scholarly journals Artefacts of circumpolar cartography in radio pulsar polarization

2020 ◽  
Vol 495 (1) ◽  
pp. L118-L122 ◽  
Author(s):  
J Dyks
Keyword(s):  
Polarization State ◽  
Single Pulse ◽  
Vertical Axis ◽  
Radio Pulsar ◽  
Orthogonal Polarization ◽  
Polarization Angle ◽  
Polarization Effects ◽  
Poincaré Sphere ◽  
Power Content ◽  
Poincare Sphere

ABSTRACT Single-pulse data on radio pulsar polarization are traditionally presented in the form of two-dimensional grey-scale patterns with the pulse longitude and polarization angle (PA) on the horizontal and vertical axis, respectively. Such diagrams reveal several enigmatic polarization effects: (1) bifurcations and loops of PA curve under central pulse components, (2) vertical spread of flux at all PA values, (3) exchange of power content between PA tracks of two orthogonal polarization modes (OPMs), and (4) peripherically flat PA swings that span more than 180 deg. It is shown that all these phenomena result from passage of observed polarization state near the pure-V pole of Poincaré sphere. Much of their complexity results from cartographic transformation from Poincaré sphere to the longitude–PA plane. An odd number of near-pole passages produce apparent replacement of OPM power in the profile wings, although the same amount of flux keeps staying in each modal patch on the Poincaré sphere. The fitting of pulsar PA curves should therefore allow for transitions between the primary (strong) and secondary (weak) PA tracks. The Stokes space (or Poincaré sphere) representation of pulsar polarization data contains crucial polarization information and needs to accompany the traditional viewing if the published figures are to be fully useful for interpretation.

scholarly journals Circular polarization in radio pulsar PSR B1451−68: coherent mode transitions and intrabeam interference

2020 ◽  
Vol 501 (2) ◽  
pp. 2156-2173
Author(s):  
J Dyks ◽  
P Weltevrede ◽  
C Ilie
Keyword(s):  
Radio Pulsar ◽  
Vector Model ◽  
Polarization Degree ◽  
Orthogonal Polarization ◽  
Polarization Angle ◽  
Phase Lag ◽  
Pulse Profile ◽  
Oscillation Phase ◽  
Leave No Trace ◽  
Mode Transitions

ABSTRACT The radio emission of pulsar B1451−68 contains two polarization modes of similar strength, which produce two clear orthogonal polarization angle tracks. When viewed on a Poincaré sphere, the emission is composed of two flux patches that rotate meridionally as a function of pulse longitude and pass through the Stokes V poles, which results in transitions between orthogonal polarization modes (OPMs). Moreover, the ratio of power in the patches is inversed once within the profile window. It is shown that the meridional circularization is caused by a coherent OPM transition (COMT) produced by a varying mode ratio at a fixed quarter-wave phase lag. The COMTs may be ubiquitous and difficult to detect in radio pulsar data, because they can leave no trace in polarized fractions and they are described by equation similar to the rotating vector model. The circularization, which coincides with flux minima at lower frequency, requires that profile components are formed by radiation with an oscillation phase that increases with longitude in steps of 90○ per component. The properties can be understood as an interference pattern involving two pairs of linear orthogonal modes (or two non-orthogonal elliptic waves). The frequency-dependent coherent superposition of coplanar oscillations can produce the minima in the pulse profile, and thereby the illusion of components as separate entities. The orthogonally polarized signal that is left after such negative interference explains the enhancement of polarization degree that is commonly observed in the minima between profile components.

scholarly journals Radio pulsar polarization as a coherent sum of orthogonal proper mode waves

2019 ◽  
Vol 488 (2) ◽  
pp. 2018-2040 ◽  
Author(s):  
J Dyks
Keyword(s):  
Amplitude Ratio ◽  
Radio Pulsar ◽  
Vector Model ◽  
Natural Mode ◽  
Propagation Mode ◽  
Orthogonal Polarization ◽  
Polarization Angle ◽  
Phase Lag ◽  
Complex Behaviour ◽  
Mode Amplitude

ABSTRACT Radio pulsar polarization exhibits a number of complex phenomena that are classified into the realm of ‘beyond the rotating vector model’ (RVM). It is shown that these effects can be understood in geometrical terms, as a result of coherent and quasi-coherent addition of elliptically polarized natural mode waves. The coherent summation implies that the observed tracks of polarization angle (PA) do not always correspond to the natural propagation mode (NPM) waves. Instead, they are statistical average of coherent sum of the NPM waves, and can be observed at any (and frequency-dependent) distance from the natural modes. Therefore, the observed tracks of PA can wander arbitrarily far from the RVM, and may be non-orthogonal. For equal amplitudes of the NPM waves two pairs of orthogonal polarization modes (OPMs), displaced by 45°, can be observed, depending on the width of lag distribution. Observed pulsar polarization mainly results from two independent effects: the change of mode amplitude ratio and the change of phase lag. In the core region both effects are superposed on each other, which can produce so complex behaviour as observed in the cores of PSR B1933+16, B1237+25, and J0437−4715. Change of the phase lag with frequency ν is mostly responsible for the observed strong evolution of these features with ν. The coherent addition of orthogonal natural waves is a useful interpretive tool for the observed radio pulsar polarization.

Methods to Describe Optical Polarization State in Reflective Fiber Optic Current Sensor

2010 ◽  
Vol 44-47 ◽  
pp. 2254-2258
Author(s):  
Li Hui Wang ◽  
Xue Feng Wu ◽  
Jian Sun ◽  
Yu Ping Lu
Keyword(s):  
Fiber Optic ◽  
Light Wave ◽  
Polarization State ◽  
Current Sensor ◽  
Mathematical Representation ◽  
Jones Matrix ◽  
Optical Polarization ◽  
Poincaré Sphere ◽  
Poincare Sphere ◽  
Polarization Models

Evolution process of optical polarization state in reflective fiber optic current sensor(R-FOCS) is complex, light wave travels from polarization maintaining (PM) fiber with linear polarization state, and light wave travels from sensing head with circular polarization state. Focused on characteristics of optical polarization state in R-FOCS, we analyze the characteristics of optical polarization state in R-FOCS, and demonstrate the methods to build optical polarization models by using Poincare sphere and Jones matrix respectively. Jones matrix provides a mathematically rigorous method of tracking optical polarization state, however, it often leads to a less intuitive description. Despite the mathematical complexity of some phenomena observed in R-FOCS, the Poincare sphere provides elegant and simple geometrical interpretations. The two methods are combined and offer both a mathematical representation and an intuitive interpretation of nonreciprocal polarization effects in R-FOCS.

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

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Shuai Wang ◽  
Zi-Lan Deng ◽  
Yujie Wang ◽  
Qingbin Zhou ◽  
Xiaolei Wang ◽  
...  
Keyword(s):  
Circular Polarization ◽  
Polarization State ◽  
Essential Property ◽  
Polarization Conversion ◽  
Optical Elements ◽  
Arbitrary Polarization ◽  
Poincaré Sphere ◽  
Orthogonal State ◽  
Arbitrary Position ◽  
Poincare Sphere

AbstractThe 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 Poincaré 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 Poincaré 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 Poincaré sphere directly from unpolarized light can substantially extend the scope of meta-optics and dramatically promote state-of-the-art nanophotonic devices.

scholarly journals Orthogonality derivation of polarization state based on Poincaré sphere

2021 ◽  
Vol 1978 (1) ◽  
pp. 012015
Author(s):  
Zhanling Wang ◽  
Jiankai Huang ◽  
Chen Pang
Keyword(s):  
Polarization State ◽  
Poincaré Sphere ◽  
Poincare Sphere

scholarly journals Detection of degenerate Stokes index states

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Gauri Arora ◽  
S. Deepa ◽  
Saba N. Khan ◽  
P. Senthilkumaran
Keyword(s):  
Angular Momentum ◽  
Phase Distribution ◽  
Polarization State ◽  
Polarization Distribution ◽  
Detection Scheme ◽  
Detection Techniques ◽  
Poincaré Sphere ◽  
Phase Singularities ◽  
Poincare Sphere ◽  
Stokes Polarimetry

AbstractStokes phase is the phase difference between orthogonal component states in the decomposition of any polarization state. Phase singularities in the Stokes phase distribution are Stokes singularities of an inhomogeneous polarization distribution. Under circular decomposition, Stokes phase distribution $$(\phi _{12})$$ ( ϕ 12 ) represents polarization azimuth $$(\gamma )$$ ( γ ) distribution and the singularities present in it are polarization singularities. Therefore, the charge of the Stokes vortices depicted as Stokes index $$\sigma _{12}$$ σ 12 is an important parameter associated with the polarization singularity. The Hybrid order Poincaré sphere (HyOPS)/Higher order Poincaré sphere (HOPS) beams, all having same Stokes index, contain a Stokes singularity at the center of the beam as these beams are constructed by vortex superposition. These beams, being superposition of orthogonal orbital angular momentum (OAM) states in orthogonal spin angular momentum (SAM) states can offer great multiplexing capabilities in communication. In this article, we identify these degenerate Stokes index states and discuss the ways and means of lifting this degeneracy. Otherwise, there are limitations on intensity based detection techniques, where demultiplexing or segregation of different HOPS/HyOPS beams is warranted. The method adduced here uses the diffraction of these beams through an equilateral triangular aperture in combination with polarization transformation as a probe to lift the Stokes index/Stokes phase degeneracy. Successively, the novelty of the detection scheme is discussed in the context of beams with alike polarization distributions where even the technique of Stokes polarimetry fails to predict the OAM and SAM content of the beam.

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