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  • 1990-1994  (17)
  • 1985-1989  (14)
  • 1930-1934  (1)
  • 1
    Digitale Medien
    Digitale Medien
    Implosion-driven hypervelocity accelerator (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 5254-5256 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A hypervelocity accelerator has been developed utilizing the extreme condition produced by the collapse of the cylindrical imploding shock wave. The cylindrical shell of the explosive is detonated by the explosion of rows of copper wires bound around it. The wire explosion is caused by the application of an impulsive electric current. The energy concentrated at the implosion center is imparted to the projectile accelerating it. The launch velocity of 1.2 km/s has been attained for a 2 g launched weight with a 60 g explosive (PETN: pentaerythritoltetranitrate). A further increase of the launch velocity is expected by increasing either the explosive thickness or the height of the cylindrical shell within practical limit.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.350585
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  • 2
    Digitale Medien
    Digitale Medien
    Numerical simulation of cylindrical converging shocks in solids (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 2605-2611 
    Details
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Cylindrically converging shock waves in solids have been analyzed by the random choice method (RCM). A Riemann solver for fluidlike solids with the Grüneisen-type equation of state is constructed and incorporated into the RCM. It is then applied to the cylindrical shock tube problems for solid copper with driving pressures of 20 and 200 GPa. The numerical results are compared with those of the finite difference method (FDM). The shock speed is smaller and the discontinuity at the shock front is smeared out due to the artificial viscosity in the FDM calculation. Spatial distributions of pressure, density, and particle velocity calculated by the RCM show that the steepness at the shock front is maintained both in the converging and reflecting stages. It is shown that the pressure on the shock front and the total energy contained in the central circular area are much larger in the reflecting stage than in the focusing stage. The dimensional analysis has shown that the similarity solution exists; however the numerical result shows that the flow does not fall within the similarity regime in the region of calculation. It suggests that the self-similar flow is only limited in extreme proximity to the axis.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.351560
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  • 3
    Digitale Medien
    Digitale Medien
    Radiative properties of a highly excited quantum well (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1485-1487 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We study by time-resolved luminescence, the radiative recombination from a single quantum well placed inside a graded confinement structure. We are able to produce a cold (T〈50 K), high-density (5×1011〈N〈5×1012 cm−2) plasma. We compare our spectra with usual lineshape fitting procedures and give evidence for the shortcomings of such an analysis. We detail the consequences of the present work for the determination of band-gap renormalization, the conservation of k-selection rule, and the measurement of the radiative recombination rate.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.105204
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  • 4
    Digitale Medien
    Digitale Medien
    Observation of free excitons in room-temperature photoluminescence of GaAs/AlGaAs single quantum wells (1988)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 53 (1988), S. 675-677 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: Observation of free excitons is reported in room-temperature photoluminescence of nominally undoped GaAs/AlGaAs single quantum wells grown by molecular beam epitaxy. A comparative study with parallel-conduction photocurrent spectroscopy shows that a sharp luminescence peak with a linewidth of 14 meV observed for the 6.1-nm-wide well coincides within 2 meV with the n=1 heavy-hole free-exciton resonance line at excess carrier densities less than 1017 cm−3. Excitonic decay channels dominate the luminescence spectrum even at room temperature as a result of quantum confinement effects, although photogenerated carriers are also provided for photocurrents by exciton dissociations.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.99847
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  • 5
    Digitale Medien
    Digitale Medien
    Electro-optical multistability in GaAs/AlAs superlattices at room temperature (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 605-607 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have studied the optical absorption properties of a GaAs/AlAs short-period superlattice at room temperature in an electric field perpendicular to the layers. Several pronounced optical transitions related to Wannier–Stark localization are observed indicating a coherence length of at least five superlattice periods. These transitions produce multiple regions of negative differential photoconductivity which are used to realize a multistable self-electro-optic effect device.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.102711
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  • 6
    Digitale Medien
    Digitale Medien
    Linear polarization effects in anisotropic photoemission from GaAs/AlAs short-period superlattices (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 1717-1719 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: By investigating the linear polarization dependence of intrinsic emissions from undoped GaAs/AlAs short-period superlattices at room temperature, it is shown that a dominating peak observed in the normal emission spectra is due to the free-carrier recombination associated with the lowest electron to mixed-hole subbands with an unexpectedly large light-hole character instead of with the lowest electron to pure heavy-hole subbands expected in an ideal superlattice. Origins of the extensive valence-band mixing in the synthesized superlattices are discussed in relation to microscopic fluctuations in the layer thicknesses observed in the transmission electron microscope lattice image.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.98554
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  • 7
    Digitale Medien
    Digitale Medien
    Capture of photoexcited carriers by a laser structure (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 55 (1989), S. 2646-2648 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The capture of photoexcited carriers in different laser structures is investigated by subpicosecond luminescence spectroscopy. The capture time at 20 and 80 K is monitored by the decay of the luminescence of the confinement layers. It is found to range between 2 and 3 ps for both linear and parabolic grading, and to be much longer in nongraded structures. The improvement of the capture in the case of graded structures is due to the quasi-electric field experienced by the carriers, and might allow the devices to run at much higher frequencies.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.101962
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  • 8
    Digitale Medien
    Digitale Medien
    Carrier trapping in single quantum wells with different confinement structures (1987)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 51 (1987), S. 226-228 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The trapping efficiency and trapping dynamics of photoexcited carriers in GaAs/AlGaAs single quantum wells with different confinement structures are examined at low temperature by means of picosecond luminescence as well as photoluminescence excitation spectroscopy. The trapping efficiency is 100% only in graded-index separate confinement heterostructures with a linear band-gap profile. The lower trapping efficiency of other confinement structures is due to radiative and nonradiative recombination in the confinement layers.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.98456
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  • 9
    Digitale Medien
    Digitale Medien
    New method of generating cylindrical imploding shocks using a flyer disk (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 61 (1992), S. 3110-3112 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A pancake-like explosive layer loaded over a circular disk (flyer) was detonated from the periphery. The flyer was locally accelerated downward causing a deformation front to propagate toward the center as it was swept by the detonation front. This acted as a cylindrical piston and a cylindrical imploding shock was generated. Shocks were observed by framing camera photographs. The motion of the flyer was also investigated analytically assuming a simple theoretical model.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.107976
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  • 10
    Digitale Medien
    Digitale Medien
    Dual wavelength optical bistability and multistability in a symmetric self-electro-optic effect device based on Wannier–Stark localization (1992)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 60 (1992), S. 1679-1681 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A tunable optical switch has been studied of a symmetric self-electro-optic effect device based on Wannier–Stark localization (WSL) in GaAs/AlAs superlattices. This device is driven by two different wavelengths for a signal beam and a control beam. Clear bistability and/or triple stability are demonstrated by controlling the illumination wavelengths. The tunability of the switching properties is clearly explained by the WSL mechanism.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.107235
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