Abstract Vector vortex beams, featuring spatially structured polarization states and helical phase fronts, emerge as a critical solution for enhancing optical information capacity beyond the constraints of traditional communication paradigms. In this paper, a coherent modulation strategy is established for creating two dimension (2D) vector vortex far‐field diffraction arrays through light‐atom interactions under electromagnetically induced transparency (EIT). A dynamically reconfigurable optical lattice is engineered via interference between a Gaussian‐coupled field and a vortex‐coupled field with adjustable topological charge. The atomic medium, when subjected to this lattice modulation, facilitates the diffraction of probe vector light fields into high‐order vector vortex diffracted spots. This system enables multi‐parameter tuning to significantly enhance diffraction efficiency. Results demonstrate that Comprehensive optimization of coupling field intensity, interference beam power distribution, and frequency detuning significantly enhances the relative diffraction efficiency. Moreover, the polarization state distribution of diffraction fields can be reconfigured by controlling optical lattice topological charges. This atomic medium‐based optical lattice modulation framework offers flexibility in tailoring structured light arrays, bridging fundamental studies of structured light‐matter interactions with advanced applications in high‐dimensional optical encoding, quantum state engineering, and multifunctional optical manipulation systems.

Analytical expressions are obtained that describe the nonparaxial diffraction in free space of the TM01 mode with radial polarization of the field of the dielectric waveguide resonator of a terahertz laser during its interaction with a spiral phase plate with different topological charge (n). The physical features of the obtained vortex beams during their propagation and tight focusing are studied by numerical simulation. The integral diffraction Rayleigh-Sommerfeld transforms are used to simulate the propagation and focusing of the obtained beams. In free space the use of the spiral phase plate at the waveguide output with a topological charge of n = 1 leads to a change in the transverse beam profile from annular to a beam that has a field maximum on the axis, and then for n = 2 again to annular. During focusing the transverse distribution of the total field intensity in the absence of a spiral phase plate has a ring structure. In this case there is a slight intensity on the axis due to the contribution of the longitudinal component of the field. The transverse profile of the beam changes in the same way as during its propagation when using a phase plate. In this case the phase front changes from spherical to spiral with the presence of two (n = 1) and four (n = 2) branching vortices.

Analytical study of a flame propagation front in a solid phase driven by chain-branching reactions at large Zel’dovich numbers: Steady states, stability and influence of the radicals Lewis number

Abstract We present a statistical analysis of the interplanetary magnetic field (IMF) discontinuity normals across solar cycle 23 and 24 for different solar wind types. We employ both the Minimum variance analysis (MVA) and Cross‐product methods to determine phase front normals using ACE observations. We confirm that most discontinuity normals point earthward and dawnward at longitudes from 180 to 250 and lie between latitudes −40 and 40. A wider range of normals is observed during the solar minimum and declining phases compared to the solar maximum and ascending phases. Discontinuities point strongly northward or southward more frequently during solar minimum than during solar maximum. We categorize the data into four solar wind types, Coronal Mass Ejections‐Magnetic Ejecta (CME‐ME), CME‐SH (Sheath), Stream Interaction Regions (SIR), and Non‐CME/Non‐SIR for the years 2001–2002 (solar maximum) and 2008–2009 (solar minimum). The discontinuity normals are strongly oriented antisunward during CMEs (CME‐MEs and CME‐SHs). The distributions during SIRs are similar to those observed in the absence of any particular solar wind type.

This study proposed a double-pulse laser-induced breakdown spectroscopy (DP-LIBS) signal enhancement method based on the shaping of vortex beams, effectively addressing the low-energy utilization of the second pulse in collinear DP-LIBS systems and significantly improving the detection sensitivity of trace elements in aluminum (Al) alloys. This study built a conventional collinear DP- LIBS system, and the second pulse laser was shaped into a vortex beam using a vortex half-wave plate. This study confirms that vortex beam shaping can enhance the spectral signal intensity and improve the stability of the plasma. The effects of spectral acquisition delay and inter-pulse delay on the performance of the vortex beam shaping technique in DP-LIBS were systematically investigated through experimental studies. The results demonstrate that compared with the traditional Gaussian beam method, the vortex beam shaping technology on average increases the spectral line intensity of the characteristic elements in the Al alloy sample by an average factor of 2.22, and the signal-to-background ratio increases significantly to 1.58. Additionally, the average value of relative standard deviation of the characteristic spectral lines was reduced from 8.54% to 4.39%. Trace elements such as Pb and Ti were also detected. Further analysis of transient plasma images confirmed that the vortex beam shaping technique enhances LIBS signals by modulating the spatial energy distribution and helical phase fronts of the second pulse laser, thereby altering the plasma evolution dynamics.

Terahertz (THz) generation by optical rectification in LiNbO3 (LN) is a widely used technique for generating intense THz radiation. The spatiotemporal characterization of THz pulses from these sources is currently limited to far-field methods. While simulations of tilted pulse front THz generation have been published, little work has been done to measure the near-field properties of the THz source. A better understanding of the THz near-field properties will improve optimization of THz generation efficiency, transport, and coupling. We demonstrate a technique for quantitative spatiotemporal characterization of single-cycle strong-field THz pulses with 2-D near-field electro-optic imaging. We have reconstructed the full temporal 3D THz near-field and shown how the phase front can be tailored by controlling the incident pump pulse.

Abstract Large‐amplitude ultra‐low frequency (ULF) waves in Earth's ion foreshock play a crucial role in the dayside dynamics and solar wind‐magnetosphere coupling. This study uses global hybrid‐Vlasov simulation results from Vlasiator to investigate the detailed physical processes in the early growth phase of the foreshock ULF waves. Using both spatial and temporal information, the wave phase speed is determined and used to track a specific phase front as the wave evolves. The space‐time evolution of the foreshock waves and the backstreaming ions responsible for the wave growth is analyzed and presented in the wave frame for the first time. We employ a state‐of‐the‐art linear dispersion solver, LEOPARD, to solve the wave dispersion relations using the ion distributions and compare the theoretical predictions with the measured wave phase speed and growth rate. The measured phase speed in the spacecraft (or stationary) frame is unexpectedly high at the initial growth stage but later decreases to the predicted level and exhibits an increasing trend over time that aligns with theoretical expectations. The measured and predicted growth rates share the same decreasing trend over time, but the predicted values are consistently lower than the measured growth rate by 25%. The comparison suggests that the foreshock waves in the Vlasiator simulation are likely generated through the ion‐ion right‐hand resonant instability, but there are discrepancies with linear theory that are not explained yet and require further investigation.

This paper introduces a multi-layered multi-dielectric (MLMD) stacked substrate-integrated waveguide (SIW) H-plane horn antenna, incorporating a metallic transition and a metal-via array. Despite recent development in techniques to enhance the performance of Substrate Integrated Waveguide based horn antennas, it is found that one performance parameter is often improved at the cost of the others. The presented antenna is designed with the aim of improving key antenna parameters simultaneously in the same structure. For that metallic transition with metal via array is proposed to modify the phase front of the radiated waves. Additionally, multi layered multi dielectric is used to improve the impedance matching and improve the front-to-back ratio. The antenna has high gain, decent BW, narrow beamwidth in both E and H-planes, low sidelobe level, and high front-to-back ratio. The proposed antenna is modelled and a physical prototype is fabricated, and characterized; the results ensure very promising performance. The simulated impedance bandwidth ranges from 23.67 GHz to 28.8 GHz. Moreover, the peak realized gain achieved is 14.24 dBi at 27 GHz. The average front-to-back-ratio achieved for the antenna is 24.7 dB. This antenna is useful for point-to-point data communication and various other mm-Wave 5G applications.

A comparison between neural network clustering (NNC), hierarchical clustering (HC) and k-means clustering (KMC) is performed to evaluate the computational superiority of these three machine learning (ML) techniques for organizing large datasets into clusters. For NNC, a self-organizing map (SOM) training was applied to a collection of wavefront sensor reconstructions, decomposed in terms of 15 Zernike coefficients, characterizing the optical aberrations of the phase front transmitted by fluidic lenses. In order to understand the distribution and structure of the 15 Zernike variables within an input space, SOM-neighboring weight distances, SOM-sample hits, SOM-weight positions and SOM-weight planes were analyzed to form a visual interpretation of the system's structural properties. In the case of HC, the data were partitioned using a combined dissimilarity-linkage matrix computation. The accuracy of this method was confirmed by a high cophenetic correlation coefficient value (c = 0.9651). Additionally, a maximum number of clusters was established by setting an inconsistency cutoff of 0.8, yielding a total of 7 clusters, while reducing the inconsistency cutoff to 0.7 resulted in 13 clusters for system segmentation. In addition, a KMC approach was employed to establish a quantitative measure of clustering segmentation efficiency, obtaining a silhouette average value of 0.905 for data segmentation into K = 5 non-overlapping clusters. On the other hand, the NNC analysis revealed that the 15 variables could be characterized through the collective influence of 8 clusters. It was established that the formation of clusters through the combined linkage and dissimilarity algorithms of HC alongside KMC is a more dependable clustering solution than separate assessment via NNC or HC, where altering the SOM size or inconsistency cutoff can lead to completely new clustering configurations.

Extreme ultraviolet (XUV) light sources allow for the probing of bound electron dynamics on attosecond scales, interrogation of high-energy-density matter, and access to novel regimes of strong-field quantum electrodynamics. Despite the importance of these applications, coherent XUV sources remain relatively rare, and those that do exist are limited in their peak intensity and spatio-polarization structure. Here, we demonstrate that photon acceleration of an optical vector vortex pulse in the moving density gradient of an electron beam–driven plasma wave can produce a high-intensity, tunable-wavelength XUV pulse with the same vector vortex structure as the original pulse. Quasi-3D, boosted-frame particle-in-cell simulations show the transition of optical vector vortex pulses with 800-nm wavelengths and intensities below 1018 W/cm2 to XUV vector vortex pulses with 36-nm wavelengths and intensities exceeding 1020 W/cm2 over a distance of 1.2 cm. The XUV pulses have sub-femtosecond durations and nearly flat phase fronts. The production of such high-quality, high-intensity XUV vector vortex pulses could expand the utility of XUV light as a diagnostic and driver of novel light–matter interactions.

Assessing wave overtopping for coastal defense design is crucial, as it is vital for the evaluation of flood protections and essential to safety and risk mitigation. There is a debate about whether the average overtopping or the largest waves, which can cause the most damage, should be the primary design criterion. The EurOtop manual (2018) provides guidance, suggesting adaptability based on specific conditions and site use. The proposed study implements focused wave groups in an experimental flume facility aiming to investigate the variability of maximum individual overtopping volumes at sea dikes with shallow water conditions and/or emergent toes. By employing focused wave groups, it is crucial to comprehend how the combination of focus phase, focus location, water levels, and sea front characteristics are affecting the measured volumes and represent a sea state storm. The ultimate objective is to achieve a parametric optimization of focused wave groups for laboratory practices and analyses of extreme overtopping events at coastal defenses. Here, we compare two different foreshore slopes and four different sea dike slopes, in combination with varying water levels and three different wave conditions, to provide a preliminary comparison of all cases. This will pave the way for further parametrization of the focused wave groups technique applied to model extreme overtopping events.

Abstract Prior observational uncertainties have hindered the clear understanding of the link between tropospheric Lamb waves and ionospheric disturbances. In this study, we precisely extracted ionospheric Lamb waves originating from the epicenter of the 15 January 2022 Tonga eruption, propagating upward in a conical structure. This was achieved by using line‐of‐sight observations from the BeiDou geostationary satellites, which eliminated the spatiotemporal ambiguity introduced by the relative motion of Global Positioning System satellites, enabling the clear extraction of the Lamb signal in the ionosphere. The observed L0 mode speed (∼323 m/s) and period (∼30 min) were consistent with those of the tropospheric Lamb wave. It suggested that the ionospheric Lamb wave is likely driven by the surface Lamb wave, leading to a conical wave‐front that extends in altitude. This study highlights the significant role of Lamb waves in transmitting energy from epicenters through Earth's atmosphere and plasma systems.

This study presents a concept of a new architecture for liquid crystal on silicon (LCoS) devices for phase modulation with a much-reduced pixel pitch. This is studied here with an example with 2 µm pixel pitch. At this scale, the liquid crystal induces a non-uniform wavefront response across the pixel, varying in both amplitude and phase. To reflect this behavior, we refer to this pixel architecture as phase front elements (PFEs) instead of pixels. To confirm the feasibility of this design, we developed a modification to the Gerchberg-Saxton algorithm to enable Fourier-plane hologram generation. The new algorithm quantizes the complex modulation distributions within the PFEs, thus allowing for projection of target far-field intensity patterns. This work presents a theoretical concept verified in simulations and is intended as a proof-of-concept for such devices.

Determining the solid diffusion coefficient of lithium in graphite anode active materials for lithium-ion batteries is challenging due to the complex intercalation dynamics, the structural complexity, particle size/shape distribution, and the superposition of liquid electrolyte transport processes in the pores of an electrode. To minimize these influences, we examined the lithiation of highly oriented pyrolytic graphite (HOPG) disk electrodes, with the basal planes stacked normal to the disk thickness (0.5 mm). At first, the radially progressing lithiation of the HOPG disks was followed in situ by top-view optical monitoring of the golden LiC6 phase. However, post-mortem analysis of split HOPG disks revealed that HOPG crystal surface imperfections lead to the artefact that the apparent LiC6 phase progression determined from top-view images does not correspond to that in the bulk of the disks. Thus, the LiC6 phase front position can only be quantified through post-mortem analysis of split HOPG disks. The intercalation time and temperature dependence of the LiC6 phase progression can be reasonably well described by a Fickian diffusion model in cylindrical geometry, yielding an apparent diffusion coefficient of the LiC6 phase front of D 0 = 0.6–1.0 × 10−13 m2 s−1 at 25 °C, with an activation energy of E a = 35.4–39.0 kJ mol−1 (between 10–55 °C).

Vortex beams, characterized by their helical phase fronts and annular intensity profiles, have emerged as a transformative tool in optical communications due to their capacity to carry orbital angular momentum (OAM). However, conventional vortex beam generators, such as spiral phase plates and spatial light modulators, suffer from narrow operational bandwidths (<200 nm), limiting their applicability in multi-wavelength systems.To address this challenge, we present a metasurface-based approach leveraging the geometric phase (Pancharatnam-Berry phase) principle to achieve broadband OAM generation. We propose a C2-symmetric silicon nanorod metasurface optimized for the near-infrared (1390–1500 nm) regime, demonstrating 84%–96% polarization conversion efficiency for right-circularly polarized (RCP) light. Through systematic parameter sweeps and finite-difference time-domain (FDTD) simulations, we identify an optimal nanorod geometry (major axis = 320 nm, minor axis = 250 nm, height = 923 nm) that enables full 0–2π phase modulation while maintaining wavelength-independent topological charge stability. The metasurface array, arranged in four quadrant-discrete phase sectors, generates high-purity OAM modes with annular intensity distributions and helical wavefronts across the entire bandwidth. Key innovations include the unification of polarization conversion and geometric phase control in a single nanostructure, eliminating the need for cascaded optical elements. This work advances the state-of-the-art in OAM multiplexing by enabling low-crosstalk, dispersionfree vortex beams for next-generation optical networks, free-space communications, and 6G systems. The design’s compatibility with standard semiconductor fabrication techniques further underscores its potential for scalable integration in photonic circuits.

Creation of structured light at‐source with determinate orbital angular momentum (OAM) states is a fascinating branch of modern optics, owing to their integrability, wavelength insensitivity, and high mode purity. However, mode degeneracy in spatially column‐symmetric cylindrical coordinate systems leads to a total zero OAM states which seriously limits their development and applications. Here, a strategy is proposed for symmetry breaking of the degenerate OAM states relying on the natural anisotropy of crystal gain, to select the handedness of the spatial spiral phase front and further tunable Raman‐like OAM states by thermal‐driven, experimentally realized arbitrary OAM states from −2ћ to ћ. The concept presented herein clarifies the contribution of intrinsic crystal property to the OAM states and opens a new route for an at‐source solution of structure light with high integrability and controllable OAM states.

The electrohydrodynamics of compound liquid thread formation under an electric field in a flow-focusing microchannel is numerically studied via the phase-field method and the dielectric model. The influences of electric potential and flow rate on the morphology and size of compound liquid thread are clarified. A regime diagram is provided to distinguish the thread formation regimes (i.e., dripping–threading, jetting–threading, and threading–threading regimes) from the non-thread formation regimes. It is found that the electric force and interfacial tension, both acting in the same direction, suppress the growth of the inner phase. Conversely, these two forces oppose each other in the middle phase, counteracting the capillary instability of the middle phase. Therefore, the larger electric force contributes to the elongation and stability of jets, facilitating the generation of continuous compound thread. Moreover, as the larger electric force hinders the growth of the inner phase front under the dripping regime, the formation time and size of the inner droplet are increased, while, under the jetting regime, a larger electric force has a stronger squeezing action on the neck of the inner phase and thus reduces the pinch-off time and size of the inner droplet. Additionally, the straightened thread is widened with increasing electric capillary number. In particular, to control the preferred regime of jet template for producing the peapod-like microfibers, two scaling laws are correspondingly developed to predict the inner droplet radius and outer thread thickness for the dripping–threading regime, which achieve good predict precision with relative error less than ±18%.

Structured light fields with high degrees of freedom, particularly those with orbital angular momentum (OAM) states associated with the rotation of the phase front, give rise to a range of novel physical phenomena in light–matter interactions. However, direct generation of scalar OAM states at source faces limitations in power scaling, and their amplification remains an open challenge due to limited gain and mode purity. In this work, we present a straightforward approach to directly amplify scalar optical vortices by employing a two-stage single-crystal fiber (SCF) amplifier system, delivering 104.8 W laser with the OAM state of ℏ and 90.3 W of −8ℏ state. Both of the OAM states exhibit a high modal purity of >90%, indicating that such a multi-stage SCF amplifier system is particularly well-suited for direct amplification of scalar OAM light with different states. The strategy presented here paves the way for power scaling of structured light, and the generated high-power and high modal purity OAM laser beams are expected to reveal complex physical phenomena in light–matter interactions.

We report herein, an accurate, precise, specific and robust high-performance thin layer chromatographic technique along with forced degradation testing was established and validated for analysis of Levodropropizine and Chlorpheniramine Maleate in pharmaceutical formulation. Robustness study was conducted by using fractional factorial design. The 24–1 design examined at both high level (+1) and low level (-1). Four factors were selected in the design matrix which includes chamber saturation time, solvent front, wavelength, and methanol volume in mobile phase. Base, acid, oxidation, dry heat, and photodegradation tests were performed on both medications. The developed technique employed silica gel (60 F254) as a stationary component and Triethylamine: Toluene: Methanol (0.5:3:16 v/v/v) as the mobile phase mixture. A densitometric investigation conducted at 270 nm showed a strong, symmetrical peak for Chlorpheniramine maleate and Levodropropizine, with Rf values of 0.59 and 0.39, respectively. The ICH Q2(R2) recommendation was implemented in the validation of the procedure. For Levodropropizine and Chlorpheniramine maleate, the calibration curve regression coefficients were determined to be 0.9959 and 0.9943 in the range of concentrations of 1500–7500 and 100–500 ng/band, respectively. The technique had a correctness of 97.07% for Levodropropizine and 96.12% for Chlorpheniramine Maleate, respectively. In Robustness study methanol volume in mobile phase, chamber saturation time and wavelength have minor effect on response of Rf value. Levodropropizine and Chlorpheniramine Maleate are susceptible to chemical oxidation, photolytic study, base hydrolysis, and dry heat degradation while both the drugs have less degradation in wet heat and acid hydrolysis.

Laser-driven free-electron lasers (LDFELs) replace magnetostatic undulators with the electromagnetic fields of a laser pulse. Because the undulator period is half the wavelength of the laser pulse, LDFELs can amplify X rays using lower electron energies and over shorter interaction lengths than a traditional free-electron laser. In LDFELs driven by conventional laser pulses, the undulator uniformity required for high gain necessitates large laser-pulse energies. Here, we show that a flying-focus pulse provides the undulator uniformity required to reach high gain with a substantially lower energy than a conventional pulse. The flying-focus pulse features an intensity peak that travels in the opposite direction of its phase fronts. This enables an LDFEL configuration where an electron beam collides head-on with the phase fronts and experiences a near-constant undulator strength as it co-propagates with the intensity peak. Three-dimensional simulations of this configuration demonstrate the generation of megawatts of coherent X-ray radiation with 20 × less energy than a conventional laser pulse.