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  • 1990-1994  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    Photoelastic AlGaAs/GaAs waveguide polarizer (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2047-2049 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: AlGaAs/GaAs double heterostructure transverse-electric (TE) waveguide polarizers, 5 mm long, with extinction ratios exceeding 20 dB and excess losses of 〈1 dB have been fabricated using simple thin film technology. The single-mode photoelastic waveguides were made by depositing either a thin Ni film (∼1000 A(ring)) with a 5-μm-wide window stripe pattern followed by thermal annealing or a thin W film (∼900 A(ring)) with a 5-μm stripe pattern using rf sputtering with the substrate under negative dc bias. The polarization mode selection is caused by the stress-induced birefrigence of the photoelastic waveguides. The change in dielectric constant due to stresses in the thin film structure was obtained from the experimental intensity output profile using an iterative calculation method. The tensile stress is 3×109 dyn/cm2 in the fully reacted Ni3GaAs stressor layer. The stress in the as-sputtered W films was compressive and decreased from 1×1010 dyn/cm2 to 4×109 dyn/cm2 after annealing between 300 and 500 °C for 30 min.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.110587
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Photoelastic waveguides formed by interfacial reactions (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 62 (1993), S. 2944-2946 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The fabrication of low-loss photoelastic waveguides in GaAs/AlGaAs layered structures by thin film reactions is investigated. The waveguides are formed by opening a narrow window stripe, a few microns wide, in an otherwise continuous Ni layer under tension deposited on a semiconductor structure. The local tensile stress induced by the Ni layer in the semiconductor causes the local refractive index to increase, thus providing the guiding mechanism. Annealing the sample at 250 °C for 1 h induced an interfacial reaction between the Ni film and the substrate to form Ni3GaAs. The formation of an interfacial compound stabilizes the stresses, making the stress state independent of the deposition system and technique. Single-mode waveguide propagation losses as low as 1.4 dB/cm at 1.53 μm wavelength have been obtained on annealed waveguides. Further annealing up to 600 °C did not cause degradation in the optical confinement, thus indicating a thermally stable planar waveguide fabricated by this process. Other photoelastic optical devices such as polarizers, splitters, and couplers are also demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.109204
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Multiscale adaptive estimation of the conductivity field from head and tracer data (1993)
    Springer
    Stochastic environmental research and risk assessment 7 (1993), S. 66-82 
    Details
    ISSN: 1436-3259
    Keywords: Parameter identification ; multiscale ; transport ; adaptive
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract Large scale fluctuations in the conductivity field are regionalized and estimated via a maximum likelihood, adjoint-state methodology. Small-scale fluctuations within each region are estimated adaptively via a Kalman-like stochastic filter. The variance and integral scale within each region are assumed to control the small-scale fluctuations. A Monte Carlo technique is used to examine the distribution of large-scale conductivity estimates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581567
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Proterozoic depletion of the lithosphere recorded in mantle xenoliths from Inner Mongolia (1992)
    [s.l.] : Nature Publishing Group
    Nature 360 (1992), S. 333-336 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Alkali and tholeiitic basalts of Pleistocene age, the former often carrying ultramafic xenoliths, occur over wide areas of the Chinese province of Inner Mongolia, and also extend into TABLE 1 Analytical data for xenolith minerals and host rocks Sm Nd Rb Sr Equilibration Sample ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/360333a0
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    Paper (German National Licenses)
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