Wavelength dependence of the degree of polarization in cloud-free skies: simulations of real environments

Pust, Nathan J.; Shaw, Joseph A.

doi:10.1364/oe.20.015559

Cited by 37 publications

(18 citation statements)

References 28 publications

(41 reference statements)

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“…[1][2][3][4][5][6][7]32 In several previous measurements with thick wildfire smoke, the spatial skylight polarization pattern was essentially unchanged, but with a significantly decreased maximum DoLP. 4,32 However, the August 2012 case differed in at least one interesting way: the reduction of the DoLP varied across the "band of maximum polarization" located 90° from the Sun when the smoke was seemingly uniformly spread throughout the overhead sky.…”

Section: Skylight Polarization Measurementsmentioning

confidence: 90%

“…[2][3][4][5][6][7]32,34 This is a division-of-time imaging polarimeter that uses liquid crystal variable retarders (LCVRs) to tune rapidly through four polarization states rapidly enough to minimize adverse effects of cloud motion. All-sky images are acquired at each of the four polarization states and used in a system-matrix-inversion approach 1 to recover a 4-element Stokes vector at each pixel.…”

Section: All-sky Polarization Imagermentioning

confidence: 99%

“…1 This also elevates the need for quantitative measurements and models of the effects of scattering by atmospheric gas molecules, aerosols, clouds, and underlying surfaces. [2][3][4][5][6][7] There have been numerous studies of mitigating the optical and infrared effects of smoke on battlefield conditions, [8][9][10][11] and recently there are increasing studies on using polarization for mitigating the adverse effects on imaging by haze and smoke. [12][13][14][15] However, there has been a shortage of studies that quantify the effects of smoke on skylight polarization.…”

Section: Introductionmentioning

confidence: 99%

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Effects of wildfire smoke on atmospheric polarization

Shaw¹,

Pust

Forbes

2014

SPIE Proceedings

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A continuously operating all-sky polarization imager recorded the skylight polarization pattern as conditions transitioned from clear and clean to extremely smoky. This transition included a period when a local wildfire plume filled part of the sky with smoke, creating a highly asymmetric distribution of aerosols. Multiple scattering in the smoke plume strongly reduced the degree of polarization in the smoky region of the sky. Once the smoke plume spread out to cover the entire local sky, the degree of polarization was strongly reduced everywhere. However, this example differed from previously observed smoke events because, even though the usual skylight polarization pattern generally persisted throughout the event, this time the smoke-covered sky exhibited a spatially asymmetric profile along the band of maximum polarization. This pattern of reduced polarization toward the horizon is hypothesized to be a result of an optically thick but physically thin smoke layer. The skylight polarization observations are supplemented with optical depth measurements and aerosol size distribution retrievals from a solar radiometer.

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Section: Skylight Polarization Measurementsmentioning

confidence: 90%

Section: All-sky Polarization Imagermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of wildfire smoke on atmospheric polarization

Shaw¹,

Pust

Forbes

2014

SPIE Proceedings

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“…Furthermore, as mentioned above, the presence of aerosol particles in the atmosphere influences the DoLP. Pust and Shaw (2012) showed that higher DoLP of red light exists for oceanic regions, while the opposite can occur in desert regions, with the types of aerosol present contributing to this difference.…”

Section: Two-dimensional Maps Of Dolp and Aolpmentioning

confidence: 99%

Linear Polarization Characteristics Within the Rosh HaNikra Mid-Littoral Cave, Israel

et al. 2018

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Light polarization characteristics, i. e., degree of linear polarization (DoLP) and angle of linear polarization (AoLP), were documented in the depth of the littoral cave system of Rosh HaNikra on the northern Mediterranean shore of Israel (33 • 5 ′ 35.24 ′′ N, 35 • 6 ′ 17.16 ′′ E), based on light intensity sampled through polarizing filters at different hours of the day on different days of the year. This is the first study to investigate the state of light polarization in such a unique habitat in which photosynthetic organisms, such as cyanobacteria, microalgae, and macroalgae thrive. Such organisms play an essential ecological role as the energy base for the cave's fauna. Using these two methods, we found unique winter polarization characteristics within the cave, including high values of DoLP in the morning and at noon, reaching 50%, and nearly constant AoLP throughout the day. Given the low levels of light intensity that typically exist within the cave in the winter months, the relatively high DoLP and the nearly constant AoLP throughout the day may play a significant role in improving the ability of photosynthetic organisms within the cave to harvest light by orienting their light-harvesting receptors with respect to the AoLP. Using the polarization photograph analysis method, we were able to determine the polarization characteristics originating from the sky, reflection off of (including refraction into followed by refraction out of) the far sea surface, and reflection off of the cave wall separately. The maximum DoLP values originating from the sky, far ocean, and cave walls were found to be 27, 50, and 35%, respectively. The lowest daily variation in AoLP was that of light reflecting off the cave walls. The present study lays the foundation for any subsequent study of the role of light polarization in the distribution of the algal flora on the cave walls in and out of the water in the Rosh HaNikra cave and in sea caves in general.

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“…(7) with the error rate due to noise, e 0 , taken to be 1/2 under the assumption the background is random. It should be noted that the polarization distribution of sky radiance has been studied in detail, 60 but is not included in this analysis. The probability of a projective polarization measurement in a matched polarization basis yielding an incorrect result due to depolarization in propagation and improper alignment has been measured experimentally in a satellite-Earth optical link.…”

Section: Satellite-to-earth Quantum Channel Parametersmentioning

confidence: 99%

Adaptive spatial filtering of daytime sky noise in a satellite quantum key distribution downlink receiver

et al. 2016

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Abstract. Spatial filtering is an important technique for reducing sky background noise in a satellite quantum key distribution downlink receiver. Atmospheric turbulence limits the extent to which spatial filtering can reduce sky noise without introducing signal losses. Using atmospheric propagation and compensation simulations, the potential benefit of adaptive optics (AO) to secure key generation (SKG) is quantified. Simulations are performed assuming optical propagation from a low-Earth-orbit satellite to a terrestrial receiver that includes AO. Higherorder AO correction is modeled assuming a Shack-Hartmann wavefront sensor and a continuous-face-sheet deformable mirror. The effects of atmospheric turbulence, tracking, and higher-order AO on the photon capture efficiency are simulated using statistical representations of turbulence and a time-domain wave-optics hardware emulator. SKG rates are calculated for a decoy-state protocol as a function of the receiver field of view for various strengths of turbulence, sky radiances, and pointing angles. The results show that at fields of view smaller than those discussed by others, AO technologies can enhance SKG rates in daylight and enable SKG where it would otherwise be prohibited as a consequence of background optical noise and signal loss due to propagation and turbulence effects. Keywords: quantum key distribution; adaptive optics; decoy states; quantum information; cryptography; sky radiance.Paper 151557P received Nov. 5, 2015; accepted for publication Dec. 24, 2015; published online Feb. 2, 2016; corrected Apr. 26, 2016. IntroductionThe threat quantum computing poses to public key cryptography is motivating the development of alternatives to modern key sharing techniques that rely on computational complexity for security.1,2 Presently, there is interest in developing quantum key distribution (QKD), presented by Bennett and Brassard in 1984 (BB84), as a provably secure alternative.2-5 QKD lends itself to mathematical proofs of theoretical security and offers the potential for secure generation of symmetric encryption keys in real time over optical channels.

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Wavelength dependence of the degree of polarization in cloud-free skies: simulations of real environments

Cited by 37 publications

References 28 publications

Effects of wildfire smoke on atmospheric polarization

Effects of wildfire smoke on atmospheric polarization

Linear Polarization Characteristics Within the Rosh HaNikra Mid-Littoral Cave, Israel

Adaptive spatial filtering of daytime sky noise in a satellite quantum key distribution downlink receiver

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