Specific Polarization Research Articles

Deterministic Approach to Achieve Full-Polarization Cloak.

Achieving full-polarization (σ) invisibility on an arbitrary three-dimensional (3D) platform is a long-held knotty issue yet extremely promising in real-world stealth applications. However, state-of-the-art invisibility cloaks typically work under a specific polarization because the anisotropy and orientation-selective resonant nature of artificial materials made the σ-immune operation elusive and terribly challenging. Here, we report a deterministic approach to engineer a metasurface skin cloak working under an arbitrary polarization state by theoretically synergizing two cloaking phase patterns required, respectively, at spin-up (σ+) and spin-down (σ−) states. Therein, the wavefront of any light impinging on the cloak can be well preserved since it is a superposition of σ+ and σ− wave. To demonstrate the effectiveness and applicability, several proof-of-concept metasurface cloaks are designed to wrap over a 3D triangle platform at microwave frequency. Results show that our cloaks are essentially capable of restoring the amplitude and phase of reflected beams as if light was incident on a flat mirror or an arbitrarily predesigned shape under full polarization states with a desirable bandwidth of ~17.9%, conceiving or deceiving an arbitrary object placed inside. Our approach, deterministic and robust in terms of accurate theoretical design, reconciles the milestone dilemma in stealth discipline and opens up an avenue for the extreme capability of ultrathin 3D cloaking of an arbitrary shape, paving up the road for real-world applications.

De-scattering method of underwater image based on imaging of specific polarization state

De-scattering method of underwater image based on imaging of specific polarization state

MiRNAs in Microglia: Important Players in Multiple Sclerosis Pathology.

Microglia are the resident immune cells of the central nervous system and important regulators of brain homeostasis. Central to this role is a dynamic phenotypic plasticity that enables microglia to respond to environmental and pathological stimuli. Importantly, different microglial phenotypes can be both beneficial and detrimental to central nervous system health. Chronically activated inflammatory microglia are a hallmark of neurodegeneration, including the autoimmune disease multiple sclerosis (MS). By contrast, microglial phagocytosis of myelin debris is essential for resolving inflammation and promoting remyelination. As such, microglia are being explored as a potential therapeutic target for MS. MicroRNAs (miRNAs) are short non-coding ribonucleic acids that regulate gene expression and act as master regulators of cellular phenotype and function. Dysregulation of certain miRNAs can aberrantly activate and promote specific polarisation states in microglia to modulate their activity in inflammation and neurodegeneration. In addition, miRNA dysregulation is implicated in MS pathogenesis, with circulating biomarkers and lesion specific miRNAs identified as regulators of inflammation and myelination. However, the role of miRNAs in microglia that specifically contribute to MS progression are still largely unknown. miRNAs are being explored as therapeutic agents, providing an opportunity to modulate microglial function in neurodegenerative diseases such as MS. This review will focus firstly on elucidating the complex role of microglia in MS pathogenesis. Secondly, we explore the essential roles of miRNAs in microglial function. Finally, we focus on miRNAs that are implicated in microglial processes that contribute directly to MS pathology, prioritising targets that could inform novel therapeutic approaches to MS.

The gravitational-wave landscape

In the fall of 1609, Galileo Galilei opened a window to observe the divine heaven by pointing the telescope skywards. Since then enormous achievements were made in the field of astronomy with dedicated telescopes and satellites, towards a deep understanding of the “electromagnetic universe”. About four hundred years later, the LIGO/Virgo Collaboration discovered, via operating the Michelson interferometers at an unprecedented sensitivity level, a gravitational wave (GW) event, the so-called GW150914, from the merger of a binary black hole. It opened a completely novel window to observe the “gravitational universe”, which is vastly different from the “electromagnetic universe”. The discovery triggered intense researches in the GW field, and many more GW events were observed since then. The summit of the field was delivered by the multimessenger observation of a binary neutron star merger, the so-called GW170817. The event was examined in great detail with joint observations from both GW and electromagnetic instruments. In electromagnetic bands, the counterpart of GW170817 was seen by observations from radio waves, to optical bands, and to X-rays and gamma-rays. The physics revealed by them is extremely rich, and it helped scientists to better understand the equation of state of the supranuclear matters of neutron stars, short gamma-ray bursts, kilonovae, alternative gravity theories, and so on. Despite of many exciting discoveries, the landscape of GWs is much broader than the kilohertz waveband as was already demonstrated. A new era of GWs with extended wavebands is yet to come, with a lot of promising scientific targets. The whole spectrum of GWs will be revealed by: (a) The ground-based laser interferometers that aim for kilohertz GWs, (b) the space-based laser interferometers that aim for millihertz GWs, (c) the pulsar timing arrays that aim for nanohertz GWs, and (d) the specific polarization pattern of cosmic microwave background that was influenced by GWs at the ultra-low frequency at today. To embrace the modern time of GWs, there are still catalogs of puzzles to handle with, in particular, (a) how to build accurate gravitational waveforms that cover a large parameter space with affordable computational costs, (b) how to inversely derive astrophysical information from GWs thus to interpret and learn the physical environments in an unbiased way, (c) how to deal with the increasing complexity of GW time-series data with the help of advanced data-analysis means. These aspects are intrinsically mutually interdependent and the solution of them requests close collaboration of GW scientists from different research sub-fields. A deep understanding of GWs from multiband, as well as multimessenger, aspects is desirable to extract the maximum science output from GW data. Fortunately, both domestically or internationally, great work is being done constantly by groups of researchers and collaboration of them. New patterns among GW scientists are emerging that try to coherently combine relevant knowledge from astronomy, physics, data science, and engineering science. This is crucial for building a big science field, namely, the GW science, to have a great impact on our understanding of the world. These excellent prospects will eventually open up the GW window to our “gravitational universe” thoroughly in the near future, with extremely promising scientific returns.

Polarization-independent multi-channel retroreflective metasurfaces based on extraordinary optical diffraction.

Retroreflection can be achieved by phase gradient imparted by super-cells of metasurfaces. Nevertheless, in most cases, retroreflection can only be achieved for one specific polarization. In this paper, we propose an alternative design strategy and reveal that a polarization-independent multi-channel metasurface based on extraordinary optical diffraction (EOD) can achieve high-efficient retroreflection. A unary unit cell, instead of binary unit cells, is employed to canalize impinging EM waves along targeted diffraction channels. Under oblique incidence, only the -1st diffraction order is maintained and the 0th order and others are suppressed through structural design while the reflection is unaffected under normal incidence. In this way, we can achieve retroreflection in three channels. A proof-of-principle prototype was designed, fabricated and measured to verify this design strategy. The prototype can operate at 20.0 GHz under the incident angle of ±48.6° and 0° with the efficiency of retroreflection about 90%. Both the simulated and measured results show an excellent performance of retroreflection along the three channels, regardless of the polarization state of incident waves. This method offers a fast implementation for retrodirective characteristics with facile planar fabrication and can also be easily extended to THz or optical regimes.

An Adaptive Direction-Dependent Polarization State Configuration Method for High Isolation in Polarimetric Phased Array Radar

High cross-polarization isolation (CPI) is crucial to the accurate polarization measurement using polarimetric phased array radar (PPAR). In this article, we propose an adaptive direction-dependent polarization state configuration ( AD <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> PSC) method to improve the polarization isolation. Compared with the conventional fixed polarization state of radiated wave whether it is linear, circular, or elliptical polarization state, our AD <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> PSC approach configures the polarization state on basis of beam steering. To achieve the adaptive configuration of magnitude and phase of the dual-polarization antenna, an improved steepest descent algorithm is put forward. To facilitate the uniform representation for the polarization measurement application of PPAR, the universal expressions of intrinsic and measured backscatter matrices are derived for arbitrary polarization state. The dual-polarization dipole array is used to assess the priority of our proposed method. Compared with the conventional approaches, our approach could obtain higher CPI while being available for a larger scanning range. The configured CPI meets the specific polarization requirement for PPAR.

El catolicismo social en la Semana Trágica de Buenos Aires (1919)

La Semana Trágica de enero de 1919 catalizó distintas tendencias sociales presentes en la ciudad de Buenos Aires durante la inmediata posguerra. En un contexto de polarización política, la Iglesia Católica y el catolicismo asumieron un rol activo en la defensa del orden. En el artículo se analizan las perspectivas con que el catolicismo social porteño –especialmente aquel organizado en torno a los Círculos de Obreros (1892) – intervino en la coyuntura del final de la I Guerra Mundial, qué posición tomaron en relación a la violencia estatal y paraestatal durante la huelga general, y qué tipo de iniciativas promovieron en lo sucesivo.

Generating a 64 × 64 beam lattice by geometric phase modulation from arbitrary incident polarizations.

A laser beam lattice from tailoring spatial dimensions of lights is a kind of structured optical field, which already have found many applications in lots of domains. Here we propose a geometric phase element made from polymerized liquid crystals to transform Gaussian beams into a 64×64 beam lattice with high performance. Different from other geometric phase elements, the proposed element can introduce identical phase modulations for any polarizations, indicating that the beam lattice could be well generated with arbitrary incident homogeneous polarizations but not limited to specific circular polarizations. In the experiment, a 64×64 beam lattice is well generated. It is estimated that the uniformity of the obtained lattice fluctuates about 60% among various incident polarizations, which is very close to the prediction. This work opens a new site for producing high-dimensional beam lattices and will inspire more advanced applications.

Self-organized fractal-like behaviors of electromagnetic solitons induced via a radially polarized laser

The specific polarization of radially polarized lasers with cylindrical structures and longitudinal electric fields at their focal spots are of interest, as are the fundamental characteristics of electromagnetic (EM) solitons. Compared with linearly and circularly polarized lasers, radially polarized lasers have a more perfect symmetry, which makes them more suitable for studying the topological structure in laser–plasma interaction. We report the structural features of EM solitons induced via a radially polarized laser on the basis of three-dimensional particle-in-cell simulations. It has been discovered that a fractal-like structure is produced due to the interaction between the radially polarized laser and the plasma, and that this structure indirectly originates from the Weibel instability of the electron ring. This novel regime will allow potential applications such as the manipulation of relativistic electrons, mode filtering, and fractal-like particle acceleration.

Bi2S3 Nanorods Hosted on rGO Sheets from Pyrolysis of Molecular Precursors for Efficient Li‐Ion Storage

Bismuth‐based compounds with high capacity and durability are still challenging in Li‐ion batteries (LIBs). In this article, Bi2S3 nanorods hosted on reduced graphene oxide nanosheets (Bi2S3/rGO, BSG) are successfully prepared using molecular precursor pyrolysis strategy. 1D nanorod architecture possesses preeminent kinetic characteristics, shortening the ion diffusion path and increasing the contact area between electrode and electrolyte. The large specific surface area and charge polarization of rGO at the interface promote charge transfer. The capacity of material (BSG‐400) reaches 558.4 mAh g−1 at 0.2 A g−1 after 200 cycles. The anode properties of the composite outperform those of pristine Bi2S3. The introduction of graphene enables the interfacial interaction between rGO and Bi2S3. The closely contact interface improves the conductivity and lithium storage performances of Bi2S3. The regulatory effect of rGO on the electronic density of states and band gap of Bi2S3 has been demonstrated by theoretical calculation. The synthetic approach has the advantages of universality, simple operation procedure, and strong repeatability. This research provides some ideas for the preparation of other metal sulfides/rGO nanomaterials and their application in battery research.

High wavelength-resolved state of polarization monitoring method based on stimulated Brillouin scattering effect

A state of polarization (SOP) monitoring method with high wavelength resolution, based on the stimulated Brillouin scattering (SBS) in optical fiber is presented. By scanning the wavelength of pump which stimulates SBS effect, the signal spectrum with high resolution of ~ 0.1 pm can be obtained. Then, through measuring the signal spectra under six specific polarization states of pump, the Stokes vectors of each wavelength component of signal are retrieved. The results show that a mean error which is 0.018 is achieved for the wavelength-resolved SOP monitoring of a 40-Gb/s nonreturn-to-zero differential quadrature phase-shift keying (NRZ-DQPSK) signal. This monitoring method provides effective capability for estimation of polarization mode dispersion (PMD).

Polarization Independent Unidirectional Scattering With Turnstile Nanoantennas

We study the scattering behavior of a dielectric cross-dipole nanoantenna in the near-infrared spectral range when it is excited by a circular polarized plane wave. We theoretically demonstrate, for optimized geometrical parameters of the proposed turnstile structure, the possibility to simultaneously obtain a unidirectional scattering and a specific circular polarization of the scattered field. Our results open new functionalities for metamaterials and optical nanoantennas.

Hidden physical effects in noncentrosymmetric crystals

Symmetry forbidden effects in crystals may emerge in a local environment that breaks the symmetries. Yet these hidden physical effects were only discussed in centrosymmetric crystals. Here we propose that hidden physical effects can be generalized to almost all crystallographic symmetric groups and hence reveal their universality and diversity. We systematically discuss certain symmetries in crystals that may induce hidden spin polarization (HSP), hidden Berry curvature, and hidden valley polarization, with a focus on a specific pattern of HSP whose winding directions of the in-plane spin vectors are the same for adjacent bands, dubbed anomalous HSP. Such an unprecedented spin pattern arises from relatively weak spin-dependent intersector interaction and is demonstrated in mirror-symmetric InSe by first-principles calculations. Unique electric field dependent splitting into specific spatial polarization patterns may serve as an experimental signature of anomalous HSP. Our results reveal abundant hidden physical effects beyond centrosymmetric crystals and provide platforms to discuss them for emergent physical effects and future applications.

Optical multiple images encryption system based on ellipsometry reconstruction

In this paper, an optical multiple image encryption method based on ellipsometry reconstruction is proposed. In our proposal, the cryptosystem is designed as multiple paths, and each path is used to encrypt one image. In each path, one original image is decomposed into two phase only masks (POMs) using the interference method. Then, every two masks decomposed from the same original image are encoded onto the spatial light modulator (SLM) to generate an elliptically polarized light (EPL) with specific amplitude and polarization. After that, each light passes through a linear polarizer. CCD is used to record the sum of the intensity of these path outputs, which is ciphertext. Jones matrix is used to describe these procedures. Moreover, our proposed encryption system has certain anti-attack ability. Computer simulations are conducted to verify the correctness and validity of our proposed method.

Spatially and temporally polarization shaped laser pulses for two-photon excited fluorescence

We present simultaneous spatial and temporal polarization pulse shaping for two-photon excited fluorescence of dyes. A temporal pulse shaper and a subsequent spatial pulse shaper are used to generate laterally and axially tailored two-photon excited fluorescence profiles. The induced fluorescence is recorded for different polarization directions by utilizing the anisotropy of the dyes embedded in glycerol. We achieve an increased fluorescence contrast between different dyes by employing specific polarization shaped laser pulses and by taking polarization dependent emission into account. This versatile pulse shaping method is prospective for novel biophotonic imaging.

Experimental validation of solid oxide fuel cell polarization modeling: An LSM-YSZ/YSZ/Ni-YSZ case study

Polarization modeling based on the measured I-V curves is a useful tool for analyzing SOFC performance and diagnosing performance limitations. Using the polarization model, the overpotential of a cell is usually separated into different polarization contributions, including area specific ohmic polarization, activation polarization, and anodic and cathodic concentration polarizations. In this study, we aim to experimentally validate the accuracy of the polarization model. As a case study, anode-supported cells with LSM-YSZ/YSZ/Ni-YSZ configuration are used. By curve-fitting the I-V curves of a cell tested under different cathode oxygen partial pressures into the polarization model, the contributions of different polarization losses are quantified. To validate the polarization model, independent experiments/studies including electrochemical impedance spectroscopy, cathode kinetics study, ex-situ diffusivity measurement, and tortuosity measurement using 3D reconstructed anode are conducted. The results from polarization modeling and from validation studies are in good agreement, thereby validating the polarization model for SOFC performance analysis.

Optical Computation of Divergence Operation for Vector Fields

Topological physics desires stable methods to measure the polarization singularities in optical vector fields. Here a periodic plasmonic metasurface is proposed to perform divergence computation of vectorial paraxial beams. We design such an optical device to compute spatial differentiation along two directions, parallel and perpendicular to the incident plane, simultaneously. The divergence operation is achieved by creating the constructive interference between two derivative results. We demonstrate that such optical computations provide a new direct pathway to elucidate specific polarization singularities of vector fields.

Synthesis of polyacrylamide/polystyrene interpenetrating polymer networks and the effect of textural properties on adsorption performance of fermentation inhibitors from sugarcane bagasse hydrolysate

Economical removal of fermentation inhibitors from lignocellulosic hydrolysate plays a considerable role in bioconversion of lignocellulose biomass. In this work, the textural properties of polyacrylamide/polystyrene interpenetrating polymer networks (PAM/PS IPNs) on adsorption of fermentation inhibitors from sugarcane bagasse hydrolysate (SCBH) were investigated for the first time. The results showed that, the specific surface area, pore diameter and surface polarity had important influence on its adsorption performance towards sugars, organic acids, furans and acid-soluble lignin. The PAM/PS IPNs under the optimal copolymerization situation achieved the high selectivity coefficients of 4.07, 14.9, 21.2 and 25.8 with respective to levulinic acid, furfural, hydroxymethylfurfural (HMF) and acid-soluble lignin, and had a low total sugar loss of 2.09%. Overall, this research puts forward a design and synthetic strategy for adsorbent to remove fermentation inhibitors from lignocellulosic hydrolysate.

Magnon–phonon interaction in antiferromagnetic two-dimensional MXenes

Antiferromagnetic material possesses excellent robustness to an external magnetic field perturbation, which makes it promising in application of spintronic devices. The magnon–phonon interaction plays a vital role in spintronic devices. In this work, we performed first-principles calculation to study the effect of magnon–phonon interaction on magnon spectra of the antiferromagnetic MXenes Cr2TiC2FCl, and calculated the phonon dominated magnon relaxation time based on the magnon spectra broadening. Due to the large exchange constants across Cr–Cr pairs, high magnon energy is found in Cr2TiC2FCl. We find that compared with the acoustic magnons, the optical magnons have stronger interaction with phonon modes. Moreover, relaxation time of optical magnons and acoustic magnons have quite different wavevector dependence. Our results about spin coupling to specific phonon polarizations can shed light on the understanding of magnon damping and energy dissipation in two-dimensional antiferromagnetic materials.

Nanoassembly of gold nanoparticles: An active substrate for size-dependent surface-enhanced Raman scattering.

Nanoassembly of gold nanoparticles has been achieved through a simple and facile process without using any surfactants or linkers. Atomic force microscopy confirmed assemblies of several tens of microns, whereas tiny interparticle gaps less than 5nm was revealed by scanning electron microscopy. Such nanoassemblies with tiny interparticle gaps were found to be highly surface-enhanced Raman scattering (SERS)-active with enhancement factor in the order of 6 to 8. Contrary to usual trends in nanoparticles size dependent SERS enhancement, such 2D nanoassemblies of different sizes of nanoparticles showed relatively broadened SERS enhancement distribution. Finite difference time domain (FDTD) analysis was employed to highlight the EM-field distribution in connection to such giant SERS enhancement. In depth and hotsite-wise analysis on EM near-field distributions for monomers, dimers and septamers of 50nm of gold nanoparticles were carried out at three specific incident polarizations (i.e. s-, 45° and p-polarizations). At s- and p-polarization the strongest hotsites were having the EM near-field distributions in the range of 124.8 and 133.3V/m respectively with lower population of confined EM near-fields. Such correlated investigation will be indispensable to understand and interpret hierarchical and functional nanoassemblies from its unit nanoparticle blocks for the advances of technological breakthroughs.