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Summary form only given. We present femtosecond time-resolved investigations of non-equilibrium coherent 1.0 phonon dynamics in CdS/sub 0.7/Se/sub 0.3/ quantum dots embedded in a glass matrix. The three-dimensional quantum confinement of the LO phonons has been demonstrated by means of linear Raman spectroscopy. For the electron and hole states the size of the microcrystallites is in the regime of...
Summary form only given. Reversible phase change materials such as compounds of the pseudo-binary GeTe-Sb/sub 2/Te/sub 3/ system are applicable as high-density optical data storage media based on the relatively high difference in the reflection coefficients of the amorphous and the crystalline states. Although this principle is already employed in commercial DVD disks, the physics of the phase transitions...
Summary form only given. In recent years, nanoparticles of metals, such as gold, silver, and copper, have attracted much attention because they have electrical and optical properties that are different from those of bulk metals. Electron dynamics and optical nonlinear response of metallic nanoparticles have been studied extensively and suggested that metallic nanoparticles are promising candidates...
Summary form only given. Recently, various spectral interferometries have been developed to measure separately ultrafast phase and transmission change induced by short pulses. Our group developed a femtosecond Sagnac interferometer in order to obtain time-resolved difference phase and transmission spectra, which are hereafter abbreviated to TRDPS and TRDTS, respectively. In the present study, we obtained...
Summary form only given. Since the discovery of high transition temperature superconductivity more than decade ago a controversial debate still exists on the underlying pairing mechanism not yet resolved. A key parameter is the carrier concentration in the conducting copper-oxide planes, which, in the case of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO), is varied by altering the oxygen content...
Summary form only given. Recent experiments have revealed ultrafast optically-induced dynamics in the time-resolved magneto-optical (MO) signals obtained in metallic ferromagnetic samples. The very short time scales that have been reported seem to exclude the role of spin-lattice interactions in the dynamics and open several fundamental questions about the physical mechanism responsible for fast demagnetization...
Summary form only given. Reduction of the size of a material to a nanometric scale leads to drastic modifications of its properties. In metallic systems, they are largely conditioned by the alteration of the conduction electron scattering processes whose study is thus of both technological and fundamental interests. Time-resolved femtosecond techniques have been shown to be powerful tools for their...
Summary form only given. It is usually assumed that first-order interband transitions in crystalline solids occur almost vertically in the band structure since the photon momentum is negligible compared to the reciprocal lattice vector. Especially, optical excitation and probing of free excitons in direct semiconductors is considered possible only in the center of the Brillouin zone and with photon...
Summary form only given. Molecular J-aggregates have attracted much attention because of the ultrafast and large optical nonlinearity caused by the excitonic resonance.
Summary form only given. The dynamics of phonon-polaritons generated with ultrafast pulses has been an active area of investigation in the past decade. Efforts have been concentrated on the wide-gap perovskites that undergo phase transformations associated with the softening of an optical phonon in order to determine what roles anharmonicity and photon-phonon coupling play in structural phase transitions...
Summary form only given. Intense investigations of Bloch oscillations in semiconductor superlattices have been performed in four-wave mixing, THz emissions and resonant transmittive electro-optic sampling experiments. An intriguing objective of the studies is the experimental determination of the spatial amplitude of the oscillating electronic wavepackets in the artificial heterostructures. We present...
Summary form only given. Devices using quantum wires (QWR) are of much current interest. In recent times, several investigations have focussed attention on optical properties of QWRs at high excitation densities. In comparison, studies of excitonic interactions in QWRs are few. We perform femtosecond degenerate four wave mixing (DFWM) and picosecond photoluminescence measurements at 8 K on GaAs/AlAs...
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