Co-Package Technology Platform for Low-Power and Low-Cost Data Centers

We report recent advances in photonic–electronic integration developed in the European research project L3MATRIX. The aim of the project was to demonstrate the basic building blocks of a co-packaged optical system. Two-dimensional silicon photonics arrays with 64 modulators were fabricated. Novel modulation schemes based on slow light modulation were developed to assist in achieving an efficient performance of the module. Integration of DFB laser sources within each cell in the matrix was demonstrated as well using wafer bonding between the InP and SOI wafers. Improved semiconductor quantum dot MBE growth, characterization and gain stack designs were developed. Packaging of these 2D photonic arrays in a chiplet configuration was demonstrated using a vertical integration approach in which the optical interconnect matrix was flip-chip assembled on top of a CMOS mimic chip with 2D vertical fiber coupling. The optical chiplet was further assembled on a substrate to facilitate integration with the multi-chip module of the co-packaged system with a switch surrounded by several such optical chiplets. We summarize the features of the L3MATRIX co-package technology platform and its holistic toolbox of technologies to address the next generation of computing challenges

Mineral phosphorus drives glacier algal blooms on the Greenland Ice Sheet

Melting of the Greenland Ice Sheet is a leading cause of land-ice mass loss and cryosphere-attributed sea level rise. Blooms of pigmented glacier ice algae lower ice albedo and accelerate surface melting in the ice sheet’s southwest sector. Although glacier ice algae cause up to 13% of the surface melting in this region, the controls on bloom development remain poorly understood. Here we show a direct link between mineral phosphorus in surface ice and glacier ice algae biomass through the quantification of solid and fluid phase phosphorus reservoirs in surface habitats across the southwest ablation zone of the ice sheet. We demonstrate that nutrients from mineral dust likely drive glacier ice algal growth, and thereby identify mineral dust as a secondary control on ice sheet melting.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Overexpression of endothelial nitric oxide synthase suppresses features of allergic asthma in mice

BACKGROUND: Asthma is associated with airway hyperresponsiveness and enhanced T-cell number/activity on one hand and increased levels of exhaled nitric oxide (NO) with expression of inducible NO synthase (iNOS) on the other hand. These findings are in paradox, as NO also relaxes airway smooth muscle and has immunosuppressive properties. The exact role of the endothelial NOS (eNOS) isoform in asthma is still unknown. We hypothezised that a delicate regulation in the production of NO and its bioactive forms by eNOS might be the key to the pathogenesis of asthma. METHODS: The contribution of eNOS on the development of asthmatic features was examined. We used transgenic mice that overexpress eNOS and measured characteristic features of allergic asthma after sensitisation and challenge of these mice with the allergen ovalbumin. RESULTS: eNOS overexpression resulted in both increased eNOS activity and NO production in the lungs. Isolated thoracic lymph nodes cells from eNOS overexpressing mice that have been sensitized and challenged with ovalbumin produced significantly less of the cytokines IFN-γ, IL-5 and IL-10. No difference in serum IgE levels could be found. Further, there was a 50% reduction in the number of lymphocytes and eosinophils in the lung lavage fluid of these animals. Finally, airway hyperresponsiveness to methacholine was abolished in eNOS overexpressing mice. CONCLUSION: These findings demonstrate that eNOS overexpression attenuates both airway inflammation and airway hyperresponsiveness in a model of allergic asthma. We suggest that a delicate balance in the production of bioactive forms of NO derived from eNOS might be essential in the pathophysiology of asthma

Loss minimisation for intersecting waveguides in InP based photonic integrated circuits

Measurements on extremely low-loss waveguide intersections and tapers in InP based Photonic Integrated Circuits are presented and compared to simulation. An approach is presented to reduce the loss of waveguide intersections further

Semiconductor optical amplifiers in a non-linear Mach-Zehnder interferometer

Semiconductor Optical Amplifiers (SOAs) are widely used as non-linear elements for optical data processing. For optimal use, high values of the phase change should accompany low changes in gain. The gain itself should be as high as possible. The relation between these two effects is described by the linewidth enhancement factor (a-factor). Here a method is proposed to unambiguously determine it on-chip. The method uses an integrated SOA in a Mach-Zehnder Interferometer with unequal power distribution. The MZI output depends on the gain saturation and the phase shift, due to self-phase modulation. Analyzing this signal gives information about the a-factor

A configuration for high flow rate, high efficiency and low pressure loss micromachined active air filtration element for airborne micro-nanoscale particles separation and removal

To address the demand for high performance localized air filtration systems, we developed a configuration for high flow rate, high efficiency and low pressure loss micromachined active air filtration element for airborne micro-nanoscale particles separation and removal. It consumes low power of less than 4mW and is able to operate at a flowrate of 1.6L/min per device. The unipolar charger and separator electrodes are fabricated on the same substrate for close proximity to minimize charge loss due to particle diffusion. A straight air channel with uniform cross-section between the inlet and outlet minimizes pressure loss, maximizes operational flow rate, and ensures laminar flow for effective particle separation and removal. A flow divider before the outlet physically separates the particle-laden and cleaned air before they exit the separator electrodes' electric field. © 2005 IEEE.link_to_subscribed_fulltex