Polarization Separation Research Articles

High-sensitivity fiber temperature sensor based on composite film structure and lossy mode resonance

In this work, we proposed and demonstrated a high-sensitivity optical fiber temperature sensor based on lossy mode resonance (LMR). The sensor is composed of a D-shaped fiber and a thin composite film. The composite film consists of tin dioxide (SnO2) and polydimethylsiloxane (PDMS). PDMS is inserted as an intermediate layer between D-shaped fiber and SnO2 layer, realizing the separation of TM and TE polarization to reduce polarization crosstalk, while also serving as a temperature sensitive layer. The polarization state of the excited LMR can be freely controlled by adjusting the thickness of the composite film. The proposed sensor exhibits a high temperature sensitivity of −1.1883 nm/°C with a measurement range of 10–90 °C. Meanwhile, a fast response time of ∼ 109 ms was observed due to the ultra-thin PDMS interlayer.

Simultaneous metabolomics and lipidomics analysis based on 4in1 online analysis system reveal metabolic signatures in atherosclerotic mice

Developing efficient and comprehensive analysis methods for metabolomics and lipidomics in the biological tissues and body fluids is essential for understanding the disease mechanisms. Although various two-dimensional liquid chromatography-mass spectrometry (2D-LC-MS) methods have been proposed to expand metabolite coverage, achieving higher efficiency in integrated metabolomics and lipidomics studies remains a technical challenge. In this work, a novel 4in1 online analysis system with excellent reproducibility and mass accuracy was constructed for metabolomics and lipidomics study in various biological samples from atherosclerotic mice. This system enabled the simultaneous detection in both positive and negative ion modes with extensive polarity separation in a single analytical run. Using the 4in1 online analysis system, we identified distinct but complementary metabolic signatures associated with atherosclerosis in different biological samples. Specifically, a total of 230 and 170 differential metabolites or lipids were detected in mice plasma samples and aortic tissue samples, respectively, including glycerophospholipids, sphingolipids, fatty acyls, glycerolipids, carboxylic acids, and pyrimidine nucleosides. Additionally, atherosclerosis-related metabolic pathways involved in biosynthesis of unsaturated fatty acids, sphingolipid metabolism, cholesterol metabolism, glycerophospholipid metabolism, and choline metabolism further revealed. These findings demonstrate that the novel 4in1 online analysis system is a faithful, stable and powerful tool for comprehensive metabolomics and lipidomics studies in complex biological matrices.

Highly polarized energetic electrons via intense laser-irradiated tailored targets

A method for the generation of ultrarelativistic electron beams with high spin polarization is put forward, where a tightly focused linearly polarized ultraintense laser pulse interacts with a nonprepolarized transverse-size-tailored solid target. The radiative spin polarization and angular separation is facilitated by the standing wave formed via the incident and reflected laser pulses at the overdense plasma surface. Strong electron heating caused by transverse instability enhances photon emission in the density spikes injected into the standing wave near the surface. Two groups of electrons with opposite transverse polarization emerge, antialigned to the magnetic field, which are angularly separated in the standing wave due to the phase-matched oscillation of the magnetic field and the vector potential. The polarized electrons propelled into the plasma slab are focused at the exit by the self-generated quasistatic fields. Our particle-in-cell simulations demonstrate the feasibility of highly polarized electrons with a single 10 PW laser beam, e.g., with polarization of 60% and charge of 8 pC selected at energy of 200 MeV within 15 mrad angle and 10% energy spread. Published by the American Physical Society 2024

The Overlooked Role of Humin in Dark Hydroxyl Radical Production during Oxygenation.

Humin, endowed with abundant redox functional groups, can be reduced anaerobically under dark. When reduced humin encounters O2, the possibility of ·OH formation arises. However, the exploration of ·OH generation mediated by humin has not been comprehensively conducted. The study found that O2 oxidized the reduced humin, generating 8.61 μmol/g of ·OH. After isolating humin using the methyl isobutyl ketone (MIBK) method, the lipid component was identified as the primary contributor to ·OH generation. Subsequent polar separation revealed that the lipid fraction extracted from the ethanol-water mixture with a volume ratio of 7:3 (LFEW7:3) played the most significant role in ·OH production. Further characterization confirmed that the simultaneous presence of aromatic C═C and C═O were the predominant features contributing to the ·OH generation. The ·OH generation experiments with humin-pyridine analogue compound demonstrated that polycyclic pyridine N (≥3 rings) played a significant role in promoting the ·OH generation. Most importantly, the study compared the ·OH production by humin and homologous humic acid, indicating that ·OH generated by humin was higher than that of humic acid. Overall, these affirmative findings manifested the overlooked role of humin in ·OH production and offered valuable insights into the mechanism of ·OH generation by humin in the dark.

Spectroscopic, anti-cancer, anti-bacterial and theoretical studies of new bivalent Schiff base complexes derived from 4-bromo-2,6-dichloroaniline

In this paper, four new mono-nuclear Ni(II), Pd(II), Pt(II) and Zn(II) complexes were prepared by using a bi-dentate Schiff base ligand, (E)-2-(((4-bromo-2,6-dichlorophenyl)imino)methyl)-5-chlorophenol (BrcOH), with bivalent ions in a methanol and distil water mixture as solvent in presence of NaOH as base. The structures of the prepared compounds were characterized by spectroscopic techniques (IR and 1H NMR), CHN analysis, and molar conductivity. The M(II) (Ni, Pd and Pt) ions are four-coordinated by a bi-dentate N2O2 donor ligand, forming square planar geometry, whereas the Zn(II) is coordinated as a tetrahedral geometry. The newly synthesized compounds, which include the Schiff base ligand and its complexes, underwent antibacterial screening against E. coli and S. aureus. The results demonstrated a remarkable and noteworthy biological activity of these compounds against these pathogenic bacterial strains. Different binding energies showed good correlation, with Pd showing the strongest binding. Small energy differences indicated high reactivity, with Ni and Pd complexes being the most reactive. Electrophilicity index exhibited electron-accepting properties, with Zn showing the highest reactivity. The dipole moments showed polarity and charge separation, with Pt having the highest polarity. We evaluated the pharmacokinetic properties (ADME) of a ligand and its metal complexes using the Swiss ADME website. The results of the in-silico prediction of physicochemical properties revealed that ten compounds in total adhered to Lipinski's rule.

Topological polarization beam splitter based on directional coupling between asymmetric valley photonic crystal waveguides.

Compared with symmetric directional couplers (DCs), asymmetric DCs constructed by two or over two different parallel waveguides offer a more flexible structure and allow for easier expansion of mode channels. In this Letter, we propose a kind of asymmetric topological DC based on two different valley photonic crystal waveguides (VPCWs). According to the coupled-mode theory, phase matching induces the complete coupling for the guide modes of two different VPCWs, whereas significant phase mismatching indicates no coupling occurs. Furthermore, the asymmetric topological DCs exhibit backscattering immunity and anti-disturbance robustness owing to the topological edge states (TESs), which greatly improve the performance of asymmetric DCs. We further design a new, to the best of our knowledge, kind of topological polarization beam splitter (TPBS) at the communication wavelength of 1550 nm by ensuring that the transverse electric mode satisfies the phase matching condition, while the transverse magnetic mode is phase-mismatched. The simulated results demonstrate that the proposed TPBS exhibits highly effective polarization separation and is robust against defects. This design holds significant potential for applications in optical communication systems.

An adhesive hydrogel functionalized silica sphere for polar analytes separation and analysis

In response to the challenges associated with the chromatographic separation of polar compounds, this study aims to devise a solution by introducing a novel stationary phase. Hydrogels, characterized by a three-dimensional network structure, have aroused wide attention owing to its functional designability, multiple interaction sites and good adhesion, etc. In this work, an adhesive hydrogel functionalized silica stationary phase (Sil@PVA/TA) was synthesized using physical coating technique. Due to the co-existence of hydroxyl and benzene ring in the hydrogel structure, the obtained composites materials exhibited excellent separation performance for various of compounds and excellent column efficiency up to 71385.6 plates/m for thymidine. Furthermore, the hydrogel functionalized silica demonstrated superior selectivity to bare silica, diol-column and NH2-column for the separation of various of polar molecules, including, nucleosides/bases, alkaloids, organic acids, antibiotics and amino acids. Notably, for alkaloids, which frequently encounter peak tailing issues, Sil@PVA/TA demonstrated superior peak shape compared with C18 column. In short, this study successfully synthesized a hydrogel functionalized silica stationary phase, offering a novel method for the separation and analysis of polar compounds.

Comprehensive analysis of chemical and enantiomeric stability of terpenes in Cannabis sativa L. flowers.

Cannabis sativa L. is renowned for its medicinal and recreational uses. With the increasing global legalization of C.sativa L.-based products for medicinal purposes, there is a growing need for well-characterized products. While the stability of cannabinoids such as tetrahydrocannabinol and cannabidiol is well understood, information on the chemical and enantiomeric stability of terpenes remains scarce. This is despite the fact that terpenes are also thought to have pharmacological activity and may contribute to the overall effect of C.sativa L. To address these challenges, four analytical methods based on chiral, polar, and apolar gas chromatographic separation combined with either MS or FID detection were developed and validated. These methods successfully separated and quantified a total of 29 terpenes, including 13 enantiomers and 5 diastereomers specific to C.sativa L. Furthermore, terpenes and authentic C.sativa L. flowers and extracts were subjected to UV and heat treatments to observe potential degradation reactions over time. Each terpene generates a unique pattern of degradation products resulting in a diverse array of oxidation and cyclization products. P-cymene was identified as a major product of terpene aging. Notably, no enantiomeric conversion was detected, suggesting that the formation of (-)-α-pinene in cannabis extracts, for example, originates from other terpenes. Terpenes have different degradation rates, even though they are structurally similar. In addition, cultivar- and growth-condition-specific enantiomeric ratios were observed in C.sativa L., confirming that enantiomer production is species-specific and has to be considered for therapeutical applications.

Snapshot spectropolarimeter based on a six-fold separating prism operating from 360 nm to 1 µm

We describe a new type of spectropolarimeter in which light is separated to simultaneously measure six spectra carrying polarimetric information on a 2D CMOS camera. The polarization separation along one of the camera axes was obtained using a novel prism, and the spectral dispersion along the other camera axis was obtained using an imaging spectrometer. An ideal version of the six-fold separating prism is first described, in which polarimetric separation is performed along the canonical polarization states used to define the Stokes vector, and it can be explained without any math. The real version is then presented, with math that is simple for those familiar with polarization. The operation of the spectropolarimeter is described. Experimental results show that the polarimetric accuracy is a few 10−3, and noise (mainly due to shot noise) is in the same range for a single acquisition. The spectral resolution depends on the entrance pinhole width and can be as low as 2 nm. Several examples are presented that feature how informative snapshots, high spectral resolution, spectropolarimetric measurements can be. The anticipated applications of this spectropolarimeter and, more broadly, for this novel polarization-separating prism are discussed. Technical details, such as the calibration procedure, noise levels, and consistency checks, are presented as supplementary material.

IQ-channel multiplexed DP-4ASK signal using power loading for downlink coherent PON system with access-span length difference

This study explores the integration of dual-polarized (DP) four-level amplitude shift keying (4ASK) signals within an intensity and quadrature division multiplexing framework, mainly focusing on coherent passive optical network (PON) systems. The primary objective is to address the challenges associated with distance disparities in downstream transmissions, which are prevalent in coherent PON architectures. We introduce a novel approach that significantly reduces the power consumption of digital-to-analog converters by implementing power loading strategies tailored explicitly for IQ channel division multiplexing (IQDM)-DP-4ASK signals. Our simulations confirm that ASK standard frequency offset compensation is adaptable to these signals, providing a robust method for managing frequency offsets in a dynamic network environment. Moreover, we propose and empirically validate an energy-efficient adaptive downlink solution capable of supporting 128 Gb/s per optical network unit (ONU), utilizing IQ-imbalanced DP-4ASK signals. This solution is particularly advantageous for systems where the transmission conditions include a 10 km variance in access span lengths between ONUs. Results from our experimental setup demonstrate that reducing the digital-to-analog converter output current for the Q channel by 137 mA is feasible without compromising signal integrity or system performance. Additionally, the research verifies the effectiveness of the automatic bias controller on the transmitter side, ensuring stable operation across varying conditions. Equally, the receiver-side digital signal processing effectively handles polarization separation, illustrating the system's capability to maintain high data integrity and reliability under diverse operational scenarios. These findings highlight the technical feasibility and operational benefits of using IQDM-DP-4ASK signals in coherent PON systems and underscore the potential for significant power savings and enhanced system efficiency in optical networks. The study paves the way for future research into scalable, energy-efficient solutions suitable for high-capacity optical access networks striving for increased sustainability and reduced operational costs.

Forward-backward wavefront manipulation of orthogonal linearly polarized waves based on a metasurface zone plate.

Metasurface zone plates exhibit stronger optical control capabilities than traditional Fresnel zone plates, especially in polarization transformation and multiplexing. However, there are still few studies on metasurface zone plates that can be used for simultaneous control of forward and backward waves. In this work, we propose what is to our knowledge a new scheme that utilizes metasurface zone plates for orthogonal linear polarization separation and wavefront manipulation at the same time. We demonstrate the separation of linearly polarized components and transmission-reflection focusing by using the destructive and constructive interference between different meta-atoms in the super-cell, as well as the phase difference between the super-cells. The metasurface not only needs a simple binary phase design but also shows a working bandwidth more than 30 nm with a central wavelength of 875 nm. This scheme can be extended to other electromagnetic bands such as visible and terahertz ones, providing an important way for the multi-dimensional light field manipulations.

Analysis of BMR Tilt from AutoTAB Catalog: Hinting toward the Thin Flux Tube Model?

One of the intriguing mechanisms of the Sun is the formation of bipolar magnetic regions (BMRs) in the solar convection zone (CZ), which are observed as regions of concentrated magnetic fields of opposite polarity on the photosphere. These BMRs are tilted with respect to the equatorial line, which statistically increases with latitude. The thin flux tube model, employing the rise of magnetically buoyant flux loops and their twist by Coriolis force, is a popular paradigm for explaining the formation of tilted BMRs. In this study, we assess the validity of the thin flux tube model by analyzing the tracked BMR data obtained through the Automatic Tracking Algorithm for BMRs. Our observations reveal that the tracked BMRs exhibit the expected collective behaviors. We find that the polarity separation of BMRs increases over their normalized lifetime, supporting the assumption of a rising flux tube from the CZ. Moreover, we observe an increasing trend of the tilt with the flux of the BMR, suggesting that rising flux tubes associated with lower flux regions are primarily influenced by drag force and Coriolis force, while in higher flux regions, magnetic buoyancy dominates. Furthermore, we observe Joy’s law dependence for emerging BMRs from their first detection, indicating that at least a portion of the tilt observed in BMRs can be attributed to the Coriolis force. Notably, lower flux regions exhibit a higher amount of fluctuations associated with their tilt measurement compared to stronger flux regions, suggesting that lower flux regions are more susceptible to turbulent convection.

Integrating inverse design and partially etched platform: an ultra-compact polarization splitter and rotator as an example

Silicon photonics devices benefit greatly from a partially etched platform and inverse design. Herein, we propose a bi-layer polarization splitter and rotator with a topology pattern and demonstrate it on a silicon-on-insulator platform. Our device exhibits a significantly reduced physical footprint of only 2µm×6µm, compared to traditional directional couplers and tapered waveguides. The device accomplishes the functions of polarization conversion and separation in such a compact design without redundant tapered or bending waveguides. The tested minimum insertion loss with the fabrication batch reaches 0.57 and 0.67 dB for TE and TM modes, respectively. The TE mode demonstrates a wider bandwidth and lower ILs than the TM modes, averaging around 1 dB from 1530 to 1565 nm. The M modes exhibit approximately 2 dB ILs at the same wavelength range, decreasing to about 1 dB between 1565 and 1580 nm. Improved designs and fabrication conditions strongly suggest the potential for further performance enhancement in the device. This successful initiative validates the exceptional performance resulting from the integration of the partially etched platform and inverse design, providing valuable insights for future photonic integrated device designs.

Mathematical model of an antenna-waveguide path with signal separation by polarization – frequency

Background. The need to create antenna-waveguide paths for multi-band reflector antennas of satellite communication systems requires the use of various methods for selecting the structure, determining and optimizing the parameters of antenna-waveguide paths.
 Aim. Development of a mathematical model of antenna-waveguide paths of multi-band reflector antennas, built on the basis of the «polarization separation – frequency separation» method with the implementation of the auto-tracking function.
 Methods. A mathematical model of antenna-waveguide paths of multi-band reflector antennas, built on the basis of the «polarization separation – frequency separation» method, allows us to determine the main characteristics of antenna-waveguide paths and incoming devices with an auto-tracking function.
 Results. The main elements of the mathematical model of multi-band antenna-waveguide paths built on the basis of the «polarization separation – frequency separation» method are determined.
 Conclusion. A mathematical model has been proposed that makes it possible to reduce the requirements for the computing tools used when developing antenna-waveguide paths in terms of RAM capacity and performance. The ability to analyze and determine the characteristics of antenna-waveguide paths using a mathematical model has been implemented. The stages of determining the parameters of antenna-waveguide paths are presented, based on the developed mathematical model of the corresponding design option, as well as theoretical and experimental data confirming the correctness of the model of antenna-waveguide paths.

Polarization-separating Alvarez metalens.

The rapid advancements in optical communication technologies have highlighted traditional optical components' limitations, particularly in size, adaptability, and integration capabilities, underscoring the need for more compact and versatile solutions. Metalenses offer a promising pathway to address these challenges, with their ability to provide high-functionality, miniaturized optical components. We developed a varifocal metalens with a polarization separation function designed for the wavelength of 1550 nm for potential application for next-generation communication technologies. To integrate the varifocal and polarization separation functions, polarization-dependent phase profiles for an off-axis Alvarez lens were derived and encoded by amorphous silicon pillar meta-atoms with rectangular cross sections to provide independent 0-2π phase delays for both orthogonal linear polarization components. The fabricated metalens achieved a varifocal range of 0.75 mm to 10.65 mm and a polarization extinction ratio of 18.5 dB.

Polarization-separated feedback spectral beam combining source.

A novel, to the best of our knowledge, structure for spectral beam combining (SBC) is proposed, utilizing a polarization-separated feedback (PSF). A polarization separation element is introduced to separate the laser beam into a TE-polarized light and a TM-polarized light. The lower-power light is selected as the external feedback to adjust the resonant wavelength, while the other light is combined spectrally. Compared to the conventional SBC source with a similar feedback, the power and efficiency of the PSFSBC are improved by approximately 20%. Additionally, the beam quality in the non-SBC direction is optimized by 10%, and the power on the output coupler is reduced to nearly one-third. This provides an effective method for achieving an optimized SBC performance.

Alternating current electric field modifies structure and flavor of peanut proteins

The impacts of intensity and treating time of alternating current (AC) electric field (EF) on structure and volatile compounds of peanut protein were investigated for low denaturation. The secondary and tertiary structures, polar and weakly polar volatiles were characterized qualitatively and quantitatively using ultraviolet and fluorescence photospectrometry, free sulfhydryl and disulfide groups determination, and combination of gas chromatography and mass spectrometry. The results showed that the ACEF affected significantly proportions of α-helices, β-sheets, β-turns, and random coils as evidenced by Fourier transform infrared spectrometry. Blue shifts of UV and fluorescence spectra, increased surface hydrophobicity and disulfide bonds could be observed after ACEF treatments. The DB-WAX and DB-5MS columns for the polar and weakly polar volatile compound separation revealed that ACEF caused either disappearance or emerging of volatile compounds. The PCA demonstrated that the two principal components contributed about 70 % or more to the flavor and PLS-DA discriminated 18 key compounds.

AN ENTREPRENEURIAL CREATIVE THINKING TEST FOR HIGH SCHOOL STUDENTS IN STEM EDUCATION

Instruments have been developed to measure entrepreneurial thinking. However, those instruments did not assess the commercial aspects of product marketing using digital technology. Consequently, the Entrepreneurial Creative Thinking Test (ECTT) was developed to assess the level of entrepreneurial creative thinking among Form Four high school students in STEM education. ECTT consists of five constructs derived from integrating the steps between the Socioscientific Issue Approach Model and the Design Thinking Process Model. The five constructs are Investigation, New Idea, Design, Create, and Commercial. The sample consisted of 187 Form Four students aged 15 to 16 years from four high schools in Sabah, Malaysia. The sample comprised 103 females (55.1%) and 84 males (44.9%). A survey research design was conducted to ascertain the extent to which the validity and reliability of this instrument can meet the psychometric characteristics of a research. The survey research design focused on the validity and reliability assessment of ten open-ended questions. This study utilised the Rasch Measurement Model to evaluate the validity and reliability of the ECTT instrument. Person fit, item fit, item polarity, unidimensionality, reliability, and item-person separation were analysed. The study's findings revealed that the ECTT instrument has good item reliability, with a score of .97. In conclusion, the ECTT is a valid and reliable instrument for assessing the level of entrepreneurial creative thinking among Form Four students in STEM education.

Chiral recognition mechanism studies of Tyr-Arg-Phe-Lys-NH2 tetrapeptide on crown ether-based chiral stationary phase.

Even though chiral recognition for crown-ether CSPs is generally understood, on a molecular level, exact mechanisms for the resolution are still unclear. Furthermore, short peptide analytes often contain multiple amino moieties capable of binding to the crown ether selector. In order to extend the understanding in chiral recognition mechanisms, polar organic mode separation of Tyr-Arg-Phe-Lys-NH2 tetrapeptide llll/dddd enantiomers on S- and R-(3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 stationary phases was studied with 50-mM perchloric acid in methanol as mobile phase. Deviation from the generally acceptable 1:1 stoichiometry was supported by mass spectroscopy analysis of the formed complexes between tetrapeptide enantiomer and crown ether selectors, which revealed adducts possessing 1:1, 1:2, and 1:3 stoichiometry. Further investigation of complexation induced shifts by NMR indicated on different binding mechanisms between llll/dddd enantiomers of Tyr-Arg-Phe-Lys-NH2 and crown ether selectors. Enantioselective proton shifts were observed in studied tetrapeptide tyrosine and phenylalanine residues exclusively for llll enantiomer upon binding with S-(3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 selector (and dddd enantiomer with R-(3,3'-diphenyl-1,1'-binaphthyl)-20-crown-6 selector), indicating that these two amino acid residues contribute to chiral recognition. The obtained results were in agreement with the LC data.

Generalized chiral kinetic equations

We derive the generalized chiral kinetic equations which are applicable to the fermions with arbitrary mass. We show how the dynamical magnetic-moment distribution function could lead to spin polarization and electric charge separation. We also show how the electric/magnetic moment distribution and pseudoscalar distribution could be induced by vorticity and electromagnetic field in global equilibrium.