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Circular polarization

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


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Journal ArticleDOI
TL;DR: In this article, the Stokes parameters from the last scattering surface for an oscillating and a monotonic decreasing pseudoscalar field were computed analytically and numerically.
Abstract: 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.

114 citations

Journal ArticleDOI
TL;DR: The polarization parameters introduced are formulated in the frequency domain, thereby further generalizing the theory to allow for wide-band electromagnetic waves in contrast to the traditional quasi-monochromatic formulation.
Abstract: In this paper, generalizations of the Stokes parameters and alternative characterizations of three-dimensional (3D) time-varying electromagnetic fields is introduced. One of these characteristics is the normal of the polarization plane, which, in many cases of interest, is parallel (or antiparallel) to the direction of propagation. Others are the two spectral density Stokes parameters which describe spectral intensity and circular polarization. The analysis is based on the spectral density tensor. This tensor is expanded in a base composed of the generators of the SU(3) symmetry group, as given by Gell-Mann and Y. Ne'eman [The Eight-fold Way (Benjamin, New York, 1964)] and the coefficients of this expansion are identified as generalized spectral density polarization parameters. The generators have the advantage that they obey the same algebra as the Pauli spin matrices, which is the base for expanding the 2D spectral density tensor with the Stokes parameters as coefficients. The polarization parameters introduced are formulated in the frequency domain, thereby further generalizing the theory to allow for wide-band electromagnetic waves in contrast to the traditional quasi-monochromatic formulation.

113 citations

Journal ArticleDOI
TL;DR: In this paper, it was shown that the simple line zeros predicted for interference fringes by scalar wave theory have an underlying polarization structure consisting of two C lines and an S surface.
Abstract: Electromagnetic waves generally contain three kinds of singularities called C lines, S surfaces and disclinations. These singularities are features of the transverse electric and transverse magnetic fields of the waves and all three kinds usually occur in any given wavefield. We show that in the case of nominally uniformly polarized waves, the simple line zeros predicted for interference fringes by scalar wave theory in fact have an underlying polarization structure consisting of two C lines and an S surface. In consequence, virtually all monochromatic electromagnetic waves contain polarization states ranging from right-hand circular, through linear to left-hand circular polarization. Singularities of the electric and magnetic fields are not generally coincident in space; in fact they can be separated by arbitrarily large distances. The separation of the electric and magnetic S surfaces means that there are regions where the transverse electric and transverse magnetic vectors counterrotate. C lines are probably the most significant of the singularities, since they are not only structural features of polarization, but also organize the time structure of electromagnetic waves. They play a crucial role in determining the topology of disclinations in paraxial wavefields. In pulsed electromagnetic waves all three singularities move through space. Their behaviour, including interactions between pairs of C lines, S surfaces or disclinations, which are likely to be frequent events in pulsed waves, is discussed.

113 citations

Journal ArticleDOI
TL;DR: It is shown that an azimuthal vortex beam provides good images for a variety of object structures and pinhole sizes, and plays an important role in high-numerical-aperture optical imaging.
Abstract: Imaging of object structures using cylindrical vector beams in an aplanatic solid immersion lens (SIL) microscope is investigated. Based on a complete optical model of an aplanatic SIL microscope, images of some object structures using radial polarization, azimuthal polarization, and azimuthal vortex beams are simulated. Some interesting imaging effects of these object structures are observed. For example, counterintuitively, it is found that, compared to linear and circular polarizations, radial polarization requires a larger pinhole to acquire a good image and resolution. Similarly, it is shown that an azimuthal vortex beam provides good images for a variety of object structures and pinhole sizes. Theories and explanations are provided to justify the observed effects. The presented results play an important role in high-numerical-aperture optical imaging.

113 citations

Journal ArticleDOI
TL;DR: In this paper, the magnetic field strength of the H2O masers around the Mira variable stars U Her and U Ori and the supergiant VX Sgr was analyzed.
Abstract: Through polarization observations, circumstellar masers are excellent probes of the magnetic field in the envelopes of late-type stars. Whereas observations of the polarization of the SiO masers close to the star and on the OH masers much further out were fairly commonplace, observations of the magnetic field strength in the intermediate density and temperature region where the 22 GHz H2O masers occur have only recently become possible. Here we present the analysis of the circular polarization, due to Zeeman splitting, of the H2O masers around the Mira variable stars U Her and U Ori and the supergiant VX Sgr. We present an upper limit of the field around U Her that is lower but consistent with previous measurements, reflecting possible changes in the circumstellar envelope. The field strengths around U Ori and VX Sgr are shown to be of the order of several Gauss. Moreover, we show for the first time that large scale magnetic fields permeate the circumstellar envelopes of an evolved star; the polarization of the H2O masers around VX Sgr reveals a dipole field structure. We discuss the coupling of the magnetic field with the stellar outflow, as such fields could possibly be the cause of distinctly aspherical mass-loss.

113 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023384
2022821
2021685
2020927
20191,060
2018968