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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 73-78 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Basic experimental results obtained with a GaAs/AlGaAs double-heterojunction bipolar transistor (DHBT) waveguide structure carrier-injected optical intensity modulator/switch are fully described. Typical common-emitter dc current gain obtained with a 0.25-μm-thick base/waveguide was ∼40, and the switching times have been determined as 1.5 ns. Optical on/off modulation ratios of up to 2.1:1 have been demonstrated at an input base current of as small as 3 mA for a device with emitter/waveguide width of 7 μm and length of 190 μm. Design and analysis of the optical switching characteristics expected for a reflection-type X-crossing optical switch of DHBT waveguide structure are also presented on the basis of these experimental results.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3966-3974 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An increase of surface refractive index and a recovery of the r33 electro-optic coefficient have been observed for proton-exchanged LiTaO3 optical waveguides after annealing. On the basis of the results of nuclear reaction analysis, x-ray rocking curve analysis, and infrared-absorption spectroscopy, a qualitative model to explain these phenomena is proposed. The evolutions of the index profile and the r33 coefficient after proton exchange and annealing are considered to be caused by the movement of protons in the crystal lattice and the interdiffusion of protons and Li ions. The condition required for the fabrication of waveguides with good electro-optic performance is also shown.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 57 (1990), S. 227-228 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Device structure, fabrication method, and experimental results of a GaAs/AlGaAs traveling-wave directional coupler optical modulator/switch operated at 1.06 μm wavelength are described for the first time. An extinction ratio of 13.7 dB has been measured at the switching voltage of 10.4 V, and a 3 dB bandwidth of 9.1 GHz has been demonstrated for a device with a waveguide width of 5.5 μm, waveguide spacing of 3.5 μm, and length of 8 mm.
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  • 4
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2591-2593 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Device fabrication and basic experimental results obtained with a heterojunction bipolar transistor waveguide structure optical intensity modulator, whose device structure is particularly suitable for possible monolithic integrated circuits, are described for the first time. Common emitter dc current gain hFE obtained with a 0.25-μm-thick base/waveguide was 38, and the switching times have been determined as 1.5 ns. Free-carrier injection modulates the absorption coefficient α in the waveguide mainly by the band filling and plasma dispersion effects and consequently, the output light intensity can be modulated. The optical on/off modulation ratio of up to 2.1:1, corresponding to a modulation efficiency of Δα/α∼89%, has been demonstrated at a base current of 3 mA for a device with an emitter/waveguide width of 7 μm and a length of 190 μm.
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  • 5
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 1606-1608 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: By loading periodic loss perturbation into a GaAlAs/GaAs distributed feedback laser, we have realized complete single longitudinal mode oscillation which is hardly disturbed by cleaved facet reflection. Our coupled-mode analysis explains this empirical result well.
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  • 6
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 387-389 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A modulated stripe width structure (MSW) has been applied to a GaAlAs/GaAs distributed feedback buried heterostructure laser to obtain complete single longitudinal mode oscillation. An MSW device having a gradual modulation scheme and antireflecting films on the cleaved facets has been fabricated using reactive ion etching (RIE). Principal results include realization of a reactive ion etched second-order grating with the grooves as deep as 0.15 μm after regrowth and a modulated stripe having extremely fine definition made possible by RIE. The device had a spectrum which agreed markedly well with an analytical result. The effective functioning of the MSW structure has thereby been confirmed experimentally.
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 4494-4498 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: When a chalcogenide glass film of composition As10Ge22.5Se67.5 is sensitized with evaporated silver selenide and is exposed to an electron beam, it is suggested that, as is the case for photodoping, silver will migrate from the unexposed region into the exposed one. This results in different silver distributions in the exposed regions. The distribution has been found, for the first time, to depend on various factors other than dosage, namely, the thicknesses of sensitized layers and glass films, and the size of the exposed region. Moreover, the form of the distribution is affected by the thickness of the sensitized layer but not that of the glass film, while it is not the thickness of the sensitized layer but that of the glass film which has an effect on the rate of change of silver concentration at the periphery or at the center versus dosage. By considering the amount of silver selenide remaining on the top of the exposed region, and by further assuming that silver diffusivity in the doped region is small when its concentration is low and that it will increase as the concentration is sufficiently large, one may be able to qualitatively explain the dependence of the distribution on the thickness of the sensitized layer.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 64 (1988), S. 1378-1383 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In photodoping, it is well known that the silver concentration of the exposed region is somewhat higher at the edge than at its interior. This is termed the "edge sharpening'' effect. Exposure by electrons or ions has been reported to produce no such effect, which leads to the conjecture that it might be dependent on the kind of irradiation involved. However, we have shown here by electron probe microbeam analysis, without ambiguity, that the edge-sharpening effect does occur in regions of a chalcogenide glass film As10Ge22.5Se67.5 that is coated with silver selenide and exposed by electrons of 25 keV. Furthermore, we have observed, for the first time, that silver concentration at the periphery of the exposed region increases with dosage. It has then been shown that such a silver distribution is not due to the temperature gradient of a highly focused electron beam. Finally, exposure by electron beam has been found to induce surface-topological changes in the exposed regions at a dosage of about 1 C/cm2, which is similar to photoinduced surface-topological changes studied recently. These characteristics have an important effect on patterning in the submicron range by electron beam lithography using the induced silver doping effect.
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  • 9
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 59 (1991), S. 2778-2780 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In a parabolic quantum well, the shift in optical transition energy due to the quantum confined Stark effect is independent of the carrier effective mass. This fact enables us to realize polarization-independent optical waveguide intensity switches with high on/off ratio. An absorption-type switch with GaAs/Al0.3Ga0.7As equivalent parabolic quantum wells is fabricated with molecular beam epitaxy. Both transverse-electric and transverse-magnetic mode lights exhibit an on/off ratio of 27.6 dB at an applied voltage of 6.84 V at 850 nm wavelength. To our knowledge, this is the first polarization-independent optical waveguide intensity switch based on the electric-field-induced effect in the semiconductor quantum well.
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  • 10
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 68 (1996), S. 832-834 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Signal delays in interlayer films limit the performance of very large scale integrated (VLSI) circuits. Signal delays can be reduced by using interlayer films with low dielectric constants, such as fluorine-doped (F-doped) SiO2 films. We were able to fabricate F-doped SiO2 films with dielectric constants as low as 2.3 and with good step coverage, by adding CF4 to SiH4/N2O plasma-enhanced chemical vapor deposition (PECVD). The reduction of the dielectric constant apparently results from a decrease of the ionic polarization. The improvement of step coverage is due to a decrease of the sticking probability of the film-forming species. © 1996 American Institute of Physics.
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