Leaving no one behind: Supporting women, poor people, and indigenous people in wheat-maize innovations in Bangladesh

This guidance note for scientists and research teams acknowledges the complexity of marginalization processes and provides recommendations for making sure no one is left behind. It draws on GENNOVATE findings from a community in Bangladesh where the indigenous Santals, Bengali Muslims, and Hindus live and work together

High-Dimensional Stochastic Design Optimization by Adaptive-Sparse Polynomial Dimensional Decomposition

This paper presents a novel adaptive-sparse polynomial dimensional decomposition (PDD) method for stochastic design optimization of complex systems. The method entails an adaptive-sparse PDD approximation of a high-dimensional stochastic response for statistical moment and reliability analyses; a novel integration of the adaptive-sparse PDD approximation and score functions for estimating the first-order design sensitivities of the statistical moments and failure probability; and standard gradient-based optimization algorithms. New analytical formulae are presented for the design sensitivities that are simultaneously determined along with the moments or the failure probability. Numerical results stemming from mathematical functions indicate that the new method provides more computationally efficient design solutions than the existing methods. Finally, stochastic shape optimization of a jet engine bracket with 79 variables was performed, demonstrating the power of the new method to tackle practical engineering problems.Comment: 18 pages, 2 figures, to appear in Sparse Grids and Applications--Stuttgart 2014, Lecture Notes in Computational Science and Engineering 109, edited by J. Garcke and D. Pfl\"{u}ger, Springer International Publishing, 201

Design of a Compact Polarization Splitter by Using Identical Coupled Silicon Nanowires

Design of an ultra-compact polarization splitter (PS) based on silicon-on-insulator platform is presented. The design incorporates two simply coupled identical silicon nanowires, which can be easily fabricated by using standard Complementary Metal-Oxide-Semiconductor technology and fully compatible with standard active silicon photonics platforms. It is shown here that a low-loss, 17.90 μm long compact PS, and wide bandwidth over the entire C-band can be achieved. Important waveguide design parameters such as the guide width, height, and separation between them have been optimized, and modal birefringence and wavelength dependence have been calculated by using a full-vectorial H-Field finite element method. The optical power transfer characteristics have been calculated by using a rigorous least squares boundary residual method

Design of compact polarization rotator using simple silicon nanowires

In this paper, an ultracompact design of a polarization rotator (PR) based on a silicon-on-insulator (SOI) platform is presented. The design contains two simple silicon nanowires but with unequal width, which will be easier to fabricate. It is shown here that a low-loss, wide-bandwidth, and 52.8-μm-long compact PR with polarization cross talk of −20  dB can be achieved. A full-vectorial finite element method and the least-squares boundary residual method are used to study the effects of the fabrication tolerances. This design shows reasonably stable performances

Evolution of Plasmonic Modes in a Metal Nano-Wire Studied by a Modified Finite Element Method

A finite width thin metal film plasmonic nanowire with its unique feature of subwavelength light guiding is finding many applications in compact integrated nanophotonic circuits and sensors. Full-vectorial finite element method (FV-FEM) is becoming an important simulation tool for the analyses of such exotic waveguides. Instead of a penalty approach reported earlier, a more direct divergence formulation considering each discretized element's optical properties to eliminate nonphysical modal eigenvectors has been exploited and is reported here. Long and short-range fundamental and higher order plasmonic modes and supermodes of a pure metal nanowire and their evolutions with waveguide geometry, surrounding identical, and nonidentical dielectric cladding materials and operating wavelength are thoroughly studied. Interesting long-range modal properties such as, supermode formation, complex phase matching, and mode evolution in identical and non-identical clad metal nanowires have been observed and explained in detail including supermode profiles. This study is expected to help in understanding the evolution of plasmonic guided modes in compact active and passive integrated photonic devices containing metal narrow strips

Design and optimization of compact silicon photonic sensors

Although optical sensors incorporating grating inscribed and etched fibres are now sufficiently mature and well established in the market, however, designs based on more exotic nanowires and photonic crystal fibres are becoming increasingly important and showing much improved sensitivity by accessing a larger evanescent field. Similarly, novel planar design concepts, such as the silicon slot guide-based design is showing even greater promise, allowing the exploitation of well-developed CMOS fabrication technologies for potentially low-cost sensor elements. In compact Integrated Optic format, dielectric slots, plasmonic slots, Mach-Zehnder interferometer, and ring resonators are also emerging as novel photonic sensors. However, high index contrast also makes the modes in such sensing structures fully hybrid in nature and in such a case, full-vectorial rigorous numerical approaches will be necessary for their design optimization. Some selected results for silicon based compact photonic sensors will be presented illustrating the value and potential of the computationally efficient finite element method in such designs

A Compact Mach-Zehnder Interferometer Using Composite Plasmonic Waveguide for Ethanol Vapor Sensing

The finite element method (FEM) has attracted a considerable interest in the past few decades for the analysis of a wide range of dielectric waveguides. This method can handle isotropic and anisotropic material properties and arbitrary-shaped complex dielectric discontinuities more efficiently and accurately than any other methods. A modified H-field based full-vectorial finite element method is used for a rigorous analysis of a composite plasmonic waveguide as an efficient ethanol vapor sensor where a porous ZnO (P-ZnO) layer is used as low index material in between high index silicon and silver metal layer. Enhanced field confined into low index slot is utilized for ethanol vapor sensing which has many potential applications in chemical industries. It is reported here that a high waveguide sensitivity over 0.7 per RIU could be realized with our proposed design depending on the porosity of the ZnO layer. For accurate detection of refractometric changes, a compact Mach-Zehnder interferometer is designed where maximum phase sensitivities of 0.30, 0.34, 0.38, and 0.40 are shown to be achieved for ~ 50% volume fraction of ethanol into porous ZnO layer with porosity, P = 30%, 40%, 50%, and 60%, respectively. The complete investigation has been carried out at the well-known telecommunication wavelength 1550 nm and with our in-house, accurate full-vectorial FEM code

An Innovative Straight Resonator Incorporating a Vertical Slot as an Efficient Bio-Chemical Sensor

A compact and integrated label-free refractometric bio-chemical sensor based on silicon-on-insulator (SOI) is proposed and comprehensively studied at the telecommunication wavelength of λ = 1550 nm. This device incorporated a three-dimensional (3D) Fabry-Perot cavity in the nano-scale regime with maximum footprint area around 470 × 473 nm2. A resonance shift (Δλres) of 5.2 nm is reported for an ultrathin (5 nm) bio-layer sensing. Besides, an improved maximum sensitivity (S = 820 nm/RIU) is also achieved for bulk refractive index change in surroundings. As a chemical sensor, very low detection limit (DL = 6.1 × 106 RIU) also can be possible to achieve by this device. All the numerical investigations and optimizations were carried out in frequency domain by a numerically efficient and rigorous full vectorial H-field based 2-D and 3-D finite element methods (FEM). A 3D-FEM code is developed and used to find out the wavelength dependencies of the resonator. Possibility of easy CMOS fabrication and integration opportunities make this structure as a prospective and efficient lab-on-chip device