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We suggest that the force F exerted upon a chiral molecule by light assumes the form under appropriate circumstances, where a and b pertain to the molecule whilst w and h are the local densities of electric energy and helicity in the optical field; the gradients of these quantities thus governing the molecule's centre-of-mass motion. Whereas a is identical for the mirror-image forms or enantiomers of the molecule, b has opposite signs; the associated contribution to F therefore pointing in opposite directions. A simple optical field is presented for which vanishes but does not, so that F is absolutely discriminatory. We then present two potential applications: a Stern-Gerlach-type deflector capable of spatially separating the enantiomers of a chiral molecule and a diffraction grating to which chiral molecules alone are sensitive; the resulting diffraction patterns thus encoding information about their chiral geometry.

Controlling light properties with diffractive planar elements requires full-polarization channels and accurate reconstruction of optical signal for real applications. Here, we present a general method that enables wavefront shaping with arbitrary output polarization by encoding both phase and polarization information into pixelated metasurfaces. We apply this concept to convert an input plane wave with linear polarization to a holographic image with arbitrary spatial output polarization. A vectorial ptychography technique is introduced for mapping the Jones matrix to monitor the reconstructed metasurface output field and to compute the full polarization properties of the vectorial far field patterns, confirming that pixelated interfaces can deflect vectorial images to desired directions for accurate targeting and wavefront shaping. Multiplexing pixelated deflectors that address different polarizations have been integrated into a shared aperture to display several arbitrary polarized images, leading to promising new applications in vector beam generation, full color display and augmented/virtual reality imaging. Controlling light with planar elements requires full polarization channels and reconstruction of optical signals. Here, the authors have demonstrated a general method relying on pixelated metasurfaces that enables wavefront shaping with arbitrary output polarization, allowing full utilization of polarization channels.

Deploying advanced imaging solutions to robotic and autonomous systems by mimicking human vision requires simultaneous acquisition of multiple fields of views, named the peripheral and fovea regions. Among 3D computer vision techniques, LiDAR is currently considered at the industrial level for robotic vision. Notwithstanding the efforts on LiDAR integration and optimization, commercially available devices have slow frame rate and low resolution, notably limited by the performance of mechanical or solid-state deflection systems. Metasurfaces are versatile optical components that can distribute the optical power in desired regions of space. Here, we report on an advanced LiDAR technology that leverages from ultrafast low FoV deflectors cascaded with large area metasurfaces to achieve large FoV (150°) and high framerate (kHz) which can provide simultaneous peripheral and central imaging zones. The use of our disruptive LiDAR technology with advanced learning algorithms offers perspectives to improve perception and decision-making process of ADAS and robotic systems. Mimicking human vision with metasurfaces, the authors propose a new paradigm for high field of view and ultrafast LiDAR, achieving performances also relevant for the next generation of imaging system for ADAS and robotic systems.

Rigid barrier deflectors can effectively prevent overspilling landslides, and can satisfy disaster prevention requirements. However, the mechanisms of interaction between natural granular flow and rigid barrier deflectors require further investigation. To date, few studies have investigated the impact of deflectors on controlling viscous debris flows for geological disaster prevention. To investigate the effect of rigid barrier deflectors on impact mechanisms, a numerical model using the smoothed particle hydrodynamics (SPH) method with the Herschel–Bulkley model is proposed to simulate the interaction between natural viscous flow and single/dual barriers with and without deflectors. This model was validated using laboratory flume test data from the literature. Then, the model was used to investigate the influence of the deflector angle and multi-barrier arrangements. The optimal configuration of multi-barriers was analyzed with consideration to the barrier height and distance between the barriers, because these metrics have a significant impact on the viscous flow pile-up, run-up, and overflow mechanisms. The investigation considered the energy dissipation process, retention efficiency, and dead-zone formation. Compared with bare barriers with similar geometric characteristics and spatial distribution, rigid barriers with deflectors exhibit superior effectiveness in preventing the overflow and overspilling of viscous debris flow. Recommendations for the rational design of deflectors and the optimal arrangement of multi-barriers are provided to mitigate geological disasters.

The cambered deflectors in aquacultural facilities are applied to enhance hydrodynamic efficiencies or enable flow fields to be fully developed. Given the anticipated improvements with the bio-inspired profiles or tandem configurations, the hydrodynamics of cambered deflectors with the above features are investigated at Re=1×10[sup.5]. The relationship between force coefficients and local flow behaviors for both bionic and non-bionic isolated deflectors, as well as tandem deflectors, is revealed using k−ω SST simulation. The dependencies of force coefficients on gap (G), stagger (S), and inclination angles (θ) in tandem deflectors are illustrated using an updated metamodeling workflow with simulated data. It is demonstrated that the variations of force coefficients over angles of attack are related to flow physics in boundary-layer regions. The non-bionic isolated deflector with the θ=10[sup.∘] prevails as the decent performances of C[sub.L] and γ globally, which is chosen in the following studies. Regarding tandem deflectors, θ plays a more vital role in drag coefficients (C[sub.D]) and lift coefficients (C[sub.L]), while the influence of S is not quite considerable compared to G. Aiming for cost minimizations and lift improvements, an optimized tandem case is obtained and justified with the superiorities in flow fields. This study has provided novel insights into the designs and optimizations of cambered deflectors in aquacultural engineering.

The strong interaction of light with micro- and nanostructures plays a critical role in optical sensing, nonlinear optics, active optical devices, and quantum optics. However, for wavefront shaping, the required local control over light at a subwavelength scale limits this interaction, typically leading to low-quality-factor optical devices. Here, we demonstrate an avenue towards high-quality-factor wavefront shaping in two spatial dimensions based on all-dielectric higher-order Mie-resonant metasurfaces. We design and experimentally realize transmissive band stop filters, beam deflectors and high numerical aperture radial lenses with measured quality factors in the range of 202–1475 at near-infrared wavelengths. The excited optical mode and resulting wavefront control are both local, allowing versatile operation with finite apertures and oblique illumination. Our results represent an improvement in quality factor by nearly two orders of magnitude over previous localized mode designs, and provide a design approach for a new class of compact optical devices. Wavefront manipulation with metasurfaces is typically limited to low quality factors. Here, the authors show how higher-order Mie modes can be leveraged to design high quality factor optical metasurfaces for wavefront manipulation in two dimensions.

We introduce the use of the fast multipole method (FMM) to speed up gravitational lensing ray tracing calculations. The method allows very fast calculation of ray deflections when a large number of deflectors, N *, are involved, while keeping rigorous control on the errors. In particular, we apply this method, in combination with the inverse polygon mapping (IPM) technique, to quasar microlensing to generate microlensing magnification maps with very high workloads (high magnification, large size, and/or high resolution) that require a very large number of deflectors. Using FMM-IPM, the computation time can be reduced by a factor of ∼105 with respect to standard inverse ray shooting (IRS), making the use of this algorithm on a personal computer comparable to the use of standard IRS on GPUs. We also provide a flexible web interface for easy calculation of microlensing magnification maps using FMM-IPM (see https://gloton.ugr.es/microlensing/). We exemplify the power of this new method by applying it to some challenging interesting astrophysical scenarios, including clustered primordial black holes and extremely magnified stars close to the giant arcs of galaxy clusters. We also show the performance/use of FMM to calculate ray deflection for a halo resulting from cosmological simulations composed of a large number (N ≳ 107) of elements.

We present spectroscopic confirmation of candidate strong gravitational lenses using the Keck Observatory and Very Large Telescope as part of our ASTRO 3D Galaxy Evolution with Lenses (AGEL) survey. We confirm that (1) search methods using convolutional neural networks (CNNs) with visual inspection successfully identify strong gravitational lenses and (2) the lenses are at higher redshifts relative to existing surveys due to the combination of deeper and higher-resolution imaging from DECam and spectroscopy spanning optical to near-infrared wavelengths. We measure 104 redshifts in 77 systems selected from a catalog in the DES and DECaLS imaging fields (r ≤ 22 mag). Combining our results with published redshifts, we present redshifts for 68 lenses and establish that CNN-based searches are highly effective for use in future imaging surveys with a success rate of at least 88% (defined as 68/77). We report 53 strong lenses with spectroscopic redshifts for both the deflector and source (z src > z defl), and 15 lenses with a spectroscopic redshift for either the deflector (z defl > 0.21) or source (z src ≥ 1.34). For the 68 lenses, the deflectors and sources have average redshifts and standard deviations of 0.58 ± 0.14 and 1.92 ± 0.59 respectively, and corresponding redshift ranges of z defl = 0.21–0.89 and z src = 0.88–3.55. The AGEL systems include 41 deflectors at z defl ≥ 0.5 that are ideal for follow-up studies to track how mass density profiles evolve with redshift. Our goal with AGEL is to spectroscopically confirm ∼100 strong gravitational lenses that can be observed from both hemispheres throughout the year. The AGEL survey is a resource for refining automated all-sky searches and addressing a range of questions in astrophysics and cosmology.

As an important source of train aerodynamic drag, the pantograph area is a key region which takes up about 10% contribution of the total. Thus, improving the pressure distribution in the pantograph area becomes a potential and effective method of reducing train aerodynamic drag. Based on the biological pattern of Coleoptera, a novel bionic elytron (i. e., deflector) installed on the pantograph areas of an eight-car grouping high-speed train was proposed to smooth the flow. Four calculation cases were set up, i. e., the original model (Model I), pantograph I with a deflector (Model II), pantograph II with a deflector (Model III), and pantograph I and II with deflectors (Model IV), to explore the mechanism of aerodynamic drag reduction for the train and improve its aerodynamic performance. The results show that after installing the pantograph deflector the aerodynamic drag force of the pantograph area is significantly reduced. The maximum drag reduction in pantograph I region is up to 84.5%, and the maximum drag reduction in pantograph II region is 25.0%. When the deflectors are installed in both pantograph I and pantograph II areas, the total drag reduction in pantographs I and II areas can be achieved by 49.6%. The air flows over the pantograph area in a smoother way with less blockage effect as compared to the base case without deflectors. However, the downstream flow velocity speeds up and impacts the corresponding region, e.g., windshields, leading to an increase of aerodynamic drag. When the deflector is installed in the area of pantograph I or pantograph II alternatively, the total drag of the eight-car group train reduces by up to 4.6% and 1.8%, respectively, while the drag reduction can be up to 6.3% with deflectors installed in both pantograph I and II areas. This paper can provide references for the aerodynamic design of a new generation of highspeed trains.

Abstract We have conducted a parameter study on the performance of the ion optics for a±± 45° deflection system used in space plasma measurements. The deflection system consists of a pair of electrodes mounted on an electrostatic analyzer. Our numerical model of the ion optics demonstrates its performance, including deflection efficiency for various parameters, and investigates the empirically known upper limit of deflection efficiency. The results reveal that the deflection system essentially involves canceling the kinetic energy perpendicular to the midplane of the deflectors using the electric potential. This implies that the energy of ions capable of±± 45° deflection is limited to approximately twice the applied voltage. Based on the insight, an approximate analytical solution has been derived, enabling the prediction of deflection efficiency for deflector shapes represented by power functions. For future development of space plasma analyzers, deflectors can now be designed with theoretical support, similar to the electrostatic analyzers. Graphical Abstract