A GaAs/AlAs planar cavity containing a collection of InAs quantum boxes in its core region has been grown in a single step by molecular beam epitaxy, and processed by electron-beam lithography and reactive ion etching into pillar microresonators. The optical study by photoluminescence of these localized light emitters allows a systematic and precise determination of the energies of the first confined photon modes of such microstructures, in good agreement with theoretical estimates. More generally, such probes facilitate the experimental study of the modes of complex photonic microstructures and of the spontaneous emission alteration they entail on a quasimonochromatic light emitter.

We report on experimental evidence of neuronlike excitable behavior in a micropillar laser with saturable absorber. We show that under a single pulsed perturbation the system exhibits subnanosecond response pulses and analyze the role of the laser bias pumping. Under a double pulsed excitation we study the absolute and relative refractory periods, similarly to what can be found in neural excitability, and interpret the results in terms of a dynamical inhibition mediated by the carrier dynamics. These measurements shed light on the analogy between optical and biological neurons and pave the way to fast spike-time coding based optical systems with a speed several orders of magnitude faster than their biological or electronic counterparts.

We show that a monolithic and compact vertical cavity laser with intracavity saturable absorber can emit short excitable pulses. These calibrated optical pulses can be excited as a response to an input perturbation whose amplitude is above a certain threshold. Subnanosecond excitable response is promising for applications to novel all-optical devices for information processing or logical gates.

We report experiments on spatial switching dynamics and steady state structures of passive nonlinear semiconductor resonators of large Fresnel number. Extended patterns and switching front dynamics are observed and investigated. Evidence of localization of structures is given.Comment: 5 pages with 9 figure

Transport-reaction processes at individual Ag nanoparticles (NPs) are studied using electrochemistry coupled with in situ 3D light scattering microscopy. Electrochemistry is used to trigger a (i) diffusiophoretic transport mode capable of accelerating and preconcentrating NPs toward an electrode and (ii) subsequent diffusion-controlled oxidation of NPs. Individual NP dissolution rate, analyzed using optical modeling, suggests the intervention of insoluble products. New insights into diverse NPs behaviors highlight the strength of coupled optical-electrochemical 3D microscopies for single-NP studies.

We report on a new type of optical nonlinearity in a polariton p-i-n microcavity. Abrupt switching between the strong and weak coupling regime is induced by controlling the electric field within the cavity. As a consequence bistable cycles are observed for low optical powers (2-3 orders of magnitude less than for Kerr induced bistability). Signatures of switching fronts propagating through the whole 300 x 300 µm 2 mesa surface are evidenced.PACS numbers: 71.36.+c, 42.65.Pc, 73.50.Pz, 78.55.Cr After its first observation in a Fabry Perot cavity containing Na vapor [1], optical bistability has been widely explored in solid state systems for its possible application in all optical circuits and optical computing [2]. A common approach is the use of a microcavity in which the resonance frequency depends on the stored optical energy: optical χ (3) nonlinearities, of electronic or thermal origin, have been used to obtain bistability in 1-dimensional [3,4] and 2 dimensional [5,6] photonic devices, with switching incident powers around 1 kW/cm 2 . When part of a spatially extended bistable system is switched from one stable state to the other, a front is formed between spatial regions in different states. If this front is locked, spatial solitons can be observed [7,8], otherwise the front propagates along the surface until the whole sample has switched state [9]. Recently optical bistability of microcavity polaritons has been theoretically proposed to generate propagation of switching fronts which can be used for all optical computation [10]. Polaritons are mixed exciton-photon quasiparticles resulting from the strong coupling regime of excitons with a resonant cavity mode [11]. Polaritonpolariton scattering gives rise to giant χ (3) -type nonlinearities [12,13] which have been recently shown to generate optical bistability [14]; indications of spatial solitons were also reported [15]. Another approach for optical bistability is to use the switch from strong to weak coupling regime due to exciton bleaching at high pumping power [16,17]. This method has been theoretically proposed in 1996 [18], and some experimental indication has been reported in 2004 [19]. In this work, we experimentally demonstrate low-power optical bistability based on a new non-linear mechanism. Switching between strong and weak coupling regime is induced controlling the internal electric field of a p-i-n microcavity. Well defined hysteresis cycles are observed both scanning the external bias or the optical power. * now at CNISM UDR Pavia and Dipartimento di Elettronica, Università degli studi di Pavia, via Ferrata 1, 27100 Pavia, Italy A model including the changes of optical and electronic properties between the strong and weak coupling regime is developed and gives a good overall description of the observed cycles. Finally we show that a local excitation can produce commutation of the whole mesa. The sample (see Fig. 1 a)) is described in details in ref. [20]. Grown on an n-doped GaAs substrate, an undoped GaAs cavity containing 3 In 0.05 Ga 0....

No abstract

No abstract