Showing papers on "Circular polarization published in 1968"

Thermal anisotropies and electromagnetic instabilities in the solar wind.

Abstract: Thermal anisotropy of electrons and instability of circularly polarized electromagnetic waves propagating along magnetic field in solar wind

Second harmonic light generation in crystals with natural optical activity.

Abstract: Whenever a circularly polarized laser beam propagates along an axis of threefold symmetry in a piezo-electric crystal, the second-harmonic polarization is circularly polarized in the opposite sense. Rabin and Bey have discussed the theory of second-harmonic generation in crystals with natural optical activity. We have observed this circular polarization and also the difference in coherence lengths for opposite senses of circular polarization, with both fundamental and second-harmonic beams propagating along the [111] direction in single crystals of NaCl${\mathrm{O}}_{3}$ and NaBr${\mathrm{O}}_{3}$, belonging to the cubic class 23, for which the proper eigenmodes are circularly polarized waves. The nonlinear susceptibility of both NaCl${\mathrm{O}}_{3}$ and NaBr${\mathrm{O}}_{3}$ has been measured and compared with the nonlinear susceptibility of $\ensuremath{\alpha}$-quartz. The relative sign of the susceptibilities has been determined in second-harmonic interference experiments with the same laser beam traversing two crystals in succession. The interesting questions of the sign of the nonlinear susceptibility, piezoelectric constant, optical activity, and the absolute atomic configuration of the antipodes are discussed. The question of conservation of angular momentum is resolved by taking into account the crystal-line-field potential of threefold symmetry, which gives rise to a torque on the crystal lattice.

Optical rotatory power of liquid crystals

Abstract: A theory of the very high rotatory power exhibited by cholesteric liquid crystals is developed by the use of the Jones calculus for optical systems. The calculations are based on the model proposed by de Vries in which the liquid crystal is regarded as built up of a large number of thin birefringent layers arranged helically. When light is incident normal to the layers, i.e. along the screw axis, selective reflexion of one of the circularly polarized components takes place and the rotatory dispersion in the neighbourhood of the region of reflexion is anomalous. The reflexion curve and the amplitude attenuation factor, exp (−ξ), for circularly polarized light at normal incidence are derived as functions of wavelength by setting up difference equations closely similar to those formulated by Darwin in his dynamical theory of X-ray diffraction. Within the range of total reflexion, ξ is real, primary extinction occurs and the medium is highly circularly dichroic. The spectral width of the reflexion and the primary extinction coefficient predicted by theory compare favourably with the experimental values. Outside the region of total reflexion, ξ is imaginary and opposite in sign on opposite sides of the reflected band. This is responsible for the reversal of the sign of the rotation on crossing the band. The anomalous part of the rotation is a direct measure of the phase of the primary wave given by the dynamical theory.

The analysis of circular waveguide phased arrays

Abstract: In this work, a planar phased array of circular waveguides arranged in an equilateral triangular grid is analyzed. The boundary value problem is first formulated rather generally in terms of a vector two dimensional integral equation for an array of elements that are arranged in a doubly periodic grid along two skewed (nonorthogonal) coordinates. Dielectric plugs, covers, and loading, as well as thin irises at the aperture, are accounted for in the formulation. Numerical solutions are obtained by using the Ritz-Galerkin method to solve the integral equation. Excellent agreement with experimental measurements using a waveguide simulator is observed. The existence of forced surface wave phenomena in equilateral triangular grid arrays and their strong dependence upon the mode of excitation is also demonstrated. These phenomena are shown to exist at isolated points in the scan coordinates. Reflection characteristics as well as the polarization characteristics of the radiation pattern are illustrated at selected planes of scan for both linear and circular polarization excitation.

Properties of Rubidium Atoms Trapped in a Solid Argon Matrix

Abstract: This paper reports studies of the optical absorption spectrum and the $X$-band electron spin resonance spectrum of rubidium atoms trapped in an argon matrix. The samples were formed by deposition from a mixed beam of the two constituents onto a cold plate. The optical absorption measurements showed two groups of lines. The red group, whose absorption lines are near those of the free atom, has a triplet structure; the blue group, whose absorption lines are shifted roughly 1650 ${\mathrm{cm}}^{\ensuremath{-}1}$ to the blue, has four lines. The ESR measurements showed three major trapping sites. A motorized circular polarizer was used to measure the differential absorption of right and left circularly polarized light. By monitoring the differential absorption of right and left circularly polarized light in the presence of a microwave field, a correlation was found between the optical absorption sites and the microwave absorption sites. A crystal-field model is employed in an attempt to fit the data and to understand the nature of the sites.

The Description of Polarization in Classical Physics

Abstract: An alternate derivation of the Stokes polarization parameters is presented; the parameters are obtained from the elliptic equation of polarization rather than the plane wave equations. As a result of deriving the parameters in this manner, the relationship between the polarization ellipse and the Stokes parameters is clarified. The Stokes parameters for various states of polarized light are briefly reviewed. The remainder of this article is then devoted to obtaining the Stokes parameters for a number of important physical phenomena such as the classical Zeeman effect, synchrotron radiation, Thomson scattering, reflection of electromagnetic waves by dielectric surfaces, and wave propagation in a plasma.

Electromagnetic Wave Propagation in Cholesteric Materials

Abstract: Equations are derived for the propagation of electromagnetic waves along the axis of a cholesteric material, using constitutive equations based on a theoretical model for the structure of this type of material The resulting time-independent equations are a pair of coupled equations for left- and right-hand circularly polarized waves Solutions are obtained for these equations and are shown to provide good agreement with experimental observations on the circular dichroism and reflection of circularly polarized light for cholesteric materials

Suspended organic particles monitor using circularly polarized light

Abstract: Method for detecting optically active organic particles suspended in a fluid, including water, air or a vacuum, by measuring circular dichroic absorption. The method comprising the steps of alternately transmitting right circularly polarized light and left circularly polarized light through the fluid being analyzed whereby the circularly polarized light is scattered by the particulate matter in the sample. The scattered radiation is analyzed by separating the circularly polarized components in the resulting scattered light and measuring the intensity of the resulting scattered light components. The circular dichroic absorption in the scattered lights is represented by the ratio of the component intensity of when starting with right circularly polarized light to that of the intensity when starting with left circularly polarized light.

Apparatus and method for optical read-out of internal electric field

Abstract: 1,274,317. Electro-optic data storage. ITEK CORP. 31 March, 1969 [8 April, 1968], No. 16693/69. Heading H3B. [Also in Divisions Gl and G4] An information storage and retrieval element 110 comprises a photo-electret medium which stores an optical image as a patterned persistant internal electric field when it is simultaneously illuminated with the image and subjected to an electric field and an electro-optic medium associated with the photo-electret so that it modulates light transmitted therethrough as a function of the local persistant internal field intensity. The element 110 may comprise adjacent layers of photo-electret (hexagonal ZnS) and electro-optic (KDP) material between two electrodes, Fig. 8 (not shown), or a single layer, e.g. of cubic ZnS, may be employed as a photoelectret and also as exhibiting the Pockels effect, and in the latter case, it is not necessary for the thickness of the layer to be uniform for consistant modulation of the light over the whole layer. As shown, plane polarized light from a laser 112 is reflected by an oscillating mirror 116 and a rotating mirror prism 120 to scan the element 110. The variably polarized light from element 110 is analysed 134 and sensed at 140 as a negative or positive of the stored pattern, depending on the relative disposition of analyser 134 and the original polarization plane of the laser light. When using Pockels device in which the slow and fast axis of each crystallite are misaligned with respect to those axes in every other crystallite, a quater wave plate 144 provides circularly polarized light, and this also gives small changes in the analyser output which are essentially linearly related to changes in retardation caused by the element 110, Fig. 11 (not shown). A further quarter wave plate 152 compensates for plate 144. For parallel readout, Fig. 12 (not shown), the whole element 110 is simultaneously illuminated and the transmitted analysed light is received on an image storage tube for subsequent serial read-out. The analyser 134 may be replaced by, e.g. a Glan, Glan-Thompson, or Rockon prism, for resolving the output from element 110 into two polarization components directed in different directions, and outputs from two corresponding sensors are fed to a differencing amplifier to provide an output representing the light-dark pattern stored in the element 110, Fig. 13 (not shown). The read-out radiation may have an energy such that the electret is not discharged thereby.

Circular Polarizer for Lyman-alpha Flux*

Abstract: Polarization and phase shifts of Lyman-alpha flux reflected from Al, Al2O3, ZnS, MgF2, and SiO films were measured. A circular polarizer having a 5° angle of acceptance and 12% transmittance was constructed using Al2O3 and Al mirrors. The amount of flux in the desired state of circular polarization was between 83% and 90%.

The polarization of the Jupiter radiation at 18 Mc/s.

Abstract: Jupiter radiation bursts polarization degree and axial ratio, discussing agreement with Doppler shifted cyclotron theory

Propagation of Circularly Polarized Electromagnetic Waves in a Finite Temperature Electromagnetoplasma

Abstract: The dispersion relation for circularly polarized electromagnetic waves in a warm two‐component plasma subject to parallel static electric and magnetic fields has been derived from the linearized coupled Boltzmann‐Maxwell equations with the collision frequency assumed to be independent of the particle velocity. The effect of a weak longitudinal electrostatic field, E0, on the propagation characteristic of the right‐ and left‐hand circularly polarized waves in an isothermal electron‐proton plasma is examined in detail and illustrated numerically for a conveniently chosen set of the system parameters. For the right‐hand polarized wave the electrostatic field effect is found to be significant for a wave with frequency ω in the vicinity of the electron cyclotron frequency ωz ≡ (eB0/m). For example, for a given ω and δ ≡ (eE0/mcω) > 0 an increase in δ, or in E0, leads to the increase or decrease of the attenuation constant α, of the wave according to whether Y ≡ (ωz/ω) 1. Moreover, for Y = 1.10, when...

Lens polarization control

Abstract: The invention is for a geodesic Luneberg lens antenna structure of nonplanar construction excited by horizontally and vertically polarized electromagnetic energy. Excitation of the lens by a single dual polarized feed will produce two divergent beams - one horizontally and the other vertically polarized. Excitation of the lens by two separate feeds at locations indicated by application of the criteria disclosed herein will result in the capability of providing arbitrary elliptical polarization including linear and circular polarization.

Suspended solids concentration measurement using circular polarized light

Abstract: A device for optically measuring the amount of particulates in a fluid. Circularly polarized light is directed at a fluid to be analyzed and light which is scattered preferably in a backward direction, that is more than 90* from the direction of the incident beam is analyzed and the ratio of the intensity of light resulting from multiple scattering to the intensity of light resulting from both multiple and primary scattering is determined.

High-Energy Polarized-Photon Reactions

Abstract: A general formalism is presented for the analysis of production and decay distributions of meson-baryon final states resulting from interactions of polarized photons and nucleons. Particular emphasis is given to high-energy reactions and Regge-pole exchange models. Circular polarization is shown to provide a test for the presence of two or more exchanges. Linear polarization parallel or perpendicular to the production plane allows the contributions of opposite $J$-parity exchanges to be separated. This formalism enables one to make use of data at all angles, rather than limit consideration to discrete points. Applications include the separation of diffractive and pion-exchange contributions to vector-meson production, and tests for non-pole-type exchanges in baryon-resonance production. Examination of pion photoproduction reveals that no simple test exists for the discrimination between pion conspiracy and evasion models.

Arrangement for interferometric measurement of two lengths

Abstract: An arrangement for simultaneous interferometric measurement of a plurality of lengths utilizes a single monochromatic circularly polarized light beam which is divided up by intensity in a first optical divider into an outgoing reference beam and an outgoing primary measuring beam. This measurement beam is then divided up by intensity in a second optical divider after traversing one of the lengths to be measured into a pair of outgoing secondary measurement beams which are then polarized in mutually perpendicular planes of polarization. One of these outgoing secondary measurement beams is reversed and returned to the second optical divider and the other outgoing secondary measurement beam is also similarly reversed and returned but after it has traversed the second length to be measured. The two returning secondary measurement beams are then recombined in the second optical divider and returned to the first optical divider where they are combined with the reference beam which has been reversed and returned thus to form an outgoing light beam which is differently intensity-modulated in two mutually perpendicular planes of polarization. This outgoing light beam is then divided up in a third optical divider into a pair of modulated light beams which are then delivered respectively to photodetectors. One photodetector receives only the component of the modulated light beam which is polarized in one plane and the other photodetector receives only the component which is polarized in the other plane.

VRO 42 22 01: a Variable Source with Circular Polarization

Abstract: THE radio source VRO 42 22 01 was recently identified with a variable stellar object, BL Lac (ref. 1), and we have obtained results which show that the source is radio variable and probably circularly polarized. Since September 1967, a 2,695 MHz receiver has been in operation at the Nancay radiotelescope. It allows simultaneous measurements of flux densities with electric vectors at position angles 0° (V) and 90° (H), and of the products, in phase and through a quarter-wavelength delay, of the two corresponding voltages. It is thus possible to determine the complete polarization, linear or circular, of the most intense sources. One of the programmes in progress with this receiver is the measurement of flux variations for known variable sources, and of possible polarization variations. The radio source VRO 42 22 01 was included in that programme. This source has a flux density at 610.5 MHz of S610 = 4.0 flux units (ref. 2) (1 flux umt = 10−26 W/m−2 Hz−1), but it does not appear in the 4C catalogue3, so S178<2.0 flux units. Its flux density was measured at 1,417 MHz by Williams, and Stewart4, who give S1417 = 7.3 flux units. Its radio spectrum resembles that of the variable components of well known radio sources.

Broadband circularly polarized antenna having a continuous rectangular aperture

Abstract: A BROADBAND CIRCULARLY POLARIZED ANTENNA HAVING A CONTINUOUS RECTANGULAR APERTURE TO OBTAIN CIRCULAR POLARIZATION, HAVING UNIFORM PHASE AND TAPERED AMPLITUDE ILLUMINATION OVER THE BROAD DIMENSION OF THE APERTURE. THE DEVICE FEATURES A LARGER EFFECTIVE RADIATING OR RECEIVING APERTURE THAN COMPARABLE RECTANGULAR ARRAY OF CIRCULARLY POLARIZED SPIRALS DUR TO THE USE OF VIRTUALLY LOSSLESS RADIATING ELEMENTS TO PROVIDE HIGHER GAIN. LINEARLY POLARIZED RADIATING ELEMENTS ARE UTILIZED TO FEED AN APERTURE WITH LINEARLY POLARIZED ENERGY WHICH IS THEN TRANSFORMED INTO CIRCULARLY POLARIZED ENERGY BY MEANS OF A POLARIZER GRID.

Observed Limits to the Circular Polarization of Nine Quasars at Radio Frequencies

Abstract: Sciama and Rees1 have suggested that the radio emission of compact quasars will show appreciable circular polarization (≳ 1 per cent) at frequencies greater than about 1,000 MHz. This suggestion is based on assumed magnetic fields within the variable components of these objects as large as 1 to 100 gauss. At 10.6 cm wavelength, Seielstad2 has set upper limits of between 1 per cent and 3 per cent on the circular polarization of fourteen objects of which five are known to be quasars. We now report measurements of the circular polarization of nine quasars and thirty-seven radio galaxies and unidentified sources at frequencies of 437 MHz, 630 MHz and 1,410 MHz. In no case was any significant component of circular polarization detected.

One-dimensional polarization distributions over four supernova remnants at 1418 mhz,

Abstract: : Distributions of the linearly polarized radiation at a frequency of 1418 MHz from the four supernova remnants 3C 10 (Tycho's supernova), Taurus A (Crab Nebula), 3C358 (Kepler's supernova), and Cassiopeia A have been determined by synthesizing a fan beam whose small dimension is along a circle of constant declination. In addition, extremely low upper limits have been placed on the net degree of circular polarization in the integrated radiation from Tau A, 3C358, and Cas A. For the latter two sources, no smaller circularly polarized regions were found within the source dimensions using a resolution of better than 1'. Upper limits to the magnetic field strengths, modified by geometrical factors have also been calculated. (Author)

The radiation from a charge moving in a plane wave field and a magnetic field

Abstract: The methods of classical electrodynamics are used to consider the problem of the radiation from an electron moving in the field of a monochromatic circularly polarized wave and a uniform magnetic field directed parallel to the direction of propagation of the wave. Expressions for the total radiation intensity and for the angular spectral distribution of the radiation are derived. Certain particular cases are studied.

Polarization bursts in the sun observed at microwave frequencies.

Abstract: There are microwave bursts not observable in the total flux from the Sun, but only in circular polarization. The production of these events in the Sun requires equivalent changes of the magnetic field imposed on the emission regions during the bursts.

Hameka theory of optical rotation

Abstract: sRosenfeld's formula, for off-resonance optical rotation, is derived by an alternative approach. The scattering amplitudes are determined for the scattering of right circularly polarized light and left circularly polarized light by a molecule. The calculation is carried out to the order of approximation which includes electric quadrupole and magnetic dipole terms. From the real parts of the forward scattering amplitudes the corresponding indices of refraction are determined for left and right circularly polarized light. Rosenfeld's formula then follows from the difference between the two refractive indices.

Microwave‐Optical Double Resonance Using Circularly Polarized Light: Spectrum of Yb3 + in CaWO4

Abstract: A double‐resonance technique using circularly polarized light and microwave paramagnetic resonance is described. The use of the circular polarization will, in many cases, allow one to uniquely determine the representations of the states being probed. Satisfactory signal levels are obtained in most cases where Kramers doublets are being investigated. This technique is applied to CaWO4: Yb3+. Several interesting results are obtained including definite proof that there is considerable magnetic‐dipole character in one of the optical transitions and very little in the others. The satellite structure of the lines is discussed but the nature of these extra lines is still an open question.

Motion of Charged Particles in Growing or Decaying Circularly Polarized Waves

Abstract: A constant of motion is derived for a charged particle in the magnetic and electric fields of a circularly polarized wave with time‐variable amplitude. The wave is assumed to propagate along a uniform external magnetic field.