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  • 1
    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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  • 2
    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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  • 3
    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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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
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    Infrared spectroscopy and photometry of Comet Austin 1990 V (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: 3-micron and 10-micron spectra and IR photometry of the dynamically new Comet Austin 1990 V were obtained for March-May 1990. An unusual 9-11 micron emission feature 15-20 percent above the continuum is evident at 0.78 AU postperihelion. The shape, in particular a peak at 11.06 micron, differs from that seen in Halley and several other comets, suggesting a difference in the mineralogy of the silicate grains. The 3.1-7.7 micron spectrum at 0.35 AU shows no obvious feature; feature/continuum contrast of the 3.36 micron emission feature is less than about 5 percent. Based on the IR photometry and a dust model weighted toward small grains, the dust production rate on 6 May at 0.78 AU was about 3 x 10 exp 5 g/s. The corresponding dust/gas mass ratio was about 0.1, classifying Austin as a dust-poor comet. This designation refers only to the relative dust cross section, not to the total mass.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 101; 1; p. 64-70.
    Format: text
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    NASA TECHNICAL REPORTS
  • 8
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    8-13 micron spectroscopy and IR photometry of Comet P/Brorsen-Metcalf (1989o) near perihelion (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Thermal IR spectrophotometry of Comet P/Brorsen-Metcalf near perihelion was obtained during August 28-September 6, 1989, by the NASA IRTF; these data are presently compared with results for Comet P/Halley. The spectra, which lacked silicate emission, are consistent with 400-430 K grey body emission. The grains are on these bases inferred to have been larger than typical for either new comets or P/Halley. Attention is given to the composition, mass, temperature, and character of the cometary dust in view of Comet P/Halley study results.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 97; 2, Ju; 269-275
    Format: text
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  • 9
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    8- to 13-micron spectroscopy of Comet Levy 1990 XX (1992)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The results are reported of IR spectroscopy of Comet Levy 1990 XX over a three-day period when the comet was about 1.54 AU from the sun roughly 70 days before perihelion. Comet Levy 1990 XX was bright, and for at least part of its inbound journey toward perihelion, active. At a distance of 1.54 AU from the sun it showed strong structured silicate emission with peaks or shoulders at 9.8 and 11.2 microns. These features resemble those of Comets P/Halley and Bradfield 1987 XXIX. The comet was variable in brightness. Specifically, the contrast of the silicate features changed by a factor of two relative to the continuum level and showed some evidence for a shape change as well.
    Keywords: ASTROPHYSICS
    Type: Icarus (ISSN 0019-1035); 100; 1; p. 197-202.
    Format: text
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    NASA TECHNICAL REPORTS
  • 10
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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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