Monolithic integration in InGaAs-InGaAsP multiquantum-wellstructure using laser processing

We report the use of a laser irradiation process, which combines irradiation by continuous wave and Q-switched pulsed Nd:YAG lasers, to promote quantum-well intermixing. Differential shifts up to 70 meV have been obtained in GaInAsP structures. Extended cavity-ridge lasers with 800-μm-long active sections and 1000-μm-long passive sections, were fabricated. The slope efficiency of the extended cavity lasers is very close to that of 800-μm-long all-active lasers, and the threshold current is 10 mA higher than for an 800-μm-long all-active device. The loss in the intermixed single-mode waveguide is 2.1 cm^-1     

Monolithically integrated InGaAs-AlGaInAs Mach-Zehnder Interferometer optical switch using quantum-well intermixing

A highly efficient monolithically integrated Mach-Zehnder interferometer (MZI) optical switch based on a 1.5-/spl mu/m InGaAs-AlGaInAs multiple-quantum-well structure is reported. The device was fabricated by integrating phase shifter sections with bandgap-shifted low-loss waveguides obtained by a single step sputtered SiO/sub 2/-annealing quantum-well intermixing technique. Evaluation of the refractive index change induced by current injection (plasma, band-filling, band-shrinkage effects) and applied electric field (quantum confined Stark effect) based on the MZI was investigated. A device with an active length of 400 /spl mu/m in one of the MZI arms had an extinction ratio /spl ges/20 dB with a half-wavelength current (I/sub /spl pi//) and half-wavelength voltage V/sub /spl pi// as low as 3.2 mA and 3.5 V (1.9 V in push-pull configuration), respectively.     

Spatially resolved hydrogen desorption from aluminum hydride observed by magnetic resonance imaging

Light metal hydrides represent a promising class of materials for hydrogen storage. However, there are several technical challenges to overcome before their potential can be realized. Key among these is the often adverse absorption and desorption kinetics, which are a function of intrinsic reaction rates and practical operating temperatures. Modifying and controlling these kinetics require a thorough understanding of the hydrogen absorption and desorption processes. In this study, we have investigated the thermal decomposition of aluminum hydride, AlH₃, with Magnetic Resonance Imaging in order to visualize spatially the progress and extent of the reaction.     

Inhibitory Effect of Fusarium Mycotoxins on Growth of Brewing Yeasts. 2. Deoxynivalenol and Nivalenol*

The effect of the trichothecene mycotoxins deoxynivalenol (DON) and nivalenol (NIV) on growth of Saccharomyces cerevisiae lager and ale strains has been studied. The toxins were added into the growth medium in low and high concentrations. Yeast growth was assessed by measurement of dry weight or relative growth, cell number, viability and conductance change of the growth medium using direct and indirect methods. The inhibitory effect of both DON and NIV on yeast growth was dependent on toxin concentration. Additionally, when the extent of inhibition of yeast growth caused by high concentrations of both toxins was observed, it was subject to yeast strain, length of incubation and method used to assess yeast growth. The lowest concentrations of mycotoxin causing significant inhibition on growth of brewing yeasts were: 100 μg/ml DON for the lager strain and 50 μg/ml for the ale strain, and 50 μg/ml NIV for the ale strain.