1-mW CW-RT monolithic VCSEL at 1.55 μm

In this letter, we demonstrate the first result of a high-power (1 mW) continuous-wave room-temperature vertical-cavity surface-emitting laser emitting at 1.55 μm using a single InP substrate. The whole structure was grown monolithically using gas source molecular beam epitaxy and incorporates two original approaches. The first originality consists in the growth of a metamorphic GaAs-AlAs Bragg mirror directly on an InP-based cavity. The second novel idea is to use a tunnel junction for current injection. Moreover by using these two approaches the processing is very simple and, therefore, fulfills the goal for low-cost laser production in access and interconnections applications     

How to take into account general and contextual knowledge for interactive aiding design: Towards the coupling of CSP and CBR approaches

The goal of this paper is to show how it is possible to support design decisions with two different tools relying on two kinds of knowledge: case-based reasoning operating with contextual knowledge embodied in past cases and constraint filtering that operates with general knowledge formalized using constraints. Our goals are, firstly to make an overview of existing works that analyses the various ways to associate these two kinds of aiding tools essentially in a sequential way. Secondly, we propose an approach that allows us to use them simultaneously in order to assist design decisions with these two kinds of knowledge. The paper is organized as follows. In the first section, we define the goal of the paper and recall the background of case-based reasoning and constraint filtering. In the second section, the industrial problem which led us to consider these two kinds of knowledge is presented. In the third section, an overview of the various possibilities of using these two aiding decision tools in a sequential way is drawn up. In the fourth section, we propose an approach that allows us to use both aiding decision tools in a simultaneous and iterative way according to the availability of knowledge. An example dealing with helicopter maintenance illustrates our proposals.     

Effect of Nanostructuring on the Thermoelectric Properties of Co0.97Pd0.03Sb3

We synthesized n-type CeO₂/Co_0.97Pd_0.03Sb₃ composites with nanometric grain sizes (200 nm to 300 nm) by spark plasma sintering in order to promote phonon scattering at grain boundaries. Powdered samples were initially obtained by ball milling Co_0.97Pd_0.03Sb₃ together with x vol.% (x = 0, 0.5, 1, 2) of CeO₂ nanoparticles. This additive slows down the grain size growth of the skutterudite matrix which occurs during sintering, thereby contributing to phonon scattering. The nanostructured samples display reduced Hall electron concentration compared with that of the reference Co_0.97Pd_0.03Sb₃ because of Fe contamination by the steel balls and vials. However, the electronic transport properties are nearly identical to those of Co_0.98Pd_0.02Sb₃, which allows for comparison with this latter compound. The lattice thermal conductivity is strongly decreased in nano-Co_0.97Pd_0.03Sb₁₂ (?40% at 300 K). This results in an enhanced (+32%) ZT value peaking at 0.65 at 650 K in nano-Co_0.97Pd_0.03Sb₁₂ + 2% CeO₂ when compared with micro-Co_0.98Pd_0.02Sb₃.     

DBR module with 20-mW constant coupled output power, over 16 nm(40×50-GHz spaced channels)

To replace DFB lasers in wavelength-division-multiplexing (WDM) systems, tunable lasers should provide the same output power (20 mW) and remain simple devices. We propose a two-section DBR laser with optimized design. The required settings to reach all the achievable ITU wavelengths with constant output power are simply derived from very few initial characterizations. We obtain a record 20-mW coupled output power, constant over 16 nm (=40 channels 50-GHz spaced). For the first time, power performances comparable with DFB lasers are obtained; DBR lasers are now competitive candidates for an integration in WDM systems     

Design, realization, and characterization of a ten-wavelengthmonolithic source for WDM applications integrating DBR lasers with aPHASAR

We present here the design, fabrication, and static as well as dynamic characteristics of a ten-wavelength, 200-GHz channel spacing emitter for wavelength-division multiplexing applications. The source is based on the monolithic integration on InP of a ten distributed Bragg reflector laser array with a square-shaped transmission response PHASAR. The specific design of the PHASAR is detailed. The continuous-wave operation-one channel at a time-demonstrates a high monomode stability with a rejection better than 32 dB for all channels and all injected currents; the 200-GHz channel spacing can be reached with an accuracy better than 25 GHz. High-speed characteristics demonstrate a 6.5-GHz direct modulation bandwidth at -3 dB for a 70-mA current in the 900-μm-long active section. The chirp measured for a 2.5-Gb/s modulation with a 10-dB extinction ratio is less than 1.5 Å for every wavelength     

10-wavelength 200-GHz channel spacing emitter integrating DBRlasers with a PHASAR on InP for WDM applications

A 10-wavelength 200-GHz channel spacing emitter was realized by monolithically integrating on InP a 10 distributed-Bragg-reflector laser array and a PHASAR used as a 10→1 combiner. The design of a wide-squared spectral bandwidth for the PHASAR as well as the lasers tunability ensure wavelength matching between the PHASAR transmission comb and the laser array comb. The channel spacing accuracy of the source is better than 25 GHz and the rejection is higher than 32 dB for all bias     

Hydrotreating properties of mixed NbxMo1−xS2 alumina supported catalysts

Niobium-molybdenum disulfide solid solution (Nb_xMo_1−xS₂) has been prepared in a dispersed state on gamma alumina. The existence of this solid solution supported on alumina carrier has been proven with the help of EXAFS technique. The catalytic properties of these materials have been studied in hydrogenation and hydrodesulfurization reactions. Interestingly, as already observed for niobium sulfide, the activity of the Nb_xMo_1−xS₂ solid solution (HDS of DBT, P_tot=33 bar) is not decreased in the presence of H₂S up to p(H₂S)=200 Torr, at least up to x=0.4.     

Preparation of the mixed sulfide Nb2Mo3S10 catalyst from the mixed oxide precursor

Mixed sulfide Nb₂Mo₃S₁₀ was obtained by reaction of H₂S with the mixed oxide Nb₂Mo₃O₁₄ at 873 K. High‐resolution electron microscopy and X‐ray diffraction show the formation of homogeneous lamellar mixed sulfide. Due to the increased lability of oxygen, the sulfidation of the mixed oxide is easier compared to that of Nb₂O₁₅ oxide. As follows from the characterization of transient solid products, the transformation from the oxide to the sulfide includes the intermediate formation of a partially reduced “bronze” compound. For the thiophene hydrodesulfurization model reaction, the catalytic properties of Nb₂Mo₃S₁₀ mixed sulfide are intermediate between those of the individual MS₂ sulfides (M = Mo, Nb), but closer to those of the Nb compound. This revised version was published online in July 2006 with corrections to the Cover Date.     

Design, optical characterization, and operation of large transmission gratings for the laser integration line and laser megajoule facilities

Within the framework of the laser integration line (LIL) and the laser megajoule, we describe the design, optical characterization, mounting, alignment, and operation on the LIL of large 420 mm x 470 mm transmission gratings. Two types of grating were manufactured. The first, operating at a wavelength of 1.053 microm, was used for deviation purposes. The second, operating at a wavelength of 0.351 microm, was used for both deviation and focusing purposes. We demonstrate that these large transmission gratings are suitable for nanosecond-regime operation on high-power laser facilities.     

Building renovation adopts mass customization

This work is motivated by an industrial need of manufacturing façades insulating envelopes in order to reduce energy consumption in residential buildings. An insulating envelope is a configuration of a set of rectangular panels that respects a set of limitations. Due to the number of façades to be renovated and the number of possible configurations for a single façade, the envelope configuration is both a mass customization problem as well as a combinatorial one. The paper then introduces a decision support system based on the framework of constraint satisfaction, as it fits neatly the constrained nature of the problem. Two configuration tasks have been identified as prerequisite to envelopes configurations: (1) the configuration of a questionnaire for information inputs and (2) the configuration of a constraint satisfaction problem for each one of the façades to be renovated. The system architecture promotes maintenance, modularity and efficiency as different configuration tasks are divided into web-services. Conception and implementation of the massive building thermal renovation are then supported.