Optical polarization

About: Optical polarization is a research topic. Over the lifetime, 13992 publications have been published within this topic receiving 244284 citations.

Discovery of VHE gamma-rays from the blazar 1ES 1215+303 with the MAGIC Telescopes and simultaneous multi-wavelength observations

Abstract: Context. We present the discovery of very high energy (VHE, E > 100GeV) gamma-ray emission from the BL Lac object 1ES 1215+303 by the MAGIC telescopes and simultaneous multi-wavelength data in a broad energy range from radio to gamma-rays. Aims. We study the VHE gamma-ray emission from 1ES 1215+303 and its relation to the emissions in other wavelengths. Methods. Triggered by an optical outburst, MAGIC observed the source in January-February 2011 for 20.3 hrs. The target was monitored in the optical R-band by the KVA telescope that also performed optical polarization measurements. We triggered target of opportunity observations with the Swift satellite and obtained simultaneous and quasi-simultaneous data from the Fermi Large Area Telescope and from the Metsahovi radio telescope. We also present the analysis of older MAGIC data taken in 2010. Results. The MAGIC observations of 1ES 1215+303 carried out in January-February 2011 resulted in the first detection of the source at VHE with a statistical significance of 9.4 sigma. Simultaneously, the source was observed in a high optical and X-ray state. In 2010 the source was observed in a lower state in optical, X-ray, and VHE, while the GeV gamma-ray flux and the radio flux were comparable in 2010 and 2011. The spectral energy distribution obtained with the 2011 data can be modeled with a simple one zone SSC model, but it requires extreme values for the Doppler factor or the electron energy distribution.

Generation, transmission and coherent detection of 11.2 Tb/s (112×100Gb/s) single source optical OFDM superchannel

Abstract: A novel scheme to generate coherent 112 optical sub-carriers with subcarrier spacing of 25GHz is proposed and experimentally demonstrated. By using these coherent optical subcarriers, we have successfully generated 10-Tbit/s (112×100Gbit/s) single channel optical OFDM polarization multiplexing QPSK signal with the bandwidth of 2.8THz and the optical signal noise ratio greater than 20dB (0.1nm bandwidth for each subchannel). We have transmitted the 11.2-Tbit/s optical OFDM signal over 640-km SMF-28 with an amplifier span of 80km and EDFA-only.

Directed metalation route to ferroelectric liquid crystals with a chiral fluorenol core: the effect of restricted rotation on polar order.

Abstract: A new series of smectic C* (SmC*) mesogens containing a chiral (R)-2-octyloxy side chain and either a fluorenone (2a−e) or chiral fluorenol (3a−e) core were synthesized using a combined directed ortho metalation−directed remote metalation strategy. The SmC* phase formed by the fluorenol mesogens is more stable and has a wider temperature range than that formed by the fluorenone mesogens, which may be ascribed to intermolecular hydrogen bonding according to variable-temperature FT-IR measurements. The C11 fluorenol mesogens (R,R)-3d and (S,R)-3d were obtained in diastereomerically pure form and gave reduced polarization (Po) values of +106 and +183 nC/cm2, respectively, at 10 K below the SmA*−SmC* phase transition temperature. The difference in Po values suggests that the chiral fluorenol core contributes to the spontaneous polarization of the SmC* phase. This is ascribed to the bent shape of the fluorenol core, which should restrict its rotation with respect to the side chains in the SmC* phase and favor ...

Light scattering by multiple red blood cells

Abstract: The interaction of light with multiple red blood cells was systematically investigated by the finite-difference time-domain method (FDTD). The simulations showed that the lateral multiple scattering between red blood cells is very weak and that the polarization has an almost insignificant influence on the distribution of the scattered light. The numerical results of the FDTD method were compared with the results from the Rytov approximation and the discrete dipole approximation (DDA). The agreement with the DDA was excellent.

A panchromatic review of thermal and nonthermal active galactic nuclei

Abstract: The first short part of this review is a general, but very detailed, critique of the literature advocating a class of Seyfert galaxies intrinsically lacking broad emission lines. My conclusion is that there is little or no evidence for such objects. Panchromatic properties of all types of radio loud AGN are then reviewed in detail. Radio galaxies usually show subparsec-scale radio core sources, jets, and a pair of giant radio lobes. The optical spectra sometimes show only relatively weak lines of low-ionization ionic species, and no clear nuclear continuum in the optical or UV region of the spectrum. Some show strong high-ionization narrow lines. Finally, a few radio galaxies add broad bases onto the permitted lines. These spectral categories are the same as those for radio-quiet AGN and quasars. By the 1980s, data from optical polarization and statistics of the radio properties required that many narrow line radio galaxies do in fact produce strong optical/UV continuum. This continuum and the broad line emission are hidden from the line of sight by dusty, roughly toroidal gas distributions, but they are seen in polarized flux. The radio galaxies with hidden quasars are referred to as "thermal." Do all radio galaxies harbor hidden quasars? We now know the answer using the radio, infrared, optical and X-ray properties. Near the top of the radio luminosity function, for FRII, GPS, and CSS galaxies, the answer is yes. At somewhat lower luminosities, many do not. At the lowest radio luminosities, most do not. Instead these "nonthermal" weakly-accreting galaxies manifest their energetic output only as kinetic energy in the form of synchrotron jets. This applies to all types of radio galaxies, big FR II doubles, as well as the small young GPS and CSS sources. Only a few FR I sources are of the thermal type.