The Experts below are selected from a list of 267 Experts worldwide ranked by ideXlab platform
Matteo Galaverni - One of the best experts on this subject based on the ideXlab platform.
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Rotation of Linear Polarization Plane from Cosmological Pseudoscalar Fields
Nuclear Physics B - Proceedings Supplements, 2009Co-Authors: Matteo Galaverni, Fabio FinelliAbstract:We discuss the rotation of the Linear Polarization plane generated by a cosmological pseudoscalar field acting as dark matter. We compare the Polarization power spectra obtained in the widely used approximation in which the Linear Polarization rotation angle is assumed constant along the line of sight and the exact result.
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rotation of Linear Polarization plane and circular Polarization from cosmological pseudoscalar fields
Physical Review D, 2009Co-Authors: Fabio Finelli, Matteo GalaverniAbstract:We discuss the rotation of the Linear Polarization plane and the production of circular Polarization generated by a cosmological pseudoscalar field. We compute analytically and numerically the propagation of the Stokes parameters from the last scattering surface for an oscillating and a monotonic decreasing pseudoscalar field. For the models studied in this paper, we show the comparison between the widely used approximation in which the Linear Polarization rotation angle is constant in time and the exact result.
Fabio Finelli - One of the best experts on this subject based on the ideXlab platform.
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Rotation of Linear Polarization Plane from Cosmological Pseudoscalar Fields
Nuclear Physics B - Proceedings Supplements, 2009Co-Authors: Matteo Galaverni, Fabio FinelliAbstract:We discuss the rotation of the Linear Polarization plane generated by a cosmological pseudoscalar field acting as dark matter. We compare the Polarization power spectra obtained in the widely used approximation in which the Linear Polarization rotation angle is assumed constant along the line of sight and the exact result.
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rotation of Linear Polarization plane and circular Polarization from cosmological pseudoscalar fields
Physical Review D, 2009Co-Authors: Fabio Finelli, Matteo GalaverniAbstract:We discuss the rotation of the Linear Polarization plane and the production of circular Polarization generated by a cosmological pseudoscalar field. We compute analytically and numerically the propagation of the Stokes parameters from the last scattering surface for an oscillating and a monotonic decreasing pseudoscalar field. For the models studied in this paper, we show the comparison between the widely used approximation in which the Linear Polarization rotation angle is constant in time and the exact result.
Gregg A. Wade - One of the best experts on this subject based on the ideXlab platform.
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Strong variable Linear Polarization in the cool active star II Peg
Proceedings of the International Astronomical Union, 2020Co-Authors: L. Rosén, Oleg Kochukhov, Gregg A. WadeAbstract:AbstractMagnetic fields of cool active stars are currently studied polarimetrically using only circular Polarization observations. This provides limited information about the magnetic field geometry since circular Polarization is only sensitive to the line-of-sight component of the magnetic field. Reconstructions of the magnetic field topology will therefore not be completely trustworthy when only circular Polarization is used. On the other hand, Linear Polarization is sensitive to the transverse component of the magnetic field. By including Linear Polarization in the reconstruction the quality of the reconstructed magnetic map is dramatically improved. For that reason, we wanted to identify cool stars for which Linear Polarization could be detected at a level sufficient for magnetic imaging. Four active RS CVn binaries, II Peg, HR 1099, IM Peg, and σ Gem were observed with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. Mean Polarization profiles in all four Stokes parameters were derived using the multi-line technique of least-squares deconvolution (LSD). Not only was Linear Polarization successfully detected in all four stars in at least one observation, but also, II Peg showed an extraordinarily strong Linear Polarization signature throughout all observations. This qualifies II Peg as the first promising target for magnetic Doppler imaging in all four Stokes parameters and, at the same time, suggests that other such targets can possibly be identified.
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Strong variable Linear Polarization in the cool active star II Peg
Monthly Notices of the Royal Astronomical Society, 2013Co-Authors: L. Rosén, Oleg Kochukhov, Gregg A. WadeAbstract:Magnetic fields of cool active stars are currently studied polarimetrically using only circular Polarization observations. Including Linear Polarization in the reconstruction of stellar magnetic fields allows more information about the magnetic field to be extracted and significantly improves the reliability of stellar magnetic field maps. The goal of this study is to initiate systematic observations of active stars in all four Stokes parameters and to identify cool stars for which Linear Polarization can be detected at a level sufficient for Zeeman-Doppler Imaging (ZDI). Four active RS CVn binaries, II Peg, HR 1099, IM Peg and sigma Gem, were observed with the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope during a time period from 2012 February to 2013 January. The least-squares deconvolution procedure was applied to derive mean Polarization profiles of all four Stokes parameters. Linear Polarization was detected in all four stars in at least one observation. At the same time, II Peg showed an exceptionally strong and highly variable Linear Polarization signature throughout all observations. This establishes II Peg as the first promising target for ZDI in all four Stokes parameters and suggests the feasibility of such an analysis with existing equipment for at least a few of the most active cool stars.
Songnian Fu - One of the best experts on this subject based on the ideXlab platform.
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SOA NonLinear Polarization Rotation With Linear Polarization Maintenance: Characterization and Applications
IEEE Journal of Selected Topics in Quantum Electronics, 2008Co-Authors: Songnian Fu, Minxue Wang, Wen-de Zhong, Ping Shum, Jian WuAbstract:We present characterization and applications of the nonLinear Polarization rotation (NPR) with Linear Polarization maintenance arising in Polarization-insensitive semiconductor optical amplifiers (SOAs). The NPR with Linear Polarization maintenance is characterized in terms of probe and pump power, bias current, pump Polarization, as well as wavelength. The NPR with Linear Polarization maintenance is then exploited for simultaneous inverted and noninverted Polarization-insensitive wavelength conversions (WCs) with 2R regeneration using a single Polarization beam splitter (PBS). WC of 10 Gb/s with 2R regeneration is experimentally demonstrated in the whole C-band with a power penalty reduction of 1.2 dB for the inverted WC and 0.8 dB for the noninverted WC. The NPR with Linear Polarization maintenance is also applied to perform on-off-keying (OOK) to Polarization-shift-keying (PolSK) format conversion in conjunction with WC function, where the power fluctuation caused by the SOA cross gain modulation (XGM) is successfully mitigated using two cascaded SOAs. The power fluctuation of the converted PolSK signal is reduced to less than 0.6 dB, while the extinction ratio (ER) of Polarization modulation is maintained at larger than 30 dB.
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NonLinear Polarization Rotation in Semiconductor Optical Amplifiers With Linear Polarization Maintenance
IEEE Photonics Technology Letters, 2007Co-Authors: Songnian Fu, Wen-de Zhong, P. Shum, Chongqing Wu, J. Q. ZhouAbstract:We propose a geometrical model based on the concept of dynamic eigenstates of Polarization to describe the behavior of nonLinear Polarization rotation (NPR) arising in semiconductor optical amplifiers (SOAs). The rotation axis with respect to either the bias current or the optical power variation is demonstrated on the Poincare sphere (PS), meanwhile a procedure to find the rotation axis is presented. Thus, the SOA-based NPR with Linear Polarization maintenance (zero Polarization ellipticity angle) can be achieved experimentally. The rotation of Polarization azimuth on the PS with respect to the bias current, the probe signal power, and the pump signal power variation is measured experimentally. The 180deg phase difference between the transverse electric and the transverse magnetic modes can be all achieved with Linear Polarization maintenance.
J. Q. Zhou - One of the best experts on this subject based on the ideXlab platform.
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NonLinear Polarization Rotation in Semiconductor Optical Amplifiers With Linear Polarization Maintenance
IEEE Photonics Technology Letters, 2007Co-Authors: Songnian Fu, Wen-de Zhong, P. Shum, Chongqing Wu, J. Q. ZhouAbstract:We propose a geometrical model based on the concept of dynamic eigenstates of Polarization to describe the behavior of nonLinear Polarization rotation (NPR) arising in semiconductor optical amplifiers (SOAs). The rotation axis with respect to either the bias current or the optical power variation is demonstrated on the Poincare sphere (PS), meanwhile a procedure to find the rotation axis is presented. Thus, the SOA-based NPR with Linear Polarization maintenance (zero Polarization ellipticity angle) can be achieved experimentally. The rotation of Polarization azimuth on the PS with respect to the bias current, the probe signal power, and the pump signal power variation is measured experimentally. The 180deg phase difference between the transverse electric and the transverse magnetic modes can be all achieved with Linear Polarization maintenance.