Quantum dot-cavity strong-coupling regime measured through coherent reflection spectroscopy in a very high-Q micropillar

We report on the coherent reflection spectroscopy of a high-quality factor micropillar, in the strong coupling regime with a single InGaAs annealed quantum dot. The absolute reflectivity measurement is used to study the characteristics of our device at low and high excitation power. The strong coupling is obtained with a g=16 \mueV coupling strength in a 7.3\mum diameter micropillar, with a cavity spectral width kappa=20.5 \mueV (Q=65 000). The factor of merit of the strong-coupling regime, 4g/kappa=3, is the current state-of-the-art for a quantum dot-micropillar system

Spectroscopic Signatures for the Dark Bose-Einstein Condensation of Spatially Indirect Excitons

We study semiconductor excitons confined in an electrostatic trap of a GaAs bilayer heterostructure. We evidence that optically bright excitonic states are strongly depleted while cooling to sub-Kelvin temperatures. In return, the other accessible and optically dark states become macroscopically occupied so that the overall exciton population in the trap is conserved. These combined behaviours constitute the spectroscopic signature for the mostly dark Bose-Einstein condensation of excitons, which in our experiments is restricted to a dilute regime within a narrow range of densities, below a critical temperature of about 1K.Comment: 7 pages and 5 figure

Exciton photon strong-coupling regime for a single quantum dot in a microcavity

We report on the observation of the strong coupling regime between a single GaAs quantum dot and a microdisk optical mode. Photoluminescence is performed at various temperatures to tune the quantum dot exciton with respect to the optical mode. At resonance, we observe an anticrossing, signature of the strong coupling regime with a well resolved doublet. The Vacuum Rabi splitting amounts to 400 μeV and is twice as large as the individual linewidths.Comment: submitted on November 7th 200

High frequency GaAs nano-optomechanical disk resonator

Optomechanical coupling between a mechanical oscillator and light trapped in a cavity increases when the coupling takes place in a reduced volume. Here we demonstrate a GaAs semiconductor optomechanical disk system where both optical and mechanical energy can be confined in a sub-micron scale interaction volume. We observe giant optomechanical coupling rate up to 100 GHz/nm involving picogram mass mechanical modes with frequency between 100 MHz and 1 GHz. The mechanical modes are singled-out measuring their dispersion as a function of disk geometry. Their Brownian motion is optically resolved with a sensitivity of 10^(-17)m/sqrt(Hz) at room temperature and pressure, approaching the quantum limit imprecision.Comment: 7 pages, 3 figure

Real Space Observation of Electronic Coupling between Self-Assembled Quantum Dots

International audienceThe control of quantum coupling between nano-objects is essential to quantum technologies. Confined nanostructures, such as cavities, resonators, or quantum dots, are designed to enhance interactions between electrons, photons, or phonons, giving rise to new properties, on which devices are developed. The nature and strength of these interactions are often measured indirectly on an assembly of dissimilar objects. Here, we adopt an innovative point of view by directly mapping the coupling of single nanostructures using scanning tunneling microscopy and spectroscopy (STM and STS). We take advantage of the unique capabilities of STM/STS to map simultaneously the nano-object's morphology and electronic density in order to observe in real space the electronic coupling of pairs of In(Ga)As/GaAs self-assembled quantum dots (QDs), forming quantum dot molecules (QDMs). Differential conductance maps dI/dV (E, x, y) demonstrate the presence of an effective electronic coupling, leading to bonding and antibonding states, even for dissymmetric QDMs. The experimental results are supported by numerical simulations. The actual geometry of the QDMs is taken into account to determine the strength of the coupling, showing the crucial role of quantum dot size and pair separation for device growth optimizatio

Polariton-polariton interaction potentials determination by pump-probe degenerate scattering in a multiple microcavity

International audienceWe study the polarisation-dependent polariton-polariton interaction through its effect on a parametric scattering process in a microcavity (MC). The ratio of the anti-circular interaction strength V2 over its co-circular counterpart V1 is involved in defining the regime in which many nonlinear processes arise in MCs, such as parametric conversion or condensation. We measure the ratio V2/V1 using a stimulated energy-degenerate parametric scattering process in a multiple MC. The sample is pumped at normal incidence, probed with a non-zero angle, and the phase-matched idler is observed at the opposite angle. The idler behaviour, both in power and polarisation, is compared to a hamiltonian interaction model that takes into account the two polarisation-dependent parametric scattering channels characterized by V1 and V2. The proposed method to measure the ratio V2/V1 is convenient and precise. The flexibility of the triple MC allows to observe the process and measure this ratio over a large range of detunings, where we find it to be highly dependent on the detuning. These measurements complement the previous study of Vladimirova et al. [Phys. Rev. B 82, 075301 (2010)] with an original approach and for detunings that were unexplored up to now

Backscattering suppression in supersonic 1D polariton condensates

We investigate the effects of disorder on the propagation of one-dimensional polariton condensates in semiconductor microcavities. We observe a strong suppression of the backscattering produced by the imperfections of the structure when increasing the condensate density. This suppression occurs in the supersonic regime and is simultaneous to the onset of parametric instabilities which enable the "hopping" of the condensate through the disorder. Our results evidence a new mechanism for the frictionless flow of polaritons at high speeds.Comment: 5 pages, 3 figure