Polarization Parameters Research Articles

Harnessing Polar Interactions Tunes the Stability of Ultrathin Polymer Solution Films.

The stability of ultrathin (<100 nm) polymer films is essential in applications like protective coatings. On the contrary, their instability may actually be desirable for the emergence of self-assembled nanoscale patterns utilized in the fabrication of functional devices. Polymer solution films exhibit two distinct kinds of instabilities, viz., dewetting (long-wave) and decomposition (short-wave). Dewetting refers to the rupture of the continuous film to form isolated domains, while decomposition leads to phase separation within the polymer solution. The focus of this work is on leveraging polar interactions between the solute and solvent molecules to tune the stability of the film. A gradient dynamics-based thin film model is developed to investigate pattern formation in a thin polar polymer solution film. The Flory-Huggins theory is suitably modified by introducing a polar interaction parameter that depends upon the concentration of the polymer and the dipole moments of monomer (μ1) and solvent molecules (μ0). A linear stability analysis is performed to determine the characteristic length scale and growth rate of the instabilities. It is shown that the range of concentration space for the occurrence of the decomposition mode is directly affected by the Flory interaction parameter (χ0), μ0, and μ1, thereby serving as control parameters to tune the width of the concentration range. It is further shown that ignoring polar interactions may lead to incorrect predictions of the instability mode, including a complete loss of the decomposition mode. In addition, the long-wave dewetting length scale is found to decrease due to bulk dipolar interactions at higher polymer concentrations. Finally, numerical simulations are carried out to track the nonlinear evolution of the interface and concentration field for both the decomposition and dewetting modes of instability.

New approach: Solvent effects of benzaldehyde in aliphatic alcohol solvents with FT-IR spectroscopy and augmented vertex-adjacency matrices

In this study of benzaldehyde (BNZ) in 7 aliphatic alcohol solvents, were undertaken to investigate the solvent/solute interaction with Fouirer Transform Infrared Spectroscopy (FT-IR), BNZ produced carbonyl group stretching vibration frequencies (ν(C=O)1 and ν(C=O)2). In the present paper, ν(C=O)1 and ν(C=O)2 of BNZ are observed and correlated with the solvent acceptor number (AN), dipolarity/polarizability (π*), hydrogen-bond donor acidity (α), hydrogen-bond acceptor basicity (β), solvent polarity parameter [ET(30)], KBM parameter ƒ(ε), boiling point (bp) and the linear solvation energy relationship (LSER) using single and multiple regression analysis. All calculations were performed for ν(C=O)1 and ν(C=O)2 and compared. ν(C=O)1 was believed to correspond to a single hydrogen bonded BNZ-alcohol complex, while ν(C=O)2 was believed to correspond to a multiple hydrogen bonded BNZ-alcohol complex and multiple hydrogen-bonded alcohol molecules. It was seen that LSER equation as multiple regression analysis was better than single regression analysis in explaining solute-solvent interactions due to the higher correlation coefficients obtained. The correlations of a set of the mathematical characteristics of the augmented vertex-adjacency matrices (AV-AM) obtained by the chemical structure of BNZ with solvent parameters and ν(C=O) were investigated. It was determined that the correlation factors (R2 > 0.999) of the multiparameter regression models obtained using the matrix results were higher than the correlation factors (R2 > 0.99) of the LSER equations including solvent parameters.

Permeability and Induced Polarization of Mudstones

AbstractElectrical measurements can be used to estimate hydraulic properties such as permeability (k) in sedimentary rocks. Previous work has focused on sandstones, siltstones, and carbonates, while investigations on mudstones have rarely been reported. In this study, we report on electrical geophysical measurements for 23 mudstone samples using an experimental approach designed to reliably saturate these low permeability mudstones. The modified Hagen‐Poiseuille model linking permeability to the formation factor (F) and an effective pore radius (r) provides an excellent fit to the data set with a near‐constant pore radius, indicating that the effective porosity (1/F) is the controlling factor on k. In these samples, the surface area normalized to pore volume (Spor), frequently used in permeability estimation models, varies by 1–2 orders of magnitude and is thus not a reliable proxy of the inverse effective hydraulic radius. The formation factor also exerts the primary control on induced polarization (IP) parameters, whereas Spor shows no relation to the IP parameters. A strong linear relationship is found between IP parameters (imaginary conductivity and normalized chargeability) and surface conductivity, although the proportionality factor is significantly lower than those observed in more permeable rocks and sediments. Apparent relationships between the polarization strength‐derived and time constant‐derived geophysical length scales and the effective hydraulic radius appear to be driven by variations in the electrochemical parameters (i.e., specific polarizability and diffusion coefficient). Overall, these findings emphasize that predicting hydraulic properties from electrical measurements in fine‐grained rocks remains challenging and requires further investigation into the electrochemical properties involved.

Robust polarimetric dehazing algorithm based on low-rank approximation and multiple virtual-exposure fusion

Polarimetric dehazing is an effective way to enhance the quality of images captured in foggy weather. However, images of essential polarization parameters are vulnerable to noise, and the brightness of dehazed images is usually unstable due to different environmental illuminations. These two weaknesses reveal that current polarimetric dehazing algorithms are not robust enough to deal with different scenarios. This paper proposes a novel, to our knowledge, and robust polarimetric dehazing algorithm to enhance the quality of hazy images, where a low-rank approximation method is used to obtain low-noise polarization parameter images. Besides, in order to improve the brightness stability of the dehazed image and thus keep the image have more details within the standard dynamic range, this study proposes a multiple virtual-exposure fusion (MVEF) scheme to process the dehazed image (usually having a high dynamic range) obtained through polarimetric dehazing. Comparative experiments show that the proposed dehazing algorithm is robust and effective, which can significantly improve overall quality of hazy images captured under different environments.

Fullertubes: A 30-Year Story of Prediction, Experimental Validation, and Applications for a Long-Missing Family of Soluble Carbon Molecules.

ConspectusDuring the last 30 years, theoretical scientists imagined segmental families of monolayer carbon tubules with fullerene-based end-caps. These fullertube molecules would possess structural features of both fullerenes (hemispherical end-caps) and tubular belts of single-walled carbon nanotubes (SWCNTs). Yet, their experimental verification remained elusive for decades. It was not until 2020-2023 that segmental families of fullertubes were finally confirmed in the lab. The shocking irony is that these fullertubes were unwittingly coproduced alongside fullerenes (e.g., C60, C70, C84) in both flame and electric arc soot since the 1990s. Yet, nobody knew these "hidden" families of fullertubes were experimentally present in their extracted soot due to their low abundance and the absence of isolation methodology.This eruption of fullertube discoveries in 2020-2023 was brought to fruition by structural data, both DFT and experimental. This "Treasure Trove" of new molecules during this four-year window occurred with only microgram quantities. Typically, milligram levels of purified samples are required for X-ray crystallography and 13C NMR structural analysis. The breakthrough for experimentally verifying the missing fullertubes was an aminopropanol reagent to selectively react with and remove spheroidal carbon (e.g., C60, C70, C84) as hydrophilic derivatives. In contrast, there was suppressed reaction with fullertubes, which remained in organic solvent. It is well established that high symmetry (3-, 5-, and 6-fold) hemispheres for C60-Ih and other fullerenes and metallofullerenes are prerequisite end-caps for fullertubes. For the case of [5,5] C130 fullertubes, this requirement results in only eight 3-, 5-, and 6-fold symmetry structural isomers possible from a total of 39,393 possible isolated pentagon rule (IPR) isomers. From this C130 list of 8 candidate isolated pentagon rule (IPR) high symmetry isomers, surprisingly only one structure matched the DFT polarizability versus chromatographic retention parameter (a new gold standard for isomer identification). The simultaneous emergence of DFT computations of other properties (e.g., total energy, HOMO-LUMO gap, UV-vis) for large carbon molecules provided support for structural determination. Experimental approaches (e.g., mass spectrometry, UV-vis, XPS, Raman, and STEM) provided additional layers of structural elucidation at the microgram level. For the first time, we developed a chemical isolation protocol that would allow the preparation and isolation of soluble pristine fullertubes in the range of C90-C200. To date, applications of SWCNTs for use in nanoscale computer applications requires purities greater than 99.999%. Although this stringent mandate has not yet been demonstrated using SWCNT samples, this high level of purity appears achievable for metallic [5,5] D5d-C120 and semiconductor [10,0] D5h-C120 [10,766] fullertubes. Moreover, commercial production of pristine fullertubes should easily be feasible by the flame method due to its continuous operation and inexpensive feedstock. For application development, theoretical and electrochemical experimental data show that fullertubes exhibit high catalytic activity in oxygen reduction reactions. In the medical sector, pristine fullertube dispersions exhibit antimicrobial effects on Mycobacterium smegmatis and M. abscessus.

Solubility behavior and solvation effect of a photomechanical molecular crystal trans-4-chlorocinnamic acid in twelve neat solvents at temperatures from 283.15 to 323.15 K

Solubility of trans-4-chlorocinnamic acid as a photomechanical molecular crystal material in twelve pure solvents (water, ethanol, methanol, n-propanol, isopropanol, n-butanol, isobutanol, acetonitrile, 1,4-dioxane, acetone, methyl acetate and ethyl acetate) were measured from 283.15 to 325.15 K at 101.2 kPa. The results showed that the trans-4-chlorocinnamic acid solubility increased with the temperature, the order is: 1,4-dioxane > acetone > n-butanol > ethanol > n-propanol > isopropanol > isobutanol > methanol > methyl acetate > ethyl acetate > acetonitrile > water. Powder X-ray diffraction pattern (PXRD) and differential scanning calorimetry (DSC) were used to identify and characterize the equilibrated solid phase samples. The solubility behavior and the solute–solvent interaction of trans-4-chlorocinnamic acid in each selected mono-solvent were explored by the empirical solvents polarity parameter (ET(30)), hydrogen bonding, cohesive energy density, molecular structure, and Hansen solubility parameters (HSPs). In addition, the experimental solubility data were correlated by the modified Apelblat model and Yaws model, and the fitting results of this models were all satisfactory. The intermolecular forces were determined through molecular simulations, including Hirshfeld surface (HS) and Molecular Electrostatic Potential Surface (MEPS) analysis. The results showed that hydrogen bond can be formed between trans-4-chlorocinnamic acid and the selected solvents, which can help to further explain the dissolution behavior of trans-4-chlorocinnamic acid in the solvents.

Natural source-field induced polarisation exploration of an iron-oxide copper-gold (IOCG) deposit under thick cover

Induced polarisation (IP) is a common geophysical method of exploration for disseminated sulphides. However, in areas with deep (>200 m) and conductive (10 Ωm or less) cover, the technique is less successful as it requires a significant transmitter source and large-offset dipoles. An alternative approach is to use natural-variations in Earth’s external magnetic field as the polarising source of the signal, known as natural-field IP. This paper presents a study of extracting IP information from electrical dipole observations during a broadband magnetotelluric (MT) program with a 9 km by 9 km grid of 100 sites above the Vulcan IOCG deposit beneath 750 m of cover, ∼40 km north of the Olympic Dam IOCG mine in South Australia. Inter-site transfer functions between 95 sites and five reference sites at the southeast and southwest corners of the grid were computed to determine a phase shift between horizontal electric fields in the bandwidth of 1–100 s period. Phase shifts of up to – 5 degrees were centred on a region of brecciated hematite where drill holes intersected pyrite, and an inferred fault-zone from passive seismics that marks the boundary between upper crust that is resistive (>100 Ω.m) with high magnetic susceptibility to the south of the fault, and a region of conductive crust (<10 Ω.m) which is low magnetic susceptibility. Our study suggests that the natural-field IP method can identify regions of polarizable minerals beneath deep cover where artificial power sources cannot be feasibly deployed. Such surveys are cheaper, safer, and easier to deploy as only receivers are required, and 3D coverage can be obtained as the source-field is of much larger dimension than the survey array. In addition, the natural-field IP signals are observed as part of the MT program so that both electrical resistivity and polarisation parameters can be determined.

Near-infrared polarity fluorescent probe for wash-free imaging lipid droplets and the application in the diagnosis of non-alcoholic fatty liver tissue

Lipid droplets (LDs), as primary cellular energy storage organelles, play essential roles not only in energy conservation but also in inflammatory responses, apoptosis, and the progression of diseases such as non-alcoholic fatty liver disease (NAFLD). Studies indicate that alterations in the polarity of LDs are closely linked to pathological factors like oxidative stress, ferroptosis, and lipophagy. Therefore, developing biological probes for precisely monitoring LDs polarity is crucial for understanding these biological phenomena and devising new therapeutic strategies. In this context, we synthesized four fluorescent probes (CNL1-CNL4) to precisely monitor the polarity of LDs using triphenylamine and carbazole derivatives as electron donors and isophorone and benzopyranonitrile units as electron acceptors, employing intramolecular charge transfer (ICT) mechanism. Our findings demonstrated that all four probes exhibited high sensitivity and specificity for polarity changes. Probes CNL2 and CNL4 were sensitive to polarity, and their maximum fluorescence intensity and maximum emission wavelength demonstrated a good linear relationship with polarity parameters within a certain range. Biological experiments demonstrated that both CNL2 and CNL4 possess excellent wash-free imaging capabilities and superior LDs targeting abilities but also enable dynamic monitoring of LDs and respond well to changes in LDs polarity under varying concentrations of oleic acid stimulation. Due to its longer emission wavelength (>650 nm), boasting excellent photostability, and featuring a larger Stokes shift (≈168 nm in acetonitrile), probe CNL4 was selected for further studies. Furthermore, probe CNL4 effectively monitors changes in LDs polarity under conditions of ferroptosis and oxidative stress. It has shown potential in the diagnosis of NAFLD tissue and during the process of lipophagy, highlighting its value in disease diagnostics and biological research. These findings not only deepen our understanding of the mechanisms underlying NAFLD progression but also provide new tools for diagnosing and treating related diseases.

Deciphering the thermal, physical, structural, and optical characteristics of sodium-doped vanadophosphate glasses

Ionic glasses offer a multitude of prospects for a wide range of electrochemical applications such as solid-state batteries, which eventually require more accessible, secure, and ecologically sound electrolytes and electrode materials. Here, sodium-doped vanadium phosphate (NVP) glasses in the chemical composition, xNa2O.(50-x)V2O5.50P2O5 (where, x = 0, 10, 20, 30, 40, and 50 mol%) were effectively synthesized via the melt-quenching technique, and their amorphous nature was confirmed by the appearance of broad humps in X-ray diffraction technique. Numerous physical parameters, namely, density, molar volume, oxygen packing density (OPD), polaron radius, field strength, etc., were studied as a function of Na2O concentration. Furthermore, the structural alterations of the glass network were examined in relation to the modifications in the FTIR and Raman spectra brought about by varying concentrations of sodium ions, such as the formation of more bridging oxygen sites. The optical characteristics were investigated using UV–vis spectroscopy, and the transmittance in the as-prepared glass series elevated as Na2O content was increased. The presence of three absorption peaks centered at 320, 650, and 864 nm points towards the possibility of V4+ ions in the as-prepared glass samples. They are unequivocally amorphous semiconductors because their Urbach energy values fall between 0.12 and 0.57 eV. Optical band gap energy, refractive index, polarizability, dielectric constant, and additional parameters were also examined.

A description of χcJ → VV decays within the effective field theory framework

We study χcJ → VV decays using the QCD effective field theory approach. The helicity suppressed decay amplitudes are also considered. The colour-singlet contributions of these amplitudes suffer from the endpoint singularities, it is shown that they can be absorbed into renormalisation of the nonfactorisable colour-octet matrix element. The latter can be associated with the colour-octet component of the charmonium wave function. The heavy quark spin symmetry makes it possible to establish the relationships between colour-octet matrix elements for different states χcJ up to higher order corrections in small velocity v. This allows us to estimate the polarisation parameters for χc2→ VV using data for χc0,1→ VV. This analysis is carried out for the available data on the χcJ→ ϕϕ decays.

Free Surface Energy and Hansen Solubility Parameter Vector Field. Interface Thickness

In this paper, a three-dimensional vector field model is proposed, whose dimensions are the Hansen Solubility Parameters: dispersion parameter (δD), polarity parameter (δP), and hydrogen bonding parameter (δH). The vector space that defines the field has the peculiarity of having a dispersion vector with a magnitude of 2 as its base vector, while the polarity and hydrogen bonding vectors have a magnitude of 1. A substance is characterised as a position vector, and the interaction between two substances is determined by calculating the vector difference of both, known as the interaction vector. The interaction among substances may involve solubility, swelling, cracking, surface tension, interface tension, and any physical phenomena where the intermolecular energies of dispersion, polarity or hydrogen bonding come into play. This paper studies free surface energy (surface and interfacial tension). It has been found that free surface energy is directly proportional to the square of the magnitude of the interaction vector. The proportionality constant, τ, is expressed in length units, has a value of 0.025 nm, and does not depend on the chemical nature of the substance or state of matter (solid, liquid or gas). The constant value τ appears universal and aligns with the thickness of interfaces, thereby supporting Guggenheim’s hypothesis. This hypothesis asserts that interfaces possess actual thickness and are not merely mathematical surfaces, as originally postulated by Gibbs. Moreover, it also has been found that the interface thickness, τ, is approximately equal to half of the Bohr radius, a0, which is defined by universal constants. Because the solubility parameters of thousands of substances are known and can be easily determined from their molecular structure, a good approximation of the surface and interfacial tension of any given substance can now be calculated. It has also been found that the contact angles of sessile droplets in three-phased systems can be calculated from the interaction vectors of the implicated substances.

Interference correction for polarization spectral intensity modulation (PSIM) with spatial heterodyne spectroscopy (SHS)

Spectropolarimetry, capable of measuring both the polarization parameters and spectral information of light, is widely utilized in astrophysical research and atmospheric remote sensing. Spatial Static Polarization Modulation Interferometric Spectroscopy merges polarization spectral intensity modulation (PSIM) with spatial heterodyne spectroscopy to achieve high spectral resolution and static synchronous measurement of continuous band polarization spectral information. This article is based on spatial static polarization modulation interferometric spectroscopy principles and describes correction techniques for non-uniform response and phase errors observed in interferograms. A quantitative relationship was established through simulation between the non-uniform response, phase errors in the interferograms, and the demodulation accuracy of polarization parameters. An experimental setup based on these principles was constructed to validate the effectiveness of the correction. The experimental results demonstrated that by using the reported data processing workflow the error in the degree of polarization was reduced from 0.1354 to 0.0095.

Polarization-Dependent Formation of Extremely Compressed Femtosecond Wave Packets and Supercontinuum Generation in Fused Silica

Previous studies of formation of extremely compressed wave packets during femtosecond filamentation in the region of anomalous group velocity dispersion in solid dielectrics mostly considered the case of linearly polarized laser pulses. However, recent results suggest potential applications of polarization state manipulation for ultrafast laser writing of optical structures in bulk solid-state media. In the present work, evolution of radiation polarization parameters during formation of such extreme wave packets at the pump wavelength of 1900 nm in fused silica is studied numerically on the basis of the carrier-resolved unidirectional pulse propagation equation (UPPE). It was revealed that initial close-to-circular polarization leads to higher intensity of the anti-Stokes wing in the spectrum of the generated supercontinuum. Numerical simulations indicate a complex, space–time variant polarization state, and the resulting spatiotemporal electric field distribution exhibits a strong dependence on the initial polarization of the femtosecond pulse. At the same time, electric field polarization tends to linear one in the region with the highest field strength regardless of the initial parameters. The origin of this behavior is attributed to the properties of the supercontinuum components generation during filament-induced plasma formation.

New approach for processing chitosan as low cost protective hybrid coating for C-steel in acid media

The novelty of this study is that it the first time blending and formulation of chitosan as a new hybrid (organometallic) protective coatings for achieving synergistic protection for carbon steel alloy during acid pickling. The role of coated silica (by 0.1 wt % stearic acid lubricant) in the improvement of coating performance was highlighted. Variable weight percentage of chitosan and silica in addition to a fixed weight percentage (35 %) of guar gum natural plant resin, 5 × 10−6 mmol (2-Hydrazinyl-6-methyl (or phenyl) −4, 5-di-H pyrimidinone) as organic corrosion inhibitors were compounding as hot melt in the presence of a low cost surfactant as an emulsifying agent improved compatibility between coating constituents. Guar gum increased coating flow during application and grafted chitosan into high molecular copolymer resin insoluble in acid media. Phosphorous acid improved coating flexibility during application by hot dipping. Hybrid coating decreased corrosion potential of carbon steel and retarded both redox reactions of corrosion acting as adsorbed mixed-type inhibitor. Percentages protection (%P) approached hundred percentage as confirmed from the agreement between impedance and polarization parameters. Guar gum plant resin and slice powder increased gloss of coating. The coated silica filled the pores and increased stiffness of coating. Super hydrophobicity of coating was confirmed by the measured contact angle above 150oC indicating good spreading of coating sample as insulating adherent surface film.

Optimization of polarization balance in beam splitter films for weak star simulator

In the weak star simulator, the background stray light of the self-excited star image and the simulated target star light are mixed with each other, which is difficult to separate and reduces the simulation accuracy of the star position. Therefore, based on the polarized light tracing method, this paper explores the induction mechanism of the polarization effect of the weak star simulator on the background stray light field of the star map, and proposes a polarization balance optimization method for the beam splitter film. At the same time, the mapping model of star position simulation accuracy, polarization parameters of beam splitter and polarization stray light suppression degree is established. Based on this evaluation function, the polarization balance optimization process of beam splitter is constructed to reduce the influence of polarization effect of beam splitter on the background stray light field of star image. The simulation and experimental results show that the stray light suppression ability of the weak star simulator is improved by 2.1 times and the simulation accuracy of the star position is improved by 1.64 times after the polarization balance optimization of the beam splitter film.

Influence of ionospheric resonators on daily dynamics of the first Schumann resonance spectral parameters according to data from a meridional chain of ULF magnetometers

We have experimentally studied the influence of the local ionosphere, namely the ionospheric Alfvén resonator (IAR) and the lower ionospheric resonator at altitudes 80–300 km (sub-IAR) on the amplitude and polarization of the first Schumann resonance. The study is based on spectral analysis of data from simultaneous monitoring of ULF magnetic noise components at a meridional chain of stations: high-latitude stations Barentsburg and Lovozero, mid-latitude observatory NNGU NIRFI (NL, Nizhny Novgorod Region), a low-latitude station in Israel. We have also used monitoring data from the Borok and Crete observatories. At the stations in dark conditions, significant variations were found in the spectrum of the polarization parameter ε at the frequency of the first Schumann resonance (SR). Moreover, these variations had different character at different observatories. Analysis of the daily dynamics of the parameter ε has shown that these variations are associated with the influence of local sub-IAR having different optical thickness and quality factor at these observatories. The influence of sub-IAR on polarization in the SR band was found to depend on the ratio of the boundary frequency fb (the frequency that separates the negative and positive polarization of ULF magnetic noise) to the frequency of the first SR. The IAR influence on the polarization and amplitude of magnetic fields in the frequency band of the first Schumann resonance was discovered only at the NL and Lovozero stations: a high-quality Alfvén resonator in the ionosphere above the NL station could cause the SR frequency band to change and its central frequency to shift. Analysis of low-frequency data from the observatories separated by distances of 400 km has revealed that the influence of local ionospheric resonators can lead to a difference in the amplitude characteristics of the first SR even at such distances. It has also been shown that the influence of the IAR and sub-IAR resonators on the azimuthal angle of the magnetic field vector in the frequency band of the first SR is less noticeable and can generate variations in this parameter by 10°–20°. Numerical calculations performed for the spherical waveguide model made it possible to adequately interpret the features of the daily dynamics of the parameter ε in the frequency range of the first SR.

Влияние ионосферных резонаторов на суточную динамику спектральных параметров первого шумановс-кого резонанса по данным меридиональной сети УНЧ-магнито-метров

We have experimentally studied the influence of the local ionosphere, namely the ionospheric Alfvén resonator (IAR) and the lower ionospheric resonator at altitudes 80–300 km (sub-IAR) on the amplitude and polarization of the first Schumann resonance. The study is based on spectral analysis of data from simultaneous monitoring of ULF magnetic noise components at a meridional chain of stations: high-latitude stations Barentsburg and Lovozero, mid-latitude observatory NNGU NIRFI (NL, Nizhny Novgorod Region), a low-latitude station in Israel. We have also used monitoring data from the Borok and Crete observatories. At the stations in dark conditions, significant variations were found in the spectrum of the polarization parameter ε at the frequency of the first Schumann resonance (SR). Moreover, these variations had different character at different observatories. Analysis of the daily dynamics of the parameter ε has shown that these variations are associated with the influence of local sub-IAR having different optical thickness and quality factor at these observatories. The influence of sub-IAR on polarization in the SR band was found to depend on the ratio of the boundary frequency fb (the frequency that separates the negative and positive polarization of ULF magnetic noise) to the frequency of the first SR. The IAR influence on the polarization and amplitude of magnetic fields in the frequency band of the first Schumann resonance was discovered only at the NL and Lovozero stations: a high-quality Alfvén resonator in the ionosphere above the NL station could cause the SR frequency band to change and its central frequency to shift. Analysis of low-frequency data from the observatories separated by distances of 400 km has revealed that the influence of local ionospheric resonators can lead to a difference in the amplitude characteristics of the first SR even at such distances. It has also been shown that the influence of the IAR and sub-IAR resonators on the azimuthal angle of the magnetic field vector in the frequency band of the first SR is less noticeable and can generate variations in this parameter by 10°–20°. Numerical calculations performed for the spherical waveguide model made it possible to adequately interpret the features of the daily dynamics of the parameter ε in the frequency range of the first SR.

Mueller matrix-based calculation model for extracting polarization parameters in full-wave simulation of all-dielectric Pancharatnam–Berry (PB)-phase metasurfaces

In this study, the Mueller matrix of all-dielectric Pancharatnam–Berry (PB)-phase metasurfaces was retrieved using finite-difference time-domain (FDTD) simulation, Stokes–Mueller calculus, and Lu–Chipman decomposition. The polarization properties are discussed for nanofin-shaped PB-phase metasurfaces made of GaN and Nb2O5 and L-shaped PB-phase metasurfaces made of GaN. The results show that both the nanofin-shaped and L-shaped PB-phase GaN metasurfaces are optically equivalent to a linear-diattenuating retarder, and the nanofin-shaped PB-phase Nb2O5 metasurface is optically equivalent to a linear phase retarder. The PB-phase GaN metasurface exhibits stronger diattenuation and lower transmittance than the Nb2O5 metasurface due to the inherent defect absorption in the visible range. With a similar refractive index but barely any absorption, Nb2O5 is a more suitable material for PB-phase metasurfaces in the visible range than GaN.

Augmenting the effect of solvents on optical nonlinearity by spectroscopic, DFT, solvatochromism and z-scan studies of push-pull chalcone: (2E)-1-(4-ethoxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one

In this article, the structural and nonlinear optical behaviour of a chalcone derivative, (2E)-1-(4-ethoxyphenyl)-3-(4-methoxyphenyl)prop-2-en-1-one have been studied. FT-IR, FT-Raman, and NMR spectroscopy were analyzed to validate the molecular structure. To predict the nonlinear optical characteristics of the chalcone, the DFT approach was used and the experimental results were corroborated by the computations. The bathochromic shift is obtained in linear absorbance spectra and is validated using TD-DFT. Also, the broad emission in the blue region demonstrates the blue light emission property of the sample. Using the finite-field method, the dipole moments, polarizability, first-order and second-order hyperpolarizability parameters have been computed. Ground and excited state dipole moments were quantified by solvatochromism. The third-order nonlinear optical characteristics of chalcone in polar and non-polar solvent media were examined using the open/closed-aperture z-scan technique. The chalcone displayed considerable two-photon absorption with a positive nonlinear absorption coefficient and a positive index of refraction due to the self-focussing effect. Furthermore, the optical limiting study manifests that the investigated chalcone might well be favourable for NLO applications.

Broadband spectropolarimeter based on spatial heterodyne spectroscopy and channeled polarimetric technique

A spectropolarimeter based on spatial heterodyne spectroscopy and the channeled polarimetric technique (SSHSCP) is introduced. The SSHSCP uses a polarization grating for channel modulation, meaning that the Stokes parameter is no longer dependent on the wavenumber; this suppresses channel aliasing considerably and improves the polarization parameter reconstruction accuracy. The SSHSCP’s optical path structure is based on the Mach–Zehnder interferometer, ensuring efficient energy use. The spectral detection and polarization detection principles of the SSHSCP are derived, and a specific design example is presented. Simulations indicate that the SSHSCP can restore the target’s spectral and complete Stokes parameters with high accuracy for a broadband source and narrowband lines. The reconstructed Stokes parameter errors are of the order of 10−3 or less. The SSHSCP acquires spectral and polarization parameters in a single step and has no moving parts in a compact structure.