Polarization Of Emission Research Articles

Spin polarization effect on linear polarization of photon emission following resonant electron capture of lithiumlike ions

Spin polarization effect on linear polarization of photon emission following resonant electron capture of lithiumlike ions

An X-Ray Shell Reveals the Supernova Explosion for Galactic Microquasar SS 433

How black holes are formed remains an open and fundamental question in astrophysics. Despite theoretical predictions, it lacks observations to understand whether the black hole formation experiences a supernova explosion. Here we report the discovery of an X-ray shell north of the Galactic microquasar SS 433 harboring a stellar-mass black hole spatially associated with radio continuum and polarization emissions and an H i cloud. Its spectrum can be reproduced by a 1 keV underionized plasma, from which the shell is inferred to have been created by a supernova explosion 20–30 kyr ago, and its properties constitute evidence for canonical supernova explosions to create some black holes. Our analysis precludes other possible origins including heated by jets or blown by disk winds. According to the lower mass limit of the compact object in SS 433, we roughly deduced that the progenitor should be more massive than 25 M ⊙. The existence of such a young remnant in SS 433 can also lead to new insights into the supercritical accretion in young microquasars and the γ-ray emission of this system. The fallback ejecta may provide accretion materials within tens of thousands of years, while the shock of the supernova remnant may play a crucial role in the cosmic-ray (re)acceleration.

Auroral 3D structure retrieval from the Juno/UVS data

Context. Jovian auroras, the most powerful in the Solar System, result from the interaction between the magnetosphere and atmosphere of Jupiter. While the horizontal morphology of these phenomena has been widely studied, their vertical structure, determined by the penetration depth of the magnetospheric electron into the auroral regions, remains relatively unexplored. Previous observations, including those from the Hubble Space Telescope (HST), have addressed this question to a limited extent. Aims. In this study we aim to map the vertical structure of Jovian auroral emissions. Methods. Using observations from Juno’s UltraViolet Spectrograph (UVS), we examined the vertical structure of the auroral emissions. Building on a recent study of auroral energy mapping based on UVS observations that mapped the average energy of precipitating electrons in the Jovian auroral regions, we find a relationship between this average energy and the volume emission rate (VER) of H2 for two types of electron energy distributions: monoenergetic and a kappa distribution with κ = 2.5. Results. Using brightness maps, we derived the 3D VER structure of Jovian auroras in both northern and southern regions, across multiple spacecraft perijoves (PJs). By considering the example of PJ11, we find that the average altitude of the VER peak in the polar emission region is approximately ~250 km for the monoenergetic distribution case and ~190 km for kappa distribution case. In the main emission region, we find that the average altitude of the VER peak is approximately ~260 km for the case of monoenergetic distribution and ~197 km for kappa distribution case. For the other PJs, we obtained results that are very similar to those of PJ11. Conclusions. Our findings are, on average, consistent with measurements from the Galileo probe and the HST observations. This study contributes to a better understanding of the complexity of Jovian auroras and highlights the importance of using Juno observations when probing their vertical structure. Considering the variability in the κ parameter in the auroral region, we also studied the impact of this variability on the vertical structure of the auroral emission. This sensitivity study reveals that the influence of the κ parameter on our results was very weak. However, the impact of the κ variability on the VER amplitude shows that there is an influence on the thermal structure and chemical composition of the atmosphere in the auroral regions.

Using polarization sensitive SMLM to infer the interaction strength of dye-plasmonic nanosphere systems

Single-molecule microscopy is an effective tool for the characterization of fluorophore–plasmonic structure interaction. However, sophisticated evaluation is required as specific information is hidden in the emission. Here, we theoretically and experimentally investigated the emission polarization of rotationally mobile fluorophores near plasmonic Au–Ag alloy nanospheres. We developed an elaborate calculation based on the Mie theory, which considers the rotational mobility of dyes near spherical plasmonic nanoparticles of any size. Furthermore, we have created a simplified model that describes the emission’s degree of polarization within 10% accuracy in the case of small nanoparticles, when dipole approximation is valid. Our results indicate the close relation of the polarization degree of the emission, which can reach up to be ∼0.8 in the resonant case, to fluorescence scattering. DNA-PAINT single-molecule localization microscopy experiments conducted using AF488 and Atto647N dyes revealed that the measured polarization degree distribution followed the tendency predicted by calculations.

Mapping and characterizing magnetic fields in the Rho Ophiuchus-A molecular cloud with SOFIA/HAWC+

Context. Together with gravity, turbulence, and stellar feedback, magnetic fields (B-fields) are thought to play a critical role in the evolution of molecular clouds and star formation processes. The polarization of thermal dust emission is a popular tracer of B-fields in star-forming regions. Aims. We aim to map the morphology and measure the strength of B-fields of the nearby molecular cloud, rho Ophiuchus-A (ρ Oph-A), to understand the role of B-fields in regulating star formation and in shaping the cloud. Methods. We analyzed the far-infrared (FIR) polarization of thermal dust emission observed by SOFIA/HAWC+ at 89 and 154 μm toward the densest part of ρ Oph-A, which is irradiated by the nearby B3/4 star, Oph-S1. These FIR polarimetric maps cover an area of ~4.5′ × 4.5′ (corresponding to 0″.18 × 0″.18 pc2) with an angular resolution of 7.8″ and 13.6″ respectively. Results. The ρ Oph-A cloud exhibits well-ordered B-fields with magnetic orientations that are mainly perpendicular to the ridge of the cloud toward the densest region. We obtained a map of B-field strengths in the range of 0.2–2.5 mG, using the Davis-Chandrasekhar-Fermi (DCF) method. The B-fields are strongest at the densest part of the cloud, which is associated with the starless core SM1, and then decrease toward the outskirts of the cloud. By calculating the map of the mass-to-flux ratio, Alfvén Mach number, and plasma β parameter in ρ Oph-A, we find that the cloud is predominantly magnetically sub-critical, sub-Alfvénic, which implies that the cloud is supported by strong B-fields that dominate over gravity, turbulence, and thermal gas energy. The measured B-field strengths at the two densest subsregions using other methods that account for the compressible mode are relatively lower than that measured with the DCF method. However, these results do not significantly change our conclusions on the roles of B-fields relative to gravity and turbulence on star formation. Our virial analysis suggests that the cloud is gravitationally unbound, which is consistent with the previous detection of numerous starless cores in the cloud. By comparing the magnetic pressure with the radiation pressure from the Oph-S1 star, we find that B-fields are sufficiently strong to support the cloud against radiative feedback and to regulate the shape of the cloud.

B-fields and Dust in Interstellar Filaments Using Dust Polarization (BALLAD-POL). II. Testing the Radiative Torque Paradigm in Musca and OMC-1

Polarization of starlight and thermal dust emission caused by aligned dust grains is a valuable tool to characterize magnetic fields (B-fields) and constrain dust properties. However, the grain alignment physics is not fully understood. To test the radiative torque (RAT) paradigm, including RAT alignment (RAT-A) and disruption (RAT-D), we use dust polarization observed by Planck and Stratosphere Observatory for Infrared Astronomy/High-resolution Airborne Wideband Camera Plus toward two filaments, Musca and OMC-1, with contrasting physical conditions. Musca, a quiescent filament, is ideal for testing RAT-A, while OMC-1, an active star-forming region OMC-1, is most suitable for testing RAT-D. We found that polarization fraction, P, decreases with increasing polarization angle dispersion function, S , and increasing column density, N(H2), consistent with RAT-A. However, P increases with increasing dust temperature, T d, but decreases when T d reaches a certain high value. We compute the polarization fraction for the ideal models with B-fields in the plane of sky based on the RAT paradigm, accounting for the depolarization effect by B-field tangling. We then compare the realistic polarization model with observations. For Musca with well-ordered B-fields, our numerical model successfully reproduces the decline of P toward the filament spine (aka polarization hole), having higher N(H2) and lower T d, indicating the loss of grain alignment efficiency due to RAT-A. For OMC-1, with stronger B-field variations and higher temperatures, our model can reproduce the observed P–T d and P−N(H2) relations only if the B-field tangling and RAT-D effect are incorporated. Our results provide more robust observational evidence for the RAT paradigm, particularly the recently discovered RAT-D.

Magnetic Field Geometry of the Gamma-Ray Binary PSR B1259–63 Revealed via X-Ray Polarization

Some X-ray binaries containing an energetic pulsar in orbit around a normal star accelerate particles to high energies in the shock cone formed where the pulsar and stellar winds collide. The magnetic field geometry in the acceleration region in such binaries is unknown. We performed the first measurement of the polarization of the X-ray synchrotron emission from a gamma-ray-emitting binary system. We observed PSR B1259–63 with the Imaging X-ray Polarimetry Explorer during an X-ray bright phase following the periastron passage in 2024 June. X-ray polarization is detected with a polarization degree of 8.3% ± 1.5% at a significance of 5.3σ. The X-ray polarization angle is aligned with the axis of the shock cone at the time of the observation. This indicates that the predominant component of the magnetic field in the acceleration region is oriented perpendicular to the shock-cone axis.

Spatiotemporally modulated full-polarized light emission for multiplexed optical encryption

Spatiotemporal control of full freedoms of polarized light emission is crucial in multiplexed optical computing, encryption and communication. Although recent advancements have been made in active emission or passive conversion of polarized light through solution-processed nanomaterials or metasurfaces, these design paths usually encounter limitations, such as small polarization degrees, low light utilization efficiency, limited polarization states, and lack of spatiotemporal control. Here, we addressed these challenges by integrating the spatiotemporal modulation of the LED device, the precise control and efficient polarization emission through nanomaterial assembly, and the programmable patterning/positioning using 3D printing. We achieved an extremely high degree of polarization for both linearly and circularly polarized emission from ultrathin inorganic nanowires and quantum nanorods thanks to the shear-force-induced alignment effect during the protruding of printing filaments. Real-time polarization modulation covering the entire Poincaré sphere can be conveniently obtained through the programming of the on-off state of each LED pixel. Further, the output polarization states can be encoded by an ordered chiral plasmonic film. Our device provides an excellent platform for multiplexing spatiotemporal polarization information, enabling visible light communication with an exceptionally elevated level of physical layer security and multifunctional encrypted displays that can encode both 2D and 3D information.

6-Methoxy-2-Naphthoate as a Standard Chromophore for Chiroptical Studies by Fluorescence-Detected Exciton-Coupled Circular Dichroism.

This study investigated the applicability of fluorescent chromophores for exciton-coupled circular dichroism (ECCD) exploiting fluorescence-detected circular dichroism (FDCD). FDCD had been previously reported useful in allowing the sensitive detection of ECCD in favorable conditions. However, fluorescence detection may prevent applications of the combined method especially when solutions are polarized in emission. Even without polarization of emission, FDCD deviates from circular dichroism (CD) in some cases when the fluorophore of interest interacts with nonfluorescent chromophore. Herein, it was confirmed that employing 6-methoxy-2-naphthoate always yielded interpretable exciton-coupled FDCD spectra even when coupling with nonfluorescent p-substituted benzoates. The 6-methoxy-2-naphthoate chromophore (6-MN) is prescribed in special cases when only a small amount of sample is available for determining the absolute stereochemistry by the CD exciton chirality method observed by FDCD.

Non-thermal outflows of the Milky Way traced by radio polarization and gamma-ray emission

Non-thermal outflows of the Milky Way traced by radio polarization and gamma-ray emission

Off-Normal Polarized Single-Photon Emission with Anisotropic Holography Metasurfaces.

Solid-state quantum emitters (QEs) with arbitrary direction emission and well-defined polarization are critical for scalable single-photon sources and quantum information processing. However, the design strategy for on-chip generation of off-normal photon emission with high-purity polarization characteristics has so far remained elusive. Here, we introduce the anisotropic holography metasurfaces for efficiently manipulating the emission direction and polarization of QE. The proposed method offers a flexible way to realize phase matching in surface plasmon scattering with spatially varying filling factors and provides an efficient route for designing advanced QE-coupled metasurfaces. By nonradiatively coupling nanodiamonds with metasurfaces, we experimentally demonstrate on-chip generation of well-collimated single-photon emission propagating along off-normal directions (i.e., 20° and 30°) featuring a divergence angle lower than 2.5°. The experimental average degree of linear polarization attains up to >0.98, thereby revealing markedly high polarization purity. This study facilitates applications of QEs in the deployment of integrated quantum networks.

Unveiling the spin evolution in van der Waals antiferromagnets via magneto-exciton effects

Among the fascinating phenomena observed in two-dimensional (2D) magnets, the magneto-exciton effect stands out as a pivotal link between optics and magnetism. Although the excitonic effect has been revealed and exhibits a considerable correlation with the spin structures in certain 2D magnets, the underlying mechanism of the magneto-exciton effect remains underexplored, especially under high magnetic fields. Here we perform a systematic investigation of the spin-exciton coupling in 2D antiferromagnetic NiPS3 under high magnetic fields. When an in-plane magnetic field is applied, the exceptional sharp excitonic emission at ~1.4756 eV exhibits a Zeeman-like splitting with g ≈ 2.0, experimentally identifying the exciton as an excitation of dominant triplet-singlet character. By examining the polarization of excitonic emission and simulating the spin evolution, we further verify the correlation between excitonic emission and Néel vector in NiPS3. Our work elucidates the mechanism behind the spin-exciton coupling in NiPS3 and establishes a strategy for optically probing the spin evolutions in 2D magnets.

Sb2S3/AlGaAs-based reconfigurable metasurface for dynamic polarization and directionality control of quantum emitter emission.

In this article, we report, to the best of our knowledge, for the first time, phase change material (PCM)-based reconfigurable metasurfaces for tailoring different degrees of freedom (DoF) of the quantum emitter (QE) emission, namely polarization and directionality, two key controlling factors in applications such as quantum computing, communication, and chiral optics. We have used a hybrid plasmon-QE coupled bullseye grating system utilizing the unexplored concept of composite nano-antennas in quantum photonics as the basic building block of the structures. Carefully engineered azimuthal width profile of the Sb2S3/AlGaAs composite ridge and selectively controlled transition of PCM (Sb2S3) states provide dynamic control over the amplitude and phase of the scattered radiation. Based on this methodology, we have designed five different metasurfaces for on-demand switching of target DoFs of QE emission, ensuring high collection efficiency due to the near-field coupling scheme. The first two metasurfaces switch the majority of the outgoing radiation from radially polarized to circularly polarized, whereas the next two switch the direction of circularly polarized outgoing radiation by a maximum of 9.23° while maintaining the spin state (or polarization chirality) in the simulation environment. The third metasurface category is capable of on-demand generation and separation of opposite spin states of outgoing radiation by 11.48° utilizing the selectively controlled phase transition of Sb2S3. Such reconfigurable multi-dimensional manipulation of QE radiation has not been investigated previously. This work proves the vast potential of active metasurfaces to modify the DoFs of QE emission, paving the way for high-dimensional quantum sources for high-speed quantum communication, higher dimensional quantum processing, and switchable chiral optics.

Observation of near-scission “polar” and “equatorial” proton emission in heavy-ion induced fission

Proton and α-particle energy spectra were measured in coincidence with fission fragments at different relative angles in 16O (96 MeV) + 232Th reaction. The multiplicity spectra were analyzed within the framework of a Moving Source Disentangling Analysis (MSDA) to determine contributions from different emission stages. The MSDA conclusively shows “Near Scission Emission (NSE)” as an essential component in the multiplicity spectra. In contrast to NSE α particles which emit mainly perpendicular (“equatorial emission”), the NSE protons are observed to be emitted perpendicular as well as parallel (“polar emission”) to the fission axis with similar intensities (~20% for each). Thus, around 40% of total pre-scission protons are emitted near the scission stage, whereas the same fraction for α particles is only around 10%. The inevitable presence of “polar” and “equatorial” NSE protons in a heavy-ion induced fission has been observed for the first time. Present results open up a new avenue to study the heavy-ion induced fission dynamics.

3D hybrid fluid-particle jet simulations and the importance of synchrotron radiative losses

Relativistic jets in active galactic nuclei are known for their exceptional energy output, and imaging the synthetic synchrotron emission of numerical jet simulations is essential for a comparison with observed jet polarization emission. Through the use of 3D hybrid fluid-particle jet simulations (with the PLUTO code), we overcome some of the commonly made assumptions in relativistic magnetohydrodynamic (RMHD) simulations by using non-thermal particle attributes to account for the resulting synchrotron radiation. Polarized radiative transfer and ray-tracing (via the RADMC-3D code) highlight the differences in total intensity maps when (i) the jet is simulated purely with the RMHD approach, (ii) a jet tracer is considered in the RMHD approach, and (iii) a hybrid fluid-particle approach is used. The resulting emission maps were compared to the example of the radio galaxy Centaurus A. We applied the Lagrangian particle module implemented in the latest version of the PLUTO code. This new module contains a state-of-the-art algorithm for modeling diffusive shock acceleration and for accounting for radiative losses in RMHD jet simulations. The module implements the physical postulates missing in RMHD jet simulations by accounting for a cooled ambient medium and strengthening the central jet emission. We find a distinction between the innermost structure of the jet and the back-flowing material by mimicking the radio emission of the Seyfert II radio galaxy Centaurus\,A when considering an edge-brightened jet with an underlying purely toroidal magnetic field. We demonstrate the necessity of synchrotron cooling as well as the improvements gained when directly accounting for non-thermal synchrotron radiation via non-thermal particles.

Phonon Directionality Impacts Electron-Phonon Coupling and Polarization of the Band-Edge Emission in Two-Dimensional Metal Halide Perovskites.

Two-dimensional metal halide perovskites are highly versatile for light-driven applications due to their exceptional variety in material composition, which can be exploited for the tunability of mechanical and optoelectronic properties. The band-edge emission is defined by the structure and composition of both organic and inorganic layers, and electron-phonon coupling plays a crucial role in the recombination dynamics. However, the nature of the electron-phonon coupling and what kind of phonons are involved are still under debate. Here we investigate the emission, reflectance, and phonon response from single two-dimensional lead iodide microcrystals with angle-resolved polarized spectroscopy. We find an intricate dependence of the emission polarization with the vibrational directionality in the materials, which reveals that several bands of low-frequency phonons with nonorthogonal directionality contribute to the band-edge emission. Such complex electron-phonon coupling requires adequate models to predict the thermal broadening of the emission and provides opportunities to design polarization properties.

Interplay of Phonon Directionality and Emission Polarization in Two-Dimensional Layered Metal Halide Perovskites.

ConspectusLayered metal halide perovskites represent a natural quantum well system for charge carriers that provides rich physics, and the organic encapsulation of the inorganic metal halide layers not only increases their stability in devices but also provides an immense freedom to design their functionality. Intriguingly, these organic moieties strongly impact the optical, electrical, and mechanical properties, not only through their dielectric, elastic, and chemical properties but also because of induced mechanical distortions in the inorganic lattice. This tunability makes two-dimensional layered perovskites (2DLPs) highly attractive as light emitters. Common consensus is that exciton-phonon coupling plays an important role in radiative recombination. For bulk and some two-dimensional (2D) materials, the band edge emission broadening can be described by the classic models for polar inorganic semiconductors, while for the temperature dependence of the self-trapped exciton emission, an analysis developed for color centers has been successfully applied. For many 2DLPs these approaches do not work because of the complexity of their vibrational spectra. However, their emission is still strongly determined by phonons, and therefore, an adequate understanding of the electron-phonon coupling needs to be developed.With polarized and angle-resolved Raman spectroscopy studies on single 2DLP flakes based on different ammonium molecules as organic cations, in 2020 we revealed very rich phonon spectra in the low-frequency regime. Although the phonon bands at low frequency can generally be attributed to the vibrations of the inorganic lattice, we found very different responses by only changing the type of organic cations. In addition, the intensity of the different phonon modes depended strongly on the angle of the linearly polarized excitation beam with respect to the in-plane axes of the octahedron lattice. In 2022, we mapped this angular dependence of the phonon modes, which allowed identification of the directionality of the different lattice vibrations. By correlating the phonon spectra with the temperature-dependent emission for a set of 2DLPs that featured very different self-trapped exciton (STE) emission, we demonstrated that the exciton relaxation cannot be related to coupling with a single (longitudinal-optical) phonon band and that several phonon bands should be involved in the emission process. To gain insights into the exciton-phonon coupling effects on the band edge emission, we performed both angle-resolved polarized emission and Raman spectroscopy on single 2D lead iodide perovskite microcrystals. These experiments revealed the impact of the organic cations on the linear polarization of the emission and corroborated that multiple phonon bands should be involved in the radiative recombination process. Analysis of the temperature-dependent line width broadening of the band edge emission showed that for many systems, the behavior cannot be described by assuming the involvement of only one phonon mode in the electron-phonon coupling process. Our studies revealed a wealth of highly directional low-frequency phonons in 2DLPs from which several bands are involved in the emission process, which leads to diverse optical and vibrational properties depending on the type of organic cation in the material.

Thermal emission and pyroelectric current in manganese chalcogenides

Manganese chalcogenides, which are promising for the manufacture of thermoelements, are being studied. The current is measured in the temperature range of 80–500 K, in the absence of external voltage, which can be caused by a temperature gradient (thermopower), a change in electrical polarization (pyroelectric current), piezoelectric current (when the sample is deformed, a potential difference arises) or thermionic emission (thermal emission current) . Temperatures of current anomalies and their relationship with thermionic current and polarization current are found. A change in electrical polarization withtemperature will cause a pyroelectric current. Compensation for excess electrical charge will result in local electrical polarization. Partial decompensation will cause the formation of an electric field in the sample. The critical temperatures for the disappearance of electric polarization were determined for different concentrations. In the region of concentration of thulium ions flowing through the lattice, the activation nature of the thermionic current was established and the activation energy was found. The pyroelectric current has a smaller value compared to the thermionic current. The current mechanism is determined by the emission of electrons from deep traps and the temperatures of the maximum thermionic current correlate with the temperatures at which IR absorption disappears. The electric current density and its value depend on the type of substituted rare earth element are calculated.

Characterization of quantum dot-like emitters in programmable arrays of nanowrinkles of 1L-WSe2

When combined with nanostructured substrates, two-dimensional semiconductors can be engineered with strain to tailor light–matter interactions on the nanoscale. Recently, room-temperature nanoscale exciton localization with controllable wrinkling in 1L-WSe2 was achieved using arrays of gold nanocones. Here, the characterization of quantum dot-like states and single-photon emitters in the 1L-WSe2/nanocone system is reported. The nanocones induce a wide range of strains, and as a result, a diverse ensemble of narrowband, potential single-photon emitters is observed. The distribution of emitter energies reveals that most reside in two spectrally isolated bands, leaving a less populated intermediate band that is spectrally isolated from the ensembles. The spectral isolation is advantageous for high-purity quantum light emitters, and anti-bunched emission from one of these states is confirmed up to 25 K. Although the spatial distribution of strain is expected to influence the orientation of the transition dipoles of the emitters, multimodal emission polarization anisotropy and atomic force microscopy reveal that the macroscopic orientation of the wrinkles is not a good predictor of dipole orientation. Finally, the emission is found to change with thermal cycling from 4 to 290 K and back to 4 K, highlighting the need to control factors such as temperature-induced strain to enhance the robustness of this quantum emitter platform. The initial characterization here shows that controlled nanowrinkles of 1L-WSe2 generate quantum light in addition to uncovering potential challenges that need to be addressed for their adoption into quantum photonic technologies.

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.