Showing papers on "Circular polarization published in 1986"
TL;DR: In this paper, a method for generating circularly polarized radiation from an array composed of linearly polarized elements having unique angular and phase arrangements is presented, which can significantly reduce the complexity, weight, and RF loss of the array feed.
Abstract: A method is presented for generating circularly polarized radiation from an array composed of linearly polarized elements having unique angular and phase arrangements. With this technique the complexity, weight, and RF loss of the array feed can be significantly reduced, especially in a large array. This uniquely formed array has the capability of generating excellent circular polarization (CP) over a relatively wide frequency bandwidth. In addition, the array is capable of scanning its main beam in the principal planes to relatively wide angles from its broadside direction without serious degradation to its CP quality. Another feature of this uniquely arranged array is a reduction in the occurrence of mutual coupling. The discussion in this paper places special emphasis on the microstrip type of radiator, although the technique presented can be adapted to most types of linearly polarized antenna elements.
508 citations
TL;DR: In this paper, an Archimedean planar spiral antenna is numerically analyzed in the presence of a conducting plane reflector, and it is shown that the spiral antenna has two distinct regions in the current distribution, which explain the radiation of a circularly polarized wave for the outer circumference C ranging over about 1.3 λ and C > 2.9 λ, where λ is a free-space wavelength.
Abstract: An Archimedean planar spiral antenna is numerically analyzed in the presence of a conducting plane reflector. The analysis shows that the spiral antenna backed by the plane reflector has two distinct regions in the current distribution, which explain the radiation of a circularly polarized wave for the outer circumference C ranging over about 1.3 \lambda and C > 2.9 \lambda , where \lambda is a free-space wavelength. Further consideration is given to a truncated spiral antenna whose outer circumference is on the order of 1.4 \lambda . The truncated spiral antenna maintains a decaying current distribution and radiates a circularly polarized wave over a 1:1.2 frequency bandwidth. It is also demonstrated that a power gain on the order of 8.5 dB is realized over the same frequency range.
350 citations
TL;DR: In this article, a set of coupled-wave equations that characterize the Bragg regime has been derived for the 〈110〉 and the ¾¾ ¾ crystallographic orientations typically employed in volume holographic storage and multi-wave-mixing applications.
Abstract: The polarization properties of diffraction from volume phase gratings in photorefractive sillenite crystals such as bismuth silicon oxide (Bi12SiO20), bismuth germanium oxide (Bi12GeO20), and bismuth titanium oxide (Bi12TiO20) are strongly modified by the presence of concomitant natural optical activity and electric-field-induced linear birefringence. A set of coupled-wave equations that characterize the Bragg regime has been derived for the 〈110〉 and the 〈001〉 crystallographic orientations typically employed in volume holographic storage and multiwave-mixing applications. The predicted anisotropic behavior of the grating diffraction is experimentally confirmed, and a significant efficiency improvement is shown to occur for proper choice of the operating mode and the probe beam polarization in a given configuration.
174 citations
TL;DR: This approach clearly shows the possibility of realizing a new class of devices, namely, a linear coherent amplifier–mixer and an optically activated polarization switch or a phase-sensitive optical discriminator with high fanout.
Abstract: Exact solutions for the evolution of the state of polarization along a nonlinear single-mode birefringent fiber are given by means of the Poincare sphere representation. This approach clearly shows the possibility of realizing a new class of devices, namely, a linear coherent amplifier–mixer and an optically activated polarization switch or a phase-sensitive optical discriminator with high fanout.
106 citations
TL;DR: If the electrons are emitted in single-step, nonresonant coherent processes, rather than stepwise excitation, the centrifugal potential barrier in the atomic Hamiltonian produces this suppression of the cross section.
Abstract: Multiphoton ionization in xenon has been studied with 1064-nm circularly polarized coherent light, producing electrons with energies up to 15 eV. A strong suppression of the cross section is observed for electrons below 4 eV, but not for linearly polarized light at the same intensity. We show that if the electrons are emitted in single-step, nonresonant coherent processes, rather than stepwise excitation, the centrifugal potential barrier in the atomic Hamiltonian produces this suppression.
104 citations
TL;DR: In this paper, the discovery and study of a PG white dwarf which shows strong linear and circular polarization modulated with a rotation period of 3 hr 24 min is reported. But the star is more highly magnetic than even Grw +70 deg 8247, with absorption components of hydrogen in its optical and UV spectra corresponding to fields from 200 to more than 500 MG.
Abstract: The discovery and study of a PG white dwarf which shows strong linear and circular polarization modulated with a rotation period of 3 hr 24 min is reported. The new star, PG 1031 + 234, is more highly magnetic than even Grw +70 deg 8247, with absorption components of hydrogen in its optical and UV spectra corresponding to fields from 200 to more than 500 MG. An asymmetric dependence of polarization on rotational phase shows that the surface field structure on the star is more complex than a simple centered dipole. The basic observational features can be well reproduced by a rotating star containing an oblique centered dipole punctuated near its magnetic equator by a high-field spot containing primarily radial field lines.
88 citations
TL;DR: In this article, a 6.5m normal incidence monochromator installed at the storage ring BESSY was optimized for a high throughput of circularly polarized off-plane radiation at moderate resolution.
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.
88 citations
80 citations
Book•
01 Jan 1986
TL;DR: An Introduction to Antennas as mentioned in this paper describes wave polarization in terms of wave reflection and transmission and partial polarization, and describes the characteristics of some antennas, as well as their properties.
Abstract: An Introduction to Antennas. Representation of Wave Polarization. Polarization Matching of Antennas. Polarization Characteristics of Some Antennas. Generation of General Polarizations. Polarization Changes by Reflection and Transmission. Partial Polarization. Polarization Measurements. Appendixes.
76 citations
TL;DR: In ellipsometry of rough surfaces, the commonly used parameters, psi and delta, are insufficient to characterize completely the changes in polarization state which occur when light is reflected from a rough surface.
Abstract: In ellipsometry of rough surfaces, the commonly used parameters, psi and delta, are insufficient to characterize completely the changes in polarization state which occur when light is reflected from a rough surface. When an experimentally determined Mueller matrix is available, parameters indicative of depolarization, cross polarization, and change in ellipticity can be found. When the Mueller matrix is regarded as an operator mapping input polarization states depicted on a Poincare sphere to output states in a similar coordinate system, these new parameters can be illustrated in terms of their effects on the Poincare sphere. The depolarization and cross polarization parameters correlate with specimen roughness and reflectance.
70 citations
Patent•
14 Nov 1986TL;DR: In this article, a switchable color filter employs chiral liquid crystal circular polarizers to minimize the attenuation of light passing through a system in which it is incorporated, which can be applied to a wide range of applications.
Abstract: A switchable color filter employs chiral liquid crystal circular polarizers to minimize the attenuation of light passing through a system in which it is incorporated. One preferred embodiment (12) of the switchable color filter includes a light modulator (32) positioned between the light polarizing assembly (20) and first and second chiral liquid crystal cells (36 and 38). The light polarizing assembly receives unpolarized light and transmits circularly polarized light of colors included within first and second narrow color bands. The first chiral cell reflects incident light within the first color band and in a first polarization state, and the second chiral cell reflects incident light within the second color band and in a second polarization state. The light modulator cooperates with a switching circuit (34) to selectively provide first and second polarization switching states. The first switching state causes light within the first color band to exit the color filter and blocks light within the second color band from exiting the color filter, and the second switching state causes light within the second color band to exit the color filter and block light within the first color band from exiting the color filter. Another preferred embodiment (100) of the switchable color filter is capable of receiving light within three color bands and selectively providing a light output of one of three colors. Either embodiment of the switchable color filter can be advantageously implemented in systems (10 and 100) that are insensitive to a restricted viewing angle, which stems from the use of chiral liquid crystal circular polarizers.
TL;DR: It is argued that even at low doping concentrations, excitons are heavily dressed by charge- and spin-density excitations of the Fermi sea, implying, already in that limit, a Stokes shift between emission and absorption.
Abstract: We investigate the physical processes which determine the optical spectra of modulation-doped semiconductor quantum-well structures as a function of doping. We argue that even at low doping concentrations, excitons are heavily dressed by charge- and spin-density excitations of the Fermi sea, implying, already in that limit, a Stokes shift between emission and absorption. For all doping concentrations, the charge and spin polarization of the Fermi sea due to many-body effects leads to an enhancement of the symmetry breaking in quantum-well structures, which may explain polarization anomalies observed in luminescence.
TL;DR: The first application of a cross-beam polarization spectrometry technique with a pulsed dye laser in flames indicates that polarization spectroscopy is a promising technique in the area of combustion diagnostics.
Abstract: We report the first application of a cross-beam polarization spectrometry technique with a pulsed dye laser in flames. Saturation, curve of growth, and dependence of the polarization signal on the crossing angle between the probe and pump beams have been experimentally investigated. The results indicate that polarization spectroscopy is a promising technique in the area of combustion diagnostics.
TL;DR: Richmond's reaction integral equation method was used to design a rectangular microstrip patch to produce a circular polarization in this article, where a rectangular patch with the aspect ratio a = W{x}/W_{y}, in the range 1.015-1.02 and corner fed by a microstrip line, produces circular polarization.
Abstract: Richmond's reaction integral equation method is used to design a rectangular microstrip patch to produce a circular polarization. A rectangular patch with the aspect ratio a = W_{x}/W_{y} , in the range 1.015- 1.02 and corner fed by a microstrip line, produces circular polarization. For substrate with thickness d = 0.16 cm, a = 1.017 the nearly square patch gives maximum bandwidth.
Patent•
11 Dec 1986TL;DR: In this article, a microstrip antenna employing a rectangular radiating element having a Uaped slot oriented parallel to the length of the radiating elements and employing a single feedline coplanar with the radii was proposed.
Abstract: A microstrip antenna employing a rectangular radiating element having a Uaped slot oriented parallel to the length of the radiating element and employing a single feedline coplanar with the radiating element. The slotted radiating element has three resonances: a length resonance polarized parallel to the length of the element; a width resonance polarized parallel to the width of the element; and a slot resonance polarized parallel to the length of the element. By proper selection of the length and location of the slot, the frequency of the slot resonance can be placed such that a region of circular polarization occurs between the width resonance and the slot resonance. Alternatively, a region of circular polarization can be created between the length resonance and the width resonance since they are also polarized perpendicular to each other. Thus the U-slotted antenna provides either triple-frequency operation or dual-frequency operation in which one frequency is circularly polarized and the other frequency is elliptically polarized.
Patent•
05 Jun 1986
TL;DR: A dual mode circularly polarized horn radiator was used in this article for the measurement of near field radiation pattern of an anechoic chamber with a buffered radiating aperture, which allowed a plurality of horns to be arranged in an array with minimal mutual coupling between the horns.
Abstract: A dual mode circularly polarized horn radiator is useful in the testing of radiation apparatus in an anechoic chamber. The horn has a buffered radiating aperture which permits a plurality of the horns to be arranged in an array with minimal mutual coupling between the horns. The radiating aperture is located at an end of a conic section, of low flare angle, and has a diameter of one free-space wavelength of the radiation to be radiated from or received at the horn. This permits use of the horn for measurement of near field radiation pattern of apparatus under test. The horn includes an orthomode tee having mutually perpendicular rectangular waveguides extending therefrom, and being coupled thereby to a circular port. A polarizer connects the circular port of the tee to the conic section, and includes two sets of diametrically opposed pins for conversion of both right-hand and left-hand circular polarizations to linearly polarized radiation. A multiple-vaned structure at the tee and the ports thereof isolates the two linearly polarized waves to their respective rectangular waveguide ports.
TL;DR: In this paper, the polarization due to the overlap of Zeeman components that arises in the radiation from astrophysical masers was investigated and the essential simplicity of this previously unrecognized effect is a compelling argument in its favor as the basic cause for the strong, net circular polarization of the OH masers.
Abstract: Calculational methods are presented and utilized in an idealized case to evaluate the polarization due to the overlap of Zeeman components that arises in the radiation from astrophysical masers. The essential simplicity of this previously unrecognized effect is a compelling argument in its favor as the basic cause for the strong, net circular polarization of the OH masers. Observations can then be interpreted to yield an estimate for the strength of the magnetic fields in the masing regions, even when Zeeman pairs cannot be identified as is usually the situation. Magnetic fields of approximately a milligauss or greater are inferred to be common in the masing gas associated with regions of star formation. This estimate should be considerably more general than the specific assumptions of our calculation.
TL;DR: In this article, a sample of 10 decimetric broadband pulsations were observed in 1980-1983 and analyzed in polarization, and the high circular polarization was interpreted to be determined by the emission mechanism itself, not by propagation effects or cut-offs (contrary to the metric type I noise storms).
Abstract: A sample of 10 decimetric broadband pulsations were observed in 1980–1983 and analyzed in polarization. Half of the data set was 85–100% circularly polarized, the other half showed a mild polarization of 15–55%. The polarization is constant in time and frequency for the strongly polarized group. All the mildly polarized bursts originate from near the limb; the lower degree of circular polarization is likely to be caused by depolarization due to propagation effects. The degree of polarization is constant throughout the event, but varies in frequency for the mild polarized group. Following the leading spot hypothesis, the magneto-ionic mode of the emission was found to be extraordinary. The high circular polarization of the pulsations was interpreted to be determined by the emission mechanism itself, not by propagation effects or cut-offs (contrary to the metric type I noise storms). Implications for pulsation models are discussed.
TL;DR: In this article, a segmentation technique coupled with cavity model has been used to analyze square ring and crossed-strip microstrip patch antennas for circular polarization, which is found to predict the characteristics of antennas correctly, as evident from the close agreement between the calculated and measured results for resonant frequency, input impedance, radiation patterns, and bandwidth.
Abstract: Segmentation technique coupled with cavity model have been used to analyze square ring and crossed-strip microstrip patch antennas for circular polarization. This technique is found to predict the characteristics of antennas correctly, as is evident from the close agreement between the calculated and measured results for resonant frequency, input impedance, radiation patterns, and bandwidth. Square ring antenna has been found to have larger impedance bandwidth and axial ratio bandwidth because of lower Q . Crossed-strip antenna has larger size and thus fabrication tolerances can be relaxed.
TL;DR: In this paper, the analysis of two-photon absorption by atomic hydrogen is generalized to the case of two incident beams with arbitrary direction and polarization (including circular polarization), and the second-order matrix elements responsible for two-poton absorption are transformed into a finite sum consisting of the product of a radial part and an angular part.
Abstract: Within the framework of nonrelativistic quantum mechanics, the analysis of the two-photon absorption by atomic hydrogen is generalized to the case of two incident beams with arbitrary direction and polarization (including circular polarization). In the dipole approximation, the second-order matrix elements responsible for two-photon absorption are transformed into a finite sum consisting of the product of a radial part and an angular part. Exact calculation of the angular part predicts that, for the s–s transition only, transparency is obtained regardless of the frequencies of the two beams with perpendicular polarizations. In addition, circularly polarized light is found to be more efficient (up to a factor of 1.5) for the s–d two-photon transition. The radial parts of the matrix elements are accurately evaluated by using the Coulomb Green’s function technique and an implicit technique of Dalgarno and Lewis. Their calculation indicates that “zeros” exist in the two-photon absorption spectrum, thereby predicting that absorption is not possible at certain frequencies. It should be noted that in the calculated spectrum, near or at resonance points, the linewidths of the intermediate levels must be included in order to obtain accurate results.
TL;DR: In this article, a model of two closely connected emitting regions is proposed to account for the asymmetries observed in the light curve and polarization data for this and other AM Her systems.
Abstract: White light simultaneous photometry and linear and circular polarimetry is presented for the AM Her variable ST LMi. Linear polarization evident throughout the faint phase is tentatively attributed to electron scattering from gas in the accretion column at heights greater than 5R wd above the surface. The values of inclination and magnetic colatitude are revised to take into account the height and extent of the cyclotron emitting region which are also determined. A model of two closely connected emitting regions is proposed to account for the asymmetries observed in the light curve and polarization data for this and other AM Her systems. The cyclotron and hard x-ray emitting regions are found to be coincident, which eliminates the region above the shock as the source of polarized light. The shock height is found to be too low and the soft x-ray flux too large for the standard radiative shock model to apply.
TL;DR: In this paper, the problems of polarization rotation losses, in meteor burst communication systems, are examined using a theoretical model developed for the purpose, taking into account both the polarization changes due to ionospheric Faraday rotation and the rotation of the wave polarization that takes place as a result of scattering from underdense meteor trails.
Abstract: The problems of polarization rotation losses, in meteor burst communication systems, are examined using a theoretical model developed for the purpose. The paper takes into account both the polarization changes due to ionospheric Faraday rotation and the rotation of the wave polarization that takes place as a result of scattering from underdense meteor trails. Linearly polarized systems, employing copolar transmitting and receiving antennas, and hybrid systems, employing a linearly polarized transmitting antenna and a circularly polarized receiving antenna, are studied. It is shown that, particularly in linearly polarized systems, polarization rotation may introduce unexpected diurnal performance variations in systems operating at frequencies ∼40 MHz. For the two 40-MHz linearly polarized links investigated in detail the model predicts that, for noon summer solstice conditions during periods with a high solar sunspot number, these losses cause a reduction in data throughput to between 15 and 70% of the value expected had no polarization rotation occurred. By using a cross polarization approach, qualitative experimental confirmation of the predictions is also given.
TL;DR: In this paper, the broad-band circular polarization of sunspots is discussed on the basis of the observations made in the Okayama Astrophysical Observatory, and it is shown that it is the integrated polarization of spectral lines in the observed spectral range.
Abstract: The broad-band circular polarization of sunspots is discussed on the basis of the observations made in the Okayama Astrophysical Observatory. The observation with the spectrograph proves that it is the integrated polarization of spectral lines in the observed spectral range. A velocity gradient in the line-of-sight can produce this integrated polarization due to the differential saturation between Zeeman components of magnetically sensitive lines. The observed degree of polarization and its spatial distribution in sunspots is explained when we introduce a differentially twisted magnetic field in addition to the velocity gradient. The differential twist has the azimuth rotation of the magnetic field along the line-of-sight and generates the circular polarization from the linear polarization due to the magneto-optical effect. The required azimuth rotation is reasonable and amounts at most to 30°. The required velocity gradient is compatible with the line asymmetry and its spatial distribution observed in sunspots. The observed polarity rule leads to the conclusion that the sunspot magnetic field has the differential twist with the right-handed azimuth rotation relative to the direction of the main magnetic field, without regard to the magnetic polarity and to the solar cycle. The twist itself is left-handed under the photosphere, when the sunspot is assumed to be a unwinding emerging magnetic field.
TL;DR: Magnetic circular dichroism (MCD) as mentioned in this paper is a measure of the Faraday effect, which is the determination of the differential absorption of left and right circularly polarized light.
Abstract: Publisher Summary This chapter discusses the instrumental and application developments of magnetic circular dichroism (MCD). MCD arises when an external applied magnetic field perturbs the ground or excited states of a molecule resulting in differential absorption of polarized light. MCD spectra can be analyzed by various techniques including Gaussian curve fitting or moment analysis. Magnetic circular dichroism, a measure of the Faraday effect, is the determination of the differential absorption of left and right circularly polarized light, as is circular dichroism, except that in MCD a magnetic field (H) either parallel (the standard convention) or antiparallel to the direction of propagation of the beam of light is applied to the sample, thus inducing magnetic optical activity. Details of the procedures involved in routine MCD spectroscopy have been described and only pertinent points are reviewed. Two frequently quoted advantages of MCD over absorption spectroscopy, which have led to its analytical application are the ability to resolve transitions hidden under absorption envelopes, and with certain chromophores, such as those containing the tetrapyrrole nucleus—for example, heme proteins, porphyrins, and so on—an increased detection sensitivity.
TL;DR: In this article, a Stokes parameter analysis was carried out for the excitation of neon and argon by 80-eV incident electrons and the results showed that the transfer of angular momentum to the atom is positive and is in fact surprisingly ''heliumlike''.
Abstract: The recent development of a circular polarization analyzer for the vacuum ultraviolet spectral region has enabled a Stokes parameter analysis to be carried out for the excitation of neon and argon by 80-eV incident electrons. The results show that the transfer of angular momentum to the atom is positive and is in fact surprisingly ''heliumlike.'' Small deviations from total coherence were observed and are discussed.
TL;DR: In this article, the optical activity of uniaxial media by measuring the difference between the intensities of reflected electromagnetic waves (emw) of different circular polarization (reflection optical activity) is discussed.
Abstract: The possibility to investigate optical activity of uniaxial media by measuring the difference between the intensities of reflected electromagnetic waves (emw) of different circular polarization (reflection optical activity—ROA) is discussed. The components of the gyration tensor and the polarization of the normal emw in uniaxial media are found. The reflection of emw is studied in two cases: (a) optical axis normal to the boundary; (b) optical axis normal to the plane of incidence. Three modifications of differential spectroscopy are proposed: (1) left and right circularly polarized waves—usual reflection; (2) total reflection–circular polarization (TROA); (3) total reflection of linearly polarized waves with different azimuths of vibration. The specific features of the proposed methods (ROA and TROA) are discussed as well as the possibility of studying the optical activity induced by nondegenerate and degenerate excitations (vibrations).
TL;DR: In this paper, the first measurement of a tokamak plasma internal magnetic field based on the analysis of polarization of Zeeman components of a magnetic dipole transition in heavy impurity ion was presented.
Abstract: We present the first measurement of a tokamak plasma internal magnetic field based on the analysis of polarization of Zeeman components of a magnetic dipole transition in heavy impurity ion. The circular polarization of the Ti XVII 3834 A line is studied. The values of the component of the toroidal magnetic field in the direction of observation are measured for several observation angles and good agreement with expected values is found. The result indicates that the method may be useful for measuring the local magnetic field and in particular, the poloidal component of the field, in a tokamak.
TL;DR: In this article, the discovery of an AM Herculis-type magnetic variable, an accreting binary system that contains a magnetic white dwarf and a late-type companion, is reported.
Abstract: The discovery of an AM Herculis-type magnetic variable, an accreting binary system that contains a magnetic white dwarf and a late-type companion, is reported. The proposed optical counterpart to the detected X-ray source exhibits all the optical emission characteristics of its class: circular polarization, strongly modulated brightness variations, intense flickering on time scales of seconds, historical 'low states', and intense emission lines, including very strong lines of He II. The modulations in the polarization and the photometric magnitude suggest an orbital period of 3.1 + or -0.2 hr.
Patent•
25 Nov 1986
TL;DR: In this article, a linearly polarized light in the direction perpendicular to this paper is made incident, the light is reflected to the upper side by a polarized beam splitter 16 and focus is formed on a recording medium 21.
Abstract: PURPOSE:To access both faces of an optical disc with one pickup in high speed with simple constitution by providing a polarized beam splitter transmitting a light or reflecting a 90 deg. direction depending on the linearly polarized direction from a laser. CONSTITUTION:When a linearly polarized light in the direction perpendicular to this paper is made incident, the light is reflected to the upper side by a polarized beam splitter 16 and focus is formed on a recording medium 21. Simi larly, the reflected light from a recording medium face is reflected in the splitter 16 and returns to the incident direction 23. When a linearly polarized light in parallel with this paper is made incident, the polarized beam splitter 16 transmits the light beam. The light becomes a circularly polarized light once through a 1/4 wavelength plate 19 and the light beam incident on the reflecting plate 20 is transmitted again through the 1/4 wavelength plate 19 and converted into a linearly polarized light in perpendicular to this paper. Thus, the light beam incident on the splitter 16 is made incident on the 2nd objective lens 18 and focus is formed to the 2nd recording medium face. Further, the light passes through the same path as the incidence and is reflected into a light beam 23.