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Conference on Lasers and Electro-Optics (CLEO)

作者： Hui Zhan Michael Hvasta Victoria Astley Jason A. Deibel Daniel M. Mittleman Y. Lim Department of Electrical and Computer Engineering MS 366 Rice University Houston TX USA Department of Applied Physics Konkuk University Chungbuk South Korea

We report the application of terahertz apertureless near-field microscopy to vanadium dioxide thin films. We observe an enhancement of the terahertz amplitude due to the metal-insulator transition induced by an applie... 详细信息

ISBN: (纸本)1557528349

关键词： Microscopy Transistors Voltage Optical films Metal-insulator structures Optical scattering Ultrafast optics Semiconductivity Frequency Temperature

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Erratum: “Impact of strain on free-exciton resonance energies in wurtzite AlN” [J. Appl. Phys. 102, 123707 (2007)]

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Journal of applied physics 2008年第8期103卷

作者： Hirokatsu Ikeda Takahiro Okamura Kodai Matsukawa Takayuki Sota Mariko Sugawara Takuya Hoshi Pablo Cantu Rajat Sharma John F. Kaeding Stacia Keller Umesh K. Mishra Kei Kosaka Keiichiro Asai Shigeaki Sumiya Tomohiko Shibata Mitsuhiro Tanaka James S. Speck Steven P. DenBaars Shuji Nakamura Takahiro Koyama Takeyoshi Onuma Shigefusa F. Chichibu 1Department of Electrical Engineering and Bioscience Waseda University Shinjuku Tokyo 169-8555 Japan 2Institute of Applied Physics University of Tsukuba Tsukuba 305-8573 Japan 3Department of Electrical and Computer Engineering and Materials University of California Santa Barbara California 93106 USA 4NGK Insulators Limited 2-56 Suda-cho Mizuho-ku Nagoya Aichi 467-8507 Japan 5NICP ERATO Japan Science and Technology Agency Kawaguchi 332-0012 Japan 6Institute of Multidisciplinary Research for Advanced Materials Tohoku University Aoba Sendai 980-8577 Japan

The formula of lattice constant a in the third paragraph in the left column on page 4 is not correct and the sign of δa should be negative. The correct formula

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On Delay-Tolerant Distributed Space-Time Codes

On Delay-Tolerant Distributed Space-Time Codes

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MILCOM, Military Communications Conference

作者： A. Roger Hammons Mohamed Oussama Damen Applied Physics Laboratory Johns Hopkins University Laurel MD USA Department of Electrical and Computer Engineering University of Waterloo Waterloo Ontario Canada

In cooperative networks using a decode-and-forward strategy, the multiple relays effectively transmit a distributed space-time code, the performance of which can be severely degraded when timing synchronization among the relays is not assured. Recent work by Xia et al., Hammons et al., and Damen et al. has investigated the design of distributed space-time codes that are delay tolerant, in the sense that full spatial diversity is achieved regardless of relative timing offsets. In this paper, we survey these contributions.

关键词： Space time codes Relays Decoding Timing Modulation coding Receiving antennas Transmitting antennas Delay effects physics Laboratories

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Delay-Tolerant Space-Time Block Codes for Asynchronous Cooperative Relaying

Delay-Tolerant Space-Time Block Codes for Asynchronous Coope...

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International Symposium on Wireless Pervasive Computing (ISWPC)

作者： Mohamed Oussama Damen A. Roger Hammons Department of Electrical and Computer Engineering University of Waterloo Waterloo ONT Canada Applied Physics Laboratory Johns Hopkins University Laurel MD USA

In cooperative networks using a decode-and-forward strategy, the multiple relays effectively transmit a distributed space-time code, the performance of which can be severely degraded when timing synchronization among the relays is not assured. Recent work by Xia et al. and Hammons et al. have investigated the design of distributed space-time codes that are delay tolerant, in the sense that full spatial diversity is achieved regardless of relative timing offsets. In this paper, new distributed space-time codes are introduced that are fully delay tolerant

关键词： Block codes Relays Space time codes Decoding Timing Receiving antennas MIMO Modulation coding Delay effects physics

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Optimization Based Load Management for the NEPTUNE Power System

Optimization Based Load Management for the NEPTUNE Power Sys...

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IEEE General Meeting Power& Energy Society

作者： Ting Chan Chen-Ching Liu Bruce M. Howe Department of Electrical Engineering University of Washington Seattle WA USA Department of Electrical and Computer Engineering Iowa State University Ames IA USA Applied Physics Laboratory University of Washington Seattle WA USA

The objective of the North-East Pacific Time-Series Undersea Networked Experiment (NEPTUNE) program is to construct an underwater cabled observatory on the floor of the Pacific Ocean. While the goal is to provide as much power as possible to users of the system, the system conditions need to be monitored on line in order to determine whether or not any corrective action is needed. Due to the unique nature of the underwater observatory system and load characteristics, an analytical tool is needed to calculate the optimal operating condition that serves the maximum number of loads while satisfying all the constraints. In this paper, an optimization based load management algorithm is presented. The method takes into account all system constraints as well as priorities of the loads.

关键词： Load management Power system management Spine Voltage Power system analysis computing Observatories Communication cables Underwater cables Oceans Energy management

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On lattice decoding of space-time block codes for asynchronous cooperative relaying

On lattice decoding of space-time block codes for asynchrono...

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IEEE Princeton Section Sarnoff Symposium

Li and Xia have recently investigated the design of space-time codes that achieve full spatial diversity for asynchronous cooperative communications. They show that certain of the binary space-time trellis codes derived from the Hammons-El Gamal stacking construction are delay tolerant and can be used in the multilevel code constructions by Lu and Kumar to produce delay tolerant space-time codes for PSK and QAM signaling. In prior work, the first author has developed generalizations of the Lu-Kumar construction for more general AM-PSK constellations that also preserve the delay tolerance of the underlying constituent codes and exhibited a new construction of short block codes that achieve significant levels of delay tolerance. This paper discusses how lattice decoding techniques can be adapted to perform decoding of such STBC for asynchronous diversity.

关键词： Lattices Decoding Block codes Relays Delay Space time codes Convolutional codes Stacking Phase shift keying Quadrature amplitude modulation

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Loss of Quantum Efficiency in Green Light Emitting Diode Dies at Low Temperature

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MRS Online Proceedings Library 2007年第1期955卷 1-5页

作者： Yufeng Li Wei Zhao Yong Xia Mingwei Zhu Jayantha Senawiratne Theeradetch Detchprohm E. Fred Schubert Christian M. Wetzel Future Chips Constellation Rensselaer Polytechnic Institute Troy USA Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy USA Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute Troy USA

The electroluminescence, photoluminescence and cathodoluminescence of GaInN/GaN multiple quantum well light emitting diode dies are analyzed at variable low temperature. Three dies of nominally identical structure but strongly different RT performance from 510 nm to 525 nm have been studied. The electroluminescence peak energy exhibits a blue shift from RT to 158 K followed by a red shift for lower temperature. In the same low-temperature range, a secondary emission peak appears near 390 nm (3.18 eV) that resembles a donor-acceptor pair transition from GaN. Depth profiling spectroscopy of this transition at 77 K reveals its location either in the unintentionally doped quantum barriers or within the n-GaN layer, rather than the commonly believed Mg doped p-type GaN layers. The external quantum efficiency of each die increases as the temperature is lowered. A maximum is reached for all near 158 K while for lower temperature as low as 7.7 K, the efficiency continuously drops. The pronounced efficiency maximum is tentatively assigned to a combination of temperature dependent mobility and shift of the actual pn-junction location.

关键词： Ga III-V optical properties

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High Power MQW Electroabsorption Modulator with a Waveguide Taper

High Power MQW Electroabsorption Modulator with a Waveguide ...

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International Topical Meeting on Microwave Photonics (MWP)

作者： I. Shubin X. B. Xie J. R. Bickford W. S. C. Chang P. K. L. Yu D. S. Shin Department of Electrical and Computer Engineering University of California San Diego La Jolla CA USA Department of Applied Physics Hanyang University Ansan South Korea

Peripheral coupled waveguide (PCW) electro-absorption modulator (EAM) with different dimensions is studied. By incorporating a waveguide taper in the PCW to reduce the absorption at the input facet of the EAM, we show... 详细信息

关键词： Quantum well devices Optical waveguides Optical saturation Optical surface waves Optical modulation Optical scattering Optical buffering Radio frequency Optical design Propagation losses

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Chiral-selective excitation of lattice vibrations in carbon nanotubes using femtosecond pulse shaping

Chiral-selective excitation of lattice vibrations in carbon ...

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2007 Quantum Electronics and Laser Science Conference, QELS

作者： Yee, K.J. Kim, J.H. Lim, Y.S. Haroz, E.H. Han, K.J. Kim, N.J. Kono, J. Hauge, R.H. Smalley, R.E. Department of Physics Chungnam National University Daejeon 305-764 Korea Republic of Department of Applied Physics Konkuk University Chungju Chungbuk 380-701 Korea Republic of Department of Electrical and Computer Engineering Rice University MS 366 6100 Main Street TX 77005 United States Carbon Nanotechnology Laboratory Rice University MS 366 6100 Main Street TX 77005 United States

Multiple pulse trains produced by femtosecond pulse shaping were used for chiral-selective excitation of coherent radial breading modes (RBM) in carbon nanotubes. Detection scheme and chirality-dependent phonon lifeti... 详细信息

ISBN: (纸本)1557528349

关键词： Carbon nanotubes

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Nanoparticle-loaded encapsulation materials for light-emitting diode applications

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MRS Online Proceedings Library 2007年第1期955卷 1-6页

作者： Frank Wilhelm Mont H. Luo M. F. Schubert J. K. Kim E. F. Schubert R. W. Siegel Future Chips Constellation Department of Electrical Computer and Systems Engineering Rensselaer Polytechnic Institute Troy USA Future Chips Constellation Department of Physics Applied Physics and Astronomy Rensselaer Polytechnic Institute Troy USA Department of Materials Science and Engineering and Rensselaer Nanotechnology Center Rensselaer Polytechnic Institute Troy USA

Nanoparticle-loaded encapsulants provide unique optical and material properties for the enhancement of light extraction efficiency in light-emitting diodes (LEDs). We report on the uniform dispersion of TiO2 nanoparticles with average diameter of 40 nm in epoxy, and the demonstration of a refractive index (n)of 1.68 at 400 nm wavelength, higher than that of pure epoxy (n = 1.53). It is found that proper chemical surfactants and nanoparticle preparation are critical to eliminate agglomeration of nanoparticles. Theoretical analysis of optical scattering in nanoparticle-loaded encapsulation materials reveals that although the size and loading factor of nanoparticles greatly influence scattering, specular transparency of the encapsulant film occurs if the thicknesses of the films are kept below the optical scattering length. Furthermore, the encapsulants benefit from an optimized scattering coefficient as demonstrated by three-dimensional ray-tracing simulations showing light extraction efficiency enhancements greater than 50%.

关键词： optical properties optical packaging

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