Polarization Mode Research Articles

A small-scale silica gel column chromatography method for separating carbazole compounds from highly mature crude oil

The concentration of carbazoles in highly mature crude oil is quite low, making it challenging to separate carbazole compounds for the gas chromatography-mass spectrometry (GC–MS) detection. This study presents a small-scale column chromatography method for separating carbazoles from highly mature crude oil using silica gel as a solid phase adsorbent and a Pasteur pipette as a separation device. The carbazole-rich crude oil from the Pearl River Mouth Basin was selected to explore the impact of reagent polarity and injection mode on the separation of carbazoles. The oil sample was eluted with solvents mixed with different volume proportions of n-hexane and dichloromethane and each eluted fraction was collected for GC–MS testing. The results indicated that increasing the reagent polarity caused the aromatic hydrocarbons and carbazole compounds in crude oil to be eluted sequentially. Most aromatic compounds in the crude oil could be selectively eluted using a reagent polarity ratio of 9:1 (Vn-hexane: Vdichloromethane), with no carbazole compounds. A significant amount of carbazole compounds were eluted in the polar segments of 8:2–6:4, with the eluted carbazoles concentration accounting for more than 98 % of the total concentration. Moreover, the concentration and recovery of carbazoles eluted by direct injection mode were about 10 % higher than those after adsorption by silica gel. The standard deviation of the parameter ratio for the separated carbazole compounds in the three groups of repeatable parallel experiments was less than 0.2 %. Our method is superior to traditional two-step method and C18 column method in separation efficiency and damage to human body. This method can be applied to both highly mature crude oil and other kinds of oils including biodegradable oil. It could be a versatile method for the carbazoles separation and provide technical support in unveiling the geochemical implications of these compounds in complex areas.

A wide band polarizing beam splitter based on complementary mode modulation in the hyperbolic metamaterial structures

An optimal beam splitter using the polarization mode modulation technique in different alignments of layered hyperbolic metamaterials is presented. The transmission and reflection modes in different arrangements of layered HMMs are studied in the presence of TM and TE waves by analyzing dispersion relations. Results show a duality in the mode modulations between structures aligned in the Y and Z axes. The response of one structure to a beam with zero polarization in terms of transmission and reflection is the same as the response of another to a beam with 90-degree polarization. We utilize this approach to propose a polarizing beam splitter (PBS) based on layered Ag-SiO2 unit cell HMM. FDTD simulations show that in a structure with two complementary outputs, when one of the outputs is in transmission mode, the other output is in reflection mode, and when the incident wave mode is changed from TM to TE, the operating modes of the outputs are reversed. Our structure can be used from 340 nm to Mid-IR with a high extinction ratio, and considering that the outputs work independently, the proposed PBS can prevent the destructive effect of waveguides on each other, which limits conventional beam splitters based on HMMs.

A wideband and high-gain circularly polarized reconfigurable antenna array based on the solid-state plasma

In this paper, a wideband and high-gain circularly polarized (CP) antenna array with polarization-reconfigurable characteristics is presented based on the solid-state plasma (SSP). The proposed antenna is composed of switchable rotating radiation structures and a switchable feed network by simulating the different SSP branches. To investigate the CP operating mechanism, a reconfigurable CP element is designed through characteristic mode analysis (CMA). A switchable sequential-phase feed network is then proposed which can provide separately two rotational excitations. A spoof surface plasmon polariton (SSPP) is adopted for radiation patches to improve gain and axial ratio (AR) bandwidth. Finally, a high-gain and wideband 2 × 2 CP reconfigurable antenna array is designed. This array achieves left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP) modes when different SSP branches are excited. The array has an overlapped impedance bandwidth of 61.9 % (3.17 to 6.01 GHz) and an overlapped AR bandwidth of 40.2 % (4.01 to 6.03 GHz) in two CP states, and the peak gain is 11.68 dBic.

First-principles investigation of the magnetoelectric properties of Ba7Mn4O15

Type-II multiferroics, in which the magnetic order breaks inversion symmetry, are appealing for both fundamental and applied research due their intrinsic coupling between magnetic and electrical orders. Using first-principles calculations we study the ground state magnetic behaviour of Ba7Mn4O15 which has been classified as a type-II multiferroic in recent experiments. Our constrained moment calculations with the proposed experimental magnetic structure shows the spontaneous emergence of a polar mode giving rise to an electrical polarisation comparable to other known type-II multiferroics. When the constraints on the magnetic moments are removed, the spins self-consistently relax into a canted antiferromagnetic ground state configuration where two magnetic modes transforming as distinct irreducible representations coexist. While the dominant magnetic mode matches well with the previous experimental observations, the second mode is found to possess a different character resulting in a non-polar ground state. Interestingly, the non-polar magnetic ground state exhibits a significantly strong linear magnetoelectric (ME) coupling comparable to the well-known multiferroic BiFeO3, suggesting strategies to design new linear MEs.

Applications of Deep Learning-Based Super-Resolution Networks for AMSR2 Arctic Sea Ice Images

Studies have indicated that the decrease in the extent of Arctic sea ice in recent years has had a significant impact on the Arctic ecosystem and global climate. In order to understand the evolution of sea ice, it is becoming increasingly imperative to have continuous observations of Arctic-wide sea ice with high spatial resolution. Passive microwave sensors have the benefit of being less susceptible to weather, wider coverage, and higher temporal resolution. However, it is challenging to retrieve accurate parameters of sea ice due to the low spatial resolution of passive microwave images. Therefore, improving the spatial resolution of passive microwave images is beneficial for reducing the uncertainty of sea ice parameters. In this paper, four competitive multi-image super-resolution (MISR) networks are selected to explore the applicability of the networks on multi-frequency Advanced Microwave Scanning Radiometer 2 (AMSR2) images of Arctic sea ice. The upsampling factor is set to 4 in the experiment. Firstly, the optimal input lengths of the image sequence for the four MISR networks are found, and then the best network on different frequency band images is further identified. Furthermore, some factors, including seasons, sea ice motion, and polarization mode of images, that may affect the super-resolution (SR) results are analyzed. The experimental results indicate that utilizing images from winter yields superior SR results. Conversely, SR results are the worst during summer across all four MISR networks, exhibiting the largest difference in PSNR of 4.48 dB. Additionally, the SR performance is observed to be better for images with smaller magnitudes of sea ice motion compared to those with larger motions, with the maximum PSNR difference of 2.04 dB. Finally, the SR results for vertically polarized images surpass those for horizontally polarized images, showcasing an average advantage of 4.02 dB in PSNR and 0.0061 in SSIM. In summary, valuable suggestions for selecting MISR models for passive microwave images of Arctic sea ice at different frequency bands are offered in this paper. Additionally, the quantification of the various impact factors on SR performance is also discussed in this paper, which provides insights into optimizing MISR algorithms for passive microwave sea ice imagery.

Combined intra symbol frequency domain averaging channel estimation for polarization division multiplexed coherent optical OFDM/OQAM systems

Intrinsic imaginary interference (IMI) induced by chromatic dispersion (CD) and polarization mode dispersion (PMD) seriously degrades the performance of optical orthogonal frequency division multiplexing offset-quadrature amplitude modulation (O-OFDM/OQAM) systems. Therefore, effective channel estimations are required for such systems to maintain good transmission performance. In the previous publications, both the full loaded (FL) and the half loaded (HL) frequency-domain channel estimation methods for polarization-division-multiplexed (PDM) coherent optical OFDM/OQAM (CO-OFDM/OQAM) systems have been proposed. However, for these frequency-domain methods, the channel frequency-domain responses caused by the correlation of the amplified spontaneous emission (ASE) noise are not considered. In this paper, we systematically discuss the frequency-domain channel transmission model for PDM CO-OFDM/OQAM systems. With the analysis of the correlation of the ASE noise, we propose a combined intra symbol frequency-domain averaging (CISFDA) channel estimation method for PDM OFDM/OQAM systems. Compared with the full-loaded frequency-domain channel estimation (FL-FD) method, the CISFDA method promotes the system robustness against the ASE noise and fiber nonlinear effect significantly. The proposed method is validated by numerical Monte Carlo simulations of the PDM CO-OFDM/OQAM system. Our new algorithm outperforms the FL-FD method in the 36 Gb/s PDM OFDM CO-OFDM/OQAM system, and the transmission distance is improved by 500 km with the bit-error-rate (BER) target at 3.8×10-3.

Ultrabroadband metastructure absorber with angular stability for conformal applications

The sustained growth and development of numerous microwave electronic facilities have boosted the demands for microwave absorbers with high performance in bandwidth, wide incident angle, and adaptability of the curved surface. To satisfy these requirements, a 3D-printed electromagnetic metastructure based on a new design methodology with comprehensive microwave absorption properties was proposed and manufactured in this work. The multi-resonant metastructure based on the composite of polyether-ether-ketone and flaky carbonyl iron was designed, and then the gradient impedance distribution was optimized via simulation and comparison of the broadband impedance matching and microwave attenuation properties in different polarization modes under oblique incidence, followed by structural parameters optimization to achieve the optimal absorption performance with broadband and wide incident angle. In the meantime, the conformal capacity of the metastructure under different types of curved surfaces was also investigated. Experimental results correlated well with simulations and demonstrated excellent absorption performance with effective absorption in the broad frequency range of 3.3–30 GHz, stable absorption in the wide incident angle of 0°–70° for both transverse electric and transverse magnetic polarization modes, and strong backward scattering suppression for different conformal states. This effective strategy will provide a novel and promising route toward the development of microwave absorption metastructures with comprehensive electromagnetic performance and accelerate the applications in electromagnetic protection.

Theoretical approach to ferroelectricity in hafnia and related materials

Hafnia ferroelectrics combine technological promise and remarkable behaviors. Their peculiarity stems from the many active extrinsic mechanisms that contribute to their properties and from a continuously growing number of novel intrinsic features. Partly because of their unconventional nature, basic questions about these materials remain open and one may wonder about the pertinence of some frequent theoretical assumptions. Here, aided by first-principles simulations, we show that, by adopting an original high-symmetry reference phase as the starting point of the analysis, we can develop a mathematically simple and physically transparent treatment of the ferroelectric state of hafnia. The proposed approach describes hafnia as a uniaxial ferroic, as suggested by recent studies of (woken-up) samples with well-developed polarization. Also, it is compatible with the occurrence of polar soft modes and proper ferroelectric order. Further, our theory provides a straightforward and unified description of all low-energy polymorphs, shedding light on old questions such as the prevalence of the monoclinic ground state, pointing at exciting possibilities like an antiferroelastic behavior, and facilitating the future development of perturbative theories, from Landau to second-principles potentials. Our work thus yields a deeper understanding of hafnia ferroelectrics, improving our ability to optimize their properties and induce new ones.

Dual polarized optical multi‐input multi‐output transmission over 7‐core few‐mode fiber using adaptive recursive least squares constant modulus algorithm

AbstractWe describe a system with multi‐input multi‐output (MIMO) transmission over 7‐core few‐mode fiber (FMF) by incorporating polarization division multiplexing and mode division multiplexing. Three optical modes with x and y polarizations were used for 42 × 42 MIMO transmission over 7‐core FMF. We simulate the optical MIMO transmission at 20 Gbps with quadrature phase‐shift keying signals. By using the adaptive recursive least squares constant modulus algorithm (RLSCMA) at the receiver side, transmission data is successfully recovered by mitigating the effects of modal delay and mode coupling of received signals. The simulation results show that adaptive RLSCMA can improve the system performance of optical MIMO transmission systems.

TE/TM mode electro-optic conversion based on a titanium diffusion lithium niobate waveguide with a polarization-maintained fiber structure.

For the development of photonic integrated circuits and lithium niobate (L i N b O 3, LN) optical waveguide technology, the implementation and application of polarization devices based on LN are also becoming more widespread, where titanium (Ti)-diffused LN waveguides form the basis of many important electro-optic (EO) integrated optical devices. Moreover, utilizing polarization conversion has the potential to enhance both the effectiveness and capacity of optical transmission. Thus, we have presented an EO polarization mode converter packaging with PANDA polarization-maintaining optical fibers (PMFs) in the broadband wavelength range (1440-1620nm) to obtain the multiwavelength modulation, featuring the wavelength tunability. Additionally, the fabricated device is able to achieve transverse electric (TE) to transverse magnetic (TM) mode conversion efficiently with the applied voltage of ±, which provides high conversion efficiency. Importantly, our device also features a high-frequency response of about 600MHz with overall insertion loss below 5dB. The rapid development of LN-based polarization devices holds great promise for chip-integrated systems in the field of polarization telecommunication.

Black Hole Polarimetry I. A Signature of Electromagnetic Energy Extraction

In 1977, Blandford and Znajek showed that the electromagnetic field surrounding a rotating black hole can harvest its spin energy and use it to power a collimated astrophysical jet, such as the one launched from the center of the elliptical galaxy M87. Today, interferometric observations with the Event Horizon Telescope (EHT) are delivering high-resolution, event-horizon-scale, polarimetric images of the supermassive black hole M87* at the jet launching point. These polarimetric images offer an unprecedented window into the electromagnetic field structure around a black hole. In this paper, we show that a simple polarimetric observable—the phase ∠β 2 of the second azimuthal Fourier mode of the linear polarization in a near-horizon image—depends on the sign of the electromagnetic energy flux and therefore provides a direct probe of black hole energy extraction. In Boyer–Lindquist coordinates, the Poynting flux for axisymmetric electromagnetic fields is proportional to the product B ϕ B r . The phase ∠β 2 likewise depends on the ratio B ϕ /B r , thereby enabling an observer to determine the direction of electromagnetic energy flow in the near-horizon environment experimentally. Data from the 2017 EHT observations of M87* are consistent with electromagnetic energy outflow. Currently envisioned multifrequency observations of M87* will achieve higher dynamic range and angular resolution, and hence deliver measurements of ∠β 2 closer to the event horizon as well as better constraints on Faraday rotation. Such observations will enable a definitive test for energy extraction from the black hole M87*.

Polar Mode Amplification Techniques for Aeronautical Radio Navigation Transmitters: Power Efficiency and Linearity Enhancements

Polar Mode Amplification Techniques for Aeronautical Radio Navigation Transmitters: Power Efficiency and Linearity Enhancements

Polarization-insensitive silicon optic switch based on mode manipulated power splitters and phase shifters

A polarization-insensitive thermo-optic switch is proposed and demonstrated on the silicon-on-insulator platform with a 220 nm silicon core layer. The present device is based on the Mach–Zehnder interferometer structure, consisting of polarization-insensitive power splitters and polarization-insensitive phase shifters (PIPSs). The polarization-insensitive power splitter has been realized by employing an adiabatic directional coupler, which utilizes the fast adiabatic mode evolution by introducing cubic Bézier curves on outer contours, providing broadband 3-dB power splitting for TE and TM polarization modes with only 70 µm coupling length. For the novel PIPSs, the ridge waveguide with large aspect ratio, based on the mode hybridness property, could obtain the same power consumption (Pπ) for an optical switch working at TE and TM polarizations. Experimental results indicate that the measured insertion losses are less than 2 dB and the extinction ratios are larger than 15 dB over a 40 nm wavelength band (covering the C-band).

Bio-inspired Sky Polarized Orientation based on the atmospheric polarization symmetry mode and Inertial Sensors

This paper presents a sky polarized orientation method based on the symmetry of the atmospheric polarization mode and the inertial sensors. Firstly, a method of extracting solar meridians based on canny operator and Hough Transform is proposed by using the symmetry of atmospheric polarization pattern. Then using the horizontal Angle information of the inertial sensor and the ephemeris information of the sun, a method for solving the yaw Angle of the polarized light is designed. Finally, a single axis rotation experiment and a vehicle-mounted dynamic experiment are carried out to verify and compare the proposed method. Compared with the least square method, the positioning accuracy of the single-axis turntable experiment is improved by 22.61%~73.86%, and that of the vehicle-mounted dynamic experiment is improved by 47.71%, which shows that the method can provide a new orientation means for unmanned vehicles and unmanned aerial vehicles.

A test of gravity with Pulsar Timing Arrays

A successful measurement of the Stochastic Gravitational Wave Background (SGWB) in Pulsar Timing Arrays (PTAs) would open up a new window through which to test the predictions of General Relativity (GR). We consider how these measurements might reveal deviations from GR by studying the overlap reduction function — the quantity that in GR is approximated by the Hellings-Downs curve — in some sample modifications of gravity, focusing on the generic prediction of a modified dispersion relation for gravitational waves. We find a distinct signature of such modifications to GR — a shift in the minimum angle of the angular distribution — and demonstrate that this shift is quantitatively sensitive to any change in the phase velocity. In a given modification of gravity, this result can be used, in some regions of parameter space, to distinguish the effect of a modified dispersion relation from that due to the presence of extra polarization modes.

Study of stress dichroism of the thin-wall hollow core fiber based on geometric nonlinearity model

In this paper, we studied the effect of the stress on the propagation modes of the thin-wall hollow core fiber based on geometric nonlinearity model by employing the finite element method. For this special fiber, strong dichroism is observed and the leakage losses of the two orthogonal polarization modes are very sensitive to the applied force. We found that the deformation (the reshaped configuration) majorly contributes to this dichroism effect, so that the effect of the nonuniform distribution of the refractive indices induced by the stress can be omitted. The simulation process can be also appropriate in all kinds of the micro- and nano-system with complicated thin-wall or thin-arm configurations.

Performance of the merged APPLE-Knot undulator for soft x-ray beamline in medium energy ring

APPLE-Knot undulator can effectively solve the on-axis heat load problem and is proven to perform well in VUV beamline and soft x-ray beamline in high energy storage ring. However, for soft x-ray beamline in a medium energy ring, whether the APPLE-Knot undulator excels the APPLE undulator is still a question. Here, a merged APPLE-Knot undulator is studied to generate soft x-ray in a medium energy ring. Its advantages and problems are discussed. Though the on-axis heat load of the APPLE-Knot undulator is lower in linear polarization modes compared to the APPLE undulator, its flux is lower. The APPLE-Knot undulator shows no advantage when only fundamental harmonic is needed. However, in circular polarization mode, the APPLE-Knot undulator shows the ability to cover a broader energy range which can remedy the notable shortcoming of the APPLE undulator.

Partially coherent twisted vector vortex beam enabling manipulation of high-dimensional classical entanglement.

In this paper, we present a novel form of a partially coherent beam characterized by classical entanglement in higher dimensions. We coin the term "twisted vector vortex (TVV) beam" to describe this phenomenon. Similar to multi-partite quantum entangled states in higher dimensions, the partially coherent twisted vector vortex beam possesses distinct properties such as non-uniform polarization, vortex phase, and twist phase. Through experiments, we offer empirical evidence for these three degrees-of-freedom in the light field. The results demonstrate that the state of the light is inseparable in terms of polarization and orbital angular momentum (OAM) modes. Additionally, the twist phase introduces an additional dimension in controlling the vector vortex beam. This research reveals the possibility of new controlling dimensions in classical entanglement through the chirality of coherence within partially coherent light. Consequently, this opens up new avenues for the utilization of partially coherent light in both classical and quantum domains.

Effect of microstructure and environmental conditions on the dielectric properties of plasma sprayed Al2O3 insulating coatings

The effect mechanism of microstructure and environmental conditions on the dielectric properties of plasma-sprayed Al2O3 insulating coatings was systematically investigated in this study. Two kinds of Al2O3 powders with different particle sizes were used to deposit the coatings under the same spraying parameters. The microstructures of the coatings (including porosity, pore size, crack density, and phase composition) were analyzed using scanning electron microscopy (SEM), electron backscattered diffraction (EBSD), and X-ray diffraction (XRD). The dielectric properties (including breakdown strength, resistivity, dielectric constant, dielectric loss, and complex impedance) were characterized by a two-electrode measurement cell. The results indicated that the coating deposited with the larger-sized powder (D50=45.8 μm) exhibited higher porosity, α-Al2O3 content, and connected crack density, than the coating with the other kinder of powder (D50=22 μm). The DC and AC breakdown strengths were found to be related to the porosity of the coatings and the partial discharge in the pores results in the eventual breakdown. The resistivity of the coatings decreased significantly with increasing humidity due to the moisture adsorbed on the pores and cracks. In high-humidity environments, the water molecule enhanced space charge polarization (WESCP), as the main polarization mode, contributed to the dramatic increase of the dielectric constant and dielectric loss. Moreover, the complex impedance and phase angle showed frequency-dependent changes in different environments, suggesting a combined effect of humidity and temperature on the polarization and conductance of coatings. The obtained results of this study could pave the way for the design and application of high-performance plasma-sprayed insulating coatings.

Comparison of tandem pumping and direct pumping on high-power linearly polarized fiber laser.

In this article, a thorough model of linearly polarized fiber laser considering polarization coupling, mode coupling, SBS, and SRS effects is established. The output results of direct pumping and tandem pumping linearly polarized fiber laser under different SBS and SRS intensity settings are simulated. The results show that direct pumping is a better pumping scheme at present, and if the doping concentration of gain fiber can be further increased and the mode field quality of corresponding passive fiber can be optimized, the disadvantages of tandem pumping can be suppressed. To explore the potential of tandem pumping, a backward tandem pumped linearly polarized fiber amplifier is built and 875 W over 13 dB linearly polarized laser output is obtained.