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  • 1
    Digitale Medien
    Digitale Medien
    Escape tunneling out of shallow multiple quantum wells studied by transient four-wave mixing (1993)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 63 (1993), S. 2372-2374 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We demonstrate that transient optical dephasing experiments on electrically biased, shallow multiple quantum wells offer the unique possibility of studying the first step in carrier sweep-out, namely, the tunneling escape out of the individual quantum wells. We find that the electron tunneling times out of the quasibound n=1 quantum well states into the continuum states lie in the subpicosecond regime at high electric fields. In addition, the experimentally determined escape rate is resonantly enhanced when the quasibound n=1 quantum well state couples with the resonant n=2 continuum state originating from the second-nearest neighbor well.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.110479
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  • 2
    Digitale Medien
    Digitale Medien
    Optical bistability in symmetrically strained (GaIn)As/Ga(PAs) superlattices (1996)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 69 (1996), S. 308-310 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have studied the electroabsorptive properties of symmetrically strained (GaIn)As/Ga(PAs) superlattices consisting of 100 periods. Photocurrent measurements at 4 K reveal a pronounced pseudo-blue shift and a Wannier–Stark splitting of the heavy-hole exciton transition. A self-electro-optic effect device has been realized which makes use of the pseudo-blue shift due to the Wannier–Stark localization and of the transparency of the GaAs substrate. The self-electro-optic effect devices show on–off contrast ratios of 2.1 at 77 K and of 1.3 at room temperature. © 1996 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.118042
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  • 3
    Digitale Medien
    Digitale Medien
    Spectroscopy of single metallic nanoparticles using total internal reflection microscopy (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 77 (2000), S. 2949-2951 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We have developed a simple, fast, and flexible technique to measure optical scattering spectra of individual metallic nanoparticles. The particles are placed in an evanescent field produced by total internal reflection of light from a halogen lamp in a glass prism. The light scattered by individual particles is collected using a conventional microscope and is spectrally analyzed by a nitrogen-cooled charge-coupled-device array coupled to a spectrometer. This technique is employed to measure the effect of particle diameter on the dephasing time of the particle plasmon resonance in gold nanoparticles. We also demonstrate the use of this technique for measurements in liquids, which is important for the potential application of particle plasmons in chemical or biological nanosensors. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1323553
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  • 4
    Digitale Medien
    Digitale Medien
    Dynamics of amplified spontaneous emission in InAs/GaAs quantum dots (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 3507-3509 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We investigate the dynamics of amplified spontaneous emission (ASE) in self-assembled InAs/GaAs quantum dots, using pulsed optical excitation of an edge-emitting sample at room temperature. A material gain of 1.5×104 cm−1 is determined for 800 nm excitation with 1.5 μJ/cm2 pulses. Using photoluminescence up-conversion, we show that increases in both electron–hole pair density and photon density in the excited stripe cause a significant decrease in the decay time from 2.2 ns, corresponding to spontaneous emission, to about 0.9 ns, corresponding to stimulated emission or ASE. A carrier capture time of 10 ps limits the onset of the ASE process for short stripe lengths. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.126689
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  • 5
    Digitale Medien
    Digitale Medien
    Launching surface plasmons into nanoholes in metal films (2000)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 76 (2000), S. 140-142 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We investigate optical transmission through individual nanometer-sized holes in opaque metal films using scanning near-field optical microscopy. We show unambiguously that excitation and lateral propagation of surface plasmons support the light transmission through these nanoholes. The direction of the surface plasmon propagation is given by the light polarization, thus controlled addressing of individual holes is possible. In addition, we find characteristic interference effects due to scattering of surface plasmons off holes. © 2000 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.125682
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  • 6
    Digitale Medien
    Digitale Medien
    Capture and thermal re-emission of carriers in long-wavelength InGaAs/GaAs quantum dots (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 3968-3970 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: We investigate the ultrafast carrier dynamics in metalorganic chemical vapor deposition-grown InGaAs/GaAs quantum dots emitting at 1.3 μm. Time-resolved photoluminescence upconversion measurements show that the carriers photoexcited in the barriers relax to the quantum-dot ground state within a few picoseconds. At low temperatures and high carrier densities, the relaxation dynamics is dominated by carrier–carrier scattering. In contrast, at room temperature, the dominant relaxation process for electrons is scattering between quantum-dot levels via multiple longitudinal optical (LO)-phonon emission. The reverse process, i.e., multiple LO-phonon absorption, governs the thermal re-emission of electrons from the quantum-dot ground state. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1421235
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  • 7
    Digitale Medien
    Digitale Medien
    Electrically controlled light scattering with single metal nanoparticles (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 81 (2002), S. 171-173 
    Details
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A concept to electrically control the scattering of light is introduced. The idea is to embed noble metal nanoparticles in an electro-optical material such as a liquid crystal in order to induce a spectral shift of the particle plasmon resonance by applying an electric field. Light scattering experiments on single gold nanoparticles show that spherically shaped nanoparticles become optically spheroidal when covered by an anisotropic liquid crystal. The two particle plasmon resonances of the optically spheroidal gold nanoparticles can be spectrally shifted by up to 50 meV when electric fields of more than 10 kV/cm are applied. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1491003
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  • 8
    Digitale Medien
    Digitale Medien
    Formation dynamics of layer-by-layer self-assembled films probed by second harmonic generation (2002)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 3956-3960 
    Details
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We investigate the formation dynamics of self-assembled polyelectrolyte multilayers on glass substrates by in situ and ex situ second harmonic generation (SHG) measurements and atomic force microscopy (AFM). The time dependence of the SHG signal during the adsorption process is attributed to a time dependent surface potential of the polyelectrolyte film. The dynamics can be quantitatively understood using a random sequential adsorption (RSA) model for the buildup of a film consisting of polyelectrolyte disks with polydisperse sizes. Differences between wet and dry films are also investigated. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1063/1.1495839
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  • 9
    Digitale Medien
    Digitale Medien
    Ultrafast relaxation dynamics of electronic excitations in noble-metal clusters (2000)
    Springer
    Applied physics 71 (2000), S. 381-384 
    Details
    ISSN: 1432-0649
    Schlagwort(e): PACS: 78.47.+p; 65.70.+g; 62.30.+d
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract. We investigate non-equilibrium relaxation processes in optically excited large gold and silver clusters. Time-resolved pump-probe experiments and model calculations show that optical excitation of the clusters by femtosecond laser pulses results in a heating of the electron system, which is followed by electron cooling via phonon emission. The electron heating leads to an enhanced damping of the surface-plasmon resonance in the clusters. This enhanced damping is caused by an enhancement of the Landau damping and electron scattering rates at high electron temperatures. Furthermore, we find that the rate of electron cooling in the clusters changes with electron temperature; this is a consequence of the temperature-dependent specific heat of the conduction electrons. Finally, pump-probe experiments on ellipsoidal silver clusters show that the thermal expansion of the heated clusters triggers mechanical vibrations at the acoustic eigenfrequencies of the clusters.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/s003400000398
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  • 10
    Digitale Medien
    Digitale Medien
    Electric-field-induced exciton ionization in a GaAs/AlGaAs superlattice (1995)
    Springer
    Il nuovo cimento della Società Italiana di Fisica 17 (1995), S. 1759-1762 
    Details
    ISSN: 0392-6737
    Schlagwort(e): Optical transient phenomena (including quantum beats, dephasings and revivals, photon echoes, free induction decay, and optical mutation) ; Excitons and related phenomena (including electron-hole drops) ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Optical properties of thin films, surfaces and thin layer structures (including superlattices, heterostructures, and intercalation compounds) ; Conference proceedings
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Summary We study exciton ionization induced by an axial electric field in a strongly coupled GaAs/Al0.3 Ga0.7 As superlattice at low temperatures. The field-induced ionization times of the heavy-hole 1s exciton in the miniband field regime are determined from transient four-wave-mixing experiments and theoretical model calculations. They are found to lie between the field ionization times of excitons in bulk semiconductors, and in strongly confined quantum well systems.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02457276
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