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Zhongyi Guo, Zixiang Li, Jingran Zhang, Kai Guo, Fei Shen, Qingfeng Zhou, Hongping Zhou
Here, we have reviewed some typical plasmonic structures based on Archimedes' spiral (AS) architectures, which can produce polarization-sensitive focusing phenomenon and generate plasmonic vortices (PVs) carrying controllable orbital angular momentum (OAM) because of the relation between the incident polarized states and the chiralities of the spiral structures. These features can be used to analyze different circular polarization states, which has been one of the rapidly developing researching topics in nanophotonics in recent years...
November 22, 2017: Nanomaterials
Christopher J Schultz, Lawrence D Carey, Elise V Schultz, Richard J Blakeslee
Thirty-nine thunderstorms are examined using multiple-Doppler, polarimetric and total lightning observations to understand the role of mixed phase kinematics and microphysics in the development of lightning jumps. This sample size is larger than those of previous studies on this topic. The principal result of this study is that lightning jumps are a result of mixed phase updraft intensification. Larger increases in intense updraft volume (≥ 10 m s(-1)) and larger changes in peak updraft speed are observed prior to lightning jump occurrence when compared to other non-jump increases in total flash rate...
February 2017: Weather Forecast
Matthieu Dubreuil, Sylvain Rivet, Yann Le Grand
A new high-speed second-harmonic generation (SHG) polarimetric method is reported. It is based on the spectral analysis of the SHG radiation emitted by a nonlinear medium excited with circularly polarized femtosecond laser pulses. The setup uses only passive components for polarization encoding and a fast spectrometer for spectral analysis. The method is validated on a z-cut quartz plate, then on a collagen-rich biological tissue with a view to single image polarization-resolved SHG microscopy.
November 15, 2017: Optics Letters
Ji Qi, Honghui He, Jianyu Lin, Yang Dong, Dongsheng Chen, Hui Ma, Daniel S Elson
Tissue depolarization and linear retardance are the main polarization characteristics of interest for bulk tissue characterization, and are normally interpreted from Mueller polarimetry. Stokes polarimetry can be conducted using simpler instrumentation and in a shorter time. Here we use Stokes polarimetric imaging with circularly polarized illumination to assess the circular depolarization and linear retardance properties of tissue. Results obtained were compared with Mueller polarimetry in transmission and reflection geometry respectively...
November 13, 2017: Journal of Biophotonics
Jason C Vap, Stephen E Nauyoks, Michael R Benson, Michael A Marciniak
Nanostructured optical materials, for example, metamaterials, have unique spectral, directional, and polarimetric properties. Samples designed and fabricated for infrared (IR) wavelengths have been characterized using broadband instruments to measure specular polarimetric transmittance or reflectance as in ellipsometry or integrated hemisphere transmittance or reflectance. We have developed a wavelength-tunable IR Mueller-matrix (Mm) polarimetric scatterometer which uses tunable external-cavity quantum-cascade lasers (EC-QCLs) to tune onto and off of the narrowband spectral resonances of nanostructured optical materials and performed full polarimeteric and directional evaluation to more fully characterize their behavior...
October 2017: Review of Scientific Instruments
Thomas Fromenteze, Okan Yurduseven, Michael Boyarsky, Jonah Gollub, Daniel L Marks, David R Smith
We propose a polarimetric microwave imaging technique that exploits recent advances in computational imaging. We utilize a frequency-diverse cavity-backed metasurface, allowing us to demonstrate high-resolution polarimetric imaging using a single transceiver and frequency sweep over the operational microwave bandwidth. The frequency-diverse metasurface imager greatly simplifies the system architecture compared with active arrays and other conventional microwave imaging approaches. We further develop the theoretical framework for computational polarimetric imaging and validate the approach experimentally using a multi-modal leaky cavity...
October 30, 2017: Optics Express
Bin Yang, Junqiang Zhang, Changxiang Yan, Xueping Ju
Polarimetric calibration and reconstruction methods for a fieldable channeled dispersive imaging spectropolarimeter (CDISP) are presented. A theoretical model for the polarimetric calibration is derived first. In the polarimetric calibration for the CDISP, the alignment errors of the polarimetric spectral intensity modulation module, and the polarization effects of the optical system and phase factors of the high-order retarders at different viewing angles, are considered and determined independently. Based on the results of the polarimetric calibration, the Stokes vector of the target is reconstructed through the derived reconstruction model...
October 20, 2017: Applied Optics
Razvigor Ossikovski, Jérémy Vizet
We generalize an existing algebraic procedure for the polar decomposition of Mueller matrices with negative determinants [Opt. Commun.281, 2406 (2008)OPCOB80030-401810.1016/j.optcom.2007.12.076] to the case of nondiagonal depolarizer matrix factors. The generalized procedure is applied to experimental Mueller matrices illustrating its potential for the phenomenological interpretation of complex polarimetric data.
October 20, 2017: Applied Optics
Péter Takács, András Barta, David Pye, Gábor Horváth
When the sun is near the horizon, a circular band with approximately vertically polarized skylight is formed at 90° from the sun, and this skylight is only weakly reflected from the region of the water surface around the Brewster's angle (53° from the nadir). Thus, at low solar heights under a clear sky, an extended dark patch is visible on the water surface when one looks toward the north or south quarter perpendicular to the solar vertical. In this work, we study the radiance distribution of this so-called Brewster's dark patch (BDP) in still water as functions of the solar height and sky conditions...
October 20, 2017: Applied Optics
Joseph Chue-Sang, Yuqiang Bai, Susan Stoff, David Straton, Sharan Ramaswamy, Jessica C Ramella-Romana
This erratum corrects two errors in the original paper.
October 2017: Journal of Biomedical Optics
Xiao Huang, Yujie Luo, Jian Bai, Ruiqi Cheng, Kejing He, Kaiwei Wang, Qun Liu, Yupeng Luo, Juan Du
Depth sensing is a basic issue in three-dimensional computer vision, and structured light is one of the most prevailing methods for it. However, complex surroundings and strong ambient illumination are fairly unfavorable to depth sensing based on structured light. Complex surroundings increase computation overhead and require extra effort to be separated from the target object. Strong ambient illumination is unfavorable to the signal-noise ratio of structured light and, thus, increases the difficulty of decoding...
September 20, 2017: Applied Optics
Ibrahim Watad, Ibrahim Abdulhalim
There is a debate on whether phase measurement in surface plasmon resonance (SPR) sensors give better resolution than intensity measurement. In this work, we show that each one of the modes can give better resolution depending on the metal layer thickness chosen, as well as the available noise levels in the system. We propose a three point polarimetric approach to extract the ellipsometric parameters and phase information in the spectral mode. It is shown that the polarimetric measurement at its optimal thickness range gives up to seven-fold higher resolution than the intensity, especially at noise levels of off the shelf spectrometers...
September 20, 2017: Applied Optics
Alok Ranjan Tiwary, A Raja Bayanna, Shibu K Mathew
We use a liquid crystal variable retarder (LCVR) for polarization modulation of the input beam in a polarimeter intended for solar observations. It is known that the retardance of LCVR depends on the voltage and temperature. Voltage at a constant temperature is used for fast modulation. However, fluctuations in the temperature reduce the accuracy in the polarimetric measurements. In order to understand these, we have performed calibration of the LCVR with respect to temperature and estimated the different parameters, critical exponent (β), maximum retardance (δ0), and order parameter (S) of the liquid crystal using Haller's approximation...
May 10, 2017: Applied Optics
Tavakol Nazari, Boram Joo, Ji-Hyun Hwang, Bjorn Paulson, Jiyoung Park, Young Min Jhon, Kyunghwan Oh
We report a new efficient light guidance along a liquid core using an open V-groove. Guiding properties were analyzed using finite element method in terms of the single mode guidance condition, and the corresponding modal birefringence. We experimentally demonstrated a silica V-groove fiber with an opening angle of 40°, which was spliced to single mode fibers at both ends. A liquid with the refractive index of 1.455 was filled to serve as a core along a maximum length of 47cm. We confirmed the single mode guidance and birefringence consistent to theory, which will enable polarimetric liquid sensing...
October 2, 2017: Optics Express
Meredith K Kupinski, Jaden Bankhead, Adriana Stohn, Russell Chipman
A new binary classification method for Mueller matrix images is presented which optimizes the polarization state analyzer (PSA) and the polarization state generator (PSG) using a statistical divergence between pixel values in two regions of an image. This optimization generalizes to multiple PSA/PSG pairs so that the classification performance as a function of number of polarimetric measurements can be considered. Optimizing PSA/PSG pairs gives insight into which polarimetric measurements are most useful for the binary classification...
June 1, 2017: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Albert Van Eeckhout, Angel Lizana, Enric Garcia-Caurel, José J Gil, Razvigor Ossikovski, Juan Campos
In this work, we discuss the interest of using the indices of polarimetric purity (IPPs) as a criterion for the characterization and classification of depolarizing samples. We prove how differences in the depolarizing capability of samples, not seen by the commonly used depolarization index PΔ, are identified by the IPPs. The above-stated result is analyzed from a theoretical point of view and experimentally verified through a set of polarimetric measurements. We show how the approach presented here can be useful in easily synthetizing depolarizing samples with controlled depolarizing features, just by properly combining low-cost fully polarizing elements (such as linear retarders or polarizers)...
October 15, 2017: Optics Letters
Dénes Száz, Alexandra Farkas, András Barta, Balázs Kretzer, Miklós Blahó, Ádám Egri, Gyula Szabó, Gábor Horváth
According to Thorkild Ramskou's theory proposed in 1967, under overcast and foggy skies, Viking seafarers might have used skylight polarization analysed with special crystals called sunstones to determine the position of the invisible Sun. After finding the occluded Sun with sunstones, its elevation angle had to be measured and its shadow had to be projected onto the horizontal surface of a sun compass. According to Ramskou's theory, these sunstones might have been birefringent calcite or dichroic cordierite or tourmaline crystals working as polarizers...
September 2017: Proceedings. Mathematical, Physical, and Engineering Sciences
Pyung-Gang Lee, Joonwon Kim, Eun-Jung Kim, Sang-Hyuk Lee, Kwon-Young Choi, Romas J Kazlauskas, Byung-Gee Kim
Equols are isoflavandiols formed by reduction of soy isoflavones such as daidzein and genistein by gut microorganisms. These phytoestrogens are of interest for their various biological effects. We report biosynthesis from genistein to (-)-5-hydroxy-equol in recombinant E. coli expressing three reductases (daidzein reductase DZNR, dihidrodaidzein reductase DHDR, tetrahydrodaidzein reductase THDR) and a racemase (dihydrodaidzein racemase, DDRC) originating from the gut bacterium, Slackia isoflavoniconvertens...
November 17, 2017: ACS Chemical Biology
Albert Van Eeckout, Angel Lizana, Enric Garcia-Caurel, José J Gil, Adrià Sansa, Carla Rodríguez, Irene Estévez, Emilio González, Juan Carlos Escalera, Ignacio Moreno, Juan Campos
We highlight the interest of using the Indices of Polarimetric Purity (IPPs) to the inspection of biological tissues. The IPPs were recently proposed in the literature and they result in a further synthetization of the depolarizing properties of samples. Compared with standard polarimetric images of biological samples, IPPs based images lead to larger image contrast of some biological structures and to a further physical interpretation of the depolarizing mechanisms inherent to the samples. In addition, unlike other methods, their calculation do not require advanced algebraic operations (as is the case of polar decompositions), and they result in three indicators of easy implementation...
October 5, 2017: Journal of Biophotonics
Priyanka Lahiri, Kenneth B Wiberg, Patrick H Vaccaro
The dispersive optical activity of a homoconjugated bicyclic diene, (R)-methylene norbornene (R-MNB), was interrogated under complementary vapor-phase and solution-phase conditions to elucidate the structural/electronic provenance of its unusual chiroptical signatures and to explore the marked influence of environmental perturbations. The intrinsic (isolated-molecule) values of specific rotation measured at 355 and 633 nm (1623.5 ± 5.5 and 390.4 ± 3.7 deg dm(-1) (g/mL)(-1)) were found to be factors of 3.9 and 2...
October 13, 2017: Journal of Physical Chemistry. A
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