arXiv subjects

Thierry Guillet

Publications and source records attributed to Thierry Guillet.

24 records · Page 2Linked to original sources

arXiv2008

Experimental observation of strong light-matter coupling in ZnO microcavities: influence of large excitonic absorption

We present experimental observation of the strong light-matter coupling regime in ZnO bulk microcavities grown on silicon. Angle resolved reflectivity measurements, corroborated by transfer-matrix simulations, show that Rabi splittings in the order of 70 meV are achieved even for low finesse cavities. The impact of the large excitonic absorption, which enables a ZnO bulk-like behavior to be observed even in the strong coupling regime, is illustrated both experimentally and theoretically by considering cavities with increasing thickness.

cond-mat.other↗

arXiv2008

Polarized emission of GaN/AlN quantum dots : single dot spectroscopy and symmetry-based theory

We report micro-photoluminescence studies of single GaN/AlN quantum dots grown along the (0001) crystal axis by molecular beam epitaxy on Si(111) substrates. The emission lines exhibit a linear polarization along the growth plane, but with varying magnitudes of the polarization degree and with principal polarization axes that do not necessarily correspond to crystallographic directions. Moreover, we could not observe any splitting of polarized emission lines, at least within the spectral resolution of our setup (1 meV). We propose a model based on the joint effects of electron-hole exchange interaction and in-plane anisotropy of strain and/or quantum dot shape, in order to explain the quantitative differences between our observations and those previously reported on, e.g. CdTe- or InAs-based quantum dots.

cond-mat.other↗

arXiv2006

Engineering the spatial confinement of exciton-polaritons in semiconductors

We demonstrate the spatial confinement of electronic excitations in a solid state system, within novel artificial structures that can be designed having arbitrary dimensionality and shape. The excitations under study are exciton-polaritons in a planar semiconductor microcavity. They are confined within a micron-sized region through lateral trapping of their photon component. Striking signatures of confined states of lower and upper polaritons are found in angle-resolved light emission spectra, where a discrete energy spectrum and broad angular patterns are present. A theoretical model supports unambiguously our observations.

cond-mat.mtrl-sci↗

arXiv2006

Polariton quantum boxes in semiconductor microcavities

We report on the realization of polariton quantum boxes in a semiconductor microcavity under strong coupling regime. The quantum boxes consist of mesas that confine the cavity photon, etched on top of the spacer of a microcavity. For mesas with sizes of the order of a few micron in width and nm in depth, we observe quantization, caused by the lateral confinement, of the polariton modes in several peaks. We evidence the strong exciton-photon coupling regime through a typical/clear anticrossing curve for each quantized level. Moreover the growth technique is of high quality, which opens the way for the conception of new optoelectronic devices.

cond-mat.mes-hall↗

arXiv2003

Mott transition from a diluted exciton gas to a dense electron-hole plasma in a single V-shaped quantum wire

We report on the study of many-body interactions in a single high quality V-shaped quantum wire by means of continuous and time-resolved microphotoluminescence. The transition from a weakly interacting exciton gas when the carrier density n is less than 10^5 cm^-1 (i.e. n aX < 0.1, with aX the exciton Bohr radius), to a dense electron-hole plasma (n > 10^6 cm^-1, i.e. n aX > 1) is systematically followed in the system as the carrier density is increased. We show that this transition occurs gradually : the free carriers first coexist with excitons for n aX > 0.1, then the electron-hole plasma becomes degenerate at n aX = 0.8. We also show that the non-linear effects are strongly related to the kind of disorder and localization properties in the structure especially in the low density regime.

cond-mat↗

arXiv2003

Local disorder and optical properties in V-shaped quantum wires : towards one-dimensional exciton systems

The exciton localization is studied in GaAs/GaAlAs V-shaped quantum wires (QWRs) by high spatial resolution spectroscopy. Scanning optical imaging of different generations of samples shows that the localization length has been enhanced as the growth techniques were improved. In the best samples, excitons are delocalized in islands of length of the order of 1 micron, and form a continuum of 1D states in each of them, as evidenced by the sqrt(T) dependence of the radiative lifetime. On the opposite, in the previous generation of QWRs, the localization length is typically 50 nm and the QWR behaves as a collection of quantum boxes. These localization properties are compared to structural properties and related to the progresses of the growth techniques. The presence of residual disorder is evidenced in the best samples and explained by the separation of electrons and holes due to the large in-built piezo-electric field present in the structure.

cond-mat↗