Showing papers on "Optical polarization published in 1974"
TL;DR: In this article, the authors proposed very stable CW operation, very high pulsed output, linear polarization, high gain, and many other advantages over discharge excitation over the submillimeter-wave region.
Abstract: Optical pumping of polar molecules by means of infrared lasers is expected to lead to thousands of laser lines throughout the submillimeter-wave region. Already, 282 new laser lines between 34 mu m and 1.814 mm in 18 different molecules have been reported. Very stable CW operation, very high pulsed output, linear polarization, high gain, and many other advantages over discharge excitation are offered.
85 citations
01 Sep 1974
TL;DR: In this article, the authors used Spectrophotometry with resolution of about 0.015 over the 8-14 microns wavelength range of several stars with different chemical compositions indicates excess emission characteristic of three types of grains: (1) "blackbody" grains, (2) silicate grains, and (3) silicon carbide grains.
Abstract: Twenty-five long-period variable stars exhibiting intrinsic variable polarization have been monitored over the range 3.5-11 microns for several cycles. No conclusive evidence for gross changes in amount of circumstellar grains has been found. Thus circumstellar infrared emission is attributed to the total abundance of grains surrounding the star, which does not change by a large amount with time, while intrinsic polarization is attributed to more localized scattering and absorption effects. Spectrophotometry with resolution of about 0.015 over the 8-14 microns wavelength range of several stars with different chemical compositions indicates excess emission characteristic of 3 types of grains: (1) 'blackbody' grains, (2) silicate grains, and (3) silicon carbide grains.
83 citations
TL;DR: A theoretical justification for a holographic method of polarization recording utilizing the Weigert effect (the optically induced pure birefringence) in light-sensitive media is given in this article.
Abstract: A theoretical justification is given for a holographic method of polarization recording utilizing the Weigert effect (the optically induced pure birefringence) in light-sensitive media. The paraxial approximation is used to demonstrate the reconstruction of the vector field of an object.
59 citations
TL;DR: The photochromic system has a bi-directional photo-response, high-writing sensitivity, practically non-destructive low-temperature read-out, and permits good recyclability.
47 citations
Patent•
01 Feb 1974
TL;DR: In this article, an optical polarization converter comprising a specially fabricated planoramp shaped disc of birefringent material followed by an ordinary quarterwave plate is described. And the combined effect of the two components is to transform monochromatic linearly polarized light to ring polarized light when the former is transmitted through the device in one direction and to perform the reverse transformation when the latter is transmitted in the opposite direction.
Abstract: There is disclosed an optical polarization converter comprising a specially fabricated planoramp shaped disc of birefringent material followed by an ordinary quarterwave plate. The combined effect of the two components is to transform monochromatic linearly polarized light to ring polarized light when the former is transmitted through the device in one direction and to perform the reverse transformation when the latter is transmitted through the device in the opposite direction.
35 citations
TL;DR: The first measurements of the linear polarization of sunlight scattered by the Jupiter atmosphere at phase angles greater than 12 deg, using the imaging photopolarimeter on Pioneer 10, were made in this article.
Abstract: The first measurements have been made of the linear polarization of sunlight scattered by the Jupiter atmosphere at phase angles greater than 12 deg, using the imaging photopolarimeter on Pioneer 10. The data are of high accuracy, in spite of several problems in the instrument. The polarization is positive at 440 nm. There is no direct evidence for spherical particles in the Jupiter clouds. Using a simple model of Rayleigh scattering above a Lambertian cloud layer, a unique fit is found to the observed intensity and polarization at each point on the planet. The resulting Rayleigh optical depths, if they are attributed to molecular scattering alone (i.e., no aerosols above the cloud tops), can be converted into physical altitudes of the cloud tops. The first results suggest that the north tropical zone, parts of the equatorial zone, and the red spot are all elevated regions.
34 citations
Patent•
09 May 1974
TL;DR: A detector for differential optical polarization effects comprises a television camera incorporating a polarization analyzing system, the camera generating two similar video signals representing two views of the same scene which are derived by means of light components differing only in respect of their polarization characteristics.
Abstract: A detector for differential optical polarization effects comprises a television camera incorporating a polarization analyzing system, the camera generating two similar video signals representing two views of the same scene which are derived by means of light components differing only in respect of their polarization characteristics. The two video signals are compared over the whole scene on a point-by-point basis, the result of the comparison suitably being displayed in pictorial form.
31 citations
TL;DR: In this article, the reflectance for a bowl-feed polished Cer-Vit sample was measured at nine wavelengths and five angles of incidence from 15 to 85 degrees and the optical constants were derived by the reflectances-vs-angle-of-incidence method.
Abstract: The reflectance for a bowl-feed polished Cer-Vit sample was measured at nine wavelengths and five angles of incidence from 15 to 85 deg. Optical constants were derived by the reflectance-vs-angle-of-incidence method and compared to previously reported values for ultralow-expansion fused silica and several other glasses. Surface-roughness corrections of the reflectance data and optical constants are discussed.
27 citations
01 Jan 1974
TL;DR: In this article, the main investigations of the local magnetic field are reviewed and are found to contain some conflict in interpretation, and the results are consistent with a large-scale field parallel to the galactic plane, with a field strength of about 2 μG, and which is directed towards l=90°.
Abstract: The main investigations of the local magnetic field are reviewed and are found to contain some conflict in interpretation. At radio wavelengths, studies have been made using both the Faraday rotation of the polarized radiation from extragalactic sources and pulsars, and the polarization of the galactic background radiation. With the former type of observation, although more data are available for extragalactic sources, any interpretation may be complicated by the influence of distant field structure. The results are consistent with a large-scale field parallel to the galactic plane, with a field strength of about 2 μG, and which is directed towards l=90°. This field contains irregularities in direction and strength on a scale of about 100–200 pc. The polarization of galactic background radiation may yield the most detailed information about the local field structure - the results to date show loops of magnetic fields extending along the radio spurs.
22 citations
TL;DR: The cloud particles on Venus are sufficiently small for their vertical distribution to be strongly affected by atmospheric turbulence as discussed by the authors, which enables very firm upper limits to be placed on average vertical mass diffusion coefficients in the visible atmosphere.
Abstract: The cloud particles on Venus are sufficiently small for their vertical distribution to be strongly affected by atmospheric turbulence. Reasonably firm estimates of the vertical distribution of cloud particles can be made from current interpretations of refraction, polarization, and absorption band data. These enable very firm upper limits to be placed on average vertical mass diffusion coefficients in the visible atmosphere. These upper limits are independent of the cloud particle composition or mode of formation, and of changes in the particle size distribution with altitude.
TL;DR: In this article, coherent reshaping of short-duration (2 to 40 nsec) N2O laser pulses in a resonant NH3 absorber for a variable number of absorption lengths was investigated.
Abstract: Investigation of the coherent reshaping of short-duration (2 to 40 nsec) N2O laser pulses in a resonant NH3 absorber for a variable number of absorption lengths. It is found that, for small-area square pulses, the reshaping can produce subnanosecond pulses at the leading and trailing edges. A rapid phase reversal gives rise to amplification for times comparable to the transverse relaxation time.
TL;DR: In this paper, a 72-in. telescope and a polarimeter of the Wollaston type with a focalplane scanning mechanism were used in the investigations reported, and it was concluded that in the ultraviolet and close to opposition the vectors are consistently radial and decrease to nearly zero near the center of the disk.
TL;DR: In this paper, an account is given of optical coherence theory as it existed in the 1950's when only thermal sources and slow detectors were available and it sufficed to characterize the coherence and polarization properties of an electromagnetic field by second-order correlation functions.
Abstract: An account is given of optical coherence theory as it existed in the 1950's when, essentially, only thermal sources and slow detectors were available and it sufficed to characterize the coherence and polarization properties of an electromagnetic field by second-order correlation functions. The necessity for a more sophisticated specification of the coherence properties of fields, involving the use of higher-order correlation functions, first hinted at by the Hanbury-Brown-Twiss experiments and emphasized by the advent of the laser, is then introduced. Both classical and quantum mechanical treatments are discussed, each leading, in almost all cases of practical interest, to similar results. It is seen that the development of fast detectors enabled the higher-order correlation functions to be measured using photon counting techniques and an account of experimental work verifying the complete theory using such techniques is given. The review concludes with a discussion of some developments in associated areas whose origin lies in the resurgence of interest in coherence theory during the last decade.
01 Dec 1974
TL;DR: A polarization Fourier spectrometer is described that improves on the previous versions built by others and can be used from 0.3 micro to 2.5 micro, and several practical problems in the construction and data reduction are discussed.
Abstract: A polarization Fourier spectrometer is described that improves on the previous versions built by others and can be used from 0.3 micro to 2.5 micro. Several practical problems in the construction and data reduction are discussed, and a number of typical results are presented to show the performance of the instrument.
Journal Article•
TL;DR: Alternative handedness and sign conventions for relating the orientation of elliptical polarization are discussed, and snapshot picture and angular momentum consideration are discussed.
Abstract: Alternative handedness and sign conventions for relating the orientation of elliptical polarization are discussed. The discussion proceeds under two headings: (1) snapshot picture, where the emphasis for the convention is contained in the concept of handedness; and (2) angular momentum consideration, where the emphasis for the convention is strongly associated with mathematical convention and the sign of the fourth Stokes parameter.
TL;DR: In this article, the authors used the nonlinear absorption of intense laser light to obtain information about the times required for spectral cross relaxation (T3) and collisional dephasing (T2) in organic dye solutions.
Abstract: The nonlinear absorption of intense laser light is used to obtain information about the times required for spectral cross relaxation (T3) and collisional dephasing (T2) in organic-dye solutions. The steady-state transmission experiment of Huff and DeShazer indicates that T2 is in the range 0.1-1 psec for cryptocyanine-methanol, while T3 is in the range 1-10 psec. For DDI-glycerin (1, 1′-diethyl-2, 2′-dicarbocyanine-iodide-glycerin), measurements of ultrashort-pulse transmission as a function of incident energy and optical polarization suggest a value T2=0.4±0.2 psec for that system. These results are based on a new set of rate equations for absorption by inhomogeneously broadened organic-dye solutions. The equations display the effects of spectral cross relaxation and are not limited to light intensities less than those at which coherent interaction effects become important. For the case of ultrashort incident pulses, the equations are extended to account for excited-state absorption, the dependence of absorption on optical polarization, and the existence of a multiplicity of interacting excited states.
TL;DR: In this article, the phase-velocity tuning of thin-film liquid-crystal waveguides was analyzed by a numerical method, and a three-layer model of the waveguide was provided, which is in good agreement with the measured data.
Abstract: An external electric field exerts volume torque on the nematic liquid crystal due to the anisotropic molecular polarizability and tends to reorient the molecular axes. Phase-velocity tuning in these materials is thus possible. Eigenmodes of thin-film liquid-crystal waveguides are analyzed by a numerical method. A three-layer model of the waveguides is found to be in good agreement with the measured data, thus providing a simplified model for conceptual thinking as well as for computation.
TL;DR: The sensitivity of LiTaO3 crystals to hologram formation has been observed to vary with impurity concentration as discussed by the authors, and the sensitivity varied from a value comparable to the most sensitive doped LiNbO3 for an impure crystal to a value more than 5 orders of magnitude smaller for a purer crystal.
Abstract: The sensitivity of LiTaO3 crystals to hologram formation has been observed to vary with impurity concentration. For a writing wavelength of 488.0 nm and power density of 1.1 W/cm2 the sensitivity varied from a value comparable to the most sensitive doped LiNbO3 for an impure crystal to a value more than 5 orders of magnitude smaller for a purer crystal. Fatigue effects were observed upon write‐erase cycling. These effects were dependent upon writing and erasure polarization and power density and could be minimized by proper choice of optical parameters.
TL;DR: In this article, the authors recall the principle of interference comparator for comparing end standards and using an additive polarization interferometer, which can be interpreted by the phase difference between two rectilinear vibrations which are polarized on two perpendicular directions.
Abstract: In this paper, we recall the principle of interference comparator for comparing end standards and using an additive polarization interferometer. Then, the length difference between two samples can be interpreted by the phase difference between two rectilinear vibrations which are polarized on two perpendicular directions. This phase difference is measured by the means of phase modulation. Owing to these concepts a display was imagined to assure the differential measure of thermal expansion. It is allowing to compare elongations of one sample and one standard. As the samples are magnetic materials measured under variable directions and force magnetic fields, it results a conception of interferometer taking account of sizes and characteristics of thermal expansion chamber. The assembled described display is allowing to show variations of optical phase with 10-8 relative uncertainly in terms of length differential variation.
TL;DR: A novel method of inversion of experimental results to the end of determining the BS physical parameters is proposed, which makes use of the variations with incident light direction of the BS reflectivity, transmissivity, or efficiency curves.
Abstract: Computations of the reflectivity, transmissivity, and efficiency properties for TE, TM, and T45 degrees waves of far ir beam splitters (BS) and of the polarizations induced at both reflection and transmission are described. Effects of variations in the state of polarization, orientation, pointing accuracy, and wavelength of the incident light, as well as variations in refractive index and thickness of the BS, are discussed. These results apply directly to Fourier interferometer-spectrometers. They can be used for optimizingthe performance of these instruments. They indicate, in particular, that some advantages may begained by the use of incident polarized light (angle of polarization smaller than about 45 degrees or negative elliptical polarization) or light of large incidence angle (larger than approximately 60 degrees ) or both. A novel method of inversion of experimental results to the end of determining the BS physical parameters is proposed. It makes use of the variations with incident light direction of the BS reflectivity, transmissivity, or efficiency curves.
TL;DR: In this article, the relationship between PMDR spectroscopy, coherent triplet exciton migration and density of states functions in molecular crystals is illustrated for crystals which can be considered as models for one-dimensional excitons.
Abstract: Saturation of the zero-field electron spin transitions of a phosphorescent triplet state by a microwave field causes changes in the intensity and/or polarization of the emission and thus forms the basis for phosphorescence microwave double resonance (PMDR)† in excited triplet states. Because of the sensitivity of photon detection, the technique is capable of detecting as few as 10 4 molecules in a sample depending upon the details of the radiative channels being monitored. If phosphorescence is monitored from an exciton band, PMDR can be used to experimentally differentiate between diffusion limited exciton migration and migration describable by the group velocity of the wave packet of k states, i.e. coherent exciton migration. In the following paper the relationships between PMDR spectroscopy, coherent triplet exciton migration and density of states functions in molecular crystals will be illustrated for crystals which can be considered as models for one-dimensional excitons. In particular, a resonance theory will be outlined that incorporates explicitly exciton–phonon scattering into the Bloch equations and allows one to extract both the lifetime of a k state of the band and the coherence length of the exciton. PMDR experiments in ‘one-dimensional’ molecular crystals are presented which illustrate the salient features of the theory. The experimental results are interpreted using a statistical theory which explicitly includes the exciton band dispersion, the density of state function of band and trap states, and the group velocity of the exciton wave packets. From the above experiments, a coherence length between 300 and 10 4 a and a coherence lifetime of 10 -7 s have been found for k states in the centre of the band for certain substituted benzene crystals at 4 K. Finally, some new PMDR methods for studying the coherent spin properties of mobile and non-mobile states based on optically detected electron spin echoes and echo trains in excited molecular states will be presented. Specifically, a technique will be presented that is capable of measuring any state of the coherence of the spin ensemble, regardless of the optical polarization of emission from the spin sublevels utilizing virtually all of the phosphorescence emission from excited states.
01 Jan 1974
TL;DR: In this paper, the magnetic field strength and the density of thermal electrons in the line of sight were estimated by measuring the rotation of the plane of polarization, known as Faraday rotation, which is one of the most important tools for studying the galactic magnetic field.
Abstract: Radio astronomical observations of such widely differing types of objects as extra-galactic nonthermal radio emitters, both quasars and galaxies, galactic supernova remnants, pulsars, and neutral hydrogen clouds, as well as observations of the non-thermal galactic background radiation, give information about the magnetic fields in interstellar space. This information is complemented by data on the optical polarization of starlight. Since rigorous models of the galactic magnetic field are difficult to formulate, our discussion is necessarily qualitative.All the various types of observations pertaining to the galactic magnetic field involve the existence of polarization of electromagnetic radiation. The continuum radiation from the so-called galactic “background,” presumably synchrotron emission, is intrinsically linearly polarized. The polarized signal propagating through the interstellar medium, which contains both thermal electrons and magnetic fields, can be decomposed into two oppositely circularly polarized components having different phase velocities. On emergence from the medium the waves can be recombined, but with relative phases which may be different from those which they had on entering the medium. The effect of this is a rotation of the plane of polarization, the amount of rotation varying as the square of the wavelength, and, as will be shown below, it is possible to estimate the magnetic field strength and the density ofthermal electrons in the line of sight by measuring this rotation. Furthermore, by extrapolating measurements at several wavelengths to zero wavelength we can derive the orientation of the magnetic field component transverse to the line of sight in the region in which the radiation originates. This rotation of the plane of polarization, known as Faraday rotation, also affects the polarized emission from pulsars and extra-galactic radio sources. The amount of Faraday rotation is given in terms of a parameter, known as the rotation measure, which is one of the most important tools for studying the galactic magnetic field.
01 Jan 1974
TL;DR: A review of the instrumentation used for the measurement of optical polarization from aircraft, balloon, rocket, satellite, and spacecraft platforms is presented in this article, along with questions of instrument operation in space along with details of polarization analysis, aspects of accuracy and calibration, and scientific studies conducted with the polarimeters.
Abstract: A review is presented of the instrumentation used for the measurement of optical polarization from aircraft, balloon, rocket, satellite, and spacecraft platforms. The four parameters which can be measured at a given wavelength, time, and direction in an incoherent beam of radiation include intensity, linear polarization, its position angle, and circular polarization. An instrument that by design is made sensitive to any of the three polarization parameters is considered a polarimeter. Attention is given to passive polarimeters operating in the range from 0.1 to 1000 micrometers. All known optical space polarimeters are listed in a table. Questions of instrument operation in space are discussed along with details of polarization analysis, aspects of accuracy and calibration, and the scientific studies conducted with the polarimeters.
TL;DR: In this paper, the decay-type parametric instabilities involving the lower hybrid mode in a magnetized plasma were investigated and the theories of two decay type parametric instability involving lower hybrid modes were presented.
Abstract: The theories of two decay-type parametric instabilities involving the lower hybrid mode in a magnetized plasma are presented. In the first of these, a pump wave of ordinary polarization causes the growth of a backward propagating transverse wave and a longitudinal lower hybrid wave, all with wave vectors perpendicular to the external magnetic field. The second instability concerns the parametric excitation of the upper hybrid and the lower hybrid modes.