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  • 1
    Electronic Resource
    Electronic Resource
    Borrmann-like anomalous effects in volume holography (1980)
    Springer
    Applied physics 22 (1980), S. 335-353 
    Details
    ISSN: 1432-0630
    Keywords: 42.30 ; 42.10 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In this review, a surgey of the evidence for the appearance in volume holography of certain anomalous effects (akin to the Borrmann effect in x-ray crystallography) is conducted, with reference to both experimental observations and theoretical models. The main part of the paper is devoted to the application of a recently-developed two-dimensional coupled-wave theory (an extension of Kogelnik's one-dimensional theory) to the modelling of such anomalous phenomena. Extensive calculations based upon this theory, for the case of Gaussian wave incidence on a uniform mixed grating for various boundary conditions, are presented in a unified two-dimensional description of Borrmann-like effects in volume holography. In particular, certain qualitative predictions of the dynamical theory of x-ray diffraction are expressed quantitatively in the two-dimensional theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00901055
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Thick-grating non-divergent focussing device: 2-D analysis (1981)
    Springer
    Applied physics 26 (1981), S. 89-98 
    Details
    ISSN: 1432-0649
    Keywords: 42.80 ; 42.82 ; 42.10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The two-dimensional analysis of a recently reported thick grating Bragg diffraction focussing device is carried out using Solymar's coupled-wave approach. It is shown that the device is capable of operating as a non-divergent lens with beam contraction ratios of better than 100:1, and conversion efficiencies of nearly 100%. It is also shown that it can operate as a novel kind of Fourier spectrum analyser, the focussed diffracted intensity being proportional (as a function of Bragg condition violation) to the modulus squared of the Fourier transform of the incident finite beam. The focussing properties are studied as functions of incident beam profile, width and position, grating strength and Bragg condition violation. Poynting vector optics is used successfully to predict (in conjunction with the dispersion surfaces of x-ray dynamical theory) the off-Bragg behaviour in the focal plane. It is likely that the device could be used as avariable ratio beam contractor in integrated optics, where the grating strength could be controlled (interdigital electrode system) electrooptically.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01284908
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Bragg diffraction of gaussian beams by thick gratings: Numerical evaluations by plane-wave decomposition (1982)
    Springer
    Applied physics 28 (1982), S. 383-390 
    Details
    ISSN: 1432-0649
    Keywords: 42.10 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The validity of 2-D coupled-wave theory is investigated for the case of Bragg diffraction of a Gaussian beam by a thick unslanted phase grating in transmission mode. Fourier plane wave decomposition theory, as presented in a companion article, is used to test 2-D coupled-wave theory under circumstances when its validity is in question, namely when the incident distribution is very narrow or fast-varying, or when the parameterv o, due to Kogelnik (1969), which is proportional to the product of coupling rate and grating thickness, is very large. Numerical evaluations of the field patterns at output from the grating, obtained using plane-wave decomposition, are used to explore the effect of the gradual violation of the conditions (from the previous article) under which 2-D coupled-wave theory is valid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00686370
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  • 4
    Electronic Resource
    Electronic Resource
    Thick grating focussing-device-design using poynting-vector-optics (1981)
    Springer
    Applied physics 26 (1981), S. 37-42 
    Details
    ISSN: 1432-0649
    Keywords: 42.80 ; 42.82 ; 42.10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Novel thick grating focussing and de-focussing devices are described which employ uniform phase gratings with special boundary shapes. The analysis used is based upon an eigenmodal approach to Kogelnik's coupled-wave equations, akin to the dynamical theory of x-ray diffraction. The relationship between the direction of phase progression of the coupled-waves at Bragg incidence, and the direction of the Poynting vector is carefully delineated. As a consequence, a new technique-Poynting Vector Optics — is suggested as potentially an important means of designing thick gratings to fulfil certain beam processing roles, especially in integrated optics applications. The two-dimensional coupled-wave equations are briefly employed to illustrate the effectiveness of a particular focussing device.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00702685
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  • 5
    Electronic Resource
    Electronic Resource
    Optics of Floquet-Bloch waves in dielectric gratings (1986)
    Springer
    Applied physics 39 (1986), S. 231-246 
    Details
    ISSN: 1432-0649
    Keywords: 42.10 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The behavior of light in dielectric gratings is discussed in terms of the optical Floquet-Bloch waves (or modes). The emphasis is on the development of a good physical understanding of the nature of these waves, using the wavevector diagram to summarize their spatial dispersion and spectra. It is shown that Floquet-Bloch theory offers some advantages conceptually over the commonly used coupled-wave theory, because the rays of the Floquet-Bloch waves (given by their group velocities) play the same role in a periodic medium as do those of plane waves in isotropic or graded-index media. The effect on power conservation of truncating the Floquet expansions for the Floquet-Bloch waves is considered in detail. Using the greater intuitive power of Floquet-Bloch theory, it is shown (in contrast to recent claims to the contrary) how rigorous coupled-wave theory can be applied to symmetrical reflection gratings, and secondly how the light in these gratings can be viewed in terms of the multiple-beam interference of Floquet-Bloch waves, leading to behavior reminiscent of a low-finesse Fabry-Perot cavity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00697490
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  • 6
    Electronic Resource
    Electronic Resource
    Bragg diffraction of finite beams by thick gratings: Two rival theories (1982)
    Springer
    Applied physics 28 (1982), S. 63-72 
    Details
    ISSN: 1432-0649
    Keywords: 42.10 ; 42.80
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two rival techniques used in the analysis of Bragg diffraction of two-dimensional light beams by thick unslanted phase gratings, namely Fourier plane wave decomposition and 2-D coupled-wave theory, are compared. The advantages and regions of applicability of each are discussed, and the conditions found under which they yield identical results. In particular, the results of plane-wave decomposition are used to provide quantitative conditions for validity of 2-D coupled-wave theory. These conditions are not easily derived using any other technique, and set quantitative limits to how narrow or fast-varying the incident distribution may be before 2-D coupled-wave theory fails. It is also shown that 2-D coupled-wave theory is inadequate when the parameterv 0, due to Kogelnik (1969), which is proportional to the product of coupling rate and grating thickness, is very large.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00693894
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  • 7
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    Pioneer Venus and near-earth observations of interplanetary shocks (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Twenty-three transient interplanetary shocks observed near earth during 1978-1982, and mostly reported in the literature, have also been identified at the Pioneer Venus Orbiter spacecraft. There seems to be a fairly consistent trend for lower shock speeds, farther from the sun. Shock normals obtained using the Pioneer Venus data correspond well with published values from near earth. By referring to the portion of the Pioneer Venus plasma data used here from locations at longitudes within 37 deg of earth, it is found that shocks are weaker at earth, compared with those closer to the sun.
    Keywords: ASTROPHYSICS
    Type: Journal of Geophysical Research (ISSN 0148-0227); 92; 3385-339
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    Intercontinental antenna arraying by symbol stream combining at ICE Giacobini-Zinner encounter (1986)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Deep space tracking stations on different continents were arrayed during the encounter of the International Cometary Explorer (ICE) spacecraft with the comet Giacobini-Zinner during September 9 through 12, 1985. This is the first time that telemetry signals received on different continents have been combined to enhance signal to noise ratio. The arraying was done in non-real time using the method of symbol stream combining. The improvement in signal to noise ratio was typically 2 dB over the stronger of the two stations in each array.
    Keywords: ASTROPHYSICS
    Type: The Telecommunications and Data Acquisition Report; p 220-228
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 9
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    Dust in space and comets; Proceedings of the Topical Meeting, Graz, Austria, June 25-July 7, 1984 (1984)
    In:  Other Sources
    Details
    Publication Date: 2016-03-09
    Description: Consideration is given to: the mass loading of planetary magnetospheres by rocky satellites; the effects of electrostatic forces on the vertical structure of planetary rings; and dust motion in Jupiter's tilted magnetic field. Other topics include: IRAS observations of cometary dust; dust environment models for Comet P/Halley; plasma processes and solar wind interaction; and cometary interplanetary field enhancements in the solar wind. Consideration is also given to: the impact of dust grains on fast fly-by spacecraft; EUV observations of Comet Halley; and the thermal model and thermo-mechanical stresses in cometary nuclei.
    Keywords: ASTROPHYSICS
    Type: (ISSN 0273-1177)
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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    The 10 micron spectral structure in comets (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The 10 micron spectra of comets Halley (1982i), Wilson (1986l), Kohoutek (1973f) and Bradfield (1987s) are presented and compared. The silicate emission profiles of Halley and Bradfield are seen to be remarkably similar in that both contain a sharp break in the spectrum at 11.3 microns. Comet Bradfield does not show the same double peak structure seen in olivine and reported in Comet Halley be Campins and Ryan (1988) and Bregman, et al. (1987). The authors interpret the 11.3 micron signature as being due to olivine-type dust grains with at least some degree of crystallinity. Olivine alone is not enough to reproduce the shape of the 10 micron structure. However, in view of the authors' past success in fitting interstellar dust features with the emissivity profile obtained from amorphous grains produced by laser-vaporizing olivine, this is a very appealing identification. They note that there are significant variations in olivine spectra due to compositional differences, grain size distribution and related grain temperature variations to make the olivine identification tentative. They further tentatively identify the 9.8 micron feature in Halley as being due to either amorphorous olivine or a phyllosilicate (layer lattice). Neither the spectra of Halley, Kohoutek, nor Bradfield exhibited the 12.2 micron feature seen in Comet Wilson, which may prove diagnostic of the composition or thermal history differences between these comets. IR spectra of various mineral samples are discussed in terms of their match to cometary spectra.
    Keywords: ASTROPHYSICS
    Type: NASA, Ames Research Center, Interstellar Dust: Contributed Papers; p 417-422
    Format: application/pdf
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    NASA TECHNICAL REPORTS
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