Unpolarized Light Research Articles

Receptive field structures for two celestial compass cues at the input stage of the central complex in the locust brain.

Successful navigation depends on an animal's ability to perceive its spatial orientation relative to visual surroundings. Heading direction in insects is represented in the central complex (CX), a navigation center in the brain, to generate steering commands. In insects that navigate relative to sky compass signals, CX neurons are tuned to celestial cues indicating the location of the sun. The desert locust CX contains a compass-like representation of two related celestial cues: the direction of unpolarized direct sunlight and the pattern of polarized light, which depends on the sun position. Whether congruent tuning to these two compass cues emerges within the CX network or is inherited from CX input neurons is unclear. To address this question, we intracellularly recorded from GABA-immunoreactive TL neurons, which are input elements to the locust CX (corresponding to R neurons in Drosophila), while applying visual stimuli simulating unpolarized sunlight and polarized light across the hemisphere above the animal. We show that TL neurons have large receptive fields for both types of stimuli. However, faithful integration of polarization angles across the dorsal hemisphere, or matched-filter ability to encode particular sun positions, was found in only two out of 22 recordings. Those two neurons also showed a good match in sun position coding through polarized and unpolarized light signaling, whereas 20 neurons showed substantial mismatch in signaling of the two compass cues. The data, therefore, suggest that considerable refinement of azimuth coding based on sky compass signals occurs at the synapses from TL neurons to postsynaptic CX compass neurons.

Performance of polarization-sensitive neurons of the locust central complex at different degrees of polarization

The polarization pattern of the sky is exploited by many insects for spatial orientation and navigation. It derives from Rayleigh scattering in the atmosphere and depends directly on the position of the sun. In the insect brain, the central complex (CX) houses neurons tuned to the angle of polarization (AoP), that together constitute an internal compass for celestial navigation. Polarized light is not only characterized by the AoP, but also by the degree of polarization (DoP), which can be highly variable, depending on sky conditions. Under a clear sky, the DoP of polarized sky light may reach up to 0.75 but is usually much lower especially when light is scattered by clouds or haze. To investigate how the polarization-processing network of the CX copes with low DoPs, we recorded intracellularly from neurons of the locust CX at different stages of processing, while stimulating with light of different DoPs. Significant responses to polarized light occurred down to DoPs of 0.05 indicating reliable coding of the AoP even at unfavorable sky conditions. Moreover, we found that the activity of neurons at the CX input stage may be strongly influenced by nearly unpolarized light, while the activity of downstream neurons appears less affected.

レーザー散乱光の多方向偏光検出によるSiウエハ上微小欠陥の高精度凹凸分類

Wafer defect inspection is essential to control quality and yield of semiconductor device manufacturing. Wafer surface inspection tools with laser scattering method are employed for high-throughput and high-sensitivity inspection of defects with sizes of about several microns to sub-20 nm. In addition to detecting defects with various shapes and sizes, classification of defect types is required. Classification by multi-directional scattered light detection is known, which captures defect scattered light at multiple scatter direction and compares the intensities in different angles. We simulate concave-convex defect classification with multi-directional detection by analyzing polarized angular scattering distributions, obtained with discrete dipole approximation method, from defects that differ in shapes, sizes, and materials. As a result of classification performance evaluation with support vector machine classifier, when using only unpolarized light intensities, the maximum defect diameter that is accurately classified is limited to from 0.62 times as much as the illumination wavelength. By using both +45 and -45 deg linearly polarized light intensities, the limit is extended to from 1.47 times as much as the wavelength.

Coronal Cavities in CoMP Observations

Abstract Quiescent coronal cavities can provide insight into solar magnetic fields. They are observed in the coronal emission lines in both polarized and unpolarized light. In the total linear polarization fraction (L/I), they often possess a “lagomorphic,” or “rabbit-shaped,” structure that reflects the underlying magnetic field configuration. We studied quiescent coronal cavities observed between 2012 and 2018 by the Coronal Multichannel Polarimeter (CoMP). The majority of cavities in our study had a characteristic lagomorphic structure in linear polarization. We additionally compared cavity widths as observed in intensity with sizes of their linear polarization signatures for 70 cavities and found that both features are strongly correlated. Our results indicate that chances for observing a lagomorphic structure increase greatly with cavity lifetime, suggesting that the visibility depends on the spatial orientation of the cavity. Forward-modeled observations in linear polarization of flux ropes confirmed this assumption. We conclude that observations of the solar coronal cavities in linear polarization are consistent with the theoretical model of flux rope formation and structure.

Light Intensity Control Using Polaroids

Abstract: In today’s era of illuminating devices, there are a wide variety of devices available in aesthetics but the none with variable intensity of light. Using the basic principle of polarization of light using a Polaroid filter or polarizer, the designing of a light intensity control was done. The polarizing angle of the filter decides the intensity of the light that would pass through the filters. According to the principle of propagation of light, the electric and magnetic vibrations of a light wave occur perpendicularly to each other. A light wave that is vibrating in more than one plane is known as unpolarized light. The light emitted by the sun, by a lamp or a tube light are all unpolarized light sources. The other kind of wave is a polarized wave. A Plane polarized light vibrates on only one plane. The process of transforming unpolarized light into the polarized light is known as polarization. Using the same principle and with the use of a LDR (light dependent resister) as a sensor to sense the intensity of the surrounding light and then rotate the polaroid filter sheets accordingly using a stepper motor for the required change in intensity. The sensing and sending of feedback and subsequent rotation of the Polaroid filter sheets would be automated by ATMEGA32 microcontroller and L293D. Keywords: Polaroids, LDR, Light Variation, ATMEGA32, L293D

Cross-Polarized Optical Coherence Tomography System with Unpolarized Light

Cross-polarized optical coherence tomography offers improved contrast for samples which can alter the polarization of light when it interacts with the sample. This property has been utilized to screen pathological conditions in several organs. Existing cross-polarized optical coherence tomography systems require several polarization-controlling elements to minimize the optical fiber movement-related image artifacts. In this work, we demonstrate a cross-polarized optical coherence tomography system using unpolarized light and only two quarter-wave plates, which is free from fiber-induced image artifacts. The simplicity of the approach will find many applications in clinical settings.

Unravelling Rashba-Dresselhaus Splitting Assisted Magneto-Photoelectrochemical Water Splitting in Asymmetric MoSSe-GaN Heterostructures.

Among two-dimensional (2D) materials, asymmetric Janus structures (MoSSe, WSSe) have many exciting properties, such as out-of-plane piezoelectricity, spatial isolation of charge carriers, and strong spin-orbit coupling (SOC), resulting in a significant Rashba effect. However, the experimental validation to utilize SOC along with advanced optical properties for catalytic applications remains unexplored. Herein, for the first time, we demonstrate a proof-of-concept for spin-manipulated photo-electrochemical water splitting using Janus MoSSe/GaN heterostructures under an external low magnetic field. Further, the activation with delaminated 2D-MXene (Ti3C2Tx/MoSSe/GaN) for efficient electron channeling manifests ∼1.37 times photocurrent enhancement and ∼1.50-fold enhancement in product (H2/O2) formation under a low applied magnetic field (0.4 T). The external magnetic field supports spin manipulation even under unpolarized light by a spin-to-charge conversion in Janus MoSSe/GaN heterostructures. Density functional theory simulations were performed to understand the role of the Rashba-Dresselhaus effect for efficient charge transport.

Interactions of Linearly Polarized and Unpolarized Light on Kiwifruit Using Aquaphotomics.

Near infrared (NIR) spectroscopy is an important tool for predicting the internal qualities of fruits. Using aquaphotomics, spectral changes between linearly polarized and unpolarized light were assessed on 200 commercially grown yellow-fleshed kiwifruit (Actinidia chinensis var. chinensis ‘Zesy002’). Measurements were performed on different configurations of unpeeled (intact) and peeled (cut) kiwifruit using a commercial handheld NIR instrument. Absorbance after applying standard normal variate (SNV) and second derivative Savitzky–Golay filters produced different spectral features for all configurations. An aquagram depicting all configurations suggests that linearly polarized light activated more free water states and unpolarized light activated more bound water states. At depth (≥1 mm), after several scattering events, all radiation is expected to be fully depolarized and interactions for incident polarized or unpolarized light will be similar, so any observed differences are attributable to the surface layers of the fruit. Aquagrams generated in terms of the fruit soluble solids content (SSC) were similar for all configurations, suggesting the SSC in fruit is not a contributing factor here.

Isopachic method with unpolarized light

An isopachic method with unpolarized light using a Mach-Zehnder interferometer is proposed. In the case of unpolarized light, isopachics are observed not only due to a change in the thickness of the model but also due to induced birefringence. In contrast to the existing methods, the proposed method allows you to study sections of three-dimensional models or flat stressed samples with no thickness variation. A brief theoretical consideration based on the formalism of the coherence matrix is given, as well as the experimentally obtained isopachic field for a model made from high-modulus material. The method is convenient and simple in technical implementation. Keywords: photoelasticity, interferometry, stresses, isopachic, isochrome, isocline.

Метод изопах в неполяризованном свете

An isopachic method with unpolarized light using a Mach-Zehnder interferometer is proposed. In the case of unpolarized light, isopachics are observed not only due to a change in the thickness of the model but also due to induced birefringence. In contrast to the existing methods, the proposed method allows you to study sections of three-dimensional models or flat stressed samples with no thickness variation. A brief theoretical consideration based on the formalism of the coherence matrix is given, as well as the experimentally obtained isopachic field for a model made from high-modulus material. The method is convenient and simple in technical implementation.

Synchronous control of transmitted and reflected light in semicomducting chromiumchalcogenide spinels

A way for synchronous control of the intensity of transmitted and reflected light in magnetic semiconductors by an external magnetic field is proposed in the infrared spectral region. For illustration, we obtained the magnetoreflection and magnetotransmission spectra of unpolarized light in single crystals of Hg(Cd)Cr2Se4 spinel. Keywords: Magnetoreflection, magnetotransmission, spinel, infrared range, unpolarized light, single crystals.

Calibration, sensitivity analysis, and demonstration of a basic polarimeter for artificial satellite observations

The Department of Physics at the United States Air Force Academy has a DFM Engineering f/8.2, 16-inch telescope outfitted with a 9-position filter wheel populated with broadband photometric filters (Johnson-Cousins B, V, R, and a blue-blocking exoplanet filter) and a 100 lines per millimeter diffraction grating. As part of their senior capstone project, physics cadets developed a simple, four-channel linear Stokes polarimeter by populating the open slots in the filter wheel with linear polarization filters oriented at 0°, 45°, 90°, and 135° relative to the vertical axis of the imaging camera. Size and weight restrictions on the back of the telescope prohibited the use of more elaborate polarimeters. They also developed the process and procedures to characterize the effect of the telescope optical elements on the polarization of incident light. Using an unpolarized uniform flat light source, along with a polarized film rotated at 10° increments from 0° to 180°, the intensity of the light source was measured as it passed through the entire optical system including the previously mentioned linear polarized filters. The measured intensities were fitted to Malus Law using a least squares method. From this fit, a modified Mueller matrix was created that describes how the telescope’s optical elements, including the polarizing filters, alter the incident light measured by the telescope’s camera. To relate the measured intensities of light to the Stokes parameters of the light reflected from a satellite, a calibration matrix was computed using a pseudoinverse of the modified Mueller matrix. The sensitivity of the pseudoinverse process was analyzed by perturbing input data and measuring the root mean square (RMS) error between the perturbed and ideal matrices. This process for employing the pseudoinverse introduced minimal error into the system as the RMS error for the calibration matrix was within an acceptable error range. The calibration matrix was applied to observations of three different satellites, AMC-15, DirecTV-10, and DirecTV-14, resulting in their measured Stokes parameters, Degree of Linear Polarization, and Angle of Linear Polarization.

Особенности поглощения тонких пленок La-=SUB=-0.69-=/SUB=-Ba-=SUB=-0.31-=/SUB=-MnO-=SUB=-3-delta-=/SUB=-, полученных методом импульсного лазерного осаждения

The electrical, optical, and magneto-optical properties of La0.69Ba0.31MnO3 – δ thin films with a Curie temperature near room temperature are studied. It is shown that in the region of the phase transition there is a sharp change in the behavior of the temperature dependences of the electrical resistance and optical transparency of the films, which is associated with the insulator-metal transition. In a narrow temperature region near the transition, a change in the external magnetic field leads to the appearance of negative magnetoresistance and magnetotransmission of unpolarized light in the spectral range from 1 to 12 μm. It is shown that the effect of magnetic transmission (magnetoabsorption) in films is mainly due to the contribution of free charge carriers. The magnetic transmission spectra are sensitive to the magnetic and electronic inhomogeneities of the films.

Синхронное управление прошедшим и отраженными светом в полупроводниковых хромхалькогенидных шпинелях

A way for synchronous control of the intensity of transmitted and reflected light in magnetic semiconductors by an external magnetic field is proposed in the infrared spectral region. For illustration, we obtained the magnetoreflection and magnetotransmission spectra of unpolarized light in single crystals of Hg(Cd)Cr2Se4 spinel.

Features of absorption of thin films La-=SUB=-0.69-=/SUB=-Ba-=SUB=-0.31-=/SUB=-MnO-=SUB=-3-delta-=/SUB=- obtained using the method of pulsed laser deposition

The electrical, optical, and magneto-optical properties of La0.69Ba0.31MnO3-delta thin films with a Curie temperature near room temperature are studied. It is shown that in the region of the phase transition there is a sharp change in the behavior of the temperature dependences of the electrical resistance and optical transparency of the films, which is associated with the insulator-metal transition. In a narrow temperature region near the transition, a change in the external magnetic field leads to the appearance of negative magnetoresistance and magnetotransmission of unpolarized light in the spectral range from 1 to 12 μm. It is shown that the effect of magnetic transmission (magnetoabsorption) in films is mainly due to the contribution of free charge carriers. The magnetic transmission spectra are sensitive to the magnetic and electronic inhomogeneities of the films. Keywords: Thin films, manganites, magnetoabsorption, colossal magnetoresistance, IR spectroscopy, metal-insulator transition, magnetic inhomogeneities.

Multi-mode plasmonic resonance broadband LWIR metamaterial absorber based on lossy metal ring.

Broadband perfect infrared wave absorption of unpolarized light over a wide range of angles in an ultrathin film is critical for applications such as thermal emitters and imaging. Although many efforts have been made in infrared broadband absorption, it is still challenging to cover the perfect absorption of broadband in the long-wave infrared band. We propose a long-wave infrared broadband, polarization, and incident angle insensitivity metamaterial absorber based on the supercell with four rings of two sizes. Broadband absorption covering the long-wave infrared band is realized by combining four PSPRs and LSPRs absorption peaks excited by the supercell structure. The absorptivity of our absorber exceeds 90% in the wavelength range of 7.76∼14µm, and the average absorptivity reaches 93.8%. The absorber maintains more than 80% absorptivity as the incident angle of unpolarized light reaches 60°, which may have promising applications for thermal emitters, infrared imaging, thermal detection.

Gold nanodoughnut as an outstanding nanoheater for photothermal applications.

Photoinduced hyperthermia is a cancer therapy technique that induces death to cancerous cells via heat generated by plasmonic nanoparticles. While previous studies have shown that some nanoparticles can be effective at killing cancer cells under certain conditions, there is still a necessity (or the need) to improve its heating efficiency. In this work, we perform a detailed theoretical study comparing the thermoplasmonic response of the most effective nanoparticle geometries up to now with a doughnut-shaped nanoparticle. We numerically demonstrate that the latter exhibits a superior tunable photothermal response in practical illumination conditions (unpolarized light). Furthermore, we show that nanoparticle heating in fluidic environments, i.e., nanoparticles undergoing Brownian rotations, strongly depends on the particle orientation with respect to the illumination source. We conclude that nanodoughnuts are the best nanoheaters in our set of structures, with an average temperature increment 40% higher than the second best nanoheater (nanodisk). Furthermore, nanodoughnuts feature a weak dependence on orientation, being therefore ideal candidates for photothermal therapy applications. Finally, we present a designing guide, covering a wide range of toroid designs, which can help on its experimental implementation.

Aperiodic perforated graphene in optical nanocavity absorbers

Aperiodic perforated graphene layers were synthesized and used in fabrication of optical nanocavity absorbers. Chemical vapor deposition-grown graphene (Gr) layers were exposed to oxygen plasma etching to obtain the perforated graphene (pGr). The fabricated pGr/SiO2 (68 nm)/Ag (150 nm) nanocavity could present significant higher optical absorption, especially at around 530 nm wavelength region, as compared to a benchmark Gr/SiO2 (68 nm)/Ag (150 nm) sample. The effect of pore size of the pGr layer on the absorption property of the nanocavity has been studied by both experimental and numerical methods. The dependence of the absorption property of the nanocavity on the incident angles of unpolarized light and also the electrical/magnetical portion of transverse polarized light have been examined. The electrical interaction between the nanopores of the pGr and the incident light was found as the main reason for the absorption. The proposed graphene-based nanocavity resonator can further excite designing high efficient electromagnetic wave absorbers highly demanding two-dimensional coatings with effective optical absorption features.

Dynamic valley polarization in moiré quantum dots

We describe the effects of the crossing of the exciton levels in moire quantum dots in external magnetic field. We demonstrate that the unpolarized light can create significant dynamic valley polarization of interlayer excitons in the conditions where the Zeeman energy is much smaller than the thermal energy. The angular momentum is gained by the excitons from the nuclear spin fluctuations. In the $n$-type moire quantum dots for the typical experimental parameters, the unpolarized light can lead to the complete valley polarization of the resident electrons.

Prospects for the use of bacterial lysates in the complex therapy of chronic adenoiditis

Introduction. Adenotomy is a common surgical procedure in childhood. In children with recurrent infections of the respiratory tract, hypertrophy of the pharyngeal tonsil, a sign of lymphoproliferative syndrome of a secondary immunodeficiency state, is characterized by reduced adaptive abilities of mucosal immunity with impaired biocenosis in chronic inflammation. Pharyngeal tonsil surgery is considered stressful in frequently ill children and therefore requires preoperative preparation. In this context, it is relevant to study the nature of changes in the factors of mucosal immunity in terms of cell destruction in the nasal secretion in the complex treatment of children with hypertrophy of the pharyngeal tonsil and chronic adenoiditis, as prevention of complications in the postoperative period of adenotomy.Aim. To increase the effectiveness of the treatment of chronic adenoiditis in children with recurrent infections of the respiratory tract using the combined effect of low-frequency ultrasonic cavitation with monochromatic unpolarized light and bacterial lysates.Materials and methods. In order to test the hypothesis about the possibility of canceling adenotomy in 77 children aged 3-6 years with hypertrophy of the pharyngeal tonsil, accompanied by chronic inflammation. The effectiveness of the complex treatment was assessed by the functional and metabolic status of nonspecific resistance factors in the nasal lavage.Results and discussion. The combined effect of low-frequency ultrasonic cavitation with photochromotherapy and bacterial lysates leads to the normalization of pathophysiological changes on the surface of the mucous membrane, leading to a balance of the qualitative and quantitative composition of the functional-metabolic status of NG, which makes it possible to postpone adenotomy. The best clinical result is observed when bacterial lysates are used in complex therapy in combination with physiotherapy in children with chronic adenoiditis and, to a certain extent, substantiate the advisability of a combined effect as a non-invasive and effective method.Conclusions. Topical bacteriolysate in a complex treatment regimen for children with recurrent infections of the respiratory tract against a background of chronic inflammation eliminates bacterial antigens and enhances the intrinsic defenses of the mucous membrane of the pharyngeal tonsil.