High temperature, high power InGaAs/GaAs quantum-well lasers withlattice-matched InGaP cladding layers

The authors report the high-temperature and high-power operation of strained-layer InGaAs/GaAs quantum well lasers with lattice-matched InGaP cladding layers grown by gas-source molecular beam epitaxy. Self-aligned ridge waveguide lasers of 3-μm width were fabricated. These lasers have low threshold currents (7 mA for 250-μm-long cavity and 12 mA for 500-μm-long cavity), high external quantum efficiencies (0.9 mW/mA), and high peak powers (160 mW for 3-μm-wide lasers and 285 mW for 5-μm-wide laser) at room temperature under continuous wave (CW) conditions. The CW operating temperature of 185°C is the highest ever reported for InGaAs/GaAs/InGaP quantum well lasers, and is comparable to the best result (200°C) reported for InGaAs/GaAs/AlGaAs lasers     

New ternary molybdenum chalcogenides containing Mo6 and Mo9 clusters: M2Mo15Se19 (M = K,Ba, In,Tl) and K2Mo15S19

New superconducting Mo^II compounds M₂Mo₁₅X₁₉ (M = K, Ba, In, Tl and X = Se; M = K and X = S have been found. These materials crystallize in a new structural type containing isolated Mo₆X₈ and Mo₉X₁₁ units. They are superconducting (T_c = 3.32 K for K₂Mo₁₅S₁₉), and have high initial slopes $\text{dHc}{}_2\text{dT}$ of the upper critical field.     

A new class of supersaturated design: Application to a sensitivity study of a photochemical model

The use of experimental designs in the field of numerical simulation improves global sensitivity analysis compared to Monte Carlo based method by decreasing the number of simulations. More particularly, supersaturated designs can be applied to decrease the number of calculations, because the number of simulations is inferior to the number of studied factors but its use is risky and depends on “parsimony principle”. This paper shows new supersaturated designs that use the a priori knowledge and thus overcome this difficulty.     

Active mode locking of broadband quantum cascade lasers

Active mode locking in broadband quantum cascade (QC) lasers with a repetition rate of about 14.3 GHz has been achieved through the modulation of the laser bias current. At low driving currents, the active mode locking in broadband QC lasers resembles the active mode locking in single-wavelength QC lasers, while at high driving currents, the mode locking properties are governed by the broad spectral gain of these lasers. At high bias currents, the active modulation excites Fabry-Perot modes across the entire gain spectrum from 6.7 to 7.4 /spl mu/m, with clear evidence of mode locking. The spectral width of the optical gain in the broadband QC lasers exceeds 2 THz and indicates the potential for generating subpicosecond pulses.     

Self-assembled liquid crystalline nanoparticles as an ophthalmic drug delivery system. Part II: optimization of formulation variables using experimental design

In the field of keratoconus treatment, a lipid-based liquid crystal nanoparticles system has been developed to improve the preocular retention and ocular bioavailability of riboflavin, a water-soluble drug. The formulation of this ophthalmic drug delivery system was optimized by a simplex lattice experimental design. The delivery system is composed of three main components that are mono acyl glycerol (monoolein), poloxamer 407 and water and two secondary components that are riboflavin and glycerol (added to adjust the osmotic pressure). The amounts of these three main components were selected as the factors to systematically optimize the dependent variables that are the encapsulation efficiency and the particle size. In this way, 12 formulas describing experimental domain of interest were prepared. Results obtained using small angle X-rays scattering (SAXS) and cryo-transmission electron microscopy (cryo-TEM) evidenced the presence of nano-objects with either sponge or hexagonal inverted structure. In the zone of interest, the percentage of each component was determined to obtain both high encapsulation efficiency and small size of particles. Two optimized formulations were found: F7 and F1. They are very close in the ternary phase diagram as they contain 6.83% of poloxamer 407; 44.18% and 42.03% of monoolein; 46.29% and 48.44% of water for F7 and F11, respectively. These formulations displayed a good compromise between inputs and outputs investigated.     

Transition ordre-desordre dans le spinelle deficitaire Ga1,33Cr4S8

The spinel compound Ga_1.33Cr₄S₈ may be prepared in two different varieties. The low-temperature α-form exhibits a well-defined gallium occupancy on the tetrahedral sites, while the high-temperature β-phase is a disordered form. Single-crystal structural studies show a continuous order-disorder transition between these two limits, as a function of the synthesis temperature. Magnetic studies have been done by statical and dynamical methods.     

Investigation of the Intrinsic Activity of ZrxCe1−xO2 Mixed Oxides in the CO + NO Reactions: Influence of Pd Incorporation

The intrinsic activity of various Zr _x Ce_1–x O₂ mixed oxides and after a Pd deposition has been investigated in the CO + NO reactions from temperature-programmed experiments performed under stoichiometric conditions. It has been found that the activity of Zr _x Ce_1–x O₂ depends on either the specific surface area or the number of Ce cations and their intrinsic activity, Zr_0.5Ce_0.5O₂ being the most active support. The addition of palladium strongly enhances the catalytic activity of the supports probably due to a synergistic effect between CeO₂ and the metal since the initial activity of palladium-based catalysts is directly related to their Ce content. Such a catalytic enhancement has been explained by a bifunctional mechanism involving active sites probably composed of Pd and ceria. A strong deactivation operates leading to the disappearance of the beneficial effect of ceria. Such a deactivation seems to be dependent on the support composition, Pd supported Zr_0.25Ce_0.75O₂ being the most resistant to deactivation.     

High temperature (T⩾425 K) pulsed operation of quantum cascadelasers

High temperature pulsed operation of quantum cascade lasers is reported. At 425 K and 8.4 μm wavelength a peak output power of 17 mW was measured for a laser incorporating 75 stages of alternated active regions and injectors