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Results for “Optical Properties Polarization”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Polarization Imaging Apparatus

A polarization imaging apparatus has shown promise as a prototype of instruments for medical imaging with contrast greater than that achievable by use of non-polarized light. The underlying principles of design and operation are derived from observations that light interacts with tissue ultrastructures that affect reflectance, scattering, absorption, and polarization of light. The apparatus utilizes high-speed electro-optical components for generating light properties and acquiring polarization images through aligned polarizers. These components include phase retarders made of OptoCeramic (registered TradeMark) material - a ceramic that has a high electro-optical coefficient. The apparatus includes a computer running a program that implements a novel algorithm for controlling the phase retarders, capturing image data, and computing the Stokes polarization images. Potential applications include imaging of superficial cancers and other skin lesions, early detection of diseased cells, and microscopic analysis of tissues. The high imaging speed of this apparatus could be beneficial for observing live cells or tissues, and could enable rapid identification of moving targets in astronomy and national defense. The apparatus could also be used as an analysis tool in material research and industrial processing.

Zou, Yingyin K.↗
NASA NTRS1965

Optical reflection properties of natural surfaces.

Optical reflection characteristics of various natural sands and soils measured at wavelengths of 4920, 6430 and 7960 angstroms show strong dependence of intensity and degree of polarization on angle of incidence

OPTICAL REFLECTIVITY↗
NASA NTRS1991

Optical polarization of a complete sample of radio sources

The radio and optical properties of a complete 5 GHz sample of strong radio sources are studied. High polarization is strongly correlated with the fraction of the total 5 GHz flux density found in a milliarcsec core. The detection rate of radio galaxies containing optical cores with high polarization is consistent with the hypothesis that all radio sources contain optically polarized cores, with strength proportional to the core radio flux density. High optical polarization, optical power-law fraction, line-to-continuum ratio, emission lines of small equivalent widths, and large amplitude flux variability are all strongly correlated with the fraction of the 5 GHz radio flux density that is unresolved on VLBI scales. The distributions of these properties are well matched by a model where radio and optical radiation have the same beaming geometry and with Doppler boosting of a factor of 10-100 in the optical. A striking alignment of the position angle of the VLBI structure axis and the position angle of optical polarization in highly polarized sources is confirmed.

Impey, C. D.↗
NASA NTRS1993

Hubble Space Telescope ultraviolet spectroscopy of the highly polarized but quiescent quasar OI 287

The quasar OI 287 has a unique combination of properties, including a high and constant optical polarization oriented parallel to the radio axis, a quiescent optical flux, and a lobe-dominant radio source. Previous studies have led to the picture of an edge-on thin dusty torus occulting a featureless continuum (FC) source and a broad line region (BLR) in this object. The FC source and the BLR are seen only in reflected (polarized) light. In the unified models, this makes OI 287 a 'quasar 2', analogous to the type 2 Seyfert galaxies and the narrow-line radio galaxies. Our UV spectrum adds two bits of information consistent with the above ideas. First, the spectrum neither turns up in the UV, as expected for optically thin dust scattering, nor turns down as expected for polarization by dust transmission. It is consistent with reflection by free electrons or optically thick dust. Second, there are in fact blueshifted absorption troughs associated with the C IV 1549 A line, supporting the analogy with BALs, as well as the idea that the BALs are objects which present a nearly edge-on view of a disk structure.

Antonucci, Robert↗
DOE OSTI2022

The Structural Origin of Chiroptical Properties in Perovskite Nanocrystals with Chiral Organic Ligands

Abstract The authors investigate how chiral ligands attached to perovskite nanocrystal (PNC) surfaces structurally distort the perovskite lattice. Chiral electro‐optical properties of the resulting PNCs are demonstrated through the fabrication of a circularly polarized light (CPL) detector with a discrimination of up to 14% between left‐ and right‐handed CPL. Both experimental and electronic‐structure‐based simulations are combined to provide insights into the interactions (both structural and electronic) between chiral organic ligands and PNCs. The major finding is a centro‐asymmetric distortion of the surface lattice that penetrates up to five atomic unit cells deep into the PNCs, which is the likely cause of the chiral‐optical properties. Spin‐polarized transport through chiral‐PNCs results from the chiral‐induced spin selectivity effect and amplifies the discrimination between left and right‐handed CPL as is experimentally demonstrated in the detectors.

36 MATERIALS SCIENCE↗
NASA NTRS1992

Quasars, blazars, and gamma rays

The paper discusses the extragalactic sources that have been discovered with the Energetic Gamma Ray Experiment Telescope. All of the sources demonstrate evidence of blazar properties at other wavelengths, including high optical polarization, extreme optical variability, flat-spectrum radio emission associated with a compact core, and apparent superluminal motion. These properties are believed to be produced by those few rare extragalactic quasars and radio galaxies that are favorably aligned to make it possible to observe almost directly down a relativistically outflowing jet of matter expelled from a supermassive black hole.

Dermer, Charles D.↗
NASA NTRS2001

Correlation Between Cirrus Particle Optical Properties: Microphysics and Implications for Spaceborne Remote Sensing

Cirrus measurements obtained with a ground-based polarization Raman lidar at 67.9 deg N in arctic winter reveal a strong correlation between the particle optical properties, specifically depolarization ratio and extinction-to-backscatter ratio, for ambient cloud temperatures above approximately -45 C, and an anti-correlation for colder temperatures. Similar correlations are evident in a 2-year midlatitude (53.4 deg N) cirrus data set. Scattering calculations show that the observed dependences can be interpreted in terms of the shapes and sizes of the cirrus ice particles. These findings suggest a retrieval method for determining cirrus extinction profiles from spaceborne lidar polarization data.

Reichardt, Jens↗
DOE OSTI2023

Anisotropic optical and magnetic response in self-assembled TiN–CoFe 2 nanocomposites

Transition metal nitrides (e.g., TiN) have shown tremendous promise in optical metamaterials for nanophotonic devices due to their plasmonic properties comparable to noble metals and superior high temperature stability. Vertically aligned nanocomposites (VANs) offer a great platform for combining two dissimilar functional materials with a one-step deposition technique toward multifunctionality integration and strong structural/property anisotropy. Here, we report a two-phase nanocomposite design combining ferromagnetic CoFe 2 nanosheets in the plasmonic TiN matrix as a new hybrid plasmonic metamaterial. The hybrid metamaterials exhibit anisotropic optical and magnetic responses, as well as a pronounced magneto-optical coupling response evidenced by Magneto-optic Kerr Effect measurement, owing to the novel vertically aligned structure. This work demonstrates a new TiN-based metamaterial with anisotropic properties and multifunctionality toward light polarization modulation, optical switching, and integrated optics.

36 MATERIALS SCIENCE↗
NASA NTRS1985

Polarization of light scattered by vegetation

The potential information in polarization data of both single leaves and plant canopies is investigated. Measurements demonstrate the relationship between polarization data and various optical and botanical properties of both pieces of foliage and plant canopies. The results provide a basis for gaining fundamental understanding of how light is scattered and polarized by a plant canopy. The results show the polarized and nonpolarized portions of the light scattered by a remotely sensed ground scene potentially are independent sources of information for discriminating species and assessing the condition of plant canopies.

Vanderbilt, V. C.↗
DOE OSTI2026

Molecular Diradical Spin Qubits in a Crystalline Host as a Platform for Quantum Sensing

Doping a luminescent tris(2,4,6-trichlorophenyl)methyl diradical m (TTM) 2 into a host crystal of its diamagnetic precursor m (HTTM) 2 creates a molecular color center with enhanced optical-spin interface properties important for quantum sensing. Optical polarization of the |T 0 ⟩ sublevel of the diradical triplet ground state is achieved by spin-selective intersystem crossing from the |T + ⟩ and |T – ⟩ sublevels of the triplet excited state at ambient and cryogenic temperatures. Coherent spin control of m (TTM) 2 doped into m (HTTM) 2 using pulsed optically detected magnetic resonance (ODMR) spectroscopy results in a 10-fold improvement in ODMR contrast over that observed for randomly oriented m (TTM)2 using continuous-wave ODMR. The diradical doped crystal powders achieve spin coherence times of 2.8, 3.4, and 7.4 μs at 294, 85, and 5 K, respectively. The diradical photoluminescence is sensitive to weak applied magnetic fields independent of temperature, excitation wavelength, and dopant concentration, providing a promising pathway toward robust quantum sensing of anisotropic magnetic fields under ambient conditions.

crystal structure↗
NASA NTRS2002

Correlations among the Optical Properties of Cirrus-Cloud Particles: Microphysical Interpretation

Cirrus measurements obtained with a ground-based polarization Raman lidar at 67.9 deg N in January 1997 reveal a strong positive correlation between the particle optical properties, specifically depolarization ratio delta(sub par) and extinction- to-backscatter (lidar) ratio S, for delta(sub par) less than approximately 40%, and an anti-correlation for delta(sub par) greater than approximately 40%. Over the length of the measurements the particle properties vary systematically. Initially, delta (sub par) approximately equals 60% and S approximately equals 10sr are observed. Then, with decreasing delta(sub par), S first increases to approximately 27sr (delta(sub par) approximately equals 40%) before decreasing to values around 10sr again (delta(sub par) approximately equals 20%). The analysis of lidar humidity and radiosonde temperature data shows that the measured optical properties stem from scattering by dry solid ice particles, while scattering by supercooled droplets, or by wetted or subliming ice particles can be excluded. For the microphysical interpretation of the lidar measurements, ray-tracing computations of particle scattering properties have been used. The comparison with the theoretical data suggests that the observed cirrus data can be interpreted in terms of size, shape, and, under the assumption that the lidar measurements of consecutive cloud segments can be mapped on the temporal development of a single cloud parcel moving along its trajectory, growth of the cirrus particles: Near the cloud top in the early stage of cirrus development, light scattering by nearly isometric particles that have the optical characteristics of hexagonal columns (short, column-like particles) is dominant. Over time the ice particles grow, and as the cloud base height extends to lower altitudes characterized by warmer temperatures they become morphologically diverse. For large S and depolarization values of approximately 40%, the scattering contributions of column- and plate-like particles are roughly the same. In the lower ranges of the cirrus clouds, light scattering is predominantly by plate-like ice particles. This interpretation assumes random orientation of the cirrus particles. Simulations with a simple model suggest, however, that the positive correlation between S and delta(sub par) which is observed for depolarization ratios less than 40% mainly at low cloud altitudes, can be alternatively explained by horizontal alignment of a fraction of the cirrus particle population.

Reichardt, J.↗
NASA NTRS1986

Characteristics of Arctic polar stratospheric clouds and as measured by airborne lidar

Airborne lidar measurements of backscattering from polar stratospheric clouds (PSCs) obtained in January 1984 are examined. The flights, principal characteristics of the lidar system, and the meteorological conditions during the flights are described. The characteristics and conditions for the formation of PSCs and the optical characteristics of the clouds are discussed. The properties of the North Polar vortex and El Chichon stratospheric aerosol are studied. Variations in the aerosol optical properties with temperature and water vapor concentrations are analyzed and modeled using a model based on volcanic aerosols and water vapor concentration. The modeled and experimental backscattering-temperature relationship are compared and good correlation is observed at pressure levels of 100 and 70 mb.

Kent, G. S.↗
NASA NTRS2020

The NASA MODIS-VIIRS Continuity Cloud Optical Properties Products

The NASA Aqua MODIS and Suomi National Polar-Orbiting Partnership (SNPP) Visible Infrared Imaging Radiometer Suite (VIIRS) climate data record continuity cloud properties products (CLDPROP) were publicly released in April 2019 with an update later that year (Version 1.1). These cloud products, having heritage with the NASA Moderate-resolution Imaging Spectroradiometer (MODIS) MOD06 cloud optical properties product and the NOAA GOES-R Algorithm Working Group (AWG) Cloud Height Algorithm (ACHA), represent an effort to bridge the multispectral imager records of NASA’s Earth Observing System (EOS) and NOAA’s current generation of operational weather satellites to achieve a continuous, multi-decadal climate data record for clouds that can extend well into the 2030s. CLDPROP offers a “continuity of approach,” applying common algorithms and ancillary datasets to both MODIS and VIIRS, including utilizing only a subset of spectral channels available on both sensors to help mitigate instrument differences. The initial release of the CLDPROP_MODIS and CLDPROP_VIIRS data records spans the SNPP observational record (2012-present). Here, we present an overview of the algorithms and an evaluation of the intersensor continuity of the core CLDPROP_MODIS and CLDPROP_VIIRS cloud optical property datasets, i.e., cloud thermodynamic phase, optical thickness, effective particle size, and derived water path. The evaluation includes analyses of pixel-level MODIS/VIIRS co-locations as well as spatial and temporal aggregated statistics, with a focus on identifying and understanding the root causes of individual dataset discontinuities. The results of this evaluation will inform future updates to the CLDPROP products and help scientific users determine the appropriate use of the product datasets for their specific needs.

satellite remote sensing↗
DOE OSTI2022

First-Principles Study of Ferroelectric and Optical Properties in Derivatives of Thiourea

Organic ferroelectric materials in the form of molecular crystals are promising alternatives to well-known ferroelectric perovskite oxides due to their structural flexibility, tunability, and ease of processing. First-principles density functional theory calculations combined with group theory analyses are employed in this work to discuss polar nature of a class of derivatives of thiourea: CH 4 N 2 A where A = O, S, Se, and Te. Further, optical properties in the UV range along with thermodynamic and dynamic stability of such materials are also evaluated in the study. We find that CH 4 N 2 Te with bandgap energy of ~3.33 eV shows large spontaneous polarization of P = 10.92 μC/cm 2 . The electronic and optical properties become tunable under strain.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1990

Optical properties of KD*P modulators

Longitudinal KD*P modulators are used in ground-based solar magnetographs to eliminate seeing effects. Although the modulators can be used as variable retarders, the optical properties when zero voltage is applied influences the performance on instruments requiring very accurate polarization measurements. Measurements at the Marshall Space Flight Center are discussed in terms of the optical properties of KD*P modulators when zero voltage is applied. The measurements can be used to predict the modulation characteristics of the devices and to determine the polarization accuracy that can be expected from the vector magnetograph.

West, E. A.↗
NASA NTRS2022

Polarization as a Discriminator of Light-Absorbing Impurities in or Above Snow

This conceptual study presents advanced radiative transfer computations of light polarization originating from a snowpack consisting of nonspherical grains and variable content of light-absorbing impurities, either embedded in the snowpack or (with the same optical properties) lofted above it in the form of atmospheric aerosols. The results highlight the importance of considering shapes other than spherical for the snow grains, which otherwise can lead to non-negligible errors in the retrieval of snow albedo from remote sensing observations. More importantly, it is found that polarimetric measurements provide a means to partition light-absorbing impurities embedded in the snowpack from absorbing aerosols aloft, a task traditionally prohibitive for sensors capable exclusively of measurements of total reflectance. Heritage techniques to obtain snow grain size from shortwave infrared observations of total reflectance are well established, as are those that leverage polarimetric, multiangular observations across the entire optical spectrum to characterize the optical and microphysical properties of atmospheric aerosols. The polarization signatures of near-infrared (e.g., 864 nm) observations carry critical information on snow grain shape. The prospected launch of space-borne polarimeters with proven accuracy, therefore, advocates for the development of data inversion schemes, to boost the accuracy of simultaneous retrievals of atmospheric and surface parameters in the polar and snow-covered regions, critical to climate studies.

light polarization↗
NASA NTRS2013

Heterogeneous Formation of Polar Stratospheric Clouds- Part 1: Nucleation of Nitric Acid Trihydrate (NAT)

Satellite-based observations during the Arctic winter of 2009/2010 provide firm evidence that, in contrast to the current understanding, the nucleation of nitric acid trihydrate (NAT) in the polar stratosphere does not only occur on preexisting ice particles. In order to explain the NAT clouds observed over the Arctic in mid-December 2009, a heterogeneous nucleation mechanism is required, occurring via immersion freezing on the surface of solid particles, likely of meteoritic origin. For the first time, a detailed microphysical modelling of this NAT formation pathway has been carried out. Heterogeneous NAT formation was calculated along more than sixty thousand trajectories, ending at Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP) observation points. Comparing the optical properties of the modelled NAT with these observations enabled a thorough validation of a newly developed NAT nucleation parameterisation, which has been built into the Zurich Optical and Microphysical box Model (ZOMM). The parameterisation is based on active site theory, is simple to implement in models and provides substantial advantages over previous approaches which involved a constant rate of NAT nucleation in a given volume of air. It is shown that the new method is capable of reproducing observed polar stratospheric clouds (PSCs) very well, despite the varied conditions experienced by air parcels travelling along the different trajectories. In a companion paper, ZOMM is applied to a later period of the winter, when ice PSCs are also present, and it is shown that the observed PSCs are also represented extremely well under these conditions.

Hoyle, C. R.↗
DOE OSTI2021

Radically Tunable n-Type Organic Semiconductor via Polymorph Control

Polymorphism has emerged as an important design consideration in organic semiconductors (OSCs). Previously, in many OSCs, even small changes in molecular stacking can cause drastic changes to the optical and electronic properties. However, investigation into n-type semiconductors has significantly lagged behind their p-type counterparts. In this work, we present the prolific polymorphism of 2-dimensional quinoidal terthiophene (2DQTT-o-B) and systematically investigate each of 5 polymorphs, 3 of which have been previously unreported. Grazing incidence X-ray diffraction provided a key method to understanding the structure of each polymorph. Via the polymorphic transitions mapped, we tuned the electron mobility by 5 orders of magnitude, from 5.63 × 10 –5 to 0.22 cm 2 V –1 s –1 . These were accompanied by modifications to the optical properties, namely we observed substantial differences in the refractive index noted by intensity differences under polarized optical microscopy and a large shift in optical band gap from 1.18 eV up to 1.40 eV. Lastly, we suggest that changes to these properties may be related to the unique quinoidal to aromatic transition observed in quinoidal molecules.

36 MATERIALS SCIENCE↗