Depolarization Of Light Research Articles

Single-channel high-precision laser rangefinder

The article deals with the construction of a single-channel light rangefinder. At the same time, one of the main difficulties is the presence of depolarization of light, which forms residual light at the output of the analyzer, which greatly affects the measurement accuracy. It is shown that in order to exclude residual light by compensating for depolarization, a KDP crystal plate with the possibility of rotation in a plane parallel to the optical axis is installed at the input of the demodulator.The possibility of using an optical delay line on a single mirror with the possibility of moving along the axis of the radiation source is also considered. The normal to the mirror surface and the optical axes of the KDP crystals are located to the axis of the light source at an angle of 0.7–0.9∘.

Influence of Compression Loading on Acoustic Emission and Light Polarization Features in TeO2 Crystal.

Monitoring the processes inside crystalline materials under their operating conditions is of great interest in optoelectronics and scientific instrumentation. Early defect detection ensures the proper functioning of multiple crystal-based devices. In this study, a combination of acoustic emission (AE) sensing and cross-polarization imaging is proposed for the fast characterization of the crystal's structure. For the experiments, tellurium dioxide (TeO2) crystal was chosen due to its wide use in acousto-optics. Studies were performed under uniaxial compression loading with a simultaneous acquisition of AE signals and four polarized optical images. An analysis of the temporal dependencies of the AE data and two-dimensional maps of the light depolarization features was carried out in order to establish quantitative criteria for irreversible damage initiation and crack-like defect formation. The obtained results reveal the polarization image patterns and the AE pulse duration alteration specific to these processes, and they open up new possibilities for non-destructively monitoring in real-time the structure of optically transparent crystals under their operating conditions.

Polycations as Aptamer-Binding Modulators for Sensitive Fluorescence Anisotropy Assay of Aflatoxin B1.

Fluorescence induced by the excitation of a fluorophore with plane-polarized light has a different polarization depending on the size of the fluorophore-containing reagent and the rate of its rotation. Based on this effect, many analytical systems have been implemented in which an analyte contained in a sample and labeled with a fluorophore (usually fluorescein) competes to bind to antibodies. Replacing antibodies in such assays with aptamers, low-cost and stable oligonucleotide receptors, is complicated because binding a fluorophore to them causes a less significant change in the polarization of emissions. This work proposes and characterizes the compounds of the reaction medium that improve analyte binding and reduce the mobility of the aptamer-fluorophore complex, providing a higher analytical signal and a lower detection limit. This study was conducted on aflatoxin B1 (AFB1), a ubiquitous toxicant contaminating foods of plant origins. Eight aptamers specific to AFB1 with the same binding site and different regions stabilizing their structures were compared for affinity, based on which the aptamer with 38 nucleotides in length was selected. The polymers that interact reversibly with oligonucleotides, such as poly-L-lysine and polyethylene glycol, were tested. It was found that they provide the desired reduction in the depolarization of emitted light as well as high concentrations of magnesium cations. In the selected optimal medium, AFB1 detection reached a limit of 1 ng/mL, which was 12 times lower than in the tris buffer commonly used for anti-AFB1 aptamers. The assay time was 30 min. This method is suitable for controlling almond samples according to the maximum permissible levels of their contamination by AFB1. The proposed approach could be applied to improve other aptamer-based analytical systems.

Line shapes of isotropic and depolarized CILS spectra of neon: Interaction potential and pair polarizability

The present work proposes three interaction potentials between two gaseous neon atoms and applies them to the study of models representing the anisotropy and trace of the induced pair polarizability tensor. The proposed empirical interatomic potentials for the gaseous Ne-Ne interaction are developed by fitting the Improved Lennard-Jones (ILJ), Modified Tang-Toennies (MTT) and Barker et al. (BFW) potentials simultaneously to the spectroscopic and transport properties over a wide temperature range. The validity of the proposed interatomic potentials is verified by comparing the calculated and experimental second pressure virial coefficient over a wide temperature range. In addition to this, the results show satisfactory accordance between the experimental and calculated vibrational energy levels using the deduced pair potential parameters compared to those reported for neon gas. These comparisons exhibit acceptable accuracy when the present work potential parameters are inserted to reproduce the transport and thermo-physical properties, besides the spectral moments and the spectral line-shape intensities for neon gas. The isotropic and depolarized collision-induced light scattering (CILS) spectra are produced and analyzed as functions of the potential considered. They exhibit sensitivity to both the attractive part of the potential and the short-range values of the polarizability anisotropy or mean at intermediate and high frequencies. Mean and anisotropy are deduced directly from spectral line shapes using a new inversion method.

Diagnostics of luminescent recording media based on the polarized scattering spectra of hologram sensors formed in the substance analyzed

The article is devoted to the diagnosis and identification of luminescent holographic information carriers in particular wine products using polarization holographic spectroscopy methods. For the first time, to our best knowledge, a technique has been developed for measuring and analyzing scattered polarized light (depolarization spectra) on polarization-holographic sensors formed in analyte. Polarized scattering spectra on a hologram sensor (measuring transducers) are of particular interest, since they provide information not only about the chemical composition of the media, for example, luminescence and absorption spectra, but also about particles that may be present in the analyte – the higher the anisotropy of the molecules and atoms, the greater the depolarization. Methods for measuring polarized scattering and excitation spectra carried out for various samples of holographic materials, as well as methods for processing and presenting the obtained spectral data are described. This may be of interest, since recording media, in particular wine, are complex colloidal systems. For the diagnosis, classification and identification of recording materials, it is proposed for the first time to use reflective holographic sensors (Yu.N. Denisyuk) of various physical natures (the concept of a spectral holographic portrait).

Swept-wavelength null polarimetry for highly sensitive birefringence laser scanning microscopy

We have recently demonstrated a high-speed null polarimeter [Opt. Express 30, 18889 (2022)10.1364/OE.454193OPEXFF1094-4087] based on passive polarization optics and using a fast swept-wavelength laser source. We report here its implementation in a laser-scanning microscope setup, enabling highly sensitive linear retardance imaging with a pixel dwell time of 10 μs. The instrument is also able to measure light depolarization induced by the sample. Images of biological samples, including cancerous tissue and cells, illustrate its performances.

A simple, isotropic depolarized light source.

Unpolarized light can be an important tool in optical experiments. Producing it, however, can prove to be a challenge. Natural sources of light that are commonly thought of as unpolarized are, in fact, either weakly polarized or not practical sources of light in a laboratory setting. Standard, commercially available light depolarizers produce unpolarized light only after the polarization state of the light across the diameter of the output beam has been averaged. Locally, such beams are highly polarized. In this work, we report a simple, low cost light depolarizer capable of producing light with a total polarization of less than 1% for a 15-mm diameter output beam. Based upon diffuse scattering, the light transmitted through the depolarizer discussed here produces only small polarizations locally, with the total polarization for a 1.25-mm diameter area being <6%. The effects of the depolarizer on the transmitted beam's intensity are also reported.

Geometric phase and photonic spin Hall effect in thin films with architected columnar morphology

We have detected spin-dependent splitting of light, the signature of the photonic spin Hall effect (PSHE), via quantum weak measurements on two types of thin films with architected columnar morphology. Specifically, we fabricated columnar thin films comprising parallel tilted nanocolumns and chiral sculptured thin films comprising parallel upright nanohelices by resistively heating zinc selenide (ZnSe) in a low-pressure chamber and collecting the collimated vapor flux of ZnSe on planar substrates with dynamically varying orientation. The architected columnar morphology creates a spin-dependent geometric Pancharatnam–Berry (PB) phase corresponding to the evolution of polarization states on the Poincaré sphere. Morphology-controlled anisotropy and spatial inhomogeneity result in the depolarization and optical rotation of incident plane-polarized light, and intrinsic spin-precession coupling with the propagation vector, contributing to the efficient generation and two-dimensional manipulation of both in-plane and out-of-plane spin splitting and steering the PB phase in the propagation process. The first experimental observations of widely tailorable PSHE and PB phase in thin films with architected columnar morphology may lead to new applications ranging from spin-controlled nanophotonics to optoelectronic devices for quantum information processing and optical communication.

P‐7.8: Study on the effect of large angle compensation POL on FFS product contrast ratio

Angle compensation polarizers are usually used in VA and TN products to improve the side angle light leakage problem. With the increasingly fierce market competition, FFS products also began to try to use angle compensation film to improve the competitiveness of products, and achieved good angle compensation effect. However, due to the phase delay property of the angle‐compensated polarizer itself and the weak resistance of the material to deformation, it often leads to the depolarization of the initial positive light. Therefore, the orthogonal state of the polarizer is destroyed, resulting in the light leakage and uneven dark state of the product, which leads to the reduction of the contrast ratio of the product; In this paper, the problem of product contrast reduction caused by FFS STW (super true wide angle of view compensation) polarizer is systematically studied, the reason of contrast ratio reduction is analyzed from the STW polarizer compensation mechanism and fault phenomenon, the influence of depolarization, adhesion stress, film distribution and optical path difference fluctuation of STW polarizer on its contrast ratio is clarified, and the improvement method is proposed, which provides important technical support for the application of STW polarizer in FFS mode.

Polarimetric imaging of back-scattered terahertz speckle fields using a portable scanner.

Speckle patterns observed in coherent optical imaging reflect important characteristic information of the scattering object. To capture speckle patterns, angular resolved or oblique illumination geometries are usually employed in combination with Rayleigh statistical models. We present a portable and handheld 2-channel polarization-sensitive imaging instrument to directly resolve terahertz (THz) speckle fields in a collocated telecentric back-scattering geometry. The polarization state of the THz light is measured using two orthogonal photoconductive antennas and can be presented in the form of the Stokes vectors of the THz beam upon interaction with the sample. We report on the validation of the method in surface scattering from gold-coated sandpapers, demonstrating a strong dependence of the polarization state on the surface roughness and the frequency of the broadband THz illumination. We also demonstrate non-Rayleigh first-order and second-order statistical parameters, such as degree of polarization uniformity (DOPU) and phase difference, for quantifying the randomness of polarization. This technique provides a fast method for broadband THz polarimetric measurement in the field and has the potential for detecting light depolarization in applications ranging from biomedical imaging to non-destructive testing.

Light transmission polarization patterns and depolarization from water fog concentration variation

We present both experimental measurements and Monte-Carlo-based simulations of transmission polarization to analyze the concentration variation effects of the water fog particles. Simulations based on Monte Carlo program have been conducted for tracking photon transmission process with the radius and refractive index of water fog samples under different optical thicknesses. Correspondingly, experiments with an environment modulation system show that by controlling the water fog concentration, the Mueller matrix and the depolarization characteristic change in a regular way. Both the simulation and the experimental results show a good distinction of Mueller matrix among the light, moderate, and thick fog samples, and the depolarization property of thick fog environment is more prominent. Moreover, circular polarization persists better than linear polarization in more serious fog. These works can provide a tool to examine different media concentrations by the polarization patterns and broaden the application range of polarization.

Influence of intramolecular dynamics on the relaxation spectra of simple liquids.

The shape of the structural relaxation peak in the susceptibility spectra of liquids is of great interest, as it promises to provide information about the distribution of molecular mobilities and dynamic heterogeneity. However, recent studies suggest a generic shape of this peak near the glass transition temperature irrespective of the liquid under investigation, which somehow reduces the information contained in the peak shape. By contrast, at higher temperatures, say, around the melting point, the situation is different and the peak shape varies strongly between different liquids. In this study, we investigate molecules with a ring-tail structure and address the question how intramolecular dynamics influences the peak shape at these temperatures. Using depolarized light scattering and dielectric spectroscopy, we observe a bimodal relaxation, which we attribute to the fact that the reorientation of the ring group to some extent decouples from the rest of the molecule. This shows that the relaxation spectra are sensitive to details of the molecular motions at high temperatures, whereas in the supercooled state this microscopic information seems to give way to a generic shape, probably due to the onset of cooperativity which extends across different intramolecular moieties.

Real-time detection of response regulator phosphorylation dynamics in live bacteria

Bacteria utilize two-component system (TCS) signal transduction pathways to sense and adapt to changing environments. In a typical TCS, a stimulus induces a sensor histidine kinase (SHK) to phosphorylate a response regulator (RR), which then dimerizes and activates a transcriptional response. Here, we demonstrate that oligomerization-dependent depolarization of excitation light by fused mNeonGreen fluorescent protein probes enables real-time monitoring of RR dimerization dynamics in live bacteria. Using inducible promoters to independently express SHKs and RRs, we detect RR dimerization within seconds of stimulus addition in several model pathways. We go on to combine experiments with mathematical modeling to reveal that TCS phosphosignaling accelerates with SHK expression but decelerates with RR expression and SHK phosphatase activity. We further observe pulsatile activation of the SHK NarX in response to addition and depletion of the extracellular electron acceptor nitrate when the corresponding TCS is expressed from both inducible systems and the native chromosomal operon. Finally, we combine our method with polarized light microscopy to enable single-cell measurements of RR dimerization under changing stimulus conditions. Direct invivo characterization of RR oligomerization dynamics should enable insights into the regulation of bacterial physiology.

Cleaner Skies during the COVID-19 Lockdown

Abstract During spring 2020, the COVID-19 pandemic caused massive reductions in emissions from industry and ground and airborne transportation. To explore the resulting atmospheric composition changes, we conducted the BLUESKY campaign with two research aircraft and measured trace gases, aerosols, and cloud properties from the boundary layer to the lower stratosphere. From 16 May to 9 June 2020, we performed 20 flights in the early COVID-19 lockdown phase over Europe and the Atlantic Ocean. We found up to 50% reductions in boundary layer nitrogen dioxide concentrations in urban areas from GOME-2B satellite data, along with carbon monoxide reductions in the pollution hot spots. We measured 20%–70% reductions in total reactive nitrogen, carbon monoxide, and fine mode aerosol concentration in profiles over German cities compared to a 10-yr dataset from passenger aircraft. The total aerosol mass was significantly reduced below 5 km altitude, and the organic aerosol fraction also aloft, indicative of decreased organic precursor gas emissions. The reduced aerosol optical thickness caused a perceptible shift in sky color toward the blue part of the spectrum (hence BLUESKY) and increased shortwave radiation at the surface. We find that the 80% decline in air traffic led to substantial reductions in nitrogen oxides at cruise altitudes, in contrail cover, and in resulting radiative forcing. The light extinction and depolarization by cirrus were also reduced in regions with substantially decreased air traffic. General circulation–chemistry model simulations indicate good agreement with the measurements when applying a reduced emission scenario. The comprehensive BLUESKY dataset documents the major impact of anthropogenic emissions on the atmospheric composition.

Optical birefringence changes in myelinated and unmyelinated nerves: A comparative study.

The measurement of birefringence variations related to nerve activity is a promising label-free technique for sensing compound neural action potentials (CNAPs). While widely applied in crustaceans, little is known about its efficiency on mammal peripheral nerves. In this work, birefringence recordings to detect CNAPs, and Stokes parameters measurements were performed in rat and lobster nerves. While single-trial detection of nerve activity in crustaceans was achieved successfully, no optical signal was detected in rats, even after extensive signal filtering and averaging. The Stokes parameters showed that a high degree of polarization of light is maintained in lobster sample, whereas an almost complete light depolarization occurs in rat nerve. Our results indicate that depolarization itself is not sufficient to explain the absence of birefringence signals in rats. We hypothesize that this absence comes from the myelin sheets, which constraint the birefringence changes to only take place at the nodes of Ranvier.

Single‐shot Mueller‐matrix imaging of zebrafish tissues: In vivo analysis of developmental and pathological features

Zebrafish is a well-established animal model for developmental and disease studies. Its optical transparency at early developmental stages allows in vivo tissues visualization. Interaction of polarized light with these tissues provides information on their structure and properties. This approach is effective for muscle tissue analysis due to its birefringence. To enable real-time Mueller-matrix characterization of unanesthetized fish, we assembled a microscope for single-shot Mueller-matrix imaging. First, we performed a continuous observation of 48 species within the period of 2 to 96 hpf and measured temporal dependencies of the polarization features in different tissues. These measurements show that hatching was accompanied by a sharp change in the angle and degree of linearly polarized light after interaction with muscles. Second, we analyzed nine species with skeletal disorders and demonstrated that the spatial distribution of light depolarization features clearly indicated them. Obtained results demonstrated that real-time Mueller-matrix imaging is a powerful tool for label-free monitoring zebrafish embryos.

Based on reflected light depolarization characteristics optimization method for improving indoor visible light positioning accuracy

Visible light-based positioning (VLP) is envisioned to be a promising solution to indoor positioning, orientation, and navigation because of the widespread use of light-emitting diodes for illumination. At present, several VLP schemes have been proposed, with most researchers using the line-of-sight channel and ignore the multipath reflection. However, some research works have shown that multipath reflections degrade the performance of VLP systems greatly. We propose an optimization positioning method based on reflected light depolarization characteristics to subtract the multipath reflection signals from the received signals, which can eliminate or mitigate the impact of multipath reflection to improve positioning accuracy. Further, a model is established theoretically, and simulations are carried out in a 0.82 m × 0.82 m × 0.62 m area. The simulation results show that the average positioning error and maximal error are reduced by 94.9% and 85.1%, respectively, when using the method. In the experiments, the performances are assessed and match well with our simulation results, achieving an average positioning error of 4.2 cm and a maximal positioning error of 8.4 cm, corresponding to a decrease of 62.5% and 66.0%.

Hydration Dynamics of Model Peptides with Different Hydrophobic Character.

The multi-scale dynamics of aqueous solutions of the hydrophilic peptide N-acetyl-glycine-methylamide (NAGMA) have been investigated through extended frequency-range depolarized light scattering (EDLS), which enables the broad-band detection of collective polarizability anisotropy fluctuations. The results have been compared to those obtained for N-acetyl-leucinemethylamide (NALMA), an amphiphilic peptide which shares with NAGMA the same polar backbone, but also contains an apolar group. Our study indicates that the two model peptides induce similar effects on the fast translational dynamics of surrounding water. Both systems slow down the mobility of solvating water molecules by a factor 6–8, with respect to the bulk. Moreover, the two peptides cause a comparable far-reaching spatial perturbation extending to more than two hydration layers in diluted conditions. The observed concentration dependence of the hydration number is explained considering the random superposition of different hydration shells, while no indication of solute aggregation phenomena has been found. The results indicate that the effect on the dynamics of water solvating the amphiphilic peptide is dominated by the hydrophilic backbone. The minor impact of the hydrophobic moiety on hydration features is consistent with structural findings derived by Fourier transform infrared (FTIR) measurements, performed in attenuated total reflectance (ATR) configuration. Additionally, we give evidence that, for both systems, the relaxation mode in the GHz frequency range probed by EDLS is related to solute rotational dynamics. The rotation of NALMA occurs at higher timescales, with respect to the rotation of NAGMA; both processes are significantly slower than the structural dynamics of hydration water, suggesting that solute and solvent motions are uncoupled. Finally, our results do not indicate the presence of super-slow water (relaxation times in the order of tens of picoseconds) around the peptides investigated.

Origin of Apparent Slow Solvent Dynamics in Concentrated Polymer Solutions

Due to their size disparity, the dynamics of solvent molecules in concentrated polymer solutions can be faster by several orders of magnitude compared to the polymer matrix. Despite these observations, past research suggests that a fraction of the solvent contributes to the slow dynamics on the timescale of the macromolecules. By combining depolarized dynamic light scattering and molecular dynamics simulations, we show that long-lived solvent–solvent cross-correlations cause these slow solvent contributions. They originate from the energy landscape that the solute imprints onto the neighboring solvent, leading to enhanced correlations between the positions and orientations of different solvent molecules until the solute relaxes. This mechanism explains the discrepancies found between the results of techniques probing collective and single-particle dynamics, such as dielectric and nuclear magnetic resonance spectroscopy. Our findings shed new light on how solvents behave in the vicinity of macromolecules and are of relevance for materials ranging from polymer-plasticizer systems to hydrated proteins.

Evidence of supercoolable nanoscale water clusters in an amorphous ionic liquid matrix.

Nanoscale water clusters in an ionic liquid matrix, also called "water pockets," were previously found in some mixtures of water with ionic liquids containing hydrophilic anions. However, in these systems, at least partial crystallization occurs upon supercooling. In this work, we show for mixtures of 1-butyl-3-methylimidazolium dicyanamide with water that none of the components crystallizes up to a water content of 72 mol. %. The dynamics of the ionic liquid matrix is monitored from above room temperature down to the glass transition by combining depolarized dynamic light scattering with broadband dielectric and nuclear magnetic resonance spectroscopy, revealing that the matrix behaves like a common glass former and stays amorphous in the whole temperature range. Moreover, we demonstrate by a combination of Raman spectroscopy, small angle neutron scattering, and molecular dynamics simulation that, indeed, nanoscale water clusters exist in this mixture.