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  • 1
    ISSN: 1434-601X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Thick layers of iron, cobalt and nickel were evaporated on glas-substrates in a vacuum of 2 · 10−7 Torr. The thickness of the layers was about 95 to 200 nm. The dispersion of the optical constants, the dispersion of rotation and ellipticity of the polar magnetooptic Kerreffect at normal incidence, and the dispersion of the ellipticity of the equatorial magnetooptic Kerreffect at two different angles of incidence were measured in the range of frequencies from 400 to 2,000 nm in the magnetically saturated state. The measurements of the equatorial effect are compared with those calculated from the polar effect according to Voigt. There arise discrepancies which are larger than the error of measurement. These differences prove, that it is insufficient only to consider the interaction of the light wave with the electron orbits like in Voigt's theory; in a uniform description of all magnetooptic effects the influence of the spins has to be regarded, too. It is possible to separate the “electric” and the “magnetic” contribution of the interaction of light. Both parts are of the same order of magnitude.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract The transient optical response of quantum wells (QWs) after optical and electrical carrier injection into the barrier layers is studied experimentally and theoretically. We have varied the transport geometry in GaAs/AlGaAs and InGaAs/InAlGaAs heterostructures and emphasize the basic principles for a theoretical treatment of electron and hole capture into QWs for a proper description of vertical carrier transport in the barriers of QW heterostructures. Comparing our experimental data with the results of theoretical model calculations, we determine the capture, reflection and transmission probabilities, the ambipolar diffusivities and the ambipolar mobilities in the barriers of GaAs/AlGaAs, as a model system. The temporal evolution of the electron and the hole capture current densities at the QWs are studied in detail for a wide variation of the injected carrier densities. Amplitude modulation experiments are performed for InGaAs/InAlGaAs QW laser devices providing increasing 3 dB frequencies for decreasing confinement layer thickness, indicating the influence of carrier transport in the barriers.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Asymmetrically confined multiple quantum well laser structures have recently been very successful in reaching high modulation bandwidths up to 26 GHz, reported in the InGaAs/InGaAlAs material system. We have measured the effective carrier transport time in structures of this kind by performing parasitic-free optical modulation experiments. The result is one specific transport time for each confinement layer width. We show that down to layer widths of about 100 nm this effective time for both types of carriers is given by a pure diffusion process for InGaAs/InGaAlAs. Finally, a diffusion constant for the barrier/confinement carriers results in InGaAlAs material which is in very good agreement with reported mobilities. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Coupling coefficients as high as 300 cm−1 have been achieved and investigated in the performance of distributed feedback lasers. High coupling has several important advantages like lower feedback sensitivity, and lower influence on facet reflectivity, thus easy handling for coatings without any penalty in terms of mode hopping. We obtain a side-mode suppression ratio as high as 51.2 dB. 8 Gb/s "nonreturn to zero'' modulation is demonstrated.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Physical laser parameters such as differential gain and differential refractive index are determined for InGaAs/InAlGaAs quantum well structures by comparing experimental results of different lasers with theoretical data from transfer matrix model calculations. By using the determined parameter set, the wavelength shift with current λ(I) is found to depend strongly in shape and magnitude on the end facet phases. Within one order of magnitude we found weak and strong variations related to the variation of the axial nonuniformity of the carrier and photon densities with current.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 478-480 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Epitaxial layers of nominally undoped GaAs have been grown by metalorganic chemical vapor deposition using liquid tertiarybutylarsine and triethylgallium. n-type layers were obtained having total residual shallow acceptor concentrations of ∼1013 cm−3 and Hall mobilities comparable to those obtained with arsine and triethylgallium in the same reactor. Liquid-nitrogen Hall mobilities up to 116 000 cm2 /V s were observed.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2029-2031 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The growth of high-purity gallium arsenide using tertiarybutylarsine (TBA) and trimethylgallium is reported. The availability of high-purity TBA has permitted the growth of material with liquid-nitrogen mobilities of up to 80 000 cm2/V s, the highest value yet reported for growth with any alkyl arsine. The residual donor species have been identified by magnetophotoluminescence.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 7138-7144 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have investigated inhomogeneously pumped index-coupled distributed feedback (DFB) laser structures both theoretically and experimentally. Using a transfer matrix method, an optimized device structure was designed which drastically suppresses the longitudinal sidemodes by concentrating the injection current in the region close to the phase-shift position. In this way, a high yield of monomode lasers together with an easy fabrication technique was achieved without the necessity of end facet antireflection coating. Experimental evidence of the improvement of the single-mode stability is given first by three-section DFB lasers operated by two different injection currents. Second, the proposed three-segment laser pumped with a single drive current was implemented simply by splitting up the contact of a mushroom type 2×λ/8 phase-shifted DFB laser. We observed the theoretically predicted enhanced stability of the Bragg mode with a sidemode suppression ratio of 52 dB and a higher yield of monomode lasers compared with uniformly pumped conventional DFB laser devices.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The residual donor species in undoped GaAs epilayers grown by metalorganic chemical vapor deposition have been characterized by magnetophotoluminescence (MPL) measurements at high magnetic fields (7 T). Most samples were grown using trimethylgallium and arsine, but samples grown using the liquid group-V source t-butylarsine were also studied. The results show good agreement with identifications previously made in high-purity samples (NA+ND≤5×1014 cm−3) at zero magnetic field, but with greatly improved spectral resolution and signal levels. With the MPL technique, residual donor species were resolved even in relatively impure samples (NA+ND=1×1016) for which no information was obtained at zero magnetic field. For the samples grown with arsine, Ge donors were observed to predominate in the high-purity samples, but Si was the dominant donor in the lower-purity samples. The Si impurity was traced to contamination from a quartz baffle in the growth chamber. Lower levels of sulfur donors were observed in many samples. Sulfur was found to be the second most predominant donor after Ge in samples grown with t-butylarsine.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 16 (1990), S. 77-81 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: InP wafers were ion-beam-etched using different energies. The damaged surfaces were investigated by ellipsometry at different angles of incidence as a function of wavelength. Penetration depths and changes in refractive indices nD - iKD are shown. Si3N4- coated sputter-etched InP wafers are also measured with multiple angle of incidence (MAI) ellipsometry. Coatings are removed step by step by wet chemical etching, and MAI ellipsometry is carried out after each step. The results are fitted to the model InP/sputter-damaged layer/Si3N4. The parameters for the damaged layers are given.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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