Biomedical subjects

Pierre M Petroff

Publications and source records attributed to Pierre M Petroff.

8 recordsLinked to original sources

PubMed2007

Enhancement of the luminescence intensity of InAs/GaAs quantum dots induced by an external electric field.

InAs/GaAs quantum dots have been subjected to a lateral external electric field in low-temperature microphotoluminescence measurements. It is demonstrated that the dot PL signal could be increased several times depending on the magnitude of the external field and the strength of the internal (built-in) electric field, which could be altered by an additional infrared illumination of the sample. The observed effects are explained by a model that accounts for the essentially faster lateral transport of the photoexcited carriers achieved in an electric field.

Arsenicals↗

PubMed2006

Photonic crystal-assisted light extraction from a colloidal quantum dot/GaN hybrid structure.

We present a study of the light extraction from CdSe/ZnS core/shell colloidal quantum dot thin films deposited on quantum well InGaN/GaN photonic crystal structures. The two-dimensional photonic crystal defined by nanoimprint lithography is used to efficiently extract the guided light modes originating from both the quantum dot thin films and the InGaN quantum wells. Far-field photoluminescence spectra are used to measure the extraction enhancement factor of the quantum dot emission (x1.4). Microphotoluminescence measurements show that the guided mode effective extraction lengths range between 70 and 180 microm, depending on the wavelength of light.

Computer Simulation↗

PubMed2005

Photon statistics from coupled quantum dots.

We present an optical study of two closely stacked self-assembled InAs/GaAs quantum dots. The energy spectrum and correlations between photons subsequently emitted from a single pair provide not only clear evidence of coupling between the quantum dots but also insight into the coupling mechanism. Our results are in agreement with recent theories predicting that tunneling is largely suppressed between nonidentical quantum dots and that the interaction is instead dominated by dipole-dipole coupling and phonon-assisted energy transfer processes.

Journal Article↗

PubMed2005

Deterministic coupling of single quantum dots to single nanocavity modes.

We demonstrate a deterministic approach to the implementation of solid-state cavity quantum electrodynamics (QED) systems based on a precise spatial and spectral overlap between a single self-assembled quantum dot and a photonic crystal membrane nanocavity. By fine-tuning nanocavity modes with a high quality factor into resonance with any given quantum dot exciton, we observed clear signatures of cavity QED (such as the Purcell effect) in all fabricated structures. This approach removes the major hindrances that had limited the application of solid-state cavity QED and enables the realization of experiments previously proposed in the context of quantum information processing.

Journal Article↗

PubMed2005

Effects of separate carrier generation on the emission properties of InAs/GaAs quantum dots.

Individual quantum dots have been studied by means of microphotoluminescence with dual-laser excitation. The additional infrared laser influences the dot charge configuration and increases the dot luminescence intensity. This is explained in terms of separate generation of excess electrons and holes into the dot from the two lasers. With increasing dot density and/or sample temperature, the increase of the luminescence intensity vanishes progressively, while the possibility to control the dot charge remains.

Journal Article↗

PubMed2004

Voltage-controlled optics of a quantum dot.

We show how the optical properties of a single semiconductor quantum dot can be controlled with a small dc voltage applied to a gate electrode. We find that the transmission spectrum of the neutral exciton exhibits two narrow lines with approximately 2 mueV linewidth. The splitting into two linearly polarized components arises through an exchange interaction within the exciton. The exchange interaction can be turned off by choosing a gate voltage where the dot is occupied with an additional electron. Saturation spectroscopy demonstrates that the neutral exciton behaves as a two-level system. Our experiments show that the remaining problem for manipulating excitonic quantum states in this system is spectral fluctuation on a mueV energy scale.

Journal Article↗

PubMed2004

Hybridization of electronic states in quantum dots through photon emission.

The self-assembly of semiconductor quantum dots has opened up new opportunities in photonics. Quantum dots are usually described as 'artificial atoms', because electron and hole confinement gives rise to discrete energy levels. This picture can be justified from the shell structure observed as a quantum dot is filled either with excitons (bound electron-hole pairs) or with electrons. The discrete energy levels have been most spectacularly exploited in single photon sources that use a single quantum dot as emitter. At low temperatures, the artificial atom picture is strengthened by the long coherence times of excitons in quantum dots, motivating the application of quantum dots in quantum optics and quantum information processing. In this context, excitons in quantum dots have already been manipulated coherently. We show here that quantum dots can also possess electronic states that go far beyond the artificial atom model. These states are a coherent hybridization of localized quantum dot states and extended continuum states: they have no analogue in atomic physics. The states are generated by the emission of a photon from a quantum dot. We show how a new version of the Anderson model that describes interactions between localized and extended states can account for the observed hybridization.

Journal Article↗

PubMed2003

Ultrahigh-density nanowire lattices and circuits.

We describe a general method for producing ultrahigh-density arrays of aligned metal and semiconductor nanowires and nanowire circuits. The technique is based on translating thin film growth thickness control into planar wire arrays. Nanowires were fabricated with diameters and pitches (center-to-center distances) as small as 8 nanometers and 16 nanometers, respectively. The nanowires have high aspect ratios (up to 10(6)), and the process can be carried out multiple times to produce simple circuits of crossed nanowires with a nanowire junction density in excess of 10(11) per square centimeter. The nanowires can also be used in nanomechanical devices; a high-frequency nanomechanical resonator is demonstrated.

Journal Article↗