Optical polarization

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

Multi-wavelength variability properties of Fermi blazar S5 0716+714

Abstract: S5 0716+714 is a typical BL Lacertae object. In this paper we present the analysis and results of long term simultaneous observations in the radio, near-infrared, optical, X-ray and $\gamma$-ray bands, together with our own photometric observations for this source. The light curves show that the variability amplitudes in $\gamma$-ray and optical bands are larger than those in the hard X-ray and radio bands and that the spectral energy distribution (SED) peaks move to shorter wavelengths when the source becomes brighter, which are similar to other blazars, i.e., more variable at wavelengths shorter than the SED peak frequencies. Analysis shows that the characteristic variability timescales in the 14.5 GHz, the optical, the X-ray, and the $\gamma$-ray bands are comparable to each other. The variations of the hard X-ray and 14.5 GHz emissions are correlated with zero-lag, so are the V band and $\gamma$-ray variations, which are consistent with the leptonic models. Coincidences of $\gamma$-ray and optical flares with a dramatic change of the optical polarization are detected. Hadronic models do not have the same nature explanation for these observations as the leptonic models. A strong optical flare correlating a $\gamma$-ray flare whose peak flux is lower than the average flux is detected. Leptonic model can explain this variability phenomenon through simultaneous SED modeling. Different leptonic models are distinguished by average SED modeling. The synchrotron plus synchrotron self-Compton (SSC) model is ruled out due to the extreme input parameters. Scattering of external seed photons, such as the hot dust or broad line region emission, and the SSC process are probably both needed to explain the $\gamma$-ray emission of S5 0716+714.

Large‐scale alignment of optical polarizations from distant QSOs using coordinate‐invariant statistics

Abstract: We introduce several coordinate-invariant statistical procedures in order to test for alignment of polarizations of electromagnetic radiation from astrophysical sources. A large-scale alignment of optical polarizations from distant quasi-stellar objects (QSOs) has recently been observed by Hutsemekers and collaborators. The new statistical procedures are based on comparing polarizations at different angular coordinates by making a parallel transport. The results of these statistical procedures continue to support the existence of the large-scale alignment effect in the QSO optical polarization data. The alignment is found to be much more pronounced in the data sample with low degrees of polarization, p ≤ 2 per cent. This suggests that the alignment may be attributed to some propagation effect. The distance scale over which the alignment effect is dominant is found to be of order 1 Gpc. We also find that a very large-scale alignment is present in the large-redshift, z ≥ 1, data sample. In fact, the data sample with z ≥ 1 appears to be aligned over the entire celestial sphere. This alignment is seen independent of the degree of polarization of the sources. We discuss possible physical effects, such as extinction and pseudoscalar-photon mixing, which may be responsible for the observations.

Polarization optics of index-gradient optical waveguide fibers.

Abstract: An investigation of the polarization optical properties of index-gradient glass fibers confirmed the applicability of the linear birefringent model to fibers of this type. The phase retardation (delta(s) = 58 degrees /cm) is homogeneously distributed along the whole length of the fiber. The depolarization occurring when the incident polarization angle coincides with the fast (or slow) axis of the fiber is negligibly small. The measuring technique employed allows the phase retardation between the wave components in the privileged directions within the fiber to be determined as a function of the temperature (Deltadelta(s)/DeltaT = 0.09 degrees /K cm). As the fiber is twisted the polarization vector rotates synchronously with the twisted endface of the fiber.

Polarisation modulation-the measurement of linear and circular dichroism

Abstract: Dichroism is usually measured using two separate polarisation spectra. However, when the difference in the transmission of oppositely polarised light is very small, the superior method of modulating the polarisation of a single light beam should be used. The techniques involved in this method are reviewed.