Spherical Reference Research Articles

Steady state oscillations of circular currents in concentric polariton condensates

Concentric ring exciton polariton condensates emerging under non-resonant laser pump in an annular trapping potential support persistent circular currents of polaritons. The trapping potential is formed by a cylindrical micropillar etched in a semiconductor microcavity with embedded quantum wells and a repulsive cloud of optically excited excitons under the pump spot. The symmetry of the potential is subject to external control via manipulation by its pump-induced component. In the manuscript, we demonstrate excitation of concentric ring polariton current states with predetermined vorticity which we trace using interferometry measurements with a spherical reference wave. We also observe the polariton condensate dynamically changing its vorticity during observation, which results in pairs of fork-like dislocations on the time-averaged interferogram coexisting with azimuthally homogeneous photoluminescence distribution in the micropillar.

Research on Shape Adjustment of Large Aperture Reflector Based on Differential Equation

The FAST active reflector can transform the reference state's spherical surface into the working condition's parabolic surface by adjusting the system so that the radio telescope has high sensitivity. This paper mainly studies the structure of the ideal paraboloid in the working state and the influence of various factors of the adjustment system on signal reception. The primary cable node distribution model is established based on the paraboloid equation and coordinate rotation. The optimization model, the difference method and the stochastic simulation are used to solve the problem. Firstly, the ideal paraboloid focus selection range is determined as an interval near the feed cabin according to the properties of the focused parallel rays of the paraboloid and the receiving area as the central disk. At the same time, considering the adjustment factors of the reflective panel, the ideal paraboloid endpoint is given. With the constraint interval, an optimization model can be established for the two variables, the distance d from the focal point to the feed cabin and the z-coordinate b of the vertex of the ideal parabola, with the perfect paraboloid and the reference sphere as close as possible as the objective function. It is formed by rotating around the central axis. Therefore, to simplify the operation, the plane because is selected to analyze the ideal parabola, and finally, the optimal solution is obtained by using the two-dimensional grid search algorithm as , , The resulting ideal paraboloid equation is . The FAST active reflector can transform the reference state's spherical surface into the working condition's parabolic surface by adjusting the system so that the radio telescope has high sensitivity. This paper mainly studies the structure of the ideal paraboloid in the working state and the influence of various factors of the adjustment system on signal reception. The primary cable node distribution model is established based on the paraboloid equation and coordinate rotation. The optimization model, the difference method and the stochastic simulation are used to solve the problem.The average vector of each reflective panel can be obtained according to Cramer's law. Then according to the reflection properties of the wave, the direction vector of the reflected electromagnetic wave can be obtained from the incident electromagnetic wave and the average vector. The end of the panel is projected to the feed along the direction of the reflected electromagnetic wave. The cabin's plane can obtain the area reflected from each panel to the plane of the feed cabin. To simplify the calculation and improve efficiency, the Monte Carlo stochastic simulation algorithm is used to obtain the reflected signal receiving ratio of the working paraboloid. The receiving ratio is that the signal receiving the effect of the working paraboloid is much better than that of the reference reflective spherical surface.

Inverse Design of Focused Vector Beams for Mode Excitation in Optical Nanoantennas

We propose a free-space, inverse design of nanostructure's effective mode-matching fields via a backward propagation of tightly focused vector beams to the pupil plane of an aplanatic system of high numerical aperture. First, we study the nanostructure's eigenmodes without considering any excitation fields and then extract the modal near fields in the focal plane. Each modal field is then taken as the desired focal field, the band-limited waves of which are backward propagated to the pupil plane via a reversal of the Richards--Wolf vector diffraction formula. The pupil fields can be designed to be genuinely paraxial by associating the longitudinal electric/magnetic field component with the radial one on the reference sphere. The inversely designed pupil field in turn is propagated forwardly into the focal region to generate the designed focal field, whose distribution over the nanostructure's surface is used to evaluate the overlap between the designed focal field and the modal fields, i.e., the modal expansion coefficients. Studies for a silicon nanodisk monomer, dimer, and tetramer demonstrate the ability of our inverse approach to design the necessary tightly focused vector field that can effectively and exclusively match a certain eigenmode of interest. Compared with the forward beam-shaping method, the inverse design approach tends to yield quantitatively more precise mode-matching field profiles. This work can have a significant impact on optical applications that rely on controllable and tunable mode excitation and light scattering.

Study of a Shack-Hartmann wavefront sensor with adjustable spatial sampling based on spherical reference wave

For the astronomical adaptive optics systems, the observation condition is constantly changing or in a regime of low photon flux. Besides, for various brightness seeing conditions, the Shack-Hartmann wavefront sensor has a matching spatial sampling that avoids extra wavefront reconstruction error. To integrate advantageous spatial samplings, we propose a novel Shack-Hartmann wavefront sensor with adjustable spatial sampling (ASS-WFS) based on spherical reference wave. In principle, only a simple movement of the microlens array (MLA) and the CCD detector in the direction of the optical axis is required to achieve variable spatial sampling. This is also obviously advantageous in the adaptive optics performance as it allows the wavefront sensor to dynamically match brightness of the observation. To demonstrate the performance of the ASS-WFS, we present the sensor in terms of the principles, the simulation, and the experiment. Results show that the ASS-WFS is able to precisely measure and reconstruct the wavefront, and also demonstrate that advantages resulting from adjusting the spatial samplings can efficiently reduce the disadvantages of low signal-to-noise ratio to boost wavefront reconstruction accuracy.

λ-Spheres as a New Reference Model for Geoid: Explicit Solutions of the Direct and Inverse Problems for Loxodromes (Rhumb Lines)

In this paper, we present a new reference model that approximates the actual shape of the Earth, based on the concept of the deformed spheres with the deformation parameter λ. These surfaces, which are called λ-spheres, were introduced in another setting by Faridi and Schucking as an alternative to the spheroids (i.e., ellipsoids of revolution). Using their explicit parametrizations that we have derived in our previous papers, here we have defined the corresponding isothermal (conformal) coordinates as well as obtained and solved the differential equation describing the loxodromes (or rhumb lines) on such surfaces. Next, the direct and inverse problems for loxodromes have been formulated and the explicit solutions for azimuths and arc lengths have been presented. Using these explicit solutions, we have assessed the value of the deformation parameter λ for our reference model on the basis of the values for the semi-major axis of the Earth a and the quarter-meridian mp (i.e., the distance between the Equator and the North or South Pole) for the current best ellipsoidal reference model for the geoid, i.e., WGS 84 (World Geodetic System 1984). The latter is designed for use as the reference system for the GPS (Global Positioning System). Finally, we have compared the results obtained with the use of the newly proposed reference model for the geoid with the corresponding results for the ellipsoidal (WGS 84) and spherical reference models used in the literature.

Evaluation of cilazapril release profiles with the use of lignin-based spherical particles

The main focus of this study is the preparation of lignin-based spherical particles as drug delivery systems. First, particles were prepared with the use of kraft lignin and the cationic surfactant hexadecyl (trimethyl)ammonium bromide (CTAB), and their physicochemical and structural characteristics were also determined. It was observed that the particles had a spherical shape and a low polydispersity index (PdI). The lignin particles were combined with the active compound cilazapril (CIL), and the system was tested for its drug-releasing ability. Cilazapril was combined with kraft lignin or lignin-based spherical particles to prepare different formulations. Mixtures with cilazapril as a reference (CIL-DB), kraft lignin (LIG-DB) and lignin-based spheres (LC-DB) were prepared with the use of a liquid base to obtain suspensions. The dialysis bag method was employed for the evaluation of drug release profiles. Release tests were performed at three pH values: 2.0, 5.8 and 6.8. It was observed that the lignin-based material is pH-sensitive, and better results were obtained at low or high pH values. The LC-DB formulation exhibited the best dissolution rates in all pH ranges. At pH 2.0, 5.8 and 6.8 the maximum release of cilazapril was around 80%, 62% and 90%, respectively. Lignin-based spherical particles enabled more efficient, sustainable and controlled release of cilazapril and may therefore have a potential for use in the medical industry, especially in drug delivery systems.

Inline holography of miniaturized objects with an intrinsic reference angle determined by the sagitta

The twin image problem, well known in Gabor holography, greatly obstructs the output of high-quality holograms. Previous solutions include numerical and instrumental means to eliminate or mitigate the issue. The proposed method demonstrates the feasibility of using the sagitta angle in a spherical reference beam as an intrinsic reference angle within in-line holography. Along with a miniaturized version of the object, to allow for a wide range of object sizes, from millimeters to meters, with a small variation within the original optical system. The inherent reference angle allows for a separation of the twin images in the reconstruction of a Gabor hologram, while maintaining the system on axis. Under lens-less Fourier criteria, the peripheral information of the visual field interferes with a spherical wave to generate an interference pattern that results in a hologram with separated images.

Point diffraction interferometer based on a silicon nitride waveguide spherical wave source.

A point diffraction interferometer based on silicon nitride waveguide (WG-PDI), adopting a silicon nitride waveguide spherical wave source (WG-SWS) with Si substrate and SiO2 cladding, is proposed for spherical surface testing. The WG-SWS is used to overcome the drawbacks of the existing spherical wave sources, which can generate high accuracy and high numerical aperture spherical reference wave. In this paper, the theory of the WG-PDI is described, and the possible errors introduced by the device are analyzed. In addition, the lateral deviation between the curvature center of the test wave and the curvature center of the reference wave cannot be eliminated in the reflected configuration of the pinhole diffraction interferometer. After analyzing the influence of the systematic error introduced by the lateral deviation, the semi-reflective film was coated on the output facet of the waveguide spherical wave source to realize point diffraction interference without lateral deviation. Finally, the surface error of a spherical surface was measured by WG-PDI. The experimental results agree well with those measured by the ZYGO interferometer.

Construction of the Guide Star Catalog for Double Fine Guidance Sensors Based on SSBK Clustering.

In the Chinese Survey Space Telescope (CSST), the Fine Guidance Sensor (FGS) is required to provide high-precision attitude information of the space telescope. The fine star guide catalog is an essential part of the FGS. It is not only the basis for star identification and attitude determination but also the key to determining the absolute attitude of the space telescope. However, the capacity and uniformity of the fine guide star catalog will affect the performance of the FGS. To build a guide star catalog with uniform distribution of guide stars and catalog capacity that is as small as possible, and to effectively improve the speed of star identification and the accuracy of attitude determination, the spherical spiral binary K-means clustering algorithm (SSBK) is proposed. Based on the selection criteria, firstly, the spherical spiral reference point method is used for global uniform division, and then, the K-means clustering algorithm in machine learning is introduced to divide the stars into several disjoint subsets through the use of angular distance and dichotomy so that the guide stars are uniformly distributed. We assume that the field of view (FOV) is 0.2° × 0.2°, the magnitude range is 9∼15 mag, and the threshold for the number of stars (NOS) in the FOV is 9. The simulation shows that compared with the magnitude filtering method (MFM) and the spherical spiral reference point brightness optimization algorithm (SSRP), the guide star catalog based on the SSBK algorithm has the lowest standard deviation of the NOS in the FOV, and the probability of 5∼15 stars is the highest (over 99.4%), which can ensure a higher identification probability and attitude determination accuracy.

Applicability Assessment of Different Materials for Standards Ensuring Comparability of Optical and Tactile Coordinate Measurements.

Multisensor CMMs are systems with an established position on the market, but their popularity still grows, as they provide access to the advantages offered by tactile and contactless measurement methods. Yet there are still questions of the comparability of results obtained using the optical and tactile operation modes of multisensor system. This phenomenon can be assessed by measuring appropriate gauges, most often reference rings or spheres. Due to the completely different nature of probing processes for tactile and contactless measurements, the material from which reference object is made may significantly affect measurement results. In order to assess the influence of this factor on measurement accuracy, three reference spheres made from different materials were measured on optical multisensor CMMs. Measurements involved tactile measurements as well as optical measurements made using different probing systems: a video probe and white light sensor. Results obtained from performed experiments show large differences depending on the material used for spherical standard production. On the basis of obtained results, it can be stated that the best material for a reference object that can be used for comparability tests of tactile and optical measurements is a composite of alumina with at least one oxidic additive.

Error correction algorithms in non-null aspheric testing next generation sequencing data

Non-null tests are more versatile than null tests and could give fast, generic tests with sufficient performance. The non-null testing methods are able to measure aspheric surfaces with substantial deviations from a reference sphere. The ray will return along a different path and interfere with a separate reference ray in a non-null arrangement. The retrace error occurs because of the significant disparity between the aspheric and the reference. To correct retracing errors and replicate aspheric fabrication imperfections, complex systems modelling and simulations are required. We propose a ray-tracing-based technique for simulating the non-null interferometer that estimates the optical path differences by tracking lasers across the reference and testing paths. An error correction method is used by ray trace analysis to correct the retracing errors in non-null tests of aspheric surfaces. Experiments were conducted to demonstrate the effectiveness of this strategy. The result of the study shows that the proposed system successfully and effectively rectifies the retracing error compared to other practical findings and computer simulation methods. It is more versatile, faster, and provides adequate aspheric assessment performance.

Lensless Fourier-Transform Terahertz Digital Holography for Full-Field Reflective Imaging

Continuous-wave terahertz digital holography (TDH) is a full-field lensless phase imaging approach usually with the coherent THz laser. It has the potential to be applied to nondestructive testing. In order to simplify the reconstruction and utilize the THz radiation with higher efficiency, a full-field reflective lensless Fourier-transform TDH (RLF-TDH) configuration is proposed with oblique illumination mode based on 2.52 THz radiation. A spherical reference beam is generated by a reflective concave mirror in order to reduce the loss of THz radiation, which is different from other configurations of the same kind. In the reconstruction process, the complex-amplitude image can be obtained by directly applying single Fourier transform to the digital hologram; thus, it is very possible to achieve real-time imaging. A tilted plane correction method is implemented to correct the anamorphism caused by the nonparallel planes between the object and recording plane. The profile information of the object can be measured from the unwrapped, aberration-free phase image. Two reflective gold-coated samples are adopted to demonstrate the validity of the RLF-TDH imaging system.

Lensless Fourier-transform terahertz digital holography for real-time full-field phase imaging

With the development of continuous-wave terahertz (THz) sources and array detectors, the pursuit of high-fidelity real-time imaging is receiving significant attention within the THz community. Here, we report a real-time full-field THz phase imaging approach based on lensless Fourier-transform THz digital holography. A triangular interferometric layout is proposed based on an oblique illumination of 2.52 THz radiation, which is different from other lensless holographic configurations at other frequencies. A spherical reference beam is generated by a reflective parabolic mirror with minor propagation loss. The complex-valued images are reconstructed using a single inverse Fourier transform of the hologram without complex calculation of the diffraction propagation. The experimental result for a Siemens star validates the lateral resolution of ∼ 346 μm in the diagonal direction. Sub-pixel image registration and image stitching algorithms are applied to enlarge the area of the reconstructed images. The dehydration process of an aquatic plant leaf (Hottonia inflata) is monitored for the first time, to the best of our knowledge, at the THz band. Rapid variations in water content and morphology are measured with a time interval of 0.6 s and a total time of 5 min from a series of reconstructed amplitude and phase images, respectively. The proposed method has the potential to become a powerful tool to investigate spontaneous phenomena at the THz band.

Multi-Objective Optimization Model and Genetic Algorithm Based on "FAST" Active Reflecting Surface Dynamic Optimization Research

FAST requires the active reflector to be dynamically adjusted to an ideal paraboloid in real time when tracking the celestial motion, but the real paraboloid is not ideal due to the interconnection of the main cable nodes and the adjustment constraint of the reflector panel. First, the ideal paraboloid is determined when the object S is located directly above the reference sphere, and the reflecting panel adjustment is considered.

Research on FAST Optimum Parabolic Surface Based on Active Reflection

For the problem, to obtain the best-receiving effect of celestial electromagnetic waves reflected by the reflective surface, analyze the celestial body S directly above the reference spherical surface, to make all the reflected light reach the feed bin, according to the question given parameters, this paper establishes a space rectangular coordinate system at the center of the reference sphere and designs the parameter equation. By analyzing the relationship between the physics and geometry of the reflecting surface, the optimal paraboloid function is obtained.

Analysis of Russian Foreign Action Decision-Making under Prospect Theory

Prospect theory, as a meso-theory of foreign policy-making, has shown unique advantages in analyzing foreign policy-making problems. The Russian-specific complex frame of reference plays an important role in decision-making on high-political issues, framing itself in a constant-loss framework through complex reference dependence, and thus exhibiting dynamic loss characteristics. The Russian complex frame of reference is a three-dimensional dynamic framework consisting of four main reference spheres: the Slavic ethnic sphere, the Orthodox cultural belt, the collection of Russian-speaking communities, and the focus of geopolitical interests, and thus exhibits different subjective value judgments, i.e., psychological reactions. The compounding of the different spheres leads to a superimposed effect in framing Russia's situation and to a strong representation of its behavioral responses.

The Wavefront Power Spectral Density Measurement of Aspheric Lens with Long Focal-Length Using a Computer-Generated Hologram

To ensure the performance of the optical system, the machining accuracy of lens with long focal lengths is required to ensure the image quality. A new method for lens transmission wavefront power spectral density (PSD) in mid-frequency domain measurement using binary phase computer-generated hologram (CGH) is presented. This technique is widely applicable and is particularly useful for measuring large-size lenses with long focal lengths. A comparison experiment of the CGH measurement with results from a Fizeau sphere interferometry method is carried out to verify the accuracy and convenience of the measurement. Furthermore, measurement uncertainty due to CGH fabrication process is analysed. Analysis of the CGH test showed the overall accuracy of less than 1 nm RMS for a sphere lens with over 30 m focal length and Φ410 mm clear aperture. CGH can provide reference spheres with high precision, in the meantime greatly shorten air space, thus reducing the effect of vibration and air turbulence, therefore is of great importance for lens transmission wavefront PSD measurement. The realization of high precision, high efficiency and nondestructive testing of long focal-lens wavefront PSD ensure the ultra-precision and certainty level of machining, hence improving the comprehensive performance of the optical system.

Rough-Surface Polarimetry in Companion SAR Missions

Bistatic scattering from rough surfaces is typically approached through the analysis of the scattered field in the conventional H and V polarization basis, which coincides with the zenith and azimuth unit vectors in a spherical reference frame. This study delves into the impacts of different choices of the transmit and receive linear basis on the performance and design of a synthetic aperture radar (SAR) mission receive-only companion. This article formalizes the rotation of the scattered wave orientation at the antenna axes of the companion with respect to the transmitted one and introduces a novel set of linear polarizations, named principal polarizations, in transmit and receive, deemed more suited to represent the scattering mechanisms of rough surfaces. Such a set is defined by the polarization bases that maximize the radar cross section. It is shown that the theoretical estimates from the proposed geometrical framework provide a good agreement with analytical and numerical simulations, performed considering state-of-the-art numerical solutions. In addition, this article promotes the hypothesis that a bistatic radar configuration, defined through the conventional H and V linear basis, presents a strong similarity, from a target information retrieval standpoint, to a monostatic compact <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varphi $ </tex-math></inline-formula> -pol mode, i.e., with the transmission of a linear polarization rotated by an angle <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varphi $ </tex-math></inline-formula> . The rotation <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\varphi $ </tex-math></inline-formula> varies over the swath and as a function of satellite separation. For baselines of 250–300 km, such as those envisioned by the European Space Agency (ESA) Harmony Earth Explorer candidate, and for steep incidence angles, an equivalent <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi /8$ </tex-math></inline-formula> -pol can be achieved for rough surfaces.

NEW VISION OF CONCEPT EUROPE (A LINGUISTIC PERSPECTIVE)

This article presents a study of the concept EUROPE, done in the area of cognitive linguistics. The concept EUROPE is considered a conceptual quantum of structured knowledge, possessing of different meanings. The article analyzes the concept EUROPE from a linguistic point of view, which allowed to reveal a number of specific features of its semantics, to get a more comprehensive and diverse view of it by constructing cognitive schemes implementing concept EUROPE, as well as to identify basic metaphorical models. Involvement of methods of conceptual analysis allows to present the analised concept in the form of a certain conceptual model, a special way organized conceptual scheme. With the help of the conceptual model of the Subject frame the cognitive dynamics of the concept development in the European integration discourse is revealed.&#x0D; Political metaphor is one of the most common and effective policy tools. The research material is characterized by the use of metaphors belonging to such basic types, which are related to the reference spheres as the sociomorphic sphere, the anthropomorphic sphere, the sphere of artifacts and the sphere of nature. Conceptual metaphors of European integration discourse use in their codes the conceptual fields “space”, “travel”, “movement”, “construction”, “work results”, “family relations”, “nature”, “sports”, “art”, etc.

Interferometric microscope with a confocal focusing for inner surface defect detection of ICF capsule.

Inner surface defects of inertial confinement fusion (ICF) capsule are a key factor leading to ignition failure; however, there are still no effective and non-destructive detection methods available. To solve this problem, we propose the first interferometric microscope with confocal focusing (CFIM). CFIM first uses confocal technology to achieve accurate axial positioning of both capsule and the camera, thereby ensuring that the inner surface of the capsule is precisely and clearly imaged at the camera. Then, phase-shifting interferometry based on a short-coherence source and a spherical reference is applied to obtain inner defects result from null inner surface interferograms. In addition, in-situ focusing is realized by the axial adjustment of camera, but not by the capsule, to ensure that the outer defects and the fake inner defects caused by it have the same pixel coordinates, thereby solving the confusion of fake inner defects. The comparative experimental results of the CFIM and the scanning electron microscope (destructive detection) prove the feasibility of the proposed method. With unique precision confocal focusing and in-situ focusing ability, CFIM provides the first approach for non-destructive detection of inner surface defects of ICF capsule to the best of our knowledge.