Linearly Polarized Research Articles

Multi-band reflective metasurface for efficient linear and circular polarization conversion

This paper introduces a novel reflective metasurface for efficient polarization conversion in the X, Ku, and K bands. Through rigorous simulations and experimental validation, high polarization conversion ratios (PCR) exceeding 90% were achieved, even at incidence angles up to 45∘. Superior performance in the axial ratio (AR) and ellipticity values was demonstrated, showcasing the versatility of the designed metasurface in linear-to-linear and linear-to-circular polarization conversions. Comparative analysis against existing metasurfaces revealed the superiority of the proposed design in polarization conversion, particularly in Linear polarization, left-hand circular polarization, and right-hand circular polarization scenarios. The experimental results closely align with simulation outcomes, with minor discrepancies attributed to fabrication imperfections and antenna misalignments. This study advances metasurface-based polarization converters, offering promising applications in wireless communication, radar systems, quantum optics, and sensing technologies.

Distinguishing abiotic corrosion from two types of microbiologically influenced corrosion (MIC) using a new electrochemical biofilm/MIC test kit.

Biofilms can cause biofouling, water quality deterioration, and transmission of infectious diseases. They are also responsible for microbiologically influenced corrosion (MIC) which can cause leaks, resulting in environmental disasters. A new disposable biofilm/MIC test kit was demonstrated to distinguish abiotic corrosion of carbon steel from MIC. It used two solid-state electrodes inside a standard 10mL serum vial to form a miniature electrochemical cell. In this work, abiotic corrosion was exemplified using CO2 corrosion and acetic acid corrosion. Sulfate reducing Desulfovibrio ferrophilus IS5, nitrate reducing Pseudomonas aeruginosa, and an oilfield biofilm consortium were grown anaerobically as examples of MIC systems. Tafel curves from dual-half scans and continuous upward scans did not differ significantly in each of the two abiotic corrosion systems. However, obvious distortions in Tafel curve shapes with corrosion potentials (Ecorr) shifts and corrosion current density (icorr) deviations (Tafel skews) were observed in each of the three MIC systems. The polarization resistance (Rp) trend from linear polarization resistance (LPR) for an MIC system decreased in several days due to biofilm buildup while an abiotic system did not have this delay. The abiotic corrosion systems did not respond to electron mediators or biocide injections with negligible Rp changes, while electron mediators accelerated extracellular electron transfer-MIC but not metabolite-MIC, and biocide injection reduced MIC rates as reflected by Rp changes. The results in this work demonstrated that the new kit is a useful tool in MIC diagnosis, biofilm/MIC monitoring and assessment of biocide efficacy.

Polarization-dependent metasurface for vector Zernike wavefront sensing with increased dynamic range.

Metasurfaces have unique properties that make them suitable for a variety of optical applications. Not only do metasurfaces allow a great deal of design flexibility by controlling phase, amplitude, and polarization of reflected or transmitted light, they are also manufactured using mature semiconductor microprocessing techniques. Here we demonstrate a metasurface that can increase the dynamic range of Zernike wavefront sensors (ZWSs) by introducing phase diversity between two orthogonal linear polarizations in the near-infrared. The metasurface works in transmission and consists of elliptically shaped amorphous silicon nanopillars on a fused silica substrate. Wavefront sensors play an important role in segmented-mirror telescopes and enable the precise alignment needed between the segments in order to provide high-quality observations. This work has near-term implications for ground-based telescopes and is of importance for current and future mission concept formulations for exoplanet direct detection and characterization.

A thin, wideband transmissive cross polarization converter.

This study presents a very thin wideband linear polarization converter in transmission mode with near-unity conversion efficiency. The suggested converter consists of a periodic array on a single-layer substrate, two metallic layers and six vias. Metallic vias connect the upper and lower layers of the construction. The radiated electromagnetic wave with linear polarization can be transformed into its orthogonal component in the transmission mode by the proposed converter. The suggested polarization converter operates well in the 9.53-13.35 GHz frequency band (36%). Additionally, The structure provides a larger than 90% Polarization Conversion Ratio (PCR) through the frequency range of 8.89-14.21 GHz. The conversion mechanism has been explained and confirmed through both surface current distribution, electric charge distribution and experimental tests. Over the whole frequency range, there is good agreement between the simulated and measured results.

Defective ground structure loaded polarization reconfigurable ring-shaped patch antenna for multiband applications

ABSTRACT A novel stub-loaded polarization-reconfigurable ring-shaped circular patch antenna designed for multi-band operation and switchable polarization is presented, having advantages such as ease in manufacturing and compact size (20 mm × 20 mm). The circular ring is segmented into four sectors, and two stubs are loaded on the inner side of the ring to disrupt the current distribution and create two orthogonal electric field vectors, generating circular polarization. The antenna supports it in switching three distinct polarization states: linear polarization, left-hand circular polarization, and right-hand circular polarization, selectable with different combinations of diodes. From the measured results, ARBW (<3 dB) is 32.12% and 6.06% for CP bands. Additionally, eight LP bands with IBW of 71.66%, 3.55%, 3.94%, 35.88%, 45%, 45.5%, 34.77%, and 8.2% are achieved. The antenna exhibits satisfactory stable gain across all frequency bands and excellent radiation performance, making it a promising candidate for modern wireless communication applications (C-band, ITS2 fixed, X-band, and Ku-band satellite downlink operations).

Assessment of the Effectiveness of Protective Coatings in Preventing Steel Corrosion in the Marine Environment

This research aims to evaluate the effectiveness of protective coatings in preventing the corrosion of steel in the marine environment. Electrochemical tests were performed on S355JR steel immersed in natural seawater (Black Sea, Port Constanta) over a period of 22 weeks, using electrochemical techniques such as the evolution of the open circuit potential (OCP) and linear polarization resistance to calculate Rp and the corrosion rate (Vcorr). The investigated steel surfaces included (a) S355JR steel blasted with Al2O3, (b) S355JR steel blasted and coated with epoxy primer enriched with zinc, (c) S355JR steel blasted and coated with epoxy primer and polyurethane paint, and (d) S355JR steel blasted and subsequently coated with epoxy primer and then polyurethane paint to which kreutzonit particles had been added. The proportion of kreutzonit particles added to the polyurethane paint was 2 wt% of the total mass of the paint. Subsequently, the samples were subjected to morphological analyses and cross-sectional analysis by scanning electron microscopy (SEM), topographical characterization (roughness and microhardness), and structural assessments (FTIR and XRD), as well as an analysis of hydrophobicity (contact angle). The results of this study revealed significant differences in corrosion behavior between the different surfaces and coatings tested. Electrochemical analysis revealed that the coating with epoxy primer and polyurethane paint to which kreutzonit particles had been added provided the best corrosion protection in the marine environment during immersion.

Structural transitions of ionic microgel solutions driven by circularly polarized electric fields.

In this work, a theoretical approach is developed to investigate the structural properties of ionic microgels induced by a circularly polarized (CP) electric field. Following a similar study on chain formation in the presence of linearly polarized fields [T. Colla et al., ACS Nano, 2018, 12, 4321-4337], we propose an effective potential between microgels which incorporates the field-induced interactions via a static, time averaged polarizing charge at the particle surface. In such a coarse-graining framework, the induced dipole interactions are controlled by external parameters such as the field strength and frequency, ionic strength, as well as microgel charge and concentration, thus providing a convenient route to induce different self-assembly scenarios through experimentally adjustable quantities. In contrast to the case of linearly polarized fields, dipole interactions in the case of CP light are purely repulsive in the direction perpendicular to the polarization plane, while featuring an in-plane attractive well. As a result, the CP field induces layering of planar sheets arranged perpendicularly to the field direction, in strong contrast to the chain formation observed in the case of linear polarizations. Depending on the field strength and particle concentration, in-plane crystallization can also take place. Combining molecular dynamics (MD) simulations and the liquid-state hypernetted-chain (HNC) formalism, we herein investigate the emergence of layering formation and in-plane crystal ordering as the dipole strength and microgel concentration are changed over a wide region of parameter space.

Multi‐fold Phase Metasurface Holography Based on Frequency and Hybrid Decoupling Polarizations

AbstractMetasurfaces are artificially intelligent planar optical devices that can realize excellent functions by optimizing the design of nanostructures and arrays. Metasurfaces have become the preferred approach for fabricating integrated and compact optical systems with micro‐ and nano‐scale solutions for realizing multi‐dimensional modulated optical devices. Herein, the realization of multi‐fold phase holography is demonstrated by combining switchable optical frequencies with hybrid circular and linear polarization states. The original holographic phase distribution can be inversely optimized using an adaptive momentum gradient descent algorithm. Furthermore, completely different images can be reconstructed when the phase values are several times the original values. The multi‐fold phase modulation can be achieved by optimizing the structural distribution of the dielectric metasurface with the incident changeable light frequency and decoupled circular and linear polarization. Different polarization combinations enhance the flexibility of multiple holographic modulations. This technology provides new solutions for dynamic multi‐fold beam directional refraction and excitation, orbital angular momentum communication, multi‐fold holographic displays, optical encryption and camouflage, light switching, and shaping.

Wavelength-dependent far-infrared polarization of HL Tau observed with SOFIA/HAWC+

We present the first polarimetric observations of a circumstellar disk in the far-infrared wavelength range. We report flux and linear polarization measurements of the young stellar object HL Tau in the bands A ( um ), C ( um ), D ( um ), and E ( um ) with the High-resolution Airborne Wideband Camera-plus (HAWC+) on board of the Stratospheric Observatory for Infrared Astronomy (SOFIA). The orientation of the polarization vectors is strongly wavelength-dependent and can be attributed to different wavelength-dependent polarization mechanisms in the disk and its local environment. In bands A, C, and D ( um to um ), the orientation of the polarization is roughly consistent with a value of at the maximum emission. Hereby, the magnetic field direction is close to that of the spin axis of the disk. In contrast, in band E ( um ), the orientation is nearly parallel to the minor axis of the projection of the inclined disk. Based on a viscous accretion disk model combined with a surrounding envelope, we performed polarized three-dimensional Monte Carlo radiative transfer simulations. In particular, we considered polarization due to emission and absorption by aligned dust grains, and polarization due to scattering of the thermal reemission (self-scattering). At wavelengths of um um and um we were able to reproduce the observed orientation of the polarization vectors. Here, the origin of polarization is consistent with polarized emission by aligned non-spherical dust grains. In contrast, at a wavelength of um the polarization pattern could not be fully matched, however, applying self-scattering and assuming dust grain radii up to um we were able to reproduce the flip in the orientation of polarization. We conclude that the polarization is caused by dichroic emission of aligned dust grains in the envelope, while at longer wavelengths, the envelope becomes transparent and the polarization is dominated by self-scattering in the disk.

Vectorial acousto-optic Raman–Nath diffraction effect of chiral liquid media

The acousto-optic Raman–Nath (RN) diffraction effects of vector beams diffracted by the chiral ultrasonic grating are demonstrated experimentally and theoretically. The deviation of left- and right-handed circularly polarized components in higher-order diffraction light leads to the rearrangement of their polarization states and intensity due to the different refractive indices of left- and right-hand circularly polarized lights. When the difference between the refractive indices for left- and right-hand circular polarizations is small, linear polarization components of the higher-order diffraction light with the input localized linearly polarized vector optical field rotate compared to the zero-order diffraction light. Novel, to the best of our knowledge, intensity distributions of linear polarization components appear for the input hybridly polarized vector beam.

Polarimetric imaging of peripheral nerves: an intraoperative aid

In this work, we present a real-time method to aid intraoperative peripheral nerve identification. Using LEDs as the light sources, the device contains a driving motor that rotates a pair of orthogonally oriented linear polarizers. By performing lock-in processing to frames taken under the rotating crossed polarization imaging (RXPI) system, the AC components of the periodic intensity signal of chicken tissues are acquired and compared. With an area under the curve (AUC) of 93%, the chicken sciatic nerve is distinct for automatic identification. In both chicken thigh and cadaver arm models, the contrasts of nerve tissues are successfully enhanced in the lock-in processed output image. Real-time automatic nerve masking is successfully demonstrated in the chicken model using a portable prototype weighing 525 g. In conclusion, the RXPI system with lock-in processing methods can potentially serve as an intraoperative nerve identification aid.

Switchable Bifunctional Chiral Metasurface Based on Vanadium Dioxide for Terahertz Waves

A switchable chiral metasurface (CM) with high polarization conversion ratio (PCR) and absorptivity based on vanadium dioxide (VO2) is proposed and numerically demonstrated in the terahertz (THz) regime. The proposed design consists of VO2–Au‐mixed resonant pattern layer, Si dielectric layer, and Au ground plate, which can achieve tunable bifunctional linear polarization conversion (LPC) and absorption (ABS) by varying the conductivity of VO2 (). For = 10 S m−1, the designed CM possesses a function of broadband LPC. More than 90% PCR is obtained in 1.79–2.46 THz, and the corresponding relative bandwidth (RBW) is 31.28%. For = 2 × 105 S m−1, the designed CM can efficiently absorb incident electromagnetic (EM) waves in 1.54–2.76 THz with the absorptivity exceeding 90% (RBW = 56.47%). The mechanisms of LPC and ABS are analyzed. The effects of geometric and EM parameters, incident angle, and polarization angle on its bifunctional characteristics are also studied. The LPC and ABS performances are maintained within a certain range of incident angles. Furthermore, the proposed CM exhibits polarization insensitivity. The developed switchable bifunctional CM has great potential application value in advanced THz research and smart device.

High-Speed Pulsing Circuit for Continuous Wave Laser Beams.

Abstract Tunable continuous wave (CW) lasers produce the highest optical resolution for pumping and&amp;#xD;probing atomic and molecular transitions. These lasers adopt sophisticated electronic control of&amp;#xD;optical components within the cavity to set the wavelength and ensure a narrow bandwidth. The low cost&amp;#xD;circuit described here gates a CW laser beam on and off for high resolution timing experiments,&amp;#xD;using an electro-optic modulator that acts as a switchable waveplate between linear polarizers. The&amp;#xD;switch can operate at rates of up to 100 kHz with a minimum pulse width of 650 ns, or it can be&amp;#xD;configured to deliver laser pulses with widths ≥ 35 ns at lower rates. Multiple laser pulses of equal&amp;#xD;or non-equal widths can also be delivered within each repetition cycle.

Multilayer Printed Circuit Board Design Based on Copper Paste Sintering Technology for Satellite Communication Receiving Phased Array

A 2048-element dual-polarized receive (RX) phased array for Ku-band (10.7–12.7 GHz) satellite communication (SATCOM) is presented in this paper. The design of the multilayer printed circuit board (PCB) it uses adopts a novel copper paste sintering interconnection technology that allows for more flexibility in the design of vias and can reduce the PCB’s lamination number. This technology is more suitable for manufacturing multilayer and complex PCBs than traditional processes. The array is designed to consist of sixteen 8 × 16 element subarrays, each based on the silicon RX beamformer and multilayer PCB. Dual-polarized antenna elements are arranged in a regular rectangle with a spacing of 0.5 for a wavelength of 12.7 GHz, thus achieving a scanning range of ±70° in all planes. By adjusting the amplitude and phase of two line polarizations with cross-polarization levels better than −25 dB at boresight, the array can generate linear or circular polarization. Moreover, the antenna gain-to-noise temperature is above 12 dB/K (Tant = 20 K) at boresight. The aperture of the 2048-element RX phased array is 768 × 450 mm. With its low profile, the array is appropriate for usage in Ku-band SATCOM terminals.

Filterless vector light field photodetector based on photonic-electronic co-designed non-Hermitian silicon nanostructures.

Recent advances in near-field interference detection, inspired by the non-Hermitian coupling-induced directional sensing of Ormia ochracea, have demonstrated the potential of paired semiconductor nanowires for compact light field detection without optical filters. However, practical implementation faces significant challenges including limited active area, architectural scaling constraints, and incomplete characterization of angular and polarization information. Here, we demonstrate a filterless vector light field photodetector, leveraging the angle- and polarization-sensitive near-field interference of non-Hermitian semiconductor nanostructures. Our design unit comprises four devices, each containing identical silicon nanowires but varying in orientation and electric connection configuration, of which the four-dimensional photoconductive output can be uniquely mapped to key vector light field parameters: intensity, polar angle, azimuth angle, and the linear polarization difference (Stokes parameter, S 1). Optimization of the geometry and doping concentration of these optoelectronic nanostructures yields a theoretical polar angle detectivity of 4 × 10-5 °/Hz0.5. This work establishes a paradigm for multi-output photodetectors with full-rank response matrices for multi-dimensional light field characterization, paving the way for integrated vector light field sensing systems.

High efficiency high gain low side lobe level and slant polarization monopulse antenna using cavity backed slot coupled patch antenna

In this paper, a multilayer monopulse antenna at Ku-Band with high efficiency, high power handling capability, high gain, 45° linear polarization and low sidelobe is presented. A new slot antenna is proposed as a radiating element based on a cavity-backed slot-coupled patch antenna. Using an enclosed cavity structure reduces coupling between antenna elements, thus increasing the antenna efficiency. The sub-array antenna has been designed to reduce the feed network complexity. A cavity power divider and feeding slots are inserted between the layers of the sub-array to compact it. An innovative feeding network has been designed with two-dimensional Chebyshev distribution. The simulated impedance bandwidth is 11%. The peak gain is 38.4 dBi and the sidelobe level of lower than 18 dB with a half-power beamwidth of approximately 2.4° for sum patterns at the center frequency and efficiency is more than 86% across the bandwidth. The maximum value of null depth for the difference patterns is − 38 dB. The radiation patterns have good symmetry in both E- and H-planes. The simulation results are compared with the results obtained from the built part of the antenna. the measurements results are in good agreement with the simulation.

Molten Salt Corrosion Studies of Sanicro‐25 by Electrochemical Techniques at High Temperature

ABSTRACTNickel and chromium‐based alloys are being considered structural materials for crucibles for electrorefining in pyrochemical reprocessing. LiCl–KCl molten salt is used as an electrolyte under an inert argon atmosphere. In the present work, the corrosion behavior of the Sanicro‐25 steel exposed to LiCl–KCl molten salt at 500°C with inert argon cover gas was explored using electrochemical methods like open circuit potential (OCP), linear polarization resistance, and electrochemical impedance spectroscopy (EIS). A change in the OCP of Sanicro‐25 towards the noble direction was observed. The linear polarization resistance, measured at various exposure intervals, decreased with the increase of molten salt exposure. The Nyquist plot consists of two semi‐circles with an incomplete semi‐circle at the lower frequency end, indicating the existence of three‐time constants and formation of intermittent oxide film. The oxide films formed over the surface are characterized by Raman analysis, X‐ray diffraction, X‐ray photoelectron spectroscopy, and scanning electron microscope coupled with elemental analysis. The formation of Fe3O4, Cr2O3, iron hydroxide, W‐oxides, and spinels are evidenced.

Compact single-shot multispectral polarization imager through joint spectral-polarization encoding.

The technique of spectral polarization imaging (SPI) is a potent detection tool in various fields due to its ability to capture multi-dimensional information. However, existing SPI systems usually face challenges associated with architectural complexity and computational requirements, rendering them unsuitable for handheld, on-board, and real-time applications. Consequently, a compact single-shot multispectral polarization imager (CSMPI) is proposed, which employs a combined spectral-polarization encoding strategy to address the aforementioned issues. It incorporates a coded aperture for encoding multiple spectral channels together with linear polarization into a single measurement, enabling the simultaneous detection of up to nine light components with just one exposure. The resulting prototype consists solely of a color polarization detector and an imaging lens inserted with the small and easily fabricable coded aperture, which features compact dimensions of Φ5.5 cm × 21.5 cm and a light weight of approximately 670 g. This is particularly advantageous for application areas that require system miniaturization and rapid multi-dimensional detection.

Resolving Artifacts and Improving the Detection Limit in Circular Differential Scattering Measurement of Chiral and Achiral Gold Nanorods.

Circular differential scattering (CDS) spectroscopy has been developed as a powerful method for the characterization of the optical activity of individual plasmonic nanostructures and their complexes with chiral molecules. However, standard measurement setups often result in artifacts that have long raised concerns on the interpretation of spectral data. In fact, the detection limit of CDS setups is constrained by the high level of artifacts, to ±10%. We address this issue by means of a detailed theoretical description of changes in the polarization state when circularly polarized light is reflected at a dark-field condenser. As a result, we propose a modified CDS configuration based on sequentially placing the quarter-wave plate and linear polarizer within the detection optical path, to analyze the circular polarization state of the light scattered by individual particles. Extensive analysis demonstrates a detection limit of ±1.5% for the modified configuration, which is significantly lower than that for the conventional setup. As a standard system for CDS measurements, both achiral and chiral gold nanorods (AuNRs) were characterized using both setups. With achiral AuNRs, linear dichroism (LD) artifacts in the conventional setup are found to originate from LD present in the excitation light and are only present if anisotropic excitation is produced as a result of the misalignment of the excitation light to the condenser. With chiral AuNRs, CDS spectra recorded with the conventional setup depend on the orientation of the chiral AuNRs with respect to the x-axis of the microscope and are reversed compared to those on the colloid and measured in the modified configuration. The results are in good agreement with theoretical simulations for both configurations.

Focused polarization hologram with arbitrary polarization to a specified polarization conversion.

Polarization devices play a key role in many optical technologies and applications. However, traditional polarization devices are often large and lack integration, and achieving polarization conversion typically requires combining multiple devices, which makes it challenging to realize integrated optical systems. Following the current trend of optical devices, we propose a method using polarization holographic exposure to prepare polarization conversion devices. This approach allows for the fabrication of devices that can convert arbitrary polarization states into specified polarization states while also incorporating a focusing function. Specifically, two types of polarization conversion holograms are fabricated. One is a linear polarizer with a focusing function, and the other is a circular polarizer with a focusing function. Their polarization extinction ratio is around 35 dB, which has a certain competitiveness in similar devices. This method simplifies the preparation process of multifunctional polarizing devices while ensuring their performance. Our work has potential applications in the fields such as polarization emission, imaging, and sensing. Additionally, this approach broadens the design concept of polarization conversion devices, which may promote the development of optical devices with lower cost and higher integration.