated with geometric quantities diagnosed from an analysis framework based on eddy variance ellipses. The result is noteworthy in that the geometric framework makes no explicit reference to the edge-wave structures in its construction, and the correlation suggests the geometric framework can be used in problems where edge-wave structures are not so well defined or readily available. Some implications for parametrization of baroclinic instability and relevant eddy-mean feedbacks are discussed. For completeness, we also provide an explicit demonstration that the linear instability problem of the present modified Eady problem is parity-time symmetric, and speculate about some suggestive links between parity-time symmetry, shear instability, and the edge-wave interaction mechanism. Published by the American Physical Society 2024

Complementary phase interleaving-based fringe order recognition for temporal phase unwrapping

This paper introduces a complementary phase interleaving-based fringe order recognition method, designed to rectify phase errors encountered in temporal phase unwrapping. Addressing challenges arising from noise interference or misalignment between fringe order and the wrapped phase, this method employs an innovative integration of a smooth-wrapped phase and the interleaved complementary phases with precise π phase shifts. Furthermore, it maximizes measurement accuracy and prevents filtering-induced degradation by back-calculating the fringe order of noise-disturbed phases from the smooth-continuous phase. Its remarkable adaptability across various temporal phase unwrapping methods, without necessitating additional structural patterns, underscores its versatility in addressing a broad spectrum of phase error suppression challenges. Experimental validation substantiates the accuracy and adaptability of this method, demonstrating its efficacy in handling diverse types of phase errors within TPU methods. This advancement stands as a pivotal solution for achieving precise and comprehensive phase error suppression, particularly for multiple isolated objects.

Investigation of Phase Shift and Travel Time of Acoustic Waves in the Lower Solar Atmosphere Using Multiheight Velocities

We report and discuss the phase shift and phase travel time of low-frequency (ν < 5.0 mHz) acoustic waves estimated within the photosphere and photosphere–chromosphere interface regions, utilizing multiheight velocities in the quiet Sun. The bisector method has been employed to estimate seven height velocities in the photosphere within the Fe i 6173 Å line scan, while nine height velocities are estimated from the chromospheric Ca ii 8542 Å line scan observations obtained from the narrowband imager instrument installed on the Multi-Application Solar Telescope operational at the Udaipur Solar Observatory, India. Utilizing a fast Fourier transform at each pixel over the full field of view, phase shift and coherence have been estimated. The frequency and height-dependent phase shift integrated over the regions having an absolute line-of-sight magnetic field of less than 10 G indicates the nonevanescent nature of low-frequency acoustic waves within the photosphere and photosphere–chromosphere interface regions. Phase travel time estimated within the photosphere shows nonzero values, aligning with previous simulations and observations. Further, we report that the nonevanescent nature persists beyond the photosphere, encompassing the photospheric–chromospheric height range. We discuss possible factors contributing to the nonevanescent nature of low-frequency acoustic waves. Additionally, our observations reveal a downward propagation of high-frequency acoustic waves indicating refraction from higher layers in the solar atmosphere. This study contributes valuable insights into the understanding of the complex dynamics of acoustic waves within different lower solar atmospheric layers, shedding light on the nonevanescent nature and downward propagation of the acoustic waves.

Chip-scale optical phased array for broadband two-dimensional beam steering at visible wavelengths

An optical phased array (OPA) on a chip, as a novel non-mechanical beam steering technique, has attracted much attention in various applications. However, due to the challenges in fabrication and the limited transparency window of the material for visible wavelengths, current OPAs are mainly focuses on the infrared wavelengths. Despite the progress, the visible light OPAs remain the challenges to not only simultaneously work in blue, green and red light, but also implement beam steering in two dimensions for the single-wavelength. In this paper, an 8-channel broadband OPA is demonstrated, which enables two-dimensional beam steering in visible light. Along the longitudinal direction, the beam steering angle of 0.7° at 585 nm is achieved by tuning phase shifts. Along the transverse direction, the demonstrated OPA implements beam steering angle of 4.49° at 585 nm by tuning polarization degrees and 25.97° at 488–610 nm by tuning wavelengths. Therefore, the demonstrated OPA holds significant promise for commercial applications such as visual projection and free-space optical communications.

Performance prediction of dielectric resonator based mm-wave MIMO antenna using machine learning algorithm

The alumina ceramic-based dual port radiator is structured and analyzed in this communication. Cylindrical-shaped ceramic is fed by using modified circular aperture. The designed aperture creates dual orthogonal modes i.e. HEM11δx and HEM11δy mode inside the ceramic with 90° phase shifts. This property generates circularly polarized waves from 27.6 GHz–28.4 GHz. Anti-parallel placements of antenna ports introduce the concept of space diversity and improve the isolation level by more than 25 dB. To reduce the computational time, two machine learning algorithms i.e. Random Forest and XGBoost are utilized to predict the reflection coefficient variation. Testing of a fabricated prototype of the proposed radiating structure confirms that the designed radiator works well between 26.8 GHz–28.7 GHz. Asymmetrical placement of ports concerning substrate tilts the radiation pattern obtained from different ports in different directions i.e. ±30°. Stable radiation features and good diversity performance make the designed antenna suitable for mm-wave 5G communication system.

Minimize BER without CSI for dynamic RIS-assisted wireless broadcast communication systems

This paper studies a dynamic reconfigurable intelligent surface (RIS)-assisted broadcast communication system where a transmitter broadcasts information to multiple receivers with time-varying locations via a RIS. The goal is to minimize the maximum bit error rate (BER) at the receivers by optimizing RIS phase shifts, subject to a given discrete phase shift constraint. Unlike most existing works where channel state information (CSI) is required, only location information of the receivers is needed in our work, due to the great challenge of instantaneous CSI estimation in RIS-assisted communications and the reason that statistical CSI does not apply to the dynamic scenario. The involved optimization problem is hard to tackle, because the BERs at the receivers cannot be calculated by classical CSI-dependent analytical expressions for lack of CSI and exhaustive searching is computationally prohibitive to achieve the optimal discrete phase shifts. To address this issue, a deep reinforcement learning (DRL) approach is proposed to solve the problem by reformulating the optimization problem as a Markov decision process (MDP), where the BERs are measured by the Monte Carlo method. Furthermore, to tackle the issue of the high-dimensional action space in the MDP, a novel action-composition based proximal policy optimization (PPO) algorithm is proposed to solve the MDP. Simulation results verify the effectiveness of the proposed PPO-based DRL approach.

Lithium extraction via capacitive deionization: AlF3 coated LiMn2O4 spheres for enhanced performance

The escalating demand within the lithium battery sector has intensified the pursuit of efficient methods for lithium's selective extraction from brines. Particularly, LiMn2O4 (LMO) emerges as a prime candidate, celebrated for its robust redox properties and considerable theoretical adsorption capacity. Nonetheless, its application is hampered by structural instability due to Jahn-Teller distortion, which triggers a phase shift from cubic to tetragonal and Mn dissolution, undermining the material's lithium extraction efficiency. In response, this study introduces an innovative, multifunctional amorphous AlF3 coating on LMO spheres, employing a novel synthesis approach combining co-precipitation, solid-phase transformation, and a final AlF3 deposition. This method not only mitigates Mn leaching but also curtails the adverse effects of Jahn-Teller distortion by integrating trace amounts of Al3+ into the LMO lattice, thus fortifying both the surface and bulk structure of the material. Significantly, the AlF3-coated LMO demonstrates an enhanced lithium extraction capacity of 31.5 mg g−1 at 1.2 V with feedwater concentration of 150 mg L−1. Additionally, the optimally coated sample exhibits superior cycling stability, maintaining high-capacity retention and minimal manganese dissolution across multiple absorption-desorption cycles. Furthermore, the optimized electrode exhibits exceptional selectivity for lithium over magnesium in solutions with high Mg2+/Li+ ratios, achieving a notable separation factor of 7.66. Additionally, this electrode demonstrates efficient separation capabilities in synthetic brine, effectively distinguishing Li+ from competing ions such as Na+, K+, Ca2+, and Mg2+, which underscores its substantial potential for effective lithium recovery from complex brines.

The analysis of the non-Kolmogorov turbulence effect on the performance of uplink coherent DPSK laser satellite communication system in the presence of tilt-corrected beam wander

AbstractIn the present study, a model for analyzing the performance of laser-based satellite uplinks that account for beam wander and atmospheric turbulence is presented. The developed scintillation index model is a continuation of the recent works considering the effects of non-Kolmogorov turbulence on the propagation of Gaussian beams across turbulent media. We specifically concentrate on the specific regime under the tilt-corrected beam wander. The on-axis scintillation index is developed assuming an isotropic non-Kolmogorov spectrum model where the power law exponent (PLE) effective value, $$\alpha$$ α , is taken to be 3 &lt; $$\alpha$$ α &lt; 4. Within that regime, effective irradiance models for tilt-corrected beam wander are presented, using the Gamma and Gamma-Gamma distributions. Closed-form expressions of the average bit error rate (BER) are derived to evaluate the performance of the optical communication system considering coherent detection of differential phase shift keying. The obtained numerical results show the impact of the Gaussian beam radius at the transmitter, the PLE effective value, and the zenith angle on the on-axis scintillation index and the average BER of the system under consideration. Due to beam wander, the link performance in terms of scintillation index and average BER depends on the beam radius at the transmitter. With tilt-corrected beam wander the link performance becomes best at an intermediate value of beam radius. With the non-Kolmogorov turbulent medium model, the PLE effective value has a major effect on the beam radius with the best performance. The obtained results guide the choice of the optimum beam radius for best performance for each PLE effective value.

Mechanical properties of AlCoCrCuFeNi high-entropy alloys using molecular dynamics and machine learning

High-entropy alloys (HEAs) stand out from multi-component alloys due to their attractive microstructures and mechanical properties. In this investigation, molecular dynamics (MD) simulation and machine learning (ML) were used to ascertain the deformation mechanism of AlCoCrCuFeNi HEAs under the influence of temperature, strain rate, and grain sizes. First, the MD simulation shows that the yield stress decreases significantly as the strain and temperature increase. In other cases, changes in strain rate and grain size have less effect on mechanical properties than changes in strain and temperature. The alloys exhibited superplastic behavior under all test conditions. The deformity mechanism discloses that strain and temperature are the main sources of beginning strain, and the shear bands move along the uniaxial tensile axis inside the workpiece. Furthermore, the fast phase shift of inclusion under mild strain indicates the relative instability of the inclusion phase of hexagonal close-packed (HCP). Ultimately, the dislocation evolution mechanism shows that the dislocations are transported to free surfaces under increased strain when they nucleate around the grain boundary. Surprisingly, the ML prediction results also confirm the same characteristics as those confirmed from the MD simulation. Hence, the combination of MD and ML reinforces the confidence in the findings of mechanical characteristics of HEA. Consequently, this combination fills the gaps between MD and ML, which can significantly save time, human power, and cost to conduct real experiments for testing HEA deformation in practice.

Configurable dual-band inverted-E type phase shifter

In this paper, we propose dual-band phase shifters based on the Inverted-E topology, which can be configured for independent phase shift values at the two design frequencies. The simple structure comprises of a 50 Ω Main Transmission Line (MTL), whose electrical length is proportional to the frequency, loaded with three equally spaced open circuited stubs, which provide the required susceptance values at the two design frequencies. The required parameter values of the open circuited stubs are extracted using a Genetic Algorithm (GA). For validation, two prototype dual-band phase shifters with equal phase shifts of 45° and independent phase shifts of 45° and 90° at f 1 = 1 GHz and f 2 = 5.5 GHz are designed and developed. The measured results closely align with simulations, demonstrating that the proposed design achieves the required phase shifts at both frequencies with phase error less than 1° and insertion losses < 2 dB.

Resource allocation for practical phase shift STAR-RIS enabled MISO-NOMA wireless network with non ideal hardware

This study investigates the sum secrecy rate SRsum of a simultaneous transmission and reflection reconfigurable intelligent surface (STAR-RIS)-enabled multiple input single-output (MISO) non-orthogonal multiple access (NOMA) downlink network with non-ideal hardware defects (HWDs) at the transceivers. Earlier STAR-RIS studies assumed an ideal phase shift model, with each element reflect and transmit the signal without regard to its phase shift. The proposed practical phase shift model accounts for the phase-dependent amplitude variation in the reflection and transmission (RAT) coefficients. The goal is to maximize the SRsum through an alternating optimization (AO) iterative algorithm, leverages a classical semidefinite relaxation (SDR) for beamformer vector design (BVD), and employs an interior point method (IPM) to calculate NOMA power allocation factors αt,αr. The analysis focuses on the evaluation of the SRsum in scenarios with eavesdroppers, under the consideration of both ideal and practical phase shift cases. The study examines the impact of different non-ideal HWDs on the SRsum of the system and provides insights into vulnerabilities and limitations arising from these effects.