Search query: electrical detection of confined gap

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abstract: Plasmonic waveguides offer promise in providing a solution to the bandwidth limitations of classical electrical interconnections1,2,3. Fast, low loss and error free signal transmission has been achieved in long range surface plasmon polariton waveguides4,5. Deep subwavelength plasmonic waveguides with short propagation lengths have also been demonstrated6,7, showing the possibility of matching the sizes of optics and today's electronic components. However, in order to combine surface plasmon waveguides with electronic circuits, new high bandwidth electro optical transducers need to be developed. Here, we experimentally demonstrate the electrical detection of surface plasmon polaritons in metallic slot waveguides. By means of an integrated metal semiconductor metal photodetector, highly confined surface plasmon polaritons in a metal insulator metal waveguide are detected and characterized. This approach of integrating electro optical components in metallic waveguides could lead to the development of advanced active plasmonic devices and high bandwidth on chip plasmonic circuits. Electrical detection and characterization of gap plasmons is achieved by means of an integrated metal semiconductor metal photodetector. Integration of electro optical components in metallic waveguides may lead to active high bandwidth on chip nano optical circuits.
author_names: Pieter Neutens

Pol van Dorpe

Iwijn De Vlaminck

Liesbet Lagae

G Borghs
title: Electrical detection of confined gap plasmons in metal insulator metal waveguides
year: 2009

abstract: Recent experiments and theories have suggested that strong spin orbit coupling effects in certain band insulators can give rise to a new phase of quantum matter, the so called topological insulator, which can show macroscopic quantum entanglement effects. Such systems feature two dimensional surface states whose electrodynamic properties are described not by the conventional Maxwell equations but rather by an attached axion field, originally proposed to describe interacting quarks. It has been proposed that a topological insulator with a single Dirac cone interfaced with a superconductor can form the most elementary unit for performing fault tolerant quantum computation. Here we present an angle resolved photoemission spectroscopy study that reveals the first observation of such a topological state of matter featuring a single surface Dirac cone realized in the naturally occurring Bi_2Se_3 class of materials. Our results, supported by our theoretical calculations, demonstrate that undoped Bi_2Se_3 can serve as the parent matrix compound for the long sought topological device where in plane carrier transport would have a purely quantum topological origin. Our study further suggests that the undoped compound reached via n to p doping should show topological transport phenomena even at room temperature.
author_names: Yuqi Xia

Dong Qian

D Hsieh

L Andrew Wray

Arijeet Pal

Hsin Lin

Arun Bansil

D Grauer

Yew San Hor

Robert J Cava

M Zahid Hasan
title: Observation of a large gap topological insulator class with a single Dirac cone on the surface
year: 2009

abstract: The innexin family of gap junction proteins has 25 members in Caenorhabditis elegans. Here, we describe the first high resolution expression map of all members through analysis of live worms transformed with green fluorescent protein under the control of entire promoter regions. Our analyses show that innexins have dynamic expression patterns throughout development and are found in virtually all cell types and tissues. Complex tissues, such as the pharynx, intestine, gonad, as well as scaffolding tissues and guidepost cells express a variety of innexins in overlapping or complementary patterns, suggesting they may form heteromeric and heterotypic channels. Innexin expression occurs in several types of cells that are not known to form gap junctions as well as in a pair of migrating cells, suggesting they may have hemichannel function. Therefore, innexins likely play roles in almost all body functions, including embryonic development, cell fate determination, oogenesis, egg laying, pharyngeal pumping, excretion, and locomotion. Developmental Dynamics 238:1936 1950, 2009. (c) 2009 Wiley Liss, Inc.
author_names: Zeynep F Altun

Bojun Chen

Zhao-Weng Wang

David H Hall
title: High resolution map of Caenorhabditis elegans gap junction proteins
venue: Developmental dynamics an official publication of the American Association of Anatomists
year: 2009

abstract: Cells undergo a variety of physiological processes, including division, migration and differentiation, under the influence of endogenous electrical cues, which are generated physiologically and pathologically in the extracellular and sometimes intracellular spaces. These signals are transduced to regulate cell behaviours profoundly, both in vitro and in vivo. Bioelectricity influences cellular processes as fundamental as control of the cell cycle, cell proliferation, cancer cell migration, electrical signalling in the adult brain, embryonic neuronal cell migration, axon outgrowth, spinal cord repair, epithelial wound repair, tissue regeneration and establishment of left right body asymmetry. In addition to direct effects on cells, electrical gradients interact with coexisting extracellular chemical gradients. Indeed, cells can integrate and respond to electrical and chemical cues in combination. This Commentary details how electrical signals control multiple cell behaviours and argues that study of the interplay between combined electrical and chemical gradients is underdeveloped yet necessary.
author_names: Colin D McCaig

Bing Song

Ann M Rajnicek
title: Electrical dimensions in cell science
venue: Journal of Cell Science
year: 2009

abstract: We report the design, fabrication and optical investigation of electrically tunable single quantum dots photonic crystal defect nanocavities operating in both the weak and strong coupling regimes of the light matter interaction. Unlike previous studies where the dot cavity spectral detuning was varied by changing the lattice temperature, or by the adsorption of inert gases at low temperatures, we demonstrate that the quantum confined Stark effect can be employed to quickly and reversibly switch the dot cavity coupling simply by varying a gate voltage. Our results show that exciton transitions from individual dots can be tuned by ~4 meV relative to the nanocavity mode before the emission quenches due to carrier tunneling escape. This range is much larger than the typical linewidth of the high Q cavity modes ~100 meV) allowing us to explore and contrast regimes where the dots couple to the cavity or decay by spontaneous emission into the two dimensional photonic bandgap. In the weak coupling regime, we show that the dot spontaneous emission rate can be tuned using a gate voltage, with Purcell factors =7. New information is obtained on the nature of the dot cavity coupling in the weak coupling regime, and electrical control of zero dimensional polaritons is demonstrated for the highest Q cavities (Q>=12 000) Vacuum Rabi splittings up to ~120 meV are observed, larger than the linewidths of either the decoupled exciton (g<=40 meV) or cavity mode. These observations represent a voltage switchable optical nonlinearity at the single photon level, paving the way towards on chip dot based nano photonic devices that can be integrated with passive optical components.
author_names: Arne Laucht

Felix Hofbauer

Norman Hauke

Jacques Angele

Soren Stobbe

Michael Kaniber

Gisela Bohm

Peter Lodahl

Markus-Christian Amann

J J Finley Walter Schottky Institut

Technische Universitat Munchen

Dtu Fotonik

Department of Electrical Engineering

Technical University of Denmark
title: Electrical control of spontaneous emission and strong coupling for a single quantum dot
year: 2009

abstract: We report broadband visible photoluminescence from solid graphene oxide, and modifications of the emission spectrum by progressive chemical reduction. The data suggest a gapping of the two dimensional electronic system by removal of p electrons. We discuss possible gapping mechanisms, and propose that a Kekule pattern of bond distortions may account for the observed behavior.
author_names: Zhengtang Luo

Patrick M Vora

Eugene J Mele

A T Charlie Johnson

James Makoto Kikkawa
title: Photoluminescence and band gap modulation in graphene oxide
year: 2009

abstract: This letter presents a new metamaterial based waveguide technology referred to as ridge gap waveguides. The main advantages of the ridge gap waveguides compared to hollow waveguides are that they are planar and much cheaper to manufacture, in particular at high frequencies such as for millimeter and sub millimeter waves. The latter is due to the fact that there are no mechanical joints across which electric currents must float. The gap waveguides have lower losses than microstrip lines, and they are completely shielded by metal so no additional packaging is needed, in contrast to the severe packaging problems associated with microstrip circuits. The gap waveguides are realized in a narrow gap between two parallel metal plates by using a texture or multilayer structure on one of the surfaces. The waves follow metal ridges in the textured surface. All wave propagation in other directions is prohibited (in cutoff) by realizing a high surface impedance (ideally a perfect magnetic conductor) in the textured surface at both sides of all ridges. Thereby, cavity resonances do not appear either within the band of operation. The present letter introduces the gap waveguide and presents some initial simulated results.
author_names: Per-Simon Kildal

Esperanza Alfonso

Alejandro Valero-Nogueira

Eva Rajo-Iglesias
title: Local Metamaterial Based Waveguides in Gaps Between Parallel Metal Plates
venue: IEEE Antennas and Wireless Propagation Letters
year: 2009

author_names: Glenn F Knoll
title: Radiation Detection And Measurement, 3rd Ed
year: 2009

abstract: We show how the quantum Hall effect in an inverted gap semiconductor (with electron and hole like states at the conduction and valence band edges interchanged) can be used to inject, precess, and detect the electron spin along a one dimensional pathway. The restriction of the electron motion to a single spatial dimension ensures that all electrons experience the same amount of precession in a parallel magnetic field, so that the full electrical current can be switched on and off. As an example, we calculate the magnetoconductance of a p n interface in a HgTe quantum well and show how it can be used to measure the spin precession due to bulk inversion asymmetry.
author_names: Anton Akhmerov

Christoph Groth

Jakub Tworzydlo

C W J Beenakker
title: Switching of electrical current by spin precession in the first Landau level of an inverted gap semiconductor
year: 2009

abstract: This article is based on a consensus conference, which took place in Certosa di Pontignano, Siena (Italy) on March 7 9, 2008, intended to update the previous safety guidelines for the application of transcranial magnetic stimulation (TMS) in research and clinical settings. Over the past decade the scientific and medical community has had the opportunity to evaluate the safety record of research studies and clinical applications of TMS and repetitive TMS (rTMS) In these years the number of applications of conventional TMS has grown impressively, new paradigms of stimulation have been developed (e.g. patterned repetitive TMS) and technical advances have led to new device designs and to the real time integration of TMS with electroencephalography (EEG) positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) Thousands of healthy subjects and patients with various neurological and psychiatric diseases have undergone TMS allowing a better assessment of relative risks. The occurrence of seizures (i.e. the most serious TMS related acute adverse effect) has been extremely rare, with most of the few new cases receiving rTMS exceeding previous guidelines, often in patients under treatment with drugs which potentially lower the seizure threshold. The present updated guidelines review issues of risk and safety of conventional TMS protocols, address the undesired effects and risks of emerging TMS interventions, the applications of TMS in patients with implanted electrodes in the central nervous system, and safety aspects of TMS in neuroimaging environments. We cover recommended limits of stimulation parameters and other important precautions, monitoring of subjects, expertise of the rTMS team, and ethical issues. While all the recommendations here are expert based, they utilize published data to the extent possible.
author_names: Simone Rossi

Mark Hallett

Paolo Maria Rossini

Alvaro Pascual-Leone
title: Safety, ethical considerations, and application guidelines for the use of transcranial magnetic stimulation in clinical practice and research
venue: Clinical Neurophysiology
year: 2009