Plane Of Lens Research Articles

Gravitational imaging through a triple source plane lens: revisiting the ΛCDM-defying dark subhalo in SDSSJ0946+1006

ABSTRACT The ΛCDM paradigm successfully explains the large-scale structure of the Universe, but is less well constrained on subgalactic scales. Gravitational lens modelling has been used to measure the imprints of dark substructures on lensed arcs, testing the small-scale predictions of ΛCDM. However, the methods required for these tests are subject to degeneracies among the lens mass model and the source light profile. We present a case study of the unique compound gravitational lens SDSSJ0946+1006, wherein a dark, massive substructure has been detected, whose reported high concentration would be unlikely in a ΛCDM universe. For the first time, we model the first two background sources in both I- and U-band HST imaging, as well as VLT-MUSE emission line data for the most distant source. We recover a lensing perturber at a 5.9σ confidence level with mass $\log _{10}(M_\mathrm{sub}/{\rm M}_{\odot })=9.2^{+0.4}_{-0.1}$ and concentration $\log _{10}c=2.4^{+0.5}_{-0.3}$. The concentration is more consistent with CDM subhaloes than previously reported, and the mass is compatible with that of a dwarf satellite galaxy whose flux is undetectable in the data at the location of the perturber. A wandering black hole with mass $\log _{10}(M_\mathrm{BH}/{\rm M}_{\odot })=8.9^{+0.2}_{-0.1}$ is a viable alternative model. We systematically investigate alternative assumptions about the complexity of the mass distribution and source reconstruction; in all cases the subhalo is detected at around the ≥5σ level. However, the detection significance can be altered substantially (up to 11.3σ) by alternative choices for the source regularization scheme.

Parameter-free Hubble constant from the quadruply lensed quasar SDSS J1004+4112

We present a free-form lens model for the multiply lensed quasar in the galaxy cluster SDSS J1004+4112. Our lens model draws minimal assumptions on the distribution of mass in the lens plane. We have paid particular attention to the model uncertainties on the predicted time delay originating from the particular configuration of model variables. Taking into account this uncertainty, we obtained a value of the Hubble constant of H0 = 74−13+9 km s−1 Mpc−1, which is consistent with recent independent estimates. The predicted time delay between the central image E and image C (the first to arrive) is ΔTE−C = 3200 ± 200 days for the estimated Hubble constant. Future measurements of ΔTE−C will allow for a tighter constraint to be imposed on H0 in this cluster-QSO system.

The sub-wavelength focusing of flexural waves achieved by splitting one plane lens into two halves with a controllable angle

The flexural wave focusing in plates and shells is of great importance for energy harvesting and vibration control. Traditional plane lens based on gradient index and metasurface usually exhibits normal focusing, i.e., the focusing spot size is larger than half wavelength. In order to improve its working performance, increase energy at the focal point, reduce the focusing spot size and further achieve subwavelength focusing, a novel design scheme is proposed, i.e., splitting one traditional plane lens into two halves with a controllable inner angle. Firstly, the transmission and phase are calculated by using the Timoshenko beam theory, utilizing which the lens design is finalized via changing beam thickness perpendicular to wave propagation. After that, the working performance of two sub-lenses is compared with that of one single lens via numerical simulations, including the focal position, energy distribution, and spot size, which are further validated through experimental measurements. It is demonstrated that the flexural wave can exhibit subwavelength focusing after traveling across two adjacent halves, with the focusing spot size smaller than half wavelength. Specifically, the subwavelength focusing is broadband, and still occurs in a frequency region centered at the designed frequency. The proposed design scheme is expected to provide an innovative approach for the lens design in acoustics and optics.

Polariton Microfluidics for Nonreciprocal Dragging and Reconfigurable Shaping of Polaritons.

Dielectric environment engineering is an efficient and general approach to manipulating polaritons. Liquids serving as the surrounding media of polaritons have been used to shift polariton dispersions and tailor polariton wavefronts. However, those liquid-based methods have so far been limited to their static states, not fully unleashing the promise offered by the mobility of liquids. Here, we propose a microfluidic strategy for polariton manipulation by merging polaritonics with microfluidics. The diffusion of fluids causes gradient refractive indices over microchannels, which breaks the symmetry of polariton dispersions and realizes the microfluidic analogue to nonreciprocal polariton dragging. Based on polariton microfluidics, we also designed a set of on-chip polaritonic elements to actively shape polaritons, including planar lenses, off-axis lenses, Janus lenses, bends, and splitters. Our strategy expands the toolkit for the manipulation of polaritons at the subwavelength scale and possesses potential in the fields of polariton biochemistry and molecular sensing.

Multiplexed terahertz multifocal metalens based on stretchable single-, dual-, and quad-axis synthetic rectangular optical sparse aperture

As ultrathin optical elements with subwavelength structures densely arranged, planar lens or called metalens can effectively focus incident wave. Due to the compact design and wide operating frequency of metalens, it becomes promising in applications like information encryption, imaging, and wireless communication fields. However, the fabrication of large-aperture metalens is still time-consuming and costly while the focusing performances are commonly tuned by introducing active materials requiring extra stimuli, such as laser and electrical pulses. In this study, five designs of metalenses with synthetic rectangular aperture are proposed and demonstrated with excellent focusing performances. By reconfiguring the synthetic aperture, focusing properties like focusing lengths, full width at half maximum values, and modulation transfer function can be tuned with great flexibility. With a polarization-dependent phase-shifting structure, the proposed metalens shows different focusing performances with incident wave under transverse magnetic field and transverse electric field modes. By utilizing spatial multiplexing, terahertz variable foci metalenses based on a stretchable single-, dual- and quad-axis synthetic rectangular optical sparse aperture are investigated to achieve tunable multifocal performances. These designs provide a novel strategy that can reconfigure the synthetic aperture with stretchable substrate to make metalens with multifunction and active tunability, which show promising applications in imaging, information encryption, and space telescope areas.

Light-field imaging from position-momentum correlations

Correlation plenoptic imaging (CPI) is a light-field imaging technique employing intensity correlation measurements to simultaneously detect the spatial distribution and the propagation direction of light. Compared to standard methods, in which light-field images are directly encoded in intensity, CPI provides a significant enhancement of the volumetric reconstruction performance in terms of both achievable depth of field and 3D resolution. In this article, we present a novel CPI configuration where light-field information is encoded in correlations between position and momentum measurements, namely, points on a given object plane and points of the Fourier plane of the imaging lens. Besides the fundamental interest in retrieving the properties of position-momentum correlation, the proposed scheme overcomes practical limitations of previously proposed setups, providing higher axial homogeneity and robustness with respect to the identification of reference planes.

Ultracompact computational spectroscopy with a detour-phased planar lens

Ultracompact computational spectroscopy with a detour-phased planar lens

Simple broadband planar acoustic lenses design with a velocity gradient structure

Compared to curved acoustic lens, planar acoustic lens fits better with other surfaces like human body or additional lenses due to its profile. Traditional planar lens designs such as Fresnel lens and metamaterial lens suffer from poor bandwidth in frequency and complexities in fabrication, limiting the use in medical ultrasound. By curing epoxy mixtures in a 3D-print mold, a simple planar lens planar lens is designed and tested with a velocity gradient matching layer. Its Total cost is no higher than 8 dollars. Since the focusing relies on material velocity instead of wavelength, it makes the single planar lens designed for 1 MHz functions from 0.5 to 1.2 MHz (82 %). For concept validation, transducers with single circular planar lens and a lens set are fabricated and compared to traditional lens design. At 1 MHz, single planar lens reaches a focal length of 64.24 mm, which is similar to traditional concave lens design but shows less near field effect and less prone to cavitation at the interface. The planar-lens-added lens set also shows similarity to traditional lens set including a shorter focal length, a smaller focal spot and a better directivity. With the merit of easy fabrication and less cost, the proposed planar lens design strategy has the potential to be a complement of Fresnel lenses and metamaterial lenses in medical treatment applications.

Planar Compound Eye Lens for Enhanced Light Extraction Efficiency in AlGaN‐Based Deep Ultraviolet LEDs

Total internal reflection prevents photons from escaping deep‐ultraviolet (DUV) LED, resulting in serious energy waste and reduced service life. To lift the limitation of extraction ability of AlGaN‐based DUV LEDs, an inspiration was drawn from biological visual systems with wide field, which have obtained highly optimized features through evolution. By reconfiguring planar compound eye lens (PCEL) on the n‐AlGaN surface utilizing bio‐inspired features acquired from praying mantis, light extraction efficiency (LEE) enhancement over 180% is demonstrated both for transverse electric (TE) and magnetic fields by finite difference‐time domain (FDTD) simulation. Owing to its ultrathin planar structure and compatibility of material, PCEL provides a pathway to improve energy utilization efficiency of DUV‐LED utilizing one‐step nanoimprint.

Multi-Objective Optimization of Injection Molding Process Parameters for Moderately Thick Plane Lens Based on PSO-BPNN, OMOPSO, and TOPSIS

Injection molding (IM) is an ideal technique for the low-cost mass production of moderately thick plane lenses (MTPLs). However, the optical performance of injection molded MTPL is seriously degraded by the warpage and sink marks induced during the molding process with complex historical thermal field changes. Thus, it is essential that the processing parameters utilized in the molding process are properly assigned. And the challenges are further compounded when considering the MTPL molding energy consumption. This paper presents a set of procedures for the optimization of injection molding process parameters, with warpage, sink marks reflecting the optical performance, and clamping force reflecting the molding energy consumption as the optimization objectives. First, the orthogonal experiment was carried out with the Taguchi method, and the S/N response shows that these three objectives cannot reach the optimal values simultaneously. Second, considering the experimental data scale, the back propagation neural network updated by the particle swarm optimization method (PSO-BPNN) was applied to establish the complex nonlinear mapping relationship between the process parameters and these three trade-off objectives respectively. Then, the Pareto optimal frontier of the multi-objective optimization problem was attained by multi-objective particle swarm optimization using a mutation operator and dominance coefficient algorithm (OMOPSO). And the competitive relationship between these objectives was further confirmed by the corresponding pairwise Pareto frontiers. Additionally, the TOPSIS method with equal weights was employed to achieve the best optimal solution from the Pareto optimal frontier. The simulation results yielded that the maximum values of warpage, sink marks, and clamping force could be reduced by 7.44%, 40.56%, and 5.56%, respectively, after optimization. Finally, MTPL products were successfully fabricated.

Virial coefficients of hard, two-dimensional, convex particles up to the eighth order

We calculated virial coefficients for hard ellipses, stadia, rectangles, planar lenses and rhombi up to the eighth order employing Mayer-sampling Monte Carlo simulations. We improved and extended available data for ellipses, stadia, and rectangles and provide virial coefficients for planar lenses and rhombi. The influence of the aspect ratio ν on the virial coefficients is discussed, including hard discs as the limit of ellipses, stadia, and planar lenses and hard squares as the limit of rectangles and rhombi with aspect ratio ν → 1 . In two dimensions, both in the limit ν → 0 and ν → ∞ , anisotropic figures approach hard needles. The dependence of reduced virial coefficients B ~ i = B i / B 2 i − 1 on the shape parameter α = B 2 ∗ − 1 , with B 2 ∗ = B 2 / V P and V P the particle area is analysed. The reduced virial coefficients B ~ i ( α ) are approximated as functions of the shape parameter employing third-order polynomials, enabling an interpolation for all aspect ratios ν.

Investigation of the Space-Variance Effect of Imaging Systems with Digital Holography

In classical Fourier optics, an optical imaging system is regarded as a linear space-invariant system, which is only an approximation. Especially in digital holography, the space-variance effect has a great impact on the image quality and cannot be ignored. Therefore, it is comprehensively investigated in this article. Theoretical analyses indicate that the space-variance effect is caused by linear frequency modulation and ideal low-pass filtering, and it can be divided into three states: the approximate space-invariance state, the high-frequency distortion state, and the boundary-diffraction state. Classical Fourier optics analysis of optical imaging systems only considers the first. Regarding the high-frequency distortion state, the closer the image field is to the edge, the more severe the distortion of high-frequency information is. As for the boundary-diffraction state, in addition to the distortion of high-frequency information in the margin, a prominent boundary-diffraction phenomenon is observed. If the space-variance effect of the imaging lens is ignored, we predict that no space-variance effect in image holography will occur when the hologram is recorded at the back focal plane of the imaging lens. Simulation and experimental results are presented to validate our theoretical prediction.

4D mmW/5G Metasurfaces and Wireless Sensors Combining Additive Manufacturing, Morphing and ML Technologies

The paper will introduce fully printed 4D metasurfaces and wireless sensors operating up to 5G/mmW frequency range. Multiple morphing (shape-changing) approaches will be presented for massively scalable additively manufactured implementations , while modulation, signal redirection and energy harvesting features will be thoroughly covered in terms of integrability, flexibility and power consumption requirements. The talk will also refer to multiple reconfigurable intelligent surfaces (RIS) being enabled by newly reported fully printed planar lenses (Rotman, Van Atta, …) and dielectric reflectarrays enabling ultra long interrogation ranges when combined with “zero-power” backscattering interrogation techniques. Major challenges of flexible hybrid electronic implementations as well as ultra-low-power printable structures for self-diagnostic and anti-counterfeiting packages will be discussed in depth and numerous ML techniques will be comparatively evaluated for their optimization, calibration and on-demand reconfigurability. The paper will conclude with fully printable mmW/5G RF modules for wireless sensing applications spanning a wide range of fully passive tags to energy autonomous long-range RFID systems and low-cost miniaturized tags for orientation and rotational sensing for VR applications as well as environmental sensing and structural health monitoring.

Grazing incidence to total internal reflection fluorescence structured illumination microscopy enabled by a prism telescope.

In super-resolution structured illumination microscopy (SR-SIM) the separation between opposing laser spots in the back focal plane of the objective lens affects the pattern periodicity, and, thus, the resulting spatial resolution. Here, we introduce a novel hexagonal prism telescope which allows us to seamlessly change the separation between parallel laser beams for 3 pairs of beams, simultaneously. Each end of the prism telescope is composed of 6 Littrow prisms, which are custom-ground so they can be grouped together in the form of a tight hexagon. By changing the distance between the hexagons, the beam separation can be adjusted. This allows us to easily control the position of opposing laser spots in the back focal plane and seamlessly adjust the spatial frequency of the resulting interference pattern. This also enables the seamless transition from 2D-SIM to total internal reflection fluorescence (TIRF) excitation using objective lenses with a high numerical aperture. In linear SR-SIM the highest spatial resolution can be achieved for extreme TIRF angles. The prism telescope allows us to investigate how the spatial resolution and contrast depend on the angle of incidence near, at, and beyond the critical angle. We demonstrate this by imaging the cytoskeleton and plasma membrane of liver sinusoidal endothelial cells, which have a characteristic morphology consisting of thousands of small, transcellular pores that can only be observed by super-resolution microscopy.

Graphene-Enabled Tunable Phase Gradient Metasurface for Broadband Dispersion Manipulation of Terahertz Wave.

With the increasing demand for the miniaturization and flexibility of optical devices, graphene-based metasurfaces have emerged as a promising ideal design platform for realizing planar and tunable electromagnetic or optical devices. In this paper, we propose a tunable metasurface with low-dispersion phase gradient characteristics that is composed of an array of double-layer graphene ribbons sandwiched with a thin insulating layer and a polymer substrate layer with a gold ground plane. As two typical proof-of-concept examples, metasurfaces act as a planar prism and a planar lens, respectively, and the corresponding performances of tunable broadband dispersion are demonstrated through full-wave simulation experiments. By changing the Fermi level of each graphene ribbon individually to introduce abrupt phase shifts along the metasurface, the broadband continuous dispersion effect of abnormal reflection and beam focusing is achieved within a terahertz (THz) frequency region from 3.0 THz to 4.0 THz, and the dispersion results can be freely regulated by reconfiguring the sequence of Fermi levels via the bias voltage. The presented graphene metasurface provides an avenue for the dispersion manipulation of a broadband terahertz wave and may have great prospects in the fields of optics, imaging, and wireless communication.

Techniques in pediatric refractive surgery.

Pediatric refractive surgery treats refractive errors and their associated comorbidities such as amblyopia and strabismus in special needs children intolerant of spectacles or contact lenses. Children with neurobehavioral disorders undergoing refractive surgery have improvements in visual acuity, communication, socialization, motor skills, adaptive behaviors, visual perception, and cognitive function. Contrary to adults, amblyopia is frequently an indication for refractive surgery in special needs children. Pediatric refractive surgery techniques modify ametropia at the corneal, anterior chamber, posterior chamber, and lens planes. This article will discuss the most common modalities used today in pediatric refractive surgery, including laser keratorefractive surgery, phakic intraocular lenses, and refractive lens exchange. Practical pearls are discussed for the implementation of pediatric refractive surgery, reviewing preoperative diagnostics, surgical techniques, and postoperative care.

Principles of self-calibration and visual effects for digital camera distortion

Abstract Producing accurate spatial data with stereo photogrammetric techniques is a challenging task, and the central projection of the space needs to be defined as closely as possible to its real form in each image taken for the relevant production. Interior camera parameters that define the exact imaging geometry of the camera and the exterior orientation parameters that locate and rotate the imaging directions in a coordinate system have to be known accurately for this correct definition. All distortions sourcing from lens and sensor planes and their recording geometry are significant as they are not suitable for detection with manual measurements. It is of vital importance to clearly understand the camera self-calibration concept with respect to the lens and the sensor plane geometry and include every possible distortion source as an unknown parameter in the calibration adjustments as they are all modellable systematic errors. In this study, possible distortion sources and self-calibration adjustments are explained in detail with a recently developed visualization software. The distortion sources investigated in the study are radial, tangential, differential scale, and axial skewing distortion. Thanks to the developed software, image center point, distorted grids, undistorted grids, and principal points were visualized. As a result, the most important element of obtaining accurate and precise photogrammetric productions is the correct definition of the central projection of the space for each image, and therefore, the study explains an accurate and robust procedure with the correct definition and use of correct camera internal parameters.

Exotic image formation in strong gravitational lensing by clusters of galaxies – IV. Elliptical NFW lenses and hyperbolic umbilics

ABSTRACT A source lying near a hyperbolic umbilic (HU) singularity leads to a ring-like image formation, constituting four images with high magnification factors and lying in a small region of the lens plane. Since (based on our earlier work) the observed number of HU image formations in cluster lenses is expected to increase in the future, it is timely to investigate them in more detail. Like fold and cusp singularities, HU also satisfies the magnification relation, i.e. the signed magnification sum of the four images equals zero. This work presents a detailed study of the HU magnification relation (Rhu) considering the elliptical Navarro–Frenk–White (eNFW) lens profile suitable for cluster scale dark matter haloes. Our results show that for an isolated eNFW lens, Rhu is more sensitive to ellipticity than its mass or concentration parameter. An ellipticity greater than 0.3 results in Rhu lying close to zero with a small scatter around it. A substructure near the HU image formation causes the average Rhu value to deviate from zero and increases the scatter, with the amount of deviation depending on the image type near which the substructure lies. However, a population of substructures in the lens plane (equivalent to the galaxies inside the cluster) does not significantly shift the average Rhu value from zero but increases the scatter around it. We find that Rhu ≃ 0 for HU image formation in the Abell 1703 cluster. Repeating this test in other clusters with HU formations can be a useful indicator of substructure in cluster haloes.

Much ado about no offset – characterizing the anomalous multiple-image configuration and the model-driven displacement between light and mass in the multiplane strong lens Abell 3827

ABSTRACT Abell 3827 is a unique galaxy cluster with a dry merger in its core causing a highly resolved multiple-image configuration of a blue spiral galaxy at zs = 1.24. The surface brightness profiles of four merging galaxies around zd = 0.099 complicate a clear identification of the number of images and finding corresponding small-scale features across them. The entailed controversies about offsets between luminous and dark matter have never been settled and dark matter characteristics in tension with bounds from complementary probes and simulations seemed necessary to explain this multiple-image configuration. We resolve these issues with a systematic study of possible feature matchings across all images and their impact on the reconstructed mass density distribution. From the local lens properties directly constrained by these feature matchings without imposing any global lens model, we conclude that none of them are consistent with expected local characteristics from standard single-lens-plane lensing, nor can they be motivated by the light distribution in the cluster. Inspecting complementary spectroscopic data, we show that all these results originate from an insufficient constraining power of the data and seem to hint at a thick lens and not at exotic forms of dark matter or modified gravity. If the thick-lens hypothesis can be corroborated with follow-up multiplane lens modelling, A3827 suffers from a full three-dimensional degeneracy in the distribution of dark matter because combinations of shearings and scalings in a single lens plane can also be represented by an effective shearing and a rotation caused by multiple lens planes.

Experimental realization of an ultra-thin and continuous scanning metasurface mimicking a Luneburg lens

Luneburg lens is traditionally a spherical dielectric with centro-symmetric and graded refractive index, which has been widely applied in civilian and military fields due to its outstanding abilities of focusing or collimating electromagnetic waves. However, the existing designs of Luneburg lens generally suffer from the disadvantages of bulkiness, complex fabrication process, and limited scanning angles, etc. Herein, a planar metasurface that could mimic the planar Luneburg lens is designed by utilizing the addition theorem. It has been experimentally verified that the Luneburg-like lens has large and continuous scanning angles from −52° to 52° at a frequency of 10 GHz if an excitation antenna is moved along a straight line. Besides, the total thickness of the proposed lens is only 3 mm and it has the advantages of low cost, ease of fabrication, as well as being isolated from the feeder. As a result, the proposed Luneburg-like lens has great potential values of being flexibly applied in numerous fields.