Intensity Polarization Research Articles

Effect of polarization on tunnelling electroresistance in ferroelectric tunnel junctions

High-quality epitaxial BiFeO3 (BFO) films were grown on (001)-, (110)- and (111)-oriented Nb:SrTiO3 (NSTO) substrates by pulsed laser deposition. The type of domain structure can be modulated using BFO ferroelectric films with different crystalline orientations. The ON/OFF ratios obtained in (001)-, (110)- and (111)-oriented Au/BFO/NSTO ferroelectric tunnel junctions (FTJs) are 6 × 103, 3 × 104 and 2 × 105, respectively. Analysis of the I–V curves of tunnelling current and average BFO ferroelectric barrier height proves that the polarization intensity of the BFO films modulates both the ferroelectric barrier and the Schottky barrier profile, which further influences the electronic tunnelling probability in BFO FTJs. This work will be useful for further study on achieving a giant ON/OFF ratio and developing insights into the barrier profile and transport mechanism of metal/ferroelectric/semiconductor-type FTJs.

Magnetic Field Enhanced Cobalt Iridium Alloy Catalyst for Acidic Oxygen Evolution Reaction.

Magnetic field mediated magnetic catalysts provide a powerful pathway for accelerating their sluggish kinetics toward the oxygen evolution reaction (OER) but remain great challenges in acidic media. The key obstacle comes from the production of an ordered magnetic domain catalyst in the harsh acidic OER. In this work, we form an induced local magnetic moment in the metallic Ir catalyst via the significant 3d-5d hybridization by introducing cobalt dopants. Interestingly, CoIr nanoclusters (NCs) exhibit an excellent magnetic field enhanced acidic OER activity, with the lowest overpotential of 220 mV at 10 mA cm-2 and s long-term stability of 120 h under a constant magnetic field (vs 260 mV/20 h without a magnetic field). The turnover frequency reaches 7.4 s-1 at 1.5 V (vs RHE), which is 3.0 times higher than that without magnetization. Density functional theory results show that CoIr NCs have a pronounced spin polarization intensity, which is preferable for OER enhancement.

The poly (arylene ether urea) double interface layer formed in PEEU@HfO2/PEI nanocomposites enables enhanced dielectric and energy storage performance

Polyetherimide (PEI) has great potential as a dielectric because of its high-temperature resistance, but its low energy storage density limits practical applications. Incorporating hafnium dioxide (HfO2) with a moderate dielectric constant (k) and wide bandgap can simultaneously enhance the polarization intensity of PEI and potential barriers for charge injection. Nevertheless, the poor compatibility between HfO2 and PEI inevitably introduces defects, thereby weakening the inhibitory effect on dielectric loss. To tackle this issue, an organic double interface layer is introduced to enhance dielectric performance, where the polar poly(arylene ether urea) (PEEU) containing hydrogen bonds can ensure the layer's compactness. Notably, its non-bonding urea groups serve as deep traps to capture migrating carriers, and the gradient k values of HfO2, PEEU, and PEI help mitigate electric field distortions at the interface, therefore enhancing the suppression of conduction loss. The polarity of PEEU and the introduction of multiple interfaces significantly contribute to an increased k (maximum 9.7, at 1 kHz). At 300 kV mm−1, 5 vol% PEEU@HfO2/PEI achieves a discharged energy density of 3.3 J cm−3 and a high charge-discharge efficiency of 83 %, surpassing 5 vol% HfO2/PEI by 1.95 and 2.44 times, respectively. The further COMSOL simulation verifies and proves this work as a novel design strategy for nanocomposite dielectrics.

Transient dynamics of magneto-optic rotation with elliptically polarized light

In this paper, we analyze the transient behavior of nonlinear magneto-optical rotation in a 87Rb vapor cell. Our focus is on optimizing the optical rotation signal by identifying influential factors. We investigate the impact of cell temperature on alkali atom density and consider characteristics of the light field, such as polarization direction, frequency, intensity, and beam diameter. Low scanning magnetic field rates produce the usual absorption signal, whereas high rates show an asymmetric transient response with oscillatory decay. To further investigate this phenomenon, we evaluate signal amplitude and resonant peaks along the x-, y-, and z-axis directions. Notably, we establish a one-dimensional quadratic equation that describes the relationship between magnetic field scan rate and signal amplitude/peak value. Our findings facilitate the quick evaluation of cell performance, provide insights into the dynamics of ground-state coherence generation, and have potential applications in detecting transient spin coupling or monitoring magnetic fields.

Giant and controllable nonlinear magneto-optical effects in two-dimensional magnets

The interplay of polarization and magnetism in materials with light can create rich nonlinear magneto-optical (NLMO) effects, and the recent discovery of two-dimensional (2D) van der Waals magnets provides remarkable control over NLMO effects due to their superb tunability. Here, based on first-principles calculations, we reported giant NLMO effects in CrI3-based 2D magnets, including a dramatic change of second-harmonics generation (SHG) polarization direction (90°) and intensity (on/off switch) under magnetization reversal and a 100% SHG circular dichroism effect. We further revealed that these effects could not only be used to design ultra-thin multifunctional optical devices but also to detect subtle magnetic orderings. Remarkably, we analytically derived conditions to achieve giant NLMO effects and proposed general strategies to realize them in 2D magnets. Our work not only uncovers a series of intriguing NLMO phenomena but also paves the way for both fundamental research and device applications of ultra-thin NLMO materials.

The Effect of the Barrier Layer on the Uniformity of the Transport Characteristics of AlGaN/GaN Heterostructures on HR-Si(111).

The high transport characteristics of AlGaN/GaN heterostructures are critical components for high-performance electronic and radio-frequency (RF) devices. We report the transport characteristics of AlGaN/GaN heterostructures grown on a high-resistivity (HR) Si(111) substrate, which are unevenly distributed in the central and edge regions of the wafer. The relationship between the composition, stress, and polarization effects was discussed, and the main factors affecting the concentration and mobility of two-dimensional electron gas (2DEG) were clarified. We further demonstrated that the mechanism of changes in polarization intensity and scattering originates from the uneven distribution of Al composition and stress in the AlGaN barrier layer during the growth process. Furthermore, our results provide an important guide on the significance of accomplishing 6 inch AlGaN/GaN HEMT with excellent properties for RF applications.

Vortex polarization and circulation statistics in isotropic turbulence.

We carry out an in-depth analysis of a recently introduced vortex gas model of homogeneous and isotropic turbulence. Direct numerical simulations are used to provide a concrete physical interpretation of one of the model's constituent fields: the degree of vortex polarization. Our investigations shed light on the complexity underlying vortex interactions and reveal, furthermore, that despite some striking similarities, classical and quantum turbulence exhibit distinct structural characteristics, even at inertial range scales. Crucially, these differences arise due to correlations between the polarization and circulation intensity within vortex clusters.

Enhanced Generation of Reactive Oxygen Species via Piezoelectrics based on p-n Heterojunctions with Built-In Electric Field.

Tuning the charge transfer processes through a built-in electric field is an effective way to accelerate the dynamics of electro- and photocatalytic reactions. However, the coupling of the built-in electric field of p-n heterojunctions and the microstrain-induced polarization on the impact of piezocatalysis has not been fully explored. Herein, we demonstrate the role of the built-in electric field of p-type BiOI/n-type BiVO4 heterojunctions in enhancing their piezocatalytic behaviors. The highly crystalline p-n heterojunction is synthesized by using a coprecipitation method under ambient aqueous conditions. Under ultrasonic irradiation in water exposed to air, the p-n heterojunctions exhibit significantly higher production rates of reactive species (·OH, ·O2-, and 1O2) as compared to isolated BiVO4 and BiOI. Also, the piezocatalytic rate of H2O2 production with the BiOI/BiVO4 heterojunction reaches 480 μmol g-1 h-1, which is 1.6- and 12-fold higher than those of BiVO4 and BiOI, respectively. Furthermore, the p-n heterojunction maintains a highly stable H2O2 production rate under ultrasonic irradiation for up to 5 h. The results from the experiments and equation-driven simulations of the strain and piezoelectric potential distributions indicate that the piezocatalytic reactivity of the p-n heterojunction resulted from the polarization intensity induced by periodic ultrasound, which is enhanced by the built-in electric field of the p-n heterojunctions. This study provides new insights into the design of piezocatalysts and opens up new prospects for applications in medicine, environmental remediation, and sonochemical sensors.

Birefringence mapping of biological tissues based on polarization sensitive non-interferometric quantitative phase imaging technique

ObjectiveOral cancer is a leading cause of mortality globally, particularly affecting developing regions where oral hygiene is often overlooked. The optical properties of tissues are vital for diagnostics, with polarization imaging emerging as a label-free, contrast-enhancing technique widely employed in medical and scientific research over past few decades. Materials and methodsWe present a novel polarization sensitive quantitative phase imaging of biological tissues by incorporating the conventional polarization microscope and transport of intensity equation-based phase retrieval algorithm. This integration provides access to the birefringence mapping of biological tissues. The inherent optical anisotropy in biological tissues induces the polarization dependent refractive index variations which can provide the detailed insights into the birefringence characteristics of their extracellular constituents. Experimental investigations were conducted on both normal and cancerous oral tissue samples by recording a set of three polarization intensity images for each case with a step size of 2 μm. ResultsA noteworthy increment in birefringence quantification was observed in cancerous as compared to the normal tissues, attributed to the proliferation of abnormal cells during cancer progression.The mean birefringence values were calculated for both normal and cancerous tissues, revealing a significant increase in birefringence of cancerous tissues (2.1 ± 0.2) × 10−2 compared to normal tissues (0.8 ± 0.2) × 10−2. Data were collected from 8 patients in each group under identical experimental conditions. ConclusionThis polarization sensitive non-interferometric optical approach demonstrated effective discrimination between cancerous and normal tissues, with various parameters indicating elevated values in cancerous tissues.

Integrin and N-cadherin Co-Regulate the Polarity of Mesenchymal Stem Cells via Mechanobiological Mechanisms

To investigate the synergistic regulation of the polarization of mesenchymal stem cells by integrin and N-cadherin-mediated mechanical adhesion and the underlying mechanobiological mechanisms. Bilayer polyethylene glyeol (PEG) hydrogels were formulated and modified with RGD and HAVDI peptides, respectively, to achieve mechanical adhesion to integrin and N-cadherin and to replicate the integrin-mediated mechanical interaction between cells and the extracellular matrix and the N-cadherin-mediated cell-cell mechanical interaction. The polar proteins, phosphatidylinositol 3-kinase (PI3K) and phosphorylated myosin light chain (pMLC), were characterized through immunofluorescence staining in individual cells with or without contact with HAVDI peptides under integrin-mediated adhesion, N-cadherin-mediated adhesion, and different intracellular forces. Their expression levels and polar distribution were analyzed using Image J. Integrin-mediated adhesion induced significantly higher polar strengths of PI3K and pMLC in the contact group than in those in the no contact group, resulting in the concentration of the polar angle of PI3K to β-catenin in the range of 135° to 180° and the concentration of the polar angle of pMLC to β-catenin in the range of 0° to 45° in the contact group. Inhibition of integrin function led to inhibition of the polarity distribution of PI3K in the contact group, but did not change the polarity distribution of pMLC protein. The effect of N-cadherin on the polarity distributions of PI3K and pMLC was similar to that of integrin. However, inhibition of the mechanical adhesion of N-cadherin led to inhibition of the polarity intensity and polarity angle distribution of PI3K and pMLC proteins in the contact group. Furthermore, inhibition of the mechanical adhesion of N-cadherin caused weakened polarity intensity of integrin β1, reducing the proportion of cells with polarity angles between integrin β1 and β-catenin concentrating in the range of 135° to 180°. Additionally, intracellular forces influenced the polar distribution of PI3K and pMLC proteins. Reducing intracellular forces weakened the polarity intensity of PI3K and pMLC proteins and their polarity distribution, while increasing intracellular forces enhanced the polarity intensity of PI3K and pMLC proteins and their polarity distribution. Integrin and N-cadherin co-regulate the polarity distribution of cell proteins and N-cadherin can play an important role in the polarity regulation of stem cells through local inhibition of integrin.

Polarization image demosaicking based on homogeneity space

The advent of the micro-polarizer array allows focal plane sensors to capture polarized light information, resulting in the acquisition of subsampled polarization intensity images. The process of reconstructing a comprehensive representation of polarization information is called polarization demosaicking. Current polarization demosaicking methods are susceptible to encountering polarization artifacts along complex edges due to their failure to account for the intrinsic correlation between polarization channels. We define the homogeneity space by employing the metric neighborhood model to capture the underlying correlation among individual polarization channels. Using the homogeneity space as the foundation, we propose a DI-Fusion method that effectively adaptively diminishes polarization artifacts in the initial demosaicking performance. Additionally, our homogeneity space can be extended in other advanced polarization demosaicking techniques, effectively enhancing the overall demosaicking performance. The experimental results demonstrate the high efficacy of our method in reducing polarization artifacts and enhancing the initial polarization demosaicking performance across two widely recognized benchmark datasets. Our method significantly improves objective metrics and visual performance compared to the initial demosaicking performance.

Effect of Ti4+ and Pb2+ on negative thermal expansion and polarization behaviors of KSr2Nb5O15: First-principles investigation

The utilization of both negative and positive thermal expansion coefficients presents a potential means of mitigating internal stress in high-temperature materials, hence offering a novel approach to enhance the impact strength of those materials. The investigation of the thermal expansion coefficient and polarization characteristics of KSr2Nb5O15 doped with Ti4+ and Pb2+ was conducted by the utilization of first-principles calculations. The introduction of Ti4+ and Pb2+ into the KSr2Nb5O15 lattice resulted in an increase in lattice distortion. This effect was particularly pronounced when Ti4+ and Pb2+ were co-doped, leading to the largest lattice distortion observed in KSr2Nb5O15. Furthermore, the negative thermal expansion coefficient of KSr2Nb5O15 was also found to be the highest under these co-doping conditions, with a value of −0.560×10−5 K−1 compared to the original value of −0.011×10−5 K−1. Conversely, when Ti4+ was doped individually, the lattice distortion and negative thermal expansion coefficient of KSr2Nb5O15 were found to be the smallest. Furthermore, the inclusion of Ti4+ and Pb2+ leads to an enhancement in the dielectric constant. This effect is particularly pronounced when Ti4+ and Pb2+ are simultaneously incorporated into the KSr2Nb5O15 lattice. Consequently, the dielectric constant of the material exhibits a substantial improvement. The greatest polarization intensity is achieved when KSr2Nb5O15 is co-doped with Ti4+ and Pb2+, resulting in a polarization intensity of 38.61 μC/cm2. The dense ceramics comprising of KSr2Nb5O15, with the addition of Ti4+ and Pb2+ dopants, were synthesized using the solid-state reaction method. Subsequently, the thermal expansion coefficients and dielectric characteristics of these ceramics were evaluated. The experimental results are not in good agreement with the calculated results, but qualitatively, the trend predicted by the theory is confirmed by experiment. This study establishes the groundwork for the synthesis of KSr2Nb5O15 materials exhibiting pronounced negative thermal expansion characteristics.

SOFIA/HAWC+ Far-Infrared Polarimetric Large Area CMZ Exploration Survey. I. General Results from the Pilot Program

We present the first data release of the Far-Infrared Polarimetric Large Area CMZ Exploration (FIREPLACE) survey. The survey was taken using the 214 μm band of the HAWC+ instrument with the SOFIA telescope (19.″6 resolution; 0.7 pc). In this first data release we present dust polarization observations covering a ∼0.°5 region of the Galactic center’s central molecular zone (CMZ), approximately centered on the Sgr B2 complex. We detect ∼25,000 Nyquist-sampled polarization pseudovectors, after applying the standard SOFIA cuts for minimum signal-to-noise ratios in fractional polarization and total intensity of three and 200, respectively. Analysis of the magnetic field orientation suggests a bimodal distribution in the field direction. This bimodal distribution shows enhancements in the distribution of field directions for orientations parallel and perpendicular to the Galactic plane, which are suggestive of a CMZ magnetic field configuration with polodial and torodial components. Furthermore, a detailed analysis of individual clouds included in our survey (i.e., Sgr B2, Sgr B2-NW, Sgr B2-Halo, Sgr B1, and Cloud E/F) shows they have fractional polarization values of 1%–10% at 214 μm, with most of the emission having values <5%. A few of these clouds (i.e., Sgr B2 and Cloud E/F) show relatively low fractional polarization values toward their cores and higher fractional polarization values toward their less dense peripheries. We also observe higher fractional polarization toward compact H ii regions, which could indicate an enhancement in the grain alignment in the dust surrounding these sources.

How to enhance the polarization intensity of two-dimensional sliding ferroelectricity for hexagonal boron- or nitrogen-based binary compounds?

In recent years, two-dimensional (2D) sliding ferroelectric (SFE) materials have received widespread attention due to their unique ferroelectric mechanism, which exists in van der Waals bilayer and multilayer systems. However, compared to traditional ferroelectric materials, their relatively weak polarization intensity and low energy barrier limit their practical applications. Here, using the first-principles calculations, we focus on hexagonal layered structures formed by group III–V elements and propose a design principle that utilizes bilayer materials composed of elements with significant differences in atomic electronegativity to address this issue. The results show that materials composed of two atoms with significant electronegativity differences can effectively increase the polarization intensity and possess moderate energy barriers. Furthermore, the polarization intensity can be effectively modulated by adjusting interlayer distance. The research findings have important significance for the exploration of other 2D SFE materials with high polarization intensity.

Programming Polarity Heterogeneity of Energy Storage Dielectrics by Bidirectional Intelligent Design.

Dielectric capacitors, characterized by ultra-high power densities, are considered as fundamental energy storage components in electronic and electrical systems. However, synergistically improving energy densities and efficiencies remains a daunting challenge. Understanding the role of polarityheterogeneity at the nanoscale in determining polarization response is crucial to the domain engineering of high-performance dielectrics. Here, a bidirectional design with phase-field simulation and machine learning is performed to forward reveal the structure-property relationship and reversely optimize polarity heterogeneity to improve energy storage performance. Taking BiFeO3-based dielectrics as typical systems, this work establishes the mapping diagrams of energy density and efficiency dependence on the volume fraction, size and configuration of polar regions. Assisted by CatBoost and Wolf Pack algorithms, this work analyzes the contributions of geometric factors and intrinsic features and find that nanopillar-like polar regions show great potential in achieving both high polarization intensity and fast dipole switching. Finally, a maximal energy density of 188 J cm-3 with efficiency above 95% at 8 MV cm-1 is obtained in BiFeO3-Al2O3 systems. This work provides a general method to study the influence of local polar heterogeneity on polarization behaviors and proposes effective strategies to enhance energy storage performance by tuning polarity heterogeneity.

Preparation and Ferroelectric Properties of Er Doped BaTiO3 Nanotubes

In this paper, erbium-doped barium titanate nanotubes with different concentrations were prepared by combining the anodic oxidation method with the low-temperature hydrothermal method. The TiO2 nanotubes produced by electrolysis using titanium flakes as substrate were put into barium hydroxide octahydrate solution for hydrothermal reaction, and different concentrations of Er-doped barium titanate nanotubes were prepared by adding different concentrations of Er(NO3)3·5H2O to the reaction solution. The samples with different doping concentrations were analyzed for their morphological structure, physical phase composition and ferroelectric properties. All samples were found to have complete barium titanate nanotube structure, and the diffraction peaks of XRD were compared with the standard Cope, and the doped samples were all tetragonal phase chalcogenide structure with no other impurities generated. From the hysteresis loop diagram of the samples measured by the TF-2000 ferroelectric analyzer, it can be found that the residual polarization intensity of the samples showed a characteristic of increasing and then decreasing with the increase of the doping concentration, and the residual polarization intensity was the largest at 0.151 uC/cm2 under the hydrothermal reaction condition of 180°C and 3 h with the Er3+ concentration of 0.0025 mol/L.

Optical and Electrical properties of KNN-SBN:Ho/xYb Transmittance Luminescent Ferroelectric Ceramics

Transparent luminescent ceramics 0.94(K0.5Na0.5)NbO3-0.06Sr(Bi0.5Nb0.5)O3: 0.1Ho2O3/xYb2O3 (KNN-SBN:Ho/xYb, x=0.5, 1.0, 1.5, 2.0) have been synthesized using a solid-state reaction method.All the ceramic materials exhibit a pseudo-cubic structure without heterogeneous phases at room temperature. In addition, the microstructure of KNN-SBN:Ho/xYb transparent luminescent ceramics is very dense, and at the same time, good optical transparency is obtained, with a transmittance of 70.19% when x is 0.5. KNN-SBN:Ho/xYb transparent luminescent ceramics exhibit upconversion luminescence properties, and the best upconversion luminescence intensity is obtained when x is 1.5. The KNN-SBN:Ho/xYb transparent luminescent ceramics are ferroelectrics with good ferroelectric properties under an applied electric field of 120 kV·cm−1, and the maximum polarization intensity is the highest when x is 0.5, which is 21.32 μC·cm−2.

Enhancing energy storage performance of PVDF-based composites through semiconducting AZO-BT heterostructure

Commercially available flexible dielectric capacitors with high energy density (Ud) still present a significant challenge due to the inherent trade-off between breakdown strength (Eb) and dielectric constant (εr). In this context, a novel strategy is proposed to synchronously improve the Eb and εr of PVDF-based polymer capacitors by incorporating AZO-BT heterostructure nanoparticles, forming AZO-BT/PVDF composite films. Initially, the tightly polarized AZO affixed to the surface of BT particles create a localized electric field that enhances and sustains the polarization intensity of BT. Additionally, the heterojunction electric field generated inhibits the migration of the injected electron. Furthermore, the semiconducting AZO with high electron affinity effectively captures and traps the injected and excited electrons. Notably, the existed oxygen vacancies in AZO significantly enhances Eb and polarization reverse. Consequently, the AZO-BT/PVDF composite film achieves the highest Ud of 9.10 J·cm−3 at 460 MV·m−1. The innovative approach of constructing a semiconducting-ferroelectric heterostructure offers a promising avenue for designing and fabricating high energy density polymer capacitors.

Double-clad ytterbium-doped tapered fiber with circular birefringence as a gain medium for structured light.

Amplifying radially and azimuthally polarized beams is a significant challenge due to the instability of the complex beam shape and polarization in inhomogeneous environment. In this Letter, we demonstrated experimentally an efficient approach to directly amplify cylindrical-vector beams with axially symmetric polarization and doughnut-shaped intensity profile in a picosecond MOPA system based on a double-clad ytterbium-doped tapered fiber. To prevent polarization and beam shape distortion during amplification, for the first time to the best of our knowledge, we proposed using the spun architecture of the tapered fiber. In contrast to an isotropic fiber architecture, a spun configuration possessing nearly circular polarization eigenstates supports stable wavefront propagation. Applying this technique, we amplified the cylindrical-vector beam with 10 ps pulses up to 22 W of the average power at a central wavelength of 1030 nm and a repetition rate of 15 MHz, maintaining both mode and polarization stability.

Laser doppler device for simultaneous measurement of the velocity and size of aerosols in the nozzle flame

Liquid aerosol is used in technological processes in mechanical engineering, instrument building, chemical industry, medicine and agriculture and other areas. Nozzles are used to spray liquids, which allow to obtain their uniform distribution on the surface or in the volume. In aviation jet engines, fuel is sprayed using nozzles. The thrust of an aircraft engine depends on the quality of fuel atomization. Information on the distribution of droplet sizes and their movement velocity is required to assess the properties of the entire droplet-air system of the nozzle torch. To determine the main characteristics of the nozzle, you need to have a device that measures the velocity of aerosols and the size of aerosols in the nozzle flame. In order to solve this problem, the possibility of using a laser Doppler velocitymeter is investigated. Analysis of the radiation scattered by aerosols by intensity and state of polarization was carried out. It is proposed to increase the signal/interference ratio of the device by ensuring the matching of scattered radiation by intensity and polarization state. For this purpose, it is proposed to install a spatial filter of scattered laser radiation in the device. Such a filter should have the form of a diaphragm with two holes in the form of a narrow slit. Within the limits of one hole, the condition of complete matching of radiation in terms of intensity will be fulfilled, and within the limits of the other hole, the condition of matching according to the state of polarization will be fulfilled. It is shown that if such a receiving diaphragm is inserted into a differential-type laser velocity meter, it can be used to simultaneously measure the velocity and size of aerosols in the nozzle plume. The laser velocity meter photo detector must contain a built-in amplifier with a wide bandwidth. Doppler signals must then be sent simultaneously to an amplitude detector and a digital device. Using a digital device, the frequency of the variable component of the signal will be measured, which is proportional to the velocity of the aerosol and the amplitude of the signal is measured which is proportional to the size of the aerosol.