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In terahertz (THz) wireless communication systems, non-diffraction vortex beams carrying an orbital angular momentum (OAM) have attracted extensive attention due to their ability to transmit information over long distances with high capacity. However, existing metasurfaces can only generate a single OAM mode non-diffracting vortex beam at reflection space for circular polarization (CP) incidence, limiting practical applications. To address this issue, we propose and design a polarization-frequency multiplexing transmissive THz metasurface to realize multi-mode non-diffracting vortex beams at linear polarization (LP) incidence. The meta-atom of this metasurface is composed of three anisotropic rectangular metallic structures embedded in vanadium dioxide (VO2) square rings, two circular aperture metallic grid layers, and four dielectric layers. By reasonably designing the size of the metal patch and the state of VO2, the designed metasurface can achieve polarization multiplexing and frequency multiplexing for LP incidence. Based on the phase response of the proposed meta-atoms, the transmissive metasurface can implement not only multi-mode non-diffraction vortex beams but also their space separation at two frequency ranges of 0.80–0.90 THz and 1.50–1.80 THz by changing the state of VO2. Therefore, the proposed multiple multiplexing metasurfaces can effectively shape the wavefront of non-diffraction vortex beams, which have broad application prospects in 6G THz communication. [ABSTRACT FROM AUTHOR]

An absorptive coding metasurface (ACM) is proposed to achieve radar cross section (RCS) reduction in this paper. In the design progress of the ACM, two different lossy coding elements are proposed at first, which can both be regarded as a composite composed of a two-layer resistive frequency selective surface (RFSS) and a polarization conversion metasurface (PCM). The two-layer RFSS has a certain wave-absorbing property due to ohmic loss. In addition, the PCM can achieve ultra-wideband linear polarization conversion, and the polarization-converted reflected waves in the two coding elements under the same incidence will differ by nearly 180° in phase because the sub-unit-cell structures in them are perpendicular to each other. Thus, based on the two lossy coding elements, the ACM is proposed, which can achieve ultra-wideband RCS reduction due to absorption and phase cancelation. Numerical simulations demonstrate that the RCS of the ACM under normal incidence can be reduced more than 10 dB in the ultra-wide frequency band from 6.9 to 41.2 GHz with a relative bandwidth of 142.6%. Moreover, it has the advantages of polarization-insensitivity and wide incident angle. Finally, one effective experimental verification is carried out, and a reasonable agreement is observed between the simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this work, we combine the concepts of magnetic circular dichroism, nanocavities, and magneto-optical hyperbolic metamaterials (MO-HMMs) to demonstrate an approach for sensing down to a few molecules. Our proposal comprises a multilayer MO-HMM with a square, two-dimensional arrangement of nanocavities. The magnetization of the system is considered in polar configuration, i.e., in the plane of polarization and perpendicular to the plane of the multilayer structure. This allows for magneto-optical chirality to be induced through the polar magneto-optical Kerr effect, which is exhibited by reflected light from the nanostructure. Numerical analyses under the magnetization saturation condition indicate that magnetic circular dichroism peaks can be used instead of reflectance dips to monitor refractive index changes in the analyte region. Significantly, we obtained a relatively high sensitivity value of S = 40 nm/RIU for the case where refractive index changes are limited to the volume inside nanocavities, i.e., in the limit of a few molecules (or ultralow concentrations), while a very large sensitivity of S = 532 nm/RIU is calculated for the analyte region distributed along the entire superstrate layer. [ABSTRACT FROM AUTHOR]

In this paper, we report a reconfigurable multifunctional polarization converter (RMPC) based on positive-intrinsic-negative (PIN) diodes, enabling to achieve different functions in different bands and states. The simulations and experiments show that when the PIN diode is off, it acts as a broadband linear polarization (LP) converter at 9.12–15.93 GHz. Simultaneously, when the PIN diode is on, the LP incident wave is converted into a left-handed circular polarization wave at 8.69–11.41 GHz and a cross-polarization wave at 13.40–14.97 GHz, whereas full reflection is obtained at 12.05–12.54 GHz. The RMPC consists of two dielectric plates and three layers of metal copper plates. Finally, a sample was fabricated and measured, the simulated and experimental results were in good agreement. Compared with other works, the RMPC has more working states and wider operating frequency bands, which has an application potential in the field of radar stealth and satellite communication. [ABSTRACT FROM AUTHOR]

We report an unexplored type-II multiferroic order in NiMn 2 O 4 , exhibiting strong linear magnetoelectric coupling above liquid-nitrogen (LN) temperature. The compound becomes ferroelectric at ∼ 100 K, coinciding with ferrimagnetic ordering, with a polarization value of ∼ 535 μ C/m 2 for a poling field of 5 kV/cm. At LN temperature, the polarization value increases linearly (∼ 21 %) with a magnetic field up to 30 kOe. Rietveld refinement of neutron diffraction patterns reveals a ferrimagnetic model with antiparallel moments at tetrahedral and octahedral sites, as well as a canting of octahedral moment persisting up to ∼ 100 K. Low-temperature synchrotron diffraction confirms a step-like oxygen displacement during multiferroic ordering, suggesting that the Dzyaloshinskii–Moriya interaction polarizes the intervening oxygen atoms through magnetostriction, providing a microscopic mechanism for spontaneous electric polarization in this linear magnetoelectric multiferroic compound. [ABSTRACT FROM AUTHOR]

We report an unexplored type-II multiferroic order in NiMn 2 O 4 , exhibiting strong linear magnetoelectric coupling above liquid-nitrogen (LN) temperature. The compound becomes ferroelectric at ∼ 100 K, coinciding with ferrimagnetic ordering, with a polarization value of ∼ 535 μ C/m 2 for a poling field of 5 kV/cm. At LN temperature, the polarization value increases linearly (∼ 21 %) with a magnetic field up to 30 kOe. Rietveld refinement of neutron diffraction patterns reveals a ferrimagnetic model with antiparallel moments at tetrahedral and octahedral sites, as well as a canting of octahedral moment persisting up to ∼ 100 K. Low-temperature synchrotron diffraction confirms a step-like oxygen displacement during multiferroic ordering, suggesting that the Dzyaloshinskii–Moriya interaction polarizes the intervening oxygen atoms through magnetostriction, providing a microscopic mechanism for spontaneous electric polarization in this linear magnetoelectric multiferroic compound. [ABSTRACT FROM AUTHOR]

Summary: In today's intricate wireless communication environment, ensuring system quality demands the use of a reliable and versatile antenna system. This research article introduces a polarization reconfigurable antenna integrated with a 4 × 4 Artificial Magnetic Conductor (AMC) surface. The AMC unit cell exhibits a triple‐band reflection phase response at 1.8GHz, 4.5GHz, and 5.5GHz, demonstrating double negative metamaterial behavior. The antenna features two distinct C‐shaped metal strips connected to two PIN diodes, enabling dynamic current distribution adjustment. Consequently, the proposed antenna offers three reconfigurable states, facilitating seamless switching between dual circular polarization (left and right‐hand circular polarization) and linear polarization. With a frequency coverage ranging from 1.29 to 2.52GHz and 3.59 to 6.15GHz, the antenna boasts a maximum axial ratio (AR) bandwidth of 31.96%. Additionally, it achieves a maximum peak gain of 5.5 dB and maintains front‐to‐back ratio (FBR) values exceeding 25 dB, while recording a minimum specific absorption rate (SAR) value of 0.1059 W/kg. The integration of the AMC surface ensures enhanced performance of the antenna. Experimental results from constructed prototypes closely align with simulation outcomes, validating the effectiveness of the proposed antenna. Consequently, this antenna holds significant promise for next‐generation wireless applications. [ABSTRACT FROM AUTHOR]

PSR J0737−3039A/B is unique among double neutron star systems. Its near-perfect edge-on orbit causes the fast spinning pulsar A to be eclipsed by the magnetic field of the slow spinning pulsar B. Using high-sensitivity MeerKAT radio observations combined with updated constraints on the system geometry, we studied the impact of these eclipses on the incident polarization properties of pulsar A. Averaging light curves together after correcting for the rotation of pulsar B revealed enormous amounts of circular polarization and rapid changes in the linear polarization position angle, which occur at phases where emission from pulsar A is partially transmitted through the magnetosphere of pulsar B. These behaviours confirm that the eclipse mechanism is the result of synchrotron absorption in a relativistic pair-plasma confined to the closed-field region of pulsar B's truncated dipolar magnetic field. We demonstrate that changes in circular polarization handedness throughout the eclipses are directly tied to the average line of sight magnetic field direction of pulsar B, from which we unambiguously determine the complete magnetic and viewing geometry of the pulsar. [ABSTRACT FROM AUTHOR]

Bright dipolar excitons, which contain electrical dipoles and have high oscillator strength, are an ideal platform for studying correlated quantum phenomena. They usually rely on carrier tunneling between two quantum wells or two layers to hybridize with nondipolar excitons to gain oscillator strength. In this work, we uncovered a new type of bright infrared dipolar exciton by stacking 90°-twisted black phosphorus (BP) structures. These excitons, inherent to the reconstructed band structure, exhibit high oscillator strength. Most importantly, they inherit the linear polarization from BP, which allows light polarization to be used to select the dipole direction. Moreover, the dipole moment and resonance energy can be widely tuned by the thickness of the BP. Our results demonstrate a useful platform for exploring tunable correlated dipolar excitons. [ABSTRACT FROM AUTHOR]

We present the discovery of possibly the youngest Galactic supernova remnant (SNR) with associated pulsar-wind nebula (PWN), which we name Perun (G329.9−0.5). Perun was serendipitously discovered in the Australian Square Kilometre Array Pathfinder–Evolutionary Map of the Universe survey at 943 MHz, and subsequent follow-up observations were conducted with the Australia Telescope Compact Array observatory at 5500 and 9000 MHz. We combine these with additional radio observations from the MeerKAT, Molonglo Observatory Synthesis Telescope, and Murchison Widefield Array telescopes, infrared (IR) observations from the SpitzerSpace Telescope , and X-ray observations from the Chandra X-ray observatory to perform a multifrequency analysis. The radio morphology shows a small angular size shell (D  = 70 arcsec) with a luminous, central PWN. We measure a total spectral index of |$\alpha = -0.49\pm 0.05$|⁠ , which should be typical for a young, composite SNR. Crucial evidence for Perun's SNR classification comes from the detection of linear fractional polarization at radio frequencies of |$\sim$| 7 per cent–10 per cent with both radial and tangential orientations, similar to the young SNR G1.9+0.3. We use data from the Southern Galactic Plane Survey to perform an H  i analysis and estimate a favoured distance range of 6–9 kpc, and thus a favoured age range of |$\sim$| 70–500 yr. We find no high-energy emission in Fermi- Large Area Telescope data. We detect Perun's outer shell in 24  |$\mu$| m indicating the possible presence of [O  iv ] and [Fe  iii ] emission, also typical for young SNRs. Overall, these observations and analysis confirm Perun as a young, Galactic SNR with a prominent PWN. [ABSTRACT FROM AUTHOR]

Fast radio bursts (FRBs) are short-time-scale transients of extragalactic origin. The number of detected FRBs has grown dramatically since their serendipitous discovery from archival data. Some FRBs have also been seen to repeat. The polarimetric properties of repeating FRBs show diverse behaviour and, at times, extreme polarimetric morphology, suggesting a complex magneto-ionic circumburst environment for this class of FRB. The polarimetric properties such as circular polarization behaviour of FRBs are crucial for understanding their surrounding magnetic-ionic environment. The circular polarization previously observed in some of the repeating FRB sources has been attributed to propagation effects such as generalized Faraday rotation (GFR), where conversion from linear to circular polarization occurs due to the non-circular modes of transmission in relativistic plasma. The discovery burst from the repeating FRB 20180301A showed significant frequency-dependent circular polarization behaviour, which was initially speculated to be instrumental due to a sidelobe detection. Here, we revisit the properties given the subsequent interferometric localization of the burst, which indicates that the burst was detected in the primary beam of the Parkes/Murriyang 20-cm multibeam receiver. We develop a Bayesian Stokes-Q, U, and V fit method to model the GFR effect, which is independent of the total polarized flux parameter. Using the GFR model we show that the rotation measure (RM) estimated is two orders of magnitude smaller and opposite sign (⁠|$\sim$| 28 rad m |$^{-2}$|⁠) than the previously reported value. We interpret the implication of the circular polarization on its local magnetic environment and reinterpret its long-term temporal evolution in RM. [ABSTRACT FROM AUTHOR]

A simple and compact polarization reconfigurable patch antenna design is proposed to operate in WLAN band at a resonant frequency of 2.4 GHz. This antenna consists of a rectangular patch placed on an FR4 substrate. A rectangular slot is cut in the rectangular patch. Two L shaped microstrip strips are placed inside the slot and joined together at the centre of the rectangular patch by inverting the L shaped microstrip. There are three different methods of achieving the reconfigurability namely electrical, mechanical and optical. This proposed structure uses electrical reconfiguration technique. This proposed antenna structure uses PIN diodes for achieving the polarization reconfigurability because of its ease in biasing. Two PIN diodes both being placed on the inverted L shaped structure in order to achieve the polarization modes and these PIN diodes are used to connect this microstrip with the rectangular patch. By switching these two PIN diodes for various biasing conditions, four different polarization modes namely two linear polarization (LP) modes, one Left Hand Circular polarization (LHCP) and one Right Hand Circular polarization (RHCP) mode is achieved. The antenna produces simulated gain of around 1.5416 dB for LP1 mode at 2.41 GHz, 1.7175 dB for LP2 mode at 2.45 GHz, 1.6062 dB for RHCP mode and 1.5922 dB for LHCP mode both at 2.4 GHz. The antenna structure is simulated using Ansys HFSS. [ABSTRACT FROM AUTHOR]

Emerging miniaturized atomic sensors such as optically pumped magnetometers (OPMs) have attracted widespread interest due to their application in high-spatial-resolution biomagnetism imaging. While optical probing systems in conventional OPMs require bulk optical devices including linear polarizers and lenses for polarization conversion and wavefront shaping, which are challenging for chip-scale integration. In this study, an integrated optical probing scheme based on localized-interference metasurface for chip-scale OPM is developed. Our monolithic metasurface allows tailorable linear polarization conversion and wavefront manipulation. Two silicon-based metasurfaces namely meta-polarizer and meta-polarizer-lens are fabricated and characterized, with maximum transmission efficiency and extinction ratio (ER) of 86.29 % and 14.2 dB for the meta-polarizer as well as focusing efficiency and ER of 72.79 % and 6.4 dB for the meta-polarizer-lens, respectively. A miniaturized vapor cell with 4 × 4 × 4 mm3 dimension containing 87Rb and N2 is combined with the meta-polarizer to construct a compact zero-field resonance OPM for proof of concept. The sensitivity of this sensor reaches approximately 9 fT/Hz1/2 with a dynamic range near zero magnetic field of about ±2.3 nT. This study provides a promising solution for chip-scale optical probing, which holds potential for the development of chip-integrated OPMs as well as other advanced atomic devices where the integration of optical probing system is expected. [ABSTRACT FROM AUTHOR]

Featured Application: Photo-induced chirality in thin films of Ge2Sb2Te5 can be used to store covert information with application in authentication labels. This information can be revealed by a suitable simple reading device. A new technology to write and read covert information in authentication labels is described. This technology uses the phenomenon of photo-induced chirality in Ge2Sb2Te5 thin films to encode the left- or right-circular or linear polarization of the laser beam used to write the label. The written polarization can be revealed by a simple reading device, which is demonstrated to provide the same qualitative information as reading based on cyclotron circular dichroism spectroscopy and imaging. The suggested method, while based on existing manufacturing approaches, offers a balance between technological complexity for writing and simplicity for reading, and may be advantageous as a new authentication technology. [ABSTRACT FROM AUTHOR]

Electromagnetically induced transparency (EIT), nonlinearity, and optical chirality hold significant applications in many areas such as optical switches, slow-light devices, chiral harmonic conversion, and optical storage. In this work, we theoretically propose an asymmetric all-dielectric metasurface supporting toroidal dipole-quasi-bound states in the continuum (TD-q-BICs). High quality (Q) EIT, strong third harmonic generation (THG), and giant nonlinear chirality are achieved via the extremely enhanced electric field energy localized in the Si plate by the TD-q-BIC. A huge transition from high Q EIT with transmission of ∼0.99 to strong chirality with circular dichroism (CD) of ∼0.9 is realized by tuning the angle and polarization state of incident light. Strong THG with efficiency of 4.5 × 10−3 under linear polarization light is due to the highly localized electric field supported by the TD-q-BIC and perfect nonlinear CD chirality with theoretically value of ∼1 originates from the large discrepancy in electric field distributions under different circularly polarized light. Our work provides an innovative paradigm to construct TD-q-BICs-governed EIT analogs, THG, and nonlinear chirality for the development of multifunction nanophotonic meta-devices. [ABSTRACT FROM AUTHOR]

This research work presents the design of a multiband dual‐polarized eight‐element MIMO antenna having dimensions (0.51 λ × 0.66 λ × 0.009 λ). The antenna is observed to be radiating between 1.7 GHz and 2.4 GHz, 4.1 GHz and 10 GHz and 10.6 GHz and 19.8 GHz, featuring 3 dB axial ratio bandwidth between 9.7 and 10 GHz, 12.1 and 13.1 GHz, 14.4 and 14.5 GHz and 17.9 and 18.9 GHz. In the proposed MIMO antenna, the triangular‐shaped monopole antenna is tapered at its two sides. The isolation between the various elements of the proposed antenna is observed to be in range of −20 dB–−70 dB for the concerned frequency range. On the basis of comparison with similar existing structures, the proposed antenna demonstrates superior performance in terms of total active reflection coefficient (TARC < −5 dB), diversity gain (DG around 10 dB), channel capacity loss (CCL < 0.3 bits/s/Hz), mean effective gain (MEG) and envelope correlation coefficient (ECC < 0.024). The proposed antenna provides wide bandwidth (15.8 GHz) and high value of peak gain (6 dB). The proposed geometry is novel as it exhibits both linear as well as circular polarization with multiband response and it provides the least ECC and maximum isolation. The experimental results are found to be in agreement with the simulated results, so the proposed antenna can be useful for WLAN, C‐band, X band and Ku band applications. [ABSTRACT FROM AUTHOR]

Infrared polarization detection has attracted wide applications in military and civilian fields by demonstrating more accurate target detection and identification capabilities due to more dimensional target information. A multifocal metalens for simultaneous detection of the polarization state of incident light at dual wavelengths is proposed based on the independent control of orthogonally polarized light. When light is incident at different wavelengths, the metalens array splits and focuses the light on three different polarization bases to form six focal points with various positions. When the incident light with varying states of polarization of dual wavelengths to be detected passes through the substrate and reaches the metalens array, the incident light detected in each wavelength forms six focal points at different positions of the focal plane of the metalens. The Stokes parameters are calculated based on the intensities of the six polarization components in the same focal plane to determine the polarization data of the azimuthal and elliptic angles of the incident light detected in each wavelength. In addition, the theoretical Stokes parameters of incident light with different polarization states at two wavelengths are compared with the reconstructed Stokes parameters, proving our method's validity. The device can directly examine the polarization state of the incident light in mid-wave infrared and long-wave infrared, significantly simplifying the polarization detection system. [ABSTRACT FROM AUTHOR]

The in‐plane anisotropic properties of 2D group IV monochalcogenides offer an additional degree of freedom which can be advantageous in optoelectronic applications. Here, it is demonstrated that the third harmonic generation (THG) produced by ultrathin tin (II) sulfide (SnS) is in‐plane anisotropic with respect to the direction of the excitation linear polarization. The polarization‐resolved THG (P‐THG) measurements are described with a nonlinear optics model, which accounts for the orthorhombic crystal structure of the 2D SnS. The relative magnitudes of the χ(3) tensor components are calculated by recording and simultaneously fitting two orthogonal polarization components of the P‐THG signals. Furthermore, the "THG anisotropy ratio" is introduced, which compares the THG intensity produced when the excitation linear polarization is along the armchair crystallographic direction, with the case when it is along the zigzag direction. The experimental findings provide quantitative information on the anisotropic nature of the THG process in various SnS flakes. Nonlinear anisotropic 2D materials can be used in future optoelectronic devices, where anisotropic polarization sensitivity is required. Having an optical tool that quantitatively probes the effect of the in‐plane anisotropy among different 2D materials, could be of considerable importance for evaluating the performance of such materials and devices. [ABSTRACT FROM AUTHOR]

Non‐diffraction Airy beams with self‐accelerating properties have many potential applications in the microwave band, such as providing a viable solution to bypass obstacles for microwave‐based wireless power transfer (WPT) and communication. However, most of the recent work on Airy beams exhibits singular functionality and operates solely in linear polarization, with complex generation setups, which will constrain the applications of the beam in the microwave band. In this paper, based on the anisotropic holographic impedance metasurface (AHIM) with low complexity, a new method is proposed to manipulate Airy beams in multiple dimensions, including circularly polarization state, number of beams, direction of acceleration, and launch position of beam. The underlying principle is the combination of plane coordinate transformation, anisotropy of AHIM, and impedance superposition theory. Further, to validate the proposed method, an AHIM prototype for simultaneously generating two Airy beams with orthogonal circular polarization, different directions of acceleration, and different spatial distribution is designed, simulated, and measured. The proposed method based on AHIM for manipulating the Airy beams multidimensionally in the microwave band offers an efficient strategy to control the energy coverage and polarization state of the beam in different WPT scenarios. [ABSTRACT FROM AUTHOR]

Over the past 50 years, a principal approach to controlling conventional photochemical reactions has relied on imposing geometric constraints on reactant or transition state via conducting photochemistry in the organized or constraining media. Herein, we describe a fundamentally different approach to affect the course of photochemical reactions (photochemical rearrangements) by utilizing spatially selective excitation of specific electronic transitions with plane‐polarized light in the reactant molecules uniformly aligned in the nematic liquid crystal phase. In particular, we focused on the Type B enone rearrangement of 4,4‐diarylcyclohexenones – one of the most common photochemical rearrangements. We demonstrated that the aryl migratory aptitude in this reaction was attenuated in response to changing an angle between the polarization plane of the incident light and the alignment direction of the nematic liquid crystal, with the enhanced aryl migration achieved when the polarization plane coincided with the transition dipole moment leading to the excited state responsible for this migration. The spatially‐selective initial excitation therefore was overruling the electronic factors responsible for the relative ratio of the two alternative photoproducts. The experimental findings were further supported by the results of a computational study. This work showcases a new fundamental paradigm in controlling photochemical reactivity and selectivity of photoreactions. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) antiferromagnetic (AFM) semiconductors are promising components of opto‐spintronic devices due to terahertz operation frequencies and minimal interactions with stray fields. However, the lack of net magnetization significantly limits the number of experimental techniques available to study the relationship between magnetic order and semiconducting properties. Here, they demonstrate conditions under which photocurrent spectroscopy can be employed to study many‐body magnetic excitons in the 2D AFM semiconductor NiI2. The use of photocurrent spectroscopy enables the detection of optically dark magnetic excitons down to bilayer thickness, revealing a high degree of linear polarization that is coupled to the underlying helical AFM order of NiI2. In addition to probing the coupling between magnetic order and dark excitons, this work provides strong evidence for the multiferroicity of NiI2 down to bilayer thickness, thus demonstrating the utility of photocurrent spectroscopy for revealing subtle opto‐spintronic phenomena in the atomically thin limit. [ABSTRACT FROM AUTHOR]

The multi‐dimensional light‐field manipulation capability of metasurfaces positions them as promising candidates for displaying nanoprinting and holographic images at ultra‐short distances with subwavelength resolution. In recent years, merging nanoprinting and holographic images into a single‐layer metasurface has emerged as a research focus to enhance information storage capacity. However, existing multi‐channel metasurface designs often limit the number of polarization states available for the holographic image. Here, a scheme is proposed and demonstrated to encode both a continuous grayscale image and a vectorial hologram with a continuously varying linear polarization distribution onto a complex amplitude‐modulated metasurface. The nanoprinting and holographic images generated from dielectric metasurface exhibit broadband response for the visible light. This method paves the way for compact optical devices tailored for applications in information encoding, high‐density optical storage, and information anti‐counterfeiting. [ABSTRACT FROM AUTHOR]

Conventional approaches for designing metasurfaces with the desired scattering response are often a time‐consuming and onerous process that heavily relies on the design experience and empirical methods. In this paper, a time and resource‐efficient design method is proposed for the synthesis of multiple metasurface polarizers with an efficient automated data generation process by utilizing the structure validation surrogate model (SVSM). Moreover, a novel attention and space‐to‐depth enhanced adaptive tandem network (ASE‐ATN) is proposed which integrates symmetry‐aware space‐to‐depth (SA‐SPD) along with the attention mechanism for efficient feature extraction. Several design examples of metasurfaces with linear polarization to orthogonal linear polarization (LP‐OLP) and/or linear polarization to circular polarization (LP‐CP) conversion capabilities are provided to verify the performance of the proposed method. The feasibility of the proposed method is demonstrated through the fabrication and measurement of a dual‐band dual‐polarization converter. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) antiferromagnetic (AFM) semiconductors are promising components of opto‐spintronic devices due to terahertz operation frequencies and minimal interactions with stray fields. However, the lack of net magnetization significantly limits the number of experimental techniques available to study the relationship between magnetic order and semiconducting properties. Here, they demonstrate conditions under which photocurrent spectroscopy can be employed to study many‐body magnetic excitons in the 2D AFM semiconductor NiI2. The use of photocurrent spectroscopy enables the detection of optically dark magnetic excitons down to bilayer thickness, revealing a high degree of linear polarization that is coupled to the underlying helical AFM order of NiI2. In addition to probing the coupling between magnetic order and dark excitons, this work provides strong evidence for the multiferroicity of NiI2 down to bilayer thickness, thus demonstrating the utility of photocurrent spectroscopy for revealing subtle opto‐spintronic phenomena in the atomically thin limit. [ABSTRACT FROM AUTHOR]

The polarized bidirectional reflectance distribution function (pBRDF) can describe the changes between the Stokes vectors of incident and reflected light. The existing model can only describe the spatial distribution of the target's polarization characteristics at a single wavelength, so further research is needed for the description of the target's polarized spectral characteristics. In this paper, a modified three-component polarized spectral bidirectional reflectance distribution function (pSBRDF) is proposed, which combines Fresnel equation in the specular reflection component with Cauchy's empirical dispersion equation, by introducing the wavelength variable and dispersion constants that do not change with wavelength. The degree of the linear polarization (DoLP) of two types of coated fabric samples was measured at three incident angles and 400 to 760 nm wavelength. The error of the model in describing the spectral and the spatial distribution of DoLP are controlled within 0.00743 and 0.0757 respectively, which proves the accuracy of the model. This research provides the model basis for analysis of the target's polarization characteristics and the theoretical basis for the application of polarization detection. [ABSTRACT FROM AUTHOR]

Cracks are extensively existing in rocks and play a significant role in the acoustic anisotropy of cracked rocks. Rocks in nature are affected by pore pressure, whereas the crack deformation with pore pressure and the impacts of the crack deformation on the anisotropic acoustic properties remain little known. Combining the theoretical model with the laboratory measurements of the anisotropic velocities of artificial sandstone samples with and without aligned penny‐shaped cracks, we invert for the crack parameters that characterize the crack deformation as a function of pore pressure and theoretically simulate the impacts of pore pressure–induced variation in the crack parameters on the anisotropic velocities. The results show that with increasing pore pressure, the inverted crack porosity increases exponentially, whereas the inverted crack aspect ratio decreases exponentially and the two crack parameters are linearly correlated. Moreover, model calculation demonstrates that the anisotropic velocities exhibit distinct reductions with the variation in the crack parameters caused by increasing pore pressure. In particular, the reduction in the velocity of the shear wave travelling parallel to the crack plane with polarization perpendicular to the crack plane is the most pronounced. We also demonstrate that the effects of the pore pressure–induced increasing crack porosity on the anisotropic velocities are more pronounced than the impacts of the decreasing crack aspect ratio. The findings not only reveal the variation of the crack geometry with pore pressure and the effects of the crack deformation on the anisotropic velocities of the cracked rocks but also can provide theoretical support for improving the characterization of the cracks through seismic survey. [ABSTRACT FROM AUTHOR]

The corrosion inhibition action of Phalaris canariensis extract on 316 L stainless steel in the H2O-35 (wt%) LiCl mixture at different temperatures has been evaluated with the aid of weight loss, potentiodynamic polarization curves, linear polarization resistance and electrochemical impedance spectroscopy tests. These studies were complemented by Fourier Transformed Infrared spectroscopy, FTIR, gas/mass chromatography analytical techniques and detailed scanning electronic microscopy studies. Results have indicated that Phalaris canariensis extract is an efficient inhibitor, with an efficiency that increases with its concentration, but it decreases as the temperature increases. Phalaris canariensis extract is physically adsorbed onto stainless steel according to a Temkin type of adsorption isotherm. Phalaris canariensis extract affected both anodic and cathodic electrochemical reactions with a stronger effect on the anodic ones, acting, thus, as a mixed type of inhibitor. Main compounds contained in the Phalaris canariensis extract were palmitic and oleic acids, responsible for its inhibitory properties. [ABSTRACT FROM AUTHOR]

The Airborne Hyper-Angular Rainbow Polarimeter (AirHARP) is a new imaging polarimeter instrument capable of sampling a single Earth target from up to 120 viewing angles, in four spectral channels, and in three linear polarization states across a 114° field of view (FOV). AirHARP is telecentric in the image space and simultaneously images three linear polarization states with no moving parts. These two aspects of the design allow for a simple and efficient quantitative calibration. Using coefficients derived at the center of the lens and the detector flatfields, we can calibrate the entire AirHARP sensor in a variety of laboratory, field, and space environments. We show that this telecentric calibration technique yields a 1 σ absolute uncertainty of 0.25 % in degree of linear polarization (DOLP) in the laboratory for all channels and for pixels around the optical axis. To validate across the FOV, we compare our multi-angle reflectance and polarization data with the Research Scanning Polarimeter (RSP) over targets sampled during the NASA Aerosol Characterization from Polarimeter and Lidar (ACEPOL) campaign. We use the error-normalized difference technique to estimate how well the instruments compare relative to their error models. We find that AirHARP and the RSP reasonably agree for reflectance and DOLP within 2 standard deviations of their mutual uncertainty at 550, 670, and 870 nm and over a limited set of ocean and desert scenes. This calibration technique makes the Hyper-Angular Rainbow Polarimeter (HARP) design attractive for new spaceborne climate missions: HARP CubeSat (2020–2022), HARP2 (2024–) on the NASA Plankton, Aerosol, Cloud, ocean Ecosystem (PACE), and beyond. [ABSTRACT FROM AUTHOR]

In the centre of mass frame, we have investigated the electroweak process e + e - → μ + μ - in the presence of a plane and monochromatic laser wave of linear polarization. We provide the theoretical calculations of the differential cross-section for this process by using the scattering-matrix approach and Dirac-Volkov formalism. The laser-assisted cross-section is computed, and its dependence on the laser parameters is analyzed. We have found that this cross-section increases significantly inside a linearly polarized laser wave co-propagating with the incident particle's beam, and it passes its corresponding laser-free cross-section by several orders of magnitude. [ABSTRACT FROM AUTHOR]

The current study investigates the influence of immersion time (7, 14, 21, and 28 days) on the corrosion behaviour of American Petroleum Institute (API) X70 and X80 steel grades in freely aerated simulated concrete pore solution (pH ~ 12 to 13.8) utilizing electrochemical techniques such as electrochemical impedance spectroscopy, linear polarization, and cyclic polarization. The electrochemical results suggest that the corrosion resistance of X70 line pipe steel increases as immersion time increases (from 7 to 28 days) due to the formation of a stable protective oxide layer on the surface. In the case of X80 line pipe steel, however, the corrosion resistance increases as immersion time increases from 7 to 14 days due to the preferential dissolution of bainite as a result of its higher activity, which initiates the formation of passive film. Furthermore, after 21 days of immersion of X80 line pipe steel in simulated pore solution, a considerable decline in corrosion resistance was observed, which indicates de-passivation, as a result of an increase in oxide film thickness and subsequent spalling off. Intriguingly, as compared to X80 line pipe steel, X70 line pipe steel has a greater potential for producing a stable protective oxide layer without the appearance of minor cracks after a 28-day immersion period, thereby preventing further corrosion and enhancing corrosion resistance. [ABSTRACT FROM AUTHOR]

This paper presents the design of a strain-sensitive, dual ball-shaped tunable zone (DBT) taper structure for light intensity modulation. Unlike conventional tapered optical fibers, the DBT incorporates a central light field modulation zone within the taper. By precisely controlling the fusion parameters between single-mode fiber (SMF) and polarization-maintaining fiber (PMF), the ellipticity of the modulation zone can be finely adjusted, thereby optimizing spectral characteristics. Theoretical analysis based on polarization mode interference (PMI) coupling confirms that the DBT structure achieves a more uniform spectral response. In cantilever beam strain tests, the DBT exhibits high sensitivity and a highly linear intensity–strain response (R² = 0.99), with orthogonal linear polarization mode interference yielding sensitivities of 0.049 dB/με and 0.023 dB/με over the 0–244.33 με strain range. Leveraging the DBT's light intensity sensitivity, a temperature-compensated intensity difference and ratio calculation method is proposed, effectively minimizing the influence of light source fluctuations on sensor performance and enabling high-precision strain measurements with errors as low as ±6 με under minor temperature variations. The DBT fiber device, combined with this innovative demodulation technique, is particularly suitable for precision optical sensing applications. The DBT structure, combined with the novel demodulation method, is particularly well-suited for high-precision and stable measurements in industrial monitoring, aerospace, civil engineering, and precision instruments for micro-deformation sensing. [ABSTRACT FROM AUTHOR]

Micro-polarizer array (MPA) is the core optical component of the Division of Focal-Plane (DoFP) imaging system, and its design is very important to the system's performance. Traditional design methods rely on theoretical analysis and simulation, which is complicated and requires designers to have profound theoretical foundations. In order to simplify the design process and improve efficiency, this paper proposes a 2 × 2 MPA reverse-design strategy based on particle swarm optimization (PSO). This strategy uses intelligent algorithms to automatically explore the design space in order to discover MPA structures with optimal optical properties. In addition, the all-pass filter is introduced to the MPA superpixel unit in the design, which effectively reduces the crosstalk and frequency aliasing between pixels. In this study, two MPA models were designed: a traditional MPA and an MPA with an all-pass filter. The Degree of Linear Polarization (DOLP) image contrast is used as the evaluation standard and compared with the traditional MPA; the results show that the contrast of the newly designed traditional MPA image is increased by 21%, and the MPA image with the all-pass filter is significantly increased by 82%. Therefore, the reverse-design method proposed in this paper not only simplifies the design process but also can design an MPA with enhanced optical performance, which has obvious advantages over the traditional method. [ABSTRACT FROM AUTHOR]

Patterned polarizers are prepared using liquid crystals (LC) doped with a black dichroic dye and in combination with a linear polarizer. The pattern is achieved with a nanostructured LC alignment surface, that is generated using a two-photon polymerization direct laser write (2PP-DLW). This technique creates a pattern of high-resolution grooves in the photoresist at any arbitrary angle. The angle governs the LC orientation at any substrate surface point, determining the transmitted light linear polarization angle. This paper presents the first use of a 2PP-DLW cured positive tone photoresist for dichroic dye-doped LC alignment. Two complementary photoresists have been employed: conventional negative tone SU-8 photoresist and, in this context novel, positive tone S1805 photoresist. The alignment quality of the polarizers has been assessed by analyzing the transmission using an additional polarizer. For SU-8, the resulting grayscale pattern and a contrast ratio (CR) of 14 has measured. The uniformity of the alignment has been measured to be 65% using normalized Shannon entropy (H). For S1805, a CR of 37 was measured, and a uniformity of 63% was obtained. 2PP-DLW allows for shaping complex patterns in submicron dimensions and for the fabrication of arbitrarily patterned polarizers and other LC devices. [ABSTRACT FROM AUTHOR]

We report observations of the highly active FRB 20240114A with MeerKAT using the ultra-high frequency (UHF; |$544\!-\!1088$|  MHz) and L band (⁠|$856\!-\!1712$|  MHz) receivers. A total of 62 bursts were detected in coherent tied-array beams using the MeerTRAP real-time transient detection pipeline. We measure a structure-optimizing dispersion measure of |$527.65\pm 0.01\, \text{pc}\, \text{cm}^{-3}$| using the brightest burst in the sample. We find the bursts of FRB 20240114A are generally detected in part of the broad-band of MeerKAT, |$\sim 40~{{\ \rm per\ cent}}$| in the UHF and |$\sim 30~{{\ \rm per\ cent}}$| in the L band, indicating the band limited nature. We analyse the fluence distribution of the 44 bursts detected at UHF, constraining the fluence completeness limit to |$\sim 1$|  Jy ms, above which the cumulative burst rate follows a power law |$R (\gt F)\propto (F/1\, \text{Jy}\, \text{ms})^\gamma$| with |$\gamma =-1.8\pm 0.2$|⁠. Using channelized telescope data captured in our transient buffer we localize FRB 20240114A in the image domain to RA = 21h27m39.86s, Dec. = +04d19m45.01s with an uncertainty of 1.4 arcsec. This localization allows us to confidently identify the host galaxy of FRB 20240114A. Also using the transient buffer data, we perform a polarimetric study and demonstrate that most of the bursts have |$\sim 100~{{\ \rm per\ cent}}$| linear polarization fractions and up to |$\sim 20~{{\ \rm per\ cent}}$| circular polarization fractions. Finally, we predict the flux density of a potential persistent radio source (PRS) associated with FRB 20240114A is |$\backsimeq [0.6\!-\!60]\, \mu \text{Jy}$| based on the simple relation between the luminosity of the PRS and the rotation measure arising from the FRB local environment. [ABSTRACT FROM AUTHOR]

Summary A wearable dual‐band dual‐polarized fabric antenna is screen printed on a cotton polyester substrate to operate at the industrial scientific and medical band at 2.45 GHz and wireless local area network at 5.2 GHz. A rectangular slot with a pair of L‐shaped branches are used to excite dual bands. The rectangular slot is used to achieve lower band resonance at 2.45 GHz with linear polarization, and an L‐shaped branch with a stub is used to obtain the circular polarization at 5.2 GHz. A 3 × 3 electromagnetic bandgap (EBG) structure is enabled behind the antenna to minimize the back radiation and specific absorption rate (SAR). The antenna provides a measured impedance bandwidth (BW) of 25% from 2.1 to 2.7 GHz (600 MHz), and 18% from 4.5 to 5.7 GHz (1.2 GHz), respectively. The antenna also has a 3‐dB axial ratio BW of 15% from 4.6 to 5.35 GHz (750 MHz). The antenna exhibits a measured gain of 5.1 dB at 5.2 GHz and 6.4 dB at 2.45 GHz. The SAR is validated by using a CST (computer simulation technology) voxel human body model and found to be 0.0949 and 0.127 W/kg for 1 g tissue at 5.2 and 2.45 GHz, respectively. The dimension of the proposed EBG integrated antenna is (0.52 λ × 0.52 λ × 0.07 λ). The antenna and EBG structure are screen printed with silver conductive ink, which provides good conductivity, conformability, comfort, wearability, and being lightweight. [ABSTRACT FROM AUTHOR]

2D moiré superlattices offer a versatile platform for manipulating quantum materials, exploiting their spatially varying atomic registry to modify electronic structures, resulting in the emergence of flat electronic minibands, enhanced electronic interactions, and the onset of novel quantum phenomena. Despite extensive investigations into moiré excitons within twisted bilayer moiré superlattices, the interplay between moiré superlattices and optical microcavities remains elusive. Here, a WSe2 homobilayer with a small twist angle positioned on optical microcavities atop a SiO2 (285 nm)/Si substrate is investigated. Utilizing low‐temperature photoluminescence (PL) spectroscopy, it is observed that the twisted homobilayer at the edge of the optical cavity (Edge‐THB) exhibits enhanced localization of moiré excitons and a deeper moiré potential. This behavior is attributed to the combined influence of strain induced by the optical microcavity structure on the moiré superlattice and the amplification of the electromagnetic field. Furthermore, the existence of moiré excitons through a comprehensive analysis, encompassing temperature‐dependent PL spectra, circularly polarized PL spectra, and Landé g‐factor measurements for Edge‐THB is validated. These findings provide valuable insights into the intricate interaction between moiré superlattices and optical microcavities, paving the way for future applications in quantum technologies. [ABSTRACT FROM AUTHOR]

In WiFi 7 (IEEE 802.11be), Multiple Input Multiple Output (MIMO) technology plays a crucial role in enhancing throughput. This combination enables numerous applications for wearable WiFi devices. For instance, WiFi can be utilized for tracking and fall detection purposes. Additionally, wearable devices used in gaming, vital signal monitoring, and tracking can benefit from the implementation of wearable MIMO antennas. Despite the demand for wearable WiFi antennas, specifically in the new 6 GHz band, a significant gap exists in the investigation of antennas that are completely made of textile, are low profile, and provide vertical polarization and omnidirectional patterns. Addressing this gap, in this paper, a wearable planar antenna is introduced, which is specifically designed to offer an omnidirectional pattern and linear polarization. To ensure its practicality and ease of use, the antenna utilizes lightweight and wearable textile material. The design details and performance of the proposed antenna are presented. The antenna covers all three bands of WiFi, namely, 2.4 GHz, 5 GHz, and 6 GHz bands. The 10-dB return loss bandwidth is 2.4 GHz-2.5 GHz, and 4.6 GHz-7.2 GHz. The maximum Specific Absorption Rate (SAR) for an input power of 500 mW is calculated at 1.053 W/Kg for a 2 mm air gap between the antenna and tissue surface. The size of the antenna is given by a circular area of π x (50 mm)², and a thickness of 6 mm. [ABSTRACT FROM AUTHOR]

Achieving independent multitasked wavefront control by using an ultrathin plate is a challenge to increase information capacity in integration optics and radar applications. Transmission-reflection-integrated metasurface provides an efficient recipe primarily for multifunctional meta-device, however it is challenging to synergize both linear polarization (LP) and circular polarization (CP) using a single meta-plate. Here, a multichannel full-space coding metasurface composed of interleaved shared-aperture meta-atom is proposed to achieve large information capacity by capsulating judiciously engineered high efficiency triple sub-elements (modes) in four-layer scheme. By rotating dual-gap split ring resonator and varying size of "L" type structure insulating by a metallic ring with electrostatic-analogue shielding effect, both Pancharatnam–Berry (PB) and dynamic phases are independently realized under CP and LP waves, respectively. Such an extraordinary insulating strategy completely suppresses crosstalk among three modes and unprecedentedly increases the capability in yielding kaleidoscopic wavefront control. To verify the significance, a proof-of-concept metadevice is devised and experimentally demonstrated with tri-channel wavefront manipulations, exhibiting reflective dual-vortex beam and Bessel beam for forward and backward CP wave, respectively at high frequency, while transmissive polarization beam splitting for 45°-LP wave at low frequency. Our finding in polarization-direction multiplexing is expected to generate great interest in electromagnetic integration with emerging degree of freedoms. [ABSTRACT FROM AUTHOR]

General Relativity predicts the existence of quadratic quasi-normal modes at second order in perturbation theory. Building on our recent work, we compute the amplitudes and polarizations of these modes for non-rotating black holes, showing that they are completely determined by the amplitudes and polarizations of linear modes. We obtain the ratio of quadratic to linear amplitudes, which still depends on the initial conditions of the merger through the polarization of linear modes. However, we demonstrate that this dependence is captured by four fundamental numbers, independent of initial conditions, representing four different combinations of linear modes parities. Additionally, we prove two selection rules regarding the vanishing of classes of quadratic modes. Our results are available online as a package which provides the ratio of amplitudes across a broad spectrum of angular momenta. [ABSTRACT FROM AUTHOR]

Deep learning techniques provide a new approach to the design and optimization of electromagnetic metamaterials. This study used a convolutional neural network and long short-term memory (CNN–LSTM) hybrid network to design and optimize a broadband metamaterial reflective linear polarization converter. The data augmentation method was also employed in few-shot learning to reduce optimization costs and improve model prediction performance. With the inverse prediction, a linear polarization converter that perfectly covers the Ku-band was obtained and fabricated with flexible printed circuit technology. Both simulation and experimental results indicate that this network can accurately predict the structural parameters. The polarization converter not only achieves remarkable broadband polarization conversion efficiency spanning the 2.2–18 GHz range but also maintains precise cross-polarization control across the entire Ku-band. The mean polarization conversion ratio in the Ku-band was calculated to be an impressive 99.69%. Finally, the mechanism of polarization conversion and the influence of each structural parameter on its performance further verify the optimality of the inverse design model. The use of CNN–LSTM deep learning methods significantly simplified the design process of electromagnetic metamaterials, reducing design costs while ensuring high design precision and excellent performance. [ABSTRACT FROM AUTHOR]

This study evaluates the effectiveness of KMnO4, MK3 and 1-butanol inhibitors on corrosion of AISI 314 and AISI 304 stainless steels using linear and potentiodynamic polarization in 0.1 M HNO3. The metrics like corrosion potential (Ecorr), current density (jcorr) and polarization resistance (Rp) influence the inhibitor efficacy. The inhibitors improved electrochemical parameters significantly, indicating strong anti-corrosive properties. 1-Butanol had the strongest effect, enhancing corrosion potential and drastically reducing corrosion current density, demonstrating superior protection. The results indicated that without inhibitors, both steels showed higher corrosion rates and more negative potentials, reflecting their susceptibility to corrosion. The introduction of inhibitors markedly improved these parameters, particularly with 1-butanol, which significantly enhanced the polarization resistance and shifted the corrosion potential towards less negative values. The potentiodynamic results highlighted the dynamic effectiveness of inhibitors, reinforcing their role in mitigating corrosion under varied conditions. The study underscores the importance of selecting the appropriate inhibitors to enhance the durability and longevity of stainless steels in acidic environments, with 1-butanol showing the potential for industrial applications requiring high corrosion resistance. This necessitates comprehensive testing to accurately measure inhibitor capabilities in different conditions. [ABSTRACT FROM AUTHOR]

A theoretical analysis is presented on the photoexcitation of a macroscopic atomic target by a Hermite–Gaussian (HG) beam within the framework of density matrix theory. Special emphasis is paid to the influence of the incoming HG mode on the population of an excited state and the emitted fluorescence radiation. In particular, a general expression for the alignment parameter of the excited state is derived, which depends on the beam parameters of the HG mode. Although the developed theory can be applied to any atomic system, here the electric dipole transition 3s2S1/2→3p2P3/2$3s\; {}^{2}S_{1/2}\nobreakspace \rightarrow \nobreakspace 3p \; {}^{2}P_{3/2}$ in neutral sodium atoms is investigated when driven by three HG10${\rm HG}_{10}$, HG01,${\rm HG}_{01,}$ and HG11${\rm HG}_{11}$ modes. For this optical (valence‐shell) excitation, it is demonstrated that the population of the excited state is sensitive to the beam waist and the mode index of the HG beam. Furthermore, the influence of beam parameters on the angular distribution and linear polarization of the emitted fluorescence radiation is discussed. [ABSTRACT FROM AUTHOR]

In this article, an ultrathin (λ0/14.9), single layer, reflective type polarization converter for either linear-to-circular (LP-to-CP) or linear-to-linear (LP-to-LP) polarization conversion is reported. It has been demonstrated to achieve the LP-to-CP conversion at two separate frequency bands, including 11.52-11.84GHz and 19.83-20.01GHz. The circular polarization type is specified as a right-hand circular polarization (RHCP) for the first band and a left-hand circular polarization (LHCP) for the second band. In both of frequency bands, the metasurface structure reveals highly efficient features. Besides that, the metasurface structure exhibits highly efficient features within 3-dB bandwidths of 10.29-12.58GHz and 19.32-20.50GHz. Crucial parameters of polarization conversion such as ellipticity, axial ratio, and |Eco|/|Ecross| are confirmed to be in good agreement with another one. The metasurface structure's angular stability up to 200 oblique incidence angles makes it useful for beam scanning antennas. CST Microwave Studio program is utilized to carry out extensive simulations. This presented study offers a low cost, relatively high-performance, ultrathin polarization converter capable of linear-to-linear and circular polarization conversion in the X-, Ku-, and K-bands. [ABSTRACT FROM AUTHOR]

In this work, a method for measuring tow angles in carbon fiber components, based on the use of a polarized camera, is analyzed from a metrological point of view. Carbon fibers alter the direction of the reflected light's electrical field, so that in each point of the surface of a composite piece, the angle of polarization of reflected light matches the fiber orientation. A statistical analysis of the angle of linear polarization (AoLP) in each pixel of each examined area allows to evaluate the average winding angle. An evaluation of the measurement uncertainty of the method on a cylinder obtained by a filament winding process is carried out, and the result appears adequate for the study of the distribution of angles along the surface of the piece, in order to optimize the process. [ABSTRACT FROM AUTHOR]

A THz-to-IR converter can be an effective solution for the detection of low-IR-signature targets by combining the advantages of mature IR detection mechanisms with high atmospheric transmittance in the THz region. A metallic metasurface (MS)-based absorber with linear polarization dependence based on a split-ring resonator (SRR) unit cell has been previously studied as a preliminary example of a THz-to-IR converter structure in the literature. In this simulation-based study, a new cross-shaped unit cell-based metallic MS absorber structure sensitive to dual polarization is designed to eliminate linear polarization dependency, thereby allowing for incoherent detection of THz radiation. A model is developed to calculate the temperature difference and the response time for this new cross-shaped absorber structure, and its performance is compared to the SRR structure for both coherent and incoherent illumination. This model allows for understanding the efficiency of these structures by considering all loss mechanisms which previously had not been considered. It is found that both structures show similar performance under linearly polarized coherent illumination. However, under incoherent illumination, the IR emittance efficiency as gauged by the temperature difference for the cross-shaped structure is found to be twice as high as compared to the SRR structure. The results also imply that calculated temperature differences for both structures under coherent and incoherent illumination are well above the limit of the minimum resolvable temperature difference of the state-of-the-art IR cameras. Therefore, dual-polarized or multi-polarization-sensitive MS absorber structures can be crucial for developing cost-effective THz-to-IR converters and be implemented in THz imaging solutions. [ABSTRACT FROM AUTHOR]

The inhibitory effect of Rosemary oil on the corrosion of aluminum alloy EN AW-2011 in 1M H2SO4 solution was studied by weight loss and electrochemical methods such as open circuit potential (OCP), linear sweep voltammetry (LSV) and linear polarization resistance (LPR). The inhibition efficiency increases with increasing the concentration and shows maximum inhibition efficiency (70.7 %) at optimum concentration (0.05 g.L-1). The linear polarization resistance measurements show that the presence of Rosemary oil in 1M H2SO4 solution influences polarization resistance increasing and corrosion current decreasing. The voltammetric curve shows that Rosemary oil reduces the anodic process. Open circuit potential results confirmed that organic compounds present in Rosemary oil can form a protective layer on aluminum surfaces. The inhibitive effect was probably caused by the adsorption of organic compounds such as 1,8-cineole, α-pinene, borneol, limonene, and myrcene on aluminum surfaces which are non-toxic and environmentally friendly. This study showed that the essential oil of Rosemary could be used as an environmentally friendly inhibitor of the corrosion of alloy EN AW-2011 in an acidic medium. [ABSTRACT FROM AUTHOR]

The polarization direction-dependent SBS threshold was investigated, and the terminal polarization control technique was demonstrated to restore the linear polarization state. By increasing the relative angle of the injecting polarization direction from 0° to 90°, the measured SBS threshold increased until reaching a maximum value, beyond which it decreased in a nearly symmetrical trend. The highest SBS threshold was achieved with the relative polarization angle being 45°, delivering a 67% threshold enhancement compared with that at 0°. A quarter-wave-plate was used to restore the polarization state of the output laser manually from an elliptic to a linearly polarized state, and temperature-dependent polarization fluctuation was observed, which intensified as the laser power was scaled. By reducing the cooling temperature, a 1 kW laser with a linearly polarized state was demonstrated using a 45° polarization direction-injected monolithic PM amplifier. [ABSTRACT FROM AUTHOR]

The ultra-wideband polarization converters have been of interest to researcher due to their demand in satellite communication and navigation systems. This paper presents an ultra-wideband reflective cross-polarization converter comprising a stair-shaped metasurface. By observation, the alleged structure allows the conversion of linearly polarized waves to orthogonal components, having a polarization conversion ratio of greater than 90% spread across the large frequency range of 12.94 to 16.54 GHz and 17.54 to 26 GHz. A highly efficient, ultra-high frequency polarization conversion is achieved by the utilization of strong electromagnetic resonance coupling between the upper and lower layers of the metasurface. Further, it is depicted that the polarization converter has a wide obliquity of incidence wave. Moreover, the simulation and measured results show a good match. The linear polarization converter is simple in design but is of high performance, and therefore, might be useful in satellite communication, imaging systems, and navigation systems. [ABSTRACT FROM AUTHOR]

In this paper, the degree of polarization of the fluorescent L X-ray lines L ℓ , Lα1 and Lα2, is studied theoretically with respect to incident energy for some high-Z elements from tungsten to Uranium. The linear polarization for each characteristic line is evolved through alignment parameter assessed by nonrelativistic dipole approximation (NDA) in a point Coulomb potential (A20), and accommodating the effect of screening in a screened Coulomb potential (A20*) and analytical perturbation theory (A20**). The values of degree of linear polarization predicted using alignment parameters (A20,A20*and A20**) are not exactly the same as reported by Kämpfer et al. (Phys Rev A 93:033409, 2016) but the trends are almost the same. Since alignment is model sensitive, therefore, the degree of linear polarization will also be dependent on the theoretical approximation/model used. For L ℓ lines, polarization is found to be in the range (12 to 43) %, whereas for the Lα1 line, the ultimate vigorous line of the L-shell emission, the estimated polarization is positive with value range from (+ 2.5 to + 7.5)% and for the Lα2 line the polarization is negative with value range from (− 9.5 to − 27) %. These calculations are in exemplary compromise with the earlier theoretical results and manifest barely a feeble vulnerability of polarization on the vibrancy of the incident radiation. The present polarization trends show resemblance with the results of Kämpfer et al. (2016) and Özdemir et al. (Appl Radiat Isotopes 69:991, 2011), although the values are not absolutely matching. [ABSTRACT FROM AUTHOR]

A wideband polarization-insensitive bistatic radar cross-section (RCS) reduction design under linear and circular polarization incidence is proposed based on spherical-chessboard metasurfaces. A new metasurface element with wideband characteristics was designed, including a double split-ring structure, single-layer media, and metal board. In the proposed RCS-reduction design, the Pancharatnam–Berry (P-B) phase theory is applied with the designed metasurface element to realize phase distribution mimicking the low-scattering sphere, and thus realizing RCS reduction. In addition, the chessboard configuration is combined with spherical phase distribution to further improve the performance of monostatic and bistatic RCS reduction. Finally, the proposed RCS reduction design can not only realize wideband RCS reduction but also exhibit polarization-insensitive characteristics. It realized 10 dB monostatic and bistatic RCS reduction in a frequency band ranging from 8.5 to 21 GHz (84.8% relative bandwidth) under linear polarization (LP) and circular polarization (CP) incidence. The straightforward and efficient design method of the hybrid spherical chessboard can effectively avoid the complex and time-consuming optimization process in RCS-reduction design. [ABSTRACT FROM AUTHOR]