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Sample records for near-field coupled processes

  1. Panel discussion on near-field coupled processes with emphasis on performance assessment

    SciTech Connect

    Codell, R.B.; Baca, R.G.; Ahola, M.P.

    1996-04-01

    The presentations in this panel discussion involve the general topic of near-field coupled processes and postclosure performance assessment with an emphasis on rock mechanics. The potential impact of near-field rock mass deformation on repository performance was discussed, as well as topics including long term excavation deterioration, the performance of geologic seals, and coupled processes concerning rock mechanics in performance assessments.

  2. Report on Modeling Coupled Processes in the Near Field of a Clay Repository

    SciTech Connect

    Liu, Hui -Hai; Houseworth, Jim; Rutqvist, Jonny; Li, Lianchong; Asahina, Daisuke; Chen, Fei; Birkholzer, Jens

    2012-08-01

    Clay/shale has been considered as potential host rock for geological disposal of high-level radioactive waste throughout the world. Coupled thermal, hydrological, mechanical, and chemical (THMC) processes have a significant impact on the long-term safety of a clay repository. For example, the excavation damaged zone (EDZ) near repository tunnels can modify local permeability (resulting from induced fractures), potentially leading to less confinement capability. This report documents results from three R&D activities: (1) implementation and validation of constitutive relationships, (2) development of a discrete fracture network (DFN) model for investigating coupled processes in the EDZ, and (3) development of a THM model for the FE tests at Mont Terri, Switzerland, for the purpose of model validation. The overall objective of these activities is to provide an improved understanding of EDZ evolution in clay repositories and the associated coupled processes, and to develop advanced relevant modeling capabilities.

  3. Modeled near-field environment porosity modifications due to coupled thermohydrologic and geochemical processes

    SciTech Connect

    Glassley, W. E.; Nitao, J. J.

    1998-10-30

    Heat deposited by waste packages in nuclear waste repositories can modify rock properties by instigating mineral dissolution and precipitation along hydrothermal flow pathways. Modeling this reactive transport requires coupling fluid flow to permeability changes resulting from dissolution and precipitation. Modification of the NUFT thermohydrologic (TH) code package to account for this coupling in a simplified geochemical system has been used to model the time- dependent change in porosity, permeability, matrix and fracture saturation, and temperature in the vicinity of waste-emplacement drifts, using conditions anticipated for the potential Yucca Mountain repository. The results show, within a few hundred years, dramatic porosity reduction approximately 10 m above emplacement drifts. Most of this reduction is attributed to deposition of solute load at the boiling front, although some of it also results from decreasing temperature along the flow path. The actual distribution of the nearly sealed region is sensitive to the time- dependent characteristics of the thermal load imposed on the environment and suggests that the geometry of the sealed region can be engineered by managing the waste-emplacement strategy.

  4. Near Field Environment Process Model Report

    SciTech Connect

    R.A. Wagner

    2000-11-14

    Waste emplacement and activities associated with construction of a repository system potentially will change environmental conditions within the repository system. These environmental changes principally result from heat generated by the decay of the radioactive waste, which elevates temperatures within the repository system. Elevated temperatures affect distribution of water, increase kinetic rates of geochemical processes, and cause stresses to change in magnitude and orientation from the stresses resulting from the overlying rock and from underground construction activities. The recognition of this evolving environment has been reflected in activities, studies and discussions generally associated with what has been termed the Near-Field Environment (NFE). The NFE interacts directly with waste packages and engineered barriers as well as potentially changing the fluid composition and flow conditions within the mountain. As such, the NFE defines the environment for assessing the performance of a potential Monitored Geologic Repository at Yucca Mountain, Nevada. The NFe evolves over time, and therefore is not amenable to direct characterization or measurement in the ambient system. Analysis or assessment of the NFE must rely upon projections based on tests and models that encompass the long-term processes of the evolution of this environment. This NFE Process Model Report (PMR) describes the analyses and modeling based on current understanding of the evolution of the near-field within the rock mass extending outward from the drift wall.

  5. Visualizing near-field coupling in terahertz dolmens

    NASA Astrophysics Data System (ADS)

    Halpin, Alexei; Mennes, Christiaan; Bhattacharya, Arkabrata; Gómez Rivas, Jaime

    2017-03-01

    Strong interactions between resonant structures in the near-field occur at length scales shorter than the wavelength, and can be exploited for modifying the propagation of electromagnetic radiation. Dolmen-like structures, formed by a rod supporting a dipolar (bright) resonance and two orthogonal rods with a quadrupolar (dark) resonance at the same frequency, represent a geometry of significant interest for near-field electromagnetic coupling. These structures demonstrate electromagnetically induced transparency (EIT) through coupling between these resonances, concurrently providing a sharp spectral selectivity in transmission and large group velocity reduction. We use near-field terahertz scanning microscopy to map the electric fields in the vicinity of a metallic dolmen in both amplitude and phase. In this way, we directly measure the interaction between bright and dark modes in the time-domain, revealing the physics resulting in EIT. We experimentally demonstrate the hybridization of bright and dark modes accompanying the near-field coupling, as well as the excitation of the dark mode at the frequency of the far-field transparency.

  6. Thermoradiative device enhanced by near-field coupled structures

    NASA Astrophysics Data System (ADS)

    Wang, Bingnan; Lin, Chungwei; Teo, Koon Hoo; Zhang, Zhuomin

    2017-07-01

    Thermoradiative (TR) technology was recently proposed as a new mechanism to efficiently convert low-temperature waste heat into electric energy. It has been shown that near-field coupling between a TR cell and a heat sink is an effective way in boosting the performance of the TR device. The enhancement becomes more significant when surface resonant modes are supported by the heat sink. Surface plasmon polaritons on metal surfaces, and surface phonon polaritons on Lorentz materials, are two major types of materials investigated in the near-field enhancement. However, to significantly boost the performance, the resonant mode energy needs to match the bandgap energy of the TR cell, which is often difficult to realize with natural material selections. Typical metals have plasma frequency much higher than the bandgap of TR cell. In this paper, we show that new resonant modes with energy close to the bandgap of TR cell can be created with nanostructured gratings on the heat sink. This enables use to build the heat sink using commonly available metallic materials, whose typical surface resonant frequency is much higher than the TR bandgap.

  7. Near-field environment/processes working group summary

    SciTech Connect

    Murphy, W.M.

    1995-09-01

    This article is a summary of the proceedings of a group discussion which took place at the Workshop on the Role of Natural Analogs in Geologic Disposal of High-Level Nuclear Waste in San Antonio, Texas on July 22-25, 1991. The working group concentrated on the subject of the near-field environment to geologic repositories for high-level nuclear waste. The near-field environment may be affected by thermal perturbations from the waste, and by disturbances caused by the introduction of exotic materials during construction of the repository. This group also discussed the application of modelling of performance-related processes.

  8. Near-field spectral properties of coupled plasmonic nanoparticle arrays.

    PubMed

    Yu, Han; Sun, Quan; Yang, Jinghuan; Ueno, Kosei; Oshikiri, Tomoya; Kubo, Atsushi; Matsuo, Yasutaka; Gong, Qihuang; Misawa, Hiroaki

    2017-03-20

    We investigated the grating effect in complex gold dolmen structures, in which multiple plasmon modes are present due to plasmon hybridization, experimentally from both the far field and the near field. In particular, the near-field properties were investigated using photoemission electron microscopy, and it was demonstrated that two hybridized plasmon modes on the dolmen structures could be influenced by the grating effect. For comparison, we also investigated the grating effect in arrays of simple nanoblocks and heptamer structures, which were supposed to support a strong bright plasmon mode and a strong dark plasmon mode, respectively, in the near field. We found that the spectral responses of the two hybridized modes on the dolmen structures as the pitch size changed evolved in a manner similar to that of the bright dipole mode on the nanoblocks, whereas the dark mode on the heptamer structures is less sensitive to the pitch size.

  9. Probing dark excitons in atomically thin semiconductors via near-field coupling to surface plasmon polaritons

    NASA Astrophysics Data System (ADS)

    Zhou, You; Scuri, Giovanni; Wild, Dominik S.; High, Alexander A.; Dibos, Alan; Jauregui, Luis A.; Shu, Chi; de Greve, Kristiaan; Pistunova, Kateryna; Joe, Andrew Y.; Taniguchi, Takashi; Watanabe, Kenji; Kim, Philip; Lukin, Mikhail D.; Park, Hongkun

    2017-09-01

    Transition metal dichalcogenide (TMD) monolayers with a direct bandgap feature tightly bound excitons, strong spin-orbit coupling and spin-valley degrees of freedom. Depending on the spin configuration of the electron-hole pairs, intra-valley excitons of TMD monolayers can be either optically bright or dark. Dark excitons involve nominally spin-forbidden optical transitions with a zero in-plane transition dipole moment, making their detection with conventional far-field optical techniques challenging. Here, we introduce a method for probing the optical properties of two-dimensional materials via near-field coupling to surface plasmon polaritons (SPPs). This coupling selectively enhances optical transitions with dipole moments normal to the two-dimensional plane, enabling direct detection of dark excitons in TMD monolayers. When a WSe2 monolayer is placed on top of a single-crystal silver film, its emission into near-field-coupled SPPs displays new spectral features whose energies and dipole orientations are consistent with dark neutral and charged excitons. The SPP-based near-field spectroscopy significantly improves experimental capabilities for probing and manipulating exciton dynamics of atomically thin materials, thus opening up new avenues for realizing active metasurfaces and robust optoelectronic systems, with potential applications in information processing and communication.

  10. Probing dark excitons in atomically thin semiconductors via near-field coupling to surface plasmon polaritons.

    PubMed

    Zhou, You; Scuri, Giovanni; Wild, Dominik S; High, Alexander A; Dibos, Alan; Jauregui, Luis A; Shu, Chi; De Greve, Kristiaan; Pistunova, Kateryna; Joe, Andrew Y; Taniguchi, Takashi; Watanabe, Kenji; Kim, Philip; Lukin, Mikhail D; Park, Hongkun

    2017-09-01

    Transition metal dichalcogenide (TMD) monolayers with a direct bandgap feature tightly bound excitons, strong spin-orbit coupling and spin-valley degrees of freedom. Depending on the spin configuration of the electron-hole pairs, intra-valley excitons of TMD monolayers can be either optically bright or dark. Dark excitons involve nominally spin-forbidden optical transitions with a zero in-plane transition dipole moment, making their detection with conventional far-field optical techniques challenging. Here, we introduce a method for probing the optical properties of two-dimensional materials via near-field coupling to surface plasmon polaritons (SPPs). This coupling selectively enhances optical transitions with dipole moments normal to the two-dimensional plane, enabling direct detection of dark excitons in TMD monolayers. When a WSe2 monolayer is placed on top of a single-crystal silver film, its emission into near-field-coupled SPPs displays new spectral features whose energies and dipole orientations are consistent with dark neutral and charged excitons. The SPP-based near-field spectroscopy significantly improves experimental capabilities for probing and manipulating exciton dynamics of atomically thin materials, thus opening up new avenues for realizing active metasurfaces and robust optoelectronic systems, with potential applications in information processing and communication.

  11. Active control of near-field coupling in conductively coupled microelectromechanical system metamaterial devices

    NASA Astrophysics Data System (ADS)

    Pitchappa, Prakash; Manjappa, Manukumara; Ho, Chong Pei; Qian, You; Singh, Ranjan; Singh, Navab; Lee, Chengkuo

    2016-03-01

    We experimentally report a structurally reconfigurable metamaterial for active switching of near-field coupling in conductively coupled, orthogonally twisted split ring resonators (SRRs) operating in the terahertz spectral region. Out-of-plane reconfigurable microcantilevers integrated into the dark SRR geometry are used to provide active frequency tuning of dark SRR resonance. The geometrical parameters of individual SRRs are designed to have identical inductive-capacitive resonant frequency. This allows for the excitation of classical analogue of electromagnetically induced transparency (EIT) due to the strong conductive coupling between the SRRs. When the microcantilevers are curved up, the resonant frequency of dark SRR blue-shifts and the EIT peak is completely modulated while the SRRs are still conductively connected. EIT modulation contrast of ˜50% is experimentally achieved with actively switchable group delay of ˜2.5 ps. Electrical control, miniaturized size, and readily integrable fabrication process of the proposed structurally reconfigurable metamaterial make it an ideal candidate for the realization of various terahertz communication devices such as electrically controllable terahertz delay lines, buffers, and tunable data-rate channels.

  12. Modulating the Near Field Coupling through Resonator Displacement in Planar Terahertz Metamaterials

    NASA Astrophysics Data System (ADS)

    Mohan Rao, S. Jagan; Kumar, Deepak; Kumar, Gagan; Chowdhury, Dibakar Roy

    2017-01-01

    We present the effect of vertical displacements between the resonators inside the unit cell of planar coupled metamaterials on their near field coupling and hence on the terahertz (THz) wave modulation. The metamolecule design consists of two planar split- ring resonators (SRRs) in a unit cell which are coupled through their near fields. The numerically simulated transmission spectrum is found to have split resonances due to the resonance mode hybridization effect. With the increase in displacement between the near field coupled SRRs, this metamaterial system shows a transition from coupled to uncoupled state through merging of the split resonances to the single intrinsic resonance. We have used a semi-analytical model describing the effect of displacements between the resonators and determine that it can predict the numerically simulated results. The outcome could be useful in modulating the terahertz waves employing near field coupled metamaterials, hence, can be useful in the development of terahertz modulators and frequency tunable devices in future.

  13. Thermodynamic coupling of heat and matter flows in near-field regions of nuclear waste repositories

    SciTech Connect

    Carnahan, C.L.

    1983-11-01

    In near-field regions of nuclear waste repositories, thermodynamically coupled flows of heat and matter can occur in addition to the independent flows in the presence of gradients of temperature, hydraulic potential, and composition. The following coupled effects can occur: thermal osmosis, thermal diffusion, chemical osmosis, thermal filtration, diffusion thermal effect, ultrafiltration, and coupled diffusion. Flows of heat and matter associated with these effects can modify the flows predictable from the direct effects, which are expressed by Fourier's law, Darcy's law, and Fick's law. The coupled effects can be treated quantitatively together with the direct effects by the methods of the thermodynamics of irreversible processes. The extent of departure of fully coupled flows from predictions based only on consideration of direct effects depends on the strengths of the gradients driving flows, and may be significant at early times in backfills and in near-field geologic environments of repositories. Approximate calculations using data from the literature and reasonable assumptions of repository conditions indicate that thermal-osmotic and chemical-osmotic flows of water in semipermeable backfills may exceed Darcian flows by two to three orders of magnitude, while flows of solutes may be reduced greatly by ultrafiltration and chemical osmosis, relative to the flows predicted by advection and diffusion alone. In permeable materials, thermal diffusion may contribute to solute flows to a smaller, but still significant, extent.

  14. Exploring Coupled Plasmonic Nanostructures in the Near Field by Photoemission Electron Microscopy.

    PubMed

    Yu, Han; Sun, Quan; Ueno, Kosei; Oshikiri, Tomoya; Kubo, Atsushi; Matsuo, Yasutaka; Misawa, Hiroaki

    2016-11-22

    The extraordinary optical properties of coupled plasmonic nanostructures make these materials potentially useful in many applications; thus, they have received enormous attention in basic and applied research. Coupled plasmon modes have been characterized predominantly using far-field spectroscopy. In near-field spectroscopy, the spectral response of local field enhancement in coupled plasmonic nanostructures remains largely unexplored, especially experimentally. Here, we investigate the coupled gold dolmen nanostructures in the near field using photoemission electron microscopy, with wavelength-tunable femtosecond laser pulses as an excitation source. The spatial evolution of near-field mapping of an individual dolmen structure with the excitation wavelength was successfully obtained. In the near field, we spatially resolved an anti-bonding mode and a bonding mode as the result of plasmon hybridization. Additionally, the quadrupole plasmon mode that could be involved in the formation of a Fano resonance was also revealed by spatially resolved near-field spectra, but it only contributed little to the total near-field enhancement. On the basis of these findings, we obtained a better understanding of the near-field properties of coupled plasmonic nanostructures, where the plasmon hybridization and the plasmonic Fano resonance were mixed.

  15. Resonance hybridization and near field properties of strongly coupled plasmonic ring dimer-rod nanosystem

    SciTech Connect

    Koya, Alemayehu Nana; Ji, Boyu; Hao, Zuoqiang; Lin, Jingquan

    2015-09-21

    Combined effects of polarization, split gap, and rod width on the resonance hybridization and near field properties of strongly coupled gold dimer-rod nanosystem are comparatively investigated in the light of the constituent nanostructures. By aligning polarization of the incident light parallel to the long axis of the nanorod, introducing small split gaps to the dimer walls, and varying width of the nanorod, we have simultaneously achieved resonance mode coupling, huge near field enhancement, and prolonged plasmon lifetime. As a result of strong coupling between the nanostructures and due to an intense confinement of near fields at the split and dimer-rod gaps, the extinction spectrum of the coupled nanosystem shows an increase in intensity and blueshift in wavelength. Consequently, the near field lifespan of the split-nanosystem is prolonged in contrast to the constituent nanostructures and unsplit-nanosystem. On the other hand, for polarization of the light perpendicular to the long axis of the nanorod, the effect of split gap on the optical responses of the coupled nanosystem is found to be insignificant compared to the parallel polarization. These findings and such geometries suggest that coupling an array of metallic split-ring dimer with long nanorod can resolve the huge radiative loss problem of plasmonic waveguide. In addition, the Fano-like resonances and immense near field enhancements at the split and dimer-rod gaps imply the potentials of the nanosystem for practical applications in localized surface plasmon resonance spectroscopy and sensing.

  16. Near field fluid coupling between internal motion of the organ of Corti and the basilar membrane

    SciTech Connect

    Elliott, Stephen J.; Ni, Guangjian

    2015-12-31

    The pressure distribution in each of the fluid chambers of the cochlea can be decomposed into a 1D, or plane wave, component and a near field component, which decays rapidly away from the excitation point. The transverse motion of the basilar membrane, BM, for example, generates both a 1D pressure field, which couples into the slow wave, and a local near field pressure, proportional to the BM acceleration, that generates an added mass on the BM due to the fluid motion. When the organ of Corti, OC, undergoes internal motion, due for example to outer hair cell activity, this motion will not itself generate any 1D pressure if the OC is incompressible and the BM is constrained not to move volumetrically, and so will not directly couple into the slow wave. This motion will, however, generate a near field pressure, proportional to the OC acceleration, which will act on the OC and thus increases its effective mass. The near field pressure due to this OC motion will also act on the BM, generating a force on the BM proportional to the acceleration of the OC, and thus create a “coupling mass” effect. By reciprocity, this coupling mass is the same as that acting on the OC due to the motion of the BM. This near field fluid coupling is initially observed in a finite element model of a slice of the cochlea. These simulations suggest a simple analytical formulation for the fluid coupling, using higher order beam modes across the width of the cochlear partition. It is well known that the added mass due to the near field pressure dominates the overall mass of the BM, and thus significantly affects the micromechanical dynamics. This work not only quantifies the added mass of the OC due its own motion in the fluid, and shows that this is important, but also demonstrates that the coupling mass effect between the BM and OC significantly affects the dynamics of simple micromechanical models.

  17. Near field fluid coupling between internal motion of the organ of Corti and the basilar membrane

    NASA Astrophysics Data System (ADS)

    Elliott, Stephen J.; Ni, Guangjian

    2015-12-01

    The pressure distribution in each of the fluid chambers of the cochlea can be decomposed into a 1D, or plane wave, component and a near field component, which decays rapidly away from the excitation point. The transverse motion of the basilar membrane, BM, for example, generates both a 1D pressure field, which couples into the slow wave, and a local near field pressure, proportional to the BM acceleration, that generates an added mass on the BM due to the fluid motion. When the organ of Corti, OC, undergoes internal motion, due for example to outer hair cell activity, this motion will not itself generate any 1D pressure if the OC is incompressible and the BM is constrained not to move volumetrically, and so will not directly couple into the slow wave. This motion will, however, generate a near field pressure, proportional to the OC acceleration, which will act on the OC and thus increases its effective mass. The near field pressure due to this OC motion will also act on the BM, generating a force on the BM proportional to the acceleration of the OC, and thus create a "coupling mass" effect. By reciprocity, this coupling mass is the same as that acting on the OC due to the motion of the BM. This near field fluid coupling is initially observed in a finite element model of a slice of the cochlea. These simulations suggest a simple analytical formulation for the fluid coupling, using higher order beam modes across the width of the cochlear partition. It is well known that the added mass due to the near field pressure dominates the overall mass of the BM, and thus significantly affects the micromechanical dynamics. This work not only quantifies the added mass of the OC due its own motion in the fluid, and shows that this is important, but also demonstrates that the coupling mass effect between the BM and OC significantly affects the dynamics of simple micromechanical models.

  18. Johnson-Nyquist Noise Coupling Formulation of Near-Field Heat Transfer for 1D Conductors

    NASA Astrophysics Data System (ADS)

    Prunnila, Mika; Laakso, Sampo; Gunnarsson, David

    Near-field heat transfer has been formulated using different levels of theoretical sophistication and complexity ranging from fluctuational electrodynamics to quasi-static Coulomb interaction description. Our goal is to find a simple description for the near-field heat transfer between coupled 1D electron systems (conductors). We will show that by considering distributed Johnson-Nyquist voltage sources, arising from the dissipative part of the electron systems' response, a compact fundamental formula for the near-field heat transfer can be found. We will describe the details of the derivation and discuss the regime of validity of our approach. Several special cases will be considered and experimental configurations will be discussed. The presented analysis is especially suitable for closely spaced graphene ribbons and nanowires. We will also show that by including inductive responses, which are necessary at high frequencies, speed of light emerges in the heat flow formula, thereby showing the link between fundamental physical quantities/constants and near-field heat transfer in coupled 1D systems. Our formulation also provides the possibility to use different boundary conditions for the physical system and this enables design of near-field heat transfer circuits.

  19. Resonance tuning due to Coulomb interaction in strong near-field coupled metamaterials

    SciTech Connect

    Roy Chowdhury, Dibakar; Xu, Ningning; Zhang, Weili; Singh, Ranjan

    2015-07-14

    Coulomb's law is one of the most fundamental laws of physics that describes the electrostatic interaction between two like or unlike point charges. Here, we experimentally observe a strong effect of Coulomb interaction in tightly coupled terahertz metamaterials where the split-ring resonator dimers in a unit cell are coupled through their near fields across the capacitive split gaps. Using a simple analytical model, we evaluated the Coulomb parameter that switched its sign from negative to positive values indicating the transition in the nature of Coulomb force from being repulsive to attractive depending upon the near field coupling between the split ring resonators. Apart from showing interesting effects in the strong coupling regime between meta-atoms, Coulomb interaction also allows an additional degree of freedom to achieve frequency tunable dynamic metamaterials.

  20. Near-field coupling and resonant cavity modes in plasmonic nanorod metamaterials

    NASA Astrophysics Data System (ADS)

    Song, Haojie; Zhang, Junxi; Fei, Guangtao; Wang, Junfeng; Jiang, Kang; Wang, Pei; Lu, Yonghua; Iorsh, Ivan; Xu, Wei; Jia, Junhui; Zhang, Lide; Kivshar, Yuri S.; Zhang, Lin

    2016-10-01

    Plasmonic resonant cavities are capable of confining light at the nanoscale, resulting in both enhanced local electromagnetic fields and lower mode volumes. However, conventional plasmonic resonant cavities possess large Ohmic losses at metal-dielectric interfaces. Plasmonic near-field coupling plays a key role in a design of photonic components based on the resonant cavities because of the possibility to reduce losses. Here, we study the plasmonic near-field coupling in the silver nanorod metamaterials treated as resonant nanostructured optical cavities. Reflectance measurements reveal the existence of multiple resonance modes of the nanorod metamaterials, which is consistent with our theoretical analysis. Furthermore, our numerical simulations show that the electric field at the longitudinal resonances forms standing waves in the nanocavities due to the near-field coupling between the adjacent nanorods, and a new hybrid mode emerges due to a coupling between nanorods and a gold-film substrate. We demonstrate that this coupling can be controlled by changing the gap between the silver nanorod array and gold substrate.

  1. Near-field coupling and resonant cavity modes in plasmonic nanorod metamaterials.

    PubMed

    Song, Haojie; Zhang, Junxi; Fei, Guangtao; Wang, Junfeng; Jiang, Kang; Wang, Pei; Lu, Yonghua; Iorsh, Ivan; Xu, Wei; Jia, Junhui; Zhang, Lide; Kivshar, Yuri S; Zhang, Lin

    2016-10-14

    Plasmonic resonant cavities are capable of confining light at the nanoscale, resulting in both enhanced local electromagnetic fields and lower mode volumes. However, conventional plasmonic resonant cavities possess large Ohmic losses at metal-dielectric interfaces. Plasmonic near-field coupling plays a key role in a design of photonic components based on the resonant cavities because of the possibility to reduce losses. Here, we study the plasmonic near-field coupling in the silver nanorod metamaterials treated as resonant nanostructured optical cavities. Reflectance measurements reveal the existence of multiple resonance modes of the nanorod metamaterials, which is consistent with our theoretical analysis. Furthermore, our numerical simulations show that the electric field at the longitudinal resonances forms standing waves in the nanocavities due to the near-field coupling between the adjacent nanorods, and a new hybrid mode emerges due to a coupling between nanorods and a gold-film substrate. We demonstrate that this coupling can be controlled by changing the gap between the silver nanorod array and gold substrate.

  2. Near-Field Infrared Pump-Probe Imaging of Surface Phonon Coupling in Boron Nitride Nanotubes.

    PubMed

    Gilburd, Leonid; Xu, Xiaoji G; Bando, Yoshio; Golberg, Dmitri; Walker, Gilbert C

    2016-01-21

    Surface phonon modes are lattice vibrational modes of a solid surface. Two common surface modes, called longitudinal and transverse optical modes, exhibit lattice vibration along or perpendicular to the direction of the wave. We report a two-color, infrared pump-infrared probe technique based on scattering type near-field optical microscopy (s-SNOM) to spatially resolve coupling between surface phonon modes. Spatially varying couplings between the longitudinal optical and surface phonon polariton modes of boron nitride nanotubes are observed, and a simple model is proposed.

  3. Temporal coupled-mode theory model for resonant near-field thermophotovoltaics

    SciTech Connect

    Karalis, Aristeidis; Joannopoulos, J. D.

    2015-10-05

    A temporal Coupled-Mode Theory model is developed to predict performance of resonant near-field ThermoPhotoVoltaic systems, which typically requires numerically intensive calculations. It is formulated for both orthogonal and non-orthogonal (coupled) modes and includes load-voltage dependencies and non-idealities, such as background absorption and radiation losses. Its good accuracy is confirmed by comparing with exact transfer-matrix calculations for two simple planar systems: a plasmonic emitter across a bulk semiconductor absorber and a metal-backed thin-film semiconductor emitter across an identical absorber.

  4. On the coupling efficiency of metal-coated near-field probes.

    PubMed

    Alvarez, L; Xiao, M

    2001-05-01

    A theory for calculating the optical transmission of nanometric circular apertures in a thick and perfectly conducting screen coated upon an optical fibre has been developed. The theory is intended for the study of near-field probes and differs from other well known theories of radiation transmission through subwavelength apertures in the fact that it includes an optical fibre, making possible to distinguish which part of energy passing through the aperture is effectively coupled in guided modes. In a scanning near-field optical microscope tip, only the guided modes will reach the photodetector, and will contribute to the final read-out. A numerical calculation for different fibre parameters, to show the dependence of the guided transmission coefficient for the guided modes of the fibre, is presented. The agreement of the theory with earlier calculations where the optical fibre is not included is emphasized.

  5. Near-field mediated plexcitonic coupling and giant Rabi splitting in individual metallic dimers.

    PubMed

    Schlather, Andrea E; Large, Nicolas; Urban, Alexander S; Nordlander, Peter; Halas, Naomi J

    2013-07-10

    Strong coupling between resonantly matched localized surface plasmons and molecular excitons results in the formation of new hybridized energy states called plexcitons. Understanding the nature and tunability of these hybrid nanostructures is important for both fundamental studies and the development of new applications. We investigate the interactions between J-aggregate excitons and single plasmonic dimers and report for the first time a unique strong coupling regime in individual plexcitonic nanostructures. Dark-field scattering measurements and finite-difference time-domain simulations of the hybrid nanostructures show strong plexcitonic coupling mediated by the near-field inside each dimer gap, which can be actively controlled by rotating the polarization of the optical excitation. The plexciton dispersion curves, obtained from coupled harmonic oscillator models, show anticrossing behavior at the exciton transition energy and giant Rabi splitting ranging between 230 and 400 meV. These energies are, to the best of our knowledge, the largest obtained on individual hybrid nanostructures.

  6. Light transport in dense composite media: role of near-field coupling

    NASA Astrophysics Data System (ADS)

    Rezvani Naraghi, Roxana; Sukhov, Sergey; Sáenz, Juan José; Dogariu, Aristide

    In scattering media, optical waves comprise both homogeneous and evanescent components. At very high concentrations of scatterers, particles are located in close proximity and interact through evanescent near fields. Thus, in this regime the energy is not only carried by propagating waves but it also evolves through evanescent coupling between individual scatterers. We have shown that in dense composite media additional transmission channels open because of these near-field interactions between close proximity scatters and, consequently, a new regime of transport emerges. This is clearly beyond simple descriptions of scatterers acting independently of their environment and framed in terms of far-field characteristics such as Mie cross-sections. We will show that, because in the dense media the energy can transfer through both diffusion and evanescent channels, the total transmittance is T =TCS +TNF = 1 1 L (lCS* +lNF*) L (lCS* +lNF*) . Correcting the total transmission in this manner is appealing because it is done in terms of physically meaningful and measurable quantities such a near-field (NF) scattering cross-section σNF.

  7. Theoretical study of nanophotonic directional couplers comprising near-field-coupled metal nanoparticles.

    PubMed

    Holmström, Petter; Yuan, Jun; Qiu, Min; Thylén, Lars; Bratkovsky, Alexander M

    2011-04-11

    The properties of integrated-photonics directional couplers composed of near-field-coupled arrays of metal nanoparticles are analyzed theoretically. It is found that it is possible to generate very compact, submicron length, high field-confinement and functionality devices with very low switch energies. The analysis is carried out for a hypothetical lossless silver to demonstrate the potential of this type of circuits for applications in telecom and interconnects. Employing losses of real silver, standalone devices with the above properties are still feasible in optimized metal nanoparticle structures.

  8. Genetic algorithm optimization of grating coupled near-field interference lithography systems at extreme numerical apertures

    NASA Astrophysics Data System (ADS)

    Bourke, Levi; Blaikie, Richard J.

    2017-09-01

    Grating coupled near-field interference lithography has the ability to produce deep-subwavelength interference patterns. Simulations of these systems is very computationally intensive. An inverse design procedure employing a genetic algorithm is utilized here to massively reduce the computational load and allow for the design of systems capable of interfering extremely high numerical apertures. This method is used to optimize systems with an interference patterns with a half pitch of λ /40 corresponding to a numerical aperture of 20. It is also used to demonstrate interference of higher | m| diffraction orders.

  9. An ab-initio coupled mode theory for near field radiative thermal transfer.

    PubMed

    Chalabi, Hamidreza; Hasman, Erez; Brongersma, Mark L

    2014-12-01

    We investigate the thermal transfer between finite-thickness planar slabs which support surface phonon polariton modes (SPhPs). The thickness-dependent dispersion of SPhPs in such layered materials provides a unique opportunity to manipulate and enhance the near field thermal transfer. The key accomplishment of this paper is the development of an ab-initio coupled mode theory that accurately describes all of its thermal transfer properties. We illustrate how the coupled mode parameters can be obtained in a direct fashion from the dispersion relation of the relevant modes of the system. This is illustrated for the specific case of a semi-infinite SiC substrate placed in close proximity to a thin slab of SiC. This is a system that exhibits rich physics in terms of its thermal transfer properties, despite the seemingly simple geometry. This includes a universal scaling behavior of the thermal conductance with the slab thickness and spacing. The work highlights and further increases the value of coupled mode theories in rapidly calculating and intuitively understanding near-field transfer.

  10. Effects of spherical mode coupling on near-field focusing by clusters of dielectric microspheres.

    PubMed

    Pikulin, Alexander; Afanasiev, Andrei; Agareva, Nadezhda; Alexandrov, Alexander P; Bredikhin, Vladimir; Bityurin, Nikita

    2012-04-09

    Colloidal particle lens array (CPLA) proved to be an efficient near-field focusing device for laser nanoprocessing of materials. Within CPLA, spherical particles do not act as independent microlenses. Due to the coupling of the spherical modes, the field near the clusters of spherical microparticles cannot be calculated by means of the superposition of Mie solutions for individual spheres. In the paper, the electromagnetic field distributions near laser-irradiated clusters of dielectric microspheres with configurations that match the fragments of the close-packed CPLA are studied. It is shown that some practically important mode coupling effects can be understood in terms of an effective immersion medium formed for the spherical particle by its surrounding.

  11. Far-Field to Near-Field Coupling for Enhancing Light-Matter Interaction

    NASA Astrophysics Data System (ADS)

    Bonakdar, Alireza

    This thesis reports on theoretical, modeling, and experimental research within the framework of a key scientific question, which is enhancing the coupling between diffraction-limited far-field and sub-wavelength quantum emitter/absorber. A typical optoelectronic device delivers an optical process such as light detection (e.g. photodetector) or light intensity modulation (e.g. electro-absorptive modulator). In conventional devices, optical process is in the form of far-field or guided wave modes. The main aim of this thesis is to show that converting these modes into near-field domain can enhance the performance of the optoelectronic device. Light in the form of far-field can be converted into near-field domain by the optical antenna. Among different optoelectronic devices, this thesis focuses mainly on integrating the optical antenna with infrared photodetectors. The available semiconductors have weak infrared absorption that reduces light detection efficiency. Integration of the optical antenna with infrared absorber (such as quantum wells in quantum well infrared photodetector (QWIP)) increases the infrared absorption. Particularly this integration is favorable as the optical antenna has low metallic loss in infrared region. The author of this thesis believes that optical antenna has unique properties in confining light on the scale of deep sub-wavelength, enhancing electric field intensity and delivering optical energy to semiconductor absorbers. These properties are reaching into practical applications only if overall optical performance is low loss, parameter free (independent of optical parameters such a polarization and angle of incident) and broadband. In this thesis, the integration of optical antenna with infrared photodetectors and thermophotovoltaic are researched and developed which satisfy the aforementioned criteria. In addition, several different optical antennas have been designed, fabricated and characterized in order to analyze and demonstrate

  12. Enhanced energy transfer by near-field coupling of a nanostructured metamaterial with a graphene-covered plate

    NASA Astrophysics Data System (ADS)

    Chang, Jui-Yung; Yang, Yue; Wang, Liping

    2016-11-01

    Coupled surface plasmon/phonon polaritons and hyperbolic modes are known to enhance radiative transfer across nanometer vacuum gaps but usually require identical materials. It becomes crucial to achieve strong near-field energy transfer between dissimilar materials for applications like near-field thermophotovoltaic and thermal rectification. In this work, we theoretically demonstrate enhanced near-field radiative transfer between a nanostructured metamaterial emitter and a graphene-covered planar receiver. Strong near-field coupling with two orders of magnitude enhancement in the spectral heat flux is achieved at the gap distance of 20 nm. By carefully selecting the graphene chemical potential and doping levels of silicon nanohole emitter and silicon plate receiver, the total near-field radiative heat flux can reach about 500 times higher than the far-field blackbody limit between 400 K and 300 K. The physical mechanism is elucidated by the near-field surface plasmon coupling with fluctuational electrodynamics and dispersion relations. The effects of graphene chemical potential, emitter and receiver doping levels, and vacuum gap distance on the near-field coupling and radiative energy transfer are analyzed in detail.

  13. Pitch-dependent resonances and near-field coupling in infrared nanoantenna arrays.

    PubMed

    Simpkins, B S; Long, J P; Glembocki, O J; Guo, J; Caldwell, J D; Owrutsky, J C

    2012-12-03

    We investigate coupling in arrays of nanoparticles resonating as half-wave antennas on both silicon and sapphire, and find a universal behavior when scaled by antenna length and substrate index. Three distinct coupling regimes are identified and characterized by rigorous finite-difference time domain simulations. As interparticle pitch is reduced below the oft-described radiative to evanescent transition, resonances blue shift and narrow and exhibit an asymmetric band consistent with a Fano lineshape. Upon further pitch reduction, a transition to a third regime, termed here as near-field coupling, is observed in which the resonance shifts red, becomes more symmetric, and broadens dramatically. This latter regime occurs when the extension of the resonant mode beyond the physical antenna end overlaps that of its neighbor. Simulations identify a clear rearrangement of field intensity accompanying this regime, illustrating that longitudinal modal fields localize in the air gap rather than in the higher index substrate at a pitch consistent with the experimentally observed transition.

  14. Maximum achievable efficiency in near-field coupled power-transfer systems.

    PubMed

    Zargham, Meysam; Gulak, P Glenn

    2012-06-01

    Wireless power transfer is commonly realized by means of near-field inductive coupling and is critical to many existing and emerging applications in biomedical engineering. This paper presents a closed form analytical solution for the optimum load that achieves the maximum possible power efficiency under arbitrary input impedance conditions based on the general two-port parameters of the network. The two-port approach allows one to predict the power transfer efficiency at any frequency, any type of coil geometry and through any type of media surrounding the coils. Moreover, the results are applicable to any form of passive power transfer such as provided by inductive or capacitive coupling. Our results generalize several well-known special cases. The formulation allows the design of an optimized wireless power transfer link through biological media using readily available EM simulation software. The proposed method effectively decouples the design of the inductive coupling two-port from the problem of loading and power amplifier design. Several case studies are provided for typical applications.

  15. Hybrid modelling of near-field coupling onto grounded wire under ultra-short duration perturbation

    NASA Astrophysics Data System (ADS)

    Ravelo, B.; Liu, Y.

    2014-10-01

    A time-frequency (TF) hybrid model (HM) for investigating the interaction between EM near-field (NF) aggression and grounded wire is addressed. The HM is based on the combination of techniques for extracting the EM NF radiated by electronic structures and the calculation of electrical disturbances across the wire due to EM coupling. The computation method is fundamentally inspired from transmission line (TL) theory under EM illumination. The methodology including flow chart interpreting the routine algorithm based on the combination of frequency and time domain approaches is featured. An experimental result showing the EM coupling between patch antenna-wire from 1.5-3.5GHz reveals the efficiency of the HM in frequency domain. The relevance of this HM was illustrated with a structure comprised of 20cm aggressor and 5cm victim I-shaped wires placed above a planar ground plane. The aggressor was excited with 40ns duration perturbation signal. After Matlab implementation of the HM, the disturbance voltages across the extremity of the victim wire were extracted. This simple and fast HM is useful for the EMC engineering during the design and fabrication phases of electrical and electronic systems.

  16. Coupled near-field and far-field exposure assessment framework for chemicals in consumer products.

    PubMed

    Fantke, Peter; Ernstoff, Alexi S; Huang, Lei; Csiszar, Susan A; Jolliet, Olivier

    2016-09-01

    Humans can be exposed to chemicals in consumer products through product use and environmental emissions over the product life cycle. Exposure pathways are often complex, where chemicals can transfer directly from products to humans during use or exchange between various indoor and outdoor compartments until sub-fractions reach humans. To consistently evaluate exposure pathways along product life cycles, a flexible mass balance-based assessment framework is presented structuring multimedia chemical transfers in a matrix of direct inter-compartmental transfer fractions. By matrix inversion, we quantify cumulative multimedia transfer fractions and exposure pathway-specific product intake fractions defined as chemical mass taken in by humans per unit mass of chemical in a product. Combining product intake fractions with chemical mass in the product yields intake estimates for use in life cycle impact assessment and chemical alternatives assessment, or daily intake doses for use in risk-based assessment and high-throughput screening. Two illustrative examples of chemicals used in personal care products and flooring materials demonstrate how this matrix-based framework offers a consistent and efficient way to rapidly compare exposure pathways for adult and child users and for the general population. This framework constitutes a user-friendly approach to develop, compare and interpret multiple human exposure scenarios in a coupled system of near-field ('user' environment), far-field and human intake compartments, and helps understand the contribution of individual pathways to overall human exposure in various product application contexts to inform decisions in different science-policy fields for which exposure quantification is relevant. Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

  17. Temporal coupled mode theory linking to surface-wave dispersion relations in near-field electromagnetic heat transfer

    NASA Astrophysics Data System (ADS)

    Iizuka, Hideo; Fan, Shanhui

    2016-11-01

    We provide a detailed discussion of the use of coupled mode theory to describe near-field heat transfer. We consider a simple physical model system of coupled harmonic oscillators with each oscillator maintaining at a different temperature, where heat transfer between the oscillators can be analytically treated from first-principles using the Newton's equation and the fluctuation dissipation theorem. Applying a slowly varying envelope approximation to the Newton's equation, we derive a coupled mode theory formalism. We then apply this coupled mode theory formalism in the study of the near-field heat transfer between either silicon carbide plates or between two graphene sheets. The coupled mode theory provides a quantitative link between the dispersion relation of the coupled system and the heat transfer, and agrees with exact numerical results over all range of wavevectors. To obtain such complete agreement, the key observation here is that one should include the frequency shift, that is, the frequency of the individual mode used in the coupled mode theory should be different from the frequency of the mode of an isolated structure. Finally, we show that the coupled mode theory can be applied even when more than two modes are involved in the heat transfer. As an example, we extend our formalism to the near-field heat transfer in a four-layer graphene structure.

  18. Enhancement of near-field radiative heat transfer via multiple coupling of surface waves with graphene plasmon

    NASA Astrophysics Data System (ADS)

    Zhou, Ting; Song, Chen-Cai; Wang, Tong-Biao; Liu, Wen-Xing; Liu, Jiang-Tao; Yu, Tian-Bao; Liao, Qing-Hua; Liu, Nian-Hua

    2017-05-01

    Coated silicon carbide (SiC) thin films can efficiently enhance near-field radiative heat transfer among metamaterials. In this study, the near-field heat transfer among graphene-SiC-metamaterial (GSM) multilayer structures was theoretically investigated. Graphene plasmons could be coupled both with electric surface plasmons supported by the metamaterial and with symmetric and anti-symmetric surface phonon polaritons (SPhPs) supported by SiC. The heat transfer among GSM structures was considerably improved compared to that among SiC-coated metamaterials when the chemical potential of graphene was not very high. In addition, the near-field heat transfer was enhanced among SiC-graphene-metamaterial multilayer structures, though the heat transfer among these structures was less than that among GSMs owing to the absence of coupling between symmetric SPhPs and graphene plasmons. Hence, heat transfer could be flexibly tuned by modifying the chemical potential of graphene in both configurations. These results provide a basis for active control of the near-field radiative heat transfer in the far-infrared region.

  19. Surface phonon coupling within boron nitride resolved by a novel near-field infrared pump-probe imaging technique

    NASA Astrophysics Data System (ADS)

    Gilburd, Leonid; Xu, Xiaoji G.; de Beer, Sissi; Bando, Yoshio; Golberg, Dmitri; Walker, Gilbert C.

    2016-09-01

    The excitation of surface phonon-polariton (SPhP) modes in polar materials using scattering type near-field optical microscopy (s-SNOM) has recently become an area of interest because of its potential for application as naturally occurring meta-materials and in low-loss energy transfer. Within this area, hexagonal boron nitride (h-BN) and boron nitride nanotubes (BNNTs) are the primary structures under investigation. Here we present pump-probe continuous wave (CW) scattering-type scanning near-field optical microscopy (s-SNOM) - a novel two color pump-probe infrared technique which uses two continuous wave tunable light sources and is based on s-SNOM. The technique allows us to spatially resolve coupling of the longitudinal optical and surface phonon polariton modes in BNNTs. However, no similar coupling is observed in two-dimensional h-BN crystals.

  20. Tunable Lattice Coupling of Multipole Plasmon Modes and Near-Field Enhancement in Closely Spaced Gold Nanorod Arrays

    PubMed Central

    Huang, Yu; Zhang, Xian; Ringe, Emilie; Hou, Mengjing; Ma, Lingwei; Zhang, Zhengjun

    2016-01-01

    Considering the nanogap and lattice effects, there is an attractive structure in plasmonics: closely spaced metallic nanoarrays. In this work, we demonstrate experimentally and theoretically the lattice coupling of multipole plasmon modes for closely spaced gold nanorod arrays, offering a new insight into the higher order cavity modes coupled with each other in the lattice. The resonances can be greatly tuned by changes in inter-rod gaps and nanorod heights while the influence of the nanorod diameter is relatively insignificant. Experimentally, pronounced suppressions of the reflectance are observed. Meanwhile, the near-field enhancement can be further enhanced, as demonstrated through surface enhanced Raman scattering (SERS). We then confirm the correlation between the near-field and far-field plasmonic responses, which is significantly important for maximizing the near-field enhancement at a specific excitation wavelength. This lattice coupling of multipole plasmon modes is of broad interest not only for SERS but also for other plasmonic applications, such as subwavelength imaging or metamaterials. PMID:26983501

  1. Modeling of the Near Field Coupling Between an External Loop and an Implantable Spiral Chip Antennas in Biosensor Systems

    NASA Technical Reports Server (NTRS)

    Simons, Rainee N.; Miranda, Felix A.

    2006-01-01

    In this paper, the near field coupling between an external hand-held loop antenna and an implantable miniature (1x1 mm) printed square spiral chip antenna used in bio-MEMS sensors for contact-less powering and RF telemetry is investigated. The loop and the spiral are inductively coupled and effectively form a transformer. The numerical results include the quasi-stationary magnetic field pattern of the implanted antenna, near zone wave impedance as a function of the radial distance and the values of the lumped elements in the equivalent circuit model for the transformer.

  2. Near-field coupling of gold plasmonic antennas for sub-100 nm magneto-thermal microscopy

    NASA Astrophysics Data System (ADS)

    Karsch, Jonathan C.; Bartell, Jason M.; Fuchs, Gregory D.

    2017-08-01

    The development of spintronic technology with increasingly dense, high-speed, and complex devices will be accelerated by accessible microscopy techniques capable of probing magnetic phenomena on picosecond time scales and at deeply sub-micron length scales. A recently developed time-resolved magneto-thermal microscope provides a path towards this goal if it is augmented with a picosecond, nanoscale heat source. We theoretically study adiabatic nanofocusing and near-field heat induction using conical gold plasmonic antennas to generate sub-100 nm thermal gradients for time-resolved magneto-thermal imaging. Finite element calculations of antenna-sample interactions reveal focused electromagnetic loss profiles that are either peaked directly under the antenna or are annular, depending on the sample's conductivity, the antenna's apex radius, and the tip-sample separation. We find that the thermal gradient is confined to 40 nm to 60 nm full width at half maximum for realistic ranges of sample conductivity and apex radius. To mitigate this variation, which is undesirable for microscopy, we investigate the use of a platinum capping layer on top of the sample as a thermal transduction layer to produce heat uniformly across different sample materials. After determining the optimal capping layer thickness, we simulate the evolution of the thermal gradient in the underlying sample layer and find that the temporal width is below 10 ps. These results lay a theoretical foundation for nanoscale, time-resolved magneto-thermal imaging.

  3. Electromagnetically induced transparency with large delay-bandwidth product induced by magnetic resonance near field coupling to electric resonance

    SciTech Connect

    Li, Hai-ming; Liu, Shao-bin Liu, Si-yuan; Zhang, Hai-feng; Bian, Bo-rui; Kong, Xiang-kun; Wang, Shen-yun

    2015-03-16

    In this paper, we numerically and experimentally demonstrate electromagnetically induced transparency (EIT)-like spectral response with magnetic resonance near field coupling to electric resonance. Six split-ring resonators and a cut wire are chosen as the bright and dark resonator, respectively. An EIT-like transmission peak located between two dips can be observed with incident magnetic field excitation. A large delay bandwidth product (0.39) is obtained, which has potential application in quantum optics and communications. The experimental results are in good agreement with simulated results.

  4. Density controlled nanophotonic waveguide gratings for efficient on-chip out-coupling in the near field (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Vercruysse, Dries; Mukund, Vignesh; Jansen, Roelof; Stahl, Richard; Van Dorpe, Pol; Lagae, Liesbet; Rottenberg, Xavier

    2016-05-01

    Waveguide optics takes up a prominent role in the progressing miniaturization of optical devices. Chip integrated photonic waveguides especially allow for complex routing schemes of light across a chip. In/out-coupling diffraction gratings form an essential tool in waveguide systems, as they facilitate the interaction between the waveguide system and the near or far-field.[1,2] Ideally, these gratings would couple out all light in the waveguide into a beam with a predefined polarization and, phase and intensity profile. As such they should be able to produce any functional beam that is typically prepared by free space optics. Yet, in practice there is typically a design trade-off between beam quality and out-coupling efficiency.[2] Light in the waveguide has to travel laterally through the grating to be coupled out. The light therefore decays exponentially over the grating, causing much more light to be coupled out at the start of the grating than at the end. This asymmetry results in a warped out-coupling intensity that heavily influences the light beam's intensity profile. Especially when the grating is addressing points in the near field, as is the case for focusing waveguide grating couplers, this effect can be highly disruptive. In this work we present a grating constructed from a field of sub-wavelength scatterers, rather than full grating lines. By tuning the position and the density of the scatterers, the phase and the intensity of the out-coupled light can be set precisely over large grating areas. An iterative design algorithm is developed that carefully tunes the density so as to control the light intensity in the waveguide and the amount of out-coupled light. Using FDTD simulations we show that these gratings can efficiently couple out light into a nearly diffraction limited spot with an even angular intensity. We verify this experimentally by fabricating these gratings in the SiN/SiO2 system using e-beam lithography. In addition, we also show that

  5. Detection and processing of electromagnetic and near-field acoustic signals in elasmobranch fishes.

    PubMed Central

    Kalmijn, A D

    2000-01-01

    The acoustic near field of quietly moving underwater objects and the bio-electric field of aquatic animals exhibit great similarity, as both are predominantly governed by Laplace's equation. The acoustic and electrical sensory modalities thus may, in directing fishes to their prey, employ analogous processing algorithms, suggesting a common evolutionary design, founded on the salient physical features shared by the respective stimulus fields. Sharks and rays are capable of orientating to the earth's magnetic field and, hence, have a magnetic sense. The electromagnetic theory of orientation offers strong arguments for the animals using the electric fields induced by ocean currents and by their own motions in the earth's magnetic field. In the animal's frame of reference, in which the sense organs are at rest, the classical concept of motional electricity must be interpreted in relativistic terms. In the ampullae of Lorenzini, weak electric fields cause the ciliated apical receptor-cell membranes to produce graded, negative receptor currents opposite in direction to the fields applied. The observed currents form part of a positive-feedback mechanism, supporting the generation of receptor potentials much larger than the input signal. Acting across the basal cell membranes, the receptor potentials control the process of synaptic transmission. PMID:11079385

  6. Synthesis and fabrication of silver nanowires embedded in PVP fibers by near-field electrospinning process

    NASA Astrophysics Data System (ADS)

    Yang, T. L.; Pan, C. T.; Chen, Y. C.; Lin, L. W.; Wu, I. C.; Hung, K. H.; Lin, Y. R.; Huang, H. L.; Liu, C. F.; Mao, S. W.; Kuo, S. W.

    2015-01-01

    In this study, polyol process was used to synthesize anisotropic silver nanowires (AgNWs). The ranges of synthesis temperature from 100 to 200 degrees were explored, and the ranges from 4.53 to 13.75 wt% Polyvinylpyrrolidone (PVP) were investigated. The lengths and diameters of AgNWs from 15 to 30 μm and from 10 to 50 nm can be obtained, respectively. Then, the AgNWs embedded in PVP fibers (PVP/AgNWs) were fabricated by the near-field electrospinning (NFES) process. The AgNWs were broken down into nanoparticles when the applied electric field was over 1.4 × 107 V/m. However, the AgNWs could remain undamaged when the electric field was controlled between 8 × 106 and 1.2 × 107 V/m. Therefore, the threshold electric field can be determined and the diameter of the PVP/AgNWs fibers from 500 nm to 10 μm can be obtained. Next, the characteristics of the PVP/AgNWs were examined by N&K analyzer, four-point probe, EDS and FTIR. The transmittance of PVP/AgNWs films was 51.29-68.97% and the sheet resistance of purified AgNWs was 0.125 Ω/sq which was superior to that of commercial ITO. In addition, the haze of PVP/AgNWs with 30-90 nm thick was from 11.5% to 13.3%. In the near future, the PVP/AgNWs fibers can be used as transparent conductive electrodes.

  7. Strongly coupled near-field radiative and conductive heat transfer between planar bodies

    NASA Astrophysics Data System (ADS)

    Messina, Riccardo; Jin, Weiliang; Rodriguez, Alejandro W.

    2016-09-01

    We study the interplay of conductive and radiative heat transfer (RHT) in planar geometries and predict that temperature gradients induced by radiation can play a significant role on the behavior of RHT with respect to gap sizes, depending largely on geometric and material parameters and not so crucially on operating temperatures. Our findings exploit rigorous calculations based on a closed-form expression for the heat flux between two plates separated by vacuum gaps d and subject to arbitrary temperature profiles, along with an approximate but accurate analytical treatment of coupled conduction-radiation in this geometry. We find that these effects can be prominent in typical materials (e.g., silica and sapphire) at separations of tens of nanometers, and can play an even larger role in metal oxides, which exhibit moderate conductivities and enhanced radiative properties. Broadly speaking, these predictions suggest that the impact of RHT on thermal conduction, and vice versa, could manifest itself as a limit on the possible magnitude of RHT at the nanoscale, which asymptotes to a constant (the conductive transfer rate when the gap is closed) instead of diverging at short separations.

  8. Near-field examination of perovskite-based superlenses and superlens-enhanced probe-object coupling

    PubMed Central

    Kehr, S.C.; Liu, Y.M.; Martin, L.W.; Yu, P.; Gajek, M.; Yang, S.-Y.; Yang, C.-H.; Wenzel, M.T.; Jacob, R.; von Ribbeck, H.-G.; Helm, M.; Zhang, X.; Eng, L.M.; Ramesh, R.

    2011-01-01

    A planar slab of negative-index material works as a superlens with sub-diffraction-limited resolution, as propagating waves are focused and, moreover, evanescent waves are reconstructed in the image plane. Here we demonstrate a superlens for electric evanescent fields with low losses using perovskites in the mid-infrared regime. The combination of near-field microscopy with a tunable free-electron laser allows us to address precisely the polariton modes, which are critical for super-resolution imaging. We spectrally study the lateral and vertical distributions of evanescent waves around the image plane of such a lens, and achieve imaging resolution of λ/14 at the superlensing wavelength. Interestingly, at certain distances between the probe and sample surface, we observe a maximum of these evanescent fields. Comparisons with numerical simulations indicate that this maximum originates from an enhanced coupling between probe and object, which might be applicable for multifunctional circuits, infrared spectroscopy and thermal sensors. PMID:21427720

  9. Two-photon luminescence contrast by tip-sample coupling in femtosecond near-field optical microscopy

    NASA Astrophysics Data System (ADS)

    Horneber, Anke; Wackenhut, Frank; Braun, Kai; Wang, Xiao; Wang, Jiyong; Zhang, Dai; Meixner, Alfred J.

    2017-01-01

    We investigate the role of tip-sample interaction in nonlinear optical scanning near-field microscopy. The experiment was performed by tightly focusing femtosecond laser pulses onto a sharp gold tip that was positioned in close proximity to the surface of a sample with gold nanostructures on a Si-substrate by shear force feedback. The nonlinear optical signal consists of two-photon photoluminescence and second harmonic signal from the gold tip and the gold nanostructures. These signals can be used to characterize different coupling parameters such as geometry, material and width of the tip-sample gap and enable to reveal the mechanism responsible for the image contrast. Under the excitation with 776-nm and 110-fs laser pulses nonlinear imaging is almost background free and yields super resolution showing features with dimensions significantly below the diffraction limit with a signal intensity following quadratic excitation power law.

  10. An imaging dataset of cervical cells using scanning near-field optical microscopy coupled to an infrared free electron laser

    NASA Astrophysics Data System (ADS)

    Halliwell, Diane E.; Morais, Camilo L. M.; Lima, Kássio M. G.; Trevisan, Júlio; Siggel-King, Michele R. F.; Craig, Tim; Ingham, James; Martin, David S.; Heys, Kelly; Kyrgiou, Maria; Mitra, Anita; Paraskevaidis, Evangelos; Theophilou, Georgios; Martin-Hirsch, Pierre L.; Cricenti, Antonio; Luce, Marco; Weightman, Peter; Martin, Francis L.

    2017-07-01

    Using a scanning near-field optical microscope coupled to an infrared free electron laser (SNOM-IR-FEL) in low-resolution transmission mode, we collected chemical data from whole cervical cells obtained from 5 pre-menopausal, non-pregnant women of reproductive age, and cytologically classified as normal or with different grades of cervical cell dyskaryosis. Imaging data are complemented by demography. All samples were collected before any treatment. Spectra were also collected using attenuated total reflection, Fourier-transform (ATR-FTIR) spectroscopy, to investigate the differences between the two techniques. Results of this pilot study suggests SNOM-IR-FEL may be able to distinguish cervical abnormalities based upon changes in the chemical profiles for each grade of dyskaryosis at designated wavelengths associated with DNA, Amide I/II, and lipids. The novel data sets are the first collected using SNOM-IR-FEL in transmission mode at the ALICE facility (UK), and obtained using whole cells as opposed to tissue sections, thus providing an 'intact' chemical profile. These data sets are suited to complementing future work on image analysis, and/or applying the newly developed algorithm to other datasets collected using the SNOM-IR-FEL approach.

  11. A coupled soil-fluid-structure simulation of the near-field earthquake effects on gravity type quay-walls

    NASA Astrophysics Data System (ADS)

    Zeinoddini, M.; Matin Nikoo, H.; Ahmadpour, F.

    2013-08-01

    This study focuses on non-linear seismic response of concrete gravity quay-wall structures subjected to near-fault ground motions, a subject which seems not to have received much attention in the literature. A two-dimensional coupled fluid-structure-soil finite element modelling is employed to obtain the quay-wall response. The seawater medium is represented by acoustic type, potential based fluid elements. The elasto-plastic behavior of the soil medium is idealized using Drucker-Prager yield criterion based on associated flow rule assumption. Four nodded plane strain elements are used to model the concrete wall, foundation, subsoil, backfill and seabed zones. Fluid Structure Interface (FSI) elements are considered between the seawater interfaces with the quay-wall and the seabed. Frictional contact elements are employed between the wall and soil interfaces. The numerical model is validated using field measurements available for permanent drifts in a quay-wall damaged during Kobe earthquake. Reasonable agreements are obtained between the model predictions and the field measurements. Non-linear seismic analyses of the selected quay-wall subjected to both near-fault and far-fault ground motions are performed. An incremental dynamic analysis approach (IDA) is used. In general, at least for models examined in the current study, the gravity quay-walls are found to be more vulnerable to near-field, in comparison with the corresponding far-field, earthquakes.

  12. An imaging dataset of cervical cells using scanning near-field optical microscopy coupled to an infrared free electron laser.

    PubMed

    Halliwell, Diane E; Morais, Camilo L M; Lima, Kássio M G; Trevisan, Júlio; Siggel-King, Michele R F; Craig, Tim; Ingham, James; Martin, David S; Heys, Kelly; Kyrgiou, Maria; Mitra, Anita; Paraskevaidis, Evangelos; Theophilou, Georgios; Martin-Hirsch, Pierre L; Cricenti, Antonio; Luce, Marco; Weightman, Peter; Martin, Francis L

    2017-07-11

    Using a scanning near-field optical microscope coupled to an infrared free electron laser (SNOM-IR-FEL) in low-resolution transmission mode, we collected chemical data from whole cervical cells obtained from 5 pre-menopausal, non-pregnant women of reproductive age, and cytologically classified as normal or with different grades of cervical cell dyskaryosis. Imaging data are complemented by demography. All samples were collected before any treatment. Spectra were also collected using attenuated total reflection, Fourier-transform (ATR-FTIR) spectroscopy, to investigate the differences between the two techniques. Results of this pilot study suggests SNOM-IR-FEL may be able to distinguish cervical abnormalities based upon changes in the chemical profiles for each grade of dyskaryosis at designated wavelengths associated with DNA, Amide I/II, and lipids. The novel data sets are the first collected using SNOM-IR-FEL in transmission mode at the ALICE facility (UK), and obtained using whole cells as opposed to tissue sections, thus providing an 'intact' chemical profile. These data sets are suited to complementing future work on image analysis, and/or applying the newly developed algorithm to other datasets collected using the SNOM-IR-FEL approach.

  13. Adaptive and robust statistical methods for processing near-field scanning microwave microscopy images.

    PubMed

    Coakley, K J; Imtiaz, A; Wallis, T M; Weber, J C; Berweger, S; Kabos, P

    2015-03-01

    Near-field scanning microwave microscopy offers great potential to facilitate characterization, development and modeling of materials. By acquiring microwave images at multiple frequencies and amplitudes (along with the other modalities) one can study material and device physics at different lateral and depth scales. Images are typically noisy and contaminated by artifacts that can vary from scan line to scan line and planar-like trends due to sample tilt errors. Here, we level images based on an estimate of a smooth 2-d trend determined with a robust implementation of a local regression method. In this robust approach, features and outliers which are not due to the trend are automatically downweighted. We denoise images with the Adaptive Weights Smoothing method. This method smooths out additive noise while preserving edge-like features in images. We demonstrate the feasibility of our methods on topography images and microwave |S11| images. For one challenging test case, we demonstrate that our method outperforms alternative methods from the scanning probe microscopy data analysis software package Gwyddion. Our methods should be useful for massive image data sets where manual selection of landmarks or image subsets by a user is impractical. Published by Elsevier B.V.

  14. Hollow-pyramid based scanning near-field optical microscope coupled to femtosecond pulses: a tool for nonlinear optics at the nanoscale.

    PubMed

    Celebrano, Michele; Biagioni, Paolo; Zavelani-Rossi, Margherita; Polli, Dario; Labardi, Massimiliano; Allegrini, Maria; Finazzi, Marco; Duò, Lamberto; Cerullo, Giulio

    2009-03-01

    We describe an aperture scanning near-field optical microscope (SNOM) using cantilevered hollow pyramid probes coupled to femtosecond laser pulses. Such probes, with respect to tapered optical fibers, present higher throughput and laser power damage threshold, as well as greater mechanical robustness. In addition, they preserve pulse duration and polarization in the near field. The instrument can operate in two configurations: illumination mode, in which the SNOM probe is used to excite the nonlinear response in the near field, and collection mode, where it collects the nonlinear emission following far-field excitation. We present application examples highlighting the capability of the system to observe the nonlinear optical response of nanostructured metal surfaces (gold projection patterns and gold nanorods) with sub-100-nm spatial resolution.

  15. Propulsion of gold nanoparticles with surface plasmon polaritons: evidence of enhanced optical force from near-field coupling between gold particle and gold film.

    PubMed

    Wang, Kai; Schonbrun, Ethan; Crozier, Kenneth B

    2009-07-01

    We experimentally demonstrate the enhanced propulsion of gold nanoparticles by surface plasmon polaritons (SPPs). Three dimensional finite difference time domain (FDTD) simulations indicate considerably enhanced optical forces due to the field enhancement provided by SPPs and the near-field coupling between the gold particles and the film. This coupling is an important part of the enhanced propulsion phenomenon. Finally, the measured optical force is compared with that predicted by FDTD simulations and proven to be reasonable.

  16. Direct-write PVDF nonwoven fiber fabric energy harvesters via the hollow cylindrical near-field electrospinning process

    NASA Astrophysics Data System (ADS)

    Liu, Z. H.; Pan, C. T.; Lin, L. W.; Huang, J. C.; Ou, Z. Y.

    2014-02-01

    One-dimensional piezoelectric nanomaterials have attracted great attention in recent years for their possible applications in mechanical energy scavenging devices. However, it is difficult to control the structural diameter, length, and density of these fibers fabricated by micro/nano-technologies. This work presents a hollow cylindrical near-field electrospinning (HCNFES) process to address production and performance issues encountered previously in either far-field electrospinning (FFES) or near-field electrospinning (NFES) processes. Oriented polyvinylidene fluoride (PVDF) fibers in the form of nonwoven fabric have been directly written on a glass tube for aligned piezoelectricity. Under a high in situ electrical poling field and strong mechanical stretching (the tangential speed on the glass tube collector is about 1989.3 mm s-1), the HCNFES process is able to uniformly deposit large arrays of PVDF fibers with good concentrations of piezoelectric β-phase. The nonwoven fiber fabric (NFF) is transferred onto a polyethylene terephthalate (PET) substrate and fixed at both ends using copper foil electrodes as a flexible textile-fiber-based PVDF energy harvester. Repeated stretching and releasing of PVDF NFF with a strain of 0.05% at 7 Hz produces a maximum peak voltage and current at 76 mV and 39 nA, respectively.

  17. Using the near-field coupling of a sharp tip to tune fluorescence-emission fluctuations during quantum-dot blinking.

    PubMed

    Shafran, Eyal; Mangum, Benjamin D; Gerton, Jordan M

    2011-07-15

    We demonstrate that the cycling between internal states of quantum dots during fluorescence blinking can be used to tune the near-field coupling with a sharp tip. In particular, the fluorescence emission from states with high quantum yield is quenched due to energy transfer, while that from low-yield states is elevated due to field enhancement. Thus, as a quantum dot blinks, its emission fluctuations are progressively suppressed upon approach of a tip.

  18. Near-field optics for nanoprocessing

    NASA Astrophysics Data System (ADS)

    Terakawa, Mitsuhiro; Nedyalkov, Nikolay N.

    2016-02-01

    The recent progress in laser processing reaches a level where a precise fabrication that overcomes the diffraction limit of the far-field optics can be achieved. Laser processing mediated by enhanced near field is one of the attractive methods to provide highly precise structuring with a simple apparatus. In this review, we describe the fundamentals of the electromagnetic near field in the vicinity of small structures and the application of its specific properties for nanomodification. Theoretical and experimental results on nanoablation based on electromagnetic field enhancement due to plasmon polariton excitation and Mie scattering are discussed. High-throughput nanohole fabrication mediated by arrayed nanospheres is discussed, as the coupling effect of near field is also considered. In addition, recent fabrication techniques and their potential applications in nanopatterning, nanoscale deformation, and biophotonics are discussed.

  19. Source processes of near-field deformation accompanying recent lava lake level decrease at Nyiragongo, DR. Congo

    NASA Astrophysics Data System (ADS)

    Geirsson, Halldor; Smets, Benoît; d'Oreye, Nicolas; Cayol, Valerie; Samsonov, Sergey; De Rauw, Dominique; Kervyn, Francois

    2016-04-01

    Nyiragongo volcano in the Democratic Republic of Congo, Central Africa, is one of the rare volcanoes that host a long-living lava lake. The evolution of this lava lake is very dynamic, with height changes spanning hundreds of meters over the past decades and including drastic height changes in relation to flank eruptions of the volcano in 1977 and 2002 (Smets et al., this meeting). Since September 30, 2011, the level of the lava lake has been progressively falling, reaching ~70 m below the lowest platform (termed "platform P3" hereafter) in July 2014. Platform P3 is constructed from successive overflows of the lava lake from 2002 to 2011, amounting to ~400 m thickness since the emptying of the lava lake following the 2002 flank eruption. Coinciding with the recent fall of the lava lake, differences of photogrammetry-derived DEM models, and InSAR time series, show a very near-field (out to ~200-300 m distance from the ~200 m-wide lava lake, i.e. on platform P3) deformation signal with up to meter-scale deformation near the crater. Ring-fractures have also formed in platform P3. Here we compare and contrast plausible models of processes contributing to this near-field deformation, including thermal contraction, elastic response, block rotation, structural weaknesses, and subsurface shape of the lava lake.

  20. Super-Resolution Defect Characterization Using Microwave Near-Field Resonance Reflectometry and Cross-correlation Image Processing

    NASA Astrophysics Data System (ADS)

    Malyuskin, Oleksandr; Fusco, Vincent

    2017-12-01

    A super-resolution defect characterization technique based on near-field resonance reflectometry and cross-correlation image processing is proposed in this paper. The hardware part of the microwave imaging system employs a novel loaded aperture (LA) probe which allows collimation of the electromagnetic field to approximately λ/10 focal spot(s) at λ/100 to λ/10 stand-off distances, λ being the wavelength of radiation in free space. The characteristic raw image spatial resolution of the LA probe is around λ/10 in one dimension with amplitude contrast/sensitivity exceeding 10-20 dB. It is demonstrated that the LA spatial resolution can be at least two times enhanced in two dimensions in the image plane using basic cross-correlation image processing while retaining a very high level of amplitude contrast of at least 10 dB.

  1. Departures from plane-wave-like coupling to a Maverick missile in the radiating near-field region of a horn antenna

    NASA Astrophysics Data System (ADS)

    Voss, D. E.; Koslover, R. A.; Cremer, C. D.; Silvestro, J.; Miner, L. M.

    1990-05-01

    The High Power Microwaves (HPM) susceptibility testing often requires irradiating test objects at the highest fluences possible. For aperture antennas, the highest fluences are generally found in the radiating near field region. For valid effects testing, the energy coupled to the object interior must accurately replicate that which would occur in a true weapon environment (plane wave illumination). Some believe that valid testing requires object placement at distances from the aperture exceeding 2 D squared/lambda (D=antenna effective diameter). Many also believe testing at farther away than 2 D squared/lambda guarantees plane wave-like coupling conditions. Neither view is correct. Testing in the reactive field region (less than lambda from the aperture) is generally invalid due to dominance of reactive coupling. For testing in the radiating near field, determination of validity is less trivial. An investigation was performed quantifying deviations from plane wave coupling. The measurements, using an instrumented Maverick missile in an anechoic chamber, and supported by theory, indicate conditions for which testing the Maverick missile accurately simulates plane wave coupling.

  2. Numerical study of the THM effects on the near-field safety of ahypothetical nuclear waste repository - BMT1 of the DECOVALEX IIIproject. Part 3: Effects of THM coupling in sparsely fracturedrocks

    SciTech Connect

    Rutqvist, J.; Chijimatsu, M.; Jing, L.; Millard, A.; Nguyen,T.S.; Rejeb, A.; Sugita, Y.; Tsang, C.F.

    2004-09-09

    BENCHPAR project, the impact of thermal-hydrological-mechanical (THM) couplings on the performance of a bentonite-back-filled nuclear waste repository in near-field crystalline rocks is evaluated in a Bench-Mark Test problem (BMT1) and the results are presented in a series of three companion papers in this issue. This is the third paper with focus on the effects of THM processes at a repository located in a sparsely fractured rock. Several independent coupled THM analyses presented in this paper show that THM couplings have the most significant impact on the mechanical stress evolution, which is important for repository design, construction and post-closure monitoring considerations. The results show that the stress evolution in the bentonite-back-filled excavations and the surrounding rock depends on the post-closure evolution of both fields of temperature and fluid pressure.It is further shown that the time required to full resaturation may play an important role for the mechanical integrity of the repository drifts.In this sense, the presence of hydraulically conducting fractures in the near-field rock might actually improve the mechanical performance of the repository. Hydraulically conducting fractures in the near-field rocks enhances the water supply to the buffers/back-fills, which promotes a more timely process of resaturation and development of swelling pressures in the back-fill, thus provides timely confining stress and support to the rock walls. In one particular case simulated in this study, it was shown that failure in the drift walls could be prevented if the compressive stresses in back-fill were fully developed within 50 years,which is when thermally induced rock strain begins to create high differential (failure-prone) stresses in the near-field rocks.

  3. Imaging cervical cytology with scanning near-field optical microscopy (SNOM) coupled with an IR-FEL

    PubMed Central

    Halliwell, Diane E.; Morais, Camilo L. M.; Lima, Kássio M. G.; Trevisan, Julio; Siggel-King, Michele R. F.; Craig, Tim; Ingham, James; Martin, David S.; Heys, Kelly A.; Kyrgiou, Maria; Mitra, Anita; Paraskevaidis, Evangelos; Theophilou, Georgios; Martin-Hirsch, Pierre L.; Cricenti, Antonio; Luce, Marco; Weightman, Peter; Martin, Francis L.

    2016-01-01

    Cervical cancer remains a major cause of morbidity and mortality among women, especially in the developing world. Increased synthesis of proteins, lipids and nucleic acids is a pre-condition for the rapid proliferation of cancer cells. We show that scanning near-field optical microscopy, in combination with an infrared free electron laser (SNOM-IR-FEL), is able to distinguish between normal and squamous low-grade and high-grade dyskaryosis, and between normal and mixed squamous/glandular pre-invasive and adenocarcinoma cervical lesions, at designated wavelengths associated with DNA, Amide I/II and lipids. These findings evidence the promise of the SNOM-IR-FEL technique in obtaining chemical information relevant to the detection of cervical cell abnormalities and cancer diagnosis at spatial resolutions below the diffraction limit (≥0.2 μm). We compare these results with analyses following attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy; although this latter approach has been demonstrated to detect underlying cervical atypia missed by conventional cytology, it is limited by a spatial resolution of ~3 μm to 30 μm due to the optical diffraction limit. PMID:27406404

  4. Imaging cervical cytology with scanning near-field optical microscopy (SNOM) coupled with an IR-FEL.

    PubMed

    Halliwell, Diane E; Morais, Camilo L M; Lima, Kássio M G; Trevisan, Julio; Siggel-King, Michele R F; Craig, Tim; Ingham, James; Martin, David S; Heys, Kelly A; Kyrgiou, Maria; Mitra, Anita; Paraskevaidis, Evangelos; Theophilou, Georgios; Martin-Hirsch, Pierre L; Cricenti, Antonio; Luce, Marco; Weightman, Peter; Martin, Francis L

    2016-07-12

    Cervical cancer remains a major cause of morbidity and mortality among women, especially in the developing world. Increased synthesis of proteins, lipids and nucleic acids is a pre-condition for the rapid proliferation of cancer cells. We show that scanning near-field optical microscopy, in combination with an infrared free electron laser (SNOM-IR-FEL), is able to distinguish between normal and squamous low-grade and high-grade dyskaryosis, and between normal and mixed squamous/glandular pre-invasive and adenocarcinoma cervical lesions, at designated wavelengths associated with DNA, Amide I/II and lipids. These findings evidence the promise of the SNOM-IR-FEL technique in obtaining chemical information relevant to the detection of cervical cell abnormalities and cancer diagnosis at spatial resolutions below the diffraction limit (≥0.2 μm). We compare these results with analyses following attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy; although this latter approach has been demonstrated to detect underlying cervical atypia missed by conventional cytology, it is limited by a spatial resolution of ~3 μm to 30 μm due to the optical diffraction limit.

  5. A case study on the influence of THM coupling on the near field safety of a spent fuel repository in sparsely fractured granite

    SciTech Connect

    Nguyen, T.S.; Borgesson, L.; Chijimatsu, M.; Hernelind, J.; Jing, L.; Kobayashi, A.; Rutqvist, J.

    2009-03-01

    In order to demonstrate the feasibility of geological disposal of spent CANDU fuel in Canada, a safety assessment was performed for a hypothetical repository in the Canadian Shield. The assessment shows that such repository would meet international criteria for dose rate; however, uncertainties in the assumed evolution of the repository were identified. Such uncertainties could be resolved by the consideration of coupled Thermal-Hydro-Mechanical-Chemical (THMC) processes. In Task A of the DECOVALEX-THMC project, THM models were developed within the framework of the theory of poroelasticity. Such model development was performed in an iterative manner, using experimental data from laboratory and field tests. The models were used to perform near-field simulations of the evolution of the repository in order to address the above uncertainties. This paper presents the definition and rationale of task A and the results of the simulations. From a repository safety point of view, the simulations predict that the maximum temperature would be well below the design target of 100 C, however the load on the container can marginally exceed the design value of 15 MPa. However, the most important finding from the simulations is that a rock damage zone could form around the emplacement borehole. Such damage zone can extend a few metres from the walls of the emplacement holes, with permeability values that are orders of magnitude higher than the initial values. The damage zone has the potential to increase the radionuclide transport flux from the geosphere; the effect of such an increase should be taken into account in the safety assessment and mitigated if necessary by the provision of sealing systems.

  6. Plasmon-induced transparency in metamaterials: Active near field coupling between bright superconducting and dark metallic mode resonators

    NASA Astrophysics Data System (ADS)

    Cao, Wei; Singh, Ranjan; Zhang, Caihong; Han, Jiaguang; Tonouchi, Masayoshi; Zhang, Weili

    2013-09-01

    Structured plasmonic metamaterial devices offer the design flexibility to be size scaled for operation across the electromagnetic spectrum and are extremely attractive for generating electromagnetically induced transparency and slow-light behaviors via coupling of bright and dark subwavelength resonators. Here, we experimentally demonstrate a thermally active superconductor-metal coupled resonator based hybrid terahertz metamaterial on a sapphire substrate that shows tunable transparency and slow light behavior as the metamaterial chip is cooled below the high-temperature superconducting phase transition temperature. This hybrid metamaterial opens up the avenues for designing micro-sized active circuitry with switching, modulation, and "slowing down terahertz light" capabilities.

  7. Solute-solvent intermolecular vibronic coupling as manifested by the molecular near-field effect in resonance hyper-Raman scattering.

    PubMed

    Shimada, Rintaro; Hamaguchi, Hiro-o

    2011-01-21

    Vibronic coupling within the excited electronic manifold of the solute all-trans-β-carotene through the vibrational motions of the solvent cyclohexane is shown to manifest as the "molecular near-field effect," in which the solvent hyper-Raman bands are subject to marked intensity enhancements under the presence of all-trans-β-carotene. The resonance hyper-Raman excitation profiles of the enhanced solvent bands exhibit similar peaks to those of the solute bands in the wavenumber region of 21,700-25,000 cm(-1) (10,850-12,500 cm(-1) in the hyper-Raman exciting wavenumber), where the solute all-trans-β-carotene shows a strong absorption assigned to the 1A(g) → 1B(u) transition. This fact indicates that the solvent hyper-Raman bands gain their intensities through resonances with the electronic states of the solute. The observed excitation profiles are quantitatively analyzed and are successfully accounted for by an extended vibronic theory of resonance hyper-Raman scattering that incorporates the vibronic coupling within the excited electronic manifold of all-trans-β-carotene through the vibrational motions of cyclohexane. It is shown that the major resonance arises from the B-term (vibronic) coupling between the first excited vibrational level (v = 1) of the 1B(u) state and the ground vibrational level (v = 0) of a nearby A(g) state through ungerade vibrational modes of both the solute and the solvent molecules. The inversion symmetry of the solute all-trans-β-carotene is preserved, suggesting the weak perturbative nature of the solute-solvent interaction in the molecular near-field effect. The present study introduces a new concept, "intermolecular vibronic coupling," which may provide an experimentally accessible∕theoretically tractable model for understanding weak solute-solvent interactions in liquid.

  8. The Role of Turbulence in Chemical and Dynamical Processes in the Near-Field Wake of Subsonic Aircraft

    NASA Technical Reports Server (NTRS)

    Lewellen, D. C.; Lewellen, W. Steve

    2002-01-01

    During this grant, covering the period from September 1998 to December 2001, we continued the investigation of the role of turbulent mixing in the wake of subsonic aircraft initiated in 1994 for NASA's Atmospheric Effects of Aviation Project. The goal of the research has been to provide sufficient understanding and quantitative analytical capability to assess the dynamical, chemical, and microphysical interactions in the near-field wake that have the greatest potential to influence the global atmospheric impact of the projected fleet of subsonic aircraft. Through large-eddy simulations we have shown that turbulence in the early wake dynamics can have a strong effect on both the ice microphysics of contrail evolution and on wake chemistry. The wake vortex dynamics are the primary determinant of the vertical extent of the contrail; this together with the local wind shear largely determines the horizontal extent. The fraction of the initial ice crystals surviving the wake vortex dynamics, their spatial distribution, and the ice mass distribution are all sensitive to the aircraft type, assumed initial ice crystal number, and ambient humidity and turbulence conditions. Our model indicates that there is a significant range of conditions for which a smaller aircraft such as a B737 produces as significant a persistent contrail as a larger aircraft such as a B747, even though the latter consumes almost five times as much fuel. Large-eddy simulations of the near wake of a B757 provided a fine-grained chemical-dynamical representation of simplified NOx - HOx chemistry in wakes of ages from a few seconds to several minutes. By sampling the simulated data in a manner similar to that of in situ aircraft measurements it was possible to provide a likely explanation for a puzzle uncovered in the 1996 SUCCESS flight measurements of OH and HO2 The results illustrate the importance of considering fluid dynamics effects in interpreting chemistry results when mixing rates and species

  9. Coupled field analysis of heat flow in the near field of a microwave applicator for tumor ablation.

    PubMed

    Hardie, Donald; Sangster, Alan J; Cronin, Nigel J

    2006-01-01

    Microwave tumor ablation (MTA) offers a new approach for the treatment of hepatic neoplastic disease. Reliable and accurate information regarding the heat distribution inside biological tissue subjected to microwave thermal ablation is important for the efficient design of microwave applicators and for optimizing experiments, which aim to assess the effects of therapeutic treatments. Currently there are a variety of computational methods based on different vascular structures in tissue, which aim to model heat distribution during ablation. This paper presents results obtained from two such computational models for temperature distributions produced by a clinical 2.45 GHz MTA applicator immersed in unperfused ex vivo bovine liver, and compares them with measured results from a corresponding ex vivo experiment. The computational methods used to model the temperature distribution in tissue caused by the insertion of a 5.6 mm diameter "wandlike" microwave applicator are the Green's function method and the finite element method (FEM), both of which provide solutions of the heat diffusion partial differential equation. The results obtained from the coupled field simulations are shown to be in good agreement with a simplified analysis based on the bio-heat equation and with ex vivo measurements of the heat distribution produced by the clinical MTA applicator.

  10. Communication: Dynamical embedding: Correct quantum response from coupling TDDFT for a small cluster with classical near-field electrodynamics for an extended region

    SciTech Connect

    Gao Yi; Neuhauser, Daniel

    2013-05-14

    We show how to obtain the correct electronic response of a large system by embedding; a small region is propagated by TDDFT (time-dependent density functional theory) simultaneously with a classical electrodynamics evolution using the Near-Field method over a larger external region. The propagations are coupled through a combined time-dependent density yielding a common Coulomb potential. We show that the embedding correctly describes the plasmonic response of a Mg(0001) slab and its influence on the dynamical charge transfer between an adsorbed H{sub 2}O molecule and the substrate, giving the same spectral shape as full TDDFT (similar plasmon peak and molecular-dependent differential spectra) with much less computational effort. The results demonstrate that atomistic embedding electrodynamics is promising for nanoplasmonics and nanopolaritonics.

  11. Communication: dynamical embedding: correct quantum response from coupling TDDFT for a small cluster with classical near-field electrodynamics for an extended region.

    PubMed

    Gao, Yi; Neuhauser, Daniel

    2013-05-14

    We show how to obtain the correct electronic response of a large system by embedding; a small region is propagated by TDDFT (time-dependent density functional theory) simultaneously with a classical electrodynamics evolution using the Near-Field method over a larger external region. The propagations are coupled through a combined time-dependent density yielding a common Coulomb potential. We show that the embedding correctly describes the plasmonic response of a Mg(0001) slab and its influence on the dynamical charge transfer between an adsorbed H2O molecule and the substrate, giving the same spectral shape as full TDDFT (similar plasmon peak and molecular-dependent differential spectra) with much less computational effort. The results demonstrate that atomistic embedding electrodynamics is promising for nanoplasmonics and nanopolaritonics.

  12. Robust multispectral transparency in continuous metal film structures via multiple near-field plasmon coupling by a finite-difference time-domain method.

    PubMed

    Liu, Gui-qiang; Hu, Ying; Liu, Zheng-qi; Chen, Yuan-hao; Cai, Zheng-jie; Zhang, Xiang-nan; Huang, Kuan

    2014-03-07

    We propose a robust multispectral transparent plasmonic structure and calculate its transparency response by using the three-dimensional finite-difference time-domain (FDTD) method. The proposed structure is composed of a continuous ultrathin metal film sandwiched by double two-dimensional (2D) hexagonal non-close-packed metal-dielectric multilayer core-shell nanoparticle arrays. The top and bottom plasmonic arrays in such a structure, respectively, act as the light input and output couplers to carry out the efficient trapping and release of light. Near-perfect multispectral optical transparency in the visible and near-infrared regions is achieved theoretically. The calculated electric field distribution patterns show that the near-perfect multispectral optical transparency mainly originates from the excitation and hybridization of shell and core plasmon modes, strong near-field coupling of dipole plasmon modes between adjacent nanoparticles as well as the excitation of surface plasmon waves of the metal film. The robust transparency bands can be efficiently tuned in a large range by varying the structural parameters and the surrounding dielectric environment. The proposed structure also shows additional merits such as a deep sub-wavelength size and fully retained electrical and mechanical properties of the natural metal. These features might provide promising applications in highly integrated optoelectronic devices including plasmonic filters, nanoscale multiplexers, and non-linear optics.

  13. Near-field magnetoabsorption of quantum dots

    NASA Astrophysics Data System (ADS)

    Simserides, Constantinos; Zora, Anna; Triberis, Georgios

    2006-04-01

    We investigate the effect of an external magnetic field of variable orientation and magnitude (up to 20T ) on the linear near-field optical absorption spectra of single and coupled III-V semiconductor quantum dots. We focus on the spatial as well as on the magnetic confinement, varying the dimensions of the quantum dots and the magnetic field. We show that the ground-state exciton binding energy can be manipulated utilizing the spatial and magnetic confinement. The effect of the magnetic field on the absorption spectra, increasing the near-field illumination spot, is also investigated. The zero-magnetic-field “structural” symmetry can be destroyed varying the magnetic field orientation and this affects the near-field spectra. The asymmetry induced (except for specific orientations along symmetry axes) by the magnetic field can be revealed in the near-field but not in the far-field spectra. We predict that near-field magnetoabsorption experiments, of realistic spatial resolution, will be in the position to bring to light the quantum dot symmetry. This exceptional symmetry-resolving power of the near-field magnetoabsorption is lost in the far field. The influence of the Coulomb interactions on the absorption spectra is also discussed. Finally, we show that certain modifications of the magnetoexcitonic structure can be uncovered using a realistically acute near-field probe of ≈20nm .

  14. Evaluation of a highly nonlinear microstructured optical fiber by near-field scanning optical microscopy and simulations: nonlinear coefficient and coupling losses

    NASA Astrophysics Data System (ADS)

    Moison, J. M.; Apetrei, A. M.; Levenson, J. A.; Mélin, G.; Lempereur, S.; Fleureau, A.; Bourov, E.; Gasca, L.

    2005-01-01

    We report on the evaluation of a microstructured optical fiber (MOF) designed for non-linear signal processing applications, i.e., with a very small guided mode (waist ˜1 μm). Calculations predict an intrinsic (assuming propagation in the fundamental mode and zero-loss coupling) non-linear γ coefficient of 40 W-1 km-1 at λ=1.55 μm, but they also predict a basic multimode character. NSOM measurements validate directly the high intrinsic γ value (32±10 W-1 km-1) and also show that with an optimized coupling, the overall losses in efficiency taking into account coupling losses and weak excitation of higher-order modes and leaky modes are only 2.5 dB. This performance is adequate for use in all-optical data processing lines, all the more since it is maintained for relevant propagation lengths and peak power densities.

  15. Study on the near-field recording spot

    NASA Astrophysics Data System (ADS)

    Pei, Xiandeng; Xia, You-xin; Huang, Hao; Xie, Changsheng; Wang, Haiwei

    2003-04-01

    Evanescent energy can be used to get extremely small optical spots. For the data storage applications, optical near field is defined in terms of Evanescent coupling between the system used to read or write data and recording layer. Near-field techniques can be applied to optical data storage systems to greatly increase recording density. So near-field recording technique has great potential in optical disc recording system and hybrid recording system. The characteristic of near-field recording spot is of vital importance in the data storage system basing the near-field theory, so it is absolutely necessary to be analyzed and measured. This paper analyses characteristic of near-field spots. The heat response time of the near field to overcome super paramagnetic effect is calculated basing the heat transfer theory. A novel measuring method for the diameter of near-field recording spot is also presented. Since the grain of the recording media is tiny enough, with the aid of atomic force microscope (AFM), near-field optical lithography can be accomplished. The diameter of near-field recording spot can be obtained by specifically designed computer either. So the relationship between the near-field recording spot diameter and the probe size of near-field recording system, the near field recording distance coupling between head and disc can be got.

  16. Nanofabrication using near-field optical probes

    PubMed Central

    McLeod, Euan; Ozcan, Aydogan

    2012-01-01

    Nanofabrication using near-field optical probes is an established technique for rapid prototyping and automated maskless fabrication of nanostructured devices. In this review, we present the primary types of near-field probes and their physical processing mechanisms. Highlights of recent developments include improved resolution by optimizing the probe shape, incorporation of surface plasmonics in probe design, broader use in biological and magnetic storage applications, and increased throughput using probe arrays as well as high speed writing and patterning. PMID:22713756

  17. DECOVALEX-THMC Task D: Long-Term Permeability/Porosity Changes inthe EDZ and Near Field due to THM and THC Processes in Volcanic andCrystaline-Bentonite Systems, Status Report October 2005

    SciTech Connect

    Birkholzer, J.; Rutqvist, J.; Sonnenthal, E.; Barr, D.

    2005-11-01

    The DECOVALEX project is an international cooperativeproject initiated by SKI, the Swedish Nuclear Power Inspectorate, withparticipation of about 10 international organizations. The name DECOVALEXstands for DEvelopment of COupled models and their VALidation againstExperiments. The general goal of this project is to encouragemultidisciplinary interactive and cooperative research on modelingcoupled processes in geologic formations in support of the performanceassessment for underground storage of radioactive waste. Three multi-yearproject stages of DECOVALEX have been completed in the past decade,mainly focusing on coupled thermal-hydrological-mechanicalprocesses.Currently, a fourth three-year project stage of DECOVALEX isunder way, referred to as DECOVALEX-THMC. THMC stands for Thermal,Hydrological, Mechanical, and Chemical processes. The new project stageaims at expanding the traditional geomechanical scope of the previousDECOVALEX project stages by incorporating geochemical processes importantfor repository performance. The U.S. Department of Energy (DOE) leadsTask D of the new DECOVALEX phase, entitled "Long-termPermeability/Porosity Changes in the EDZ and Near Field due to THC andTHM Processes for Volcanic and Crystalline-Bentonite Systems." In itsleadership role for Task D, DOE coordinates and sets the direction forthe cooperative research activities of the international research teamsengaged in Task D.

  18. Abstraction of Drift-Scale Coupled Processes

    SciTech Connect

    N.D. Francis; D. Sassani

    2000-03-31

    This Analysis/Model Report (AMR) describes an abstraction, for the performance assessment total system model, of the near-field host rock water chemistry and gas-phase composition. It also provides an abstracted process model analysis of potentially important differences in the thermal hydrologic (TH) variables used to describe the performance of a geologic repository obtained from models that include fully coupled reactive transport with thermal hydrology and those that include thermal hydrology alone. Specifically, the motivation of the process-level model comparison between fully coupled thermal-hydrologic-chemical (THC) and thermal-hydrologic-only (TH-only) is to provide the necessary justification as to why the in-drift thermodynamic environment and the near-field host rock percolation flux, the essential TH variables used to describe the performance of a geologic repository, can be obtained using a TH-only model and applied directly into a TSPA abstraction without recourse to a fully coupled reactive transport model. Abstraction as used in the context of this AMR refers to an extraction of essential data or information from the process-level model. The abstraction analysis reproduces and bounds the results of the underlying detailed process-level model. The primary purpose of this AMR is to abstract the results of the fully-coupled, THC model (CRWMS M&O 2000a) for effects on water and gas-phase composition adjacent to the drift wall (in the near-field host rock). It is assumed that drift wall fracture water and gas compositions may enter the emplacement drift before, during, and after the heating period. The heating period includes both the preclosure, in which the repository drifts are ventilated, and the postclosure periods, with backfill and drip shield emplacement at the time of repository closure. Although the preclosure period (50 years) is included in the process models, the postclosure performance assessment starts at the end of this initial period

  19. Novel concepts in near-field optics: from magnetic near-field to optical forces

    NASA Astrophysics Data System (ADS)

    Yang, Honghua

    near-field response of a linear rod antenna is studied with Babinet's principle. Babinet's principle connects the magnetic field of a structure to the electric field of its complement structure. Using combined far- and near-field spectroscopy, imaging, and theory, I identify magnetic dipole and higher order bright and dark magnetic resonances at mid-infrared frequencies. From resonant length scaling and spatial field distributions, I confirm that the theoretical requirement of Babinet's principle for a structure to be infinitely thin and perfectly conducting is still fulfilled to a good approximation in the mid-infrared. Thus Babinet's principle provides access to spatial and spectral magnetic field properties, leading to targeted design and control of magnetic optical antennas. Lastly, a novel form of nanoscale optical spectroscopy based on mechanical detection of optical gradient force is explored. It is to measure the optical gradient force between induced dipole moments of a sample and an atomic force microscope (AFM) tip. My study provides the theoretical basis in terms of spectral behavior, resonant enhancement, and distance dependence of the optical gradient force from numerical simulations for a coupled nanoparticle model geometry. I show that the optical gradient force is dispersive for local electronic and vibrational resonances, yet can be absorptive for collective polaronic excitations. This spectral behavior together with the distance dependence scaling provides the key characteristics for its measurement and distinction from competing processes such as thermal expansion. Furthermore, I provide a perspective for resonant enhancement and control of optical forces in general.

  20. Ultrafast infrared near-field molecular nano-spectroscopy

    NASA Astrophysics Data System (ADS)

    Xu, Xiaoji; Craig, Ian M.; Rang, Matthias; Raschke, Markus B.

    2013-03-01

    We demonstrate molecular radiative infrared vibrational free-induction decay on the nano-scale and its control via near-field coupling between the transient molecular polarization and optical antenna properties of the metallic scanning near-field probe tip. This allows for pushing the sensitivity of infrared vibrational spectroscopy into the single molecule regime.

  1. Near Field Antenna Measurement System.

    DTIC Science & Technology

    1982-03-01

    beam pointing accuracy and .6 dB gain accuracy. These antennas are both planar arrays with the X-band antenna scanning with ferrite phase shifters in...AD-A114 125 M[ES AIRCRAFT CO FULLERTON CA F/ 17/9 NEAR FIELD ANTENNA MEASUREMENT SYSTEM. (U) MAR 82 A E HOLLEY DAABO7-7?-C-1 87 UNCLASSIFIED NL...IllIHE El. onhEnoh IIIIhh --h h I~m I I Research and Development Technical Report I DAABO7-77-C-0587-F1 NEAR FIELD ANTENNA I MEASUREMENT SYSTEM I A.E

  2. A near-field optical microscopy nanoarray

    SciTech Connect

    Semin, D.J.; Ambrose, W.P.; Goodwin, P.M.; Kwller, A.; Wendt, J.R.

    1996-12-31

    Multiplexing near-field scanning optical microscopy (NSOM) by the use of a nanoarray with parallel imaging is studied. The fabrication, characterization, and utilization of nanoarrays with {approximately} 100 nm diameter apertures spaced 500 nm center-to- center is presented. Extremely uniform nanoarrays with {approximately} 10{sup 8} apertures were fabricated by electron beam lithography and reactive ion etching. The nanoarrays were characterized by atomic force microscopy (AFM) and scanning electron microscopy (SEM). In this paper we utilize these nanoarrays in a laser-illuminated microscope with parallel detection on a charge- coupled device (CCD). Detection of B-phycoerythrin (B-PE) molecules using near-field illumination is presented. In principle, our system can be used to obtain high lateral resolution NSOM images over a wide-field of view (e.g. 50-100 {mu}m) within seconds.

  3. Antenna Near-Field Probe Station Scanner

    NASA Technical Reports Server (NTRS)

    Zaman, Afroz J. (Inventor); Lee, Richard Q. (Inventor); Darby, William G. (Inventor); Barr, Philip J. (Inventor); Lambert, Kevin M (Inventor); Miranda, Felix A. (Inventor)

    2011-01-01

    A miniaturized antenna system is characterized non-destructively through the use of a scanner that measures its near-field radiated power performance. When taking measurements, the scanner can be moved linearly along the x, y and z axis, as well as rotationally relative to the antenna. The data obtained from the characterization are processed to determine the far-field properties of the system and to optimize the system. Each antenna is excited using a probe station system while a scanning probe scans the space above the antenna to measure the near field signals. Upon completion of the scan, the near-field patterns are transformed into far-field patterns. Along with taking data, this system also allows for extensive graphing and analysis of both the near-field and far-field data. The details of the probe station as well as the procedures for setting up a test, conducting a test, and analyzing the resulting data are also described.

  4. Near-field/altered-zone models report

    SciTech Connect

    Hardin, E. L., LLNL

    1998-03-01

    lithophysal units. These units are made up of moderately to densely welded, devitrified, fractured tuff. The rock's chemical composition is comparable to that of typical granite, but has textural features and mineralogical characteristics of large-scale, silicic volcanism. Because the repository horizon will be approximately 300 m below the ground surface and 200 m above the water table, the repository will be partially saturated. The welded tuff matrix in the host units is highly impermeable, but water and gas flow readily through fractures. The degree of fracturing in these units is highly variable, and the hydrologic significance of fracturing is an important aspect of site investigation. This report describes the characterization and modeling of a region around the potential repository--the altered zone--a region in which the temperature will be increased significantly by waste-generated heat. Numerical simulation has shown that, depending on the boundary conditions, rock properties, and repository design features incorporated in the models, the altered zone (AZ) may extend from the water table to the ground surface. This report also describes models of the near field, the region comprising the repository emplacement drifts and the surrounding rock, which are critical to the performance of engineered components. Investigations of near-field and altered-zone (NF/AZ) processes support the design of underground repository facilities and engineered barriers and also provide constraint data for probabilistic calculations of waste-isolation performance (i.e., performance assessment). The approach to investigation, which is an iterative process involving hypothesis testing and experimentation, has relied on conceptualizing engineered barriers and on performance analysis. This report is a collection, emphasizing conceptual and numerical models, of the recent results contributed from studies of NF/AZ processes and of quantitative measures of NF/AZ performance. The selection and

  5. Near-Field Based Communication and Electrical Systems

    NASA Astrophysics Data System (ADS)

    Azad, Umar

    A near-field power transfer equation for an inductively coupled near-field system is derived based on the equivalent circuit model of the coupled resonant loops. Experimental results show that the proposed near-field coupling equation is trustworthy as it correctly predicts the transferred power versus distance relationship for different values of loaded quality factors at the transmitter and the receiver. Capacity performance of near-field communication (NFC) links is analyzed for noise limited and interference limited scenarios based on information theory. The analytical results provide guidelines for design of inductively coupled antenna systems as the power and capacity budget of the link is carried out. Examples of inductively coupled VLF NFC links are evaluated for different operating scenarios, demonstrating the efficacy and importance of the proposed near-field link budget. However, in a conventional setup of inductively coupled NFC link, the power coupled through and the bandwidth must be traded off. Direct Antenna Modulation (DAM) is a feasible scheme to break this dilemma. With DAM utilized in NFC link, the power and bandwidth product limit in a high Q system can be circumvented because the non-linear/time-varying nature of the operation allows high speed modulations decoupled from the charging and discharging process of the high-Q resonator. In this work, the theory of NFC link with DAM on the transmitter is presented and validated with an experimental setup. Improvement in reception of the high-speed modulation information is observed in the experiment, implying that a superior capacity performance of a NFC link is achieved through DAM versus the traditional scheme. The resonant coupling efficiency is limited by the product of the quality factors Q, of the transmitter and receiver and the coupling coefficient k. We observe that in order to achieve maximum efficiency, the ratio of the load-to-loss impedances at both the source and load should be equal

  6. Radiation Entropy and Near-Field Thermophotovoltaics

    NASA Astrophysics Data System (ADS)

    Zhang, Zhuomin M.

    2008-08-01

    Radiation entropy was key to the original derivation of Planck's law of blackbody radiation, in 1900. This discovery opened the door to quantum mechanical theory and Planck was awarded the Nobel Prize in Physics in 1918. Thermal radiation plays an important role in incandescent lamps, solar energy utilization, temperature measurements, materials processing, remote sensing for astronomy and space exploration, combustion and furnace design, food processing, cryogenic engineering, as well as numerous agricultural, health, and military applications. While Planck's law has been fruitfully applied to a large number of engineering problems for over 100 years, questions have been raised about its limitation in micro/nano systems, especially at subwavelength distances or in the near field. When two objects are located closer than the characteristic wavelength, wave interference and photon tunneling occurs that can result in significant enhancement of the radiative transfer. Recent studies have shown that the near-field effects can realize emerging technologies, such as superlens, sub-wavelength light source, polariton-assisted nanolithography, thermophotovoltaic (TPV) systems, scanning tunneling thermal microscopy, etc. The concept of entropy has also been applied to explain laser cooling of solids as well as the second law efficiency of devices that utilize thermal radiation to produce electricity. However, little is known as regards the nature of entropy in near-field radiation. Some history and recent advances are reviewed in this presentation with a call for research of radiation entropy in the near field, due to the important applications in the optimization of thermophotovoltaic converters and in the design of practical systems that can harvest photon energies efficiently.

  7. Nanomanipulation using near field photonics.

    PubMed

    Erickson, David; Serey, Xavier; Chen, Yih-Fan; Mandal, Sudeep

    2011-03-21

    In this article we review the use of near-field photonics for trapping, transport and handling of nanomaterials. While the advantages of traditional optical tweezing are well known at the microscale, direct application of these techniques to the handling of nanoscale materials has proven difficult due to unfavourable scaling of the fundamental physics. Recently a number of research groups have demonstrated how the evanescent fields surrounding photonic structures like photonic waveguides, optical resonators, and plasmonic nanoparticles can be used to greatly enhance optical forces. Here, we introduce some of the most common implementations of these techniques, focusing on those which have relevance to microfluidic or optofluidic applications. Since the field is still relatively nascent, we spend much of the article laying out the fundamental and practical advantages that near field optical manipulation offers over both traditional optical tweezing and other particle handling techniques. In addition we highlight three application areas where these techniques namely could be of interest to the lab-on-a-chip community, namely: single molecule analysis, nanoassembly, and optical chromatography.

  8. Near-field single molecule spectroscopy

    SciTech Connect

    Xie, X.S.; Dunn, R.C.

    1995-02-01

    The high spatial resolution and sensitivity of near-field fluorescence microscopy allows one to study spectroscopic and dynamical properties of individual molecules at room temperature. Time-resolved experiments which probe the dynamical behavior of single molecules are discussed. Ground rules for applying near-field spectroscopy and the effect of the aluminum coated near-field probe on spectroscopic measurements are presented.

  9. NASA-JSC antenna near-field measurement system

    NASA Technical Reports Server (NTRS)

    Cooke, W. P.; Friederich, P. G.; Jenkins, B. M.; Jameson, C. R.; Estrada, J. P.

    1988-01-01

    Work was completed on the near-field range control software. The capabilities of the data processing software were expanded with the addition of probe compensation. In addition, the user can process the measured data from the same computer terminal used for range control. The design of the laser metrology system was completed. It provides precise measruement of probe location during near-field measurements as well as position data for control of the translation beam and probe cart. A near-field range measurement system was designed, fabricated, and tested.

  10. Report of near field group

    SciTech Connect

    Palmer, R.B.; Baggett, N.; Claus, J.; Fernow, R.; Stumer, I.; Figueroa, H.; Kroll, N.; Funk, W.; Lee-Whiting, G.; Pickup, M.

    1985-04-01

    Substantial progress since the Los Alamos Workshop two years ago is reported. A radio-frequency model of a grating accelerator has been tested at Cornell, and extensive calculations compared with observations. Alternative structures consisting of either hemispherical bumps on a plane, or conducting spheres in space, have also been rf modeled. The use of liquid droplets to form such structures has been proposed and a conceptual design studied. Calculations and experiments have examined the effects of surface plasmas, and shown that in this case the reflectivity is low. However, calculations and observations suggest that gradients in excess of 1 GeV/meter should be obtainable without forming such plasma. An examination of wake fields shows that, with Landau damping, these are independent of wavelength. The use of near field structures to act as high gradient focusing elements has been studied and shows promise, independent of the acceleration mechanism. A proposal has been made to establish a facility that would enable ''proof of principle experiments'' to be performed on these and other laser driven accelerator mechanisms. 11 refs., 10 figs.

  11. Near field zones of quiet

    NASA Astrophysics Data System (ADS)

    Joseph, P.; Elliott, S. J.; Nelson, P. A.

    1994-05-01

    This paper examines the consequences of driving a single secondary loudspeaker to cancel the pressure due to some primary source at a point in its near field. This simple technique has been applied to the sound field in a highly reverberant room to produce zones of quiet in the vicinity of the loudspeaker, which have diameters that are typically equal to one-tenth of the acoustic wavelength, within which the sound pressure level is attenuated by at least 10 dB. The principal advantage gained with this strategy over other active techniques for controlling the sound field in rooms is that the sound pressure level well away from the control point is largely unaffected, an increase of only a small fraction of one dB being typical. Such a loudspeaker-microphone configuration could be located, for example, in the head rests of cars or aeroplanes, or indeed anywhere where the listener is seated for significant lengths of time and subjected to high ambient noise levels such that auditory comfort may be disturbed.

  12. Near-field Approaches to Subcellular Tissue Abalation

    NASA Astrophysics Data System (ADS)

    Raghu, Deepa; Hoffmann, Joan; Gamari, Benjamin; Gomella, Andrew; Reeves, Mark

    2011-03-01

    We report on the development of a near-field approach to MALDI (Matrix-assisted laser desorption and Ionization). In this technique analytes embedded in an energy- absorbing matrix are ablated from the surface of a sample. In the infrared region, the matrix can be water by exciting the 3-micron vibrational mode of the water molecule. We use a 3-micron wavelength lasers, coupled with a near-field scanning microscope to ablate material from cells of different membrane stiffness. We have been able to reproducibly ablate features as small as 1 micron in diameter in cell and have characterized the power-dependence of the ablation process. We will review our findings and describe demonstrations of tissue modification by this approach at length scales smaller than a single cell. This approach has the potential to allow the identification and mapping of proteins expressed in intact cells and tissues, which is of great interest as protein expression connects genomic information with the functioning of an organism.

  13. Tailoring the Electromagnetic Near Field with Patterned Surfaces: Near-Field Plates

    DTIC Science & Technology

    2014-12-10

    single layer processing. 3 Near-field plates can be viewed as metamaterial surfaces ( metasurfaces or metafilms) [20]. They are textured/structured at a...Applied Physics Letters, vol. 103, 041104, July 2013. 3. C. Pfeiffer and A. Grbic, ”Cascaded metasurfaces for complete phase and polarization control...Antennas and Propagation, pp. 1-2, Memphis, TN, July 6-12, 2014. 5. Pfeiffer and A. Grbic, ”Analysis and synthesis of bianisotropic metasurfaces

  14. Tip size dependence of passive near-field microscopy.

    PubMed

    Lin, Kuan-Ting; Komiyama, Susumu; Kajihara, Yusuke

    2016-02-01

    We improve the spatial resolution and investigate the tip-sample coupling in a passive scattering-type scanning near-field optical microscope (s-SNOM), which probes thermally excited surface waves without any external light source. We study the spatial resolution, the intensity, and the decay behavior of the thermally excited near-field signals with different radii of curvatures of tungsten-tip apexes. We also study the tip size dependence of the interference pattern in the far-field region. The spatial resolution is closely related to the tip size, but the decay behavior of the near field is unrelated. These results suggest that the strength of the tip-sample coupling is unrelated to the tip size in the passive s-SNOM. We propose a theoretical model able to interpret the experimental data for the passive s-SNOM.

  15. Near-field optics: The nightmare of the photon

    NASA Astrophysics Data System (ADS)

    Keller, Ole

    2000-05-01

    A first-quantized theory describing the birth process of a single photon in the near-field zone of a pointlike particle (atom, molecule, etc.) is established. The space-time description of the photon energy wave function embryo is shown to be useful for the understanding of the role played by (unborn) photons in near-field interactions where the spatial confinement of light plays a crucial role.

  16. Spectral frustration and coherence in thermal near-field spectroscopy

    NASA Astrophysics Data System (ADS)

    O'Callahan, Brian; Lewis, William; Jones, Andrew; Raschke, Markus

    2014-03-01

    The thermal near-field is characterized by fundamentally distinct spatial, spectral, and coherence properties compared to far-field thermal radiation. Scattering scanning near-field microscopy (s-SNOM) has recently opened spectroscopic access to the enhanced electromagnetic local density of states associated with electronic and vibrational resonances. We study the influence of the tip on the scattered near-field spectral response due to the frustration of the evanescent thermal field by the tip. With the example of the extrinsic resonance of the surface phonon polariton (SPhP) in SiC we demonstrate redshifts by 0 cm-1 to 50 cm-1 of the unperturbed 948 cm-1 resonance. We model the behavior as a result of tip-sample coupling or effective medium change due to the presence of the tip. We show that the effect is most significant for momentum dependent and strongly dispersive resonances. In addition, distance dependence measurements demonstrate a competition between scattering of the near-field associated with the thermally driven stochastically fluctuating optical polarization and that of the spatially coherent SPhP which is excited. The results indicate the possibility for local tuning of SPhP resonant conditions via evanescent thermal near-field coupling.

  17. Optical branching effect in Ti:LiNbO3 waveguides: near-field pattern studies.

    PubMed

    Jerominek, H; Delisle, C; Tremblay, R

    1986-03-01

    The paper presents a detailed study of a single optical beam splitting into several beams (the branching effect) in photorefractive sensitive Ti:LiNbO3 optical slab waveguides. The near-field patterns of the multibeam structures are presented for different values of optical power coupled into TE guided modes of different orders. The process of partial recovery of the optically damaged waveguide (the partial shrinking of the multibeam bundle created) is also described.

  18. Optical Near-Field Plates

    DTIC Science & Technology

    2015-04-08

    nanostructures was studied theoretically and experimentally. We introduced a model of an aperture coupled to an oscillator that gives perfect ...subwavelength scales, and it is be- lieved to be responsible for the nearly perfect ab- sorption of periodic metallic nanoslit structures. However, an...much attention, FIG. 10. Funneling in circular nanogroves fabricated in Au films. 7 | P a g e motivated by claims that it provides perfect imaging

  19. Signal of microstrip scanning near-field optical microscope in far- and near-field zones.

    PubMed

    Morozov, Yevhenii M; Lapchuk, Anatoliy S

    2016-05-01

    An analytical model of interference between an electromagnetic field of fundamental quasi-TM(EH)00-mode and an electromagnetic field of background radiation at the apex of a near-field probe based on an optical plasmon microstrip line (microstrip probe) has been proposed. The condition of the occurrence of electromagnetic energy reverse flux at the apex of the microstrip probe was obtained. It has been shown that the nature of the interference depends on the length of the probe. Numerical simulation of the sample scanning process was conducted in illumination-reflection and illumination-collection modes. Results of numerical simulation have shown that interference affects the scanning signal in both modes. However, in illumination-collection mode (pure near-field mode), the signal shape and its polarity are practically insensible to probe length change; only signal amplitude (contrast) is slightly changed. However, changing the probe length strongly affects the signal amplitude and shape in the illumination-reflection mode (the signal formed in the far-field zone). Thus, we can conclude that even small background radiation can significantly influence the signal in the far-field zone and has practically no influence on a pure near-field signal.

  20. Collective near-field thermal emission from polaritonic nanoparticle arrays

    NASA Astrophysics Data System (ADS)

    Tervo, Eric; Zhang, Zhuomin; Cola, Baratunde

    2017-06-01

    The spectral characteristics of near-field thermal emission from nanoparticle arrays are explained by comparison to the dispersions for propagating modes. Using the coupled dipole model, we analytically calculate the spectral emission from single particles, chains, planes, and three-dimensional arrays of Si O2 and SiC. We show that the differences in their spectra are due to the existence or absence of propagating surface phonon polariton modes and that the emission is dominated by these modes when they are present. This work paves the way for understanding and control of near-field radiation in nanofluids, nanoparticle beds, and certain metamaterials.

  1. Near Field Communication: Introduction and Implications

    ERIC Educational Resources Information Center

    McHugh, Sheli; Yarmey, Kristen

    2012-01-01

    Near field communication is an emerging technology that allows objects, such as mobile phones, computers, tags, or posters, to exchange information wirelessly across a small distance. Though primarily associated with mobile payment, near field communication has many different potential commercial applications, ranging from marketing to nutrition,…

  2. Near Field Communication: Introduction and Implications

    ERIC Educational Resources Information Center

    McHugh, Sheli; Yarmey, Kristen

    2012-01-01

    Near field communication is an emerging technology that allows objects, such as mobile phones, computers, tags, or posters, to exchange information wirelessly across a small distance. Though primarily associated with mobile payment, near field communication has many different potential commercial applications, ranging from marketing to nutrition,…

  3. Terahertz diffraction enhanced transparency probed in the near field

    NASA Astrophysics Data System (ADS)

    Halpin, Alexei; van Hoof, Niels; Bhattacharya, Arkabrata; Mennes, Christiaan; Gomez Rivas, Jaime

    2017-08-01

    Electromagnetically induced transparency in metamaterials allows to engineer structures which transmit narrow spectral ranges of radiation while exhibiting a large group index. Implementation of this phenomenon frequently calls for strong near-field coupling of bright (dipolar) resonances to dark (multipolar) resonances in the metamolecules comprising the metamaterials. The sharpness and contrast of the resulting transparency windows thus depends strongly on how closely these metamolecules can be placed to one another, placing constraints on fabrication capabilities. In this manuscript, we demonstrate that the reliance on near-field interaction strength can be relaxed, and the magnitude of the electromagnetic-induced transparency enhanced, by exploiting the long-range coupling between metamolecules in periodic lattices. By placing dolmen structures resonant at THz frequencies in a periodic lattice, we show a significant increase of the transparency window when the in-plane diffraction is tuned to the resonant frequency of the metamolecules, as confirmed by direct mapping of the THz near-field amplitude across a lattice of dolmens. Through the direct interrogation of the dark resonance in the near field, we show the interplay of near- and far-field couplings in optimizing the response of planar dolmen arrays via diffraction-enhanced transparency.

  4. Source Rupture Process for the February 21, 2011, Mw6.1, New Zealand Earthquake and the Characteristics of Near-field Strong Ground Motion

    NASA Astrophysics Data System (ADS)

    Meng, L.; Shi, B.

    2011-12-01

    time duration to the observations, especially for the vertical component. Synthetics Fourier spectra are reasonably similar to the recordings. The simulated PGA values of vertical and S26W components are consistent with the recorded, and for the S64E component, the PGA derived from our simulation is smaller than that from observation. The resultant Fourier spectra both for the synthetic and observation is much similar with each other for three components of acceleration time histories, except for the vertical component, where the derived spectra from synthetic data is smaller than that resultant from observation when the frequency is above 10 Hz. Both theoretical study and numerical simulation indicate that, for the 2011 Mw 6.1, New Zealand Earthquake, the higher dynamic stress drop during the source rupture process could play an important role to the anomalous ground-motion amplification beside to the other site-related seismic effects. The composite source modeling based on the simple Brune's pulse model could approximately provide us a good insight into earthquake source related rupture processes for a moderate-sized earthquake.

  5. Attosecond nanoscale near-field sampling

    SciTech Connect

    Forg, B.; Schotz, J.; SuBmann, F.; Forster, M.; Kruger, M.; Ahn, B.; Okell, W. A.; Wintersperger, K.; Zherebtsov, S.; Guggenmos, A.; Pervak, V.; Kessel, A.; Trushin, S. A.; Azzeer, A. M.; Stockman, M. I.; Kim, D.; Krausz, F.; Hommelhoff, P.; Kling, M. F.

    2016-05-31

    The promise of ultrafast light-field-driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite for advancing this new area is the ability to characterize optical near fields from light interaction with nanostructures, with sub-cycle resolution. Here we experimentally demonstrate attosecond near-field retrieval for a tapered gold nanowire. Furthermore, by comparison of the results to those obtained from noble gas experiments and trajectory simulations, the spectral response of the nanotaper near field arising from laser excitation can be extracted.

  6. Attosecond nanoscale near-field sampling

    PubMed Central

    Förg, B.; Schötz, J.; Süßmann, F.; Förster, M.; Krüger, M.; Ahn, B.; Okell, W. A.; Wintersperger, K.; Zherebtsov, S.; Guggenmos, A.; Pervak, V.; Kessel, A.; Trushin, S. A.; Azzeer, A. M.; Stockman, M. I.; Kim, D.; Krausz, F.; Hommelhoff, P.; Kling, M. F.

    2016-01-01

    The promise of ultrafast light-field-driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite for advancing this new area is the ability to characterize optical near fields from light interaction with nanostructures, with sub-cycle resolution. Here we experimentally demonstrate attosecond near-field retrieval for a tapered gold nanowire. By comparison of the results to those obtained from noble gas experiments and trajectory simulations, the spectral response of the nanotaper near field arising from laser excitation can be extracted. PMID:27241851

  7. Attosecond nanoscale near-field sampling

    DOE PAGES

    Forg, B.; Schotz, J.; SuBmann, F.; ...

    2016-05-31

    The promise of ultrafast light-field-driven electronic nanocircuits has stimulated the development of the new research field of attosecond nanophysics. An essential prerequisite for advancing this new area is the ability to characterize optical near fields from light interaction with nanostructures, with sub-cycle resolution. Here we experimentally demonstrate attosecond near-field retrieval for a tapered gold nanowire. Furthermore, by comparison of the results to those obtained from noble gas experiments and trajectory simulations, the spectral response of the nanotaper near field arising from laser excitation can be extracted.

  8. Drift-Scale Coupled Processes (DST and THC Seepage) Models

    SciTech Connect

    E. Gonnenthal; N. Spyoher

    2001-02-05

    The purpose of this Analysis/Model Report (AMR) is to document the Near-Field Environment (NFE) and Unsaturated Zone (UZ) models used to evaluate the potential effects of coupled thermal-hydrologic-chemical (THC) processes on unsaturated zone flow and transport. This is in accordance with the ''Technical Work Plan (TWP) for Unsaturated Zone Flow and Transport Process Model Report'', Addendum D, Attachment D-4 (Civilian Radioactive Waste Management System (CRWMS) Management and Operating Contractor (M and O) 2000 [153447]) and ''Technical Work Plan for Nearfield Environment Thermal Analyses and Testing'' (CRWMS M and O 2000 [153309]). These models include the Drift Scale Test (DST) THC Model and several THC seepage models. These models provide the framework to evaluate THC coupled processes at the drift scale, predict flow and transport behavior for specified thermal loading conditions, and predict the chemistry of waters and gases entering potential waste-emplacement drifts. The intended use of this AMR is to provide input for the following: (1) Performance Assessment (PA); (2) Abstraction of Drift-Scale Coupled Processes AMR (ANL-NBS-HS-000029); (3) UZ Flow and Transport Process Model Report (PMR); and (4) Near-Field Environment (NFE) PMR. The work scope for this activity is presented in the TWPs cited above, and summarized as follows: continue development of the repository drift-scale THC seepage model used in support of the TSPA in-drift geochemical model; incorporate heterogeneous fracture property realizations; study sensitivity of results to changes in input data and mineral assemblage; validate the DST model by comparison with field data; perform simulations to predict mineral dissolution and precipitation and their effects on fracture properties and chemistry of water (but not flow rates) that may seep into drifts; submit modeling results to the TDMS and document the models. The model development, input data, sensitivity and validation studies described in

  9. Drift-Scale Coupled Processes (DST and THC Seepage) Models

    SciTech Connect

    E. Sonnenthale

    2001-04-16

    The purpose of this Analysis/Model Report (AMR) is to document the Near-Field Environment (NFE) and Unsaturated Zone (UZ) models used to evaluate the potential effects of coupled thermal-hydrologic-chemical (THC) processes on unsaturated zone flow and transport. This is in accordance with the ''Technical Work Plan (TWP) for Unsaturated Zone Flow and Transport Process Model Report'', Addendum D, Attachment D-4 (Civilian Radioactive Waste Management System (CRWMS) Management and Operating Contractor (M&O) 2000 [1534471]) and ''Technical Work Plan for Nearfield Environment Thermal Analyses and Testing'' (CRWMS M&O 2000 [153309]). These models include the Drift Scale Test (DST) THC Model and several THC seepage models. These models provide the framework to evaluate THC coupled processes at the drift scale, predict flow and transport behavior for specified thermal loading conditions, and predict the chemistry of waters and gases entering potential waste-emplacement drifts. The intended use of this AMR is to provide input for the following: Performance Assessment (PA); Near-Field Environment (NFE) PMR; Abstraction of Drift-Scale Coupled Processes AMR (ANL-NBS-HS-000029); and UZ Flow and Transport Process Model Report (PMR). The work scope for this activity is presented in the TWPs cited above, and summarized as follows: Continue development of the repository drift-scale THC seepage model used in support of the TSPA in-drift geochemical model; incorporate heterogeneous fracture property realizations; study sensitivity of results to changes in input data and mineral assemblage; validate the DST model by comparison with field data; perform simulations to predict mineral dissolution and precipitation and their effects on fracture properties and chemistry of water (but not flow rates) that may seep into drifts; submit modeling results to the TDMS and document the models. The model development, input data, sensitivity and validation studies described in this AMR are required

  10. Hydromechanical coupling in geologic processes

    USGS Publications Warehouse

    Neuzil, C.E.

    2003-01-01

    Earth's porous crust and the fluids within it are intimately linked through their mechanical effects on each other. This paper presents an overview of such "hydromechanical" coupling and examines current understanding of its role in geologic processes. An outline of the theory of hydromechanics and rheological models for geologic deformation is included to place various analytical approaches in proper context and to provide an introduction to this broad topic for nonspecialists. Effects of hydromechanical coupling are ubiquitous in geology, and can be local and short-lived or regional and very long-lived. Phenomena such as deposition and erosion, tectonism, seismicity, earth tides, and barometric loading produce strains that tend to alter fluid pressure. Resulting pressure perturbations can be dramatic, and many so-called "anomalous" pressures appear to have been created in this manner. The effects of fluid pressure on crustal mechanics are also profound. Geologic media deform and fail largely in response to effective stress, or total stress minus fluid pressure. As a result, fluid pressures control compaction, decompaction, and other types of deformation, as well as jointing, shear failure, and shear slippage, including events that generate earthquakes. By controlling deformation and failure, fluid pressures also regulate states of stress in the upper crust. Advances in the last 80 years, including theories of consolidation, transient groundwater flow, and poroelasticity, have been synthesized into a reasonably complete conceptual framework for understanding and describing hydromechanical coupling. Full coupling in two or three dimensions is described using force balance equations for deformation coupled with a mass conservation equation for fluid flow. Fully coupled analyses allow hypothesis testing and conceptual model development. However, rigorous application of full coupling is often difficult because (1) the rheological behavior of geologic media is complex

  11. Millimeter wave near-field study

    NASA Technical Reports Server (NTRS)

    Kefauver, Neill

    1990-01-01

    The possibility is evaluated of current technology measuring large aperture millimeter wave antennas. Included are a mathematical modeling of system errors, experimental data supporting error model, predictions of system accuracy at millimeter wavelengths, advantage of near-field measurements, and a cost estimate for a facility upgrade. The use is emphasized of software compensation and other inexpensive alternatives to develop a near optimum solution to near-field measurement problems at millimeter wavelengths.

  12. Direct interpretation of near-field optical images.

    PubMed

    Dereux, A; Devaux, E; Weeber, J C; Goudonnet, J P; Girard, C

    2001-05-01

    The interpretation of the detection process in near-field optical microscopy is reviewed on the basis of a discussion about the possibility of establishing direct comparisons between experimental images and the solutions of Maxwell equations or the electromagnetic local density of states. On the basis of simple physical arguments, it is expected that the solutions of Maxwell equations should agree with images obtained by collecting mode near-field microscopes, while the electromagnetic local density of states should be considered to provide a practical interpretation of illumination mode near-field microscopes. We review collecting mode near-field microscope images where the conditions to obtain good agreement with the solutions of Maxwell equations have indeed been identified. In this context of collecting mode near-field microscopes, a fundamentally different functionality between dielectric and gold-coated tips has been clearly identified experimentally by checking against the solutions of Maxwell equations. It turns out that dielectric tips detect a signal proportional to the optical electric field intensity, whereas gold-coated tips detect a signal proportional to the optical magnetic field intensity. The possible implications of this surprising phenomenon are discussed.

  13. Near-field levitated quantum optomechanics with nanodiamonds

    NASA Astrophysics Data System (ADS)

    Juan, M. L.; Molina-Terriza, G.; Volz, T.; Romero-Isart, O.

    2016-08-01

    We theoretically show that the dipole force of an ensemble of quantum emitters embedded in a dielectric nanosphere can be exploited to achieve near-field optical levitation. The key ingredient is that the polarizability from the ensemble of embedded quantum emitters can be larger than the bulk polarizability of the sphere, thereby enabling the use of repulsive optical potentials and consequently the levitation using optical near fields. In levitated cavity quantum optomechanics, this could be used to boost the single-photon coupling by combining larger polarizability to mass ratio, larger field gradients, and smaller cavity volumes while remaining in the resolved sideband regime and at room temperature. A case study is done with a nanodiamond containing a high density of silicon-vacancy color centers that is optically levitated in the evanescent field of a tapered nanofiber and coupled to a high-finesse microsphere cavity.

  14. Single-ion microwave near-field quantum sensor

    NASA Astrophysics Data System (ADS)

    Wahnschaffe, M.; Hahn, H.; Zarantonello, G.; Dubielzig, T.; Grondkowski, S.; Bautista-Salvador, A.; Kohnen, M.; Ospelkaus, C.

    2017-01-01

    We develop an intuitive model of 2D microwave near-fields in the unusual regime of centimeter waves localized to tens of microns. Close to an intensity minimum, a simple effective description emerges with five parameters that characterize the strength and spatial orientation of the zero and first order terms of the near-field, as well as the field polarization. Such a field configuration is realized in a microfabricated planar structure with an integrated microwave conductor operating near 1 GHz. We use a single 9 Be+ ion as a high-resolution quantum sensor to measure the field distribution through energy shifts in its hyperfine structure. We find agreement with simulations at the sub-micron and few-degree level. Our findings give a clear and general picture of the basic properties of oscillatory 2D near-fields with applications in quantum information processing, neutral atom trapping and manipulation, chip-scale atomic clocks, and integrated microwave circuits.

  15. Near-Field Photothermal Heating with a Plasmonic Nanofocusing Probe

    NASA Astrophysics Data System (ADS)

    Chen, Xiang; Dong, Biqing; Balogun, Oluwaseyi

    2016-03-01

    Noble metal nanostructures support plasmon resonances—collective oscillation of charge carriers at optical frequencies—and serve as effective tools to create bright light sources at the nanoscale. These sources are useful in broad application areas including, super-resolution imaging and spectroscopy, nanolithography, and near-field optomechanical transducers. The feasibility of these applications relies on efficient conversion of free-space propagating light to plasmons. Recently, we demonstrated a hybrid nanofocusing scheme for efficient coupling of light to plasmons at the apex of a scanning probe. In the approach, free-space light is coupled to propagating surface plasmon polaritons (SPPs) on the tapered shaft of the scanning probe. The SPPs propagate adiabatically towards the probe tip where they are coupled to localized plasmons (LSPs). The nanofocusing scheme was explored in a near-field scanning optical microscope for super-resolution imaging, near-field transduction of nanomechanical vibrations, and local detection of ultrasound. Owing to the strong concentration of light at the probe, significant heating of the tip and a sample positioned in the optical near-field is expected. This paper investigates the local heating produced by the plasmonic nanofocusing probe under steady-state conditions using the tip-enhanced Raman scattering approach. In addition, a finite element model is explored to study the coupling of free propagating light to LSPs, and to estimate the temperature rise expected in a halfspace heated by absorption of the LSPs. This study has implications for exploring the plasmonic nanofocusing probe in heat-assisted nanofabrication and fundamental studies of nanoscale heat transport in materials.

  16. Parallel scanning near-field photolithography: the snomipede.

    PubMed

    ul Haq, Ehtsham; Liu, Zhuming; Zhang, Yuan; Ahmad, Shahrul A Alang; Wong, Lu-Shin; Armes, Steven P; Hobbs, Jamie K; Leggett, Graham J; Micklefield, Jason; Roberts, Clive J; Weaver, John M R

    2010-11-10

    The “Millipede”, developed by Binnig and co-workers (Bining, G. K.; et al. IBM J. Res. Devel. 2000, 44, 323.), elegantly solves the problem of the serial nature of scanning probe lithography processes, by deploying massive parallelism. Here we fuse the “Millipede” concept with scanning near-field photolithography to yield a “Snomipede” that is capable of executing parallel chemical transformations at high resolution over macroscopic areas. Our prototype has sixteen probes that are separately controllable using a methodology that is, in principle, scalable to much larger arrays. Light beams generated by a spatial modulator or a zone plate array are coupled to arrays of cantilever probes with hollow, pyramidal tips. We demonstrate selective photodeprotection of nitrophenylpropyloxycarbonyl-protected aminosiloxane monolayers on silicon dioxide and subsequent growth of nanostructured polymer brushes by atom-transfer radical polymerization, and the fabrication of 70 nm structures in photoresist by a Snomipede probe array immersed under water. Such approaches offer a powerful means of integrating the top-down and bottom-up fabrication paradigms, facilitating the reactive processing of materials at nanometer resolution over macroscopic areas.

  17. Near-field heat transfer between graphene monolayers: Dispersion relation and parametric analysis

    NASA Astrophysics Data System (ADS)

    Yin, Ge; Yang, Jiang; Ma, Yungui

    2016-12-01

    Plasmon polaritons in graphene can enhance near-field heat transfer. In this work, we give a complete parametric analysis on the near-field heat transfer between two graphene monolayers that allows transfer efficiencies several orders-of-magnitude larger than blackbody radiation. Influences of major parameters are conclusively clarified from the changes of the interlayer supermode coupling and their dispersion relations. The method to maximize the near-field heat flux is discussed. The generalized Stefan-Boltzmann formula is proposed to describe the near-field heat transfer dominated by evanescent wave tunneling. Our results are of practical significance in guiding the design of thermal management systems.

  18. Near-Field Optical Propertiesof Super-Resolution Near-Field Structures

    NASA Astrophysics Data System (ADS)

    Tsai, Din Ping

    Super-resolution near-field structures, glass/SiN(170 nm)/Sb(15 nm)/SiN(20 nm) and glass/ZnS-SiO2 (20 nm)/AgOx (15 nm)/ZnS-SiO2 (20 nm), have been studied by a tapping-mode tuning-fork near-field scanning optical microscope in transmission mode. Both propagating and evanescent field intensities were found at the focused spots of the surface of the super-resolution near-field structure. Images of the near-field intensity gradients at different excited laser powers showed that the area of the static evanescent intensity could be stably controlled. The enhancement of the near-field intensity, and the reduction of the focused spot through super-resolution near-field structure, glass/SiN(170 nm)/Sb(15 nm)/SiN(20 nm) or glass/ZnS-SiO2 (20 nm)/AgOx (15 nm)/ZnS-SiO2 (20 nm) have been directly observed in the near field. The near-field interactions of the 15 nm Sb and AgOx Layers have been investigated, respectively, and the localized surface plasmons excited at the focused laser spot were shown to be the key sources of the strong enhancement in the near field.

  19. Volumetric Near-Field Microwave Plasma Generation

    NASA Technical Reports Server (NTRS)

    Exton, R. J.; Balla, R. Jeffrey; Herring, G. C.; Popovic, S.; Vuskovic, L.

    2003-01-01

    A periodic series of microwave-induced plasmoids is generated using the outgoing wave from a microwave horn and the reflected wave from a nearby on-axis concave reflector. The plasmoids are spaced at half-wavelength separations according to a standing-wave pattern. The plasmoids are enhanced by an effective focusing in the near field of the horn (Fresnel region) as a result of a diffractive narrowing. Optical imaging, electron density, and rotational temperature measurements characterize the near field plasma region. Volumetric microwave discharges may have application to combustion ignition in scramjet engines.

  20. Near-field diffraction of chirped gratings.

    PubMed

    Sanchez-Brea, Luis Miguel; Torcal-Milla, Francisco Jose; Morlanes, Tomas

    2016-09-01

    In this Letter, we analyze the near-field diffraction pattern produced by chirped gratings. An intuitive analytical interpretation of the generated diffraction orders is proposed. Several interesting properties of the near-field diffraction pattern can be determined, such as the period of the fringes and its visibility. Diffraction orders present different widths and also, some of them present focusing properties. The width, location, and depth of focus of the converging diffraction orders are also determined. The analytical expressions are compared to numerical simulation and experimental results, showing a high agreement.

  1. Near-field scanning study for radio frequency interference estimation

    NASA Astrophysics Data System (ADS)

    Pan, Jingnan

    This dissertation discusses the novel techniques using near-fields scanning to do radio frequency interference (RFI) estimation. As the electronic products are becoming more and more complicated, the radio frequency (RF) receiver in the system is very likely interfered by multiple noise sources simultaneously. A method is proposed to identify the interference from different noise sources separately, even when they are radiating at the same time. This method is very helpful for engineers to identify the contribution of the coupling from different sources and further solve the electromagnetic interference issues efficiently. On the other hand, the equivalent dipole-moment models and a decomposition method based on reciprocity theory can also be used together to estimate the coupling from the noise source to the victim antennas. This proposed method provides convenience to estimate RFI issues in the early design stage and saves the time of RFI simulation and measurements. The finite element method and image theory can also predict the far fields of the radiation source, locating above a ground plane. This method applies the finite element method (FEM) to get the equivalent current sources from the tangential magnetic near fields. With the equivalent current sources, the far-field radiation can be calculated based on Huygens's Principle and image theory. By using only the magnetic near fields on the simplified Huygens's surface, the proposed method significantly saves measurement time and cost while also retaining good far-field prediction.

  2. Near-field optical thin microcavity theory

    NASA Astrophysics Data System (ADS)

    Wu, Jiu Hui; Hou, Jiejie

    2016-01-01

    The thin microcavity theory for near-field optics is proposed in this study. By applying the power flow theorem and the variable theorem,the bi-harmonic differential governing equation for electromagnetic field of a three-dimensional thin microcavity is derived for the first time. Then by using the Hankel transform, this governing equation is solved exactly and all the electromagnetic components inside and outside the microcavity can be obtained accurately. According to the above theory, the near-field optical diffraction from a subwavelength aperture embedded in a thin conducting film is investigated, and numerical computations are performed to illustrate the edge effect by an enhancement factor of 1.8 and the depolarization phenomenon of the near-field transmission in terms of the distance from the film surface. This thin microcavity theory is verified by the good agreement between our results and those in the previous literatures. The thin microcavity theory presented in the study should be useful in the possible applications of the thin microcavities in near-field optics and thin-film optics.

  3. THz near-field Faraday imaging in hybrid metamaterials.

    PubMed

    Kumar, Nishant; Strikwerda, Andrew C; Fan, Kebin; Zhang, Xin; Averitt, Richard D; Planken, Paul C M; Adam, Aurèle J L

    2012-05-07

    We report on direct measurements of the magnetic near-field of metamaterial split ring resonators at terahertz frequencies using a magnetic field sensitive material. Specifically, planar split ring resonators are fabricated on a single magneto-optically active terbium gallium garnet crystal. Normally incident terahertz radiation couples to the resonator inducing a magnetic dipole oscillating perpendicular to the crystal surface. Faraday rotation of the polarisation of a near-infrared probe beam directly measures the magnetic near-field with 100 femtosecond temporal resolution and (λ/200) spatial resolution. Numerical simulations suggest that the magnetic field can be enhanced in the plane of the resonator by as much as a factor of 200 compared to the incident field strength. Our results provide a route towards hybrid devices for dynamic magneto-active control of light such as isolators, and highlight the utility of split ring resonators as compact probes of magnetic phenomena in condensed matter.

  4. Near-field NanoThermoMechanical memory

    SciTech Connect

    Elzouka, Mahmoud; Ndao, Sidy

    2014-12-15

    In this letter, we introduce the concept of NanoThermoMechanical Memory. Unlike electronic memory, a NanoThermoMechanical memory device uses heat instead of electricity to record, store, and recover data. Memory function is achieved through the coupling of near-field thermal radiation and thermal expansion resulting in negative differential thermal resistance and thermal latching. Here, we demonstrate theoretically via numerical modeling the concept of near-field thermal radiation enabled negative differential thermal resistance that achieves bistable states. Design and implementation of a practical silicon based NanoThermoMechanical memory device are proposed along with a study of its dynamic response under write/read cycles. With more than 50% of the world's energy losses being in the form of heat along with the ever increasing need to develop computer technologies which can operate in harsh environments (e.g., very high temperatures), NanoThermoMechanical memory and logic devices may hold the answer.

  5. Near-field NanoThermoMechanical memory

    NASA Astrophysics Data System (ADS)

    Elzouka, Mahmoud; Ndao, Sidy

    2014-12-01

    In this letter, we introduce the concept of NanoThermoMechanical Memory. Unlike electronic memory, a NanoThermoMechanical memory device uses heat instead of electricity to record, store, and recover data. Memory function is achieved through the coupling of near-field thermal radiation and thermal expansion resulting in negative differential thermal resistance and thermal latching. Here, we demonstrate theoretically via numerical modeling the concept of near-field thermal radiation enabled negative differential thermal resistance that achieves bistable states. Design and implementation of a practical silicon based NanoThermoMechanical memory device are proposed along with a study of its dynamic response under write/read cycles. With more than 50% of the world's energy losses being in the form of heat along with the ever increasing need to develop computer technologies which can operate in harsh environments (e.g., very high temperatures), NanoThermoMechanical memory and logic devices may hold the answer.

  6. Near-field heat transfer between gold nanoparticle arrays

    SciTech Connect

    Phan, Anh D.; Phan, The-Long; Woods, Lilia M.

    2013-12-07

    The radiative heat transfer between gold nanoparticle layers is presented using the coupled dipole method. Gold nanoparticles are modelled as effective electric and magnetic dipoles interacting via electromagnetic fluctuations. The effect of higher-order multipoles is implemented in the expression of electric polarizability to calculate the interactions at short distances. Our findings show that the near-field radiation reduces as the radius of the nanoparticles is increased. Also, the magnetic dipole contribution to the heat exchange becomes more important for larger particles. When one layer is displayed in parallel with respect to the other layer, the near-field heat transfer exhibits oscillatory-like features due to the influence of the individual nanostructures. Further details about the effect of the nanoparticles size are also discussed.

  7. Near-Field CARS with Micro- and Nano-Particle

    NASA Astrophysics Data System (ADS)

    Ooi, C. H. Raymond

    2010-08-01

    Spatial dependence of coherent anti-Stokes Raman scattering (CARS) intensity and spectra for a spherical particle are studied for different sizes, ranging from micrometers to nanometers. Effects of near field on the spectra are analyzed, showing potential application as nano-sensor in microscopy and imaging. The results can be extended to an array of nanospheres. The CARS process has been developed into a versatile real-time detection technique in spectroscopy and microscopy [1]. In particularly, backscattered ultra-violet CARS implemented on LIDAR system [2] is promising for remote detection of molecular species present in hazardous biological aerosols with microscale dimension. In practice, the aerosols could be in any dimension. Thus, we need to know study a modified the setup of the CARS technique for reliable detection of chemicals in micro- and nano-particles using near-field effects. We have developed a nonlinear semiclassical microscopic theory to describe the CARS spectra for a particle composed of a collection of arbitrarily complex molecules [3] as well as simple few levels quantum systems [2]. The theory provides useful results on the CARS spectra for any observation angle and for any form of laser pulses [3]. Here, we focus on the spectra in the near field. We wish to study how the spectra vary with the near field distance with focused laser pulses. We also analyze to what extend the dimension of the particle and the focusing laser affect the lensing effect which could enhance the backscattered light.

  8. From classical to modern near-field optics and the future

    NASA Astrophysics Data System (ADS)

    Ohtsu, Motoichi

    2014-11-01

    This paper reviews the framework of classical near-field optics and recent progress in modern near-field optics. Some applications are also reviewed, including novel optical functional devices, nano-fabrication technologies, energy conversion technologies, and information processing systems. Novel theoretical models based on mathematical science are also presented, as well as an outlook for the future, hinting at the possibilities of near-field optics.

  9. Fabrication of micro-patterns via near-field electrospray

    NASA Astrophysics Data System (ADS)

    Li, Wenwang; Zheng, Gaofeng; Xu, Lei; Wang, Xiang

    2016-11-01

    A near-field electrospray process is developed to deposited micro-patterns. Compared with conventional electrospray, near field electrospray uses a steel probe instead of capillary nozzle, and its nozzle-to-substrate distance is shortened to several millimeters to realize micro-scale deposition area. The liquid is supplied by discretely dipping the probe into solution in advance so that electrospray process maintains until the consumption of liquid adhered at the probe tip. The influence of solution conductivity and applied voltage on deposition are investigated, as increasing solution conductivity and high applied voltage may promote the electrospray process and enlarge the line width. In addition, micro-patterns with various materials are directly electrosprayed.

  10. Coping Processes of Couples Experiencing Infertility

    ERIC Educational Resources Information Center

    Peterson, Brennan D.; Newton, Christopher R.; Rosen, Karen H.; Schulman, Robert S.

    2006-01-01

    This study explored the coping processes of couples experiencing infertility. Participants included 420 couples referred for advanced reproductive treatments. Couples were divided into groups based on the frequency of their use of eight coping strategies. Findings suggest that coping processes, which are beneficial to individuals, may be…

  11. Coping Processes of Couples Experiencing Infertility

    ERIC Educational Resources Information Center

    Peterson, Brennan D.; Newton, Christopher R.; Rosen, Karen H.; Schulman, Robert S.

    2006-01-01

    This study explored the coping processes of couples experiencing infertility. Participants included 420 couples referred for advanced reproductive treatments. Couples were divided into groups based on the frequency of their use of eight coping strategies. Findings suggest that coping processes, which are beneficial to individuals, may be…

  12. Near-field millimeter - wave imaging of nonmetallic materials

    SciTech Connect

    Gopalsami, N.; Bakhtiari, S.; Raptis, A.C.

    1996-12-31

    A near-field millimeter-wave (mm-wave) imaging system has been designed and built in the 94-GHz range for on-line inspection of nonmetallic (dielectric) materials. The imaging system consists of a transceiver block coupled to an antenna that scans the material to be imaged; a reflector plate is placed behind the material. A quadrature IF mixer in the transceiver block enables measurement of in-phase and quadrature-phase components of reflected signals with respect to the transmitted signal. All transceiver components, with the exception of the Gunn-diode oscillator and antenna, were fabricated in uniform blocks and integrated and packaged into a compact unit (12.7 x 10.2 x 2.5 cm). The objective of this work is to test the applicability of a near-field compact mm-wave sensor for on-line inspection of sheetlike materials such as paper, fabrics, and plastics. This paper presents initial near-field mm-wave images of paper and fabric samples containing known artifacts.

  13. Evaluation of near-field earthquake effects

    SciTech Connect

    Shrivastava, H.P.

    1994-11-01

    Structures and equipment, which are qualified for the design basis earthquake (DBE) and have anchorage designed for the DBE loading, do not require an evaluation of the near-field earthquake (NFE) effects. However, safety class 1 acceleration sensitive equipment such as electrical relays must be evaluated for both NFE and DBE since they are known to malfunction when excited by high frequency seismic motions.

  14. Hill Ciphers over Near-Fields

    ERIC Educational Resources Information Center

    Farag, Mark

    2007-01-01

    Hill ciphers are linear codes that use as input a "plaintext" vector [p-right arrow above] of size n, which is encrypted with an invertible n x n matrix E to produce a "ciphertext" vector [c-right arrow above] = E [middle dot] [p-right arrow above]. Informally, a near-field is a triple [left angle bracket]N; +, *[right angle bracket] that…

  15. Near-field radiofrequency electromagnetic exposure assessment.

    PubMed

    Rubtsova, Nina; Perov, Sergey; Belaya, Olga; Kuster, Niels; Balzano, Quirino

    2015-09-01

    Personal wireless telecommunication devices, such as radiofrequency (RF) electromagnetic field (EMF) sources operated in vicinity of human body, have possible adverse health effects. Therefore, the correct EMF assessment is necessary in their near field. According to international near-field measurement criteria, the specific absorption rate (SAR) is used for absorbed energy distribution assessment in tissue simulating liquid phantoms. The aim of this investigation is to validate the relationship between the H-field of incident EMF and absorbed energy in phantoms. Three typical wireless telecommunication system frequencies are considered (900, 1800 and 2450 MHz). The EMF source at each frequency is an appropriate half-wave dipole antenna and the absorbing medium is a flat phantom filled with the suitable tissue simulating liquid. Two methods for SAR estimation have been used: standard procedure based on E-field measured in tissue simulating medium and a proposed evaluation by measuring the incident H-field. Compared SAR estimations were performed for various distances between sources and phantom. Also, these research data were compared with simulation results, obtained by using finite-difference time-domain method. The acquired data help to determine the source near-field space characterized by the smallest deviation between SAR estimation methods. So, this region near the RF source is suitable for correct RF energy absorption assessment using the magnetic component of the RF fields.

  16. Ideal near-field thermophotovoltaic cells

    NASA Astrophysics Data System (ADS)

    Molesky, Sean; Jacob, Zubin

    2015-05-01

    We ask the question, what are the ideal characteristics of a near-field thermophotovoltaic cell? Our search leads us to a reformulation of near-field radiative heat transfer in terms of the joint density of electronic states of the emitter-absorber pair in the thermophotovoltaic system. This form reveals that semiconducting materials with narrowband absorption spectra are critical to the energy-conversion efficiency. This essential feature is unavailable in conventional bulk semiconductor cells but can be obtained using low-dimensional materials. Our results show that the presence of matched van Hove singularities resulting from quantum confinement in the emitter and absorber of a thermophotovoltaic cell boosts both the magnitude and spectral selectivity of radiative heat transfer, dramatically improving energy-conversion efficiency. We provide a model near-field thermophotovoltaic system design making use of this idea by employing the van Hove singularities present in carbon nanotubes. Shockley-Queisser analysis shows that the predicted heat transfer characteristics of this model device are fundamentally better than existing thermophotovoltaic designs. Our work paves the way for the use of quantum dots, quantum wells, two-dimensional semiconductors, semiconductor nanowires, and carbon nanotubes as future materials for thermophotovoltaic cells.

  17. Dual-wavelength scanning near-field optical microscopy

    NASA Astrophysics Data System (ADS)

    Leblanc, Philip R.

    A dual-wavelength Scanning Near-Field Optical Microscope was developed in order to investigate near-field contrast mechanisms as well as biological samples in air. Using a helium-cadmium laser, light of wavelengths 442 and 325 nanometers is coupled into a single mode optical fiber. The end of the probe is tapered to a sub-wavelength aperture, typically 50 nanometers, and positioned in the near-field of the sample. Light from the aperture is transmitted through the sample and detected in a confocal arrangement by two photomultiplier tubes. The microscope has a lateral topographic resolution of 10 nanometers, a vertical resolution of 0.1 nanometer and an optical resolution of 30 nanometers. Two alternate methods of producing the fiber probes, heating and pulling, or acid etching, are compared and the metal coating layer defining the aperture is discussed. So-called "shear-force" interactions between the tip and sample are used as the feedback mechanism during raster scanning of the sample. An optical and topographic sample standard was developed to calibrate the microscope and extract the ultimate resolution of the instrument. The novel use of two wavelengths enables the authentication of true near-field images, as predicted by various models, as well as the identification of scanning artifacts and the deconvolution of often highly complicated relationships between the topographical and optical images. Most importantly, the use of two wavelengths provides information on the chemical composition of the sample. Areas of a polystyrene film are detected by a significant change in the relative transmission of the two wavelengths with a resolution of 30 nanometers. As a biological application, a preliminary investigation of the composition of Black Spruce wood cell fibers was performed. Comparisons of the two optical channels reveal the expected lignin distributions in the cell wall.

  18. Near-field diffraction of gratings with surface defects.

    PubMed

    Sanchez-Brea, Luis Miguel; Torcal-Milla, Francisco Jose

    2010-04-10

    Diffraction gratings produce self-images in the near field. Defects on the surface of the grating may occur due to the manufacturing process. These devices are often placed in dirty industrial environments. Dust particles or drops of liquid can be deposited over their surface. In this work, we analyze the effect of surface defects placed over the grating on the self-imaging process. We analytically show how the self-images gradually recover as we separate from the grating when one defect is present. Also a random distribution of surface defects over the grating is analyzed. In particular, we focus on how the contrast of the self-images decreases in terms of the density of the defects. Analytical expressions for the near field are derived, considering a stochastic description of the spatial distribution of defects. In addition, numerical simulations based on the Rayleigh-Sommerfeld formulation are performed to validate the analytical results.

  19. Tip-enhanced near-field optical microscopy

    PubMed Central

    Mauser, Nina; Hartschuh, Achim

    2013-01-01

    Tip-enhanced near-field optical microscopy (TENOM) is a scanning probe technique capable of providing a broad range of spectroscopic information on single objects and structured surfaces at nanometer spatial resolution and with highest detection sensitivity. In this review, we first illustrate the physical principle of TENOM that utilizes the antenna function of a sharp probe to efficiently couple light to excitations on nanometer length scales. We then discuss the antenna-induced enhancement of different optical sample responses including Raman scattering, fluorescence, generation of photocurrent and electroluminescence. Different experimental realizations are presented and several recent examples that demonstrate the capabilities of the technique are reviewed. PMID:24100541

  20. Clinical processes in behavioral couples therapy.

    PubMed

    Fischer, Daniel J; Fink, Brandi C

    2014-03-01

    Behavioral couples therapy is a broad term for couples therapies that use behavioral techniques based on principles of operant conditioning, such as reinforcement. Behavioral shaping and rehearsal and acceptance are clinical processes found across contemporary behavioral couples therapies. These clinical processes are useful for assessment and case formulation, as well as teaching couples new methods of conflict resolution. Although these clinical processes assist therapists in achieving efficient and effective therapeutic change with distressed couples by rapidly stemming couples' corrosive affective exchanges, they also address the thoughts, emotions, and issues of trust and intimacy that are important aspects of the human experience in the context of a couple. Vignettes are provided to illustrate the clinical processes described. (PsycINFO Database Record (c) 2014 APA, all rights reserved).

  1. Near-field Optical Measurements of Semiconductor Materials and Devices

    NASA Astrophysics Data System (ADS)

    Farahi, R. H.; Wetsel, G. C., Jr.; Cunningham, A. J.

    1998-03-01

    We are applying a Reflection-mode Apertureless Near-field Scanning Optical Microscope (RANSOM) to study defect detection in semiconductor devices and materials. Optical data from approach curves show a characteristic near-field optical signal. Evaluation of lateral definition is accomplished by correlation with known features of 100 nm or less. The RANSOM regulates on the force between the tip and sample; probe tips are made of etched tungsten wires which vibrate in the pecking mode. Since the metallic tip is conductive, we have a multi-purpose scanned probe capable of simultaneously gathering current, force (topographical), and optical data. With the RANSOM, leakage currents through a SiO2 layer can be detected along with topographical and optical information. Such capability could be applied to the current leakage problem across field-oxide edges. Knowledge of the leakage current across the field oxide and the thickness gradient of its edge is very important in process development of CMOS devices.

  2. Near-field beamforming analysis for acoustic emission source localization.

    PubMed

    He, Tian; Pan, Qiang; Liu, Yaoguang; Liu, Xiandong; Hu, Dayong

    2012-07-01

    This paper attempts to introduce a near-field acoustic emission (AE) beamforming method to estimate the AE source locations by using a small array of sensors closely placed in a local region. The propagation characteristics of AE signals are investigated based on guided wave theory to discuss the feasibility of using beamforming techniques in AE signal processing. To validate the effectiveness of the AE beamforming method, a series of pencil lead break tests at various regions of a thin steel plate are conducted. The potential of this method for engineering applications are explored through rotor-stator rubbing tests. The experimental results demonstrate that the proposed method can effectively determine the region where rubbing occurs. It is expected that the work of this paper may provide a helpful analysis tool for near-field AE source localization.

  3. Near-field Interferometric Imaging of Lightning

    NASA Astrophysics Data System (ADS)

    Stock, M.; Wu, T.; Akiyama, Y.; Kawasaki, Z.; Ushio, T.

    2015-12-01

    In the past, lightning interferometric mapping systems assumed that a source is very far from the measurement location. The assumption greatly simplifies the mathematics needed to locate the source, but the resulting source positions are limited to two spatial dimensions (azimuth and elevation). For short baseline systems, this assumption is very good because the source is almost always much farther away than the diameter of the array, making three-dimensional location all but impossible. By removing the far-field assumption, if the array is large enough it is possible to locate the source in three spatial dimensions using purely interferometric techniques. The purely interferometric method is quite different from the more typical time-of-arrival method. Instead of measuring arrival times or time differences of the radiation arriving at each station, a volume is imaged over a some integration period and then searched for a source. It is not necessary to know that a source exists in the integration period for the interferometric imaging technique to produce a well defined solution. Interferometric imaging can locate sources buried in noise, can locate both continuous and impulsive emission, and is capable of locating multiple simultaneously radiating sources. If the waveforms are corrected for propagation delay to the search volume, the integration period can be made arbitrarily small (limited only by the frequencies being observed), allowing the progression of lightning to be examined in detail. Near-field interferometry works equally well on a wide range of different signal types, from the LF to VHF bands in radio, or even on acoustic emissions from lightning. Near-field imaging can be used to correct the angular locations of short baseline systems when a source is very close to the array, or to produce full three-dimensional maps of lightning with long baseline arrays. Presented here are preliminary results of applying near-field interferometric imaging to the

  4. Scanning tip microwave near field microscope

    DOEpatents

    Xiang, Xiao-Dong; Schultz, Peter G.; Wei, Tao

    1998-01-01

    A microwave near field microscope has a novel microwave probe structure wherein the probing field of evanescent radiation is emitted from a sharpened metal tip instead of an aperture or gap. This sharpened tip, which is electrically and mechanically connected to a central electrode, extends through and beyond an aperture in an endwall of a microwave resonating device such as a microwave cavity resonator or a microwave stripline resonator. Since the field intensity at the tip increases as the tip sharpens, the total energy which is radiated from the tip and absorbed by the sample increases as the tip sharpens. The result is improved spatial resolution without sacrificing sensitivity.

  5. Scanning tip microwave near field microscope

    DOEpatents

    Xiang, X.D.; Schultz, P.G.; Wei, T.

    1998-10-13

    A microwave near field microscope has a novel microwave probe structure wherein the probing field of evanescent radiation is emitted from a sharpened metal tip instead of an aperture or gap. This sharpened tip, which is electrically and mechanically connected to a central electrode, extends through and beyond an aperture in an end wall of a microwave resonating device such as a microwave cavity resonator or a microwave stripline resonator. Since the field intensity at the tip increases as the tip sharpens, the total energy which is radiated from the tip and absorbed by the sample increases as the tip sharpens. The result is improved spatial resolution without sacrificing sensitivity. 17 figs.

  6. The near-field scanning thermal microscope

    NASA Astrophysics Data System (ADS)

    Wischnath, Uli F.; Welker, Joachim; Munzel, Marco; Kittel, Achim

    2008-07-01

    We report on the design, characterization, and performance of a near-field scanning thermal microscope capable to detect thermal heat currents mediated by evanescent thermal electromagnetic fields close to the surface of a sample. The instrument operates in ultrahigh vacuum and retains its scanning tunneling microscope functionality, so that its miniature, micropipette-based thermocouple sensor can be positioned with high accuracy. Heat currents on the order of 10-7W are registered in z spectroscopy at distances from the sample ranging from 1 to about 30nm. In addition, the device provides detailed thermographic images of a sample's surface.

  7. Near field imaging with resonant cavity lens.

    PubMed

    Li, Guixin; Li, Jensen; Tam, H L; Chan, C T; Cheah, K W

    2010-02-01

    We showed that a Ag-SiO(2)-Ag Fabry-Pérot cavity can be used in near-field imaging based on omnidirectional resonance tunneling. The omnidirectional resonance was experimentally demonstrated in the Ag-SiO(2)-Ag resonant cavity working at a wavelength of 365 nm. The resonant cavity lens with high transmittance and high image fidelity was fabricated using standard photolithography method. Grating source with 190 nm line resolution was imaged through the resonant cavity lens with a total thickness of 128 nm.

  8. Energy transfer in near-field optics.

    PubMed

    Colas des Francs, Gérard; Girard, Christian; Juan, Mathieu; Dereux, Alain

    2005-11-01

    When the probe tip of a near-field optical microscope illuminates nanoparticles with marked absorption bands, a large number of photons are absorbed before reaching the detector. These energy losses enhance the dark contrast usually observed in the vicinity of metallic nanoparticles. We demonstrate theoretically that this phenomenon can be exploited to image, in the optical frequency range, dissipative domains with a nanometer scale resolution. Simulations performed with noble-metal particles indicate that the detected signal significantly drops down when the excitation frequency is approaching the plasmon resonance of the particles.

  9. Near Field Trailing Edge Tone Noise Computation

    NASA Technical Reports Server (NTRS)

    Loh, Ching Y.

    2002-01-01

    Blunt trailing edges in a flow often generate tone noise due to wall-jet shear layer and vortex shedding. In this paper, the space-time conservation element (CE/SE) method is employed to numerically study the near-field noise of blunt trailing edges. Two typical cases, namely, flow past a circular cylinder (aeolian noise problem) and flow past a flat plate of finite thickness are considered. The computed frequencies compare well with experimental data. For the aeolian noise problem, comparisons with the results of other numerical approaches are also presented.

  10. Localizing periodicity in near-field images

    NASA Astrophysics Data System (ADS)

    Fraundorf, P.

    1990-02-01

    We show that Bayesian Physical inference, like that used in statistical mechanics, can guide the systematic construction of Fourier dark-field methods for localizing periodicity in near-field (e.g., scanning tunneling and electron phase contrast) images. For crystals in an aperiodic field, the Fourier coefficient Zeicphi combines with a prior estimate for background amplitude B to predict background phase (β) values distributed with a probability p(β-φ||Z,φ,B) inversely proportional to amplitude P of the signal of interest, when the latter is treated as an unknown translation scaled to B.

  11. Near-field radiofrequency thermoacoustic tomography with impulse excitation.

    PubMed

    Razansky, Daniel; Kellnberger, Stephan; Ntziachristos, Vasilis

    2010-09-01

    Imaging performance of radiofrequency and microwave-based thermoacoustic tomography systems is mainly determined by the ability to deposit a substantial amount of electromagnetic energy within ultrashort time duration. Pulses of nanosecond-range duration that can carry hundreds of millijoules energy are ideal for obtaining good signal-to-noise and spatial resolution in many biological imaging applications. However, existing implementations are based on modulated-carrier-frequency amplification solutions, which are generally costly and cannot achieve ultrahigh-peak-power requirements essential for optimal thermoacoustic signal generation. Herein the authors suggest and experimentally validate a near-field radiofrequency tomography (NRT) method for high resolution imaging of biological tissues using ultrashort electromagnetic impulses. The solution includes a low-cost pulsing system while the imaged objects are placed in the near field of the energy-emitting aperture for improved coupling using nonradiative fields. In the current design, the authors were able to achieve excitation impulse energies of hundreds of millijoules with durations in the order of a few nanoseconds, corresponding to peak power levels of multiple megawatts. The phantom imaging experiments demonstrated image features with characteristic sizes of around 170 microm, but the impulse durations used herein allow in principle spatial resolutions in the order of a few tens of microns when using an appropriate ultrasonic detection bandwidth. The proposed NRT method makes it possible to attain very high spatial resolution without compromising the thermoacoustic signal strength. This makes the imaging performance to be limited by the available bandwidth of the ultrasonic detector rather than by the microwave pulse duration. It is overall expected that the combination of pulsed near-field coupling with optimal choice of energy dissipation elements will generate a practical modality that can scale its

  12. Enhancing Near-Field Radiative Heat Transfer with Si-based Metasurfaces

    NASA Astrophysics Data System (ADS)

    Fernández-Hurtado, V.; García-Vidal, F. J.; Fan, Shanhui; Cuevas, J. C.

    2017-05-01

    We demonstrate in this work that the use of metasurfaces provides a viable strategy to largely tune and enhance near-field radiative heat transfer between extended structures. In particular, using a rigorous coupled wave analysis, we predict that Si-based metasurfaces featuring two-dimensional periodic arrays of holes can exhibit a room-temperature near-field radiative heat conductance much larger than any unstructured material to date. We show that this enhancement, which takes place in a broad range of separations, relies on the possibility to largely tune the properties of the surface plasmon polaritons that dominate the radiative heat transfer in the near-field regime.

  13. Near-Field Acoustic Holography of Chladni Plate

    NASA Astrophysics Data System (ADS)

    Kim, Hyunhee; Kim, Yunbog; Jeon, Dongryul

    2007-03-01

    Characteristic modes of a Chladni plate can be visualized by sand gathering along the nodal lines. Although one can view two-dimensional vibration patterns, the sand pattern does not show a bending of antinode. We used near-field acoustic holography to reconstruct a three-dimensional image of circular and rectangular Chladni plates. The sound pressure was measured using four scanning microphones located 3 mm above a Chladni plate. A reference microphone was placed close to a speaker which drives the plate. A total of 60x60 data were collected from 30x30 cm^2 area and processed using MATLAB in accordance with the algorithm of near-field acoustic holography. The three-dimensional graphic image of the vibrating plate reconstructed this way not only matched the sand pattern but also visualized the bending of the plate. Propagation of the sound pressure could be also visualized three-dimensionally. The plot of sound pressure against the distance showed the 1/distance^2 dependence as expected. Sound is a difficult subject in physics class because it is invisible. Our results demonstrate that near-field acoustic holography combined with computer graphic is an effective tool to visualize the generation of a sound.

  14. Active Thermal Extraction and Temperature Sensing of Near-field Thermal Radiation

    PubMed Central

    Ding, D.; Kim, T.; Minnich, A. J.

    2016-01-01

    Recently, we proposed an active thermal extraction (ATX) scheme that enables thermally populated surface phonon polaritons to escape into the far-field. The concept is based on a fluorescence upconversion process that also occurs in laser cooling of solids (LCS). Here, we present a generalized analysis of our scheme using the theoretical framework for LCS. We show that both LCS and ATX can be described with the same mathematical formalism by replacing the electron-phonon coupling parameter in LCS with the electron-photon coupling parameter in ATX. Using this framework, we compare the ideal efficiency and power extracted for the two schemes and examine the parasitic loss mechanisms. This work advances the application of ATX to manipulate near-field thermal radiation for applications such as temperature sensing and active radiative cooling. PMID:27595609

  15. Electromagnetic Compatibility (EMC) for Integration and Use of Near Field Communication (NFC) in Aircraft

    NASA Astrophysics Data System (ADS)

    Nalbantoglu, Cemal; Kiehl, Thorsten; God, Ralf; Stadtler, Thiemo; Kebel, Robert; Bienert, Renke

    2016-05-01

    For portable electronic devices (PEDs), e.g. smartphones or tablets, near field communication (NFC) enables easy and convenient man-machine interaction by simply tapping a PED to a tangible NFC user interface. Usage of NFC technology in the air transport system is supposed to facilitate travel processes and self-services for passengers and to support digital interaction with other participating stakeholders. One of the potential obstacles to benefit from NFC technology in the aircraft cabin is the lack of an explicit qualification guideline for electromagnetic compatibility (EMC) testing. In this paper, we propose a methodology for EMC testing and for characterizing NFC devices and their emissions according to aircraft industry standards (RTCA DO-160, DO-294, DO-307 and EUROCAE ED- 130). A potential back-door coupling scenario of radiated NFC emissions and possible effects to nearby aircraft wiring are discussed. A potential front-door- coupling effect on NAV/COM equipment is not investigated in this paper.

  16. Active Thermal Extraction and Temperature Sensing of Near-field Thermal Radiation

    NASA Astrophysics Data System (ADS)

    Ding, D.; Kim, T.; Minnich, A. J.

    2016-09-01

    Recently, we proposed an active thermal extraction (ATX) scheme that enables thermally populated surface phonon polaritons to escape into the far-field. The concept is based on a fluorescence upconversion process that also occurs in laser cooling of solids (LCS). Here, we present a generalized analysis of our scheme using the theoretical framework for LCS. We show that both LCS and ATX can be described with the same mathematical formalism by replacing the electron-phonon coupling parameter in LCS with the electron-photon coupling parameter in ATX. Using this framework, we compare the ideal efficiency and power extracted for the two schemes and examine the parasitic loss mechanisms. This work advances the application of ATX to manipulate near-field thermal radiation for applications such as temperature sensing and active radiative cooling.

  17. Near-field thermoacoustic imaging with transmission line pulsers.

    PubMed

    Omar, Murad; Kellnberger, Stephan; Sergiadis, George; Razansky, Daniel; Ntziachristos, Vasilis

    2012-07-01

    Near-field radiofrequency thermoacoustic (NRT) tomography has been recently introduced for imaging electromagnetic (EM) properties of tissues using ultrawideband, high-energy impulses, which induce thermoacoustic responses. Operation in the near-field allows for more effective energy coupling into tissue, compared to using radiating sources, which in turn enables the use of shorter excitation pulses and leads to higher image resolution. This work aimed at investigating transmission lines as a method to generate excitation pulses to improve the NRT resolution over previous implementations without compromising the energy coupled into tissue. The authors implemented a number of custom-made transmission lines to overcome the challenges of the broadband nature of the impulse excitation required in NRT. The authors further constructed phantoms and investigated the performance of the lines in regard to the pulse duration, energy coupling and the resulting resolution, and image quality achieved. Finally, the authors employed mice in order to investigate the performance of the approach in tissue imaging. The authors found that the use of transmission lines resulted in the generation of RF impulses in the range of tens of nanoseconds and shorter. This performance resulted to resolution improvements over previous thermoacoustic imaging implementations, reaching 45 μm resolution, while retaining several tens to hundreds of milli-Joules of energy per pulse. This performance further allowed the visualization and clear differentiation of different mouse structures such as the heart, lung, or spinal cord. The use of transmission lines significantly improved the NRT performance leading to high thermoacoustic tomography imaging quality by coupling adequate amounts of energy within short times at a relatively low cost.

  18. Near-field thermoacoustic imaging with transmission line pulsers.

    PubMed

    Omar, Murad; Kellnberger, Stephan; Sergiadis, George; Razansky, Daniel; Ntziachristos, Vasilis

    2012-07-01

    Near-field radiofrequency thermoacoustic (NRT) tomography has been recently introduced for imaging electromagnetic (EM) properties of tissues using ultrawideband, high-energy impulses, which induce thermoacoustic responses. Operation in the near-field allows for more effective energy coupling into tissue, compared to using radiating sources, which in turn enables the use of shorter excitation pulses and leads to higher image resolution. This work aimed at investigating transmission lines as a method to generate excitation pulses to improve the NRT resolution over previous implementations without compromising the energy coupled into tissue. The authors implemented a number of custom-made transmission lines to overcome the challenges of the broadband nature of the impulse excitation required in NRT. The authors further constructed phantoms and investigated the performance of the lines in regard to the pulse duration, energy coupling and the resulting resolution, and image quality achieved. Finally, the authors employed mice in order to investigate the performance of the approach in tissue imaging. The authors found that the use of transmission lines resulted in the generation of RF impulses in the range of tens of nanoseconds and shorter. This performance resulted to resolution improvements over previous thermoacoustic imaging implementations, reaching 45 μm resolution, while retaining several tens to hundreds of milli-Joules of energy per pulse. This performance further allowed the visualization and clear differentiation of different mouse structures such as the heart, lung, or spinal cord. The use of transmission lines significantly improved the NRT performance leading to high thermoacoustic tomography imaging quality by coupling adequate amounts of energy within short times at a relatively low cost. © 2012 American Association of Physicists in Medicine.

  19. Near-field acoustic streaming jet

    NASA Astrophysics Data System (ADS)

    Moudjed, B.; Botton, V.; Henry, D.; Millet, S.; Garandet, J. P.; Ben Hadid, H.

    2015-03-01

    A numerical and experimental investigation of the acoustic streaming flow in the near field of a circular plane ultrasonic transducer in water is performed. The experimental domain is a parallelepipedic cavity delimited by absorbing walls to avoid acoustic reflection, with a top free surface. The flow velocities are measured by particle image velocimetry, leading to well-resolved velocity profiles. The theoretical model is based on a linear acoustic propagation model, which correctly reproduces the acoustic field mapped experimentally using a hydrophone, and an acoustic force term introduced in the Navier-Stokes equations under the plane-wave assumption. Despite the complexity of the acoustic field in the near field, in particular in the vicinity of the acoustic source, a good agreement between the experimental measurements and the numerical results for the velocity field is obtained, validating our numerical approach and justifying the planar wave assumption in conditions where it is a priori far from obvious. The flow structure is found to be correlated with the acoustic field shape. Indeed, the longitudinal profiles of the velocity present a wavering linked to the variations in acoustic intensity along the beam axis and transverse profiles exhibit a complex shape strongly influenced by the transverse variations of the acoustic intensity in the beam. Finally, the velocity in the jet is found to increase as the square root of the acoustic force times the distance from the origin of the jet over a major part of the cavity, after a strong short initial increase, where the velocity scales with the square of the distance from the upstream wall.

  20. Nanoscale infrared absorption spectroscopy of individual nanoparticles enabled by scattering-type near-field microscopy.

    PubMed

    Stiegler, Johannes M; Abate, Yohannes; Cvitkovic, Antonija; Romanyuk, Yaroslav E; Huber, Andreas J; Leone, Stephen R; Hillenbrand, Rainer

    2011-08-23

    Infrared absorption spectroscopy is a powerful and widely used tool for analyzing the chemical composition and structure of materials. Because of the diffraction limit, however, it cannot be applied for studying individual nanostructures. Here we demonstrate that the phase contrast in substrate-enhanced scattering-type scanning near-field optical microscopy (s-SNOM) provides a map of the infrared absorption spectrum of individual nanoparticles with nanometer-scale spatial resolution. We succeeded in the chemical identification of silicon nitride nanoislands with heights well below 10 nm, by infrared near-field fingerprint spectroscopy of the Si-N stretching bond. Employing a novel theoretical model, we show that the near-field phase spectra of small particles correlate well with their far-field absorption spectra. On the other hand, the spectral near-field contrast does not scale with the volume of the particles. We find a nearly linear scaling law, which we can attribute to the near-field coupling between the near-field probe and the substrate. Our results provide fundamental insights into the spectral near-field contrast of nanoparticles and clearly demonstrate the capability of s-SNOM for nanoscale chemical mapping based on local infrared absorption.

  1. Near-Field Thermal Radiation for Solar Thermophotovoltaics and High Temperature Thermal Logic and Memory Applications

    NASA Astrophysics Data System (ADS)

    Elzouka, Mahmoud

    This dissertation investigates Near-Field Thermal Radiation (NFTR) applied to MEMS-based concentrated solar thermophotovoltaics (STPV) energy conversion and thermal memory and logics. NFTR is the exchange of thermal radiation energy at nano/microscale; when separation between the hot and cold objects is less than dominant radiation wavelength (˜1 mum). NFTR is particularly of interest to the above applications due to its high rate of energy transfer, exceeding the blackbody limit by orders of magnitude, and its strong dependence on separation gap size, surface nano/microstructure and material properties. Concentrated STPV system converts solar radiation to electricity using heat as an intermediary through a thermally coupled absorber/emitter, which causes STPV to have one of the highest solar-to-electricity conversion efficiency limits (85.4%). Modeling of a near-field concentrated STPV microsystem is carried out to investigate the use of STPV based solid-state energy conversion as high power density MEMS power generator. Numerical results for In 0.18Ga0.82Sb PV cell illuminated with tungsten emitter showed significant enhancement in energy transfer, resulting in output power densities as high as 60 W/cm2; 30 times higher than the equivalent far-field power density. On thermal computing, this dissertation demonstrates near-field heat transfer enabled high temperature NanoThermoMechanical memory and logics. Unlike electronics, NanoThermoMechanical memory and logic devices use heat instead of electricity to record and process data; hence they can operate in harsh environments where electronics typically fail. NanoThermoMechanical devices achieve memory and thermal rectification functions through the coupling of near-field thermal radiation and thermal expansion in microstructures, resulting in nonlinear heat transfer between two temperature terminals. Numerical modeling of a conceptual NanoThermoMechanical is carried out; results include the dynamic response under

  2. Near-field thermoacoustic tomography of small animals.

    PubMed

    Kellnberger, Stephan; Hajiaboli, Amir; Razansky, Daniel; Ntziachristos, Vasilis

    2011-06-07

    Near-field radiofrequency thermoacoustic (NRT) tomography is a new imaging method that was developed to mitigate limitations of conventional thermoacoustic imaging approaches, related to hard compromises between signal strength and spatial resolution. By utilizing ultrahigh-energy electromagnetic impulses at ∼20 ns duration along with improved energy absorption coupling in the near-field, this method can deliver high-resolution images without compromising signal to noise ratio. NRT is a promising modality, offering cost-effectiveness and ease of implementation and it can be conveniently scaled to image small animals and humans. However, several of the performance metrics of the method are not yet documented. In this paper, we characterize the expected imaging performance via numerical simulations based on a finite-integration time-domain (FITD) technique and experiments using tissue mimicking phantoms and different biological samples. Furthermore, we show for the first time whole-body tomographic imaging results from mice, revealing clear anatomical details along with highly dissipative inclusions introduced for control. The best spatial resolution achieved for those experiments was 150 µm.

  3. Surface Wave Multipath Signals in Near-Field Microwave Imaging

    PubMed Central

    Meaney, Paul M.; Shubitidze, Fridon; Fanning, Margaret W.; Kmiec, Maciej; Epstein, Neil R.; Paulsen, Keith D.

    2012-01-01

    Microwave imaging techniques are prone to signal corruption from unwanted multipath signals. Near-field systems are especially vulnerable because signals can scatter and reflect from structural objects within or on the boundary of the imaging zone. These issues are further exacerbated when surface waves are generated with the potential of propagating along the transmitting and receiving antenna feed lines and other low-loss paths. In this paper, we analyze the contributions of multi-path signals arising from surface wave effects. Specifically, experiments were conducted with a near-field microwave imaging array positioned at variable heights from the floor of a coupling fluid tank. Antenna arrays with different feed line lengths in the fluid were also evaluated. The results show that surface waves corrupt the received signals over the longest transmission distances across the measurement array. However, the surface wave effects can be eliminated provided the feed line lengths are sufficiently long independently of the distance of the transmitting/receiving antenna tips from the imaging tank floor. Theoretical predictions confirm the experimental observations. PMID:22566992

  4. MOUNTAIN-SCALE COUPLED PROCESSES (TH/THC/THM)MODELS

    SciTech Connect

    Y.S. Wu

    2005-08-24

    This report documents the development and validation of the mountain-scale thermal-hydrologic (TH), thermal-hydrologic-chemical (THC), and thermal-hydrologic-mechanical (THM) models. These models provide technical support for screening of features, events, and processes (FEPs) related to the effects of coupled TH/THC/THM processes on mountain-scale unsaturated zone (UZ) and saturated zone (SZ) flow at Yucca Mountain, Nevada (BSC 2005 [DIRS 174842], Section 2.1.1.1). The purpose and validation criteria for these models are specified in ''Technical Work Plan for: Near-Field Environment and Transport: Coupled Processes (Mountain-Scale TH/THC/THM, Drift-Scale THC Seepage, and Drift-Scale Abstraction) Model Report Integration'' (BSC 2005 [DIRS 174842]). Model results are used to support exclusion of certain FEPs from the total system performance assessment for the license application (TSPA-LA) model on the basis of low consequence, consistent with the requirements of 10 CFR 63.342 [DIRS 173273]. Outputs from this report are not direct feeds to the TSPA-LA. All the FEPs related to the effects of coupled TH/THC/THM processes on mountain-scale UZ and SZ flow are discussed in Sections 6 and 7 of this report. The mountain-scale coupled TH/THC/THM processes models numerically simulate the impact of nuclear waste heat release on the natural hydrogeological system, including a representation of heat-driven processes occurring in the far field. The mountain-scale TH simulations provide predictions for thermally affected liquid saturation, gas- and liquid-phase fluxes, and water and rock temperature (together called the flow fields). The main focus of the TH model is to predict the changes in water flux driven by evaporation/condensation processes, and drainage between drifts. The TH model captures mountain-scale three-dimensional flow effects, including lateral diversion and mountain-scale flow patterns. The mountain-scale THC model evaluates TH effects on water and gas

  5. Probing optical near-fields with photoreactive azo-polymers

    NASA Astrophysics Data System (ADS)

    Dmitrieva, M. D.; Asadullina, A. R.; Salakhov, M. Kh

    2017-06-01

    In this work, we demonstrate a method to visualize optical near-fields on photosensitive azo-polymer thin films with scanning near-field optical microscopy. A near-field intensity profile is determined in a basis of surface deformations of the azo-polymer thin film exposed to linearly polarized light.

  6. Infrared near-field imaging and spectroscopy based on thermal or synchrotron radiation

    SciTech Connect

    Peragut, Florian; De Wilde, Yannick; Brubach, Jean-Blaise; Roy, Pascale

    2014-06-23

    We demonstrate the coupling of a scattering near-field scanning optical microscope combined with a Fourier transform infrared spectrometer. The set-up operates using either the near-field thermal emission from the sample itself, which is proportional to the electromagnetic local density of states, or with an external infrared synchrotron source, which is broadband and highly brilliant. We perform imaging and spectroscopy measurements with sub-wavelength spatial resolution in the mid-infrared range on surfaces made of silicon carbide and gold and demonstrate the capabilities of the two configurations for super-resolved near-field mid-infrared hyperspectral imaging and that the simple use of a properly chosen bandpass filter on the detector allows one to image the spatial distribution of materials with sub-wavelength resolution by studying the contrast in the near-field images.

  7. Theory of near-field magneto-optical imaging

    NASA Astrophysics Data System (ADS)

    Walford, Julian N.; Porto, Juan-Antonio; Carminati, Rémi; Greffet, Jean-Jacques

    2002-03-01

    Scanning near-field optical microscopy has been recently applied to the imaging of magnetic samples. It was shown experimentally that an apertureless microscope suffers a substantial loss of resolution when used for magneto-optical imaging compared with that for conventional imaging. No such change is observed for aperture microscopes. We explain this observation by developing a model for the imaging process that incorporates the response of the probe. We calculate real observable properties such as the rotation of polarization at the detector or the circular dichroism signal and thus simulate magneto-optical images of a domain structure in cobalt for both aperture and apertureless microscopes.

  8. Electrooptic sensor module fabrication for near-field intrabody communication

    NASA Astrophysics Data System (ADS)

    Furuya, Akinori; Sasaki, Ai-ichiro; Morimura, Hiroki; Kagami, Osamu; Shinagawa, Mitsuru

    2014-09-01

    In this paper, we describe how to obtain a low cost electrooptic (EO) sensor module for the mass production of near-field intrabody communication devices. In our previous study, we used a bulk cleavage technique to fabricate EO modulators without the need for any optical polishing or washing processes. In this study, we fabricated EO modulators as a miniaturized chip sensor without a base portion, and clarified the feasibility of assembling optical components by only a passive alignment technique with a compact housing.

  9. The Survey on Near Field Communication.

    PubMed

    Coskun, Vedat; Ozdenizci, Busra; Ok, Kerem

    2015-06-05

    Near Field Communication (NFC) is an emerging short-range wireless communication technology that offers great and varied promise in services such as payment, ticketing, gaming, crowd sourcing, voting, navigation, and many others. NFC technology enables the integration of services from a wide range of applications into one single smartphone. NFC technology has emerged recently, and consequently not much academic data are available yet, although the number of academic research studies carried out in the past two years has already surpassed the total number of the prior works combined. This paper presents the concept of NFC technology in a holistic approach from different perspectives, including hardware improvement and optimization, communication essentials and standards, applications, secure elements, privacy and security, usability analysis, and ecosystem and business issues. Further research opportunities in terms of the academic and business points of view are also explored and discussed at the end of each section. This comprehensive survey will be a valuable guide for researchers and academicians, as well as for business in the NFC technology and ecosystem.

  10. The Survey on Near Field Communication

    PubMed Central

    Coskun, Vedat; Ozdenizci, Busra; Ok, Kerem

    2015-01-01

    Near Field Communication (NFC) is an emerging short-range wireless communication technology that offers great and varied promise in services such as payment, ticketing, gaming, crowd sourcing, voting, navigation, and many others. NFC technology enables the integration of services from a wide range of applications into one single smartphone. NFC technology has emerged recently, and consequently not much academic data are available yet, although the number of academic research studies carried out in the past two years has already surpassed the total number of the prior works combined. This paper presents the concept of NFC technology in a holistic approach from different perspectives, including hardware improvement and optimization, communication essentials and standards, applications, secure elements, privacy and security, usability analysis, and ecosystem and business issues. Further research opportunities in terms of the academic and business points of view are also explored and discussed at the end of each section. This comprehensive survey will be a valuable guide for researchers and academicians, as well as for business in the NFC technology and ecosystem. PMID:26057043

  11. Near Field Scanning Optical Microscopy (NSOM)

    PubMed Central

    Betzig, E.; Lewis, A.; Harootunian, A.; Isaacson, M.; Kratschmer, E.

    1986-01-01

    A new method for high-resolution imaging, near-field scanning optical microscopy (NSOM), has been developed. The concepts governing this method are discussed, and the technical challenges encountered in constructing a working NSOM instrument are described. Two distinct methods are presented for the fabrication of well-characterized, highly reproducible, subwavelength apertures. A sample one-dimensional scan is provided and compared to the scanning electron micrograph of a test pattern. From this comparison, a resolution of > 1,500 Å (i.e., ≃λ/3.6) is determined, which represents a significant step towards our eventual goal of 500 Å resolution. Fluorescence has been observed through apertures smaller than 600 Å and signal-to-noise calculations show that fluorescent imaging should be feasible. The application of such imaging is then discussed in reference to specific biological problems. The NSOM method employs nonionizing visible radiation and can be used in air or aqueous environments for nondestructive visualization of functioning biological systems with a resolution comparable to that of scanning electron microscopy. ImagesFIGURE 4FIGURE 7FIGURE 9FIGURE 10 PMID:19431633

  12. Gold Coating of Fiber Tips in Near-Field Scanning Optical Microscopy

    NASA Technical Reports Server (NTRS)

    Vikram, Chandra S.; Witherow, William K.

    2000-01-01

    We report what is believed to be the first experimental demonstration of gold coating by a chemical baking process on tapered fiber tips used in near-field scanning optical microscopy. Many tips can be simultaneously coated.

  13. Gold Coating of Fiber Tips in Near-Field Scanning Optical Microscopy

    NASA Technical Reports Server (NTRS)

    Vikram, Chandra S.; Witherow, William K.

    2000-01-01

    We report what is believed to be the first experimental demonstration of gold coating by a chemical baking process on tapered fiber tips used in near-field scanning optical microscopy. Many tips can be simultaneously coated.

  14. Near-field spectroscopy of graphene during ultrafast photoexcitation

    NASA Astrophysics Data System (ADS)

    Wagner, Martin; Fei, Zhe; McLeod, Alexander; Rodin, Aleksandr; Bao, Wenzhong; Zhang, Lingfeng; Zhao, Zeng; Iwinski, Eric; Thiemens, Mark; Fogler, Michael; Castro-Neto, Antonio; Lau, Chunning; Keilmann, Fritz; Basov, Dimitri

    2013-03-01

    Recently, impressive progress in nanoplasmonics of graphene using near-field spectroscopy and imaging has been reported [Z. Fei et al., Nano Lett. 11, 4701 (2011); Z. Fei et al., Nature 487, 82 (2012)]. However, these studies of the interaction of the graphene plasmon with the SiO2 substrate surface phonon were time-independent. Here we combine imaging and material characterization on the nano scale with ultrafast sub-picosecond time resolution and present optical pump broadband mid-infrared probe spectroscopy of graphene. We discuss the optical pump induced changes of the coupled plasmon-phonon modes with respect to carrier density and time-dependence. The difference between ultrafast photoexcitation and conventional electrostatic doping via the field effect is analyzed and compared with modeling.

  15. Mechanical Behavior of the Near-field Host Rock Surrounding Excavations

    SciTech Connect

    Kelkar, Sharad M.; Stauffer, Philip H.; Robinson, Bruce Alan

    2015-01-09

    This report is being prepared under the FY14 activity FT-14LA0818069, Mechanical and Hydrological Behavior of the Near-Field Host Rock Surrounding Excavations, and fulfills the Los Alamos National Laboratory deliverable M4FT-14LA08180610, which in PICS:NE is titled “Draft report, Test Plan for Mechanical and Hydrological Behavior of the Near-field Host Rock Surrounding Excavations.” Since the report is an intermediate deliverable intended as input to the eventual test plan for this test, rather than being an actual test plan, the activity title is used as the title of this document to avoid confusion as to the contents in the report. This report summarizes efforts to simulate mechanical processes occurring within a hypothetical high-level waste (HLW) repository in bedded salt. The report summarizes work completed since the last project deliverable, “Coupled model for heat and water transport in a high level waste repository in salt “, a Level 2 milestone submitted to DOE in September 2013 (Stauffer et al., 2013).

  16. Near-field imaging of optical antenna modes in the mid-infrared.

    PubMed

    Olmon, Robert L; Krenz, Peter M; Jones, Andrew C; Boreman, Glenn D; Raschke, Markus B

    2008-12-08

    Optical antennas can enhance the coupling between free-space propagating light and the localized excitation of nanoscopic light emitters or receivers, thus forming the basis of many nanophotonic applications. Their functionality relies on an understanding of the relationship between the geometric parameters and the resulting near-field antenna modes. Using scattering-type scanning near-field optical microscopy (s-SNOM) with interferometric homodyne detection, we investigate the resonances of linear Au wire antennas designed for the mid-IR by probing specific vector near-field components. A simple effective wavelength scaling is observed for single wires with lambda(eff) = lambda /(2.0+/- 0.2), specific to the geometric and material parameters used. The disruption of the coherent current oscillation by introducing a gap gives rise to an effective multipolar mode for the two near-field coupled segments. Using antenna theory and numerical electrodynamics simulations two distinct coupling regimes are considered that scale with gap width or reactive near-field decay length, respectively. The results emphasize the distinct antenna behavior at optical frequencies compared to impedance matched radio frequency (RF) antennas and provide experimental confirmation of theoretically predicted scaling laws at optical frequencies.

  17. Vibrational near-field mapping of planar and buried three-dimensional plasmonic nanostructures

    PubMed Central

    Dregely, Daniel; Neubrech, Frank; Duan, Huigao; Vogelgesang, Ralf; Giessen, Harald

    2013-01-01

    Nanoantennas confine electromagnetic fields at visible and infrared wavelengths to volumes of only a few cubic nanometres. Assessing their near-field distribution offers fundamental insight into light–matter coupling and is of special interest for applications such as radiation engineering, attomolar sensing and nonlinear optics. Most experimental approaches to measure near-fields employ either diffraction-limited far-field methods or intricate near-field scanning techniques. Here, using diffraction-unlimited far-field spectroscopy in the infrared, we directly map the intensity of the electric field close to plasmonic nanoantennas. We place a patch of probe molecules with 10 nm accuracy at different locations in the near-field of a resonant antenna and extract the molecular vibrational excitation. We map the field intensity along a dipole antenna and gap-type antennas. Moreover, this method is able to assess the near-field intensity of complex buried plasmonic structures. We demonstrate this by measuring for the first time the near-field intensity of a three-dimensional plasmonic electromagnetically induced transparency structure. PMID:23892519

  18. Vibrational near-field mapping of planar and buried three-dimensional plasmonic nanostructures.

    PubMed

    Dregely, Daniel; Neubrech, Frank; Duan, Huigao; Vogelgesang, Ralf; Giessen, Harald

    2013-01-01

    Nanoantennas confine electromagnetic fields at visible and infrared wavelengths to volumes of only a few cubic nanometres. Assessing their near-field distribution offers fundamental insight into light-matter coupling and is of special interest for applications such as radiation engineering, attomolar sensing and nonlinear optics. Most experimental approaches to measure near-fields employ either diffraction-limited far-field methods or intricate near-field scanning techniques. Here, using diffraction-unlimited far-field spectroscopy in the infrared, we directly map the intensity of the electric field close to plasmonic nanoantennas. We place a patch of probe molecules with 10 nm accuracy at different locations in the near-field of a resonant antenna and extract the molecular vibrational excitation. We map the field intensity along a dipole antenna and gap-type antennas. Moreover, this method is able to assess the near-field intensity of complex buried plasmonic structures. We demonstrate this by measuring for the first time the near-field intensity of a three-dimensional plasmonic electromagnetically induced transparency structure.

  19. Infrared Phonon Fingerprinting of Nanocrystals through Broadband Near-Field Spectroscopy

    NASA Astrophysics Data System (ADS)

    McLeod, Alexander S.; Dominguez, Gerardo; Kelly, Priscilla; Thiemens, Mark; Zhang, Lingfeng M.; Rodin, Alex; Fogler, Michael M.; Keilmann, Fritz; Basov, D. N.

    2012-02-01

    Near-field infrared spectroscopy has recently been demonstrated with the capability to resolve optical properties of sub-wavelength sample areas across a broad range of infrared frequencies. This method holds promise for the direct identification of sub-wavelength chemical composition in nanostructured and heterogeneous samples. We apply this technique to the study of phonon-resonant silicon carbide nanocrystals tens of nanometers in size using an apertureless scanning near-field optical microscope (SNOM) coupled to a pulsed broadband infrared laser source and FTIR spectrometer. We present measurements of nanocrystal near-field spectra in the range of 700-1200 cm-1 evaluated in comparison with the near-field spectra of bulk silicon carbide, calibrated using ellipsometry. A detailed analytic model of the probe-sample near-field interaction is applied for the identification of nanoscale resonant size effects. These techniques provide a powerful method for identifying and characterizing sub-wavelength nanocrystals in heterogeneous samples via near-field infrared ``phonon fingerprinting.''

  20. Far-field subwavelength imaging with near-field resonant metalens scanning at microwave frequencies

    PubMed Central

    Wang, Ren; Wang, Bing-Zhong; Gong, Zhi-Shuang; Ding, Xiao

    2015-01-01

    A method for far-field subwavelength imaging at microwave frequencies using near-field resonant metalens scanning is proposed. The resonant metalens is composed of switchable split-ring resonators (SRRs). The on-SRR has a strong magnetic coupling ability and can convert evanescent waves into propagating waves using the localized resonant modes. In contrast, the off-SRR cannot achieve an effective conversion. By changing the switch status of each cell, we can obtain position information regarding the subwavelength source targets from the far field. Because the spatial response and Green’s function do not need to be measured and evaluated and only a narrow frequency band is required for the entire imaging process, this method is convenient and adaptable to various environment. This method can be used for many applications, such as subwavelength imaging, detection, and electromagnetic monitoring, in both free space and complex environments. PMID:26053074

  1. Coupled transport processes in semipermeable media

    SciTech Connect

    Jacobsen, J.S.; Carnahan, C.L.

    1990-03-01

    The thermodynamics of irreversible processes leads to nonlinear governing equations for direct and coupled mass transport processes. Analytical solutions of linearized versions of these equations can be used to verify numerical solutions of the nonlinear equations under conditions such that nonlinear terms are relatively small. This report presents derivations of the analytical solutions for one-dimensional and axisymmetric geometries. 7 refs.

  2. Assessment of Near-Field Sonic Boom Simulation Tools

    NASA Technical Reports Server (NTRS)

    Casper, J. H.; Cliff, S. E.; Thomas, S. D.; Park, M. A.; McMullen, M. S.; Melton, J. E.; Durston, D. A.

    2008-01-01

    A recent study for the Supersonics Project, within the National Aeronautics and Space Administration, has been conducted to assess current in-house capabilities for the prediction of near-field sonic boom. Such capabilities are required to simulate the highly nonlinear flow near an aircraft, wherein a sonic-boom signature is generated. There are many available computational fluid dynamics codes that could be used to provide the near-field flow for a sonic boom calculation. However, such codes have typically been developed for applications involving aerodynamic configuration, for which an efficiently generated computational mesh is usually not optimum for a sonic boom prediction. Preliminary guidelines are suggested to characterize a state-of-the-art sonic boom prediction methodology. The available simulation tools that are best suited to incorporate into that methodology are identified; preliminary test cases are presented in support of the selection. During this phase of process definition and tool selection, parallel research was conducted in an attempt to establish criteria that link the properties of a computational mesh to the accuracy of a sonic boom prediction. Such properties include sufficient grid density near shocks and within the zone of influence, which are achieved by adaptation and mesh refinement strategies. Prediction accuracy is validated by comparison with wind tunnel data.

  3. Dynamic near-field optical interaction between oscillating nanomechanical structures

    DOE PAGES

    Ahn, Phillip; Chen, Xiang; Zhang, Zhen; ...

    2015-05-27

    Near-field optical techniques exploit light-matter interactions at small length scales for mechanical sensing and actuation of nanomechanical structures. Here, we study the optical interaction between two mechanical oscillators—a plasmonic nanofocusing probe-tip supported by a low frequency cantilever, and a high frequency nanomechanical resonator—and leverage their interaction for local detection of mechanical vibrations. The plasmonic nanofocusing probe provides a confined optical source to enhance the interaction between the two oscillators. Dynamic perturbation of the optical cavity between the probe-tip and the resonator leads to nonlinear modulation of the scattered light intensity at the sum and difference of their frequencies. This double-frequencymore » demodulation scheme is explored to suppress unwanted background and to detect mechanical vibrations with a minimum detectable displacement sensitivity of 0.45pm/Hz1/2, which is limited by shot noise and electrical noise. We explore the demodulation scheme for imaging the bending vibration mode shape of the resonator with a lateral spatial resolution of 20nm. We also demonstrate the time-resolved aspect of the local optical interaction by recording the ring-down vibrations of the resonator at frequencies of up to 129MHz. The near-field optical technique is promising for studying dynamic mechanical processes in individual nanostructures.« less

  4. Dynamic near-field optical interaction between oscillating nanomechanical structures

    SciTech Connect

    Ahn, Phillip; Chen, Xiang; Zhang, Zhen; Ford, Matthew; Rosenmann, Daniel; Jung, II Woong; Sun, Cheng; Balogun, Oluwaseyi

    2015-05-27

    Near-field optical techniques exploit light-matter interactions at small length scales for mechanical sensing and actuation of nanomechanical structures. Here, we study the optical interaction between two mechanical oscillators—a plasmonic nanofocusing probe-tip supported by a low frequency cantilever, and a high frequency nanomechanical resonator—and leverage their interaction for local detection of mechanical vibrations. The plasmonic nanofocusing probe provides a confined optical source to enhance the interaction between the two oscillators. Dynamic perturbation of the optical cavity between the probe-tip and the resonator leads to nonlinear modulation of the scattered light intensity at the sum and difference of their frequencies. This double-frequency demodulation scheme is explored to suppress unwanted background and to detect mechanical vibrations with a minimum detectable displacement sensitivity of 0.45pm/Hz1/2, which is limited by shot noise and electrical noise. We explore the demodulation scheme for imaging the bending vibration mode shape of the resonator with a lateral spatial resolution of 20nm. We also demonstrate the time-resolved aspect of the local optical interaction by recording the ring-down vibrations of the resonator at frequencies of up to 129MHz. The near-field optical technique is promising for studying dynamic mechanical processes in individual nanostructures.

  5. Dynamic near-field optical interaction between oscillating nanomechanical structures

    PubMed Central

    Ahn, Phillip; Chen, Xiang; Zhang, Zhen; Ford, Matthew; Rosenmann, Daniel; Jung, II Woong; Sun, Cheng; Balogun, Oluwaseyi

    2015-01-01

    Near-field optical techniques exploit light-matter interactions at small length scales for mechanical sensing and actuation of nanomechanical structures. Here, we study the optical interaction between two mechanical oscillators—a plasmonic nanofocusing probe-tip supported by a low frequency cantilever, and a high frequency nanomechanical resonator—and leverage their interaction for local detection of mechanical vibrations. The plasmonic nanofocusing probe provides a confined optical source to enhance the interaction between the two oscillators. Dynamic perturbation of the optical cavity between the probe-tip and the resonator leads to nonlinear modulation of the scattered light intensity at the sum and difference of their frequencies. This double-frequency demodulation scheme is explored to suppress unwanted background and to detect mechanical vibrations with a minimum detectable displacement sensitivity of 0.45 pm/Hz1/2, which is limited by shot noise and electrical noise. We explore the demodulation scheme for imaging the bending vibration mode shape of the resonator with a lateral spatial resolution of 20 nm. We also demonstrate the time-resolved aspect of the local optical interaction by recording the ring-down vibrations of the resonator at frequencies of up to 129 MHz. The near-field optical technique is promising for studying dynamic mechanical processes in individual nanostructures. PMID:26014599

  6. Approximate expression to estimate signal-to-noise ratio improvement in cylindrical near-field measurements

    NASA Astrophysics Data System (ADS)

    Romeu, Jordi; Jofre, Lluis; Cardama, Angel

    1994-07-01

    A very simple approximate expression for the process gain (PG) for the cylindrical case is derived. The different approximations and assumptions required to obtain this expression are shown. This expression might be useful for most practical cylindrical near-field measurements, providing a very simple mean to assess the near-field dynamic range requirements to obtain a desired far-field signal-to-noise ratio (SNR).

  7. Accurate near-field lithography modeling and quantitative mapping of the near-field distribution of a plasmonic nanoaperture in a metal.

    PubMed

    Kim, Yongwoo; Jung, Howon; Kim, Seok; Jang, Jinhee; Lee, Jae Yong; Hahn, Jae W

    2011-09-26

    In nanolithography using optical near-field sources to push the critical dimension below the diffraction limit, optimization of process parameters is of utmost importance. Herein we present a simple analytic model to predict photoresist profiles with a localized evanescent exposure that decays exponentially in a photoresist of finite contrast. We introduce the concept of nominal developing thickness (NDT) to determine the proper developing process that yields the best topography of the exposure profile fitting to the isointensity contour. Based on this model, we experimentally investigated the NDT and obtained exposure profiles produced by the near-field distribution of a bowtie-shaped nanoaperture. The profiles were properly fit to the calculated results obtained by the finite differential time domain method. Using the threshold exposure dose of a photoresist, we can determine the absolute intensity of the intensity distribution of the near field and analyze the difference in decay rates of the near field distributions obtained via experiment and calculation. For maximum depth of 41 nm, we estimate the uncertainties in the measurements of profile and intensity to be less than 6% and about 1%, respectively. We expect this method will be useful in detecting the absolute value of the near-field distribution produced by nano-scale devices.

  8. A unidirectional subwavelength focusing near-field plate

    SciTech Connect

    Imani, Mohammadreza F.; Grbic, Anthony

    2014-01-28

    Near-field plates consist of non-periodically patterned surfaces that can overcome the diffraction limit and confine electromagnetic fields to subwavelength dimensions. Previous near-field plates experimentally demonstrated extreme field tailoring capabilities. However, their performance suffered from radiation/reflection in undesired directions, those other than the subwavelength focus. This issue can limit the practical use of near-field plates. In this paper, we address this issue by designing a unidirectional near-field plate that can form a subwavelength focal pattern, while suppressing the field radiated/reflected in other directions. The design and operation of the proposed unidirectional near-field plate are verified through full-wave simulation. The unidirectional near-field plate may find application in high resolution imaging and probing, high density data storage, and wireless power transfer systems. As an example, its utility as a high resolution probe is demonstrated through full-wave electromagnetic simulation.

  9. Near Field Ocean Surface Waves Acoustic Radiation Observation and Modeling

    NASA Astrophysics Data System (ADS)

    Ardhuin, F.; Peureux, C.; Royer, J. Y.

    2016-12-01

    The acoustic noise generation by nonlinearly interacting surface gravity waves has been studied for a long time both theoretically and experimentally [Longuet-Higgins 1951]. The associated far field noise is continuously measured by a vast network of seismometers at the ocean bottom and on the continents. It can especially be used to infer the time variability of short ocean waves statistics [Peureux and Ardhuin 2016]. However, better quantitative estimates of the latter are made difficult due to a poor knowledge of the Earth's crust characteristics, whose coupling with acoustic modes can affect large uncertainties to the frequency response at the bottom of the ocean.The pressure field at depths less than an acoustic wave length to the surface is made of evanescent modes which vanish away from their sources (near field) [Cox and Jacobs 1989]. For this reason, they are less affected by the ocean bottom composition. This near field is recorded and analyzed in the frequency range 0.1 to 0.5 Hz approximately, at two locations : at a shallow site in the North-East Atlantic continental shelf and a deep water site in the Southern Indian ocean, where pressure measurements are performed at the ocean bottom (ca. 100 m) and at 300 m water depth respectively. Evanescent and propagating Rayleigh modes are compared against theoretical predictions. Comparisons against surface waves hindcast based on WAVEWATCH(R) III modeling framework help assessing its performances and can be used to help future model improvements.References Longuet-Higgins, M. S., A Theory of the Origin of Microseisms, Philos. Trans. Royal Soc. A, 1950, 243, 1-3. Peureux, C. and Ardhuin, F., Ocean bottom pressure records from the Cascadia array and short surface gravity waves, J. Geophys. Res. Oceans, 2016, 121, 2862-2873. Cox, C. S. & Jacobs, D. C., Cartesian diver observations of double frequency pressure fluctuations in the upper levels of the ocean, Geophys. Res. Lett., 1989, 16, 807-810.

  10. Theory of Near-Field Scanning with a Probe Array

    DTIC Science & Technology

    2014-01-01

    AFRL-RY-WP-TR-2013-0239 THEORY OF NEAR-FIELD SCANNING WITH A PROBE ARRAY Kristopher T. Kim and Bradley A. Kramer Antennas...Final 15 March 2010 – 30 September 2013 4. TITLE AND SUBTITLE THEORY OF NEAR-FIELD SCANNING WITH A PROBE ARRAY 5a. CONTRACT NUMBER IN-HOUSE 5b...December 2013. Report contains color. 14. ABSTRACT In near-field scanning , as the electrical size of a device under test increases, it becomes

  11. Fabrication of nanochannels via near-field electrospinning

    NASA Astrophysics Data System (ADS)

    Wang, Xiang; Zheng, Gaofeng; Xu, Lei; Cheng, Wei; Xu, Bulei; Huang, Yongfang; Sun, Daoheng

    2012-09-01

    A simple and low-cost method is suggested to fabricate nanochannels via Near-Field Electrospinning (NFES). In this process, orderly and patterned nanofibers direct-written by NFES are used as sacrificial templates. Well-defined nanochannels are available after the removal process of both sacrificial fibers and material coating over the fibers. The sacrificial fiber, controlled by NFES, dominates the channel geometry. The channel width ranges from 133 nm to 13.54 µm while the applied voltage increases from 1.2 kV to 2.5 kV. Complicated wave-shape and grid pattern channels are presented under a corresponding movement of substrate. This method integrates electrospinning with conventional MEMS fabrication technology and has a potential in micro/nano manufacturing.

  12. Drift-Scale Coupled Processes (DST and TH Seepage) Models

    SciTech Connect

    J. Birkholzer; S. Mukhopadhyay

    2004-09-29

    The purpose of this report is to document drift-scale modeling work performed to evaluate the thermal-hydrological (TH) behavior in Yucca Mountain fractured rock close to waste emplacement drifts. The heat generated by the decay of radioactive waste results in rock temperatures elevated from ambient for thousands of years after emplacement. Depending on the thermal load, these temperatures are high enough to cause boiling conditions in the rock, giving rise to water redistribution and altered flow paths. The predictive simulations described in this report are intended to investigate fluid flow in the vicinity of an emplacement drift for a range of thermal loads. Understanding the TH coupled processes is important for the performance of the repository because the thermally driven water saturation changes affect the potential seepage of water into waste emplacement drifts. Seepage of water is important because if enough water gets into the emplacement drifts and comes into contact with any exposed radionuclides, it may then be possible for the radionuclides to be transported out of the drifts and to the groundwater below the drifts. For above-boiling rock temperatures, vaporization of percolating water in the fractured rock overlying the repository can provide an important barrier capability that greatly reduces (and possibly eliminates) the potential of water seeping into the emplacement drifts. In addition to this thermal process, water is inhibited from entering the drift opening by capillary forces, which occur under both ambient and thermal conditions (capillary barrier). The combined barrier capability of vaporization processes and capillary forces in the near-field rock during the thermal period of the repository is analyzed and discussed in this report.

  13. DRIFT-SCALE COUPLED PROCESSES (DST AND TH SEEPAGE) MODELS

    SciTech Connect

    J.T. Birkholzer; S. Mukhopadhyay

    2005-01-13

    The purpose of this report is to document drift-scale modeling work performed to evaluate the thermal-hydrological (TH) behavior in Yucca Mountain fractured rock close to waste emplacement drifts. The heat generated by the decay of radioactive waste results in rock temperatures elevated from ambient for thousands of years after emplacement. Depending on the thermal load, these temperatures are high enough to cause boiling conditions in the rock, giving rise to water redistribution and altered flow paths. The predictive simulations described in this report are intended to investigate fluid flow in the vicinity of an emplacement drift for a range of thermal loads. Understanding the TH coupled processes is important for the performance of the repository because the thermally driven water saturation changes affect the potential seepage of water into waste emplacement drifts. Seepage of water is important because if enough water gets into the emplacement drifts and comes into contact with any exposed radionuclides, it may then be possible for the radionuclides to be transported out of the drifts and to the groundwater below the drifts. For above-boiling rock temperatures, vaporization of percolating water in the fractured rock overlying the repository can provide an important barrier capability that greatly reduces (and possibly eliminates) the potential of water seeping into the emplacement drifts. In addition to this thermal process, water is inhibited from entering the drift opening by capillary forces, which occur under both ambient and thermal conditions (capillary barrier). The combined barrier capability of vaporization processes and capillary forces in the near-field rock during the thermal period of the repository is analyzed and discussed in this report.

  14. Near-field spectroscopy of silicon dioxide thin films

    NASA Astrophysics Data System (ADS)

    Zhang, L. M.; Andreev, G. O.; Fei, Z.; McLeod, A. S.; Dominguez, G.; Thiemens, M.; Castro-Neto, A. H.; Basov, D. N.; Fogler, M. M.

    2012-02-01

    We analyze the results of scanning near-field infrared spectroscopy performed on thin films of a-SiO2 on Si substrate. The measured near-field signal exhibits surface-phonon resonances whose strength has a prominent thickness dependence in the range from 2 to 300nm. These observations are compared with calculations in which the tip of the near-field infrared spectrometer is modeled either as a point dipole or an elongated spheroid. The latter model accounts for the antenna effect of the tip and gives a better agreement with the experiment. Possible applications of the near-field technique for depth profiling of layered nanostructures are discussed.

  15. Induction coupled thermomagnetic processing: A disruptive technology

    DOE PAGES

    Ahmad, Aquil; Mackiewicz-Ludtka, Gail; Pfaffmann, George; ...

    2016-06-01

    Here, one of the major goals of the U.S. Department of Energy (DoE) is to achieve energy savings with a corresponding reduction in the carbon footprint. With this in mind, the DoE sponsored the Induction Coupled Thermomagnetic Processing (ITMP) project with major partners Eaton Corp., Ajax Tocco Magnethermic, and Oak Ridge National Laboratory (ORNL) to evaluate the viability of processing metals in a strong magnetic field.

  16. Nanospectrofluorometry inside single living cell by scanning near-field optical microscopy

    NASA Astrophysics Data System (ADS)

    Lei, F. H.; Shang, G. Y.; Troyon, M.; Spajer, M.; Morjani, H.; Angiboust, J. F.; Manfait, M.

    2001-10-01

    Near-field fluorescence spectra with subdiffraction limit spatial resolution have been taken in the proximity of mitochondrial membrane inside breast adenocarcinoma cells (MCF7) treated with the fluorescent dye (JC-1) by using a scanning near-field optical microscope coupled with a confocal laser microspectrofluorometer. The probe-sample distance control is based on a piezoelectric bimorph shear force sensor having a static spring constant k=5 μN/nm and a quality factor Q=40 in a physiological medium of viscosity η=1.0 cp. The sensitivity of the force sensor has been tested by imaging a MCF7 cell surface.

  17. Near field laser transmission with bidirectional beacon tracking for Tbps class wireless communications

    NASA Astrophysics Data System (ADS)

    Arimoto, Yoshinori

    2010-02-01

    This paper discusses a new concept of free-space optical (FSO) communication terminals, characterized as the mutual tracking of near field Gaussian beams and the direct single mode fiber coupling to achieve Tera-bit/seconds (Tbps) class FSO link in short range outdoor environments. It first shows the required optical configurations including beacon transmitters, tracking sensors and fast steering mirrors to construct the mutual tracking system and then discusses their capabilities and performance for this specific near field operation in which conventional tracking system is not enough to assure stable and reliable link performance. It also presents one of the simplest realizations of the new FSO terminals and their test results.

  18. Evolution of Biomass Burning Aerosols in the Near Field

    NASA Astrophysics Data System (ADS)

    Sedlacek, Arthur; Kleinman, Lawrence; Arnott, W. Patrick; Adachi, Kouji; Buseck, Peter; Lewis, Ernest; Onasch, Timothy; pikridas, Michail; Shilling, John; Springston, Stephen; Wang, Jian; Yokelson, Robert

    2014-05-01

    Biomass burning is a significant source of aerosols that can perturb Earth's climate through the direct (both scattering and absorption), indirect (cloud formation and precipitation), and semi-direct (cloud dissipation) radiative effects. Despite much effort, quantities important to determining radiative forcing for these events still remain highly uncertain due to the inherent difficultly of conducting the required measurements and instrumentation limitations. Further adding to this uncertainty is that few field campaigns have been conducted in the northern temperate latitudes in spite of biomass burning producing about one-third of the PM2.5 in the US. During the summer and early fall of 2013, the Atmospheric Radiation Measurement (ARM) program of the U. S. Department of Energy (DOE) sponsored an aircraft-based field campaign to study the near-field evolution of particulate emissions from biomass burning. Key scientific objectives for the Biomass Burning Observation Project (BBOP) are to 1) quantify the downwind time evolution of microphysical, morphological, chemical, hygroscopic, and optical properties of aerosols generated by biomass burning, 2) use the time sequences of observations to constrain processes and parameterizations in a Lagrangian model of aerosol evolution, and 3) incorporate time evolution information into a single-column radiative transfer model for determining forcing per unit carbon burned. Discussion will be on the near-field evolution of particle mixing state and morphology, chemical composition, and microphysical processes that determine aerosol size distribution and single scattering albedo (SSA) of light absorbing aerosols. In cases studied, increases in the coating thickness of refractive black carbon (rBC) particles, organic aerosol/rBC ratio, scattering/CO ratio, and aerosol size distributions have been observed. Results are based on wildfires sampled in the US northwest and on controlled agricultural burns in the south

  19. Heat flux splitter for near-field thermal radiation

    SciTech Connect

    Ben-Abdallah, P.; Belarouci, A.; Frechette, L.; Biehs, S.-A.

    2015-08-03

    We demonstrate the possibility to efficiently split the near-field heat flux exchanged between graphene nano-disks by tuning their doping. This result paves the way for the development of an active control of propagation directions for heat fluxes exchanged in the near field throughout integrated nanostructured networks.

  20. A fast and flexible library-based thick-mask near-field calculation method

    NASA Astrophysics Data System (ADS)

    Ma, Xu; Gao, Jie; Chen, Xuanbo; Dong, Lisong; Li, Yanqiu

    2015-03-01

    Aerial image calculation is the basis of the current lithography simulation. As the critical dimension (CD) of the integrated circuits continuously shrinks, the thick mask near-field calculation has increasing influence on the accuracy and efficiency of the entire aerial image calculation process. This paper develops a flexible librarybased approach to significantly improve the efficiency of the thick mask near-field calculation compared to the rigorous modeling method, while leading to much higher accuracy than the Kirchhoff approximation method. Specifically, a set of typical features on the fullchip are selected to serve as the training data, whose near-fields are pre-calculated and saved in the library. Given an arbitrary test mask, we first decompose it into convex corners, concave corners and edges, afterwards match each patch to the training layouts based on nonparametric kernel regression. Subsequently, we use the matched near-fields in the library to replace the mask patches, and rapidly synthesize the near-field for the entire test mask. Finally, a data-fitting method is proposed to improve the accuracy of the synthesized near-field based on least square estimate (LSE). We use a pair of two-dimensional mask patterns to test our method. Simulations show that the proposed method can significantly speed up the current FDTD method, and effectively improve the accuracy of the Kirchhoff approximation method.

  1. Mesoscopic near-field radiative heat transfer at low temperatures

    NASA Astrophysics Data System (ADS)

    Maasilta, Ilari; Geng, Zhuoran; Chaudhuri, Saumyadip; Koppinen, Panu

    2015-03-01

    Near-field radiative heat transfer has mostly been discussed at room temperatures and/or macroscopic scale geometries. Here, we discuss our recent theoretical and experimental advances in understanding near-field transfer at ultra-low temperatures below 1K. As the thermal wavelengths increase with lowering temperature, we show that with sensitive tunnel junction bolometers it is possible to study near-field transfer up to distances ~ 10 μm currently, even though the power levels are low. In addition, these type of experiments correspond to the extreme near-field limit, as the near-field region starts at ~ mm distances at 0.1 K, and could have theoretical power enhancement factors of the order of 1010. Preliminary results on heat transfer between two parallel metallic wires are presented. We also comment on possible areas were such heat transfer might be relevant, such as densely packed arrays of low-temperature detectors.

  2. Ultrafast modulation of near-field heat transfer with tunable metamaterials

    NASA Astrophysics Data System (ADS)

    Cui, Longji; Huang, Yong; Wang, Ju; Zhu, Ke-Yong

    2013-02-01

    We propose a mechanism of active near-field heat transfer modulation relying on externally tunable metamaterials. A large modulation effect is observed and can be explained by the coupling of surface modes, which is dramatically varied in the presence of controllable magnetoelectric coupling in metamaterials. We finally discuss how a practical picosecond-scale thermal modulator can be made. This modulator allows manipulating nanoscale heat flux in an ultrafast and noncontact (by optical means) manner.

  3. Coupled transport processes in semipermeable media

    SciTech Connect

    Jacobsen, J.S.; Carnahan, C.L.

    1990-04-01

    A numerical simulator has been developed to investigate the effects of coupled processes on heat and mass transport in semipermeable media. The governing equations on which the simulator is based were derived using the thermodynamics of irreversible processes. The equations are nonlinear and have been solved numerically using the n-dimensional Newton's method. As an example of an application, the numerical simulator has been used to investigate heat and solute transport in the vicinity of a heat source buried in a saturated clay-like medium, in part to study solute transport in bentonite packing material surrounding a nuclear waste canister. The coupled processes considered were thermal filtration, thermal osmosis, chemical osmosis and ultrafiltration. In the simulations, heat transport by coupled processes was negligible compared to heat conduction, but pressure and solute migration were affected. Solute migration was retarded relative to the uncoupled case when only chemical osmosis was considered. When both chemical osmosis and thermal osmosis were included, solute migration was enhanced. 18 refs., 20 figs.

  4. Processivity and Coupling in Messenger RNA Transcription

    PubMed Central

    Aitken, Stuart; Robert, Marie-Cécile; Alexander, Ross D.; Goryanin, Igor; Bertrand, Edouard; Beggs, Jean D.

    2010-01-01

    Background The complexity of messenger RNA processing is now being uncovered by experimental techniques that are capable of detecting individual copies of mRNA in cells, and by quantitative real-time observations that reveal the kinetics. This processing is commonly modelled by permitting mRNA to be transcribed only when the promoter is in the on state. In this simple on/off model, the many processes involved in active transcription are represented by a single reaction. These processes include elongation, which has a minimum time for completion and processing that is not captured in the model. Methodology In this paper, we explore the impact on the mRNA distribution of representing the elongation process in more detail. Consideration of the mechanisms of elongation leads to two alternative models of the coupling between the elongating polymerase and the state of the promoter: Processivity allows polymerases to complete elongation irrespective of the promoter state, whereas coupling requires the promoter to be active to produce a full-length transcript. We demonstrate that these alternatives have a significant impact on the predicted distributions. Models are simulated by the Gillespie algorithm, and the third and fourth moments of the resulting distribution are computed in order to characterise the length of the tail, and sharpness of the peak. By this methodology, we show that the moments provide a concise summary of the distribution, showing statistically-significant differences across much of the feasible parameter range. Conclusions We conclude that processivity is not fully consistent with the on/off model unless the probability of successfully completing elongation is low—as has been observed. The results also suggest that some form of coupling between the promoter and a rate-limiting step in transcription may explain the cell's inability to maintain high mRNA levels at low noise—a prediction of the on/off model that has no supporting evidence. PMID

  5. Process-independent strong running coupling

    NASA Astrophysics Data System (ADS)

    Binosi, Daniele; Mezrag, Cédric; Papavassiliou, Joannis; Roberts, Craig D.; Rodríguez-Quintero, Jose

    2017-09-01

    We unify two widely different approaches to understanding the infrared behavior of quantum chromodynamics (QCD), one essentially phenomenological, based on data, and the other computational, realized via quantum field equations in the continuum theory. Using the latter, we explain and calculate a process-independent running coupling for QCD, a new type of effective charge that is an analogue of the Gell-Mann-Low effective coupling in quantum electrodynamics. The result is almost identical to the process-dependent effective charge defined via the Bjorken sum rule, which provides one of the most basic constraints on our knowledge of nucleon spin structure. This reveals the Bjorken sum to be a near direct means by which to gain empirical insight into QCD's Gell-Mann-Low effective charge.

  6. Regularization methods for near-field acoustical holography.

    PubMed

    Williams, E G

    2001-10-01

    The reconstruction of the pressure and normal surface velocity provided by near-field acoustical holography (NAH) from pressure measurements made near a vibrating structure is a linear, ill-posed inverse problem due to the existence of strongly decaying, evanescentlike waves. Regularization provides a technique of overcoming the ill-posedness and generates a solution to the linear problem in an automated way. We present four robust methods for regularization; the standard Tikhonov procedure along with a novel improved version, Landweber iteration, and the conjugate gradient approach. Each of these approaches can be applied to all forms of interior or exterior NAH problems; planar, cylindrical, spherical, and conformal. We also study two parameter selection procedures, the Morozov discrepancy principle and the generalized cross validation, which are crucial to any regularization theory. In particular, we concentrate here on planar and cylindrical holography. These forms of NAH which rely on the discrete Fourier transform are important due to their popularity and to their tremendous computational speed. In order to use regularization theory for the separable geometry problems we reformulate the equations of planar, cylindrical, and spherical NAH into an eigenvalue problem. The resulting eigenvalues and eigenvectors couple easily to regularization theory, which can be incorporated into the NAH software with little sacrifice in computational speed. The resulting complete automation of the NAH algorithm for both separable and nonseparable geometries overcomes the last significant hurdle for NAH.

  7. Entropic and Near-Field Improvements of Thermoradiative Cells

    PubMed Central

    Hsu, Wei-Chun; Tong, Jonathan K.; Liao, Bolin; Huang, Yi; Boriskina, Svetlana V.; Chen, Gang

    2016-01-01

    A p-n junction maintained at above ambient temperature can work as a heat engine, converting some of the supplied heat into electricity and rejecting entropy by interband emission. Such thermoradiative cells have potential to harvest low-grade heat into electricity. By analyzing the entropy content of different spectral components of thermal radiation, we identify an approach to increase the efficiency of thermoradiative cells via spectrally selecting long-wavelength photons for radiative exchange. Furthermore, we predict that the near-field photon extraction by coupling photons generated from interband electronic transition to phonon polariton modes on the surface of a heat sink can increase the conversion efficiency as well as the power generation density, providing more opportunities to efficiently utilize terrestrial emission for clean energy. An ideal InSb thermoradiative cell can achieve a maximum efficiency and power density up to 20.4% and 327 Wm−2, respectively, between a hot source at 500 K and a cold sink at 300 K. However, sub-bandgap and non-radiative losses will significantly degrade the cell performance. PMID:27734902

  8. Entropic and near-field improvements of thermoradiative cells

    SciTech Connect

    Hsu, Wei -Chun; Tong, Jonathan K.; Liao, Bolin; Huang, Yi; Boriskina, Svetlana V.; Chen, Gang

    2016-10-13

    A p-n junction maintained at above ambient temperature can work as a heat engine, converting some of the supplied heat into electricity and rejecting entropy by interband emission. Such thermoradiative cells have potential to harvest low-grade heat into electricity. By analyzing the entropy content of different spectral components of thermal radiation, we identify an approach to increase the efficiency of thermoradiative cells via spectrally selecting long-wavelength photons for radiative exchange. Furthermore, we predict that the near-field photon extraction by coupling photons generated from interband electronic transition to phonon polariton modes on the surface of a heat sink can increase the conversion efficiency as well as the power generation density, providing more opportunities to efficiently utilize terrestrial emission for clean energy. An ideal InSb thermoradiative cell can achieve a maximum efficiency and power density up to 20.4% and 327 Wm-2, respectively, between a hot source at 500 K and a cold sink at 300 K. Furthermore, sub-bandgap and non-radiative losses will significantly degrade the cell performance.

  9. High Temperature Near-Field NanoThermoMechanical Rectification

    NASA Astrophysics Data System (ADS)

    Elzouka, Mahmoud; Ndao, Sidy

    2017-03-01

    Limited performance and reliability of electronic devices at extreme temperatures, intensive electromagnetic fields, and radiation found in space exploration missions (i.e., Venus & Jupiter planetary exploration, and heliophysics missions) and earth-based applications requires the development of alternative computing technologies. In the pursuit of alternative technologies, research efforts have looked into developing thermal memory and logic devices that use heat instead of electricity to perform computations. However, most of the proposed technologies operate at room or cryogenic temperatures, due to their dependence on material’s temperature-dependent properties. Here in this research, we show experimentally—for the first time—the use of near-field thermal radiation (NFTR) to achieve thermal rectification at high temperatures, which can be used to build high-temperature thermal diodes for performing logic operations in harsh environments. We achieved rectification through the coupling between NFTR and the size of a micro/nano gap separating two terminals, engineered to be a function of heat flow direction. We fabricated and tested a proof-of-concept NanoThermoMechanical device that has shown a maximum rectification of 10.9% at terminals’ temperatures of 375 and 530 K. Experimentally, we operated the microdevice in temperatures as high as about 600 K, demonstrating this technology’s suitability to operate at high temperatures.

  10. High Temperature Near-Field NanoThermoMechanical Rectification

    PubMed Central

    Elzouka, Mahmoud; Ndao, Sidy

    2017-01-01

    Limited performance and reliability of electronic devices at extreme temperatures, intensive electromagnetic fields, and radiation found in space exploration missions (i.e., Venus & Jupiter planetary exploration, and heliophysics missions) and earth-based applications requires the development of alternative computing technologies. In the pursuit of alternative technologies, research efforts have looked into developing thermal memory and logic devices that use heat instead of electricity to perform computations. However, most of the proposed technologies operate at room or cryogenic temperatures, due to their dependence on material’s temperature-dependent properties. Here in this research, we show experimentally—for the first time—the use of near-field thermal radiation (NFTR) to achieve thermal rectification at high temperatures, which can be used to build high-temperature thermal diodes for performing logic operations in harsh environments. We achieved rectification through the coupling between NFTR and the size of a micro/nano gap separating two terminals, engineered to be a function of heat flow direction. We fabricated and tested a proof-of-concept NanoThermoMechanical device that has shown a maximum rectification of 10.9% at terminals’ temperatures of 375 and 530 K. Experimentally, we operated the microdevice in temperatures as high as about 600 K, demonstrating this technology’s suitability to operate at high temperatures. PMID:28322324

  11. Entropic and Near-Field Improvements of Thermoradiative Cells

    NASA Astrophysics Data System (ADS)

    Hsu, Wei-Chun; Tong, Jonathan K.; Liao, Bolin; Huang, Yi; Boriskina, Svetlana V.; Chen, Gang

    2016-10-01

    A p-n junction maintained at above ambient temperature can work as a heat engine, converting some of the supplied heat into electricity and rejecting entropy by interband emission. Such thermoradiative cells have potential to harvest low-grade heat into electricity. By analyzing the entropy content of different spectral components of thermal radiation, we identify an approach to increase the efficiency of thermoradiative cells via spectrally selecting long-wavelength photons for radiative exchange. Furthermore, we predict that the near-field photon extraction by coupling photons generated from interband electronic transition to phonon polariton modes on the surface of a heat sink can increase the conversion efficiency as well as the power generation density, providing more opportunities to efficiently utilize terrestrial emission for clean energy. An ideal InSb thermoradiative cell can achieve a maximum efficiency and power density up to 20.4% and 327 Wm-2, respectively, between a hot source at 500 K and a cold sink at 300 K. However, sub-bandgap and non-radiative losses will significantly degrade the cell performance.

  12. Entropic and near-field improvements of thermoradiative cells

    DOE PAGES

    Hsu, Wei -Chun; Tong, Jonathan K.; Liao, Bolin; ...

    2016-10-13

    A p-n junction maintained at above ambient temperature can work as a heat engine, converting some of the supplied heat into electricity and rejecting entropy by interband emission. Such thermoradiative cells have potential to harvest low-grade heat into electricity. By analyzing the entropy content of different spectral components of thermal radiation, we identify an approach to increase the efficiency of thermoradiative cells via spectrally selecting long-wavelength photons for radiative exchange. Furthermore, we predict that the near-field photon extraction by coupling photons generated from interband electronic transition to phonon polariton modes on the surface of a heat sink can increase themore » conversion efficiency as well as the power generation density, providing more opportunities to efficiently utilize terrestrial emission for clean energy. An ideal InSb thermoradiative cell can achieve a maximum efficiency and power density up to 20.4% and 327 Wm-2, respectively, between a hot source at 500 K and a cold sink at 300 K. Furthermore, sub-bandgap and non-radiative losses will significantly degrade the cell performance.« less

  13. Near-Field Heat Flow Between Two Quantum Oscillators

    NASA Astrophysics Data System (ADS)

    Barton, Gabriel

    2016-12-01

    We calculate the exact steady-state heat flow P between two Ohmically damped quantum oscillators 1 and 2, with natural frequency ω 0, interacting through their near-field dipole-dipole potential V. To keep them at nominally constant temperatures T1, T2 respectively, they have to be coupled to thermostats functioning in a way one must specify explicitly unless one assumes local thermal equilibrium, which would, inadequately as a rule, restrict the calculation to leading order in V. Here the thermostats are modelled as stretched strings, one end attached to the oscillator, and the other to an infinitely distant device ensuring that the string carries thermal noise appropriate to T1 or T2 in addition to whatever motion is enforced by the oscillator. Aiming at insight rather than numerics, we focus mainly on simple approximations by powers of T1 and T2 for weak damping in the essentially quantum low-temperature regime where kBT_{1,2}≪ ω 0. From P it is easy to find the heat flux between two insulating Drude-modelled half-spaces.

  14. Influence as a challenger to induction for near-field wireless power transfer

    NASA Astrophysics Data System (ADS)

    Bondar, H.; Oree, S.; Ichikawa, K.

    2013-04-01

    We introduce what we call "Influence" WPT technology, which can be perceived as the dual of magnetic induction WPT. In Influence systems, two or more electric circuits are coupled by electric fields whereas Induction systems involve magnetic field coupling. We propose an unconventional approach to describe and study Influence, using coupling matrices, in analogy with the treatment of Inductive coupling, albeit with a larger number of parameters. In spite of their different natures, both technologies enable non-radiative near-field energy transfer at mid-range, and display interesting and sometimes counter-intuitive behaviors.

  15. Atomic force microscope based near-field imaging for probing cell surface interactions

    NASA Astrophysics Data System (ADS)

    Amini, Sina

    Near-membrane and trans-membrane proteins and their interactions with the extracellular matrix (ECM) can yield valuable information about cell dynamics. However, advances in the field of nanoscale cellular processes have been hindered, in part, due to limits imposed by current technology. In this work, a novel evanescent field (EF) imaging technique is designed, modeled, created and tested for near-field imaging in the apical surface of cells. This technique and Forster resonance energy transfer (FRET) were used to investigate interactions between integrins on the cell surface and the ECM protein, fibronectin. The goal was to monitor changes in the integrin density at the cell surface as a function of clustering after binding to fibronectin on the microsphere surface. For the EF technique, quantum dot (QD)-embedded polystyrene microspheres were used to couple light into whispering gallery modes (WGMs) inside the microspheres; the resulting EF at the surface of the microsphere was used as a near-field excitation source with ~50 nm axial resolution for exciting fluorescently-labeled integrins. For FRET measurements (~10 nm axial resolution), QDs (donors) were coated on the surface of microspheres and energy transfer to red fluorescent protein (RFP)-integrin constructs (acceptors) studied. In both techniques, the QD-modified microspheres were mounted on atomic force microscope (AFM) cantilevers, functionalized with fibronectin, and brought into contact with fluorescently-labeled HeLa or vascular smooth muscle (VSM) cells. The results obtained from both methods show the clustering and activity of the integrins and are in good agreement with each other. Amsterdam discrete dipole approximation (ADDA) was used to study the effects of inhomogeneous surrounding refractive index on the quality factor and position of the WGMs due to the attachment of a microsphere to an AFM cantilever. WGMs of various QD-embedded microspheres mounted on AFM cantilevers were experimentally

  16. Modeling of Inner Magnetosphere Coupling Processes

    NASA Technical Reports Server (NTRS)

    Khazanov, George V.

    2011-01-01

    The Ring Current (RC) is the biggest energy player in the inner magnetosphere. It is the source of free energy for Electromagnetic Ion Cyclotron (EMIC) wave excitation provided by a temperature anisotropy of RC ions, which develops naturally during inward E B convection from the plasmasheet. The cold plasmasphere, which is under the strong influence of the magnetospheric electric field, strongly mediates the RC-EMIC wave-particle-coupling process and ultimately becomes part of the particle and energy interplay. On the other hand, there is a strong influence of the RC on the inner magnetospheric electric and magnetic field configurations and these configurations, in turn, are important to RC dynamics. Therefore, one of the biggest needs for inner magnetospheric research is the continued progression toward a coupled, interconnected system with the inclusion of nonlinear feedback mechanisms between the plasma populations, the electric and magnetic fields, and plasma waves. As we clearly demonstrated in our studies, EMIC waves strongly interact with electrons and ions of energies ranging from approx.1 eV to approx.10 MeV, and that these waves strongly affect the dynamics of resonant RC ions, thermal electrons and ions, and the outer RB relativistic electrons. As we found, the rate of ion and electron scattering/heating in the Earth's magnetosphere is not only controlled by the wave intensity-spatial-temporal distribution but also strongly depends on the spectral distribution of the wave power. The latter is also a function of the plasmaspheric heavy ion content, and the plasma density and temperature distributions along the magnetic field lines. The above discussion places RC-EMIC wave coupling dynamics in context with inner magnetospheric coupling processes and, ultimately, relates RC studies with plasmaspheric and Superthermal Electrons formation processes as well as with outer RB physics.

  17. Near-field enhanced Raman spectroscopy using side illumination optics

    NASA Astrophysics Data System (ADS)

    Hayazawa, Norihiko; Tarun, Alvarado; Inouye, Yasushi; Kawata, Satoshi

    2002-12-01

    We demonstrate near-field enhanced Raman spectroscopy with the use of a metallized cantilever tip and highly p-polarized light directed onto the tip with side illumination optics using a long working distance objective lens. The highly p-polarized light field excites surface plasmon polaritons localized at the tip apex, which results in the enhanced near-field Raman scattering. In this article, we achieved an enhancement factor of 4000 for Rhodamine 6G molecules adsorbed on a silver island film. The side illumination is also applicable to an opaque sample and to near-field photolithography.

  18. Coupled transport processes in semipermeable media

    SciTech Connect

    Carnahan, C.L.; Jacobsen, J.S.

    1990-04-01

    The thermodynamics of irreversible processes (TTIP) is used to derive governing equations and phenomenological equations for transport processes and chemical reactions in water-saturated semipermeable media. TTIP is based on three fundamental postulates. The first postulate, the assumption of local equilibrium, allows the formulation of balance equations for entropy. These equations are the bases for the derivation of governing equations for the thermodynamic variables, temperature, pressure, and composition. The governing equations involve vector fluxes of heat and mass and scalar rates of chemical reactions; in accordance with the second postulate of TTIP, these fluxes and rates are related, respectively, to all scalar driving forces (gradients of thermodynamic variables) acting within the system. The third postulate of TTIP states equality (the Onsager reciprocal relations) between certain of the phenomenological coefficients relating forces and fluxes. The description by TTIP of a system undergoing irreversible processes allows consideration of coupled transport processes such as thermal osmosis, chemical osmosis, and ultrafiltration. The coupled processes can make significant contributions to flows of mass and energy in slightly permeable, permselective geological materials such as clays and shales.

  19. Near field wireless power transfer using curved relay resonators for extended transfer distance

    NASA Astrophysics Data System (ADS)

    Zhu, D.; Clare, L.; Stark, B. H.; Beeby, S. P.

    2015-12-01

    This paper investigates the performance of a near field wireless power transfer system that uses curved relay resonator to extend transfer distance. Near field wireless power transfer operates based on the near-field electromagnetic coupling of coils. Such a system can transfer energy over a relatively short distance which is of the same order of dimensions of the coupled coils. The energy transfer distance can be increased using flat relay resonators. Recent developments in printing electronics and e-textiles have seen increasing demand of embedding electronics into fabrics. Near field wireless power transfer is one of the most promising methods to power electronics on fabrics. The concept can be applied to body-worn textiles by, for example, integrating a transmitter coil into upholstery, and a flexible receiver coil into garments. Flexible textile coils take on the shape of the supporting materials such as garments, and therefore curved resonator and receiver coils are investigated in this work. Experimental results showed that using curved relay resonator can effectively extend the wireless power transfer distance. However, as the curvature of the coil increases, the performance of the wireless power transfer, especially the maximum received power, deteriorates.

  20. Near-field fluorescence thermometry using highly efficient triple-tapered near-field optical fiber probe

    NASA Astrophysics Data System (ADS)

    Fujii, T.; Taguchi, Y.; Saiki, T.; Nagasaka, Y.

    2012-12-01

    A novel local temperature measurement method using fluorescence near-field optics thermal nanoscopy (Fluor-NOTN) has been developed. Fluor-NOTN enables nanoscale temperature measurement in situ by detecting the temperature-dependent fluorescence lifetime of CdSe quantum dots (QDs). In this paper, we report a novel triple-tapered near-field optical fiber probe that can increase the temperature measurement sensitivity of Fluor-NOTN. The performance of the proposed probe was numerically evaluated by the finite difference time domain method. Due to improvements in both the throughput and collection efficiency of near-field light, the sensitivity of the proposed probe was 1.9 times greater than that of typical double-tapered probe. The proposed shape of the triple-tapered core was successfully fabricated utilizing a geometrical model. The detected signal intensity of dried layers of QDs was greater by more than two orders than that of auto-fluorescence from the fiber core. In addition, the near-field fluorescence lifetime of the QDs and its temperature dependence were successfully measured by the fabricated triple-tapered near-field optical fiber probe. These measurement results verified the capability of the proposed triple-tapered near-field optical fiber probe to improve the collection efficiency of near-field fluorescence.

  1. Synthesis report on thermally driven coupled processes

    SciTech Connect

    Hardin, E.L.

    1997-10-15

    The main purpose of this report is to document observations and data on thermally coupled processes for conditions that are expected to occur within and around a repository at Yucca Mountain. Some attempt is made to summarize values of properties (e.g., thermal properties, hydrologic properties) that can be measured in the laboratory on intact samples of the rock matrix. Variation of these properties with temperature, or with conditions likely to be encountered at elevated temperature in the host rock, is of particular interest. However, the main emphasis of this report is on direct observation of thermally coupled processes at various scales. Direct phenomenological observations are vitally important in developing and testing conceptual models. If the mathematical implementation of a conceptual model predicts a consequence that is not observed, either (1) the parameters or the boundary conditions used in the calculation are incorrect or (2) the conceptual basis of the model does not fit the experiment; in either case, the model must be revised. For example, the effective continuum model that has been used in thermohydrology studies combines matrix and fracture flow in a way that is equivalent to an assumption that water is imbibed instantaneously from fractures into adjacent, partially saturated matrix. Based on this approximation, the continuum-flow response that is analogous to fracture flow will not occur until the effective continuum is almost completely saturated. This approximation is not entirely consistent with some of the experimental data presented in this report. This report documents laboratory work and field studies undertaken in FY96 and FY97 to investigate thermally coupled processes such as heat pipes and fracture-matrix coupling. In addition, relevant activities from past years, and work undertaken outside the Yucca Mountain project are summarized and discussed. Natural and artificial analogs are also discussed to provide a convenient source of

  2. Near-Field Scanning Optical Microscopy and Raman Microscopy.

    NASA Astrophysics Data System (ADS)

    Harootunian, Alec Tate

    1987-09-01

    Both a one dimensional near-field scanning optical microscope and Raman microprobe were constructed. In near -field scanning optical microscopy (NSOM) a subwavelength aperture is scanned in the near-field of the object. Radiation transmitted through the aperture is collected to form an image as the aperture scans over the object. The resolution of an NSOM system is essentially wavelength independent and is limited by the diameter of the aperture used to scan the object. NSOM was developed in an effort to provide a nondestructive in situ high spatial resolution probe while still utilizing photons at optical wavelengths. The Raman microprobe constructed provided vibrational Raman information with spatial resolution equivalent that of a conventional diffraction limited microscope. Both transmission studies and near-field diffration studies of subwavelength apertures were performed. Diffraction theories for a small aperture in an infinitely thin conducting screen, a slit in a thick conducting screen, and an aperture in a black screen were examined. All three theories indicate collimation of radiation to the size to the size of the subwavelength aperture or slit in the near-field. Theoretical calculations and experimental results indicate that light transmitted through subwavelength apertures is readily detectable. Light of wavelength 4579 (ANGSTROM) was transmitted through apertures with diameters as small as 300 (ANGSTROM). These studies indicate the feasibility of constructing an NSOM system. One dimensional transmission and fluorescence NSOM systems were constructed. Apertures in the tips of metallized glass pipettes width inner diameters of less than 1000 (ANGSTROM) were used as a light source in the NSOM system. A tunneling current was used to maintain the aperture position in the near-field. Fluorescence NSOM was demonstrated for the first time. Microspectroscopic and Raman microscopic studies of turtle cone oil droplets were performed. Both the Raman vibrational

  3. Non-contact transportation using near-field acoustic levitation

    PubMed

    Ueha; Hashimoto; Koike

    2000-03-01

    Near-field acoustic levitation, where planar objects 10 kg in weight can levitate stably near the vibrating plate, is successfully applied both to non-contact transportation of objects and to a non-contact ultrasonic motor. Transporting apparatuses and an ultrasonic motor have been fabricated and their characteristics measured. The theory of near-field acoustic levitation both for a piston-like sound source and a flexural vibration source is also briefly described.

  4. Thermal Diodes Based on Near-Field Radiation

    DTIC Science & Technology

    2015-10-01

    AFRL-RY-WP-TR-2015-0163 THERMAL DIODES BASED ON NEAR-FIELD RADIATION Michal Lipson Cornell University OCTOBER 2015...DD-MM-YY) 2. REPORT TYPE 3. DATES COVERED (From - To) October 2015 Final 31 January 2014 – 31 July 2015 4. TITLE AND SUBTITLE THERMAL DIODES ...rectification, diodes , near-field radiation 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT: SAR 18. NUMBER OF PAGES 48 19a. NAME OF

  5. MR Monitoring of the Near-Field HIFU Heating

    NASA Astrophysics Data System (ADS)

    Mougenot, Charles; Köhler, Max O.; Enholm, Julia; Quesson, Bruno; Partanen, Ari; Moonen, Chrit T. W.; Ehnholm, Gösta J.

    2009-04-01

    The ablation of tumoral tissue with High Intensity Focused Ultrasound under MRI control has become clinical practice.[1,2] However, the most common adverse effect is skin burns induced in the near-field between the transducer and the focal point.[3] We present a study, based on animal trials, with monitoring and quantification of near field temperature increase in order to prevent skin burns.

  6. Near field communication: getting in touch with mobile users.

    PubMed

    Hoy, Matthew B

    2013-01-01

    Near field communication is a method for sending and receiving small amounts of data across very short distances wirelessly. This technology is already available in a number of mobile devices and has many possible uses, including electronic payment, access control, and information exchange. This article will explain the basic principles of near field communication, discuss some of the ways it can be used in libraries, and explore some possible concerns with the technology. A list of resources for additional information is also included.

  7. Chemical Silver Coating of Fiber Tips in Near-Field Scanning Optical Microscopy

    NASA Technical Reports Server (NTRS)

    Vikram, Chandra S.; Witherow, William K.

    1998-01-01

    We report what is believed to be the first experimental demonstration of silver coating by a wet chemical process on tapered fiber tips used in near-field scanning optical microscopy. The process is at room temperature and pressure and takes only a few minutes to complete. Many tips can be simultaneously coated.

  8. Electromagnetic time reversal focusing of near field waves in metamaterials

    NASA Astrophysics Data System (ADS)

    Chabalko, Matthew J.; Sample, Alanson P.

    2016-12-01

    Precise control of electromagnetic energy on a deeply subwavelength scale in the near field regime is a fundamentally challenging problem. In this letter we demonstrate the selective focusing of electromagnetic energy via the electromagnetic time reversal in the near field of a metamaterial. Our analysis begins with fundamental mathematics, and then is extended to the experimental realm where focusing in space and time of the magnetic fields in the near field of a 1-Dimensional metamaterial is shown. Under time reversal focusing, peak instantaneous fields at receiver locations are at minimum ˜200% greater than other receivers. We then leverage the strong selective focusing capabilities of the system to show individual and selective powering of light emitting diodes connected to coil receivers placed in the near field of the metamaterial. Our results show the possibility of improving display technologies, near field imaging systems, increasing channel capacity of near field communication systems, and obtaining a greater control of energy delivery in wireless power transfer systems.

  9. Mid Infrared Near Field Study of Monolayer Graphene

    NASA Astrophysics Data System (ADS)

    Fei, Z.; Andreev, G. O.; Bao, W.; Zhang, L. M.; Zhao, Z.; Dominguez, G.; Thiemens, M.; Fogler, M. M.; Lau, C. N.; Keilmann, F.; Basov, D. N.

    2011-03-01

    We have performed near-field spectroscopic studies of both monolayer suspended graphene (SG) and graphene on Si O2 /Si substrate (GOS) using scattering-type scanning near-field optical microscope (s-SNOM). Our data show that SG produces reliable near-field signal in mid-infrared frequencies. Images taken with high spatial resolution (~ 20 nm) show nanoscopic features such as ripples and electronic inhomogeneities. The Si O2 /Si substrate contributes a phonon resonance in the near-field signal around 1130 cm-1 . This resonance is remarkably strengthened and broadened by just a single layer of graphene in the case of GOS. By probing the resonance spectrum we find over 400% contrast in near field signal between GOS and the bare substrate. The detailed analysis of the contrast suggests that GOS is slightly doped. This study therefore provides much needed insight into the thickness resolution of the s-SNOM technique, proving it can be sensitive to just a single layer of atoms, and advances the fundamental understanding of graphene-light interactions by probing in the near-field regime.

  10. Near-field scanning optical microscopy investigations of conjugated polymers

    NASA Astrophysics Data System (ADS)

    Dearo, Jessie Ann

    The Near-Field Scanning Optical Microscopy (NSOM) studies of novel, optically active, conjugated polymers are presented. NSOM is a relatively new technique which produces super resolution (˜50--100 nm) optical images simultaneously with topography. The conjugated polymer poly(p-phenylene vinylene) (PPV) and derivatives of PPV are organic semiconductor-like materials with interesting and unique optical properties. Derivatives of PPV have been used in LEDs and have potential in other optoelectronic devices. NSOM provides a tool for investigation of the photoluminescence, absorption/reflection, photo-dynamics and photoconductivity of films of PPV and PPV derivatives on the length scale that these properties are fundamentally defined. The NSOM experiments have revealed mesoscale domains (˜100 nm) of varying photoluminescence emission and average molecular order in drop cast films of PPV. NSOM of stretch-oriented PPV have shown domains of perpendicular molecular orientation with low photoluminescence emission. Near-field photoconductivity experiments of stretch-oriented PPV have correlated the mesoscale topography with the photoconductivity properties of the polymer. NSOM experiments of films of poly(2-methoxy, 5-(2'-(ethyl(hexyloxy)-p-phenylene vinylene) (MEH-PPV) have shown that there is mesoscale spatial inhomogeneity in the photo-oxidation process which reduces photoluminescence emission. NSOM has also been used to create nanoscale photo-patterning in MEH-PPV films. The NSOM experiments of blended films of MEH-PPV in polystyrene have shown mesoscale phase separation directly correlated to variations in the optical properties of the film. Derivatives of PPV, stretch-oriented in polyethylene, show photoluminescence intensity variations perpendicular and parallel to the stretch-direction correlated to topography features. As a complement to the NSOM studies of conjugated polymers, single polymer molecule experiments of MEH-PPV are also presented. The

  11. Nanoscale mechanical actuation and near-field read-out of photonic crystal molecules

    NASA Astrophysics Data System (ADS)

    Petruzzella, M.; La China, F.; Intonti, F.; Caselli, N.; De Pas, M.; van Otten, F. W. M.; Gurioli, M.; Fiore, A.

    2016-09-01

    We employed the contact forces induced by a near-field tip to tune and probe the optical resonances of a mechanically compliant photonic crystal molecule. Here, the pressure induced by the near-field tip is exploited to control the spectral proprieties of the coupled cavities in an ultrawide spectral range, demonstrating a reversible mode shift of 37.5 nm . Besides, by monitoring the coupling strength variation due to the vertical nanodeformation of the dielectric structure, distinct tip-sample interaction regimes have been unambiguously reconstructed with a nano-Newton sensitivity. These results demonstrate an optical method for mapping mechanical forces at the nanoscale with a lateral spatial resolution below 100 nm.

  12. Active control of near-field radiative heat transfer between graphene-covered metamaterials

    NASA Astrophysics Data System (ADS)

    Zhao, Qimei; Zhou, Ting; Wang, Tongbiao; Liu, Wenxing; Liu, Jiangtao; Yu, Tianbao; Liao, Qinghua; Liu, Nianhua

    2017-04-01

    In this study, the near-field radiative heat transfer between graphene-covered metamaterials is investigated. The electric surface plasmons (SPs) supported by metamaterials can be coupled with the SPs supported by graphene. The near-field heat transfer between the graphene-covered metamaterials is significantly larger than that between metamaterials because of the strong coupling in our studied frequency range. The relationship between heat flux and chemical potential is studied for different vacuum gaps. Given that the chemical potential of graphene can be tuned by the external electric field, heat transfer can be actively controlled by modulating the chemical potential. The heat flux for certain vacuum gaps can reach a maximum value when the chemical potential is at a particular value. The results of this study are beneficial for actively controlling energy transfer.

  13. Vectorial modeling of near-field imaging with uncoated fiber probes: transfer function and resolving power.

    PubMed

    Gregersen, Niels; Tromborg, Bjarne; Bozhevolnyi, Sergey I

    2006-12-01

    Using exact 3D vectorial simulations of radiation coupling into uncoated dielectric fiber probes, we calculate amplitude transfer functions for conical single-mode fiber tips at the light wavelength of 633 nm. The coupling efficiency of glass fiber tips is determined in a wide range of spatial frequencies of the incident radiation for opening angles varying from 30 degrees to 120 degrees . The resolution in near-field imaging with these tips is considered for field distributions limited in both direct and spatial-frequency space. The characteristics of the transfer functions describing the relation between probed optical fields and near-field images are analyzed in detail. The importance of utilizing a perfectly sharp tip is also examined.

  14. Three-dimensional near-field MIMO array imaging using range migration techniques.

    PubMed

    Zhuge, Xiaodong; Yarovoy, Alexander G

    2012-06-01

    This paper presents a 3-D near-field imaging algorithm that is formulated for 2-D wideband multiple-input-multiple-output (MIMO) imaging array topology. The proposed MIMO range migration technique performs the image reconstruction procedure in the frequency-wavenumber domain. The algorithm is able to completely compensate the curvature of the wavefront in the near-field through a specifically defined interpolation process and provides extremely high computational efficiency by the application of the fast Fourier transform. The implementation aspects of the algorithm and the sampling criteria of a MIMO aperture are discussed. The image reconstruction performance and computational efficiency of the algorithm are demonstrated both with numerical simulations and measurements using 2-D MIMO arrays. Real-time 3-D near-field imaging can be achieved with a real-aperture array by applying the proposed MIMO range migration techniques.

  15. Far-field errors due to random noise in cylindrical near-field measurements

    NASA Astrophysics Data System (ADS)

    Romeu, Jordi; Jofre, Luis; Cardama, Angel

    1992-01-01

    A full characterization of the far-field noise obtained from cylindrical near- to far-field transformation, for a white Gaussian, space stationary, near-field noise is derived. A possible source for such noise is the receiver additive noise. The noise characterization is done by obtaining the autocorrelation of the far-field noise, which is shown to be easily computed during the transformation process. Even for this simple case, the far-field noise has complex behavior dependent on the measurement probe. Once the statistical properties of the far-field noise are determined, it is possible to compute upper and lower bounds for the radiation pattern for a given probability. These bounds define a strip within the radiation pattern with the desired probability. This may be used as part of a complete near-field error analysis of a particular cylindrical near-field facility.

  16. Noise analysis for near field 3-D FM-CW radar imaging systems

    SciTech Connect

    Sheen, David M.

    2015-06-19

    Near field radar imaging systems are used for several applications including concealed weapon detection in airports and other high-security venues. Despite the near-field operation, phase noise and thermal noise can limit the performance in several ways including reduction in system sensitivity and reduction of image dynamic range. In this paper, the effects of thermal noise, phase noise, and processing gain are analyzed in the context of a near field 3-D FM-CW imaging radar as might be used for concealed weapon detection. In addition to traditional frequency domain analysis, a time-domain simulation is employed to graphically demonstrate the effect of these noise sources on a fast-chirping FM-CW system.

  17. Planar Near-Field Phase Retrieval Using GPUs for Accurate THz Far-Field Prediction

    NASA Astrophysics Data System (ADS)

    Junkin, Gary

    2013-04-01

    With a view to using Phase Retrieval to accurately predict Terahertz antenna far-field from near-field intensity measurements, this paper reports on three fundamental advances that achieve very low algorithmic error penalties. The first is a new Gaussian beam analysis that provides accurate initial complex aperture estimates including defocus and astigmatic phase errors, based only on first and second moment calculations. The second is a powerful noise tolerant near-field Phase Retrieval algorithm that combines Anderson's Plane-to-Plane (PTP) with Fienup's Hybrid-Input-Output (HIO) and Successive Over-Relaxation (SOR) to achieve increased accuracy at reduced scan separations. The third advance employs teraflop Graphical Processing Units (GPUs) to achieve practically real time near-field phase retrieval and to obtain the optimum aperture constraint without any a priori information.

  18. Far-field patterns of spaceborne antennas from plane-polar near-field measurements

    NASA Technical Reports Server (NTRS)

    Rahmat-Samii, Y.; Gatti, M. S.

    1985-01-01

    Certain unique features of a recently constructed plane-polar near-field measurement facility for determining the far-field patterns of large and fragile spaceborne antennas are described. In this facility, the horizontally positioned antenna rotates about its axis while the measuring probe is advanced incrementally in a fixed radial direction. The near-field measured data is then processed using a Jacobi-Bessel expansion to obtain the antenna far fields. A summary of the measurement and computational steps is given. Comparisons between the outdoor far-field measurements and the constructed far-field patterns from the near-field measured data are provided for different antenna sizes and frequencies. Application of the substitution method for the absolute gain measurement is discussed. In particular, results are shown for the 4.8-m mesh-deployable high-gain antenna of the Galileo spacecraft which has the mission of orbiting Jupiter in 1988.

  19. Far-field patterns of spaceborne antennas from plane-polar near-field measurements

    NASA Technical Reports Server (NTRS)

    Rahmat-Samii, Y.; Gatti, M. S.

    1985-01-01

    Certain unique features of a recently constructed plane-polar near-field measurement facility for determining the far-field patterns of large and fragile spaceborne antennas are described. In this facility, the horizontally positioned antenna rotates about its axis while the measuring probe is advanced incrementally in a fixed radial direction. The near-field measured data is then processed using a Jacobi-Bessel expansion to obtain the antenna far fields. A summary of the measurement and computational steps is given. Comparisons between the outdoor far-field measurements and the constructed far-field patterns from the near-field measured data are provided for different antenna sizes and frequencies. Application of the substitution method for the absolute gain measurement is discussed. In particular, results are shown for the 4.8-m mesh-deployable high-gain antenna of the Galileo spacecraft which has the mission of orbiting Jupiter in 1988.

  20. Laser wavelength effects in ultrafast near-field laser nanostructuring of Si

    SciTech Connect

    Zormpa, Vasileia; Mao, Xianglei; Russo, Richard E.

    2010-03-18

    We study the effect of laser wavelength (400 nm and 800 nm) on the near-field processing of crystalline silicon (Si) in the femtosecond (fs) pulse duration regime through sub-wavelength apertures. Distinct differences in the obtained nanostructures are found in each case both in terms of their physical sizes as well as their structure which can be tuned between craters and protrusions. A single or a few fs pulses can deliver enough energy on the substrate to induce sub-diffraction limited surface modification, which is among the smallest ever reported in sub-wavelength apertured Near-field Scanning Optical Microscope (NSOM) schemes.

  1. A novel mathematical model for controllable near-field electrospinning

    NASA Astrophysics Data System (ADS)

    Ru, Changhai; Chen, Jie; Shao, Zhushuai; Pang, Ming; Luo, Jun

    2014-01-01

    Near-field electrospinning (NFES) had better controllability than conventional electrospinning. However, due to the lack of guidance of theoretical model, precise deposition of micro/nano fibers could only accomplished by experience. To analyze the behavior of charged jet in NFES using mathematical model, the momentum balance equation was simplified and a new expression between jet cross-sectional radius and axial position was derived. Using this new expression and mass conservation equation, expressions for jet cross-sectional radius and velocity were derived in terms of axial position and initial jet acceleration in the form of exponential functions. Based on Slender-body theory and Giesekus model, a quadratic equation for initial jet acceleration was acquired. With the proposed model, it was able to accurately predict the diameter and velocity of polymer fibers in NFES, and mathematical analysis rather than experimental methods could be applied to study the effects of the process parameters in NFES. Moreover, the movement velocity of the collector stage can be regulated by mathematical model rather than experience. Therefore, the model proposed in this paper had important guiding significance to precise deposition of polymer fibers.

  2. Near-field ptychography using lateral and longitudinal shifts

    NASA Astrophysics Data System (ADS)

    Robisch, A.-L.; Kröger, K.; Rack, A.; Salditt, T.

    2015-07-01

    Image reconstruction of in-line holography depends crucially on the probing wave front used to illuminate an object. Aberrations inherent to the illumination can mix with the features imposed by the object. Conventional raw data processing methods rely on the division of the measured hologram by the intensity profile of the probe and are not able to fully eliminate artifacts caused by the illumination. Here we present a generalized ptychography approach to simultaneously reconstruct object and probe in the optical near-field. Combining the ideas of ptychographic lateral shifts of the object with variations of the propagation distance by longitudinal shifts, simultaneous reconstruction of object and probe was achieved equally well for a highly aberrated and a mildly disturbed probe without the need for an additional wave front diffuser. The method overcomes the image deterioration by a non-ideal probe and at the same time any restrictions due to linearization of the object’s transmission function or the Fresnel propagator. The method is demonstrated experimentally using visible light and hard x-rays, in both parallel beam and cone beam geometry, which is relevant for high resolution x-ray imaging. It also opens up a new approach to characterize extended wave fronts by phase retrieval.

  3. A novel mathematical model for controllable near-field electrospinning

    SciTech Connect

    Ru, Changhai E-mail: luojun@shu.edu.cn; Chen, Jie; Shao, Zhushuai; Pang, Ming; Luo, Jun E-mail: luojun@shu.edu.cn

    2014-01-15

    Near-field electrospinning (NFES) had better controllability than conventional electrospinning. However, due to the lack of guidance of theoretical model, precise deposition of micro/nano fibers could only accomplished by experience. To analyze the behavior of charged jet in NFES using mathematical model, the momentum balance equation was simplified and a new expression between jet cross-sectional radius and axial position was derived. Using this new expression and mass conservation equation, expressions for jet cross-sectional radius and velocity were derived in terms of axial position and initial jet acceleration in the form of exponential functions. Based on Slender-body theory and Giesekus model, a quadratic equation for initial jet acceleration was acquired. With the proposed model, it was able to accurately predict the diameter and velocity of polymer fibers in NFES, and mathematical analysis rather than experimental methods could be applied to study the effects of the process parameters in NFES. Moreover, the movement velocity of the collector stage can be regulated by mathematical model rather than experience. Therefore, the model proposed in this paper had important guiding significance to precise deposition of polymer fibers.

  4. Far-Field Super-resolution Detection of Plasmonic Near-Fields.

    PubMed

    Boutelle, Robert Charles; Neuhauser, Daniel; Weiss, Shimon

    2016-08-23

    We demonstrate a far-field single molecule super-resolution method that maps plasmonic near-fields. The method is largely invariant to fluorescence quenching (arising from probe proximity to a metal), has reduced point-spread-function distortion compared to fluorescent dyes (arising from strong coupling to nanoscopic metallic features), and has a large dynamic range (of 2 orders of magnitude) allowing mapping of plasmonic field-enhancements regions. The method takes advantage of the sensitivity of quantum dot (QD) stochastic blinking to plasmonic near-fields. The modulation of the blinking characteristics thus provides an indirect measure of the local field strength. Since QD blinking can be monitored in the far-field, the method can measure localized plasmonic near-fields at high throughput using a simple far-field optical setup. Using this method, propagation lengths and penetration depths were mapped-out for silver nanowires of different diameters and for different dielectric environments, with a spatial accuracy of ∼15 nm. We initially use sparse sampling to ensure single molecule localization for accurate characterization of the plasmonic near-field with plans to increase density of emitters in further studies. The measured propagation lengths and penetration depths values agree well with Maxwell finite-difference time-domain calculations and with published literature values. This method offers advantages such as low cost, high throughput, and superresolved mapping of localized plasmonic fields at high sensitivity and fidelity.

  5. Near-field thermal radiation between homogeneous dual uniaxial electromagnetic metamaterials

    SciTech Connect

    Chang, Jui-Yung; Basu, Soumyadipta; Yang, Yue; Wang, Liping

    2016-06-07

    Recently, near-field thermal radiation has attracted much attention in several fields since it can exceed the Planck blackbody limit through the coupling of evanescent waves. In this work, near-field radiative heat transfer between two semi-infinite dual uniaxial electromagnetic metamaterials with two different material property sets is theoretically analyzed. The near-field radiative heat transfer is calculated using fluctuational electrodynamics incorporated with anisotropic wave optics. The underlying mechanisms, namely, magnetic hyperbolic mode, magnetic surface polariton, electrical hyperbolic mode, and electrical surface polariton, between two homogeneous dual uniaxial electromagnetic metamaterials are investigated by examining the transmission coefficient and the spectral heat flux. The effect of vacuum gap distance is also studied, which shows that the enhancement at smaller vacuum gap is mainly due to hyperbolic mode and surface plasmon polariton modes. In addition, the results show that the contribution of s-polarized waves is significant and should not be excluded due to the strong magnetic response regardless of vacuum gap distances. The fundamental understanding and insights obtained here will facilitate the finding and application of novel materials for near-field thermal radiation.

  6. A near-field scanning microwave microscope based on a superconducting resonator for low power measurements

    NASA Astrophysics Data System (ADS)

    de Graaf, S. E.; Danilov, A. V.; Adamyan, A.; Kubatkin, S. E.

    2013-02-01

    We report on the design and performance of a cryogenic (300 mK) near-field scanning microwave microscope. It uses a microwave resonator as the near-field sensor, operating at a frequency of 6 GHz and microwave probing amplitudes down to 100 {μ V}, approaching low enough photon population (N ˜ 1000) of the resonator such that coherent quantum manipulation becomes feasible. The resonator is made out of a miniaturized distributed fractal superconducting circuit that is integrated with the probing tip, micromachined to be compact enough such that it can be mounted directly on a quartz tuning-fork, and used for parallel operation as an atomic force microscope (AFM). The resonator is magnetically coupled to a transmission line for readout, and to achieve enhanced sensitivity we employ a Pound-Drever-Hall measurement scheme to lock to the resonance frequency. We achieve a well localized near-field around the tip such that the microwave resolution is comparable to the AFM resolution, and a capacitive sensitivity down to 6.4 × 10-20 F/sqrt{Hz}, limited by mechanical noise. We believe that the results presented here are a significant step towards probing quantum systems at the nanoscale using near-field scanning microwave microscopy.

  7. Hybridized plasmon modes and near-field enhancement of metallic nanoparticle-dimer on a mirror

    PubMed Central

    Huang, Yu; Ma, Lingwei; Hou, Mengjing; Li, Jianghao; Xie, Zheng; Zhang, Zhengjun

    2016-01-01

    For the attractive plasmonic structure consisting of metal nanoparticles (NPs) on a mirror, the coexistence of near-field NP-NP and NP-mirror couplings is numerically studied at normal incidence. By mapping their 3D surface charge distributions directly, we have demonstrated two different kinds of mirror-induced bonding dipole plasmon modes and confirmed the bonding hybridizations of the mirror and the NP-dimer which may offer a much stronger near-field enhancement than that of the isolated NP dimers over a broad wavelength range. Further, it is revealed that the huge near-field enhancement of these two modes exhibit different dependence on the NP-NP and NP-mirror hot spots, while both of their near-field resonance wavelengths can be tuned to the blue exponentially by increasing the NP-NP gaps or the NP-mirror separation. Our results here benifit significantly the fundamental understanding and practical applications of metallic NPs on a mirror in plasmonics. PMID:27418039

  8. A near-field scanning microwave microscope based on a superconducting resonator for low power measurements.

    PubMed

    de Graaf, S E; Danilov, A V; Adamyan, A; Kubatkin, S E

    2013-02-01

    We report on the design and performance of a cryogenic (300 mK) near-field scanning microwave microscope. It uses a microwave resonator as the near-field sensor, operating at a frequency of 6 GHz and microwave probing amplitudes down to 100 μV, approaching low enough photon population (N ∼ 1000) of the resonator such that coherent quantum manipulation becomes feasible. The resonator is made out of a miniaturized distributed fractal superconducting circuit that is integrated with the probing tip, micromachined to be compact enough such that it can be mounted directly on a quartz tuning-fork, and used for parallel operation as an atomic force microscope (AFM). The resonator is magnetically coupled to a transmission line for readout, and to achieve enhanced sensitivity we employ a Pound-Drever-Hall measurement scheme to lock to the resonance frequency. We achieve a well localized near-field around the tip such that the microwave resolution is comparable to the AFM resolution, and a capacitive sensitivity down to 6.4 × 10(-20) F/Hz, limited by mechanical noise. We believe that the results presented here are a significant step towards probing quantum systems at the nanoscale using near-field scanning microwave microscopy.

  9. Hybridized plasmon modes and near-field enhancement of metallic nanoparticle-dimer on a mirror.

    PubMed

    Huang, Yu; Ma, Lingwei; Hou, Mengjing; Li, Jianghao; Xie, Zheng; Zhang, Zhengjun

    2016-07-15

    For the attractive plasmonic structure consisting of metal nanoparticles (NPs) on a mirror, the coexistence of near-field NP-NP and NP-mirror couplings is numerically studied at normal incidence. By mapping their 3D surface charge distributions directly, we have demonstrated two different kinds of mirror-induced bonding dipole plasmon modes and confirmed the bonding hybridizations of the mirror and the NP-dimer which may offer a much stronger near-field enhancement than that of the isolated NP dimers over a broad wavelength range. Further, it is revealed that the huge near-field enhancement of these two modes exhibit different dependence on the NP-NP and NP-mirror hot spots, while both of their near-field resonance wavelengths can be tuned to the blue exponentially by increasing the NP-NP gaps or the NP-mirror separation. Our results here benifit significantly the fundamental understanding and practical applications of metallic NPs on a mirror in plasmonics.

  10. Near-field thermal radiation transfer between semiconductors based on thickness control and introduction of photonic crystals

    NASA Astrophysics Data System (ADS)

    Inoue, Takuya; Asano, Takashi; Noda, Susumu

    2017-03-01

    We numerically investigate the spectral control of near-field thermal radiation transfer using interband absorption in semiconductors and the band-folding effect in photonic crystals (PCs) for highly efficient thermophotovoltaics. We reveal that the near-field coupling between two semiconductors (Si and GaSb) realizes frequency-selective thermal radiation transfer concentrated above their bandgap energy when their thicknesses are optimized considering their absorption coefficient spectra. Moreover, we elucidate the role of PC structures in the near-field thermal radiation transfer and demonstrate that the band-folding effect in PCs can further increase both the radiation power and frequency selectivity of the near-field thermal radiation transfer.

  11. Rupture process of the 2010 Mw 7.8 Mentawai tsunami earthquake from joint inversion of near-field hr-GPS and teleseismic body wave recordings constrained by tsunami observations

    NASA Astrophysics Data System (ADS)

    Yue, Han; Lay, Thorne; Rivera, Luis; Bai, Yefei; Yamazaki, Yoshiki; Cheung, Kwok Fai; Hill, Emma M.; Sieh, Kerry; Kongko, Widjo; Muhari, Abdul

    2014-07-01

    The 25 October 2010 Mentawai tsunami earthquake (Mw 7.8) ruptured the shallow portion of the Sunda megathrust seaward of the Mentawai Islands, offshore of Sumatra, Indonesia, generating a strong tsunami that took 509 lives. The rupture zone was updip of those of the 12 September 2007 Mw 8.5 and 7.9 underthrusting earthquakes. High-rate (1 s sampling) GPS instruments of the Sumatra GPS Array network deployed on the Mentawai Islands and Sumatra mainland recorded time-varying and static ground displacements at epicentral distances from 49 to 322 km. Azimuthally distributed tsunami recordings from two deepwater sensors and two tide gauges that have local high-resolution bathymetric information provide additional constraints on the source process. Finite-fault rupture models, obtained by joint inversion of the high-rate (hr)-GPS time series and numerous teleseismic broadband P and S wave seismograms together with iterative forward modeling of the tsunami recordings, indicate rupture propagation ~50 km up dip and ~100 km northwest along strike from the hypocenter, with a rupture velocity of ~1.8 km/s. Subregions with large slip extend from 7 to 10 km depth ~80 km northwest from the hypocenter with a maximum slip of 8 m and from ~5 km depth to beneath thin horizontal sedimentary layers beyond the prism deformation front for ~100 km along strike, with a localized region having >15 m of slip. The seismic moment is 7.2 × 1020 N m. The rupture model indicates that local heterogeneities in the shallow megathrust can accumulate strain that allows some regions near the toe of accretionary prisms to fail in tsunami earthquakes.

  12. THz near-field imaging of biological tissues employing synchrotronradiation

    SciTech Connect

    Schade, Ulrich; Holldack, Karsten; Martin, Michael C.; Fried,Daniel

    2004-12-23

    Terahertz scanning near-field infrared microscopy (SNIM) below 1 THz is demonstrated. The near-field technique benefits from the broadband and highly brilliant coherent synchrotron radiation (CSR) from an electron storage ring and from a detection method based on locking onto the intrinsic time structure of the synchrotron radiation. The scanning microscope utilizes conical wave guides as near-field probes with apertures smaller than the wavelength. Different cone approaches have been investigated to obtain maximum transmittance. Together with a Martin-Puplett spectrometer the set-up enables spectroscopic mapping of the transmittance of samples well below the diffraction limit. Spatial resolution down to about lambda/40 at 2 wavenumbers (0.06 THz) is derived from the transmittance spectra of the near-field probes. The potential of the technique is exemplified by imaging biological samples. Strongly absorbing living leaves have been imaged in transmittance with a spatial resolution of 130 mu-m at about 12 wave numbers (0.36 THz). The THz near-field images reveal distinct structural differences of leaves from different plants investigated. The technique presented also allows spectral imaging of bulky organic tissues. Human teeth samples of various thicknesses have been imaged between 2 and 20 wavenumbers (between 0.06and 0.6 THz). Regions of enamel and dentin within tooth samples are spatially and spectrally resolved, and buried caries lesions are imaged through both the outer enamel and into the underlying dentin.

  13. Coupling Processes Between Atmospheric Chemistry and Climate

    NASA Technical Reports Server (NTRS)

    Ko, Malcolm K. W.; Weisenstein, Debra; Shia, Run-Lie; Sze, N. D.

    1998-01-01

    The overall objective of this project is to improve the understanding of coupling processes between atmospheric chemistry and climate. Model predictions of the future distributions of trace gases in the atmosphere constitute an important component of the input necessary for quantitative assessments of global change. We will concentrate on the changes in ozone and stratospheric sulfate aerosol, with emphasis on how ozone in the lower stratosphere would respond to natural or anthropogenic changes. The key modeling tools for this work are the AER 2-dimensional chemistry-transport model, the AER 2-dimensional stratospheric sulfate model, and the AER three-wave interactive model with full chemistry. We will continue developing our three-wave model so that we can help NASA determine the strength and weakness of the next generation assessment models.

  14. Coupling Processes Between Atmospheric Chemistry and Climate

    NASA Technical Reports Server (NTRS)

    Ko, M. K. W.; Weisenstein, Debra; Shia, Run-Lie; Sze, N. D.

    1998-01-01

    The overall objective of this project is to improve the understanding of coupling processes between atmospheric chemistry and climate. Model predictions of the future distributions of trace gases in the atmosphere constitute an important component of the input necessary for quantitative assessments of global change. We will concentrate on the changes in ozone and stratospheric sulfate aerosol, with emphasis on how ozone in the lower stratosphere would respond to natural or anthropogenic changes. The key modeling tools for this work are the AER two-dimensional chemistry-transport model, the AER two-dimensional stratospheric sulfate model, and the AER three-wave interactive model with full chemistry. We will continue developing our three-wave model so that we can help NASA determine the strength and weakness of the next generation assessment models.

  15. Coupling Processes Between Atmospheric Chemistry and Climate

    NASA Technical Reports Server (NTRS)

    Ko, Malcolm K. W.; Weisenstein, Debra; Rodriguez, Jose; Danilin, Michael; Scott, Courtney; Shia, Run-Lie; Eluszkiewicz, Junusz; Sze, Nien-Dak

    1999-01-01

    This is the final report. The overall objective of this project is to improve the understanding of coupling processes among atmospheric chemistry, aerosol and climate, all important for quantitative assessments of global change. Among our priority are changes in ozone and stratospheric sulfate aerosol, with emphasis on how ozone in the lower stratosphere would respond to natural or anthropogenic changes. The work emphasizes two important aspects: (1) AER's continued participation in preparation of, and providing scientific input for, various scientific reports connected with assessment of stratospheric ozone and climate. These include participation in various model intercomparison exercises as well as preparation of national and international reports. and (2) Continued development of the AER three-wave interactive model to address how the transport circulation will change as ozone and the thermal properties of the atmosphere change, and assess how these new findings will affect our confidence in the ozone assessment results.

  16. Coupling Processes between Atmospheric Chemistry and Climate

    NASA Technical Reports Server (NTRS)

    Ko, M. K. W.; Weisenstein, Debra; Shia, Run-Lie; Sze, N. D.

    1998-01-01

    This is the third semi-annual report for NAS5-97039, covering January through June 1998. The overall objective of this project is to improve the understanding of coupling processes between atmospheric chemistry and climate. Model predictions of the future distributions of trace gases in the atmosphere constitute an important component of the input necessary for quantitative assessments of global change. We will concentrate on the changes in ozone and stratospheric sulfate aerosol, with emphasis on how ozone in the lower stratosphere would respond to natural or anthropogenic changes. The key modeling for this work are the AER 2-dimensional chemistry-transport model, the AER 2-dimensional stratospheric sulfate model, and the AER three-wave interactive model with full chemistry. We will continue developing our three-wave model so that we can help NASA determine the strengths and weaknesses of the next generation assessment models.

  17. Coupled process modeling and waste package performance

    SciTech Connect

    McGrail, B.P.; Engel, D.W.

    1992-11-01

    The interaction of borosilicate waste glasses with water has been studied extensively and reasonably good models are available that describe the reaction kinetics and solution chemical effects. Unfortunately, these models have not been utilized in performance assessment analyses, except in estimating radionuclide solubilities at the waste form surface. A geochemical model has been incorporated in the AREST code to examine the coupled processes of glass dissolution and transport within the engineering barrier system. Our calculations show that the typical assumptions used in performance assessment analyses, such as fixed solubilities or constant reaction rate at the waste form surface, do not always give conservative or realistic predictions of radionuclide release. Varying the transport properties of the waste package materials is shown to give counterintuitive effects on the release rates of some radionuclides. The use of noncoupled performance assessment models could lead a repository designer to an erroneous conclusion regarding the relative benefit of one waste package design or host rock setting over another.

  18. Coupled time integration of multiphase processes

    NASA Astrophysics Data System (ADS)

    Sehili, A. M.; Wolke, R.; Knoth, O.

    2003-04-01

    The objective of this subproject is the development of a cloud module which combines a complex multiphase chemistry with detailed microphysics. We investigate several numerical approaches for treating such multiphase processes in a parcel model. The chemical conversions within cloud droplets are essentially determined by the mass transfer between gaseous and aqueous phase. The gas uptake depends strongly on resolution of the droplet spectrum. Therefore the droplets are subdivided into several classes. The decomposition of the droplet spectrum into classes is based on the droplets size and, if required, on the amount of scavenged material inside the droplets. This multi-fractional distribution, all microphysical parameters and the transfer rates of liquid water between the different droplet classes are simultaneously generated by a microphysical cloud model. The phase transfer between the gaseous phase and the aqueous phase species in each class is described by the Schwartz approach. The fast dissociation s in the aqueous phase chemistry are treated as forward and backward reactions. As a first step, the usual "operator splitting" approach is used for coupling multiphase chemistry and microphysics . For the multiphase chemistry, we propose implicit schemes for the time integration of the resulting extremely stiff systems of ordinary differential equations. The aqueous phase and gaseous phase chemistry, the mass transfer between the different droplet classes among themselves and with the gaseous phase are integrated in an implicit and coupled manner by higher order BDF methods. For this part we apply a modification of the code LSODE (Hindmarsh, 1983) with an adapted step size control and special linear system solver. These direct sparse techniques exploit the special block structure of the corresponding Jacobian. Furthermore, we utilise an approximate matrix factorisation which decouples multiphase chemistry and microphysical exchange processes of liquid water (e

  19. Near-field acoustical holography of military jet aircraft noise

    NASA Astrophysics Data System (ADS)

    Wall, Alan T.; Gee, Kent L.; Neilsen, Tracianne; Krueger, David W.; Sommerfeldt, Scott D.; James, Michael M.

    2010-10-01

    Noise radiated from high-performance military jet aircraft poses a hearing-loss risk to personnel. Accurate characterization of jet noise can assist in noise prediction and noise reduction techniques. In this work, sound pressure measurements were made in the near field of an F-22 Raptor. With more than 6000 measurement points, this is the most extensive near-field measurement of a high-performance jet to date. A technique called near-field acoustical holography has been used to propagate the complex pressure from a two- dimensional plane to a three-dimensional region in the jet vicinity. Results will be shown and what they reveal about jet noise characteristics will be discussed.

  20. Near-field radiative thermal transport: From theory to experiment

    SciTech Connect

    Song, Bai Fiorino, Anthony; Meyhofer, Edgar; Reddy, Pramod

    2015-05-15

    Radiative thermal transport via the fluctuating electromagnetic near-field has recently attracted increasing attention due to its fundamental importance and its impact on a range of applications from data storage to thermal management and energy conversion. After a brief historical account of radiative thermal transport, we summarize the basics of fluctuational electrodynamics, a theoretical framework for the study of radiative heat transfer in terms of thermally excited propagating and evanescent electromagnetic waves. Various approaches to modeling near-field thermal transport are briefly discussed, together with key results and proposals for manipulation and utilization of radiative heat flow. Subsequently, we review the experimental advances in the characterization of both near-field heat flow and energy density. We conclude with remarks on the opportunities and challenges for future explorations of radiative heat transfer at the nanoscale.

  1. Near-field energy extraction with hyperbolic metamaterials.

    PubMed

    Shi, Jiawei; Liu, Baoan; Li, Pengfei; Ng, Li Yen; Shen, Sheng

    2015-02-11

    Although blackbody radiation described by Planck's law is commonly regarded as the maximum of thermal radiation, thermal energy transfer in the near-field can exceed the blackbody limit due to the contribution from evanescent waves. Here, we demonstrate experimentally a broadband thermal energy extraction device based on hyperbolic metamaterials that can significantly enhance near-field thermal energy transfer. The thermal extractor made from hyperbolic metamaterials does not absorb or emit any radiation but serves as a transparent pipe guiding the radiative energy from the emitter. At the same gap between an emitter and an absorber, we observe that near-field thermal energy transfer with thermal extraction can be enhanced by around 1 order of magnitude, compared to the case without thermal extraction. The novel thermal extraction scheme has important practical implications in a variety of technologies, e.g., thermophotovoltaic energy conversion, radiative cooling, thermal infrared imaging, and heat assisted magnetic recording.

  2. Diagnose human colonic tissues by terahertz near-field imaging

    NASA Astrophysics Data System (ADS)

    Chen, Hua; Ma, Shihua; Wu, Xiumei; Yang, Wenxing; Zhao, Tian

    2015-03-01

    Based on a terahertz (THz) pipe-based near-field imaging system, we demonstrate the capability of THz imaging to diagnose freshly surgically excised human colonic tissues. Through THz near-field scanning the absorbance of the colonic tissues, the acquired images can clearly distinguish cancerous tissues from healthy tissues fast and automatically without pathological hematoxylin and eosin stain diagnosis. A statistical study on 58 specimens (20 healthy tissues and 38 tissues with tumor) from 31 patients (mean age: 59 years; range: 46 to 79 years) shows that the corresponding diagnostic sensitivity and specificity on colonic tissues are both 100%. Due to its capability to perform quantitative analysis, our study indicates the potential of the THz pipe-based near-field imaging for future automation on human tumor pathological examinations.

  3. Modeling of the 2011 Tohoku Near-field Tsunami from Finite-fault Inversion of Seismic Waves

    NASA Astrophysics Data System (ADS)

    Yamazaki, Y.; Cheung, K.; Lay, T.

    2012-12-01

    The Mw 9.0 March 11, 2011 Tohoku earthquake ruptured the megathrust fault offshore of northeastern Honshu and generated a devastating near-field tsunami that caused over 24,000 casualties in Japan. While both the earthquake and tsunami caused extensive infrastructure damage in the region, most of the casualties were caused by inundation of coastal towns and villages. The extensive global seismic networks, dense geodetic instruments, well-positioned water level stations, and comprehensive post-event surveys along the northeast Japan coasts provide datasets of unprecedented quality and coverage for investigation of the tsunami source mechanism and near-field wave characteristics. We utilize the shock-capturing, dispersive wave model NEOWAVE (Non-hydrostatic Evolution of Ocean WAVEs) to reconstruct the tsunami from a finite-fault solution based on teleseismic P-wave inversion. The depth-integrated model describes dispersive waves through non-hydrostatic pressure and vertical velocity, which also account for tsunami generation from time histories of seafloor deformation and transfer of kinetic energy to the water mass. These model capabilities are important for the timing and evolution of the tsunami waves near the earthquake source. The finite-fault model produces seafloor uplift patches at the epicenter and near the trench that are crucial in reproducing the near-field tsunami recorded by coastal and deep-water buoys around the source as well as runup variation along east Japan coasts. The model tsunami allows investigation of the generation mechanism in terms of the rupture process and the ocean wave dynamics over the continental margin. A confluence of physical processes associated with the rupture and the bathymetry and topography led to the devastating impact of the 2011 Tohoku tsunami along the northeastern Japan coasts. The large slip near the trench produced a long-crested wave directed toward the continental shelf. The superposition of this long-crested wave

  4. Near-Field Diffraction Imaging from Multiple Detection Planes

    NASA Astrophysics Data System (ADS)

    Loetgering, L.; Golembusch, M.; Hammoud, R.; Wilhein, T.

    2017-06-01

    We present diffraction imaging results obtained from multiple near-field diffraction constraints. An iterative phase retrieval algorithm was implemented that uses data redundancy achieved by measuring near-field diffraction intensities at various sample-detector distances. The procedure allows for reconstructing the exit surface wave of a sample within a multiple constraint satisfaction framework neither making use of a priori knowledge as enforced in coherent diffraction imaging (CDI) nor exact scanning grid knowledge as required in ptychography. We also investigate the potential of the presented technique to deal with polychromatic radiation as important for potential application in diffraction imaging by means of tabletop EUV and X-ray sources.

  5. Processes of Change in Self-Directed Couple Relationship Education

    ERIC Educational Resources Information Center

    Wilson, Keithia L.; Halford, W. Kim

    2008-01-01

    The current study examined the learning processes involved in professionally supported self-directed couple relationship education (CRE). Fifty-nine couples completed Couple CARE, a systematic, self-directed CRE program designed in flexible delivery mode to be completed at home. Couples watched a DVD introducing key relationship ideas and skills…

  6. Couple-responsible therapy process: positive proximal outcomes.

    PubMed

    Butler, M H; Wampler, K S

    1999-01-01

    Therapist-couple struggle vs. cooperation is linked to clinical outcome. This research conceptualizes and investigates treatment process as it relates to the occurrence of struggle versus cooperation. Models of couple-responsible and therapist-responsible process in couple therapy were developed. Couple-responsible process consists of enactments, accommodation, and inductive process. Therapist-responsible process consists of primary therapist-couple interaction, therapist interpretation, and direct instruction. In counterbalanced order, 25 couples were exposed to couple-responsible and therapist-responsible episodes during one therapy session. Couples reviewed videotapes of the episodes and completed measures of responsibility, struggle, and cooperation. Perceived responsibility was higher and struggle was lower during couple-responsible episodes. No difference in cooperation was found. Presence or absence of a contrast condition, where couples reported on one therapist process after already experiencing its opposite, led to main effects for responsibility and struggle, and mediated effects of struggle and cooperation. Generally speaking, responsibility was even higher during couple-responsible episodes and even lower during therapist-responsible episodes when contrast was present. Similarly, struggle was even lower during couple-responsible episodes and even higher during therapist-responsible episodes when contrast was present. For both couple-responsible and therapist-responsible episodes, cooperation was negatively affected by a shift from the prior, opposite therapist process. Significant proportions of the variance in responsibility, struggle, and cooperation, however, were not accounted for by therapist process alone.

  7. Near-field infrared vibrational dynamics and tip-enhanced decoherence.

    PubMed

    Xu, Xiaoji G; Raschke, Markus B

    2013-04-10

    Ultrafast infrared spectroscopy can reveal the dynamics of vibrational excitations in matter. In its conventional far-field implementation, however, it provides only limited insight into nanoscale sample volumes due to insufficient spatial resolution and sensitivity. Here, we combine scattering-scanning near-field optical microscopy (s-SNOM) with femtosecond infrared vibrational spectroscopy to characterize the coherent vibrational dynamics of a nanoscopic ensemble of C-F vibrational oscillators of polytetrafluoroethylene (PTFE). The near-field mode transfer between the induced vibrational molecular coherence and the metallic scanning probe tip gives rise to a tip-mediated radiative IR emission of the vibrational free-induction decay (FID). By increasing the tip–sample coupling, we can enhance the vibrational dephasing of the induced coherent vibrational polarization and associated IR emission, with dephasing times up to T2(NF) is approximately equal to 370 fs in competition against the intrinsic far-field lifetime of T2(FF) is approximately equal to 680 fs as dominated by nonradiative damping. Near-field antenna-coupling thus provides for a new way to modify vibrational decoherence. This approach of ultrafast s-SNOM enables the investigation of spatiotemporal dynamics and correlations with nanometer spatial and femtosecond temporal resolution.

  8. Near-field modeling in Frenchman Flat, Nevada Test Site

    SciTech Connect

    Pohlmann, K.; Shirley, C.; Andricevic, R.

    1996-12-01

    The US Department of Energy (DOE) is investigating the effects of nuclear testing in underground test areas (the UGTA program) at the Nevada Test Site. The principal focus of the UGTA program is to better understand and define subsurface radionuclide migration. The study described in this report focuses on the development of tools for generating maps of hydrogeologic characteristics of subsurface Tertiary volcanic units at the Frenchman Flat corrective Action Unit (CAU). The process includes three steps. The first step involves generation of three-dimensional maps of the geologic structure of subsurface volcanic units using geophysical logs to distinguish between two classes: densely welded tuff and nonwelded tuff. The second step generates three-dimensional maps of hydraulic conductivity utilizing the spatial distribution of the two geologic classes obtained in the first step. Each class is described by a correlation structure based on existing data on hydraulic conductivity, and conditioned on the generated spatial location of each class. The final step demonstrates the use of the maps of hydraulic conductivity for modeling groundwater flow and radionuclide transport in volcanic tuffs from an underground nuclear test at the Frenchman Flat CAU. The results indicate that the majority of groundwater flow through the volcanic section occurs through zones of densely welded tuff where connected fractures provide the transport pathway. Migration rates range between near zero to approximately four m/yr, with a mean rate of 0.68 m/yr. This report presents the results of work under the FY96 Near-Field Modeling task of the UGTA program.

  9. Near-Field Noise Computation for a Supersonic Circular Jet

    NASA Technical Reports Server (NTRS)

    Loh, Ching Y.; Hultgren, Lennart S.

    2005-01-01

    A fully expanded, high-Reynolds-number, supersonic circular jet of Mach number 1.4 is simulated, using a 3-D finite-volume Navier-Stokes solver, with emphasis on the near field noise. The numerical results are generally in good agreement with existing experimental findings.

  10. Near-Field Spectroscopy with Nanoparticles Deposited by AFM

    NASA Technical Reports Server (NTRS)

    Anderson, Mark S.

    2008-01-01

    An alternative approach to apertureless near-field optical spectroscopy involving an atomic-force microscope (AFM) entails less complexity of equipment than does a prior approach. The alternative approach has been demonstrated to be applicable to apertureless near-field optical spectroscopy of the type using an AFM and surface enhanced Raman scattering (SERS), and is expected to be equally applicable in cases in which infrared or fluorescence spectroscopy is used. Apertureless near-field optical spectroscopy is a means of performing spatially resolved analyses of chemical compositions of surface regions of nanostructured materials. In apertureless near-field spectroscopy, it is common practice to utilize nanostructured probe tips or nanoparticles (usually of gold) having shapes and dimensions chosen to exploit plasmon resonances so as to increase spectroscopic-signal strengths. To implement the particular prior approach to which the present approach is an alternative, it is necessary to integrate a Raman spectrometer with an AFM and to utilize a special SERS-active probe tip. The resulting instrumentation system is complex, and the tasks of designing and constructing the system and using the system to acquire spectro-chemical information from nanometer-scale regions on a surface are correspondingly demanding.

  11. Near-Field Noise Computation for a Subsonic Coannular Jet

    NASA Technical Reports Server (NTRS)

    Loh, Ching Y.; Hultgren, Lennart S.; Jorgenson, Philip C. E.

    2008-01-01

    A high-Reynolds-number, subsonic coannular jet is simulated, using a three-dimensional finite-volume LES method, with emphasis on the near field noise. The nozzle geometry used is the NASA Glenn 3BB baseline model. The numerical results are generally in good agreement with existing experimental findings.

  12. Low-noise Instrumentation for Near-field Microwave Microscopy

    NASA Astrophysics Data System (ADS)

    Chisum, Jonathan David

    This thesis addresses circuits and systems optimized for the unique requirements of near-field microwave microscopy (NFMM). A suite of qualification measurements is conducted for the systematic characterization of the NFMM measurement system. Finally, modeling methods and quantitative analysis are performed for the interpretation of resulting measurements. An NFMM measurement typically suffers from small signal in the presence of seemingly overwhelming white and 1/f noise. As such, it requires instrumentation that provides signal enhancement, noise reduction, and long-term stability. This thesis describes the design and characterization of probe circuits and probe tips which enable sensitive and high-resolution NFMM with enhanced signals. The space efficient probe circuit is designed for ease of integration and eventual MMIC implementation. The scanning Lock-in Vector Near-field Probe (LVNP) instrument is designed for the readout of the near-field probe circuit. Selection of measurement topology for the purpose of noise reduction/mitigation is described. The LVNP is characterized with respect to noise, stability, and maximum signal sensitivity. In summary, this thesis details the design of a complete system for near-field microwave microscopy including probe tip, probe circuit, and instrument design. Performance limitations are quantified throughout the thesis in the hope of promoting a systematic approach to NFMM instrumentation, and quantitative data analysis techniques are proposed.

  13. Photon-induced near-field electron microscopy.

    PubMed

    Barwick, Brett; Flannigan, David J; Zewail, Ahmed H

    2009-12-17

    In materials science and biology, optical near-field microscopies enable spatial resolutions beyond the diffraction limit, but they cannot provide the atomic-scale imaging capabilities of electron microscopy. Given the nature of interactions between electrons and photons, and considering their connections through nanostructures, it should be possible to achieve imaging of evanescent electromagnetic fields with electron pulses when such fields are resolved in both space (nanometre and below) and time (femtosecond). Here we report the development of photon-induced near-field electron microscopy (PINEM), and the associated phenomena. We show that the precise spatiotemporal overlap of femtosecond single-electron packets with intense optical pulses at a nanostructure (individual carbon nanotube or silver nanowire in this instance) results in the direct absorption of integer multiples of photon quanta (nhomega) by the relativistic electrons accelerated to 200 keV. By energy-filtering only those electrons resulting from this absorption, it is possible to image directly in space the near-field electric field distribution, obtain the temporal behaviour of the field on the femtosecond timescale, and map its spatial polarization dependence. We believe that the observation of the photon-induced near-field effect in ultrafast electron microscopy demonstrates the potential for many applications, including those of direct space-time imaging of localized fields at interfaces and visualization of phenomena related to photonics, plasmonics and nanostructures.

  14. Near-field thermal imaging of nanostructured surfaces

    NASA Astrophysics Data System (ADS)

    Kittel, A.; Wischnath, U. F.; Welker, J.; Huth, O.; Rüting, F.; Biehs, S.-A.

    2008-11-01

    We show that a near-field scanning thermal microscope, which essentially detects the local density of states of the thermally excited electromagnetic modes at nanometer distances from some material, can be employed for nanoscale imaging of structures on that material's surface. This finding is explained theoretically by an approach which treats the surface structure perturbatively.

  15. Near-field transport imaging applied to photovoltaic materials

    DOE PAGES

    Xiao, Chuanxiao; Jiang, Chun -Sheng; Moseley, John; ...

    2017-05-26

    We developed and applied a new analytical technique - near-field transport imaging (NF-TI or simply TI) - to photovoltaic materials. Charge-carrier transport is an important factor in solar cell performance, and TI is an innovative approach that integrates a scanning electron microscope with a near-field scanning optical microscope, providing the possibility to study luminescence associated with recombination and transport with high spatial resolution. In this paper, we describe in detail the technical barriers we had to overcome to develop the technique for routine application and the data-fitting procedure used to calculate minority-carrier diffusion length values. The diffusion length measured bymore » TI agrees well with the results calculated by time-resolved photoluminescence on well-controlled gallium arsenide (GaAs) thin-film samples. We report for the first time on measurements on thin-film cadmium telluride using this technique, including the determination of effective carrier diffusion length, as well as the first near-field imaging of the effect of a single localized defect on carrier transport and recombination in a GaAs heterostructure. Furthermore, by changing the scanning setup, we were able to demonstrate near-field cathodoluminescence (CL), and correlated the results with standard CL measurements. In conclusion, the TI technique shows great potential for mapping transport properties in solar cell materials with high spatial resolution.« less

  16. Radiative heat transfer in the extreme near field

    NASA Astrophysics Data System (ADS)

    Kim, Kyeongtae; Song, Bai; Fernández-Hurtado, Víctor; Lee, Woochul; Jeong, Wonho; Cui, Longji; Thompson, Dakotah; Feist, Johannes; Reid, M. T. Homer; García-Vidal, Francisco J.; Cuevas, Juan Carlos; Meyhofer, Edgar; Reddy, Pramod

    2015-12-01

    Radiative transfer of energy at the nanometre length scale is of great importance to a variety of technologies including heat-assisted magnetic recording, near-field thermophotovoltaics and lithography. Although experimental advances have enabled elucidation of near-field radiative heat transfer in gaps as small as 20-30 nanometres (refs 4, 5, 6), quantitative analysis in the extreme near field (less than 10 nanometres) has been greatly limited by experimental challenges. Moreover, the results of pioneering measurements differed from theoretical predictions by orders of magnitude. Here we use custom-fabricated scanning probes with embedded thermocouples, in conjunction with new microdevices capable of periodic temperature modulation, to measure radiative heat transfer down to gaps as small as two nanometres. For our experiments we deposited suitably chosen metal or dielectric layers on the scanning probes and microdevices, enabling direct study of extreme near-field radiation between silica-silica, silicon nitride-silicon nitride and gold-gold surfaces to reveal marked, gap-size-dependent enhancements of radiative heat transfer. Furthermore, our state-of-the-art calculations of radiative heat transfer, performed within the theoretical framework of fluctuational electrodynamics, are in excellent agreement with our experimental results, providing unambiguous evidence that confirms the validity of this theory for modelling radiative heat transfer in gaps as small as a few nanometres. This work lays the foundations required for the rational design of novel technologies that leverage nanoscale radiative heat transfer.

  17. Ultra-sensitive near-field Raman detection technique

    NASA Astrophysics Data System (ADS)

    Wu, Shifa; Liu, Kun; Pan, Shi

    2006-02-01

    In this report, based on the near-field Raman theory which mechanism is fundamental different with the far-field Raman, a new viewpoint of near-field Raman was brought out. In this view, to be the excitation light, the effect of evanescent light in near-field Raman was emphasized, at same time, the evanescent light component in the Raman scattering light was noticed, too. The sample could be excited through evanescent light and the component of evanescent light in Raman scattering light was collected entirely in the novel ultra-sensitive near-field Raman sample cell. According to the sample cell, initial experiment was performed. The high aperture oil immersed object lens was employed to form excitation light which included evanescent light component. High signal-to-noise surface enhanced Raman scattering (SERS) signal of rat serum was obtained. By analysing the Raman spectrum, it was found that the new Raman peaks come out because of the excitation light including evanescent light.

  18. Lower corner of Face B Array with near field horn, ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    Lower corner of Face B Array with near field horn, foreground left, looking north/northwest - Beale Air Force Base, Perimeter Acquisition Vehicle Entry Phased-Array Warning System, Techinical Equipment Building, End of Spencer Paul Road, north of Warren Shingle Road (14th Street), Marysville, Yuba County, CA

  19. Epidermal electronics with advanced capabilities in near-field communication.

    PubMed

    Kim, Jeonghyun; Banks, Anthony; Cheng, Huanyu; Xie, Zhaoqian; Xu, Sheng; Jang, Kyung-In; Lee, Jung Woo; Liu, Zhuangjian; Gutruf, Philipp; Huang, Xian; Wei, Pinghung; Liu, Fei; Li, Kan; Dalal, Mitul; Ghaffari, Roozbeh; Feng, Xue; Huang, Yonggang; Gupta, Sanjay; Paik, Ungyu; Rogers, John A

    2015-02-25

    Epidermal electronics with advanced capabilities in near field communications (NFC) are presented. The systems include stretchable coils and thinned NFC chips on thin, low modulus stretchable adhesives, to allow seamless, conformal contact with the skin and simultaneous capabilities for wireless interfaces to any standard, NFC-enabled smartphone, even under extreme deformation and after/during normal daily activities.

  20. Generation of single-crystalline domain in nano-scale silicon pillars by near-field short pulsed laser

    NASA Astrophysics Data System (ADS)

    In, Jung Bin; Xiang, Bin; Hwang, David J.; Ryu, Sang-Gil; Kim, Eunpa; Yoo, Jae-Hyuck; Dubon, Oscar; Minor, Andrew M.; Grigoropoulos, Costas P.

    2014-01-01

    We observe laser-induced grain morphology change in silicon nanopillars under a transmission electron microscopy (TEM) environment. We couple the TEM with a near-field scanning optical microscopy pulsed laser processing system. This novel combination enables immediate scrutiny on the grain morphologies that the pulsed laser irradiation produces. We find unusual transformation of the tip of the amorphous or polycrystalline silicon pillar into a single crystalline domain via melt-mediated crystallization. On the basis of the three-dimensional finite difference simulation result and the dark field TEM data, we propose that the creation of the distinct single crystalline tip originates from the dominant grain growth initiated at the apex of the non-planar liquid-solid interface. Our microscopic observation provides a fundamental basis for laser-induced conversion of amorphous nanostructures into coarse-grained crystals.

  1. Electric field measurements of the LH wave and ICRF near-field utilizing non-perturbative spectroscopic techniques

    NASA Astrophysics Data System (ADS)

    Martin, E. H.; Caughman, J. B. O.; Klepper, C. C.; Goniche, M.; Isler, R. C.; Hillairet, J.; Bottereau, C.

    2015-12-01

    The physics of wave heating and current drive processes in the bulk hot plasma are generally well identified. However, details of the wave-plasma interaction in the cold plasma edge are still not fully understood. In this paper a spectroscopic technique allowing for measurements of the electric field driving wave-plasma interactions in the edge region for LH current drive and ICRH systems will be discussed. Experimental results obtained in Tore Supra near the LH C3 antenna and in the magnetized capacitively coupled RF sheath from an experiment designed to mimic the ICRF near-field are presented. In conclusion, future plans to implement a laser-based spectroscopic technique to acquire the high resolution measurements needed for model validation is discussed.

  2. Sub-10 nm near-field localization by plasmonic metal nanoaperture arrays with ultrashort light pulses

    PubMed Central

    Lee, Hongki; Kim, Chulhong; Kim, Donghyun

    2015-01-01

    Near-field localization by ultrashort femtosecond light pulses has been investigated using simple geometrical nanoapertures. The apertures employ circular, rhombic, and triangular shapes to localize the distribution of surface plasmon. To understand the geometrical effect on the localization, aperture length and period of the nanoapertures were varied. Aperture length was shown to affect the performance more than aperture period due mainly to intra-aperture coupling of near-fields. Triangular apertures provided the strongest spatial localization below 10 nm in size as well as the highest enhancement of field intensity by more than 7000 times compared to the incident light pulse. Use of ultrashort pulses was found to allow much stronger light localization than with continuous-wave light. The results can be used for super-localization sensing and imaging applications where spatially localized fields can break through the limits in achieving improved sensitivity and resolution. PMID:26628326

  3. Deterministic optical-near-field-assisted positioning of nitrogen-vacancy centers.

    PubMed

    Geiselmann, Michael; Marty, Renaud; Renger, Jan; García de Abajo, F Javier; Quidant, Romain

    2014-03-12

    Nanopositioning of single quantum emitters to control their coupling to integrated photonic structures is a crucial step in the fabrication of solid-state quantum optics devices. We use the optical near-field enhancement produced by nanofabricated gold antennas subject to near-infrared illumination to deterministically trap and position single nanodiamonds (NDs) hosting nitrogen-vacancy (NV) centers. The positioning of the NDs at the antenna regions of maximum field intensity is first characterized using both fluorescence and electron microscopy imaging. We further study the interaction between the nanoantenna and the delivered NV center by analyzing its change in fluorescence lifetime, which is driven by the increase in the local density of optical states at the trapping positions. Additionally, the plasmonic enhancement of the near-field intensity allows us to optically control the NV excited lifetime using relatively low NIR illumination intensities, some 20 times lower than in the absence of the antennas.

  4. Compact surface plasmon holographic microscopy for near-field film mapping.

    PubMed

    Zhang, Jiwei; Dai, Siqing; Ma, Chaojie; Di, Jianglei; Zhao, Jianlin

    2017-09-01

    We develop a compact objective-coupling surface plasmon holographic microscopy with a common-path configuration by introducing a Wollaston prism. Through off-axis hologram recording and numerical reconstruction, amplitude- and phase-contrast surface plasmon resonance (SPR) images can be obtained simultaneously. Based on the four-layer SPR model, the thin film thickness distribution in near field can be mapped unambiguously using a novel demodulation method without a priori knowledge. The technique demonstrates nondestructive and full-field measurement capabilities with sub-nanometer resolution theoretically. Furthermore, owing to the high temporal stability, the recommended system shows great potential for dynamic measurement of near-field tiny refractive index or thickness variation in fields such as chemistry and biomedicine, etc.

  5. Near-field analysis of metallic DFB lasers at telecom wavelengths.

    PubMed

    Greusard, L; Costantini, D; Bousseksou, A; Decobert, J; Lelarge, F; Duan, G-H; De Wilde, Y; Colombelli, R

    2013-05-06

    We image in near-field the transverse modes of semiconductor distributed feedback (DFB) lasers operating at λ ≈ 1.3 μm and employing metallic gratings. The active region is based on tensile-strained InGaAlAs quantum wells emitting transverse magnetic polarized light and is coupled via an extremely thin cladding to a nano-patterned gold grating integrated on the device surface. Single mode emission is achieved, which tunes with the grating periodicity. The near-field measurements confirm laser operation on the fundamental transverse mode. Furthermore--together with a laser threshold reduction observed in the DFB lasers--it suggests that the patterning of the top metal contact can be a strategy to reduce the high plasmonic losses in this kind of systems.

  6. Electrically tunable near-field radiative heat transfer via ferroelectric materials

    SciTech Connect

    Huang, Yi; Boriskina, Svetlana V.; Chen, Gang

    2014-12-15

    We explore ways to actively control near-field radiative heat transfer between two surfaces that relies on electrical tuning of phonon modes of ferroelectric materials. Ferroelectrics are widely used for tunable electrical devices, such as capacitors and memory devices; however, their tunable properties have not yet been examined for heat transfer applications. We show via simulations that radiative heat transfer between two ferroelectric materials can be enhanced by over two orders of magnitude over the blackbody limit in the near field, and can be tuned as much as 16.5% by modulating the coupling between surface phonon polariton modes at the two surfaces via varying external electric fields. We then discuss how to maximize the modulation contrast for tunable thermal devices using the studied mechanism.

  7. Three-Dimensional Near-Field Microwave Holography for Tissue Imaging

    PubMed Central

    Amineh, Reza K.; Khalatpour, Ali; Xu, Haohan; Baskharoun, Yona; Nikolova, Natalia K.

    2012-01-01

    This paper reports the progress toward a fast and reliable microwave imaging setup for tissue imaging exploiting near-field holographic reconstruction. The setup consists of two wideband TEM horn antennas aligned along each other's boresight and performing a rectangular aperture raster scan. The tissue sensing is performed without coupling liquids. At each scanning position, wideband data is acquired. Then, novel holographic imaging algorithms are implemented to provide three-dimensional images of the inspected domain. In these new algorithms, the required incident field and Green's function are obtained from numerical simulations. They replace the plane (or spherical) wave assumption in the previous holographic methods and enable accurate near-field imaging results. Here, we prove that both the incident field and Green's function can be obtained from a single numerical simulation. This eliminates the need for optimization-based deblurring which was previously employed to remove the effect of realistic non-point-wise antennas. PMID:22550472

  8. GNSS Antenna Caused Near-Field Interference Effect in Precise Point Positioning Results

    NASA Astrophysics Data System (ADS)

    Dawidowicz, Karol; Baryła, Radosław

    2017-06-01

    Results of long-term static GNSS observation processing adjustment prove that the often assumed "averaging multipath effect due to extended observation periods" does not actually apply. It is instead visible a bias that falsifies the coordinate estimation. The comparisons between the height difference measured with a geometrical precise leveling and the height difference provided by GNSS clearly verify the impact of the near-field multipath effect. The aim of this paper is analysis the near-field interference effect with respect to the coordinate domain. We demonstrate that the way of antennas mounting during observation campaign (distance from nearest antennas) can cause visible changes in pseudo-kinematic precise point positioning results. GNSS measured height differences comparison revealed that bias of up to 3 mm can be noticed in Up component when some object (additional GNSS antenna) was placed in radiating near-field region of measuring antenna. Additionally, for both processing scenario (GPS and GPS/GLONASS) the scattering of results clearly increased when additional antenna crosses radiating near-field region of measuring antenna. It is especially true for big choke ring antennas. In short session (15, 30 min.) the standard deviation was about twice bigger in comparison to scenario without additional antenna. When we used typical surveying antennas (short near-field region radius) the effect is almost invisible. In this case it can be observed the standard deviation increase of about 20%. On the other hand we found that surveying antennas are generally characterized by lower accuracy than choke ring antennas. The standard deviation obtained on point with this type of antenna was bigger in all processing scenarios (in comparison to standard deviation obtained on point with choke ring antenna).

  9. Coupling Processes between Atmospheric Chemistry and Climate

    NASA Technical Reports Server (NTRS)

    Ko, Malcolm K. W.; Weisenstein, Debra K.; Shia, Run-Lie; Scott, Courtney J.; Sze, Nien Dak

    1998-01-01

    This is the fourth semi-annual report for NAS5-97039, covering the time period July through December 1998. The overall objective of this project is to improve the understanding of coupling processes between atmospheric chemistry and climate. Model predictions of the future distributions of trace gases in the atmosphere constitute an important component of the input necessary for quantitative assessments of global change. We will concentrate on the changes in ozone and stratospheric sulfate aerosol, with emphasis on how ozone in the lower stratosphere would respond to natural or anthropogenic changes. The key modeling tools for this work are the Atmospheric and Environmental Research (AER) two-dimensional chemistry-transport model, the AER two-dimensional stratospheric sulfate model, and the AER three-wave interactive model with full chemistry. For this six month period, we report on a modeling study of new rate constant which modify the NOx/NOy ratio in the lower stratosphere; sensitivity to changes in stratospheric water vapor in the future atmosphere; a study of N2O and CH4 observations which has allowed us to adjust diffusion in the 2-D CTM in order to obtain appropriate polar vortex isolation; a study of SF6 and age of air with comparisons of models and measurements; and a report on the Models and Measurements II effort.

  10. Coupling Processes Between Atmospheric Chemistry and Climate

    NASA Technical Reports Server (NTRS)

    Ko, Malcolm; Weisenstein, Debra; Rodriquez, Jose; Danilin, Michael; Scott, Courtney; Shia, Run-Lie; Eluszkiewicz, Janusz; Sze, Nien-Dak; Stewart, Richard W. (Technical Monitor)

    1999-01-01

    This is the final report for NAS5-97039 for work performed between December 1996 and November 1999. The overall objective of this project is to improve the understanding of coupling processes among atmospheric chemistry, aerosol and climate, all important for quantitative assessments of global change. Among our priority are changes in ozone and stratospheric sulfate aerosol, with emphasis on how ozone in the lower stratosphere would respond to natural or anthropogenic changes. The work emphasizes two important aspects: (1) AER's continued participation in preparation of, and providing scientific input for, various scientific reports connected with assessment of stratospheric ozone and climate. These include participation in various model intercomparison exercises as well as preparation of national and international reports. (2) Continued development of the AER three-wave interactive model to address how the transport circulation will change as ozone and the thermal properties of the atmosphere change, and assess how these new findings will affect our confidence in the ozone assessment results.

  11. Coupling Processes Between Atmospheric Chemistry and Climate

    NASA Technical Reports Server (NTRS)

    Ko, M. K. W.; Weisenstein, Debra; Shia, Run-Li; Sze, N. D.

    1997-01-01

    This is the first semi-annual report for NAS5-97039 summarizing work performed for January 1997 through June 1997. Work in this project is related to NAS1-20666, also funded by NASA ACMAP. The work funded in this project also benefits from work at AER associated with the AER three-dimensional isentropic transport model funded by NASA AEAP and the AER two-dimensional climate-chemistry model (co-funded by Department of Energy). The overall objective of this project is to improve the understanding of coupling processes between atmospheric chemistry and climate. Model predictions of the future distributions of trace gases in the atmosphere constitute an important component of the input necessary for quantitative assessments of global change. We will concentrate on the changes in ozone and stratospheric sulfate aerosol, with emphasis on how ozone in the lower stratosphere would respond to natural or anthropogenic changes. The key modeling tools for this work are the AER two-dimensional chemistry-transport model, the AER two-dimensional stratospheric sulfate model, and the AER three-wave interactive model with full chemistry.

  12. Scanning near-field lithography with high precision flexure orientation stage control

    NASA Astrophysics Data System (ADS)

    Qin, Jin; Zhang, Liang; Tan, Haosen; Wang, Liang

    2017-09-01

    A new design of an orientation stage for scanning near-field lithography is presented based on flexure hinges. Employing flexure mechanisms in place of rigid-body mechanisms is one of the most promising techniques to efficiently implement high precision motion and avoid problems caused by friction. For near-field scanning lithography with evanescent wave, best resolution can be achieved in contact mode. However, if the mask is fixed on a rigid stage, contact friction will deteriorate the lithography surface. To reduce friction while maintaining good contact between the mask and the substrate, the mask should be held with high lateral stiffness and low torsion stiffness. This design can hold the mask in place during the scanning process and achieve passive alignment. Circular flexure hinges, whose parameters are determined by motion requirements based on Schotborgh's equation, are used as the basic unit of the stage to achieve passive alignment by compensating motions from elastic deformation. A finite-element analysis is performed to verify this property of the stage. With the aid of this stage, 21 nm resolution is achieved in static near-field lithography and 18 nm line-width in scanning near-field lithography.

  13. The thermal near-field: Coherence, spectroscopy, heat-transfer, and optical forces

    NASA Astrophysics Data System (ADS)

    Jones, Andrew C.; O'Callahan, Brian T.; Yang, Honghua U.; Raschke, Markus B.

    2013-12-01

    One of the most universal physical processes shared by all matter at finite temperature is the emission of thermal radiation. The experimental characterization and theoretical description of far-field black-body radiation was a cornerstone in the development of modern physics with the groundbreaking contributions from Gustav Kirchhoff and Max Planck. With its origin in thermally driven fluctuations of the charge carriers, thermal radiation reflects the resonant and non-resonant dielectric properties of media, which is the basis for far-field thermal emission spectroscopy. However, associated with the underlying fluctuating optical source polarization are fundamentally distinct spectral, spatial, resonant, and coherence properties of the evanescent thermal near-field. These properties have been recently predicted theoretically and characterized experimentally for systems with thermally excited molecular, surface plasmon polariton (SPP), and surface phonon polariton (SPhP) resonances. We review, starting with the early historical developments, the emergence of theoretical models, and the description of the thermal near-field based on the fluctuation-dissipation theory and in terms of the electromagnetic local density of states (EM-LDOS). We discuss the optical and spectroscopic characterization of distance dependence, magnitude, spectral distribution, and coherence of evanescent thermal fields. Scattering scanning near-field microscopy proved instrumental as an enabling technique for the investigations of several of these fundamental thermal near-field properties. We then discuss the role of thermal fields in nano-scale heat transfer and optical forces, and the correlation to the van der Waals, Casimir, and Casimir-Polder forces. We conclude with an outlook on the possibility of intrinsic and extrinsic resonant manipulation of optical forces, control of nano-scale radiative heat transfer with optical antennas and metamaterials, and the use of thermal infrared near-field

  14. Near-field effects of asteroid impacts in deep water

    SciTech Connect

    Gisler, Galen R; Weaver, Robert P; Gittings, Michael L

    2009-06-11

    Our previous work has shown that ocean impacts of asteroids below 500 m in diameter do not produce devastating long-distance tsunamis. Nevertheless, a significant portion of the ocean lies close enough to land that near-field effects may prove to be the greatest danger from asteroid impacts in the ocean. Crown splashes and central jets that rise up many kilometres into the atmosphere can produce, upon their collapse, highly non-linear breaking waves that could devastate shorelines within a hundred kilometres of the impact site. We present illustrative calculations, in two and three dimensions, of such impacts for a range of asteroid sizes and impact angles. We find that, as for land impacts, the greatest dangers from oceanic impacts are the short-term near-field, and long-term atmospheric effects.

  15. Thermal excitation of plasmons for near-field thermophotovoltaics

    SciTech Connect

    Guo, Yu; Molesky, Sean; Hu, Huan; Cortes, Cristian L.; Jacob, Zubin

    2014-08-18

    The traditional approaches of exciting plasmons consist of either using electrons (e.g., electron energy loss spectroscopy) or light (Kretchman and Otto geometry) while more recently plasmons have been excited even by single photons. A different approach: thermal excitation of a plasmon resonance at high temperatures using alternate plasmonic media was proposed by S. Molesky et al. [Opt. Express 21, A96–A110 (2013)]. Here, we show how the long-standing search for a high temperature narrowband near-field emitter for thermophotovoltaics can be fulfilled by thermally exciting plasmons. We also describe a method to control Wein's displacement law in the near-field using high temperature epsilon-near-zero metamaterials. Finally, we show that our work opens up an interesting direction of research for the field of slow light: thermal emission control.

  16. Percolation of optical excitation mediated by near-field interactions

    NASA Astrophysics Data System (ADS)

    Naruse, Makoto; Kim, Song-Ju; Takahashi, Taiki; Aono, Masashi; Akahane, Kouichi; D'Acunto, Mario; Hori, Hirokazu; Thylén, Lars; Katori, Makoto; Ohtsu, Motoichi

    2017-04-01

    Optical excitation transfer in nanostructured matter has been intensively studied in various material systems for versatile applications. Herein, we theoretically and numerically discuss the percolation of optical excitations in randomly organized nanostructures caused by optical near-field interactions governed by Yukawa potential in a two-dimensional stochastic model. The model results demonstrate the appearance of two phases of percolation of optical excitation as a function of the localization degree of near-field interaction. Moreover, it indicates sublinear scaling with percolation distances when the light localization is strong. Furthermore, such a character is maximized at a particular size of environments. The results provide fundamental insights into optical excitation transfer and will facilitate the design and analysis of nanoscale signal-transfer characteristics.

  17. Design considerations for near-field enhancement in optical antennas

    NASA Astrophysics Data System (ADS)

    Fernández-García, Roberto; Sonnefraud, Yannick; Fernández-Domínguez, Antonio I.; Giannini, Vincenzo; Maier, Stefan A.

    2014-01-01

    Nanoantennas for visible and infrared radiation can strongly enhance the interaction of light with matter by their ability to localise electromagnetic fields on nanometric scales. This allows for the engineering of the absorption and radiation capabilities of nanoemitters, such as dye molecules or quantum dots. In this article, we discuss the main parameters influencing the near-field enhancement provided by dimer-type nanoantennas, the configuration most thoroughly studied in the literature. To facilitate the design of structures, we analyse the influence of the substrate, adhesion layers and a reflective metal underlayer, as well as their arrangement in a periodic fashion. We also highlight the factors which increase the damping of the localised plasmonic modes and the spectral differences between far and near-field resonances.

  18. Near-field radiative heat transfer between metamaterial thin films.

    PubMed

    Basu, Soumyadipta; Francoeur, Mathieu

    2014-03-01

    We investigate near-field radiative heat transfer between two thin films made of metamaterials. The impact of film thickness on magnetic and electric surface polaritons (ESPs) is analyzed. It is found that the strength as well as the location of magnetic resonance does not change with film thickness until the film behaves as semi-infinite for the dielectric function chosen in this study. When the film is thinner than vacuum gap, both electric and magnetic polaritons contribute evenly to near-field radiative heat transfer. At larger film thicknesses, ESPs dominate heat transfer due to excitation of a larger number of modes. Results obtained from this study will facilitate applications of metamaterials as thin-film coatings for energy systems.

  19. Relation between near field and far field acoustic measurements

    NASA Technical Reports Server (NTRS)

    Bies, D. A.; Scharton, T. D.

    1974-01-01

    Several approaches to the problem of determining the far field directivity of an acoustic source located in a reverberant environment, such as a wind tunnel, are investigated analytically and experimentally. The decrease of sound pressure level with distance is illustrated; and the spatial extent of the hydrodynamic and geometric near fields, the far field, and the reverberant field are described. A previously-prosposed analytical technique for predicting the far field directivity of the acoustic source on the basis of near field data is investigated. Experiments are conducted with small acoustic sources and an analysis is performed to determine the variation with distance from the source of the directionality of the sound field. A novel experiment is conducted in which the sound pressure measured at various distances from an acoustic driver located in the NASA Ames 40 x 80 ft wind tunnel is crosscorrelated with the driver excitation voltage.

  20. Near-field model of ultrasonic array data

    NASA Astrophysics Data System (ADS)

    Velichko, Alexander

    2017-02-01

    One method of efficiently modelling of ultrasonic array data is based on a combination of a ray-tracing approach and far-field scattering amplitude of a scatterer. This technique uses two main assumptions: all scatterers are located in the far-field from each array element and the size of each scatterer is small relative to its distance to array elements. The key part of the model is the so-called scattering matrix, which provides the amplitude and phase of scattered waves in the far-field of the scatterer. However, the far-field approximation fails when the size of the scatterer becomes comparable to its distance to array elements. In this paper a near-field model of ultrasonic array data is developed. In particular, it is shown that the near-field scattering behavior can be extracted from the scattering matrix. The applications of the model are discussed and supported with modelling examples.

  1. Near-field optically driven Brownian motors (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Wu, Shao-Hua; Huang, Ningfeng; Jaquay, Eric; Povinelli, Michelle L.

    2016-09-01

    Brownian ratchets are of fundamental interest in fields from statistical physics to molecular motors. The realization of Brownian ratchets in engineered systems opens up the potential to harness thermal energy for directed motion, with applications in transport and sorting of nanoparticles. Implementations based on optical traps provide a high degree of tunability along with precise spatiotemporal control. Near-field optical methods provide particular flexibility and ease of on-chip integration with other microfluidic components. Here, we demonstrate the first all-optical, near-field Brownian ratchet. Our approach uses an asymmetrically patterned photonic crystal and yields an ultra-stable trap stiffness of 253.6 pN/nm-W, 100x greater than conventional optical tweezers. By modulating the laser power, optical ratcheting with transport speed of 1 micron/s can be achieved, allowing a variety of dynamical lab-on-a-chip applications. The resulting transport speed matches well with the theoretical prediction.

  2. Plasmonic and photonic scattering and near fields of nanoparticles.

    PubMed

    Schmid, Martina; Andrae, Patrick; Manley, Phillip

    2014-01-29

    We theoretically compare the scattering and near field of nanoparticles from different types of materials, each characterized by specific optical properties that determine the interaction with light: metals with their free charge carriers giving rise to plasmon resonances, dielectrics showing zero absorption in wide wavelength ranges, and semiconductors combining the two beforehand mentioned properties plus a band gap. Our simulations are based on Mie theory and on full 3D calculations of Maxwell's equations with the finite element method. Scattering and absorption cross sections, their division into the different order electric and magnetic modes, electromagnetic near field distributions around the nanoparticles at various wavelengths as well as angular distributions of the scattered light were investigated. The combined information from these calculations will give guidelines for choosing adequate nanoparticles when aiming at certain scattering properties. With a special focus on the integration into thin film solar cells, we will evaluate our results.

  3. Plasmonic and photonic scattering and near fields of nanoparticles

    PubMed Central

    2014-01-01

    We theoretically compare the scattering and near field of nanoparticles from different types of materials, each characterized by specific optical properties that determine the interaction with light: metals with their free charge carriers giving rise to plasmon resonances, dielectrics showing zero absorption in wide wavelength ranges, and semiconductors combining the two beforehand mentioned properties plus a band gap. Our simulations are based on Mie theory and on full 3D calculations of Maxwell’s equations with the finite element method. Scattering and absorption cross sections, their division into the different order electric and magnetic modes, electromagnetic near field distributions around the nanoparticles at various wavelengths as well as angular distributions of the scattered light were investigated. The combined information from these calculations will give guidelines for choosing adequate nanoparticles when aiming at certain scattering properties. With a special focus on the integration into thin film solar cells, we will evaluate our results. PMID:24475923

  4. Near-field electromagnetic theory for thin solar cells.

    PubMed

    Niv, A; Gharghi, M; Gladden, C; Miller, O D; Zhang, X

    2012-09-28

    Current methods for evaluating solar cell efficiencies cannot be applied to low-dimensional structures where phenomena from the realm of near-field optics prevail. We present a theoretical approach to analyze solar cell performance by allowing rigorous electromagnetic calculations of the emission rate using the fluctuation-dissipation theorem. Our approach shows the direct quantification of the voltage, current, and efficiency of low-dimensional solar cells. This approach is demonstrated by calculating the voltage and the efficiency of a GaAs slab solar cell for thicknesses from several microns down to a few nanometers. This example highlights the ability of the proposed approach to capture the role of optical near-field effects in solar cell performance.

  5. Rewritable organic films for near-field recording

    NASA Astrophysics Data System (ADS)

    Lee, Hyo Won; Kim, Young Mi; Jeon, Dong Ju; Kim, Eunkyoung; Kim, Jeongyong; Park, Kangho

    2003-01-01

    Photochromic thin films were prepared for near-field recording. Acetyl substituted diarylethene were synthesized from 1,2-bis(2-methylbenzo[ b]thiophene-3-yl)hexafluorocyclopentene in one step. Transparent and homogeneous thin films were coated on a substrate by vacuum deposition method. A colorless vacuum deposited diarylethene film turned to deep red hue upon exposure to a UV light. Near-field scanning optical microscopy (NSOM) was used to characterize nanoscale color change of the films. NSOM images showed distinct recording mark by 514 nm laser with mark speed of 30 ms. The records were completely erased upon excitation with a UV light, and rewritable with visible light (514 nm) on a UV activated colored film.

  6. Simulated annealing algorithm applied in adaptive near field beam shaping

    NASA Astrophysics Data System (ADS)

    Yu, Zhan; Ma, Hao-tong; Du, Shao-jun

    2010-11-01

    Laser beam shaping is required in many applications for improving the efficiency of the laser systems. In this paper, the near field beam shaping based on the combination of simulated annealing algorithm and Zernike polynomials is demonstrated. Considering phase distribution can be represented by the expansion of Zernike polynomials, the problem of searching appropriate phase distribution can be changed into a problem of optimizing a vector made up of Zernike coefficients. The feasibility of this method is validated theoretically by translating the Gaussian beam into square quasi-flattop beam in the near field. Finally, the closed control loop system constituted by phase only liquid crystal spatial light modulator and simulated annealing algorithm is used to prove the validity of the technique. The experiment results show that the system can generate laser beam with desired intensity distributions.

  7. Plasmonic and photonic scattering and near fields of nanoparticles

    NASA Astrophysics Data System (ADS)

    Schmid, Martina; Andrae, Patrick; Manley, Phillip

    2014-01-01

    We theoretically compare the scattering and near field of nanoparticles from different types of materials, each characterized by specific optical properties that determine the interaction with light: metals with their free charge carriers giving rise to plasmon resonances, dielectrics showing zero absorption in wide wavelength ranges, and semiconductors combining the two beforehand mentioned properties plus a band gap. Our simulations are based on Mie theory and on full 3D calculations of Maxwell's equations with the finite element method. Scattering and absorption cross sections, their division into the different order electric and magnetic modes, electromagnetic near field distributions around the nanoparticles at various wavelengths as well as angular distributions of the scattered light were investigated. The combined information from these calculations will give guidelines for choosing adequate nanoparticles when aiming at certain scattering properties. With a special focus on the integration into thin film solar cells, we will evaluate our results.

  8. Probe Station and Near-Field Scanner for Testing Antennas

    NASA Technical Reports Server (NTRS)

    Zaman, Afroz; Lee, Richard Q.; Darby, William G.; Barr, Philip J.; Miranda, Felix A.; Lambert, Kevin

    2006-01-01

    A facility that includes a probe station and a scanning open-ended waveguide probe for measuring near electromagnetic fields has been added to Glenn Research Center's suite of antenna-testing facilities, at a small fraction of the cost of the other facilities. This facility is designed specifically for nondestructive characterization of the radiation patterns of miniaturized microwave antennas fabricated on semiconductor and dielectric wafer substrates, including active antennas that are difficult to test in traditional antenna-testing ranges because of fragility, smallness, or severity of DC-bias or test-fixture requirements. By virtue of the simple fact that a greater fraction of radiated power can be captured in a near-field measurement than in a conventional far-field measurement, this near-field facility is convenient for testing miniaturized antennas with low gains.

  9. Mars Pathfinder Near-Field Rock Distribution Re-Evaluation

    NASA Technical Reports Server (NTRS)

    Haldemann, A. F. C.; Golombek, M. P.

    2003-01-01

    We have completed analysis of a new near-field rock count at the Mars Pathfinder landing site and determined that the previously published rock count suggesting 16% cumulative fractional area (CFA) covered by rocks is incorrect. The earlier value is not so much wrong (our new CFA is 20%), as right for the wrong reason: both the old and the new CFA's are consistent with remote sensing data, however the earlier determination incorrectly calculated rock coverage using apparent width rather than average diameter. Here we present details of the new rock database and the new statistics, as well as the importance of using rock average diameter for rock population statistics. The changes to the near-field data do not affect the far-field rock statistics.

  10. Near-field terahertz probes with room-temperature nanodetectors for subwavelength resolution imaging

    PubMed Central

    Mitrofanov, Oleg; Viti, Leonardo; Dardanis, Enrico; Giordano, Maria Caterina; Ercolani, Daniele; Politano, Antonio; Sorba, Lucia; Vitiello, Miriam S.

    2017-01-01

    Near-field imaging with terahertz (THz) waves is emerging as a powerful technique for fundamental research in photonics and across physical and life sciences. Spatial resolution beyond the diffraction limit can be achieved by collecting THz waves from an object through a small aperture placed in the near-field. However, light transmission through a sub-wavelength size aperture is fundamentally limited by the wave nature of light. Here, we conceive a novel architecture that exploits inherently strong evanescent THz field arising within the aperture to mitigate the problem of vanishing transmission. The sub-wavelength aperture is originally coupled to asymmetric electrodes, which activate the thermo-electric THz detection mechanism in a transistor channel made of flakes of black-phosphorus or InAs nanowires. The proposed novel THz near-field probes enable room-temperature sub-wavelength resolution coherent imaging with a 3.4 THz quantum cascade laser, paving the way to compact and versatile THz imaging systems and promising to bridge the gap in spatial resolution from the nanoscale to the diffraction limit. PMID:28287123

  11. On the slow dynamics of near-field acoustically levitated objects under High excitation frequencies

    NASA Astrophysics Data System (ADS)

    Ilssar, Dotan; Bucher, Izhak

    2015-10-01

    This paper introduces a simplified analytical model describing the governing dynamics of near-field acoustically levitated objects. The simplification converts the equation of motion coupled with the partial differential equation of a compressible fluid, into a compact, second order ordinary differential equation, where the local stiffness and damping are transparent. The simplified model allows one to more easily analyse and design near-field acoustic levitation based systems, and it also helps to devise closed-loop controller algorithms for such systems. Near-field acoustic levitation employs fast ultrasonic vibrations of a driving surface and exploits the viscosity and the compressibility of a gaseous medium to achieve average, load carrying pressure. It is demonstrated that the slow dynamics dominates the transient behaviour, while the time-scale associated with the fast, ultrasonic excitation has a small presence in the oscillations of the levitated object. Indeed, the present paper formulates the slow dynamics under an ultrasonic excitation without the need to explicitly consider the latter. The simplified model is compared with a numerical scheme based on Reynolds equation and with experiments, both showing reasonably good results.

  12. Hyperbolic metamaterial-based near-field thermophotovoltaic system for hundreds of nanometer vacuum gap.

    PubMed

    Jin, Seokmin; Lim, Mikyung; Lee, Seung S; Lee, Bong Jae

    2016-03-21

    Artificially designed hyperbolic metamaterial (HMM) possesses extraordinary electromagnetic features different from those of naturally existing materials. In particular, the dispersion relation of waves existing inside the HMM is hyperbolic rather than elliptical; thus, waves that are evanescent in isotropic media become propagating in the HMM. This characteristic of HMMs opens a novel way to spectrally control the near-field thermal radiation in which evanescent waves in the vacuum gap play a critical role. In this paper, we theoretically investigate the performance of a near-field thermophotovoltaic (TPV) energy conversion system in which a W/SiO2-multilayer-based HMM serves as the emitter at 1000 K and InAs works as the TPV cell at 300 K. By carefully designing the thickness of constituent materials of the HMM emitter, the electric power of the near-field TPV devices can be increased by about 6 times at 100-nm vacuum gap as compared to the case of the plain W emitter. Alternatively, in regards to the electric power generation, HMM emitter at experimentally achievable 100-nm vacuum gap performs equivalently to the plain W emitter at 18-nm vacuum gap. We show that the enhancement mechanism of the HMM emitter is due to the coupled surface plasmon modes at multiple metal-dielectric interfaces inside the HMM emitter. With the minority carrier transport model, the optimal p-n junction depth of the TPV cell has also been determined at various vacuum gaps.

  13. Near-field terahertz probes with room-temperature nanodetectors for subwavelength resolution imaging

    NASA Astrophysics Data System (ADS)

    Mitrofanov, Oleg; Viti, Leonardo; Dardanis, Enrico; Giordano, Maria Caterina; Ercolani, Daniele; Politano, Antonio; Sorba, Lucia; Vitiello, Miriam S.

    2017-03-01

    Near-field imaging with terahertz (THz) waves is emerging as a powerful technique for fundamental research in photonics and across physical and life sciences. Spatial resolution beyond the diffraction limit can be achieved by collecting THz waves from an object through a small aperture placed in the near-field. However, light transmission through a sub-wavelength size aperture is fundamentally limited by the wave nature of light. Here, we conceive a novel architecture that exploits inherently strong evanescent THz field arising within the aperture to mitigate the problem of vanishing transmission. The sub-wavelength aperture is originally coupled to asymmetric electrodes, which activate the thermo-electric THz detection mechanism in a transistor channel made of flakes of black-phosphorus or InAs nanowires. The proposed novel THz near-field probes enable room-temperature sub-wavelength resolution coherent imaging with a 3.4 THz quantum cascade laser, paving the way to compact and versatile THz imaging systems and promising to bridge the gap in spatial resolution from the nanoscale to the diffraction limit.

  14. Surface-emitting, distributed-feedback diode lasers with uniform near-field intensity profile

    NASA Astrophysics Data System (ADS)

    Lopez, James; Kasraian, Masoud; Botez, Dan

    1998-10-01

    Theoretical analysis of second-order surface-emitting, complex-coupled distributed feedback diode lasers with first-order distributed Bragg reflectors (DBR) is presented. The DBR reflectors are shown to insure simultaneous operation in a virtually uniform near-field profile with high efficiency and adequate intermodal discrimination. Such devices display symmetric-mode (single-lobe) surface emission with relatively high external differential quantum efficiency (30%), low gain threshold (18 cm-1), and <8% near-field intensity profile variations (in the longitudinal direction). The devices have the potential to provide >100 mW of stable, single-mode cw power, significantly higher than it is possible with vertical-cavity surface-emitting lasers. It is also shown that the device studied here can be combined with a resonant optical waveguide array device to produce a 2D uniform near-field surface-emitting source capable of providing greater than 1 W cw power in a stable, single-lobed beam.

  15. Engineering Near-Field Transport of Energy using Nanostructured Materials

    DTIC Science & Technology

    2015-12-12

    SECURITY CLASSIFICATION OF: The transport of heat at the nanometer scale is becoming increasingly important for a wide range of nanotechnology ...increasingly important for a wide range of nanotechnology applications. Recent computational studies on near-field radiative heat transfer (NFRHT) suggest...Nature Nanotechnology , (02 2015): 253. doi: 10.1038/nnano.2015.6 Kyeongtae Kim, Bai Song, Víctor Fernández-Hurtado, Woochul Lee, Wonho Jeong, Longji Cui

  16. Near-Field Optical Microscopy and Spectroscopy with Pointed Probes

    DTIC Science & Technology

    2006-01-01

    metal nanostructure can be viewed as an optical antenna . Of course, the efficiency depends on the material composition and the geometry of the...nanostructure. A simple form of optical antenna is a single ellipsoidal particle. This particle ex- hibits a distinct resonance for which the field...Grober RD, Schoelkopf RJ, Prober DE. 1997. Optical antenna : towards a unity efficiency near-field optical probe. Appl. Phys. Lett. 70:1354 54. Farahani

  17. Near-Field Heat Transfer between Multilayer Hyperbolic Metamaterials

    NASA Astrophysics Data System (ADS)

    Biehs, Svend-Age; Ben-Abdallah, Philippe

    2017-02-01

    We review the near-field radiative heat flux between hyperbolic materials focusing on multilayer hyperbolic meta-materials. We discuss the formation of the hyperbolic bands, the impact of ordering of the multilayer slabs, as well as the impact of the first single layer on the heat transfer. Furthermore, we compare the contribution of surface modes to that of hyperbolic modes. Finally, we also compare the exact results with predictions from effective medium theory.

  18. Turbulent structure of a wingtip vortex in the near field

    NASA Technical Reports Server (NTRS)

    Zilliac, Gregory G.; Chow, Jim S.; Dacles-Mariani, Jennifer; Bradshaw, Peter

    1993-01-01

    The turbulent rollup of a vortex generated by a rectangular wing has been investigated. Extensive mean and turbulence measurements of the flowfield on a wingtip and in the near field have been completed. Velocity fluctuation measurements show that the near-field core is not laminar. A large axial velocity excess was found to exist in the core of the vortex. A momentum balance in the near-field of the wingtip showed that the magnitude of the core Reynolds-stress gradient terms are the same order as the largest terms in the governing equations. Navier-Stokes computations of the identical configuration, including wind tunnel walls and using measured inflow and outflow boundary conditions, reproduced many of the features of the experiment. Inherent limitations of the Baldwin-Barth turbulence model combined with limited grid resolution caused the computed vortex core to be more diffuse than desired. The momentum balance also demonstrated that the level of numerically generated false diffusion in the vortex core is relatively high.

  19. Near-field photometry for organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Li, Rui; Harikumar, Krishnan; Isphording, Alexandar; Venkataramanan, Venkat

    2013-03-01

    Organic Light Emitting Diode (OLED) technology is rapidly maturing to be ready for next generation of light source for general lighting. The current standard test methods for solid state lighting have evolved for semiconductor sources, with point-like emission characteristics. However, OLED devices are extended surface emitters, where spatial uniformity and angular variation of brightness and colour are important. This necessitates advanced test methods to obtain meaningful data for fundamental understanding, lighting product development and deployment. In this work, a near field imaging goniophotometer was used to characterize lighting-class white OLED devices, where luminance and colour information of the pixels on the light sources were measured at a near field distance for various angles. Analysis was performed to obtain angle dependent luminous intensity, CIE chromaticity coordinates and correlated colour temperature (CCT) in the far field. Furthermore, a complete ray set with chromaticity information was generated, so that illuminance at any distance and angle from the light source can be determined. The generated ray set is needed for optical modeling and design of OLED luminaires. Our results show that luminance non-uniformity could potentially affect the luminaire aesthetics and CCT can vary with angle by more than 2000K. This leads to the same source being perceived as warm or cool depending on the viewing angle. As OLEDs are becoming commercially available, this could be a major challenge for lighting designers. Near field measurement can provide detailed specifications and quantitative comparison between OLED products for performance improvement.

  20. Complex Near-Field Plasmonic Response of Au Nanospirals

    NASA Astrophysics Data System (ADS)

    Hachtel, Jordan; Davidson, Roderick; Lupini, Andrew; Lawrie, Benjamin; Haglund, Richard; Pantelides, Sokrates

    Complex metallic nanostructures that support unique near-field surface plasmon modes have shown applications across the fields of photovoltaics, bio-sensing, and even quantum computing. Chiral Au nanospirals not only possess a non-symmetric morphology that results in second-harmonic generation, but possess multiple distinct near-field plasmonic modes that cover a wide range of plasmon frequencies. We use cathodoluminescence (CL) and electron energy loss spectroscopy (EELS) within a scanning transmission electron microscopy (STEM) to study the surface plasmons and map them with nanoscale precision. The two techniques are complementary as EELS measures excitations in the sample, while CL measures the subsequent radiative decays. We STEM-EELS/CL to map and analyze the spatial profile, intensity and polarization response of the intricate near-field plasmon modes in these versatile nanostructures. This work was funded by the Department of Energy Grant DE-FG02-09ER46554 and the Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

  1. Near-field thermal electromagnetic transport: An overview

    NASA Astrophysics Data System (ADS)

    Edalatpour, Sheila; DeSutter, John; Francoeur, Mathieu

    2016-07-01

    A general near-field thermal electromagnetic transport formalism that is independent of the size, shape and number of heat sources is derived. The formalism is based on fluctuational electrodynamics, where fluctuating currents due to thermal agitation are added to Maxwell's curl equations, and is thus valid for heat sources in local thermodynamic equilibrium. Using a volume integral formulation, it is shown that the proposed formalism is a generalization of the classical electromagnetic scattering framework in which thermal emission is implicitly assumed to be negligible. The near-field thermal electromagnetic transport formalism is afterwards applied to a problem involving three spheres with size comparable to the wavelength, where all multipolar interactions are taken into account. Using the thermal discrete dipole approximation, it is shown that depending on the dielectric function, the presence of a third sphere slightly affects the spatial distribution of power absorbed compared to the two-sphere case. A transient analysis shows that despite a non-uniform spatial distribution of power absorbed, the sphere temperature remains spatially uniform at any instant due to the fact that the thermal resistance by conduction is much smaller than the resistance by radiation. The formalism proposed in this paper is general, and could be used as a starting point for adapting solution methods employed in traditional electromagnetic scattering problems to near-field thermal electromagnetic transport.

  2. Near-field heat transfer between graphene/hBN multilayers

    NASA Astrophysics Data System (ADS)

    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.

  3. Nanograting formation in air through plasmonic near-field ablation induced by femtosecond laser pulses

    NASA Astrophysics Data System (ADS)

    Miyaji, Godai; Miyazaki, Kenzo

    2017-02-01

    Superimposed multiple shots of low-fluence femtosecond (fs) laser pulses form a periodic nanostructure on solid surfaces through ablation. We have demonstrated that the self-organization process of nanostructuring can be regulated to fabricate a homogeneous nanograting on the target surface in air. A simple two-step ablation process and an ablation technique using interfering fs laser beams were developed to control plasmonic near-fields generated by fs laser pulses. The results have shown the nature of a single spatial standing wave mode of surface plasmon polaritons of which periodically enhanced near-fields ablate the target surface, to fabricate the nanograting on gallium nitride (GaN) and metals such as stainless steel (SUS) and titanium (Ti).

  4. Optical near-field analysis of spherical metals: Application of the FDTD method combined with the ADE method.

    PubMed

    Yamaguchi, Takashi; Hinata, Takashi

    2007-09-03

    The time-average energy density of the optical near-field generated around a metallic sphere is computed using the finite-difference time-domain method. To check the accuracy, the numerical results are compared with the rigorous solutions by Mie theory. The Lorentz-Drude model, which is coupled with Maxwell's equation via motion equations of an electron, is applied to simulate the dispersion relation of metallic materials. The distributions of the optical near-filed generated around a metallic hemisphere and a metallic spheroid are also computed, and strong optical near-fields are obtained at the rim of them.

  5. Multistatic Array Sampling Scheme for Fast Near-Field Image Reconstruction

    DTIC Science & Technology

    2016-01-01

    1 Multistatic Array Sampling Scheme for Fast Near-Field Image Reconstruction William F. Moulder, James D. Krieger, Denise T. Maurais-Galejs, Huy...reconstruction. The array topology samples the scene on a regular grid of phase centers, using a tiling of Boundary Arrays (BAs). Following a simple correction...the sampled data can then be processed with the well-known and highly efficient monostatic FFT imaging algorithm. In this work, the approach is

  6. Coupling Effects of Heat and Moisture on the Saturation Processes of Buffer Material in a Deep Geological Repository

    NASA Astrophysics Data System (ADS)

    Huang, Wei-Hsing

    2017-04-01

    Clay barrier plays a major role for the isolation of radioactive wastes in a underground repository. This paper investigates the resaturation behavior of clay barrier, with emphasis on the coupling effects of heat and moisture of buffer material in the near-field of a repository during groundwater intrusion processes. A locally available clay named "Zhisin clay" and a standard bentotine material were adopted in the laboratory program. Water uptake tests were conducted on clay specimens compacted at various densities to simulate the intrusion of groundwater into the buffer material. Soil suction of clay specimens was measured by psychrometers embedded in clay specimens and by vapor equilibrium technique conducted at varying temperatures. Using the soil water characteristic curve, an integration scheme was introduced to estimate the hydraulic conductivity of unsaturated clay. The finite element program ABAQUS was then employed to carry out the numerical simulation of the saturation process in the near field of a repository. Results of the numerical simulation were validated using the degree of saturation profile obtained from the water uptake tests on Zhisin clay. The numerical scheme was then extended to establish a model simulating the resaturation process after the closure of a repository. It was found that, due to the variation in suction and thermal conductivity with temperature of clay barrier material, the calculated temperature field shows a reduction as a result of incorporating the hydro-properties in the calculations.

  7. Probing the plasmonic near-field by one- and two-photon excited surface enhanced Raman scattering

    PubMed Central

    Kneipp, Harald

    2013-01-01

    Summary Strongly enhanced and spatially confined near-fields in the vicinity of plasmonic nanostructures open up exciting new capabilities for photon-driven processes and particularly also for optical spectroscopy. Surface enhanced Raman signatures of single molecules can provide us with important information about the optical near-field. We discuss one- and two-photon excited surface enhanced Raman scattering at the level of single molecules as a tool for probing the plasmonic near-field of silver nanoaggregates. The experiments reveal enhancement factors of local fields in the hottest hot spots of the near-field and their dependence on the photon energy. Also, the number of the hottest spots and their approximate geometrical size are found. Near-field amplitudes in the hottest spots can be enhanced by three orders of magnitudes. Nanoaggregates of 100 nm dimensions provide one hot spot on this highest enhancement level where the enhancement is confined within less than 1nm dimension. The near-field enhancement in the hottest spots increases with decreasing photon energy. PMID:24367752

  8. Analytical treatment of near-field electromagnetic heat transfer at the nanoscale

    NASA Astrophysics Data System (ADS)

    Iizuka, Hideo; Fan, Shanhui

    2015-10-01

    Near-field thermal transfer between material bodies is generally obtained by numerical calculation methods. We present simple close-form analytic results for heat transfer between planar structures, derived by explicitly relating the heat transfer to the dispersion relations of the coupled systems. In the conventional case of heat transfer between SiC slabs, the closed-form analytic results agree excellently with numerical simulations. In the case where two graphene sheets are separated by a distance d , our theory shows that the heat transfer scales as 1 /d , rather than 1 /d2 as in the conventional cases, due to the unique dispersion relation of two-dimensional plasmons.

  9. Remote sensing of a low pressure plasma in the radio near field

    NASA Astrophysics Data System (ADS)

    Kelly, Seán; McNally, Patrick J.

    2017-09-01

    A novel approach to remotely monitor low pressure non-equilibrium plasmas is reported. A magnetic field antenna is positioned in the near field of a capacitively coupled plasma. Magnetic flux from plasma currents, present near the viewport, is intercepted by a calibrated loop antenna placed outside the chamber. The induced signal current is correlated to bulk plasma currents. The comparison of relative harmonic amplitudes shows resonance features for lower operating pressures. The geometric resonance and electron-neutral collision frequencies are evaluated from resonant harmonic features. This approach advances remote, noninvasive, and installation-free plasma monitoring, which is of particular interest to industrial scenarios.

  10. Coupling entropy of co-processing model on social networks

    NASA Astrophysics Data System (ADS)

    Zhang, Zhanli

    2015-08-01

    Coupling entropy of co-processing model on social networks is investigated in this paper. As one crucial factor to determine the processing ability of nodes, the information flow with potential time lag is modeled by co-processing diffusion which couples the continuous time processing and the discrete diffusing dynamics. Exact results on master equation and stationary state are achieved to disclose the formation. In order to understand the evolution of the co-processing and design the optimal routing strategy according to the maximal entropic diffusion on networks, we propose the coupling entropy comprehending the structural characteristics and information propagation on social network. Based on the analysis of the co-processing model, we analyze the coupling impact of the structural factor and information propagating factor on the coupling entropy, where the analytical results fit well with the numerical ones on scale-free social networks.

  11. Local observation of modes from three-dimensional woodpile photonic crystals with near-field microspectroscopy under supercontinuum illumination.

    PubMed

    Jia, Baohua; Norton, Andrew H; Li, Jiafang; Rahmani, Adel; Asatryan, Ara A; Botten, Lindsay C; Gu, Min

    2008-05-15

    A near-field microscope coupled with a near-infrared (NIR) supercontinuum source is developed and applied to characterize optical modes in a three-dimensional (3D) woodpile photonic crystal (PC) possessing a NIR partial bandgap. Spatially resolved near-field intensity distributions under different illumination wavelengths demonstrate that the electric fields preferentially dwell in the polymer rods or in the gaps between rods, respectively, for frequencies below or above the stop gap, as predicted by the 3D finite-difference time-domain modeling. Near-field microspectroscopy further reveals that the position-dependent band-edge effect plays an important role in PC-based all-optical integrated devices.

  12. Thermal Moore's law and near-field thermal conductance in carbon-based electronics

    NASA Astrophysics Data System (ADS)

    Rotkin, Slava V.

    2009-08-01

    The novel thermal conductance mechanism, theoretically predicted and experimentally measured in nanotube field-effect transistors (FET), is discussed with respect to the power dissipation problem of modern carbon-based electronics. Such an effect is due to the near-field coupling of the charge carriers in the transistor channel with the local electric field of the surface electromagnetic modes. The coupling leads to a quantum electrodynamic (QED) energy exchange between the hot electrons in FET channel and the optical polar phonon bath being in thermal equilibrium with the substrate. For an example of a NT on silica, this QED coupling mechanism is shown to exceed significantly the interface Kapitza conductance, that is, the classical phonon heat transport. The QED thermal conductance is proposed to play dominant role in the energy dissipation in nanoelectronics with a hetero-interface between the device channel and the polar substrate.

  13. On-chip near field fluorescence excitation and detection with nanophotonic waveguides for enhanced surface sensitivity (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Mahmud-Ul-Hasan, Md.; Neutens, Pieter; Lagae, Liesbet; Van Dorpe, Pol

    2017-02-01

    Fluorescence is a widely used transduction mechanism in bio-imaging, sensing or physical chemistry characterization applications. The ability to selectively excite desired molecules without generating considerable bulk background from nearby molecules is very important for all these applications. A near field excitation using an exponentially decaying evanescent field is often used to reduce the bulk background by selectively exciting molecules near to the surface. We propose an on-chip platform to improve the surface and bulk fluorescence separation by combining near-field excitation and near-field collection. We used the exponentially decaying evanescent tail of a Silicon Nitride rib waveguide to excite molecules and coupled the subsequent emission back via the same waveguide. We observe from the finite difference time domain simulation that both the excitation and coupling efficiency depend exponentially on the surface-molecule distance. Thus, combination of near field excitation and collection improves surface-bulk separation. A reduction by half in effective 1/e decay length was found experimentally for this combined near-field excitation and collection technique compare to the conventional only near-field excitation based technique . An analytical model is derived to find the optimum device efficiency for bio-sensing applications and established a general condition for sensor length to maximize the device efficiency and validated by experimental data. Finally, we used this platform for Fluorescence Correlation Spectroscopy and steady-state fluorescence anisotropy measurement. In this talk, I will present the fabrication, characterization and experimental results obtained using this proposed waveguide based platform.

  14. [Transmission efficiency analysis of near-field fiber probe using FDTD simulation].

    PubMed

    Huang, Wei; Dai, Song-Tao; Wang, Huai-Yu; Zhou, Yun-Song

    2011-10-01

    A fiber probe is the key component of near-field optical technology which is widely used in high resolution imaging, spectroscopy detection and nano processing. How to improve the transmission efficiency of the fiber probe is a very important problem in the application of near-field optical technology. Based on the results of 3D-FDTD computation, the dependence of the transmission efficiency on the cone angle, the aperture diameter, the wavelength and the thickness of metal cladding is revealed. The authors have also made a comparison between naked probe and the probe with metal cladding in terms of transmission efficiency and spatial resolution. In addition, the authors have discovered the fluctuation phenomena of transmission efficiency as the wavelength of incident laser increases.

  15. Decision making based on optical excitation transfer via near-field interactions between quantum dots

    NASA Astrophysics Data System (ADS)

    Naruse, Makoto; Nomura, Wataru; Aono, Masashi; Ohtsu, Motoichi; Sonnefraud, Yannick; Drezet, Aurélien; Huant, Serge; Kim, Song-Ju

    2014-10-01

    Optical near-field interactions between nanostructured matters, such as quantum dots, result in unidirectional optical excitation transfer when energy dissipation is induced. This results in versatile spatiotemporal dynamics of the optical excitation, which can be controlled by engineering the dissipation processes and exploited to realize intelligent capabilities such as solution searching and decision making. Here, we experimentally demonstrate the ability to solve a decision making problem on the basis of optical excitation transfer via near-field interactions by using colloidal quantum dots of different sizes, formed on a geometry-controlled substrate. We characterize the energy transfer behavior due to multiple control light patterns and experimentally demonstrate the ability to solve the multi-armed bandit problem. Our work makes a decisive step towards the practical design of nanophotonic systems capable of efficient decision making, one of the most important intellectual attributes of the human brain.

  16. Decision making based on optical excitation transfer via near-field interactions between quantum dots

    SciTech Connect

    Naruse, Makoto; Nomura, Wataru; Ohtsu, Motoichi; Aono, Masashi; Sonnefraud, Yannick; Drezet, Aurélien; Huant, Serge; Kim, Song-Ju

    2014-10-21

    Optical near-field interactions between nanostructured matters, such as quantum dots, result in unidirectional optical excitation transfer when energy dissipation is induced. This results in versatile spatiotemporal dynamics of the optical excitation, which can be controlled by engineering the dissipation processes and exploited to realize intelligent capabilities such as solution searching and decision making. Here, we experimentally demonstrate the ability to solve a decision making problem on the basis of optical excitation transfer via near-field interactions by using colloidal quantum dots of different sizes, formed on a geometry-controlled substrate. We characterize the energy transfer behavior due to multiple control light patterns and experimentally demonstrate the ability to solve the multi-armed bandit problem. Our work makes a decisive step towards the practical design of nanophotonic systems capable of efficient decision making, one of the most important intellectual attributes of the human brain.

  17. Near-field radiative heat transfer in mesoporous alumina

    NASA Astrophysics Data System (ADS)

    Jing, Li; Yan-Hui, Feng; Xin-Xin, Zhang; Cong-Liang, Huang; Ge, Wang

    2015-01-01

    The thermal conductivity of mesoporous material has aroused the great interest of scholars due to its wide applications such as insulation, catalyst, etc. Mesoporous alumina substrate consists of uniformly distributed, unconnected cylindrical pores. Near-field radiative heat transfer cannot be ignored, when the diameters of the pores are less than the characteristic wavelength of thermal radiation. In this paper, near-field radiation across a cylindrical pore is simulated by employing the fluctuation dissipation theorem and Green function. Such factors as the diameter of the pore, and the temperature of the material are further analyzed. The research results show that the radiative heat transfer on a mesoscale is 2˜4 orders higher than on a macroscale. The heat flux and equivalent thermal conductivity of radiation across a cylindrical pore decrease exponentially with pore diameter increasing, while increase with temperature increasing. The calculated equivalent thermal conductivity of radiation is further developed to modify the thermal conductivity of the mesoporous alumina. The combined thermal conductivity of the mesoporous alumina is obtained by using porosity weighted dilute medium and compared with the measurement. The combined thermal conductivity of mesoporous silica decreases gradually with pore diameter increasing, while increases smoothly with temperature increasing, which is in good agreement with the experimental data. The larger the porosity, the more significant the near-field effect is, which cannot be ignored. Project supported by the National Natural Science Foundation of China (Grant No. 51422601), the National Basic Research Program of China (Grant No. 2012CB720404), and the National Key Technology Research and Development Program of China (Grant No. 2013BAJ01B03).

  18. Near-field optical control of doughnut-shaped nanostructures

    NASA Astrophysics Data System (ADS)

    Dubrovkin, A. M.; Barillé, R.; Ortyl, E.; Zielinska, S.

    2015-01-01

    The application of a local near-field optical excitation with a control of the illumination time can be used to manage step-by-step the reshape of individual doughnut-shaped azopolymer nano-objects demonstrating their performances as a promising functional nano-objects. The possibility to provide a photoinduced reshaping opens a way to the fundamental study of size-dependent scaling laws of optical properties, photoinduced reshaping efficiency and possible nanoreactor or nanoresonator behaviors at nanometer scales. As an example the created nano-object is used to self-assembly polystyrene nanospheres in a supraball.

  19. Magnetic dipole moment determination by near-field analysis

    NASA Technical Reports Server (NTRS)

    Eichhorn, W. L.

    1972-01-01

    A method for determining the magnetic moment of a spacecraft from magnetic field data taken in a limited region of space close to the spacecraft. The spacecraft's magnetic field equations are derived from first principles. With measurements of this field restricted to certain points in space, the near-field equations for the spacecraft are derived. These equations are solved for the dipole moment by a least squares procedure. A method by which one can estimate the magnitude of the error in the calculations is also presented. This technique was thoroughly tested on a computer. The test program is described and evaluated, and partial results are presented.

  20. Near-field spillover from a subreflector: Theory and experiment

    NASA Technical Reports Server (NTRS)

    Lee, S. W.; Acosta, R.; Cherrette, A. R.; Lam, P. T.

    1986-01-01

    In a dual reflector antenna, the spillover from the subreflector is important in determining the accuracy of near-field measurements. This is especially so when some of the feed elements are placed far away from the focus. In this paper, we present a high-frequency GTD analysis of the spillover field over a plane just behind the subreflector. Special attention is given to the field near the incident shadow boundary and the role played by the slope diffraction term. Our computations are in excellent agreement with experimental results.

  1. Near-field spillover from a subreflector: Theory and experiment

    NASA Technical Reports Server (NTRS)

    Lee, S. W.; Acosta, R.; Cherrette, A. R.; Lam, P. T.

    1986-01-01

    In a dual reflector antenna, the spillover from the subreflector is important in determining the accuracy of near-field measurements. This is especially so when some of the feed elements are placed far away from the focus. A high-frequency GTD analysis of the spillover field over a plane just behind the subreflector is presented. Special attention is given to the field near the incident shadow boundary and the role played by the slope diffraction term. Computations are in excellent agreement with experimental results.

  2. Near Field Imaging at Microwave and Millemeter Wave Frequencies

    SciTech Connect

    Sheen, David M.; McMakin, Douglas L.; Hall, Thomas E.

    2007-06-03

    Near field imaging at microwave and millimeter wave frequencies is useful for a wide variety of applications including concealed weapon detection, through-wall and inner-wall imaging, ground penetrating radar imaging, radar cross section analysis, and non-destructive evaluation of materials. A variety of novel imaging techniques have been developed for many of these applications at the Pacific Northwest National Laboratory (PNNL) . These techniques make use of wideband holographic wavefront reconstruction methods, and have been developed to optimize the image quality and resolution. This paper will summarize several of these techniques and show imaging results for several interesting application areas.

  3. Near-field observation of light propagation in nanocoax waveguides.

    PubMed

    Merlo, Juan M; Ye, Fan; Rizal, Binod; Burns, Michael J; Naughton, Michael J

    2014-06-16

    We report the observation of propagating modes of visible and near infrared light in nanoscale coaxial (metal-dielectric-metal) structures, using near-field scanning optical microscopy. Together with numerical calculations, we show that the propagated modes have different nature depending on the excitation wavelength, i.e., plasmonic TE11 and TE21 modes in the near infrared and photonic TE31, TE41 and TM11 modes in the visible. Far field transmission out of the nanocoaxes is dominated by the superposition of Fabry-Perot cavity modes resonating in the structures, consistent with theory. Such coaxial optical waveguides may be useful for future nanoscale photonic systems.

  4. Scanning near-field optical microscopy: application to biological sciences

    NASA Astrophysics Data System (ADS)

    Lim, Tuan-Kay

    2001-12-01

    Recent developments in genetic engineering and medical informatics offer enormous potential for biotechnology. However, key enabling technologies, such as medical instrumentation and analytical tools, are required to support further research in this field. The scanning near-field optical microscopy (SNOM) is one of the key instruments for research in these areas. In this paper, we review the synergy of the SNOM with other technologies for the imaging and characterization of biological materials. Based on this review, the components and systems design parameters are summarized.

  5. Near-field Optical Imagigng and Chemical Analysis

    NASA Astrophysics Data System (ADS)

    Andres, La Rosa

    1998-03-01

    Identification of molecular structures in complex mixtures represents a major challenge in chemical research today. Microfabricated devices or lab-on-a-chip that perform chemical analysis allows dynamic sampling of picoliter microenvironments and separation. The long-term goals of nanochemistry down to the femtoliter scale involve refinement of the detection limit to single-molecule. Our approach consists in designing a very sensitive near-field optical microscope (NSOM-SIAM) to explore the mesoscopic properties of organic compounds. The validity, sensitivity and unique spatial resolution of this system will be discussed for multiple analyte chemosensing.

  6. Bessel beams as virtual tips for near-field optics.

    PubMed

    Grosjean, T; Courjon, D; Van Labeke, D

    2003-06-01

    In the previous NFO meeting, we proposed the use of confined evanescent light beams as 'virtual' or 'immaterial' tips. Unfortunately, this technique was hindered by the need for perfectly radially polarized light beams. In this communication, we propose a simple, stable and cheap method allowing the generation of beams of any polarization and more especially of purely radially polarized light beams. We also demonstrate both theoretically and experimentally that for near-field imaging systems polarization is a limiting factor of resolution and light confinement. Finally, we present the very first experimental results dealing with virtual tips.

  7. Nonresonant radiative exciton transfer by near field between quantum wells

    SciTech Connect

    Aleshkin, V. Ya.; Gavrilenko, L. V. Gaponova, D. M.; Kadykov, A. M.; Lysenko, V. G.; Krasil’nik, Z. F.

    2013-11-15

    We experimentally observed an increase in the intensity of photoluminescence from a wider quantum well (QW) when an exciton transition was induced in the neighboring narrower QW separated from the former one by a tunneling-nontransparent AlGaAs barrier. The dependence of the efficiency of the near-field radiative transfer of excitons on the distance between QWs was studied in heterostructures without coincidence of exciton resonances in the adjacent QWs. Theoretical results were qualitatively consistent with the available experimental data.

  8. Mode detection in turbofan inlets from near field sensor arrays.

    PubMed

    Castres, Fabrice O; Joseph, Phillip F

    2007-02-01

    Knowledge of the modal content of the sound field radiated from a turbofan inlet is important for source characterization and for helping to determine noise generation mechanisms in the engine. An inverse technique for determining the mode amplitudes at the duct outlet is proposed using pressure measurements made in the near field. The radiated sound pressure from a duct is modeled by directivity patterns of cut-on modes in the near field using a model based on the Kirchhoff approximation for flanged ducts with no flow. The resulting system of equations is ill posed and it is shown that the presence of modes with eigenvalues close to a cutoff frequency results in a poorly conditioned directivity matrix. An analysis of the conditioning of this directivity matrix is carried out to assess the inversion robustness and accuracy. A physical interpretation of the singular value decomposition is given and allows us to understand the issues of ill conditioning as well as the detection performance of the radiated sound field by a given sensor array.

  9. Near-Field Microscopy Studies of Lung Surfactant Collapse

    NASA Astrophysics Data System (ADS)

    Aga, Rachel; Dunn, Robert

    2003-03-01

    Respiratory distress syndrome (RDS), the fourth leading cause of infant mortality in the United States, arises from an insufficiently developed lung surfactant (LS). Healthy LS, a mixture of lipids and proteins that coats the inner surface of the lungs, reduces the alveolar surface tension to a few millinewtons per meter and, thus, facilitates breathing by stabilizing the large surface area changes associated with respiration. In the absence of an effective LS, surfactant collapse pressure (i.e., monolayer compressibility) and the ability of the monolayer to re-spread during the breathing cycle are reduced, resulting in labored breathing, reduced oxygen transport, and often death in those afflicted. In this study, we investigate the mechanism of collapse and re-spreading of a monolayer formed by a replacement surfactant commonly used in treatment of RDS. Through confocal microscopy fluorescence images obtained at a series of pressures near collapse, we find evidence for multilayer formation in the films. A further understanding of the collapse mechanism is obtained by comparing high resolution fluorescence and topography information measured with near-field scanning optical microscopy. The combined data from both confocal and near-field measurements are used to develop a model of lung surfactant collapse and re-spreading.

  10. Unidirectional wireless power transfer using near-field plates

    SciTech Connect

    Imani, Mohammadreza F.; Grbic, Anthony

    2015-05-14

    One of the obstacles preventing wireless power transfer from becoming ubiquitous is their leakage of power: high-amplitude electromagnetic fields that can interfere with other electronic devices, increase health concerns, or hinder power metering. In this paper, we present near-field plates (NFPs) as a novel method to tailor the electromagnetic fields generated by a wireless power transfer system while maintaining high efficiency. NFPs are modulated arrays or surfaces designed to form prescribed near-field patterns. The NFP proposed in this paper consists of an array of loaded loops that are designed to confine the electromagnetic fields of a resonant transmitting loop to the desired direction (receiving loop) while suppressing fields in other directions. The step-by-step design procedure for this device is outlined. Two NFPs are designed and examined in full-wave simulation. Their performance is shown to be in close agreement with the design predictions, thereby verifying the proposed design and operation. A NFP is also fabricated and experimentally shown to form a unidirectional wireless power transfer link with high efficiency.

  11. External Luminescence and Photon Recycling in Near-Field Thermophotovoltaics

    NASA Astrophysics Data System (ADS)

    DeSutter, John; Vaillon, Rodolphe; Francoeur, Mathieu

    2017-07-01

    The importance of considering near-field effects on photon recycling and spontaneous emission in a thermophotovoltaic device is investigated. Fluctuational electrodynamics is used to calculate external luminescence from a photovoltaic cell as a function of emitter type, vacuum gap thickness between the emitter and cell, and cell thickness. The observed changes in external luminescence suggest strong modifications of photon recycling caused by the presence of the emitter. Photon recycling for propagating modes is affected by reflection at the vacuum-emitter interface and is substantially decreased by the leakage towards the emitter through the tunneling of frustrated modes. In addition, spontaneous emission by the cell can be strongly enhanced by the presence of an emitter supporting surface-polariton modes. It follows that using a radiative recombination model with a spatially uniform radiative lifetime, even corrected by a photon-recycling factor, is inappropriate. Applying the principles of detailed balance and accounting for nonradiative recombination mechanisms, the impact of external luminescence enhancement in the near field on thermophotovoltaic performance is investigated. It is shown that unlike isolated cells, the external luminescence efficiency is not solely dependent on cell quality but significantly increases as the vacuum gap thickness decreases below 400 nm for the case of an intrinsic silicon emitter. In turn, the open-circuit voltage and power density benefit from this enhanced external luminescence toward the emitter. This benefit is larger as cell quality, characterized by the contribution of nonradiative recombination, decreases.

  12. Multifunctional plasmonic film for recording near-field optical intensity.

    PubMed

    Roxworthy, Brian J; Bhuiya, Abdul M; Inavalli, V V G Krishna; Chen, Hao; Toussaint, Kimani C

    2014-08-13

    We demonstrate the plasmonic equivalent of photographic film for recording optical intensity in the near field. The plasmonic structure is based on gold bowtie nanoantenna arrays fabricated on SiO2 pillars. We show that it can be employed for direct laser writing of image data or recording the polarization structure of optical vector beams. Scanning electron micrographs reveal a careful sculpting of the radius of curvature and height of the triangles composing the illuminated nanoantennas, as a result of plasmonic heating, that permits spatial tunability of the resonance response of the nanoantennas without sacrificing their geometric integrity. In contrast to other memory-dedicated approaches using Au nanorods embedded in a matrix medium, plasmonic film can be used in multiple application domains. To demonstrate this functionality, we utilize the structures as plasmonic optical tweezers and show sequestering of SiO2 microparticles into optically written channels formed between exposed sections of the film. The plasmonic film offers interesting possibilities for photonic applications including optofluidic channels "without walls," in situ tailorable biochemical sensing assays, and near-field particle manipulation and sorting.

  13. Cryogenic apparatus for study of near-field heat transfer

    SciTech Connect

    Kralik, T.; Hanzelka, P.; Musilova, V.; Srnka, A.; Zobac, M.

    2011-05-15

    For bodies spaced in vacuum at distances shorter than the wavelength of the thermal radiation, radiative heat transfer substantially increases due to the contribution of evanescent electromagnetic waves. Experimental data on heat transfer in near-field regime are scarce. We have designed a cryogenic apparatus for the study of heat transfer over microscopic distances between metallic and non-metallic surfaces. Using a mechanical positioning system, a planeparallel gap between the samples, concentric disks, each 35 mm in diameter, is set and varied from 10{sup 0} to 10{sup 3} {mu}m. The heat transferred from the hot (10 - 100 K) to the cold sample ({approx}5 K) sinks into a liquid helium bath through a thermal resistor, serving as a heat flux meter. Transferred heat power within {approx}2 nW/cm{sup 2} and {approx}30 {mu}W/cm{sup 2} is derived from the temperature drop along the thermal resistor. For tungsten samples, the distance of the near-field effect onset was inversely proportional to temperature and the heat power increase was observed up to three orders of magnitude greater than the power of far-field radiative heat transfer.

  14. 'Squeezing' near-field thermal emission for ultra-efficient high-power thermophotovoltaic conversion.

    PubMed

    Karalis, Aristeidis; Joannopoulos, J D

    2016-07-01

    We numerically demonstrate near-field planar ThermoPhotoVoltaic systems with very high efficiency and output power, at large vacuum gaps. Example performances include: at 1200 °K emitter temperature, output power density 2 W/cm(2) with ~47% efficiency at 300 nm vacuum gap; at 2100 °K, 24 W/cm(2) with ~57% efficiency at 200 nm gap; and, at 3000 °K, 115 W/cm(2) with ~61% efficiency at 140 nm gap. Key to this striking performance is a novel photonic design forcing the emitter and cell single modes to cros resonantly couple and impedance-match just above the semiconductor bandgap, creating there a 'squeezed' narrowband near-field emission spectrum. Specifically, we employ surface-plasmon-polariton thermal emitters and silver-backed semiconductor-thin-film photovoltaic cells. The emitter planar plasmonic nature allows for high-power and stable high-temperature operation. Our simulations include modeling of free-carrier absorption in both cell electrodes and temperature dependence of the emitter properties. At high temperatures, the efficiency enhancement via resonant mode cross-coupling and matching can be extended to even higher power, by appropriately patterning the silver back electrode to enforce also an absorber effective surface-plasmon-polariton mode. Our proposed designs can therefore lead the way for mass-producible and low-cost ThermoPhotoVoltaic micro-generators and solar cells.

  15. Tailoring the near-field guiding properties of magnetic metamaterials with two resonant elements per unit cell

    NASA Astrophysics Data System (ADS)

    Sydoruk, O.; Radkovskaya, A.; Zhuromskyy, O.; Shamonina, E.; Shamonin, M.; Stevens, C. J.; Faulkner, G.; Edwards, D. J.; Solymar, L.

    2006-06-01

    A theoretical and experimental study of magnetic metamaterials with unit cells containing two resonant elements is presented. The properties of these structures, consisting of split rings, are governed by strongly anisotropic magnetic coupling between individual elements. This coupling leads to propagation of slow magnetoinductive waves in the vicinity of the resonant frequency. The wavelength of magnetoinductive waves is much smaller than the free-space wavelength of the electromagnetic radiation. This opens up the possibility of manipulating the near field on a subwavelength scale. We develop a theoretical formulation for coupled chains of metamaterial elements allowing the tailoring of their guiding properties in the near field. In a comprehensive analysis modes of coupled waveguides supporting forward and/or backward waves are identified and the corresponding hybridization mechanisms for dispersion equations of magnetoinductive waves are determined. Analytical predictions are verified both experimentally and numerically on a variety of coupled waveguides. The approach can be employed for the design of near-field manipulating devices.

  16. Near-field localization by two dimensional metallic nano-post arrays with ultrashort light pulses

    NASA Astrophysics Data System (ADS)

    Lee, Hongki; Kim, Chulhong; Kim, Donghyun

    2016-03-01

    Locally amplified near-fields can be induced with nanostructures within a sub-diffraction-limited volume, which is useful for biomedical imaging and sensing applications. Employment of field localization in the biomedical applications where the pulsed light is used necessitates the spatial and temporal characteristics of fields near nanostructures. We considered the gold nano-post arrays of three different shapes to localize the near-fields which are circular, rhombic, and triangular. They were modeled to be located on an ITO film and a quartz substrate with periods changing from 300 to 900 nm by 200 nm. Their size changes from 50 to 250 nm which corresponds to the radius for the case of circular nanoposts and the distance between the center and the vertices for equilateral rhombic and triangular nanoposts. Numerical calculation of near-fields at the top of nanoposts was performed with finite difference time domain method when the Gaussian pulses at center wavelengths of 532, 633, and 850 nm were normally incident. Near-fields localization occurred mainly at vertices of the nanoposts, which makes the triangular nanoposts of primary interest with an observation of the strongest field intensity within a diffraction limited field-of-view. The observed fields on the triangular vertices were enhanced by 7.85, 51.54, and 7268 when the center wavelengths were 532, 633, and 850 nm respectively. Their temporal peaks were delayed by 2.05, 4.03, and 14.49 fs, which indicates the correlation between field enhancement and time delay associated with electron damping process. It was shown that with rhombic and triangular nanoposts fields can be localized below 10 nm on vertices and their signal-to-noise ratio increased with a larger period.

  17. Coupling Computer-Aided Process Simulation and ...

    EPA Pesticide Factsheets

    A methodology is described for developing a gate-to-gate life cycle inventory (LCI) of a chemical manufacturing process to support the application of life cycle assessment in the design and regulation of sustainable chemicals. The inventories were derived by first applying process design and simulation of develop a process flow diagram describing the energy and basic material flows of the system. Additional techniques developed by the U.S. Environmental Protection Agency for estimating uncontrolled emissions from chemical processing equipment were then applied to obtain a detailed emission profile for the process. Finally, land use for the process was estimated using a simple sizing model. The methodology was applied to a case study of acetic acid production based on the Cativa tm process. The results reveal improvements in the qualitative LCI for acetic acid production compared to commonly used databases and top-down methodologies. The modeling techniques improve the quantitative LCI results for inputs and uncontrolled emissions. With provisions for applying appropriate emission controls, the proposed method can provide an estimate of the LCI that can be used for subsequent life cycle assessments. As part of its mission, the Agency is tasked with overseeing the use of chemicals in commerce. This can include consideration of a chemical's potential impact on health and safety, resource conservation, clean air and climate change, clean water, and sustainable

  18. Thermodynamically coupled mass transport processes in a saturated clay

    SciTech Connect

    Carnahan, C.L.

    1984-11-01

    Gradients of temperature, pressure, and fluid composition in saturated clays give rise to coupled transport processes (thermal and chemical osmosis, thermal diffusion, ultrafiltration) in addition to the direct processes (advection and diffusion). One-dimensional transport of water and a solute in a saturated clay subjected to mild gradients of temperature and pressure was simulated numerically. When full coupling was accounted for, volume flux (specific discharge) was controlled by thermal osmosis and chemical osmosis. The two coupled fluxes were oppositely directed, producing a point of stagnation within the clay column. Solute flows were dominated by diffusion, chemical osmosis, and thermal osmosis. Chemical osmosis produced a significant flux of solute directed against the gradient of solute concentration; this effect reduced solute concentrations relative to the case without coupling. Predictions of mass transport in clays at nuclear waste repositories could be significantly in error if coupled transport processes are not accounted for. 14 references, 8 figures, 1 table.

  19. Synchronization and information processing by an on-off coupling.

    PubMed

    Wei, G W; Zhao, Shan

    2002-05-01

    This paper proposes an on-off coupling process for chaos synchronization and information processing. An in depth analysis for the net effect of a conventional coupling is performed. The stability of the process is studied. We show that the proposed controlled coupling process can locally minimize the smoothness and the fidelity of dynamical data. A digital filter expression for the on-off coupling process is derived and a connection is made to the Hanning filter. The utility and robustness of the proposed approach is demonstrated by chaos synchronization in Duffing oscillators, the spatiotemporal synchronization of noisy nonlinear oscillators, the estimation of the trend of a time series, and restoration of the contaminated solution of the nonlinear Schrödinger equation.

  20. Process for fabricating a charge coupled device

    DOEpatents

    Conder, Alan D.; Young, Bruce K. F.

    2002-01-01

    A monolithic three dimensional charged coupled device (3D-CCD) which utilizes the entire bulk of the semiconductor for charge generation, storage, and transfer. The 3D-CCD provides a vast improvement of current CCD architectures that use only the surface of the semiconductor substrate. The 3D-CCD is capable of developing a strong E-field throughout the depth of the semiconductor by using deep (buried) parallel (bulk) electrodes in the substrate material. Using backside illumination, the 3D-CCD architecture enables a single device to image photon energies from the visible, to the ultra-violet and soft x-ray, and out to higher energy x-rays of 30 keV and beyond. The buried or bulk electrodes are electrically connected to the surface electrodes, and an E-field parallel to the surface is established with the pixel in which the bulk electrodes are located. This E-field attracts charge to the bulk electrodes independent of depth and confines it within the pixel in which it is generated. Charge diffusion is greatly reduced because the E-field is strong due to the proximity of the bulk electrodes.

  1. Plasmonic electric near-field enhancement in self-organized gold nanoparticles in macroscopic arrays

    NASA Astrophysics Data System (ADS)

    Mondes, V.; Antonsson, E.; Plenge, J.; Raschpichler, C.; Halfpap, I.; Menski, A.; Graf, C.; Kling, M. F.; Rühl, E.

    2016-06-01

    When plasmonic nanoparticles are incorporated into nanostructures and they are exposed to external optical fields, plasmonic coupling causes electric near-field enhancement which is significantly larger than that of isolated nanoparticles. We report on the plasmonic coupling in arrays of gold nanospheres (20 ± 3 and 50 ± 4 nm) prepared by colloidal chemistry and self-organization. This yields field enhancement in arrays with areas of several mm2 and provides an alternative approach to lithographic methods for preparation of nanostructures for plasmonic applications. Gold nanospheres are surface-functionalized by organic ligands, which define the interparticle distance in the array upon self-organization of the nanoparticles. The experiments are accompanied by finite-difference time-domain simulations, which quantify the dependence of the field enhancement on the interparticle distance.

  2. Detection of Extremely Low Concentrations of Biological Substances Using Near-Field Illumination

    NASA Astrophysics Data System (ADS)

    Yasuura, Masato; Fujimaki, Makoto

    2016-12-01

    An external force-assisted near-field illumination biosensor (EFA-NI biosensor) detects a target substance that is propelled through an evanescent field by an external force. The target substance is sandwiched between an antibody coupled to a magnetic bead and an antibody coupled to a polystyrene bead. The external force is supplied by a magnetic field. The magnetic bead propels the target substance and the polystyrene bead emits an optical signal. The detection protocol includes only two steps; mixing the sample solution with a detection reagent containing the antibody-coated beads and injecting the sample mixture into a liquid cell. Because the system detects the motion of the beads, the sensor allows detection of trace amounts of target substances without a washing step. The detection capability of the sensor was demonstrated by the detection of norovirus virus-like particles at a concentration of ~40 particles per 100 μl in contaminated water.

  3. Detection of Extremely Low Concentrations of Biological Substances Using Near-Field Illumination

    PubMed Central

    Yasuura, Masato; Fujimaki, Makoto

    2016-01-01

    An external force-assisted near-field illumination biosensor (EFA-NI biosensor) detects a target substance that is propelled through an evanescent field by an external force. The target substance is sandwiched between an antibody coupled to a magnetic bead and an antibody coupled to a polystyrene bead. The external force is supplied by a magnetic field. The magnetic bead propels the target substance and the polystyrene bead emits an optical signal. The detection protocol includes only two steps; mixing the sample solution with a detection reagent containing the antibody-coated beads and injecting the sample mixture into a liquid cell. Because the system detects the motion of the beads, the sensor allows detection of trace amounts of target substances without a washing step. The detection capability of the sensor was demonstrated by the detection of norovirus virus-like particles at a concentration of ~40 particles per 100 μl in contaminated water. PMID:27991539

  4. Phase transformations coupled to deformation processes

    NASA Astrophysics Data System (ADS)

    Lookman, Turab

    2013-06-01

    Phase transformation processes have a substantial impact on the inelastic and damage response of materials. Yet, our understanding of how different loading conditions affect volume fractions of transformed phases, microstructure and transformation pathways is very much in its infancy. With an emphasis on distilling single crystal physics that can, in principle, be incorporated into higher length scale models, I will discuss how recent atomistic simulations on Ti are beginning to provide insights into transformation pathways and the interplay of phase transformations and deformation processes. These simulations are complemented by shock experiments on Zr, Ti together with characterization studies at the Advanced Photon Source.

  5. Optical near-field induced visible response photoelectrochemical water splitting on nanorod TiO2

    NASA Astrophysics Data System (ADS)

    Huong Le, Thu Hac; Mawatari, Kazuma; Pihosh, Yuriy; Kawazoe, Tadashi; Yatsui, Takashi; Ohtsu, Motoichi; Tosa, Masahiro; Kitamori, Takehiko

    2011-11-01

    Here we report a way to induce the visible response of non-doped TiO2 in the photocatalytic electrochemical water splitting, which is achieved by utilizing the optical near-field (ONF) generated on nanorod TiO2. The visible response is attributed to the ONF-induced phonon-assisted excitation process, in which TiO2 is excited by sub-bandgap photons via phonon energy. Our approach directly gets involved in the excitation process without chemical modification of materials; accordingly it is expected to have few drawbacks on the photocatalytic performance. This study may offer another perspective on the development of solar harvesting materials.

  6. Near-field photocurrent nanoscopy on bare and encapsulated graphene

    PubMed Central

    Woessner, Achim; Alonso-González, Pablo; Lundeberg, Mark B.; Gao, Yuanda; Barrios-Vargas, Jose E.; Navickaite, Gabriele; Ma, Qiong; Janner, Davide; Watanabe, Kenji; Cummings, Aron W.; Taniguchi, Takashi; Pruneri, Valerio; Roche, Stephan; Jarillo-Herrero, Pablo; Hone, James; Hillenbrand, Rainer; Koppens, Frank H. L.

    2016-01-01

    Optoelectronic devices utilizing graphene have demonstrated unique capabilities and performances beyond state-of-the-art technologies. However, requirements in terms of device quality and uniformity are demanding. A major roadblock towards high-performance devices are nanoscale variations of the graphene device properties, impacting their macroscopic behaviour. Here we present and apply non-invasive optoelectronic nanoscopy to measure the optical and electronic properties of graphene devices locally. This is achieved by combining scanning near-field infrared nanoscopy with electrical read-out, allowing infrared photocurrent mapping at length scales of tens of nanometres. Using this technique, we study the impact of edges and grain boundaries on the spatial carrier density profiles and local thermoelectric properties. Moreover, we show that the technique can readily be applied to encapsulated graphene devices. We observe charge build-up near the edges and demonstrate a solution to this issue. PMID:26916951

  7. Engineering two-wire optical antennas for near field enhancement

    NASA Astrophysics Data System (ADS)

    Yang, Zhong-Jian; Zhao, Qian; Xiao, Si; He, Jun

    2017-07-01

    We study the optimization of near field enhancement in the two-wire optical antenna system. By varying the nanowire sizes we obtain the optimized side-length (width and height) for the maximum field enhancement with a given gap size. The optimized side-length applies to a broadband range (λ = 650-1000 nm). The ratio of extinction cross section to field concentration size is found to be closely related to the field enhancement behavior. We also investigate two experimentally feasible cases which are antennas on glass substrate and mirror, and find that the optimized side-length also applies to these systems. It is also found that the optimized side-length shows a tendency of increasing with the gap size. Our results could find applications in field-enhanced spectroscopies.

  8. Imaging of Microwave Circuits Using Near-Field Microwave Microscopy

    NASA Astrophysics Data System (ADS)

    Anlage, Steven M.; Dutta, Sudeep; Vlahacos, C. P.; Steinhauer, David E.; Wellstood, F. C.

    1997-03-01

    Detailed models and simulations have been a major tool in the development and evaluation of microwave devices (e.g. circulators, superconducting filters, antennas). However actual quantitative measurements of performance are generally limited to global characteristics (such as reflection/transmission coefficients) leaving the models unverified in detail. With the near-field scanning microwave microscope(C. P. Vlahacos, et al.) Appl. Phys. Lett. 69 (21), 3272 (1996) (which uses an open-ended coaxial cable scanned in proximity to the surface to be imaged), we present a method of probing the internal fields of devices. By imaging simple device configurations (e.g. microstrip), where field patterns are easily calculated, we show how quantitative values for the electric field and potential can be calculated directly from the data. Resolution is dependent on the size of the coaxial cable, and has a limit of approximately 20 μm. Images of both data and models will be shown for comparison.

  9. Theoretical and experimental examination of near-field acoustic levitation.

    PubMed

    Nomura, Hideyuki; Kamakura, Tomoo; Matsuda, Kazuhisa

    2002-04-01

    A planar object can be levitated stably close to a piston sound source by making use of acoustic radiation pressure. This phenomenon is called near-field acoustic levitation [Y. Hashimoto et al., J. Acoust. Soc. Am. 100, 2057-2061 (1996)]. In the present article, the levitation distance is predicted theoretically by numerically solving basic equations in a compressible viscous fluid subject to the appropriate initial and boundary conditions. Additionally, experiments are carried out using a 19.5-kHz piston source with a 40-mm aperture and various aluminum disks of different sizes. The measured levitation distance agrees well with the theory, which is different from a conventional theory, and the levitation distance is not inversely proportional to the square root of the surface density of the levitated disk in a strict sense.

  10. Near-field hyperspectral quantum probing of multimodal plasmonic resonators

    NASA Astrophysics Data System (ADS)

    Cuche, A.; Berthel, M.; Kumar, U.; Colas des Francs, G.; Huant, S.; Dujardin, E.; Girard, C.; Drezet, A.

    2017-03-01

    Quantum systems, excited by an external source of photons, display a photodynamics that is ruled by a subtle balance between radiative or nonradiative energy channels when interacting with metallic nanostructures. We apply and generalize this concept to achieve a quantum probing of multimodal plasmonic resonators by collecting and filtering the broad emission spectra generated by a nanodiamond (ND) hosting a small set of nitrogen-vacancy (NV) color centers attached at the apex of an optical tip. Spatially and spectrally resolved information on the photonic local density of states (ph-LDOS) can be recorded with this technique in the immediate vicinity of plasmonic resonators, paving the way for a complete near-field optical characterization of any kind of nanoresonators in the single photon regime.

  11. Analytic Optimization of Near-Field Optical Chirality Enhancement

    PubMed Central

    2017-01-01

    We present an analytic derivation for the enhancement of local optical chirality in the near field of plasmonic nanostructures by tuning the far-field polarization of external light. We illustrate the results by means of simulations with an achiral and a chiral nanostructure assembly and demonstrate that local optical chirality is significantly enhanced with respect to circular polarization in free space. The optimal external far-field polarizations are different from both circular and linear. Symmetry properties of the nanostructure can be exploited to determine whether the optimal far-field polarization is circular. Furthermore, the optimal far-field polarization depends on the frequency, which results in complex-shaped laser pulses for broadband optimization. PMID:28239617

  12. Plasmonic Near-Field Absorbers for Ultrathin Solar Cells.

    PubMed

    Hägglund, Carl; Apell, S Peter

    2012-05-17

    If the active layer of efficient solar cells could be made 100 times thinner than in today's thin film devices, their economic competitiveness would greatly benefit. However, conventional solar cell materials do not have the optical capability to allow for such thickness reductions without a substantial loss of light absorption. To address this challenge, the use of plasmon resonances in metal nanostructures to trap light and create charge carriers in a nearby semiconductor material is an interesting opportunity. In this Perspective, recent progress with regards to ultrathin (∼10 nm) plasmonic nanocomposites is reviewed. Their optimal internal geometry for plasmon near-field induced absorption is discussed, and a zero thickness effective medium representation is used to optimize stacks including an Al back reflector for photovoltaics. This shows that high conversion efficiencies (>20%) are possible even when taking surface scattering effects and thin passivating layers inserted between the metal and semiconductor into account.

  13. Numerical calculations of ultrasonic fields I: transducer near fields

    SciTech Connect

    Johnson, J.A.

    1982-03-01

    A computer code for the calculation of linear acoustic wave propagation in homogeneous fluid and solid materials has been derived from the thermal-hydraulics code STEALTH. The code uses finite-difference techniques in a two-dimensional mesh made up of arbitrarily shaped quadrilaterals. Problems with two-dimensional plane strain or two-dimensional axial symmetries can be solved. Free, fixed, or stressed boundaries can be used. Transducers can be modeled by time dependent boundary conditions or by moving pistons. This paper gives a brief description of the method and shows the results of the calculation of the near fields of circular flat and focused transducers. These results agree with analytic theory along the axis of symmetry and with other codes that use a Huygens reconstruction technique off-axis.

  14. Near-field investigations of nanoshell cylinder dimers

    NASA Astrophysics Data System (ADS)

    Höflich, Katja; Gösele, Ulrich; Christiansen, Silke

    2009-10-01

    Metallic nanoparticles are known to exhibit strong particle size dependent localized surface plasmon resonances due to their specific optical response described via the complex dielectric function. Using the two-dimensional finite element method, the near-field behavior of core-shell nanocylinder dimers with either a dielectric or a gold core and a silver shell was investigated. With a detailed analysis the positions of maximum field enhancement usable for highly sensitive spectroscopy were unveiled and the surface charge distributions of the different kinds of resonances were visualized. It is shown that the usual far-field spectra do not give reliable estimates of local electric field peaks. Furthermore one observes a distinct mode at the natural plasma frequency of the silver shell which is independent of the core material. This mode is identified as a volume plasmon mode.

  15. Photocurrent mapping of near-field optical antenna resonances.

    PubMed

    Barnard, Edward S; Pala, Ragip A; Brongersma, Mark L

    2011-08-21

    An increasing number of photonics applications make use of nanoscale optical antennas that exhibit a strong, resonant interaction with photons of a specific frequency. The resonant properties of such antennas are conventionally characterized by far-field light-scattering techniques. However, many applications require quantitative knowledge of the near-field behaviour, and existing local field measurement techniques provide only relative, rather than absolute, data. Here, we demonstrate a photodetector platform that uses a silicon-on-insulator substrate to spectrally and spatially map the absolute values of enhanced fields near any type of optical antenna by transducing local electric fields into photocurrent. We are able to quantify the resonant optical and materials properties of nanoscale (∼50 nm) and wavelength-scale (∼1 µm) metallic antennas as well as high-refractive-index semiconductor antennas. The data agree well with light-scattering measurements, full-field simulations and intuitive resonator models.

  16. Near-field phase singularity in subwavelength metallic microstructures

    NASA Astrophysics Data System (ADS)

    Kang, Ming; Guo, Qing-Hua; Chen, Jing; Gu, Bing; Li, Yongnan; Wang, Hui-Tian

    2011-10-01

    A near-field phase singularity (NFPS) depending on the spin state of the incident electromagnetic (EM) radiation is very fascinating because it can enrich the functionality of the EM radiation in metamaterials. Here we present a microscopic dipole model to describe the NFPS effect under the time-harmonic quasistatic limit. The results reveal that NFPS exists for the longitudinal components of both electric and magnetic fields as well as the transverse component of time-averaged Poynting vector. The localized surface plasmon polariton in the subwavelength metallic structure contributes to enhance the generation efficiency of NFPS by introducing the resonance of the electric dipole. This effect not only is promising for microtrapping and manipulation but also enriches the functionality of the existing metamaterials.

  17. Lightning rod resonance of a plasmonic near-field transducer.

    PubMed

    Peng, Chubing; Ko, Kaspar D

    2017-06-26

    We demonstrate the lightning-rod resonance of a lollipop near-field transducer integrated in magnetic writer for heat-assisted magnetic recording by collecting the two-photon excited photoluminescence (TPL) signal when excited by a pulsed femto-second fiber laser tuned to the desired mode resonance. The lollipop transducer consists of a round disk and a protruding peg to take advantage of the lightning-rod effect. It is found that the TPL signal is extremely sensitive to the peg length where even a 3-5 nm deviation from the optimal peg length halves the TPL signal. This method conveniently quantifies the optical performance of an NFT device in situ as a function of geometry with a resolution of better than the light wavelength (λ) divided by 200.

  18. Near-field and SERS enhancement from rough plasmonic nanoparticles

    NASA Astrophysics Data System (ADS)

    Trügler, Andreas; Tinguely, Jean-Claude; Jakopic, Georg; Hohenester, Ulrich; Krenn, Joachim R.; Hohenau, Andreas

    2014-04-01

    The lithographic fabrication of metal nanoparticles usually involves the thermal vacuum deposition of metals, which leads to polycrystallinity and surface roughness. In recent years, strong efforts have been made to clarify the role of such roughness in surface-enhanced Raman scattering (SERS). In this paper, we provide a systematic experimental and theoretical study of single lithographically fabricated nanoparticles to unravel the role of surface roughness and morphology on the optical far- and near-field properties. We find that the experimentally observed reduction of the SERS signal upon thermal annealing of particle arrays is caused by a complex interplay of changes in the dielectric response of gold, the resonance wavelength, and the reduced nanoscopic roughness.

  19. Near-Field, On-Chip Optical Brownian Ratchets.

    PubMed

    Wu, Shao-Hua; Huang, Ningfeng; Jaquay, Eric; Povinelli, Michelle L

    2016-08-10

    Nanoparticles in aqueous solution are subject to collisions with solvent molecules, resulting in random, Brownian motion. By breaking the spatiotemporal symmetry of the system, the motion can be rectified. In nature, Brownian ratchets leverage thermal fluctuations to provide directional motion of proteins and enzymes. In man-made systems, Brownian ratchets have been used for nanoparticle sorting and manipulation. Implementations based on optical traps provide a high degree of tunability along with precise spatiotemporal control. Here, we demonstrate an optical Brownian ratchet based on the near-field traps of an asymmetrically patterned photonic crystal. The system yields over 25 times greater trap stiffness than conventional optical tweezers. Our technique opens up new possibilities for particle manipulation in a microfluidic, lab-on-chip environment.

  20. Radiant Flux of Near Field in Temperature Measurements

    SciTech Connect

    Suarez-Romero, J. G.; Resendiz Barron, A. J.; Farias Arguello, J. O.

    2008-04-15

    In this work we present a calculation of the radiant flux exiting from an object which is at a constant temperature. The flux calculation is based in the propagation model of irradiance and it permit to predict the small variations in measurements of infrared radiation sources when the pyrometer is going far from the source, this variation is known as distance effect. The classical radiometry defines the quantity radiance, which is used in temperature measurements of objects through the infrared radiation they emit. Unfortunately the radiance does not permit to take into account the variations of the radiant flux measured by the pyrometer due to the wave propagation of the radiation given that the radiance definition is based in ray propagation, the geometrical model. Due to the anterior in this work we present a radiant flux calculation using wave model and considering the approximation of the near field or Fresnel approximation. We show experimental results that confirm our proposal.

  1. Fatigue crack localization with near-field acoustic emission signals

    NASA Astrophysics Data System (ADS)

    Zhou, Changjiang; Zhang, Yunfeng

    2013-04-01

    This paper presents an AE source localization technique using near-field acoustic emission (AE) signals induced by crack growth and propagation. The proposed AE source localization technique is based on the phase difference in the AE signals measured by two identical AE sensing elements spaced apart at a pre-specified distance. This phase difference results in canceling-out of certain frequency contents of signals, which can be related to AE source direction. Experimental data from simulated AE source such as pencil breaks was used along with analytical results from moment tensor analysis. It is observed that the theoretical predictions, numerical simulations and the experimental test results are in good agreement. Real data from field monitoring of an existing fatigue crack on a bridge was also used to test this system. Results show that the proposed method is fairly effective in determining the AE source direction in thick plates commonly encountered in civil engineering structures.

  2. Study of Near Field Communication Technology in University Scenarios

    NASA Astrophysics Data System (ADS)

    Ruiz, Irene Luque; Miraz, Guillermo Matas; Gómez-Nieto, Miguel Ángel

    2009-08-01

    In this paper we present an introduction to the possibilities of NFC (Near Field Communication) technology in the University environment. NFC is the key for the development of interactive systems where "intelligent" objects interact with the user just only by touching the objects with a NFC device. We support that a University environment with active objects dispatching information and services to the users (students and teachers) can introduce an appropriate environment for the fulfillment of the new Educational European directives. Here, we briefly describe some of the possibilities of the NFC technology and we include an example of the use of NFC through a Smart Poster for a scenario where a Department directory is considered.

  3. Experimental studies on near-field holographic antenna measurement

    NASA Astrophysics Data System (ADS)

    Zuo, Yingxi; Xu, Linfen; An, Hongye; Sun, Jixian; Lou, Zheng; Yang, Ji; Zhang, Xuguo; Li, Zhenqiang; Lu, Dengrong; Pang, Xinghai; Li, Yang

    2016-07-01

    A near-field millimeter-wave holography system operating in the 3-mm waveband have been developed as a prototype for DATE5, a 5-m terahertz telescope proposed to be deployed at Dome A, Antarctica. Experimental measurements at 92 GHz have been made on a 1.45-m test antenna. During the night time at which the ambient temperature doesn't vary rapidly, a 75-minute repeatability (repeating measurement 3 times) of 2.3 μm rms has been achieved with an aperture resolution of 46 mm. A local surface change of known value is correctly detected. After long-time repeating measurements, thermal-induced feed displacement is also detected with an accuracy of approximately 20 μm. Random error factors of the experiment system are evaluated and their contributions to the derived surface error are also simulated, showing that relative poor pointing of the test antenna is the major factor limiting the measurement repeatability.

  4. Second harmonic generation at the probe tip for background-free near-field optical imaging.

    PubMed

    Dong, Zhaogang; Soh, Yeng Chai

    2012-08-13

    Second harmonic generation (SHG) has been applied to reduce background signals in near-field optical imaging, but this technique is usually limited to samples with strong second-order nonlinear susceptibilities. To overcome this limitation, in this paper, we present a versatile background-free SHG configuration, where it utilizes the second-order nonlinear susceptibility of the probe which essentially functions as a near-field polarizer capable of filtering out the background signal component. In the theoretical analysis, we first model the probe-sample optical interactions at both the fundamental frequency and the second harmonic frequency by using the coupled dipole method. The theoretical model reveals that the proposed versatile background-free SHG configuration requires two conditions. The first condition is that the incident optical field must be s-polarized. The second condition is that the probe must be made of crystals from symmetry class 222, symmetry class 622, symmetry class 422, symmetry class 42m, symmetry class 43m or symmetry class 23. To demonstrate the effectiveness of the proposed versatile background-free SHG configuration, a probe made of deuterated potassium dideuterium phosphate (DKDP) crystal from symmetry class 42m is analyzed numerically. It is shown that when imaging samples with negligible second-order nonlinear susceptibilities, the proposed background-free SHG configuration improves the imaging contrast by more than one-order of magnitude as compared to all other imaging configurations. Moreover, we also investigate the dependence of its performance on other parameters, such as the probe-sample distance, the relative size between probe and sample, and the tilt angle of probe crystal. It is believed that the proposed configuration could be widely used to achieve high contrast near-field optical imaging.

  5. Detection of reflector surface from near field phase measurements

    NASA Technical Reports Server (NTRS)

    Ida, Nathan

    1991-01-01

    The deviation of a reflector antenna surface from a perfect parabolic shape causes degradation of the performance of the antenna. The problem of determining the shape of the reflector surface in a reflector antenna using near field phase measurements is not a new one. A recent issue of the IEEE tansactions on Antennas and Propagation (June 1988) contained numerous descriptions of the use of these measurements: holographic reconstruction or inverse Fourier transform. Holographic reconstruction makes use of measurement of the far field of the reflector and then applies the Fourier transform relationship between the far field and the current distribution on the reflector surface. Inverse Fourier transformation uses the phase measurements to determine the far field pattern using the method of Kerns. After the far field pattern is established, an inverse Fourier transform is used to determine the phases in a plane between the reflector surface and the plane in which the near field measurements were taken. These calculations are time consuming since they involve a relatively large number of operations. A much faster method can be used to determine the position of the reflector. This method makes use of simple geometric optics to determine the path length of the ray from the feed to the reflector and from the reflector to the measurement point. For small physical objects and low frequencies, diffraction effects have a major effect on the error, and the algorithm provides incorrect results. It is believed that the effect is less noticeable for large distortions such as antenna warping, and more noticeable for small, localized distortions such as bumps and depressions such as might be caused by impact damage.

  6. A study on the benefits of including near-field effects in active-source surface wave data collection and interpretation

    NASA Astrophysics Data System (ADS)

    McCaskill, Alexander

    Geotechnical analyses for earthquake engineering and other applications are often predicated on the accurate determination of shear wave velocity (VS) profiles. Surface wave methods (SWM) are a non-invasive approach to developing VS profiles that involve measurement of Rayleigh wave propagation between a wave-generating source and a receiver array placed on the ground surface. There are several variations of SWM, but all utilize the same three-step process for developing a VS profile, namely: (1) data collection - measuring ground surface vibrations emanating from a source; (2) data processing - developing an experimental dispersion curve relating wave velocity to wavelength or frequency; and (3) inversion - finding the VS profile that produces a theoretical dispersion curve matching the experimental dispersion curve. In current practice, the theoretical model used to fit the experimental data is a far-field model that only simulates motions from planar Rayleigh waves. Therefore, the receiver array used to collect the data in step 1 must be located far from the source (or "far-field"), where body waves have largely dissipated (due to greater damping) and Rayleigh wavefronts are nearly planar. Closer to the source - in the so-called "near-field" - the ground motions include coupled interactions of body waves and non-planar Rayleigh waves and is inconsistent with a far-field theoretical model. The primary objective of this study was to investigate the effectiveness and potential benefits of including near-field contributions in both the surface wave data collection and modeling. First, it was hypothesized that source offset distance criteria currently used to mitigate near-field effects could be greatly reduced without affecting the quality of surface wave results. Second, it was hypothesized that additional information about the soil profile could be determined if the near-field portion of the dispersion curve was included in both the data collection and theoretical

  7. Polarization effects in near-field excitation-collection probe optical microscopy of a single quantum dot.

    PubMed

    Chavez-Pirson, A; Chu, S T

    1999-01-01

    We solve numerically the three-dimensional vector form of Maxwell's equation for the situation of near-field excitation and collection of luminescence from a single quantum dot, using a scanning near-field optical fibre probe with subwavelength resolution. We highlight the importance of polarization-dependent effects in both the near-field excitation and collection processes. Applying a finite-difference time domain method, we calculate the complete vector fields emerging from a realistic probe structure which is in close proximity to a semiconductor surface. We model the photoluminescence from the quantum dot in terms of electric dipoles of different polarization directions, and determine the near-field luminescence images of the dot captured by the same probe. We show that a collimating effect in the high index semiconductor significantly improves the spatial resolution in the excitation-collection mode. We find that the spatial resolution, image shape and collection efficiency of near-field luminescence imaging strongly depend on the polarization direction as represented by the orientation of the radiating electric dipoles inside the quantum dot.

  8. Solar terrestrial coupling through space plasma processes

    SciTech Connect

    Birn, J.

    2000-12-01

    This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project investigates plasma processes that govern the interaction between the solar wind, charged particles ejected from the sun, and the earth's magnetosphere, the region above the ionosphere governed by the terrestrial magnetic field. Primary regions of interest are the regions where different plasma populations interact with each other. These are regions of particularly dynamic plasma behavior, associated with magnetic flux and energy transfer and dynamic energy release. The investigations concerned charged particle transport and energization, and microscopic and macroscopic instabilities in the magnetosphere and adjacent regions. The approaches combined space data analysis with theory and computer simulations.

  9. Coupled THM processes in EDZ of crystalline rocks using an elasto-plastic cellular automaton

    NASA Astrophysics Data System (ADS)

    Pan, Peng-Zhi; Feng, Xia-Ting; Huang, Xiao-Hua; Cui, Qiang; Zhou, Hui

    2009-05-01

    This paper aims at a numerical study of coupled thermal, hydrological and mechanical processes in the excavation disturbed zones (EDZ) around nuclear waste emplacement drifts in fractured crystalline rocks. The study was conducted for two model domains close to an emplacement tunnel; (1) a near-field domain and (2) a smaller wall-block domain. Goodman element and weak element were used to represent the fractures in the rock mass and the rock matrix was represented as elasto-visco-plastic material. Mohr-Coulomb criterion and a non-associated plastic flow rule were adopted to consider the viscoplastic deformation in the EDZ. A relation between volumetric strain and permeability was established. Using a self-developed EPCA2D code, the elastic, elasto-plastic and creep analyses to study the evolution of stress and deformations, as well as failure and permeability evolution in the EDZ were conducted. Results indicate a strong impact of fractures, plastic deformation and time effects on the behavior of EDZ especially the evolution of permeability around the drift.

  10. High throughput optical lithography by scanning a massive array of bowtie aperture antennas at near-field

    PubMed Central

    Wen, X.; Datta, A.; Traverso, L. M.; Pan, L.; Xu, X.; Moon, E. E.

    2015-01-01

    Optical lithography, the enabling process for defining features, has been widely used in semiconductor industry and many other nanotechnology applications. Advances of nanotechnology require developments of high-throughput optical lithography capabilities to overcome the optical diffraction limit and meet the ever-decreasing device dimensions. We report our recent experimental advancements to scale up diffraction unlimited optical lithography in a massive scale using the near field nanolithography capabilities of bowtie apertures. A record number of near-field optical elements, an array of 1,024 bowtie antenna apertures, are simultaneously employed to generate a large number of patterns by carefully controlling their working distances over the entire array using an optical gap metrology system. Our experimental results reiterated the ability of using massively-parallel near-field devices to achieve high-throughput optical nanolithography, which can be promising for many important nanotechnology applications such as computation, data storage, communication, and energy. PMID:26525906

  11. High throughput optical lithography by scanning a massive array of bowtie aperture antennas at near-field.

    PubMed

    Wen, X; Datta, A; Traverso, L M; Pan, L; Xu, X; Moon, E E

    2015-11-03

    Optical lithography, the enabling process for defining features, has been widely used in semiconductor industry and many other nanotechnology applications. Advances of nanotechnology require developments of high-throughput optical lithography capabilities to overcome the optical diffraction limit and meet the ever-decreasing device dimensions. We report our recent experimental advancements to scale up diffraction unlimited optical lithography in a massive scale using the near field nanolithography capabilities of bowtie apertures. A record number of near-field optical elements, an array of 1,024 bowtie antenna apertures, are simultaneously employed to generate a large number of patterns by carefully controlling their working distances over the entire array using an optical gap metrology system. Our experimental results reiterated the ability of using massively-parallel near-field devices to achieve high-throughput optical nanolithography, which can be promising for many important nanotechnology applications such as computation, data storage, communication, and energy.

  12. High throughput optical lithography by scanning a massive array of bowtie aperture antennas at near-field

    NASA Astrophysics Data System (ADS)

    Wen, X.; Datta, A.; Traverso, L. M.; Pan, L.; Xu, X.; Moon, E. E.

    2015-11-01

    Optical lithography, the enabling process for defining features, has been widely used in semiconductor industry and many other nanotechnology applications. Advances of nanotechnology require developments of high-throughput optical lithography capabilities to overcome the optical diffraction limit and meet the ever-decreasing device dimensions. We report our recent experimental advancements to scale up diffraction unlimited optical lithography in a massive scale using the near field nanolithography capabilities of bowtie apertures. A record number of near-field optical elements, an array of 1,024 bowtie antenna apertures, are simultaneously employed to generate a large number of patterns by carefully controlling their working distances over the entire array using an optical gap metrology system. Our experimental results reiterated the ability of using massively-parallel near-field devices to achieve high-throughput optical nanolithography, which can be promising for many important nanotechnology applications such as computation, data storage, communication, and energy.

  13. Dissociative identity disorder and the process of couple therapy.

    PubMed

    Macintosh, Heather B

    2013-01-01

    Couple therapy in the context of dissociative identity disorder (DID) has been neglected as an area of exploration and development in the couple therapy and trauma literature. What little discussion exists focuses primarily on couple therapy as an adjunct to individual therapy rather than as a primary treatment for couple distress and trauma. Couple therapy researchers have begun to develop adaptations to provide effective support to couples dealing with the impact of childhood trauma in their relationships, but little attention has been paid to the specific and complex needs of DID patients in couple therapy (H. B. MacIntosh & S. Johnson, 2008 ). This review and case presentation explores the case of "Lisa," a woman diagnosed with DID, and "Don," her partner, and illustrates the themes of learning to communicate, handling conflicting needs, responding to child alters, and addressing sexuality and education through their therapy process. It is the hope of the author that this discussion will renew interest in the field of couple therapy in the context of DID, with the eventual goal of developing an empirically testable model of treatment for couples.

  14. Coupling Backbarrier Shorelines to Geomorphologic Processes

    NASA Astrophysics Data System (ADS)

    Trimble, S. M.

    2013-12-01

    Recent evidence suggests that back-barrier structure may act as an historical record of island development, and that back-barrier shorelines can be used as a proxy of an island's past and future transgressive response to sea-level rise. The structure and stability of back-barrier shorelines are dependent on the geologic framework, defined here as the combination of nearshore topography, underlying geology, and modern geomorphologic forces. This antecedent framework controls and influences the present morphology, nearshore dynamics, and rates of transgression in response to sea-level rise while also acting as a feedback to the estuary ecology on the bayside. This project establishes a link between process regimes and an island's geomorphological history. Results show that shorelines and bathymetric isolines share quantitative shape signatures indicative of their shared morphological past. Four United States National Seashores are examined: Fire Island, NY; Assateague Island, MD; Santa Rosa Island, FL; and North Padre Island, TX. The alongshore variation of the back-barrier shoreline, mainland shoreline, lagoon bathymetry, and nearshore bathymetry are digitized from aerial imagery. They are quantified through wavelet analysis and their shape signatures are examined for spatial correspondence. Large and small scale variations are identified and attributed to the geomorphologic controls operating on the same scale and alongshore variation. The result is an improved understanding of how the geologic framework controls back-barrier shoreline shape, which is essentially an expression of the underlying geology.

  15. Manipulating quantum dot fluorescence by utilizing Brownian induced near-field interactions with plasmonic nanoparticles

    NASA Astrophysics Data System (ADS)

    Palombo, Nola

    Quantum dots (QDs) are semiconductor nanocrystals with size-dependent optical properties; thus making them supreme fluorophores. Plasmonic nanoparticles (PNPs), such as gold and silver nanoparticles, support localized surface plasmons on their surface. When the localized surface plasmons are excited, a highly concentrated electromagnetic field is formed near the particle. Therefore, if a QD is within the near-field of a PNP, the emission or excitation of the QD can be enhanced. However, due to Forster Resonance Energy Transfer (FRET), the QD fluorescence could instead be quenched by the proximity of PNPs. Whether enhancement or quenching occurs, is dependent upon the distance and geometry of the nanoparticles. Enhanced QD fluorescence would be helpful in biomedical sensing and imaging and solar energy conversion applications. In addition, quenched QD fluorescence caused by FRET could be applied to FRET-based sensing and imaging in medical diagnosis. This master's thesis first theoretically models the stochastic movement of QDs and PNPs in an aqueous solution. The simulation is based upon the Direct Simulation Monte Carlo method coupled with Langevin equations. Using this simulation, we were able to predict the percentage of QDs in the near-field region of PNPs. The percentage of QDs in the near-field region of GNPs for a concentration of 1 × 1013 QDs/mL and 5 × 108 GNPs/mL, is a very small percentage of 2 × 10-5%. Yet, the concentration of QDs in the near-field region of GNPs was calculated to be 1,510,000 QDs mL-1. In addition, this master's thesis experimentally explores the enhancement and quenching of QD emission for different concentrations and sizes of PNPs in aqueous solutions. The fluorescence spectra of two types of QD-PNP mixtures were measured. The first mixture was QDs and gold nanoparticles (GNPs) dispersed in distilled water, where the emission wavelength of the QDs matches the localized surface plasmon excitation wavelength of the GNPs. The second

  16. Direct Measurements of Terahertz Meta-atoms with Near-Field Emission of Terahertz Waves

    NASA Astrophysics Data System (ADS)

    Serita, Kazunori; Darmo, Juraj; Kawayama, Iwao; Murakami, Hironaru; Tonouchi, Masayoshi

    2017-09-01

    We present the direct measurements of terahertz meta-atoms, an elementary unit of metamaterials, by using locally generated terahertz waves in the near-field region. In contrast to a conventional far-field terahertz spectroscopy or imaging, our technique features the localized emission of coherent terahertz pulses on a sub-wavelength scale, which has a potential for visualizing details of dynamics of each meta-atom. The obtained data show the near-field coupling among the meta-atoms and the impact of the electric field distribution from the excited meta-atom to neighbor meta-atoms. The observable LC resonance response is enhanced with an increase of numbers of meta-atoms. Furthermore, our approach also has a potential for visualizing the individual mode of meta-atom at different terahertz irradiation spots. These data can help us to understand the important role of the meta-atom in metamaterials and develop the novel terahertz components and devices such as active terahertz metamaterial and compact, high-sensitive bio-sensor devices.

  17. Optical near-field excitations on plasmonic nanoparticle-based structures.

    PubMed

    Foteinopoulou, S; Vigneron, J P; Vandenbem, C

    2007-04-02

    We investigate optical excitations on single silver nanospheres and nanosphere composites with the Finite Difference Time Domain (FDTD) method. Our objective is to achieve polarization control of the enhanced local field, pertinent to SERS applications. We employ dimer and quadrumer structures, which can display broadband and highly confined near-field-intensity enhancement comparable to or exceeding the resonant value of smaller sized isolated spheres. Our results demonstrate that the polarization of the enhanced field can be controlled by the orientation of the multimers in respect to the illumination, rather than the illumination itself. In particular, we report cases where the enhanced field shares the same polarization with the exciting field, and cases where it is predominantly perpendicular to the source field. We call the later phenomenon depolarized enhancement. Furthermore, we study a realizable nanolens based on a tapered self-similar silver nanosphere array. The time evolution of the fields in such structures show conversion of a diffraction limited Gaussian beam to a focused spot, through sequential coupling of the nano-array spheres' Mie-plasmons. For a longitudinally excited nanolens design we observed the formation of an isolated focus with size about one tenth the vacuum wavelength. We believe such nanolens will aid scanning near-field optical microscopy (SNOM) detection and the excitation of surface plasmon based guiding devices.

  18. Ultrasonic near-field optical microscopy using a plasmonic nanofocusing probe

    NASA Astrophysics Data System (ADS)

    Ahn, Phillip; Zhang, Zhen; Sun, Cheng; Balogun, Oluwaseyi

    2013-06-01

    Ultrasonic waves are sensitive to the elastic properties of solids and have been applied in a variety of nondestructive materials characterization and metrology applications. The spatial resolution of established ultrasound techniques is limited to the order of the ultrasound wavelength, which is insufficient for nanomechanical characterization and imaging of nanoscale aspects of a material microstructure. Here, we report of an ultrasonic near-field optical microscopy (UNOM) technique that enables local mapping of ultrasound with deep sub-optical wavelength spatial resolution. In this technique, ultrasonic waves generated by a pulsed laser are detected by a scanning near-field optical probe over a broad frequency bandwidth. The scanning probe features a plasmonic nano-focusing lens that concentrates light to a strongly localized focal spot at the tip of the probe. The plasmonic probe enhances the scattering of evanescent light at the probe-tip and enables reliable measurement of the dynamic motion of a vibrating surface. The measurements made by the UNOM are purely optical; therefore, it is independent of mechanical coupling between the probe and the sample, which is one of the limitations of force based scanning probe microscopy methods. The UNOM technique allows for spatially and temporally resolved optical measurements of ultrasound with greater penetration depth, and it combines the benefits of local sensitivity to elastic and optical properties. Experimental results are presented, which demonstrate the potential of the technique for local mapping of subsurface optical absorbers in a soft material with high spatial resolution.

  19. Direct Measurements of Terahertz Meta-atoms with Near-Field Emission of Terahertz Waves

    NASA Astrophysics Data System (ADS)

    Serita, Kazunori; Darmo, Juraj; Kawayama, Iwao; Murakami, Hironaru; Tonouchi, Masayoshi

    2017-07-01

    We present the direct measurements of terahertz meta-atoms, an elementary unit of metamaterials, by using locally generated terahertz waves in the near-field region. In contrast to a conventional far-field terahertz spectroscopy or imaging, our technique features the localized emission of coherent terahertz pulses on a sub-wavelength scale, which has a potential for visualizing details of dynamics of each meta-atom. The obtained data show the near-field coupling among the meta-atoms and the impact of the electric field distribution from the excited meta-atom to neighbor meta-atoms. The observable LC resonance response is enhanced with an increase of numbers of meta-atoms. Furthermore, our approach also has a potential for visualizing the individual mode of meta-atom at different terahertz irradiation spots. These data can help us to understand the important role of the meta-atom in metamaterials and develop the novel terahertz components and devices such as active terahertz metamaterial and compact, high-sensitive bio-sensor devices.

  20. Analysis of near-field data from a Soviet decoupling experiment

    SciTech Connect

    Saikia, C K; McLaren, J P; Helmberger, D V

    1993-11-01

    Recently Adushkin et al. (1992a) presented some results on a decoupling experiment performed in a salt dome in Azghir near the Caspian Sea. A large coupled shot (64 kT) was followed five years later by a decoupled shot (8 kT) fired in the cavity formed by the earlier event. Both events were recorded locally and this data has been provided by the Soviet scientists in a cooperative effort to better understand the seismic coupling problem. This data, in conjunction with WWSSN observations, is analyzed in an effort to determine the RDP`s and an estimate of t. Our preliminary results suggest that RDP appropriate for the large event is quite similar to that of LONGSHOT (80 kT event). Their teleseismic observations are difficult to distinguish in waveshape. The M{sub s} for LONGSHOT is 3.9 while that for the coupled Russian event is 3.3. The m{sub b} for the LONGSHOT (5.8) is slightly smaller than for the Russian event (m{sub b} = 6.0, ISC). This comparison of m{sub b}:M{sub s} appears to be common to most Azghir events as compared to the US experience. The t* appropriate for Amchitka (t* = 0.9) was established by near-field and teleseismic modeling of waveform data similar to this study where we obtain a t* = 0.5 to 0.6. The RDP for the small event is less well resolved but appears to be only partially decoupled. Prior estimates of decoupling factors range from 30 (based on this data by Adushkin) to 70 (for the Sterling/Salmon experiment). Our analysis produces a decoupling factor of about 15 using near-field data which is similar to the teleseismic modeling result.

  1. Near-field photochemical and radiation-induced chemical fabrication of nanopatterns of a self-assembled silane monolayer

    PubMed Central

    Hentschel, Carsten; Fontein, Florian; Stegemann, Linda; Hoeppener, Christiane; Fuchs, Harald; Hoeppener, Stefanie

    2014-01-01

    Summary A general concept for parallel near-field photochemical and radiation-induced chemical processes for the fabrication of nanopatterns of a self-assembled monolayer (SAM) of (3-aminopropyl)triethoxysilane (APTES) is explored with three different processes: 1) a near-field photochemical process by photochemical bleaching of a monomolecular layer of dye molecules chemically bound to an APTES SAM, 2) a chemical process induced by oxygen plasma etching as well as 3) a combined near-field UV-photochemical and ozone-induced chemical process, which is applied directly to an APTES SAM. All approaches employ a sandwich configuration of the surface-supported SAM, and a lithographic mask in form of gold nanostructures fabricated through colloidal sphere lithography (CL), which is either exposed to visible light, oxygen plasma or an UV–ozone atmosphere. The gold mask has the function to inhibit the photochemical reactions by highly localized near-field interactions between metal mask and SAM and to inhibit the radiation-induced chemical reactions by casting a highly localized shadow. The removal of the gold mask reveals the SAM nanopattern. PMID:25247126

  2. Direct measurement of source RDP`s and yields from near-field Soviet seismic data. Final report

    SciTech Connect

    Saikia, C.K.; McLaren, J.P.; Helmberger, D.V.

    1994-08-01

    The objective of this study was to investigate the source characteristics represented in the form of a reduced displacement potential (RDP) of Soviet nuclear explosions and was based on the availability of in-country near-field data. At the start of the project, it was thought that data would be readily accessible to us with the start of the open exchange of seismic data between the US and the Soviet Union. In fact, we did receive near-field waveforms of two Soviet nuclear explosions from Azghir test site near the Caspian Sea following which the transfer of data stopped till the end of the project. Consequently, the research effort was descoped. Only recently, some additional data have become available at CSS (Center for Seismic Studies). We have undertaken a thorough investigation of the limited data available from a large coupled shot (64 kT) in Azghir followed five years later by a decoupled shot (8 kT). We have successfully modeled the near-field data from these events to determine their source RDP`s and establish a decoupling factor of 15 using a time-domain waveform modeling technique. The results of this study are presented in the enclosed manuscript: Analysis of near-field data from a Soviet decoupling experiment.

  3. Electrically-controlled near-field radiative thermal modulator made of graphene-coated silicon carbide plates

    NASA Astrophysics Data System (ADS)

    Yang, Yue; Wang, Liping

    2017-08-01

    In this work, we propose a hybrid near-field radiative thermal modulator made of two graphene-covered silicon carbide (SiC) plates separated by a nanometer vacuum gap. The near-field photon tunneling between the emitter and receiver is modulated by changing graphene chemical potentials with symmetrically or asymmetrically applied voltage biases. The radiative heat flux calculated from fluctuational electrodynamics significantly varies with graphene chemical potentials due to tunable near-field coupling strength between graphene plasmons across the vacuum gap. Thermal modulation and switching, which are the key functionalities required for a thermal modulator, are theoretically realized and analyzed. Newly introduced quantities of the modulation factor, the sensitivity factor and switching factor are studied quite extensively in a large parameter range for both graphene chemical potential and vacuum gap distance. This opto-electronic device with faster operating mode, which is in principle only limited by electronics and not by the thermal inertia, will facilitate the practical application of active thermal management, thermal circuits, and thermal computing with photon-based near-field thermal transport.

  4. Automated Near-Field Displacement Estimates from Mobile Laser Scanning - Case Study for the Mw 6.0 August 24, 2014 Napa Earthquake

    NASA Astrophysics Data System (ADS)

    Glennie, C. L.; Kusari, A.; Brooks, B. A.; Ericksen, T.

    2016-12-01

    Quantification of near-field displacements can greatly enhance shallow fault physical investigations. However, to date, established remote sensing techniques such as InSAR and GNSS have failed to recover precise near-field displacements at the scale and resolution required for detailed near-field investigations. To overcome these limitations, we present an automated methodology to extract planar primitives from temporally spaced mobile laser scanning (MLS) point clouds, and then use common planar features in each data set coupled with a least-squares registration approach that enables a precise estimation of near-field displacement. To validate the utility of this method, we present a case study using MLS to measure afterslip immediately following the Mw 6.0 August 24, 2014 Napa earthquake, and show that the MLS estimates of displacement agree with independent alinement array estimates of afterslip at the sub-centimeter level.

  5. Nanomovement of azo polymers induced by metal tip enhanced near-field irradiation

    SciTech Connect

    Ishitobi, Hidekazu; Tanabe, Mamoru; Sekkat, Zouheir; Kawata, Satoshi

    2007-08-27

    Nanomovement of azo polymers induced by metal tip enhanced near-field illumination was studied. A protrusion with 47 nm full width at half maximum was induced with a resolution beyond the diffraction limit. At the top of the protrusion, an anisotropic movement occurs in a direction nearly parallel to the polarization of the incident light, and suggests the existence at the tip end of not only a longitudinal but also a lateral component of the electric field of light. The anisotropic photofluidity and the optical gradient force played important roles in the process of the light induced polymer movement.

  6. Ultrasensitive Ultrafast Vibrational Spectroscopy Employing the Near Field of Gold Nanoantennas

    NASA Astrophysics Data System (ADS)

    Selig, O.; Siffels, R.; Rezus, Y. L. A.

    2015-06-01

    We introduce a novel method to perform nonlinear vibrational spectroscopy on nanoscale volumes. Our technique uses the intense near field of infrared nanoantennas to amplify the nonlinear vibrational signals of molecules located in the vicinity of the antenna surface. We demonstrate the capabilities of the method by performing infrared pump-probe spectroscopy and two-dimensional infrared spectroscopy on 5 nm layers of polymethylmetacrylate. In these experiments we observe enhancement factors of the nonlinear signals of more than 4 orders of magnitude. We discuss the mechanism underlying the amplification process as well as strategies for further increasing the sensitivity of the technique.

  7. Hot Carrier-Based Near-Field Thermophotovoltaic Energy Conversion.

    PubMed

    St-Gelais, Raphael; Bhatt, Gaurang Ravindra; Zhu, Linxiao; Fan, Shanhui; Lipson, Michal

    2017-03-28

    Near-field thermophotovoltaics (NFTPV) is a promising approach for direct conversion of heat to electrical power. This technology relies on the drastic enhancement of radiative heat transfer (compared to conventional blackbody radiation) that occurs when objects at different temperatures are brought to deep subwavelength distances (typically <100 nm) from each other. Achieving such radiative heat transfer between a hot object and a photovoltaic (PV) cell could allow direct conversion of heat to electricity with a greater efficiency than using current solid-state technologies (e.g., thermoelectric generators). One of the main challenges in the development of this technology, however, is its incompatibility with conventional silicon PV cells. Thermal radiation is weak at frequencies larger than the ∼1.1 eV bandgap of silicon, such that PV cells with lower excitation energies (typically 0.4-0.6 eV) are required for NFTPV. Using low bandgap III-V semiconductors to circumvent this limitation, as proposed in most theoretical works, is challenging and therefore has never been achieved experimentally. In this work, we show that hot carrier PV cells based on Schottky junctions between silicon and metallic films could provide an attractive solution for achieving high efficiency NFTPV electricity generation. Hot carrier science is currently an important field of research and several approaches are investigated for increasing the quantum efficiency (QE) of hot carrier generation beyond conventional Fowler model predictions. If the Fowler limit can indeed be overcome, we show that hot carrier-based NFTPV systems-after optimization of their thermal radiation spectrum-could allow electricity generation with up to 10-30% conversion efficiencies and 10-500 W/cm(2) generated power densities (at 900-1500 K temperatures). We also discuss how the unique properties of thermal radiation in the extreme near-field are especially well suited for investigating recently proposed approaches

  8. The integrated project NF-PRO: recent advances in European research on the near-field system

    SciTech Connect

    Sneyers, Alain; Grambow, Bernd; Aranyossy, Jean-Francois; Johnson, Lawrence

    2007-07-01

    The Integrated Project NF-PRO (Sixth Framework Programme by the European Commission) investigates key-processes in the near-field of a geological repository for the disposal of high-level vitrified waste and spent fuel. The paper discusses the project scope and content and gives a summary overview of advances made by NF-PRO. (authors)

  9. Dyadic Coping in Couple Therapy Process: An Exploratory Study.

    PubMed

    Margola, Davide; Donato, Silvia; Accordini, Monica; Emery, Robert E; Snyder, Douglas K

    2017-07-10

    This study aimed at moving beyond previous research on couple therapy efficacy by examining moment-by-moment proximal couple and therapist interactions as well as final treatment outcomes and their reciprocal association. Seven hundred four episodes of dyadic coping within 56 early therapy sessions, taken from 28 married couples in treatment, were intensively analyzed and processed using a mixed-methods software (T-LAB). Results showed that negative dyadic coping was self-perpetuating, and therapists tended to passively observe the negative couple interaction; on the contrary, positive dyadic coping appeared to require a therapist's intervention to be maintained, and successful interventions mainly included information gathering as well as interpreting. Couples who dropped out of treatment were not actively engaged from the outset of therapy, and they used more negative dyadic coping, whereas couples who successfully completed treatment showed more positive dyadic coping very early in therapy. Results highlight the role of therapist action and control as critical to establishing rapport and credibility in couple therapy and suggest that dyadic coping patterns early in therapy may contribute to variable treatment response. © 2017 Family Process Institute.

  10. Effect of superconductivity on near-field radiative heat transfer

    NASA Astrophysics Data System (ADS)

    Králík, Tomáš; Musilová, Věra; Fořt, Tomáš; Srnka, Aleš

    2017-02-01

    Near-field (NF) radiative heat transfer (RHT) over vacuum space between bodies can exceed the far-field (FF) heat transfer by orders of magnitude. A large portion of the heat flux transferred between metals in NF is at very low frequencies, much lower than in FF. Thus a strong effect of superconductivity on NF RHT can be expected even at radiation temperatures above the superconducting critical temperature, where nearly no effect in FF is observed. We have examined experimentally the RHT between plane-parallel surfaces of niobium. Up to a fivefold decrease in NF heat flux was observed when the colder sample passed from the normal to the superconducting state. We found that a maximum decrease occurs at sample spacings ten times shorter than the spacing of crossover between the NF and FF heat flux, being ≈1000/T (μm). Applying Polder's and Van Hove's relations for NF RHT and BCS theory of superconductivity, we explain this effect and show the roles of transversal electric and magnetic modes in the steep decrease of heat flux below the critical temperature and the subsequent flux saturation at low temperatures.

  11. Interfacing external sensors with Android smartphones through near field communication

    NASA Astrophysics Data System (ADS)

    Leikanger, Tore; Häkkinen, Juha; Schuss, Christian

    2017-04-01

    In this paper, we present and evaluate a new approach to communicate with inter-integrated circuit (I2C) enabled circuits such as sensors over near field communication (NFC). The NFC-to-I2C interface was designed using a non-standard NFC command to control the I2C bus directly from a smartphone, which was controlling both, the read and write operations on the I2C bus. The NFC-to-I2C interface was reporting back the data bytes on the bus to the smartphone when the transaction was completed successfully. The proposed system was tested experimentally, both, with write and read requests to a commercial microcontroller featuring a hardware I2C port, as well as reading a commercial I2C enabled humidity and temperature sensor. We present experimental results of the system which show that our approach enables an easy interface between smartphones and external sensors. Interfacing external sensors is useful and beneficial for smartphone users, especially, if certain types of sensors are not available on smartphones.

  12. Relativistic effects in photon-induced near field electron microscopy.

    PubMed

    Park, Sang Tae; Zewail, Ahmed H

    2012-11-26

    Electrons and photons, when interacting via a nanostructure, produce a new way of imaging in space and time, termed photon-induced near field electron microscopy or PINEM [Barwick et al. Nature 2009, 462, 902]. The phenomenon was described by considering the evanescent field produced by the nanostructure, but quantification of the experimental results was achieved by solving the Schrödinger equation for the interaction of the three bodies. The question remained, is the nonrelativistic formulation sufficient for this description? Here, relativistic and nonrelativistic quantum mechanical formulations are compared for electron-photon interaction mediated by nanostructures, and it is shown that there is an exact equivalence for the two formulations. The nonrelativistic formulation was found to be valid in the relativistic regime when using in the former formulation the relativistically corrected velocity (and the corresponding values of momentum and energy). In the PINEM experiment, 200 keV electrons were utilized, giving the experimental (relativistically corrected) velocity to be 0.7c(v without relativistic correction is 0.885c). When this value (0.7c), together with those of the corresponding momentum (p(c) = mv) and energy (E(c) = (1/2)mv(2)), is used in the first order solution of the Schrödinger formulation, an exact equivalence is obtained.

  13. Generalized method of eigenoscillations for near-field optical microscopy

    NASA Astrophysics Data System (ADS)

    Jiang, Bor-Yuan; Zhang, Lingfeng; Castro Neto, Antonio; Basov, Dimitri; Fogler, Michael

    2015-03-01

    Electromagnetic interaction between a sub-wavelength particle (the ``probe'') and a material surface (the ``sample'') is studied theoretically. The interaction is shown to be governed by a series of resonances (eigenoscillations), corresponding to surface polariton modes localized near the probe. The resonance parameters depend on the dielectric function and geometry of the probe, as well as the surface reflectivity of the material. Calculation of such resonances is carried out for several axisymmetric particle shapes (spherical, spheroidal, and pear-shaped). For spheroids an efficient numerical method is proposed, capable of handling cases of large or strongly momentum-dependent surface reflectivity. The method is applied to modeling near-field spectroscopy studies of various materials. For highly resonant materials such as aluminum oxide (by itself or covered with graphene) a rich structure of the simulated signal is found, including multi-peak spectra and nonmonotonic approach curves. These features have a strong dependence on physical parameters, e.g., the probe shape. For less resonant materials such as silicon oxide the dependence is weaker, and the spheroid model is generally applicable.

  14. Viscoacoustic model for near-field ultrasonic levitation

    NASA Astrophysics Data System (ADS)

    Melikhov, Ivan; Chivilikhin, Sergey; Amosov, Alexey; Jeanson, Romain

    2016-11-01

    Ultrasonic near-field levitation allows for contactless support and transportation of an object over vibrating surface. We developed an accurate model predicting pressure distribution in the gap between the surface and levitating object. The formulation covers a wide range of the air flow regimes: from viscous squeezed flow dominating in small gap to acoustic wave propagation in larger gap. The paper explains derivation of the governing equations from the basic fluid dynamics. The nonreflective boundary conditions were developed to properly define air flow at the outlet. Comparing to direct computational fluid dynamics modeling our approach allows achieving good accuracy while keeping the computation cost low. Using the model we studied the levitation force as a function of gap distance. It was shown that there are three distinguished flow regimes: purely viscous, viscoacoustic, and acoustic. The regimes are defined by the balance of viscous and inertial forces. In the viscous regime the pressure in the gap is close to uniform while in the intermediate viscoacoustic and the acoustic regimes the pressure profile is wavy. The model was validated by a dedicated levitation experiment and compared to similar published results.

  15. Viscoacoustic model for near-field ultrasonic levitation.

    PubMed

    Melikhov, Ivan; Chivilikhin, Sergey; Amosov, Alexey; Jeanson, Romain

    2016-11-01

    Ultrasonic near-field levitation allows for contactless support and transportation of an object over vibrating surface. We developed an accurate model predicting pressure distribution in the gap between the surface and levitating object. The formulation covers a wide range of the air flow regimes: from viscous squeezed flow dominating in small gap to acoustic wave propagation in larger gap. The paper explains derivation of the governing equations from the basic fluid dynamics. The nonreflective boundary conditions were developed to properly define air flow at the outlet. Comparing to direct computational fluid dynamics modeling our approach allows achieving good accuracy while keeping the computation cost low. Using the model we studied the levitation force as a function of gap distance. It was shown that there are three distinguished flow regimes: purely viscous, viscoacoustic, and acoustic. The regimes are defined by the balance of viscous and inertial forces. In the viscous regime the pressure in the gap is close to uniform while in the intermediate viscoacoustic and the acoustic regimes the pressure profile is wavy. The model was validated by a dedicated levitation experiment and compared to similar published results.

  16. Near-field tsunami edge waves and complex earthquake rupture

    USGS Publications Warehouse

    Geist, Eric L.

    2013-01-01

    The effect of distributed coseismic slip on progressive, near-field edge waves is examined for continental shelf tsunamis. Detailed observations of edge waves are difficult to separate from the other tsunami phases that are observed on tide gauge records. In this study, analytic methods are used to compute tsunami edge waves distributed over a finite number of modes and for uniformly sloping bathymetry. Coseismic displacements from static elastic theory are introduced as initial conditions in calculating the evolution of progressive edge-waves. Both simple crack representations (constant stress drop) and stochastic slip models (heterogeneous stress drop) are tested on a fault with geometry similar to that of the M w = 8.8 2010 Chile earthquake. Crack-like ruptures that are beneath or that span the shoreline result in similar longshore patterns of maximum edge-wave amplitude. Ruptures located farther offshore result in reduced edge-wave excitation, consistent with previous studies. Introduction of stress-drop heterogeneity by way of stochastic slip models results in significantly more variability in longshore edge-wave patterns compared to crack-like ruptures for the same offshore source position. In some cases, regions of high slip that are spatially distinct will yield sub-events, in terms of tsunami generation. Constructive interference of both non-trapped and trapped waves can yield significantly larger tsunamis than those that produced by simple earthquake characterizations.

  17. Imaging Nanoscale Electromagnetic Near-Field Distributions Using Optical Forces

    PubMed Central

    Huang, Fei; Ananth Tamma, Venkata; Mardy, Zahra; Burdett, Jonathan; Kumar Wickramasinghe, H.

    2015-01-01

    We demonstrate the application of Atomic Force Microscopy (AFM) for mapping optical near-fields with nanometer resolution, limited only by the AFM probe geometry. By detecting the optical force between a gold coated AFM probe and its image dipole on a glass substrate, we profile the electric field distributions of tightly focused laser beams with different polarizations. The experimentally recorded focal force maps agree well with theoretical predictions based on a dipole-dipole interaction model. We experimentally estimate the aspect ratio of the apex of gold coated AFM probe using only optical forces. We also show that the optical force between a sharp gold coated AFM probe and a spherical gold nanoparticle of radius 15 nm, is indicative of the electric field distribution between the two interacting particles. Photo Induced Force Microscopy (PIFM) allows for background free, thermal noise limited mechanical imaging of optical phenomenon over wide range of wavelengths from Visible to RF with detection sensitivity limited only by AFM performance. PMID:26073331

  18. Near field acoustic holography with particle velocity transducers

    NASA Astrophysics Data System (ADS)

    Jacobsen, Finn; Liu, Yang

    2005-11-01

    Near field acoustic holography is usually based on measurement of the pressure. This paper describes an investigation of an alternative technique that involves measuring the normal component of the acoustic particle velocity. A simulation study shows that there is no appreciable difference between the quality of predictions of the pressure based on knowledge of the pressure in the measurement plane and predictions of the particle velocity based on knowledge of the particle velocity in the measurement plane. However, when the particle velocity is predicted close to the source on the basis of the pressure measured in a plane further away, high spatial frequency components corresponding to evanescent modes are not only amplified by the distance but also by the wave number ratio (kz/k). By contrast, when the pressure is predicted close to the source on the basis of the particle velocity measured in a plane further away, high spatial frequency components are reduced by the reciprocal wave number ratio (k/kz). For the same reason holography based on the particle velocity is less sensitive to transducer mismatch than the conventional technique based on the pressure. These findings are confirmed by an experimental investigation made with a p-u sound intensity probe produced by Microflown.

  19. Wearable near-field communication antennas with magnetic composite films

    NASA Astrophysics Data System (ADS)

    Zhan, Bihong; Su, Dan; Liu, Sheng; Liu, Feng

    2017-06-01

    The flexible near-field communication (NFC) antennas integrated with Fe3O4/ethylene-vinyl acetate copolymer (EVA) magnetic films were presented, and the influence of the magnetic composite films on the performance and miniaturization capability of the NFC antennas was investigated. Theoretical analysis and experimental results show that the integration of the magnetic composite films is conducive to the miniaturization of the NFC antennas. However, the pattern design of the integrated magnetic film is very important to improve the communication performance of NFC antenna. When magnetic film covers whole antenna, the inductance (L) and quality factor (Q) of the NFC antenna at 13MHz are increased by 60% and 5% respectively, but the communication distance of NFC system is decreased by 70%. When the magnetic film is located at the center of the antenna, the L value, Q value and communication distance of the NFC antenna are increased by 16.5%, 15.5% and 20% respectively. It can be seen that the application of the integrated magnetic film with optimized pattern to the NFC antenna can not only reduce the size of the antenna, but also improve the overall performance of the antenna.

  20. Flexible Passive near Field Communication Tag for Multigas Sensing.

    PubMed

    Escobedo, P; Erenas, M M; López-Ruiz, N; Carvajal, M A; Gonzalez-Chocano, S; de Orbe-Payá, I; Capitán-Valley, L F; Palma, A J; Martínez-Olmos, A

    2017-02-07

    In this work we present a full-passive flexible multigas sensing tag for the determination of oxygen, carbon dioxide, ammonia, and relative humidity readable by a smartphone. This tag is based on near field communication (NFC) technology for energy harvesting and data transmission to a smartphone. The gas sensors show an optic response that is read through high-resolution digital color detectors. A white LED is used as the common optical excitation source for all the sensors. Only a reduced electronics with very low power consumption is required for the reading of the optical responses and data transmission to a remote user. An application for the Android operating system has been developed for the power supplying and data reception from the tag. The responses of the sensors have been calibrated and fitted to simple functions, allowing a fast prediction of the gases concentration. Cross-sensitivity has also been evaluated, finding that in most of the cases it is negligible or easily correctable using the rest of the readings. The election of the target gases has been due to their importance in the monitoring of modified atmosphere packaging. The resolutions and limits of detection measured are suitable for such kinds of applications.

  1. Investigation of moderately turbid suspensions by heterodyne near field scattering.

    PubMed

    Escobedo-Sánchez, M A; Rojas-Ochoa, L F; Laurati, M; Egelhaaf, S U

    2017-08-03

    Light scattering has proven to be a very powerful technique to characterize soft matter systems. However, many samples are turbid and hence suffer from multiple scattering which can affect the signal considerably. Multiple scattering can be reduced by diluting the sample or changing the solvent, but often this alters the sample and hence is precluded. Here we study the dynamics of a model system. In particular, we investigate the effects of moderate multiple scattering on small-angle heterodyne near field scattering (HNFS). Varying the particle concentration and size we change the degree of multiple scattering, which is quantified by the transmission of light. In dependence of the degree of multiple scattering, we analyze the statistical properties of the HNFS signal, which is the difference between two intensity patterns separated by a delay time. The distribution of intensity differences follows a Gaussian distribution if single scattering dominates and a Laplace distribution in the presence of extreme multiple scattering. We also investigate the effects of multiple scattering on the measured intermediate scattering function and the hydrodynamic radius of the particles. Reliable data are obtained for sample transmissions down to about 0.7. This is confirmed by a comparison with results from a far field cross-correlation instrument that suppresses multiple scattering contributions. Therefore, HNFS represents a technically simple but powerful method to investigate samples that are moderately multiple scattering.

  2. Investigation of the Arcjet near Field Plume Using Electrostatic Probes

    NASA Technical Reports Server (NTRS)

    Sankovic, John M.

    1990-01-01

    The near field plume of a 1 kW class arcjet thruster was investigated using electrostatic probes of various geometries. The electron number densities and temperatures were determined in a simulated hydrazine plume at axial distances between 3 cm (1.2 in.) and 15 cm (5.9 in.) and radial distances extending to 10 cm (3.9 in.) off centerline. Values of electron number densities obtained using cylindrical and spherical probes of different geometries agreed very well. The electron density on centerline followed a source flow approximation for axial distances as near as 3 cm (1.2 in.) from the nozzle exit plane. The model agreed well with previously obtained data in the far field. The effects of propellant mass flow rate and input power level were also studied. Cylindrical probes were used to obtain ion streamlines by changing the probe orientation with respect to the flow. The effects of electrical configuration on the plasma characteristics of the plume were also investigated by using a segmented anode/nozzle thruster. The results showed that the electrical configuration in the nozzle affected the distribution of electrons in the plume.

  3. Investigation of the arcjet plume near field using electrostatic probes

    NASA Technical Reports Server (NTRS)

    Sankovic, John M.

    1990-01-01

    The near field plum of a 1 kW class arcjet thruster was investigated using electrostatic probes of various geometries. The electron number densities and temperatures were determined in a simulated hydrazine plume at axial distances between 3 cm (1.2 in) and 15 cm (5.9 in) and radial distances extending to 10 cm (3.9 in) off centerline. Values of electron number densities obtained using cylindrical and spherical probes of different geometries agreed very well. The electron density on centerline followed a source flow approximation for axial distances as near as 3 cm (1.2 in) from the nozzle exit plane. The model agreed well with previously obtained data in the far field. The effects of propellant mass flow rate and input power level were also studied. Cylindrical probes were used to obtain ion streamlines by changing the probe orientation with respect to the flow. The effects of electrical configuration on the plasma characteristics of the plume were also investigated by using a segmented anode/nozzle thruster. The results showed that the electrical configuration in the nozzle affected the distribution of electrons in the plume.

  4. Nonlinear spectroscopy in the near-field: time resolved spectroscopy and subwavelength resolution non-invasive imaging

    NASA Astrophysics Data System (ADS)

    Namboodiri, Mahesh; Khan, Tahirzeb; Karki, Khadga; Kazemi, Mehdi Mohammad; Bom, Sidhant; Flachenecker, Günter; Namboodiri, Vinu; Materny, Arnulf

    2014-04-01

    The combination of near-field microscopy along with nonlinear optical spectroscopic techniques is presented here. The scanning near-field imaging technique can be integrated with nonlinear spectroscopic techniques to improve spatial and axial resolution of the images. Additionally, ultrafast dynamics can be probed down to nano-scale dimension. The review shows some examples for this combination, which resulted in an exciton map and vibrational contrast images with sub-wavelength resolution. Results of two-color femtosecond time-resolved pump-probe experiments using scanning near-field optical microscopy (SNOM) on thin films of the organic semiconductor 3,4,9,10 Perylenetetracarboxylic dianhydride (PTCDA) are presented. While nonlinear Raman techniques have been used to obtain highly resolved images in combination with near-field microscopy, the use of femtosecond laser pulses in electronic resonance still constitutes a big challenge. Here, we present our first results on coherent anti-Stokes Raman scattering (fs-CARS) with femtosecond laser pulses detected in the near-field using SNOM. We demonstrate that highly spatially resolved images can be obtained from poly(3-hexylthiophene) (P3HT) nano-structures where the fs-CARS process was in resonance with the P3HT absorption and with characteristic P3HT vibrational modes without destruction of the samples. Sub-diffraction limited lateral resolution is achieved. Especially the height resolution clearly surpasses that obtained with standard microCARS. These results will be the basis for future investigations of mode-selective dynamics in the near-field.

  5. Probing plasmonic hot spots on single gold nanowires using combined near-field techniques

    NASA Astrophysics Data System (ADS)

    Hsia, Patrick; Douillard, Ludovic; Charra, Fabrice; Marguet, Sylvie; Kostcheev, Sergei; Bachelot, Renaud J. B.; Fiorini-Debuisschert, Céline

    2015-08-01

    The plasmonic properties of individual gold nanowires (NW) have been investigated using both two-photon luminescence (2PL) coupled to atomic force microscopy (AFM) and photoemission electron microscopy (PEEM) associated to low-energy electron microscopy (LEEM) measurements. Using these complementary near-field characterization techniques, comparative studies between wires made either by colloidal chemistry (CC) or by e-beam lithography (EBL) have been undertaken towards a better understanding of the role of the wires crystallinity regarding its optical properties. Considering comparable excitation conditions, we show that wires made by colloidal synthesis exhibits quite similar field enhancement effects ("hot spots") as EBL NW, however their 2PL emission spectrum clearly reveals their crystalline properties.

  6. Vectorial near-field imaging of a GaN based photonic crystal cavity

    SciTech Connect

    La China, F. Intonti, F.; Caselli, N.; Lotti, F.; Vinattieri, A.; Gurioli, M.; Vico Triviño, N.; Carlin, J.-F.; Butté, R.; Grandjean, N.

    2015-09-07

    We report a full optical deep sub-wavelength imaging of the vectorial components of the electric local density of states for the confined modes of a modified GaN L3 photonic crystal nanocavity. The mode mapping is obtained with a scanning near-field optical microscope operating in a resonant forward scattering configuration, allowing the vectorial characterization of optical passive samples. The optical modes of the investigated cavity emerge as Fano resonances and can be probed without the need of embedded light emitters or evanescent light coupling into the nanocavity. The experimental maps, independently measured in the two in-plane polarizations, turn out to be in excellent agreement with numerical predictions.

  7. Addressing and imaging high optical index dielectric ridges in the optical near field.

    PubMed

    Quidant, R; Weeber, J C; Dereux, A; Peyrade, D; Colas des Francs, G; Girard, C; Chen, Y

    2001-12-01

    Experimental observation of light coupling between TiO(2) integrated waveguides of subwavelength cross section and pure three-dimensional evanescent light fields is reported. This near-field optical phenomenon is produced by controlling the location of the focusing of a laser beam totally reflected at the surface of the sample. The phenomenon is observed in direct space with a photon scanning tunneling microscope. Dielectric ridges several tens of micrometers long have been efficiently excited with this technique. Upon excitation, the extremities of the linear dielectric wires display intense light spots localized both inside and around the ridge. For ridge lengths up to 30 microm, the observed phenomenon has been reproduced numerically with a parallel implementation based on the three-dimensional Green dyadic method.

  8. Near field effects of millimeter-wave power transmission for medical applications

    NASA Astrophysics Data System (ADS)

    Yoon, Hargsoon; Song, Kyo D.; Lee, Kunik; Kim, Jaehwan; Choi, Sang H.

    2011-04-01

    An integration of micro devices system and wireless power transmission (WPT) technology offers a great potential to revolutionize current health care devices. The system integration of wireless power transmission devices with smart microsensors is crucial for replacing a power storage devices and miniaturizing wireless biomedical systems. Our research goal is to replace battery power supply with an implantable millimeter-wave rectenna. Recently, a hat system with a small millimeter-wave antenna which can feed millimeter-wave power to thin-film rectenna array embedding Schottky diodes was introduced for neural sensing and stimulation applications. In order to prove the design concept and investigate wireless power coupling efficiency under the system design, near-field wireless power transmission was studied in terms of wave frequency and distance. Also, in this paper, we will present the influence of biological objects to the wireless power transmission, simulating the experimental conditions of human objects for future medical applications.

  9. Direct coupled microwave thermal processing for photovoltaic device fabrication

    NASA Astrophysics Data System (ADS)

    Guidici, D. C.

    A microwave thermal processing technology has been developed which reduces cycle time and energy requirements for solar cell manufacture through the direct coupling of a tuned microwave field to the material processed. The microwave processing is shown to be feasible for both junction formation and metallization sintering; cells produced have an efficiency of 8%. Diffusion throughput is satisfactory if multiple wafer processing (coin stacks) is used. Metallization sintering throughput is, however, limited by the single wafer process capability, and another form of applicator would be necessary to make microwave heating economically attractive for this process.

  10. Analysis of near-field thermal and psychometric waste package environment using ventilation

    SciTech Connect

    Danko, G.; Buscheck, T.A.; Nitao, J.J.; Saterlie, S.

    1995-03-01

    The ultimate objective of the Civilian Radioactive Waste Management System (CRWMS) Program is to safely emplace and isolate the nations` spent nuclear fuel (SNF) and radioactive wastes in a geologic repository. Radioactive waste emplaced in a geologic repository will generate heat, increasing the temperature in the repository. The magnitude of this temperature increase depends upon (1) the heat source, i.e. the thermal loading of the repository, and (2) the geologic and engineered heat transport characteristics of the repository. Thermal management techniques currently under investigation include ventilation of the emplacement drifts during the preclosure period which could last as long as 100 years. Understanding the amount of heat and moisture removed from the emplacement drifts and near-field rock by ventilation, are important in determining performance of the engineered barrier system (EBS), as well as the corrosive environment of the waste packages, and the interaction of the EBS with the near-field host rock. Since radionuclide releases and repository system performance are significantly affected by the corrosion rate related to the psychometric environment, it is necessary to predict the amount of heat and moisture that are removed from the repository horizon using a realistic model for a wide range of thermal loading. This can be realized by coupling the hydrothermal model of the rock mass to a ventilation/climate model which includes the heat and moisture transport on the rock-air interface and the dilution of water vapor in the drift. This paper deals with the development of the coupled model concept, and determination of the boundary conditions for the calculations.

  11. The coupling of pathways and processes through shared components

    PubMed Central

    2011-01-01

    Background The coupling of pathways and processes through shared components is being increasingly recognised as a common theme which occurs in many cell signalling contexts, in which it plays highly non-trivial roles. Results In this paper we develop a basic modelling and systems framework in a general setting for understanding the coupling of processes and pathways through shared components. Our modelling framework starts with the interaction of two components with a common third component and includes production and degradation of all these components. We analyze the signal processing in our model to elucidate different aspects of the coupling. We show how different kinds of responses, including "ultrasensitive" and adaptive responses, may occur in this setting. We then build on the basic model structure and examine the effects of additional control regulation, switch-like signal processing, and spatial signalling. In the process, we identify a way in which allosteric regulation may contribute to signalling specificity, and how competitive effects may allow an enzyme to robustly coordinate and time the activation of parallel pathways. Conclusions We have developed and analyzed a common systems platform for examining the effects of coupling of processes through shared components. This can be the basis for subsequent expansion and understanding the many biologically observed variations on this common theme. PMID:21714894

  12. Vibronic coupling simulations for linear and nonlinear optical processes: Theory

    NASA Astrophysics Data System (ADS)

    Silverstein, Daniel W.; Jensen, Lasse

    2012-02-01

    A comprehensive vibronic coupling model based on the time-dependent wavepacket approach is derived to simulate linear optical processes, such as one-photon absorbance and resonance Raman scattering, and nonlinear optical processes, such as two-photon absorbance and resonance hyper-Raman scattering. This approach is particularly well suited for combination with first-principles calculations. Expressions for the Franck-Condon terms, and non-Condon effects via the Herzberg-Teller coupling approach in the independent-mode displaced harmonic oscillator model are presented. The significance of each contribution to the different spectral types is discussed briefly.

  13. Measurement of the permittivity and loss of high-loss materials using a Near-Field Scanning Microwave Microscope.

    PubMed

    Gregory, A P; Blackburn, J F; Lees, K; Clarke, R N; Hodgetts, T E; Hanham, S M; Klein, N

    2016-02-01

    In this paper improvements to a Near-Field Scanning Microwave Microscope (NSMM) are presented that allow the loss of high loss dielectric materials to be measured accurately at microwave frequencies. This is demonstrated by measuring polar liquids (loss tangent tanδ≈1) for which traceable data is available. The instrument described uses a wire probe that is electromagnetically coupled to a resonant cavity. An optical beam deflection system is incorporated within the instrument to allow contact mode between samples and the probe tip to be obtained. Liquids are contained in a measurement cell with a window of ultrathin glass. The calibration process for the microscope, which is based on image-charge electrostatic models, has been adapted to use the Laplacian 'complex frequency'. Measurements of the loss tangent of polar liquids that are consistent with reference data were obtained following calibration against single-crystal specimens that have very low loss. Crown Copyright © 2015. Published by Elsevier B.V. All rights reserved.

  14. Turbulence Measurements in the Near Field of a Wingtip Vortex

    NASA Technical Reports Server (NTRS)

    Chow, Jim; Zilliac, Greg; Bradshaw, Peter

    1997-01-01

    The roll-up of a wingtip vortex, at Reynolds number based on chord of 4.6 million was studied with an emphasis on suction side and near wake measurements. The research was conducted in a 32 in. x 48 in. low-speed wind tunnel. The half-wing model had a semi-span of 36 in. a chord of 48 in. and a rounded tip. Seven-hole pressure probe measurements of the velocity field surrounding the wingtip showed that a large axial velocity of up to 1.77 U(sub infinity) developed in the vortex core. This level of axial velocity has not been previously measured. Triple-wire probes have been used to measure all components of the Reynolds stress tensor. It was determined from correlation measurements that meandering of the vortex was small and did not appreciably contribute to the turbulence measurements. The flow was found to be turbulent in the near-field (as high as 24 percent RMS w - velocity on the edge of the core) and the turbulence decayed quickly with streamwise distance because of the nearly solid body rotation of the vortex core mean flow. A streamwise variation of the location of peak levels of turbulence, relative to the core centerline, was also found. Close to the trailing edge of the wing, the peak shear stress levels were found at the edge of the vortex core, whereas in the most downstream wake planes they occurred at a radius roughly equal to one-third of the vortex core radius. The Reynolds shear stresses were not aligned with the mean strain rate, indicating that an isotropic-eddy-viscosity based prediction method cannot accurately model the turbulence in the cortex. In cylindrical coordinates, with the origin at the vortex centerline, the radial normal stress was found to be larger than the circumferential.

  15. Near Field Communication-based telemonitoring with integrated ECG recordings.

    PubMed

    Morak, J; Kumpusch, H; Hayn, D; Leitner, M; Scherr, D; Fruhwald, F M; Schreier, G

    2011-01-01

    Telemonitoring of vital signs is an established option in treatment of patients with chronic heart failure (CHF). In order to allow for early detection of atrial fibrillation (AF) which is highly prevalent in the CHF population telemonitoring programs should include electrocardiogram (ECG) signals. It was therefore the aim to extend our current home monitoring system based on mobile phones and Near Field Communication technology (NFC) to enable patients acquiring their ECG signals autonomously in an easy-to-use way. We prototypically developed a sensing device for the concurrent acquisition of blood pressure and ECG signals. The design of the device equipped with NFC technology and Bluetooth allowed for intuitive interaction with a mobile phone based patient terminal. This ECG monitoring system was evaluated in the course of a clinical pilot trial to assess the system's technical feasibility, usability and patient's adherence to twice daily usage. 21 patients (4f, 54 ± 14 years) suffering from CHF were included in the study and were asked to transmit two ECG recordings per day via the telemonitoring system autonomously over a monitoring period of seven days. One patient dropped out from the study. 211 data sets were transmitted over a cumulative monitoring period of 140 days (overall adherence rate 82.2%). 55% and 8% of the transmitted ECG signals were sufficient for ventricular and atrial rhythm assessment, respectively. Although ECG signal quality has to be improved for better AF detection the developed communication design of joining Bluetooth and NFC technology in our telemonitoring system allows for ambulatory ECG acquisition with high adherence rates and system usability in heart failure patients.

  16. Near Field Communication-based telemonitoring with integrated ECG recordings

    PubMed Central

    Morak, J.; Kumpusch, H.; Hayn, D.; Leitner, M.; Scherr, D.; Fruhwald, F.M.; Schreier, G.

    2011-01-01

    Objectives Telemonitoring of vital signs is an established option in treatment of patients with chronic heart failure (CHF). In order to allow for early detection of atrial fibrillation (AF) which is highly prevalent in the CHF population telemonitoring programs should include electrocardiogram (ECG) signals. It was therefore the aim to extend our current home monitoring system based on mobile phones and Near Field Communication technology (NFC) to enable patients acquiring their ECG signals autonomously in an easy-to-use way. Methods We prototypically developed a sensing device for the concurrent acquisition of blood pressure and ECG signals. The design of the device equipped with NFC technology and Bluetooth allowed for intuitive interaction with a mobile phone based patient terminal. This ECG monitoring system was evaluated in the course of a clinical pilot trial to assess the system’s technical feasibility, usability and patient’s adherence to twice daily usage. Results 21 patients (4f, 54 ± 14 years) suffering from CHF were included in the study and were asked to transmit two ECG recordings per day via the telemonitoring system autonomously over a monitoring period of seven days. One patient dropped out from the study. 211 data sets were transmitted over a cumulative monitoring period of 140 days (overall adherence rate 82.2%). 55% and 8% of the transmitted ECG signals were sufficient for ventricular and atrial rhythm assessment, respectively. Conclusions Although ECG signal quality has to be improved for better AF detection the developed communication design of joining Bluetooth and NFC technology in our telemonitoring system allows for ambulatory ECG acquisition with high adherence rates and system usability in heart failure patients. PMID:23616890

  17. Controllable deposition distance of aligned pattern via dual-nozzle near-field electrospinning

    NASA Astrophysics Data System (ADS)

    Wang, Zhifeng; Chen, Xindu; Zeng, Jun; Liang, Feng; Wu, Peixuan; Wang, Han

    2017-03-01

    For large area micro/nano pattern printing, multi-nozzle electrohydrodynamic (EHD) printing setup is an efficient method to boost productivity in near-field electrospinning (NFES) process. And controlling EHD multi-jet accurate deposition under the interaction of nozzles and other parameters are crucial concerns during the process. The influence and sensitivity of various parameters such as the needle length, needle spacing, electrode-to-collector distance, voltage etc. on the direct-write patterning performance was investigated by orthogonal experiments with dual-nozzle NFES setup, and then the deposition distance estimated based on a novel model was compared with measurement results and proven. More controllable deposition distance and much denser of aligned naofiber can be achieved by rotating the dual-nozzle setup. This study can be greatly contributed to estimate the deposition distance and helpful to guide the multi-nozzle NFES process to accurate direct-write pattern in manufacturing process in future.

  18. Reactive Transport and Coupled THM Processes in Engineering Barrier Systems (EBS)

    SciTech Connect

    Steefel, Carl; Rutqvist, Jonny; Tsang, Chin-Fu; Liu, Hui-Hai; Sonnenthal, Eric; Houseworth, Jim; Birkholzer, Jens

    2010-08-31

    Geological repositories for disposal of high-level nuclear wastes generally rely on a multi-barrier system to isolate radioactive wastes from the biosphere. The multi-barrier system typically consists of a natural barrier system, including repository host rock and its surrounding subsurface environment, and an engineering barrier system (EBS). EBS represents the man-made, engineered materials placed within a repository, including the waste form, waste canisters, buffer materials, backfill and seals (OECD, 2003). EBS plays a significant role in the containment and long-term retardation of radionuclide release. EBS is involved in complex thermal, hydrogeological, mechanical, chemical and biological processes, such as heat release due to radionuclide decay, multiphase flow (including gas release due to canister corrosion), swelling of buffer materials, radionuclide diffusive transport, waste dissolution and chemical reactions. All these processes are related to each other. An in-depth understanding of these coupled processes is critical for the performance assessment (PA) for EBS and the entire repository. Within the EBS group of Used Fuel Disposition (UFD) Campaign, LBNL is currently focused on (1) thermal-hydraulic-mechanical-chemical (THMC) processes in buffer materials (bentonite) and (2) diffusive transport in EBS associated with clay host rock, with a long-term goal to develop a full understanding of (and needed modeling capabilities to simulate) impacts of coupled processes on radionuclide transport in different components of EBS, as well as the interaction between near-field host rock (e.g., clay) and EBS and how they effect radionuclide release. This final report documents the progress that LBNL has made in its focus areas. Specifically, Section 2 summarizes progress on literature review for THMC processes and reactive-diffusive radionuclide transport in bentonite. The literature review provides a picture of the state-of-the-art of the relevant research areas

  19. Near field imaging of refraction via the magnetic field

    NASA Astrophysics Data System (ADS)

    Kanté, Boubacar; Germain, Dylan; de Lustrac, André

    2014-01-01

    We experimentally map positive and negative refractions by probing the magnetic field after the interaction of a complex metallo-dielectric composite with electromagnetic wave. The structure consists of coupled electric dipoles and negative refractive index is achieved exclusively from coupled localized resonances. By mapping out the magnetic field, negative refraction is directly observed from the three dimensional composite using a small magnetic antenna as local probe. Our work shows that light meta-matter interaction can be equally probed from magnetic light.

  20. Coping with early breast cancer: couple adjustment processes and couple-based intervention.

    PubMed

    Naaman, Sandra; Radwan, Karam; Johnson, Susan

    2009-01-01

    Early breast cancer affects one in every nine women along with their families. Advances in screening and biomedical interventions have changed the face of breast cancer from a terminal condition to a chronic disease with biopsychosocial features. The present review surveyed the nature and extent of psychological morbidity experienced by the breast cancer survivor and her spouse during the post-treatment phase, with particular focus on the impact of disease on the marital relationship. Interpersonal processes shown to unfold in couples facing breast cancer, as well as risk factors associated with greater psychological morbidity, were reviewed. Moreover, interpersonal processes central to coping with chronic illness and adjustment were reconceptualized from the point of view of attachment theory. Attachment theory was also used as the grounding framework for an empirically supported couples-based intervention, Emotionally Focused Therapy, which is advanced as a potentially useful treatment option for couples experiencing unremitting psychological and relational distress following diagnosis and treatment for breast cancer.

  1. k-space imaging of the eigenmodes of sharp gold tapers for scanning near-field optical microscopy

    PubMed Central

    Esmann, Martin; Becker, Simon F; da Cunha, Bernard B; Brauer, Jens H; Vogelgesang, Ralf; Groß, Petra

    2013-01-01

    Summary We investigate the radiation patterns of sharp conical gold tapers, which were designed as adiabatic nanofocusing probes for scanning near-field optical microscopy (SNOM). Field calculations show that only the lowest order eigenmode of such a taper can reach the very apex and thus induce the generation of strongly enhanced near-field signals. Higher-order modes are coupled into the far field at finite distances from the apex. Here, we demonstrate experimentally how to distinguish and separate between the lowest and higher-order eigenmodes of such a metallic taper by filtering in the spatial frequency domain. Our approach has the potential to considerably improve the signal-to-background ratio in spectroscopic experiments at the nanoscale. PMID:24205454

  2. Near-field Electrical Detection of Optical Surface Plasmons and Single Plasmon Sources

    NASA Astrophysics Data System (ADS)

    Koppens, Frank; Falk, A.; Yu, C.; Kang, K.; de Leon, N.; Akimov, A.; Jo, M.; Lukin, M.; Park, H.

    2009-05-01

    Surface plasmon polaritons (SPs) are a promising basis for nanoscale photonic circuits and allow for strong coupling between single photon emitters and propagating plasmon modes. However, there is a general tradeoff between the localization of an SP and the efficiency with which it can be detected with conventional far-field optics. In this talk, I will discus a nanoscale all-electrical SP detection technique based on the near-field coupling between propagating surface plasmons and a nanowire field-effect transistor. The detection scheme consists of an Ag nanowire (NW) crossing a Ge NW field-effect transistor. The Ag NW guides SPs to the Ag/Ge junction, where they are converted to electron-hole (e-h) pairs and detected as current through the Ge NW. We use our detectors to electrically detect the plasmon emission from an individual colloidal quantum dot coupled to a SP waveguide. The detectors are highly efficient (0.1 electrons/plasmon), and a plasmonic gating effect can be used to amplify the signal even higher (up to 50 electrons/plasmon). These results enable new and efficient on-chip optical sensing applications and fulfill a key requirement for 'dark' optical frequency nanocircuits in which SPs can be generated, manipulated, and detected without involving far-field radiation.

  3. Three-Dimensional Super-Resolution Morphology by Near-Field Assisted White-Light Interferometry

    PubMed Central

    Wang, Feifei; Liu, Lianqing; Yu, Peng; Liu, Zhu; Yu, Haibo; Wang, Yuechao; Li, Wen Jung

    2016-01-01

    Recent developments in far-field fluorescent microscopy have enabled nanoscale imaging of biological entities by ingenious applications of fluorescent probes. For non-fluorescence applications, however, scanning probe microscopy still remains one of the most commonly used methods to “image” nanoscale features in all three dimensions, despite its limited throughput and invasiveness to scanned samples. Here, we propose a time-efficient three-dimensional super-resolution microscopy method: near-field assisted white light interferometry (NFWLI). This method takes advantage of topography acquisition using white-light interferometry and lateral near-field imaging via a microsphere superlens. The ability to discern structures in central processing units (CPUs) with minimum feature sizes of approximately 50 nm in the lateral dimensions and approximately 10 nm in the axial dimension within 25 s (40 times faster than atomic force microscopes) was demonstrated. We elaborate in this paper the principles of NFWLI and demonstrate its potential for becoming a practical method for high-speed and non-toxic three-dimensional nanoscale imaging. PMID:27102207

  4. Atomistic near-field nanoplasmonics: reaching atomic-scale resolution in nanooptics.

    PubMed

    Barbry, M; Koval, P; Marchesin, F; Esteban, R; Borisov, A G; Aizpurua, J; Sánchez-Portal, D

    2015-05-13

    Electromagnetic field localization in nanoantennas is one of the leitmotivs that drives the development of plasmonics. The near-fields in these plasmonic nanoantennas are commonly addressed theoretically within classical frameworks that neglect atomic-scale features. This approach is often appropriate since the irregularities produced at the atomic scale are typically hidden in far-field optical spectroscopies. However, a variety of physical and chemical processes rely on the fine distribution of the local fields at this ultraconfined scale. We use time-dependent density functional theory and perform atomistic quantum mechanical calculations of the optical response of plasmonic nanoparticles, and their dimers, characterized by the presence of crystallographic planes, facets, vertices, and steps. Using sodium clusters as an example, we show that the atomistic details of the nanoparticles morphologies determine the presence of subnanometric near-field hot spots that are further enhanced by the action of the underlying nanometric plasmonic fields. This situation is analogue to a self-similar nanoantenna cascade effect, scaled down to atomic dimensions, and it provides new insights into the limits of field enhancement and confinement, with important implications in the optical resolution of field-enhanced spectroscopies and microscopies.

  5. Aspherical Solid Immersion Lens of Integrated Optical Head for Near-Field Recording

    NASA Astrophysics Data System (ADS)

    Song, TaeSun; Kwon, Hyuck-Dong; Yoon, Yong-Joong; Jung, Kyung-Sung; Park, No-Cheol; Park, Young-Pil

    2003-02-01

    New solid immersion lenses (SILs) have been studied for a high-density optical storage system by the near-field process that can overcome the far-field diffraction limit. We have proposed the aspherical SILs, named elliptic SIL (ESIL) and Cartesian SIL (CSIL) according to geometrical optics. The SILs have a high numerical aperture (NA), for instance, the NAs of the ESIL and the CSIL are over 1, with a refractive index of 1.56 of the disc cover layer. The SILs that include the function of the objective lens are able to read/write the signals inside the disc substrate. The optical heads employing an internal recording method are expected to be utilized in an unsealed environment. Experimental results of the application of an ESIL are presented. The replicated ESIL (RESIL) has been proposed to solve critical issues such as the problems of the thickness error of the SILs or the disc substrate. These problems need to be solved for the commercialization of the near field recording (NFR) technology.

  6. Numerical Investigation of Near-Field Plasma Flows in Magnetic Nozzles

    NASA Technical Reports Server (NTRS)

    Sankaran, Kamesh; Polzin, Kurt A.

    2009-01-01

    The development and application of a multidimensional numerical simulation code for investigating near-field plasma processes in magnetic nozzles are presented. The code calculates the time-dependent evolution of all three spatial components of both the magnetic field and velocity in a plasma flow, and includes physical models of relevant transport phenomena. It has been applied to an investigation of the behavior of plasma flows found in high-power thrusters, employing a realistic magnetic nozzle configuration. Simulation of a channel-flow case where the flow was super-Alfvenic has demonstrated that such a flow produces adequate back-emf to significantly alter the shape of the total magnetic field, preventing the flow from curving back to the magnetic field coil in the near-field region. Results from this simulation can be insightful in predicting far-field behavior and can be used as a set of self-consistent boundary conditions for far-field simulations. Future investigations will focus on cases where the inlet flow is sub-Alfvenic and where the flow is allowed to freely expand in the radial direction once it is downstream of the coil.

  7. Apertureless scanning near-field optical microscopy for ion exchange channel waveguide characterization.

    PubMed

    Blaize, S; Aubert, S; Bruyant, A; Bachelot, R; Lerondel, G; Royer, P; Broquin, J-E; Minier, V

    2003-03-01

    We report the characterization of an integrated Ag+/Na+ ion exchange waveguide realized in a silicate glass substrate using apertureless scanning near-field optical microscopy. Our experimental set-up is based on the combination of a commercial atomic force microscope with an optical confocal detection system. Thanks to this system, the topography and evanescent optical field at the waveguide top surface are mapped simultaneously. Also, the process of apertureless scanning near-field optical microscopy image formation is analysed. In particular, fringe patterns appearing in the image reveal the intrinsic interferometric nature of the collected signal, due to interference between the field scattered by the tip end and background fields related to guide losses. We give a quantitative interpretation of these fringes. Evanescent intensity mapping on the sample surface allowed us to extract physical waveguide parameters. In particular, it shows an unambiguous multimode beat along the waveguide propagation axis. Furthermore, we show that analysis of this intensity profile reveals back-reflection effects from the waveguide exit facet. The resulting standing waves pattern allows us to evaluate the eigenmode propagation constants.

  8. Three-Dimensional Super-Resolution Morphology by Near-Field Assisted White-Light Interferometry

    NASA Astrophysics Data System (ADS)

    Wang, Feifei; Liu, Lianqing; Yu, Peng; Liu, Zhu; Yu, Haibo; Wang, Yuechao; Li, Wen Jung

    2016-04-01

    Recent developments in far-field fluorescent microscopy have enabled nanoscale imaging of biological entities by ingenious applications of fluorescent probes. For non-fluorescence applications, however, scanning probe microscopy still remains one of the most commonly used methods to “image” nanoscale features in all three dimensions, despite its limited throughput and invasiveness to scanned samples. Here, we propose a time-efficient three-dimensional super-resolution microscopy method: near-field assisted white light interferometry (NFWLI). This method takes advantage of topography acquisition using white-light interferometry and lateral near-field imaging via a microsphere superlens. The ability to discern structures in central processing units (CPUs) with minimum feature sizes of approximately 50 nm in the lateral dimensions and approximately 10 nm in the axial dimension within 25 s (40 times faster than atomic force microscopes) was demonstrated. We elaborate in this paper the principles of NFWLI and demonstrate its potential for becoming a practical method for high-speed and non-toxic three-dimensional nanoscale imaging.

  9. The near-field transport code Tullgarn and its use in performance assessment

    SciTech Connect

    Sellin, P.; Kjellbert, N.

    1993-12-31

    The near-field radionuclide migration code Tullgarn has been developed for performance assessment purposes. As a part of the PROPER-code package it has been successfully applied in the SKB 91 safety analysis. THe features and processes included in the code are: (1) Radioactive chain decay; (2) Different canister failure mechanisms (copper corrosion from sulphide attack, steel corrosion, internal overpressure and initially defective canisters); (3) Spent fuel dissolution. The model is based on the assumption that the dissolution rate is proportional to the {alpha}-dose rate; (4) Transport calculations are done with a resistance-network model. Tullgarn calculates the stationary release of radionuclides from a defect in the canister through the buffer and out into a fracture in the rock or up to the damaged zone under the deposition tunnel. Tullgarn can be used as a stand-alone model for near-field release calculations or as a submodel in an integrated assessment. In the SKB 91 analysis, Tullgarn gave the source term to the far-field model.

  10. Plasmonic meta-screen for alleviating the trade-offs in the near-field optics.

    PubMed

    Wang, Yan; Wong, Alex M H; Markley, Loïc; Helmy, Amr S; Eleftheriades, George V

    2009-07-20

    We propose a "meta-screen" design, consisting of a metallic sheet patterned with a dense array of nano-sized slot antennas, for inducing sub-wavelength optical spots in the near-field. Compared to other transmission screen topologies, our design overcomes the trade-off of low throughput versus resolution of a sub-wavelength aperture by inducing resonance in the slots. In addition, the antenna array serves to effectively narrow the spot size through the superposition of spatially shifted beams produced by each slot element. Such a design offers a practical approach for extending the near-field sensing/imaging distance at optical frequencies. The effectiveness of narrowing the spot size through the array topology is demonstrated by evaluating the full-width-half-maximum (FWHM) beamwidth at a distance of 0.1lambda(0) away from the screen. We show that an array with just three elements improves the beamwidth by more than 30% compared to a single resonant slot element. In this paper, important issues such as the operating principle and the design process of the meta-screen, the characteristics of plasmonic slot antenna, the impact of the number of array elements, and the effect of asymmetry due to the presence of a supporting substrate are discussed.

  11. Optical far- and near-field femtosecond laser ablation of Si for nanoscale chemical analysis

    SciTech Connect

    Zormpa, Vasileia; Mao, Xianglei; Russo, Richard E.

    2010-02-02

    Extending spatial resolution in laser-based chemical analysis to the nanoscale becomes increasingly important as nanoscience and nanotechnology develop. Implementation of femtosecond laser pulses arises as a basic strategy for increasing resolution since it is associated with spatially localized material damage. In this work we study femtosecond laser far- and near-field processing of silicon (Si) at two distinct wavelengths (400 and 800 nm), for nanoscale chemical analysis. By tightly focusing femtosecond laser beams in the far-field we were able to produce sub-micrometer craters. In order to further reduce the crater size, similar experiments were performed in the near-field through sub-wavelength apertures, resulting to the formation of sub-30 nm craters. Laser Induced Breakdown Spectroscopy (LIBS) was used for chemical analysis with a goal to identify the minimum crater size from which spectral emission could be measured. Emission from sub-micrometer craters (full-with-at-half-maximum) was possible, which are among the smallest ever reported for femtosecond LIBS.

  12. Near-field hazard assessment of March 11, 2011 Japan Tsunami sources inferred from different methods

    USGS Publications Warehouse

    Wei, Y.; Titov, V.V.; Newman, A.; Hayes, G.; Tang, L.; Chamberlin, C.

    2011-01-01

    Tsunami source is the origin of the subsequent transoceanic water waves, and thus the most critical component in modern tsunami forecast methodology. Although impractical to be quantified directly, a tsunami source can be estimated by different methods based on a variety of measurements provided by deep-ocean tsunameters, seismometers, GPS, and other advanced instruments, some in real time, some in post real-time. Here we assess these different sources of the devastating March 11, 2011 Japan tsunami by model-data comparison for generation, propagation and inundation in the near field of Japan. This study provides a comparative study to further understand the advantages and shortcomings of different methods that may be potentially used in real-time warning and forecast of tsunami hazards, especially in the near field. The model study also highlights the critical role of deep-ocean tsunami measurements for high-quality tsunami forecast, and its combination with land GPS measurements may lead to better understanding of both the earthquake mechanisms and tsunami generation process. ?? 2011 MTS.

  13. Response of marine composites subjected to near field blast loading

    NASA Astrophysics Data System (ADS)

    LiVolsi, Frank

    Experimental studies were performed to understand the explosive response of composite panels when exposed to near-field explosive loading in different environments. The panel construction under consideration was an E-glass fiber-reinforced composite laminate infused with vinyl ester resin (Derakane 8084). The panel was layered bi-axially with plain-woven fiber orientations at 0° and 90°. Panel dimensions were approximately 203 mm x 203 mm x 1 mm (8 in x 8 in x 0.04 in). Experiments were carried out with the panel fully clamped in a holding fixture, which was in turn fastened inside a water tank. The fixture was fastened in such a way as to allow for explosive loading experiments in the following environments: water submersion with water backing, water submersion with air backing, and air immersion with air backing. Experiments were performed in room temperature conditions, and additional experiments in the submerged environments were also performed at high and low water temperatures of 40°C and 0°C, respectively. A stereo Digital Image Correlation (DIC) system was employed to capture the full-field dynamic behavior of the panel during the explosive event. Results indicated that the immersion environment contributes significantly to the blast response of the material and to the specimens' appreciable damage characteristics. The water submersion with air backing environment was found to encourage the greatest panel center point deflection and the most significant damage mechanisms around the boundary. The air immersion with air backing environment was found to encourage less center point deflection and exhibited significant impact damage from the explosive capsule. The water submersion with water backing environment encouraged the least panel deflection and minimal interlaminate damage around the panel boundary and center. Water temperature was found to influence the panel center point deflection, but not damage mechanisms. Maximum positive center point

  14. Photon-induced near-field electron microscopy (PINEM): theoretical and experimental

    NASA Astrophysics Data System (ADS)

    Park, Sang Tae; Lin, Milo; Zewail, Ahmed H.

    2010-12-01

    Electron imaging in space and time is achieved in microscopy with timed (near relativistic) electron packets of picometer wavelength coincident with light pulses of femtosecond duration. The photons (with an energy of a few electronvolts) are used to impulsively heat or excite the specimen so that the evolution of structures from their nonequilibrium state can be followed in real time. As such, and at relatively low fluences, there is no interaction between the electrons and the photons; certainly that is the case in vacuum because energy-momentum conservation is not possible. In the presence of nanostructures and at higher fluences, energy-momentum conservation is possible and the electron packet can either gain or lose light quanta. Recently, it was reported that, when only electrons with gained energy are filtered, near-field imaging enables the visualization of nanoscale particles and interfaces with enhanced contrast (Barwick et al 2009 Nature 462 902). To explore a variety of applications, it is important to express, through analytical formulation, the key parameters involved in this photon-induced near-field electron microscopy (PINEM) and to predict the associated phenomena of, e.g., forty-photon absorption by the electron packet. In this paper, we give an account of the theoretical and experimental results of PINEM. In particular, the time-dependent quantum solution for ultrafast electron packets in the nanostructure scattered electromagnetic (near) field is solved in the high kinetic energy limit to obtain the evolution of the incident electron packet into a superposition of discrete momentum wavelets. The characteristic length and time scales of the halo of electron-photon coupling are discussed in the framework of Rayleigh and Mie scatterings, providing the dependence of the PINEM effect on size, polarization, material and spatiotemporal localization. We also provide a simple classical description that is based on features of plasmonics. A major part of

  15. Near-field and far-field engineering of semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Yu, Nanfang

    Plasmonics focuses on the interaction between light and metallic films or nanostructures. In the last two decades, intensive research efforts were devoted to exploring the extremely broad applications of plasmonics. My research combines the versatility of plasmonics with active light sources, i.e., quantum cascade lasers (QCLs). This thesis focuses on the application of plasmonics in near-field and far-field engineering of semiconductor lasers, specifically, subwavelength focusing in the near-field, and laser beam collimation and polarization control. The first chapter of this thesis lays out fundamental materials necessary for understanding the following chapters. Systematic simulation and experimental results are presented in Chapter 2 to demonstrate that the integration of a suitably designed one dimensional or two dimensional plasmonic structures on the facet of QCLs can reduce the beam divergence by more than one order of magnitude. The devices with optimized collimators preserve a high output power, comparable to that of the unpatterned lasers. Chapter 3 demonstrates that the polarization state of the output of semiconductor lasers can be controlled by defining plasmonic structures on the laser facet. An integrated plasmonic polarizer can project the polarization of a semiconductor laser onto other directions. By patterning a facet with two orthogonal grating-aperture structures, a QCL can produce emission consisting of a superposition of a linearly and right-circularly polarized light, a first step towards a circularly-polarized laser. Chapter 4 presents experimental work on the coupled-rod antennas and the bowtie antennas patterned on the facet of QCLs. Both designs can provide an optical field confinement on the order of lambda/50 and with peak intensity on the order of 1 GW/cm2 in the antenna gap. The bowtie devices are more advanced due to better confinement of light into a single spot. Chapter 5 and 6 discuss two side research topics. Chapter 5

  16. A novel ultrasonic clutch using near-field acoustic levitation.

    PubMed

    Chang, Kuo-Tsi

    2004-10-01

    This paper investigates design, fabrication and drive of an ultrasonic clutch with two transducers. For the two transducers, one serving as a driving element of the clutch is connected to a driving shaft via a coupling, and the other serving as a slave element of the clutch is connected to a slave shaft via another coupling. The principle of ultrasonic levitation is first expressed. Then, a series-resonant inverter is used to generate AC voltages at input terminals of each transducer, and a speed measuring system with optic sensors is used to find the relationship between rotational speed of the slave shaft and applied voltage of each transducer. Moreover, contact surfaces of the two transducers are coupled by the frictional force when both the two transducers are not energized, and separated using the ultrasonic levitation when at least one of the two transducers is energized at high voltages at resonance.

  17. Simulation of Stochastic Processes by Coupled ODE-PDE

    NASA Technical Reports Server (NTRS)

    Zak, Michail

    2008-01-01

    A document discusses the emergence of randomness in solutions of coupled, fully deterministic ODE-PDE (ordinary differential equations-partial differential equations) due to failure of the Lipschitz condition as a new phenomenon. It is possible to exploit the special properties of ordinary differential equations (represented by an arbitrarily chosen, dynamical system) coupled with the corresponding Liouville equations (used to describe the evolution of initial uncertainties in terms of joint probability distribution) in order to simulate stochastic processes with the proscribed probability distributions. The important advantage of the proposed approach is that the simulation does not require a random-number generator.

  18. Calculated Electric Near Fields of Navy Shipboard HF Antennas, Electric Near Fields of Trussed-Whip, Twin-Whip, Discone-Cage, and Bottom-Fed Fan Antennas

    DTIC Science & Technology

    1978-03-16

    LEYE T z 0 0Z0z Technical Document 168 CALCULATED ELECTRIC NEAR FIELDS OF NAVY SHIPBOARD HF ANTENNAS Electric near fields of trussed-whip, twin...x, in meters away from the antenna. 23 - -- -.~ 1 /8 ft 8 1 /2 ft 5/32 ft 11.0ft 3/16 ft 10 1/2 ft I (ve~ticall 32 ft t w / t ho. io ..tat 11 13/16

  19. Near-Field Terahertz Transmission Imaging at 0.210 Terahertz Using a Simple Aperture Technique

    DTIC Science & Technology

    2015-10-01

    diffraction-limited and near-field terahertz transmission imaging . The target is a 3-by-3 inch glass plate with a thin coating of chrome. The...TECHNICAL REPORT RDMR-WD-15-22 NEAR-FIELD TERAHERTZ TRANSMISSION IMAGING AT 0.210 TERAHERTZ USING A SIMPLE APERTURE TECHNIQUE...Final 4. TITLE AND SUBTITLE Near-Field Terahertz Transmission Imaging at 0.210 Terahertz Using a Simple Aperture Technique 5. FUNDING NUMBERS

  20. Analysis on near field scattering spectra around nanoparticles by using parametric indirect microscopic imaging

    NASA Astrophysics Data System (ADS)

    Guoyan, Liu; Kun, Gao; Xuefeng, Liu; Guoqiang, Ni

    2016-10-01

    We report the simulation and measurement results of near field spatial scattering spectra around nanoparticles. Our measurement and simulations results have indicated that Parametric Indirect Microscopic Imaging can image the near field spatial scattering to a much larger distance from the scattering source of the particle under measurement whereas this part of spatial scattering was lost in the conventional microscopy. Both FDTD modeling and measurement provided evidence that parameters of indirect optical wave vector have higher sensitivity to near field scattering.

  1. Prediction of sonic boom from experimental near-field overpressure data. Volume 1: Method and results

    NASA Technical Reports Server (NTRS)

    Glatt, C. R.; Hague, D. S.; Reiners, S. J.

    1975-01-01

    A computerized procedure for predicting sonic boom from experimental near-field overpressure data has been developed. The procedure extrapolates near-field pressure signatures for a specified flight condition to the ground by the Thomas method. Near-field pressure signatures are interpolated from a data base of experimental pressure signatures. The program is an independently operated ODIN (Optimal Design Integration) program which obtains flight path information from other ODIN programs or from input.

  2. Fiber-coupled THz spectroscopy for monitoring polymeric compounding processes

    NASA Astrophysics Data System (ADS)

    Vieweg, N.; Krumbholz, N.; Hasek, T.; Wilk, R.; Bartels, V.; Keseberg, C.; Pethukhov, V.; Mikulics, M.; Wetenkamp, L.; Koch, M.

    2007-06-01

    We present a compact, robust, and transportable fiber-coupled THz system for inline monitoring of polymeric compounding processes in an industrial environment. The system is built on a 90cm x 90cm large shock absorbing optical bench. A sealed metal box protects the system against dust and mechanical disturbances. A closed loop controller unit is used to ensure optimum coupling of the laser beam into the fiber. In order to build efficient and stable fiber-coupled antennas we glue the fibers directly onto photoconductive switches. Thus, the antenna performance is very stable and it is secured from dust or misalignment by vibrations. We discuss fabrication details and antenna performance. First spectroscopic data obtained with this system is presented.

  3. Nanoaperture formation at metal covered tips by microspark optimized for near-field optical probes

    NASA Astrophysics Data System (ADS)

    Chaigneau, M.; Louarn, G.; Minea, T. M.

    2008-03-01

    A simple and reproducible method for nanoaperture opening of metal film covered tapered optical fibers is reported as the last step of the manufacturing process for near-field scanning optical microscopy (NSOM) probes. It uses a microspark between the biased tip and another plane electrode working as a coronalike discharge in point-to-plane configuration. The resultant high electric field is enhanced at the extremity of the metallized tip self-focusing the discharge ions. The opening process is performed in situ in a specially designed plasma reactor which also allows, for the optical fiber tips, their surface cleaning and silver coating. Nanoaperture diameter can be controlled between 30 and 100nm. These probes are able to generate subwavelength resolved images and are appropriate for high resolution NSOM.

  4. Reciprocity in scanning near-field optical microscopy: illumination and collection modes of transmission measurements.

    PubMed

    Imura, Kohei; Okamoto, Hiromi

    2006-05-15

    We experimentally investigated the reciprocity of scanning near-field optical microscopy between illumination and collection modes. Near-field transmission images of single gold spheres and nanorods observed by the two modes are found to be equivalent to each other in the region from visible to near infrared. This result shows that reciprocity holds for the near-field scattering problems. We found that the conventional optical selection rule for far-field excitations does not apply not only under illumination mode but also with collection-mode arrangements. The possible origin of this observation might be the near-field probe.

  5. A dual-ported, dual-polarized spherical near-field probe

    NASA Astrophysics Data System (ADS)

    Jones, J. R.; Hardin, D. P.

    1984-03-01

    The spherical near-field measurement technique is a convenient and economical method for testing antennas. It is particularly useful for electrically small antennas at low frequencies. It requires much less real estate than conventional far-field ranges and yields more accurate results in a more controlled and secure environment. The spherical near-field measurement technique can be used to test antennas too large in physical size for the compact range technique and, unlike other near-field measurement techniques, it permits the use of standard spherical coordinate positioners. The most serious disadvantage of spherical near-field testing is the time required to perform a test.

  6. Numerical Modeling of a Near-Field Scanning Optical System

    NASA Astrophysics Data System (ADS)

    Kann, Joshua Louis

    A near-field scanning optical (NFO) system utilizes a subwavelength sized aperture to illuminate a sample. The aperture raster scans the sample. During the scan, the aperture is held in proximity to the sample. At each sampling point, the integrated far-zone energy distribution is stored. This collection of data is used to generate an image of the sample's surface. The main advantage of NFO systems is their very high spatial resolution. In this dissertation a hybrid finite-difference-time-domain (FDTD)/angular spectrum code is used to study the electromagnetic and imaging properties of a NFO scanning system. In addition, a finite-difference thermal (FD-thermal) code is used to calculate the thermal properties of a NFO system. Various aperture/sample geometries are studied numerically using both TE and TM polarization within a two-dimensional metallic waveguide that forms the aperture. The spatial properties of the electric field emitted by the aperture with no sample present are greatly influenced by the polarization. In particular, the electric field with TM polarization exhibits sharp peaks near the corners of the aperture, while the field with TE polarization is smooth and peaked at the center of the aperture. For both polarizations, the electric field remains collimated for a distance comparable to the aperture size. The electric field for both polarizations is altered when a dielectric sample is placed in proximity to the aperture. It is shown that the most representative image of the sample's topography is obtained using TE polarization and the resulting total far-zone energy as the sampled data. It is also shown that simpler scalar methods do not accurately predict the imaging behavior of a NFO system. Under certain circumstances the relationship between the sample's topography and the detected image is nearly linear. Under these conditions a system transfer function is calculated. Using the transfer function, it is shown that the spatial resolution of a NFO

  7. Gene regulation and noise reduction by coupling of stochastic processes

    NASA Astrophysics Data System (ADS)

    Ramos, Alexandre F.; Hornos, José Eduardo M.; Reinitz, John

    2015-02-01

    Here we characterize the low-noise regime of a stochastic model for a negative self-regulating binary gene. The model has two stochastic variables, the protein number and the state of the gene. Each state of the gene behaves as a protein source governed by a Poisson process. The coupling between the two gene states depends on protein number. This fact has a very important implication: There exist protein production regimes characterized by sub-Poissonian noise because of negative covariance between the two stochastic variables of the model. Hence the protein numbers obey a probability distribution that has a peak that is sharper than those of the two coupled Poisson processes that are combined to produce it. Biochemically, the noise reduction in protein number occurs when the switching of the genetic state is more rapid than protein synthesis or degradation. We consider the chemical reaction rates necessary for Poisson and sub-Poisson processes in prokaryotes and eucaryotes. Our results suggest that the coupling of multiple stochastic processes in a negative covariance regime might be a widespread mechanism for noise reduction.

  8. Gene regulation and noise reduction by coupling of stochastic processes

    PubMed Central

    Hornos, José Eduardo M.; Reinitz, John

    2015-01-01

    Here we characterize the low noise regime of a stochastic model for a negative self-regulating binary gene. The model has two stochastic variables, the protein number and the state of the gene. Each state of the gene behaves as a protein source governed by a Poisson process. The coupling between the the two gene states depends on protein number. This fact has a very important implication: there exist protein production regimes characterized by sub-Poissonian noise because of negative covariance between the two stochastic variables of the model. Hence the protein numbers obey a probability distribution that has a peak that is sharper than those of the two coupled Poisson processes that are combined to produce it. Biochemically, the noise reduction in protein number occurs when the switching of genetic state is more rapid than protein synthesis or degradation. We consider the chemical reaction rates necessary for Poisson and sub-Poisson processes in prokaryotes and eucaryotes. Our results suggest that the coupling of multiple stochastic processes in a negative covariance regime might be a widespread mechanism for noise reduction. PMID:25768447

  9. Gene regulation and noise reduction by coupling of stochastic processes.

    PubMed

    Ramos, Alexandre F; Hornos, José Eduardo M; Reinitz, John

    2015-02-01

    Here we characterize the low-noise regime of a stochastic model for a negative self-regulating binary gene. The model has two stochastic variables, the protein number and the state of the gene. Each state of the gene behaves as a protein source governed by a Poisson process. The coupling between the two gene states depends on protein number. This fact has a very important implication: There exist protein production regimes characterized by sub-Poissonian noise because of negative covariance between the two stochastic variables of the model. Hence the protein numbers obey a probability distribution that has a peak that is sharper than those of the two coupled Poisson processes that are combined to produce it. Biochemically, the noise reduction in protein number occurs when the switching of the genetic state is more rapid than protein synthesis or degradation. We consider the chemical reaction rates necessary for Poisson and sub-Poisson processes in prokaryotes and eucaryotes. Our results suggest that the coupling of multiple stochastic processes in a negative covariance regime might be a widespread mechanism for noise reduction.

  10. Near-field noise predictions of an aircraft in cruise

    NASA Technical Reports Server (NTRS)

    Rawls, John W., Jr.

    1987-01-01

    The physics of the coupling of sound waves with the boundary layer is not yet well understood. It is believed, however, that for effective coupling of the sound waves and instability waves in the boundary layer, a matching of both frequency and wave number must occur. This requires that the sound field be accurately defined in both space and time. Currently analytical prediction methods lack sufficient accuracy to predict the noise levels from components of a turbofan engine. Although empirical methods do not yield the detail required for an analysis of the receptivity of sound by a boundary layer, valuable insight can be gained as to the changes in noise levels that might be expected under various operating conditions and aircraft configurations.

  11. Wireless Links in the Radiative Near Field via Bessel Beams

    NASA Astrophysics Data System (ADS)

    Heebl, Jason D.; Ettorre, Mauro; Grbic, Anthony

    2016-09-01

    The generation of propagating Bessel beams is typically limited to optical frequencies with bulky experimental setups. Recent works have demonstrated Bessel-beam generation at microwave and millimeter-wave frequencies utilizing low-profile, planar, leaky-wave antennas. These studies have assumed a single leaky mode in the antenna. In this work, the rigorous analysis of a planar Bessel-beam launcher supporting multiple modes is presented. By employing the mode-matching technique, a complete electromagnetic solution of the structure, its supported modes, and radiated fields is obtained. Additionally, a coupled system of two planar Bessel launchers is analyzed, and it is shown that the system can both transmit and receive Bessel beams. The energy-transfer characteristics of the coupled system are analyzed and discussed. An analysis of the coupled system's even and odd modes of operation show that efficient power transfer is possible, and that an odd mode is preferred since it yields higher field confinement and power-transfer efficiency.

  12. Plasmonic nanofocused four-wave mixing for femtosecond near-field imaging

    NASA Astrophysics Data System (ADS)

    Kravtsov, Vasily; Ulbricht, Ronald; Atkin, Joanna M.; Raschke, Markus B.

    2016-05-01

    Femtosecond nonlinear optical imaging with nanoscale spatial resolution would provide access to coupled degrees of freedom and ultrafast response functions on the characteristic length scales of electronic and vibrational excitations. Although near-field microscopy provides the desired spatial resolution, the design of a broadband high-contrast nanoprobe for ultrafast temporal resolution is challenging due to the inherently weak nonlinear optical signals generated in subwavelength volumes. Here, we demonstrate broadband four-wave mixing with enhanced nonlinear frequency conversion efficiency at the apex of a nanometre conical tip. Far-field light is coupled through a grating at the shaft of the tip, generating plasmons that propagate to the apex while undergoing asymptotic compression and amplification, resulting in a nonlinear conversion efficiency of up to 1 × 10-5. We apply this nonlinear nanoprobe to image the few-femtosecond coherent dynamics of plasmonic hotspots on a nanostructured gold surface with spatial resolution of a few tens of nanometres. The approach can be generalized towards spatiotemporal imaging and control of coherent dynamics on the nanoscale, including the extension to multidimensional spectroscopy and imaging.

  13. Near-field electrical detection of optical plasmons and single-plasmon sources

    NASA Astrophysics Data System (ADS)

    Falk, Abram L.; Koppens, Frank H. L.; Yu, Chun L.; Kang, Kibum; de Leon Snapp, Nathalie; Akimov, Alexey V.; Jo, Moon-Ho; Lukin, Mikhail D.; Park, Hongkun

    2009-07-01

    Photonic circuits can be much faster than their electronic counterparts, but they are difficult to miniaturize below the optical wavelength scale. Nanoscale photonic circuits based on surface plasmon polaritons (SPPs) are a promising solution to this problem because they can localize light below the diffraction limit. However, there is a general trade-off between the localization of an SPP and the efficiency with which it can be detected with conventional far-field optics. Here, we describe a new all-electrical SPP detection technique based on the near-field coupling between guided plasmons and a nanowire field-effect transistor. We use the technique to electrically detect the plasmon emission from an individual colloidal quantum dot coupled to an SPP waveguide. Our detectors are both nanoscale and highly efficient (~0.1electrons per plasmon), and a plasmonic gating effect can be used to amplify the signal even higher (up to 50electrons per plasmon). These results may enable new on-chip optical sensing applications and are a key step towards `dark' optoplasmonic nanocircuits in which SPPs can be generated, manipulated and detected without involving far-field radiation.

  14. Intrinsic Plasmon-Phonon Interactions in Highly Doped Graphene: A Near-Field Imaging Study.

    PubMed

    Bezares, Francisco J; Sanctis, Adolfo De; Saavedra, J R M; Woessner, Achim; Alonso-González, Pablo; Amenabar, Iban; Chen, Jianing; Bointon, Thomas H; Dai, Siyuan; Fogler, Michael M; Basov, D N; Hillenbrand, Rainer; Craciun, Monica F; García de Abajo, F Javier; Russo, Saverio; Koppens, Frank H L

    2017-10-11

    As a two-dimensional semimetal, graphene offers clear advantages for plasmonic applications over conventional metals, such as stronger optical field confinement, in situ tunability, and relatively low intrinsic losses. However, the operational frequencies at which plasmons can be excited in graphene are limited by the Fermi energy EF, which in practice can be controlled electrostatically only up to a few tenths of an electronvolt. Higher Fermi energies open the door to novel plasmonic devices with unprecedented capabilities, particularly at mid-infrared and shorter-wave infrared frequencies. In addition, this grants us a better understanding of the interaction physics of intrinsic graphene phonons with graphene plasmons. Here, we present FeCl3-intercalated graphene as a new plasmonic material with high stability under environmental conditions and carrier concentrations corresponding to EF > 1 eV. Near-field imaging of this highly doped form of graphene allows us to characterize plasmons, including their corresponding lifetimes, over a broad frequency range. For bilayer graphene, in contrast to the monolayer system, a phonon-induced dipole moment results in increased plasmon damping around the intrinsic phonon frequency. Strong coupling between intrinsic graphene phonons and plasmons is found, supported by ab initio calculations of the coupling strength, which are in good agreement with the experimental data.

  15. Modeling micro-droplet formation in near-field electrohydrodynamic jet printing

    NASA Astrophysics Data System (ADS)

    Popell, George Colin

    Near-field electrohydrodynamic jet (E-jet) printing has recently gained significant interest within the manufacturing research community because of its ability to produce micro/sub-micron-scale droplets using a wide variety of inks and substrates. However, the process currently operates in open-loop and as a result suffers from unpredictable printing quality. The use of physics-based, control-oriented process models is expected to enable closed-loop control of this printing technique. The objective of this research is to perform a fundamental study of the substrate-side droplet shape-evolution in near-field E-jet printing and to develop a physics-based model of the same that links input parameters such as voltage magnitude and ink properties to the height and diameter of the printed droplet. In order to achieve this objective, a synchronized high-speed imaging and substrate-side current-detection system was used implemented to enable a correlation between the droplet shape parameters and the measured current signal. The experimental data reveals characteristic process signatures and droplet spreading regimes. The results of these studies are then used as the basis for a model that predicts the droplet diameter and height using the measured current signal as the input. A unique scaling factor based on the measured current signal is used in this model instead of relying on empirical scaling laws found in literature. For each of the three inks tested in this study, the average absolute error in the model predictions is under 4.6% for diameter predictions and under 10.6% for height predictions of the steady-state droplet. While printing under non-conducive ambient conditions of low humidity and high temperatures, the use of the environmental correction factor in the model is seen to result in average absolute errors of 10.35% and 12.5% for diameter and height predictions.

  16. Nanofocusing beyond the near-field diffraction limit via plasmonic Fano resonance

    NASA Astrophysics Data System (ADS)

    Song, Maowen; Wang, Changtao; Zhao, Zeyu; Pu, Mingbo; Liu, Ling; Zhang, Wei; Yu, Honglin; Luo, Xiangang

    2016-01-01

    paper, we propose a periodically repeated ring-disk complementary structure to break the near-field diffraction limit via plasmonic Fano resonance, originating from the interference between the complex hybrid plasmon resonance and the continuum of propagating waves through the silver film. This plasmonic Fano resonance introduces a π phase jump in the adjacent channels and amplitude modulation to achieve radiationless electromagnetic interference. As a result, deep subwavelength spots as small as 0.0045λ2 at 36 nm above the silver film have been numerically demonstrated. This plate holds promise for nanolithography, subdiffraction imaging and microscopy. Electronic supplementary information (ESI) available: The plasmon hybridization modes have been analyzed. The transmittance, reflectance and absorbance have been plotted to have a better understanding of the coupling in a silver nanoring. The dependencies of the intensity enhancement on the total numbers of building blocks have been shown. See DOI: 10.1039/c5nr06504f

  17. On the horizontal wobbling of an object levitated by near-field acoustic levitation.

    PubMed

    Kim, Cheol-Ho; Ih, Jeong-Guon

    2007-11-01

    A circular planar object can be levitated with several hundreds of microns by ultrasonic near-field acoustic levitation (NFAL). However, when both the sound source and the levitated object are circularly shaped and the center of the levitated object does not coincide with the source center, instability problem often occurs. When this happens, it becomes difficult to pick up or transport the object for the next process. In this study, when the center of the levitated object was offset from the source center, the moving direction of the levitated object was predicted by using the time averaged potential around the levitated object. The wobbling frequency of the levitated object was calculated by analyzing the nonlinear wobbling motion of the object. It was shown that the predicted wobbling frequencies agreed with measured ones well. Finally, a safe zone was suggested to avoid the unstable movement of an object.

  18. Modeling of the near-field distribution of pollutants coming from a coastal outfall

    NASA Astrophysics Data System (ADS)

    Lyubimova, T. P.; Roux, B.; Luo, S.; Parshakova, Y. N.; Shumilova, N. S.

    2013-04-01

    The present study concerns the 3-D distribution of pollutants emitted from a coastal outfall in the presence of strong sea currents. The problem is solved using the nonlinear Reynolds-averaged Navier-Stokes equations in the framework of the k-ɛ model. The constants of the logarithmic law for the vertical velocity profile in the bottom boundary layer are obtained by processing experimental data from acoustic Doppler current profilers (ADCPs). The near-field distribution of pollutants at different distances from the diffuser is obtained in terms of the ambient flow velocity (steady or with tidal effect) and outfall discharge characteristics. It is shown that even in the case where the effluent density is substantially lower than the ambient sea water density the plume can impact the seabed, creating a risk of pollution of removable bottom sediments.

  19. Characterization of uniformity and reproducibility of photoresist nanomasks fabricated by near-field scanning optical nanolithography.

    PubMed

    Kwon, Sangjin; Jeong, Youngmo; Jeong, Sungho

    2006-11-01

    The uniformity and reproducibility of the photoresist nanopatterns fabricated using near-field scanning optical nanolithography (NSOL) are investigated. The nanopatterns could be used as nanomasks for pattern transfer on a silicon wafer. In the NSOL process, uniform patterning with high reproducibility is essential for reliable transfer of the mask patterns on a silicon substrate. Using an aperture type cantilever nanoprobe operated at contact mode and a positive photoresist, various nanopatterns are produced on thin photoresist layer coated on the silicon substrate. The size and shape variations of thereby produced patterns are investigated using atomic force microscope to determine their uniformity and reproducibility. It is demonstrated that the NSOL-produced photo-resist nanomasks can be successfully applied for silicon pattern transfer by fabricating a silicon nanochannel array.

  20. Multimode near-field microwave monitoring of free water content of skin and imaging of tissue.

    PubMed

    Lofland, S E; Mazzatenta, J D; Croman, J; Tyagi, S D

    2007-03-07

    We have used the near-field scanning microwave microscopy (NSMM) technique in the 1-10 GHz range to monitor the free water content of skin. The water content is interpreted from the measured dielectric properties of the epidermis. The finger skin was first hydrated by soaking in water at 37 degrees C for 30 min followed by monitoring of water content as the free water evaporated under ambient conditions. The same technique has also been employed to image a 1 cm x 1 cm sample of chicken skin. It has been shown that variations exist in the resonant frequencies and quality factors of tissue under varying physical parameters. The samples analysed were as-received and thermally dehydrated or damaged chicken tissue samples. We contrast between the dielectric properties with the optical images. We also discuss possible application of our imaging technique in clinical monitoring of the wound healing process.

  1. Numerical Modeling of Thermal-Hydrology in the Near Field of a Generic High-Level Waste Repository

    NASA Astrophysics Data System (ADS)

    Matteo, E. N.; Hadgu, T.; Park, H.

    2016-12-01

    Disposal in a deep geologic repository is one of the preferred option for long term isolation of high-level nuclear waste. Coupled thermal-hydrologic processes induced by decay heat from the radioactive waste may impact fluid flow and the associated migration of radionuclides. This study looked at the effects of those processes in simulations of thermal-hydrology for the emplacement of U. S. Department of Energy managed high-level waste and spent nuclear fuel. Most of the high-level waste sources have lower thermal output which would reduce the impact of thermal propagation. In order to quantify the thermal limits this study concentrated on the higher thermal output sources and on spent nuclear fuel. The study assumed a generic nuclear waste repository at 500 m depth. For the modeling a representative domain was selected representing a portion of the repository layout in order to conduct a detailed thermal analysis. A highly refined unstructured mesh was utilized with refinements near heat sources and at intersections of different materials. Simulations looked at different values for properties of components of the engineered barrier system (i.e. buffer, disturbed rock zone and the host rock). The simulations also looked at the effects of different durations of surface aging of the waste to reduce thermal perturbations. The PFLOTRAN code (Hammond et al., 2014) was used for the simulations. Modeling results for the different options are reported and include temperature and fluid flow profiles in the near field at different simulation times. References:G. E. Hammond, P.C. Lichtner and R.T. Mills, "Evaluating the Performance of Parallel Subsurface Simulators: An Illustrative Example with PFLOTRAN", Water Resources Research, 50, doi:10.1002/2012WR013483 (2014). Sandia National Laboratories is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under

  2. Method of processing materials using an inductively coupled plasma

    DOEpatents

    Hull, D.E.; Bieniewski, T.M.

    1987-04-13

    A method of processing materials. The invention enables ultrafine, ultrapure powders to be formed from solid ingots in a gas free environment. A plasma is formed directly from an ingot which insures purity. The vaporized material is expanded through a nozzle and the resultant powder settles on a cold surface. An inductively coupled plasma may also be used to process waste chemicals. Noxious chemicals are directed through a series of plasma tubes, breaking molecular bonds and resulting in relatively harmless atomic constituents. 3 figs.

  3. Fibre Fabry - Perot cavity-based aperture probe for near-field optical microscopy systems

    SciTech Connect

    Kulchin, Yurii N; Vitrik, O B; Bezverbnyi, A V; Pustovalov, E V; Kuchmizhak, A A; Nepomnyashchii, A V

    2011-03-31

    We report a theoretical analysis and experimental study of the possibility of producing a novel type of interferometric near-field aperture probe for near-field optical microscopy systems using a fibre Fabry - Perot microcavity with a nanometre-scale aperture made in one of its output mirrors. The probe ensures a spatial resolution no worse than {lambda}/14. (fibre optics)

  4. Single-molecule imaging of cell surfaces using near-field nanoscopy.

    PubMed

    Hinterdorfer, Peter; Garcia-Parajo, Maria F; Dufrêne, Yves F

    2012-03-20

    Living cells use surface molecules such as receptors and sensors to acquire information about and to respond to their environments. The cell surface machinery regulates many essential cellular processes, including cell adhesion, tissue development, cellular communication, inflammation, tumor metastasis, and microbial infection. These events often involve multimolecular interactions occurring on a nanometer scale and at very high molecular concentrations. Therefore, understanding how single-molecules localize, assemble, and interact on the surface of living cells is an important challenge and a difficult one to address because of the lack of high-resolution single-molecule imaging techniques. In this Account, we show that atomic force microscopy (AFM) and near-field scanning optical microscopy (NSOM) provide unprecedented possibilities for mapping the distribution of single molecules on the surfaces of cells with nanometer spatial resolution, thereby shedding new light on their highly sophisticated functions. For single-molecule recognition imaging by AFM, researchers label the tip with specific antibodies or ligands and detect molecular recognition signals on the cell surface using either adhesion force or dynamic recognition force mapping. In single-molecule NSOM, the tip is replaced by an optical fiber with a nanoscale aperture. As a result, topographic and optical images are simultaneously generated, revealing the spatial distribution of fluorescently labeled molecules. Recently, researchers have made remarkable progress in the application of near-field nanoscopy to image the distribution of cell surface molecules. Those results have led to key breakthroughs: deciphering the nanoscale architecture of bacterial cell walls; understanding how cells assemble surface receptors into nanodomains and modulate their functional state; and understanding how different components of the cell membrane (lipids, proteins) assemble and communicate to confer efficient functional

  5. Near field to far field transformations and multiple beam forming and steering

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The feasibility of acoustic verification of microwave near field to far field transformation algorithms using the Phased Array Sonic Simulation System was studied. Existing electromagnetic near field measurement techniques and transformation algorithms (equations) were investigated. It was analytically determined that acoustic verification is valid. Acoustic simulation of electromagnetic near field to far field transformations is emphasized. The acoustic simulation of electromagnetic near field to far field transformation is verified for the modal expansion method. In the modal expansion method, data from antenna near field measurements are converted to a summation or spectrum of modes corresponding to wave numbers in the measurement coordinate system. Fourier transformation of those measurements preserves the far field information in a spectral form that is then readily extractable.

  6. The Lightning Rod Model: a Genesis for Quantitative Near-Field Spectroscopy

    NASA Astrophysics Data System (ADS)

    McLeod, Alexander; Andreev, Gregory; Dominguez, Gerardo; Thiemens, Mark; Fogler, Michael; Basov, D. N.

    2013-03-01

    Near-field infrared spectroscopy has the proven ability to resolve optical contrasts in materials at deeply sub-wavelength scales across a broad range of infrared frequencies. In principle, the technique enables sub-diffractional optical identification of chemical compositions within nanostructured and naturally heterogeneous samples. However current models of probe-sample optical interaction, while qualitatively descriptive, cannot quantitatively explain infrared near-field spectra, especially for strongly resonant sample materials. We present a new first-principles model of near-field interaction, and demonstrate its superb agreement with infrared near-field spectra measured for thin films of silicon dioxide and the strongly phonon-resonant material silicon carbide. Using this model we reveal the role of probe geometry and surface mode dispersion in shaping the measured near-field spectrum, establishing its quantitative relationship with the dielectric properties of the sample. This treatment offers a route to the quantitative determination of optical constants at the nano-scale.

  7. Results From an International Simulation Study on Couples Thermal, Hydrological, and Mechanical (THM) Processes Near Geological Nuclear Waste Repositories

    SciTech Connect

    J. Rutqvist; D. Barr; J.T. Birkholzer; M. Chijimatsu; O. Kolditz; Q. Liu; Y. Oda; W. Wang; C. Zhang

    2006-08-02

    As part of the ongoing international DECOVALEX project, four research teams used five different models to simulate coupled thermal, hydrological, and mechanical (THM) processes near waste emplacement drifts of geological nuclear waste repositories. The simulations were conducted for two generic repository types, one with open and the other with back-filled repository drifts, under higher and lower postclosure temperatures, respectively. In the completed first model inception phase of the project, a good agreement was achieved between the research teams in calculating THM responses for both repository types, although some disagreement in hydrological responses is currently being resolved. In particular, good agreement in the basic thermal-mechanical responses was achieved for both repository types, even though some teams used relatively simplified thermal-elastic heat-conduction models that neglected complex near-field thermal-hydrological processes. The good agreement between the complex and simplified process models indicates that the basic thermal-mechanical responses can be predicted with a relatively high confidence level.

  8. Calcium dynamics in astrocyte processes during neurovascular coupling

    PubMed Central

    Otsu, Yo; Couchman, Kiri; Lyons, Declan G; Collot, Mayeul; Agarwal, Amit; Mallet, Jean-Maurice; Pfrieger, Frank W; Bergles, Dwight E; Charpak, Serge

    2015-01-01

    Enhanced neuronal activity in the brain triggers a local increase in blood flow, termed functional hyperemia, via several mechanisms, including calcium (Ca2+) signaling in astrocytes. However, recent in vivo studies have questioned the role of astrocytes in functional hyperemia because of the slow and sparse dynamics of their somatic Ca2+ signals and the absence of glutamate metabotropic receptor 5 in adults. Here, we reexamined their role in neurovascular coupling by selectively expressing a genetically encoded Ca2+ sensor in astrocytes of the olfactory bulb. We show that in anesthetized mice, the physiological activation of olfactory sensory neuron (OSN) terminals reliably triggers Ca2+ increases in astrocyte processes but not in somata. These Ca2+ increases systematically precede the onset of functional hyperemia by 1–2 s, reestablishing astrocytes as potential regulators of neurovascular coupling. PMID:25531572

  9. Characterization of Coupled Hydrologic-Biogeochemical Processes Using Geophysical Data

    SciTech Connect

    Hubbard, Susan

    2005-06-01

    Biogeochemical and hydrological processes are naturally coupled and variable over a wide range of spatial and temporal scales. Many remediation approaches also induce dynamic transformations in natural systems, such as the generation of gases, precipitates and biofilms. These dynamic transformations are often coupled and can reduce the hydraulic conductivity of the geologic materials, making it difficult to introduce amendments or to perform targeted remediation. Because it is difficult to predict these transformations, our ability to develop effective and sustainable remediation conditions at contaminated sites is often limited. Further complicating the problem is the inability to collect the necessary measurements at a high enough spatial resolution yet over a large enough volume for understanding field-scale transformations.

  10. Coupled Biogeochemical Process Evaluation for Conceptualizing Trichloroethylene Co-Metabolism

    SciTech Connect

    Colwell, Frederick; Radtke, Corey; Newby, Deborah; Delwiche, Mark; Crawf, Ronald L.; Paszczynski, Andrzej; Strap, Janice; Conrad, Mark; Brodic, Eoin; Starr, Robert; Lee, Hope

    2006-04-05

    Chlorinated solvent wastes (e.g., trichloroethene or TCE) often occur as diffuse subsurface plumes in complex geological environments where coupled processes must be understood in order to implement remediation strategies. Monitored natural attenuation (MNA) warrants study as a remediation technology because it minimizes worker and environment exposure to the wastes and because it costs less than other technologies. However, to be accepted MNA requires 'lines of evidence' indicating that the wastes are effectively destroyed. Our research will study the coupled biogeochemical processes that dictate the rate of TCE co-metabolism in contaminated aquifers first at the Idaho National Laboratory and then at Paducah or the Savannah River Site, where natural attenuation of TCE is occurring. We will use flow-through in situ reactors to investigate the rate of methanotrophic co-metabolism of TCE and the coupling of the responsible biological processes with the dissolved methane flux and groundwater flow velocity. We will use new approaches (e.g., stable isotope probing, enzyme activity probes, real-time reverse transcriptase polymerase chain reaction, proteomics) to assay the TCE co-metabolic rates, and interpret these rates in the context of enzyme activity, gene expression, and cellular inactivation related to intermediates of TCE co-metabolism. By determining the rate of TCE co-metabolism at different methane concentrations and groundwater flow velocities, we will derive key modeling parameters for the computational simulations that describe the attenuation, and thereby refine such models while assessing the contribution of microbial relative to other natural attenuation processes. This research will strengthen our ability to forecast the viability of MNA at DOE and other sites that are contaminated with chlorinated hydrocarbons.

  11. Coupled Biogeochemical Process Evaluation for Conceptualizing Trichloroethylene Co-Metabolism

    SciTech Connect

    Rick Colwell; Corey Radtke; Mark Delwiche; Deborah Newby; Lynn Petzke; Mark Conrad; Eoin Brodie; Hope Lee; Bob Starr; Dana Dettmers; Ron Crawford; Andrzej Paszczynski; Nick Bernardini; Ravi Paidisetti; Tonia Green

    2006-06-01

    Chlorinated solvent wastes (e.g., trichloroethene or TCE) often occur as diffuse subsurface plumes in complex geological environments where coupled processes must be understood in order to implement remediation strategies. Monitored natural attenuation (MNA) warrants study as a remediation technology because it minimizes worker and environment exposure to the wastes and because it costs less than other technologies. However, to be accepted MNA requires different ?lines of evidence? indicating that the wastes are effectively destroyed. We are studying the coupled biogeochemical processes that dictate the rate of TCE co-metabolism first in the medial zone (TCE concentration: 1,000 to 20,000 ?g/L) of a plume at the Idaho National Laboratory?s Test Area North (TAN) site and then at Paducah or the Savannah River Site. We will use flow-through in situ reactors (FTISR) to investigate the rate of methanotrophic co-metabolism of TCE and the coupling of the responsible biological processes with the dissolved methane flux and groundwater flow velocity. TCE co-metabolic rates at TAN are being assessed and interpreted in the context of enzyme activity, gene expression, and cellular inactivation related to intermediates of TCE co-metabolism. By determining the rate of TCE co-metabolism at different groundwater flow velocities, we will derive key modeling parameters for the computational simulations that describe the attenuation, and thereby refine such models while assessing the contribution of microbial co-metabolism relative to other natural attenuation processes. This research will strengthen our ability to forecast the viability of MNA at DOE and other sites contaminated with chlorinated hydrocarbons.

  12. Superresolution of buried objects in layered media by near-field electromagnetic imaging

    NASA Astrophysics Data System (ADS)

    Lehman, Sean Kenneth

    In non-invasive wave† probing of layered media in near field conditions, few researchers outside of optical microscopists have taken advantage of the evanescent part of the scattered field to enhance resolution. In this dissertation, we propose and develop an imaging technique to be used in near-field environments which achieves resolution beyond the diffraction limit, or equivalently ``superresolution,'' by including the evanescent part of the field backscattered from objects buried in the medium. In Chapter 1, we discuss the nature of non-invasive wave probing of objects and introduce the concept of tomography. Tomographic imaging is a collection of techniques to reconstruct images of the unknown internal structure of an object from fields transmitted through, and/or reflected from it. We develop two widely used tomographic techniques: projection tomography and plane to plane backpropagation. In Chapter 2, we introduce and develop the concept of inhomogeneous diffraction tomography, the area with which this dissertation is concerned. We show the most widely used diffraction tomography technique is resolution limited to approximately a half wavelength. In Chapter 3, we study the forward scattering process in order to develop a new diffraction tomography imaging technique which achieves resolution beyond the classical limit. We propose and prove a new theorem which explains why the diffraction tomography method of Chapter 2 is resolution limited. We then derive a total field scattering relation which includes both propagating and evanescent field components. In Chapter 4, we develop a new reconstruction algorithm which is based upon the total field scattering relation. This full field tomographic reconstruction algorithm includes both propagating and evanescent field components. In Chapter 5, we present reconstruction results from both simulated and real wide-band radar data which demonstrate our new algorithm surpasses the resolution of most current techniques

  13. Regulation of conduction velocity in axons from near-field receptors of the crayfish antennule.

    PubMed

    Mellon, DeForest

    2010-11-15

    The antennular flagella of the crayfish Procambarus clarkii each possess a linear array of near-field receptors, termed standing feathered sensilla, that are extremely sensitive to movement of the surrounding water. Previously it had been shown that, within each flagellum, the axonal conduction velocity of the sensory neuron pair associated with each feathered sensillum was linearly related to the position of the sensillum along the flagellar axis. In the current studies I show that the conduction velocity of axons within the proximal three segments of the antennules, between the flagellum and the brain, is somewhat higher than the corresponding conduction velocity of the same axons in the flagellum, especially for those whose flagellar conduction velocity is between 1 and 3 m s(-1), even though there is no net change in axonal diameter within this part of the afferent pathway. One consequence of this change in axonal conduction properties is an effective compression of the temporal spread - potentially by as much as tenfold - which otherwise would occur in arrival times of initial spikes from each sensillum following a mechanical stimulus to the antennule. Furthermore, the pattern signature of initial spike volleys at the brain following a global hydrodynamic stimulus to the flagellum is remarkably consistent and conceivably could be recognized as such by central processing centers. I conclude that conduction velocity adjustments improve temporal summation and resolution from input volleys that originate in the highly sensitive and, hence, inherently noisy near-field receptors, thereby more effectively triggering startle response circuitry at the approach of potential predators.

  14. Subevent analysis for the Tabas earthquake of September 16, 1978, using near field accelerograms

    NASA Astrophysics Data System (ADS)

    Sarkar, I.; SriRam, V.; Hamzehloo, H.; Khattri, K. N.

    2005-07-01

    We analyze the strong motion accelerograms of the large magnitude ( mb = 6.4, MS = 7.7, Mw = 7.4, M0 = 1.32 × 10 20) Tabas earthquake of September 16, 1978. The earthquake occurred due to a unilaterally propagating complex rupture process on a thrust fault system. The imprints of rupture of four (and possibly five) asperities (sub-faults) have been identified on the accelerograms. Using derived 'SH-wave' records, the locations of these asperities, which lie on the main causative fault, and the relative times of their occurrence have been determined. A foreshock that occurred about 6 s prior to the main shock has also been identified and located. Further, using 'SH-wave' spectral data, we provide near field estimates of the strike, dip and slip of these asperities as well as their seismic moment, moment magnitude, fault area, released shear wave energy and average stress drop. The spectra of the sub-events conform to the ω-2 Brune spectra. The total seismic energy of the sub-events is consistent with the radiated energy estimated from teleseismic observations. The fault plane solutions show generally WNW-ESE strike, which is sub-parallel to the regional strike of the geological fault system existing in the area. The stress drops are in the range of 7-30 bar, with the exception of the main sub-event that showed a stress drop of 100 bar. Overall the sub-events show self-similarity. The average shear wave quality factor QS, which in the near field is quite sensitive to the local site geology, has been found to lie between 600 and 1200. The decay of PGA with distance is found to be compatible with Niazi and Bozorgnia's [Niazi, M., Bozorgnia, Y., 1992. The 1990 Manjil, Iran earthquake: geology and seismological overview, PGA attenuation and observed damage. Bull. Seism. Soc. Am. 82, 774-799] attenuation relation for the region.

  15. Real-time monitoring of the surface relief formation on azo-polymer films upon near-field excitation.

    PubMed

    Ambrosio, A; Camposeo, A; Maddalena, P; Patanè, S; Allegrini, M

    2008-02-01

    We use near-field optical microscopy to investigate the early state formation of photo-induced topographical structures on the free surface of azobenzene-containing polymers. The near-field technique is employed to monitor in real time the mass migration during the embossing of the surface of 50/50 copolymer films of polymethacrylate and polymethacrylate containing 3-methyl-4'-pentyloxy-azobenzene units. The dynamic of surface relief formation induced by light have been investigated as a function of the sample temperature. Furthermore, a formula derived from Navier-Stokes equations for classical laminar flow has been used to fit the mass displacement data during the embossing process. Excellent agreements between the experimental data and the fitting formula have been found for all the temperature considered.

  16. Near-field measurement of ZnS:Mn nanocrystal and bulk thin-film electroluminescent devices.

    PubMed

    Grmela, L; Macku, R; Tomanek, P

    2008-02-01

    A near-field study of the electro-optical phenomena and aging characteristics of nanostructured and bulk ZnS:Mn alternating-current thin-film electro-optical devices is presented. ZnS:Mn nanocrystals embedded in the glass matrices as well as ZnS:Mn thin-film phosphors contain four different concentrations of Mn (from 0.05 to 1.0 mol%). The activator impurity in the phosphor influences the spectral properties and, to a large extent, the temporal properties of optical emission and an aging process of the devices. Therefore, a local photoluminescence and electroluminescence investigation using a scanning near-field optical microscope technique is provided and the aging characteristics of ZnS:Mn nanocrystal structure also presented.

  17. Model coupling for predicting a developmental patterning process

    NASA Astrophysics Data System (ADS)

    Dhulekar, Nimit; Oztan, Basak; Yener, Bülent

    2016-03-01

    Physics-based-theoretical models have been used to predict developmental patterning processes such as branching morphogenesis for over half a century. While such techniques are quite successful in understanding the patterning processes in organs such as the lung and the kidney, they are unable to accurately model the processes in other organs such as the submandibular salivary gland. One possible reason is the detachment of these models from data that describe the underlying biological process. This hypothesis coupled with the increasing availability of high quality data has made discrete, data-driven models attractive alternatives. These models are based on extracting features from data to describe the patterns and their time evolving multivariate statistics. These discrete models have low computational complexity and comparable or better accuracy than the continuous models. This paper presents a case study for coupling continuous-physics-based and discrete-empirical-models to address the prediction of cleft formation during the early stages of branching morphogenesis in mouse submandibular salivary glands (SMG). Given a time-lapse movie of a growing SMG, first we build a descriptive model that captures the underlying biological process and quantifies this ground truth. Tissue-scale (global) morphological features are used to characterize the biological ground truth. Second, we formulate a predictive model using the level-set method that simulates branching morphogenesis. This model successfully predicts the topological evolution, however, it is blind to the cellular organization, and cell-to-cell interactions occurring inside a gland; information that is available in the image data. Our primary objective via this study is to couple the continuous level set model with a discrete graph theory model that captures the cellular organization but ignores the forces that determine the evolution of the gland surface, i.e. formation of clefts and buds. We compared the

  18. Wireless Communication with Nanoplasmonic Data Carriers: Macroscale Propagation of Nanophotonic Plasmon Polaritons Probed by Near-Field Nanoimaging.

    PubMed

    Cohen, Moshik; Abulafia, Yossi; Lev, Dmitry; Lewis, Aaron; Shavit, Reuven; Zalevsky, Zeev

    2017-09-13

    The ability to control the energy flow of light at the nanoscale is fundamental to modern communication and big-data technologies, as well as quantum information processing schemes. However, since photons are diffraction-limited, efforts of confining them to dimensions of integrated electronics have so far proven elusive. A promising way to facilitate nanoscale manipulation of light is through plasmon polaritons-coupled excitations of photons and charge carriers. These tightly confined hybrid waves can facilitate compression of optical functionalities to the nanoscale but suffer from huge propagation losses that limit their use to mostly subwavelength scale applications. With only weak evidence of macroscale plasmon polaritons, propagation has recently been reported theoretically and indirectly, no experiments so far have directly resolved long-range propagating optical plasmons in real space. Here, we launch and detect nanoscale optical signals, for record distances in a wireless link based on novel plasmonic nanotransceivers. We use a combination of scanning probe microscopies to provide high resolution real space images of the optical near fields and investigate their long-range propagation principles. We design our nanotransceivers based on a high-performance nanoantenna, Plantenna, hybridized with channel plasmon waveguides with a cross-section of 20 nm × 20 nm, and observe propagation for distances up to 1000 times greater than the plasmon wavelength. We experimentally show that our approach hugely outperforms both waveguide and wireless nanophotonic links. This successful alliance between Plantenna and plasmon waveguides paves the way for new generations of optical interconnects and expedites long-range interaction between quantum emitters and photomolecular devices.

  19. Parallel patterning of SiO2 wafer via near-field electrospinning of metallic salts and polymeric solution mixtures

    NASA Astrophysics Data System (ADS)

    Hu, Sanyuan; Li, Heping; Su, Zhen; Yan, Youwei

    2017-10-01

    This paper describes a near-field electrospinning technique combined with heat treatment process used to directly align parallel metal oxide and metal nitride fibers on silicon dioxide substrate. The effects of near-field electrospinning parameters (including collector-to-needle distance, applied voltage and the moving speed of the collector) on the morphology of the resulted fibers have been studied. Metallic salt-contained precursor fibers are individually aligned via near-field electrospinning of metallic salts and polymeric solution mixtures. After applying calcination process to these well aligned precursor fibers, patterning by metal oxide and metal nitride fibers such as ZnO, Ga2O3, TiO2, GaN and TiN is successfully obtained. The optical microscope images and the scanning electron microscopy show the presence of fiber patterns, whose crystalline structure is characterized by x-ray diffraction and Raman spectroscopy measurement. The results demonstrate the potential of this approach for assembling ceramic fibers into parallel arrays with controllable orientation and position.

  20. Parallel patterning of SiO2 wafer via near-field electrospinning of metallic salts and polymeric solution mixtures.

    PubMed

    Hu, Sanyuan; Li, Heping; Su, Zhen; Yan, Youwei

    2017-08-08

    This paper describes a near-field electrospinning technique combined with heat treatment process used to directly align parallel metal oxide and metal nitride fibers on silicon dioxide substrate. The effects of near-field electrospinning parameters (including collector-to-needle distance, applied voltage and the moving speed of the collector) on the morphology of the resulted fibers have been studied. Metallic salt-contained precursor fibers are individually aligned via near-field electrospinning of metallic salts and polymeric solution mixtures. After applying calcination process to these well aligned precursor fibers, patterning by metal oxide and metal nitride fibers such as ZnO, Ga2O3, TiO2, GaN and TiN is successfully obtained. The optical microscope images and the scanning electron microscopy show the presence of fiber patterns, whose crystalline structure is characterized by X-ray diffraction and Raman spectroscopy measurement. The results demonstrate the potential of this approach for assembling ceramic fibers into parallel arrays with controllable orientation and position. © 2017 IOP Publishing Ltd.