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Optical polarization
About: Optical polarization is a research topic. Over the lifetime, 13992 publications have been published within this topic receiving 244284 citations.
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TL;DR: In this paper, the free decay of nonhelical relativistic magnetohydrodynamic turbulence is studied numerically, and found to exhibit cascading of magnetic energy toward large scales, which constrains magnetic reconnection models for rapid time variability of gamma-ray burst prompt emission, blazars, and the Crab nebula.
Abstract: The free decay of nonhelical relativistic magnetohydrodynamic turbulence is studied numerically, and found to exhibit cascading of magnetic energy toward large scales. Evolution of the magnetic energy spectrum PM (k, t) is self-similar in time and well modeled by a broken power law with subinertial and inertial range indices very close to 7/2 and –2, respectively. The magnetic coherence scale is found to grow in time as t 2/5, much too slow to account for optical polarization of gamma-ray burst afterglow emission if magnetic energy is to be supplied only at microphysical length scales. No bursty or explosive energy loss is observed in relativistic MHD turbulence having modest magnetization, which constrains magnetic reconnection models for rapid time variability of GRB prompt emission, blazars, and the Crab nebula.
98 citations
TL;DR: Arguments are presented that suggest different scattering mechanisms for the two polarizations: evenly distributed Bragg scatter patches for VV and scatter from small asymmetric bore features for HH, while HH NRCS grazing angle characteristics are shown to correlate with biological activity indicators of the coastal waters.
Abstract: Reports on experiments featuring horizontally (HH) and vertically (VV) polarized X-band marine radar sea scatter imagery in the coastal environments of Bermuda and La Jolla, under light to moderate winds and the absence of long gravity waves. These conditions allowed the study of fundamental scattering mechanisms from small scale roughness and short waves of a few meters wavelength or less, shorter than the radar pulse. While a large fraction of radar data collected revealed the presence of slick bands, the authors analyze the radar echo of ambient background outside of the slicks. Sea scatter data were digitally recorded for 360/spl deg/ azimuthal coverage for grazing angles between 1-3.5/spl deg/, and were converted to normalized radar cross section (NRCS or /spl sigma//spl deg/) images. The HH and VV polarizations show quite different spatial texture, with HH exhibiting a discrete character and VV being more nearly spatially homogeneous. Grazing angle dependencies are different for HH and VV: upwind-downwind differences of mean NRCS show ratios of just 4-6 dB for VV, but are equal or greater than the 16-dB noise-imposed limit for HH for the low wind conditions. HH NRCS grazing angle characteristics are shown to correlate with biological activity indicators of the coastal waters, with a fourth power dependence in relatively unproductive waters, to a nearly quadratic in productive waters. Arguments are presented that suggest different scattering mechanisms for the two polarizations: evenly distributed Bragg scatter patches for VV and scatter from small asymmetric bore features for HH. A multipath illumination model for small bore features is outlined, and scale sizes for the small scale breakers inferred from the experimental results presented are between 2 and 4 cm in height, with crest widths between 24 and 48 cm.
98 citations
TL;DR: In this paper, a new technique is proposed for generating a tight dark focal spot surrounded by uniform light intensity in all directions, based on a single focusing lens illuminated from one side, hence the alignment sensitivities associated with 4π methods are eliminated.
98 citations
TL;DR: The design, fabrication and characterization of a multilayer polarizing grating mirror developed for an Yb:YAG thin-disk laser resonator are reported and the potential of the proposed solution is discussed together with the first demonstration of a radially polarized Yb:(YAG) thin- disk laser.
Abstract: The design, fabrication and characterization of a multilayer polarizing grating mirror developed for an Yb:YAG thin-disk laser resonator are reported. The potential of the proposed solution is discussed together with the first demonstration of a radially polarized Yb:YAG thin-disk laser.
98 citations
TL;DR: As traffic demands continue to grow, supporting data rates beyond 100 Gb/s will be required to increase optical channel capacity and support higher-rate client interfaces and advanced modulation formats that adapt to optimize spectral efficiency over a range of channel signal-tonoise ratio conditions are required.
Abstract: As traffic demands continue to grow, supporting data rates beyond 100 Gb/s will be required to increase optical channel capacity and support higher-rate client interfaces. Advanced modulation formats that adapt to optimize spectral efficiency over a range of channel signal-tonoise ratio conditions are required. Channels can be constructed by varying parameters such as symbol rate, bits per symbol, number of polarizations, and number of optical and electrical subcarriers. Channel capacity can also be increased using advanced techniques such as optical time-division multiplexing, and fibers that support multiple cores and modes. Many channel designs can support higher data rates, but there are trade-offs between complexity, spectral efficiency, and optical reach.
98 citations