High density InAlAs/GaAlAs quantum dots for non-linear optics in microcavities

Structural and optical properties of InAlAs/GaAlAs quantum dots grown by molecular beam epitaxy are studied using transmission electron microscopy, temperature- and time resolvedphotoluminescence. The control of the recombination lifetime (50 ps – 1.25 ns), and of the dot density (5.10−8 – 2.1011 cm−3) strongly suggest that these material systems can find wide applications in opto-electronic devices as focusing non linear dispersive materials as well as fast saturable absorbers

Spike latency and response properties of an excitable micropillar laser

We present experimental measurements concerning the response of an excitable micropillar laser with saturable absorber to incoherent as well as coherent perturbations. The excitable response is similar to the behavior of spiking neurons but with much faster time scales. It is accompanied by a subnanosecond nonlinear delay that is measured for different bias pump values. This mechanism provides a natural scheme for encoding the strength of an ultrafast stimulus in the response delay of excitable spikes (temporal coding). Moreover, we demonstrate coherent and incoherent perturbations techniques applied to the micropillar with perturbation thresholds in the range of a few femtojoules. Responses to coherent perturbations assess the cascadability of the system. We discuss the physical origin of the responses to single and double perturbations with the help of numerical simulations of the Yamada model and, in particular, unveil possibilities to control the relative refractory period that we recently evidenced in this system. Experimental measurements are compared to both numerical simulations of the Yamada model and analytic expressions obtained in the framework of singular perturbation techniques. This system is thus a good candidate to perform photonic spike processing tasks in the framework of novel neuroinspired computing systems.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Patterns and localized structures in bistable semiconductor resonators

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

Interaction of two modulational instabilities in a semiconductor resonator

The interaction of two neighboring modulational instabilities in a coherently driven semiconductor cavity is investigated. First, an asymptotic reduction of the general equations is performed in the limit of a nearly vertical input-output characteristic. Next, a normal form is derived in the limit where the two instabilities are close to one other. An infinity of branches of periodic solutions are found to emerge from the unstable portion of the homogeneous branch. These branches have a nontrivial envelope in the bifurcation diagram that can either smoothly join the two instability points or form an isolated branch of solutions

Nonlinear optics and saturation behavior of quantum dot samples under continuous wave driving

The nonlinear optical response of self-assembled quantum dots is relevant to the application of quantum dot based devices in nonlinear optics, all-optical switching, slow light and self-organization. Theoretical investigations are based on numerical simulations of a spatially and spectrally resolved rate equation model, which takes into account the strong coupling of the quantum dots to the carrier reservoir created by the wetting layer states. The complex dielectric susceptibility of the ground state is obtained. The saturation is shown to follow a behavior in between the one for a dominantly homogeneously and inhomogeneously broadened medium. Approaches to extract the nonlinear refractive index change by fringe shifts in a cavity or self-lensing are discussed. Experimental work on saturation characteristic of InGa/GaAs quantum dots close to the telecommunication O-band (1.24-1.28 mm) and of InAlAs/GaAlAs quantum dots at 780 nm is described and the first demonstration of the cw saturation of absorption in room temperature quantum dot samples is discussed in detail

Etched arrays of quantum well optical bistable microresonators

We report the operation of etched GaAs/AlGaAs multiple quantum well microresonators as low threshold all-optical bistable devices. The studied samples are 2-dimensional arrays of cylindrical microresonators of $6~\mu$m height, with diameters of $4~\mu$m and $6.4~\mu$m. They are realized by SiCl$_4$ reactive ion etching of an epitaxial high finesse vertical microcavity structure. Due to the lateral carrier and light confinement, optical bistability is observed with a strongly reduced threshold power, below 100$~\mu$W for the $4~\mu$m diameter devices. The optical confinement allows to achieve a high cavity $Q$ factor in a reduced volume, and leads to the observation of multiple hysteresis loops due to the transverse mode structure of $6.4~\mu$m diameter microresonators. The low bistability threshold, obtained without post-etching surface treatment, is attributed to a selfpassivation occurring during the etching process, as evidenced by the observation of a thin coating film protecting the microresonator vertical surfaces

INVESTIGATION OF ALL-EPITAXIAL GaAs/GaAlAs BISTABLE ETALONS : IMPROVEMENTS TOWARDS CONTINUOUS AND PARALLEL OPERATION

Nous rapportons la fabrication et la caractérisation optique d'étalons bistables en GaAs avec des miroirs GaAs/AlAs intégrés, obtenus par croissance MOVPE. Une puissance critique de 4 mW et un contraste de 2:1 sont observés. Nous constatons un fonctionnement quasi-continu lorsque la dissipation thermique est améliorée après suppression du substrat. Nous avons également fabriqué des matrices bidimensionnelles de résonateurs enterrés par Al0.2Ga0.8As dans le but d'assurer un bon confinement électrique et optique.We report the fabricaticm and optical characterization of MOVPE-grown GaAs bistable étalon with GaAs/AlAs integrated mirrors. A 4 mW threshold power and 2:1 reflectivity contrast are observed. Quasi-continuous is operation observed in relation with thermal dissipation improvement when the substrate is removed. Two-dimensional arrays of individual devices have been fabricated and buried with Al0.2Ga0.8 As for electrical and optical confinement

Optical data self-routing using address decoding

We present an optoelectronic self-routing packet switch for digital data commutation applications. The routing of the input data is determined by the optical decoding of the destination address coded in the packet header preceding the data bits. As proof of the operating principle, a one input 64 output demonstration system was built. The experiment is based on the association of two $8 \times 8$ arrays of GaAs/GaAlAs multiple quantum well electro-optical modulators and optical bistable devices. We have demonstrated the optical address decoding in our first experiments by operating individually the channels of the set-up.Nous présentons un autocommutateur optoélectronique pour signaux numériques organisés en paquets de bits. Le routage des paquets entrant dans le commutateur est déterminé par le décodage optique de l'adresse de destination présente dans l'en-tête de chaque paquet. Pour valider ce principe, un système démonstrateur de commutation d'une voie d'entrée vers 64 voies de sortie a été construit. L'expérience est basée sur l'association d'une matrice de $8 \times 8$ modulateurs électro-optiques et d'un composant bistable optique à structure de puits quantiques multiples en GaAs/GaAlAs. L'opération de décodage d'adresses a été montrée par nos premières expériences sur les voies du système prises une par une

Optical patterns and cavity solitons in quantum-dot microresonators

We study optical transverse instabilities in quantum-dot (QD) microresonators. We develop a model for the QD susceptibility taking into account the inhomogeneous broadening of the dot emission. A linear stability analysis and numerical integration of the resulting equations are performed. Special attention is paid to the formation of such structures as optical patterns and cavity solitons, which could play an important role in the field of optical information processing. Implications for actual QD materials are discussed in view of applications