Optimal Polarization Research Articles

Metasurface-integrated elliptically polarized laser-pumped SERF magnetometers

The emergence of biomagnetism imaging has led to the development of ultrasensitive and compact spin-exchange relaxation-free (SERF) atomic magnetometers that promise high-resolution magnetocardiography (MCG) and magnetoencephalography (MEG). However, conventional optical components are not compatible with nanofabrication processes that enable the integration of atomic magnetometers on chips, especially for elliptically polarized laser-pumped SERF magnetometers with bulky optical systems. In this study, an elliptical-polarization pumping beam (at 795 nm) is achieved through a single-piece metasurface, which results in an SERF magnetometer with a high sensitivity reaching 10.61 fT/Hz1/2 by utilizing a 87Rb vapor cell with a 3 mm inner diameter. To achieve the optimum theoretical polarization, our design combines a computer-assisted optimization algorithm with an emerging metasurface design process. The metasurface is fabricated with 550 nm thick silicon-rich silicon nitride on a 2 × 2 cm2 SiO2 substrate and features a 22.17° ellipticity angle (a deviation from the target polarization of less than 2%) and more than 80% transmittance. This study provides a feasible approach for on-chip polarization control of future all-integrated atomic magnetometers, which will further pave the way for high-resolution biomagnetism imaging and portable atomic sensing applications.

Spintronic terahertz polarization programmable system for information encoding

Terahertz (THz) wave as an important electromagnetic wave has been increasingly applied in wireless communication and imaging sensing technology. It has been an increasingly practical application. Ultra-high data rates in communication technology push toward a broadband, controllable polarization, and multiple transmission channels signal sources. Here, we propose a programmable polarization spintronics terahertz source (PP-STS), in which contains a controllable polarization spintronic THz emitter and a microcontroller unit. The PP-STS not only can generate THz waves with wide frequency bandwidth, but also has the function of switching the orthogonal linear polarization state of the generated THz waves flexibly. By coding the microcontroller unit, the designed PP-SPS can directly program the orthogonal linear polarization states as a series of information to transmit. To achieve the interconversions between digital codes and the THz polarization information, an optimum matching THz polarization beam splitter (THz-PBS) is also designed via simulations and experiments. The THz-PBS, as a decoder, can accurately split the transverse electric (TE) and transverse magnetic (TM) modes into two THz detectors. At last, a coding and decoding prototype system of spintronic THz polarization is built by integrating the PP-STS, the THz-PBS and two THz detectors. The send and receive information with high speed and accuracy are verified in this prototype system as well. We believe that our work takes THz applications for multiplexing communications one step further and sheds light on commercializing the PP-STS with exciting manufacturing lines for efficient and economical THz polarization technology.

Synthesis and characterization of dielectric, electric, and magnetic properties of vanadium doped-bismuth europium ferrites for multiferroic applications

Polycrystalline Bi0.90Eu0.10Fe1-xVxO3 (BEFVO) (where x = 0.00 to 0.10) ceramics were synthesized by the solid-state reaction method. The X-ray diffraction (XRD) pattern revealed that all the samples possess hexagonal crystal structures with some impurity peaks. Gold Schmidt’s tolerance factor of the samples was found 0.8436 to 0.8478 which represents more stability of the doped BiFeO3 (BFO) than parent BFO. The crystallite size was found in the range of 65–33 nm. The density gradually increases with increasing the V concentration and the maximum bulk density (ρB = 6.981 g/cm3) is obtained for the x = 0.10 sample. The obtained average grain size is found in the micrometer range and the values are in the range of 1.31–0.74 µm. The maximum dielectric constant of 2577 at 102 Hz is found for the x = 0.07 sample. The resistivity decreases with doping concentration as a result of ac conductivity increases. The highest transition frequency of long-range to short-range mobility of charge carriers is obtained for the x = 0.07 sample. The highest real part of the initial permeability of 25.24 is found for x = 0.07 multiferroic ceramics. For the x = 0.07 sample, the maximal saturation magnetization is found to be 1.91 emu/g. The studied samples comprise large electric polarization and the optimum polarization of 7.5 μc/cm2 is observed for the x = 0.07 composition.

Three-stage inversion improvement for forest height estimation using dual-PolInSAR data

This paper addresses an algorithm for forest height estimation using single frequency and single baseline dual polarization radar interferometry data. The proposed method is based on a physical two layer volume over ground model and is represented by using polarimetric synthetic aperture radar interferometry (PolInSAR) technique. The presented algorithm provides the opportunity to take advantages of the dual polarimetric data, i.e, better spatial resolution and wider swath width, in comparison with the full polarimetric data, in forest height estimation application. In this research, a polarimetric optimization method is utilized to choose the optimum volume polarization basis in order to improve the results of the three-stage inversion algorithm. For the performance analysis of the proposed approach, the L-band ESAR data of the European Space Agency from BioSAR 2007 campaign (ESA) which is acquired over the Remningstorp test site in southern Sweden, is employed. The experimental result shows the dual PolInSAR HH/HV data capability in the forest height estimation without decreasing the accuracy of the result compared with the full polarimetric data. The suggested method leads to the average root mean square error (RMSE) of 4.39 m and the determination of coefficient of 0.66 in the forest height estimation in 15 predetermined stands in comparison with the LiDAR reference heights.

Efficient SABRE-SHEATH Hyperpolarization of Potent Branched-Chain-Amino-Acid Metabolic Probe [1-13C]ketoisocaproate.

Efficient 13C hyperpolarization of ketoisocaproate is demonstrated in natural isotopic abundance and [1-13C]enriched forms via SABRE-SHEATH (Signal Amplification By Reversible Exchange in SHield Enables Alignment Transfer to Heteronuclei). Parahydrogen, as the source of nuclear spin order, and ketoisocaproate undergo simultaneous chemical exchange with an Ir-IMes-based hexacoordinate complex in CD3OD. SABRE-SHEATH enables spontaneous polarization transfer from parahydrogen-derived hydrides to the 13C nucleus of transiently bound ketoisocaproate. 13C polarization values of up to 18% are achieved at the 1-13C site in 1 min in the liquid state at 30 mM substrate concentration. The efficient polarization build-up becomes possible due to favorable relaxation dynamics. Specifically, the exponential build-up time constant (14.3 ± 0.6 s) is substantially lower than the corresponding polarization decay time constant (22.8 ± 1.2 s) at the optimum polarization transfer field (0.4 microtesla) and temperature (10 °C). The experiments with natural abundance ketoisocaproate revealed polarization level on the 13C-2 site of less than 1%-i.e., one order of magnitude lower than that of the 1-13C site-which is only partially due to more-efficient relaxation dynamics in sub-microtesla fields. We rationalize the overall much lower 13C-2 polarization efficiency in part by less favorable catalyst-binding dynamics of the C-2 site. Pilot SABRE experiments at pH 4.0 (acidified sample) versus pH 6.1 (unaltered sodium [1-13C]ketoisocaproate) reveal substantial modulation of SABRE-SHEATH processes by pH, warranting future systematic pH titration studies of ketoisocaproate, as well as other structurally similar ketocarboxylate motifs including pyruvate and alpha-ketoglutarate, with the overarching goal of maximizing 13C polarization levels in these potent molecular probes. Finally, we also report on the pilot post-mortem use of HP [1-13C]ketoisocaproate in a euthanized mouse, demonstrating that SABRE-hyperpolarized 13C contrast agents hold promise for future metabolic studies.

Dual broad Band-Stop Polarization-Insensitive and scanning angle stability Frequency Selective Surface

In this communication, broad dual band-stop characteristics, polarization–insensitive FSS with large scanning angle stability is developed. A simple square ring with T – shaped resonator is implemented to develop dual-band characteristics. L – Shaped and circular ring metallic layers are incorporated on the proposed unit cell FSS to get optimum polarization insensitive dual-stop frequency bands. The proposed FSS is fabricated on one side of a single layer FR4 substrate. The smallest dimension of the unit cell is 0.1λ0×0.1λ0×0.01λ0 (10.2mm×10.2mm×1.6mm), where λ0 is the free space wavelength at the lower cutoff frequency of 1.97 GHz. The proposed −10 dB dual-band FSS has rejection characteristics over the frequency ranges of (1.97 GHz – 4.06 GHz) and (8 GHz – 12.3 GHz). The achieved −20 dB bandwidth are (2.74 GHz – 3.43 GHz) and (9.5 GHz – 11 GHz) under the TE mode. Equivalent circuit model is implemented to ensure the validity of the work. The fabricated FSS can be used to shield EM wave for S–band and X–band applications.

Электрохимическое ГКР исследование некоторых эндогенных компонентов биожидкостей человека

The work describes electrochemical (EC) protocol suitable for preparation of copper electrodes which can be used as substrates in surface-enhanced Raman spectroscopy (SERS). These SERS-active electrodes have been used for electrospectral studies based on the combination of electrochemical and SERS analysis (EC-SRS analysis). Several endogenous bodyfluid components (urea, creatinine, uric acid, bilirubin) have been selected for the study because they can significantly affect the SERS-based determination of other analytes in bodyfluids (for example, drugs). The influence of the SERS-active electrode polarization (applied potential) and the pH level of the analyte solutions on the SERS signal and current value have been investigated. The polarization values corresponded to the maximum SERS signal are observed at negative values for all analytes (below −0.2 V vs. copper pseudo-reference electrode). The maximal SERS signal has been observed for most of the analytes in a neutral medium (at the optimum polarization value of the SERS-active electrode), and the weakest signal has been in an alkaline medium. The diminishing of EC-SERS signal at high pH values is explained by deprotonation of analyte molecules that deteriorates analyte adsorption onto the negatively polarized SERS-active electrodes. Analysis of the current-voltage curves has been used to estimate the possible influence of EC changes of the studied molecules on their EC-SERS signal. The results obtained in this work will be useful for the development of EC-SERS systems suitable for the determination of various endo- and exogenous compounds in human biofluids.

Local optimum underwater polarization imaging enhancement based on connected domain prior

Estimating the degree of polarization (DOP) of target signal light () is a critical step in the underwater polarization differential imaging process. It is challenging to accurately estimate the of objects containing multiple attributes in the imaging range. Inspired by the optical polarization characteristics of objects with different DOP, we find a prior of connected domains (CDs) of objects in polarization orthogonal images. Based on this prior, the CDs of low-DOP (LDOP) and high-DOP (HDOP) objects are extracted from the darkest image () and brightest image () without additional image acquisition. The of LDOP and HDOP objects in the scene can be estimated through the extracted CDs, which realizes the transition from global optimum estimation in the traditional method to local optimum estimation. According to the estimated , the enhanced results of the entire image marked by can be obtained after fusing the enhanced results of the objects in each CD. Experimental results of simple and complex combination scenes of objects show that our method can recognize CDs of LDOP and HDOP objects. We obtained the enhanced results of the entire image, verified the feasibility and robustness of our method, and found that the CDs of LDOP and HDOP objects could be effectively extracted in up to NTU of turbid water. The local optimum improves the application ability of underwater polarization imaging in unpredictable scenarios, while the enhanced result of target labeling has potential application value in underwater target recognition and classification.

Multi-path remote-excited surface plasmon resonance of a hollow gold nanosheet studied using FDTD simulations

Multi-path remote-excited surface-enhanced Raman scattering (SERS) could be achieved in a two-dimensional hollow gold nanosheet (HGNS) structure. This structure typically contains one hollow and regular cavity located concentrically in the middle of a gold nanosheet (GNS), which forms such as Triangle-Triangle (T-T) or Hexagon-Hexagon (HH) HGNS. As for T-T HGNSs, if we focused the exciting incident laser on one vertex of the outer-solid-triangle (OST) or inner-hollow-triangle (IHT), the localized surface plasmon resonance (LSPR) could be achieved on other remote vertexes. Because of this hollow cavity (e.g. IHT in T-T HGNSs), the maximum quad-path remote-excited SERS system could be developed. The optical property of equilateral triangular and solid GNS (SGNS) is comparatively simple and symmetric. However, after a hollow triangle cavity is formed within GNS, it can be used to modulate LSPR and bring in a new coupling effect between OST and IHT. FDTD simulations have shown that a red-shift of LSPR peak with the increase of IHT size were observed. Compared with single-path-excitation, the remote signal of LSPR scattering at wavelength around 0.76 μm can be enhanced, under the optimum coupling polarization, by over 228 %, 597 % and 1155 % for dual-, triple- and quad-path-excitation respectively. At given LSPR peak (e.g. around 1.061 μm), this enhancement can be doubled once again at least. Furthermore, a remarkable polarization-dependent anisotropic property in T-T HGNS was observed owing to strong OST-IHT couplings, which exhibits great potential application in remote SERS, remote sensing and optical waveguide switch.

Finite Element Analysis and Polarization Test of IDEs Piezoelectric Actuator.

A new type of actuator is presented in the paper that integrates the IDEs into a conventional piezoelectric sheet. The electrodes and polarization play a key role in the strain. Adopting constitutive equations of piezoelectric theory and variation principles in elasticity theory, the piezoelectric component dynamic equation was deduced. Several finite element models of the IDEs piezoelectric actuator were established in ANSYS. The effect of branch electrodes on the strain of the actuator was analyzed. The results show that the strain can be bigger than that of the conventional piezoelectric sheet by decreasing the gap and increasing the width of electrodes. According to the FEM result, some IDEs piezoelectric actuators were prepared. The distribution of the static electric field inside the actuator was researched to determine the polarization voltage. The 2671 high voltage power and DU-20 temperature-controlled oil bath was applied to explore the polarization process. The effect of the voltage, time and temperature on the strain of the actuator was researched by a TF2000 and SIOS laser interferometer. The results show that the optimum polarization is 800 V, for 60 min and at 150 °C. The strain of the IDEs piezoelectric actuator is 1.87 times that of the conventional piezoelectric actuator. The actuators could prove to be helpful applications for micro-nano devices.

Tuning the hybridization and charge polarization in metal nanoparticles dispersed over Schiff base functionalized SBA-15 enhances CO2 capture and conversion to formic acid

This work reports the development of metal nanoparticles dispersed over Schiff base functionalized SBA-15. Tuning the hybridization favours optimum CO2 capture and charge polarization at metal nanoparticles enhances the conversion of CO2 to formic acid.

Development of Electrochemical Surface Treatment to Visualize Critical Corrosion-Inducing Inclusions of Zr in Chloride Environments

An electrochemical surface treatment was developed to visualize the corrosion-inducing inclusions of Zr in chloride environments. Pure Zr and Zr alloy (Zr–0.5O–0.5C) were evaluated in this study. The electrochemical surface treatment consisted of repeated galvanostatic anodic polarization and potentiostatic cathodic polarization. After the electrochemical surface treatment, only one brittle and non-conductive shell of Zr oxide was observed at the corrosion initiation site on the tested surface. The corrosion-inducing inclusions were found inside the corrosion pit under the optimum polarization conditions. At the corrosion initiation site on pure Zr, the area inside the corrosion pit contained larger amounts of O, C, and Si than the surrounding matrix. In the case of the Zr-0.5O–0.5C alloy, relatively larger inclusions were observed after the treatment. Extremely large amounts of Si, together with O and C, were present in the inclusions. The inclusions that induced localized corrosion on the pure Zr and Zr-0.5O–0.5C specimens were found to be precipitated, involving the specific aggregation of Si. The surface treatment developed in this study is expected to be utilized as a powerful tool to elucidate the localized corrosion mechanism of Zr in chloride environments.

Non-iterative pose estimation method based on the polarization information via a parallelogram

As for vision-based pose estimation, which is also known as the PnP problem, non-iterative algorithms are more efficient. Precise extraction of 2D projections of feature points is important. If the projections of the feature points are not accurately extracted, the pose estimation accuracy is reduced. Under the condition of natural light, a camera captures the images of feature points, and the existence of high-light regions in the image affects the extraction accuracy of 2D projections of feature points, which reduces the number of effective feature points and leads to poor pose estimation accuracy. In the redundant cases (n > 4), redundant feature points are introduced as additional information, increasing the number of effective feature points to reduce the impact of high-light regions and improve the pose estimation accuracy. For the non-redundant cases (n = 4), it was difficult to ensure pose estimation accuracy. To solve this problem, a non-iterative pose estimation method based on the optimum polarization angle via four corner points of a parallelogram was proposed in this study. First, a model for solving optimum polarization angle was established. Thereafter, on the premise of the optimum polarization angle, the images were captured. Finally, the projections of the four corner points of a parallelogram were extracted, and the object pose was solved non-iteratively according to the four corner points. The corner point extraction experimental results show that the slope difference between the two parallel sides of each parallelogram under the condition of optimum polarization angle is less than that under the condition of natural light, thereby proving the improvement of the imaging quality. Measurement accuracy verification experiments prove that our pose estimation algorithm and the optimum polarization angle is the best combination to improve the non-iterative pose estimation accuracy in non-redundant cases. In the measurement range of −60-+60°, the angle measurement error was less than ±0.0491°. In the measurement range of 0–20 mm, the displacement measurement error was less than ±0.0435 mm.

Optimized 3-D Polarized H-Field Forming for Orientation-Insensitive Wireless Power Transfer Systems

This article addresses the angular misalignment problem in wireless power transfer (WPT) systems by a magnetic field ( H-field) forming approach using coil antennas. To power up a planar receiver coil in any orientation, 3-D rotating H-field is required. Using the transmitter coil antennas with amplitude-modulated current excitations, 3-D polarization of H-field is achieved. The power transfer efficiency depends on the polarization of the H-field and varies with receiver inclination. This is applicable for a spherically polarized H-field which is otherwise expected to provide uniform induced voltage in the receiver in any orientation. To completely mitigate the misalignment problem, mathematical analysis of H-field forming is presented followed by optimization of the 3-D polarization. This evolves in understanding the effect of various 3-D H-field polarizations on the induced voltage and results in an optimum ellipsoidal polarization achieving performance that is invariant to the receiver orientation. The results are compared for various 3-D polarizations and the best performance is shown by the proposed solution. The analytically obtained results are validated through simulations and experimental studies. The results thus obtained proved the potential of the proposed optimized 3-D H-field polarization in WPT systems where a free-orientation of the receiver is necessary.

Sea Spike Suppression Method Based on Optimum Polarization Ratio in Airborne SAR Images.

In the condition of ocean observation for high-resolution airborne synthetic aperture radar (SAR), sea spikes will cause serious interference to SAR image interpretation and marine target detection. In order to improve the ability of target detection, it is necessary to suppress sea spikes in SAR images. However, there is no report on sea spike suppression methods in SAR images. As a step forward, a sea spike suppression method based on optimum polarization ratio in airborne SAR images is proposed in this paper. This method is only applicable to the situation where VV and HH dual-polarized SAR data containing sea spikes are acquired at the same time. By calculating the optimum polarization ratio, this method further obtains the difference image of the panoramic area accomplishing sea spike suppression. This method is applied to a field airborne X-band SAR data, including ocean waves, oil spills and ships. The results show that the sea spikes are well suppressed, the contrast of ocean waves and the contrast of oil spills are improved, and the false alarm rate of ship detection is reduced. The discussions on these results demonstrate that the proposed method can effectively suppress sea spikes and improve the interpretability of SAR images.

Finding the optimum polarization boundary line for enhancing the performance of clamped piezoelectric circular plates

The piezoelectric unimorph circular diaphragm is a valuable configuration in many applications of smart structures and smart martials. Piezoelectric energy harvesting, sensing and actuating in a pressure-load system are main applications of this configuration. Structural optimization could be used to improve the performance of this configuration. In this paper, a piezoelectric unimorph energy harvester is considered for capturing energy from pressure fluctuations of a system and converting it to electrical energy. This theoretical study includes comprehensive analytical modelling followed by a parametric study to optimize the polarization boundary of a clamped piezoelectric circular diaphragm. The results indicate that by considering the generated electric field along the diameter of the piezoelectric layer, the location of zero-strain points is found to be dependant on the radii of both the piezoelectric layer and substrate. Moreover, it is observed that these points are almost independent of the thicknesses of the layers and external pressure load. Changes of these parameters can only shift the amplitude of the generated electric field to higher or lower values. The results confirm that the derived closed-form equation for the electric field in Z direction along the diameter of the piezoelectric disc is worthwhile for further investigation in this field.

Multi- and dual-wavelength Thulium-doped fluoride fiber laser assisted by four-wave mixing in S-band region

In this work, multi-wavelength lasing in the S-band region using a Sagnac loop filter in a thulium-doped fluoride fiber laser (TDFFL) was demonstrated for the first time. The Sagnac loop served as a comb-like wavelength filter, while a 10-km long dispersion compensating fiber (DCF) was utilized to induce the four-wave mixing (FWM) effect in the cavity. The FWM effect was used to suppress mode competition in the TDFFL as well as to enhance the number of lasing lines. At its optimum polarization state, 17 stable lasing lines at peak powers of less than 10 dB from the highest peak power were observed, with these lasing lines having a uniform wavelength spacing of 0.23 nm. The multi-wavelength operation exhibited minimal wavelength drifts and power fluctuations of less than 0.01 nm and 1.2 dB respectively. A tunable dual-wavelength laser output was also demonstrated, with a constant wavelength spacing throughout the tuning range.

Coherent perfect absorption in epsilon-near-zero ITO thin film in near infrared

Perfect absorption is one of the important application of epsilon-near-zero (ENZ) material. We analyze here the coherent perfect absorption (CPA) in single and bilayer of ENZ thin film of ITO by admittance matching method. To enhance the absorption, a coupling layer of dielectric is to deposit on the substrate with an ENZ ITO layer. CPA conditions are presented here in simulation results which are obtained for p-polarized light. This mode is comparable with the transverse resonance effect. In order to obtain the symmetric results, the optimum polarization direction of illumination is also extracted here. Employing the ENZ CPA property of ITO, this structure is applicable in optical switching, modulation and sensor at the telecommunication regime.

Optimum Septum Polarizer Design for Various Fractional Bandwidths

The numerical optimization results of constant thickness septum polarizer’s performances for various operating fractional bandwidths (FBW) are presented in the paper. The polarizer’s structure includes a common input square waveguide, a constant thickness septum with several steps, and two output rectangular waveguides. The polarizer design of 2-, 3-, 4-, and 5-step septums is optimized for different narrow and wide operating FBWs to obtain the simultaneously maximum values of cross-polarization discrimination and isolation between rectangular ports and return losses. The optimized dimensions of the septums for FBW = 5, 10, 15, 18, and 20% are presented. Based on the obtained results, Q- and K-band prototypes were manufactured and their performances were measured. The measurements of the prototypes are in good agreement with simulations. These optimization results can be widely used for the development of septum polarizers and prediction of their performances for various FBW in the required frequency range.

Pol-InSAR for Forest Biomass Estimation with the Transformation of the Polarization Basis

An improved method that uses polarimetric and Pol-InSAR information at the L-band and P-band was proposed in this study for estimating forest biomass. In the first phase, various polarimetric and polarimetric interferometry indicators were extracted via transformation of the polarization basis. In the second phase, the particle swarm optimization method is applied to identify optimal parameter values for biomass estimation. According to the results, the correlations between the polarimetric indicators and the biomass were stronger at the P-band compared to the L-band. Polarimetric indicators that involve HV and HH–VV show the maximum correlation with biomass prior to optimization. It is demonstrated that changing the polarization basis can significantly improve the correlations of estimators with the biomass, especially at the P-band. The globally optimal estimators involve the same scattering mechanisms (volume and double-bounce scattering), and the optimal polarization bases differ slightly among most of the cases, due to the adaptation to the forest natural geometry and/or the acquisition configuration. Regarding Pol-InSAR, several tree height retrieval estimators that are based on various assumptions have been analyzed under multiple polarization basis rotations. According to the results, the RVoG phase method, which represents the forest as a low-extinction structured volume, yielded the best accuracy, with R = 0.73 and RMSE = 4.30 m. The identification of the optimum polarization indicators via binary PSO could improve the biomass estimation accuracy by 2% and 6% at the P-band and L-band, respectively. It is demonstrated that such an approach can be employed to accurately estimate biomass via extrapolation of in situ measurements over an entire region.