Search Results - (Author, Cooperation:V. Pellegrini)

2011-06-04

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

2015-01-03

American Association for the Advancement of Science (AAAS)

0036-8075

1095-9203

Biology

Chemistry and Pharmacology

Computer Science

Medicine

Natural Sciences in General

Physics

1077-3118

AIP Digital Archive

Physics

We report the observation of cavity-induced modifications of the three-dimensional bulk exciton emission in a planar GaAs microcavity, in which the entire cavity layer is an active material. We have performed standard photoluminescence measurements at various emission angles, obtaining evidence of coupling between the exciton and the cavity mode. The modified density of photon states available for the exciton decay shows up in the angle dependence of the emission lineshape, as well as of the photoluminescence peak intensity. The experimental results are qualitatively clarified with theoretical calculations performed with an adapted transfer-matrix approach. © 1995 American Institute of Physics.

Electronic Resource

0038-1098

Elsevier Journal Backfiles on ScienceDirect 1907 - 2002

Physics

Electronic Resource

1432-1998

Springer Online Journal Archives 1860-2000

Medicine

Abstract We desribe a patient with the typical features of Hajdu-Cheney Syndrome. The previously undescribed cranial computerised tomographic (C.T.) findings in this condition are discussed. In addition we describe a possible association with bowel malrotation.

Electronic Resource

0392-6737

Polaritons (including photon-phonon and photon-magnon interactions) ; Excitons and related phenomena (including electron-hole drops) ; Quantum optics ; Electron states in low-dimensional structures (including quantum wells, superlattices, layer structures, and intercalation compounds) ; Conference proceedings

Springer Online Journal Archives 1860-2000

Physics

Summary A great interest in the study of exciton-photon coupling in resonant optical media such as semiconductor microcavities is currently developing both in experiments and in theory. We investigate the spectral response of a new semiconductor quantum system in which the cavity material itself is the active medium. If the Fabry-Perot quasi-mode is carefully tuned on the excitonic transition of the cavity bulk material, strong exciton-photon coupling takes place and produces new features such as a Rabi-like splitting as large as that observed in quantum well microcavities and comparable optical absorption. In addition, the polaritonic spatial dispersion and the quantization of the centre-of-mass motion introduce remarkable fine structures which are absent in the quantum well case. We demonstrate the above effects from a spectroscopic analysis of GaAs cavities, using standard reflectance and photoluminescence techniques. The experimental results are further clarified with theoretical calculations performed with an adapted transfer-matrix approach. The case of semi-cavities is finally considered and a new way to control the exciton-photon interaction in our system is achieved tailoring the photonic wave function with a change in the reflectivity phase of the mirrors.

Electronic Resource

0392-6737

Optoelectronic devices ; Other solid inorganic materials ; Electron states in low-dimensional structures (superlattices, quantum well-structures and multilayers) ; Quantum optics ; Conference proceedings

Springer Online Journal Archives 1860-2000

Physics

Summary The properties and preliminar applications of porous-silicon (p-Si) microcavities are here reported. These structures are based on a planar resonator formed by two narrow-band high-reflectance distributed Bragg reflectors separated by a thin active optical layer, all of which are made of p-Si layers. The accurate control of the electrochemical dissolution of Si lets us realize p-Si multilayers with the desired refractive indices sequence. Large improvements of the emission properties of p-Si microcavities with respect to standard p-Si samples are observed: 1) increased emission intensity, 2) spectral narrowing of the emission band, and 3) high directionality in the emission pattern. Resonant-cavity light-emitting diodes with higher efficiencies and stabilities with respect to standard p-Si/metal devices are demonstrated. Reflectivity changes due to absorption saturation have been observed.

Electronic Resource

0392-6737

Optoelectronic devices ; Other solid inorganic materials ; Time-resolved optical spectroscopies and other ultrafast optical measurements in condensed matter ; Interfaces ; heterostructures ; nanostructures ; Conference proceedings

Springer Online Journal Archives 1860-2000

Physics

Summary We report the observation of strong red- and blue-light emission in free-standing porous-silicon samples prepared fromn + substrates at different anodization current densities. The surface morphology of the free-standing samples has been analyzed by means of atomic-force microscopy. Upon excitation with nanosecond pulses at room temperature, both blue and red luminescence bands appear, peaked around 3.2 and 2.0 eV, respectively. An extensive study of the time-resolved behavior of the photoluminescence signal reveals different dynamical features for the two spectral regions. The observed long decay time (several μs) of the red band reflects the predominant effect of non-radiative processes and is consistent with models based on excition diffusion through the interconnected silicon nanocrystals (quantum dots) skeleton. The relatively fast blue-band decay time (≈400 ns) is shown to be related to non-radiative recombination through trap states at the silicon nanocrystal surface.

Electronic Resource

0392-6737

Optoelectronic devices ; Conference proceedings

Springer Online Journal Archives 1860-2000

Physics

Summary I–V DC characteristics have been measured on metal/ porous-silicon structures. In particular, the measurements on metal/ free-standing porous-silicon film/metal devices confirmed the result, already obtained, that the metal/poroussilicon interface plays a crucial role in the transport of any device. Four-contacts measurements on free-standing layers showed that the current linearly depends on the voltage and that the conduction process is thermally activated, the activtion energy depending on the porous silicon film production parameters. Finally, annealing experiments performed in order to improve the conduction of rectifiyng contacts, are described.

Electronic Resource

1432-5241

Rhinoplasty ; Psychology ; Rorschach

Springer Online Journal Archives 1860-2000

Medicine

Abstract Interest in the psychological problems that have always been associated with plastic surgery has been growing in the last 30 years, as moral and social prejudices have become less important. This interest has concentrated on the psychological mechanisms that induce patients to undergo surgery and on the selection criteria to be followed by surgeons. This report proposes a new method for tackling these problems. It is based on our experience as well as on the investigation, by means of interviews and tests (MMPI and Rorschach), of subjects requesting rhinoplasty. These elements have helped in propounding theories on the relationship between surgery and its psychological aspects, as based on three points: 1) the feelings of the individual that derive from the presence of an actual deformity or from the mere subjective feeling of one; 2) the nature and magnitude of the limitations on the patient's desire to get rid of the deformity; 3) the conflicts deriving from the contrast between subjective ideas of deformity and perfection and what can actually be achieved through surgery. Practical criteria for selection of patients are presented, including an analysis of the surgeon's emotional reactions during the first interview, which is regarded as a relationship already interpersonal and somewhat therapeutic. Anderson's questionnaire is discussed as an alternative possibility.

Electronic Resource