Topic
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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09 Apr 2013
TL;DR: In this paper, the authors present time-resolved broad-band observations of the quasar 3C 279 obtained from multi-wavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission.
Abstract: We present time-resolved broad-band observations of the quasar 3C 279 obtained from multiwavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission. While investigating the previously reported gamma-ray/optical flare accompanied by a change in optical polarization, we found that the optical emission appears delayed with respect to the gamma-ray emission by about 10 days. X-ray observations reveal a pair of 'isolated' flares separated. by approx. 90 days, with only weak gamma-ray/optical counterparts. The spectral structure measured by Spitzer reveals a synchrotron component peaking in the mid-infrared band with a sharp break at the far-infrared band during the gamma-ray flare, while the peak appears in the mm/sub-mm band in the low state. Selected spectral energy distributions are fitted with leptonic models including Comptonization of external radiation produced in a dusty torus or the broad-line region. Adopting the interpretation of the polarization swing involving propagation of the emitting region along a curved trajectory, we can explain the evolution of the broad-band spectra during the gamma-ray flaring event by a shift of its location from approx. 1 pc to approx. 4 pc from the central black hole. On the other hand, if the gamma-ray flare is generated instead at sub-pc distance from the central black hole, the far-infrared break can be explained by synchrotron self-absorption. We also model the low spectral state, dominated by the mm/sub-mm peaking synchrotron component, and suggest that the corresponding inverse-Compton component explains the steady X-ray emission.
73 citations
TL;DR: A heterodyne interferometric system based on optical polarization is described, which uses a simple rotating analyzer as the frequency shifter and the theory and the potential errors are analyzed.
Abstract: A heterodyne interferometric system based on optical polarization is described. The method uses a simple rotating analyzer as the frequency shifter. The theory and the potential errors of the system are analyzed.
73 citations
TL;DR: In this article, the use of lowvoltage, low power, and bistable devices to perform a variety of functions including polarization and intensity-based logic gates, input/output displays, optical crossbars, and spatial filtering masks is described.
Abstract: High-contrast, submicrosecond switching ferroelectric liquid crystal spatial light modulators have many applications to optical computing and image processing. In this paper we describe the use of these low-voltage, low-power, and bistable devices to perform a variety of functions including polarization- and intensity-based logic gates, input/output displays, optical crossbars, and spatial filtering masks.
73 citations
TL;DR: In this paper, shift and injection currents are generated in the wurtzite semiconductors CdSe and CdS at 295K using above-band-gap femtosecond pulses and detected via the emitted terahertz radiation; the optical beams are normally incident on samples with the optic axis in the plane of the surface.
Abstract: Shift and injection currents are generated in the wurtzite semiconductors CdSe and CdS at 295K using above-band-gap (ℏω>Eg) femtosecond pulses and detected via the emitted terahertz radiation; the optical beams are normally incident on samples with the optic axis in the plane of the surface. For optical intensities up to 75MWcm−2 (or carrier density <1018cm−3) the terahertz radiation amplitude shows the expected linear dependence and also varies with optical polarization and sample orientation consistent with the third-rank tensors that govern the current generation processes in the wurtzite structure. The largest shift currents are generated along the optical axis for light polarized along that axis. In CdSe with ℏω=1.80eV (690nm), the electron shift distance is ∼40% of the 0.25nm bond length and the peak current density is 5kAcm−2 for an optical intensity of 10MWcm−2; for CdS the corresponding experiment at ℏω=3.0eV (410nm) gives a shift distance ∼80% of the 0.26nm bond length with a peak current densit...
73 citations
TL;DR: In this paper, the free decay of non-helical relativistic magnetohydrodynamic turbulence is studied numerically, and found to exhibit cascading of magnetic energy toward large scales.
Abstract: The free decay of non-helical relativistic magnetohydrodynamic turbulence is studied numerically, and found to exhibit cascading of magnetic energy toward large scales. Evolution of the magnetic energy spectrum $P_M(k,t)$ is self-similar in time and well modeled by a broken power law with sub-inertial 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.
73 citations