Multiple Focusing Research Articles

MetaHDR: single shot high-dynamic range imaging and sensing using a multifunctional metasurface.

We present MetaHDR, which is a single-shot high-dynamic range (HDR) imaging and sensing system using a multifunctional metasurface. The metasurface is capable of splitting an incident beam into multiple focusing beams with different amounts of power, simultaneously forming multiple low dynamic range (LDR) images with distinct irradiance on a photosensor. Then, the LDR images are jointly processed using a gradient-based HDR fusion algorithm, which is shown to be effective in attenuating the residual light artifacts incurred by the metasurface and the lens flare. MetaHDR achieves single-shot HDR photography and videography that increases the dynamic range by at least 50 dB compared to the original dynamic range of the photosensor. It can also perform single-shot HDR sensing, including reflectance calibration and surface curvature estimation of reflective materials. MetaHDR's demonstrated functionalities could be broadly applied in surveillance and security, microscopic imaging, advanced manufacturing, etc.

Robust multiple focusing through scattering media via feedback wavefront shaping

The control of multiply-scattered light has greatly boosted the understanding of optics in complex photonic systems, leading to many applications including imaging, information processing, random lasing, to name just a few. Here, we demonstrate a real-time feedback approach to realize multiple focusing of multiply-scattered light, which is more robust to the inherent background field compared to the time reversal approach. Our method retrieves the optimized wavefront by aligning the high-dimensional vector of the measured pattern with that of the target pattern. Our theoretical simulations and experimental results show that the feedback approach is capable of constructing homogeneous diffraction-limited spots at predefined positions. Moreover, the peak-to-background ratio exhibits a sub-1/m decay with m being the number of focuses, indicating the excellent capability of the proposed approach to focus scattered light at multiple positions. This efficient approach provides a promising avenue toward complex control on scattered light in complex photonic media, and therefore would be useful in relevant applications such as optical imaging and optical manipulation.

Oppression-Based Stress and Alcohol Inequities Among Sexual and Gender Minority People: An Intersectional Multilevel Framework.

Sexual and gender minority (SGM) people are at heightened risk for alcohol use, hazardous drinking, and alcohol use disorder compared to heterosexual and cisgender individuals. This paper: (a) presents an oppression framework that integrates intersectionality, stress, stigma, and addiction-based theories to examine the complex and nuanced ways oppression-based stress (e.g., minority stress) leads to sexual orientation and gender identity inequities in alcohol use; (b) conducts a narrative review that summarizes recent and novel advancements in the literature on the impact of oppression-based stressors on alcohol use outcomes across structural, interpersonal, and intrapersonal domains among SGM people; and (c) provides future research and intervention directions for the alcohol field. A select review of the literature was conducted on July 10, 2023, using multiple electronic databases (i.e., PsycInfo, PubMed, Web of Science) and focusing on studies that had examined the associations between oppression-based stressors and alcohol use outcomes across structural, interpersonal, and intrapersonal levels. Search terms focused on alcohol consumption; SGM people, particularly SGM people of color; and oppression-based stress. Cross-sectional studies that focused on heterosexism-based and anti-bisexual oppression-based stressors at the interpersonal or intrapersonal levels and alcohol use outcomes were excluded as they have been included in prior reviews of the literature. The initial and combined search across the databases resulted in 3,205 articles. Of those, the narrative review included 50 peer-reviewed articles that focused on the following four areas of the literature on the associations between oppression-based stressors and alcohol use outcomes: (1) experimental, longitudinal, and experience sampling studies of heterosexism- and anti-bisexual oppression-based stressors (22 articles); (2) any studies of cissexism-based stressors (12 articles); (3) any studies of intersectional oppression among SGM people of color (seven articles, one article overlapped with the first category and another overlapped with the fourth category); and (4) any studies of structural oppression (11 articles). Results of this narrative review indicate that mounting evidence implicates oppression-based stress in inequities in alcohol use, hazardous drinking, and alcohol use disorder in SGM populations. This reflects SGM people's embodiment of oppression and injustice at the structural, interpersonal, and intrapersonal levels. Given some inconsistent and mixed patterns of findings, future research needs greater specificity in drinking inclusion criteria, robust and well-validated measures, more attention to culturally and developmentally relevant moderating and mediating mechanisms across the lifespan, application of sophisticated methodologies, and integration of intersectional and addiction frameworks.

Controlling beam dynamics with spectral quadratic phase modulation in the fractional Schrödinger equation.

The propagation dynamics of Gaussian beams and finite energy Airy beams with spectral quadratic phase modulation (QPM) modeled by the fractional Schrödinger equation (FSE) are numerically investigated. Compared with beam propagation in the standard Schrödinger equation, the focusing property of beams under FSE is influenced by the QPM coefficient and the Lévy index. For symmetric Gaussian beams, the focusing position increases and the focusing intensity decreases for the larger QPM coefficient or smaller Lévy index. For asymmetric Airy beams, multiple focusing positions occur, and the tendency of focusing intensity is opposite to that of Gaussian beams. Our results show the promising application of the FSE system for optical manipulation and optical splitting by controlling the QPM.

Directionally duplexed all-dielectric metalens for multifunctional structured light generation.

Directionally duplexed metalenses manipulated by the geometric phase of a silicon nano-bar are theoretically designed to generate multifunctional structured light. It is numerically demonstrated that incident light with different linear and circular polarization states, along forward and backward propagation directions, can be differentially converted into multiple focusing structured beams of arbitrary topological charges, either of vector light with azimuthally variant polarizations or of vortex light with helical phases. Due to the all-silicon and nonresonant metastructural design, the resultant high working efficiencies of our proposed metalens are promising for applications such as optical communication, nanoparticle manipulation, and other direction-duplexed multifunctional optical meta-devices.

Tight-focusing evolution of linearly polarized auto-focusing circular Bessel-Gaussian vortex beam

In this paper, we analyzed the influence of on-axis and off-axis vortex on the intensity distribution of the linearly polarized auto-focusing Bessel-Gaussian vortex beam (LABGVB). By comparing its tight-focusing properties with that of the linearly polarized circular Airy beam, it is found that when transmitted in the tight-focusing system, the LABGVB not only generates multiple focusing, but also allows the focal points to be located away from the geometric focus of the high numerical aperture (HNA) lens. In addition, changing the focal length of the HNA lens not only causes the splitting and merging of the focal points, but also results in different control effects on the depth of focus and the distance between focal points due to different focusing times. In particular, the LABGVB can not only form multiple optical bottles for particle capture in the focusing region, but also exhibit two different distributions of the spin density vectors along the optical axis after choosing the appropriate scale factor and main ring radius, one being a circular line and the other being a helical line.

On the relationship between mobile-based extramural activities and vocabulary development of EFL learners: a mixed-method study

Mobile-based extramural English (EE) activities, including watching movies, playing digital games, and listening to music outside the classroom, have played an important role in increasing learners' interest in English as a foreign language (EFL). This mixed-method design study aimed to investigate the role of EE activities in the vocabulary development of intermediate EFL learners. The study included a group of 60 learners, including 30 male and 30 female students from two language institutes. A pretest, posttest, and delayed posttest were used. The experimental group utilized WhatsApp to receive electronic vocabulary instruction four days per week for two months as part of the EE activities. In contrast, the control group received classroom instruction using the conventional approach typically employed in EFL contexts for teaching the same textbook vocabulary. A semi-structured interview was conducted to investigate the participants' beliefs regarding their preference for EE-based activities. The results of the EG group revealed that EE-based activities significantly impacted the students' vocabulary learning (p < 0.001). The findings also revealed no significant differences in vocabulary knowledge between male and female students after using EE activities (p = 0.34). The themes that emerged from the qualitative phase suggested that participants preferred EE-based activities as they can result in less mental stress, more vocabulary learning, improved conversation, and improved pronunciation and grammar. Also, the participants preferred various mobile-based EE activities, including watching movies, listening to music, playing multiple games, watching cartoons, and focusing on movie subtitles, which resulted in their vocabulary development. The findings call for language educators to integrate more virtual and online-based EE activities to supplement traditional vocabulary teaching practices.

The impact of group velocity dispersion on femtosecond laser filamentation with higher-order Kerr effect at different atmospheric pressures

The impact of group velocity dispersion (GVD) on femtosecond laser filamentation with the higher-order Kerr effect is studied at different atmospheric pressures. The results show that GVD makes the collapse distance to not meet the semi-empirical formula proposed by Dawes and Marburger, suppresses multiple focusing and splitting in time during the propagation process, and reduces the length of filament. In addition, we also compared the results with those considering only the third-order Kerr effect. This provides some information for the study of whether the defocus effect in the femtosecond laser filamentation is the higher-order Kerr effect or the plasma effect.

Establishment of a multiplex polymerase chain reaction detection assay for three common harmful microalgae in the East China Sea.

It is urgent to develop techniques that can simultaneously detect multiple microalgae, due to the diversity of harmful algal blooms (HABs)-forming algal species. The target algae species in this study are Heterosigma akashiwo, Prorocentrum donghaiense and Karenia mikimotoi. These algae are the dominant species that cause HABs in the East China Sea, and the multiple detection technique focusing on these three algae is not common. Therefore, this study established a multiplex polymerase chain reaction(mPCR) to diagnose the three algae, which is simple and low cost. First, the corresponding specific primers were designed based on the D1-D2 region of the large subunit (LSU) ribosomal DNA sequence. Then, mPCR was established and the reaction conditions were optimized. And the specificity, sensitivity, and stability of mPCR were evaluated. The result of specificity test showed that the established mPCR had good specificity for the target microalgae and did not cross-react with eighteen non-target microalgae. The sensitivity of experiment was 3.3 × 10-1ng μL-1, and the established mPCR was not affected by the interfering microalgae. Moreover, the practicability evaluation of mPCR by using the simulated natural water samples showed that the detection limit of target microalgae was 100 cells mL-1, which could meet the demand for early warning of HABs. In summary, the established mPCR is characterized by strong specificity, good stability, and multiple analysis to detect H. akashiwo, P. donghaiense, and K. mikimotoi.

Overview of diet and autoimmune demyelinating optic neuritis: a narrative review.

This review summarizes the cellular and molecular underpinnings of autoimmune demyelinating optic neuritis (ADON), a common sequela of multiple sclerosis and other demyelinating diseases. We further present nutritional interventions tested for people with multiple sclerosis focusing on strategies that have shown efficacy or associations with disease course and clinical outcomes. We then close by discuss the potential dietary guidance for preventing and/or ameliorating ADON.

Adaptive simulations of flame acceleration and detonation transition in subsonic and supersonic mixtures

Two-dimensional simulations were carried out to investigate the flame acceleration and deflagration-to-detonation transition (DDT) in a combustion chamber filled with a subsonic or supersonic mixture by employing Navier-Stokes equations together with a detailed chemistry reaction mechanism of 11 species and 27 steps under adaptive mesh refinement. The effects of the initial mixture Mach number and mesh resolution on the flame acceleration and DDT were studied in detail, and the entire processes of the flame acceleration, DDT and detonation propagation were revealed. Two DDT mechanisms are obtained in a chamber having the same low blockage ratio but with different initial velocities of the mixture. Regime I: multiple shock wave collisions, shock focusing and shock reflection result in a rapid energy deposition in a small region; a direct detonation subsequently occurs in the boundary wall for the subsonic mixture. Regime II: the classic hot-spot mechanism due to the reactive gradient mechanism is responsible for the detonation transition in the supersonic mixture when the intense leading shock wave impacts and reflects on the solid surface. By increasing the initial mixture Mach number, the run-up time and distance to DDT are dramatically reduced. The flame front structure and propagation in the supersonic flow demonstrate that the detonation cell size rapidly increases when propagating into the smooth region due to detonation attenuation and resulting pressure decrease. Additionally, a much higher combustion temperature occurs in the upper and lower walls because of the Mach stem. In comparison, the results show that the detonation overdrive degree and pressure gain ratio in the subsonic mixture are higher than in the supersonic mixture. Moreover, flame propagation upstream also suggests that increased pressure and temperature occur in the inlet isolation section, even forming a localized explosion point.

Mach cutoff phenomenon of sonic boom in temperature inversion layers

The Mach cutoff of sonic boom occurs when shock waves propagate from supersonic to subsonic regions in a stratified atmosphere. In this study, numerical simulations are performed to clarify Mach cutoff behaviors in atmospheric temperature inversion layers, which have not yet been investigated. The two-dimensional Euler equations with a gravitational source term are solved in a horizontally stratified atmosphere. Surface and non-surface temperature inversion layers include three and four supersonic–subsonic mixing layers, respectively. Computations are made to analyze the propagation characteristics of a conventional N-shaped waveform. The results show that multiple upward and downward cutoffs occur owing to atmospheric temperature inversions, with multiple outgoing and evanescent waves, and multiple shock wave focusing. The upward and downward cutoffs act similarly. The positive- and negative-pressure regions are inversed when a cutoff occurs twice; thus, each cutoff shifts a phase by π/2, as expressed in the linear theory of caustics. A waveform transition occurs owing to wave splitting in a cutoff region, in addition to the phase shift. For surface temperature inversion, upward cutoffs make the waves between the cutoff and ground surfaces persist, resulting in rumbling. For non-surface temperature inversion, upward and downward cutoffs occur alternately, and the waves between them persist as well. Therefore, multiple cutoffs in temperature inversion layers play an important role in sonic boom evaluation during low supersonic flight.

Adaptive Focused Beam Prestack Depth Migration Under the Condition of Rugged Topography

The complex topography is a challenging issue in onshore seismic exploration. The rugged terrain and lateral change of near-surface velocity pose a significant obstacle to the accurate imaging of seismic data. The adaptive focused beam migration method retains the good applicability of the ray methods for calculating the seismic wavefield under complex surface conditions. It can effectively solve the contradiction between the imaging accuracy of deep and shallow strata in traditional Gaussian beam migration. We extend the adaptive focused beam migration approach to the deep domain imaging of seismic data under complex surface conditions. Firstly, the basic principles of the adaptive focused beam are reviewed. Then, Green’s functions of the seismic source and the receiving point of rugged topography are characterized by the adaptive focused beam, and an adaptive focused beam prestack depth migration method based on cross-correlation imaging is proposed. The full-wave-arrival imaging strategy is applied to image all wave arrivals of subsurface imaging points. A single input seismic trace is adopted for imaging, which can directly emit the focused beam from the receiving point of rugged topography for wave field continuation, thus avoiding multiple focusing. As a result, the applicability of the migration approach to complex surface conditions was improved, and the imaging accuracy of the migration method was also effectively enhanced. The numerical model migration test of different rugged topography conditions and tectonic forms verified that the proposed method was an effective prestack depth migration applicable to accurately imaging seismic data under the rugged topography condition.

A Global Phase‐Modulation Mechanism for Flat‐Lens Design

AbstractFlat lens also known as metasurface lens is drawing considerable attention nowadays. Thus far, the metasurface lens has been achieved by engineering local phase profile in deep subwavelength scale according to resonant or non‐resonant (or both) responses of nanoscatters to light. Such local phase mappings require precise control over each nanoscatter. In addition, there is currently no metasurface lens that exhibits multiple functionalities. Here, a novel working mechanism, named as a global phase‐modulation mechanism, for the flat‐lens design is demonstrated. To illustrate this concept, a binary amplitude‐only hologram is introduced, resulted from an interference between an angular cosine wave and a spherical wave. The resultant flat lens can be made extremely thin (60 nm) and is comprised of spatially shaped apertures. Such a technique allows to globally manipulate the diffractive wave vectors in the reciprocal space. Multiple focusing performances with a single flat lens are demonstrated under different illumination beams including the plane‐wave beam, vortex beam, and vector beam. In addition to imaging, the flat lens is able to Fourier transforming a complex self‐accelerating Airy beam, which was not considered before. The presented global mechanism facilitates new capabilities and holds for multifunctional flat lens, with potential applications in areas such as imaging and optical information processing.

Profiling a niche actor of civil society diplomacy: the unattached diplomat

PurposeThe purpose of this study is to define the communicational profile of unattached diplomats and explore the viability of state-centric concepts such as citizen diplomacy when discussing non-state actors emerging from civil society.Design/methodology/approachThe paper uses a comparative, multiple case design focusing on descriptive case studies (Yin, 2018) that explore the diplomatic endeavours and social biographies of “citizens of the world” acting at a global or local level, not explicitly attached to or explicitly against an official, state agenda: Malala Yousafzai, Greta Thunberg and Bill Gates.FindingsThe unattached diplomats have organisational mobility but are attached to the cause they promote, a configuration that fundamentally opposes that of the traditional or organisational diplomat. Looking at individuals from a diplomatic perspective, not as instruments or as targets, but rather as agents with their own agenda, issues and diplomatic capital, the unattached diplomats define their lack of attachment through organisational mobility, adversarial positioning or personal financial autonomy with regard to state diplomatic institutions or for-profit/not-for-profit organisations.Research limitations/implicationsA higher number and diversity of case studies can enable the identification of patterns and standards.Originality/valueThis study introduces and operationalises the concept of unattached diplomats. To the best of the author’s knowledge, this study is the first to discuss it in the context of another emerging concept, currently insufficiently researched: civil society diplomacy.

Multi-beam X-ray ptychography using coded probes for rapid non-destructive high resolution imaging of extended samples

Imaging large areas of a sample non-destructively and with high resolution is of great interest for both science and industry. For scanning coherent X-ray diffraction microscopy, i. e., ptychography, the achievable scan area at a given spatial resolution is limited by the coherent photon flux of modern X-ray sources. Multibeam X-ray ptychography can improve the scanning speed by scanning the sample with several parallel mutually incoherent beams, e. g., generated by illuminating multiple focusing optics in parallel by a partially coherent beam. The main difficulty with this scheme is the robust separation of the superimposed signals from the different beams, especially when the beams and the illuminated sample areas are quite similar. We overcome this difficulty by encoding each of the probing beams with its own X-ray phase plate. This helps the algorithm to robustly reconstruct the multibeam data. We compare the coded multibeam scans to uncoded multibeam and single beam scans, demonstrating the enhanced performance on a microchip sample with regular and repeating structures.

Evolution mechanism of double-layer heavy gas column interface with sinusoidal disturbance induced by convergent shock wave

Based on Navier-Stokes equations, combining the fifth-order weighted essentially non-oscillatory scheme with the adaptive structured grid refinement technique, the interactions between converging shock and annular SF&lt;sub&gt;6&lt;/sub&gt; layers with different initial perturbation amplitudes and thickness are numerically investigated. The evolution mechanism of shock structure and interface are revealed in detail, and the variations of the circulation, mixing rate and turbulent kinetic energy are quantitatively analyzed. The dynamic mode decomposition method is used to analyze the dynamic characteristics of the vorticity. The results show that in the case with large initial perturbation amplitude, the transmitted shock wave forms Mach reflection structures both inside and outside of the inner interface of SF&lt;sub&gt;6&lt;/sub&gt; layer, and multiple shock focusing phenomena occur in the center. After the transmitted shock wave penetrates the outer interface, the circulation increases faster, and the “spike” and “bubble” structure on inner interface develop faster, so that the amplitude of the inner and outer interfaces and the gas mixing rate increase. As for the case with larger thickness of the gas layer, the phase of the transmitted shock wave changes inside the layer, which forms “bubble” at the crest of the inner interface and “spike” at the trough. When the thickness of the gas layer decreases, the crest of the inner interface does not move inside after being impacted, and “spike” and “bubble” are generated in the late stage. The dynamic modes show that the main structure of vorticity and the exchange of positive and negative vorticity on the main structure are determined by the modes with weak growth and low frequency, but the modes with weak growth and high frequency determine rapid exchange of positive and negative vorticity at the interface in the cases with weak coupling effect.

Focusing grating couplers for radio-frequency surface ion traps

We present a photonic integrated circuit design with multiple focusing grating couplers that can be used in a surface ion trap. This system allows transferring laser radiation from different laser sources to the ion trapped 240 μm above the surface for further manipulations.

Drawing structured plasmonic field with on-chip metalens.

The ability to draw a structured surface plasmon polariton (SPP) field is an important step toward many new opportunities for a broad range of nanophotonic applications. Previous methods usually require complex experimental systems or holographic optimization algorithms that limit their practical applications. Here, we propose a simple method for flexible generation of structured SPP field with on-chip plasmonic metalenses. The metalens is composed of multiple plasmonic focusing nanostructures whose focal shape and position can be independently manipulated, and through their superposition, SPP fields with specially designed patterns are obtained. Based on this method, we demonstrate several structured SPP fields including S- and W-shaped SPP focal fields and tunable SPP bottle beams. This work could provide new ideas for on-chip manipulation of optical surface waves, and contribute to applications such as on-chip photonic information processing and integrated photonic circuits.

Phase Space Considerations for a microSAXS Beamline Located on a Diamond Laue Side-Bounce Monochromator

Flux as well as spatial and angular resolution for a microbeam small-angle X-ray scattering set-up, comprising Laue optics and multiple focusing elements are modeled within five-dimensional phase space analysis. A variety of X-ray optics configurations for highest angular resolution and for highest spatial resolution are analyzed.