Magnetic polarons in a nonequilibrium polariton condensate

Science.gov (United States)

Mietki, Paweł; Matuszewski, Michał

2017-09-01

We consider a condensate of exciton polaritons in a diluted magnetic semiconductor microcavity. Such a system may exhibit magnetic self-trapping in the case of sufficiently strong coupling between polaritons and magnetic ions embedded in the semiconductor. We investigate the effect of the nonequilibrium nature of exciton polaritons on the physics of the resulting self-trapped magnetic polarons. We find that multiple polarons can exist at the same time, and we derive a critical condition for self-trapping that is different from the one predicted previously in the equilibrium case. Using the Bogoliubov-de Gennes approximation, we calculate the excitation spectrum and provide a physical explanation in terms of the effective magnetic attraction between polaritons, mediated by the ion subsystem.

Polariton condensation with localized excitons and propagating photons

International Nuclear Information System (INIS)

Keeling, Jonathan; Eastham, P.R.; Szymanska, M.H.; Littlewood, P.B.

2004-01-01

We estimate the condensation temperature for microcavity polaritons, allowing for their internal structure. We consider polaritons formed from localized excitons in a planar microcavity, using a generalized Dicke model. At low densities, we find a condensation temperature T c ∝ρ, as expected for a gas of structureless polaritons. However, as T c becomes of the order of the Rabi splitting, the structure of the polaritons becomes relevant, and the condensation temperature is that of a BCS-like mean-field theory. We also calculate the excitation spectrum, which is related to observable quantities such as the luminescence and absorption spectra

Polariton effects in naphthalene crystals

International Nuclear Information System (INIS)

Robinette, S.L.

1977-10-01

The experimental verification of the two-step nature of energy dissipation of photon energy by a crystal is the subject of this dissertation. The α(O,O) Davydov component of the lowest energy singlet transition in pure strain-free napthalene single crystals is shown to exhibit an increase in absorption with increasing temperature, due to an increase in polariton damping via polariton-phonon scattering processes

Observation of the exceptional point in cavity magnon-polaritons.

Science.gov (United States)

Zhang, Dengke; Luo, Xiao-Qing; Wang, Yi-Pu; Li, Tie-Fu; You, J Q

2017-11-08

Magnon-polaritons are hybrid light-matter quasiparticles originating from the strong coupling between magnons and photons. They have emerged as a potential candidate for implementing quantum transducers and memories. Owing to the dampings of both photons and magnons, the polaritons have limited lifetimes. However, stationary magnon-polariton states can be reached by a dynamical balance between pumping and losses, so the intrinsically nonequilibrium system may be described by a non-Hermitian Hamiltonian. Here we design a tunable cavity quantum electrodynamics system with a small ferromagnetic sphere in a microwave cavity and engineer the dissipations of photons and magnons to create cavity magnon-polaritons which have non-Hermitian spectral degeneracies. By tuning the magnon-photon coupling strength, we observe the polaritonic coherent perfect absorption and demonstrate the phase transition at the exceptional point. Our experiment offers a novel macroscopic quantum platform to explore the non-Hermitian physics of the cavity magnon-polaritons.

Resonant Magnon-Phonon Polaritons in a Ferrimagnet

Science.gov (United States)

2000-09-29

UNCLASSIFIED Defense Technical Information Center Compilation Part Notice ADPO 11604 TITLE: Resonant Magnon -Phonon Polaritons in a Ferrimagnet...part numbers comprise the compilation report: ADP011588 thru ADP011680 UNCLASSIFIED 75 Resonant Magnon -Phonon Polaritons in a Ferrimagnet I. E...susceptibilities X"aa and X’m << X’m appear, where 77 xem - DPx igEo0 i_ Xxy - hy- C1 (0)2 _ 00t2) 4= -7• 4 3. Phonon and magnon polaritons We solve the

Mass of polaritons in different dielectric media

International Nuclear Information System (INIS)

Dzedolik, I V; Lapayeva, S N

2011-01-01

Some models of electromagnetic field interactions with linear and nonlinear dielectric media based on the approach of polarization and electromagnetic wave propagation in media are considered. It is shown that quasi-particles generated in the dielectric medium, called polaritons, have mass whose quantity depends on the efficiency of the electromagnetic field and interaction with the medium. The mass and velocity of polaritons can be controlled by the external electric field. The value of the mass of polaritons was measured in a transparent crystal

Ultranarrow polaritons in a semiconductor microcavity

DEFF Research Database (Denmark)

Jensen, Jacob Riis; Borri, Paola; Langbein, Wolfgang

2000-01-01

We have achieved a record high ratio (19) of the Rabi splitting (3.6 meV) to the polariton linewidth (190 mu eV), in a semiconductor lambda microcavity with a single 25 nm GaAs quantum well at the antinode. The narrow polariton lines are obtained with a special cavity design which reduces...

Bose-Einstein Condensation of Long-Lifetime Polaritons in Thermal Equilibrium.

Science.gov (United States)

Sun, Yongbao; Wen, Patrick; Yoon, Yoseob; Liu, Gangqiang; Steger, Mark; Pfeiffer, Loren N; West, Ken; Snoke, David W; Nelson, Keith A

2017-01-06

The experimental realization of Bose-Einstein condensation (BEC) with atoms and quasiparticles has triggered wide exploration of macroscopic quantum effects. Microcavity polaritons are of particular interest because quantum phenomena such as BEC and superfluidity can be observed at elevated temperatures. However, polariton lifetimes are typically too short to permit thermal equilibration. This has led to debate about whether polariton condensation is intrinsically a nonequilibrium effect. Here we report the first unambiguous observation of BEC of optically trapped polaritons in thermal equilibrium in a high-Q microcavity, evidenced by equilibrium Bose-Einstein distributions over broad ranges of polariton densities and bath temperatures. With thermal equilibrium established, we verify that polariton condensation is a phase transition with a well-defined density-temperature phase diagram. The measured phase boundary agrees well with the predictions of basic quantum gas theory.

Spin polarized semimagnetic exciton-polariton condensate in magnetic field.

Science.gov (United States)

Król, Mateusz; Mirek, Rafał; Lekenta, Katarzyna; Rousset, Jean-Guy; Stephan, Daniel; Nawrocki, Michał; Matuszewski, Michał; Szczytko, Jacek; Pacuski, Wojciech; Piętka, Barbara

2018-04-27

Owing to their integer spin, exciton-polaritons in microcavities can be used for observation of non-equilibrium Bose-Einstein condensation in solid state. However, spin-related phenomena of such condensates are difficult to explore due to the relatively small Zeeman effect of standard semiconductor microcavity systems and the strong tendency to sustain an equal population of two spin components, which precludes the observation of condensates with a well defined spin projection along the axis of the system. The enhancement of the Zeeman splitting can be achieved by introducing magnetic ions to the quantum wells, and consequently forming semimagnetic polaritons. In this system, increasing magnetic field can induce polariton condensation at constant excitation power. Here we evidence the spin polarization of a semimagnetic polaritons condensate exhibiting a circularly polarized emission over 95% even in a moderate magnetic field of about 3 T. Furthermore, we show that unlike nonmagnetic polaritons, an increase on excitation power results in an increase of the semimagnetic polaritons condensate spin polarization. These properties open new possibilities for testing theoretically predicted phenomena of spin polarized condensate.

Microcavity polariton linewidths in the weak-disorder regime

DEFF Research Database (Denmark)

Borri, Paola; Langbein, Wolfgang Werner; Woggon, U.

2000-01-01

Polariton linewidths have been measured in a series of high-quality microcavities with different excitonic inhomogeneous broadening in the weak-disorder regime. We show experimentally that the influence of the disorder on the polariton linewidths is canceled when the polariton energies are far in...... in the tail of the excitonic absorption. The measured linewidths are quantitatively compared with an estimation using the measured excitonic absorption spectrum of the bare quantum wells, and good agreement is found....

Polariton-acoustic-phonon interaction in a semiconductor microcavity

Science.gov (United States)

Cassabois, G.; Triques, A. L. C.; Bogani, F.; Delalande, C.; Roussignol, Ph.; Piermarocchi, C.

2000-01-01

The broadening of polariton lines by acoustic phonons is investigated in a semiconductor microcavity by means of interferometric correlation measurements with subpicosecond resolution. A decrease of the polariton-acoustic phonon coupling is clearly observed for the lower polariton branch as one approaches the resonance between exciton and photon states. This behavior cannot be explained in terms of a semiclassical linear dispersion theory but requires a full quantum description of the microcavity in the strong-coupling regime.

Ultra-fast polariton dynamics in an organic microcavity

Directory of Open Access Journals (Sweden)

Polli D.

2013-03-01

Full Text Available We study an organic semiconductor microcavity operating in the strong-coupling regime using femtosecond pump-probe spectroscopy. By probing the photo-induced absorption bands, we characterize the time-dependent population densities of states in the two polariton branches. We found evidence of a scattering process from the upper-branch cavity polaritons to the exciton reservoir having a rate of (150 fs-1. A slower process similarly populates lower-branch polaritons with a rate of around (3ps-1

Elastic scattering dynamics of cavity polaritons: Evidence for time-energy uncertainty and polariton localization

DEFF Research Database (Denmark)

Langbein, Wolfgang Werner; Hvam, Jørn Märcher

2002-01-01

The directional dynamics of the resonant Rayleigh scattering from a semiconductor microcavity is investigated. When optically exciting the lower polariton branch, the strong dispersion results in a directional emission on a ring. The coherent emission ring shows a reduction of its angular width...... for increasing time after excitation, giving direct evidence for the time-energy uncertainty in the dynamics of the scattering by disorder. The ring width converges with time to a finite value, a direct measure of an intrinsic momentum broadening of the polariton states localized by multiple disorder scattering....

Competing role of Interactions in Synchronization of Exciton-Polariton condensates

Science.gov (United States)

Khan, Saeed; Tureci, Hakan E.

We present a theoretical study of synchronization dynamics in incoherently pumped exciton-polariton condensates in coupled traps. Our analysis is based on an expansion in non-Hermitian modes that take into account the trapping potential and the pump-induced complex-valued potential. We find that polariton-polariton and reservoir-polariton interactions play competing roles in the emergence of a synchronized phase as pumping power is increased, leading to qualitatively different synchronized phases. Crucially, these interactions can also act against each other to hinder synchronization. We present a phase diagram and explain the general characteristics of these phases using a generalized Adler equation. Our work sheds light on dynamics strongly influenced by competing interactions particular to incoherently pumped exciton-polariton condensates, which can lead to interesting features in recently engineered polariton lattices. This work was supported by the US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering.

Bistability of Cavity Magnon Polaritons

Science.gov (United States)

Wang, Yi-Pu; Zhang, Guo-Qiang; Zhang, Dengke; Li, Tie-Fu; Hu, C.-M.; You, J. Q.

2018-01-01

We report the first observation of the magnon-polariton bistability in a cavity magnonics system consisting of cavity photons strongly interacting with the magnons in a small yttrium iron garnet (YIG) sphere. The bistable behaviors emerged as sharp frequency switchings of the cavity magnon polaritons (CMPs) and related to the transition between states with large and small numbers of polaritons. In our experiment, we align, respectively, the [100] and [110] crystallographic axes of the YIG sphere parallel to the static magnetic field and find very different bistable behaviors (e.g., clockwise and counter-clockwise hysteresis loops) in these two cases. The experimental results are well fitted and explained as being due to the Kerr nonlinearity with either a positive or negative coefficient. Moreover, when the magnetic field is tuned away from the anticrossing point of CMPs, we observe simultaneous bistability of both magnons and cavity photons by applying a drive field on the lower branch.

Spin-Orbit Coupling for Photons and Polaritons in Microstructures

Directory of Open Access Journals (Sweden)

V. G. Sala

2015-03-01

Full Text Available We use coupled micropillars etched out of a semiconductor microcavity to engineer a spin-orbit Hamiltonian for photons and polaritons in a microstructure. The coupling between the spin and orbital momentum arises from the polarization-dependent confinement and tunneling of photons between adjacent micropillars arranged in the form of a hexagonal photonic molecule. It results in polariton eigenstates with distinct polarization patterns, which are revealed in photoluminescence experiments in the regime of polariton condensation. Thanks to the strong polariton nonlinearities, our system provides a photonic workbench for the quantum simulation of the interplay between interactions and spin-orbit effects, particularly when extended to two-dimensional lattices.

Polaritons dispersion in a composite ferrite-semiconductor structure near gyrotropic-nihility state

Energy Technology Data Exchange (ETDEWEB)

Tuz, Vladimir R., E-mail: tvr@rian.kharkov.ua

2016-12-01

In the context of polaritons in a ferrite-semiconductor structure which is influenced by an external static magnetic field, the gyrotropic-nihility can be identified from the dispersion equation related to bulk polaritons as a particular extreme state, at which the longitudinal component of the corresponding constitutive tensor and bulk constant simultaneously acquire zero. Near the frequency of the gyrotropic-nihility state, the conditions of branches merging of bulk polaritons, as well as an anomalous dispersion of bulk and surface polaritons are found and discussed. - Highlights: • Gyrotropic-nihility state is identified from the dispersion equation related to bulk polaritons in a magnetic-semiconductor superlattice. • The conditions of branches merging of bulk polaritons are found. • An anomalous dispersion of bulk and surface polaritons is found and discussed.

Polaritons dispersion in a composite ferrite-semiconductor structure near gyrotropic-nihility state

International Nuclear Information System (INIS)

Tuz, Vladimir R.

2016-01-01

In the context of polaritons in a ferrite-semiconductor structure which is influenced by an external static magnetic field, the gyrotropic-nihility can be identified from the dispersion equation related to bulk polaritons as a particular extreme state, at which the longitudinal component of the corresponding constitutive tensor and bulk constant simultaneously acquire zero. Near the frequency of the gyrotropic-nihility state, the conditions of branches merging of bulk polaritons, as well as an anomalous dispersion of bulk and surface polaritons are found and discussed. - Highlights: • Gyrotropic-nihility state is identified from the dispersion equation related to bulk polaritons in a magnetic-semiconductor superlattice. • The conditions of branches merging of bulk polaritons are found. • An anomalous dispersion of bulk and surface polaritons is found and discussed.

Surface phonon polaritons in semi-infinite semiconductor superlattices

International Nuclear Information System (INIS)

Nkoma, J.S.

1986-07-01

Surface phonon polaritons in a semi-infinite semiconductor superlattice bounded by vacuum are studied. The modes associated with the polaritons are obtained and used to obtain the dispersion relation. Numerical results show that polariton bands exist between the TO and LO phonon frequencies, and are found to approach two surface mode frequencies in the limit of large tangential wave vector. Dependency of frequencies on the ratio of layer thicknesses is shown. Results are illustrated by a GaAs-GaP superlattice bounded by vacuum. (author)

Room temperature current injection polariton light emitting diode with a hybrid microcavity.

Science.gov (United States)

Lu, Tien-Chang; Chen, Jun-Rong; Lin, Shiang-Chi; Huang, Si-Wei; Wang, Shing-Chung; Yamamoto, Yoshihisa

2011-07-13

The strong light-matter interaction within a semiconductor high-Q microcavity has been used to produce half-matter/half-light quasiparticles, exciton-polaritons. The exciton-polaritons have very small effective mass and controllable energy-momentum dispersion relation. These unique properties of polaritons provide the possibility to investigate the fundamental physics including solid-state cavity quantum electrodynamics, and dynamical Bose-Einstein condensates (BECs). Thus far the polariton BEC has been demonstrated using optical excitation. However, from a practical viewpoint, the current injection polariton devices operating at room temperature would be most desirable. Here we report the first realization of a current injection microcavity GaN exciton-polariton light emitting diode (LED) operating under room temperature. The exciton-polariton emission from the LED at photon energy 3.02 eV under strong coupling condition is confirmed through temperature-dependent and angle-resolved electroluminescence spectra.

GaAs-based high temperature electrically pumped polariton laser

Energy Technology Data Exchange (ETDEWEB)

Baten, Md Zunaid; Bhattacharya, Pallab, E-mail: pkb@eecs.umich.edu; Frost, Thomas; Deshpande, Saniya; Das, Ayan [Center for Photonic and Multiscale Nanomaterials, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109 (United States); Lubyshev, Dimitri; Fastenau, Joel M.; Liu, Amy W. K. [IQE, Inc., 119 Technology Drive, Bethlehem, Pennsylvania 18015 (United States)

2014-06-09

Strong coupling effects and polariton lasing are observed at 155 K with an edge-emitting GaAs-based microcavity diode with a single Al{sub 0.31}Ga{sub 0.69}As/Al{sub 0.41}Ga{sub 0.59}As quantum well as the emitter. The threshold for polariton lasing is observed at 90 A/cm{sup 2}, accompanied by a reduction of the emission linewidth to 0.85 meV and a blueshift of the emission wavelength by 0.89 meV. Polariton lasing is confirmed by the observation of a polariton population redistribution in momentum space and spatial coherence. Conventional photon lasing is recorded in the same device at higher pump powers.

Room Temperature Ultralow Threshold GaN Nanowire Polariton Laser

KAUST Repository

Das, Ayan

2011-08-01

We report ultralow threshold polariton lasing from a single GaN nanowire strongly coupled to a large-area dielectric microcavity. The threshold carrier density is 3 orders of magnitude lower than that of photon lasing observed in the same device, and 2 orders of magnitude lower than any existing room-temperature polariton devices. Spectral, polarization, and coherence properties of the emission were measured to confirm polariton lasing. © 2011 American Physical Society.

Quantum confinement of zero-dimensional hybrid organic-inorganic polaritons at room temperature

Science.gov (United States)

Nguyen, H. S.; Han, Z.; Abdel-Baki, K.; Lafosse, X.; Amo, A.; Lauret, J.-S.; Deleporte, E.; Bouchoule, S.; Bloch, J.

2014-02-01

We report on the quantum confinement of zero-dimensional polaritons in perovskite-based microcavity at room temperature. Photoluminescence of discrete polaritonic states is observed for polaritons localized in symmetric sphere-like defects which are spontaneously nucleated on the top dielectric Bragg mirror. The linewidth of these confined states is found much sharper (almost one order of magnitude) than that of photonic modes in the perovskite planar microcavity. Our results show the possibility to study organic-inorganic cavity polaritons in confined microstructure and suggest a fabrication method to realize integrated polaritonic devices operating at room temperature.

Quantum confinement of zero-dimensional hybrid organic-inorganic polaritons at room temperature

International Nuclear Information System (INIS)

Nguyen, H. S.; Lafosse, X.; Amo, A.; Bouchoule, S.; Bloch, J.; Han, Z.; Abdel-Baki, K.; Lauret, J.-S.; Deleporte, E.

2014-01-01

We report on the quantum confinement of zero-dimensional polaritons in perovskite-based microcavity at room temperature. Photoluminescence of discrete polaritonic states is observed for polaritons localized in symmetric sphere-like defects which are spontaneously nucleated on the top dielectric Bragg mirror. The linewidth of these confined states is found much sharper (almost one order of magnitude) than that of photonic modes in the perovskite planar microcavity. Our results show the possibility to study organic-inorganic cavity polaritons in confined microstructure and suggest a fabrication method to realize integrated polaritonic devices operating at room temperature

Stimulated emission from ZnO nanorod arrays

Energy Technology Data Exchange (ETDEWEB)

Hauschild, R.; Lange, H.; Priller, H.; Klingshirn, C.; Kalt, H. [Institut fuer Angewandte Physik, Universitaet Karlsruhe (TH), 76128 Karlsruhe (Germany); Kling, R. [Abteilung Halbleiterphysik, Universitaet Ulm, Albert-Einstein Allee 45, 89081 Ulm (Germany); Waag, A. [Institut fuer Halbleitertechnik, TU-Braunschweig, H.-Sommer-Str. 66, 38106 Braunschweig (Germany); Fan, H.J.; Zacharias, M. [Max-Planck-Institut fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany)

2006-08-15

We discuss the time-resolved photoluminescence (PL) spectra of single ZnO nanorods taken at excitation fluences above and below the laser threshold. In the latter case, P-band emission related to polariton-polariton scattering is observed for certain rod geometries while stimulated emission occurs within the electron-hole plasma band. We calculate the intensity distribution of low-order waveguide modes as well as their energy dependence for given nanorod geometries to discuss their relevance with respect to nanorod lasing and polariton propagation. Additional finite-element analysis confirms that a gold layer formed at the nanorod-substrate interface under certain growth conditions leads to an enhancement of confinement within the resonator. (2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (Abstract Copyright [2006], Wiley Periodicals, Inc.)

Room Temperature Ultralow Threshold GaN Nanowire Polariton Laser

KAUST Repository

Das, Ayan; Heo, Junseok; Jankowski, Marc; Guo, Wei; Zhang, Lei; Deng, Hui; Bhattacharya, Pallab

2011-01-01

, and 2 orders of magnitude lower than any existing room-temperature polariton devices. Spectral, polarization, and coherence properties of the emission were measured to confirm polariton lasing. © 2011 American Physical Society.

Dispersion relation for localized magnetic polaritons propagating at ...

Indian Academy of Sciences (India)

Abstract. Localized magnetic polaritons are investigated in the systems consisting of two magnetic superlattices, coupled by a ferromagnetic contact layer. The general dis- persion relation for localized magnetic polaritons are derived in the framework of the electromagnetic wave theory in the Voigt geometry by the 'transfer' ...

Nonequilibrium dynamics of polariton entanglement in a cluster of coupled traps

Energy Technology Data Exchange (ETDEWEB)

Quiroga, L [Departamento de Fisica, Universidad de Los Andes, A.A.4976, Bogota D.C. (Colombia); Tejedor, C, E-mail: lquiroga@uniandes.edu.c [Departamento de Fisica Teorica de la Materia Condensada, Universidad Autonoma de Madrid, Cantoblanco, E-28049, Madrid (Spain)

2009-05-01

We study in detail the generation and relaxation of quantum coherences (entanglement) in a system of coupled polariton traps. By exploiting a Lie algebraic based super-operator technique we provide an analytical exact solution for the Markovian dissipative dynamics (Master equation) of such system which is valid for arbitrary cluster size, polariton-polariton interaction strength, temperature and initial state. Based on the exact solution of the Master equation at T = OK, we discuss how dissipation affects the quantum entanglement dynamics of coupled polariton systems.

Excitonic surface polaritons in luminescence from ZnTe crystals

International Nuclear Information System (INIS)

Brodin, M.S.; Bandura, V.M.; Matsko, M.G.

1984-01-01

The form and structure of reflection and exciton-polariton luminescence spectra of ZnTe crystals are studied in the region of the ground (n = 1) exciton state. The longitudinal-transverse splitting magnitude ΔE/sub LT/ is determined from the shape of the reflection spectra. A detected doublet structure of an emission band from the lower polariton branch is associated with the k-linear term. The evolution of bulk and surface polariton luminescence spectra versus temperature and wavelength of the exciting light is investigated. (author)

Excitonic surface polaritons in luminescence from ZnTe crystals

Energy Technology Data Exchange (ETDEWEB)

Brodin, M.S.; Bandura, V.M.; Matsko, M.G. (AN Ukrainskoj SSR, Kiev. Inst. Fiziki)

1984-10-01

The form and structure of reflection and exciton-polariton luminescence spectra of ZnTe crystals are studied in the region of the ground (n = 1) exciton state. The longitudinal-transverse splitting magnitude ..delta..E/sub LT/ is determined from the shape of the reflection spectra. A detected doublet structure of an emission band from the lower polariton branch is associated with the k-linear term. The evolution of bulk and surface polariton luminescence spectra versus temperature and wavelength of the exciting light is investigated.

The dynamics of a polariton dimer in a disordered coupled array of cavities

Science.gov (United States)

Aiyejina, Abuenameh; Andrews, Roger

2018-03-01

We investigate the effect of disorder in the laser intensity on the dynamics of dark-state polaritons in an array of 20 cavities, each containing an ensemble of four-level atoms that is described by a Bose-Hubbard Hamiltonian. We examine the evolution of the polariton number in the cavities starting from a state with either one or two polaritons in one of the cavities. For the case of a single polariton without disorder in the laser intensity, we calculate the wavefunction of the polariton and find that it disperses away from the initial cavity with time. The addition of disorder results in minimal suppression of the dispersal of the wavefunction. In the case of two polaritons with an on-site repulsion to hopping strength ratio of 20, we find that the polaritons form a repulsively bound state or dimer. Without disorder the dimer wavefunction disperses similarly to the single polariton wavefunction but over a longer time period. The addition of sufficiently strong disorder results in localization of the polariton dimer. The localization length is found to be described by a power law with exponent - 1.31. We also find that we can localise the dimer at any given time by switching on the disorder.

Condensation of exciton polaritons

International Nuclear Information System (INIS)

Kasprzak, J.

2006-10-01

Because of their unique property of bringing pure quantum effects into the real world scale, phase transitions towards condensed phases - like Bose-Einstein condensation (BEC), superfluidity, and superconductivity - have always fascinated scientists. The BEC, appearing upon cooling a gas of bosons below a critical temperature, has been given a striking demonstration in dilute atomic gases of rubidium atoms at temperatures below 200 nK. By confining photons in a semiconductor micro-cavity, and strongly coupling them to electronic excitations, one may create polaritons. These bosonic quasi-particles are 10 9 times lighter than rubidium atoms, thus theoretically allowing a BEC at standard cryogenic temperatures. Here we detail a comprehensive set of experiments giving compelling evidence for a BEC of polaritons. Above a critical density, we observe massive occupation of the ground state, developing from a thermalized and saturated distribution of the polariton population at (16-20) K. We demonstrate as well the existence of a critical temperature for this transition. The spontaneous onset of a coherent state is manifested by the increase of temporal coherence, the build-up of long-range spatial coherence and the reduction of the thermal noise observed in second order coherence experiments. The marked linear polarization of the emission from the condensate is also measured. All of these findings indicate the spontaneous onset of a macroscopic quantum phase. (author)

Propagation and excitation of graphene plasmon polaritons

DEFF Research Database (Denmark)

Zhu, Xiaolong; Yan, Wei; Jeppesen, Claus

2013-01-01

We theoretically investigate the propagation of graphene plasmon polaritons in graphene nanoribbon waveguides and experimentally observe the excitation of the graphene plasmon polaritons in a continuous graphene monolayer. We show that graphene nanoribbon bends do not induce any additional loss...... and nanofocusing occurs in a tapered graphene nanoriboon, and we experimentally demonstrate the excitation of graphene plasmon polaritonss in a continuous graphene monolayer assisted by a two-dimensional subwavelength silicon grating....

Oscillatory solitons and time-resolved phase locking of two polariton condensates

International Nuclear Information System (INIS)

Christmann, Gabriel; Tosi, Guilherme; Baumberg, Jeremy J; Berloff, Natalia G; Tsotsis, Panagiotis; Eldridge, Peter S; Hatzopoulos, Zacharias; Savvidis, Pavlos G

2014-01-01

When pumped nonresonantly, semiconductor microcavity polaritons form Bose–Einstein condensates that can be manipulated optically. Using tightly-focused excitation spots, radially expanding condensates can be formed in close proximity. Using high time resolution streak camera measurements we study the time dependent properties of these macroscopic coherent states. By coupling this method with interferometry we observe directly the phase locking of two independent condensates in time, showing the effect of polariton–polariton interactions. We also directly observe fast spontaneous soliton-like oscillations of the polariton cloud trapped between the pump spots, which can be either dark or bright solitons. This transition from dark to bright is a consequence of the change of sign of the nonlinearity which we propose is due to the shape of the polariton dispersion leading to either positive or negative polariton effective mass. (paper)

Physics of quantum fluids. New trends and hot topics in atomic and polariton condensates

Energy Technology Data Exchange (ETDEWEB)

Bramati, Alberto [Paris Univ. (France). Laboratoire Kastler Brossel; Centre National de la Recherche Scientifique (CNRS), 75 - Paris (France); Modugno, Michele (eds.) [IKERBASQUE, Bilbao (Spain); Univ. del Pais Vasco, Bilbao (Spain). Dept. de Fisica Teorica e Historia de la Ciencia

2013-10-01

Provides an overview of the field of quantum fluids. Presents analogies and differences between polariton and atomic quantum fluids. With contributions from the major actors in the field. Explains a new type of quantum fluid with specific characteristics. The study of quantum fluids, stimulated by the discovery of superfluidity in liquid helium, has experienced renewed interest after the observation of Bose-Einstein condensation (BEC) in ultra-cold atomic gases and the observation a new type of quantum fluid with specific characteristics derived from its intrinsic out-of-equilibrium nature. The main objective of this book is to take a snapshot of the state-of-the-art of this fast moving field with a special emphasis on the hot topics and new trends. Bringing together the most active specialists of the two areas (atomic and polaritonic quantum fluids), we expect that this book will facilitate the exchange and the collaboration between these two communities working on subjects with very strong analogies.

Amplitude-Mode Dynamics of Polariton Condensates

International Nuclear Information System (INIS)

Brierley, R. T.; Littlewood, P. B.; Eastham, P. R.

2011-01-01

We study the stability of collective amplitude excitations in nonequilibrium polariton condensates. These excitations correspond to renormalized upper polaritons and to the collective amplitude modes of atomic gases and superconductors. They would be present following a quantum quench or could be created directly by resonant excitation. We show that uniform amplitude excitations are unstable to the production of excitations at finite wave vectors, leading to the formation of density-modulated phases. The physical processes causing the instabilities can be understood by analogy to optical parametric oscillators and the atomic Bose supernova.

Near-infrared exciton-polaritons in strongly coupled single-walled carbon nanotube microcavities

Science.gov (United States)

Graf, Arko; Tropf, Laura; Zakharko, Yuriy; Zaumseil, Jana; Gather, Malte C.

2016-10-01

Exciton-polaritons form upon strong coupling between electronic excitations of a material and photonic states of a surrounding microcavity. In organic semiconductors the special nature of excited states leads to particularly strong coupling and facilitates condensation of exciton-polaritons at room temperature, which may lead to electrically pumped organic polariton lasers. However, charge carrier mobility and photo-stability in currently used materials is limited and exciton-polariton emission so far has been restricted to visible wavelengths. Here, we demonstrate strong light-matter coupling in the near infrared using single-walled carbon nanotubes (SWCNTs) in a polymer matrix and a planar metal-clad cavity. By exploiting the exceptional oscillator strength and sharp excitonic transition of (6,5) SWCNTs, we achieve large Rabi splitting (>110 meV), efficient polariton relaxation and narrow band emission (<15 meV). Given their high charge carrier mobility and excellent photostability, SWCNTs represent a promising new avenue towards practical exciton-polariton devices operating at telecommunication wavelengths.

Exciton-polaritons in cuprous oxide: Theory and comparison with experiment

Science.gov (United States)

Schweiner, Frank; Ertl, Jan; Main, Jörg; Wunner, Günter; Uihlein, Christoph

2017-12-01

The observation of giant Rydberg excitons in cuprous oxide (Cu2O ) up to a principal quantum number of n =25 by T. Kazimierczuk et al. [Nature (London) 514, 343 (2014), 10.1038/nature13832] inevitably raises the question whether these quasiparticles must be described within a multipolariton framework since excitons and photons are always coupled in the solid. In this paper we present the theory of exciton-polaritons in Cu2O . To this end we extend the Hamiltonian which includes the complete valence-band structure, the exchange interaction, and the central-cell corrections effects, and which has been recently deduced by F. Schweiner et al. [Phys. Rev. B 95, 195201 (2017), 10.1103/PhysRevB.95.195201], for finite values of the exciton momentum ℏ K . We derive formulas to calculate not only dipole but also quadrupole oscillator strengths when using the complete basis of F. Schweiner et al., which has recently been proven as a powerful tool to calculate exciton spectra. Very complex polariton spectra for the three orientations of K along the axes [001 ] , [110 ] , and [111 ] of high symmetry are obtained and a strong mixing of exciton states is reported. The main focus is on the 1 S ortho-exciton-polariton, for which pronounced polariton effects have been measured in experiments. We set up a 5 ×5 matrix model, which accounts for both the polariton effect and the K -dependent splitting, and which allows treating the anisotropic polariton dispersion for any direction of K . We especially discuss the dispersions for K being oriented in the planes perpendicular to [1 1 ¯0 ] and [111 ] , for which experimental transmission spectra have been measured. Furthermore, we compare our results with experimental values of the K -dependent splitting, the group velocity, and the oscillator strengths of this exciton-polariton. The results are in good agreement. This proves the validity of the 5 ×5 matrix model as a useful theoretical model for further investigations on the 1 S

Sustained propagation and control of topological excitations in polariton superfluid

Science.gov (United States)

Pigeon, Simon; Bramati, Alberto

2017-09-01

We present a simple method to compensate for losses in a polariton superfluid. Based on a weak support field, it allows for the extended propagation of a resonantly driven polariton superfluid with minimal energetic cost. Moreover, this setup is based on optical bistability and leads to the significant release of the phase constraint imposed by resonant driving. This release, together with macroscopic polariton propagation, offers a unique opportunity to study the hydrodynamics of the topological excitations of polariton superfluids such as quantized vortices and dark solitons. We numerically study how the coherent field supporting the superfluid flow interacts with the vortices and how it can be used to control them. Interestingly, we show that standard hydrodynamics does not apply for this driven-dissipative fluid and new types of behaviour are identified.

Spectra of magnetoplasma polaritons in a semiconductor layer on a metallic substrate

International Nuclear Information System (INIS)

Beletsekii, N.N.; Gasan, E.A.; Yakovenko, V.M.

1988-01-01

The dispersion properties of volume and surface magnetoplasma polaritons in a three-layer metal-semiconductor-insulator structure are studied. It is predicted that surface magnetoplasma polaritons propagating on the two boundaries of the semiconductor layer interact resonantly. It is shown that for a certain direction of propagation the dispersion curves of surface and volume magnetoplasma polaritons contain sections with negative dispersion. Nonreciprocal propagation of volume magnetoplasma polaritons has been observed. Losses in the semiconductor layer split the starting spectral lines into dispersion curves of two types, corresponding to forward and backward waves

Influence of multi-exciton correlations on nonlinear polariton dynamics in semiconductor microcavities

International Nuclear Information System (INIS)

Wen, P; Nelson, Keith A; Christmann, G; Baumberg, J J

2013-01-01

Using two-dimensional spectroscopy, we resolve multi-polariton coherences in quantum wells embedded inside a semiconductor microcavity and elucidate how multi-exciton correlations mediate polariton nonlinear dynamics. We find that polariton correlation strengths depend on spectral overlap with the biexciton resonance and that up to at least four polaritons can be correlated, a higher-order correlation than observed to date among excitons in bare quantum wells. The high-order correlations can be attributed to coupling through the cavity mode, although the role of high-order Coulomb correlations cannot be excluded. (paper)

Amplitude oscillations in a non-equilibrium polariton condensate

Science.gov (United States)

Brierley, Richard; Littlewood, Peter; Eastham, Paul

2011-03-01

Like cold atomic gases, semiconductor nanostructures provide new opportunities for exploring non-equilibrium quantum dynamics. In semiconductor microcavities the strong coupling between trapped photons and excitons produces new quasiparticles, polaritons, which can undergo Bose-Einstein condensation. Quantum quenches can be realised by rapidly creating cold exciton populations with a laser [Eastham and Phillips, PRB 79 165303 (2009)]. The mean field theory of non-equilibrium polariton condensates predicts oscillations in the condensate amplitude due to the excitation of a Higgs mode. These oscillations are the analogs of those predicted in quenched cold atomic gases and may occur in the polariton system after performing a quench or by direct excitation of the amplitude mode. We have studied the stability of these oscillations beyond mean field theory. We show that homogeneous amplitude oscillations are unstable to decay into lower energy phase modes at finite wavevectors, suggesting the onset of chaotic behaviour. The resulting hierarchy of decay processes can be understood by analogy to optical parametric oscillators in microcavities. Polariton systems thus provide an interesting opportunity to study the dynamics of Higgs-like modes in a solid state system.

Plasmon exciton-polariton lasing

NARCIS (Netherlands)

Ramezani, M.; Halpin, H.A.; Feist, J.; Fernández-Dominguez, A.; Rodriguez, S.R.K.; Garcia-Vidal, F.J.; Gomez-Rivas, J.

2017-01-01

Strong light-matter interaction leads to the appearance of new states, i.e. exciton-polaritons, with photophysical properties rather distinct from their constituents. Recent developments in fabrication techniques allow us to make metallic structures with strong electric field confinement in

Bloch oscillations of quasispin polaritons in a magneto-optically controlled atomic ensemble

International Nuclear Information System (INIS)

Jiang, Chang; Lu, Jing; Zhou, Lan

2012-01-01

We consider the propagation of quantized polarized light in a magneto-optically-manipulated atomic ensemble with a tripod configuration. A polariton formalism is applied when the medium is subjected to a washboard magnetic field under electromagnetically-induced transparency. The dark-state polariton with multiple components is achieved. We analyze the quantum dynamics of the dark-state polariton using experimental data from the rubidium D1-line. It is found that one component propagates freely, however the wave packet trajectory of the other component performs Bloch oscillations. -- Highlights: ► We study the wave–particle dualism of quasiparticles in a magneto-optical medium. ► We generate a “spin”-component dark-state polariton. ► Magnetic fields lead to oscillation and free propagation of a dark-state polariton. ► Our approach shows the role of entanglement of degrees of freedom of photons.

Bloch oscillations of quasispin polaritons in a magneto-optically controlled atomic ensemble

Energy Technology Data Exchange (ETDEWEB)

Jiang, Chang [Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, and Department of Physics, Hunan Normal University, Changsha 410081 (China); Lu, Jing, E-mail: lujing@hunnu.edu.cn [Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, and Department of Physics, Hunan Normal University, Changsha 410081 (China); Zhou, Lan [Key Laboratory of Low-Dimensional Quantum Structures and Quantum Control of Ministry of Education, and Department of Physics, Hunan Normal University, Changsha 410081 (China)

2012-10-01

We consider the propagation of quantized polarized light in a magneto-optically-manipulated atomic ensemble with a tripod configuration. A polariton formalism is applied when the medium is subjected to a washboard magnetic field under electromagnetically-induced transparency. The dark-state polariton with multiple components is achieved. We analyze the quantum dynamics of the dark-state polariton using experimental data from the rubidium D1-line. It is found that one component propagates freely, however the wave packet trajectory of the other component performs Bloch oscillations. -- Highlights: ► We study the wave–particle dualism of quasiparticles in a magneto-optical medium. ► We generate a “spin”-component dark-state polariton. ► Magnetic fields lead to oscillation and free propagation of a dark-state polariton. ► Our approach shows the role of entanglement of degrees of freedom of photons.

Terahertz optoelectronics with surface plasmon polariton diode.

Science.gov (United States)

Vinnakota, Raj K; Genov, Dentcho A

2014-05-09

The field of plasmonics has experience a renaissance in recent years by providing a large variety of new physical effects and applications. Surface plasmon polaritons, i.e. the collective electron oscillations at the interface of a metal/semiconductor and a dielectric, may bridge the gap between electronic and photonic devices, provided a fast switching mechanism is identified. Here, we demonstrate a surface plasmon-polariton diode (SPPD) an optoelectronic switch that can operate at exceedingly large signal modulation rates. The SPPD uses heavily doped p-n junction where surface plasmon polaritons propagate at the interface between n and p-type GaAs and can be switched by an external voltage. The devices can operate at transmission modulation higher than 98% and depending on the doping and applied voltage can achieve switching rates of up to 1 THz. The proposed switch is compatible with the current semiconductor fabrication techniques and could lead to nanoscale semiconductor-based optoelectronics.

Effect of interface disorder on quantum well excitons and microcavity polaritons

International Nuclear Information System (INIS)

Savona, Vincenzo

2007-01-01

The theory of the linear optical response of excitons in quantum wells and polaritons in planar semiconductor microcavities is reviewed, in the light of the existing experiments. For quantum well excitons, it is shown that disorder mainly affects the exciton centre-of-mass motion and is modelled by an effective Schroedinger equation in two dimensions. For polaritons, a unified model accounting for quantum well roughness and fluctuations of the microcavity thickness is developed. Numerical results confirm that polaritons are mostly affected by disorder acting on the photon component, thus confirming existing studies on the influence of exciton disorder. The polariton localization length is estimated to be in the few-micrometres range, depending on the amplitude of disorder, in agreement with recent experimental findings

Nonlinear dynamics of a coherent polariton-biexciton system

International Nuclear Information System (INIS)

Nguyen Trung Dan; Vo Tinh

1994-08-01

The nonlinear dynamics of a coherent interacting polariton-biexciton system in optically excited semiconductors is investigated. We consider the case when two macroscopically coherent modes - a lower branch polariton and a biexciton existing simultaneously in a direct-gap semiconductor. The conditions for exhibiting optical bistability in stationary regime are obtained. Numerical simulation for the nonlinear dynamics equations of the system is also carried out. (author). 16 refs, 4 figs

Plasmon polaritons in cubic lattices of spherical metallic nanoparticles

Science.gov (United States)

Lamowski, Simon; Mann, Charlie-Ray; Hellbach, Felicitas; Mariani, Eros; Weick, Guillaume; Pauly, Fabian

2018-03-01

We theoretically investigate plasmon polaritons in cubic lattices of spherical metallic nanoparticles. The nanoparticles, each supporting triply-degenerate localized surface plasmons, couple through the Coulomb dipole-dipole interaction, giving rise to collective plasmons that extend over the whole metamaterial. The latter hybridize with photons forming plasmon polaritons, which are the hybrid light-matter eigenmodes of the system. We derive general analytical expressions to evaluate both plasmon and plasmon-polariton dispersions and the corresponding eigenstates. These are obtained within a Hamiltonian formalism, which takes into account retardation effects in the dipolar interaction between the nanoparticles and considers the dielectric properties of the nanoparticles as well as their surrounding. Within this model we predict polaritonic splittings in the near-infrared to the visible range of the electromagnetic spectrum that depend on polarization, lattice symmetry, and wave-vector direction. Finally, we show that the predictions of our model are in excellent quantitative agreement with conventional finite-difference frequency-domain simulations, but with the advantages of analytical insight and significantly reduced computational cost.

Terahertz Magnon-Polaritons in TmFeO3.

Science.gov (United States)

Grishunin, Kirill; Huisman, Thomas; Li, Guanqiao; Mishina, Elena; Rasing, Theo; Kimel, Alexey V; Zhang, Kailing; Jin, Zuanming; Cao, Shixun; Ren, Wei; Ma, Guo-Hong; Mikhaylovskiy, Rostislav V

2018-04-18

Magnon-polaritons are shown to play a dominant role in the propagation of terahertz (THz) waves through TmFeO 3 orthoferrite, if the frequencies of the waves are in the vicinity of the quasi-antiferromagnetic spin resonance mode. Both time-domain THz transmission and emission spectroscopies reveal clear beatings between two modes with frequencies slightly above and slightly below this resonance, respectively. Rigorous modeling of the interaction between the spins of TmFeO 3 and the THz light shows that the frequencies correspond to the upper and lower magnon-polariton branches. Our findings reveal the previously ignored importance of propagation effects and polaritons in such heavily debated areas as THz magnonics and THz spectroscopy of electromagnons. It also shows that future progress in these areas calls for an interdisciplinary approach at the interface between magnetism and photonics.

Harmonics radiation of graphene surface plasmon polaritons in terahertz regime

Energy Technology Data Exchange (ETDEWEB)

Li, D., E-mail: dazhi_li@hotmail.com [Institute for Laser Technology, Suita, Osaka 565-0871 (Japan); Wang, Y. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Nakajima, M. [Institute of Laser Engineering, Osaka University, Suita, Osaka 565-0871 (Japan); Hashida, M. [Advanced Research Center for Beam Science, ICR, Kyoto University, Gokasho, Uji, Kyoto 611-0011 (Japan); Wei, Y. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China); Miyamoto, S. [Laboratory of Advanced Science and Technology for Industry, University of Hyogo, Ako, Hyogo 678-1205 (Japan)

2016-06-03

This letter presents an approach to extract terahertz radiation from surface plasmon polaritons excited in the surface of a uniform graphene structure by an electron beam. A sidewall configuration is proposed to lift the surface plasmon mode to be close to the light line, so that some of its harmonics have chances to go above the light line and become radiative. The harmonics are considered to be excited by a train of periodic electron bunches. The physical mechanism in this scheme is analyzed with three-dimensional theory, and the harmonics excitation and radiation are demonstrated through numerical calculations. The results show that this technique could be an alternative to transform the surface plasmon polaritons into radiation. - Highlights: • An approach to extract terahertz radiation from graphene surface plasmon polaritons is presented. • A sidewall configuration is proposed to lift the surface plasmon mode. • Harmonics of surface plasmon polaritons are possible to radiate.

Spontaneous and superfluid chiral edge states in exciton-polariton condensates

Science.gov (United States)

Sigurdsson, H.; Li, G.; Liew, T. C. H.

2017-09-01

We present a scheme of interaction-induced topological band structures based on the spin anisotropy of exciton-polaritons in semiconductor microcavities. We predict theoretically that this scheme allows the engineering of topological gaps, without requiring a magnetic field or strong spin-orbit interaction (transverse electric-transverse magnetic splitting). Under nonresonant pumping we find that an initially topologically trivial system undergoes a topological transition upon the spontaneous breaking of phase symmetry associated with polariton condensation. Under either nonresonant or resonant coherent pumping we find that it is also possible to engineer a topological dispersion that is linear in wave vector—a property associated with polariton superfluidity.

Numerical modelling of surface plasmonic polaritons

Science.gov (United States)

Mansoor, Riyadh; AL-Khursan, Amin Habbeb

2018-06-01

Extending optoelectronics into the nano-regime seems problematic due to the relatively long wavelengths of light. The conversion of light into plasmons is a possible way to overcome this problem. Plasmon's wavelengths are much shorter than that of light which enables the propagation of signals in small size components. In this paper, a 3D simulation of surface plasmon polariton (SPP) excitation is performed. The Finite integration technique was used to solve Maxwell's equations in the dielectric-metal interface. The results show how the surface plasmon polariton was generated at the grating assisted dielectric-metal interface. SPP is a good candidate for signal confinement in small size optoelectronics which allow high density optical integrated circuits in all optical networks.

On the equivalence of two approaches in the exciton-polariton theory

International Nuclear Information System (INIS)

Ha Vinh Tan; Nguyen Toan Thang

1983-02-01

The polariton effect in the optical processes involving photons with energies near that of an exciton is investigated by the Bogolubov diagonalization and the Green function approaches in a simple model of the direct band gap semiconductor with the electrical dipole allowed transition. To take into account the non-resonant terms of the interaction Hamiltonian of the photon-exciton system the Green function approach derived by Nguyen Van Hieu is presented with the use of Green's function matrix technique analogous to that suggested by Nambu in the theory of superconductivity. It is shown that with the suitable choice of the phase factors the renormalization constants are equal to the diagonalization coefficients. The disperson of polaritons and the matrix elements of processes with the participation of polaritons are identically calculated by both methods. However the Green function approach has an advantage in including the damping effect of polaritons. (author)

Numerical modeling of exciton-polariton Bose-Einstein condensate in a microcavity

Science.gov (United States)

Voronych, Oksana; Buraczewski, Adam; Matuszewski, Michał; Stobińska, Magdalena

2017-06-01

A novel, optimized numerical method of modeling of an exciton-polariton superfluid in a semiconductor microcavity was proposed. Exciton-polaritons are spin-carrying quasiparticles formed from photons strongly coupled to excitons. They possess unique properties, interesting from the point of view of fundamental research as well as numerous potential applications. However, their numerical modeling is challenging due to the structure of nonlinear differential equations describing their evolution. In this paper, we propose to solve the equations with a modified Runge-Kutta method of 4th order, further optimized for efficient computations. The algorithms were implemented in form of C++ programs fitted for parallel environments and utilizing vector instructions. The programs form the EPCGP suite which has been used for theoretical investigation of exciton-polaritons. Catalogue identifier: AFBQ_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AFBQ_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: BSD-3 No. of lines in distributed program, including test data, etc.: 2157 No. of bytes in distributed program, including test data, etc.: 498994 Distribution format: tar.gz Programming language: C++ with OpenMP extensions (main numerical program), Python (helper scripts). Computer: Modern PC (tested on AMD and Intel processors), HP BL2x220. Operating system: Unix/Linux and Windows. Has the code been vectorized or parallelized?: Yes (OpenMP) RAM: 200 MB for single run Classification: 7, 7.7. Nature of problem: An exciton-polariton superfluid is a novel, interesting physical system allowing investigation of high temperature Bose-Einstein condensation of exciton-polaritons-quasiparticles carrying spin. They have brought a lot of attention due to their unique properties and potential applications in polariton-based optoelectronic integrated circuits. This is an out-of-equilibrium quantum system confined

Hyperbolic phonon polaritons in hexagonal boron nitride (Conference Presentation)

Science.gov (United States)

Dai, Siyuan; Ma, Qiong; Fei, Zhe; Liu, Mengkun; Goldflam, Michael D.; Andersen, Trond; Garnett, William; Regan, Will; Wagner, Martin; McLeod, Alexander S.; Rodin, Alexandr; Zhu, Shou-En; Watanabe, Kenji; Taniguchi, T.; Dominguez, Gerado; Thiemens, Mark; Castro Neto, Antonio H.; Janssen, Guido C. A. M.; Zettl, Alex; Keilmann, Fritz; Jarillo-Herrero, Pablo; Fogler, Michael M.; Basov, Dmitri N.

2016-09-01

Uniaxial materials whose axial and tangential permittivities have opposite signs are referred to as indefinite or hyperbolic media. While hyperbolic responses are normally achieved with metamaterials, hexagonal boron nitride (hBN) naturally possesses this property due to the anisotropic phonons in the mid-infrared. Using scattering-type scanning near-field optical microscopy, we studied polaritonic phenomena in hBN. We performed infrared nano-imaging of highly confined and low-loss hyperbolic phonon polaritons in hBN. The polariton wavelength was shown to be governed by the hBN thickness according to a linear law persisting down to few atomic layers [1]. Additionally, we carried out the modification of hyperbolic response in meta-structures comprised of a mononlayer graphene deposited on hBN [2]. Electrostatic gating of the top graphene layer allows for the modification of wavelength and intensity of hyperbolic phonon polaritons in bulk hBN. The physics of the modification originates from the plasmon-phonon coupling in the hyperbolic medium. Furthermore, we demonstrated the "hyperlens" for subdiffractional focusing and imaging using a slab of hBN [3]. References [1] S. Dai et al., Science, 343, 1125 (2014). [2] S. Dai et al., Nature Nanotechnology, 10, 682 (2015). [3] S. Dai et al., Nature Communications, 6, 6963 (2015).

Dark and bright-state polaritons in triple- Λ EIT system

Science.gov (United States)

Selvan, Karthick

2018-04-01

Properties of polaritons in triple-Λ EIT system are investigated using Sawada-Brout-Chong method. The role of dark and bright-state polaritons in the dynamics of the system is studied in detail by including the decay of excited atomic levels. Time evolution of entanglement of single and three-photon EIT modes within the system is investigated to explain this study.

Optical orientation of the homogeneous nonequilibrium Bose-Einstein condensate of exciton polaritons

Science.gov (United States)

Korenev, V. L.

2012-07-01

A simple model, describing the steady state of the nonequilibrium polarization of a homogeneous Bose-Einstein condensate of exciton polaritons, is considered. It explains the suppression of spin splitting of a nonequilibrium polariton condensate in an external magnetic field, the linear polarization, the linear-to-circular polarization conversion, and the unexpected sign of the circular polarization of the condensate all on equal footing. It is shown that inverse effects are possible, to wit, spontaneous circular polarization and the enhancement of spin splitting of a nonequilibrium condensate of polaritons.

Seeding Dynamics of Nonlinear Polariton Emission from a Microcavity

DEFF Research Database (Denmark)

Østergaard, John Erland; Langbein, Wolfgang Werner; Jensen, Jacob Riis

2000-01-01

Summary form only given. The dynamics of polaritons in microcavity samples is presently under intense debate, in particular whether or not the so-called Boser action is possible. In this work, we investigate a λ cavity with a homogeneously broadened 25 nm GaAs quantum well at the antinode...... at a temperature of 10 K. We can thus inject well-defined polariton populations in k-space revealing how different initial and final state populations may influence the dynamics....

Plasmon-exciton polaritons in two-dimensional semiconductor/metal interfaces

Science.gov (United States)

Gonçalves, P. A. D.; Bertelsen, L. P.; Xiao, Sanshui; Mortensen, N. Asger

2018-01-01

The realization and control of polaritons is of paramount importance in the prospect of novel photonic devices. Here, we investigate the emergence of plasmon-exciton polaritons in hybrid structures consisting of a two-dimensional transition-metal dichalcogenide (TMDC) deposited onto a metal substrate or coating a metallic thin film. We determine the polaritonic spectrum and show that, in the former case, the addition of a top dielectric layer and, in the latter case, the thickness of the metal film can be used to tune and promote plasmon-exciton interactions well within the strong-coupling regime. Our results demonstrate that Rabi splittings exceeding 100 meV can readily be achieved in planar dielectric/TMDC/metal structures under ambient conditions. We thus believe that this Rapid Communication provides a simple and intuitive picture to tailor strong coupling in plexcitonics with potential applications for engineering compact photonic devices with tunable optical properties.

Imaging of surface plasmon polariton interference using phase-sensitive scanning tunneling microscope

NARCIS (Netherlands)

Jose, J.; Segerink, Franciscus B.; Korterik, Jeroen P.; Herek, Jennifer Lynn; Offerhaus, Herman L.

2011-01-01

We report the surface plasmon polariton interference, generated via a ‘buried’ gold grating, and imaged using a phase-sensitive Photon Scanning Tunneling Microscope (PSTM). The phase-resolved PSTM measurement unravels the complex surface plasmon polariton interference fields at the gold-air

Raman scattering by hot and thermal polaritons in crystal quartz

Energy Technology Data Exchange (ETDEWEB)

Bogani, F.; Colocci, M.; Neri, M.; Querzoli, R.

1984-11-01

Nonlinear mixing of IR and visible radiation, i.e. coherent Raman scattering by polaritons driven by a CO/sub 2/ laser, has been used to obtain the dispersion curve and its width in q-space of the polariton associated to the E-phonon at 1065 cm/sup -1/ in crystal quartz. It is shown in this paper that a direct method to determine independently, with high precision, the refractive index and absorbance of a crystal can be obtained in this way. The results are compared with accurate data obtained from Raman scattering by polaritions in thermal equilibrium and very good agreement is found between the two measurements. It is finally shown that nonlinear-mixing techniques turn out to be completely consistent with the simple picture of scattering of light by hot polaritons.

Sagnac interferometry with coherent vortex superposition states in exciton-polariton condensates

Science.gov (United States)

Moxley, Frederick Ira; Dowling, Jonathan P.; Dai, Weizhong; Byrnes, Tim

2016-05-01

We investigate prospects of using counter-rotating vortex superposition states in nonequilibrium exciton-polariton Bose-Einstein condensates for the purposes of Sagnac interferometry. We first investigate the stability of vortex-antivortex superposition states, and show that they survive at steady state in a variety of configurations. Counter-rotating vortex superpositions are of potential interest to gyroscope and seismometer applications for detecting rotations. Methods of improving the sensitivity are investigated by targeting high momentum states via metastable condensation, and the application of periodic lattices. The sensitivity of the polariton gyroscope is compared to its optical and atomic counterparts. Due to the large interferometer areas in optical systems and small de Broglie wavelengths for atomic BECs, the sensitivity per detected photon is found to be considerably less for the polariton gyroscope than with competing methods. However, polariton gyroscopes have an advantage over atomic BECs in a high signal-to-noise ratio, and have other practical advantages such as room-temperature operation, area independence, and robust design. We estimate that the final sensitivities including signal-to-noise aspects are competitive with existing methods.

Coherence properties of exciton-polariton OPO condensates in one and two dimensions

DEFF Research Database (Denmark)

Spano, R.; Cuadra, J.; Anton, C.

2012-01-01

We give an overview of the coherence properties of exciton-polariton condensates generated by optical parametric scattering. Different aspects of the first-order coherence (g((1))) have been investigated. The spatial coherence extension of a two-dimensional (2D) polariton system, below and at the...

Dynamics of defect-induced dark solitons in an exciton-polariton condensate

Science.gov (United States)

Opala, Andrzej; Pieczarka, Maciej; Bobrovska, Nataliya; Matuszewski, Michał

2018-04-01

We study theoretically the emission of dark solitons induced by a moving defect in a nonresonantly pumped exciton-polariton condensate. The number of created dark solitons per unit of time is found to be strongly dependent on the pump power. We relate the observed dynamics of this process to the oscillations of the drag force experienced by the condensate. We investigate the stability of the polariton quantum fluid and present various types of dynamics depending on the condensate and moving obstacle parameters. Furthermore, we provide analytical expressions for dark soliton dynamics using the variational method adapted to the nonequilibrium polariton system. The determined dynamical equations are found to be in excellent agreement with the results of numerical simulations.

Visualising Berry phase and diabolical points in a quantum exciton-polariton billiard.

Science.gov (United States)

Estrecho, E; Gao, T; Brodbeck, S; Kamp, M; Schneider, C; Höfling, S; Truscott, A G; Ostrovskaya, E A

2016-11-25

Diabolical points (spectral degeneracies) can naturally occur in spectra of two-dimensional quantum systems and classical wave resonators due to simple symmetries. Geometric Berry phase is associated with these spectral degeneracies. Here, we demonstrate a diabolical point and the corresponding Berry phase in the spectrum of hybrid light-matter quasiparticles-exciton-polaritons in semiconductor microcavities. It is well known that sufficiently strong optical pumping can drive exciton-polaritons to quantum degeneracy, whereby they form a macroscopically populated quantum coherent state similar to a Bose-Einstein condensate. By pumping a microcavity with a spatially structured light beam, we create a two-dimensional quantum billiard for the exciton-polariton condensate and demonstrate a diabolical point in the spectrum of the billiard eigenstates. The fully reconfigurable geometry of the potential walls controlled by the optical pump enables a striking experimental visualization of the Berry phase associated with the diabolical point. The Berry phase is observed and measured by direct imaging of the macroscopic exciton-polariton probability densities.

Plasmon-exciton polaritons in two-dimensional semiconductor/metal interfaces

DEFF Research Database (Denmark)

Gonçalves, P. A. D.; Bertelsen, L. P.; Xiao, Sanshui

2018-01-01

The realization and control of polaritons is of paramount importance in the prospect of novel photonic devices. Here, we investigate the emergence of plasmon-exciton polaritons in hybrid structures consisting of a two-dimensional transition-metal dichalcogenide (TMDC) deposited onto a metal......-coupling regime. Our results demonstrate that Rabi splittings exceeding 100 meV can readily be achieved in planar dielectric/TMDC/metal structures under ambient conditions. We thus believe that this Rapid Communication provides a simple and intuitive picture to tailor strong coupling in plexcitonics...

Switchable directional excitation surface plasmon polaritons with dielectric nanoantennas

DEFF Research Database (Denmark)

Sinev, I.; Komissarenko, F.; Bogdanov, A.

We demonstrate directional launching of surface plasmon polaritons on thin goldfilm with a single silicon nanosphere. The directivity pattern of the excited surface waves exhibits rapid switching from forward to backward excitation, which is driven by the mutual interference of magnetic and elect......We demonstrate directional launching of surface plasmon polaritons on thin goldfilm with a single silicon nanosphere. The directivity pattern of the excited surface waves exhibits rapid switching from forward to backward excitation, which is driven by the mutual interference of magnetic...

Optical orientation of the homogeneous non-equilibrium Bose-Einstein condensate of bright excitons (polaritons)

OpenAIRE

Korenev, V. L.

2011-01-01

A simple model, describing the dynamics of the non-equilibrium pseudospin of a homogeneous Bose-Einstein condensate of exciton polaritons, has been formulated. It explains the suppression of spin splitting of a non-equilibrium polariton condensate in an external magnetic field, the optical alignment, and the conversion of alignment into orientation of polaritons. It has been shown that inverse effects are possible, to wit, the spontaneous circular polarization and the enhancement of spin spli...

Microscopic description of exciton polaritons in direct two-band semiconductors

Science.gov (United States)

Nguyen, Van Trong; Mahler, Günter

1999-07-01

Based on a quantum electrodynamical formulation, a microscopic description of exciton polaritons in a two-band semiconductor is presented. We show that the interband exchange Coulomb interaction, responsible for the coupling of the exciton with the longitudinal part of the induced field, should be treated on equal footing together with the coupling to the transverse part of the induced field (the photon field). The constitutive relation is established to connect the current density with the total electric field of polaritons. The classical Maxwell equations are derived from the quantum representation of photons to get a closed system of equations. The temporal evolution for an initial excited exciton state is studied in detail and an anisotropic polariton vacuum Rabi splitting is shown to occur. A number of up-to-now unresolved discrepancies in the literature are clarified.

Terahertz surface plasmon polariton waveguiding with periodic metallic cylinders

KAUST Repository

Zhang, Ying; Li, Shaoxian; Xu, Quan; Tian, Chunxiu; Gu, Jianqiang; Li, Yanfeng; Tian, Zhen; Ouyang, Chunmei; Han, Jiaguang; Zhang, Weili

2017-01-01

We demonstrated a structure with periodic cylinders arranged bilaterally and a thin dielectric layer covered inside that supports bound modes of surface plasmon polaritons at terahertz frequencies. This structure can confine the surface plasmon polaritons in the lateral direction, and at the same time reduce the field expansion into space. We examined and explored the characteristics of several different structures using scanning near-field terahertz microscopy. The proposed designs pave a novel way to terahertz waveguiding and may have important applications in the development of flexible, wideband and compact photonic circuits operating at terahertz frequencies.

Terahertz surface plasmon polariton waveguiding with periodic metallic cylinders

KAUST Repository

Zhang, Ying

2017-06-15

We demonstrated a structure with periodic cylinders arranged bilaterally and a thin dielectric layer covered inside that supports bound modes of surface plasmon polaritons at terahertz frequencies. This structure can confine the surface plasmon polaritons in the lateral direction, and at the same time reduce the field expansion into space. We examined and explored the characteristics of several different structures using scanning near-field terahertz microscopy. The proposed designs pave a novel way to terahertz waveguiding and may have important applications in the development of flexible, wideband and compact photonic circuits operating at terahertz frequencies.

Optical bistability and multistability in polaritonic materials doped with nanoparticles

International Nuclear Information System (INIS)

Wang, Zhiping; Yu, Benli

2014-01-01

We investigate the optical bistability and multistability in polaritonic materials doped with nanoparticles inside an optical ring cavity. It is found that the optical bistability and multistability can be easily controlled by adjusting the corresponding parameters of the system properly. The effect of the dipole–dipole interaction has also been included in the formulation, which leads to interesting phenomena. Our scheme opens up the possibility of controling the optical bistability and multistability in polaritonic materials doped with nanoparticles. (letter)

Polariton condensation phase diagram in wide-band-gap planar microcavities: GaN versus ZnO

Science.gov (United States)

Jamadi, O.; Réveret, F.; Mallet, E.; Disseix, P.; Médard, F.; Mihailovic, M.; Solnyshkov, D.; Malpuech, G.; Leymarie, J.; Lafosse, X.; Bouchoule, S.; Li, F.; Leroux, M.; Semond, F.; Zuniga-Perez, J.

2016-03-01

The polariton condensation phase diagram is compared in GaN and ZnO microcavities grown on mesa-patterned silicon substrate. Owing to a common platform, these microcavities share similar photonic properties with large quality factors and low photonic disorder, which makes it possible to determine the optimal spot diameter and to realize a thorough phase diagram study. Both systems have been investigated under the same experimental conditions. The experimental results and the subsequent analysis reveal clearly that longitudinal optical phonons have no influence in the thermodynamic region of the condensation phase diagram, while they allow a strong (slight) decrease of the polariton lasing threshold in the trade-off zone (kinetic region). Phase diagrams are compared with numerical simulations using Boltzmann equations, and are in satisfactory agreement. A lower polariton lasing threshold has been measured at low temperature in the ZnO microcavity, as is expected due to a larger Rabi splitting. This study highlights polariton relaxation mechanisms and their importance in polariton lasing.

Bistability and self-oscillations effects in a polariton-laser semiconductor microcavity

International Nuclear Information System (INIS)

Cotta, E A; Matinaga, F M

2007-01-01

We report an experimental observation of polaritonic optical bistability of the laser emission in a planar semiconductor microcavity with a 100 0 A GaAs single quantum well in the strong-coupling regime. The bistability curves show crossings that indicate a competition between a Kerr-like effect induced by the polariton population and thermal effects. Associated with the bistability, laser-like emission occurs at the bare cavity mode

Fermi-edge exciton-polaritons in doped semiconductor microcavities with finite hole mass

Science.gov (United States)

Pimenov, Dimitri; von Delft, Jan; Glazman, Leonid; Goldstein, Moshe

2017-10-01

The coupling between a 2D semiconductor quantum well and an optical cavity gives rise to combined light-matter excitations, the exciton-polaritons. These were usually measured when the conduction band is empty, making the single polariton physics a simple single-body problem. The situation is dramatically different in the presence of a finite conduction-band population, where the creation or annihilation of a single exciton involves a many-body shakeup of the Fermi sea. Recent experiments in this regime revealed a strong modification of the exciton-polariton spectrum. Previous theoretical studies concerned with nonzero Fermi energy mostly relied on the approximation of an immobile valence-band hole with infinite mass, which is appropriate for low-mobility samples only; for high-mobility samples, one needs to consider a mobile hole with large but finite mass. To bridge this gap, we present an analytical diagrammatic approach and tackle a model with short-ranged (screened) electron-hole interaction, studying it in two complementary regimes. We find that the finite hole mass has opposite effects on the exciton-polariton spectra in the two regimes: in the first, where the Fermi energy is much smaller than the exciton binding energy, excitonic features are enhanced by the finite mass. In the second regime, where the Fermi energy is much larger than the exciton binding energy, finite mass effects cut off the excitonic features in the polariton spectra, in qualitative agreement with recent experiments.

Detuning-Controlled Internal Oscillations in an Exciton-Polariton Condensate

Science.gov (United States)

Voronova, N. S.; Elistratov, A. A.; Lozovik, Yu. E.

2015-10-01

We theoretically analyze exciton-photon oscillatory dynamics within a homogenous polariton gas in the presence of energy detuning between the cavity and quantum well modes. Whereas pure Rabi oscillations consist of the particle exchange between the photon and exciton states in the polariton system without any oscillations of the phases of the two subcondensates, we demonstrate that any nonzero detuning results in oscillations of the relative phase of the photon and exciton macroscopic wave functions. Different initial conditions reveal a variety of behaviors of the relative phase between the two condensates, and a crossover from Rabi-like to Josephson-like oscillations is predicted.

Engineering absorption and blackbody radiation in the far-infrared with surface phonon polaritons on gallium phosphide

Energy Technology Data Exchange (ETDEWEB)

Streyer, W.; Law, S.; Rosenberg, A.; Wasserman, D. [Department of Electrical and Computer Engineering, University of Illinois Urbana Champaign, Urbana, Illinois 61801 (United States); Roberts, C.; Podolskiy, V. A. [Department of Physics and Applied Physics, University of Massachusetts Lowell, Lowell, Massachusetts 01854 (United States); Hoffman, A. J. [Department of Electrical Engineering, University of Notre Dame, South Bend, Indiana 46556 (United States)

2014-03-31

We demonstrate excitation of surface phonon polaritons on patterned gallium phosphide surfaces. Control over the light-polariton coupling frequencies is demonstrated by changing the pattern periodicity and used to experimentally determine the gallium phosphide surface phonon polariton dispersion curve. Selective emission via out-coupling of thermally excited surface phonon polaritons is experimentally demonstrated. Samples are characterized experimentally by Fourier transform infrared reflection and emission spectroscopy, and modeled using finite element techniques and rigorous coupled wave analysis. The use of phonon resonances for control of emissivity and excitation of bound surface waves offers a potential tool for the exploration of long-wavelength Reststrahlen band frequencies.

Excitation of fluorescent nanoparticles by channel plasmon polaritons propagating in V-grooves

DEFF Research Database (Denmark)

Cuesta, Irene Fernandez; Nielsen, Rasmus Bundgaard; Boltasseva, Alexandra

2009-01-01

Recently, it has been proven that light can be squeezed into metallic channels with subwavelength lateral dimensions. Here, we present the study of the propagation of channel plasmon polaritons confined in gold V-grooves, filled with fluorescent particles. In this way, channel plasmon polaritons......-diameter beads, we show the possibility of individual excitation, what may have applications to develop very sensitive biosensors....

A tunable dual-wavelength pump source based on simulated polariton scattering for terahertz-wave generation

International Nuclear Information System (INIS)

Sun, Bo; Liu, Jinsong; Yao, Jianquan; Li, Enbang

2013-01-01

We propose a dual-wavelength pump source by utilizing stimulated polariton scattering in a LiNbO 3 crystal. The residual pump and the generated tunable Stokes waves can be combined to generate THz-wave generation via difference frequency generation (DFG). With a pump energy of 49 mJ, Stokes waves with a tuning range from 1067.8 to 1074 nm have been generated, and an output energy of up to 14.9 mJ at 1070 nm has been achieved with a conversion efficiency of 21.7%. A sum frequency generation experiment was carried out to demonstrate the feasibility of the proposed scheme for THz-wave DFG. (paper)

Phase Transitions of the Polariton Condensate in 2D Dirac Materials.

Science.gov (United States)

Lee, Ki Hoon; Lee, Changhee; Min, Hongki; Chung, Suk Bum

2018-04-13

For the quantum well in an optical microcavity, the interplay of the Coulomb interaction and the electron-photon (e-ph) coupling can lead to the hybridizations of the exciton and the cavity photon known as polaritons, which can form the Bose-Einstein condensate above a threshold density. Additional physics due to the nontrivial Berry phase comes into play when the quantum well consists of the gapped two-dimensional Dirac material such as the transition metal dichalcogenide MoS_{2} or WSe_{2}. Specifically, in forming the polariton, the e-ph coupling from the optical selection rule due to the Berry phase can compete against the Coulomb electron-electron (e-e) interaction. We find that this competition gives rise to a rich phase diagram for the polariton condensate involving both topological and symmetry breaking phase transitions, with the former giving rise to the quantum anomalous Hall and the quantum spin Hall phases.

Phase Transitions of the Polariton Condensate in 2D Dirac Materials

Science.gov (United States)

Lee, Ki Hoon; Lee, Changhee; Min, Hongki; Chung, Suk Bum

2018-04-01

For the quantum well in an optical microcavity, the interplay of the Coulomb interaction and the electron-photon (e -ph) coupling can lead to the hybridizations of the exciton and the cavity photon known as polaritons, which can form the Bose-Einstein condensate above a threshold density. Additional physics due to the nontrivial Berry phase comes into play when the quantum well consists of the gapped two-dimensional Dirac material such as the transition metal dichalcogenide MoS2 or WSe2 . Specifically, in forming the polariton, the e -ph coupling from the optical selection rule due to the Berry phase can compete against the Coulomb electron-electron (e -e ) interaction. We find that this competition gives rise to a rich phase diagram for the polariton condensate involving both topological and symmetry breaking phase transitions, with the former giving rise to the quantum anomalous Hall and the quantum spin Hall phases.

Two-photon transitions to exciton polaritons

International Nuclear Information System (INIS)

Hassan, A.R.

1979-08-01

A semiclassical theory for the creation of excitonic polariton states by two-photon absorption, via an intermediate exciton state, is given. A band model has been introduced which gives the dominant contribution to this process. A numerical calculation is found to be in good agreement with a recent observation in CuCl. (author)

Near-field investigation of surface plasmon polaritons

NARCIS (Netherlands)

Jose, J.

2010-01-01

The interaction of light with metals contains a resonant phenomenon called the Surface Plasmon Resonance (SPR), at which the free electrons in the metal collectively oscillate. This collective oscillation of the free electrons, called Surface Plasmon Polaritons (SPPs), is highly sensitive to the

Temperature-dependent polarized luminescence of exciton polaritons in a ZnO film

Energy Technology Data Exchange (ETDEWEB)

Toropov, A.A.; Nekrutkina, O.V.; Shubina, T.V. [Ioffe Physico-Technical Institute, Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation); Gruber, Th.; Kirchner, C. [Department of Semiconductor Physics, Ulm University, 89081 Ulm (Germany); Waag, A. [Institute of Semiconductor Technology, Braunschweig Technical University, 38106 Braunschweig (Germany); Karlsson, K.F.; Monemar, B. [Linkoeping University, 581 83 Linkoeping (Sweden)

2005-02-01

We report on the studies of linearly polarized photoluminescence (PL) in a (0001) oriented ZnO epitaxial film, grown by metal organic chemical vapor deposition on a GaN template. The emission of mixed longitudinal-transverse exciton polariton modes was observed up to 130 K that evidences polaritonic nature of the excitonic spectrum up to this elevated temperature. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Dielectric-loaded surface plasmon-polariton nanowaveguides fabricated by two-photon polymerization

Energy Technology Data Exchange (ETDEWEB)

Luo, Hao; Li, Yan; Cui, Hai-Bo; Yang, Hong; Gong, Qi-Huang [Peking University, State Key Laboratory for Mesoscopic Physics and Department of Physics, Beijing (China)

2009-11-15

The design, fabrication, and characterization of dielectric-loaded surface plasmon-polariton nanowave-guides on a gold film are presented. The nanostructures are produced by two-photon polymerization with femtosecond laser pulses, and the minimum ridge height is {proportional_to}170 nm. Leakage radiation microscopy shows that these surface plasmon-polariton waveguides are single mode with strong mode confinement at the wavelength of 830 nm. The experimental results are in good agreement with the simulation by the effective-index method. (orig.)

Diversiform hybrid-polarization surface plasmon polaritons in a dielectric–metal metamaterial

Directory of Open Access Journals (Sweden)

Q. Zhang

2017-04-01

Full Text Available Hybrid-polarization surface plasmon polaritons (HSPPs at the interface between an isotropic medium and a one-dimensional metal–dielectric metamaterial (MM were discussed, where the metal-layer permittivity was described with the improved Drude model. From the obtained dispersion equations, we predicated five types of HSPPs. One type is the Dyakonov-like surface polariton and another type is the tradition-like surface polarton. The others are new types of HSPPs. We establish a numerical simulation method of the attenuated total reflection (ATR measurement to examine these HSPPs. The results from the ATR spectra are consistent with those from the dispersion equations and indicate the different polarization features of these HSPPs. The numerical results also demonstrate that the observation of each type of HSPPs requires different conditions dictated by the material parameters and the polarization direction of incident light used in the ATR spectra. These results may further widen the space of potential applications of surface plasmon polaritons.

Quantum-well exciton polariton emission from multi-quantum-well wire structures

Science.gov (United States)

Kohl, M.; Heitmann, D.; Grambow, P.; Ploog, K.

The radiative decay of quantum-well exciton (QWE) polaritons in microstructured Al0.3Ga0.7As - GaAs multi-quantum wells (MQW) has been studied by photoluminescence spectroscopy. Periodic wire structures with lateral periodicities a = 250-500 nm and lateral widths t = 100-200 nm have been fabricated by plasma etching. The thickness of the QWs was 13 nm. In the QW wire samples the free-exciton photoluminescence was strongly reduced and the QWE polariton emission was observed as a maximum peaked at a 3 meV higher energy than the free QWE transition. In samples which had only a microstructured cladding layer, the free-exciton photoluminescence was dominant in the spectrum and the QWE polariton emission was observed as a shoulder on the high-energy side of the free QWE transition. In addition, two transitions at the low energy side of the free QWE photoluminescence were present in the microstructured samples, which were related to etching induced states.

Strong nonreciprocity of phonon polaritons of an insulator at its boundary with an ideal metal or superconductor in a magnetic field

International Nuclear Information System (INIS)

Chupis, I.E.; Mamaluy, D.A.

2000-01-01

Surface phonon polaritons in a semi-infinite insulator in a constant magnetic field at the boundary with an ideal metal or a superconductor have been considered. These phonon polaritons are induced by dynamic magnetoelectric interaction, which exists in the presence of a magnetic field. The modes of these surface polaritons appreciably differ in opposite directions of the magnetic field or the propagation of the wave. As a result, polaritons of a given optical or infrared frequency propagate only in one direction with respect to the magnetic field, which is the effect of rectification of surface electromagnetic waves. The inversion of the magnetic field results in 'switching on' or 'switching off' of surface polaritons. The existence of radiant surface polariton modes is predicted. (author)

Effect of exciton polaritons of absorption edge of GaTe

International Nuclear Information System (INIS)

Kurbatov, L.N.; Dirochka, A.I.; Sosin, V.A.

1979-01-01

The experimental results, pointing to the dependence of spectral and integral coefficients of exciton absorption as well as to the exciton relaxation parameter γsub(0) over the exciton zone on the sample thickness, are presented. It is tried to explain the inverse dependences of absorption intensity in the maximum of αsub(max) and γsub(0) exciton line within the limits of polariton theory. The values of polariton free path length in GaTe at various temperatures, as well as the volume γsub(vol.) and surface γsub(surf.) parameters of exciton relaxation over the exciton zone are discussed

Surface plasmon polariton amplification in semiconductor-graphene-dielectric structure

Energy Technology Data Exchange (ETDEWEB)

Dadoenkova, Yuliya S. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Novgorod State University, Veliky Novgorod (Russian Federation); Donetsk Institute for Physics and Technology, Donetsk (Ukraine); Moiseev, Sergey G. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Kotelnikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences, Ulyanovsk (Russian Federation); Abramov, Aleksei S. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Kadochkin, Aleksei S.; Zolotovskii, Igor O. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Institute of Nanotechnologies of Microelectronics of the Russian Academy of Sciences, 32A Leninskiy Prosp., 119991, Moscow (Russian Federation); Fotiadi, Andrei A. [Ulyanovsk State University, Ulyanovsk (Russian Federation); Universite de Mons (Belgium)

2017-05-15

A mechanism of amplification of surface plasmon polaritons due to the transfer of electromagnetic energy from a drift current wave into a far-infrared surface wave propagating along a semiconductor-dielectric boundary in waveguide geometry is proposed. A necessary condition of the interaction of these waves is phase matching condition, i. e., when the phase velocity of the surface wave approaches the drift velocity of charge carriers. It is shown that in the spectral region of the surface plasmon polariton slowing-down its amplification coefficient can reach values substantially exceeding the ohmic loss coefficient of the surface wave in the structure. (copyright 2017 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Surface Plasmon Polaritons Probed with Cold Atoms

DEFF Research Database (Denmark)

Kawalec, Tomasz; Sierant, Aleksandra; Panas, Roman

2017-01-01

We report on an optical mirror for cold rubidium atoms based on a repulsive dipole potential created by means of a modified recordable digital versatile disc. Using the mirror, we have determined the absolute value of the surface plasmon polariton (SPP) intensity, reaching 90 times the intensity...

Surface plasmon—polaritons on ultrathin metal films

International Nuclear Information System (INIS)

Quan Jun; Zhang Jun; Shao Le-Xi; Tian Ying

2011-01-01

We discuss the surface plasmon—polaritons used for ultrathin metal films with the aid of linear response theory and make comparisons with the known result given by Economou E N. In this paper we consider transverse electromagnetic fields and assume that the electromagnetic field in the linear response formula is the induced field due to the current of the electrons. It satisfies the Maxwell equation and thus we replace the current (charge) term in the Maxwell equation with the linear response expectation value. Finally, taking the external field to be zero, we obtain the dispersion relation of the surface plasmons from the eigenvalue equation. In addition, the charge-density and current-density in the z direction on the surface of ultrathin metal films are also calculated. The results may be helpful to the fundamental understanding of the complex phenomenon of surface plasmon-polaritons. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Relaxation dynamics and coherent energy exchange in coupled vibration-cavity polaritons (Conference Presentation)

Science.gov (United States)

Simpkins, Blake S.; Fears, Kenan P.; Dressick, Walter J.; Dunkelberger, Adam D.; Spann, Bryan T.; Owrutsky, Jeffrey C.

2016-09-01

Coherent coupling between an optical transition and confined optical mode have been investigated for electronic-state transitions, however, only very recently have vibrational transitions been considered. Here, we demonstrate both static and dynamic results for vibrational bands strongly coupled to optical cavities. We experimentally and numerically describe strong coupling between a Fabry-Pérot cavity and carbonyl stretch ( 1730 cm 1) in poly-methylmethacrylate and provide evidence that the mixed-states are immune to inhomogeneous broadening. We investigate strong and weak coupling regimes through examination of cavities loaded with varying concentrations of a urethane monomer. Rabi splittings are in excellent agreement with an analytical description using no fitting parameters. Ultrafast pump-probe measurements reveal transient absorption signals over a frequency range well-separated from the vibrational band, as well as drastically modified relaxation rates. We speculate these modified kinetics are a consequence of the energy proximity between the vibration-cavity polariton modes and excited state transitions and that polaritons offer an alternative relaxation path for vibrational excitations. Varying the polariton energies by angle-tuning yields transient results consistent with this hypothesis. Furthermore, Rabi oscillations, or quantum beats, are observed at early times and we see evidence that these coherent vibration-cavity polariton excitations impact excited state population through cavity losses. Together, these results indicate that cavity coupling may be used to influence both excitation and relaxation rates of vibrations. Opening the field of polaritonic coupling to vibrational species promises to be a rich arena amenable to a wide variety of infrared-active bonds that can be studied in steady state and dynamically.

Terahertz instability of surface optical-phonon polaritons that interact with surface plasmon polaritons in the presence of electron drift

International Nuclear Information System (INIS)

Sydoruk, O.; Solymar, L.; Shamonina, E.; Kalinin, V.

2010-01-01

Traveling-wave interaction between optical phonons and electrons drifting in diatomic semiconductors has potential for amplification and generation of terahertz radiation. Existing models of this interaction were developed for infinite materials. As a more practically relevant configuration, we studied theoretically a finite semiconductor slab surrounded by a dielectric. This paper analyzes the optical-phonon instability in the slab including the Lorentz force and compares it to the instability in an infinite material. As the analysis shows, the slab instability occurs because of the interaction of surface optical-phonon polaritons with surface plasmon polaritons in the presence of electron drift. The properties of the instability depend on the slab thickness when the thickness is comparable to the wavelength. For large slab thicknesses, however, the dispersion relation of the slab is similar to that of an infinite material, although the coupling is weaker. The results could be used for the design of practical terahertz traveling-wave oscillators and amplifiers.

Polariton solitons and nonlinear localized states in a one-dimensional semiconductor microcavity

Science.gov (United States)

Chen, Ting-Wei; Cheng, Szu-Cheng

2018-01-01

This paper presents numerical studies of cavity polariton solitons (CPSs) in a resonantly pumped semiconductor microcavity with an imbedded spatial defect. In the bistable regime of the well-known homogeneous polariton condensate, with proper incident wave vector and pump strength, bright and/or dark cavity solitons can be found in the presence of a spatially confined potential. The minimum pump strength required to observe the CPSs or nonlinear localized states in this parametric pump scheme is therefore reported.

Thermal conductance of a surface phonon-polariton crystal made up of polar nanorods

Energy Technology Data Exchange (ETDEWEB)

Ordonez-Miranda, Jose; Joulain, Karl; Ezzahri, Younes [Univ. de Poitiers, Futuroscope Chasseneuil (France). Inst. Pprime, CNRS

2017-05-01

We demonstrate that the energy transport of surface phonon-polaritons can be large enough to be observable in a crystal made up of a three-dimensional assembly of nanorods of silicon carbide. The ultralow phonon thermal conductivity of this nanostructure along with its high surface area-to-volume ratio allows the predominance of the polariton energy over that generated by phonons. The dispersion relation, propagation length, and thermal conductance of polaritons are numerically determined as functions of the radius and temperature of the nanorods. It is shown that the thermal conductance of a crystal with nanorods at 500 K and diameter (length) of 200 nm (20 μm) is 0.55 nW.K{sup -1}, which is comparable to the quantum of thermal conductance of polar nanowires.

Physics of quantum fluids new trends and hot topics in atomic and polariton condensates

CERN Document Server

Modugno, Michele

2013-01-01

The study of quantum fluids, stimulated by the discovery of superfluidity in liquid helium, has experienced renewed interest after the observation of Bose-Einstein condensation (BEC) in ultra-cold atomic gases and the observation a new type of quantum fluid with specific characteristics derived from its intrinsic out-of-equilibrium nature. The main objective of this book is to take a snapshot of the state-of-the-art of this fast moving field with a special emphasis on the hot topics and new trends. Bringing together the most active specialists of the two areas (atomic and polaritonic quantum fluids), we expect that this book will facilitate the exchange and the collaboration between these two communities working on subjects with very strong analogies.

Interaction of the Bragg gap with polaritonic gap in opal photonic crystals

Science.gov (United States)

Nayer, Eradat; Sivachenko, Andrey Yu; Li, Sergey; Raikh, Mikhail E.; Valy Vardeny, Z.

2001-03-01

Photonic crystals (PC) are a class of artificial structures with a periodic dielectric function. PCs can be a laboratory for testing fundamental processes involving interactions of radiation with matter in novel conditions. We have studied the optical properties of opal PCs that are infiltrated with highly polarizable media such as j-aggregates of cyanine dyes. Opals are self- assembled structures of silica (SiO_2) spheres. We report our studies on clarifying the relationship between a polaritonic gap and a photonic stop band (Bragg gap) when they resonantly coexist in the same structure. Infiltration of opal with polarizable molecules combines the polaritonic and Bragg diffractive effects. Both effects exist independently when the Bragg (at ω=ω_B) and polaritonic (at ω=ω_T) resonances are well separated in frequency. A completely different situation occurs when ωT =ω_B. Such a condition was achieved in opals that were infiltrated with J-aggregates of cyanine dyes that have large Rabi frequency. Our measurements show some dramatic changes in the shape of the reflectivity plateaus, which are due to the interplay between the photonic band gap and the polaritonic gap. The experimental results on reflectivity and its dependence on the light propagation angle and concentration of the cyanie dyes are in agreement with the theoretical calculations. (The work was supported in part by Army Research office DAAD19-00-1-0406.)

Subwavelength light confinement with surface plasmon polaritons

NARCIS (Netherlands)

Verhagen, E.

2009-01-01

In free space, the diffraction limit sets a lower bound to the size to which light can be confined. Surface plasmon polaritons (SPPs), which are electromagnetic waves bound to the interface between a metal and a dielectric, allow the control of light on subwavelength length scales. This opens up a

Spoof surface plasmon polaritons based notch filter for ultra-wideband microwave waveguide

DEFF Research Database (Denmark)

Xiao, Binggang; Li, Sheng-Hua; Xiao, Sanshui

2016-01-01

Spoof surface plasmon polaritons based notch filter for ultra-wideband microwave waveguide is proposed. Owing to subwavelength confinement, such a filter has advantage in the structure size without sacrificing the performance. The spoof SPP based notch is introduced to suppress the WLAN and satel......Spoof surface plasmon polaritons based notch filter for ultra-wideband microwave waveguide is proposed. Owing to subwavelength confinement, such a filter has advantage in the structure size without sacrificing the performance. The spoof SPP based notch is introduced to suppress the WLAN...

BCS-BEC crossover in a system of microcavity polaritons

International Nuclear Information System (INIS)

Keeling, Jonathan; Eastham, P.R.; Szymanska, M.H.; Littlewood, P.B.

2005-01-01

We investigate the thermodynamics and signatures of a polariton condensate over a range of densities, using a model of microcavity polaritons with internal structure. We determine a phase diagram for this system including fluctuation corrections to the mean-field theory. At low densities the condensation temperature T c behaves like that for point bosons. At higher densities, when T c approaches the Rabi splitting, T c deviates from the form for point bosons, and instead approaches the result of a BCS-like mean-field theory. This crossover occurs at densities much less than the Mott density. We show that current experiments are in a density range where the phase boundary is described by the BCS-like mean-field boundary. We investigate the influence of inhomogeneous broadening and detuning of excitons on the phase diagram

Refracting surface plasmon polaritons with nanoparticle arrays

DEFF Research Database (Denmark)

Radko, I.P.; Evlyukhin, A.B.; Boltasseva, Alexandra

2008-01-01

Refraction of surface plasmon polaritons (SPPs) by various structures formed by a 100-nm-period square lattice of gold nanoparticles on top of a gold film is studied by leakage radiation microscopy. SPP refraction by a triangular-shaped nanoparticle array indicates that the SPP effective refractive...... to design nanoparticle arrays for specific applications requiring in-plane SPP manipulation....

Temperature dependence of the coherence in polariton condensates

Science.gov (United States)

Rozas, E.; Martín, M. D.; Tejedor, C.; Viña, L.; Deligeorgis, G.; Hatzopoulos, Z.; Savvidis, P. G.

2018-02-01

We present a time-resolved experimental study of the temperature effect on the coherence of traveling polariton condensates. The simultaneous detection of their emission both in real and reciprocal space allows us to fully monitor the condensates' dynamics. We obtain fringes in reciprocal space as a result of the interference between polariton wave packets (WPs) traveling with the same speed. The periodicity of these fringes is inversely proportional to the spatial distance between the interfering WPs. In a similar fashion, we obtain interference fringes in real space when WPs traveling in opposite directions meet. The visibility of both real- and reciprocal-space interference fringes rapidly decreases with increasing temperature and vanishes. A theoretical description of the phase transition, considering the coexistence of condensed and noncondensed particles, for an out-of-equilibrium condensate such as ours is still missing, yet a comparison with theories developed for atomic condensates allows us to infer a critical temperature for the BEC-like transition when the visibility goes to zero.

The dispersion of the polariton frequencies in orthorhombic KNbO3

International Nuclear Information System (INIS)

Claus, R.; Winter, F.X.

1975-01-01

The dispersion of the polariton frequencies in all of the three main planes of an orthorhombic crystal has been studied at the example KNbO 3 for the first time. In this case pure transverse polar modes of the species A 1 , B 1 and B 2 occur. The investigations have been carried out with Raman scattering. The experimental data have been compared with dispersion curves, which have been calculated numerically on the basis of the general theory of polaritons. In each one of the main planes the pure transverse modes of one symmetry species are independent from the direction as predicted. (orig.) [de

Bragg polaritons in a ZnSe-based unfolded microcavity at elevated temperatures

Energy Technology Data Exchange (ETDEWEB)

Sebald, K.; Rahman, SK. S.; Cornelius, M.; Kaya, T.; Gutowski, J. [Semiconductor Optics, Institute of Solid State Physics, University of Bremen, 28334 Bremen (Germany); Klein, T.; Gust, A.; Hommel, D. [Semiconductor Epitaxy, Institute of Solid State Physics, University of Bremen, 28334 Bremen (Germany); Klembt, S. [Institut Néel, Université Grenoble Alpes and CNRS, B.P. 166, 38042 Grenoble (France)

2016-03-21

In this contribution, we present strong coupling of ZnSe quantum well excitons to Bragg modes resulting in the formation of Bragg polariton eigenstates, characterized by a small effective mass in comparison to a conventional microcavity. We observe an anticrossing of the excitonic and the photonic component in our sample being a clear signature for the strong-coupling regime. The anticrossing is investigated by changing the detuning between the excitonic components and the Bragg mode. We find anticrossings between the first Bragg mode and the heavy- as well as light-hole exciton, respectively, resulting in three polariton branches. The observed Bragg-polariton branches are in good agreement with theoretical calculations. The strong indication for the existence of strong coupling is traceable up to a temperature of 200 K, with a Rabi-splitting energy of 24 meV and 13 meV for the Bragg mode with the heavy- and light-hole exciton, respectively. These findings demonstrate the advantages of this sample configuration for ZnSe-based devices for the strong coupling regime.

Dispersion of strongly confined channel plasmon polariton modes

DEFF Research Database (Denmark)

Zenin, Vladimir; Volkov, Valentyn S.; Han, Zhanghua

2011-01-01

We report on experimental (by use of scanning near-field optical microscopy) and theoretical investigations of strongly confined (∼λ/5) channel plasmon polariton (CPP) modes propagating at telecom wavelengths (1425–1630 nm) along V-grooves cut in a gold film. The main CPP characteristics (mode in...

Light modulators and deflectors based on polariton effects

DEFF Research Database (Denmark)

Skettrup, Torben

1981-01-01

, the polariton, and hence the photon part, can be deflected or modulated. The connection with geometrical optics is established, and it is shown that the deflection is due to a gradient in the refraction index created by the applied external field. Several examples with electric, magnetic, and stress fields...

A silicon-based electrical source for surface plasmon polaritons

NARCIS (Netherlands)

Walters, Robert J.; van Loon, Rob V.A.; Brunets, I.; Schmitz, Jurriaan; Polman, Albert

2009-01-01

This work demonstrates the fabrication of a silicon-based electrical source for surface plasmon polaritons (SPPs) at low temperatures using silicon nanocrystal doped alumina within a metal-insulator-metal (MIM) waveguide geometry. The fabrication method uses established microtechnology processes

Efficiency of local surface plasmon polariton excitation on ridges

DEFF Research Database (Denmark)

Radko, Ilya; Bozhevolnyi, Sergey I.; Boltasseva, Alexandra

2008-01-01

We investigate experimentally and numerically the efficiency of surface plasmon polariton excitation by a focused laser beam using gold ridges. The dependence of the efficiency on geometrical parameters of ridges and wavelength dependence are examined. The experimental measurements accomplished...

Localized magnetic polaritons in thin flims

International Nuclear Information System (INIS)

Lima, N.P.

1985-01-01

In this thesis we study the localized retarted modes (polaritons) in a ferromagnetic slab. For this we used the linear response theory to obtain the dispersion relations of the bulk, surface and guided modes, for a geometry more general than the Voigt's one. We got both the Green functions in the Voight geometry and the power spectra of these modes. Finally, we show that these Green functions fulfill the correct general symmetry requirements. (author) [pt

Light propagation in two-dimensional photonic crystals based on uniaxial polar materials: results on polaritonic spectrum

Science.gov (United States)

Gómez-Urrea, H. A.; Duque, C. A.; Pérez-Quintana, I. V.; Mora-Ramos, M. E.

2017-03-01

The dispersion relations of two-dimensional photonic crystals made of uniaxial polaritonic cylinders arranged in triangular lattice are calculated. The particular case of the transverse magnetic polarization is taken into account. Three different uniaxial materials showing transverse phonon-polariton excitations are considered: aluminum nitride, gallium nitride, and indium nitride. The study is carried out by means of the finite-difference time-domain technique for the solution of Maxwell equations, together with the method of the auxiliary differential equation. It is shown that changing the filling fraction can result in the modification of both the photonic and polaritonic bandgaps in the optical dispersion relations. Wider gaps appear for smaller filling fraction values, whereas a larger number of photonic bandgaps will occur within the frequency range considered when a larger filling fraction is used. The effect of including the distinct wurtzite III-V nitride semiconductors as core materials in the cylinders embedded in the air on the photonic properties is discussed as well, highlighting the effect of the dielectric anisotropy on the properties of the polaritonic part of the photonic spectrum.

Polariton condensation, superradiance and difference combination parametric resonance in mode-locked laser

Science.gov (United States)

Bagayev, S. N.; Arkhipov, R. M.; Arkhipov, M. V.; Egorov, V. S.; Chekhonin, I. A.; Chekhonin, M. A.

2017-11-01

The generation of the ring mode-locked laser containing resonant absorption medium in the cavity was investigated. It is shown that near the strong resonant absorption lines a condensation of polaritons arises. Intensive radiation looks like as superradiance in a medium without population inversion. We studied theoretically the microscopic mechanism of these phenomena. It was shown that in this system in absorbing medium a strong self-induced difference combination parametric resonance exists. Superradiance on polaritonic modes in the absorbing medium are due to the emergence of light-induced resonant polarization as a result of fast periodic nonadiabatic quantum jumps in the absorber.

Fundamental aspects of surface plasmon polaritons at terahertz frequencies

NARCIS (Netherlands)

Gómez Rivas, J.; Zhang, Y.; Berrier, A.; Saeedkia, D.

2013-01-01

We present in this chapter an introduction to the field of terahertz (THz) plasmonics. The characteristics of surface plasmon polaritons (SPPs) are determined by the complex permittivity of conductors. Therefore, we introduce the Drude model to describe the permittivity of conductors at THz

Topological order and thermal equilibrium in polariton condensates

Science.gov (United States)

Caputo, Davide; Ballarini, Dario; Dagvadorj, Galbadrakh; Sánchez Muñoz, Carlos; de Giorgi, Milena; Dominici, Lorenzo; West, Kenneth; Pfeiffer, Loren N.; Gigli, Giuseppe; Laussy, Fabrice P.; Szymańska, Marzena H.; Sanvitto, Daniele

2018-02-01

The Berezinskii-Kosterlitz-Thouless phase transition from a disordered to a quasi-ordered state, mediated by the proliferation of topological defects in two dimensions, governs seemingly remote physical systems ranging from liquid helium, ultracold atoms and superconducting thin films to ensembles of spins. Here we observe such a transition in a short-lived gas of exciton-polaritons, bosonic light-matter particles in semiconductor microcavities. The observed quasi-ordered phase, characteristic for an equilibrium two-dimensional bosonic gas, with a decay of coherence in both spatial and temporal domains with the same algebraic exponent, is reproduced with numerical solutions of stochastic dynamics, proving that the mechanism of pairing of the topological defects (vortices) is responsible for the transition to the algebraic order. This is made possible thanks to long polariton lifetimes in high-quality samples and in a reservoir-free region. Our results show that the joint measurement of coherence both in space and time is required to characterize driven-dissipative phase transitions and enable the investigation of topological ordering in open systems.

Topological order and thermal equilibrium in polariton condensates.

Science.gov (United States)

Caputo, Davide; Ballarini, Dario; Dagvadorj, Galbadrakh; Sánchez Muñoz, Carlos; De Giorgi, Milena; Dominici, Lorenzo; West, Kenneth; Pfeiffer, Loren N; Gigli, Giuseppe; Laussy, Fabrice P; Szymańska, Marzena H; Sanvitto, Daniele

2018-02-01

The Berezinskii-Kosterlitz-Thouless phase transition from a disordered to a quasi-ordered state, mediated by the proliferation of topological defects in two dimensions, governs seemingly remote physical systems ranging from liquid helium, ultracold atoms and superconducting thin films to ensembles of spins. Here we observe such a transition in a short-lived gas of exciton-polaritons, bosonic light-matter particles in semiconductor microcavities. The observed quasi-ordered phase, characteristic for an equilibrium two-dimensional bosonic gas, with a decay of coherence in both spatial and temporal domains with the same algebraic exponent, is reproduced with numerical solutions of stochastic dynamics, proving that the mechanism of pairing of the topological defects (vortices) is responsible for the transition to the algebraic order. This is made possible thanks to long polariton lifetimes in high-quality samples and in a reservoir-free region. Our results show that the joint measurement of coherence both in space and time is required to characterize driven-dissipative phase transitions and enable the investigation of topological ordering in open systems.

High Excitation Efficiency of Channel Plasmon Polaritons in Tailored, UV-Lithography-Defined V-Grooves

DEFF Research Database (Denmark)

Smith, Cameron; Thilsted, Anil Haraksingh; Garcia-Ortiz, Cesar E.

2014-01-01

We demonstrate >50% conversion of light to V-groove channel plasmon-polaritons (CPPs) via compact waveguide-termination mirrors. Devices are fabricated using UV-lithography and crystallographic silicon etching. The V-shape is tailored by thermal oxidation to support confined CPPs.......We demonstrate >50% conversion of light to V-groove channel plasmon-polaritons (CPPs) via compact waveguide-termination mirrors. Devices are fabricated using UV-lithography and crystallographic silicon etching. The V-shape is tailored by thermal oxidation to support confined CPPs....

Nanoimprinted reflecting gratings for long-range surface plasmon polaritons

DEFF Research Database (Denmark)

Pedersen, Rasmus Haugstrup; Boltasseva, Alexandra; Johansen, Dan Mario

2007-01-01

We present a novel design, fabrication, and characterization of reflecting gratings for long-range surface plasmon polaritons (LR-SPPs) at telecom wavelengths. LR-SPP waveguides consisting of a thin (12 nm) gold film embedded in a thick (45 μm) layer of dielectric polymer cladding are structured...

Acoustically-driven surface and hyperbolic plasmon-phonon polaritons in graphene/h-BN heterostructures on piezoelectric substrates

Science.gov (United States)

Fandan, R.; Pedrós, J.; Schiefele, J.; Boscá, A.; Martínez, J.; Calle, F.

2018-05-01

Surface plasmon polaritons in graphene couple strongly to surface phonons in polar substrates leading to hybridized surface plasmon-phonon polaritons (SPPPs). We demonstrate that a surface acoustic wave (SAW) can be used to launch propagating SPPPs in graphene/h-BN heterostructures on a piezoelectric substrate like AlN, where the SAW-induced surface modulation acts as a dynamic diffraction grating. The efficiency of the light coupling is greatly enhanced by the introduction of the h-BN film as compared to the bare graphene/AlN system. The h-BN interlayer not only significantly changes the dispersion of the SPPPs but also enhances their lifetime. The strengthening of the SPPPs is shown to be related to both the higher carrier mobility induced in graphene and the coupling with h-BN and AlN surface phonons. In addition to surface phonons, hyperbolic phonons polaritons (HPPs) appear in the case of multilayer h-BN films leading to hybridized hyperbolic plasmon-phonon polaritons (HPPPs) that are also mediated by the SAW. These results pave the way for engineering SAW-based graphene/h-BN plasmonic devices and metamaterials covering the mid-IR to THz range.

Comprehensive three-dimensional analysis of surface plasmon polariton modes at uniaxial liquid crystal-metal interface.

Science.gov (United States)

Yen, Yin-Ray; Lee, Tsun-Hsiun; Wu, Zheng-Yu; Lin, Tsung-Hsien; Hung, Yu-Ju

2015-12-14

This paper describes the derivation of surface plasmon polariton modes associated with the generalized three-dimensional rotation of liquid crystal molecules on a metal film. The calculated dispersion relation was verified by coupling laser light into surface plasmon polariton waves in a one-dimensional grating device. The grating-assisted plasmon coupling condition was consistent with the formulated k(spp) value. This provides a general rule for the design of liquid-crystal tunable plasmonic devices.

Surface plasmon polariton propagation in organic nanofiber based plasmonic waveguides

DEFF Research Database (Denmark)

Leißner, Till; Lemke, Christoph; Jauernik, Stephan

2013-01-01

Plasmonic wave packet propagation is monitored in dielectric-loaded surface plasmon polariton waveguides realized from para-hexaphenylene nanofibers deposited onto a 60 nm thick gold film. Using interferometric time resolved two-photon photoemission electron microscopy we are able to determine...

A study of polaritonic transparency in couplers made from excitonic materials

Energy Technology Data Exchange (ETDEWEB)

Singh, Mahi R.; Racknor, Chris [Department of Physics and Astronomy, Western University, London, Ontario N6A 3K7 (Canada)

2015-03-14

We have studied light matter interaction in quantum dot and exciton-polaritonic coupler hybrid systems. The coupler is made by embedding two slabs of an excitonic material (CdS) into a host excitonic material (ZnO). An ensemble of non-interacting quantum dots is doped in the coupler. The bound exciton polariton states are calculated in the coupler using the transfer matrix method in the presence of the coupling between the external light (photons) and excitons. These bound exciton-polaritons interact with the excitons present in the quantum dots and the coupler is acting as a reservoir. The Schrödinger equation method has been used to calculate the absorption coefficient in quantum dots. It is found that when the distance between two slabs (CdS) is greater than decay length of evanescent waves the absorption spectrum has two peaks and one minimum. The minimum corresponds to a transparent state in the system. However, when the distance between the slabs is smaller than the decay length of evanescent waves, the absorption spectra has three peaks and two transparent states. In other words, one transparent state can be switched to two transparent states when the distance between the two layers is modified. This could be achieved by applying stress and strain fields. It is also found that transparent states can be switched on and off by applying an external control laser field.

Spoof surface plasmon polaritons based notch filter for ultra-wideband microwave waveguide

DEFF Research Database (Denmark)

Xiao, Binggang; Li, Sheng-Hua; Xiao, Sanshui

2016-01-01

Spoof surface plasmon polaritons based notch filter for ultra-wideband microwave waveguide is proposed. Owing to subwavelength confinement, such a filter has advantage in the structure size without sacrificing the performance. The spoof SPP based notch is introduced to suppress the WLAN and satel...... and satellite communication signals. Due to planar structures proposed here, it is easy to integrate in the microwave integrated systems, which can play an important role in the microwave communication circuit and system.......Spoof surface plasmon polaritons based notch filter for ultra-wideband microwave waveguide is proposed. Owing to subwavelength confinement, such a filter has advantage in the structure size without sacrificing the performance. The spoof SPP based notch is introduced to suppress the WLAN...

Raman scattering by hot polaritons in NaClO/sub 3/

Energy Technology Data Exchange (ETDEWEB)

Bogani, F.; Vinattieri, A.

1985-01-01

By nonlinear mixing of IR and visible radiation, i.e. coherent Raman scattering by polaritons driven by a CO/sub 2/ laser, it has been possible to get high-resolution spectra for the F-modes of a NaClO/sub 3/ crystal in the region (907/957) cm/sup -1/, where several isotopic modes are present. The obtained independent measurement of the refractive index and absorbance allows an accurate determination of the polariton dispersion curve and its width in q-space. The experimental data confirm the existence of a localized isotopic mode at 931 cm/sup -1/ and a strongly damped isotopic mode near 960 cm/sup -1/. Finally, an accurate measurement of the dispersion of the second-order nonlinear polarizability in the same energy region has been obtained for the first time.

Switchable directional excitation surface plasmon polaritons with dielectric nanoantennas

DEFF Research Database (Denmark)

Sinev, I.; Komissarenko, F.; Bogdanov, A.

2017-01-01

We demonstrate directional launching of surface plasmon polaritons on thin goldfilm with a single silicon nanosphere. The directivity pattern of the excited surface waves exhibits rapid switching from forward to backward excitation, which is driven by the mutual interference of magnetic and elect...... and electric dipole moments supported by the dielectric nanoantenna....

Interference of Multiple Surface Plasmon Polaritons

International Nuclear Information System (INIS)

Wang, Dapeng; Yuan, Xiaocong; Lin, Jiao

2017-01-01

Benefiting from strongly electromagnetic confinement and enhancement effects, surface plasmon polaritons (SPPs) hold great promises for tailoring light on micro and nanoscale. By contrast with previous efforts which massively concentrate on localized SPP mode, we investigated the propagating SPPs in this paper. A number of symmetrical gratings on metal surface are employed to excite multiple SPPs. Interestingly, the exotic interfering phenomena have been observed. They show good agreement with free-space interferences and take advantage of precise controllability. These findings will be promising in the applications of optical tweezers and SPP lithography. (paper)

Response of exciton polariton spectra and electric fields to different additional boundary conditions

International Nuclear Information System (INIS)

Nkoma, J.S.

1982-08-01

The effects of three additional boundary conditions (ABC's) on the reflection and transmission spectra for exciton polaritons propagating in a spatially dispersive media are studied for both p and s configurations. An investigation of the ratios of the electric field amplitudes associated with the normal modes in these media is carried out. There is qualitative agreement among the predictions of the different ABC's, but there are significant quantitative differences, especially in the longitudinal polariton spike excited only in the p-geometry. Contact with formulations not using the ABC approach is made. The results are illustrated by parameters modelling the 1s exciton of PbI 2 . (author)

Polariton Chimeras: Bose-Einstein Condensates with Intrinsic Chaoticity and Spontaneous Long-Range Ordering

Science.gov (United States)

Gavrilov, S. S.

2018-01-01

The system of cavity polaritons driven by a plane electromagnetic wave is found to undergo the spontaneous breaking of spatial symmetry, which results in a lifted phase locking with respect to the driving field and, consequently, in the possibility of internal ordering. In particular, periodic spin and intensity patterns arise in polariton wires; they exhibit strong long-range order and can serve as media for signal transmission. Such patterns have the properties of dynamical chimeras: they are formed spontaneously in perfectly homogeneous media and can be partially chaotic. The reported new mechanism of chimera formation requires neither time-delayed feedback loops nor nonlocal interactions.

Long-range surface polaritons in thin layers of absorbing materials

NARCIS (Netherlands)

Zhang, Y.

2011-01-01

Long-range surface polaritons (LRSPs) are electromagnetic surface modes confined at the interfaces of an thin film surrounded by a homogeneous dielectric. These modes are generally characterized by the subwavelength confinement and the long propagation length. In case of a metallic thin film, the

Experimental study of surface plasmon-phonon polaritons in GaAs-based microstructures

Science.gov (United States)

Galimov, A. I.; Shalygin, V. A.; Moldavskaya, M. D.; Panevin, V. Yu; Melentyev, G. A.; Artemyev, A. A.; Firsov, D. A.; Vorobjev, L. E.; Klimko, G. V.; Usikova, A. A.; Komissarova, T. A.; Sedova, I. V.; Ivanov, S. V.

2018-03-01

Optical properties of a heavily-doped GaAs epitaxial layer with a regular grating at its surface have been experimentally investigated in the terahertz spectral range. Reflectivity spectra for the layer with a profiled surface drastically differ from those for the as-grown epilayer with a planar surface. For s-polarized radiation, this difference is totally caused by the electromagnetic wave diffraction at the grating. For p-polarized radiation, additional resonant dips arise due to excitation of surface plasmon-phonon polaritons. Terahertz radiation emission under significant electron heating in an applied pulsed electric field has also been studied. Polarization measurements revealed pronounced peaks related to surface plasmon-phonon polariton resonances of the first and second order in the emission spectra.

Chiral Modes at Exceptional Points in Exciton-Polariton Quantum Fluids

Science.gov (United States)

Gao, T.; Li, G.; Estrecho, E.; Liew, T. C. H.; Comber-Todd, D.; Nalitov, A.; Steger, M.; West, K.; Pfeiffer, L.; Snoke, D. W.; Kavokin, A. V.; Truscott, A. G.; Ostrovskaya, E. A.

2018-02-01

We demonstrate the generation of chiral modes-vortex flows with fixed handedness in exciton-polariton quantum fluids. The chiral modes arise in the vicinity of exceptional points (non-Hermitian spectral degeneracies) in an optically induced resonator for exciton polaritons. In particular, a vortex is generated by driving two dipole modes of the non-Hermitian ring resonator into degeneracy. Transition through the exceptional point in the space of the system's parameters is enabled by precise manipulation of real and imaginary parts of the closed-wall potential forming the resonator. As the system is driven to the vicinity of the exceptional point, we observe the formation of a vortex state with a fixed orbital angular momentum (topological charge). This method can be extended to generate higher-order orbital angular momentum states through coalescence of multiple non-Hermitian spectral degeneracies. Our Letter demonstrates the possibility of exploiting nontrivial and counterintuitive properties of waves near exceptional points in macroscopic quantum systems.

Chiral Modes at Exceptional Points in Exciton-Polariton Quantum Fluids.

Science.gov (United States)

Gao, T; Li, G; Estrecho, E; Liew, T C H; Comber-Todd, D; Nalitov, A; Steger, M; West, K; Pfeiffer, L; Snoke, D W; Kavokin, A V; Truscott, A G; Ostrovskaya, E A

2018-02-09

We demonstrate the generation of chiral modes-vortex flows with fixed handedness in exciton-polariton quantum fluids. The chiral modes arise in the vicinity of exceptional points (non-Hermitian spectral degeneracies) in an optically induced resonator for exciton polaritons. In particular, a vortex is generated by driving two dipole modes of the non-Hermitian ring resonator into degeneracy. Transition through the exceptional point in the space of the system's parameters is enabled by precise manipulation of real and imaginary parts of the closed-wall potential forming the resonator. As the system is driven to the vicinity of the exceptional point, we observe the formation of a vortex state with a fixed orbital angular momentum (topological charge). This method can be extended to generate higher-order orbital angular momentum states through coalescence of multiple non-Hermitian spectral degeneracies. Our Letter demonstrates the possibility of exploiting nontrivial and counterintuitive properties of waves near exceptional points in macroscopic quantum systems.

Triangular metal wedges for subwavelength plasmon-polariton guiding at telecom wavelengths

DEFF Research Database (Denmark)

Boltasseva, Alexandra; Volkov, V.S.; Nielsen, Rasmus Bundgaard

2008-01-01

We report on subwavelength plasmon-polariton guiding by triangular metal wedges at telecom wavelengths. A high-quality fabrication procedure for making gold wedge waveguides, which is also mass- production compatible offering large-scale parallel fabrication of plasmonic components, is developed...

A study of angle dependent surface plasmon polaritons in nano-hole array structures

Energy Technology Data Exchange (ETDEWEB)

Balakrishnan, Shankar [Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7 (Canada); Lawson Health Research Institute, St. Joseph' s Health Care, London, Ontario N6A 4V2 (Canada); Najiminaini, Mohamadreza; Carson, Jeffrey J. L. [Lawson Health Research Institute, St. Joseph' s Health Care, London, Ontario N6A 4V2 (Canada); Department of Medical Biophysics, University of Western Ontario, London, Ontario N6A 3K7 (Canada); Singh, Mahi R. [Department of Physics and Astronomy, University of Western Ontario, London, Ontario N6A 3K7 (Canada)

2016-07-21

We report that the light-matter interaction in metallic nano-hole array structures possess a subwavelength hole radius and periodicity. The transmission coefficient for nano-hole array structures was measured for different angles of incidence of light. Each measured transmission spectrum had several peaks due to surface plasmon polaritons. A theory of the transmission coefficient was developed based on the quantum density matrix method. It was found that the location of the surface plasmon polariton and the heights of the spectral peaks were dependent on the angle of incidence of light. Good agreement was observed between the experimental and theoretical results. This property of these structures has opened up new possibilities for sensing applications.

Biexciton relaxation associated with dissociation into a surface polariton pair in semiconductor films

Science.gov (United States)

Mitsumori, Yasuyoshi; Matsuura, Shimpei; Uchiyama, Shoichi; Saito, Kentarao; Edamatsu, Keiichi; Nakayama, Masaaki; Ajiki, Hiroshi

2018-04-01

We study the biexciton relaxation process in CuCl films ranging from 6 to 200 nm. The relaxation time is measured as the dephasing time and the lifetime. We observe a unique thickness dependence of the biexciton relaxation time and also obtain an ultrafast relaxation time with a timescale as short as 100 fs, while the exciton lifetime monotonically decreases with increasing thickness. By analyzing the exciton-photon coupling energy for a surface polariton, we theoretically calculate the biexciton relaxation time as a function of the thickness. The calculated dependence qualitatively reproduces the observed relaxation time, indicating that the biexciton dissociation into a surface polariton pair is one of the major biexciton relaxation processes.

TE and TM modes polaritons in multilayer system comprise of a PML-type magnetoelectric multiferroics and ferroelectrics

International Nuclear Information System (INIS)

Gunawan, Vincensius; Widiyandari, Hendri

2016-01-01

In this paper, we report our study on both bulk and surface polaritons generated in Multilayer system. The multilayer consists of ferroelectric and multiferroic with canted spins structure. The effective medium approximation is employed to derive the dispersion relation for both bulk and surface modes. Surface and bulk polaritons are calculated numerically for the case of Transverse electric (TE) and Transverse magnetic (TM) modes. Example results are presented using parameters appropriate for BaMnF 4 /BaAl 2 O 4 . We found in both TE and TM modes, that the region where the surface modes may exist is affected by the volume fraction of the multiferroics. The region of the surface modes decrease when the volume fraction of the multiferroic is reduced. This region decrement suppress the surface polariton curves which result in shortening the surface modes curves. (paper)

Terahertz wave parametric oscillations at polariton resonance using a MgO:LiNbO3 crystal.

Science.gov (United States)

Li, Zhongyang; Bing, Pibin; Yuan, Sheng; Xu, Degang; Yao, Jianquan

2015-06-20

Terahertz wave (THz-wave) parametric oscillations with a noncollinear phase-matching scheme at polariton resonance using a MgO:LiNbO3 crystal with a surface-emitted configuration are investigated. We investigate frequency tuning characteristics of a THz-wave via varying the wavelength of the pump wave and phase-matching angle. The effective parametric gain length under the noncollinear phase-matching condition is calculated. Parametric gain and absorption characteristics of a THz-wave in the vicinity of polariton resonances are analyzed.

Theory of Raman scattering by surface polaritons in a four media system

International Nuclear Information System (INIS)

Nkoma, J.S.

1988-08-01

The method of linear response theory is used to determine the response functions for surface polaritons in a four media system (or bounded bilayer). The dispersion relation is found when the pole of the derived response function vanishes. The expressions for the scattered intensity for both back and forward scattering are derived. The scattered intensity depends on a polarization which is the result of the coupling of the incident light to the vibrational coordinates and electric fields associated with electric-dipole-active lattice vibrations in the bilayer. Expressions for the Raman cross-section by surface polaritons in the four media system are derived for both back and forward scattering. Numerical results are presented by using parameters for a sapphire substrate-(GaP-GaAs) bilayer-vacuum system. (author). 28 refs, 5 figs

Surface plasmon polariton generation by light scattering off aligned organic nanofibers

DEFF Research Database (Denmark)

Skovsen, Esben; Søndergaard, Thomas; Fiutowski, Jacek

2012-01-01

Leakage radiation spectroscopy has been applied to study surface plasmon polariton (SPP) generation by light scattered off aligned organic nanofibers deposited on a thin silver film. The efficiency of SPP generation was studied by angularly resolved leakage radiation spectroscopy as a function of...

Dispersion anisotropy of plasmon-exciton-polaritons in lattices of metallic nanoparticles

NARCIS (Netherlands)

Ramezani, Mohammad; Halpin, Alexei; Feist, Johannes; Van Hoof, Niels; Fernández-Domínguez, Antonio I.; Garcia-Vidal, Francisco J.; Gómez Rivas, Jaime

2018-01-01

When the electromagnetic modes supported by plasmonic-based cavities interact strongly with molecules located within the cavity, new hybrid states known as plasmon-exciton-polaritons (PEPs) are formed. The properties of PEPs, such as group velocity, effective mass, and lifetime, depend on the

Dispersion Anisotropy of Plasmon–Exciton–Polaritons in Lattices of Metallic Nanoparticles

NARCIS (Netherlands)

Ramezani, M.; Halpin, A.; Feist, J.; van Hoof, N.; Fernández-Domínguez, A. I.; Garcia-Vidal, F. J.; Rivas, Gomez

2018-01-01

When the electromagnetic modes supported by plasmonic-based cavities interact strongly with molecules located within the cavity, new hybrid states known as plasmon–exciton–polaritons (PEPs) are formed. The properties of PEPs, such as group velocity, effective mass, and lifetime, depend on the

Energy dissipation of free exciton polaritons in semiconducting films

International Nuclear Information System (INIS)

De Crescenzi, M.; Harbeke, G.; Tosatti, E.

1978-08-01

The effective (thickness-dependent) light absorption coefficient K(ω,d) is discussed for thin semiconducting films in the frequency range of free, spatially dispersive exciton polaritons. We find that (i) it oscillates strongly for small film thicknesses; (ii) it exhibits a slanted peak lineshape; (iii) its integrated strength also depends upon the exciton damping and extrapolates to zero for vanishing damping

Numerical study of propagation properties of surface plasmon polaritons in nonlinear media

KAUST Repository

Sagor, Rakibul Hasan; Ghulam Saber, Md.; Alsunaidi, Mohammad

2016-01-01

We present a time-domain algorithm for simulating nonlinear propagation of surface plasmon polaritons (SPPs) in chalcogenide glass. Due to the high non-linearity property and strong dispersion and confinement chalcogenide glasses are widely known

A classroom theory of the surface plasmon polariton

International Nuclear Information System (INIS)

Barchiesi, Dominique

2012-01-01

Surface plasmon resonance, also called the surface plasmon polariton, is an attractive illustration of basic electromagnetism. The investigation of this phenomenon in textbooks is often confusing for undergraduate students. The link between classical concepts of resonance and the solution of the problem is proposed in this work to clarify the procedure. The relationship with the course of solid state physics is proposed using the dispersion curves. The experimental setups are also mentioned. (paper)

Cavity-polariton interaction mediated by coherent acoustic phonons in semiconductor microcavities

DEFF Research Database (Denmark)

de Lima, Mauricio; Hey, Rudolf; Santos, Paul

The strong coupling between excitons in a quantum well (QW) and photons in a semiconductor microcavity leads to the formation of quasi-particles known as cavity-polaritons. In this contribution, we investigate their interaction with coherent acoustic phonons in the form of surface acoustic waves...

The phonon-polariton spectrum of one-dimensional Rudin-Shapiro photonic superlattices with uniaxial polar materials

Science.gov (United States)

Gómez-Urrea, H. A.; Duque, C. A.; Mora-Ramos, M. E.

2015-11-01

The properties of the optical-phonon-associated polaritonic modes that appear under oblique light incidence in 1D superlattices made of photonic materials are studied. The investigated systems result from the periodic repetition of quasiregular Rudin-Shapiro (RS) multilayer units. It is assume that the structure consists of both passive non-dispersive layers of constant refraction index and active layers of uniaxial polar materials. In particular, we consider III-V wurtzite nitrides. The optical axis of these polaritonic materials is taken along the growth direction. Maxwell equations are solved using the transfer matrix technique for all admissible values of the incidence angle.

New surface plasmon polariton waveguide based on GaN nanowires

Directory of Open Access Journals (Sweden)

Jun Zhu

Full Text Available Lasers are nowadays widely used in industry, in hospitals and in many devices that we have at home. Random laser development is challenging given its high threshold and low integration. Surface plasmon polariton (SPP can improve random laser characteristics because of its ability to control diffraction. In this study, we establish a random laser structural model with silicon-based parcel GaN nanowires. The GaN nanowire gain and enhanced surface plasmon increase population inversion level. Our laser model is based on random particle scattering feedback mechanism, nanowire use, and surface plasmon enhancement effect, which causes stochastic laser emergence. Analysis shows that the SPP mode and nanowire waveguides coupled in the dielectric layer of low refractive index can store light energy like a capacitor under low refractive index clearance. The waveguide mode field area and limiting factors show that the modeled laser can achieve sub-wavelength constraints of the output light field. We also investigate emergent laser performance for a more limited light field capacity and lower threshold. Keywords: Random laser, Surface plasmon polariton, Feedback mechanism, Low threshold, Subwavelength constraints

Femtosecond tunneling response of surface plasmon polaritons

DEFF Research Database (Denmark)

Keil, Ulrich Dieter Felix; Ha, Taekjip; Jensen, Jacob Riis

1998-01-01

We obtain femtosecond (200 fs) time resolution using a scanning tunneling microscope on surface plasmon polaritons (SPPs) generated by two 100 fs laser beams in total internal reflection geometry. The tunneling gap dependence of the signal clearly indicates the tunneling origin of the signal...... and suggests that nanometer spatial resolution can be obtained together with femtosecond temporal resolution. This fast response, in contrast to the picosecond decay time of SPPs revealed by differential reflectivity measurements, can be attributed to a coherent superposition of SPPs rectified at the tunneling...

Bistable Topological Insulator with Exciton-Polaritons

Science.gov (United States)

Kartashov, Yaroslav V.; Skryabin, Dmitry V.

2017-12-01

The functionality of many nonlinear and quantum optical devices relies on the effect of optical bistability. Using microcavity exciton-polaritons in a honeycomb arrangement of microcavity pillars, we report the resonance response and bistability of topological edge states. A balance between the pump, loss, and nonlinearity ensures a broad range of dynamical stability and controls the distribution of power between counterpropagating states on the opposite edges of the honeycomb lattice stripe. Tuning energy and polarization of the pump photons, while keeping their momentum constant, we demonstrate control of the propagation direction of the dominant edge state. Our results facilitate the development of practical applications of topological photonics.

Exciton polariton spectra and limiting factors for the room-temperature photoluminescence efficiency in ZnO

Science.gov (United States)

Chichibu, S. F.; Uedono, A.; Tsukazaki, A.; Onuma, T.; Zamfirescu, M.; Ohtomo, A.; Kavokin, A.; Cantwell, G.; Litton, C. W.; Sota, T.; Kawasaki, M.

2005-04-01

Static and dynamic responses of excitons in state-of-the-art bulk and epitaxial ZnO are reviewed to support the possible realization of polariton lasers, which are coherent and monochromatic light sources due to Bose condensation of exciton-polaritons in semiconductor microcavities (MCs). To grasp the current problems and to pave the way for obtaining ZnO epilayers of improved quality, the following four principal subjects are treated: (i) polarized optical reflectance (OR), photoreflectance (PR) and photoluminescence (PL) spectra of the bulk and epitaxial ZnO were recorded at 8 K. Energies of PR resonances corresponded to those of upper and lower exciton-polariton branches, where A-, B- and C-excitons couple simultaneously to an electromagnetic wave. PL peaks due to the corresponding polariton branches were observed. Longitudinal-transverse splittings (ωLT) of the corresponding excitons were 1.5, 11.1 and 13.1 meV, respectively. The latter two values are more than two orders of magnitude greater than that of GaAs being 0.08 meV. (ii) Using these values and material parameters, corresponding vacuum-field Rabi splitting of exciton-polaritons coupled to a model MC mode was calculated to be 191 meV, which is the highest value ever reported for semiconductor MCs and satisfies the requirements to observe the strong exciton-light coupling regime necessary for polariton lasing above room temperature. (iii) Polarized OR and PR spectra of an out-plane nonpolar (1\\,1\\,\\bar{2}\\,0) ZnO epilayer grown by laser-assisted molecular beam epitaxy (L-MBE) were measured, since ZnO quantum wells (QWs) grown in nonpolar orientations are expected to show higher emission efficiencies due to the elimination of spontaneous and piezoelectric polarization fields normal to the QW plane. They exhibited in-plane anisotropic exciton resonances according to the polarization selection rules for anisotropically-strained wurzite material. (iv) Impacts of point defects on the nonradiative

Design of Matched Absorbing Layers for Surface Plasmon-Polaritons

Directory of Open Access Journals (Sweden)

Sergio de la Cruz

2012-01-01

Full Text Available We describe a procedure for designing metal-metal boundaries for the strong attenuation of surface plasmon-polaritons without the introduction of reflections or scattering effects. Solutions associated with different sets of matching materials are found. To illustrate the results and the consequences of adopting different solutions, we present calculations based on an integral equation formulation for the scattering problem and the use of a nonlocal impedance boundary condition.

Multi-Periodic Photonic Hyper-Crystals: Volume Plasmon Polaritons and the Purcell Effect

DEFF Research Database (Denmark)

Babicheva, Viktoriia; Iorsh, I. V.; Orlov, A. A.

2014-01-01

We theoretically demonstrate superior degree of control over volume plasmon polariton propagation and the Purcell effect in multi-period (4-layer unit cell) plasmonic multilayers, which can be viewed as multiscale hyperbolic metamaterials or multi-periodic photonic hyper-crystals. © 2014 OSA....

Data transmission in long-range dielectric-loaded surface plasmon polariton waveguides

DEFF Research Database (Denmark)

Kharitonov, S.; Kiselev, R.; Kumar, Ashwani

2014-01-01

We demonstrate the data transmission of 10 Gbit/s on-off keying modulated 1550 nm signal through a long-range dielectric-loaded surface plasmon polariton waveguide structure with negligible signal degradation. In the experiment the bit error rate penalties do not exceed 0.6 dB over the 15 nm...

Coherence properties of exciton polariton OPO condensates in one and two dimensions

International Nuclear Information System (INIS)

Spano, R; Cuadra, J; Tosi, G; Antón, C; Lingg, C A; Sanvitto, D; Martín, M D; Viña, L; Eastham, P R; Van der Poel, M; Hvam, J M

2012-01-01

We give an overview of the coherence properties of exciton-polariton condensates generated by optical parametric scattering. Different aspects of the first-order coherence (g (1) ) have been investigated. The spatial coherence extension of a two-dimensional (2D) polariton system, below and at the parametric threshold, demonstrates the development of a constant phase coherence over the entire condensate, once the condensate phase transition takes place. The effect on coherence of the photonic versus excitonic nature of the condensates is also examined. The coherence of a quasi-1D trap, composed of a line defect, is studied, showing the detrimental effect of reduced dimensionality on the establishment of the long range order. In addition, the temporal coherence decay, g (1) (τ), reveals a fast decay in contrast with the 2D case. The situation of a quasi-1D condensate coexisting with a 2D one is also presented. (paper)

Plasmon polaritons in nanostructured graphene

DEFF Research Database (Denmark)

Xiao, Sanshui

2013-01-01

Graphene has attracted considerable attention due to its unique electronic and optical properties. When graphene is electrically/chemically doped, it can support surface plasmon where the light propagates along the surface with a very short wavelength and an extremely small mode volume. The optical...... properties of graphene can be tuned by electrical gating, thus proving a promising way to realize a tunable plasmonic material. We firstly investigate the performance of bends and splitters in graphene nanoribbon waveguides, and show that bends and splitters do not induce any additional loss provided...... that the nanoribbon width is sub-wavelength. Then we experimentally demonstrate the excitation of graphene plasmon polaritons in a continuous graphene monolayer resting on a two-dimensional subwavelength silicon grating. The silicon grating is realized by a nanosphere lithography technique with a self...

Flexible long-range surface plasmon polariton single-mode waveguide for optical interconnects

DEFF Research Database (Denmark)

Vernoux, Christian; Chen, Yiting; Markey, Laurent

2018-01-01

We present the design, fabrication and characterization of long-range surface plasmon polariton waveguide arrays with materials, mainly silicones, carefully selected with the aim to be used as mechanically flexible single-mode optical interconnections, the socalled "plasmonic arc" working at 1.55μm...

Electrically Injected Polariton Lasing from a GaAs-Based Microcavity under Magnetic Field

KAUST Repository

Bhattacharya, Pallab; Das, Ayan; Jankowski, Marc; Bhowmick, Sishir; Lee, Chi-Sen; Jahangir, Shafat

2012-01-01

Suppression of relaxation bottleneck and subsequent polariton lasing is observed in a GaAs-based microcavity under the application of a magnetic field. The threshold injection current density is 0.32 A/cm2 at 7 Tesla.

Voltage control of cavity magnon polariton

Energy Technology Data Exchange (ETDEWEB)

Kaur, S., E-mail: kaurs3@myumanitoba.ca; Rao, J. W.; Gui, Y. S.; Hu, C.-M., E-mail: hu@physics.umanitoba.ca [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); Yao, B. M. [Department of Physics and Astronomy, University of Manitoba, Winnipeg, Manitoba R3T 2N2 (Canada); National Laboratory for Infrared Physics, Chinese Academy of Sciences, Shanghai 200083 (China)

2016-07-18

We have experimentally investigated the microwave transmission of the cavity-magnon-polariton (CMP) generated by integrating a low damping magnetic insulator onto a 2D microwave cavity. The high tunability of our planar cavity allows the cavity resonance frequency to be precisely controlled using a DC voltage. By appropriately tuning the voltage and magnetic bias, we can observe the cavity photon magnon coupling and the magnetic coupling between a magnetostatic mode and the generated CMP. The dispersion of the generated CMP was measured by either tuning the magnetic field or the applied voltage. This electrical control of CMP may open up avenues for designing advanced on-chip microwave devices that utilize light-matter interaction.

Interplay between electric and magnetic effect in adiabatic polaritonic systems

KAUST Repository

Alabastri, Alessandro; Toma, Andrea; Liberale, Carlo; Chirumamilla, Manohar; Giugni, Andrea; De Angelis, Francesco De; Das, Gobind; Di Fabrizio, Enzo M.; Proietti Zaccaria, Remo

2013-01-01

We report on the possibility of realizing adiabatic compression of polaritonic wave on a metallic conical nano-structure through an oscillating electric potential (quasi dynamic regime). By comparing this result with an electromagnetic wave excitation, we were able to relate the classical lighting-rod effect to adiabatic compression. Furthermore, we show that while the magnetic contribution plays a marginal role in the formation of adiabatic compression, it provides a blue shift in the spectral region. In particular, magnetic permeability can be used as a free parameter for tuning the polaritonic resonances. The peculiar form of adiabatic compression is instead dictated by both the source and the metal permittivity. The analysis is performed by starting from a simple electrostatic system to end with the complete electromagnetic one through intermediate situations such as the quasi-electrostatic and quasi-dynamic regimes. Each configuration is defined by a particular set of equations which allows to clearly determine the individual role played by the electric and magnetic contribution in the generation of adiabatic compression. We notice that these findings can be applied for the realization of a THz nano-metric generator. © 2013 Optical Society of America.

Amplitude and phase of surface plasmon polaritons excited at a step edge

DEFF Research Database (Denmark)

Klick, Alwin; de la Cruz, Sergio; Lemke, Christoph

2016-01-01

A combined experimental and theoretical study on the laser-induced excitation of surface plasmon polaritons (SPP) at well-defined step edges of a gold–vacuum interface is presented. As a relevant parameter determining the coupling efficiency between laser field and SPP, we identify the ratio betw...

Generalized Bogoliubov Polariton Model: An Application to Stock Exchange Market

International Nuclear Information System (INIS)

Anh, Chu Thuy; Anh, Truong Thi Ngoc; Lan, Nguyen Tri; Viet, Nguyen Ai

2016-01-01

A generalized Bogoliubov method for investigation non-simple and complex systems was developed. We take two branch polariton Hamiltonian model in second quantization representation and replace the energies of quasi-particles by two distribution functions of research objects. Application to stock exchange market was taken as an example, where the changing the form of return distribution functions from Boltzmann-like to Gaussian-like was studied. (paper)

The complex dispersion relation of surface plasmon polaritons at gold/para-hexaphenylene interfaces

DEFF Research Database (Denmark)

Lemke, Christoph; Leißner, Till; Klick, Alwin

2014-01-01

Two-photon photoemission electron microscopy (2P-PEEM) is used to measure the real and imaginary part of the dispersion relation of surface plasmon polaritons at different interface systems. A comparison of calculated and measured dispersion data for a gold/vacuum interface demonstrates...

Anisotropic excitation of surface plasmon polaritons on a metal film by a scattering-type scanning near-field microscope with a non-rotationally-symmetric probe tip

Directory of Open Access Journals (Sweden)

Walla Frederik

2018-01-01

Full Text Available We investigated the excitation of surface plasmon polaritons on gold films with the metallized probe tip of a scattering-type scanning near-field optical microscope (s-SNOM. The emission of the polaritons from the tip, illuminated by near-infrared laser radiation, was found to be anisotropic and not circularly symmetric as expected on the basis of literature data. We furthermore identified an additional excitation channel via light that was reflected off the tip and excited the plasmon polaritons at the edge of the metal film. Our results, while obtained for a non-rotationally-symmetric type of probe tip and thus specific for this situation, indicate that when an s-SNOM is employed for the investigation of plasmonic structures, the unintentional excitation of surface waves and anisotropic surface wave propagation must be considered in order to correctly interpret the signatures of plasmon polariton generation and propagation.

Local excitation of surface plasmon polaritons by second-harmonic generation in crystalline organic nanofibers

DEFF Research Database (Denmark)

Skovsen, Esben; Søndergaard, Thomas; Fiutowski, Jacek

2012-01-01

Coherent local excitation of surface plasmon polaritons (SPPs) by second-harmonic generation (SHG) in aligned crystalline organic functionalized para-phenylene nanofibers deposited on a thin silver film is demonstrated. The excited SPPs are characterized using angle-resolved leakage radiation...

Luminescence of quantum-well exciton polaritons from microstructured AlxGa1-xAs-GaAs multiple quantum wells

Science.gov (United States)

Kohl, M.; Heitmann, D.; Grambow, P.; Ploog, K.

1988-06-01

Periodic multiple-quantum-well wires have been prepared by etching five-layer quantum-well structures through a holographically prepared mask. The periodicity was 380 nm, the lateral confinement 180 nm, and the quantum-well width 13, nm. The luminescence from these microstructured systems in the frequency regime of the one-electron-one-heavy-hole transition was strongly polarized with the electric field perpendicular to the periodic structure. This effect was caused by the resonantly enhanced emission of quantum-well-exciton (QWE) polaritons. Excitation of QWE polaritons was also observed in reflection measurements on the microstructured samples.

Interaction of surface plasmon polaritons and acoustic waves inside an acoustic cavity.

Science.gov (United States)

Khokhlov, Nikolai; Knyazev, Grigoriy; Glavin, Boris; Shtykov, Yakov; Romanov, Oleg; Belotelov, Vladimir

2017-09-15

In this Letter, we introduce an approach for manipulation of active plasmon polaritons via acoustic waves at sub-terahertz frequency range. The acoustic structures considered are designed as phononic Fabry-Perot microresonators where mirrors are presented with an acoustic superlattice and the structure's surface, and a plasmonic grating is placed on top of the acoustic cavity so formed. It provides phonon localization in the vicinity of the plasmonic grating at frequencies within the phononic stop band enhancing phonon-light interaction. We consider phonon excitation by shining a femtosecond laser pulse on the plasmonic grating. Appropriate theoretical model was used to describe the acoustic process caused by the pump laser pulse in the GaAs/AlAs-based acoustic cavity with a gold grating on top. Strongest modulation is achieved upon excitation of propagating surface plasmon polaritons and hybridization of propagating and localized plasmons. The relative changes in the optical reflectivity of the structure are more than an order of magnitude higher than for the structure without the plasmonic film.

Plasmon-polariton modes of dense Au nanowire arrays

Energy Technology Data Exchange (ETDEWEB)

Yan, Hongdan; Lemmens, Peter; Wulferding, Dirk; Cetin, Mehmet Fatih [IPKM, TU-BS, Braunschweig (Germany); Tornow, Sabine; Zwicknagl, Gertrud [IMP, TU-BS, Braunschweig (Germany); Krieg, Ulrich; Pfnuer, Herbert [IFP, LU Hannover (Germany); Daum, Winfried; Lilienkamp, Gerhard [IEPT, TU Clausthal (Germany); Schilling, Meinhard [EMG, TU-BS, Braunschweig (Germany)

2011-07-01

Using optical absorption and other techniques we study plasmon-polariton modes of dense Au nanowire arrays as function of geometrical parameters and coupling to molecular degrees of freedom. For this instance we electrochemically deposit Au nanowires in porous alumina with well controlled morphology and defect concentration. Transverse and longitudinal modes are observed in the absorption spectra resulting from the anisotropic plasmonic structure. The longitudinal mode shows a blue shift of energy with increasing length of the wires due to the more collective nature of this response. We compare our observations with model calculations and corresponding results on 2D Ag nanowire lattices.

Efficiency of local surface plasmon polariton excitation on ridges

DEFF Research Database (Denmark)

Radko, I.P.; Bozhevolnyi, S.I.; Brucoli, G.

2008-01-01

The issue of efficient local coupling of light into surface plasmon polariton (SPP) modes is an important concern in miniaturization of plasmonic components. Here we present experimental and numerical investigations of efficiency of local SPP excitation on gold ridges of rectangular profile...... positioned on a gold film. The excitation is accomplished by illuminating the metal surface normally with a focused laser beam. Wavelength dependence and dependence of the efficiency on geometrical parameters of ridges are examined. Using leakage radiation microscopy, the efficiency of ˜20% is demonstrated...

Experimental demonstration of CMOS-compatible long-range dielectric-loaded surface plasmon-polariton waveguides (LR-DLSPPWs)

DEFF Research Database (Denmark)

Zektzer, Roy; Desiatov, Boris; Mazurski, Noa

2015-01-01

We demonstrate the design, fabrication and experimental characterization of long-range dielectric-loaded surface plasmon-polariton waveguides (LR-DLSPPWs) that are compatible with complementary metal-oxide semiconductor (CMOS) technology. The demonstrated waveguides feature good mode confinement...

Photonic bandgap structures for long-range surface plasmon polaritons

DEFF Research Database (Denmark)

Bozhevolnyi, Sergey I.; Boltasseva, Alexandra; Søndergaard, Thomas

2005-01-01

Propagation of long-range surface plasmon polaritons (LR-SPPs) along periodically thickness-modulated metal stripes embedded in dielectric is studied both theoretically and experimentally for light wavelengths in the telecom range. We demonstrate that symmetric (with respect to the film surface) nm......-size thickness variations result in the pronounced band gap effect, and obtain very good agreement between measured and simulated (transmission and reflection) spectra. This effect is exploited to realize a compact wavelength add-drop filter with the bandwidth of -20 nm centered at 1550 nm. The possibilities...

On-Demand Dark Soliton Train Manipulation in a Spinor Polariton Condensate

KAUST Repository

Pinsker, F.

2014-04-10

We theoretically demonstrate the generation of dark soliton trains in a one-dimensional exciton-polariton condensate within experimentally accessible schemes. In particular, we show that the frequency of the train can be finely tuned fully optically or electrically to provide a stable and efficient output signal modulation. Taking the polarization of the condensate into account, we elucidate the possibility of forming on-demand half-soliton trains. © 2014 American Physical Society.

Origin of the low frequency radiation emitted by radiative polaritons excited by infrared radiation in planar La2O3 films.

Science.gov (United States)

Vincent-Johnson, Anita J; Schwab, Yosyp; Mann, Harkirat S; Francoeur, Mathieu; Hammonds, James S; Scarel, Giovanna

2013-01-23

Upon excitation in thin oxide films by infrared radiation, radiative polaritons are formed with complex angular frequency ω, according to the theory of Kliewer and Fuchs (1966 Phys. Rev. 150 573). We show that radiative polaritons leak radiation with frequency ω(i) to the space surrounding the oxide film. The frequency ω(i) is the imaginary part of ω. The effects of the presence of the radiation leaked out at frequency ω(i) are observed experimentally and numerically in the infrared spectra of La(2)O(3) films on silicon upon excitation by infrared radiation of the 0TH type radiative polariton. The frequency ω(i) is found in the microwave to far infrared region, and depends on the oxide film chemistry and thickness. The presented results might aid in the interpretation of fine structures in infrared and, possibly, optical spectra, and suggest the study of other similar potential sources of electromagnetic radiation in different physical scenarios.

Resonant Rayleigh scattering of exciton-polaritons in multiple quantum wells

DEFF Research Database (Denmark)

Malpuech, Guillaume; Kavokin, Alexey; Langbein, Wolfgang Werner

2000-01-01

A theoretical concept of resonant Rayleigh scattering (RRS) of exciton-polaritons in multiple quantum wells (QWs) is presented. The optical coupling between excitons in different QWs can strongly affect the RRS dynamics, giving rise to characteristic temporal oscillations on a picosecond scale....... Bragg and anti-Bragg arranged QW structures with the same excitonic parameters are predicted to have drastically different RRS spectra. Experimental data on the RRS from multiple QWs show the predicted strong temporal oscillations at small scattering angles, which are well explained by the presented...

Propagation of long-range surface plasmon polaritons in photonic crystals

DEFF Research Database (Denmark)

Boltasseva, Alexandra; Søndergaard, Thomas; Nikolajsen, T.

2005-01-01

We study the interaction of long-range surface plasmon polaritons (LR-SPPs), excited at telecommunication wavelengths, with photonic crystals (PCs) formed by periodic arrays of gold bumps that are arranged in a triangular lattice and placed symmetrically on both sides of a thin gold film embedded...... structures, is rather weak, so that the photonic bandgap effect might be expected to take place only for some particular propagation directions. Preliminary experiments on LR-SPP bending and splitting at large angles are reported, and further research directions are discussed....

Geometrically induced surface polaritons in planar nanostructured metallic cavities

Energy Technology Data Exchange (ETDEWEB)

Davids, P. S. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Intravia, F [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Dalvit, Diego A. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2014-01-14

We examine the modal structure and dispersion of periodically nanostructured planar metallic cavities within the scattering matrix formulation. By nanostructuring a metallic grating in a planar cavity, artificial surface excitations or spoof plasmon modes are induced with dispersion determined by the periodicity and geometric characteristics of the grating. These spoof surface plasmon modes are shown to give rise to new cavity polaritonic modes at short mirror separations that modify the density of modes in nanostructured cavities. The increased modal density of states form cavity polarirons have a large impact on the fluctuation induced electromagnetic forces and enhanced hear transfer at short separations.

Fluctuations of tunneling currents in photonic and polaritonic systems

Science.gov (United States)

Mantsevich, V. N.; Glazov, M. M.

2018-04-01

Here we develop the nonequilibrium Green's function formalism to analyze the fluctuation spectra of the boson tunneling currents. The approach allows us to calculate the noise spectra in both equilibrium and nonequilibrium conditions. The proposed general formalism is applied to several important realizations of boson transport, including the tunneling transport between two reservoirs and the case where the boson current flows through the intermediate region between the reservoirs. Developed theory can be applied for the analysis of the current noise in waveguides, coupled optical resonators, quantum microcavities, etc., where the tunneling of photons, exciton-polaritons, or excitons can be realized.

Integrated Optical Components Utilizing Long-Range Surface Plasmon Polaritons

DEFF Research Database (Denmark)

Boltasseva, Alexandra; Nikolajsen, Thomas; Leosson, Kristjan

2005-01-01

New optical waveguide technology for integrated optics, based on propagation of long-range surface plasmon polaritons (LR-SPPs) along metal stripes embedded in dielectric, is presented. Guiding and routing of electromagnetic radiation along nanometer-thin and micrometer-wide gold stripes embedded......), and a bend loss of ~5 dB for a bend radius of 15 mm are evaluated for 15-nm-thick and 8-mm-wide stripes at the wavelength of 1550 nm. LR-SPP-based 3-dB power Y-splitters, multimode interference waveguides, and directional couplers are demonstrated and investigated. At 1570 nm, coupling lengths of 1.9 and 0...

Rotational symmetry breaking and topological phase transition in the exciton-polariton condensate of gapped 2D Dirac material

Science.gov (United States)

Lee, Ki Hoon; Lee, Changhee; Jeong, Jae-Seung; Min, Hongki; Chung, Suk Bum

For the quantum well in an optical microcavity, the interplay of the Coulomb interaction and the electron-photon coupling can lead to the emergence of bosonic quasiparticles consisting of the exciton and the cavity photon known as polariton, which can form the Bose-Einstein condensate above a threshold density. Additional physics due to the nontrivial Berry phase comes into play when the quantum well consists of the gapped Dirac material such as the transition metal dichalcogenide (TMD) MoS2 or WTe2. Specifically, in forming excitons, the electron-photon coupling from the optical selection rule due to the Berry phase competes against, rather than cooperates with, the Coulomb interaction. We find that this competition gives rise to the spontaneous breaking of the rotational symmetry in the polariton condensate and also drives topological phase transition, both novel features in polariton condensation. We also investigate the possible detection of this competition through photoluminescence. This work was supported in part by the Institute for Basic Science of Korea (IBS) under Grant IBS-R009-Y1 and by the National Research Foundation of Korea (NRF) under the Basic Science Research Program Grant No. 2015R1D1A1A01058071.

Pass-band reconfigurable spoof surface plasmon polaritons

Science.gov (United States)

Zhang, Hao Chi; He, Pei Hang; Gao, Xinxin; Tang, Wen Xuan; Cui, Tie Jun

2018-04-01

In this paper, we introduce a new scheme to construct the band-pass tunable filter based on the band-pass reconfigurable spoof surface plasmon polaritons (SPPs), whose cut-off frequencies at both sides of the passband can be tuned through changing the direct current (DC) bias of varactors. Compared to traditional technology (e.g. microstrip filters), the spoof SPP structure can provide more tight field confinement and more significant field enhancement, which is extremely valuable for many system applications. In order to achieve this scheme, we proposed a specially designed SPP filter integrated with varactors and DC bias feeding structure to support the spoof SPP passband reconfiguration. Furthermore, the full-wave simulated result verifies the outstanding performance on both efficiency and reconfiguration, which has the potential to be widely used in advanced intelligent systems.

Plasmon-Polariton Properties in Metallic Nanosphere Chains

Directory of Open Access Journals (Sweden)

Witold Aleksander Jacak

2015-06-01

Full Text Available The propagation of collective wave type plasmonic excitations along infinite chains of metallic nanospheres has been analyzed, including near-, medium- and far-field contributions to the plasmon dipole interaction with all retardation effects taken into account. It is proven that there exist weakly-damped self-modes of plasmon-polaritons in the chain for which the propagation range is limited by relatively small Ohmic losses only. In this regime, the Lorentz friction irradiation losses on each nanosphere in the chain are ideally compensated by the energy income from the rest of the chain. The completely undamped collective waves were identified in the case of the presence of persistent external excitation of some fragment of the chain. The obtained characteristics of these excitations fit the experimental observations well.

Photonic band gap structures for long-range surface plasmon polaritons

DEFF Research Database (Denmark)

Bozhevolnyi, Sergey I.; Boltasseva, Alexandra; Søndergaard, Thomas

2005-01-01

Propagation of long-range surface plasmon polaritons (LR-SPPs) along periodically thickness-modulated metal stripes embedded in dielectric is studied both theoretically and experimentally for light wavelengths in the telecom range. We demonstrate that symmetric (with respect to the film surface) nm......-size thickness variations result in the pronounced band gap effect, and obtain very good agreement between measured and simulated (transmission and reflection) spectra. This effect is exploited to realize a compact wavelength add-drop filter with the bandwidth of ~20 nm centered at 1550 nm. The possibilities...

Excitations of surface plasmon polaritons by attenuated total reflection, revisited

International Nuclear Information System (INIS)

Barchesi, D.; Otto, A.

2013-01-01

Many textbooks and review papers are devoted to plasmonics based on a selection of the numerous bibliography. But none describes the details of the first culmination of plasmonics in 1968, when surface plasmons become a field of optics. The coupling of light with the surface plasmon leads to the surface plasmon polariton (SPP). Therefore, the authors chose to associate historical insight (not avoiding a personal touch), a modern mathematical formulation of the excitation of the SPP by attenuated total reflection (ATR), considered as well understood since decades, and experimental applications since 1969, including recent developments.

Single-shot quantum nondemolition measurement of a quantum-dot electron spin using cavity exciton-polaritons

Science.gov (United States)

Puri, Shruti; McMahon, Peter L.; Yamamoto, Yoshihisa

2014-10-01

We propose a scheme to perform single-shot quantum nondemolition (QND) readout of the spin of an electron trapped in a semiconductor quantum dot (QD). Our proposal relies on the interaction of the QD electron spin with optically excited, quantum well (QW) microcavity exciton-polaritons. The spin-dependent Coulomb exchange interaction between the QD electron and cavity polaritons causes the phase and intensity response of left circularly polarized light to be different than that of right circularly polarized light, in such a way that the QD electron's spin can be inferred from the response to a linearly polarized probe reflected or transmitted from the cavity. We show that with careful device design it is possible to essentially eliminate spin-flip Raman transitions. Thus a QND measurement of the QD electron spin can be performed within a few tens of nanoseconds with fidelity ˜99.95%. This improves upon current optical QD spin readout techniques across multiple metrics, including speed and scalability.

Time-domain analysis of surface-plasmon-polariton propagation in Ag nano-films using a generalized polarization approach

KAUST Repository

Al-Jabr, Ahmad; Alsunaidi, Mohammad A.

2010-01-01

A time-domain analysis of the propagation properties of surface-plasmon-polaritons (SPP) in Silver nanostructures is presented. The analysis is based on a simulation algorithm that unifies the formulation of different dispersion models and multi

Tamm-plasmon polaritons in one-dimensional photonic quasi-crystals.

Science.gov (United States)

Shukla, Mukesh Kumar; Das, Ritwick

2018-02-01

We present an investigation to ascertain the existence of Tamm-plasmon-polariton-like modes in one-dimensional (1D) quasi-periodic photonic systems. Photonic bandgap formation in quasi-crystals is essentially a consequence of long-range periodicity exhibited by multilayers and, thus, it can be explained using the dispersion relation in the Brillouin zone. Defining a "Zak"-like topological phase in 1D quasi-crystals, we propose a recipe to ascertain the existence of Tamm-like photonic surface modes in a metal-terminated quasi-crystal lattice. Additionally, we also explore the conditions of efficient excitation of such surface modes along with their dispersion characteristics.

Many-body dynamics of driven-dissipative Rydberg cavity polaritons

Science.gov (United States)

Pistorius, Tim; Fan, Jingtao; Weimer, Hendrik

2017-04-01

The usage of photons as long-range information carriers has greatly increased the interest in systems with nonlinear optical properties in recent years. The nonlinearity is easily achievable in Rydberg mediums through the strong van der Waals interaction which makes them one of the best candidates for such a system. Here, we propose a way to analyze the steady state solutions of a Rydberg medium in a cavity through the combination of the variational principle for open quantum systems and the P-distribution of the density matrix. To get a better understanding of the many-body-dynamics a transformation into the polariton picture is performed and investigated. Volkswagen Foundation, Deutsche Forschungsgemeinschaft.

Harmonics Generation by Surface Plasmon Polaritons on Single Nanowires.

Science.gov (United States)

de Hoogh, Anouk; Opheij, Aron; Wulf, Matthias; Rotenberg, Nir; Kuipers, L

2016-08-17

We present experimental observations of visible wavelength second- and third-harmonic generation on single plasmonic nanowires of variable widths. We identify that near-infrared surface plasmon polaritons, which are guided along the nanowire, act as the source of the harmonics generation. We discuss the underlying mechanism of this nonlinear process, using a combination of spatially resolved measurements and numerical simulations to show that the visible harmonics are generated via a combination of both local and propagating plasmonic modes. Our results provide the first demonstration of nanoscale nonlinear optics with guided, propagating plasmonic modes on a lithographically defined chip, opening up new routes toward integrated optical circuits for information processing.

Time-resolved detection of surface plasmon polaritons with a scanning tunneling microscope

DEFF Research Database (Denmark)

Keil, Ulrich Dieter Felix; Ha, T.; Jensen, Jacob Riis

1998-01-01

We present the time-resolved detection of surface plasmon polaritons with an STM. The results indicate that the time resolved signal is due to rectification of coherently superimposed plasmon voltages. The comparison with differential reflectivity measurements shows that the tip itself influences...... the decay of the plasmon-field coherence. Generation of the measured signal at the tunneling junction offers the possibility to observe ultrafast effects with a spatial resolution determined by the tunneling junction...

Build up of off-diagonal long-range order in microcavity exciton-polaritons across the parametric threshold

DEFF Research Database (Denmark)

Spano, R.; Cuadra, J.; Lingg, C.

2013-01-01

We report an experimental study of the spontaneous spatial and temporal coherence of polariton condensates generated in the optical parametric oscillator configuration, below and at the parametric threshold, and as a function of condensate area. Above the threshold we obtain very long coherence t...

Large-area uniform periodic microstructures on fused silica induced by surface phonon polaritons and incident laser

Science.gov (United States)

Zhang, Chuanchao; Liao, Wei; Zhang, Lijuan; Jiang, Xiaolong; Chen, Jing; Wang, Haijun; Luan, Xiaoyu; Yuan, Xiaodong

2018-06-01

A simple and convenient means to self-organize large-area uniform periodic microstructures on fused silica by using multiple raster scans of microsecond CO2 laser pulses with beam spot overlapping at normal incidence is presented, which is based on laser-induced periodic surface structures (LIPSS) attributed to the interference between surface phonon polaritons and incident CO2 laser. The evolution of fused silica surface morphologies with increasing raster scans indicates that the period of microstructures changed from 10.6 μm to 9 μm and the profiles of microstructures changed from a sinusoidal curve to a half-sinusoidal shape. Numerical simulation results suggest that the formation of the half-sinusoidal profile is due to the exponential relationship between evaporation rate and surface temperature inducing by the intensive interference between surface phonon polaritons and incident laser. The fabricated uniform periodic microstructures show excellent structural color effect in both forward-diffraction and back-diffraction.

Waveguide-Plasmon Polaritons Enhance Transverse Magneto-Optical Kerr Effect

Directory of Open Access Journals (Sweden)

Lars E. Kreilkamp

2013-11-01

Full Text Available Magneto-optical effects in ferrimagnetic or ferromagnetic materials are usually too weak for potential applications. The transverse magneto-optical Kerr effect (TMOKE in ferromagnetic films is typically on the order of 0.1%. Here, we demonstrate experimentally the enhancement of TMOKE due to the interaction of particle plasmons in gold nanowires with a photonic waveguide consisting of magneto-optical material, where hybrid waveguide-plasmon polaritons are excited. We achieve a large TMOKE that modulates the transmitted light intensity by 1.5%, accompanied by high transparency of the system. Our concept may lead to novel devices of miniaturized photonic circuits and switches, which are controllable by an external magnetic field.

Bulk-like-phonon polaritons in one-dimensional photonic superlattices

Science.gov (United States)

Gómez-Urrea, H. A.; Duque, C. A.; Mora-Ramos, M. E.

2017-05-01

We investigate the properties of a one-dimensional photonic superlattice made of alternating layers of air and wurtzite aluminum nitride. The Maxwell equations are solved for any admissible values of the angle of incidence by means of the transfer matrix formalism. The band structure of the frequency spectrum is obtained, as well as the density of states and transmittance associated to both the TM and TE modes. The dispersion relations indicate that for oblique incidence and TM modes there is a component of the electric field oriented along the growth direction of the structure that couples with the longitudinal optical phonon oscillations of the aluminum nitride thus leading to the appearance of longitudinal phonon polaritons in the system.

Direct imaging of slow, stored and stationary EIT polaritons

Science.gov (United States)

Campbell, Geoff T.; Cho, Young-Wook; Su, Jian; Everett, Jesse; Robins, Nicholas; Lam, Ping Koy; Buchler, Ben

2017-09-01

Stationary and slow light effects are of great interest for quantum information applications. Using laser-cooled Rb87 atoms, we performed side imaging of our atomic ensemble under slow and stationary light conditions, which allows direct comparison with numerical models. The polaritons were generated using electromagnetically induced transparency (EIT), with stationary light generated using counter-propagating control fields. By controlling the power ratio of the two control fields, we show fine control of the group velocity of the stationary light. We also compare the dynamics of stationary light using monochromatic and bichromatic control fields. Our results show negligible difference between the two situations, in contrast to previous work in EIT-based systems.

Surface plasmon polariton Akhmediev Breather in a dielectric-metal-dielectric geometry with subwavelength thickness

Science.gov (United States)

Devi, Koijam Monika; Porsezian, K.; Sarma, Amarendra K.

2018-05-01

We report Akhmediev Breather solutions in a nonlinear multilayer structure comprising of a metal sandwiched between two semi-infinite dielectric layers with subwavelength thickness. These nonlinear solutions inherit the properties of Surface plasmon polaritons and its dynamics is governed by the Nonlinear Schrodinger equation. The breather evolution is studied for specific values of nonlinear and dispersion parameters. An experimental scheme to observe these breathers is also proposed.

Resonant photon tunneling via surface plasmon polaritons through one-dimensional metal-dielectric metamaterials

OpenAIRE

Tomita, Satoshi; Yokoyama, Takashi; Yanagi, Hisao; Wood, Ben; Pendry, John B.; Fujii, Minoru; Hayashi, Shinji

2008-01-01

We report resonant photon tunneling (RPT) through onedimensional metamaterials consisting of alternating layers of metal and dielectric. RPT via a surface plasmon polariton state permits evanescent light waves with large wavenumbers to be conveyed through the metamaterial. This is the mechanism for sub-wavelength imaging recently demonstrated with a super-lens. Furthermore, we find that the RPT peak is shifted from the reflectance dip with increasing the number of Al layers, indicating that t...

Neutron scattering on equilibrium and nonequilibrium phonons, excitons and polaritons

International Nuclear Information System (INIS)

Broude, V.L.; Sheka, E.F.

1978-01-01

A number of problems of solid-state physics representing interest for neutron spectroscopy of future is considered. The development of the neutron inelastic scattering spectroscopy (neutron spectroscopy of equilibrium phonons) is discussed with application to nuclear dynamics of crystals in the thermodynamic equilibrium. The results of high-flux neutron source experiments on molecular crystals are presented. The advantages of neutron inelastic scattering over optical spectroscopy are discussed. The spectroscopy of quasi-equilibrium and non-equilibrium quasi-particles is discussed. In particular, the neutron scattering on polaritons, excitons in thermal equilibrium and production of light-excitons are considered. The problem of the possibility of such experiments is elucidated

Size dependent emission stimulation in ZnO nanosheets

International Nuclear Information System (INIS)

Torchynska, T.V.; El Filali, B.

2014-01-01

Photoluminescence (PL), X ray diffraction (XRD) and Raman scattering have been studied in crystalline ZnO nanosheets (NSs) of different sizes, estimated by scanning electronic microscopy (SEM). ZnO NSs with the size from the range of 60–600 nm were created by the electrochemical (anodization) method and followed thermal annealing at 400 °C for 2 h in ambient air. XRD study confirms the wurtzite structure of ZnO NSs and has revealed that the lattice parameters increase monotonically with decreasing NS sizes. Simultaneously the intensity of a set of Raman peaks increases and Raman peaks shift into the low energy range. The surface phonon has been detected in smallest size ZnO NSs. Two types of PL bands deal with a set of phonon replicas of free excitons and the defect related emission have been detected in ZnO NSs. The intensity enhancement of exciton- and defect-related PL bands with decreasing ZnO NS sizes has been detected. The intensity stimulation of exciton-related PL bands is attributed to the realization of the week confinement and the exciton-light coupling with the formation of polariton in small size ZnO NSs of 67–170 nm. The intensity rising of defect-related PL bands is attributed to the concentration enlargement of surface defects when the surface to volume ration increases at decreasing ZnO NS sizes. Numerical simulations of radiative lifetimes and exciton radiative recombination rates in ZnO NSs for different emission wavelengths have been done using the exciton-light coupling model. Then the experimental and numerically simulated PL results have been compared and discussed. - Highlights: • Optical and structural investigations of the ZnO nanosheets with the sizes 60–600 nm. • The enlargement of interplanar distances in the wurtzite ZnO crystal lattice is detected. • The change of optic phonon energy and surface phonon appearing are reveled. • ZnO emission stimulation at the week confinement and electron-light coupling with the

Terahertz spoof surface-plasmon-polariton subwavelength waveguide

KAUST Repository

Zhang, Ying; Xu, Yuehong; Tian, Chunxiu; Xu, Quan; Zhang, Xueqian; Li, Yanfeng; Zhang, Xixiang; Han, Jiaguang; Zhang, Weili

2017-01-01

Surface plasmon polaritons (SPPs) with the features of subwavelength confinement and strong enhancements have sparked enormous interest. However, in the terahertz regime, due to the perfect conductivities of most metals, it is hard to realize the strong confinement of SPPs, even though the propagation loss could be sufficiently low. One main approach to circumvent this problem is to exploit spoof SPPs, which are expected to exhibit useful subwavelength confinement and relative low propagation loss at terahertz frequencies. Here we report the design, fabrication, and characterization of terahertz spoof SPP waveguides based on corrugated metal surfaces. The various waveguide components, including a straight waveguide, an S-bend waveguide, a Y-splitter, and a directional coupler, were experimentally demonstrated using scanning near-field terahertz microscopy. The proposed waveguide indeed enables propagation, bending, splitting, and coupling of terahertz SPPs and thus paves a new way for the development of flexible and compact plasmonic circuits operating at terahertz frequencies. (C) 2017 Chinese Laser Press

Terahertz spoof surface-plasmon-polariton subwavelength waveguide

KAUST Repository

Zhang, Ying

2017-12-11

Surface plasmon polaritons (SPPs) with the features of subwavelength confinement and strong enhancements have sparked enormous interest. However, in the terahertz regime, due to the perfect conductivities of most metals, it is hard to realize the strong confinement of SPPs, even though the propagation loss could be sufficiently low. One main approach to circumvent this problem is to exploit spoof SPPs, which are expected to exhibit useful subwavelength confinement and relative low propagation loss at terahertz frequencies. Here we report the design, fabrication, and characterization of terahertz spoof SPP waveguides based on corrugated metal surfaces. The various waveguide components, including a straight waveguide, an S-bend waveguide, a Y-splitter, and a directional coupler, were experimentally demonstrated using scanning near-field terahertz microscopy. The proposed waveguide indeed enables propagation, bending, splitting, and coupling of terahertz SPPs and thus paves a new way for the development of flexible and compact plasmonic circuits operating at terahertz frequencies. (C) 2017 Chinese Laser Press

Effect of chemical and isotope substitution in LiH crystals on polariton emission

International Nuclear Information System (INIS)

Plekhanov, V.G.

1994-01-01

Measurements of fine structure of phonon-free line of free exciton radiation in mixed crystals LiH x F 1-x (o x D 1-x (O x F 1-x crystals a sharp increase in the intensity of phonon-free line of free exciton radiation as compared with its LO repetitions is observed. The experimental results suggest manifestation of polariton effects in mixed crystals produced on the basis of lithium hydride. 17 refs., 2 figs

Electronic detection of surface plasmon polaritons by metal-oxide-silicon capacitor

Directory of Open Access Journals (Sweden)

Robert E. Peale

2016-09-01

Full Text Available An electronic detector of surface plasmon polaritons (SPPs is reported. SPPs optically excited on a metal surface using a prism coupler are detected by using a close-coupled metal-oxide-silicon (MOS capacitor. Incidence-angle dependence is explained by Fresnel transmittance calculations, which also are used to investigate the dependence of photo-response on structure dimensions. Electrodynamic simulations agree with theory and experiment and additionally provide spatial intensity distributions on and off the SPP excitation resonance. Experimental dependence of the photoresponse on substrate carrier type, carrier concentration, and back-contact biasing is qualitatively explained by simple theory of MOS capacitors.

Dynamics of vortices in polariton quantum fluids : From full vortices, to half vortices and vortex pairs

Science.gov (United States)

Deveaud-Plédran, Benoit

2012-02-01

Polariton quantum fluids may be created both spontaneously through a standard phase transition towards a Bose Einstein condensate, or may be resonantly driven with a well-defined speed. Thanks to the photonic component of polaritons, the properties of the quantum fluid may be accessed rather directly with in particular the possibility of detained interferometric studies. Here, I will detail the dynamics of vortices, obtained with a picosecond time resolution, in different configurations, with in particular their phase dynamics. I will show in particular the dynamics the dynamics of spontaneous creation of a vortex, the dissociation of a full vortex into two half vortices as well as the dynamics of the dissociation of a dark soliton line into a street of pairs of vortices. Work done at EPFL by a dream team of Postdocs PhD students and collaborators: K. Lagoudakis, G. Nardin, T. Paraiso, G. Grosso, F. Manni, Y L'eger, M. Portella Oberli, F. Morier-Genoud and the help of our friend theorists V, Savona, M. Vouters and T. Liew.

Bloch-Surface-Polariton-Based Hybrid Nanowire Structure for Subwavelength, Low-Loss Waveguiding

Directory of Open Access Journals (Sweden)

Weijing Kong

2018-03-01

Full Text Available Surface plasmon polaritons (SPPs have been thoroughly studied in the past decades for not only sensing but also waveguiding applications. Various plasmonic device structures have been explored due to their ability to confine their optical mode to the subwavelength level. However, with the existence of metal, the large ohmic loss limits the propagation distance of the SPP and thus the scalability of such devices. Therefore, different hybrid waveguides have been proposed to overcome this shortcoming. Through fine tuning of the coupling between the SPP and a conventional waveguide mode, a hybrid mode could be excited with decent mode confinement and extended propagation distance. As an effective alternative of SPP, Bloch surface waves have been re-investigated more recently for their unique advantages. As is supported in all-dielectric structures, the optical loss for the Bloch surface wave is much lower, which stands for a much longer propagating distance. Yet, the confinement of the Bloch surface wave due to the reflections and refractions in the multilayer structure is not as tight as that of the SPP. In this work, by integrating a periodic multilayer structure that supports the Bloch surface wave with a metallic nanowire structure, a hybrid Bloch surface wave polariton could be excited. With the proposed hybrid nanowire structure, a hybrid mode is demonstrated with the deep subwavelength mode confinement and a propagation distance of tens of microns.

Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

KAUST Repository

Govyadinov, Alexander A.

2017-07-14

Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope.

Science.gov (United States)

Govyadinov, Alexander A; Konečná, Andrea; Chuvilin, Andrey; Vélez, Saül; Dolado, Irene; Nikitin, Alexey Y; Lopatin, Sergei; Casanova, Fèlix; Hueso, Luis E; Aizpurua, Javier; Hillenbrand, Rainer

2017-07-21

Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

Probing low-energy hyperbolic polaritons in van der Waals crystals with an electron microscope

KAUST Repository

Govyadinov, Alexander A.; Konečná , Andrea; Chuvilin, Andrey; Vé lez, Saü l; Dolado, Irene; Nikitin, Alexey Y.; Lopatin, Sergei; Casanova, Fè lix; Hueso, Luis E.; Aizpurua, Javier; Hillenbrand, Rainer

2017-01-01

Van der Waals materials exhibit intriguing structural, electronic, and photonic properties. Electron energy loss spectroscopy within scanning transmission electron microscopy allows for nanoscale mapping of such properties. However, its detection is typically limited to energy losses in the eV range-too large for probing low-energy excitations such as phonons or mid-infrared plasmons. Here, we adapt a conventional instrument to probe energy loss down to 100 meV, and map phononic states in hexagonal boron nitride, a representative van der Waals material. The boron nitride spectra depend on the flake thickness and on the distance of the electron beam to the flake edges. To explain these observations, we developed a classical response theory that describes the interaction of fast electrons with (anisotropic) van der Waals slabs, revealing that the electron energy loss is dominated by excitation of hyperbolic phonon polaritons, and not of bulk phonons as often reported. Thus, our work is of fundamental importance for interpreting future low-energy loss spectra of van der Waals materials.Here the authors adapt a STEM-EELS system to probe energy loss down to 100 meV, and apply it to map phononic states in hexagonal boron nitride, revealing that the electron loss is dominated by hyperbolic phonon polaritons.

Localized surface plasmon polariton resonance in holographically structured Al-doped ZnO

Energy Technology Data Exchange (ETDEWEB)

George, David; Lowell, David; Mao, Michelle; Hassan, Safaa; Philipose, Usha [Department of Physics and Center for Advanced Research and Technology, University of North Texas, Denton, Texas 76203 (United States); Li, Li; Jiang, Yan; Cui, Jingbiao [Department of Physics and Materials Science, University of Memphis, Memphis, Tennessee 38152 (United States); Ding, Jun; Zhang, Hualiang [Department of Electrical and Computer Engineering, University of Massachusetts Lowell, Lowell, Massachusetts 01854 (United States); Lin, Yuankun [Department of Physics and Center for Advanced Research and Technology, University of North Texas, Denton, Texas 76203 (United States); Department of Electrical Engineering, University of North Texas, Denton, Texas 76203 (United States)

2016-07-28

In this paper, we studied the localized surface plasmon polariton (SPP) resonance in hole arrays in transparent conducting aluminum-doped zinc oxide (AZO). CMOS-compatible fabrication process was demonstrated for the AZO devices. The localized SPP resonance was observed and confirmed by electromagnetic simulations. Using a standing wave model, the observed SPP was dominated by the standing-wave resonance along (1,1) direction in square lattices. This research lays the groundwork for a fabrication technique that can contribute to the core technology of future integrated photonics through its extension into tunable conductive materials.

Phase-locking in quantum and classical oscillators: polariton condensates, lasers, and arrays of Josephson junctions

OpenAIRE

EASTHAM, PAUL

2003-01-01

PUBLISHED We connect three phenomena in which a coherent electromagnetic field could be generated: polariton condensation, phase-locking in arrays of underdamped Josephson junctions, and lasing. All these phenomena have been described using Dicke-type models of spins coupled to a single photon mode. These descriptions may be distinguished by whether the spins are quantum or classical, and whether they are strongly or weakly damped.

Dynamics of polaritons in semiconductor microcavities near instability thresholds

International Nuclear Information System (INIS)

He, Peng-Bin

2012-01-01

A theoretical study is presented on the dynamics of polaritons in semiconductor microcavities near parametric instability thresholds. With upward or downward ramp of optical pump, different instability modes emerge in parameter space defined by damping and detuning. According to these modes, stationary short-wave, stationary periodic, oscillatory periodic, and oscillatory uniform parametric instabilities are distinguished. By multiple scale expansion, the dynamics near threshold can be described by a critical mode with a slowly varying amplitude for the last three instabilities. Furthermore, it is found that the evolutions of their amplitudes are governed by real or complex Ginzburg–Landau equations. -- Highlights: ► Phase diagrams for different instability in extended parameter space. ► Different instability modes near thresholds. ► Different envelop equations near thresholds obtained by multi-scale expansion.

Guiding spoof surface plasmon polaritons by infinitely thin grooved metal strip

Directory of Open Access Journals (Sweden)

Xiang Wan

2014-04-01

Full Text Available In this paper, the propagation characteristics of spoof surface plasmon polaritons (SPPs on infinitely thin corrugated metal strips are theoretically analyzed. Compared with the situations of infinitely thick lateral thickness, the infinitely thin lateral thickness leads to lower plasma frequency according to the analyses. The propagation lengths and the binding capacity of the spoof SPPs are evaluated based on the derived dispersion equation. The effects of different lateral thicknesses are also investigated. At the end, a surface wave splitter is presented using infinitely thin corrugated metal strip. Other functional planar or flexible devices can also be designed using these metal strips in microwave or terahertz regimes.

Circular polarization analyzer with polarization tunable focusing of surface plasmon polaritons

Energy Technology Data Exchange (ETDEWEB)

Wang, Sen; Zhang, Yan, E-mail: yzhang@mail.cnu.edu.cn [Department of Physics, Harbin Institute of Technology, Harbin 150001 (China); Beijing Key Laboratory for Metamaterials and Devices, and Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Department of Physics, Capital Normal University, Beijing 100048 (China); Wang, Xinke [Beijing Key Laboratory for Metamaterials and Devices, and Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Department of Physics, Capital Normal University, Beijing 100048 (China); Kan, Qiang [State Key Laboratory for Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083 (China); Qu, Shiliang [Optoelectronics Department, Harbin Institute of Technology at Weihai, Weihai 264209 (China)

2015-12-14

A practical circular polarization analyzer (CPA) that can selectively focus surface plasmon polaritons (SPPs) at two separate locations, according to the helicity of the circularly polarized light, is designed and experimentally verified in the terahertz frequency range. The CPA consists of fishbone-slit units and is designed using the simulated annealing algorithm. By differentially detecting the intensities of the two SPPs focuses, the helicity of the incident circularly polarized light can be obtained and the CPA is less vulnerable to the noise of incident light. The proposed device may also have wide potential applications in chiral SPPs photonics and the analysis of chiral molecules in biology.

A corrugated perfect magnetic conductor surface supporting spoof surface magnon polaritons.

Science.gov (United States)

Liu, Liang-liang; Li, Zhuo; Gu, Chang-qing; Ning, Ping-ping; Xu, Bing-zheng; Niu, Zhen-yi; Zhao, Yong-jiu

2014-05-05

In this paper, we demonstrate that spoof surface magnon polaritons (SSMPs) can propagate along a corrugated perfect magnetic conductor (PMC) surface. From duality theorem, the existence of surface electromagnetic modes on corrugated PMC surfaces are manifest to be transverse electric (TE) mode compared with the transverse magnetic (TM) mode of spoof surface plasmon plaritons (SSPPs) excited on corrugated perfect electric conductor surfaces. Theoretical deduction through modal expansion method and simulation results clearly verify that SSMPs share the same dispersion relationship with the SSPPs. It is worth noting that this metamaterial will have more similar properties and potential applications as the SSPPs in large number of areas.

Surface and bulk polaritons in a PML-type magnetoelectric multiferroic with canted spins: TE and TM polarization

Energy Technology Data Exchange (ETDEWEB)

Gunawan, V; Stamps, R L, E-mail: slamev01@student.uwa.edu.au [School of Physics M013, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009 (Australia)

2011-03-16

We present a theory for surface polaritons on ferroelectric-antiferromagnetic materials with canted spin structure. A small uniform canted moment is allowed, resulting in a weak ferromagnetism directed in the plane parallel to the surface. Surface and bulk polariton modes for a semi-infinite film are calculated for the case of transverse electric (TE) and transverse magnetic (TM) polarization. Example results are presented using parameters appropriate for BaMnF{sub 4}. We find that the surface modes are non-reciprocal for the TE polarization due to the magnetoelectric interaction, and the non-reciprocity can be controlled by an applied electric field. Example results for attenuated total reflection (ATR) are calculated. The magnetoelectric interaction also gives rise to 'leaky' surface modes in the case of TM polarization. These are pseudo-surface waves that exist in the pass band, and dissipate energy into the bulk of the material. We show that these pseudo-surface mode frequencies and properties can be modified by temperature and the application of external electric or magnetic fields.

Resonant photon tunneling via surface plasmon polaritons through one-dimensional metal-dielectric metamaterials.

Science.gov (United States)

Tomita, Satoshi; Yokoyama, Takashi; Yanagi, Hisao; Wood, Ben; Pendry, John B; Fujii, Minoru; Hayashi, Shinji

2008-06-23

We report resonant photon tunneling (RPT) through one-dimensional metamaterials consisting of alternating layers of metal and dielectric. RPT via a surface plasmon polariton state permits evanescent light waves with large wavenumbers to be conveyed through the metamaterial. This is the mechanism for sub-wavelength imaging recently demonstrated with a super-lens. Furthermore, we find that the RPT peak is shifted from the reflectance dip with increasing the number of Al layers, indicating that the shift is caused by the losses in the RPT.

2D surface optical lattice formed by plasmon polaritons with application to nanometer-scale molecular deposition.

Science.gov (United States)

Yin, Yanning; Xu, Supeng; Li, Tao; Yin, Yaling; Xia, Yong; Yin, Jianping

2017-08-10

Surface plasmon polaritons, due to their tight spatial confinement and high local intensity, hold great promises in nanofabrication which is beyond the diffraction limit of conventional lithography. Here, we demonstrate theoretically the 2D surface optical lattices based on the surface plasmon polariton interference field, and the potential application to nanometer-scale molecular deposition. We present the different topologies of lattices generated by simple configurations on the substrate. By explicit theoretical derivations, we explain their formation and characteristics including field distribution, periodicity and phase dependence. We conclude that the topologies can not only possess a high stability, but also be dynamically manipulated via changing the polarization of the excitation laser. Nanometer-scale molecular deposition is simulated with these 2D lattices and discussed for improving the deposition resolution. The periodic lattice point with a width resolution of 33.2 nm can be obtained when the fullerene molecular beam is well-collimated. Our study can offer a superior alternative method to fabricate the spatially complicated 2D nanostructures, with the deposition array pitch serving as a reference standard for accurate and traceable metrology of the SI length standard.

Frequency-tunable terahertz wave generation via excitation of phonon-polaritons in GaP

CERN Document Server

Tanabé, T; Nishizawa, J I; Saitô, K; Kimura, T

2003-01-01

High-power, wide-frequency-tunable terahertz waves were generated based on difference-frequency generation in GaP crystals with small-angle noncollinear phase matching. The tunable frequency range was as wide as 0.5-7 THz, and the peak power remained high, near 100 mW, over most of the frequency region. The tuning properties were well described by the dispersion relationship for the phonon-polariton mode of GaP up to 6 THz. We measured the spectra of crystal polyethylene and crystal quartz with high resolution using this THz-wave source.

Gap plasmon resonator arrays for unidirectional launching and shaping of surface plasmon polaritons

Energy Technology Data Exchange (ETDEWEB)

Lei, Zeyu; Yang, Tian, E-mail: tianyang@sjtu.edu.cn [State Key Laboratory of Advanced Optical Communication Systems and Networks, Key Laboratory for Thin Film and Microfabrication of the Ministry of Education, UM-SJTU Joint Institute, Shanghai Jiao Tong University, Shanghai 200240 (China)

2016-04-18

We report the design and experimental realization of a type of miniaturized device for efficient unidirectional launching and shaping of surface plasmon polaritons (SPPs). Each device consists of an array of evenly spaced gap plasmon resonators with varying dimensions. Particle swarm optimization is used to achieve a theoretical two-dimensional launching efficiency of about 51%, under the normal illumination of a 5-μm waist Gaussian beam at 780 nm. By modifying the wavefront of the SPPs, unidirectional SPPs with focused, Bessel, and Airy profiles are launched and imaged with leakage radiation microscopy.

Photonic-band-gap engineering for volume plasmon polaritons in multiscale multilayer hyperbolic metamaterials

DEFF Research Database (Denmark)

Zhukovsky, Sergei; Orlov, Alexey A.; Babicheva, Viktoriia E.

2014-01-01

) on a larger, wavelength scale, the propagation of volume plasmon polaritons in the resulting multiscale hyperbolic metamaterials is subject to photonic-band-gap phenomena. A great degree of control over such plasmons can be exerted by varying the superstructure geometry. When this geometry is periodic, stop......, fractal Cantor-like multiscale metamaterials are found to exhibit characteristic self-similar spectral signatures in the volume plasmonic band. Multiscale hyperbolic metamaterials are shown to be a promising platform for large-wave-vector bulk plasmonic waves, whether they are considered for use as a kind...

Frequency-tunable terahertz wave generation via excitation of phonon-polaritons in GaP

International Nuclear Information System (INIS)

Tanabe, Tadao; Suto, Ken; Nishizawa, Jun-ichi; Saito, Kyosuke; Kimura, Tomoyuki

2003-01-01

High-power, wide-frequency-tunable terahertz waves were generated based on difference-frequency generation in GaP crystals with small-angle noncollinear phase matching. The tunable frequency range was as wide as 0.5-7 THz, and the peak power remained high, near 100 mW, over most of the frequency region. The tuning properties were well described by the dispersion relationship for the phonon-polariton mode of GaP up to 6 THz. We measured the spectra of crystal polyethylene and crystal quartz with high resolution using this THz-wave source

Localized surface phonon polariton resonances in polar gallium nitride

Energy Technology Data Exchange (ETDEWEB)

Feng, Kaijun, E-mail: kfeng@nd.edu; Islam, S. M.; Verma, Jai; Hoffman, Anthony J. [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); Streyer, William; Wasserman, Daniel [Department of Electrical and Computer Engineering, University of Illinois Urbana-Champaign, Urbana, Illinois 61801 (United States); Jena, Debdeep [Department of Electrical Engineering, University of Notre Dame, Notre Dame, Indiana 46556 (United States); School of Electrical and Computer Engineering, Cornell University, Ithaca, New York 14850 (United States)

2015-08-24

We demonstrate the excitation of localized surface phonon polaritons in an array of sub-diffraction pucks fabricated in an epitaxial layer of gallium nitride (GaN) on a silicon carbide (SiC) substrate. The array is characterized via polarization- and angle-dependent reflection spectroscopy in the mid-infrared, and coupling to several localized modes is observed in the GaN Reststrahlen band (13.4–18.0 μm). The same structure is simulated using finite element methods and the charge density of the modes are studied; transverse dipole modes are identified for the transverse electric and magnetic polarizations and a quadrupole mode is identified for the transverse magnetic polarization. The measured mid-infrared spectrum agrees well with numerically simulated spectra. This work could enable optoelectronic structures and devices that support surface modes at mid- and far-infrared wavelengths.

Coupled polaritonic band gaps in the anisotropic piezoelectric superlattices

Science.gov (United States)

Tang, Zheng-Hua; Jiang, Zheng-Sheng; Chen, Tao; Jiang, Chun-Zhi; Lei, Da-Jun; Huang, Jian-Quan; Qiu, Feng; Yao, Min; Huang, Xiao-Yi

2018-01-01

Anisotropic piezoelectric superlattices (APSs) with the periodic arrangement of polarized anisotropic piezoelectric domains in a certain direction are presented, in which the coupled polaritonic band gaps (CPBGs) can be obtained in the whole Brillouin Zone and the maximum relative bandwidth (band-gap sizes divided by their midgap frequencies) of 5.1% can be achieved. The general characteristics of the APSs are similar to those of the phononic crystals composed of two types of materials, with the main difference being the formation mechanism of the CPBGs, which originate from the couplings between lattice vibrations along two different directions and electromagnetic waves rather than from the periodical modulation of density and elastic constants. In addition, there are no lattice mismatches because the APSs are made of the same material. Thus, the APSs can also be extended to the construction of novel acousto-optic devices.

Compact and broadband directional coupling and demultiplexing in dielectric-loaded surface plasmon polariton waveguides based on the multimode interference effect

DEFF Research Database (Denmark)

Zhu, Zhihong; García Ortíz, César Eduardo; Han, Zhanghua

2013-01-01

We theoretically, numerically, and experimentally demonstrate that a directional coupling function can be realized with a wide bandwidth (greater than 200 nm) in dielectric-loaded surface plasmon polariton waveguides based on the multimode interference effect. The functional size of the structure...

Engineering magnetic polariton system with distributed coefficients: Applications to soliton management

International Nuclear Information System (INIS)

Kuetche, Victor K.; Nguepjouo, Francis T.; Kofane, Timoleon C.

2014-01-01

In the wake of the recent design of a powerful method for generating higher-dimensional evolution systems with distributed coefficients Kuetche (2014) [15] illustrated on the dynamics of the current-fed membrane of zero Young’s modulus, we construct the general Lax-representation of a new higher-dimensional coupled evolution equations with varying coefficients. Discussing the physical meanings of these equations, we show that the coupled system above describes the propagation of magnetic polaritons within saturated ferrites, resulting structurally from the fast-near adiabatic magnetization dynamics combined to the Maxwell’s equations. Accordingly, we address some practical issues of the nonautonomous soliton managements underlying in the fast remagnetization process of data inputs within magnetic memory devices

Analysis of polariton dispersion in metal nanocomposite based novel superlattice system

Science.gov (United States)

DoniPon, V.; Joseph Wilson, K. S.; Malarkodi, A.

2018-06-01

The influence of metal nanoparticles in tuning the polaritonic gap in a novel piezoelectric superlattice is studied. Dielectric function of the metal nanoparticles is analyzed using Kawabata-Kubo effect and Drude's theory. The effective dielectric function of the nanocomposite system is studied using Maxwell Garnett approximation. Nanocomposite based LiTaO3 novel superlattice is formed by arranging the nanocomposite systems in such a way that their orientations are in the opposite direction. Hence there are two additional modes of propagation. The top most modes reflect the metal behavior of the nanoparticles. It is found that these modes of propagation vary with the filling factor. These additional modes of propagations can be exploited in the field of communication.

Manipulation of surface plasmon polariton propagation on isotropic and anisotropic two-dimensional materials coupled to boron nitride heterostructures

Energy Technology Data Exchange (ETDEWEB)

Inampudi, Sandeep; Nazari, Mina; Forouzmand, Ali; Mosallaei, Hossein, E-mail: hosseinm@coe.neu.edu [Department of Electrical and Computer Engineering, Northeastern University, 360 Huntington Ave., Boston, Massachusetts 02115 (United States)

2016-01-14

We present a comprehensive analysis of surface plasmon polariton dispersion characteristics associated with isotropic and anisotropic two-dimensional atomically thin layered materials (2D sheets) coupled to h-BN heterostructures. A scattering matrix based approach is presented to compute the electromagnetic fields and related dispersion characteristics of stacked layered systems composed of anisotropic 2D sheets and uniaxial bulk materials. We analyze specifically the surface plasmon polariton (SPP) dispersion characteristics in case of isolated and coupled two-dimensional layers with isotropic and anisotropic conductivities. An analysis based on residue theorem is utilized to identify optimum optical parameters (surface conductivity) and geometrical parameters (separation between layers) to maximize the SPP field at a given position. The effect of type and degree of anisotropy on the shapes of iso-frequency curves and propagation characteristics is discussed in detail. The analysis presented in this paper gives an insight to identify optimum setup to enhance the SPP field at a given position and in a given direction on the surface of two-dimensional materials.

Non-reciprocity and topology in optics: one-way road for light via surface magnon polariton.

Science.gov (United States)

Ochiai, Tetsuyuki

2015-02-01

We show how non-reciprocity and topology are used to construct an optical one-way waveguide in the Voigt geometry. First, we present a traditional approach of the one-way waveguide of light using surface polaritons under a static magnetic field. Second, we explain a recent discovery of a topological approach using photonic crystals with the magneto-optical coupling. Third, we present a combination of the two approaches, toward a broadband one-way waveguide in the microwave range.

Active tuning of surface phonon polariton resonances via carrier photoinjection

Science.gov (United States)

Dunkelberger, Adam D.; Ellis, Chase T.; Ratchford, Daniel C.; Giles, Alexander J.; Kim, Mijin; Kim, Chul Soo; Spann, Bryan T.; Vurgaftman, Igor; Tischler, Joseph G.; Long, James P.; Glembocki, Orest J.; Owrutsky, Jeffrey C.; Caldwell, Joshua D.

2018-01-01

Surface phonon polaritons (SPhPs) are attractive alternatives to infrared plasmonics for subdiffractional confinement of infrared light. Localized SPhP resonances in semiconductor nanoresonators are narrow, but that linewidth and the limited extent of the Reststrahlen band limit spectral coverage. To address this limitation, we report active tuning of SPhP resonances in InP and 4H-SiC by photoinjecting free carriers into nanoresonators, taking advantage of the coupling between the carrier plasma and optic phonons to blueshift SPhP resonances. We demonstrate state-of-the-art tuning figures of merit upon continuous-wave excitation (in InP) or pulsed excitation (in 4H-SiC). Lifetime effects cause the tuning to saturate in InP, and carrier redistribution leads to rapid (electronic and phononic excitations.

Ultracompact Refractive Index Sensor Based on Surface-Plasmon-Polariton Interference

International Nuclear Information System (INIS)

Wang Chen; Chen Jian-Jun; Tang Wei-Hua; Xiao Jing-Hua

2012-01-01

Using an ultracompact groove-slit-groove (GSG) structure, a refractive index sensor with a broadband response is proposed and experimentally demonstrated. Due to the interference of surface plasmon polaritons (SPPs), the transmission spectra in the GSG structure exhibit oscillation behaviors in a broad bandwidth, and they are quite sensitive to the refractive index of the surroundings. Based on the principle, the characteristics of its refractive index sensing are demonstrated experimentally. In the experiment, the structure is illuminated with a bulk light source (not a tightly focused light source) from the back side. This decreases the difficulty of the experimental measurement and can protect strong light sources from damaging the detection samples. Meanwhile, the whole structure of the sensor can be made more ultracompact without considering the influence of the incident waves

Integrated-Optics Components Utilizing Long-Range Surface Plasmon Polaritons

DEFF Research Database (Denmark)

Boltasseva, Alexandra

2004-01-01

This thesis describes a new class of components for integrated optics, based on the propagation of long-range surface plasmon polaritons (LR-SPPs) along metal stripes embedded in a dielectric. These novel components can provide guiding of light as well as coupling and splitting from/into a number...... with experimental results is obtained. The interaction of LR-SPPs with photonic crystals (PCs) is also studied. The PC structures are formed by periodic arrays of gold bumps that are arranged in a triangular lattice and placed symmetrically on both sides of a thin gold film. The LR-SPP transmission through...... of channels with good performance. Guiding of LR-SPPs along nm-thin and µm-wide gold stripes embedded in polymer is investigated in the wavelength range of 1250 – 1650 nm. LR-SPP guiding properties, such as the propagation loss and mode field diameter, are studied for different stripe widths and thicknesses...

Cavity Exciton-Polariton mediated, Single-Shot Quantum Non-Demolition measurement of a Quantum Dot Electron Spin

Science.gov (United States)

Puri, Shruti; McMahon, Peter; Yamamoto, Yoshihisa

2014-03-01

The quantum non-demolition (QND) measurement of a single electron spin is of great importance in measurement-based quantum computing schemes. The current single-shot readout demonstrations exhibit substantial spin-flip backaction. We propose a QND readout scheme for quantum dot (QD) electron spins in Faraday geometry, which differs from previous proposals and implementations in that it relies on a novel physical mechanism: the spin-dependent Coulomb exchange interaction between a QD spin and optically-excited quantum well (QW) microcavity exciton-polaritons. The Coulomb exchange interaction causes a spin-dependent shift in the resonance energy of the polarized polaritons, thus causing the phase and intensity response of left circularly polarized light to be different to that of the right circularly polarized light. As a result the QD electron's spin can be inferred from the response to a linearly polarized probe. We show that by a careful design of the system, any spin-flip backaction can be eliminated and a QND measurement of the QD electron spin can be performed within a few 10's of nanoseconds with fidelity 99:95%. This improves upon current optical QD spin readout techniques across multiple metrics, including fidelity, speed and scalability. National Institute of Informatics, 2-1-2 Hitotsubashi, Chiyoda-ku, Tokyo 101-8430, Japan.

Cavity magnon polaritons with lithium ferrite and three-dimensional microwave resonators at millikelvin temperatures

Science.gov (United States)

Goryachev, Maxim; Watt, Stuart; Bourhill, Jeremy; Kostylev, Mikhail; Tobar, Michael E.

2018-04-01

Single crystal lithium ferrite (LiFe) spheres of sub-mm dimension are examined at mK temperatures, microwave frequencies, and variable dc magnetic field, for use in hybrid quantum systems and condensed matter and fundamental physics experiments. Strong coupling regimes of the photon-magnon interaction (cavity magnon polariton quasiparticles) were observed with coupling strength of up to 250 MHz at 9.5 GHz (2.6%) with magnon linewidths of order 4 MHz (with potential improvement to sub-MHz values). We show that the photon-magnon coupling can be significantly improved and exceed that of the widely used yttrium iron garnet crystal, due to the small unit cell of LiFe, allowing twice the spins per unit volume. Magnon mode softening was observed at low dc fields and, combined with the normal Zeeman effect, creates magnon spin-wave modes that are insensitive to first-order magnetic-field fluctuations. This effect is observed in the Kittel mode at 5.5 GHz (and another higher order mode at 6.5 GHz) with a dc magnetic field close to 0.19 tesla. We show that if the cavity is tuned close to this frequency, the magnon polariton particles exhibit an enhanced range of strong coupling and insensitivity to magnetic field fluctuations with both first-order and second-order insensitivity to magnetic field as a function of frequency (double magic point clock transition), which could potentially be exploited in cavity QED experiments.

Exciton polaritons and their one-dimensional localization in disordered structure with quantum wells

International Nuclear Information System (INIS)

Kosobukin, V.A.

2003-01-01

The Anderson light localization theory by disordered ultrathin layers (quantum wells), uniform in lateral directions and featuring intrinsic optical resonances, is presented. A model of the layers with delta-function resonance dielectric polarization is suggested for solution of the multiple scattering problem. Allowance made for interlayer disorder, one- and two-phoron characteristics of electromagnetic transfer, i.e. average energy density and the length of the Anderson light localization were calculated in analytical form. It is shown that in disordered structure average electromagnetic field is propagated as polaritons formed due to excessive emission of excitons between the quantum wells [ru

Non-reciprocity and topology in optics: one-way road for light via surface magnon polariton

Science.gov (United States)

Ochiai, Tetsuyuki

2015-01-01

We show how non-reciprocity and topology are used to construct an optical one-way waveguide in the Voigt geometry. First, we present a traditional approach of the one-way waveguide of light using surface polaritons under a static magnetic field. Second, we explain a recent discovery of a topological approach using photonic crystals with the magneto-optical coupling. Third, we present a combination of the two approaches, toward a broadband one-way waveguide in the microwave range. PMID:27877739

Resonant scattering of surface plasmon polaritons by dressed quantum dots

Energy Technology Data Exchange (ETDEWEB)

Huang, Danhong; Cardimona, Dave [Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, New Mexico 87117 (United States); Easter, Michelle [Department of Mechanical Engineering, Stevens Institute of Technology, 1 Castle Point Terrace, Hoboken, New Jersey 07030 (United States); Gumbs, Godfrey [Department of Physics and Astronomy, Hunter College of the City University of New York, 695 Park Avenue, New York, New York 10065 (United States); Maradudin, A. A. [Department of Physics and Astronomy, University of California, Irvine, California 92697 (United States); Lin, Shawn-Yu [Department of Electrical, Computer and Systems Engineering, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180 (United States); Zhang, Xiang [Department of Mechanical Engineering, 3112 Etcheverry Hall, University of California at Berkeley, Berkeley, California 94720 (United States)

2014-06-23

The resonant scattering of surface plasmon-polariton waves (SPP) by embedded semiconductor quantum dots above the dielectric/metal interface is explored in the strong-coupling regime. In contrast to non-resonant scattering by a localized dielectric surface defect, a strong resonant peak in the spectrum of the scattered field is predicted that is accompanied by two side valleys. The peak height depends nonlinearly on the amplitude of SPP waves, reflecting the feedback dynamics from a photon-dressed electron-hole plasma inside the quantum dots. This unique behavior in the scattered field peak strength is correlated with the occurrence of a resonant dip in the absorption spectrum of SPP waves due to the interband photon-dressing effect. Our result on the scattering of SPP waves may be experimentally observable and applied to spatially selective illumination and imaging of individual molecules.

Low-loss, infrared and terahertz nanophotonics using surface phonon polaritons

Directory of Open Access Journals (Sweden)

Caldwell Joshua D.

2015-04-01

Full Text Available The excitation of surface-phonon-polariton (SPhP modes in polar dielectric crystals and the associated new developments in the field of SPhPs are reviewed. The emphasis of this work is on providing an understanding of the general phenomenon, including the origin of the Reststrahlen band, the role that optical phonons in polar dielectric lattices play in supporting sub-diffraction-limited modes and how the relatively long optical phonon lifetimes can lead to the low optical losses observed within these materials. Based on this overview, the achievements attained to date and the potential technological advantages of these materials are discussed for localized modes in nanostructures, propagating modes on surfaces and in waveguides and novel metamaterial designs, with the goal of realizing low-loss nanophotonics and metamaterials in the mid-infrared to terahertz spectral ranges.

Excitation of high density surface plasmon polariton vortex array

Science.gov (United States)

Kuo, Chun-Fu; Chu, Shu-Chun

2018-06-01

This study proposes a method to excite surface plasmon polariton (SPP) vortex array of high spatial density on metal/air interface. A doughnut vector beam was incident at four rectangularly arranged slits to excite SPP vortex array. The doughnut vector beam used in this study has the same field intensity distribution as the regular doughnut laser mode, TEM01* mode, but a different polarization distribution. The SPP vortex array is achieved through the matching of both polarization state and phase state of the incident doughnut vector beam with the four slits. The SPP field distribution excited in this study contains stable array-distributed time-varying optical vortices. Theoretical derivation, analytical calculation and numerical simulation were used to discuss the characteristics of the induced SPP vortex array. The period of the SPP vortex array induced by the proposed method had only half SPPs wavelength. In addition, the vortex number in an excited SPP vortex array can be increased by enlarging the structure.

Bessel Plasmon-Polaritons at the Boundaries of Metamaterials with Near-Zero Dielectric Constants

Science.gov (United States)

Kurilkina, S. N.; Belyi, V. N.; Kazak, N. S.; Binhussain, M. A.

2015-07-01

The conditions for and features of the excitation of Bessel plasmon-polaritons (BPP) are examined at the boundary of a hyperbolic metamaterial with a near-zero dielectric constant made of a dielectric matrix with metal nanorods embedded in it normal to its surface. This material is compared with BPP that have traditional surface plasmons. The effect of the absorption of the metamaterial on the excitation of BPP is studied. The possibility of changes in the direction of the radial energy fl ows in BPP excited at the surface of an isotropic medium, a hyperbolic metamaterial, is demonstrated and the conditions for these changes are determined.

Effect of magnetization boundary condition on cavity magnon polariton of YIG thin film

Science.gov (United States)

Jiang, H. H.; Xiao, Y.; Hu, C. M.; Guo, H.; Xia, K.

2018-06-01

Motivated by recent studies of cavity magnon polariton (CMP), we extended a previous theoretical work to generalize microwave transmission calculation with various magnetization boundary condition of YIG thin film embedded in cavity. It is found that numerical implementation given in this paper can be easily applied to other magnetization boundary condition and extended to magnetic multilayers. Numerical results show that ferromagnetic resonance mode of microwave transmission spectrum, which is absent in previous calculation, can be recovered by altering the pinning condition of surface spins. The demonstrated reliability of our theory opens attractive perspectives for studying CMP of thin film with complicated surface magnetization distribution and magnetic multilayers.

Tailoring of quantum dot emission efficiency by localized surface plasmon polaritons in self-organized mesoscopic rings.

Science.gov (United States)

Margapoti, Emanuela; Gentili, Denis; Amelia, Matteo; Credi, Alberto; Morandi, Vittorio; Cavallini, Massimiliano

2014-01-21

We report on the tailoring of quantum dot (QD) emission efficiency by localized surface plasmon polaritons in self-organized mesoscopic rings. Ag nanoparticles (NPs) with CdSe QDs embedded in a polymeric matrix are spatially organised in mesoscopic rings and coupled in a tuneable fashion by breath figure formation. The mean distance between NPs and QDs and consequently the intensity of QD photoluminescence, which is enhanced by the coupling of surface plasmons and excitons, are tuned by acting on the NP concentration.

Enhancement and Tunability of Near-Field Radiative Heat Transfer Mediated by Surface Plasmon Polaritons in Thin Plasmonic Films

Directory of Open Access Journals (Sweden)

Svetlana V. Boriskina

2015-06-01

Full Text Available The properties of thermal radiation exchange between hot and cold objects can be strongly modified if they interact in the near field where electromagnetic coupling occurs across gaps narrower than the dominant wavelength of thermal radiation. Using a rigorous fluctuational electrodynamics approach, we predict that ultra-thin films of plasmonic materials can be used to dramatically enhance near-field heat transfer. The total spectrally integrated film-to-film heat transfer is over an order of magnitude larger than between the same materials in bulk form and also exceeds the levels achievable with polar dielectrics such as SiC. We attribute this enhancement to the significant spectral broadening of radiative heat transfer due to coupling between surface plasmon polaritons (SPPs on both sides of each thin film. We show that the radiative heat flux spectrum can be further shaped by the choice of the substrate onto which the thin film is deposited. In particular, substrates supporting surface phonon polaritons (SPhP strongly modify the heat flux spectrum owing to the interactions between SPPs on thin films and SPhPs of the substrate. The use of thin film phase change materials on polar dielectric substrates allows for dynamic switching of the heat flux spectrum between SPP-mediated and SPhP-mediated peaks.

Theoretical analysis of ridge gratings for long-range surface plasmon polaritons

DEFF Research Database (Denmark)

Søndergaard, Thomas; Bozhevolnyi, Sergey I.; Boltasseva, Alexandra

2006-01-01

Optical properties of ridge gratings for long-range surface plasmon polaritons (LRSPPs) are analyzed theoretically in a two-dimensional configuration via the Lippmann-Schwinger integral equation method. LRSPPs being supported by a thin planar gold film embedded in dielectric are considered...... to be scattered by an array of equidistant gold ridges on each side of the film designed for in-plane Bragg scattering of LRSPPs at the wavelength ~1550 nm. Out-of-plane scattering (OUPS), LRSPP transmission, reflection, and absorption are investigated with respect to the wavelength, the height of the ridges...... peak it is preferable to use longer gratings with smaller ridges compared to gratings with larger ridges, because the former result in a smaller OUPS from the grating facets than the latter. The theoretical analysis and its conclusions are supported with experimental results on the LRSPP reflection...

Compact surface structures for the efficient excitation of surface plasmon-polaritons

Energy Technology Data Exchange (ETDEWEB)

De la Cruz, S.; Mendez, E.R. [Division de Fisica Applicada, Centro de Investigacion Cientifica y de Educacion Superior de Ensenada, Carretera Ensenada-Tijuana No. 3918, Ensenada 22860, BC (Mexico); Macias, D.; Salas-Montiel, R.; Adam, P.M. [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de Technologie de Troyes, 12 rue Marie Curie, BP-2060, 10010 Troyes Cedex (France)

2012-06-15

We present calculations of the efficiency of excitation of surface plasmon-polaritons (SPPs) with surface structures illuminated by focussed beams. First, it is shown that the low reflectivity observed with broad highly directional beams and periodic gratings does not necessarily imply an efficient coupling to SPPs. We then consider the coupling through surface features like steps, grooves and angled steps, and calculate efficiency maps for these structures as functions of the parameters that define them. Finally, we explore the possibilities of improving the coupling efficiency using periodic structures consisting of a small number of rectangular grooves. We find that a surface section with a length of about four wavelengths can couple as much as 45% of the incident light into a directional SPP. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Graphene surface plasmon polaritons with opposite in-plane electron oscillations along its two surfaces

International Nuclear Information System (INIS)

Liang, Huawei; Ruan, Shuangchen; Zhang, Min; Su, Hong; Li, Irene Ling

2015-01-01

We predict the existence of a surface plasmon polariton (SPP) mode that can be guided by a graphene monolayer, regardless of the sign of the imaginary part of its conductivity. In this mode, in-plane electron oscillations along two surfaces of graphene are of opposite directions, which is very different from conventional SPPs on graphene. Significantly, coating graphene with dielectric films yields a way to guide the SPPs with both sub-wavelength mode widths and ultra-long propagation distances. In particular, the mode characteristics are very sensitive to the chemical potential of graphene, so the graphene-based waveguide can find applications in many optoelectronic devices

Graphene surface plasmon polaritons with opposite in-plane electron oscillations along its two surfaces

Energy Technology Data Exchange (ETDEWEB)

Liang, Huawei; Ruan, Shuangchen, E-mail: scruan@szu.edu.cn; Zhang, Min; Su, Hong; Li, Irene Ling [Shenzhen Key Laboratory of Laser Engineering, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060 (China); Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, Shenzhen University, Shenzhen 518060 (China)

2015-08-31

We predict the existence of a surface plasmon polariton (SPP) mode that can be guided by a graphene monolayer, regardless of the sign of the imaginary part of its conductivity. In this mode, in-plane electron oscillations along two surfaces of graphene are of opposite directions, which is very different from conventional SPPs on graphene. Significantly, coating graphene with dielectric films yields a way to guide the SPPs with both sub-wavelength mode widths and ultra-long propagation distances. In particular, the mode characteristics are very sensitive to the chemical potential of graphene, so the graphene-based waveguide can find applications in many optoelectronic devices.

Strong coupling and polariton lasing in Te based microcavities embedding (Cd,Zn)Te quantum wells

Energy Technology Data Exchange (ETDEWEB)

Rousset, J.-G., E-mail: j-g.rousset@fuw.edu.pl; Piętka, B.; Król, M.; Mirek, R.; Lekenta, K.; Szczytko, J.; Borysiuk, J.; Suffczyński, J.; Kazimierczuk, T.; Goryca, M.; Smoleński, T.; Kossacki, P.; Nawrocki, M.; Pacuski, W. [Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, PL-02-093 Warszawa (Poland)

2015-11-16

We report on properties of an optical microcavity based on (Cd,Zn,Mg)Te layers and embedding (Cd,Zn)Te quantum wells. The key point of the structure design is the lattice matching of the whole structure to MgTe, which eliminates the internal strain and allows one to embed an arbitrary number of unstrained quantum wells in the microcavity. We evidence the strong light-matter coupling regime already for the structure containing a single quantum well. Embedding four unstrained quantum wells results in further enhancement of the exciton-photon coupling and the polariton lasing in the strong coupling regime.

Numerical study of propagation properties of surface plasmon polaritons in nonlinear media

KAUST Repository

Sagor, Rakibul Hasan

2016-03-29

We present a time-domain algorithm for simulating nonlinear propagation of surface plasmon polaritons (SPPs) in chalcogenide glass. Due to the high non-linearity property and strong dispersion and confinement chalcogenide glasses are widely known as ultrafast nonlinear materials. We have used the finite difference time domain (FDTD) method to develop the simulation algorithm for the current analysis. We have modeled the frequency dependent dispersion properties and third order nonlinearity property of chalcogenide glass utilizing the general polarization algorithm merged in the auxiliary differential equation (ADE) method. The propagation dynamics of the whole structure with and without third order nonlinearity property of chalcogenide glass have been simulated and the effect of nonlinearity on the propagation properties of SPP has been investigated. © 2016 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

Measuring and engineering the atomic mass density wave of a Gaussian mass-polariton pulse in optical fibers

Science.gov (United States)

Partanen, Mikko; Tulkki, Jukka

2018-02-01

Conventional theories of electromagnetic waves in a medium assume that only the energy of the field propagates inside the medium. Consequently, they neglect the transport of mass density by the medium atoms. We have recently presented foundations of a covariant theory of light propagation in a nondispersive medium by considering a light wave simultaneously with the dynamics of the medium atoms driven by optoelastic forces [Phys. Rev. A 95, 063850 (2017)]. In particular, we have shown that the mass is transferred by an atomic mass density wave (MDW), which gives rise to mass-polariton (MP) quasiparticles, i.e., covariant coupled states of the field and matter having a nonzero rest mass. Another key observation of the mass-polariton theory of light is that, in common semiconductors, most of the momentum of light is transferred by moving atoms, e.g., 92% in the case of silicon. In this work, we generalize the MP theory of light for dispersive media and consider experimental measurement of the mass transferred by the MDW atoms when an intense light pulse propagates in a silicon fiber. In particular, we consider optimal intensity and time dependence of a Gaussian pulse and account for the breakdown threshold irradiance of the material. The optical shock wave property of the MDW, which propagates with the velocity of light instead of the velocity of sound, prompts for engineering of novel device concepts like very high frequency mechanical oscillators not limited by the acoustic cutoff frequency.

Vacuum Bloch-Siegert shift in Landau polaritons with ultra-high cooperativity

Science.gov (United States)

Li, Xinwei; Bamba, Motoaki; Zhang, Qi; Fallahi, Saeed; Gardner, Geoff C.; Gao, Weilu; Lou, Minhan; Yoshioka, Katsumasa; Manfra, Michael J.; Kono, Junichiro

2018-06-01

A two-level system resonantly interacting with an a.c. magnetic or electric field constitutes the physical basis of diverse phenomena and technologies. However, Schrödinger's equation for this seemingly simple system can be solved exactly only under the rotating-wave approximation, which neglects the counter-rotating field component. When the a.c. field is sufficiently strong, this approximation fails, leading to a resonance-frequency shift known as the Bloch-Siegert shift. Here, we report the vacuum Bloch-Siegert shift, which is induced by the ultra-strong coupling of matter with the counter-rotating component of the vacuum fluctuation field in a cavity. Specifically, an ultra-high-mobility two-dimensional electron gas inside a high-Q terahertz cavity in a quantizing magnetic field revealed ultra-narrow Landau polaritons, which exhibited a vacuum Bloch-Siegert shift up to 40 GHz. This shift, clearly distinguishable from the photon-field self-interaction effect, represents a unique manifestation of a strong-field phenomenon without a strong field.

Raman scattering and attenuated-total-reflection studies of surface-plasmon polaritons

International Nuclear Information System (INIS)

Kurosawa, K.; Pierce, R.M.; Ushioda, S.; Hemminger, J.C.

1986-01-01

We have made in situ measurements of attenuated total reflection (ATR) and Raman scattering from a layered structure consisting of a glass prism, a thin silver film, an MgF 2 spacer, and a liquid mixture whose refractive index is matched to that of MgF 2 . When the incident angle of the laser beam coincides with the ATR angle, the surface-plasmon polariton (SPP) of the silver film is excited resonantly and the Raman scattering intensity of the liquid shows a maximum. The same effect is observed at the frequency of the Stokes scattered light. By measuring the decrease of the Raman scattering intensity of the liquid with increase of the thickness of the MgF 2 spacer layer, we have determined the decay length (l/sub d/) of the SPP field into the liquid. The measured value of l/sub d/ = 1539 A agrees with the calculated value, 1534 A

Propagation of long-range surface plasmon polaritons in photonic band gap structures

DEFF Research Database (Denmark)

Boltasseva, Alexandra; Søndergaard, Thomas; Nikolajsen, Thomas

2005-01-01

We study the interaction of long-range surface plasmon polaritons (LR-SPPs), excited at telecommunication wavelengths, with photonic crystals (PCs) formed by periodic arrays of gold bumps that are arranged in a triangular lattice and placed symmetrically on both sides of a thin gold fil embedded...... in polymer. Radiation is delivered to and from the PC structures with the help of LR-SPP guides that consist of 8 mm wide and 15 nm thick gold stripes attached to wide film sections (of the same thickness) covered with bumps (diameter ~300 nm, height up to 150 nm on each side of the film). We investigate......, is rather weak, so that the photonic bandgap effect might be expected to take place only for some particular propagation directions. Preliminary experiments on LR-SPP bending and splitting at large angles are reported, and further research directions are discussed....

Experimental demonstration of tunable directional excitation of surface plasmon polaritons with a subwavelength metallic double slit

Science.gov (United States)

Li, Xiaowei; Tan, Qiaofeng; Bai, Benfeng; Jin, Guofan

2011-06-01

We demonstrate experimentally the directional excitation of surface plasmon polaritons (SPPs) on a metal film by a subwavelength double slit under backside illumination, based on the interference of SPPs generated by the two slits. By varying the incident angle, the SPPs can be tunably directed into two opposite propagating directions with a predetermined splitting ratio. Under certain incident angle, unidirectional SPP excitation can be achieved. This compact directional SPP coupler is potentially useful for many on-chip applications. As an example, we show the integration of the double-slit couplers with SPP Bragg mirrors, which can effectively realize selective coupling of SPPs into different ports in an integrated plasmonic chip.

Tailor-made surface plasmon polaritons above the bulk plasma frequency: a design strategy for indium tin oxide

International Nuclear Information System (INIS)

Brand, S; Abram, R A; Kaliteevski, M A

2010-01-01

A simple phase-matching approach is employed as a design aid to engineer surface plasmon polariton states at the interface of an indium tin oxide layer on the top of a Bragg reflector. By altering the details of the reflector, and in particular the ordering of the layers and the thickness of the layer adjacent to the indium tin oxide, it is possible to readily adjust the energy of these states. Examples of structures engineered to give rise to distinctive features in the reflectivity spectra above the bulk screened plasma frequency for states of both possible polarizations are presented.

Superfocusing modes of surface plasmon polaritons in conical geometry based on the quasi-separation of variables approach

International Nuclear Information System (INIS)

Kurihara, Kazuyoshi; Otomo, Akira; Syouji, Atsushi; Takahara, Junichi; Suzuki, Koji; Yokoyama, Shiyoshi

2007-01-01

Analytic solutions to the superfocusing modes of surface plasmon polaritons in a conical geometry are theoretically studied using an ingenious method called the quasi-separation of variables. This method can be used to look for fundamental solutions to the wave equation for a field that must satisfy boundary conditions at all points on the continuous surface of tapered geometries. The set of differential equations exclusively separated from the wave equation can be consistently solved in combination with perturbation methods. This paper presents the zeroth-order perturbation solution of conical superfocusing modes with azimuthal symmetry and graphically represents them in electric field-line patterns

Time-domain analysis of surface-plasmon-polariton propagation in Ag nano-films using a generalized polarization approach

KAUST Repository

Al-Jabr, Ahmad

2010-01-01

A time-domain analysis of the propagation properties of surface-plasmon-polaritons (SPP) in Silver nanostructures is presented. The analysis is based on a simulation algorithm that unifies the formulation of different dispersion models and multi-pole relations into one form. The main objective of this work is to perform a comparative analysis between different dispersion models used for Silver, including Debye, Drude and multi-pole Lorentz-Drude models. The quantities that are used in the comparison are the SPP propagation length and propagation speed. Experimental results reported in literature are used to support the conclusions.

Corrugated metal surface with pillars for terahertz surface plasmon polariton waveguide components

KAUST Repository

Yuehong, Xu; Yanfeng, Li; Chunxiu, Tian; Jiaguang, Han; Quan, Xu; Xueqian, Zhang; Xixiang, Zhang; Ying, Zhang; Weili, Zhang

2018-01-01

In the terahertz regime, due to perfect conductivity of most metals, it is hard to realize a strong confinement of Surface plasmon polaritons (SPPs) although a propagation loss could be sufficiently low. We experimentally demonstrated a structure with periodic pillars arranged on a thin metal surface that supports bound modes of spoof SPPs at terahertz (THz) frequencies. By using scanning near-field THz microscopy, the electric field distribution above the metal surface within a distance of 130 μm was mapped. The results proved that this structure could guide spoof SPPs propagating along subwavelength waveguides, and at the same time reduce field expansion into free space. Further, for the development of integrated optical circuits, several components including straight waveguide, S-bend, Y-splitter and directional couplers were designed and characterized by the same method. We believe that the waveguide components proposed here will pave a new way for the development of flexible, wideband and compact photonic circuits operating at THz frequencies.

Corrugated metal surface with pillars for terahertz surface plasmon polariton waveguide components

KAUST Repository

Yuehong, Xu

2018-01-12

In the terahertz regime, due to perfect conductivity of most metals, it is hard to realize a strong confinement of Surface plasmon polaritons (SPPs) although a propagation loss could be sufficiently low. We experimentally demonstrated a structure with periodic pillars arranged on a thin metal surface that supports bound modes of spoof SPPs at terahertz (THz) frequencies. By using scanning near-field THz microscopy, the electric field distribution above the metal surface within a distance of 130 μm was mapped. The results proved that this structure could guide spoof SPPs propagating along subwavelength waveguides, and at the same time reduce field expansion into free space. Further, for the development of integrated optical circuits, several components including straight waveguide, S-bend, Y-splitter and directional couplers were designed and characterized by the same method. We believe that the waveguide components proposed here will pave a new way for the development of flexible, wideband and compact photonic circuits operating at THz frequencies.

Nonlinear Dynamics of Ultrashort Long-Range Surface Plasmon Polariton Pulses in Gold Strip Waveguides

DEFF Research Database (Denmark)

Lysenko, Oleg; Bache, Morten; Olivier, Nicolas

2016-01-01

We study experimentally and theoretically nonlinear propagation of ultrashort long-range surface plasmon polaritons in gold strip waveguides. The nonlinear absorption of the plasmonic modes in the waveguides is measured with femtosecond pulses revealing a strong dependence of the third......-order nonlinear susceptibility of the gold core on the pulse duration and layer thickness. A comprehensive model for the pulse duration dependence of the third-order nonlinear susceptibility is developed on the basis of the nonlinear Schrödinger equation for plasmonic mode propagation in the waveguides....... The model accounts for the intrinsic delayed (noninstantaneous) nonlinearity of free electrons of gold as well as the thickness of the gold film and is experimentally verified. The obtained results are important for the development of active plasmonic and nanophotonic components....

Quantum simulations with photons and polaritons merging quantum optics with condensed matter physics

CERN Document Server

2017-01-01

This book reviews progress towards quantum simulators based on photonic and hybrid light-matter systems, covering theoretical proposals and recent experimental work. Quantum simulators are specially designed quantum computers. Their main aim is to simulate and understand complex and inaccessible quantum many-body phenomena found or predicted in condensed matter physics, materials science and exotic quantum field theories. Applications will include the engineering of smart materials, robust optical or electronic circuits, deciphering quantum chemistry and even the design of drugs. Technological developments in the fields of interfacing light and matter, especially in many-body quantum optics, have motivated recent proposals for quantum simulators based on strongly correlated photons and polaritons generated in hybrid light-matter systems. The latter have complementary strengths to cold atom and ion based simulators and they can probe for example out of equilibrium phenomena in a natural driven-dissipative sett...

Excitonic polaritons of zinc diarsenide single crystals

Energy Technology Data Exchange (ETDEWEB)

Syrbu, N.N., E-mail: sirbunn@yahoo.com [Technical University of Moldova, Chisinau, Republic of Moldova (Moldova, Republic of); Stamov, I.G. [T.G. Shevchenko State University of Pridnestrovie, Tiraspol, Republic of Moldova (Moldova, Republic of); Zalamai, V.V. [Institute of Applied Physics, Academy of Sciences of Moldova, Chisinau, Republic of Moldova (Moldova, Republic of); Dorogan, A. [Technical University of Moldova, Chisinau, Republic of Moldova (Moldova, Republic of)

2017-02-01

Excitonic polaritons of ZnAs{sub 2} single crystals had been investigated. Parameters of singlet excitons with Г{sub 2}¯(z) symmetry and orthoexcitons 2Г{sub 1}¯(y)+Г{sub 2}¯(x) had been determined. Spectral dependencies of ordinary and extraordinary dispersion of refractive index had been calculated using interferential reflection and transmittance spectra. It was shown, that A excitonic series were due to hole (V{sub 1}) and electron (C{sub 1}) bands. The values of effective masses of electrons (m{sub c}{sup *}=0.10 m{sub 0}) and holes (m{sub v1}{sup *}=0.89 m{sub 0}) had been estimated. It was revealed that the hole mass m{sub v1}{sup *} changes from 1.03 m{sub 0} to 0.55 m{sub 0} at temperature increasing from 10 K up to 230 K and that the electron mass m{sub c}{sup *} does not depend on temperature. The integral absorption A (eV cm{sup −1}) of the states n=1, 2 and 3 of Г{sub 2}¯(z) excitons depends on the A{sub n}≈n{sup −3} equality, which it is characteristic for S-type excitonic functions. Temperature dependences of the integral absorption of ground states for Г{sub 2}¯(z) and Г{sub 2}¯(Ñ…) excitons differ. The ground states of B and C excitons formed by V{sub 3} – C{sub 1} and V{sub 4} – C{sub 1} bands and its parameters had been determined.

Solitary waves of surface plasmon polariton via phase shifts under Doppler broadening and Kerr nonlinearity

Science.gov (United States)

Ahmad, S.; Ahmad, A.; Bacha, B. A.; Khan, A. A.; Abdul Jabar, M. S.

2017-12-01

Surface Plasmon Polaritons (SPPs) are theoretically investigated at the interface of a dielectric metal and gold. The output pulse from the dielectric is used as the input pulse for the generation of SPPs. The SPPs show soliton-like behavior at the interface. The solitary form of a SPP is maintained under the effects of Kerr nonlinearity, Doppler broadening and Fresnel dragging whereas its phase shift is significantly modified. A 0.3radian phase shift is calculated in the presence of both Kerr nonlinearity and Fresnel dragging in the absence of plasma motion. The phase shift is enhanced to 60radian due to the combined effect of Doppler broadening, Kerr nonlinearity and Fresnel dragging. The results may have significant applications in nano-photonics, optical tweezers, photovoltaic devices, plasmonster and sensing technology.

Temperature-mediated transition from Dyakonov-Tamm surface waves to surface-plasmon-polariton waves

Science.gov (United States)

Chiadini, Francesco; Fiumara, Vincenzo; Mackay, Tom G.; Scaglione, Antonio; Lakhtakia, Akhlesh

2017-08-01

The effect of changing the temperature on the propagation of electromagnetic surface waves (ESWs), guided by the planar interface of a homogeneous isotropic temperature-sensitive material (namely, InSb) and a temperature-insensitive structurally chiral material (SCM) was numerically investigated in the terahertz frequency regime. As the temperature rises, InSb transforms from a dissipative dielectric material to a dissipative plasmonic material. Correspondingly, the ESWs transmute from Dyakonov-Tamm surface waves into surface-plasmon-polariton waves. The effects of the temperature change are clearly observed in the phase speeds, propagation distances, angular existence domains, multiplicity, and spatial profiles of energy flow of the ESWs. Remarkably large propagation distances can be achieved; in such instances the energy of an ESW is confined almost entirely within the SCM. For certain propagation directions, simultaneous excitation of two ESWs with (i) the same phase speeds but different propagation distances or (ii) the same propagation distances but different phase speeds are also indicated by our results.

Surface Plasmon Polariton-Assisted Long-Range Exciton Transport in Monolayer Semiconductor Lateral Heterostructure

Science.gov (United States)

Shi, Jinwei; Lin, Meng-Hsien; Chen, Yi-Tong; Estakhri, Nasim Mohammadi; Tseng, Guo-Wei; Wang, Yanrong; Chen, Hung-Ying; Chen, Chun-An; Shih, Chih-Kang; Alã¹, Andrea; Li, Xiaoqin; Lee, Yi-Hsien; Gwo, Shangjr

Recently, two-dimensional (2D) semiconductor heterostructures, i.e., atomically thin lateral heterostructures (LHSs) based on transition metal dichalcogenides (TMDs) have been demonstrated. In an optically excited LHS, exciton transport is typically limited to a rather short spatial range ( 1 micron). Furthermore, additional losses may occur at the lateral interfacial regions. Here, to overcome these challenges, we experimentally implement a planar metal-oxide-semiconductor (MOS) structure by placing a monolayer of WS2/MoS2 LHS on top of an Al2O3 capped Ag single-crystalline plate. We found that the exciton transport range can be extended to tens of microns. The process of long-range exciton transport in the MOS structure is confirmed to be mediated by an exciton-surface plasmon polariton-exciton conversion mechanism, which allows a cascaded energy transfer process. Thus, the planar MOS structure provides a platform seamlessly combining 2D light-emitting materials with plasmonic planar waveguides, offering great potential for developing integrated photonic/plasmonic functionalities.

Finite-size fluctuations and photon statistics near the polariton condensation transition in a single-mode microcavity

International Nuclear Information System (INIS)

Eastham, P. R.; Littlewood, P. B.

2006-01-01

We consider polariton condensation in a generalized Dicke model, describing a single-mode cavity containing quantum dots, and extend our previous mean-field theory to allow for finite-size fluctuations. Within the fluctuation-dominated regime the correlation functions differ from their (trivial) mean-field values. We argue that the low-energy physics of the model, which determines the photon statistics in this fluctuation-dominated crossover regime, is that of the (quantum) anharmonic oscillator. The photon statistics at the crossover are different in the high-temperature and low-temperature limits. When the temperature is high enough for quantum effects to be neglected we recover behavior similar to that of a conventional laser. At low enough temperatures, however, we find qualitatively different behavior due to quantum effects

Electromagnetically Induced Transparency in Circuit Quantum Electrodynamics with Nested Polariton States

Science.gov (United States)

Long, Junling; Ku, H. S.; Wu, Xian; Gu, Xiu; Lake, Russell E.; Bal, Mustafa; Liu, Yu-xi; Pappas, David P.

2018-02-01

Quantum networks will enable extraordinary capabilities for communicating and processing quantum information. These networks require a reliable means of storage, retrieval, and manipulation of quantum states at the network nodes. A node receives one or more coherent inputs and sends a conditional output to the next cascaded node in the network through a quantum channel. Here, we demonstrate this basic functionality by using the quantum interference mechanism of electromagnetically induced transparency in a transmon qubit coupled to a superconducting resonator. First, we apply a microwave bias, i.e., drive, to the qubit-cavity system to prepare a Λ -type three-level system of polariton states. Second, we input two interchangeable microwave signals, i.e., a probe tone and a control tone, and observe that transmission of the probe tone is conditional upon the presence of the control tone that switches the state of the device with up to 99.73% transmission extinction. Importantly, our electromagnetically induced transparency scheme uses all dipole allowed transitions. We infer high dark state preparation fidelities of >99.39 % and negative group velocities of up to -0.52 ±0.09 km /s based on our data.

Multiple surface plasmon polaritons modes on thin silver film controlled by a two-dimensional lattice of silver nanodimers

Energy Technology Data Exchange (ETDEWEB)

Chang, Ying; Jiang, Yongyuan, E-mail: jiangyy@hit.edu.cn [Harbin Institute of Technology, Department of Physics (China)

2015-01-15

We study the optical resonant spectrum of a two-dimensional periodic array of silver nanodimers on a thin silver film using multiple scattering formalism. The excited multiple plasmonic modes on two interfaces of the silver film reveal that the dispersion relationships of surface plasmon polaritons on metallic film are modified by doubly periodic lattice due to the fact that wave vectors matching conditions are satisfied. Moreover, we demonstrate that the plasmonic modes are directly controlled by the thickness of silver film, as well as the gap between nanodimer array and silver film. These effects provide novel high-efficient and steady way for excitation in future plasmonic nanodevices.

Investigations on a nano-scale periodical waveguide structure taking surface plasmon polaritons into consideration

International Nuclear Information System (INIS)

Liu Weihao; Zhong Renbin; Zhou Jun; Zhang Yaxin; Hu Min; Liu Shenggang

2012-01-01

Detailed theoretical analysis and computer simulations on the electromagnetic characteristics of a nano-scale periodical waveguide structure, taking surface plasmon polaritons (SPPs) into consideration, are carried out in this paper. The results show that SPPs will significantly influence the electromagnetic characteristics of the structure. When the operation frequency is in a certain band—the ‘radial confinement band’, neither radial surface plasmon waves nor guided waves, which both will lead to radial energy loss, can be excited in the structure. And the electromagnetic waves are completely confined within the longitudinal waveguide and propagate along it with little attenuation. The radial energy loss is then significantly reduced. These results are of great significance not only for increasing the efficiency of the radiation sources based on the nano-scale periodical waveguide structure but also for the development of high-efficiency waveguides and wide-band filters in the infrared and visible light regimes. (paper)

Imaging slit-coupled surface plasmon polaritons using conventional optical microscopy.

Science.gov (United States)

Mehfuz, R; Chowdhury, F A; Chau, K J

2012-05-07

We develop a technique that now enables surface plasmon polaritons (SPPs) coupled by nano-patterned slits in a metal film to be detected using conventional optical microscopy with standard objective lenses. The crux of this method is an ultra-thin polymer layer on the metal surface, whose thickness can be varied over a nanoscale range to enable controllable tuning of the SPP momentum. At an optimal layer thickness for which the SPP momentum matches the momentum of light emerging from the slit, the SPP coupling efficiency is enhanced about six times relative to that without the layer. The enhanced efficiency results in distinctive and bright plasmonic signatures near the slit visible by naked eye under an optical microscope. We demonstrate how this capability can be used for parallel measurement through a simple experiment in which the SPP propagation distance is extracted from a single microscope image of an illuminated array of nano-patterned slits on a metal surface. We also use optical microscopy to image the focal region of a plasmonic lens and obtain results consistent with a previously-reported results using near-field optical microscopy. Measurement of SPPs near a nano-slit using conventional and widely-available optical microscopy is an important step towards making nano-plasmonic device technology highly accessible and easy-to-use.

Intersubband surface plasmon polaritons in all-semiconductor planar plasmonic resonators

Science.gov (United States)

ZałuŻny, M.

2018-01-01

We theoretically discuss properties of intersubband surface plasmon polaritons (ISPPs) supported by the system consisting of a multiple quantum well (MQW) slab embedded into planar resonator with highly doped semiconducting claddings playing the role of cavity mirrors. Symmetric structures, where the MQW slab occupies the whole space between the claddings and asymmetric structures, where the MQW occupy only half of the space between mirrors, are considered. We focus mainly on the nearly degenerate structures where intersubband frequency is close to frequency of the surface plasmon of the mirrors. The ISPP characteristics are calculated numerically using a semiclassical approach based on the transfer matrix formalism and the effective-medium approximation. The claddings are described by the lossless Drude model. The possibility of engineering the dispersion of the ISPP branches is demonstrated. In particular, for certain parameters of the asymmetric structures we observe the formation of the multimode ISPP branches with two zero group velocity points. We show that the properties of the ISPP branches are reasonably well interpreted employing quasiparticle picture provided that the concept of the mode overlap factor is generalized, taking into account the dispersive character of the mirrors. In addition to this, we demonstrate that the lossless dispersion characteristics of the ISPP branches obtained in the paper are consistent with the angle-resolved reflection-absorption spectra of the GaAlAs-based realistic plasmonic resonators.

Extracting and focusing of surface plasmon polaritons inside finite asymmetric metal/insulator/metal structure at apex of optical fiber by subwavelength holes

Science.gov (United States)

Oshikane, Yasushi; Murai, Kensuke; Nakano, Motohiro

2013-09-01

We have been studied a finite asymmetric metal-insulator-metal (MIM) structure on glass plate for near-future visible light communication (VLC) system with white LED illuminations in the living space (DOI: 10.1117/12.929201). The metal layers are vacuum-evaporated thin silver (Ag) films (around 50 nm and 200 nm, respectively), and the insulator layer (around 150 nm) is composed of magnesium fluoride (MgF2). A characteristic narrow band filtering of the MIM structure at visible region might cause a confinement of intense surface plasmon polaritons (SPPs) at specific monochromatic frequency inside a subwavelength insulator layer of the MIM structure. Central wavelength and depth of such absorption dip in flat spectral reflectance curve is controlled by changing thicknesses of both insulator and thinner metal layers. On the other hand, we have proposed a twin-hole pass-through wave guide for SPPs in thick Ag film (DOI: 10.1117/12.863587). At that time, the twin-hole converted a incoming plane light wave into a pair of channel plasmon polaritons (CPPs), and united them at rear surface of the Ag film. This research is having an eye to extract, guide, and focus the SPPs through a thicker metal layer of the MIM with FIBed subwavelength pass-through holes. The expected outcome is a creation of noble, monochromatic, and tunable fiber probe for scanning near-field optical microscopes (SNOMs) with intense white light sources. Basic experimental and FEM simulation results will be presented.

Tunable optical response at the plasmon-polariton frequency in dielectric-graphene-metamaterial systems

Science.gov (United States)

Calvo-Velasco, D. M.; Porras-Montenegro, N.

2018-04-01

By using the scattering matrix formalism, it is studied the optical properties of one dimensional photonic crystals made of multiple layers of dielectric and uniaxial anisotropic single negative electric metamaterial with Drude type responses, with inclusions of graphene in between the dielectric-dielectric interfaces (DGMPC). The transmission spectra for transverse electric (TE) and magnetic (TM) polarization are presented as a function of the incidence angle, the graphene chemical potential, and the metamaterial plasma frequencies. It is found for the TM polarization the tunability of the DGMPC optical response with the graphene chemical potential, which can be observed by means of transmission or reflexion bands around the metamaterial plasmon-polariton frequency, with bandwidths depending on both the incidence angle and the metamaterial plasma frequency. Also, the transmission band is observed when losses in the metamaterial slabs are considered for finite systems. The conditions for the appearance of these bands are shown analytically. We consider this work contributes to open new possibilities to the design of photonic devices with DGMPCs.

Radiation loss of planar surface plasmon polaritons transmission lines at microwave frequencies.

Science.gov (United States)

Xu, Zhixia; Li, Shunli; Yin, Xiaoxing; Zhao, Hongxin; Liu, Leilei

2017-07-21

Radiation loss of a typical spoof surface plasmon polaritons (SSPPs) transmission line (TL) is investigated in this paper. A 325 mm-long SSPPs TL is designed and fabricated. Simulated results show that radiation loss contributes more to transmission loss than dielectric loss and conductor loss from 2 GHz to 10 GHz. Radiation loss of the SSPPs TL could be divided into two parts, one is caused by the input mode converter, and the other is caused by the corrugated metallic strip. This paper explains mechanisms of radiation loss from different parts, designs a loaded SSPPs TL with a series of resistors to absorb electromagnetic energy on corrugated metallic strip, and then discriminates radiation loss from the input mode converter, proposes the concept of average radiation length (ARL) to evaluate radiation loss from SSPPs of finite length, and concludes that radiation loss is mainly caused by corrugated structure of finite length at low frequency band and by the input mode converter at high frequency band. To suppress radiation loss, a mixed slow wave TL based on the combination of coplanar waveguides (CPWs) and SSPPs is presented. The designed structure, sample fabrication and experimental verification are discussed.

Composition Dependence of Surface Phonon Polariton Mode in Wurtzite InxGa1−xN (0 ≤ x ≤ 1) Ternary Alloy

International Nuclear Information System (INIS)

Ng, S. S.; Hassan, Z.; Hassan, H. Abu

2008-01-01

We present a theoretical study on the composition dependence of the surface phonon polariton (SPP) mode in wurtzite structure α-In x Ga 1-x N ternary alloy over the whole composition range. The SPP modes are obtained by the theoretical simulations by means of an anisotropy model. The results reveal that the SPP mode of α-In x Ga 1-x N semiconductors exhibits one-mode behaviour. From these data, composition dependence of the SPP mode with bowing parameter of −28.9 cm −1 is theoretically obtained

The Effect of Adjacent Materials on the Propagation of Phonon Polaritons in Hexagonal Boron Nitride.

Science.gov (United States)

Kim, Kris S; Trajanoski, Daniel; Ho, Kevin; Gilburd, Leonid; Maiti, Aniket; van der Velden, Luuk; de Beer, Sissi; Walker, Gilbert C

2017-07-06

In order to apply the ability of hexagonal boron nitride (hBN) to confine energy in the form of hyperbolic phonon polariton (HPhP) modes in photonic-electronic devices, approaches to finely control and leverage the sensitivity of these propagating waves must be investigated. Here, we show that by surrounding hBN with materials of lower/higher dielectric responses, such as air and silicon, lower/higher surface momenta of HPhPs can be achieved. Furthermore, an alternative method for preparing thin hBN crystals with minimum contamination is presented, which provides opportunities to study the sensitivity of the damping mechanism of HPhPs on adsorbed materials. Infrared scanning near-field optical microscopy (IR-SNOM) results suggest that the reflections at the upper and lower hBN interfaces are primary causes of the damping of HPhPs, and that the damping coefficients of propagating waves are highly sensitive to adjacent layers, suggesting opportunities for sensor applications.

Compensation of propagation loss of surface plasmon polaritons with a finite-thickness dielectric gain layer

International Nuclear Information System (INIS)

Zhang, Xin; Liu, Haitao; Zhong, Ying

2012-01-01

We theoretically study the compensation of propagation loss of surface plasmon polaritons (SPPs) with the use of a finite-thickness dielectric layer with optical gain. The impacts of the gain coefficient, the gain-layer thickness and the wavelength on the loss compensation and the field distribution of the SPP mode are systematically explored with a fully vectorial method. Abnormal behaviors for the loss compensation as the gain-layer thickness increases are found and explained. Critical values of the gain coefficient and of the corresponding gain-layer thickness for just compensating the propagation loss are provided. Our results show that as the SPP propagation loss is fully compensated with a gain coefficient at a reasonably low level, the gain layer is still thin enough to ensure a large exterior SPP field at the gain-layer/air interface, which is important for achieving a strong light–matter interaction for applications such as bio-chemical sensing. (paper)

Terahertz particle-in-liquid sensing with spoof surface plasmon polariton waveguides

Directory of Open Access Journals (Sweden)

Zhijie Ma

2017-11-01

Full Text Available We present a highly sensitive microfluidic sensing technique for the terahertz (THz region of the electromagnetic spectrum based on spoof surface plasmon polaritons (SPPs. By integrating a microfluidic channel in a spoof SPP waveguide, we take advantage of these highly confined electromagnetic modes to create a platform for dielectric sensing of liquids. Our design consists of a domino waveguide, that is, a series of periodically arranged rectangular metal blocks on top of a metal surface that supports the propagation of spoof SPPs. Through numerical simulations, we demonstrate that the transmission of spoof SPPs along the waveguide is extremely sensitive to the refractive index of a liquid flowing through a microfluidic channel crossing the waveguide to give an interaction volume on the nanoliter scale. Furthermore, by taking advantage of the insensitivity of the domino waveguide’s fundamental spoof SPP mode to the lateral width of the metal blocks, we design a tapered waveguide able to achieve further confinement of the electromagnetic field. Using this approach, we demonstrate the highly sensitive detection of individual subwavelength micro-particles flowing in the liquid. These results are promising for the creation of spoof SPP based THz lab-on-a-chip microfluidic devices that are suitable for the analysis of biological liquids such as proteins and circulating tumour cells in buffer solution.

Long-range propagation of plasmon and phonon polaritons in hyperbolic-metamaterial waveguides

Science.gov (United States)

Babicheva, Viktoriia E.

2017-12-01

We study photonic multilayer waveguides that include layers of materials and metamaterials with a hyperbolic dispersion (HMM). We consider the long-range propagation of plasmon and phonon polaritons at the dielectric-HMM interface in different waveguide geometries (single boundary or different layers of symmetric cladding). In contrast to the traditional analysis of geometrical parameters, we make an emphasis on the optical properties of constituent materials: solving dispersion equations, we analyze how dielectric and HMM permittivities affect propagation length and mode size of waveguide eigenmodes. We derive figures of merit that should be used for each waveguide in a broad range of permittivity values as well as compare them with plasmonic waveguides. We show that the conventional plasmonic quality factor, which is the ratio of real to imaginary parts of permittivity, is not applicable to the case of waveguides with complex structure. Both telecommunication wavelengths and mid-infrared spectral ranges are of interest considering recent advances in van der Waals materials, such as hexagonal boron nitride. We evaluate the performance of the waveguides with hexagonal boron nitride in the range where it possesses hyperbolic dispersion (wavelength 6.3-7.3 μm), and we show that these waveguides with natural hyperbolic properties have higher propagation lengths than metal-based HMM waveguides.

Side-coupled cavity model for surface plasmon-polariton transmission across a groove

International Nuclear Information System (INIS)

Liu, J.S.Q.

2010-01-01

We demonstrate that the transmission properties of surface plasmon-polaritons (SPPs) across a rectangular groove in a metallic film can be described by an analytical model that treats the groove as a side-coupled cavity to propagating SPPs on the metal surface. The coupling efficiency to the groove is quantified by treating it as a truncated metal-dielectric-metal (MDM) waveguide. Finite-difference frequency-domain (FDFD) simulations and mode orthogonality relations are employed to derive the basic scattering coefficients that describe the interaction between the relevant modes in the system. The modeled SPP transmission and reflection intensities show excellent agreement with full-field simulations over a wide range of groove dimensions, validating this intuitive model. The model predicts the sharp transmission minima that occur whenever an incident SPP resonantly couples to the groove. We also for the first time show the importance of evanescent, reactive MDM SPP modes to the transmission behavior. SPPs that couple to this mode are resonantly enhanced upon reflection from the bottom of the groove, leading to high field intensities and sharp transmission minima across the groove. The resonant behavior exhibited by the grooves has a number of important device applications, including SPP mirrors, filters, and modulators.

Exciton-polariton dynamics in quantum dot-cavity system

Energy Technology Data Exchange (ETDEWEB)

Neto, Antonio F.; Lima, William J.; Villas-Boas, Jose M. [Universidade Federal de Uberlandia (UFU), MG (Brazil). Inst. de Fisica

2012-07-01

Full text: One of the basic requirement for quantum information processing systems is the ability to completely control the state of a single qubit. This imply in know all sources of decoherence and elaborate ways to avoid them. In recent work, A. Laucht et al. [1] presented detailed theoretical and experimental investigations of electrically tunable single quantum dot (QD) - photonic crystal (PhC) nanocavity systems operating in the strong coupling regime of the light matter interaction. Unlike previous studies, where the exciton-cavity spectral detuning was varied by changing the lattice temperature, or by the adsorption of inert gases at low temperatures, they employ the quantum confined Stark-effect to electro-optically control the exciton-cavity detuning. The new built device enabled them to systematically probe the emission spectrum of the strongly coupled system as a function of external control parameters, as for example the incoherent excitation power density or the lattice temperature. Those studies reveal for the first time insights in dephasing mechanisms of 0D exciton polaritons [1]. In another study [2], using a similar device, they investigate the coupling between two different QDs with a single cavity mode. In both works, incoherent pumping was used, but for quantum information, coherent and controlled excitations are necessary. Here, we theoretically investigate the dynamics a single quantum dot inside a cavity under coherent pulse excitation and explore a wide range of parameters, as for example, the exciton-cavity detunings, the excitation power, the spontaneous decay, and pure dephasing. We use density matrix formalism in the Lindblad form, and we solve it numerically. Our results show that coherent excitation can be used to probe strong coupling between exciton and cavity mode by monitoring the exciton Rabi oscillation as function of the cavity detuning. This can give new insights for future experimental measurement focusing on quantum

Plasmon-Enhanced Photoluminescence of an Amorphous Silicon Quantum Dot Light-Emitting Device by Localized Surface Plasmon Polaritons in Ag/SiOx:a-Si QDs/Ag Sandwich Nanostructures

Directory of Open Access Journals (Sweden)

Tsung-Han Tsai

2015-01-01

Full Text Available We investigated experimentally the plasmon-enhanced photoluminescence of the amorphous silicon quantum dots (a-Si QDs light-emitting devices (LEDs with the Ag/SiOx:a-Si QDs/Ag sandwich nanostructures, through the coupling between the a-Si QDs and localized surface plasmons polaritons (LSPPs mode, by tuning a one-dimensional (1D Ag grating on the top. The coupling of surface plasmons at the top and bottom Ag/SiOx:a-Si QDs interfaces resulted in the localized surface plasmon polaritons (LSPPs confined underneath the Ag lines, which exhibit the Fabry-Pérot resonance. From the Raman spectrum, it proves the existence of a-Si QDs embedded in Si-rich SiOx film (SiOx:a-Si QDs at a low annealing temperature (300°C to prevent the possible diffusion of Ag atoms from Ag film. The photoluminescence (PL spectra of a-Si QDs can be precisely tuned by a 1D Ag grating with different pitches and Ag line widths were investigated. An optimized Ag grating structure, with 500 nm pitch and 125 nm Ag line width, was found to achieve up to 4.8-fold PL enhancement at 526 nm and 2.46-fold PL integrated intensity compared to the a-Si QDs LEDs without Ag grating structure, due to the strong a-Si QDs-LSPPs coupling.

HNO₃-assisted polyol synthesis of ultralarge single-crystalline Ag microplates and their far propagation length of surface plasmon polariton.

Science.gov (United States)

Chang, Cheng-Wei; Lin, Fan-Cheng; Chiu, Chun-Ya; Su, Chung-Yi; Huang, Jer-Shing; Perng, Tsong-Pyng; Yen, Ta-Jen

2014-07-23

We developed a HNO3-assisted polyol reduction method to synthesize ultralarge single-crystalline Ag microplates routinely. The edge length of the synthesized Ag microplates reaches 50 μm, and their top facets are (111). The mechanism for dramatically enlarging single-crystalline Ag structure stems from a series of competitive anisotropic growths, primarily governed by carefully tuning the adsorption of Ag(0) by ethylene glycol and the desorption of Ag(0) by a cyanide ion on Ag(100). Finally, we measured the propagation length of surface plasmon polaritons along the air/Ag interface under 534 nm laser excitation. Our single-crystalline Ag microplate exhibited a propagation length (11.22 μm) considerably greater than that of the conventional E-gun deposited Ag thin film (5.27 μm).

Wave refraction and backward magnon-plasmon polaritons in left-handed antiferromagnet/semiconductor superlattices

International Nuclear Information System (INIS)

Tarkhanyan, R.H.; Niarchos, D.G.

2007-01-01

Characteristics of the bulk electromagnetic waves in teraHertz frequency region are examined in a left-handed superlattice (SL) which consists of alternating layers of nonmagnetic semiconductor and nonconducting antiferromagnetic materials. General problem on the sign of the refractive index for anisotropic media is considered. It is shown that the phase refraction index is always positive while the group refractive index can be negative when some general conditions are fulfilled. Effective permittivity and permeability tensors of the SL are derived for perpendicular and parallel orientation of the magnetic anisotropy axis with respect to the plane of the layers. Problem of anomalous refraction for transverse electric and transverse magnetic-type polarized waves is examined in such media. Analytical expressions for both the phase and group refractive indices are obtained for various propagated modes. It is shown that, in general, three different types of the refracted waves with different relative orientation of the phase and group velocity vectors are possible in left-handed media. Unusual peculiarities of the backward modes corresponding to the coupled magnon-plasmon polaritons are considered. It is shown, in particular, that the number of the backward modes depends on the free charge carrier's density in semiconductor layers, variation of which allows to create different frequency regions for the wave propagation

Modulation of electromagnetic local density of states by coupling of surface phonon-polariton

Science.gov (United States)

Li, Yao; Zhang, Chao-Jie; Wang, Tong-Biao; Liu, Jiang-Tao; Yu, Tian-Bao; Liao, Qing-Hua; Liu, Nian-Hua

2017-02-01

We studied the electromagnetic local density of state (EM-LDOS) near the surface of a one-dimensional multilayer structure (1DMS) alternately stacked by SiC and Si. EM-LDOS of a semi-infinite bulk appears two intrinsic peaks due to the resonance of surface phonon-polariton (SPhP) in SiC. In contrast with that of SiC bulk, SPhP can exist at the interface of SiC and Si for the 1DMS. The SPhPs from different interfaces can couple together, which can lead to a significant modulation of EM-LDOS. When the component widths of 1DMS are large, the spectrum of EM-LDOS exhibits oscillation behavior in the frequency regime larger than the resonance frequency of SPhP. While the component widths are small, due to the strong coupling of SPhPs, another peak appears in the EM-LDOS spectrum besides the two intrinsic ones. And the position of the new peak move toward high frequency when the width ratio of SiC and Si increases. The influences of distance from the surfaces and period of 1DMS on EM-LDOS have also been studied in detail. The results are helpful in studying the near-field radiative heat transfer and spontaneous emission.

Gain-assisted superluminal propagation and rotary drag of photon and surface plasmon polaritons

Science.gov (United States)

Khan, Naveed; Amin Bacha, Bakht; Iqbal, Azmat; Ur Rahman, Amin; Afaq, A.

2017-07-01

Superluminal propagation of light is a well-established phenomenon and has motivated immense research interest that has led to state-of-the-art knowledge and potential applications in the emerging technology of quantum optics and photonics. This study presents a theoretical analysis of the gain-assisted superluminal light propagation in a four-level N -type atomic system by exploiting the scheme of electromagnetically induced gain and superluminal propagation of surface plasmon polaritons (SPPs) along the gain-assisted atomic-metal interface simultaneously. In addition, a theoretical demonstration is presented on the comparison between Fresnel's rotary photon drag and SPP drag in view of light polarization state rotation by rotating the coherent atomic medium and the atomic-metal interface, respectively. Analogous to photon drag in the superluminal anomalous dispersion region where light polarization rotation occurs opposite the rotation of the gain-assisted atomic medium, the rotation of the atomic-metal interface also rotates the polarization state of SPPs opposite the rotation of the interface. This further confirms the superluminal nature of SPPs propagating along the interface with negative group velocity. Rabi frequencies of the control and pump fields considerably modify both photon and SPP drag coefficients. Metal conductivity also controls SPP propagation.

Apertureless SNOM imaging of the surface phonon polariton waves: what do we measure?

Science.gov (United States)

Kazantsev, D. V.; Ryssel, H.

2013-10-01

The apertureless scanning near-field microscope (ASNOM) mapping of surface phonon polariton (SPP) waves being excited at the surface of the SiC polar crystal at a frequency corresponding to the lattice resonance was investigated. The wave with well-defined direction and source position, as well as a well-known propagation law, was used to calibrate the signal of an ASNOM. An experimental proof is presented showing that the signal collected by the ASNOM in such a case is proportional (as a complex number) to the local field amplitude above the surface, regardless of the tip response model. It is shown that the expression describing an ASNOM response, which is, in general case, rather complicated nonlinear function of a surface/tip dielectric constants, wavelength, tip vibration amplitude, tip shape etc., can be dramatically simplified in the case of the SPP waves mapping in a mid-IR range, due to a lucky combination of the tip and surface parameters for the case being considered. A tip vibration amplitude is much less than a running SPP wave field decay height in a normal direction. At the same time, the tip amplitude is larger than a characteristic distance at which a tip-surface electromagnetic near-field interaction plays a significant role.

Quasi-cylindrical wave contribution in experiments on extraordinary optical transmission.

Science.gov (United States)

van Beijnum, Frerik; Rétif, Chris; Smiet, Chris B; Liu, Haitao; Lalanne, Philippe; van Exter, Martin P

2012-12-20

A metal film perforated by a regular array of subwavelength holes shows unexpectedly large transmission at particular wavelengths, a phenomenon known as the extraordinary optical transmission (EOT) of metal hole arrays. EOT was first attributed to surface plasmon polaritons, stimulating a renewed interest in plasmonics and metallic surfaces with subwavelength features. Experiments soon revealed that the field diffracted at a hole or slit is not a surface plasmon polariton mode alone. Further theoretical analysis predicted that the extra contribution, from quasi-cylindrical waves, also affects EOT. Here we report the experimental demonstration of the relative importance of surface plasmon polaritons and quasi-cylindrical waves in EOT by considering hole arrays of different hole densities. From the measured transmission spectra, we determine microscopic scattering parameters which allow us to show that quasi-cylindrical waves affect EOT only for high densities, when the hole spacing is roughly one wavelength. Apart from providing a deeper understanding of EOT, the determination of microscopic scattering parameters from the measurement of macroscopic optical properties paves the way to novel design strategies.

Distinguishing Between Activated and Non-Activated Eosinophils Using a Microelectrode: Theoretical Investigations of Bulk and Surface Polaritons in Magnetic Multilayers

Science.gov (United States)

Lacy, Fred

In Part I of this dissertation, a whole cell biosensor which can detect the activation state of eosinophils (one of several types of white blood cells) will be developed and tested. This biosensor, which consists of a small gold electrode (50 μm x 50 μm) and a large gold electrode (1.5 cm x 0.5 cm) on a glass substrate, has been fabricated by photolithographic techniques. The eosinophils are known to exhibit different physical properties when they change from the activated state to the non-activated state. Based on some of these property changes, there should be a corresponding change in the measured electrical impedance. In this research, this biosensor will measure the electrical impedance of the eosinophils. This will show that the biosensor can detect the different states of the eosinophils (through the electrical impedance technique). And from these measurements, the different parameters associated with the electrical impedance can be determined. In Part II of this dissertation, a theoretical calculation will be performed in which bulk and surface magnetic polaritons in magnetic materials will be found. A polariton is the coupling of electromagnetic radiation and the elementary excitation of the given material (in our case, a magnetic material). The structure that we will be considering is a periodic semi-infinite material consisting of alternating antiferromagnetic and nonmagnetic layers. An antiferromagnetic material is a material in which individual atoms exhibit magnetic moments, but the overall magnetization of the material is zero because the moments of every other atom are antiparallel. We will use a method known as the transfer matrix technique to find an expression for the dispersion relation of the bulk and surface waves in these materials. Then we will create plots of omega(k) as we vary the geometric configurations of the layers which make-up the magnetic multilayer. We also will calculate the effect of an external magnetic field on these

Deep-subwavelength light routing in nanowire-loaded surface plasmon polariton waveguides: an alternative to the hybrid guiding scheme

International Nuclear Information System (INIS)

Bian, Yusheng; Gong, Qihuang

2013-01-01

Nanowire-loaded surface plasmon polariton waveguide is an extremely simple structure that can be naturally formed by directly dropping a dielectric cylinder onto a metallic substrate. However, despite the substantial emphasis devoted to its hybrid plasmonic counterparts, this waveguiding structure has been paid little attention to so far. Here in this paper, through comprehensive numerical analysis, we reveal that such a configuration can be leveraged to achieve deep-subwavelength field confinement with mode area more than one order of magnitude smaller than that of the conventional hybrid waveguide, while maintaining a moderate attenuation with propagation distance over tens of microns. Two-dimensional parameter mapping concerning physical dimension, shape and material of the nanowire as well as the refractive index of the cladding has disclosed the wide-range existence nature of this plasmonic mode and the feasibility to further balance its confinement and loss. (paper)

Preface

Science.gov (United States)

2003-10-01

intense concentration of research, both theoretical and experimental, over the past three years much has become clearer about how polaritons behave, including suggestions about how they can be made to work for us in producing hitherto inaccessible physical phenomena of technological interest. Thus, it is timely to collect many of the excellent contributions together into a special issue in which much of this science can be treated in the depth it deserves. We can divide the contributions into those that promise new sorts of strongly-coupled microcavity devices; those which explore how polaritons are formed, how they scatter, and how they decay; and those which identify more of the unusual polariton particularly at the bottom of the dispersion relation). This latter topic reopens the question of whether Bose-Einstein (or in this case, polariton) condensation is possible or has been seen in these unusual structures. This field then crosses a number of important research areas including micro-lasers, lasing without inversion, condensation and superfluidity, new spin properties, ultrafast optical nonlinearities and quantum optics. We have included a review article by Quatropanni and co-workers, which discusses theoretical aspects of the nonlinear optical properties of semiconductor microcavities in the strong exciton-photon coupling regime, which was planned to appear as a separate paper in Semiconductor Science and Technology, but which was considered more appropriate to be incorporated in this issue. A theoretical description of coherent nonlinearities in semiconductor microcavities is given by Savasta et al, who show that the strong energy dependence of the two exciton states damping is crucial to explain the dependence of the experimentally reported results on Rabi splitting and detuning. Stimulated polariton scattering, arising from the bosonic character of polaritons, is described by Skolnick's group, who also emphasize the role of the unusual dispersion of the lower

Silicon as a virtual plasmonic material: Acquisition of its transient optical constants and the ultrafast surface plasmon-polariton excitation

Energy Technology Data Exchange (ETDEWEB)

Danilov, P. A.; Ionin, A. A.; Kudryashov, S. I., E-mail: sikudr@sci.lebedev.ru; Makarov, S. V.; Rudenko, A. A. [Lebedev Physical Institute (Russian Federation); Saltuganov, P. N. [Moscow Institute of Physics and Technology (State University) (Russian Federation); Seleznev, L. V.; Yurovskikh, V. I.; Zayarny, D. A. [Lebedev Physical Institute (Russian Federation); Apostolova, T. [Bulgarian Academy of Sciences, Institute for Nuclear Research and Nuclear Energetics (Bulgaria)

2015-06-15

Ultrafast intense photoexcitation of a silicon surface is complementarily studied experimentally and theoretically, with its prompt optical dielectric function obtained by means of time-resolved optical reflection microscopy and the underlying electron-hole plasma dynamics modeled numerically, using a quantum kinetic approach. The corresponding transient surface plasmon-polariton (SPP) dispersion curves of the photo-excited material were simulated as a function of the electron-hole plasma density, using the derived optical dielectric function model, and directly mapped at several laser photon energies, measuring spatial periods of the corresponding SPP-mediated surface relief nanogratings. The unusual spectral dynamics of the surface plasmon resonance, initially increasing with the increase in the electron-hole plasma density but damped at high interband absorption losses induced by the high-density electron-hole plasma through instantaneous bandgap renormalization, was envisioned through the multi-color mapping.

A highly efficient surface plasmon polaritons excitation achieved with a metal-coupled metal-insulator-metal waveguide

Directory of Open Access Journals (Sweden)

Hongyan Yang

2014-12-01

Full Text Available We propose a novel metal-coupled metal-insulator-metal (MC-MIM waveguide which can achieve a highly efficient surface plasmon polaritons (SPPs excitation. The MC-MIM waveguide is formed by inserting a thin metal film in the insulator of an MIM. The introduction of the metal film, functioning as an SPPs coupler, provides a space for the interaction between SPPs and a confined electromagnetic field of the intermediate metal surface, which makes energy change and phase transfer in the metal-dielectric interface, due to the joint action of incomplete electrostatic shielding effect and SPPs coupling. Impacts of the metal film with different materials and various thickness on SPPs excitation are investigated. It is shown that the highest efficient SPPs excitation is obtained when the gold film thickness is 60 nm. The effect of refractive index of upper and lower symmetric dielectric layer on SPPs excitation is also discussed. The result shows that the decay value of refractive index is 0.3. Our results indicate that this proposed MC-MIM waveguide may offer great potential in designing a new SPPs source.

Analysis of the Complex Gross-Pitaevskii Equation for the Bose-Einstein Condensation of Exciton-Polaritons

KAUST Repository

Núñez, Jesus

2011-08-01

Considered as a fundamental step for the development of the atomic laser and quantum computing, as well as the theoretical explanation of super fluidity, the Bose- Einstein condensate (BEC) has emerged as one of the most important topics in modern physics. This project is devoted to the analysis of a condensate based on exciton-polaritons. This BEC is characterized by a high critical temperature of condensation (about 20 K) and non-equilibrium dynamics. A mathematical model called complex Gross- Pitaevskii equation (cGPE) is used to describe its behavior. The steady state solutions of the cGPE are studied and a numerical method based on a collocation method is proposed in order to find these solutions. Once the steady state solutions are found, a linear stability analysis is performed, demonstrating that the steady state solutions become unstable as the pumping spot radius increases. Finally, the manifestations of these instabilities are analyzed by direct simulation of the cGPE, using a second order time-splitting spectral method. As a result, it is possible to see the formation of quantum vortices, which increase in number as the pumping spot radius increases.

Surface plasmon polaritons in a semi-bounded degenerate plasma: Role of spatial dispersion and collisions

International Nuclear Information System (INIS)

Tyshetskiy, Yu.; Kompaneets, R.; Vladimirov, S. V.

2012-01-01

Surface plasmon polaritons (SPPs) in a semi-bounded degenerate plasma (e.g., a metal) are studied using the quasiclassical mean-field kinetic model, taking into account the spatial dispersion of the plasma (due to quantum degeneracy of electrons) and electron-ion (electron-lattice, for metals) collisions. SPP dispersion and damping are obtained in both retarded (ω/k z ∼c) and non-retarded (ω/k z ≪c) regions, as well as in between. It is shown that the plasma spatial dispersion significantly affects the properties of SPPs, especially at short wavelengths (less than the collisionless skin depth, λ ≲ c/ω pe ). Namely, the collisionless (Landau) damping of SPPs (due to spatial dispersion) is comparable to the purely collisional (Ohmic) damping (due to electron-lattice collisions) in a wide range of SPP wavelengths, e.g., from λ∼20 nm to λ∼0.8 nm for SPP in gold at T = 293 K and from λ∼400 nm to λ∼0.7 nm for SPPs in gold at T = 100 K. The spatial dispersion is also shown to affect, in a qualitative way, the dispersion of SPPs at short wavelengths λ ≲ c/ω pe .

Dynamics of coupled plasmon polariton wave packets excited at a subwavelength slit in optically thin metal films

Science.gov (United States)

Wang, Lei-Ming; Zhang, Lingxiao; Seideman, Tamar; Petek, Hrvoje

2012-10-01

We study by numerical simulations the excitation and propagation dynamics of coupled surface plasmon polariton (SPP) wave packets (WPs) in optically thin Ag films and a bulk Ag/vacuum interface under the illumination of a subwavelength slit by 400 nm continuous wave (cw) and femtosecond pulsed light. The generated surface fields include contributions from both SPPs and quasicylindrical waves, which dominate in different regimes. We explore aspects of the coupled SPP modes in Ag thin films, including symmetry, propagation, attenuation, and the variation of coupling with incident angle and film thickness. Simulations of the electromagnetic transients initiated with femtosecond pulses reveal new features of coupled SPP WP generation and propagation in thin Ag films. Our results show that, under pulsed excitation, the SPP modes in an Ag thin film break up into two distinct bound surface wave packets characterized by marked differences in symmetries, group velocities, attenuation lengths, and dispersion properties. The nanometer spatial and femtosecond temporal scale excitation and propagation dynamics of the coupled SPP WPs are revealed in detail by movies recording the evolution of their transient field distributions.

Effect of surface plasmon polaritons on the sensitivity of refractive index measurement using total internal reflection method

International Nuclear Information System (INIS)

Roshan Entezar, S.

2015-01-01

The phase difference between two p-polarized and s-polarized plane waves which are reflected under total internal reflection from the base of a prism with a thin metal coating is studied. Typically such a quantity can be used to measure the refractive index of a test material using the total internal reflection method. It is shown that due to the excitation of surface plasmon polaritons at the interface between the tested dielectric material and the thin metal layer, the p-polarized light experiences a large phase shift which enlarges the phase difference between the p-polarized and the s-polarized waves. As a result, the sensitivity of refractive index measurement increases and the error in determining the refractive index decreases. - Highlights: • Phase difference of totally internally reflected p and s polarized beams is studied. • Excitation of the surface wave increases the phase shift of the p-polarized light. • The sensitivity of refractive index measurement increases by using a coated prism. • The error in determining the refractive index decreases using the coated prism

Thermal diffusivity of electrical insulators at high temperatures: Evidence for diffusion of bulk phonon-polaritons at infrared frequencies augmenting phonon heat conduction

Science.gov (United States)

Hofmeister, Anne M.; Dong, Jianjun; Branlund, Joy M.

2014-04-01

We show that laser-flash analysis measurements of the temperature (T) dependence of thermal diffusivity (D) for diverse non-metallic (e.g., silicates) single-crystals is consistently represented by D(T) = FT-G + HT above 298 K, with G ranging from 0.3 to 2, depending on structure, and H being ˜10-4 K-1 for 51 single-crystals, 3 polycrystals, and two glasses unaffected by disorder or reconstructive phase transitions. Materials exhibiting this behavior include complex silicates with variable amounts of cation disorder, perovskite structured materials, and graphite. The high-temperature term HT becomes important by ˜1300 K, above which temperature its contribution to D(T) exceeds that of the FT-G term. The combination of the FT-G and HT terms produces the nearly temperature independent high-temperature region of D previously interpreted as the minimal phonon mean free path being limited by the finite interatomic spacing. Based on the simplicity of the fit and large number of materials it represents, this finding has repercussions for high-temperature models of heat transport. One explanation is that the two terms describing D(T) are associated with two distinct microscopic mechanisms; here, we explore the possibility that the thermal diffusivity of an electrical insulator could include both a contribution of lattice phonons (the FT-G term) and a contribution of diffusive bulk phonon-polaritons (BPP) at infrared (IR) frequencies (the HT term). The proposed BPP diffusion exists over length scales smaller than the laboratory sample sizes, and transfers mixed light and vibrational energy at a speed significantly smaller than the speed of light. Our diffusive IR-BPP hypothesis is consistent with other experimental observations such as polarization behavior, dependence of D on the number of IR peaks, and H = 0 for Ge and Si, which lack IR fundamentals. A simple quasi-particle thermal diffusion model is presented to begin understanding the contribution from bulk phonon-polaritons

Rabi like angular splitting in Surface Plasmon Polariton - Exciton interaction in ATR configuration

Science.gov (United States)

Hassan, Heba; Abdallah, T.; Negm, S.; Talaat, H.

2018-05-01

We have studied the coupling of propagating Surface Plasmon Polaritons (SPP) on silver films and excitons in CdS quantum dots (QDs). We employed the Kretschmann-Raether configuration of the attenuated total reflection (ATR) to propagate the SPP on silver film of thickness 47.5 nm at three different wavelengths. The CdS QD have been chemically synthesized with particular size such that its exciton of energy would resonate with SPP. High resolution transmission electron microscopy (HRTEM) and scan tunneling microscopy (STM) were used to measure the corresponding QDs size and confirm its shape. Further confirmation of the size has been performed by the effective mass approximation (EMA) model utilizing the band gap of the prepared QDs. The band gaps have been measured through UV-vis absorption spectra as well as scan tunneling spectroscopy (STS). The coupling has been observed as two branching dips in the ATR spectra indicating Rabi like splitting. To the best of our knowledge, this is the first time that Rabi interaction is directly observed in an ATR angular spectra. This observation is attributed to the use a high resolution angular scan (±0.005°), in addition to the Doppler width of the laser line as well as the energy distribution of the excitons. The effect of three different linker molecules (TOPO, HDA), (Pyridine) and (Tri-butylamine) as surface ligands, on SPP-Exciton interaction has been examined.

Excitation of surface plasmon polariton modes with multiple nitrogen vacancy centers in single nanodiamonds

International Nuclear Information System (INIS)

Kumar, Shailesh; Lausen, Jens L; Andersen, Sebastian K H; Roberts, Alexander S; Radko, Ilya P; Bozhevolnyi, Sergey I; Garcia-Ortiz, Cesar E; Smith, Cameron L C; Kristensen, Anders

2016-01-01

Nitrogen-vacancy (NV) centers in diamonds are interesting due to their remarkable characteristics that are well suited to applications in quantum-information processing and magnetic field sensing, as well as representing stable fluorescent sources. Multiple NV centers in nanodiamonds (NDs) are especially useful as biological fluorophores due to their chemical neutrality, brightness and room-temperature photostability. Furthermore, NDs containing multiple NV centers also have potential in high-precision magnetic field and temperature sensing. Coupling NV centers to propagating surface plasmon polariton (SPP) modes gives a base for lab-on-a-chip sensing devices, allows enhanced fluorescence emission and collection which can further enhance the precision of NV-based sensors. Here, we investigate coupling of multiple NV centers in individual NDs to the SPP modes supported by silver surfaces protected by thin dielectric layers and by gold V-grooves (VGs) produced via the self-terminated silicon etching. In the first case, we concentrate on monitoring differences in fluorescence spectra obtained from a source ND, which is illuminated by a pump laser, and from a scattering ND illuminated only by the fluorescence-excited SPP radiation. In the second case, we observe changes in the average NV lifetime when the same ND is characterized outside and inside a VG. Fluorescence emission from the VG terminations is also observed, which confirms the NV coupling to the VG-supported SPP modes. (paper)

Excitation of surface plasmon polariton modes with multiple nitrogen vacancy centers in single nanodiamonds

Science.gov (United States)

Kumar, Shailesh; Lausen, Jens L.; Garcia-Ortiz, Cesar E.; Andersen, Sebastian K. H.; Roberts, Alexander S.; Radko, Ilya P.; Smith, Cameron L. C.; Kristensen, Anders; Bozhevolnyi, Sergey I.

2016-02-01

Nitrogen-vacancy (NV) centers in diamonds are interesting due to their remarkable characteristics that are well suited to applications in quantum-information processing and magnetic field sensing, as well as representing stable fluorescent sources. Multiple NV centers in nanodiamonds (NDs) are especially useful as biological fluorophores due to their chemical neutrality, brightness and room-temperature photostability. Furthermore, NDs containing multiple NV centers also have potential in high-precision magnetic field and temperature sensing. Coupling NV centers to propagating surface plasmon polariton (SPP) modes gives a base for lab-on-a-chip sensing devices, allows enhanced fluorescence emission and collection which can further enhance the precision of NV-based sensors. Here, we investigate coupling of multiple NV centers in individual NDs to the SPP modes supported by silver surfaces protected by thin dielectric layers and by gold V-grooves (VGs) produced via the self-terminated silicon etching. In the first case, we concentrate on monitoring differences in fluorescence spectra obtained from a source ND, which is illuminated by a pump laser, and from a scattering ND illuminated only by the fluorescence-excited SPP radiation. In the second case, we observe changes in the average NV lifetime when the same ND is characterized outside and inside a VG. Fluorescence emission from the VG terminations is also observed, which confirms the NV coupling to the VG-supported SPP modes.

Electric-dipole absorption resonating with longitudinal optical phonon-plasmon system and its effect on dispersion relations of interface phonon polariton modes in metal/semiconductor-stripe structures

Science.gov (United States)

Sakamoto, Hironori; Takeuchi, Eito; Yoshida, Kouki; Morita, Ken; Ma, Bei; Ishitani, Yoshihiro

2018-01-01

Interface phonon polaritons (IPhPs) in nano-structures excluding metal components are thoroughly investigated because they have lower loss in optical emission or absorption and higher quality factors than surface plasmon polaritons. In previous reports, it is found that strong infrared (IR) absorption is based on the interaction of p-polarized light and materials, and the resonance photon energy highly depends on the structure size and angle of incidence. We report the optical absorption by metal/semiconductor (bulk-GaAs and thin film-AlN)-stripe structures in THz to mid-IR region for the electric field of light perpendicular to the stripes, where both of s- and p-polarized light are absorbed. The absorption resonates with longitudinal optical (LO) phonon or LO phonon-plasmon coupling (LOPC) modes, and thus is independent of the angle of incidence or structure size. This absorption is attributed to the electric dipoles by the optically induced polarization charges at the metal/semiconductor, heterointerfaces, or interfaces of high electron density layers and depression ones. The electric permittivity is modified by the formation of these dipoles. It is found to be indispensable to utilize our form of altered permittivity to explain the experimental dispersion relations of metal/semiconductor-IPhP and SPhP in these samples. This analysis reveals that the IPhPs in the stripe structures of metal/AlN-film on a SiC substrate are highly confined in the AlN film, while the permittivity of the structures of metal/bulk-GaAs is partially affected by the electric-dipoles. The quality factors of the electric-dipole absorption are found to be 42-54 for undoped samples, and the value of 62 is obtained for Al/AlN-IPhP. It is thought that metal-contained structures are not obstacles to mode energy selectivity in phonon energy region of semiconductors.

Mass-polariton theory of light in dispersive media

Science.gov (United States)

Partanen, Mikko; Tulkki, Jukka

2017-12-01

We have recently shown that the electromagnetic pulse in a medium is made of mass-polariton (MP) quasiparticles, which are quantized coupled states of the field and an atomic mass density wave (MDW) [M. Partanen et al., Phys. Rev. A 95, 063850 (2017), 10.1103/PhysRevA.95.063850]. In this work, we generalize the MP theory of light for dispersive media assuming that absorption and scattering losses are very small. Following our previous work, we present two different approaches to the coupled state of light: (1) the MP quasiparticle theory, which is derived by only using the fundamental conservation laws and the Lorentz transformation; (2) the classical optoelastic continuum dynamics (OCD), which is a generalization of the electrodynamics of continuous media to include the dynamics of the medium under the influence of optical forces. We show that the total momentum and the transferred mass of the light pulse can be determined in a straightforward way if we know the field energy of the pulse and the dispersion relation of the medium. In analogy to the nondispersive case, we also find unambiguous correspondence between the MP and OCD theories. For the coupled MP state of a single photon and the medium, we obtain the total MP momentum pMP=npℏ ω /c , where np is the phase refractive index. The field's share of the MP momentum is equal to pfield=ℏ ω /(ngc ) , where ng is the group refractive index and the share of the MDW is equal to pMDW=pMP-pfield . Thus, as in a nondispersive medium, the total momentum of the MP is equal to the Minkowski momentum and the field's share of the momentum is equal to the Abraham momentum. We also show that the correspondence between the MP and OCD models and the conservation of momentum at interfaces gives an unambiguous formula for the optical force. The dynamics of the light pulse and the related MDW lead to nonequilibrium of the medium and to relaxation of the atomic density by sound waves in the same way as for nondispersive media

Brain Stimulation Therapies

Science.gov (United States)

... Magnetic Seizure Therapy Deep Brain Stimulation Additional Resources Brain Stimulation Therapies Overview Brain stimulation therapies can play ... for a shorter recovery time than ECT Deep Brain Stimulation Deep brain stimulation (DBS) was first developed ...

Computationally Developed Sham Stimulation Protocol for Multichannel Desynchronizing Stimulation

Directory of Open Access Journals (Sweden)

Magteld Zeitler

2018-05-01

Full Text Available A characteristic pattern of abnormal brain activity is abnormally strong neuronal synchronization, as found in several brain disorders, such as tinnitus, Parkinson's disease, and epilepsy. As observed in several diseases, different therapeutic interventions may induce a placebo effect that may be strong and hinder reliable clinical evaluations. Hence, to distinguish between specific, neuromodulation-induced effects and unspecific, placebo effects, it is important to mimic the therapeutic procedure as precisely as possibly, thereby providing controls that actually lack specific effects. Coordinated Reset (CR stimulation has been developed to specifically counteract abnormally strong synchronization by desynchronization. CR is a spatio-temporally patterned multichannel stimulation which reduces the extent of coincident neuronal activity and aims at an anti-kindling, i.e., an unlearning of both synaptic connectivity and neuronal synchrony. Apart from acute desynchronizing effects, CR may cause sustained, long-lasting desynchronizing effects, as already demonstrated in pre-clinical and clinical proof of concept studies. In this computational study, we set out to computationally develop a sham stimulation protocol for multichannel desynchronizing stimulation. To this end, we compare acute effects and long-lasting effects of six different spatio-temporally patterned stimulation protocols, including three variants of CR, using a no-stimulation condition as additional control. This is to provide an inventory of different stimulation algorithms with similar fundamental stimulation parameters (e.g., mean stimulation rates but qualitatively different acute and/or long-lasting effects. Stimulation protocols sharing basic parameters, but inducing nevertheless completely different or even no acute effects and/or after-effects, might serve as controls to validate the specific effects of particular desynchronizing protocols such as CR. In particular, based on

Imaging surface plasmon polaritons using proximal self-assembled InGaAs quantum dots

Energy Technology Data Exchange (ETDEWEB)

Bracher, Gregor; Schraml, Konrad; Blauth, Mäx; Wierzbowski, Jakob; López, Nicolás Coca; Bichler, Max; Müller, Kai; Finley, Jonathan J.; Kaniber, Michael, E-mail: Michael.Kaniber@wsi.tum.de [Walter Schottky Institut and Physik Department, Technische Universität München, Am Coulombwall 4, 85748 Garching, Germany and Nanosystems Initiative Munich, Schellingstraße 4, 80799 München (Germany)

2014-07-21

We present optical investigations of hybrid plasmonic nanosystems consisting of lithographically defined plasmonic Au-waveguides or beamsplitters on GaAs substrates coupled to proximal self-assembled InGaAs quantum dots. We designed a sample structure that enabled us to precisely tune the distance between quantum dots and the sample surface during nano-fabrication and demonstrated that non-radiative processes do not play a major role for separations down to ∼10 nm. A polarized laser beam focused on one end of the plasmonic nanostructure generates propagating surface plasmon polaritons that, in turn, create electron-hole pairs in the GaAs substrate during propagation. These free carriers are subsequently captured by the quantum dots ∼25 nm below the surface, giving rise to luminescence. The intensity of the spectrally integrated quantum dot luminescence is used to image the propagating plasmon modes. As the waveguide width reduces from 5 μm to 1 μm, we clearly observe different plasmonic modes at the remote waveguide end, enabling their direct imaging in real space. This imaging technique is applied to a plasmonic beamsplitter facilitating the determination of the splitting ratio between the two beamsplitter output ports as the interaction length L{sub i} is varied. A splitting ratio of 50:50 is observed for L{sub i}∼9±1 μm and 1 μm wide waveguides for excitation energies close to the GaAs band edge. Our experimental findings are in good agreement with mode profile and finite difference time domain simulations for both waveguides and beamsplitters.

Towards a Switched-Capacitor Based Stimulator for Efficient Deep-Brain Stimulation

Science.gov (United States)

Vidal, Jose; Ghovanloo, Maysam

2013-01-01

We have developed a novel 4-channel prototype stimulation circuit for implantable neurological stimulators (INS). This Switched-Capacitor based Stimulator (SCS) aims to utilize charge storage and charge injection techniques to take advantage of both the efficiency of conventional voltage-controlled stimulators (VCS) and the safety and controllability of current-controlled stimulators (CCS). The discrete SCS prototype offers fine control over stimulation parameters such as voltage, current, pulse width, frequency, and active electrode channel via a LabVIEW graphical user interface (GUI) when connected to a PC through USB. Furthermore, the prototype utilizes a floating current sensor to provide charge-balanced biphasic stimulation and ensure safety. The stimulator was analyzed using an electrode-electrolyte interface (EEI) model as well as with a pair of pacing electrodes in saline. The primary motivation of this research is to test the feasibility and functionality of a safe, effective, and power-efficient switched-capacitor based stimulator for use in Deep Brain Stimulation. PMID:21095987

Ultrasound stimulation on bone healing. The optimization of stimulation time

International Nuclear Information System (INIS)

Rosim, R.C.; Paulin, J.B.P.; Goncalves, R.P.

1990-01-01

Previous works in ultrasonic simulation of bone healing dealt with parameters optimization. Albertin (1983) studied the stimulation time and found forty minutes as ideal. However, this stimulation time was the largest one employed and remained some doubt about the most appropriated value. 30, 40, 50 and 60 minutes of stimulation time were selected, while others parameters were held constant with: pulse width in 200 μs, repetition rate in 1000 pulses per second and amplitude in 30 V. Partial incomplete transverse osteotomies were done in the middle third of radio in the right forearm of rabbits. Twenty four animals divided in four subgroups, with 6 animals each were stimulated. The daily stimulation time for each subgroup was 30, 40, 50 and minutes respectively, during 15 consecutive days. The stimulation procedure started 24 hours after surgery. After the stimulation period, radiological, histological and morphometric evaluations were done and greater bone healing was found for the 50 minutes stimulation subgroup, in them new bone was also prominent. (author)

Quantum theory of the electronic and optical properties of low-dimensional semiconductor systems

Science.gov (United States)

Lau, Wayne Heung

This thesis examines the electronic and optical properties of low-dimensional semiconductor systems. A theory is developed to study the electron-hole generation-recombination process of type-II semimetallic semiconductor heterojunctions based on a 3 x 3 k·p matrix Hamiltonian (three-band model) and an 8 x 8 k·p matrix Hamiltonian (eight-band model). A novel electron-hole generation and recombination process, which is called activationless generation-recombination process, is predicted. It is demonstrated that the current through the type-II semimetallic semiconductor heterojunctions is governed by the activationless electron-hole generation-recombination process at the heterointerfaces, and that the current-voltage characteristics are essentially linear. A qualitative agreement between theory and experiments is observed. The numerical results of the eight-band model are compared with those of the threeband model. Based on a lattice gas model, a theory is developed to study the influence of a random potential on the ionization equilibrium conditions for bound electron-hole pairs (excitons) in III--V semiconductor heterostructures. It is demonstrated that ionization equilibrium conditions for bound electron-hole pairs change drastically in the presence of strong disorder. It is predicted that strong disorder promotes dissociation of excitons in III--V semiconductor heterostructures. A theory of polariton (photon dressed by phonon) spontaneous emission in a III--V semiconductor doped with semiconductor quantum dots (QDs) or quantum wells (QWs) is developed. For the first time, superradiant and subradiant polariton spontaneous emission phenomena in a polariton-QD (QW) coupled system are predicted when the resonance energies of the two identical QDs (QWs) lie outside the polaritonic energy gap. It is also predicted that when the resonance energies of the two identical QDs (QWs) lie inside the polaritonic energy gap, spontaneous emission of polariton in the polariton

Stimulating at the right time: phase-specific deep brain stimulation.

Science.gov (United States)

Cagnan, Hayriye; Pedrosa, David; Little, Simon; Pogosyan, Alek; Cheeran, Binith; Aziz, Tipu; Green, Alexander; Fitzgerald, James; Foltynie, Thomas; Limousin, Patricia; Zrinzo, Ludvic; Hariz, Marwan; Friston, Karl J; Denison, Timothy; Brown, Peter

2017-01-01

SEE MOLL AND ENGEL DOI101093/AWW308 FOR A SCIENTIFIC COMMENTARY ON THIS ARTICLE: Brain regions dynamically engage and disengage with one another to execute everyday actions from movement to decision making. Pathologies such as Parkinson's disease and tremor emerge when brain regions controlling movement cannot readily decouple, compromising motor function. Here, we propose a novel stimulation strategy that selectively regulates neural synchrony through phase-specific stimulation. We demonstrate for the first time the therapeutic potential of such a stimulation strategy for the treatment of patients with pathological tremor. Symptom suppression is achieved by delivering stimulation to the ventrolateral thalamus, timed according to the patient's tremor rhythm. Sustained locking of deep brain stimulation to a particular phase of tremor afforded clinically significant tremor relief (up to 87% tremor suppression) in selected patients with essential tremor despite delivering less than half the energy of conventional high frequency stimulation. Phase-specific stimulation efficacy depended on the resonant characteristics of the underlying tremor network. Selective regulation of neural synchrony through phase-locked stimulation has the potential to both increase the efficiency of therapy and to minimize stimulation-induced side effects. © The Author (2016). Published by Oxford University Press on behalf of the Guarantors of Brain.

[Transcranial magnetic stimulation and motor cortex stimulation in neuropathic pain].

Science.gov (United States)

Mylius, V; Ayache, S S; Teepker, M; Kappus, C; Kolodziej, M; Rosenow, F; Nimsky, C; Oertel, W H; Lefaucheur, J P

2012-12-01

Non-invasive and invasive cortical stimulation allows the modulation of therapy-refractory neuropathic pain. High-frequency repetitive transcranial magnetic stimulation (rTMS) of the contralateral motor cortex yields therapeutic effects at short-term and predicts the benefits of epidural motor cortex stimulation (MCS). The present article summarizes the findings on application, mechanisms and therapeutic effects of cortical stimulation in neuropathic pain.

Room temperature strong coupling effects from single ZnO nanowire microcavity

KAUST Repository

Das, Ayan

2012-05-01

Strong coupling effects in a dielectric microcavity with a single ZnO nanowire embedded in it have been investigated at room temperature. A large Rabi splitting of ?100 meV is obtained from the polariton dispersion and a non-linearity in the polariton emission characteristics is observed at room temperature with a low threshold of 1.63 ?J/cm2, which corresponds to a polariton density an order of magnitude smaller than that for the Mott transition. The momentum distribution of the lower polaritons shows evidence of dynamic condensation and the absence of a relaxation bottleneck. The polariton relaxation dynamics were investigated by timeresolved measurements, which showed a progressive decrease in the polariton relaxation time with increase in polariton density. © 2012 Optical Society of America.

Stimulating the Comfort of Textile Electrodes in Wearable Neuromuscular Electrical Stimulation

Science.gov (United States)

Zhou, Hui; Lu, Yi; Chen, Wanzhen; Wu, Zhen; Zou, Haiqing; Krundel, Ludovic; Li, Guanglin

2015-01-01

Textile electrodes are becoming an attractive means in the facilitation of surface electrical stimulation. However, the stimulation comfort of textile electrodes and the mechanism behind stimulation discomfort is still unknown. In this study, a textile stimulation electrode was developed using conductive fabrics and then its impedance spectroscopy, stimulation thresholds, and stimulation comfort were quantitatively assessed and compared with those of a wet textile electrode and a hydrogel electrode on healthy subjects. The equivalent circuit models and the finite element models of different types of electrode were built based on the measured impedance data of the electrodes to reveal the possible mechanism of electrical stimulation pain. Our results showed that the wet textile electrode could achieve similar stimulation performance as the hydrogel electrode in motor threshold and stimulation comfort. However, the dry textile electrode was found to have very low pain threshold and induced obvious cutaneous painful sensations during stimulation, in comparison to the wet and hydrogel electrodes. Indeed, the finite element modeling results showed that the activation function along the z direction at the depth of dermis epidermis junction of the dry textile electrode was significantly larger than that of the wet and hydrogel electrodes, thus resulting in stronger activation of pain sensing fibers. Future work will be done to make textile electrodes have similar stimulation performance and comfort as hydrogel electrodes. PMID:26193273

Stimulating the Comfort of Textile Electrodes in Wearable Neuromuscular Electrical Stimulation

Directory of Open Access Journals (Sweden)

Hui Zhou

2015-07-01

Full Text Available Textile electrodes are becoming an attractive means in the facilitation of surface electrical stimulation. However, the stimulation comfort of textile electrodes and the mechanism behind stimulation discomfort is still unknown. In this study, a textile stimulation electrode was developed using conductive fabrics and then its impedance spectroscopy, stimulation thresholds, and stimulation comfort were quantitatively assessed and compared with those of a wet textile electrode and a hydrogel electrode on healthy subjects. The equivalent circuit models and the finite element models of different types of electrode were built based on the measured impedance data of the electrodes to reveal the possible mechanism of electrical stimulation pain. Our results showed that the wet textile electrode could achieve similar stimulation performance as the hydrogel electrode in motor threshold and stimulation comfort. However, the dry textile electrode was found to have very low pain threshold and induced obvious cutaneous painful sensations during stimulation, in comparison to the wet and hydrogel electrodes. Indeed, the finite element modeling results showed that the activation function along the z direction at the depth of dermis epidermis junction of the dry textile electrode was significantly larger than that of the wet and hydrogel electrodes, thus resulting in stronger activation of pain sensing fibers. Future work will be done to make textile electrodes have similar stimulation performance and comfort as hydrogel electrodes.

Biomarkers and Stimulation Algorithms for Adaptive Brain Stimulation

Directory of Open Access Journals (Sweden)

Kimberly B. Hoang

2017-10-01

Full Text Available The goal of this review is to describe in what ways feedback or adaptive stimulation may be delivered and adjusted based on relevant biomarkers. Specific treatment mechanisms underlying therapeutic brain stimulation remain unclear, in spite of the demonstrated efficacy in a number of nervous system diseases. Brain stimulation appears to exert widespread influence over specific neural networks that are relevant to specific disease entities. In awake patients, activation or suppression of these neural networks can be assessed by either symptom alleviation (i.e., tremor, rigidity, seizures or physiological criteria, which may be predictive of expected symptomatic treatment. Secondary verification of network activation through specific biomarkers that are linked to symptomatic disease improvement may be useful for several reasons. For example, these biomarkers could aid optimal intraoperative localization, possibly improve efficacy or efficiency (i.e., reduced power needs, and provide long-term adaptive automatic adjustment of stimulation parameters. Possible biomarkers for use in portable or implanted devices span from ongoing physiological brain activity, evoked local field potentials (LFPs, and intermittent pathological activity, to wearable devices, biochemical, blood flow, optical, or magnetic resonance imaging (MRI changes, temperature changes, or optogenetic signals. First, however, potential biomarkers must be correlated directly with symptom or disease treatment and network activation. Although numerous biomarkers are under consideration for a variety of stimulation indications the feasibility of these approaches has yet to be fully determined. Particularly, there are critical questions whether the use of adaptive systems can improve efficacy over continuous stimulation, facilitate adjustment of stimulation interventions and improve our understanding of the role of abnormal network function in disease mechanisms.

Complex temperature dependence of coupling and dissipation of cavity magnon polaritons from millikelvin to room temperature

Science.gov (United States)

Boventer, Isabella; Pfirrmann, Marco; Krause, Julius; Schön, Yannick; Kläui, Mathias; Weides, Martin

2018-05-01

Hybridized magnonic-photonic systems are key components for future information processing technologies such as storage, manipulation, or conversion of data both in the classical (mostly at room temperature) and quantum (cryogenic) regime. In this work, we investigate a yttrium-iron-garnet sphere coupled strongly to a microwave cavity over the full temperature range from 290 K to 30 mK . The cavity-magnon polaritons are studied from the classical to the quantum regimes where the thermal energy is less than one resonant microwave quanta, i.e., at temperatures below 1 K . We compare the temperature dependence of the coupling strength geff(T ) , describing the strength of coherent energy exchange between spin ensemble and cavity photon, to the temperature behavior of the saturation magnetization evolution Ms(T ) and find strong deviations at low temperatures. The temperature dependence of magnonic disspation is governed at intermediate temperatures by rare-earth impurity scattering leading to a strong peak at 40 K . The linewidth κm decreases to 1.2 MHz at 30 mK , making this system suitable as a building block for quantum electrodynamics experiments. We achieve an electromagnonic cooperativity in excess of 20 over the entire temperature range, with values beyond 100 in the millikelvin regime as well as at room temperature. With our measurements, spectroscopy on strongly coupled magnon-photon systems is demonstrated as versatile tool for spin material studies over large temperature ranges. Key parameters are provided in a single measurement, thus simplifying investigations significantly.

A distributed current stimulator ASIC for high density neural stimulation.

Science.gov (United States)

Jeong Hoan Park; Chaebin Kim; Seung-Hee Ahn; Tae Mok Gwon; Joonsoo Jeong; Sang Beom Jun; Sung June Kim

2016-08-01

This paper presents a novel distributed neural stimulator scheme. Instead of a single stimulator ASIC in the package, multiple ASICs are embedded at each electrode site for stimulation with a high density electrode array. This distributed architecture enables the simplification of wiring between electrodes and stimulator ASIC that otherwise could become too complex as the number of electrode increases. The individual ASIC chip is designed to have a shared data bus that independently controls multiple stimulating channels. Therefore, the number of metal lines is determined by the distributed ASICs, not by the channel number. The function of current steering is also implemented within each ASIC in order to increase the effective number of channels via pseudo channel stimulation. Therefore, the chip area can be used more efficiently. The designed chip was fabricated with area of 0.3 mm2 using 0.18 μm BCDMOS process, and the bench-top test was also conducted to validate chip performance.

Transcranial brain stimulation: closing the loop between brain and stimulation

DEFF Research Database (Denmark)

Karabanov, Anke; Thielscher, Axel; Siebner, Hartwig Roman

2016-01-01

-related and state-related variability. Fluctuations in brain-states can be traced online with functional brain imaging and inform the timing or other settings of transcranial brain stimulation. State-informed open-loop stimulation is aligned to the expression of a predefined brain state, according to prespecified......PURPOSE OF REVIEW: To discuss recent strategies for boosting the efficacy of noninvasive transcranial brain stimulation to improve human brain function. RECENT FINDINGS: Recent research exposed substantial intra- and inter-individual variability in response to plasticity-inducing transcranial brain...... stimulation. Trait-related and state-related determinants contribute to this variability, challenging the standard approach to apply stimulation in a rigid, one-size-fits-all fashion. Several strategies have been identified to reduce variability and maximize the plasticity-inducing effects of noninvasive...

Vagal nerve stimulation therapy: what is being stimulated?

Science.gov (United States)

Kember, Guy; Ardell, Jeffrey L; Armour, John A; Zamir, Mair

2014-01-01

Vagal nerve stimulation in cardiac therapy involves delivering electrical current to the vagal sympathetic complex in patients experiencing heart failure. The therapy has shown promise but the mechanisms by which any benefit accrues is not understood. In this paper we model the response to increased levels of stimulation of individual components of the vagal sympathetic complex as a differential activation of each component in the control of heart rate. The model provides insight beyond what is available in the animal experiment in as much as allowing the simultaneous assessment of neuronal activity throughout the cardiac neural axis. The results indicate that there is sensitivity of the neural network to low level subthreshold stimulation. This leads us to propose that the chronic effects of vagal nerve stimulation therapy lie within the indirect pathways that target intrinsic cardiac local circuit neurons because they have the capacity for plasticity.

Vagal nerve stimulation therapy: what is being stimulated?

Directory of Open Access Journals (Sweden)

Guy Kember

Full Text Available Vagal nerve stimulation in cardiac therapy involves delivering electrical current to the vagal sympathetic complex in patients experiencing heart failure. The therapy has shown promise but the mechanisms by which any benefit accrues is not understood. In this paper we model the response to increased levels of stimulation of individual components of the vagal sympathetic complex as a differential activation of each component in the control of heart rate. The model provides insight beyond what is available in the animal experiment in as much as allowing the simultaneous assessment of neuronal activity throughout the cardiac neural axis. The results indicate that there is sensitivity of the neural network to low level subthreshold stimulation. This leads us to propose that the chronic effects of vagal nerve stimulation therapy lie within the indirect pathways that target intrinsic cardiac local circuit neurons because they have the capacity for plasticity.

A novel dual-wavelength laser stimulator to elicit transient and tonic nociceptive stimulation.

Science.gov (United States)

Dong, Xiaoxi; Liu, Tianjun; Wang, Han; Yang, Jichun; Chen, Zhuying; Hu, Yong; Li, Yingxin

2017-07-01

This study aimed to develop a new laser stimulator to elicit both transient and sustained heat stimulation with a dual-wavelength laser system as a tool for the investigation of both transient and tonic experimental models of pain. The laser stimulator used a 980-nm pulsed laser to generate transient heat stimulation and a 1940-nm continuous-wave (CW) laser to provide sustained heat stimulation. The laser with 980-nm wavelength can elicit transient pain with less thermal injury, while the 1940-nm CW laser can effectively stimulate both superficial and deep nociceptors to elicit tonic pain. A proportional integral-derivative (PID) temperature feedback control system was implemented to ensure constancy of temperature during heat stimulation. The performance of this stimulator was evaluated by in vitro and in vivo animal experiments. In vitro experiments on totally 120 specimens fresh pig skin included transient heat stimulation by 980-nm laser (1.5 J, 10 ms), sustained heat stimulation by 1940-nm laser (50-55 °C temperature control mode or 1.5 W, 5 min continuous power supply), and the combination of transient/sustained heat stimulation by dual lasers (1.5 J, 10 ms, 980-nm pulse laser, and 1940-nm laser with 50-55 °C temperature control mode). Hemoglobin brushing and wind-cooling methods were tested to find better stimulation model. A classic tail-flick latency (TFL) experiment with 20 Wistar rats was used to evaluate the in vivo efficacy of transient and tonic pain stimulation with 15 J, 100 ms 980-nm single laser pulse, and 1.5 W constant 1940-nm laser power. Ideal stimulation parameters to generate transient pain were found to be a 26.6 °C peak temperature rise and 0.67 s pain duration. In our model of tonic pain, 5 min of tonic stimulation produced a temperature change of 53.7 ± 1.3 °C with 1.6 ± 0.2% variation. When the transient and tonic stimulation protocols were combined, no significant difference was observed depending on the order

Cognitive stimulation in healthy older adults: a cognitive stimulation program using leisure activities compared to a conventional cognitive stimulation program.

Science.gov (United States)

Grimaud, Élisabeth; Taconnat, Laurence; Clarys, David

2017-06-01

The aim of this study was to compare two methods of cognitive stimulation for the cognitive functions. The first method used an usual approach, the second used leisure activities in order to assess their benefits on cognitive functions (speed of processing; working memory capacity and executive functions) and psychoaffective measures (memory span and self esteem). 67 participants over 60 years old took part in the experiment. They were divided into three groups: 1 group followed a program of conventional cognitive stimulation, 1 group a program of cognitive stimulation using leisure activities and 1 control group. The different measures have been evaluated before and after the training program. Results show that the cognitive stimulation program using leisure activities is as effective on memory span, updating and memory self-perception as the program using conventional cognitive stimulation, and more effective on self-esteem than the conventional program. There is no difference between the two stimulated groups and the control group on speed of processing. Neither of the two cognitive stimulation programs provides a benefit over shifting and inhibition. These results indicate that it seems to be possible to enhance working memory and to observe far transfer benefits over self-perception (self-esteem and memory self-perception) when using leisure activities as a tool for cognitive stimulation.

Dye gain gold NW array of surface plasmon polariton waveguide

Directory of Open Access Journals (Sweden)

Jun Zhu

Full Text Available Plasmon lasers can support ultrasmall mode confinement and ultrafast dynamics with device feature sizes below the diffraction limit. At present in the single visible light frequency, the optical gain method of constraint SPP on metal nanowires structure reported less. We design the gold nanowire array structure, consisting of PMMA and R6G dye molecules as gain, by 488 nm pump in the middle of the nanowires position for wide range of light, use symmetry broken overcome that momentum does not match the photonic and SPP energy conversion. Theoretical analysis shows that dyes provide coherent optical feedback, resulting in nanowires face will observe laser properties of surface plasmons. Feature analysis: the incident light and pump joint strength is greater than the sum of strength which is the incident light, pump respectively. Under the effect of dye molecules gain effective, length of SPP transmission can increase 1 µm. The results achieved in a single optical frequency of stimulated radiation, application of dye optical gain can achieve continuous gain effect. This is for the future development of plasma amplifier and the wavelength laser. Keywords: SPP, Stimulated radiation, Gold nanowires array, Dye molecules

Mechanism of orientation of stimulating currents in magnetic brain stimulation (abstract)

Science.gov (United States)

Ueno, S.; Matsuda, T.

1991-04-01

We made a functional map of the human motor cortex related to the hand and foot areas by stimulating the human brain with a focused magnetic pulse. We observed that each functional area in the cortex has an optimum direction for which stimulating currents can produce neural excitation. The present report focuses on the mechanism which is responsible for producing this anisotropic response to brain stimulation. We first obtained a functional map of the brain related to the left ADM (abductor digiti minimi muscles). When the stimulating currents were aligned in the direction from the left to the right hemisphere, clear EMG (electromyographic) responses were obtained only from the left ADM to magnetic stimulation of both hemisphere. When the stimulating currents were aligned in the direction from the right to the left hemisphere, clear EMG signals were obtained only from the right ADM to magnetic stimulation of both hemisphere. The functional maps of the brain were sensitive to changes in the direction of the stimulating currents. To explain the phenomena obtained in the experiments, we developed a model of neural excitation elicited by magnetic stimulation. When eddy currents which are induced by pulsed magnetic fields flow in the direction from soma to the distal part of neural fiber, depolarized area in the distal part are excited, and the membrane excitation propagates along the nerve fiber. In contrast, when the induced currents flow in the direction from the distal part to soma, hyperpolarized parts block or inhibit neural excitation even if the depolarized parts near the soma can be excited. The model explains our observation that the orientation of the induced current vectors reflect both the functional and anatomical organization of the neural fibers in the brain.

Highly doped InP as a low loss plasmonic material for mid-IR region.

Science.gov (United States)

Panah, M E Aryaee; Takayama, O; Morozov, S V; Kudryavtsev, K E; Semenova, E S; Lavrinenko, A V

2016-12-12

We study plasmonic properties of highly doped InP in the mid-infrared (IR) range. InP was grown by metal-organic vapor phase epitaxy (MOVPE) with the growth conditions optimized to achieve high free electron concentrations by doping with silicon. The permittivity of the grown material was found by fitting the calculated infrared reflectance spectra to the measured ones. The retrieved permittivity was then used to simulate surface plasmon polaritons (SPPs) propagation on flat and structured surfaces, and the simulation results were verified in direct experiments. SPPs at the top and bottom interfaces of the grown epilayer were excited by the prism coupling. A high-index Ge hemispherical prism provides efficient coupling conditions of SPPs on flat surfaces and facilitates acquiring their dispersion diagrams. We observed diffraction into symmetry-prohibited diffraction orders stimulated by the excitation of surface plasmon-polaritons in a periodically structured epilayer. Characterization shows good agreement between the theory and experimental results and confirms that highly doped InP is an effective plasmonic material aiming it for applications in the mid-IR wavelength range.

[Transcranial magnetic stimulation].

Science.gov (United States)

Tormos, J M; Catalá, M D; Pascual-Leone, A

Transcranial magnetic stimulation (TMS) permits stimulation of the cerebral cortex in humans without requiring open access to the brain and is one of the newest tools available in neuroscience. There are two main types of application: single-pulse TMS and repetitive TMS. The magnetic stimulator is composed of a series of capacitors that store the voltage necessary to generate a stimulus of the sufficient intensity of generate an electric field in the stimulation coil. The safety of TMS is supported by the considerable experience derived from studies involving electrical stimulation of the cortex in animals and humans, and also specific studies on the safety of TMS in humans. In this article we review historical and technical aspects of TMS, describe its adverse effects and how to avoid them, summarize the applications of TMS in the investigation of different cerebral functions, and discuss the possibility of using TMS for the treatment of neuropsychiatric disorders.

Computational analysis of transcranial magnetic stimulation in the presence of deep brain stimulation probes

Science.gov (United States)

Syeda, F.; Holloway, K.; El-Gendy, A. A.; Hadimani, R. L.

2017-05-01

Transcranial Magnetic Stimulation is an emerging non-invasive treatment for depression, Parkinson's disease, and a variety of other neurological disorders. Many Parkinson's patients receive the treatment known as Deep Brain Stimulation, but often require additional therapy for speech and swallowing impairment. Transcranial Magnetic Stimulation has been explored as a possible treatment by stimulating the mouth motor area of the brain. We have calculated induced electric field, magnetic field, and temperature distributions in the brain using finite element analysis and anatomically realistic heterogeneous head models fitted with Deep Brain Stimulation leads. A Figure of 8 coil, current of 5000 A, and frequency of 2.5 kHz are used as simulation parameters. Results suggest that Deep Brain Stimulation leads cause surrounding tissues to experience slightly increased E-field (Δ Emax =30 V/m), but not exceeding the nominal values induced in brain tissue by Transcranial Magnetic Stimulation without leads (215 V/m). The maximum temperature in the brain tissues surrounding leads did not change significantly from the normal human body temperature of 37 °C. Therefore, we ascertain that Transcranial Magnetic Stimulation in the mouth motor area may stimulate brain tissue surrounding Deep Brain Stimulation leads, but will not cause tissue damage.

Pudendal nerve stimulation and block by a wireless-controlled implantable stimulator in cats.

Science.gov (United States)

Yang, Guangning; Wang, Jicheng; Shen, Bing; Roppolo, James R; de Groat, William C; Tai, Changfeng

2014-07-01

The study aims to determine the functionality of a wireless-controlled implantable stimulator designed for stimulation and block of the pudendal nerve. In five cats under α-chloralose anesthesia, the stimulator was implanted underneath the skin on the left side in the lower back along the sacral spine. Two tripolar cuff electrodes were implanted bilaterally on the pudendal nerves in addition to one bipolar cuff electrode that was implanted on the left side central to the tripolar cuff electrode. The stimulator provided high-frequency (5-20 kHz) biphasic stimulation waveforms to the two tripolar electrodes and low-frequency (1-100 Hz) rectangular pulses to the bipolar electrode. Bladder and urethral pressures were measured to determine the effects of pudendal nerve stimulation (PNS) or block. The maximal (70-100 cmH2O) urethral pressure generated by 20-Hz PNS applied via the bipolar electrode was completely eliminated by the pudendal nerve block induced by the high-frequency stimulation (6-15 kHz, 6-10 V) applied via the two tripolar electrodes. In a partially filled bladder, 20-30 Hz PNS (2-8 V, 0.2 ms) but not 5 Hz stimulation applied via the bipolar electrode elicited a large sustained bladder contraction (45.9 ± 13.4 to 52.0 ± 22 cmH2O). During cystometry, the 5 Hz PNS significantly (p < 0.05) increased bladder capacity to 176.5 ± 27.1% of control capacity. The wireless-controlled implantable stimulator successfully generated the required waveforms for stimulation and block of pudendal nerve, which will be useful for restoring bladder functions after spinal cord injury. © 2013 International Neuromodulation Society.

A new brain stimulation method: Noninvasive transcranial magneto–acoustical stimulation

International Nuclear Information System (INIS)

Yuan Yi; Chen Yu-Dong; Li Xiao-Li

2016-01-01

We investigate transcranial magneto–acoustical stimulation (TMAS) for noninvasive brain neuromodulation in vivo. TMAS as a novel technique uses an ultrasound wave to induce an electric current in the brain tissue in the static magnetic field. It has the advantage of high spatial resolution and penetration depth. The mechanism of TMAS onto a neuron is analyzed by combining the TMAS principle and Hodgkin–Huxley neuron model. The anesthetized rats are stimulated by TMAS, resulting in the local field potentials which are recorded and analyzed. The simulation results show that TMAS can induce neuronal action potential. The experimental results indicate that TMAS can not only increase the amplitude of local field potentials but also enhance the effect of focused ultrasound stimulation on the neuromodulation. In summary, TMAS can accomplish brain neuromodulation, suggesting a potentially powerful noninvasive stimulation method to interfere with brain rhythms for diagnostic and therapeutic purposes. (paper)

Spinal cord stimulation

Science.gov (United States)

... this page: //medlineplus.gov/ency/article/007560.htm Spinal cord stimulation To use the sharing features on this page, please enable JavaScript. Spinal cord stimulation is a treatment for pain that uses ...

Stimulating thought: a functional MRI study of transcranial direct current stimulation in schizophrenia.

Science.gov (United States)

Orlov, Natasza D; O'Daly, Owen; Tracy, Derek K; Daniju, Yusuf; Hodsoll, John; Valdearenas, Lorena; Rothwell, John; Shergill, Sukhi S

2017-09-01

Individuals with schizophrenia typically suffer a range of cognitive deficits, including prominent deficits in working memory and executive function. These difficulties are strongly predictive of functional outcomes, but there is a paucity of effective therapeutic interventions targeting these deficits. Transcranial direct current stimulation is a novel neuromodulatory technique with emerging evidence of potential pro-cognitive effects; however, there is limited understanding of its mechanism. This was a double-blind randomized sham controlled pilot study of transcranial direct current stimulation on a working memory (n-back) and executive function (Stroop) task in 28 individuals with schizophrenia using functional magnetic resonance imaging. Study participants received 30 min of real or sham transcranial direct current stimulation applied to the left frontal cortex. The 'real' and 'sham' groups did not differ in online working memory task performance, but the transcranial direct current stimulation group demonstrated significant improvement in performance at 24 h post-transcranial direct current stimulation. Transcranial direct current stimulation was associated with increased activation in the medial frontal cortex beneath the anode; showing a positive correlation with consolidated working memory performance 24 h post-stimulation. There was reduced activation in the left cerebellum in the transcranial direct current stimulation group, with no change in the middle frontal gyrus or parietal cortices. Improved performance on the executive function task was associated with reduced activity in the anterior cingulate cortex. Transcranial direct current stimulation modulated functional activation in local task-related regions, and in more distal nodes in the network. Transcranial direct current stimulation offers a potential novel approach to altering frontal cortical activity and exerting pro-cognitive effects in schizophrenia. © The Author (2017). Published by Oxford

The Codacs™ direct acoustic cochlear implant actuator: exploring alternative stimulation sites and their stimulation efficiency.

Science.gov (United States)

Grossöhmichen, Martin; Salcher, Rolf; Kreipe, Hans-Heinrich; Lenarz, Thomas; Maier, Hannes

2015-01-01

This work assesses the efficiency of the Codacs system actuator (Cochlear Ltd., Sydney Australia) in different inner ear stimulation modalities. Originally the actuator was intended for direct perilymph stimulation after stapedotomy using a piston prosthesis. A possible alternative application is the stimulation of middle ear structures or the round window (RW). Here the perilymph stimulation with a K-piston through a stapes footplate (SFP) fenestration (N = 10) as well as stimulation of the stapes head (SH) with a Bell prosthesis (N = 9), SFP stimulation with an Omega/Aerial prosthesis (N = 8) and reverse RW stimulation (N = 10) were performed in cadaveric human temporal bones (TBs). Codacs actuator output is expressed as equivalent sound pressure level (eq. SPL) using RW and SFP displacement responses, measured by Laser Doppler velocimetry as reference. The axial actuator coupling force in stimulation of stapes and RW was adjusted to ~5 mN. The Bell prosthesis and Omega/Aerial prosthesis stimulation generated similar mean eq. SPLs (Bell: 127.5-141.8 eq. dB SPL; Omega/Aerial: 123.6-143.9 eq. dB SPL), being significantly more efficient than K-piston perilymph stimulation (108.6-131.6 eq. dB SPL) and RW stimulation (108.3-128.2 eq. dB SPL). Our results demonstrate that SH, SFP and RW are adequate alternative stimulation sites for the Codacs actuator using coupling prostheses and an axial coupling force of ~5 mN. Based on the eq. SPLs, all investigated methods were adequate for in vivo hearing aid applications, provided that experimental conditions including constant coupling force will be implemented.

Depletion of superfluidity in a disordered non-equilibrium quantum condensate

Energy Technology Data Exchange (ETDEWEB)

Janot, Alexander; Rosenow, Bernd [Institut fuer Theoretische Physik, Universitaet Leipzig, 04009 Leipzig (Germany); Hyart, Timo [Institute of Physics, Leiden University, Niels Bohrweg 2, 2333 CA Leiden (Netherlands); Eastham, Paul [School of Physics, Trinity College, Dublin 2 (Ireland)

2013-07-01

Observations of quantum coherence in driven systems, e.g. polariton condensates, have strongly stimulated experimental as well as theoretical efforts during the last decade. We analyze the superfluid stiffness of a non-equilibrium quantum-condensate in a disordered environment taking gain and loss of particles into account. To this end a modified effective Gross-Pitaevskii equation is employed. We find that the disorder-driven depletion of superfluidity is strongly enhanced due to the gain-loss mechanism. It turns out that the condensate remains stiff at finite length scales only.

Optical generation and control of quantum coherence in semiconductor nanostructures

CERN Document Server

Slavcheva, Gabriela

2010-01-01

The unprecedented control of coherence that can be exercised in quantum optics of atoms and molecules has stimulated increasing efforts in extending it to solid-state systems. One motivation to exploit the coherent phenomena comes from the emergence of the quantum information paradigm, however many more potential device applications ranging from novel lasers to spintronics are all bound up with issues in coherence. The book focuses on recent advances in the optical control of coherence in excitonic and polaritonic systems as model systems for the complex semiconductor dynamics towards the goal

Infrared hyperbolic metasurface based on nanostructured van der Waals materials

Science.gov (United States)

Li, Peining; Dolado, Irene; Alfaro-Mozaz, Francisco Javier; Casanova, Fèlix; Hueso, Luis E.; Liu, Song; Edgar, James H.; Nikitin, Alexey Y.; Vélez, Saül; Hillenbrand, Rainer

2018-02-01

Metasurfaces with strongly anisotropic optical properties can support deep subwavelength-scale confined electromagnetic waves (polaritons), which promise opportunities for controlling light in photonic and optoelectronic applications. We developed a mid-infrared hyperbolic metasurface by nanostructuring a thin layer of hexagonal boron nitride that supports deep subwavelength-scale phonon polaritons that propagate with in-plane hyperbolic dispersion. By applying an infrared nanoimaging technique, we visualize the concave (anomalous) wavefronts of a diverging polariton beam, which represent a landmark feature of hyperbolic polaritons. The results illustrate how near-field microscopy can be applied to reveal the exotic wavefronts of polaritons in anisotropic materials and demonstrate that nanostructured van der Waals materials can form a highly variable and compact platform for hyperbolic infrared metasurface devices and circuits.

In vitro magnetic stimulation: a simple stimulation device to deliver defined low intensity electromagnetic fields

Directory of Open Access Journals (Sweden)

Stephanie Grehl

2016-11-01

Full Text Available Non-invasive electromagnetic field brain stimulation (NIBS appears to benefit human neurological and psychiatric conditions, although the optimal stimulation parameters and underlying mechanisms remain unclear. Although in vitro studies have begun to elucidate cellular mechanisms, stimulation is delivered by a range of coils (from commercially available human stimulation coils to laboratory-built circuits so that the electromagnetic fields induced within the tissue to produce the reported effects are ill-defined.Here we develop a simple in vitro stimulation device with plug-and-play features that allow delivery of a range of stimulation parameters. We chose to test low intensity repetitive magnetic stimulation (LI-rMS delivered at 3 frequencies to hindbrain explant cultures containing the olivocerebellar pathway. We used computational modelling to define the parameters of a stimulation circuit and coil that deliver a unidirectional homogeneous magnetic field of known intensity and direction, and therefore a predictable electric field, to the target. We built the coil to be compatible with culture requirements: stimulation within an incubator; a flat surface allowing consistent position and magnetic field direction; location outside the culture plate to maintain sterility and no heating or vibration. Measurements at the explant confirmed the induced magnetic field was homogenous and matched the simulation results. To validate our system we investigated biological effects following LI-rMS at 1 Hz, 10 Hz and biomimetic high frequency (BHFS, which we have previously shown induces neural circuit reorganisation. We found that gene expression was modified by LI-rMS in a frequency-related manner. Four hours after a single 10-minute stimulation session, the number of c-fos positive cells increased, indicating that our stimulation activated the tissue. Also, after 14 days of LI-rMS, the expression of genes normally present in the tissue was differentially

The Codacs™ direct acoustic cochlear implant actuator: exploring alternative stimulation sites and their stimulation efficiency.

Directory of Open Access Journals (Sweden)

Martin Grossöhmichen

Full Text Available This work assesses the efficiency of the Codacs system actuator (Cochlear Ltd., Sydney Australia in different inner ear stimulation modalities. Originally the actuator was intended for direct perilymph stimulation after stapedotomy using a piston prosthesis. A possible alternative application is the stimulation of middle ear structures or the round window (RW. Here the perilymph stimulation with a K-piston through a stapes footplate (SFP fenestration (N = 10 as well as stimulation of the stapes head (SH with a Bell prosthesis (N = 9, SFP stimulation with an Omega/Aerial prosthesis (N = 8 and reverse RW stimulation (N = 10 were performed in cadaveric human temporal bones (TBs. Codacs actuator output is expressed as equivalent sound pressure level (eq. SPL using RW and SFP displacement responses, measured by Laser Doppler velocimetry as reference. The axial actuator coupling force in stimulation of stapes and RW was adjusted to ~5 mN. The Bell prosthesis and Omega/Aerial prosthesis stimulation generated similar mean eq. SPLs (Bell: 127.5-141.8 eq. dB SPL; Omega/Aerial: 123.6-143.9 eq. dB SPL, being significantly more efficient than K-piston perilymph stimulation (108.6-131.6 eq. dB SPL and RW stimulation (108.3-128.2 eq. dB SPL. Our results demonstrate that SH, SFP and RW are adequate alternative stimulation sites for the Codacs actuator using coupling prostheses and an axial coupling force of ~5 mN. Based on the eq. SPLs, all investigated methods were adequate for in vivo hearing aid applications, provided that experimental conditions including constant coupling force will be implemented.

Using memory-efficient algorithm for large-scale time-domain modeling of surface plasmon polaritons propagation in organic light emitting diodes

Science.gov (United States)

Zakirov, Andrey; Belousov, Sergei; Valuev, Ilya; Levchenko, Vadim; Perepelkina, Anastasia; Zempo, Yasunari

2017-10-01

We demonstrate an efficient approach to numerical modeling of optical properties of large-scale structures with typical dimensions much greater than the wavelength of light. For this purpose, we use the finite-difference time-domain (FDTD) method enhanced with a memory efficient Locally Recursive non-Locally Asynchronous (LRnLA) algorithm called DiamondTorre and implemented for General Purpose Graphical Processing Units (GPGPU) architecture. We apply our approach to simulation of optical properties of organic light emitting diodes (OLEDs), which is an essential step in the process of designing OLEDs with improved efficiency. Specifically, we consider a problem of excitation and propagation of surface plasmon polaritons (SPPs) in a typical OLED, which is a challenging task given that SPP decay length can be about two orders of magnitude greater than the wavelength of excitation. We show that with our approach it is possible to extend the simulated volume size sufficiently so that SPP decay dynamics is accounted for. We further consider an OLED with periodically corrugated metallic cathode and show how the SPP decay length can be greatly reduced due to scattering off the corrugation. Ultimately, we compare the performance of our algorithm to the conventional FDTD and demonstrate that our approach can efficiently be used for large-scale FDTD simulations with the use of only a single GPGPU-powered workstation, which is not practically feasible with the conventional FDTD.

Higher success rate with transcranial electrical stimulation of motor-evoked potentials using constant-voltage stimulation compared with constant-current stimulation in patients undergoing spinal surgery.

Science.gov (United States)

Shigematsu, Hideki; Kawaguchi, Masahiko; Hayashi, Hironobu; Takatani, Tsunenori; Iwata, Eiichiro; Tanaka, Masato; Okuda, Akinori; Morimoto, Yasuhiko; Masuda, Keisuke; Tanaka, Yuu; Tanaka, Yasuhito

2017-10-01

During spine surgery, the spinal cord is electrophysiologically monitored via transcranial electrical stimulation of motor-evoked potentials (TES-MEPs) to prevent injury. Transcranial electrical stimulation of motor-evoked potential involves the use of either constant-current or constant-voltage stimulation; however, there are few comparative data available regarding their ability to adequately elicit compound motor action potentials. We hypothesized that the success rates of TES-MEP recordings would be similar between constant-current and constant-voltage stimulations in patients undergoing spine surgery. The objective of this study was to compare the success rates of TES-MEP recordings between constant-current and constant-voltage stimulation. This is a prospective, within-subject study. Data from 100 patients undergoing spinal surgery at the cervical, thoracic, or lumbar level were analyzed. The success rates of the TES-MEP recordings from each muscle were examined. Transcranial electrical stimulation with constant-current and constant-voltage stimulations at the C3 and C4 electrode positions (international "10-20" system) was applied to each patient. Compound muscle action potentials were bilaterally recorded from the abductor pollicis brevis (APB), deltoid (Del), abductor hallucis (AH), tibialis anterior (TA), gastrocnemius (GC), and quadriceps (Quad) muscles. The success rates of the TES-MEP recordings from the right Del, right APB, bilateral Quad, right TA, right GC, and bilateral AH muscles were significantly higher using constant-voltage stimulation than those using constant-current stimulation. The overall success rates with constant-voltage and constant-current stimulations were 86.3% and 68.8%, respectively (risk ratio 1.25 [95% confidence interval: 1.20-1.31]). The success rates of TES-MEP recordings were higher using constant-voltage stimulation compared with constant-current stimulation in patients undergoing spinal surgery. Copyright © 2017

Music acupuncture stimulation method.

Science.gov (United States)

Brătilă, F; Moldovan, C

2007-01-01

Harmonic Medicine is the model using the theory that the body rhythms synchronize to an outer rhythm applied for therapeutic purpose, can restores the energy balance in acupuncture channels and organs and the condition of well-being. The purpose of this scientific work was to demonstrate the role played by harmonic sounds in the stimulation of the Lung (LU) Meridian (Shoutaiyin Feijing) and of the Kidney (KI) Meridian (Zushaoyin Shenjing). It was used an original method that included: measurement and electronic sound stimulation of the Meridian Entry Point, measurement of Meridian Exit Point, computer data processing, bio feed-back adjustment of the music stimulation parameters. After data processing, it was found that the sound stimulation of the Lung Meridian Frequency is optimal between 122 Hz and 128 Hz, with an average of 124 Hz (87% of the subjects) and for Kidney Meridian from 118 Hz to 121 Hz, with an average of 120 Hz (67% of the subjects). The acupuncture stimulation was more intense for female subjects (> 7%) than for the male ones. We preliminarily consider that an informational resonance phenomenon can be developed between the acupuncture music stimulation frequency and the cellular dipole frequency, being a really "resonant frequency signature" of an acupoint. The harmonic generation and the electronic excitation or low-excitation status of an acupuncture point may be considered as a resonance mechanism. By this kind of acupunctural stimulation, a symphony may act and play a healer role.

Low intensity transcranial electric stimulation

DEFF Research Database (Denmark)

Antal, Andrea; Alekseichuk, I; Bikson, M

2017-01-01

Low intensity transcranial electrical stimulation (TES) in humans, encompassing transcranial direct current (tDCS), transcutaneous spinal Direct Current Stimulation (tsDCS), transcranial alternating current (tACS), and transcranial random noise (tRNS) stimulation or their combinations, appears...

Quantum condensates and topological bosons in coupled light-matter excitations

Energy Technology Data Exchange (ETDEWEB)

Janot, Alexander

2016-02-29

Motivated by the sustained interest in Bose Einstein condensates and the recent progress in the understanding of topological phases in condensed matter systems, we study quantum condensates and possible topological phases of bosons in coupled light-matter excitations, so-called polaritons. These bosonic quasi-particles emerge if electronic excitations (excitons) couple strongly to photons. In the first part of this thesis a polariton Bose Einstein condensate in the presence of disorder is investigated. In contrast to the constituents of a conventional condensate, such as cold atoms, polaritons have a finite life time. Then, the losses have to be compensated by continued pumping, and a non-thermal steady state can build up. We discuss how static disorder affects this non-equilibrium condensate, and analyze the stability of the superfluid state against disorder. We find that disorder destroys the quasi-long range order of the condensate wave function, and that the polariton condensate is not a superfluid in the thermodynamic limit, even for weak disorder, although superfluid behavior would persist in small systems. Furthermore, we analyze the far field emission pattern of a polariton condensate in a disorder environment in order to compare directly with experiments. In the second part of this thesis features of polaritons in a two-dimensional quantum spin Hall cavity with time reversal symmetry are discussed. We propose a topological invariant which has a nontrivial value if the quantum spin Hall insulator is topologically nontrivial. Furthermore, we analyze emerging polaritonic edge states, discuss their relation to the underlying electronic structure, and develop an effective edge state model for polaritons.

Magnetic field integral equation analysis of interaction between a surface plasmon polariton and a circular dielectric cavity embedded in the metal.

Science.gov (United States)

Chremmos, Ioannis

2009-12-01

A rigorous integral equation (IE) analysis of the interaction between a surface plasmon polariton (SPP) and a circular dielectric cavity embedded in a metal half-space is presented. The device is addressed as the plasmonic counterpart of the established integrated optics filter comprising a whispering gallery (WG) resonator coupled to a waveguide. The mathematical formulation is that of a transverse magnetic scattering problem. Using a magnetic-type Green's function of the two-layer medium with boundary conditions that cancel the line integral contributions along the interface, an IE for the magnetic field inside the cavity is obtained. The IE is treated through an entire-domain method of moments (MoM) with cylindrical-harmonic basis functions. The entries of the MoM matrix are determined analytically by utilizing the inverse Fourier transform of Green's function and the Jacobi-Anger formula for interchanging between plane and cylindrical waves. Complex analysis techniques are applied to determine the transmitted, reflected, and radiated field quantities in series forms. The numerical results show that the scattered SPPs' spectra exhibit pronounced wavelength selectivity that is related to the excitation of WG-like cavity modes. It seems feasible to exploit the device as a bandstop or reflective filter or even as an efficient radiating element. In addition, the dependence of transmission on the cavity refractive index endows this structure with a sensing functionality.

Approximating transcranial magnetic stimulation with electric stimulation in mouse: a simulation study.

Science.gov (United States)

Barnes, Walter L; Lee, Won Hee; Peterchev, Angel V

2014-01-01

Rodent models are valuable for preclinical examination of novel therapeutic techniques, including transcranial magnetic stimulation (TMS). However, comparison of TMS effects in rodents and humans is confounded by inaccurate scaling of the spatial extent of the induced electric field in rodents. The electric field is substantially less focal in rodent models of TMS due to the technical restrictions of making very small coils that can handle the currents required for TMS. We examine the electric field distributions generated by various electrode configurations of electric stimulation in an inhomogeneous high-resolution finite element mouse model, and show that the electric field distributions produced by human TMS can be approximated by electric stimulation in mouse. Based on these results and the limits of magnetic stimulation in mice, we argue that the most practical and accurate way to model focal TMS in mice is electric stimulation through either cortical surface electrodes or electrodes implanted halfway through the mouse cranium. This approach could allow much more accurate approximation of the human TMS electric field focality and strength than that offered by TMS in mouse, enabling, for example, focal targeting of specific cortical regions, which is common in human TMS paradigms.

Interaction of transcranial magnetic stimulation and electrical transmastoid stimulation in human subjects

DEFF Research Database (Denmark)

Taylor, Janet L; Petersen, Nicolas Caesar; Butler, Jane E

2002-01-01

Transcranial magnetic stimulation activates corticospinal neurones directly and transsynaptically and hence, activates motoneurones and results in a response in the muscle. Transmastoid stimulation results in a similar muscle response through activation of axons in the spinal cord. This study...... was designed to determine whether the two stimuli activate the same descending axons. Responses to transcranial magnetic stimuli paired with electrical transmastoid stimuli were examined in biceps brachii in human subjects. Twelve interstimulus intervals (ISIs) from -6 ms (magnet before transmastoid) to 5 ms......-wave, facilitation still occurred at ISIs of -6 and -5 ms and depression of the paired response at ISIs of 0, 1, 4 and 5 ms. The interaction of the response to transmastoid stimulation with the multiple descending volleys elicited by magnetic stimulation of the cortex is complex. However, depression of the response...

Feldspar, Infrared Stimulated Luminescence

DEFF Research Database (Denmark)

Jain, Mayank

2014-01-01

This entry primarily concerns the characteristics and the origins of infrared-stimulated luminescence in feldspars.......This entry primarily concerns the characteristics and the origins of infrared-stimulated luminescence in feldspars....

Quantum fluids of light in acoustic lattices

Science.gov (United States)

Cerda-Méndez, E. A.; Krizhanovskii, D. N.; Skolnick, M. S.; Santos, P. V.

2018-01-01

In this topical review, we report on the recent advances on the manipulation of hybrid light-matter quasi-particles called exciton-polaritons and their quantum condensed phases by means of acoustic and static periodic potentials. Polaritons are a superposition of photons and excitons and form in optical microcavities with quantum wells embedded in it. They are low-mass bosons in the dilute limit and have strong inter-particle interactions inherited from the excitonic component. Their capability to form quantum-condensed phases at temperatures in the kelvin range and to behave like quantum fluids makes them very attractive for novel solid-state devices. Since their de Broglie wavelength is of the order of a few micrometers, polaritons can be manipulated using static or dynamic potentials with micrometer scales. We present here a summary of the techniques used to submit polaritons and their condensed phases to periodic potentials, with an emphasis in dynamic ones produced by surface acoustic waves. We discuss the interesting phenomena that occur under such a modulation, such as condensation in excited states of the Brillouin zone, fragmentation of a condensate, formation of self-localized wavepackets, and Dirac and massive polaritons in static hexagonal and kagome lattices, respectively. The different techniques explored open the way to implement polariton-based quantum simulators, nano-optomechanic resonators and polaritonic topological insulators.

Noninvasive Transcranial Brain Stimulation and Pain

OpenAIRE

Rosen, Allyson C.; Ramkumar, Mukund; Nguyen, Tam; Hoeft, Fumiko

2009-01-01

Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) are two noninvasive brain stimulation techniques that can modulate activity in specific regions of the cortex. At this point, their use in brain stimulation is primarily investigational; however, there is clear evidence that these tools can reduce pain and modify neurophysiologic correlates of the pain experience. TMS has also been used to predict response to surgically implanted stimulation for the tre...

Growth hormone stimulation test

Science.gov (United States)

... this page: //medlineplus.gov/ency/article/003377.htm Growth hormone stimulation test To use the sharing features on this page, please enable JavaScript. The growth hormone (GH) stimulation test measures the ability of ...

Enhanced magneto-plasmonic effect in Au/Co/Au multilayers caused by exciton–plasmon strong coupling

Energy Technology Data Exchange (ETDEWEB)

Hamidi, S.M., E-mail: m_hamidi@sbu.ac.ir; Ghaebi, O.

2016-09-15

In this paper, we have investigated magneto optical Kerr rotation using the strong coupling of exciton–plasmon. For this purpose, we have demonstrated strong coupling phenomenon using reflectometry measurements. These measurements revealed the formation of two split polaritonic extrema in reflectometry as a function of wavelength. Then we have shown exciton–plasmon coupling in dispersion diagram which presented an anti-crossing between the polaritonic branches. To assure the readers of strong coupling, we have shown an enhanced magneto-optical Kerr rotation by comparing the reflectometry results of strong coupling of surface Plasmon polariton of Au/Co/Au multilayer and R6G excitons with surface Plasmon polariton magneto-optical kerr effect experimental setup. - Highlights: • The magneto optical Kerr rotation has been investigated by using the strong coupling of exciton–plasmon. • We have shown exciton–plasmon coupling in dispersion diagram which presented an anti-crossing between the polaritonic branches. • Strong coupling of surface plasmon polariton and exciton have been yielded to the enhanced magneto-optical Kerr effect. • Plasmons in Au/Co/Au multilayer and exciton in R6G have been coupled to enhance magneto-optical activity.

Avoiding Internal Capsule Stimulation With a New Eight-Channel Steering Deep Brain Stimulation Lead.

Science.gov (United States)

van Dijk, Kees J; Verhagen, Rens; Bour, Lo J; Heida, Ciska; Veltink, Peter H

2017-10-15

Novel deep brain stimulation (DBS) lead designs are currently entering the market, which are hypothesized to provide a way to steer the stimulation field away from neural populations responsible for side effects and towards populations responsible for beneficial effects. The objective of this study is to assess the performances of a new eight channel steering-DBS lead and compare this with a conventional cylindrical contact (CC) lead. The two leads were evaluated in a finite element electric field model combined with multicompartment neuron and axon models, representing the internal capsule (IC) fibers and subthalamic nucleus (STN) cells. We defined the optimal stimulation setting as the configuration that activated the highest percentage of STN cells, without activating any IC fibers. With this criterion, we compared monopolar stimulation using a single contact of the steering-DBS lead and CC lead, on three locations and four orientations of the lead. In addition, we performed a current steering test case by dividing the current over two contacts with the steering-DBS lead in its worst-case orientation. In most cases, the steering-DBS lead is able to stimulate a significantly higher percentage of STN cells compared to the CC lead using single contact stimulation or using a two contact current steering protocol when there is approximately a 1 mm displacement of the CC lead. The results also show that correct placement and orientation of the lead in the target remains an important aspect in achieving the optimal stimulation outcome. Currently, clinical trials are set up in Europe with a similar design as the steering-DBS lead. Our results illustrate the importance of the orientation of the new steering-DBS lead in avoiding side effects induced by stimulation of IC fibers. Therefore, in clinical trials sufficient attention should be paid to implanting the steering DBS-lead in the most effective orientation. © 2017 International Neuromodulation Society.

Evaluation of intradural stimulation efficiency and selectivity in a computational model of spinal cord stimulation.

Directory of Open Access Journals (Sweden)

Bryan Howell

Full Text Available Spinal cord stimulation (SCS is an alternative or adjunct therapy to treat chronic pain, a prevalent and clinically challenging condition. Although SCS has substantial clinical success, the therapy is still prone to failures, including lead breakage, lead migration, and poor pain relief. The goal of this study was to develop a computational model of SCS and use the model to compare activation of neural elements during intradural and extradural electrode placement. We constructed five patient-specific models of SCS. Stimulation thresholds predicted by the model were compared to stimulation thresholds measured intraoperatively, and we used these models to quantify the efficiency and selectivity of intradural and extradural SCS. Intradural placement dramatically increased stimulation efficiency and reduced the power required to stimulate the dorsal columns by more than 90%. Intradural placement also increased selectivity, allowing activation of a greater proportion of dorsal column fibers before spread of activation to dorsal root fibers, as well as more selective activation of individual dermatomes at different lateral deviations from the midline. Further, the results suggest that current electrode designs used for extradural SCS are not optimal for intradural SCS, and a novel azimuthal tripolar design increased stimulation selectivity, even beyond that achieved with an intradural paddle array. Increased stimulation efficiency is expected to increase the battery life of implantable pulse generators, increase the recharge interval of rechargeable implantable pulse generators, and potentially reduce stimulator volume. The greater selectivity of intradural stimulation may improve the success rate of SCS by mitigating the sensitivity of pain relief to malpositioning of the electrode. The outcome of this effort is a better quantitative understanding of how intradural electrode placement can potentially increase the selectivity and efficiency of SCS

Development of Femtosecond Stimulated Raman Spectroscopy: Stimulated Raman Gain via Elimination of Cross Phase Modulation

International Nuclear Information System (INIS)

Jin, Seung Min; Lee, Young Jong; Yu, Jong Wan; Kim, Seong Keun

2004-01-01

We have developed a new femtosecond probe technique by using stimulated Raman spectroscopy. The cross phase modulation in femtosecond time scale associated with off-resonant interaction was shown to be eliminated by integrating the transient gain/loss signal over the time delay between the Raman pump pulse and the continuum pulse. The stimulated Raman gain of neat cyclohexane was obtained to demonstrate the feasibility of the technique. Spectral and temporal widths of stimulated Raman spectra were controlled by using a narrow band pass filter. Femtosecond stimulated Raman spectroscopy was proposed as a highly useful probe in time-resolved vibrational spectroscopy

Noninvasive transcranial brain stimulation and pain.

Science.gov (United States)

Rosen, Allyson C; Ramkumar, Mukund; Nguyen, Tam; Hoeft, Fumiko

2009-02-01

Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) are two noninvasive brain stimulation techniques that can modulate activity in specific regions of the cortex. At this point, their use in brain stimulation is primarily investigational; however, there is clear evidence that these tools can reduce pain and modify neurophysiologic correlates of the pain experience. TMS has also been used to predict response to surgically implanted stimulation for the treatment of chronic pain. Furthermore, TMS and tDCS can be applied with other techniques, such as event-related potentials and pharmacologic manipulation, to illuminate the underlying physiologic mechanisms of normal and pathological pain. This review presents a description and overview of the uses of two major brain stimulation techniques and a listing of useful references for further study.

Higher-order power harmonics of pulsed electrical stimulation modulates corticospinal contribution of peripheral nerve stimulation.

Science.gov (United States)

Chen, Chiun-Fan; Bikson, Marom; Chou, Li-Wei; Shan, Chunlei; Khadka, Niranjan; Chen, Wen-Shiang; Fregni, Felipe

2017-03-03

It is well established that electrical-stimulation frequency is crucial to determining the scale of induced neuromodulation, particularly when attempting to modulate corticospinal excitability. However, the modulatory effects of stimulation frequency are not only determined by its absolute value but also by other parameters such as power at harmonics. The stimulus pulse shape further influences parameters such as excitation threshold and fiber selectivity. The explicit role of the power in these harmonics in determining the outcome of stimulation has not previously been analyzed. In this study, we adopted an animal model of peripheral electrical stimulation that includes an amplitude-adapted pulse train which induces force enhancements with a corticospinal contribution. We report that the electrical-stimulation-induced force enhancements were correlated with the amplitude of stimulation power harmonics during the amplitude-adapted pulse train. In an exploratory analysis, different levels of correlation were observed between force enhancement and power harmonics of 20-80 Hz (r = 0.4247, p = 0.0243), 100-180 Hz (r = 0.5894, p = 0.0001), 200-280 Hz (r = 0.7002, p harmonics. This is a pilot, but important first demonstration that power at high order harmonics in the frequency spectrum of electrical stimulation pulses may contribute to neuromodulation, thus warrant explicit attention in therapy design and analysis.

Electrical stimulation in exercise training

Science.gov (United States)

Kroll, Walter

1994-01-01

Electrical stimulation has a long history of use in medicine dating back to 46 A.D. when the Roman physician Largus found the electrical discharge of torpedo fishes useful in the treatment of pain produced by headache and gout. A rival Greek physician, Dioscorides, discounted the value of the torpedo fish for headache relief but did recommend its use in the treatment of hemorrhoids. In 1745, the Leyden jar and various sized electrostatic generators were used to treat angina pectoris, epilepsy, hemiplegia, kidney stones, and sciatica. Benjamin Franklin used an electrical device to treat successfully a young woman suffering from convulsive fits. In the late 1800's battery powered hydroelectric baths were used to treat chronic inflammation of the uterus while electrified athletic supporters were advertised for the treatment of male problems. Fortunately, such an amusing early history of the simple beginnings of electrical stimulation did not prevent eventual development of a variety of useful therapeutic and rehabilitative applications of electrical stimulation. Over the centuries electrical stimulation has survived as a modality in the treatment of various medical disorders with its primary application being in the rehabilitation area. Recently, a surge of new interest in electrical stimulation has been kindled by the work of a Russian sport scientist who reported remarkable muscle strength and endurance improvements in elite athletes. Yakov Kots reported his research on electric stimulation and strength improvements in 1977 at a Canadian-Soviet Exchange Symposium held at Concordia University in Montreal. Since then an explosion of new studies has been seen in both sport science and in medicine. Based upon the reported works of Kots and the present surge of new investigations, one could be misled as to the origin of electrical stimulation as a technique to increase muscle strength. As a matter of fact, electric stimulation has been used as a technique to improve

Electrocutaneous stimulation system for Braille reading.

Science.gov (United States)

Echenique, Ana Maria; Graffigna, Juan Pablo; Mut, Vicente

2010-01-01

This work is an assistive technology for people with visual disabilities and aims to facilitate access to written information in order to achieve better social inclusion and integration into work and educational activities. Two methods of electrical stimulation (by current and voltage) of the mechanoreceptors was tested to obtain tactile sensations on the fingertip. Current and voltage stimulation were tested in a Braille cell and line prototype, respectively. These prototypes are evaluated in 33 blind and visually impaired subjects. The result of experimentation with both methods showed that electrical stimulation causes sensations of touch defined in the fingertip. Better results in the Braille characters reading were obtained with current stimulation (85% accuracy). However this form of stimulation causes uncomfortable sensations. The latter feeling was minimized with the method of voltage stimulation, but with low efficiency (50% accuracy) in terms of identification of the characters. We concluded that electrical stimulation is a promising method for the development of a simple and unexpensive Braille reading system for blind people. We observed that voltage stimulation is preferred by the users. However, more experimental tests must be carry out in order to find the optimum values of the stimulus parameters and increase the accuracy the Braille characters reading.

A fully implantable rodent neural stimulator

Science.gov (United States)

Perry, D. W. J.; Grayden, D. B.; Shepherd, R. K.; Fallon, J. B.

2012-02-01

The ability to electrically stimulate neural and other excitable tissues in behaving experimental animals is invaluable for both the development of neural prostheses and basic neurological research. We developed a fully implantable neural stimulator that is able to deliver two channels of intra-cochlear electrical stimulation in the rat. It is powered via a novel omni-directional inductive link and includes an on-board microcontroller with integrated radio link, programmable current sources and switching circuitry to generate charge-balanced biphasic stimulation. We tested the implant in vivo and were able to elicit both neural and behavioural responses. The implants continued to function for up to five months in vivo. While targeted to cochlear stimulation, with appropriate electrode arrays the stimulator is well suited to stimulating other neurons within the peripheral or central nervous systems. Moreover, it includes significant on-board data acquisition and processing capabilities, which could potentially make it a useful platform for telemetry applications, where there is a need to chronically monitor physiological variables in unrestrained animals.

Vertex Stimulation as a Control Site for Transcranial Magnetic Stimulation: A Concurrent TMS/fMRI Study.

Science.gov (United States)

Jung, JeYoung; Bungert, Andreas; Bowtell, Richard; Jackson, Stephen R

2016-01-01

A common control condition for transcranial magnetic stimulation (TMS) studies is to apply stimulation at the vertex. An assumption of vertex stimulation is that it has relatively little influence over on-going brain processes involved in most experimental tasks, however there has been little attempt to measure neural changes linked to vertex TMS. Here we directly test this assumption by using a concurrent TMS/fMRI paradigm in which we investigate fMRI blood-oxygenation-level-dependent (BOLD) signal changes across the whole brain linked to vertex stimulation. Thirty-two healthy participants to part in this study. Twenty-one were stimulated at the vertex, at 120% of resting motor threshold (RMT), with short bursts of 1 Hz TMS, while functional magnetic resonance imaging (fMRI) BOLD images were acquired. As a control condition, we delivered TMS pulses over the left primary motor cortex using identical parameters to 11 other participants. Vertex stimulation did not evoke increased BOLD activation at the stimulated site. By contrast we observed widespread BOLD deactivations across the brain, including regions within the default mode network (DMN). To examine the effects of vertex stimulation a functional connectivity analysis was conducted. The results demonstrated that stimulating the vertex with suprathreshold TMS reduced neural activity in brain regions related to the DMN but did not influence the functional connectivity of this network. Our findings provide brain imaging evidence in support of the use of vertex simulation as a control condition in TMS but confirm that vertex TMS induces regional widespread decreases in BOLD activation. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

Noninvasive Stimulation of the Human Brain

DEFF Research Database (Denmark)

Di Lazzaro, Vincenzo; Rothwell, John; Capogna, Marco

2017-01-01

Noninvasive brain stimulation methods, such as transcranial electric stimulation and transcranial magnetic stimulation are widely used tools for both basic research and clinical applications. However, the cortical circuits underlying their effects are poorly defined. Here we review the current...

Reducing interaction in simultaneous paired stimulation with CI.

Directory of Open Access Journals (Sweden)

Dirk Vellinga

Full Text Available In this study simultaneous paired stimulation of electrodes in cochlear implants is investigated by psychophysical experiments in 8 post-lingually deaf subjects (and one extra subject who only participated in part of the experiments. Simultaneous and sequential monopolar stimulation modes are used as references and are compared to channel interaction compensation, partial tripolar stimulation and a novel sequential stimulation strategy named phased array compensation. Psychophysical experiments are performed to investigate both the loudness integration during paired stimulation at the main electrodes as well as the interaction with the electrode contact located halfway between the stimulating pair. The study shows that simultaneous monopolar stimulation has more loudness integration on the main electrodes and more interaction in between the electrodes than sequential stimulation. Channel interaction compensation works to reduce the loudness integration at the main electrodes, but does not reduce the interaction in between the electrodes caused by paired stimulation. Partial tripolar stimulation uses much more current to reach the needed loudness, but shows the same interaction in between the electrodes as sequential monopolar stimulation. In phased array compensation we have used the individual impedance matrix of each subject to calculate the current needed on each electrode to exactly match the stimulation voltage along the array to that of sequential stimulation. The results show that the interaction in between the electrodes is the same as monopolar stimulation. The strategy uses less current than partial tripolar stimulation, but more than monopolar stimulation. In conclusion, the paper shows that paired stimulation is possible if the interaction is compensated.

The safety of transcranial magnetic stimulation with deep brain stimulation instruments

OpenAIRE

Shimojima, Yoshio; Morita, Hiroshi; Nishikawa, Noriko; Kodaira, Minori; Hashimoto, Takao; Ikeda, Shu-ichi

2010-01-01

Objectives: Transcranial magnetic stimulation (TMS) has been employed in patients with an implanted deep brain Stimulation (DBS) device. We investigated the safety of TMS using Simulation models with an implanted DBS device. Methods: The DBS lead was inserted into plastic phantoms filled with dilute gelatin showing impedance similar to that of human brain. TMS was performed with three different types of magnetic coil. During TMS (I) electrode movement, (2) temperature change around the lead, ...

Optical stimulator for vision-based sensors

DEFF Research Database (Denmark)

Rössler, Dirk; Pedersen, David Arge Klevang; Benn, Mathias

2014-01-01

We have developed an optical stimulator system for vision-based sensors. The stimulator is an efficient tool for stimulating a camera during on-ground testing with scenes representative of spacecraft flights. Such scenes include starry sky, planetary objects, and other spacecraft. The optical...

Mimicking muscle activity with electrical stimulation

Science.gov (United States)

Johnson, Lise A.; Fuglevand, Andrew J.

2011-02-01

Functional electrical stimulation is a rehabilitation technology that can restore some degree of motor function in individuals who have sustained a spinal cord injury or stroke. One way to identify the spatio-temporal patterns of muscle stimulation needed to elicit complex upper limb movements is to use electromyographic (EMG) activity recorded from able-bodied subjects as a template for electrical stimulation. However, this requires a transfer function to convert the recorded (or predicted) EMG signals into an appropriate pattern of electrical stimulation. Here we develop a generalized transfer function that maps EMG activity into a stimulation pattern that modulates muscle output by varying both the pulse frequency and the pulse amplitude. We show that the stimulation patterns produced by this transfer function mimic the active state measured by EMG insofar as they reproduce with good fidelity the complex patterns of joint torque and joint displacement.

Optical responses in single-crystalline organic microcavities

International Nuclear Information System (INIS)

Kondo, H.; Yamamoto, Y.; Takeda, A.; Yamamoto, S.; Kurisu, H.

2008-01-01

The anisotropic response of cavity polaritons is investigated in an organic microcavity composed of a single-crystalline anthracene film sandwiched between two distributed Bragg reflectors. Upper and lower cavity polariton modes are observed as sharp spectral peaks in the transmission spectra. Dispersion relation for cavity polaritons is obtained as a function of thickness of the thin film. Using this relation, the vacuum Rabi splitting energy for this system is estimated to be 340 meV

Optical responses in single-crystalline organic microcavities

Energy Technology Data Exchange (ETDEWEB)

Kondo, H. [Department of Physics, Ehime University, Matsuyama, 2-5 Bunkyo-cho, Matsuyama 790-8577 (Japan)], E-mail: kondo@phys.sci.ehime-u.ac.jp; Yamamoto, Y.; Takeda, A. [Department of Physics, Ehime University, Matsuyama, 2-5 Bunkyo-cho, Matsuyama 790-8577 (Japan); Yamamoto, S.; Kurisu, H. [Department of Advanced Materials Science and Engineering, Yamaguchi University, Ube, Yamaguchi 755-8611 (Japan)

2008-05-15

The anisotropic response of cavity polaritons is investigated in an organic microcavity composed of a single-crystalline anthracene film sandwiched between two distributed Bragg reflectors. Upper and lower cavity polariton modes are observed as sharp spectral peaks in the transmission spectra. Dispersion relation for cavity polaritons is obtained as a function of thickness of the thin film. Using this relation, the vacuum Rabi splitting energy for this system is estimated to be 340 meV.

Near-field heat transfer between graphene/hBN multilayers

Science.gov (United States)

Zhao, Bo; Guizal, Brahim; Zhang, Zhuomin M.; Fan, Shanhui; Antezza, Mauro

2017-06-01

We study the radiative heat transfer between multilayer structures made by a periodic repetition of a graphene sheet and a hexagonal boron nitride (hBN) slab. Surface plasmons in a monolayer graphene can couple with hyperbolic phonon polaritons in a single hBN film to form hybrid polaritons that can assist photon tunneling. For periodic multilayer graphene/hBN structures, the stacked metallic/dielectric array can give rise to a further effective hyperbolic behavior, in addition to the intrinsic natural hyperbolic behavior of hBN. The effective hyperbolicity can enable more hyperbolic polaritons that enhance the photon tunneling and hence the near-field heat transfer. However, the hybrid polaritons on the surface, i.e., surface plasmon-phonon polaritons, dominate the near-field heat transfer between multilayer structures when the topmost layer is graphene. The effective hyperbolic regions can be well predicted by the effective medium theory (EMT), thought EMT fails to capture the hybrid surface polaritons and results in a heat transfer rate much lower compared to the exact calculation. The chemical potential of the graphene sheets can be tuned through electrical gating and results in an additional modulation of the heat transfer. We found that the near-field heat transfer between multilayer structures does not increase monotonously with the number of layers in the stack, which provides a way to control the heat transfer rate by the number of graphene layers in the multilayer structure. The results may benefit the applications of near-field energy harvesting and radiative cooling based on hybrid polaritons in two-dimensional materials.

Twiddler's syndrome in spinal cord stimulation.

Science.gov (United States)

Al-Mahfoudh, Rafid; Chan, Yuen; Chong, Hsu Pheen; Farah, Jibril Osman

2016-01-01

The aims are to present a case series of Twiddler's syndrome in spinal cord stimulators with analysis of the possible mechanism of this syndrome and discuss how this phenomenon can be prevented. Data were collected retrospectively between 2007 and 2013 for all patients presenting with failure of spinal cord stimulators. The diagnostic criterion for Twiddler's syndrome is radiological evidence of twisting of wires in the presence of failure of spinal cord stimulation. Our unit implants on average 110 spinal cord stimulators a year. Over the 5-year study period, all consecutive cases of spinal cord stimulation failure were studied. Three patients with Twiddler's syndrome were identified. Presentation ranged from 4 to 228 weeks after implantation. Imaging revealed repeated rotations and twisting of the wires of the spinal cord stimulators leading to hardware failure. To the best of our knowledge this is the first reported series of Twiddler's syndrome with implantable pulse generators (IPGs) for spinal cord stimulation. Hardware failure is not uncommon in spinal cord stimulation. Awareness and identification of Twiddler's syndrome may help prevent its occurrence and further revisions. This may be achieved by implanting the IPG in the lumbar region subcutaneously above the belt line. Psychological intervention may have a preventative role for those who are deemed at high risk of Twiddler's syndrome from initial psychological screening.

Evaluation of different types of rooting stimulators

Directory of Open Access Journals (Sweden)

Petr Salaš

2012-01-01

Full Text Available This paper focuses on the assessment of selected stimulators, especially from Rhizopon product line, which are used for rooting and root system enhancement in various ornamental woody species. Two available methods of cuttings stimulation were selected from the available range of rooting stimulators: stimulation by long-term immersion in solutions or treatment of cuttings with powder stimulators. The experiment involved stimulators with two active components, currently the most commonly used phytohormones for this purpose – IBA and NAA – that were applied in different concentrations. The experiment took place in three propagation terms with twelve coniferous and deciduous shrub varieties. The results of the experiment show the different reactions of the individual species as well as varieties on the respective term of propagation and used form of stimulator.

Step-wise stimulated martensitic transformations

International Nuclear Information System (INIS)

Airoldi, G.; Riva, G.

1991-01-01

NiTi alloys, widely known both for their shape memory properties and for unusual pseudoelastic behaviour, are now on the forefront attention for step-wise induced memory processes, thermal or stress stimulated. Literature results related to step-wise stimulated martensite (direct transformation) are examined and contrasted with step-wise thermal stimulated parent phase (reverse transformation). Hypothesis are given to explain the key characters of both transformations, a thermodynamic model from first principles being till now lacking

The Underlying Mechanism of Preventing Facial Nerve Stimulation by Triphasic Pulse Stimulation in Cochlear Implant Users Assessed With Objective Measure.

Science.gov (United States)

Bahmer, Andreas; Baumann, Uwe

2016-10-01

Triphasic pulse stimulation prevents from facial nerve stimulation (FNS) because of a different electromyographic input-output function compared with biphasic pulse stimulation. FNS is sometimes observed in cochlear implant users as an unwanted side effect of electrical stimulation of the auditory nerve. The common stimulation applied in current cochlear implant consists of biphasic pulse patterns. Two common clinical remedies to prevent unpleasant FNS caused by activation of certain electrodes are to expand their pulse phase duration or simply deactivate them. Unfortunately, in some patients these methods do not provide sufficient FNS prevention. In these patients triphasic pulse can prevent from FNS. The underlying mechanism is yet unclear. Electromyographic (EMG) recordings of muscles innervated by the facial nerve (musculi orbicularis ori and oculi) were applied to quantitatively assess the effects on FNS. Triphasic and biphasic fitting maps were compared in four subjects with severe FNS. Based on the recordings, a model is presented which intends to explain the beneficial effects of triphasic pulse application. Triphasic stimulation provided by fitting of an OPUS 2 speech processor device. For three patients, EMG was successfully recorded depending on stimulation level up to uncomfortable and intolerable FNS stimulation as upper boarder. The obtained EMG recordings demonstrated high individual variability. However, a difference between the input-output function for biphasic and triphasic pulse stimulation was visually observable. Compared with standard biphasic stimulation, triphasic pulses require higher stimulation levels to elicit an equal amount of FNS, as reflected by EMG amplitudes. In addition, we assume a steeper slope of the input-output function for biphasic pulse stimulation compared with triphasic pulse stimulation. Triphasic pulse stimulation prevents from FNS because of a smaller gradient of EMG input-output function compared with biphasic pulse

Transcranial alternating current stimulation with sawtooth waves: simultaneous stimulation and EEG recording

Directory of Open Access Journals (Sweden)

James eDowsett

2016-03-01

Full Text Available Transcranial alternating current stimulation (tACS has until now mostly been administered as an alternating sinusoidal wave. Despite modern tACS stimulators being able to deliver alternating current with any arbitrary shape there has been no systematic exploration into the relative benefits of different waveforms. As tACS is a relatively new technique there is a huge parameter space of unexplored possibilities which may prove superior or complimentary to the traditional sinusoidal waveform. Here we begin to address this with an investigation into the effects of sawtooth wave tACS on individual alpha power. Evidence from animal models suggests that the gradient and direction of an electric current should be important factors for the subsequent neural firing rate; we compared positive and negative ramp sawtooth waves to test this. An additional advantage of sawtooth waves is that the resulting artefact in the electroencephalogram (EEG recording is significantly simpler to remove than a sine wave; accordingly we were able to observe alpha oscillations both during and after stimulation.We found that positive ramp sawtooth, but not negative ramp sawtooth, significantly enhanced alpha power during stimulation relative to sham (p<0.01. In addition we tested for an after-effect of both sawtooth and sinusoidal stimulation on alpha power but in this case did not find any significant effect. This preliminary study paves the way for further investigations into the effect of the gradient and direction of the current in tACS which could significantly improve the usefulness of this technique.

The combined effect of side-coupled gain cavity and lossy cavity on the plasmonic response of metal-dielectric-metal surface plasmon polariton waveguide

International Nuclear Information System (INIS)

Zhu, Qiong-gan; Wang, Zhi-guo; Tan, Wei

2014-01-01

The combined effect of side-coupled gain cavity and lossy cavity on the plasmonic response of metal-dielectric-metal (MDM) surface plasmon polariton (SPP) waveguide is investigated theoretically using Green's function method. Our result suggests that the gain and loss parameters influence the amplitude and phase of the fields localized in the two cavities. For the case of balanced gain and loss, the fields of the two cavities are always of equi-amplitude but out of phase. A plasmon induced transparency (PIT)-like transmission peak can be achieved by the destructive interference of two fields with anti-phase. For the case of unbalanced gain and loss, some unexpected responses of structure are generated. When the gain is more than the loss, the system response is dissipative at around the resonant frequency of the two cavities, where the sum of reflectance and transmittance becomes less than one. This is because the lossy cavity, with a stronger localized field, makes the main contribution to the system response. When the gain is less than the loss, the reverse is true. It is found that the metal loss dissipates the system energy but facilitates the gain cavity to make a dominant effect on the system response. This mechanism may have a potential application for optical amplification and for a plasmonic waveguide switch. (paper)

Effects of contraction mode and stimulation frequency on electrical stimulation-induced skeletal muscle hypertrophy.

Science.gov (United States)

Ashida, Yuki; Himori, Koichi; Tatebayashi, Daisuke; Yamada, Ryotaro; Ogasawara, Riki; Yamada, Takashi

2018-02-01

We compared the skeletal muscle hypertrophy resulting from isometric (Iso) or eccentric (Ecc) electrical stimulation (ES) training with different stimulation frequencies. Male Wistar rats were assigned to the Iso and Ecc groups. These were divided into three further subgroups that were stimulated at 10 Hz (Iso-10 and Ecc-10), 30 Hz (Iso-30 and Ecc-30), or 100 Hz (Iso-100 and Ecc-100). In experiment 1, the left plantarflexor muscles were stimulated every other day for 3 wk. In experiment 2, mammalian target of rapamycin complex 1 (mTORC1) signaling was investigated 6 h after one bout of ES. The contralateral right muscle served as a control (non-ES). Ecc contractions comprised forced dorsiflexion combined with ES. The peak torque and torque-time integral during ES were higher in the Ecc group than that in the Iso group in all stimulation frequencies examined. The gastrocnemius muscle weight normalized to body weight in ES side was increased compared with the non-ES side by 6, 7, and 17% in the Ecc-30, Iso-100, and Ecc-100 groups, respectively, with a greater gain in Ecc-100 than the Ecc-30 and Iso-100 groups. The p70S6K (Thr389) phosphorylation level was higher in the Ecc-30 and -100 than in the Iso-30 and -100 groups, respectively. The peak torque and torque-time integral were highly correlated with the magnitude of increase in muscle mass and the phosphorylation of p70S6K. These data suggest that ES-induced muscle hypertrophy and mTORC1 activity are determined by loading intensity and volume during muscle contraction independent of the contraction mode. NEW & NOTEWORTHY Eccentric contraction and high-frequency stimulation (HFS) are regarded as an effective way to increase muscle mass by electrical stimulation (ES) training. However, little is known about whether muscle hypertrophy is affected by contraction mode and stimulation frequency in ES training. Here, we provide the evidence that muscle hypertrophy and mammalian target of rapamycin complex 1 activity are

Avoiding Internal Capsule Stimulation With a New Eight-Channel Steering Deep Brain Stimulation Lead

NARCIS (Netherlands)

van Dijk, Kees J.; Verhagen, Rens; Bour, Lo J.; Heida, Ciska; Veltink, Peter H.

2017-01-01

Objective: Novel deep brain stimulation (DBS) lead designs are currently entering the market, which are hypothesized to provide a way to steer the stimulation field away from neural populations responsible for side effects and towards populations responsible for beneficial effects. The objective of

Brain stimulation in posttraumatic stress disorder

Directory of Open Access Journals (Sweden)

Vladan Novakovic

2011-10-01

Full Text Available Posttraumatic stress disorder (PTSD is a complex, heterogeneous disorder that develops following trauma and often includes perceptual, cognitive, affective, physiological, and psychological features. PTSD is characterized by hyperarousal, intrusive thoughts, exaggerated startle response, flashbacks, nightmares, sleep disturbances, emotional numbness, and persistent avoidance of trauma-associated stimuli. The efficacy of available treatments for PTSD may result in part from relief of associated depressive and anxiety-related symptoms in addition to treatment of core symptoms that derive from reexperiencing, numbing, and hyperarousal. Diverse, heterogeneous mechanisms of action and the ability to act broadly or very locally may enable brain stimulation devices to address PTSD core symptoms in more targeted ways. To achieve this goal, specific theoretical bases derived from novel, well-designed research protocols will be necessary. Brain stimulation devices include both long-used and new electrical and magnetic devices. Electroconvulsive therapy (ECT and Cranial electrotherapy stimulation (CES have both been in use for decades; transcranial magnetic stimulation (TMS, magnetic seizure therapy (MST, deep brain stimulation (DBS, transcranial Direct Current Stimulation (tDCS, and vagus nerve stimulation (VNS have been developed recently, over approximately the past twenty years. The efficacy of brain stimulation has been demonstrated as a treatment for psychiatric and neurological disorders such as anxiety (CES, depression (ECT, CES, rTMS, VNS, DBS, obsessive-compulsive disorder (OCD (DBS, essential tremor, dystonia (DBS, epilepsy (DBS, VNS, Parkinson Disease (DBS, pain (CES, and insomnia (CES. To date, limited data on brain stimulation for PTSD offer only modest guidance. ECT has shown some efficacy in reducing comorbid depression in PTSD patients but has not been demonstrated to improve most core PTSD symptoms. CES and VNS have shown some efficacy in

A Programmable High-Voltage Compliance Neural Stimulator for Deep Brain Stimulation in Vivo

Directory of Open Access Journals (Sweden)

Cihun-Siyong Alex Gong

2015-05-01

Full Text Available Deep brain stimulation (DBS is one of the most effective therapies for movement and other disorders. The DBS neurosurgical procedure involves the implantation of a DBS device and a battery-operated neurotransmitter, which delivers electrical impulses to treatment targets through implanted electrodes. The DBS modulates the neuronal activities in the brain nucleus for improving physiological responses as long as an electric discharge above the stimulation threshold can be achieved. In an effort to improve the performance of an implanted DBS device, the device size, implementation cost, and power efficiency are among the most important DBS device design aspects. This study aims to present preliminary research results of an efficient stimulator, with emphasis on conversion efficiency. The prototype stimulator features high-voltage compliance, implemented with only a standard semiconductor process, without the use of extra masks in the foundry through our proposed circuit structure. The results of animal experiments, including evaluation of evoked responses induced by thalamic electrical stimuli with our fabricated chip, were shown to demonstrate the proof of concept of our design.

Colony-stimulating factor (CSF) radioimmunoassay: detection of a CSF subclass stimulating macrophage production

International Nuclear Information System (INIS)

Stanley, E.R.

1979-01-01

Colony-stimulating factors (CSFs) stimulate the differentiation of immature precursor cells to mature granulocytes and macrophages. Purified 125 I-labeled murine L cell CSF has been used to develop a radioimmunoassay (RIA) that detects a subclass of CSFs that stimulates macrophage production. Murine CSF preparations that contain this subclass of CSF compete for all of the CSF binding sites on anti-L cell CSF antibody. With the exception of mouse serum, which can contain inhibitors of the bioassay, there is complete correspondence between activities determined by RIA and those determined by bioassay. The RIA is slightly more sensitive than the bioassay, detecting approximately 0.3 fmol of purified L cell CSF. It can also detect this subclass of CSF in chickens, rats, and humans. In the mouse, the subclass is distinguished from other CSFs by a murine cell bioassay dose-response curve in which 90% of the response occurs over a 10-fold (rather than a 100-fold) increase in concentration, by stimulating the formations of colonies contaning a high proportion of mononuclear (rather than granulocytic) cells, and by certain physical characteristics

growth stimulant

African Journals Online (AJOL)

Effects of timing and duration of supplementation of LIVFIT VET ® (growth stimulant) as substitute for fish meal on the growth performance, haematology and clinical enzymes concentration of growing pigs.

Tonic aortic depressor nerve stimulation does not impede baroreflex dynamic characteristics concomitantly mediated by the stimulated nerve.

Science.gov (United States)

Kawada, Toru; Turner, Michael J; Shimizu, Shuji; Kamiya, Atsunori; Shishido, Toshiaki; Sugimachi, Masaru

2018-03-01

Although electrical activation of the carotid sinus baroreflex (baroreflex activation therapy) is being explored as a device therapy for resistant hypertension, possible effects on baroreflex dynamic characteristics of interaction between electrical stimulation and pressure inputs are not fully elucidated. To examine whether the electrical stimulation of the baroreceptor afferent nerve impedes normal short-term arterial pressure (AP) regulation mediated by the stimulated nerve, we electrically stimulated the right aortic depressor nerve (ADN) while estimating the baroreflex dynamic characteristics by imposing pressure inputs to the isolated baroreceptor region of the right ADN in nine anesthetized rats. A Gaussian white noise signal with a mean of 120 mmHg and standard deviation of 20 mmHg was used for the pressure perturbation. A tonic ADN stimulation (2 or 5 Hz, 10 V, 0.1-ms pulse width) decreased mean sympathetic nerve activity (367.0 ± 70.9 vs. 247.3 ± 47.2 arbitrary units, P ADN stimulation did not affect the slope of dynamic gain in the neural arc transfer function from pressure perturbation to sympathetic nerve activity (16.9 ± 1.0 vs. 14.7 ± 1.6 dB/decade, not significant). These results indicate that electrical stimulation of the baroreceptor afferent nerve does not significantly impede the dynamic characteristics of the arterial baroreflex concomitantly mediated by the stimulated nerve. Short-term AP regulation by the arterial baroreflex may be preserved during the baroreflex activation therapy.

Avoiding Internal Capsule Stimulation With a New Eight-Channel Steering Deep Brain Stimulation Lead

NARCIS (Netherlands)

van Dijk, Kees J.; Verhagen, Rens; Bour, Lo J.; Heida, Ciska; Veltink, Peter H.

2017-01-01

Novel deep brain stimulation (DBS) lead designs are currently entering the market, which are hypothesized to provide a way to steer the stimulation field away from neural populations responsible for side effects and towards populations responsible for beneficial effects. The objective of this study

Tactile stimulation interventions: influence of stimulation parameters on sensorimotor behavior and neurophysiological correlates in healthy and clinical samples.

Science.gov (United States)

Parianen Lesemann, Franca H; Reuter, Eva-Maria; Godde, Ben

2015-04-01

The pure exposure to extensive tactile stimulation, without the requirement of attention or active training, has been revealed to enhance sensorimotor functioning presumably due to an induction of plasticity in the somatosensory cortex. The induced effects, including increased tactile acuity and manual dexterity have repeatedly been observed in basic as well as clinical research. However, results vary greatly in respect to the strength and direction of the effects on the behavioral and on the brain level. Multiple evidences show that differences in the stimulation protocols (e.g., two vs. multiple stimulation sites) and parameters (e.g., duration, frequency, and amplitude) might contribute to this variability of effects. Nevertheless, stimulation protocols have not been comprehensively compared yet. Identifying favorable parameters for tactile stimulation interventions is especially important because of its possible application as a treatment option for patients suffering from sensory loss, maladaptive plasticity, or certain forms of motor impairment. This review aims to compare the effects of different tactile stimulation protocols and to assess possible implications for tactile interventions. Our goal is to identify ways of optimizing stimulation protocols to improve sensorimotor performance. To this end, we reviewed research on tactile stimulation in the healthy population, with a focus on the effectiveness of the applied parameters regarding psychophysiological measures. We discuss the association of stimulation-induced changes on the behavioral level with alterations in neural representations and response characteristics. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effects of stimulation parameters and electrode location on thresholds for epidural stimulation of cat motor cortex

Science.gov (United States)

Wongsarnpigoon, Amorn; Grill, Warren M.

2011-12-01

Epidural electrical stimulation (ECS) of the motor cortex is a developing therapy for neurological disorders. Both placement and programming of ECS systems may affect the therapeutic outcome, but the treatment parameters that will maximize therapeutic outcomes and minimize side effects are not known. We delivered ECS to the motor cortex of anesthetized cats and investigated the effects of electrode placement and stimulation parameters on thresholds for evoking motor responses in the contralateral forelimb. Thresholds were inversely related to stimulation frequency and the number of pulses per stimulus train. Thresholds were lower over the forelimb representation in motor cortex (primary site) than surrounding sites (secondary sites), and thresholds at sites 4 mm away. Electrode location and montage influenced the effects of polarity on thresholds: monopolar anodic and cathodic thresholds were not significantly different over the primary site, cathodic thresholds were significantly lower than anodic thresholds over secondary sites and bipolar thresholds were significantly lower with the anode over the primary site than with the cathode over the primary site. A majority of bipolar thresholds were either between or equal to the respective monopolar thresholds, but several bipolar thresholds were greater than or less than the monopolar thresholds of both the anode and cathode. During bipolar stimulation, thresholds were influenced by both electric field superposition and indirect, synaptically mediated interactions. These results demonstrate the influence of stimulation parameters and electrode location during cortical stimulation, and these effects should be considered during the programming of systems for therapeutic cortical stimulation.

Pharmacological interventions for adolescents and adults with ADHD: stimulant and nonstimulant medications and misuse of prescription stimulants

Directory of Open Access Journals (Sweden)

Weyandt LL

2014-09-01

Full Text Available Lisa L Weyandt, Danielle R Oster, Marisa E Marraccini, Bergljot Gyda Gudmundsdottir, Bailey A Munro, Brynheld Martinez Zavras, Ben Kuhar Department of Psychology, University of Rhode Island, Kingston, RI, USA Abstract: Attention-deficit/hyperactivity disorder (ADHD is a neurodevelopmental disorder characterized by symptoms of inattention, hyperactivity, and impulsivity that cause functional impairment. Recent research indicates that symptoms persist into adulthood in the majority of cases, with prevalence estimates of approximately 5% in the school age population and 2.5%–4% in the adult population. Although students with ADHD are at greater risk for academic underachievement and psychosocial problems, increasing numbers of students with ADHD are graduating from high school and pursuing higher education. Stimulant medications are considered the first line of pharmacotherapy for individuals with ADHD, including college students. Although preliminary evidence indicates that prescription stimulants are safe and effective for college students with ADHD when used as prescribed, very few controlled studies have been conducted concerning the efficacy of prescription stimulants with college students. In addition, misuse of prescription stimulants has become a serious problem on college campuses across the US and has been recently documented in other countries as well. The purpose of the present systematic review was to investigate the efficacy of prescription stimulants for adolescents and young adults with ADHD and the nonmedical use and misuse of prescription stimulants. Results revealed that both prostimulant and stimulant medications, including lisdexamfetamine dimesylate, methylphenidate, amphetamines, and mixed-amphetamine salts, are effective at reducing ADHD symptoms in adolescents and adults with ADHD. Findings also suggest that individuals with ADHD may have higher rates of stimulant misuse than individuals without the disorder, and

Frequency shifts in stimulated Raman scattering

International Nuclear Information System (INIS)

Zinth, W.; Kaiser, W.

1980-01-01

The nonresonant contributions to the nonlinear susceptibility chisup(()3) produce a frequency chirp during stimulated Raman scattering. In the case of transient stimulated Raman scattering, the spectrum of the generated Stokes pulse is found at higher frequencies than expected from spontaneous Raman data. The frequency difference can be calculated from the theory of stimulated Raman scattering. (orig.)

Optimal number of stimulation contacts for coordinated reset neuromodulation

Science.gov (United States)

Lysyansky, Borys; Popovych, Oleksandr V.; Tass, Peter A.

2013-01-01

In this computational study we investigate coordinated reset (CR) neuromodulation designed for an effective control of synchronization by multi-site stimulation of neuronal target populations. This method was suggested to effectively counteract pathological neuronal synchrony characteristic for several neurological disorders. We study how many stimulation sites are required for optimal CR-induced desynchronization. We found that a moderate increase of the number of stimulation sites may significantly prolong the post-stimulation desynchronized transient after the stimulation is completely switched off. This can, in turn, reduce the amount of the administered stimulation current for the intermittent ON–OFF CR stimulation protocol, where time intervals with stimulation ON are recurrently followed by time intervals with stimulation OFF. In addition, we found that the optimal number of stimulation sites essentially depends on how strongly the administered current decays within the neuronal tissue with increasing distance from the stimulation site. In particular, for a broad spatial stimulation profile, i.e., for a weak spatial decay rate of the stimulation current, CR stimulation can optimally be delivered via a small number of stimulation sites. Our findings may contribute to an optimization of therapeutic applications of CR neuromodulation. PMID:23885239

Evaluation of various somatosensory stimulations for functional MRI

International Nuclear Information System (INIS)

Hara, Kazushi; Nakasato, Nobukazu; Mizoi, Kazuo; Yoshimoto, Takashi; Shimizu, Hiroaki.

1997-01-01

The aim of this functional magnetic resonance imaging (fMRI) study was to test detectability of activated area using various somatosensory stimulations. The following stimulations were performed in normal volunteers: regular or irregular electrical median nerve stimulation (n=5, each), tactile stimulation to the palm and fingers (n=8), pain stimulation to the index finger (n=5) or to the palm and fingers (n=5). fMRI was acquired with a spoiled gradient echo sequence at 1.5 T. Detectability of activated area was the highest when the pain stimulation was applied to the palm and fingers (80%). A successful rate for the tactile stimulation was 25%, and the other stimulations failed to demonstrate any activation. When successful, the highest signal activation on fMRI was seen on a sulcus, which presumably arose from a vein. The sulcus was defined as the central sulcus by somatosensory evoked field using a median nerve stimulation. Our study indicates that the pain stimulation to the palm and fingers may be a choice for the sensory fMRI. (author)

Economics of nuclear gas stimulation

Energy Technology Data Exchange (ETDEWEB)

Frank, G W [Austral Oil Company Incorporated, Houston, TX (United States); Coffer, H F; Luetkehans, G R [CER Geonuclear Corporation, Las Vegas, NV (United States)

1970-05-01

Nuclear stimulation of the Mesaverde Formation in the Piceance Basin appears to be the only available method that can release the contained gas economically. In the Rulison Field alone estimates show six to eight trillion cubic feet of gas may be made available by nuclear means, and possibly one hundred trillion cubic feet could be released in the Piceance Basin. Several problems remain to be solved before this tremendous gas reserve can be tapped. Among these are (1) rates of production following nuclear stimulation; (2) costs of nuclear stimulation; (3) radioactivity of the chimney gas; and (4) development of the ideal type of device to carry out the stimulations. Each of these problems is discussed in detail with possible solutions suggested. First and foremost is the rate at which gas can be delivered following nuclear stimulation. Calculations have been made for expected production behavior following a 5-kiloton device and a 40-kiloton device with different permeabilities. These are shown, along with conventional production history. The calculations show that rates of production will be sufficient if costs can be controlled. Costs of nuclear stimulation must be drastically reduced for a commercial process. Project Rulison will cost approximately $3.7 million, excluding lease costs, preliminary tests, and well costs. At such prices, nothing can possibly be commercial; however, these costs can come down in a logical step-wise fashion. Radiation contamination of the gas remains a problem. Three possible solutions to this problem are included. (author)

Economics of nuclear gas stimulation

International Nuclear Information System (INIS)

Frank, G.W.; Coffer, H.F.; Luetkehans, G.R.

1970-01-01

Nuclear stimulation of the Mesaverde Formation in the Piceance Basin appears to be the only available method that can release the contained gas economically. In the Rulison Field alone estimates show six to eight trillion cubic feet of gas may be made available by nuclear means, and possibly one hundred trillion cubic feet could be released in the Piceance Basin. Several problems remain to be solved before this tremendous gas reserve can be tapped. Among these are (1) rates of production following nuclear stimulation; (2) costs of nuclear stimulation; (3) radioactivity of the chimney gas; and (4) development of the ideal type of device to carry out the stimulations. Each of these problems is discussed in detail with possible solutions suggested. First and foremost is the rate at which gas can be delivered following nuclear stimulation. Calculations have been made for expected production behavior following a 5-kiloton device and a 40-kiloton device with different permeabilities. These are shown, along with conventional production history. The calculations show that rates of production will be sufficient if costs can be controlled. Costs of nuclear stimulation must be drastically reduced for a commercial process. Project Rulison will cost approximately $3.7 million, excluding lease costs, preliminary tests, and well costs. At such prices, nothing can possibly be commercial; however, these costs can come down in a logical step-wise fashion. Radiation contamination of the gas remains a problem. Three possible solutions to this problem are included. (author)

Multifocal visual evoked responses to dichoptic stimulation using virtual reality goggles: Multifocal VER to dichoptic stimulation.

Science.gov (United States)

Arvind, Hemamalini; Klistorner, Alexander; Graham, Stuart L; Grigg, John R

2006-05-01

Multifocal visual evoked potentials (mfVEPs) have demonstrated good diagnostic capabilities in glaucoma and optic neuritis. This study aimed at evaluating the possibility of simultaneously recording mfVEP for both eyes with dichoptic stimulation using virtual reality goggles and also to determine the stimulus characteristics that yield maximum amplitude. ten healthy volunteers were recruited and temporally sparse pattern pulse stimuli were presented dichoptically using virtual reality goggles. Experiment 1 involved recording responses to dichoptically presented checkerboard stimuli and also confirming true topographic representation by switching off specific segments. Experiment 2 involved monocular stimulation and comparison of amplitude with Experiment 1. In Experiment 3, orthogonally oriented gratings were dichoptically presented. Experiment 4 involved dichoptic presentation of checkerboard stimuli at different levels of sparseness (5.0 times/s, 2.5 times/s, 1.66 times/s and 1.25 times/s), where stimulation of corresponding segments of two eyes were separated by 16.7, 66.7,116.7 & 166.7 ms respectively. Experiment 1 demonstrated good traces in all regions and confirmed topographic representation. However, there was suppression of amplitude of responses to dichoptic stimulation by 17.9+/-5.4% compared to monocular stimulation. Experiment 3 demonstrated similar suppression between orthogonal and checkerboard stimuli (p = 0.08). Experiment 4 demonstrated maximum amplitude and least suppression (4.8%) with stimulation at 1.25 times/s with 166.7 ms separation between eyes. It is possible to record mfVEP for both eyes during dichoptic stimulation using virtual reality goggles, which present binocular simultaneous patterns driven by independent sequences. Interocular suppression can be almost eliminated by using a temporally sparse stimulus of 1.25 times/s with a separation of 166.7 ms between stimulation of corresponding segments of the two eyes.

Neurologic Complications of Psychomotor Stimulant Abuse.

Science.gov (United States)

Sanchez-Ramos, Juan

2015-01-01

Psychomotor stimulants are drugs that act on the central nervous system (CNS) to increase alertness, elevate mood, and produce a sense of well-being. These drugs also decrease appetite and the need for sleep. Stimulants can enhance stamina and improve performance in tasks that have been impaired by fatigue or boredom. Approved therapeutic applications of stimulants include attention deficit hyperactivity disorder (ADHD), narcolepsy, and obesity. These agents also possess potent reinforcing properties that can result in excessive self-administration and abuse. Chronic use is associated with adverse effects including psychosis, seizures, and cerebrovascular accidents, though these complications usually occur in individuals with preexisting risk factors. This chapter reviews the adverse neurologic consequences of chronic psychomotor stimulant use and abuse, with a focus on two prototypical stimulants methamphetamine and cocaine. © 2015 Elsevier Inc. All rights reserved.

Optical stimulation of peripheral nerves in vivo

Science.gov (United States)

Wells, Jonathon D.

This dissertation documents the emergence and validation of a new clinical tool that bridges the fields of biomedical optics and neuroscience. The research herein describes an innovative method for direct neurostimulation with pulsed infrared laser light. Safety and effectiveness of this technique are first demonstrated through functional stimulation of the rat sciatic nerve in vivo. The Holmium:YAG laser (lambda = 2.12 mum) is shown to operate at an optimal wavelength for peripheral nerve stimulation with advantages over standard electrical neural stimulation; including contact-free stimulation, high spatial selectivity, and lack of a stimulation artifact. The underlying biophysical mechanism responsible for transient optical nerve stimulation appears to be a small, absorption driven thermal gradient sustained at the axonal layer of nerve. Results explicitly prove that low frequency optical stimulation can reliably stimulate without resulting in tissue thermal damage. Based on the positive results from animal studies, these optimal laser parameters were utilized to move this research into the clinic with a combined safety and efficacy study in human subjects undergoing selective dorsal rhizotomy. The clinical Holmium:YAG laser was used to effectively stimulate human dorsal spinal roots and elicit functional muscle responses recorded during surgery without evidence of nerve damage. Overall these results predict that this technology can be a valuable clinical tool in various neurosurgical applications.

Brain stimulation in migraine.

Science.gov (United States)

Brighina, Filippo; Cosentino, Giuseppe; Fierro, Brigida

2013-01-01

Migraine is a very prevalent disease with great individual disability and socioeconomic burden. Despite intensive research effort in recent years, the etiopathogenesis of the disease remains to be elucidated. Recently, much importance has been given to mechanisms underlying the cortical excitability that has been suggested to be dysfunctional in migraine. In recent years, noninvasive brain stimulation techniques based on magnetic fields (transcranial magnetic stimulation, TMS) and on direct electrical currents (transcranial direct current stimulation, tDCS) have been shown to be safe and effective tools to explore the issue of cortical excitability, activation, and plasticity in migraine. Moreover, TMS, repetitive TMS (rTMS), and tDCS, thanks to their ability to interfere with and/or modulate cortical activity inducing plastic, persistent effects, have been also explored as potential therapeutic approaches, opening an interesting perspective for noninvasive neurostimulation for both symptomatic and preventive treatment of migraine and other types of headache. In this chapter we critically review evidence regarding the role of noninvasive brain stimulation in the pathophysiology and treatment of migraine, delineating the advantages and limits of these techniques together with potential development and future application. © 2013 Elsevier B.V. All rights reserved.

Comparing the force ripple during asynchronous and conventional stimulation.

Science.gov (United States)

Downey, Ryan J; Tate, Mark; Kawai, Hiroyuki; Dixon, Warren E

2014-10-01

Asynchronous stimulation has been shown to reduce fatigue during electrical stimulation; however, it may also exhibit a force ripple. We quantified the ripple during asynchronous and conventional single-channel transcutaneous stimulation across a range of stimulation frequencies. The ripple was measured during 5 asynchronous stimulation protocols, 2 conventional stimulation protocols, and 3 volitional contractions in 12 healthy individuals. Conventional 40 Hz and asynchronous 16 Hz stimulation were found to induce contractions that were as smooth as volitional contractions. Asynchronous 8, 10, and 12 Hz stimulation induced contractions with significant ripple. Lower stimulation frequencies can reduce fatigue; however, they may also lead to increased ripple. Future efforts should study the relationship between force ripple and the smoothness of the evoked movements in addition to the relationship between stimulation frequency and NMES-induced fatigue to elucidate an optimal stimulation frequency for asynchronous stimulation. © 2014 Wiley Periodicals, Inc.

Modulating Hippocampal Plasticity with In Vivo Brain Stimulation

Science.gov (United States)

2016-11-17

wires were left unhooked from stimulation device. Following stimulation , the animals were returned to their homecage until time of euthanasia and...current stimulation (tDCS) to enhance cognitive training: effect of timing of stimulation . Exp Brain Res 232:3345-3351. 15 DISTRIBUTION...AFRL-RH-WP-TR-2016-0082 MODULATING HIPPOCAMPAL PLASTICITY WITH IN-VIVO BRAIN STIMULATION Joyce G. Rohan Oakridge Institute

Addictive drugs and brain stimulation reward.

Science.gov (United States)

Wise, R A

1996-01-01

Direct electrical or chemical stimulation of specific brain regions can establish response habits similar to those established by natural rewards such as food or sexual contact. Cocaine, mu and delta opiates, nicotine, phencyclidine, and cannabis each have actions that summate with rewarding electrical stimulation of the medial forebrain bundle (MFB). The reward-potentiating effects of amphetamine and opiates are associated with central sites of action where these drugs also have their direct rewarding effects, suggesting common mechanisms for drug reward per se and for drug potentiation of brain stimulation reward. The central sites at which these and perhaps other drugs of abuse potentiate brain stimulation reward and are rewarding in their own right are consistent with the hypothesis that the laboratory reward of brain stimulation and the pharmacological rewards of addictive drugs are habit forming because they act in the brain circuits that subserve more natural and biologically significant rewards.

A wireless wearable surface functional electrical stimulator

Science.gov (United States)

Wang, Hai-Peng; Guo, Ai-Wen; Zhou, Yu-Xuan; Xia, Yang; Huang, Jia; Xu, Chong-Yao; Huang, Zong-Hao; Lü, Xiao-Ying; Wang, Zhi-Gong

2017-09-01

In this paper, a wireless wearable functional electrical stimulator controlled by Android phone with real-time-varying stimulation parameters for multichannel surface functional electrical stimulation application has been developed. It can help post-stroke patients using more conveniently. This study focuses on the prototype design, including the specific wristband concept, circuits and stimulation pulse-generation algorithm. A novel stimulator circuit with a driving stage using a complementary current source technique is proposed to achieve a high-voltage compliance, a large output impedance and an accurate linear voltage-to-current conversion. The size of the prototype has been significantly decreased to 17 × 7.5 × 1 cm3. The performance of the prototype has been tested with a loaded resistor and wrist extension/flexion movement of three hemiplegic patients. According to the experiments, the stimulator can generate four-channel charge-balanced biphasic stimulation with a voltage amplitude up to 60 V, and the pulse frequency and width can be adjusted in real time with a range of 100-600 μs and 20-80 Hz, respectively.

High frequency oscillations evoked by peripheral magnetic stimulation.

Science.gov (United States)

Biller, S; Simon, L; Fiedler, P; Strohmeier, D; Haueisen, J

2011-01-01

The analysis of somatosensory evoked potentials (SEP) and / or fields (SEF) is a well-established and important tool for investigating the functioning of the peripheral and central human nervous system. A standard technique to evoke SEPs / SEFs is the stimulation of the median nerve by using a bipolar electrical stimulus. We aim at an alternative stimulation technique enabling stimulation of deep nerve structures while reducing patient stress and error susceptibility. In the current study, we apply a commercial transcranial magnetic stimulation system for peripheral magnetic stimulation of the median nerve. We compare the results of simultaneously recorded EEG signals to prove applicability of our technique to evoke SEPs including low frequency components (LFC) as well as high frequency oscillations (HFO). Therefore, we compare amplitude, latency and time-frequency characteristics of the SEP of 14 healthy volunteers after electric and magnetic stimulation. Both low frequency components and high frequency oscillations were detected. The HFOs were superimposed onto the primary cortical response N20. Statistical analysis revealed significantly lower amplitudes and increased latencies for LFC and HFO components after magnetic stimulation. The differences indicate the inability of magnetic stimulation to elicit supramaximal responses. A psycho-perceptual evaluation showed that magnetic stimulation was less unpleasant for 12 out of the 14 volunteers. In conclusion, we showed that LFC and HFO components related to median nerve stimulation can be evoked by peripheral magnetic stimulation.

Consensus paper: combining transcranial stimulation with neuroimaging

DEFF Research Database (Denmark)

Siebner, Hartwig R; Bergmann, Til O; Bestmann, Sven

2009-01-01

neuroimaging (online approach), TMS can be used to test how focal cortex stimulation acutely modifies the activity and connectivity in the stimulated neuronal circuits. TMS and neuroimaging can also be separated in time (offline approach). A conditioning session of repetitive TMS (rTMS) may be used to induce...... information obtained by neuroimaging can be used to define the optimal site and time point of stimulation in a subsequent experiment in which TMS is used to probe the functional contribution of the stimulated area to a specific task. In this review, we first address some general methodologic issues that need......In the last decade, combined transcranial magnetic stimulation (TMS)-neuroimaging studies have greatly stimulated research in the field of TMS and neuroimaging. Here, we review how TMS can be combined with various neuroimaging techniques to investigate human brain function. When applied during...

Stuttering in Parkinson's disease after deep brain stimulation: A note on dystonia and low-frequency stimulation.

Science.gov (United States)

Mendonça, Marcelo D; Barbosa, Raquel; Seromenho-Santos, Alexandra; Reizinho, Carla; Bugalho, Paulo

2018-04-01

Stuttering, a speech fluency disorder, is a rare complication of Deep Brain Stimulation (DBS) in Parkinson's Disease (PD). We report a 61 years-old patient with PD, afflicted by severe On and Off dystonia, treated with Subthalamic Nucleus DBS that developed post-DBS stuttering while on 130 Hz stimulation. Stuttering reduction was noted when frequency was changed to 80 Hz, but the previously observed dystonia improvement was lost. There are no reports in literature on patients developing stuttering with low-frequency stimulation. We question if low-frequency stimulation could have a role for managing PD's post-DBS stuttering, and notice that stuttering improvement was associated with dystonia worsening suggesting that they are distinct phenomena. Copyright © 2018 Elsevier Ltd. All rights reserved.

Stimulation of hair cells with ultraviolet light

Science.gov (United States)

Azimzadeh, Julien B.; Fabella, Brian A.; Hudspeth, A. J.

2018-05-01

Hair bundles are specialized organelles that transduce mechanical inputs into electrical outputs. To activate hair cells, physiologists have resorted to mechanical methods of hair-bundle stimulation. Here we describe a new method of hair-bundle stimulation, irradiation with ultraviolet light. A hair bundle illuminated by ultraviolet light rapidly moves towards its tall edge, a motion typically associated with excitatory stimulation. The motion disappears upon tip-link rupture and is associated with the opening of mechanotransduction channels. Hair bundles can be induced to move sinusoidally with oscillatory modulation of the stimulation power. We discuss the implications of ultraviolet stimulation as a novel hair-bundle stimulus.

Excitation of hybridized Dirac plasmon polaritons and transition radiation in multi-layer graphene traversed by a fast charged particle

Science.gov (United States)

Akbari, Kamran; Mišković, Zoran L.; Segui, Silvina; Gervasoni, Juana L.; Arista, Néstor R.

2018-06-01

We analyze the energy loss channels for a fast charged particle traversing a multi-layer graphene (MLG) structure with N layers under normal incidence. Focusing on a terahertz (THz) range of frequencies, and assuming equally doped graphene layers with a large enough separation d between them to neglect interlayer electron hopping, we use the Drude model for two-dimensional conductivity of each layer to describe hybridization of graphene’s Dirac plasmon polaritons (DPPs). Performing a layer decomposition of ohmic energy losses, which include excitation of hybridized DPPs (HDPPs), we have found for N = 3 that the middle HDPP eigenfrequency is not excited in the middle layer due to symmetry constraint, whereas the excitation of the lowest HDPP eigenfrequency produces a Fano resonance in the graphene layer that is first traversed by the charged particle. While the angular distribution of transition radiation emitted in the far field region also shows asymmetry with respect to the traversal order by the incident charged particle at supra-THz frequencies, the integrated radiative energy loss is surprisingly independent of both d and N for N ≤ 5, which is explained by a dominant role of the outer graphene layers in transition radiation. We have further found that the integrated ohmic energy loss in optically thin MLG scales as ∝1/N at sub-THz frequencies, which is explained by exposing the role of dissipative processes in graphene at low frequencies. Finally, prominent peaks are observed at supra-THz frequencies in the integrated ohmic energy loss for MLG structures that are not optically thin. The magnitude of those peaks is found to scale with N for N ≥ 2, while their shape and position replicate the peak in a double-layer graphene (N = 2), which is explained by arguing that plasmon hybridization in such MLG structures is dominated by electromagnetic interaction between the nearest-neighbor graphene layers.

Can the human lumbar posterior columns be stimulated by transcutaneous spinal cord stimulation? A modeling study

OpenAIRE

Danner, Simon M.; Hofstoetter, Ursula S.; Ladenbauer, Josef; Rattay, Frank; Minassian, Karen

2011-01-01

Stimulation of different spinal cord segments in humans is a widely developed clinical practice for modification of pain, altered sensation and movement. The human lumbar cord has become a target for modification of motor control by epidural and more recently by transcutaneous spinal cord stimulation. Posterior columns of the lumbar spinal cord represent a vertical system of axons and when activated can add other inputs to the motor control of the spinal cord than stimulated posterior roots. ...

Vertex Stimulation as a Control Site for Transcranial Magnetic Stimulation: A Concurrent TMS/fMRI Study

OpenAIRE

Jung, JeYoung; Bungert, Andreas; Bowtell, Richard; Jackson, Stephen R.

2016-01-01

Background A common control condition for transcranial magnetic stimulation (TMS) studies is to apply stimulation at the vertex. An assumption of vertex stimulation is that it has relatively little influence over on-going brain processes involved in most experimental tasks, however there has been little attempt to measure neural changes linked to vertex TMS. Here we directly test this assumption by using a concurrent TMS/fMRI paradigm in which we investigate fMRI blood-oxygenation-level-depen...

Computational modeling of epidural cortical stimulation

Science.gov (United States)

Wongsarnpigoon, Amorn; Grill, Warren M.

2008-12-01

Epidural cortical stimulation (ECS) is a developing therapy to treat neurological disorders. However, it is not clear how the cortical anatomy or the polarity and position of the electrode affects current flow and neural activation in the cortex. We developed a 3D computational model simulating ECS over the precentral gyrus. With the electrode placed directly above the gyrus, about half of the stimulus current flowed through the crown of the gyrus while current density was low along the banks deep in the sulci. Beneath the electrode, neurons oriented perpendicular to the cortical surface were depolarized by anodic stimulation, and neurons oriented parallel to the boundary were depolarized by cathodic stimulation. Activation was localized to the crown of the gyrus, and neurons on the banks deep in the sulci were not polarized. During regulated voltage stimulation, the magnitude of the activating function was inversely proportional to the thickness of the CSF and dura. During regulated current stimulation, the activating function was not sensitive to the thickness of the dura but was slightly more sensitive than during regulated voltage stimulation to the thickness of the CSF. Varying the width of the gyrus and the position of the electrode altered the distribution of the activating function due to changes in the orientation of the neurons beneath the electrode. Bipolar stimulation, although often used in clinical practice, reduced spatial selectivity as well as selectivity for neuron orientation.

An Implantable Mixed Analog/Digital Neural Stimulator Circuit

DEFF Research Database (Denmark)

Gudnason, Gunnar; Bruun, Erik; Haugland, Morten

1999-01-01

This paper describes a chip for a multichannel neural stimulator for functional electrical stimulation. The chip performs all the signal processing required in an implanted neural stimulator. The power and signal transmission to the stimulator is carried out via an inductive link. From the signals...... electrical stimulation is to restore various bodily functions (e.g. motor functions) in patients who have lost them due to injury or disease....

Transmutation of skyrmions to half-solitons driven by the nonlinear optical spin Hall effect.

Science.gov (United States)

Flayac, H; Solnyshkov, D D; Shelykh, I A; Malpuech, G

2013-01-04

We show that the spin domains, generated in the linear optical spin Hall effect by the analog of spin-orbit interaction for exciton polaritons, are associated with the formation of a Skyrmion lattice. In the nonlinear regime, the spin anisotropy of the polariton-polariton interactions results in a spatial compression of the domains and in a transmutation of the Skyrmions into oblique half-solitons. This phase transition is associated with both the focusing of the spin currents and the emergence of a strongly anisotropic emission pattern.

Gamma-radiation-induced chromosal aberration in human lymphocytes: dose-rate effects in stimulated and non-stimulated cells

International Nuclear Information System (INIS)

Liniecki, J.; Bajerska, A.; Wyszynska, K.; Cisowska, B.

1977-01-01

Stimulated and non-stimulated human peripheral blood lymphocytes were irradiated acutely and chronically, over 24 h. Dose-effect relationships for dicentric chromosomes were established and various models were fitted to the data. At prolonged irradiations, the yield decreased in basic agreement with the linear-quadratic model of aberration induction. Dose-protraction experiments on PHA + and PHA - lymphocytes, irradiated under various conditions of oxygenation and suspension (culture medium, whole blood) showed that the rejoining time increased from about 3 h in non-stimulated cells to about 10 h after PHA stimulation, and that this retarded rejoining was most likely due to blastic transformation itself and not to other conditions of irradiation

Can the human lumbar posterior columns be stimulated by transcutaneous spinal cord stimulation? A modeling study.

Science.gov (United States)

Danner, Simon M; Hofstoetter, Ursula S; Ladenbauer, Josef; Rattay, Frank; Minassian, Karen

2011-03-01

Stimulation of different spinal cord segments in humans is a widely developed clinical practice for modification of pain, altered sensation, and movement. The human lumbar cord has become a target for modification of motor control by epidural and, more recently, by transcutaneous spinal cord stimulation. Posterior columns of the lumbar spinal cord represent a vertical system of axons and when activated can add other inputs to the motor control of the spinal cord than stimulated posterior roots. We used a detailed three-dimensional volume conductor model of the torso and the McIntyre-Richard-Grill axon model to calculate the thresholds of axons within the posterior columns in response to transcutaneous lumbar spinal cord stimulation. Superficially located large-diameter posterior column fibers with multiple collaterals have a threshold of 45.4 V, three times higher than posterior root fibers (14.1 V). With the stimulation strength needed to activate posterior column axons, posterior root fibers of large and small diameters as well as anterior root fibers are coactivated. The reported results inform on these threshold differences, when stimulation is applied to the posterior structures of the lumbar cord at intensities above the threshold of large-diameter posterior root fibers. © 2011, Copyright the Authors. Artificial Organs © 2011, International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Transcranial Alternating Current Stimulation Attenuates Neuronal Adaptation.

Science.gov (United States)

Kar, Kohitij; Duijnhouwer, Jacob; Krekelberg, Bart

2017-03-01

We previously showed that brief application of 2 mA (peak-to-peak) transcranial currents alternating at 10 Hz significantly reduces motion adaptation in humans. This is but one of many behavioral studies showing that weak currents applied to the scalp modulate neural processing. Transcranial stimulation has been shown to improve perception, learning, and a range of clinical symptoms. Few studies, however, have measured the neural consequences of transcranial current stimulation. We capitalized on the strong link between motion perception and neural activity in the middle temporal (MT) area of the macaque monkey to study the neural mechanisms that underlie the behavioral consequences of transcranial alternating current stimulation. First, we observed that 2 mA currents generated substantial intracranial fields, which were much stronger in the stimulated hemisphere (0.12 V/m) than on the opposite side of the brain (0.03 V/m). Second, we found that brief application of transcranial alternating current stimulation at 10 Hz reduced spike-frequency adaptation of MT neurons and led to a broadband increase in the power spectrum of local field potentials. Together, these findings provide a direct demonstration that weak electric fields applied to the scalp significantly affect neural processing in the primate brain and that this includes a hitherto unknown mechanism that attenuates sensory adaptation. SIGNIFICANCE STATEMENT Transcranial stimulation has been claimed to improve perception, learning, and a range of clinical symptoms. Little is known, however, how transcranial current stimulation generates such effects, and the search for better stimulation protocols proceeds largely by trial and error. We investigated, for the first time, the neural consequences of stimulation in the monkey brain. We found that even brief application of alternating current stimulation reduced the effects of adaptation on single-neuron firing rates and local field potentials; this mechanistic

Modern management of epilepsy: Vagus nerve stimulation.

Science.gov (United States)

Ben-Menachem, E

1996-12-01

Vagus nerve stimulation (VNS) was first tried as a treatment for seizure patients in 1988. The idea to stimulate the vagus nerve and disrupt or prevent seizures was proposed by Jacob Zabarra. He observed a consistent finding among several animal studies which indicated that stimulation of the vagus nerve could alter the brain wave patterns of the animals under study. His hypothesis formed the basis for the development of the vagus nerve stimulator, an implantable device similar to a pacemaker, which is implanted in the left chest and attached to the left vagus nerve via a stimulating lead. Once implanted, the stimulator is programmed by a physician to deliver regular stimulation 24 hours a day regardless of seizure activity. Patients can also activate extra 'on-demand' stimulation with a handheld magnet. Clinical studies have demonstrated VNS therapy to be a safe and effective mode of treatment when added to the existing regimen of severe, refractory patients with epilepsy. Efficacy ranges from seizure free to no response with the majority of patients (> 50%) reporting at least a 50% improvement in number of seizures after 1.5 years of treatment. The side-effect profile is unique and mostly includes stimulation-related sensations in the neck and throat. The mechanism of action for VNS is not clearly understood although two theories have emerged. First, the direct connection theory hypothesizes that the anticonvulsant action of VNS is caused by a threshold raising effect of the connections to the nucleus of the solitary tract and on to other structures. The second is the concept that chronic stimulation of the vagus nerve increases the amount of inhibitory neurotransmitters and decreases the amount of excitatory neurotransmitters. Additional research into the optimal use of VNS is ongoing. Animal and clinical research have produced some interesting new data suggesting there are numerous ways to improve the clinical performance of vagus nerve stimulation as a

Transcranial electrical stimulation accelerates human sleep homeostasis.

Directory of Open Access Journals (Sweden)

Davide Reato

Full Text Available The sleeping brain exhibits characteristic slow-wave activity which decays over the course of the night. This decay is thought to result from homeostatic synaptic downscaling. Transcranial electrical stimulation can entrain slow-wave oscillations (SWO in the human electro-encephalogram (EEG. A computational model of the underlying mechanism predicts that firing rates are predominantly increased during stimulation. Assuming that synaptic homeostasis is driven by average firing rates, we expected an acceleration of synaptic downscaling during stimulation, which is compensated by a reduced drive after stimulation. We show that 25 minutes of transcranial electrical stimulation, as predicted, reduced the decay of SWO in the remainder of the night. Anatomically accurate simulations of the field intensities on human cortex precisely matched the effect size in different EEG electrodes. Together these results suggest a mechanistic link between electrical stimulation and accelerated synaptic homeostasis in human sleep.

Effect of Low-Level Laser Stimulation on EEG

Directory of Open Access Journals (Sweden)

Jih-Huah Wu

2012-01-01

Full Text Available Conventional laser stimulation at the acupoint can induce significant brain activation, and the activation is theoretically conveyed by the sensory afferents. Whether the insensible low-level Laser stimulation outside the acupoint could also evoke electroencephalographic (EEG changes is not known. We designed a low-level laser array stimulator (6 pcs laser diode, wavelength 830 nm, output power 7 mW, and operation frequency 10 Hz to deliver insensible laser stimulations to the palm. EEG activities before, during, and after the laser stimulation were collected. The amplitude powers of each EEG frequency band were analyzed. We found that the low-level laser stimulation was able to increase the power of alpha rhythms and theta waves, mainly in the posterior head regions. These effects lasted at least 15 minutes after cessation of the laser stimulation. The amplitude power of beta activities in the anterior head regions decreased after laser stimulation. We thought these EEG changes comparable to those in meditation.

Effect of low-level laser stimulation on EEG.

Science.gov (United States)

Wu, Jih-Huah; Chang, Wen-Dien; Hsieh, Chang-Wei; Jiang, Joe-Air; Fang, Wei; Shan, Yi-Chia; Chang, Yang-Chyuan

2012-01-01

Conventional laser stimulation at the acupoint can induce significant brain activation, and the activation is theoretically conveyed by the sensory afferents. Whether the insensible low-level Laser stimulation outside the acupoint could also evoke electroencephalographic (EEG) changes is not known. We designed a low-level laser array stimulator (6 pcs laser diode, wavelength 830 nm, output power 7 mW, and operation frequency 10 Hz) to deliver insensible laser stimulations to the palm. EEG activities before, during, and after the laser stimulation were collected. The amplitude powers of each EEG frequency band were analyzed. We found that the low-level laser stimulation was able to increase the power of alpha rhythms and theta waves, mainly in the posterior head regions. These effects lasted at least 15 minutes after cessation of the laser stimulation. The amplitude power of beta activities in the anterior head regions decreased after laser stimulation. We thought these EEG changes comparable to those in meditation.

Electrical stimulation and motor recovery.

Science.gov (United States)

Young, Wise

2015-01-01

In recent years, several investigators have successfully regenerated axons in animal spinal cords without locomotor recovery. One explanation is that the animals were not trained to use the regenerated connections. Intensive locomotor training improves walking recovery after spinal cord injury (SCI) in people, and >90% of people with incomplete SCI recover walking with training. Although the optimal timing, duration, intensity, and type of locomotor training are still controversial, many investigators have reported beneficial effects of training on locomotor function. The mechanisms by which training improves recovery are not clear, but an attractive theory is available. In 1949, Donald Hebb proposed a famous rule that has been paraphrased as "neurons that fire together, wire together." This rule provided a theoretical basis for a widely accepted theory that homosynaptic and heterosynaptic activity facilitate synaptic formation and consolidation. In addition, the lumbar spinal cord has a locomotor center, called the central pattern generator (CPG), which can be activated nonspecifically with electrical stimulation or neurotransmitters to produce walking. The CPG is an obvious target to reconnect after SCI. Stimulating motor cortex, spinal cord, or peripheral nerves can modulate lumbar spinal cord excitability. Motor cortex stimulation causes long-term changes in spinal reflexes and synapses, increases sprouting of the corticospinal tract, and restores skilled forelimb function in rats. Long used to treat chronic pain, motor cortex stimuli modify lumbar spinal network excitability and improve lower extremity motor scores in humans. Similarly, epidural spinal cord stimulation has long been used to treat pain and spasticity. Subthreshold epidural stimulation reduces the threshold for locomotor activity. In 2011, Harkema et al. reported lumbosacral epidural stimulation restores motor control in chronic motor complete patients. Peripheral nerve or functional electrical

Shared Neural Mechanisms for the Evaluation of Intense Sensory Stimulation and Economic Reward, Dependent on Stimulation-Seeking Behavior.

Science.gov (United States)

Norbury, Agnes; Valton, Vincent; Rees, Geraint; Roiser, Jonathan P; Husain, Masud

2016-09-28

Why are some people strongly motivated by intense sensory experiences? Here we investigated how people encode the value of an intense sensory experience compared with economic reward, and how this varies according to stimulation-seeking preference. Specifically, we used a novel behavioral task in combination with computational modeling to derive the value individuals assigned to the opportunity to experience an intense tactile stimulus (mild electric shock). We then examined functional imaging data recorded during task performance to see how the opportunity to experience the sensory stimulus was encoded in stimulation-seekers versus stimulation-avoiders. We found that for individuals who positively sought out this kind of sensory stimulation, there was common encoding of anticipated economic and sensory rewards in the ventromedial prefrontal cortex. Conversely, there was robust encoding of the modeled probability of receiving such stimulation in the insula only in stimulation-avoidant individuals. Finally, we found preliminary evidence that sensory prediction error signals may be positively signed for stimulation-seekers, but negatively signed for stimulation-avoiders, in the posterior cingulate cortex. These findings may help explain why high intensity sensory experiences are appetitive for some individuals, but not for others, and may have relevance for the increased vulnerability for some psychopathologies, but perhaps increased resilience for others, in high sensation-seeking individuals. People vary in their preference for intense sensory experiences. Here, we investigated how different individuals evaluate the prospect of an unusual sensory experience (electric shock), compared with the opportunity to gain a more traditional reward (money). We found that in a subset of individuals who sought out such unusual sensory stimulation, anticipation of the sensory outcome was encoded in the same way as that of monetary gain, in the ventromedial prefrontal cortex

Effect of transcutaneous electrical nerve stimulation induced parotid stimulation on salivary flow

Directory of Open Access Journals (Sweden)

Sreenivasulu Pattipati

2013-01-01

Full Text Available Aims and Objectives: The main objective of this study was to evaluate the duration of stimulation over the parotid salivary flow following the use of transcutaneous electric nerve stimulation (TENS in different age groups. Materials and Methods: The study was carried out in three different age groups. Under group A individuals from 21 to 35 years of age, group B 36-50 years and group C above 51 years were considered. In each group 30 subjects were taken of whom 15 were males and 15 were females. The placement of pads was approximated bilaterally over the parotid glands. The working parameters of TENS unit were fixed at 50 Hz and the unit was in normal mode. Results: Subjects belonging to group B were showing statistically significant increases in the duration of stimulated parotid salivary flow following the use of TENS. Conclusion: TENS can be considered as a non-pharmacological alternative to improve salivation for longer period in xerostomia patients.

Theory of multichannel magnetic stimulation: toward functional neuromuscular rehabilitation.

Science.gov (United States)

Ruohonen, J; Ravazzani, P; Grandori, F; Ilmoniemi, R J

1999-06-01

Human excitable cells can be stimulated noninvasively with externally applied time-varying electromagnetic fields. The stimulation can be achieved either by directly driving current into the tissue (electrical stimulation) or by means of electro-magnetic induction (magnetic stimulation). While the electrical stimulation of the peripheral neuromuscular system has many beneficial applications, peripheral magnetic stimulation has so far only a few. This paper analyzes theoretically the use of multiple magnetic stimulation coils to better control the excitation and also to eventually mimic electrical stimulation. Multiple coils allow electronic spatial adjustment of the shape and location of the stimulus without moving the coils. The new properties may enable unforeseen uses for peripheral magnetic stimulation, e.g., in rehabilitation of patients with neuromuscular impairment.

[Electrical acupoint stimulation increases athletes' rapid strength].

Science.gov (United States)

Yang, Hua-yuan; Liu, Tang-yi; Kuai, Le; Gao, Ming

2006-05-01

To search for a stimulation method for increasing athletes' performance. One hundred and fifty athletes were randomly divided into a trial group and a control group, 75 athletes in each group. Acupoints were stimulated with audio frequency pulse modulated wave and multi-blind method were used to investigate effects of the electric stimulation of acupoints on 30-meter running, standing long jumping and Cybex isokinetic testing index. The acupoint electric stimulation method could significantly increase athlete's performance (P < 0.05), and the biomechanical indexes, maximal peak moment of force (P < 0.05), force moment accelerating energy (P < 0.05) and average power (P < 0.05). Electrical acupoint stimulation can enhance athlete's rapid strength.

A Chip for an Implantable Neural Stimulator

DEFF Research Database (Denmark)

Gudnason, Gunnar; Bruun, Erik; Haugland, Morten

2000-01-01

This paper describes a chip for a multichannel neural stimulator for functional electrical stimulation (FES). The purpose of FES is to restore muscular control in disabled patients. The chip performs all the signal processing required in an implanted neural stimulator. The power and digital data...

Subliminal Stimulation: Hoax or Reality?

Science.gov (United States)

Trank, Douglas M.

Subliminal stimulation is defined as that which is perceived by an individual below the threshold of awareness or cognizance. This article traces the history of research in subliminal stimulation to illustrate that under certain circumstances and conditions, this behavioral phenomenon does occur. Although subliminal stimuli do affect human…

Optimal number of stimulation contacts for coordinated reset neuromodulation

Directory of Open Access Journals (Sweden)

Borys eLysyansky

2013-07-01

Full Text Available In this computational study we investigatecoordinated reset (CR neuromodulation designed for an effective controlof synchronization by multi-site stimulation of neuronal target populations. This method was suggested to effectively counteract pathological neuronal synchronycharacteristic for several neurological disorders. We studyhow many stimulation sites are required for optimal CR-induced desynchronization. We found that a moderate increase of the number of stimulation sitesmay significantly prolong the post-stimulation desynchronized transientafter the stimulation is completely switched off. This can, in turn,reduce the amount of the administered stimulation current for theintermittent ON-OFF CR stimulation protocol, where time intervalswith stimulation ON are recurrently followed by time intervals withstimulation OFF. In addition, we found that the optimal number ofstimulation sites essentially depends on how strongly the administeredcurrent decays within the neuronal tissue with increasing distancefrom the stimulation site. In particular, for a broad spatial stimulationprofile, i.e., for a weak spatial decay rate of the stimulation current,CR stimulation can optimally be delivered via a small number of stimulationsites. Our findings may contribute to an optimization of therapeutic applications of CR neuromodulation.

Optique quantique dans les microcavités semi-conductrices

Science.gov (United States)

Giacobino, Elisabeth; Karr, Jean-Philippe; Messin, Gaëtan; Eleuch, Hichem; Baas, Augustin

Investigations of quantum effects in semiconductor quantum-well microcavities interacting with laser light in the strong-coupling regime are presented. Modifications of quantum fluctuations of the outgoing light are expected due to the non-linearity originating from coherent exciton-exciton scattering. In the strong-coupling regime, this scattering translates into a four-wave mixing interaction between the mixed exciton-photon states, the polaritons. Squeezing and giant amplification of the polariton field and of the outgoing light field fluctuations are predicted. However, polariton-phonon scattering is shown to yield excess noise in the output field, which may destroy the non-classical effects. Experiments demonstrate evidence for giant amplification due to coherent four-wave mixing of polaritons. Noise reduction below the thermal noise level was also observed. To cite this article: E. Giacobino et al., C. R. Physique 3 (2002) 41-52

Geothermal Reservoir Well Stimulation Program: technology transfer

Energy Technology Data Exchange (ETDEWEB)

1980-05-01

Each of the following types of well stimulation techniques are summarized and explained: hydraulic fracturing; thermal; mechanical, jetting, and drainhole drilling; explosive and implosive; and injection methods. Current stimulation techniques, stimulation techniques for geothermal wells, areas of needed investigation, and engineering calculations for various techniques. (MHR)

Determination of stimulation focality in heterogeneous head models during transcranial magnetic stimulation (TMS)

Science.gov (United States)

Lee, Erik; Hadimani, Ravi; Jiles, David

2015-03-01

Transcranial Magnetic Stimulation (TMS) is an increasingly popular tool used by both the scientific and medical community to understand and treat the brain. TMS has the potential to help people with a wide range of diseases such as Parkinson's, Alzheimer's, and PTSD, while currently being used to treat people with chronic, drug-resistant depression. Through computer simulations, we are able to see the electric field that TMS induces in anatomical human models, but there is no measure to quantify this electric field in a way that relates to a specific patient undergoing TMS therapy. We propose a way to quantify the focality of the induced electric field in a heterogeneous head model during TMS by relating the surface area of the brain being stimulated to the total volume of the brain being stimulated. This figure would be obtained by conducting finite element analysis (FEA) simulations of TMS therapy on a patient specific head model. Using this figure to assist in TMS therapy will allow clinicians and researchers to more accurately stimulate the desired region of a patient's brain and be more equipped to do comparative studies on the effects of TMS across different patients. This work was funded by the Carver Charitable Trust.

Gamma radiation induced chromosal aberration in human lymphocytes: dose-rate effects in stimulated and non-stimulated cells

Energy Technology Data Exchange (ETDEWEB)

Liniecki, J; Bajerska, A; Wyszynska, K [School of Medicine, Lodz (Poland). Div. of Nuclear Medicine and Radiobiology. Medical Research Center; Cisowska, B [Copernicus Municipal Hospital, Lodz (Poland). Oncology Center. Radiotherapy Dept.

1977-05-01

Stimulated and non-stimulated human peripheral blood lymphocytes were irradiated acutely and chronically, over 24 h. Dose-effect relationships for dicentric chromosomes were established and various models were fitted to the data. At prolonged irradiations, the yield decreased in basic agreement with the linear-quadratic model of aberration induction. Dose-protraction experiments on PHA/sup +/ and PHA/sup -/ lymphocytes, irradiated under various conditions of oxygenation and suspension (culture medium, whole blood) showed that the rejoining time increased from about 3 h in non-stimulated cells to about 10 h after PHA stimulation, and that this retarded rejoining was most likely due to blastic transformation itself and not to other conditions of irradiation.

Bursting behaviours in cascaded stimulated Brillouin scattering

International Nuclear Information System (INIS)

Liu Zhan-Jun; He Xian-Tu; Zheng Chun-Yang; Wang Yu-Gang

2012-01-01

Stimulated Brillouin scattering is studied by numerically solving the Vlasov—Maxwell system. A cascade of stimulated Brillouin scattering can occur when a linearly polarized laser pulse propagates in a plasma. It is found that a stimulated Brillouin scattering cascade can reduce the scattering and increase the transmission of light, as well as introduce a bursting behaviour in the evolution of the laser-plasma interaction. The bursting time in the reflectivity is found to be less than half the ion acoustic period. The ion temperature can affect the stimulated Brillouin scattering cascade, which can repeat several times at low ion temperatures and can be completely eliminated at high ion temperatures. For stimulated Brillouin scattering saturation, higher-harmonic generation and wave—wave interaction of the excited ion acoustic waves can restrict the amplitude of the latter. In addition, stimulated Brillouin scattering cascade can restrict the amplitude of the scattered light. (physics of gases, plasmas, and electric discharges)

Coupling brain-machine interfaces with cortical stimulation for brain-state dependent stimulation: enhancing motor cortex excitability for neurorehabilitation

Directory of Open Access Journals (Sweden)

Alireza eGharabaghi

2014-03-01

Full Text Available Motor recovery after stroke is an unsolved challenge despite intensive rehabilitation training programs. Brain stimulation techniques have been explored in addition to traditional rehabilitation training to increase the excitability of the stimulated motor cortex. This modulation of cortical excitability augments the response to afferent input during motor exercises, thereby enhancing skilled motor learning by long-term potentiation-like plasticity. Recent approaches examined brain stimulation applied concurrently with voluntary movements to induce more specific use-dependent neural plasticity during motor training for neurorehabilitation. Unfortunately, such approaches are not applicable for the many severely affected stroke patients lacking residual hand function. These patients require novel activity-dependent stimulation paradigms based on intrinsic brain activity. Here, we report on such brain state-dependent stimulation (BSDS combined with haptic feedback provided by a robotic hand orthosis. Transcranial magnetic stimulation of the motor cortex and haptic feedback to the hand were controlled by sensorimotor desynchronization during motor-imagery and applied within a brain-machine interface environment in one healthy subject and one patient with severe hand paresis in the chronic phase after stroke. BSDS significantly increased the excitability of the stimulated motor cortex in both healthy and post-stroke conditions, an effect not observed in non-BSDS protocols. This feasibility study suggests that closing the loop between intrinsic brain state, cortical stimulation and haptic feedback provides a novel neurorehabilitation strategy for stroke patients lacking residual hand function, a proposal that warrants further investigation in a larger cohort of stroke patients.

Stimulating Language: Insights from TMS

Science.gov (United States)

Devlin, Joseph T.; Watkins, Kate E.

2007-01-01

Fifteen years ago, Pascual-Leone and colleagues used transcranial magnetic stimulation (TMS) to investigate speech production in pre-surgical epilepsy patients and in doing so, introduced a novel tool into language research. TMS can be used to non-invasively stimulate a specific cortical region and transiently disrupt information processing. These…

Polarization-dependent solitons in the strong coupling regime of semiconductor microcavities

International Nuclear Information System (INIS)

Fu, Y.; Zhang, W.L.; Wu, X.M.

2015-01-01

This paper studies the influence of polarization on formation of vectorial polariton soliton in semiconductor microcavities through numerical simulations. It is found that the polariton solution greatly depends on the polarization of both the pump and exciting fields. By properly choosing the pump and exciting field polarization, bright–bright or bright–dark vectorial polariton solitons can be formed. Especially, when the input conditions of pump or exciting field of the two opposite polarizations are slightly asymmetric, an interesting phenomenon that the dark solitons transform into bright solitons occurs in the branch of soliton solutions.

New stimulation regimens: endogenous and exogenous progesterone use to block the LH surge during ovarian stimulation for IVF.

Science.gov (United States)

Massin, Nathalie

2017-03-01

The advent of embryo and oocyte vitrification today gives reproductive specialists an opportunity to consider new strategies for improving the practice and results of IVF attempts. As the freezing of entire cohorts does not compromise, and may even improve, the results of IVF attempts, it is possible to break away from the standard sequence of stimulation-retrieval-transfer. The constraints associated with ovarian stimulation in relation to the potential harmful effects of the hormonal environment on endometrial receptivity can be avoided. This review will look at the new stimulation protocols where progesterone is used to block the LH surge. Thanks to 'freeze all' strategies, the increase in progesterone could actually be no longer a cause for concern. There are two ways of using progesterone, whether it be endogenous, as in luteal phase stimulation, or exogenous, as in the use of progesterone in the follicular phase i.e. progestin primed ovarian stimulation. A literature search was carried out (until September 2016) on MEDLINE. The following text words were utilized to generate the list of citations: progestin primed ovarian stimulation, luteal phase stimulation, luteal stimulation, duostim, double stimulation, random start. Articles and their references were then examined in order to identify other potential studies. All of the articles are reported in this review. The use of progesterone during ovarian stimulation is effective in blocking the LH surge, whether endogenous or exogenous, and it does not affect the number of oocytes collected or the quality of the embryos obtained. Its main constraint is that it requires total freezing and delayed transfer. A variety of stimulation protocols can be derived from these two methods, and their implications are discussed, from fertility preservation to ovarian response profiles to organization for the patients and clincs. These new regimens enable more flexibility and are of emerging interest in daily practice. However

Studies in dosimetry using stimulated exoelectron emission

International Nuclear Information System (INIS)

Petel, Maurice.

1976-06-01

Some applications of the stimulated exoelectron emission in radiation dosimetry are discussed. The principles which govern the phenomenon are presented. The apparatus, in particular the counter, used to monitor the emission is discussed with reference to both optical and thermal stimulation. The correlation existing between thermoluminescence and thermally stimulated exoelectron emission were studied in both lithium fluoride and aluminium oxide. Furthermore, aluminium oxides from different sources were examined, and one of these, chosen to investigate the dosimetric properties of this material using both methods of stimulation [fr

Particle trapping in stimulated scattering processes

International Nuclear Information System (INIS)

Karttunen, S.J.; Heikkinen, J.A.

1981-01-01

Particle trapping effects on stimulated Brillouin and Raman scattering are investigated. A time and space dependent model assumes a Maxwellian plasma which is taken to be homogeneous in the interaction region. Ion trapping has a rather weak effect on stimulated Brillouin scattering and large reflectivities are obtained even in strong trapping regime. Stimulated Raman scattering is considerably reduced by electron trapping. Typically 15-20 times larger laser intensities are required to obtain same reflectivity levels than without trapping. (author)

Memory and convulsive stimulation: effects of stimulus waveform.

Science.gov (United States)

Spanis, C W; Squire, L R

1981-09-01

Electrical stimulation with brief pulses can produce a seizure requiring less energy than conventional sine-wave stimulation, and it has been suggested that brief-pulse stimulation might reduce the memory loss associated with electroconvulsive therapy (ECT). The authors evaluated the effects of electroconvulsive shock (ECS) on memory in mice by using various waveforms, current intensities, training-ECS intervals, pulse widths, and stimulus durations. When equated for ability to produce seizures, low-energy, brief-pulse stimulation caused as much amnesia as sine-wave stimulation and sometimes more. In the absence of comparisons of the amnesic effects of brief-pulse and sine-wave stimulation in humans, the use of brief pulses for administering ECT is unwarranted.

The safety of transcranial magnetic stimulation with deep brain stimulation instruments.

Science.gov (United States)

Shimojima, Yoshio; Morita, Hiroshi; Nishikawa, Noriko; Kodaira, Minori; Hashimoto, Takao; Ikeda, Shu-Ichi

2010-02-01

Transcranial magnetic stimulation (TMS) has been employed in patients with an implanted deep brain stimulation (DBS) device. We investigated the safety of TMS using simulation models with an implanted DBS device. The DBS lead was inserted into plastic phantoms filled with dilute gelatin showing impedance similar to that of human brain. TMS was performed with three different types of magnetic coil. During TMS (1) electrode movement, (2) temperature change around the lead, and (3) TMS-induced current in various situations were observed. The amplitude and area of each evoked current were measured to calculate charge density of the evoked current. There was no movement or temperature increase during 0.2 Hz repetitive TMS with 100% stimulus intensity for 1 h. The size of evoked current linearly increased with TMS intensity. The maximum charge density exceeded the safety limit of 30 muC/cm(2)/phase during stimulation above the loops of the lead with intensity over 50% using a figure-eight coil. Strong TMS on the looped DBS leads should not be administered to avoid electrical tissue injury. Subcutaneous lead position should be paid enough attention for forthcoming situations during surgery. Copyright 2009 Elsevier Ltd. All rights reserved.

Numerical dosimetry of transcranial magnetic stimulation coils

Science.gov (United States)

Crowther, Lawrence; Hadimani, Ravi; Jiles, David

2014-03-01

Transcranial magnetic stimulation (TMS) is a non-invasive neuromodulation technique capable of stimulating neurons by means of electromagnetic induction. TMS can be used to map brain function and shows promise for the diagnosis and treatment of neurological and psychiatric disorders. Calculation of fields induced in the brain are necessary to accurately identify stimulated neural tissue during TMS. This allows the development of novel TMS coil designs capable of stimulating deeper brain regions and increasing the localization of stimulation that can be achieved. We have performed numerical calculations of magnetic and electric field with high-resolution anatomically realistic human head models to find these stimulated brain regions for a variety of proposed TMS coil designs. The realistic head models contain heterogeneous tissue structures and electrical conductivities, yielding superior results to those obtained from the simplified homogeneous head models that are commonly employed. The attenuation of electric field as a function of depth in the brain and the localization of stimulating field have been methodically investigated. In addition to providing a quantitative comparison of different TMS coil designs the variation of induced field between subjects has been investigated. We also show the differences in induced fields between adult, adolescent and child head models to preemptively identify potential safety issues in the application of pediatric TMS.

Imaging transcranial direct current stimulation (tDCS) of the prefrontal cortex-correlation or causality in stimulation-mediated effects?

Science.gov (United States)

Wörsching, Jana; Padberg, Frank; Ertl-Wagner, Birgit; Kumpf, Ulrike; Kirsch, Beatrice; Keeser, Daniel

2016-10-01

Transcranial current stimulation approaches include neurophysiologically distinct non-invasive brain stimulation techniques widely applied in basic, translational and clinical research: transcranial direct current stimulation (tDCS), oscillating transcranial direct current stimulation (otDCS), transcranial alternating current stimulation (tACS) and transcranial random noise stimulation (tRNS). Prefrontal tDCS seems to be an especially promising tool for clinical practice. In order to effectively modulate relevant neural circuits, systematic research on prefrontal tDCS is needed that uses neuroimaging and neurophysiology measures to specifically target and adjust this method to physiological requirements. This review therefore analyses the various neuroimaging methods used in combination with prefrontal tDCS in healthy and psychiatric populations. First, we provide a systematic overview on applications, computational models and studies combining neuroimaging or neurophysiological measures with tDCS. Second, we categorise these studies in terms of their experimental designs and show that many studies do not vary the experimental conditions to the extent required to demonstrate specific relations between tDCS and its behavioural or neurophysiological effects. Finally, to support best-practice tDCS research we provide a methodological framework for orientation among experimental designs. Copyright © 2016 Elsevier Ltd. All rights reserved.

Stimulation Technologies for Deep Well Completions

Energy Technology Data Exchange (ETDEWEB)

Stephen Wolhart

2005-06-30

The Department of Energy (DOE) is sponsoring the Deep Trek Program targeted at improving the economics of drilling and completing deep gas wells. Under the DOE program, Pinnacle Technologies conducted a study to evaluate the stimulation of deep wells. The objective of the project was to review U.S. deep well drilling and stimulation activity, review rock mechanics and fracture growth in deep, high-pressure/temperature wells and evaluate stimulation technology in several key deep plays. This report documents results from this project.

Vagus Nerve Stimulation for Treating Epilepsy

Science.gov (United States)

... and their FAMILIES VAGUS NERVE STIMULATION FOR TREATING EPILEPSY This information sheet is provided to help you ... how vagus nerve stimulation (VNS) may help treat epilepsy. The American Academy of Neurology (AAN) is the ...

Non-invasive brain stimulation and computational models in post-stroke aphasic patients: single session of transcranial magnetic stimulation and transcranial direct current stimulation. A randomized clinical trial

Directory of Open Access Journals (Sweden)

Michele Devido dos Santos

2017-11-01

Full Text Available ABSTRACT CONTEXT AND OBJECTIVE: Patients undergoing the same neuromodulation protocol may present different responses. Computational models may help in understanding such differences. The aims of this study were, firstly, to compare the performance of aphasic patients in naming tasks before and after one session of transcranial direct current stimulation (tDCS, transcranial magnetic stimulation (TMS and sham, and analyze the results between these neuromodulation techniques; and secondly, through computational model on the cortex and surrounding tissues, to assess current flow distribution and responses among patients who received tDCS and presented different levels of results from naming tasks. DESIGN AND SETTING: Prospective, descriptive, qualitative and quantitative, double blind, randomized and placebo-controlled study conducted at Faculdade de Ciências Médicas da Santa Casa de São Paulo. METHODS: Patients with aphasia received one session of tDCS, TMS or sham stimulation. The time taken to name pictures and the response time were evaluated before and after neuromodulation. Selected patients from the first intervention underwent a computational model stimulation procedure that simulated tDCS. RESULTS: The results did not indicate any statistically significant differences from before to after the stimulation.The computational models showed different current flow distributions. CONCLUSIONS: The present study did not show any statistically significant difference between tDCS, TMS and sham stimulation regarding naming tasks. The patients’responses to the computational model showed different patterns of current distribution.

Brain stimulation methods to treat tobacco addiction.

Science.gov (United States)

Wing, Victoria C; Barr, Mera S; Wass, Caroline E; Lipsman, Nir; Lozano, Andres M; Daskalakis, Zafiris J; George, Tony P

2013-05-01

Tobacco smoking is the leading cause of preventable deaths worldwide, but many smokers are simply unable to quit. Psychosocial and pharmaceutical treatments have shown modest results on smoking cessation rates, but there is an urgent need to develop treatments with greater efficacy. Brain stimulation methods are gaining increasing interest as possible addiction therapeutics. The purpose of this paper is to review the studies that have evaluated brain stimulation techniques on tobacco addiction, and discuss future directions for research in this novel area of addiction interventions. Electronic and manual literature searches identified fifteen studies that administered repetitive transcranial magnetic stimulation (rTMS), cranial electrostimulation (CES), transcranial direct current stimulation (tDCS) or deep brain stimulation (DBS). rTMS was found to be the most well studied method with respect to tobacco addiction. Results indicate that rTMS and tDCS targeted to the dorsolateral prefrontal cortex (DLPFC) were the most efficacious in reducing tobacco cravings, an effect that may be mediated through the brain reward system involved in tobacco addiction. While rTMS was shown to reduce consumption of cigarettes, as yet no brain stimulation technique has been shown to significantly increase abstinence rates. It is possible that the therapeutic effects of rTMS and tDCS may be improved by optimization of stimulation parameters and increasing the duration of treatment. Although further studies are needed to confirm the ability of brain stimulation methods to treat tobacco addiction, this review indicates that rTMS and tDCS both represent potentially novel treatment modalities. Copyright © 2013 Elsevier Inc. All rights reserved.

Evoked Electromyographically Controlled Electrical Stimulation

Directory of Open Access Journals (Sweden)

Mitsuhiro Hayashibe

2016-07-01

Full Text Available Time-variant muscle responses under electrical stimulation (ES are often problematic for all the applications of neuroprosthetic muscle control. This situation limits the range of ES usage in relevant areas, mainly due to muscle fatigue and also to changes in stimulation electrode contact conditions, especially in transcutaneous ES. Surface electrodes are still the most widely used in noninvasive applications.Electrical field variations caused by changes in the stimulation contact condition markedly affect the resulting total muscle activation levels. Fatigue phenomena under functional electrical stimulation (FES are also well known source of time-varying characteristics coming from muscle response under ES. Therefore it is essential to monitor the actual muscle state and assess the expected muscle response by ES so as to improve the current ES system in favour of adaptive muscle-response-aware FES control. To deal with this issue, we have been studying a novel control technique using evoked electromyography (eEMG signals to compensate for these muscle time-variances under ES for stable neuroprosthetic muscle control. In this perspective article, I overview the background of this topic and highlight important points to be aware of when using ES to induce the desired muscle activation regardless of the time-variance. I also demonstrate how to deal with the common critical problem of ES to move toward robust neuroprosthetic muscle control with the Evoked Electromyographically Controlled Electrical Stimulation paradigm.

Geothermal Reservoir Well Stimulation Program: technology transfer

Energy Technology Data Exchange (ETDEWEB)

1980-05-01

A literature search on reservoir and/or well stimulation techniques suitable for application in geothermal fields is presented. The literature on stimulation techniques in oil and gas field applications was also searched and evaluated as to its relevancy to geothermal operations. The equivalent low-temperature work documented in the open literature is cited, and an attempt is made to evaluate the relevance of this information as far as high-temperature stimulation work is concerned. Clays play an important role in any stimulation work. Therefore, special emphasis has been placed on clay behavior anticipated in geothermal operations. (MHR)

Optical momentum and angular momentum in complex media: from the Abraham–Minkowski debate to unusual properties of surface plasmon-polaritons

Science.gov (United States)

Bliokh, Konstantin Y.; Bekshaev, Aleksandr Y.; Nori, Franco

2017-12-01

We examine the momentum and angular momentum (AM) properties of monochromatic optical fields in dispersive and inhomogeneous isotropic media, using the Abraham- and Minkowski-type approaches, as well as the kinetic (Poynting-like) and canonical (with separate spin and orbital degrees of freedom) pictures. While the kinetic Abraham–Poynting momentum describes the energy flux and the group velocity of the wave, the Minkowski-type quantities, with proper dispersion corrections, describe the actual momentum and AM carried by the wave. The kinetic Minkowski-type momentum and AM densities agree with phenomenological results derived by Philbin. Using the canonical spin–orbital decomposition, previously used for free-space fields, we find the corresponding canonical momentum, spin and orbital AM of light in a dispersive inhomogeneous medium. These acquire a very natural form analogous to the Brillouin energy density and are valid for arbitrary structured fields. The general theory is applied to a non-trivial example of a surface plasmon-polariton (SPP) wave at a metal-vacuum interface. We show that the integral momentum of the SPP per particle corresponds to the SPP wave vector, and hence exceeds the momentum of a photon in the vacuum. We also provide the first accurate calculation of the transverse spin and orbital AM of the SPP. While the intrinsic orbital AM vanishes, the transverse spin can change its sign depending on the SPP frequency. Importantly, we present both macroscopic and microscopic calculations, thereby proving the validity of the general phenomenological results. The microscopic theory also predicts a transverse magnetization in the metal (i.e. a magnetic moment for the SPP) as well as the corresponding direct magnetization current, which provides the difference between the Abraham and Minkowski momenta.

Optical momentum and angular momentum in complex media: from the Abraham-Minkowski debate to unusual properties of surface plasmon-polaritons

Science.gov (United States)

Y Bliokh, Konstantin; Y Bekshaev, Aleksandr; Nori, Franco

2017-12-01

We examine the momentum and angular momentum (AM) properties of monochromatic optical fields in dispersive and inhomogeneous isotropic media, using the Abraham- and Minkowski-type approaches, as well as the kinetic (Poynting-like) and canonical (with separate spin and orbital degrees of freedom) pictures. While the kinetic Abraham-Poynting momentum describes the energy flux and the group velocity of the wave, the Minkowski-type quantities, with proper dispersion corrections, describe the actual momentum and AM carried by the wave. The kinetic Minkowski-type momentum and AM densities agree with phenomenological results derived by Philbin. Using the canonical spin-orbital decomposition, previously used for free-space fields, we find the corresponding canonical momentum, spin and orbital AM of light in a dispersive inhomogeneous medium. These acquire a very natural form analogous to the Brillouin energy density and are valid for arbitrary structured fields. The general theory is applied to a non-trivial example of a surface plasmon-polariton (SPP) wave at a metal-vacuum interface. We show that the integral momentum of the SPP per particle corresponds to the SPP wave vector, and hence exceeds the momentum of a photon in the vacuum. We also provide the first accurate calculation of the transverse spin and orbital AM of the SPP. While the intrinsic orbital AM vanishes, the transverse spin can change its sign depending on the SPP frequency. Importantly, we present both macroscopic and microscopic calculations, thereby proving the validity of the general phenomenological results. The microscopic theory also predicts a transverse magnetization in the metal (i.e. a magnetic moment for the SPP) as well as the corresponding direct magnetization current, which provides the difference between the Abraham and Minkowski momenta.

Follicle-stimulating hormone (FSH) blood test

Science.gov (United States)

... ency/article/003710.htm Follicle-stimulating hormone (FSH) blood test To use the sharing features on this page, please enable JavaScript. The follicle stimulating hormone (FSH) blood test measures the level of FSH in blood. FSH ...

Aromatase inhibitors in stimulated IVF cycles

DEFF Research Database (Denmark)

Papanikolaou, Evangelos G; Polyzos, Nikolaos P; Al Humaidan, Peter Samir Heskjær

2011-01-01

are available regarding their efficacy in IVF stimulated cycles. Current available evidence support that letrozole may have a promising role in stimulated IVF cycles, either when administered during the follicular phase for ovarian stimulation. Especially for women with poor ovarian response, letrozole appears...... to have the potential to increase clinical pregnancy rates when combined with gonadotropins, whereas at the same time reduces the total gonadotropin dose required for ovarian stimulation. However, given that in all of the trials letrozole has been administered in GnRH antagonist cycles, it is intriguing...... to test in the future how it may perform when used in GnRH agonist cycles. Finally administration of letrozole during luteal phase in IVF cycles offers another treatment modality for patients at high risk for OHSS taking into account that it drastically reduces estradiol levels....

Stimulation Efficiency With Decaying Exponential Waveforms in a Wirelessly Powered Switched-Capacitor Discharge Stimulation System.

Science.gov (United States)

Lee, Hyung-Min; Howell, Bryan; Grill, Warren M; Ghovanloo, Maysam

2018-05-01

The purpose of this study was to test the feasibility of using a switched-capacitor discharge stimulation (SCDS) system for electrical stimulation, and, subsequently, determine the overall energy saved compared to a conventional stimulator. We have constructed a computational model by pairing an image-based volume conductor model of the cat head with cable models of corticospinal tract (CST) axons and quantified the theoretical stimulation efficiency of rectangular and decaying exponential waveforms, produced by conventional and SCDS systems, respectively. Subsequently, the model predictions were tested in vivo by activating axons in the posterior internal capsule and recording evoked electromyography (EMG) in the contralateral upper arm muscles. Compared to rectangular waveforms, decaying exponential waveforms with time constants >500 μs were predicted to require 2%-4% less stimulus energy to activate directly models of CST axons and 0.4%-2% less stimulus energy to evoke EMG activity in vivo. Using the calculated wireless input energy of the stimulation system and the measured stimulus energies required to evoke EMG activity, we predict that an SCDS implantable pulse generator (IPG) will require 40% less input energy than a conventional IPG to activate target neural elements. A wireless SCDS IPG that is more energy efficient than a conventional IPG will reduce the size of an implant, require that less wireless energy be transmitted through the skin, and extend the lifetime of the battery in the external power transmitter.

Validating computationally predicted TMS stimulation areas using direct electrical stimulation in patients with brain tumors near precentral regions.

Science.gov (United States)

Opitz, Alexander; Zafar, Noman; Bockermann, Volker; Rohde, Veit; Paulus, Walter

2014-01-01

The spatial extent of transcranial magnetic stimulation (TMS) is of paramount interest for all studies employing this method. It is generally assumed that the induced electric field is the crucial parameter to determine which cortical regions are excited. While it is difficult to directly measure the electric field, one usually relies on computational models to estimate the electric field distribution. Direct electrical stimulation (DES) is a local brain stimulation method generally considered the gold standard to map structure-function relationships in the brain. Its application is typically limited to patients undergoing brain surgery. In this study we compare the computationally predicted stimulation area in TMS with the DES area in six patients with tumors near precentral regions. We combine a motor evoked potential (MEP) mapping experiment for both TMS and DES with realistic individual finite element method (FEM) simulations of the electric field distribution during TMS and DES. On average, stimulation areas in TMS and DES show an overlap of up to 80%, thus validating our computational physiology approach to estimate TMS excitation volumes. Our results can help in understanding the spatial spread of TMS effects and in optimizing stimulation protocols to more specifically target certain cortical regions based on computational modeling.

Immediate effect of laryngeal surface electrical stimulation on swallowing performance.

Science.gov (United States)

Takahashi, Keizo; Hori, Kazuhiro; Hayashi, Hirokazu; Fujiu-Kurachi, Masako; Ono, Takahiro; Tsujimura, Takanori; Magara, Jin; Inoue, Makoto

2018-01-01

Surface electrical stimulation of the laryngeal region is used to improve swallowing in dysphagic patients. However, little is known about how electrical stimulation affects tongue movements and related functions. We investigated the effect of electrical stimulation on tongue pressure and hyoid movement, as well as suprahyoid and infrahyoid muscle activity, in 18 healthy young participants. Electrical stimulation (0.2-ms duration, 80 Hz, 80% of each participant's maximal tolerance) of the laryngeal region was applied. Each subject swallowed 5 ml of barium sulfate liquid 36 times at 10-s intervals. During the middle 2 min, electrical stimulation was delivered. Tongue pressure, electromyographic activity of the suprahyoid and infrahyoid muscles, and videofluorographic images were simultaneously recorded. Tongue pressure during stimulation was significantly lower than before or after stimulation and was significantly greater after stimulation than at baseline. Suprahyoid activity after stimulation was larger than at baseline, while infrahyoid muscle activity did not change. During stimulation, the position of the hyoid at rest was descended, the highest hyoid position was significantly inferior, and the vertical movement was greater than before or after stimulation. After stimulation, the positions of the hyoid at rest and at the maximum elevation were more superior than before stimulation. The deviation of the highest positions of the hyoid before and after stimulation corresponded to the differences in tongue pressures at those times. These results suggest that surface electrical stimulation applied to the laryngeal region during swallowing may facilitate subsequent hyoid movement and tongue pressure generation after stimulation. NEW & NOTEWORTHY Surface electrical stimulation applied to the laryngeal region during swallowing may facilitate subsequent hyoid movement and tongue pressure generation after stimulation. Tongue muscles may contribute to overshot recovery

Universal description of channel plasmons in two-dimensional materials

DEFF Research Database (Denmark)

Gonçalves, P. A. D.; Bozhevolnyi, Sergey I.; Mortensen, N. Asger

2017-01-01

Channeling surface plasmon-polaritons to control their propagation direction is of the utmost importance for future optoelectronic devices. Here, we develop an effective-index method to describe and characterize the properties of 2D material's channel plasmon-polaritons (CPPs) guided along a V-sh...

21 CFR 882.5830 - Implanted diaphragmatic/phrenic nerve stimulator.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Implanted diaphragmatic/phrenic nerve stimulator... Implanted diaphragmatic/phrenic nerve stimulator. (a) Identification. An implanted diaphragmatic/phrenic nerve stimulator is a device that provides electrical stimulation of a patient's phrenic nerve to...

Oligofructose stimulates calcium absorption in adolescents

NARCIS (Netherlands)

Heuvel, E.G.H.M. van den; Muys, T.; Dokkum, W. van; Schaafsma, G.

1999-01-01

Background: In rats, nondigestible oligosaccharides stimulate calcium absorption. Recently, this effect was also found in human subjects. Objective: The objective of the study was to investigate whether consumption of 15 g oligofructose/d stimulates calcium absorption in male adolescents. Design:

Evaluation of Galvanic Vestibular Stimulation System

Science.gov (United States)

Kofman, I. S.; Warren, E.; DeSoto, R.; Moroney, G.; Chastain, J.; De Dios, Y. E.; Gadd, N.; Taylor, L.; Peters, B. T.; Allen, E.;

Partially non-linear stimulation intensity-dependent effects of direct current stimulation on motor cortex excitability in humans.

Science.gov (United States)

Batsikadze, G; Moliadze, V; Paulus, W; Kuo, M-F; Nitsche, M A

2013-04-01

Transcranial direct current stimulation (tDCS) of the human motor cortex at an intensity of 1 mA with an electrode size of 35 cm(2) has been shown to induce shifts of cortical excitability during and after stimulation. These shifts are polarity-specific with cathodal tDCS resulting in a decrease and anodal stimulation in an increase of cortical excitability. In clinical and cognitive studies, stronger stimulation intensities are used frequently, but their physiological effects on cortical excitability have not yet been explored. Therefore, here we aimed to explore the effects of 2 mA tDCS on cortical excitability. We applied 2 mA anodal or cathodal tDCS for 20 min on the left primary motor cortex of 14 healthy subjects. Cathodal tDCS at 1 mA and sham tDCS for 20 min was administered as control session in nine and eight healthy subjects, respectively. Motor cortical excitability was monitored by transcranial magnetic stimulation (TMS)-elicited motor-evoked potentials (MEPs) from the right first dorsal interosseous muscle. Global corticospinal excitability was explored via single TMS pulse-elicited MEP amplitudes, and motor thresholds. Intracortical effects of stimulation were obtained by cortical silent period (CSP), short latency intracortical inhibition (SICI) and facilitation (ICF), and I wave facilitation. The above-mentioned protocols were recorded both before and immediately after tDCS in randomized order. Additionally, single-pulse MEPs, motor thresholds, SICI and ICF were recorded every 30 min up to 2 h after stimulation end, evening of the same day, next morning, next noon and next evening. Anodal as well as cathodal tDCS at 2 mA resulted in a significant increase of MEP amplitudes, whereas 1 mA cathodal tDCS decreased corticospinal excitability. A significant shift of SICI and ICF towards excitability enhancement after both 2 mA cathodal and anodal tDCS was observed. At 1 mA, cathodal tDCS reduced single-pulse TMS-elicited MEP amplitudes and shifted SICI

Short-Term Dosage Regimen for Stimulation-Induced Long-Lasting Desynchronization

Directory of Open Access Journals (Sweden)

Thanos Manos

2018-04-01

Full Text Available In this paper, we computationally generate hypotheses for dose-finding studies in the context of desynchronizing neuromodulation techniques. Abnormally strong neuronal synchronization is a hallmark of several brain disorders. Coordinated Reset (CR stimulation is a spatio-temporally patterned stimulation technique that specifically aims at disrupting abnormal neuronal synchrony. In networks with spike-timing-dependent plasticity CR stimulation may ultimately cause an anti-kindling, i.e., an unlearning of abnormal synaptic connectivity and neuronal synchrony. This long-lasting desynchronization was theoretically predicted and verified in several pre-clinical and clinical studies. We have shown that CR stimulation with rapidly varying sequences (RVS robustly induces an anti-kindling at low intensities e.g., if the CR stimulation frequency (i.e., stimulus pattern repetition rate is in the range of the frequency of the neuronal oscillation. In contrast, CR stimulation with slowly varying sequences (SVS turned out to induce an anti-kindling more strongly, but less robustly with respect to variations of the CR stimulation frequency. Motivated by clinical constraints and inspired by the spacing principle of learning theory, in this computational study we propose a short-term dosage regimen that enables a robust anti-kindling effect of both RVS and SVS CR stimulation, also for those parameter values where RVS and SVS CR stimulation previously turned out to be ineffective. Intriguingly, for the vast majority of parameter values tested, spaced multishot CR stimulation with demand-controlled variation of stimulation frequency and intensity caused a robust and pronounced anti-kindling. In contrast, spaced CR stimulation with fixed stimulation parameters as well as singleshot CR stimulation of equal integral duration failed to improve the stimulation outcome. In the model network under consideration, our short-term dosage regimen enables to robustly induce

Short-Term Dosage Regimen for Stimulation-Induced Long-Lasting Desynchronization.

Science.gov (United States)

Manos, Thanos; Zeitler, Magteld; Tass, Peter A

2018-01-01

In this paper, we computationally generate hypotheses for dose-finding studies in the context of desynchronizing neuromodulation techniques. Abnormally strong neuronal synchronization is a hallmark of several brain disorders. Coordinated Reset (CR) stimulation is a spatio-temporally patterned stimulation technique that specifically aims at disrupting abnormal neuronal synchrony. In networks with spike-timing-dependent plasticity CR stimulation may ultimately cause an anti-kindling, i.e., an unlearning of abnormal synaptic connectivity and neuronal synchrony. This long-lasting desynchronization was theoretically predicted and verified in several pre-clinical and clinical studies. We have shown that CR stimulation with rapidly varying sequences (RVS) robustly induces an anti-kindling at low intensities e.g., if the CR stimulation frequency (i.e., stimulus pattern repetition rate) is in the range of the frequency of the neuronal oscillation. In contrast, CR stimulation with slowly varying sequences (SVS) turned out to induce an anti-kindling more strongly, but less robustly with respect to variations of the CR stimulation frequency. Motivated by clinical constraints and inspired by the spacing principle of learning theory, in this computational study we propose a short-term dosage regimen that enables a robust anti-kindling effect of both RVS and SVS CR stimulation, also for those parameter values where RVS and SVS CR stimulation previously turned out to be ineffective. Intriguingly, for the vast majority of parameter values tested, spaced multishot CR stimulation with demand-controlled variation of stimulation frequency and intensity caused a robust and pronounced anti-kindling. In contrast, spaced CR stimulation with fixed stimulation parameters as well as singleshot CR stimulation of equal integral duration failed to improve the stimulation outcome. In the model network under consideration, our short-term dosage regimen enables to robustly induce long

Transcranial Magnetic Stimulation-coil design with improved focality

Science.gov (United States)

Rastogi, P.; Lee, E. G.; Hadimani, R. L.; Jiles, D. C.

2017-05-01

Transcranial Magnetic Stimulation (TMS) is a technique for neuromodulation that can be used as a non-invasive therapy for various neurological disorders. In TMS, a time varying magnetic field generated from an electromagnetic coil placed on the scalp is used to induce an electric field inside the brain. TMS coil geometry plays an important role in determining the focality and depth of penetration of the induced electric field responsible for stimulation. Clinicians and basic scientists are interested in stimulating a localized area of the brain, while minimizing the stimulation of surrounding neural networks. In this paper, a novel coil has been proposed, namely Quadruple Butterfly Coil (QBC) with an improved focality over the commercial Figure-8 coil. Finite element simulations were conducted with both the QBC and the conventional Figure-8 coil. The two coil's stimulation profiles were assessed with 50 anatomically realistic MRI derived head models. The coils were positioned on the vertex and the scalp over the dorsolateral prefrontal cortex to stimulate the brain. Computer modeling of the coils has been done to determine the parameters of interest-volume of stimulation, maximum electric field, location of maximum electric field and area of stimulation across all 50 head models for both coils.

A multi-channel stimulator and electrode array providing a rotating current whirlpool for electrical stimulation of wounds.

Science.gov (United States)

Petrofsky, J; Suh, H J; Fish, A; Hernandez, V; Abdo, A; Collins, K; Mendoza, E; Yang, T-N

2008-01-01

When electrical stimulation is used on wounds, the electrical current has difficulty penetrating areas where there is necrotic tissue. Further, for an irregularly shaped wound, current distribution is poor in some areas of the wound since conventional two-electrode delivery systems provide the greatest current in a line directly between the electrodes. A new stimulator and electrode system is described which uses three electrodes spaced around a wound to disperse current more evenly. The stimulator senses tissue impedance and then redirects current by altering its Thevenin's output impedance for each electrode; each of the three electrodes becomes the active one in sequence while the remaining are the sink electrodes. Eight subjects were examined to test the stimulator. Electrical stimulation was applied to the skin above the quadriceps muscle at currents of 15 mA in six subjects without wounds and in two subjects with wounds. The relationship between electrode position and current dispersion on the skin was examined with a two-electrode vs. a three-electrode system to set stimulation parameters for the computer. The results showed that the three-electrode system could (1) detect areas of the skin with high impedance; (2) compensate by altering the Thevenin's output impedance at each of the three electrodes to shift current to high impedance areas; (3) provide uniform current across the skin as assessed by skin current and blood flow measurements with a laser Doppler flow imager.

Coherent response of a semiconductor microcavity in the strong coupling regime

Science.gov (United States)

Cassabois, G.; Triques, A. L. C.; Ferreira, R.; Delalande, C.; Roussignol, Ph; Bogani, F.

2000-05-01

We have studied the coherent dynamics of a semiconductor microcavity by means of interferometric correlation measurements with subpicosecond time resolution in a backscattering geometry. Evidence is brought of the resolution of a homogeneous polariton line in an inhomogeneously broadened exciton system. Surprisingly, photon-like polaritons exhibit an inhomogeneous dephasing. Moreover, we observe an unexpected stationary coherence up to 8 ps for the lower polariton branch close to resonance. All these experimental results are well reproduced within the framework of a linear dispersion theory assuming a coherent superposition of the reflectivity and resonant Rayleigh scattering signals with a well-defined relative phase.

Nanoscale Mechanical Stimulation of Human Mesenchymal Stem Cells

Directory of Open Access Journals (Sweden)

H Nikukar

2014-05-01

We observed significant responses after 1 and 2-week stimulations in cell number, cell shapes and phenotypical markers. Microarray was performed for all groups. Cell count showed normal cell growth with stimulation. However, cell surface area, cell perimeter, and arboration after 1-week stimulation showed significant increases. Immunofluorescent studies have showed significant increase in osteocalcin production after stimulation. Conclusions: Nanoscale mechanical vibration showed significant changes in human mesenchymal stem cell behaviours. Cell morphology changed to become more polygonal and increased expression of the osteoblast markers were noted. These findings with gene regulation changes suggesting nanoscale mechanostimulation has stimulated osteoblastogenesis.  Keywords:  Mesenchymal, Nanoscale, Stem Cells.

Medical back belt with integrated neuromuscular electrical stimulation

NARCIS (Netherlands)

Bottenberg, E. (Eliza); Brinks, G.J. (Ger); Hesse, J. (Jenny)

2014-01-01

The medical back belt with integrated neuromuscular electrical stimulation is anorthopedic device, which has two main functions. The first function is to stimulate the backmuscles by using a neuromuscular electrical stimulation device that releases regular,electrical impulses. The second function of

Stimulation Technologies for Deep Well Completions

Energy Technology Data Exchange (ETDEWEB)

None

2003-09-30

The Department of Energy (DOE) is sponsoring the Deep Trek Program targeted at improving the economics of drilling and completing deep gas wells. Under the DOE program, Pinnacle Technologies is conducting a study to evaluate the stimulation of deep wells. The objective of the project is to assess U.S. deep well drilling & stimulation activity, review rock mechanics & fracture growth in deep, high pressure/temperature wells and evaluate stimulation technology in several key deep plays. An assessment of historical deep gas well drilling activity and forecast of future trends was completed during the first six months of the project; this segment of the project was covered in Technical Project Report No. 1. The second progress report covers the next six months of the project during which efforts were primarily split between summarizing rock mechanics and fracture growth in deep reservoirs and contacting operators about case studies of deep gas well stimulation.

Transcranial Direct Current Stimulation in Epilepsy.

Science.gov (United States)

San-Juan, Daniel; Morales-Quezada, León; Orozco Garduño, Adolfo Josué; Alonso-Vanegas, Mario; González-Aragón, Maricarmen Fernández; Espinoza López, Dulce Anabel; Vázquez Gregorio, Rafael; Anschel, David J; Fregni, Felipe

2015-01-01

Transcranial direct current stimulation (tDCS) is an emerging non-invasive neuromodulation therapy in epilepsy with conflicting results in terms of efficacy and safety. Review the literature about the efficacy and safety of tDCS in epilepsy in humans and animals. We searched studies in PubMed, MedLine, Scopus, Web of Science and Google Scholar (January 1969 to October 2013) using the keywords 'transcranial direct current stimulation' or 'tDCS' or 'brain polarization' or 'galvanic stimulation' and 'epilepsy' in animals and humans. Original articles that reported tDCS safety and efficacy in epileptic animals or humans were included. Four review authors independently selected the studies, extracted data and assessed the methodological quality of the studies using the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions, PRISMA guidelines and Jadad Scale. A meta-analysis was not possible due to methodological, clinical and statistical heterogeneity of included studies. We analyzed 9 articles with different methodologies (3 animals/6 humans) with a total of 174 stimulated individuals; 109 animals and 65 humans. In vivo and in vitro animal studies showed that direct current stimulation can successfully induce suppression of epileptiform activity without neurological injury and 4/6 (67%) clinical studies showed an effective decrease in epileptic seizures and 5/6 (83%) reduction of inter-ictal epileptiform activity. All patients tolerated tDCS well. tDCS trials have demonstrated preliminary safety and efficacy in animals and patients with epilepsy. Further larger studies are needed to define the best stimulation protocols and long-term follow-up. Copyright © 2015 Elsevier Inc. All rights reserved.

The Mechanism of Financial Stimulation of Investment Activity

Directory of Open Access Journals (Sweden)

Vasiliy Valeryevich Tarakanov

2016-03-01

Full Text Available Modernization of the Russian economy and creation of conditions for its economic growth demand activization of investment activity that is possible by means of its financial stimulation. Financial stimulation of investment activity defines the need of changes of the contents, the directions and ways of implementation of the financial relations between subjects of investment activity. Financial stimulation of investment activity is carried out via the mechanism in the context of which these financial relations are settled. For defining the mechanism of financial stimulation of investment activity the authors consider the very concept of financial mechanism. The conclusion is drawn that all elements of the financial mechanism are the integrated unity, they are interdependent and interconnected, and the combination of types, forms, methods of the organization of the financial relations forms “a design of the financial mechanism”. The article specifies the maintenance of the mechanism of financial stimulation of investment activity, and reveals its essence. The structure of the mechanism of financial stimulation of investment activity is presented by the following elements: subjects of financial stimulation of investment activity, the purpose of attraction of investments by them, set of financial methods and tools, sources of means of achievement of goals, standard - legal and information support of financial stimulation of investment activity. It is proved that in the mechanism of financial stimulation of investment activity the leading role is played by the state by means of forms of direct and indirect participation in attraction of investments, each of which is realized by means of specific methods and the corresponding tools. The widespread instrument of financial stimulation of investment activity is the investments which are carried out by the state institutes of development participating in the organization of the process of financial

GABAB Receptor Stimulation Accentuates the Locomotor Effects of Morphine in Mice Bred for Extreme Sensitivity to the Stimulant Effects of Ethanol

OpenAIRE

Holstein, Sarah E.; Phillips, Tamara J.

2006-01-01

Mice selectively bred for divergent sensitivity to the locomotor stimulant effects of ethanol (FAST and SLOW) also differ in their locomotor response to morphine. The GABAB receptor has been implicated in the mediation of locomotor stimulation to both ethanol and morphine, and a reduction in ethanol-induced stimulation has been found with the GABAB receptor agonist baclofen in FAST mice. We hypothesized that GABAB receptor activation would also attenuate the locomotor stimulant responses to m...

Stimulation of entorhinal cortex-dentate gyrus circuitry is antidepressive.

Science.gov (United States)

Yun, Sanghee; Reynolds, Ryan P; Petrof, Iraklis; White, Alicia; Rivera, Phillip D; Segev, Amir; Gibson, Adam D; Suarez, Maiko; DeSalle, Matthew J; Ito, Naoki; Mukherjee, Shibani; Richardson, Devon R; Kang, Catherine E; Ahrens-Nicklas, Rebecca C; Soler, Ivan; Chetkovich, Dane M; Kourrich, Saïd; Coulter, Douglas A; Eisch, Amelia J

2018-04-16

Major depressive disorder (MDD) is considered a 'circuitopathy', and brain stimulation therapies hold promise for ameliorating MDD symptoms, including hippocampal dysfunction. It is unknown whether stimulation of upstream hippocampal circuitry, such as the entorhinal cortex (Ent), is antidepressive, although Ent stimulation improves learning and memory in mice and humans. Here we show that molecular targeting (Ent-specific knockdown of a psychosocial stress-induced protein) and chemogenetic stimulation of Ent neurons induce antidepressive-like effects in mice. Mechanistically, we show that Ent-stimulation-induced antidepressive-like behavior relies on the generation of new hippocampal neurons. Thus, controlled stimulation of Ent hippocampal afferents is antidepressive via increased hippocampal neurogenesis. These findings emphasize the power and potential of Ent glutamatergic afferent stimulation-previously well-known for its ability to influence learning and memory-for MDD treatment.

Effects of Navigated Repetitive Transcranial Magnetic Stimulation After Stroke.

Science.gov (United States)

Chervyakov, Alexander V; Poydasheva, Alexandra G; Lyukmanov, Roman H; Suponeva, Natalia A; Chernikova, Ludmila A; Piradov, Michael A; Ustinova, Ksenia I

2018-03-01

The purpose of this study was to test the effects of navigated repetitive transcranial magnetic stimulation, delivered in different modes, on motor impairments and functional limitations after stroke. The study sample included 42 patients (58.5 ± 10.7 years; 26 males) who experienced a single unilateral stroke (1-12 months previously) in the area of the middle cerebral artery. Patients completed a course of conventional rehabilitation, together with 10 sessions of navigated repetitive transcranial magnetic stimulation or sham stimulation. Stimulation was scheduled five times a week over two consecutive weeks in an inpatient clinical setting. Patients were randomly assigned to one of four groups and received sham stimulation (n = 10), low-frequency (1-Hz) stimulation of the nonaffected hemisphere (n = 11), high-frequency (10-Hz) stimulation of the affected hemisphere (n = 13), or sequential combination of low- and high-frequency stimulations (n = 8). Participants were evaluated before and after stimulation with clinical tests, including the arm and hand section of the Fugl-Meyer Assessment Scale, modified Ashworth Scale of Muscle Spasticity, and Barthel Index of Activities of Daily Living. Participants in the three groups receiving navigated repetitive transcranial magnetic stimulation showed improvements in arm and hand functions on the Fugl-Meyer Stroke Assessment Scale. Ashworth Scale of Muscle Spasticity and Barthel Index scores were significantly reduced in groups receiving low- or high-frequency stimulation alone. Including navigated repetitive transcranial magnetic stimulation in a conventional rehabilitation program positively influenced motor and functional recovery in study participants, demonstrating the clinical potential of the method. The results of this study will be used for designing a large-scale clinical trial.

Manual evaluation of residual curarization using double burst stimulation

DEFF Research Database (Denmark)

Drenck, N E; Ueda, N; Olsen, Niels Vidiendal

1989-01-01

Double burst stimulation (DBS) is a new mode of stimulation developed to reveal residual neuromuscular blockade under clinical conditions. The stimulus consists of two short bursts of 50 Hz tetanic stimulation, separated by 750 ms, and the response to the stimulation is two short muscle contracti......Double burst stimulation (DBS) is a new mode of stimulation developed to reveal residual neuromuscular blockade under clinical conditions. The stimulus consists of two short bursts of 50 Hz tetanic stimulation, separated by 750 ms, and the response to the stimulation is two short muscle...... contractions. Fade in the response results from neuromuscular blockade as with train-of-four stimulation (TOF). The authors compared the sensitivity of DBS and TOF in the detection of residual neuromuscular blockade during clinical anaesthesia. Fifty-two healthy patients undergoing surgery were studied...... with DBS than with TOF, regardless of the TOF ratio level. Absence of fade with TOF implied a 48% chance of considerable residual relaxation as compared with 9% when fade was absent with DBS. The results demonstrate that DBS is more sensitive than TOF in the manual detection of residual neuromuscular...

Radioimmunoassay for thyroid-stimulating hormone (TSH)

International Nuclear Information System (INIS)

Blakemore, J.I.; Lewin, N.; Burgett, M.W.

1978-01-01

This invention provides a method for the radioimmunoassay of thyroid-stimulating hormone which utilizes a rapid and convenient version of a double antibody procedure. Highly purified second antibody is bound, by means of covalent bonds, to hydrolyzed polyacrylamide particles to produce a two-phase system. The solid phase comprises immobilized second antibody bound to the reaction product of labeled and unlabeled thyroid-stimulating hormone with the first antibody (first antibody-antigen complex) and the liquid phase comprises free (unbound) labeled and unlabeled thyroid-stimulating hormone. The two phases are separated and the radioactivity of either phase is measured

Spinal cord stimulation for neuropathic pain: current perspectives

Directory of Open Access Journals (Sweden)

Wolter T

2014-11-01

Full Text Available Tilman Wolter Interdisciplinary Pain Centre, University Hospital Freiburg, Freiburg, Germany Abstract: Neuropathic pain constitutes a significant portion of chronic pain. Patients with neuropathic pain are usually more heavily burdened than patients with nociceptive pain. They suffer more often from insomnia, anxiety, and depression. Moreover, analgesic medication often has an insufficient effect on neuropathic pain. Spinal cord stimulation constitutes a therapy alternative that, to date, remains underused. In the last 10 to 15 years, it has undergone constant technical advancement. This review gives an overview of the present practice of spinal cord stimulation for chronic neuropathic pain and current developments such as high-frequency stimulation and peripheral nerve field stimulation. Keywords: spinal cord stimulation, neuropathic pain, neurostimulation

Closing the loop of deep brain stimulation

Science.gov (United States)

Carron, Romain; Chaillet, Antoine; Filipchuk, Anton; Pasillas-Lépine, William; Hammond, Constance

2013-01-01

High-frequency deep brain stimulation is used to treat a wide range of brain disorders, like Parkinson's disease. The stimulated networks usually share common electrophysiological signatures, including hyperactivity and/or dysrhythmia. From a clinical perspective, HFS is expected to alleviate clinical signs without generating adverse effects. Here, we consider whether the classical open-loop HFS fulfills these criteria and outline current experimental or theoretical research on the different types of closed-loop DBS that could provide better clinical outcomes. In the first part of the review, the two routes followed by HFS-evoked axonal spikes are explored. In one direction, orthodromic spikes functionally de-afferent the stimulated nucleus from its downstream target networks. In the opposite direction, antidromic spikes prevent this nucleus from being influenced by its afferent networks. As a result, the pathological synchronized activity no longer propagates from the cortical networks to the stimulated nucleus. The overall result can be described as a reversible functional de-afferentation of the stimulated nucleus from its upstream and downstream nuclei. In the second part of the review, the latest advances in closed-loop DBS are considered. Some of the proposed approaches are based on mathematical models, which emphasize different aspects of the parkinsonian basal ganglia: excessive synchronization, abnormal firing-rate rhythms, and a deficient thalamo-cortical relay. The stimulation strategies are classified depending on the control-theory techniques on which they are based: adaptive and on-demand stimulation schemes, delayed and multi-site approaches, stimulations based on proportional and/or derivative control actions, optimal control strategies. Some of these strategies have been validated experimentally, but there is still a large reservoir of theoretical work that may point to ways of improving practical treatment. PMID:24391555

Closing the loop of deep brain stimulation.

Science.gov (United States)

Carron, Romain; Chaillet, Antoine; Filipchuk, Anton; Pasillas-Lépine, William; Hammond, Constance

2013-12-20

High-frequency deep brain stimulation is used to treat a wide range of brain disorders, like Parkinson's disease. The stimulated networks usually share common electrophysiological signatures, including hyperactivity and/or dysrhythmia. From a clinical perspective, HFS is expected to alleviate clinical signs without generating adverse effects. Here, we consider whether the classical open-loop HFS fulfills these criteria and outline current experimental or theoretical research on the different types of closed-loop DBS that could provide better clinical outcomes. In the first part of the review, the two routes followed by HFS-evoked axonal spikes are explored. In one direction, orthodromic spikes functionally de-afferent the stimulated nucleus from its downstream target networks. In the opposite direction, antidromic spikes prevent this nucleus from being influenced by its afferent networks. As a result, the pathological synchronized activity no longer propagates from the cortical networks to the stimulated nucleus. The overall result can be described as a reversible functional de-afferentation of the stimulated nucleus from its upstream and downstream nuclei. In the second part of the review, the latest advances in closed-loop DBS are considered. Some of the proposed approaches are based on mathematical models, which emphasize different aspects of the parkinsonian basal ganglia: excessive synchronization, abnormal firing-rate rhythms, and a deficient thalamo-cortical relay. The stimulation strategies are classified depending on the control-theory techniques on which they are based: adaptive and on-demand stimulation schemes, delayed and multi-site approaches, stimulations based on proportional and/or derivative control actions, optimal control strategies. Some of these strategies have been validated experimentally, but there is still a large reservoir of theoretical work that may point to ways of improving practical treatment.

Closing the loop of deep brain stimulation

Directory of Open Access Journals (Sweden)

Romain eCARRON

2013-12-01

Full Text Available High-frequency deep brain stimulation is used to treat a wide range of brain disorders, like Parkinson's disease. The stimulated networks usually share common electrophysiological signatures, including hyperactivity and/or dysrhythmia. From a clinical perspective, HFS is expected to alleviate clinical signs without generating adverse effects. Here, we consider whether the classical open-loop HFS fulfils these criteria and outline current experimental or theoretical research on the different types of closed-loop DBS that could provide better clinical outcomes. In the first part of the review, the two routes followed by HFS-evoked axonal spikes are explored. In one direction, orthodromic spikes functionally de-afferent the stimulated nucleus from its downstream target networks. In the opposite direction, antidromic spikes prevent this nucleus from being influenced by its afferent networks. As a result, the pathological synchronized activity no longer propagates from the cortical networks to the stimulated nucleus. The overall result can be described as a reversible functional de-afferentation of the stimulated nucleus from its upstream and downstream nuclei. In the second part of the review, the latest advances in closed-loop DBS are considered. Some of the proposed approaches are based on mathematical models, which emphasize different aspects of the parkinsonian basal ganglia: excessive synchronization, abnormal firing-rate rhythms, and a deficient thalamo-cortical relay. The stimulation strategies are classified depending on the control-theory techniques on which they are based: adaptive and on-demand stimulation schemes, delayed and multi-site approaches, stimulations based on proportional and/or derivative control actions, optimal control strategies. Some of these strategies have been validated experimentally, but there is still a large reservoir of theoretical work that may point to ways of improving practical treatment.

In vivo charge injection limits increased after 'unsafe' stimulation

DEFF Research Database (Denmark)

Meijs, Suzan; Sørensen, Søren; Rechendorff, Kristian

2015-01-01

was not observed with any of the stimulation protocols and no tissue damage was observed for the 20 mA – 200 Hz stimulation group. This indicates that the ‘safe potential window’ may not be applicable in vivo, as no damage was done stimulating with 20 mA at 200 Hz, while damage was done using the same current......The effect of unsafe stimulation on charge injection limits (Qinj) and pulsing capacitance (Cpulse) was investigated. Four stimulation protocols were applied: 20 mA – 200 and 400 Hz, 50 mA – 200 and 400 Hz. Increasing Qinj and Cpulse were observed for all stimulation protocols. Corrosion...

Optimized temporal pattern of brain stimulation designed by computational evolution.

Science.gov (United States)

Brocker, David T; Swan, Brandon D; So, Rosa Q; Turner, Dennis A; Gross, Robert E; Grill, Warren M

2017-01-04

Brain stimulation is a promising therapy for several neurological disorders, including Parkinson's disease. Stimulation parameters are selected empirically and are limited to the frequency and intensity of stimulation. We varied the temporal pattern of deep brain stimulation to ameliorate symptoms in a parkinsonian animal model and in humans with Parkinson's disease. We used model-based computational evolution to optimize the stimulation pattern. The optimized pattern produced symptom relief comparable to that from standard high-frequency stimulation (a constant rate of 130 or 185 Hz) and outperformed frequency-matched standard stimulation in a parkinsonian rat model and in patients. Both optimized and standard high-frequency stimulation suppressed abnormal oscillatory activity in the basal ganglia of rats and humans. The results illustrate the utility of model-based computational evolution of temporal patterns to increase the efficiency of brain stimulation in treating Parkinson's disease and thereby reduce the energy required for successful treatment below that of current brain stimulation paradigms. Copyright © 2017, American Association for the Advancement of Science.

Electrical Stimulation of Coleopteran Muscle for Initiating Flight.

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Hao Yu Choo

Full Text Available Some researchers have long been interested in reconstructing natural insects into steerable robots or vehicles. However, until recently, these so-called cyborg insects, biobots, or living machines existed only in science fiction. Owing to recent advances in nano/micro manufacturing, data processing, and anatomical and physiological biology, we can now stimulate living insects to induce user-desired motor actions and behaviors. To improve the practicality and applicability of airborne cyborg insects, a reliable and controllable flight initiation protocol is required. This study demonstrates an electrical stimulation protocol that initiates flight in a beetle (Mecynorrhina torquata, Coleoptera. A reliable stimulation protocol was determined by analyzing a pair of dorsal longitudinal muscles (DLMs, flight muscles that oscillate the wings. DLM stimulation has achieved with a high success rate (> 90%, rapid response time (< 1.0 s, and small variation (< 0.33 s; indicating little habituation. Notably, the stimulation of DLMs caused no crucial damage to the free flight ability. In contrast, stimulation of optic lobes, which was earlier demonstrated as a successful flight initiation protocol, destabilized the beetle in flight. Thus, DLM stimulation is a promising secure protocol for inducing flight in cyborg insects or biobots.

Role of sound stimulation in reprogramming brain connectivity.

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Chaudhury, Sraboni; Nag, Tapas C; Jain, Suman; Wadhwa, Shashi

2013-09-01

Sensory stimulation has a critical role to play in the development of an individual. Environmental factors tend to modify the inputs received by the sensory pathway. The developing brain is most vulnerable to these alterations and interacts with the environment to modify its neural circuitry. In addition to other sensory stimuli, auditory stimulation can also act as external stimuli to provide enrichment during the perinatal period. There is evidence that suggests that enriched environment in the form of auditory stimulation can play a substantial role in modulating plasticity during the prenatal period. This review focuses on the emerging role of prenatal auditory stimulation in the development of higher brain functions such as learning and memory in birds and mammals. The molecular mechanisms of various changes in the hippocampus following sound stimulation to effect neurogenesis, learning and memory are described. Sound stimulation can also modify neural connectivity in the early postnatal life to enhance higher cognitive function or even repair the secondary damages in various neurological and psychiatric disorders. Thus, it becomes imperative to examine in detail the possible ameliorating effects of prenatal sound stimulation in existing animal models of various psychiatric disorders, such as autism.

Facilitate insight by non-invasive brain stimulation.

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Richard P Chi

Full Text Available Our experiences can blind us. Once we have learned to solve problems by one method, we often have difficulties in generating solutions involving a different kind of insight. Yet there is evidence that people with brain lesions are sometimes more resistant to this so-called mental set effect. This inspired us to investigate whether the mental set effect can be reduced by non-invasive brain stimulation. 60 healthy right-handed participants were asked to take an insight problem solving task while receiving transcranial direct current stimulation (tDCS to the anterior temporal lobes (ATL. Only 20% of participants solved an insight problem with sham stimulation (control, whereas 3 times as many participants did so (p = 0.011 with cathodal stimulation (decreased excitability of the left ATL together with anodal stimulation (increased excitability of the right ATL. We found hemispheric differences in that a stimulation montage involving the opposite polarities did not facilitate performance. Our findings are consistent with the theory that inhibition to the left ATL can lead to a cognitive style that is less influenced by mental templates and that the right ATL may be associated with insight or novel meaning. Further studies including neurophysiological imaging are needed to elucidate the specific mechanisms leading to the enhancement.

Transcranial alternating current stimulation (tACS

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Andrea eAntal

2013-06-01

Full Text Available Transcranial alternating current stimulation (tACS seems likely to open a new era of the field of noninvasive electrical stimulation of the human brain by directly interfering with cortical rhythms. It is expected to synchronize (by one single resonance frequency or desynchronize (e.g. by the application of several frequencies cortical oscillations. If applied long enough it may cause neuroplastic effects. In the theta range it may improve cognition when applied in phase. Alpha rhythms could improve motor performance, whereas beta intrusion may deteriorate them. TACS with both alpha and beta frequencies has a high likelihood to induce retinal phosphenes. Gamma intrusion can possibly interfere with attention. Stimulation in the ripple range induces intensity dependent inhibition or excitation in the motor cortex most likely by entrainment of neuronal networks, whereas stimulation in the low kHz range induces excitation by neuronal membrane interference. TACS in the 200 kHz range may have a potential in oncology.

Effect of Parkinson's Disease in Transcranial Magnetic Stimulation Treatment

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Syeda, Farheen; Magsood, Hamzah; Lee, Erik; El-Gendy, Ahmed; Jiles, David; Hadimani, Ravi

Transcranial Magnetic Stimulation is a non-invasive clinical therapy used to treat depression and migraine, and shows further promise as treatment for Parkinson's disease, Alzheimer's disease, and other neurological disorders. However, it is yet unclear as to how anatomical differences may affect stimulation from this treatment. We use finite element analysis to model and analyze the results of Transcranial Magnetic Stimulation in various head models. A number of heterogeneous head models have been developed using MRI data of real patients, including healthy individuals as well as patients of Parkinson's disease. Simulations of Transcranial Magnetic Stimulation performed on 22 anatomically different models highlight the differences in induced stimulation. A standard Figure of 8 coil is used with frequency 2.5 kHz, placed 5 mm above the head. We compare cortical stimulation, volume of brain tissue stimulated, specificity, and maximum E-field induced in the brain for models ranging from ages 20 to 60. Results show that stimulation varies drastically between patients of the same age and health status depending upon brain-scalp distance, which is not necessarily a linear progression with age.

Stimulation of phagocytosis by sulforaphane

International Nuclear Information System (INIS)

Suganuma, Hiroyuki; Fahey, Jed W.; Bryan, Kelley E.; Healy, Zachary R.; Talalay, Paul

2011-01-01

Research highlights: → Sulforaphane stimulates the phagocytosis of RAW 264.7 macrophages under conditions of serum deprivation. → This effect does not require Nrf2-dependent induction of phase 2 genes. → Inactivation of macrophage migration inhibitory factor (MIF) by sulforaphane may be involved in stimulation of phagocytosis by sulforaphane. -- Abstract: Sulforaphane, a major isothiocyanate derived from cruciferous vegetables, protects living systems against electrophile toxicity, oxidative stress, inflammation, and radiation. A major protective mechanism is the induction of a network of endogenous cytoprotective (phase 2) genes that are regulated by transcription factor Nrf2. To obtain a more detailed understanding of the anti-inflammatory and immunomodulatory effects of sulforaphane, we evaluated its effect on the phagocytosis activity of RAW 264.7 murine macrophage-like cells by measuring the uptake of 2-μm diameter polystyrene beads. Sulforaphane raised the phagocytosis activity of RAW 264.7 cells but only in the absence or presence of low concentrations (1%) of fetal bovine serum. Higher serum concentrations depressed phagocytosis and abolished its stimulation by sulforaphane. This stimulation did not depend on the induction of Nrf2-regulated genes since it occurred in peritoneal macrophages of nrf2 -/- mice. Moreover, a potent triterpenoid inducer of Nrf2-dependent genes did not stimulate phagocytosis, whereas sulforaphane and another isothiocyanate (benzyl isothiocyanate) had comparable inducer potencies. It has been shown recently that sulforaphane is a potent and direct inactivator of macrophage migration inhibitory factor (MIF), an inflammatory cytokine. Moreover, the addition of recombinant MIF to RAW 264.7 cells attenuated phagocytosis, but sulforaphane-inactivated MIF did not affect phagocytosis. The inactivation of MIF may therefore be involved in the phagocytosis-enhancing activity of sulforaphane.

Stimulation of phagocytosis by sulforaphane

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Suganuma, Hiroyuki, E-mail: hsuganu1@jhmi.edu [Lewis B. and Dorothy Cullman Cancer Chemoprotection Center, Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205 (United States); Fahey, Jed W., E-mail: jfahey@jhmi.edu [Lewis B. and Dorothy Cullman Cancer Chemoprotection Center, Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205 (United States); Bryan, Kelley E., E-mail: kbryanm1@jhmi.edu [Lewis B. and Dorothy Cullman Cancer Chemoprotection Center, Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205 (United States); Healy, Zachary R., E-mail: zhealy1@jhmi.edu [Lewis B. and Dorothy Cullman Cancer Chemoprotection Center, Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205 (United States); Talalay, Paul, E-mail: ptalalay@jhmi.edu [Lewis B. and Dorothy Cullman Cancer Chemoprotection Center, Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, 725 N. Wolfe Street, Baltimore, MD 21205 (United States)

2011-02-04

Research highlights: {yields} Sulforaphane stimulates the phagocytosis of RAW 264.7 macrophages under conditions of serum deprivation. {yields} This effect does not require Nrf2-dependent induction of phase 2 genes. {yields} Inactivation of macrophage migration inhibitory factor (MIF) by sulforaphane may be involved in stimulation of phagocytosis by sulforaphane. -- Abstract: Sulforaphane, a major isothiocyanate derived from cruciferous vegetables, protects living systems against electrophile toxicity, oxidative stress, inflammation, and radiation. A major protective mechanism is the induction of a network of endogenous cytoprotective (phase 2) genes that are regulated by transcription factor Nrf2. To obtain a more detailed understanding of the anti-inflammatory and immunomodulatory effects of sulforaphane, we evaluated its effect on the phagocytosis activity of RAW 264.7 murine macrophage-like cells by measuring the uptake of 2-{mu}m diameter polystyrene beads. Sulforaphane raised the phagocytosis activity of RAW 264.7 cells but only in the absence or presence of low concentrations (1%) of fetal bovine serum. Higher serum concentrations depressed phagocytosis and abolished its stimulation by sulforaphane. This stimulation did not depend on the induction of Nrf2-regulated genes since it occurred in peritoneal macrophages of nrf2{sup -/-} mice. Moreover, a potent triterpenoid inducer of Nrf2-dependent genes did not stimulate phagocytosis, whereas sulforaphane and another isothiocyanate (benzyl isothiocyanate) had comparable inducer potencies. It has been shown recently that sulforaphane is a potent and direct inactivator of macrophage migration inhibitory factor (MIF), an inflammatory cytokine. Moreover, the addition of recombinant MIF to RAW 264.7 cells attenuated phagocytosis, but sulforaphane-inactivated MIF did not affect phagocytosis. The inactivation of MIF may therefore be involved in the phagocytosis-enhancing activity of sulforaphane.