Vector Nature Research Articles

Multifunctional Spin Logic Operations in Graphene Spin Circuits

Spin-based computing, combining logic and nonvolatile magnetic memory, is promising for emerging information technologies. However, the realization of a universal spin logic operation, representing a reconfigurable building block with all-electrical spin-current communication, has so far remained challenging. Here, we experimentally demonstrate reprogrammable all-electrical multifunctional spin logic operations in a nanoelectronic device architecture, utilizing graphene buses for spin communication and mixing and nanomagnets for writing and reading information at room temperature. This device realizes a multistate spin-majority logic operation, which is reconfigured to achieve (n)and, (n)or, and xnor Boolean operations, depending on the magnetization of inputs. The results are in good agreement with the predictions from a spin-circuit model, providing an experimental demonstration of a spin-based logic unit that takes advantage of the vector nature of spin, as opposed to conventional scalar charge-based devices. These spin logic operations in large-area graphene are fully compatible with industrial fabrication processes and represent a promising platform for scalable all-electric spin-based logic-in-memory computing architecture.

Arbitrary Polarization Readout with Dual-Channel Neuro-Metasurfaces.

Polarization, as a vector nature of the electromagnetic wave, plays a fundamental role in optics. Determining the polarization state of light is required by many applications, spanning from remote sensing and material analysis to biology and microscopy. To achieve this goal, conventional methods necessitate cascading of multiple optical components and consequential measurements to estimate the Stokes parameters, rendering the entire optical system bulky, complex, and sensitive. Here a brand-new strategy is introduced for direct polarization readout based on dual-channel neuro-metasurfaces. Neuro-metasurfaces can independently manipulate two orthogonal linearly-polarized waves that can synthesize arbitrary polarization waves with a linear combination. By judiciously designing the output focus points, a unique polarization atlas is created that allows one-to-one correspondence from intensity ratio to polarization state. To implement this, polarization-sensitive metasurfaces are designed and the spatial layout is optimized using a diffractive neural network. The feasibility of this strategy is validated by numerical simulation and microwave experiments. These results pave a new avenue in realizing integrated and multifunctional detectors and demonstrate the potential of neuro-metasurfaces as an add-on for discomposing and composing spatial basis.

SIMULATION OF PRECISION PARAMETERS IN FINISH GEAR MILLING

The article describes a new approach to forecasting errors in the machining of gears based on the principles of superposition, the vector nature of the components of error and statistical method of mathematical modeling by Monte Carlo. The difference between the real shaping of the nominal (ideal) is the presence of deviations of the geometry of the real profiles from the nominal. The major tasks that need to be solved in the study of real regularities of morphogenesis are forecasting problem with a given accuracy errors occur. Analysis of mechanisms of formation of the errors of the gears indicates that basic errors of process systems operations gears are characterized by a random numerical values, which determine the amount and nature of occurrences in the corresponding integrated components that, in turn, interact to determine the investigated error of gears.

Vector Staircase Noise-Like Pulses in an Er/Yb-Codoped Fiber Laser

We report on the experimental observation of vector staircase noise-like pulses (NLPs) produced by an Er/Yb-codoped fiber laser with a nonlinear optical loop mirror (NOLM) as the saturable absorber (SA). The staircase NLPs consist of two rectangular pulses with different energies and durations, such that the two pulse widths both increase linearly with increasing pump power with an almost constant slope while the pulse amplitude remains constant, similar to the case with Dissipative Soliton Resonance pulses. The polarization rotation state of the staircase NLPs has also been investigated along with multiple polarization dynamic patterns, including group velocity locked and polarization locked states. We have also observed harmonic mode-locked (HML) staircase NLPs by carefully adjusting the orientation of the intra-cavity polarization at fixed pump power. It was found that the HML staircase NLPs were identical to the fundamental staircase NLPs as regards the vector character and the changes in pulse duration. The experimental results are expected to enrich understanding of the vector nature of staircase NLPs and may lead to a new laser source for material processing.

LEXICAL-SEMANTIC REPRESENTATION OF SOLIDARITY THROUGH COLLOCATIONS IN THE RUSSIAN AND GERMAN LANGUAGES

Purpose. The study is aimed at determining the general and linguocultural specific characteristics of the lexico-semantic representation of the phenomenon of solidarity in the Russian and German linguocultures through a multi-aspect analysis of verb collocations.
 Methodology. Collocations are considered as statistically stable phrases that reflect the language usage as well as the native speakers’ concept of solidarity. The structure, internal and external transitivity / intransitivity, objectivity, subjectivity, seriality, structural-semantic models, thematic codes, pragmatic component of the meaning of collocations are described. The established characteristics of the lexical-semantic representation of solidarity in two linguistic cultures are compared. The descriptive, comparative method, structural-semantic modeling, semantic, distributive analysis, classification method, quantitative calculations are used.
 Results. The vector nature of the keywords interlingual correspondence, the predominance of a positive presentation of solidarity in both languages are established; differences in the presentation of solidarity situations as initiated by the subject / involuntary, in frequency subject codes and a tendency to form a series of collocations, in lexical-semantic differentiation of various solidarity situations and grounds for a negative assessment of solidarity are identified.
 Practical implications. The results can be used in lexicographic practice, in research on related topics; in university courses on lexicology and semantics.

EVALUATION OF QUALITY INDICATORS OF FUNCTIONING CYBER PROTECTION MANAGEMENT SYSTEMS OF INFORMATION SYSTEMS

Evidence of the complexity of the cybersecurity problem is the rapid increase in the number of information security breaches and losses on cybersecurity threats combined with an increase in the average loss from each of the breaches. Therefore, it is necessary to create requirements for a cybersecurity system that could provide more opportunities in the choice of methods in the management of the protection of automated information systems.
 The task of determining the optimal quality indicators of information resource management systems of automated systems is one of the most important problems in designing integrated information security systems. This is due to the complexity of such systems, the presence of many variable parameters, and the complexity of calculating quality indicators. In addition, the determined quality indicators should not only ensure the optimality of the target function, but also the stability of the protection system in a wide range of external adverse effects. The problem is that the existing methods of calculating integrated quadratic estimates (IQE) do not take into account errors in determining quality indicators, as well as the vector nature of these indicators.
 The aim of this work is to solve problems (development of algorithms), which are a problem of optimization of stable protection management systems using vector objective functions. Based on the model of information management system protection of information resources in the form of an automatic control system, the method of forming integrated quadratic estimates (IQE) of control error is proposed. This method takes into account the weights of the estimates at the desired installation time and standard transfer functions. Algorithms for calculating IQE according to the modified Katz formula and Ostrom's method for arbitrary order control systems are developed, including vector representation of the objective function of the protection system. The vector penalty function is proposed and the algorithm of its calculation is developed to display the degree of infringement of conditions of stability of parameters of the system of protection by the Rauss-Hurwitz criterion.

Geometric Induction in Chiral Superfluids.

We explore the properties of chiral superfluid thin films coating a curved surface. Because of the vector nature of the order parameter, a geometric gauge field emerges and leads to a number of observable effects such as anomalous vortex-geometric interaction and curvature-induced mass and spin supercurrents. We apply our theory to several well-known phases of chiral superfluid ^{3}He and derive experimentally observable signatures. We further discuss the cases of flexible geometries where a soft surface can adapt itself to compensate for the strain from the chiral superfluid. The proposed interplay between geometry and chiral superfluid order provides a fascinating avenue to control and manipulate quantum states with strain.

Chirality of optical vortex beams reflected from an air-chiral medium interface.

Chirality plays an important role in understanding of the chiral light-matter interaction. In this work, we study theoretically and numerically the chirality of optical vortex beams reflected from an air-chiral medium interface. A theoretical model that takes into full account the vectorial nature of electromagnetic fields is developed to describe the reflection of optical vortex beams at an interface between air and a chiral medium. Some numerical simulations are performed and discussed. The results show that the chirality of the reflected vortex beams can be well controlled by the relative chiral parameter of the medium and is significantly affected by the incidence angle, topological charge, and polarization state of the incident beam. Our results provide new, to the best of our knowledge, insights into the interactions between optical vortex beams with chiral matter, and may have potential application in optical chirality manipulation.

A class of vectorial pseudo-Schell model sources with structured coherence and polarization

Scalar pseudo-Schell model sources present a degree of coherence depending only on the difference between the radial coordinates of the two considered points. Here we study a class of sources of this kind, but endowed with a vectorial nature. Such sources, as well as the beams they radiate, present structured coherence and polarization features. It is shown that the polarization pattern and the degree of polarization are not uniform across the beam section but remain invariant upon paraxial propagation. Different characteristics of the source and the radiated beam can be obtained by changing the source parameters. Some synthesis procedures are also proposed.

Real-time dynamics of noise-like vector pulses in a figure-eight fiber laser.

The vector nature of noise-like pulses (NLPs) in a figure-eight erbium-doped fiber laser based on the nonlinear amplifier loop mirror (NALM) configuration is experimentally investigated. After achieving the operation regime of NLPs, both the group velocity locked noise-like vector pulses (GVL-NLVPs) and the polarization locked noise-like vector pulses (PL-NLVPs) are observed in the cavity. By virtue of the dispersive Fourier transform (DFT) technique, their spectral evolution and the energy vibration are measured and analyzed in real time. We also obtain another state of noise-like vector pulses (NLVPs) with combined characteristics of GVL-NLVPs and PL-NLVPs. It is shown that the NLVPs are sensitive to the cavity birefringence. Our results would be beneficial to complement the understanding of vector dynamics of NLPs in ultrafast fiber lasers.

Tomographic measurement of dielectric tensors at optical frequency.

The dielectric tensor is a physical descriptor of fundamental light-matter interactions, characterizing anisotropic materials with principal refractive indices and optic axes. Despite its importance in scientific and industrial applications ranging from material science to soft matter physics, the direct measurement of the three-dimensional dielectric tensor has been limited by the vectorial and inhomogeneous nature of light scattering from anisotropic materials. Here, we present a dielectric tensor tomographic approach to directly measure dielectric tensors of anisotropic structures including the spatial variations of principal refractive indices and directors. The anisotropic structure is illuminated with a polarized plane wave with various angles and polarization states. Then, the scattered fields are holographically measured and converted into vectorial diffracted field components. Finally, by inversely solving a vectorial wave equation, the three-dimensional dielectric tensor is reconstructed. Using this approach, we demonstrate quantitative tomographic measurements of various nematic liquid-crystal structures and their fast three-dimensional non-equilibrium dynamics.

Snapshot polarimetric imaging in multi-view microscopy.

Polarimetric imaging allows for the vector nature of optical information across a scene to be obtained, with recent applications ranging from remote sensing to microscopy. In polarimetric microscopy in particular, different polarization states are conventionally achieved under time-division multiplexing strategies and are mainly subject to static phenomena. In the present work, we propose a cost-effective technique for polarization sensing with the possibility of real-time imaging microscopy. By modifying a commercial camera and replacing the conventional lens with an optical system that integrates a microscope objective and a lenslet array with a polarization mask, linear Stokes parameters can be obtained in a snapshot. The proposed scheme is robust against misalignment and suitable for handling video sequences of microscopic samples. To the best of our knowledge, this is the first report on combining multi-view sensing and polarization imaging for applications to microscopy.

Quantitative Jones matrix imaging using vectorial Fourier ptychography.

This paper presents a microscopic imaging technique that uses variable-angle illumination to recover the complex polarimetric properties of a specimen at high resolution and over a large field-of-view. The approach extends Fourier ptychography, which is a synthetic aperture-based imaging approach to improve resolution with phaseless measurements, to additionally account for the vectorial nature of light. After images are acquired using a standard microscope outfitted with an LED illumination array and two polarizers, our vectorial Fourier ptychography (vFP) algorithm solves for the complex 2x2 Jones matrix of the anisotropic specimen of interest at each resolved spatial location. We introduce a new sequential Gauss-Newton-based solver that additionally jointly estimates and removes polarization-dependent imaging system aberrations. We demonstrate effective vFP performance by generating large-area (29 mm2), high-resolution (1.24 μm full-pitch) reconstructions of sample absorption, phase, orientation, diattenuation, and retardance for a variety of calibration samples and biological specimens.

A two-directional vibrational probe reveals the distinct electric field orientation at the active site of liver alcohol dehydrogenase

An increasing amount of evidence has shown that the extraordinary catalytic power of enzymes arises in part from large and pre-oriented electric fields at the active sites exerted by precisely positioned functional groups. While the field magnitudes at several enzyme’s active sites have been studied previously, the field orientation, an equally crucial quantity due to the vectorial nature of electric fields, has not been experimentally accessible despite extensive computational studies highlighting its critical role in electrostatic and enzymatic catalysis.

Multi-freedom metasurface empowered vectorial holography

Abstract Optical holography capable of the complete recording and reconstruction of light’s wavefront, plays significant roles on interferometry, microscopy, imaging, data storage, and three-dimensional displaying. Conventional holography treats light as scalar field with only phase and intensity dimensions, leaving the polarization information entirely neglected. Benefiting from the multiple degrees of freedom (DOFs) for optical field manipulation provided by the metasurface, vectorial holography with further versatile control in both polarization states and spatial distributions, greatly extended the scope of holography. As full vectorial nature of light field has been considered, the information carried out by light has dramatically increased, promising for novel photonic applications with high performance and multifarious functionalities. This review will focus on recent advances on vectorial holography empowered by multiple DOFs metasurfaces. Interleaved multi-atom approach is first introduced to construct vectorial holograms with spatially discrete polarization distributions, followed by the versatile vectorial holograms with continuous polarizations that are designed usually by modified iterative algorithms. We next discuss advances with further spectral response, leading to vivid full-color vectorial holography; and the combination between the far-field vectorial wavefront shaping enabled by vectorial holography and the near-field nano-printing functionalities by further exploiting local polarization and structure color responses of the meta-atom. The development of vectorial holography provides new avenues for compact multi-functional photonic devices, potentially useful in optical encryption, anticounterfeiting, and data storage applications.

The flow of the Berry curvature vector field

The concept of Berry phase and Berry curvature has become ubiquitous in solid state physics as it relates to variety of phenomena, such as topological insulators, polarization, and various Hall effects. It is well known that large Berry curvatures arise from close proximity of hybridizing bands, however, the vectorial nature of the Berry curvature is not utilized in current research. On bulk bcc Fe, we demonstrate the flow of the Berry curvature vector field which features not only monopoles but also higher dimensional structures with its own topological features. They can provide a novel unique view on the electronic structure in all three dimensions. This knowledge is also used to quantify particular contributions to the intrinsic anomalous Hall effect in a simple analytical form.

Information advantage from polarization-multiplexed readout of nanophotonic scattering overlay sensors

Nanophotonic structures are powerful tools for sensing, with the goal of retrieving parameters accurately at maximum speed and minimum photon budget. As information on those parameters can be distributed over multiple output scattering channels that propagate to the far field, considering well-chosen combinations of far-field optical degrees of freedom could benefit measurement precision. We explore how multiplexing readout across different polarization channels enhances parameter retrieval in nanophotonic overlay sensors. We measure the relative position between layers with nanoscale scattering structures, known as overlay in semiconductor metrology, and show that multiplexing either incident or analyzed polarization leads to improved parameter retrieval in the systems studied. At fixed photon budget, we extract additional information equivalent to more than 7 dB in signal level. These results demonstrate that significant advantages in measurement performance of nano-optical sensors can be gained by exploiting the vectorial nature of optical fields.

Reconstruction of finite deep sub-wavelength nanostructures by Mueller-matrix scattered-field microscopy.

Computational super-resolution is a novel approach to break the diffraction limit. The Mueller matrix, which contains full-polarization information about the morphology and structure of a sample, can add super-resolution information and be a promising way to further enhance the resolution. Here we proposed a new approach called Mueller-matrix scattered-field microscopy (MSM) that relies on a computational reconstruction strategy to quantitatively determine the geometrical parameters of finite deep sub-wavelength nanostructures. The MSM adopts a high numerical-aperture objective lens to collect a broad range of spatial frequencies of the scattered field of a sample in terms of Mueller-matrix images. A rigorous forward scattering model is established for MSM, which takes into account the vectorial nature of the scattered field when passing through the imaging system and the effect of defocus in the measurement process. The experimental results performed on a series of isolated Si lines have demonstrated that MSM can resolve a feature size of λ/16 with a sub-7 nm accuracy. The MSM is fast and has a great measurement accuracy for nanostructures, which is expected to have a great potential application for future nanotechnology and nanoelectronics manufacturing.

Arbitrary polarization and orbital angular momentum generation based on spontaneously broken degeneracy in helically twisted ring-core photonic crystal fibers.

Using orbital angular momentum (OAM) as a spatial information channel attracts a lot of attention due to its infinite multiplexing capability. The research on OAM carrying fibers is intensively studied and ring-core fibers are promising candidates for them. At the same time, generating OAM modes in those fibers are also important topic. Here, the evolutions of polarization states including OAM of light in helically twisted ring-core photonic crystal fibers (PCFs) are investigated for generating OAM states. The degeneracy of some of the mode sets is spontaneously broken, and the birefringence cause a geometric phase (GP) in the twisted PCFs while preserving the vectorial nature of the modes. It is demonstrated that an arbitrary polarization and OAM state can be generated by using the GP in uniformly twisted and twisted PCFs with periodical inversion. In the ring-core PCF presented in this paper, the degeneracy of HE31 and EH31 mode sets are broken, and OAM light with the topological charge of 2 and 4 can be generated. The wavelength dependence is very small compared with that of OAM generators based on long-period gratings (LPGs). Furthermore, by properly setting the period of the inversion, OAM light with different topological charges can be simultaneously generated with the same fiber structure. These results indicate that the proposed approach is effective for the generation of OAM modes with the conventional fiber modes.

All-optical encryption by a heterodyne Kerr gate in multilayer reduced graphene oxide decorated with Pt nanoparticles

Herein is reported how the inhibition of the imaginary part of the electrical impedance exhibited by reduced graphene oxide (rGO) yields to stronger conductivity together to an enhancement in its optical nonlinearities. A highly uniform incorporation of plasmonic nanoparticles in the samples was identified to be responsible for the observed effects, while protoplasmatic nanoparticles or random decoration did not promote any important change in the studied parameters. Platinum particles featuring approximately 3 nm in average size were homogeneously decorated on the surfaces of rGO following a two-steps growth procedure. The vectorial nature in the third-order nonlinear optical response exhibited by rGO decorated with platinum nanoparticles (Pt/rGO) was analyzed by a two-wave mixing experiment. Interferometric irradiance and polarization patterns seem to generate different physical mechanisms responsible for the nonlinear refractive index exhibited by the nanostructures. An ablation threshold of 0.35 J/cm 2 was measured. The contrast in the superposition of two-input binary polarized optical signals was employed to propose an exclusive disjunctive logic gate based on a heterodyne optical Kerr gate. The polarization-selectable multi-photonic properties were explored by nanosecond pulses at 532 nm wavelength and a straightforward XOR encryption function was designed. The optical Kerr effect exhibited by Pt/rGO can be contemplated for developing all-optical switching devices. Immediate applications for encrypting and processing ultrafast functions can be also considered. • Excellent dispersion of Pt nanoparticles in reduced graphene oxide is reported. • Inhibition of the imaginary part in the electrical impedance was obtained. • An enhancement in optical nonlinearities in Pt decorated rGO is presented. • Kerr signals for controlling all-optical encryption were analyzed.