Losses of optical multimode strip-waveguides made by thick film technology

Loss measurements on straight and curved multimode strip-waveguides made from photosensitive sheets by a photolithographic process are reported. The cross section of the waveguides vary from 20 μm × 50 μm to 100 μm × 100 μm. The loss is detected by measuring the light scattered out of the waveguide. Waveguides fabricated by a modified technology are compared to conventional ones at wavelengths of 0.633 μm and 0.83 μm. Using the modified technology losses of 2 dB/cm at λ = 0.83 μm have been measured for both straight and curved (radius 30 mm) guides.     

Kinetik der Alterung von anodischen Deckschichten auf Aluminium durch Farbstoffaufnahmen

Zusammenfassung Durch Messungen der Alterung (Verminderung der prozentualen Farbstoffaufnahme) der zwei aufeinander liegenden Oxyde auf anodisch oxydiertem Aluminium wurde folgendes festgestellt: Das genannteγ ₂-Al₂O₃ weist keine wesentliche Alterung in der Luft und unter Wasser auf, da es kompakt und geordnet ist. Dasγ ₁-Al₂O₃ altert in der Luft und unter Wasser proportional der Zeit. Seine Alterungsgeschwindigkeit ist proportional der Herstellungsstromdichte. Nach 12 A/dm² nimmt die Alterung nicht mehr zu, da dieses Oxyd die maximale Fehlordnung besitzt. Die Alterung in der Luft ist kleiner als unter Wasser, da dieses mit seinem L?sungsverm?gen für die Rekristallisation günstig ist. Mit zunehmender Temperatur nimmt die Alterungsgeschwindigkeit bis 90°C zu und f?llt darüber hinaus bis zu Null (120°C). Bei h?heren Temperaturen findet eine Verjüngung des Oxyds statt. Dieses Ph?nomen mit Temperaturmaximum ist zum ersten Mal bei heterogenen Reaktionen unter ?nderung eines festen Stoffes festgestellt worden und bedeutet eine Rückreaktion entweder unter Bildung von neuen Fehlordnungen (die Werte der Aktivierungsenergien der Hin- und Rückreaktion sind dafür plausibel) oder eine Freilegung von anwesenden aktiven Zentren, wegen Desorption von Wasser.     

Ruled surfaces with vanishing second Gaussian curvature

For a surface free of points of vanishing Gaussian curvature in Euclidean space the second Gaussian curvature is defined formally. It is first pointed out that a minimal surface has vanishing second Gaussian curvature but that a surface with vanishing second Gaussian curvature need not be minimal. Ruled surfaces for which a linear combination of the second Gaussian curvature and the mean curvature is constant along the rulings are then studied. In particular the only ruled surface in Euclidean space with vanishing second Gaussian curvature is a piece of a helicoid.     

Observed difference between the probabilities of recoilless resonance absorptionf′ and reemissionf″ of gamma-quanta in single crystals of Na2[Fe(CN)5NO]·2 H2O

The recoilless absorption probability factor,f, and recoilless reemission,f, both measured on Na₂[Fe(CN)₅NO]·2 H₂O single crystals using the black filter technique, were found to be different. Unexpectedly, the results found weref>f. In the calculation off, selfabsorption in the scatterer, non-ideality of the black filter and the influence of non-resonant scattering processes have all been taken into account. By varying the scattering geometry for the incoming and outgoing -beam relative to the crystallographic axes only a change in the reemitted valuesf _a, f_b, f_c could be detected because of the long lifetime of the excited nucleus (10^–7 s) relative to the lattice vibration frequencies (10¹² Hz).     

Electronic structure of lithium graphite

X-ray photoemission spectra of vacuum cleaved LiC₆, prepared from highly oriented pyrolytic graphite, provide a direct measure of the filling of the graphite π bands by electrons from Li. The resulting Fermi energy shift is in agreement with recent band structure calculations and indicates near unity charge transfer from Li. Core level spectra exhibit shifts compatible with the expected charge transger and line shapes showing strong asymmetries resulting from the metallic character of this compound.     

The structure of a stepped copper (410) surface determined by ion scattering spectroscopy

Ion Scattering Spectroscopy applied in the multiple scattering mode is used to determine the structure of a stepped Cu(410) surface. The energy of singly scattered ions is influenced by the presence of neighbour surface atoms. This effect can be used to determine interatomic distances up to about 10Å, as is shown by the results of 8 keV Ar⁺ and 11 keV Ne⁺ scattered through θ = 50°. The edge-edge distance of the stepped copper surface appears to be in accordance with the results of LEED experiments obtained by other investigators. The experiments show a good agreement with the results of the analytical 3-atom model of Poelsema. The energy of the so-called “plateau collision” appears to depend on the effective plateau length l as measured in the plane of incidence. Lengths l between 15 and 60 Å can be determined with an accuracy of 5 Å. Results are shown for 8 and 12 keV Ar⁺, θ = 40° and 60°, and 8 keV Kr⁺ θ = 40°. The experimental dependence of the energy on lis described correctly by a phenomenological model.     

Neutronh 11/2 alignments in the triaxial nucleus133La

High spin states have been studied in¹³³La via the¹²²Sn (¹⁵N, 4ny) fusion evaporation reaction. Bands build on low lying h_11/2,g_7/2 and d_5/2 proton states have been identified. At higher spin a h_11/2 neutron alignment is observed. The softness with respect to the triaxial deformation makes the nuclear shape sensitive to the quasiparticle configurations and coexistence between states withy ≈ + 30°,y ≈ ? 30° andy ≦ ? 60° was found. The results have been interpreted using total routhian surface (TRS) model calculations.