Diffractive lens fabricated with binary features less than 60 nm

We designed, fabricated, and characterized a binary diffractive lens with features less than 60nm. The lens was designed for operation in the red portion of the spectrum. Experimental measurements of lens performance agree with predictions generated by rigorous models of diffraction

Diffractive optical elements for generating arbitrary line foci

The key optical component in the architecture of the linearly variable magnification telescope presented here is a conical lens. This architecture has application to Doppler radar processing and to wavelet processing. Unfortunately, the unique surface profile of a conical lens does not allow traditional grinding techniques to be used for fabrication; therefore, its fabrication is considered custom. In addition to the requirement of custom fabrication, a refractive conical lens introduces phase aberrations that are intrinsic to its conic shape. Further, due to the large prismatic component of the lens, the variable magnification telescope architecture is off-axis. To overcome the fabrication and application difficulties of a refractive lens, we consider the construction of a hybrid diffractive-refractive lens

Toward a Comprehensive Approach to the Collection and Analysis of Pica Substances, with Emphasis on Geophagic Materials

Pica, the craving and subsequent consumption of non-food substances such as earth, charcoal, and raw starch, has been an enigma for more than 2000 years. Currently, there are little available data for testing major hypotheses about pica because of methodological limitations and lack of attention to the problem.In this paper we critically review procedures and guidelines for interviews and sample collection that are appropriate for a wide variety of pica substances. In addition, we outline methodologies for the physical, mineralogical, and chemical characterization of these substances, with particular focus on geophagic soils and clays. Many of these methods are standard procedures in anthropological, soil, or nutritional sciences, but have rarely or never been applied to the study of pica.Physical properties of geophagic materials including color, particle size distribution, consistency and dispersion/flocculation (coagulation) should be assessed by appropriate methods. Quantitative mineralogical analyses by X-ray diffraction should be made on bulk material as well as on separated clay fractions, and the various clay minerals should be characterized by a variety of supplementary tests. Concentrations of minerals should be determined using X-ray fluorescence for non-food substances and inductively coupled plasma-atomic emission spectroscopy for food-like substances. pH, salt content, cation exchange capacity, organic carbon content and labile forms of iron oxide should also be determined. Finally, analyses relating to biological interactions are recommended, including determination of the bioavailability of nutrients and other bioactive components from pica substances, as well as their detoxification capacities and parasitological profiles.This is the first review of appropriate methodologies for the study of human pica. The comprehensive and multi-disciplinary approach to the collection and analysis of pica substances detailed here is a necessary preliminary step to understanding the nutritional enigma of non-food consumption

1 Three Dimensional VLSI-Scale Interconnects

Abstract. As processor speeds rapidly approach the Giga-Hertz regime, the disparity between process time and memory access time plays an increasing role in the overall limitation of processor performance. In addition, limitations in interconnect density and bandwidth serve to exacerbate current bottlenecks, particularly as computer architectures continue to reduce in size. To address these issues, we propose a 3D architecture based on through-wafer vertical optical interconnects. To facilitate integration into the current manufacturing infrastructure, our system is monolithically fabricated in the Silicon substrate and preserves scale of integration by using meso-scopic diffractive optical elements (DOEs) for beam routing and fan-out. We believe that this architecture can alleviate the disparity between processor speeds and memory access times while increasing interconnect density by at least an order of magnitude. We are currently working to demonstrate a prototype system that consists of vertical cavity surface emitting lasers (VCSELs), diffractive optical elements, photodetectors, and processor-in-memory (PIM) units integrated on a single silicon substrate. To this end, we are currently refining our fabrication and design methods for the realization of meso-scopic DOEs and their integration with active devices. In this paper, we present our progress to date and demonstrate vertical data transmission using DOEs and discuss the application for our architecture, which is a multi-PIM (MPM) system

Hybrid Dielectric-Metallic Back Reflector for Amorphous Silicon Solar Cells

In this paper, we present the design and fabrication of hybrid dielectric-metallic back surface reflectors, for applications in thin film amorphous silicon solar cells. Standard multilayer distributed Bragg reflectors, require a large number of layers in order to achieve high reflectance characteristics. As it turns out, the addition of a metallic layer, to the base of such a multilayer mirror, enables a reduction in the number of dielectric layers needed to attain high reflectance performance. This paper explores the design, experimental realization and opportunities, in thin film amorphous silicon solar cells, afforded by such hybrid dielectric-metallic back surface reflectors