Polarization Distribution Research Articles

Simultaneous control of three degrees of freedom in perfect vector vortex beams based on metasurfaces

Abstract The perfect vector vortex beams (PVVBs) have played an important role in various fields due to their advantages of unique vortex features, flexible polarization distribution and multiple degrees of freedom (DoFs). The simultaneous and precise control over multiple DoFs, such as the polarization distribution, beam shape and position which greatly influence various characteristics of PVVBs, holds paramount importance. However, it is still difficult to manipulate various DoFs in a multiplexing way and the control precision of polarization distribution only reaches the half-integer level, notably hindering the further application and development of PVVBs. Here, an approach that integrates holographic technique with geometric phase metasurfaces, experimentally demonstrates the multiplexing control of PVVBs over three DoFs, i.e., enabling the independent manipulation of non-uniform polarization distributions, beam shapes and spatial positions. Furthermore, non-integer polarization order of the generated PVVBs can be arbitrary non-integer numbers with a high resolution of 0.1, largely improving the control precision. With such multiplexing manipulation of PVVBs with high precision, we can provide abundant processing dimensions for information science and technologies, exhibiting broad application potentials in fields such as information encryption, high-speed optical communication, and precise particle manipulation.

Fast generation of perfect vortex and vector beams through highly scattering media via discrete convolution-based vector point-spread-function engineering

Recent advancements in optics have demonstrated that it is possible to take advantage of the feasibility of leveraging wavefront shaping to focus and image through highly scattering media (HSM). Herein, we report a method to rapidly focus perfect vortex beams (PVBs) and perfect vector vortex beams (PVVBs) through the HSM via discrete convolution-based vector point-spread-function (DC-VPSF) engineering. In our method, a vector transmission matrix (VTM)-based operator can be calculated by executing a convolution operation between the measured full VTM and the conjugate of a discrete VPSF sampled from a pre-defined spatial domain mask. The input field can be obtained by performing digital optical phase conjugation on the VTM-based operator. Then the desired output field (that is the discrete VPSF) can be generated through the HSM. Experimentally, the PVBs with different topological charges and identical optical ring sizes are generated through the HSM based on our method. Further, PVBs with controllable polarization states and a high peak-to-background ratio (PBR) are also generated after the HSM by introducing polarizers and wave plates before the recording plane. In addition, our method has advantages in fast calculating the required input field and improving the PBR of the focused light through the HSM compared with the general point-spread-function engineering. Finally, the experimentally generated PVVBs demonstrate the ability to tailor the focused light with more complex polarization distribution through the HSM. Our results may contribute to generalizing the convolution concepts for multiple degrees of freedom wavefront control and provide an effective idea for optical micromanipulation and imaging through scattering media.

Atomic-Scale High-Entropy Design for Superior Capacitive Energy Storage Performance in Lead-Free Ceramics.

Dielectric ceramics with high energy storage performance are crucial for the development of advanced high-power capacitors. However, achieving ultrahigh recoverable energy storage density and efficiency remains challenging, limiting the progress of leading-edge energy storage applications. In this study, (Bi1/2Na1/2)TiO3 (BNT) is selected as the matrix, and the effects of different A-site elements on domain morphology, lattice polarization, and dielectric and ferroelectric properties are systematically investigated. Mg, La, Ca, and Sr are shown to enhance relaxation behavior by different magnitudes; hence, a high-entropy strategy for designing local polymorphic distortions is proposed. Based on atomic-scale investigations, a series of BNT-based high-entropy compositions are designed by introducing trace amounts of Mg and La to improve the electric breakdown strength and further disrupt the polar nanoscale regions (PNRs). A disordered polarization distribution and ultrasmall PNRs with a minimum size of ≈1 nm are detected in the high-entropy ceramics. Ultimately, a high recoverable energy density of 10.1 Jcm-3 and an efficiency of 90% are achieved for (Ca0.2Sr0.2Ba0.2Mg0.05La0.05Bi0.15Na0.15)TiO3. Furthermore, it displays a high-power density of 584 MWcm-3 and an ultrashort discharge time of 27 ns. This work presents an effective approach for designing dielectric energy storage materials with superior comprehensive performance via a high-entropy strategy.

Isotropic and anisotropic edge enhancement using a lemon-star polarization dipole.

A spiral phase filter can perform a radial Hilbert transform (RHT) and is useful in isotropic edge enhancement. For selective edge enhancement, the inclusion of anisotropy warrants the filter to be replaced. In this Letter, we introduce for the first time, to our knowledge, a novel and versatile filter that can be tuned between isotropic/anisotropic edge detection and contrast enhancement protocols. To achieve this, we use a lemon-star polarization dipole: a special kind of spin-orbit beam that is a superposition of spin and orbital angular momentum states of light. We devised a 4f imaging setup in microscope configuration to encode the object Fourier spectrum into inhomogeneous polarization distribution. The novelty and advantages of the proposed method lie in selecting the spatial frequency content through polarization transformations in the image reconstruction path, just before the detector, without altering the Fourier plane parameters. Considering a scalar-to-vector diffraction approach and invoking the polarization degree of freedom of light, the edge enhancement capabilities of a lemon-star polarization dipole and a monopole (star or lemon) are shown through experiment results.

Near-Native Imaging of Metal Ion-Initiated Cell State Transition.

Metal ions are indispensable to life, as they can serve as essential enzyme cofactors to drive fundamental biochemical reactions, yet paradoxically, excess is highly toxic. Higher-order cells have evolved functionally distinct organelles that separate and coordinate sophisticated biochemical processes to maintain cellular homeostasis upon metal ion stimuli. Here, we uncover the remodeling of subcellular architecture and organellar interactome in yeast initiated by several metal ion stimulations, relying on near-native three-dimensional imaging, cryo-soft X-ray tomography. The three-dimensional architecture of intact yeast directly shows that iron or manganese triggers a hormesis-like effect that promotes cell proliferation. This process leads to the reorganization of organelles in the preparation for division, characterized by the polar distribution of mitochondria, an increased number of lipid droplets (LDs), volume shrinkage, and the formation of a hollow structure. Additionally, vesicle-like structures that detach from the vacuole are observed. Oppositely, cadmium or mercury causes stress-associated phenotypes, including mitochondrial fragmentation, LD swelling, and autophagosome formation. Notably, the organellar interactome, encompassing the interactions between mitochondria and LDs and those between the nuclear envelope and LDs, is quantified and exhibits alteration with multifaceted features in response to different metal ions. More importantly, the dynamics of organellar architecture render them more sensitive biomarkers than traditional approaches for assessing the cell state. Strikingly, yeast has a powerful depuration capacity to isolate and transform the overaccumulated cadmium in the vacuole, mitochondria, and cytoplasm as a high-value product, quantum dots. This work presents the possibility of discovering fundamental links between organellar morphological characteristics and the cell state.

Focal Spot Polarization Distribution under Polarization Smoothing

Focal Spot Polarization Distribution under Polarization Smoothing

High transmission in 120-degree sharp bends of inversion-symmetric and inversion-asymmetric photonic crystal waveguides

Bending loss is one of the serious problems for constructing nanophotonic integrated circuits. Recently, many works reported that valley photonic crystals (VPhCs) enable significantly high transmission via 120-degree sharp bends. However, it is unclear whether the high bend-transmission results directly from the valley-photonic effects, which are based on the breaking of inversion symmetry. In this study, we conduct a series of comparative numerical and experimental investigations of bend-transmission in various triangular PhCs with and without inversion symmetry and reveal that the high bend-transmission is solely determined by the domain-wall configuration and independent of the existence of the inversion symmetry. Preliminary analysis of the polarization distribution indicates that high bend-transmissions are closely related to the appearance of local topological polarization singularities near the bending section. Our work demonstrates that high transmission can be achieved in a much wider family of PhC waveguides, which may provide novel designs for low-loss nanophotonic integrated circuits with enhanced flexibility and a new understanding of the nature of valley-photonics.

Unveiling Microscopic Variations during Photodynamic Therapy via Polarity-Responsive Fluorescence Lifetime Imaging.

Photodynamic therapy is a highly promising method for cancer adjuvant treatment. However, the current research on the microscopic changes during the photodynamic therapy process is still quite limited, which seriously impedes the deep understanding of the procedure. For this purpose, a novel polarity-responsive probe, MI-PPF, with excellent mitochondrial targeting and anchoring capabilities has been rationally designed and synthesized. Notably, MI-PPF has successfully realized the in situ detection of mitochondrial morphology and polarity alterations during the photodynamic therapy process in cancer cells through fluorescence lifetime imaging. The results showed that a series of phenomena such as deformation, shrinkage, vacuolation, and aggregation occurred in the mitochondrial morphology during photodynamic therapy. Concurrently, a decline in mitochondrial polarity is also noted, which may be closely linked to the mitochondrial oxidative stress response during this process. Furthermore, MI-PPF can be used for photodynamic therapy on tumor mouse models and has successfully achieved fluorescence lifetime imaging of tumor sections before and after photodynamic therapy, uncovering multifaceted changes in cell morphology, polarity, and polarity distribution within the mouse tumor model during the process. It is anticipated that this study will offer valuable insights and guidance to the research of mitochondrial-related fields and will boost the advancement of diagnostic and therapeutic areas for associated diseases.

Topology of far-field signals for photonic crystal slabs

The study of band topology in photonic crystals was primarily focused on near-field effects, including edge states and high-order corner states. However, this work investigated the polarization distribution of radiated fields for photonic crystal slabs to get their far-field properties of band topology. We introduced a topological invariant—the winding number of far-field polarization around the Brillouin zone boundary and confirmed a robust correspondence between it and the Chern number of energy bands from the perspective of symmetry, which can be used to analyze the process of topological phase transition. It is found that changes in the winding number and Chern number, associated with the exchange of far-field polarization singularities, especially for bound states in the continuum, will emerge during phase transition. These findings offer insights for further understanding the intriguing properties of topological materials.

Metasurface‐Enabled Cascaded Multispectral Polarization Structures Along the Longitudinal Direction

AbstractGeneration and manipulation of polarization structures have attracted significant interest due to their unusual optical features and extensive applications. Multispectral information can further increase the information capacity of polarization structures. However, generating multiple cascaded multispectral polarization numbers (letters) at multiple planes arranged along light propagation has not been reported. A geometric metasurface is used to experimentally realize eight cascaded multispectral polarization numbers (letters) at predesigned observation planes along the longitudinal direction. The efficacy of this approach is demonstrated by encoding a single polarization number (letter) with two wavelengths and cascading two polarization numbers with orthogonal polarization rotation angles. Different two‐color polarization numbers (letters) are generated by controlling the incident wavelength, while their polarization distributions are modulated by controlling the incident linear polarization. This approach integrates two‐dimentional (2D) polarization generation, multiple colors, longitudinal control, and cascading design, providing extra degrees of freedom for customized polarization design and enabling small‐volume polarization systems for color display, image steganography, and optical encryption.

Terahertz‐Wave Polarization Space‐Division Multiplexing Meta‐Devices based on Spin‐Decoupled Phase Control

AbstractThis study presents a generalized design strategy for novel terahertz‐wave polarization space‐division multiplexing meta‐devices, functioning as multi‐polarization generators, modulators, and analyzers. It introduces the spin‐decoupled phase control method by combining gradient phase design with circular polarization multiplexing techniques, enabling exceptional flexibility in controlling the polarization directions and spatial distributions of multiple output beams. The meta‐device M‐4D is significantly demonstrated as proof of concept, which converts an incident linearly polarized wave into four beams with distinct polarization angles. Additionally, the advanced meta‐devices M‐2B and M‐4B are designed to generate two‐vector and four‐vector Bessel beams with tunable spatial polarization distributions. These meta‐devices demonstrate dynamic multi‐polarization beam modulation, validated through simulations and experiments. The proposed method significantly expands the design methodology for multi‐beam polarization control using all‐dielectric metasurfaces and holds promising potential for applications in imaging, sensing, particle manipulation, communication, and information processing. Moreover, it holds potential for adaptation to other spectral ranges.

Finite Element Modeling of a Flat Cell of Highly Porous Piezocomposite with Inclined Edges Taking into Account Nonuniform Polarization

Introduction. Highly porous composites — metal foams — are widely used due to their mechanical properties. The literature presents various methods for their mathematical modeling, including those based on periodic Gibson-Ashby cells. Piezoactive composites have a number of properties, such as high sensor sensitivity and a large bandwidth. This is the reason for the interest in their modeling. However, when constructing such models from piezoceramic materials, a certain difficulty, associated with the selection of the distribution of preliminary polarization, arises. It should be noted that this issue, specifically for highly porous piezoceramics, has not been sufficiently studied in the literature. Therefore, the objective of this work was to establish the effect of the polarization model on the characteristics of the piezoactive composite.Materials and Methods. The design material is PZT-4 piezoceramics, whose polarization depends significantly on the conditions of its guidance (model geometry, electrode arrangement). The study was divided into two steps: in the first, the residual polarization was calculated based on the theory known in the literature, the implementation of which was performed in the ACELAN package; in the second, a number of problems for a composite cell were solved, and the dependence of its properties on the polarization model was found. The finite element method implemented in the ACELAN package was used as a method for solving the corresponding boundary value problems of electroelasticity for piecewise inhomogeneous bodies.Results. The problem of determining nonuniform polarization for two types of flat cell designs of highly porous piezoceramics was solved. Some features of the obtained polarization distribution were noted, in particular, its nonuniformity and the presence of counter polarization in some edges. The problems of determining natural frequencies and vibration modes “intra cell” and their dependence on the polarization model (homogeneous and nonhomogeneous) were solved. It was noted that some frequencies differed by 10%, while the vibration modes qualitatively coincided. The dependence of the stress-strain state and output characteristics on polarization, whose difference in some values reached 15%, was analyzed.Discussion and Conclusion. The process of polarization of highly porous piezoceramics has a number of features that must be taken into account to obtain reliable information about its mechanical and electrical behavior. Auxetic properties, the difference in the mechanical and electrical response of the cell in question are directly related to these features. Thus, the polarization model has a significant impact on the characteristics of the piezoactive composite, which determines the importance of its correct selection. The results obtained should be taken into account when modeling representative volumes of highly porous piezoelectric composites to determine their effective properties, on the basis of which models of piezoelectric devices are constructed, and their output characteristics are calculated.

Tuning planar transverse domain wall dynamics in bilayer nanostructures using transverse magnetic fields, Rashba, and spin-Hall effects

Abstract This work deals with the tunability of a planar transverse domain wall with an arbitrary azimuthal angle, achieved by applying a transverse magnetic field of tunable strength and fixed orientation. To be precise, we investigate the static and dynamic features of a planar transverse domain wall within a bilayer nanostructure consisting of a ferromagnetic layer and a non-magnetic heavy metal layer, employing the Landau-Lifshitz-Gilbert equation as our theoretical framework. The domain wall dynamics are analyzed through the collective coordinate method and regular perturbation asymptotic approach, accounting for the combined effects of axial and transverse magnetic fields, spin-polarized electric currents, Rashba effect, and spin-Hall effect. Our study comprehensively analyses the planar transverse domain wall profile, characterized by sharply defined boundaries between adjacent domains and a precise distribution of the transverse magnetic field. In addition, we detail the linear polar angle distribution within the domain wall region, the capability to freely tune the domain wall width, and the enhanced domain wall velocity in steady-state regime. The analytical results are further numerically illustrated, offering valuable insights into manipulating and controlling domain wall dynamics.

Efficient Green Extraction of Nutraceutical Compounds from Nannochloropsis gaditana: A Comparative Electrospray Ionization LC-MS and GC-MS Analysis for Lipid Profiling.

Microalgae have been described as a potential alternative source of a wide range of bioactive compounds, including polar lipids and carotenoids. Specifically, Nannochloropsis gaditana is described as producing large amounts of polar lipids, such as glycolipids and phospholipids. These natural active compounds serve as key ingredients for food, cosmetic, or nutraceutical applications. However, microalgae usually possess a rigid cell wall that complicates the extraction of these compounds. Thus, an ultrasound-assisted enzymatic pretreatment is necessary to efficiently extract bioactives from microalgae, and it was studied in this article. Pretreated biomass was extracted using different advanced and green methodologies and compared to traditional extraction. Furthermore, the analysis, characterization, and identification of valuable compounds using GC-MS and LC-MS analytical methods were also investigated. Interestingly, major results demonstrated the efficiency of the pretreatment, enriching polar lipids' distribution in all extracts produced no matter the extraction technique, although they presented differences in their concentration. Pressurized liquid extraction and microwave-assisted extraction were found to be the techniques with the highest yields, whereas ultrasound-assisted extraction achieved the highest percentage of glycolipids. In summary, green extraction techniques showed their effectiveness compared to traditional extraction.

Experimental measurement of transverse spin dynamics in the nonparaxial focal region

Abstract The superposition of complex optical fields in three-dimension is the basis of several non-trivial wave phenomena. Significant among them are the non-uniform (inhomogeneous) polarization distribution and their topological character, leading to the emergence of transverse spin angular momenta spin-momentum locking, and their dynamics. These aspects are experimentally measured in the nonparaxial focal region of a circularly-polarized Gaussian input beam. A dielectric mirror, kept in the focal region, is axially scanned to obtain the phase and polarization variations in the retroreflected output beam using an interferometer and spatially-resolved Stokes parameter measurements. The identification of phase and polarization singularities in the beam cross-section and their behaviour as a function of the mirror position enabled us to map and study the phase-polarization variations in the nonparaxial focal region. The lemon-monstar type polarization patterns surrounding the C-point singularity in the output beam are identified and tracked to study the transverse spin dynamics and spin-momentum locking for the right- and left- circular polarization of the input beam. Direct measurement of the input beam polarization helicity-independent and helicity-dependent aspects of the transverse and longitudinal spin angular momenta in the nonparaxial focal region are the significant findings reported here. The proposed and demonstrated measurement method allows us to investigate the nonparaxial focal region in more detail and has the potential to unravel other intricate optical field effects.

Spin-Orbit-Locking Vectorial Metasurface Holography.

Vectorial metasurface holography, allowing for independent control over the amplitude, phase, and polarization distribution of holographic images enabled by metasurfaces, plays a crucial role in the realm of optical display, optical, and quantum communications. However, previous research on vectorial metasurface holography has typically been restricted to single degree of freedom input and single channel output, thereby demonstrating a very limited modulation capacity. This work presents a novel method to achieve multi-channel vectorial metasurface holography by harnessing spin-orbit-locking vortex beams. In each channel, the optical vectorial field is encoded with a pair of total angular momentums (TAMs) featuring two orthogonal spin angular momentums (SAMs) independently locked with arbitrary orbital angular momentums (OAMs). The methodology relies on a modified Gerchberg-Saxton algorithm, enabling the encoding of various TAM channels within a single phase profile. Consequently, a pure geometry-phase metasurface with a non-interleaved approach can be used to support such multi-channel vectorial holography, achieving high selectivity of both SAM and OAM, and offering precise routing and manipulation of complex light channels. The work presents a paradigm shift in the field of holography, offering promising avenues for high-density optical information processing and future photonic device design.

Ohmic contact mechanism and charge redistribution of MoS2/Mn+1XnO2 heterostructures

Abstract Several M n+1 X n O2 compounds exhibit work functions higher than those of three-dimensional metals, enabling the formation of Ohmic contact heterostructures with MoS2, which enhances the catalytic activity of MoS2 for the hydrogen evolution reaction. However, the Schottky barrier height (SBH) in these Ohmic contact heterostructures does not adhere to the Schottky-Mott limit, leaving the Ohmic contact mechanism between MoS2 and M n+ 1X n O2 unclear and hindering further investigations into these heterostructures. In this study, we investigate 22 MoS2/M n+ 1X n O2 heterostructures using the unfolding method. Among these, the eight M n+ 1X n O2 compounds—Cr2CO2, Mo2CO2, V2CO2, W2CO2, Cr2NO2, V2NO2, Ti3C2O2 and V4C3O2—form p-type Ohmic contacts with MoS2. In contrast, the twelve compounds—Hf2CO2, Nb2CO2, Ta2CO2, Ti2CO2, Zr2CO2, Mo2NO2, Ti2NO2, Ti3N2O2, Zr3C2O2, Nb4C3O2, Ta4C3O2 and Ti4N3O2—create p-type Schottky contacts, while Hf2NO2 and Zr2NO2 form n-type Schottky contacts with MoS2. In the Ohmic contact heterostructures, out-of-plane orbital states hybridize to form a splitting band, allowing the highest valence band of MoS2 to cross the Fermi level and achieve hole doping. This splitting band not only results in a SBH that does not conform to the Schottky–Mott limit but also redistributes charge density. Notably, the heterostructures formed by Cr2CO2, Mo2CO2, V2CO2, W2CO2, Cr2NO2, V2NO2, V4C3O2, and MoS2 exhibit charge polarity distribution, whereas MoS2/Ti3C2O2 does not demonstrate charge polarity distribution.

Experimental analysis of a rotating cylinder electrode reactor: Hydrodynamics and mass transport

AbstractThis report deals with the hydrodynamic and mass transport characterization in an rotating cylinder electrode (RCE) in continuous and batch configuration employing relatively simple techniques like obtaining the mixing time, polarization, and residence time distribution (RTD) curves. For batch configuration, the limiting current and Sh values were higher than for continuous configuration, indicating that the mixing pattern is influenced by possible flow inhomogeneities during the operation as a continuous mixing stirrer. This could diminish the amount of electroactive reactant that reaches the electrode surface, due to the possible shrinking of recirculation zones during the rotation of the cylindrical stirrer, forming channeling and by‐pass flow zones. These results could evidence the existence of slight deviations from the ideal mixer and other non‐ideality flow zones associated with the width of curves upon analyzing age function through RTD curves, at the different flow rates employed in continuous configurations.

Inversion of induced polarization-affected electrical-source transient electromagnetic data observed in the groundwater survey from eastern Tibet, China

Recent advancements in the signal-to-noise ratio of transient electromagnetic (TEM) devices have highlighted the significance of induced polarization (IP) effects in areas containing polarizable materials such as clays or sulfide minerals. These effects are characterized by an abnormally rapid decay followed by late-time negative values in the voltage response, which often lead to unsatisfactory outcomes in conventional resistivity-only inversion workflows. Previous research demonstrates that incorporating the Cole-Cole complex resistivity model into an inversion workflow enhances the characterization of this phenomenon. In a recent hydrologic survey in eastern Tibet, China, significant TEM-IP-affected phenomena are observed during the implementation of an electrical-source TEM system to map the distribution of groundwater. In this instance, data from two representative survey lines are inverted using a modified quasi-2D regularized Newton inversion scheme that simultaneously extracted the direct current resistivity and three IP parameters: chargeability, time constant, and frequency dependence. The results reveal clear conductive polarization distributions against the resistive host, correlating well with groundwater-enriched weathered layers, as confirmed by borehole lithologic logs. Consequently, conductive polarization signatures are identified as potential key indicators of groundwater presence considering potential associations with clay and shale. This case study emphasizes the significance of accounting for potential IP effects in TEM surveys and highlights the advantages of multiparametric inversion for achieving more accurate results and enhancing the interpretation of subsurface properties.

Resolving the differential distribution of structural proteins in baculovirus using single-molecule localization microscopy

Baculovirus is one of the most complex viruses found in nature. Proteomic analysis of budded viruses (BVs) indicates that they are formed by at least 50 different structural proteins. The function of most of these structural proteins and their specific localization in individual virions remain unknown. In the present study, we have conducted single-molecule localization microscopy analysis of the spatial distribution of the nucleocapsid protein P24 and the envelope proteins GP64 and E25. Our results show that P24 and GP64 are polarized to one end of the baculovirus, while E25 distributes more homogenously along the viral envelope. This is the first study using optical microscopy to demonstrate the polarized distribution of structural proteins in individual baculoviruses.