Circular polarization

About: Circular polarization is a research topic. Over the lifetime, 15201 publications have been published within this topic receiving 234418 citations.

Circular polarization in pulsar integrated profiles

Abstract: We present a systematic study of the circular polarization in pulsar integrated profiles, based on published polarization data. For core components, we find no significant correlation between the sense change of circular polarization and the sense of linear position-angle variation. Circular polarization is not restricted to core components and, in some cases, reversals of circular polarization sense are observed across the conal emission. In conal double profiles, the sense of circular polarization is found to be correlated with the sense of position-angle variation. Pulsars with a high degree of linear polarization often have one hand of circular polarization across the whole profile. For most pulsars, the sign of circular polarization is the same at 50-cm and 20-cm wavelengths, and the degree of polarization is similar, albeit with a wide scatter. However, at least two cases of frequency-dependent sign reversals are known. This diverse behaviour may require more than one mechanism to generate circular polarization.

High-flux normal incidence monochromator for circularly polarized synchrotron radiation

Abstract: A 6.5‐m normal incidence monochromator installed at the storage ring BESSY, which is optimized for a high throughput of circularly polarized off‐plane radiation at moderate resolution is described. The monochromator employs two exit slits and is specially designed and used for low‐signal experiments such as spin‐ and angle‐resolved photoelectron spectroscopy on solids, adsorbates, free atoms, and molecules. The Monk–Gillieson mounting (plane grating in a convergent light beam) allows for large apertures with relatively little astigmatism. With two gratings, a flux of more than 1011 photons s−1 bandwidth−1 (0.2–0.5 nm) with a circular polarization of more than 90% in the wavelength range from 35 to 675 nm is achieved.

MOJAVE: Monitoring of jets in active galactic nuclei with VLBA experiments. II. First-epoch 15 GHz circular polarization results

Abstract: We report first-epoch circular polarization results for 133 active galactic nuclei in the MOJAVE program to monitor the structure and polarization of a flux-limited sample of extragalactic radio jets with the VLBA at 15 GHz. We found strong circular polarization (≥0.3%) in approximately 15% of our sample. The circular polarization was usually associated with jet cores; however, we did find a few strong jet components to be circularly polarized. The levels of circular polarization were typically in the range of 0.3%-0.5% of the local Stokes I value. We found no strong correlations between fractional circular polarization of jet cores and source type, redshift, EGRET detections, linear polarization, or other observed parsec-scale jet properties. There were differences between the circular-to-linear polarization ratios of two nearby galaxies versus more distant quasars and BL Lac objects. We suggest this is because the more distant sources have either (1) less depolarization of their linear polarization, and/or (2) poorer effective linear resolution, and therefore, their VLBA cores apparently contain a larger amount of linearly polarized jet emission. The jet of 3C 84 shows a complex circular polarization structure, similar to observations by Homan & Wardle 5 years earlier; however, much of the circular polarization seems to have moved, consistent with a proper motion of 0.06c. The jet of 3C 273 also has several circularly polarized components, and we find that their fractional circular polarization decreases with distance from the core.

Arbitrary polarization conversion dichroism metasurfaces for all-in-one full Poincaré sphere polarizers.

Abstract: The control of polarization, an essential property of light, is of broad scientific and technological interest. Polarizers are indispensable optical elements for direct polarization generation. However, arbitrary polarization generation, except that of common linear and circular polarization, relies heavily on bulky optical components such as cascading linear polarizers and waveplates. Here, we present an effective strategy for designing all-in-one full Poincare sphere polarizers based on perfect arbitrary polarization conversion dichroism and implement it in a monolayer all-dielectric metasurface. This strategy allows preferential transmission and conversion of one polarization state located at an arbitrary position on the Poincare sphere to its handedness-flipped state while completely blocking its orthogonal state. In contrast to previous methods that were limited to only linear or circular polarization, our method manifests perfect dichroism of nearly 100% in theory and greater than 90% experimentally for arbitrary polarization states. By leveraging this attractive dichroism, our demonstration of the generation of polarization beams located at an arbitrary position on a Poincare sphere directly from unpolarized light can substantially extend the scope of meta-optics and dramatically promote state-of-the-art nanophotonic devices.

Generation of Airy vortex and Airy vector beams based on the modulation of dynamic and geometric phases.

Abstract: We propose a novel method for the generation of Airy vortex and Airy vector beams based on the modulation of dynamic and geometric phases. In our scheme, the Airy beam is generated by the dynamic phase with a spatial light modulator, and the vortex phase or the vector polarization is modulated by the geometric phase with a dielectric metasurface. The modulation of the geometric phase provides an extra degree of freedom to manipulate the phase and the polarization of Airy beams. This scheme can be extended to generate any other types of optical beams with desirable phase and polarization.