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Fabrication techniques for grating-based optical devices

Journal of Vacuum science and Technology B: Microelectronics and Nanometer Structures 1999年第6期17卷 3208-3211页

作者： Lim, Michael H. Murphy, T.E. Ferrera, J. Damask, J.N. Smith, Henry I. Department of Electrical Engineering and Computer Science MIT Cambridge Massachusetts 02139

We describe a novel, versatile process for fabricating integrated Bragg-grating devices. Our process addresses many of the critical challenges presented by such devices, including period selection, alignment, spatial coherence, and nanolithography. Using a combination of e-beam, x-ray, optical, and interference lithographies, we have successfully employed this process to construct 244 nm period, quarter-wave-shifted Bragg gratings on top of 1-μm-tall waveguide structures in InP. © 1999 American Vacuum Society.

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Optical space communications: a key building block for wide area space networks

Optical space communications: a key building block for wide ...

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IEEE Photonics Conference (IPC)

作者： V.W.S. Chan Department of Electrical Engineering & Computer Science MIT Cambridge MA USA

Space laser communications technology has been under development for over thirty years. The technology promises high capacity, low power consumption, light weight, small sizes and low costs for satellite crosslinks. It will be a key and critical building block for wide area space networks, supporting mobile users (terrestrial, airborne and spaceborne), high speed data services for small satellite terminals and serving as a backbone network for high speed trunking.

关键词： Optical fiber networks Space technology High speed optical techniques Optical feedback Optical receivers Optical transmitters Costs Satellite broadcasting Optical beams Optical design

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Measured back scattering cross section of thin wires

Measured back scattering cross section of thin wires

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1999 IEEE Antennas and Propagation Society International Symposium, APSURSI 1999

作者： Liepa, Valdis V. Chang, Seichoong Radiation Laboratory Department of Electrical Engineering and Computer Science University of Michigan Ann ArborMI48109-2122 United States MIT Lincoln Laboratory LexingtonMA02420 United States

ISBN: (纸本)078035639X

Prof. Ralph E. Hiatt was instrumental in designing the first anechoic chamber at the Radiation Laboratory Willow Run Facility of the University of Michigan. During the nineteen sixties it was one of the largest such facilities in the world. It is therefore appropriate to describe some of the basic RCS measurements, such as these wires, carried out in this chamber. A set of back scattering patterns was measured for a thin (metallic) wire (a/λ, = 6.27x10-3) for 1/λ. = 0.3(0.25)0.5(0.5)1.60(0.10)5.42, where a is the radius of the wire, 1 is the wire length, and λ is the wavelength. From the set of patterns a number of curves were extracted showing the amplitude and phase of each back scattering lobe as a function of the wire length. These curves provide a convenient means of cross section estimation and may be used to reconstruct with reasonable accuracy the back scattering pattern for any value of I/λ, 1/λ, ≤ 5.42. These data have been found useful in studies dealing with scattering form composite geometrical shapes where it is often found useful to compare the back scattering patterns with those of a thin wire, especially in the resonance region. Figure 1 gives a block diagram of a CW system used for the measurement. The frequency was 2.710 Ghz (λ, = 11.07), the polarization horizontal, and the distance for the transmit/receive antenna to the model was about 30 feet. Since no distinguishable differences between the back scattering patterns of similar rods of aluminum and silverplated stainless steel rods were observed, it was decided to use aluminum rods of 1/32 inch radius and variable length for the present study. Figure 2 gives a typical back scattering pattern for 1/λ = 5.221. A series of such patterns were obtained for various 1/λ.. The important feature of these back scattering patterns are the amplitudes and displacements of various lobes as a function of wire length. Figure 3 gives a familiar curve for broadside back scattering cross section vs. 1/λ. Other se

关键词： Wire

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Linear consistency testing 3rd

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3rd International Workshop on Randomization and Approximation Techniques in computer science and 2nd International Workshop on Approximation Algorithms for Combinatorial Optimization Problems, RANDOM-APPROX 1999

作者： Aumann, Yonatan Håstad, Johan Rabin, Michael O. Sudany, Madhu Department of Mathematics and Computer Science Bar-Ilan University Ramat-Gan52900 Israel Department of Numerical Analysis and Computing Science Royal Institute of Technology Stockholm Sweden DEAS Harvard University CambridgeMA02138 United States Institute of Computer Science Hebrew University Jerusalem Israel Department of Electrical Engineering and Computer Science MIT 545 Technology Square CambridgeMA02139 United States

ISBN: (纸本)3540663290

We extend the notion of linearity testing to the task of checking linear-consistency of multiple functions. Informally, functions are "linear" if their graphs form straight lines on the plane. Two such functions are "consistent" if the lines have the same slope. We propose a variant of a test of Blum, Luby and Rubinfeld [8] to check the linear- consistency of three functions f1;f2;f3 mapping a finite Abelian group G to an Abelian group H: Pick x;y ϵ G uniformly and independently at random and check if f1(x) + f2(y) = f3(x + y). We analyze this test for two cases: (1) G and H are arbitrary Abelian groups and (2) G = {formula presened} and H = F2. Questions bearing close relationship to linear-consistency testing seem to have been implicitly considered in recent work on the construction of PCPs (and in particular in the work of Håstad [9]). It is abstracted explicitly for the first time here. We give an application of this problem (and of our results): A (yet another) new and tight characterization of NP, namely 8∀ ϵ> 0;NP = MIP{formula presnted}. I.e., every language in NP has 3-prover 1-round proof systems in which the verifier tosses O(log n) coins and asks each of the three provers one question each. The provers respond with one bit each such that the verifier accepts instance of the language with probability 1–ϵ and rejects non-instances with probability at least {formula presented}. Such a result is of some interest in the study of probabilistically checkable proofs. © Springer-Verlag Berlin Heidelberg 1999.

关键词： Group theory

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A wide frequency range surface integral formulation for 3-D RLC extraction 99

A wide frequency range surface integral formulation for 3-D ...

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IEEE International Conference on computer-Aided Design

作者： J. Wang J. Tausch J. White Department of Electrical Engineering and Computer Science MIT-Cambridge MA USA Southern Methodist University USA

ISBN: (纸本)9780780358324

A new surface integral formulation and discretization approach for computing electromagnetoquasistatic impedance of general conductors is described. The key advantages of the formulation is that it avoids volume discretization of the conductors and the substrate, and a single discretization is accurate over the entire frequency range. Computational results from an on-chip inductor, a connector and a transmission line are used to show that the formulation is accurate and is "acceleration" ready. That is, the results demonstrate that an efficiently computed preconditioner insures rapid iterative method convergence and tests with projection show the required kernels can be approximated easily using a coarse grid.

关键词： Frequency Conductors Surface impedance Inductors Connectors Transmission lines Grid computing Iterative methods Convergence Testing

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Evaluation of a new method for CVD estimation

Evaluation of a new method for CVD estimation

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Annual International Conference of the IEEE engineering in Medicine and Biology Society (EMBC)

作者： M.D. Wells S.N. Gozani Department of Electrical Engineering and Computer Science MIT Cambridge MA USA Harvard-MIT Division of Health Sciences and Technology MIT NeuroMetrix Inc. Cambridge MA USA

A new technique for improving the estimation of conduction velocity distributions (CVDs) over a short segment of nerve is investigated experimentally. The technique involves normalizing the nerve-to-electrode transfer functions (NETFs) at a plurality of closely spaced recording sites. CVD's are estimated from short-segment nerve recordings before and after NETF normalization and the results are compared with a long-distance CVD estimated from the same nerve. Normalization is found to dramatically improve short-distance CVD and to substantially duplicate the long-distance estimate.

关键词： Electrodes Wrist Dispersion Transfer functions Data mining Fingers Cathodes Elbow Gold Electroencephalography

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Theoretical modeling of thermoelectricity in Bi nanowires

Theoretical modeling of thermoelectricity in Bi nanowires

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International Conference on Thermoelectrics (ICT)

作者： X. Sun Y.M. Lin S.B. Cronin M.S. Dresselhaus J.Y. Ying G. Chen Department of Physics MIT Cambridge MA USA Department of Electrical Engineering and Computer Science MIT Cambridge MA USA Department of Chemical Engineering MIT Cambridge MA USA Department of Mechanical and Aerospace Engineering UCLA Los Angeles CA USA

A theoretical model based on the basic electronic band structure of bulk Bi is developed to predict the dependence of the band structure and thermoelectric properties on the nanowire width. By carefully tailoring the Bi wire size and carrier concentration, substantial enhancement in the thermoelectric figure of merit is expected for small (/spl les/10 nm) nanowire widths.

关键词： Thermoelectricity Bismuth Nanowires Electrons Effective mass Ellipsoids Tensile stress Wire Potential well Charge carrier processes

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Imaging and evaluation of neoplasia using optical coherence tomography

Imaging and evaluation of neoplasia using optical coherence ...

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Quantum Electronics and Laser science Conference, QELS 1999

作者： Pitris, Costas Drexler, Wolfgang Li, Xingde Jesser, Christine Goodman, Annekathrine Brezinski, Mark E. Fujimoto, James G. Department of Electrical Engineering and Computer Science Research Laboratory of Electronics Massachusetts Institute of Technology CambridgeMA United States Harvard-MIT Division of Health Sciences and Technology MIT United States Gynecologic Oncology Harvard Medical School Massachusetts General Hospital BostonMA United States Cardiac Unit Harvard Medical School Massachusetts General Hospital BostonMA United States

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Adaptive security for threshold cryptosystems 19th

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19th Annual International Cryptology Conference, CRYPTO 1999

作者： Canetti, Ran Gennaro, Rosario Jarecki, Stanislaw Krawczyk, Hugo Rabin, Tal IBM T.J.Watson Research Center PO Box 704 Yorktown HeightsNY10598 United States MIT Laboratory for Computer Science 545 Tech Square CambridgeMA02139 United States Department of Electrical Engineering Technion Haifa32000 Israel IBM T.J. Watson Research Center New York United States

ISBN: (纸本)3540663479

We present adaptively-secure efficient solutions to several central problems in the area of threshold cryptography. We prove these solutions to withstand adaptive attackers that choose parties for corruption at any time during the run of the protocol. In contrast, all previously known efficient protocols for these problems were proven secure only against less realistic static adversaries that choose and fix the subset of corrupted parties before the start of the protocol run. Specifically, we provide adaptively-secure solutions for distributed key generation in discrete-log based cryptosystems, and for the problem of distributed generation of DSS signatures (threshold DSS). We also show how to transform existent static solutions for threshold RSA and proactive schemes to withstand the stronger adaptive attackers. In doing so, we introduce several techniques for the design and analysis of adaptively-secure protocols that may well find further applications. © Springer-Verlag Berlin Heidelberg 1999.

关键词： Network security

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Advances in 1D and 2D thermoelectric materials

Advances in 1D and 2D thermoelectric materials

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International Conference on Thermoelectrics (ICT)

作者： M.S. Dresselhaus Y.M. Lin G. Dresselhaus X. Sun Z. Zhang S.B. Cronin T. Koga J.Y. Ying Dept. of Phys. MIT Cambridge MA USA Department of Electrical Engineering and Computer Science Cambridge MA USA Francis Bitter National Magnet Laboratory Cambridge MA USA Departmentof Physics Cambridge MA USA Division of Engineering and Applied Sciences Harvard University Cambridge MA USA Department of Chemical Engineering MIT Cambridge MA USA

Recent advances in our understanding of 1D and 2D thermoelectric materials in the form of quantum wires (1D) and quantum wells (2D) are reviewed, with emphasis given to the physical mechanisms responsible for the enhanced thermoelectric figure of merit (ZT) in these low dimensional systems. Starting with 2D superlattices, progress in demonstrating proof-of-principle in the PbTe/Pb/sub 1-x/Eu/sub x/Te and Si/Si/sub 1-x/Ge/sub x/ systems is presented. The concept of carrier pocket engineering regarding improved thermoelectric performance for the whole superlattice Z/sub 3D/T, including both the quantum well and the barrier region, is reviewed. Particular attention is given to recent results obtained for 1D bismuth nanowire arrays and for individual Bi nanowires.

关键词： Thermoelectricity Conducting materials Quantum mechanics Magnetic materials Superlattices Bismuth Thermal conductivity Quantum dots Quantum computing Wires

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