Polarization Of Emission Research Articles

Probing 3D Magnetic Fields Using Thermal Dust Polarization and Grain Alignment Theory

Magnetic fields are ubiquitous in the Universe and are thought to play an important role in various astrophysical processes. Polarization of thermal emission from dust grains aligned with the magnetic field is widely used to measure the 2D magnetic field projected onto the plane of the sky, but its component along the line of sight is not yet constrained. Here, we introduce a new method to infer 3D magnetic fields using thermal dust polarization and grain alignment physics. We first develop a physical model of thermal dust polarization using the modern grain alignment theory based on the magnetically enhanced radiative torque alignment theory. We then test this model with synthetic observations of magnetohydrodynamic simulations of a filamentary cloud with our updated POLARIS code. Combining the tested physical polarization model with synthetic polarization, we show that the B-field inclination angles can be accurately constrained by the polarization degree from synthetic observations. Compared to the true 3D magnetic fields, our method based on grain alignment physics is more accurate than the previous methods that assume uniform grain alignment. This new technique paves the way for tracing 3D B-fields using thermal dust polarization and grain alignment theory and for constraining dust properties and grain alignment physics.

Simultaneously Enhanced Emission and Valley Polarization of Dark Excitons of Monolayer WSe2 Using the Dual Effect of Strain and Magnetic Proximity

Simultaneously Enhanced Emission and Valley Polarization of Dark Excitons of Monolayer WSe₂ Using the Dual Effect of Strain and Magnetic Proximity

Effect of the configuration mixing on the polarization and angular distribution of x-ray line emissions following electron-impact excitation of Ne-like ions.

We present a systematic theoretical study on the angular distribution and linear polarization of x-ray line emissions of neon-like ions following the electron-impact excitation from the ground state to the excited levels [(2p5)1/23d3/2]J=1, [(2p5)3/23d5/2]J=1, [(2p5)3/23d3/2]J=1, and [(2p5)1/23s]J=1. The cross sections are calculated by using the flexible atomic code under configuration-interaction plus many-body perturbation theory method. The angular distribution and linear polarization are obtained based on density matrix theory. Emphasis has been placed on the effect of the configuration mixing on the angular distribution and polarization. It has been proved that the strong mixing of configuration [(2p5)3/23d3/2]J=1 with configuration [(2p5)1/23s]J=1 can result in the abrupt change of Z-dependence of angular distribution and polarization. It indicates that angular distribution and polarization can be expected to serve as a tool for investigation of configuration mixing effect.

Lyman Continuum Emission from Active Galactic Nuclei at 2.3 ≲ z ≲ 3.7 in the UVCANDELS Fields

We present the results of our search for Lyman continuum (LyC)-emitting (weak) active galactic nuclei (AGN) at redshifts 2.3 ≲ z ≲ 4.9 from Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) F275W observations in the Ultraviolet Imaging of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (UVCANDELS) fields. We also include LyC emission from AGN using HST WFC3 F225W, F275W, and F336W imaging found in Early Release Science (ERS) and Hubble Deep UV Legacy Survey data. We performed exhaustive queries of the Vizier database to locate AGN with high-quality spectroscopic redshifts. In total, we found 51 AGN that met our criteria within the UVCANDELS and ERS footprints. Out of these 51, we find 12 AGN that had ≥4σ detected LyC flux in the WFC3/UVIS images. Using a wide variety of space-based plus ground-based data, ranging from X-ray to radio wavelengths, we fit the multiwavelength photometric data of each AGN to a CIGALE spectral energy distribution (SED) using AGN models and correlate various SED parameters to the LyC flux. Kolmogorov–Smirnov tests of the SED parameter distributions for the LyC-detected and nondetected AGN showed they are likely not distinct samples. However, we find that the X-ray luminosity, star formation onset age, and disk luminosity show strong correlations relative to their emitted LyC flux. We also find strong correlations of the LyC flux to several dust parameters, i.e., polar and toroidal dust emission and 6 μm luminosity, and anticorrelations with metallicity and A FUV. We simulate the LyC escape fraction (f esc) using the CIGALE and intergalactic medium transmission models for the LyC-detected AGN and find an average f esc ≃ 18%, weighted by uncertainties. We stack the LyC fluxes of subsamples of AGN according to the wavelength continuum region in which they are detected and find no significant distinctions in their LyC emission, although our submillimeter-detected F336W sample (3.15 < z < 3.71) shows the brightest stacked LyC flux. These findings indicate that LyC production and escape in AGN are more complicated than the simple assumption of thermal emission and a 100% escape fraction. Further testing of AGN models with larger samples than presented here is needed.

Investigation into the Effects of Cross-Sectional Shape and Size on the Light-Extraction Efficiency of GaN-Based Blue Nanorod Light-Emitting Diode Structures

We investigated the effect of cross-sectional shape and size on the light-extraction efficiency (LEE) of GaN-based blue nanorod light-emitting diode (LED) structures using numerical simulations based on finite-difference time-domain methods. For accurate determination, the LEE and far-field pattern (FFP) were evaluated by averaging them over emission spectra, polarization, and source positions inside the nanorod. The LEE decreased as rod size increased, owing to the nanorods’ increased ratio of cross-sectional area to sidewall area. We compared circular, square, triangular, and hexagonal cross-sectional shapes in this study. To date, nanorod LEDs with circular cross sections have been mainly demonstrated experimentally. However, circular shapes were found to show the lowest LEE, which is attributed to the coupling with whispering-gallery modes. For the total emission of the nanorod, the triangular cross section exhibited the highest LEE. When the angular dependence of the LEE was calculated using the FFP simulation results, the triangular and hexagonal shapes showed relatively high LEEs for direction emission. The simulation results presented in this study are expected to be useful in designing high-efficiency nanorod LED structures with optimum nanorod shape and dimensions.

On the Magnetic Field Properties of Protostellar Envelopes in Orion

We present 870 μm polarimetric observations toward 61 protostars in the Orion molecular clouds with ∼400 au (1″) resolution using the Atacama Large Millimeter/submillimeter Array. We successfully detect dust polarization and outflow emission in 56 protostars; in 16 of them the polarization is likely produced by self-scattering. Self-scattering signatures are seen in several Class 0 sources, suggesting that grain growth appears to be significant in disks at earlier protostellar phases. For the rest of the protostars, the dust polarization traces the magnetic field, whose morphology can be approximately classified into three categories: standard-hourglass, rotated-hourglass (with its axis perpendicular to outflow), and spiral-like morphology. A total of 40.0% (±3.0%) of the protostars exhibit a mean magnetic field direction approximately perpendicular to the outflow on several × 102–103 au scales. However, in the remaining sample, this relative orientation appears to be random, probably due to the complex set of morphologies observed. Furthermore, we classify the protostars into three types based on the C17O (3–2) velocity envelope’s gradient: perpendicular to outflow, nonperpendicular to outflow, and unresolved gradient (≲1.0 km s−1 arcsec−1). In protostars with a velocity gradient perpendicular to outflow, the magnetic field lines are preferentially perpendicular to outflow, with most of them exhibiting a rotated hourglass morphology, suggesting that the magnetic field has been overwhelmed by gravity and angular momentum. Spiral-like magnetic fields are associated with envelopes having large velocity gradients, indicating that the rotation motions are strong enough to twist the field lines. All of the protostars with a standard-hourglass field morphology show no significant velocity gradient due to the strong magnetic braking.

Deep ultraviolet AlGaN-multiple quantum wells with photoluminescence enhanced by topological corner state

The AlGaN-based deep ultraviolet light-emitting diode (DUV LED) has advantages of environmentally friendly materials, tunable emission wavelength, and easy miniaturization. However, an increase in Al composition leads to a decline in the lattice quality, thereby reducing the internal quantum efficiency (IQE). In addition, the light extraction efficiency (LEE) is limited due to the strong transverse magnetization polarization emission from the multiple quantum wells. Here, we designed the topological corner structure in AlGaN-MQWs, and the high electric field intensity in a tiny space at the corner results in an extremely high local density of optical states (LDOS), which could shorten the luminescence decay time of the emitter and increase the radiative rate by 26 times. Meanwhile, because the excited topological corner state resonance mode is a transverse-electric mode, enhancing only the transverse-electric luminescence without any gain for transverse-magnetic luminescence, thereby significantly improving the light extraction efficiency. Finally, according to theoretical calculations, the IQE could reach 68.75% at room temperature.

Tunable and responsive photonic bio‐inspired materials and their applications

AbstractBio‐enabled and bio‐mimetic nanomaterials represent functional materials, which use bio‐derived materials and synthetic components to bring the better of two, natural and synthetic, worlds. Prospective broad applications are flexibility and mechanical strength of lightweight structures, adaptive photonic functions and chiroptical activity, ambient processing and sustainability, and potential scalability along with broad sensing/communication abilities. Here, we summarize recent results on relevant functional photonic materials with responsive behavior under mechanical stresses, magnetic field, and changing chemical environment. We focus on recent achievements and trends in tuning optical materials' properties such as light scattering, absorption and reflection, light emission, structural colors, optical birefringence, linear and circular polarization for prospective applications in biosensing, optical communication, optical encoding, fast actuation, biomedical fields, and tunable optical appearance.

KAT8 functions in redox homeostasis and mitochondrial dynamics during mouse oocyte meiosis progression.

As a histone acetyltransferase, lysine acetyltransferase 8 (KAT8) participates in diverse biological processes. However, the effect of KAT8 on oocyte maturation in mice remains unclear. In this study, we found that mouse oocytes overexpressing Kat8-OE induced maturation failure manifested reduced rates of GVBD and first polar body emission. In addition, immunostaining results revealed that Kat8 overexpressing oocytes showed inappropriate mitochondrial distribution patterns, overproduction of reactive oxygen species (ROS), accumulation of phosphorylated γH2AX, hyperacetylation of α-tubulin, and severely disrupted spindle/chromosome organization. Moreover, we revealed that Kat8 overexpression induced a decline in SOD1 proteins and KAT8's interaction with SOD1 in mouse ovaries via immunoprecipitation. Western blotting data confirmed that Kat8-OE induced downregulation of SOD1 expression, which is a key factor for the decline of oocyte quality in advanced maternal age. Also, the injection of Myc-Sod1 cRNA could partially rescue maternal age-induced meiotic defects in oocytes. In conclusion, our data demonstrated that high level of KAT8 inhibited SOD1 activity, which in turn induced defects of mitochondrial dynamics, imbalance of redox homeostasis, and spindle/chromosome disorganization during mouse oocyte maturation.

An Electrically Tunable Dual‐Mode Laser Based on Self‐Assembled Soft Photonic Liquid Crystals

AbstractSoft photonic liquid crystals with electrically responsive properties are among the most promising intelligent materials for optoelectronic applications. This work demonstrates an ultra‐fast electrically tunable dual‐mode laser by introducing dye‐doped chiral liquid crystals. Due to the strong chirality of the chiral liquid crystal, two self‐assembled structures form depending on the temperatures. One is the chiral nematic phase (N*) with a 1D helical structure; the other is the blue phases (BPs) with 3D cubic structures. By tuning the strength of an electric field, the dye‐doped chiral liquid crystals are operated in two different modes: a band‐edge laser and a random laser. In the band‐edge mode, due to the electrostriction effect of the BPs, the electric‐tuning range of the laser emission is from 537 to 645 nm, and the switching times are less than 20 ms. When the electric field goes beyond a threshold value to force the occurrence of the BPs‐chiral‐nematic transition, the band‐edge laser with elliptical polarization emission is switched to a random laser with an immediate unpolarization emission (0.9 ms). Furthermore, the reversibility of the effects mentioned above points out the potential applications of self‐assembled soft photonic materials, spanning from solid‐state lighting to bio‐imaging.

Image scanning microscopy: a vectorial physical optics analysis.

Image scanning microscopy (ISM) achieves resolution beyond the diffraction limit by a factor of 2. However, prior ISM research predominantly employs scalar diffraction theory, neglecting critical physical effects such as polarization, aberrations, and Stokes shift. This paper presents a comprehensive vectorial ISM point spread function (PSF) model that accounts for these phenomena. By considering the effect of polarization in emission and excitation paths, as well as aberrations and Stokes shift, our model provides a more accurate representation of ISM. We analyze the differences between scalar and vectorial theories in ISM and investigate the impact of pinhole size and aberration strength on resolution. At a numerical aperture of 1.2, the full width half maximum (FWHM) discrepancy between scalar and vectorial ISM PSFs can reach 45 nm, representing a 30% deviation from the vectorial model. Additionally, we explore multiphoton excitation in ISM and observe increased FWHM for 2-photon and 3-photon excitation compared to 1-photon excitation. The FWHM of the 2-photon excitation ISM PSF increases by 20% and the FWHM of the 3-photon excitation ISM PSF increases by 28% compared to the 1-photon excitation ISM. In addition, we found that the optimal sweep factor for 2-photon ISM is 1.22, and the optimal sweep factor of 3-photon ISM is 1.12 instead of the 2 predicted by the one-photon scalar ISM theory. Our work improves the understanding of ISM and contributes to its advancement as a high-resolution imaging technique.

Crystalline architectures of C84 with tunable morphology and linearly polarized red emission.

Fullerene-based micro/nano-architectures (FMNAs) with remarkable photoluminescence (PL) emissions have attracted considerable interest as potential building blocks for optical and biolabeling applications, by virtue of their low toxicity and environmentally friendly nature. Nevertheless, the PL polarization properties of FMNAs have rarely been explored. Herein, we demonstrate the preparation of highly crystalline architectures of C84, which exhibit polymorphism depending on the preparation conditions but possess similar hexagonal close-packed (hcp) structures. The PL data demonstrate that the as-prepared carambola-like hexagonal microprisms (c-HPs) show enhanced red emission compared to regular hexagonal microprisms (r-HPs). More importantly, the linear polarization of the PL emission is verified and estimated through single-prism spectroscopy, which changes from 0.42 (r-HP) to 0.58 (c-HP), comparable to those of traditional rod-like semiconductors. Thus, we demonstrate a significant correlation between the morphology and emission characteristics of C84-based microprisms, highlighting the possibility of controlling the photophysical properties of FMNAs by finely tailoring their external morphologies. This study expands the range of carbon materials with linearly polarized emissions and offers potential for use in polarization-based micro-scale sensors or detectors.

Photon energy dependence of photoneutron production from heavy targets

The double differential cross-sections (DDXs) of photoneutron production via the photonuclear reaction on tantalum, tungsten, and bismuth for 13 and 17 MeV linearly polarized photon beams were measured using the time-of-flight method at the NewSUBARU-BL01 facility. Polarized photons were obtained by the Laser Compton backscattering (LCS) technique. Two distinct components were observed on the spectra: the lowenergy component up to 4 MeV and the high-energy above 4 MeV. The angular distribution of the low-energy component was isotropic, whereas the high-energy was distributed anisotropically and influenced by the angle between direction of photon polarization and neutron emission, especially for 17 MeV photon energy. These phenomena were similar to those of 197Au target observed in the previous studies. The low-energy neutron distributions at 13 and 17 MeV photon energies were almost identical for all three targets. The DDX energy integration was calculated and compared among the three targets for two-photon energies. Given the horizontal polarization (plane parallel to the x-axis) of the incident photons, the emission angles of 90° on the x-axis and y-axis recorded the maximum and minimum photoneutron yield, respectively. The differences between these two positions were minor for 181Ta and natW at 13 MeV photon energy and noticeable for other cases. An underestimation of the TENDL nuclear data library was observed on the photoneutron DDXs compared to the experimental results for 181Ta and 209Bi.

Tunable emission of an external-cavity Yb:KGW monolithic solid-state laser

Tunable microchip/monolithic lasers are expected to show promising applications. In this work external cavity techniques are applied to a Yb:KGW monolithic laser achieving 35 nm tuning by balancing Nm and Np emission polarizations.

Circularly polarised luminescence from intramolecular excimer emission of bis-1,8-naphthalimide derivatives.

Chiral excimers exhibit unique photophysical behaviour. However, further molecular design is required along with systematic studies on the effect of spacer groups and solvent polarity. In this study, we prepared four circularly polarised luminescence (CPL)-active molecules that exhibit intramolecular excimer emission. Bis-1,8-naphthalimide (bNI) derivatives D-LybNI, L-LybNI, D-LyMebNI, and L-LyMebNI were prepared with chiral backbones and alkyl linkages between the NI rings with chain lengths of five carbon atoms, suitable for excimer fluorescence. The fluorescence properties were investigated experimentally and theoretically using density functional theory. The molecules exhibited intramolecular excimer fluorescence in polar organic solvents. Mirror-image circular dichroism and CPL spectra were obtained for the D and L forms. D- and L-LyMebNI exhibited relatively large luminescence dissymmetry factors (|glum|) in acetonitrile of 1.9 × 10-3 and 1.6 × 10-3, respectively. Thus, this study demonstrates chiral bNI derivatives with simple synthesis procedures that emit intramolecular excimer fluorescence and have effective CPL properties. These molecules are promising for developing organic molecular systems with bright, highly polarised emission.

Polarization of the third harmonic emission from the filamentation of femtosecond cylindrical vector beams.

We experimentally generate a third harmonic (TH) vector optical field in deep ultraviolet wavelength range using femtosecond vector laser beams. The generated TH beams are characterized by analyzing the Stokes parameters with different input laser energies. The results show that the TH predominantly preserves the vector polarization distribution of the fundamental frequency beam. Moreover, the intensity profile of the TH exhibits a multiple-ring structure. A hybrid polarization pattern is observed in the TH, where the ellipticity is influenced by the input laser energy. Our work provides an effective and straightforward method for producing TH vector optical fields, which may facilitate potential applications such as micro/nanofabrication and super-resolution microscopy.

Optical Nonlinearity Enabled Super-Resolved Multiplexing Microscopy.

Optical multiplexing for nanoscale object recognition is of great significance within the intricate domains of biology, medicine, anti-counterfeiting, and microscopic imaging. Traditionally, the multiplexing dimensions of nanoscopy are limited to emission intensity, color, lifetime, and polarization. Here, a novel dimension, optical nonlinearity, is proposed for super-resolved multiplexing microscopy. This optical nonlinearity is attributable to the energy transitions between multiple energy levels of the doped lanthanide ions in upconversion nanoparticles (UCNPs), resulting in unique optical fingerprints for UCNPs with different compositions. A vortex beam is applied to transport the optical nonlinearity onto the imaging point-spread function (PSF), creating a robust super-resolved multiplexing imaging strategy for differentiating UCNPs with distinctive optical nonlinearities. The composition information of the nanoparticles can be retrieved with variations of the corresponding PSF in the obtained image. Four channels multiplexing super-resolved imaging with a single scanning, applying emission color and nonlinearity of two orthogonal imaging dimensions with a spatial resolution higher than 150nm (1/6.5λ), are demonstrated. This work provides a new and orthogonal dimension - optical nonlinearity - to existing multiplexing dimensions, which shows great potential in bioimaging, anti-counterfeiting, microarray assays, deep tissue multiplexing detection, and high-density data storage.

X-ray polarization properties of thermal-radiative disc winds in binary systems

ABSTRACT New X-ray polarization results are challenging our understanding of the accretion flow geometry in black hole binary systems. Even spectra dominated by a standard disc can give unexpected results, such as the high-inclination black hole binary 4U 1630−472, where the observed X-ray polarization is much higher than predicted. This system also shows a strong, highly ionized wind, consistent with thermal-radiative driving from the outer disc, leading to speculation that scattering in the wind is responsible for the unexpectedly high polarization degree from a standard optically thick disc. Here, we show that this is not the case. The optically thin(ish) wind polarizes the scattered light in a direction orthogonal to that predicted from a standard optically thick disc, reducing about 2 per cent rather than enhancing the predicted polarization of the total emission. This value is consistent with the polarization difference between the disc-dominated soft state, where absorption lines by the wind are clearly seen, and the steep power-law state, where no absorption lines are seen. If this difference is genuinely due to the presence or absence of wind, the total polarization direction must be orthogonal to the disc plane rather than parallel as expected from optically thick material.

Circumnuclear Multiphase Gas in the Circinus Galaxy. V. The Origin of the X-Ray Polarization in the Circinus Galaxy

The Imaging X-ray Polarimetry Explorer (IXPE) detected X-ray polarization in the nearest Seyfert 2 galaxy, the Circinus galaxy, for the first time. To reproduce the IXPE results, we computed the degree of polarization based on two types of radiative hydrodynamic simulations: a parsec-scale three-dimensional model and a sub-parsec-scale axisymmetric model with a higher spatial resolution. In a series of papers, we confirmed that these models naturally explain the multiwavelength observations of the Circinus galaxy from radio to X-rays. We used a Monte Carlo Simulation for Astrophysics and Cosmology code to compute the linear polarization of continuum emission. We found that the degree of polarization based on the parsec-scale radiation-driven fountain model was smaller than that observed with the IXPE. The degree of polarization based on the sub-parsec-scale model depends on the hydrogen number density of the disk (d), and the degree of polarization obtained from our simulation is consistent with that observed with the IXPE in the case of . We investigate where the photons are Compton scattered and imply that the origin of the X-ray polarization in the Circinus galaxy is the outflow inside 0.01 pc. In this case, the degree of polarization may change over a timescale of approximately 10 yr.

Effects of a N-Maleimide-derivatized Phosphatidylethanolamine on the Architecture and Properties of Lipid Bilayers

N-maleimide-derivatized phospholipids are often used to facilitate protein anchoring to membranes. In autophagy studies, this is applied to the covalent binding of Atg8, an autophagy protein, to a phosphatidylethanolamine (PE) in the nascent autophagosome. However, the question remains on how closely the N-maleimide PE derivative (PE-mal) mimicks the native PE in the bilayer. In the present paper, spectroscopic and calorimetric techniques have been applied to vesicles containing either PE or PE-mal (together with other phospholipids) to compare the properties of the native and derivatized forms of PE. According to differential scanning calorimetry, and to infrared spectroscopy, the presence of PE-mal did not perturb the fatty acyl chains in the bilayer. Fluorescence spectroscopy and microscopy showed that PE-mal did not alter the bilayer permeability either. However, fluorescence emission polarization of the Laurdan and DPH probes indicated an increased order, or decreased fluidity, in the bilayers containing PE-mal. In addition, the infrared spectral data from the phospholipid phosphate region revealed a PE-mal-induced conformational change in the polar heads, accompanied by increased hydration. Globally considered, the results suggest that PE-mal would be a reasonable substitute for PE in model membranes containing reconstituted proteins.