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International audience; The strong evolution of silicon photonics towards very low power consumption circuits leads to the development of new strategies for photonic devices, especially for power-hungry components such as optical modulators. One strategy is to use Pockels effect in Si waveguides. However, bulk Si is a centrosymmetric semiconductor, which cannot exhibit any second order optical nonlinearities. Nonetheless, under a strain gradient, generated by depositing a stressed layer on Si waveguides, this restriction vanishes. In our work, we experimentally demonstrated a Pockels effect based electro-optic modulation at high frequency (> 5GHz) using a strained silicon Mach-Zehnder modulator.

International audience; We present on experimental results of straininduced Pockels effect in silicon based on Mach-Zehnder interferometer modulators. We theoretically studied both Pockels effect and carrier parasitic effect in silicon under an electric field. We demonstrated high speed Pockels-based optical modulation up to 25 GHz.

International audience; A new Si/Ge/Si heterojunction based waveguide photodetector has been demonstrated in order to reduce the fabrication cost, increase the responsivity, and improve process robustness. State of the art characteristics in terms of dark current, responsivity and bandwidth have been obtained. Furthermore, such photodetectors were characterized in avalanche mode in order to improve the sensitivity and reduce the overall power consumption of the optical circuit

International audience; Silicon is the mainstream material in the electronic industry and it is rapidly expanding its dominance into the field of photonics. Indeed, silicon photonics has been the subject of intense research activities to pave the way for next generation of energy-efficient high-speed computing, information processing and communications systems. The trend is to use optics in intimate proximity to the electronic circuit, which implies a high level of optoelectronic integration. Over the last decade, the field of silicon photonics has advanced at a remarkable pace. Recent advances in integrated germanium receiver will be presented including the developments of a new Ge-based detector integration and avalanche Ge structures.

Here, we report the gigahertz-rate modulation of a tunable terahertz carrier. Terahertz radiation, tunable from 300 GHz to 1.2 THz, is generated by mixing two telecom lasers with an offset frequency in an ultrafast In0.53Ga0.47As photoconductive device coupled to a broadband antenna. The microwave modulation applied to the telecom lasers is directly transferred to the terahertz carrier. A maximum modulation rate of 20 GHz has been achieved, and the bandwidth is independent of the carrier frequency.

We report the generation of continuous terahertz waves from microwave frequencies of up to 2THz obtained by photomixing two optical waves at 1.55μm wavelengths in ion-irradiated In0.53Ga0.47As interdigitated photomixers. A 200nm thick silicon nitride coating is used for antireflection and passivation layer, improving the reliability and the heat tolerance of the photomixer. In such devices, output powers greater than 40nW at 0.5THz and 10nW at 1THz have been achieved. Considering the observed saturation of the output power with the increase of bias voltage, the optimum excitation conditions regarding optical power and bias voltage are discussed.

We investigate terahertz (THz) emission from heavy-ion-irradiated In0.53Ga0.47As photoconductive antennas excited at 1550 nm. The carrier lifetime in the highly irradiated In0.53Ga0.47As layer is less than 200 fs, the steady-state mobility is 490 cm2 V–1 s–1, and the dark resistivity is 3 Omega cm. The spectrum of the electric field radiating from the Br+-irradiated In0.53Ga0.47As antenna extends beyond 2 THz. The THz electric field magnitude is shown to saturate at high optical pump fluence, and the saturation fluence level increases with the irradiation dose, indicating that defect center scattering has a significant contribution to the transient mobility.

Un modèle de MESFET AsGa est développé pour la conception des circuits logiques picosecondes à moyenne et grande intégration. La formulation des paramètres du modèle est optimisée à la fois pour un bon comportement dynamique des portes logiques et pour une grande efficacité en temps de calcul. Ce modèle est implanté sur le macro-simulateur MACPRO qui a été conçu pour l'étude des effets de propagation et de couplage dans les circuits intégrés ultrarapides. Le modèle est présenté de façon exhaustive et il est comparé à des mesures statiques (caractéristiques I-V de transistors hyperfréquence) et dynamiques (comportement en paramètres S d'un MESFET hyperfréquence, oscillateur en anneau en technologie BFL). La dernière partie de l'article étudie l'influence des paramètres importants de ce modèle sur le régime transitoire des portes logiques BFL.

On présente une technique reproductible de fabrication de microponts supraconducteurs applicable aux supraconducteurs « durs » (Ta, V, Nb) par bombardement ionique. L'usinage de microponts est obtenu globalement en formant sur un film mince une image ionique représentant la structure à usiner. Les propriétés de microponts de niobium ainsi réalisés sont ensuite décrites : température critique, résistance normale, caractéristique (I, V), action d'un champ magnétique continu et d'un champ hyperfréquence.