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Sample records for dtu-esa spherical near-field

  1. Recent Advances in Antenna Measurement Techniques at the DTU-ESA Spherical Near-Field Antenna Test Facility

    DEFF Research Database (Denmark)

    Breinbjerg, Olav; Pivnenko, Sergey; Kim, Oleksiy S.

    2014-01-01

    This paper reports recent antenna measurement projects and research at the DTU-ESA Spherical Near-Field Antenna Test Facility at the Technical University of Denmark. High-accuracy measurement projects for the SMOS, SENTINEL-1, and BIOMASS missions of the European Space Agency were driven...... by uncertainty requirements of a few hundredths of dB for the directivity and correspondingly strong requirements for gain and/or phase. Research and development of 1:3 bandwidth range probes, and the near-field to far-field transformation algorithm accounting for the higher-order azimuthal modes...

  2. Spherical near-field antenna measurements — The most accurate antenna measurement technique

    DEFF Research Database (Denmark)

    Breinbjerg, Olav

    2016-01-01

    The spherical near-field antenna measurement technique combines several advantages and generally constitutes the most accurate technique for experimental characterization of radiation from antennas. This paper/presentation discusses these advantages, briefly reviews the early history and present...... status, and addresses future challenges for spherical near-field antenna measurements; in particular, from the viewpoint of the DTU-ESA Spherical Near-Field Antenna Test Facility....

  3. Advanced spherical near-field antenna measurement techniques

    DEFF Research Database (Denmark)

    Nielsen, Jeppe Majlund; Pivnenko, Sergey; Breinbjerg, Olav

    2011-01-01

    The DTU-ESA facility has since the 1980es provided highly accurate antenna radiation pattern measurements and gain calibration by use of the probe corrected spherical nearfield technique, both for ESA (the European Space Agency) and other customers and continues to do so. Recent years activities...... and showing the capabilities of each participating facility. A special campaign was carried out with the aim of establishing a reference radiation pattern for the DTU-ESA VAST-12 antenna. The on-ground calibration of the MIRAS space radiometer for ESA's SMOS mission was carried out at the DTU-ESA facility...

  4. Advanced spherical near-field antenna measurement techniques

    DEFF Research Database (Denmark)

    Nielsen, Jeppe Majlund; Pivnenko, Sergey; Breinbjerg, Olav

    2011-01-01

    The DTU-ESA facility has since the 1980es provided highly accurate antenna radiation pattern measurements and gain calibration by use of the probe corrected spherical nearfield technique, both for ESA (the European Space Agency) and other customers and continues to do so. Recent years activities ...

  5. Spherical wave rotation in spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Wu, Jian; Larsen, Flemming Holm; Lemanczyk, J.

    1991-01-01

    The rotation of spherical waves in spherical near-field antenna measurement is discussed. Considering the many difficult but interesting features of the rotation coefficients, an efficient rotation scheme is derived. The main feature of the proposed scheme is to ignore the calculation of the very...

  6. Definition of accurate reference pattern for the DTU-ESA VAST12 antenna

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Breinbjerg, Olav; Burgos, Sara

    2009-01-01

    In this paper, the DTU-ESA 12 GHz validation standard (VAST12) antenna and a dedicated measurement campaign carried out in 2007-2008 for the definition of its accurate reference pattern are first described. Next, a comparison between the results from the three involved measurement facilities...

  7. The DTU-ESA Millimeter-Wave Validation Standard Antenna – Manufacturing and Testing

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Pivnenko, Sergey; Breinbjerg, Olav;

    2015-01-01

    A new precision tool for antenna test range qualification and inter-comparisons at mm-waves – the mm-VAST antenna – is under development at the Technical University of Denmark (DTU) in collaboration with TICRA under a European Space Agency (ESA) contract. The DTU-ESA mm-VAST antenna will facilitate...

  8. Wideband scalable probe for Spherical Near-Field Antenna measurements

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Pivnenko, Sergey; Breinbjerg, Olav

    2011-01-01

    The paper presents a design of an open-boundary quad-ridged horn to be used as a wideband scalable dual-linearly polarized probe for spherical near-field antenna measurements. With a new higher-order probe correction technique developed at the Technical University of Denmark, the probe will enabl...

  9. Directivity of Spherical Polyhedron Sound Source Used in Near-Field HRTF Measurements

    Institute of Scientific and Technical Information of China (English)

    YU Guang-Zheng; XIE Bo-Sun; RAO Dan

    2010-01-01

    @@ The omnidirectional character is one of important requirements for the sound source used in near-field headrelated transfer function(HRTF)measurements.Based on the analysis on the radiation sound pressure and directivity character of various spherical polyhedron sound sources,a spherical dodecahedral sound source with radius of 0.035 m is proposed and manufactured.Theoretical and measured results indicate that the sound source is approximately omnidirectional below the frequency of 8 kHz.In addition,the sound source has reasonable magnitude response from 350Hz to 20kHz and linear phase characteristics.Therefore.it is suitahle for the near-field HRTF measurements.

  10. Reduction of truncation errors in partial spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Cano Facila, Francisco J.

    2010-01-01

    In this report, a new and effective method for reduction of truncation errors in partial spherical near-field (SNF) antenna measurements is proposed. This method is based on the Gerchberg-Papoulis algorithm used to extrapolate functions and it is able to extend the valid region of the far...

  11. Double phi-Step theta-Scanning Technique for Spherical Near-Field Antenna Measurements

    DEFF Research Database (Denmark)

    Laitinen, Tommi

    2008-01-01

    Probe-corrected spherical near-field antenna measurements with an arbitrary probe set certain requirements on an applicable scanning technique. The computational complexity of the general high-order probe correction technique for an arbitrary probe, that is based on the Phi scanning, is O(N4), wh...

  12. Suppression of reflections by directive probes in spherical near-field measurements

    DEFF Research Database (Denmark)

    Hansen, Per Christian; Larsen, Flemming H.

    1984-01-01

    The influence of probe correction in spherical near-field measurements on signals from outside the test volume is investigated theoretically and experimentally. It is found that the suppression of reflections obtained by a directive probe is not disturbed by the probe correction. A geometric rela...

  13. Practical aspects of spherical near-field antenna measurements using a high-order probe

    DEFF Research Database (Denmark)

    Laitinen, Tommi; Pivnenko, Sergey; Nielsen, Jeppe Majlund

    2006-01-01

    Two practical aspects related to accurate antenna pattern characterization by probe-corrected spherical near-field antenna measurements with a high-order probe are examined. First, the requirements set by an arbitrary high-order probe on the scanning technique are pointed out. Secondly, a channel...... balance calibration procedure for a high-order dual-port probe with non-identical ports is presented, and the requirements set by this procedure for the probe are discussed....

  14. Aspects of probe correction for odd-order probes in spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Laitinen, Tommi; Pivnenko, Sergey N.; Breinbjerg, Olav

    2004-01-01

    Probe correction aspects for the spherical near-field antenna measurements are investigated. First, the spherical mode analyses of the radiated fields of several antennas are performed. It is shown that many common antennas are essentially so-called odd-order antennas. Second, the errors caused...... by the use of the first-order probe correction [1] for a rectangular waveguide probe, that is an odd-order antenna, are demonstrated. Third, a recently developed probe correction technique for odd-order probes is applied for the rectangular waveguide probe and shown to provide accurate results....

  15. Acceleration of near-field scattering from an inhomogeneous spherical shell

    Indian Academy of Sciences (India)

    M D Sharma

    2005-08-01

    The three dimensional scattering of near-field, from a point source, is studied for acceleration in the time domain. The perturbation method is applied to define the acceleration for the first order scattering from a weak inhomogeneity in a homogeneous surrounding. A body force, arising from the interaction between the primary waves and the inhomogeneity, acts as the source generating the scattered motion. The acceleration of scattered waves is related to the velocity and density fluctuations of the inhomogeneity. No restrictions are placed on the inhomogeneity size or locations of the source and receiver. Decoupling of scattered motion enables the identification of different phases. Integral expressions are derived for the scattering acceleration due to the incidence of near-field wave (from an impulsive point force) at a radially inhomogeneous volume element. These integrals are solved further for scattering from an inhomogeneous spherical shell. The accelerations for back scattering are obtained as a special case. These accelerations are simple analytically solvable expressions in closed form. Only spherical asymmetry of wave velocity inhomogeneity can affect the scattered acceleration. Scattered acceleration is affected by the gradient of wave velocity inhomogeneity. The back scattering of near-field from a spherical shell, is independent of radial inhomogeneity of wave velocity. Inhomogeneity with smoothly perturbed wave velocity does not back-scatter any acceleration. Accelerations are computed numerically for scattering from a part of inhomogeneous spherical shell. Hypothetical models are considered to study the effects of the distances of spherical shell from source, receiver, its thickness and its position relative to the direction of impulsive force.

  16. A First/Third-Order Probe Correction Technique for Spherical Near-Field Antenna Measurements Using Three Probe Orientations

    DEFF Research Database (Denmark)

    Laitinen, Tommi; Breinbjerg, Olav

    2008-01-01

    A probe correction technique is described for spherical near-field antenna measurements based on sampling the near field for three probe orientations in each measurement direction. The technique applies to odd-order probes whose radiated field contains (significant) power only in the first (µ=±1)...

  17. Errors of first-order probe correction for higher-order probes in spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Laitinen, Tommi; Nielsen, Jeppe Majlund; Pivnenko, Sergiy

    2004-01-01

    An investigation is performed to study the error of the far-field pattern determined from a spherical near-field antenna measurement in the case where a first-order (mu=+-1) probe correction scheme is applied to the near-field signal measured by a higher-order probe....

  18. Reduction of Truncation Errors in Planar, Cylindrical, and Partial Spherical Near-Field Antenna Measurements

    Directory of Open Access Journals (Sweden)

    Francisco José Cano-Fácila

    2012-01-01

    Full Text Available A method to reduce truncation errors in near-field antenna measurements is presented. The method is based on the Gerchberg-Papoulis iterative algorithm used to extrapolate band-limited functions and it is able to extend the valid region of the calculated far-field pattern up to the whole forward hemisphere. The extension of the valid region is achieved by the iterative application of a transformation between two different domains. After each transformation, a filtering process that is based on known information at each domain is applied. The first domain is the spectral domain in which the plane wave spectrum (PWS is reliable only within a known region. The second domain is the field distribution over the antenna under test (AUT plane in which the desired field is assumed to be concentrated on the antenna aperture. The method can be applied to any scanning geometry, but in this paper, only the planar, cylindrical, and partial spherical near-field measurements are considered. Several simulation and measurement examples are presented to verify the effectiveness of the method.

  19. Experimental study of the mapping relationship based near-field acoustic holography with spherical fundamental solutions

    Science.gov (United States)

    Wu, Haijun; Jiang, Weikang

    2017-04-01

    This paper is a consequent work of the previously proposed mapping relationship based near-field acoustic holography (MRS-based NAH), [H.J.Wu W.K. Jiang and H.B. Zhang, JSV, 373:66-88, 2016]. It is devoted to the performance study of its practical application with error analysis and experimental validation. Two types of errors, the truncation errors due to the limited number of participant modes, and the inevitable measurement errors caused by uncertainties in the experiment, are considered in the analysis. The influences of the errors on the performance of MRS-based NAH are systematically investigated. First of all, expression of the relative reconstruction error of the pressure energy is derived based on the two types of errors. An approach is developed to estimate the lower and upper bounds of the relative error. It gives a guide to predict the error for a reconstruction under the condition that the truncation error and the signal-to-noise ratio are given. Then, the condition number of the inverse operator is investigated to measure the sensitivity of the reconstruction to the input errors. Asymptotic expressions of the condition number for a special case, conformal spherical model and hologram, are obtained, which indicates the condition number has a geometric growth with the number of participant modes. Numerical examples with different kinds of errors are elaborately designed to validate the stability as well as the correctness of the error analysis. At last, the MRS-based NAH is further examined and verified by a physical experiment, a vibrating cubic model reconstructed from measurement on a spherical hologram. A satisfied agreement with the directly measured pressure on a validation surface is observed for both quantity and distribution of the reconstructed pressure.

  20. Spatial distribution of the internal and near-field intensities of large cylindrical and spherical scatterers

    Science.gov (United States)

    Benincasa, Daniel S.; Barber, Peter W.; Zhang, Jian-Zhi; Hsieh, Wen-Feng; Chang, Richard K.

    1987-04-01

    Spatial distributions of the near-field and internal electromagnetic intensities have been calculated and experimentally observed for dielectric cylinders and spheres which are large relative to the incident wavelength. Two prominent features of the calculated results are the high intensity peaks which exist in both the internal and near fields of these objects, even for nonresonant conditions, and the well-defined shadow behind the objects. Such intensity distributions were confirmed by using the fluorescence from iodine vapor to image the near-field intensity distribution and the fluorescence from ethanol droplets impregnated with rhodamine 590 to image the internal-intensity distribution.

  1. Comparison of Antenna Measurement Facilities with the DTU-ESA 12 GHz Validation Standard Antenna within the EU Antenna Centre of Excellence

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Pallesen, Janus Engberg; Breinbjerg, Olav

    2009-01-01

    The primary objective of many antenna measurement facilities is to provide a specified high accuracy of the measured data. The validation of an antenna measurement facility is the process of proving that such a specified accuracy can be achieved. Since this constitutes a very challenging task......, antenna measurement accuracy has been the subject of much research over many years and a range of useful measures have been introduced. Facility comparisons, together with antenna standards, error budgets, facility accreditations, and measurement procedure standards, constitute an effective measure...... towards facility validations. This paper documents the results of a comparison between 8 European antenna measurement facilities with a specially designed reference antenna, the DTU-ESA 12 GHz Validation Standard Antenna (VAST-12). The electrical and mechanical properties of the VAST-12 antenna...

  2. Sensitivities of various probe correction techniques to noise and inaccurate channel balance in spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Laitinen, Tommi; Pivnenko, Sergey; Breinbjerg, Olav

    2005-01-01

    Sensitivities of various probe correction techniques to noise and inaccurate channel balance in the spherical near-field antenna measurements are investigated. The simulation results show the level of uncertainty in the determination of the directivity of an antenna in the presence of -60 dB noise......, and as a function of the level of error in the channel balance for the different probe correction techniques....

  3. Reduction of truncation errors in planar, cylindrical, and partial spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Cano-Fácila, Francisco José; Pivnenko, Sergey; Sierra-Castaner, Manuel

    2012-01-01

    A method to reduce truncation errors in near-field antenna measurements is presented. The method is based on the Gerchberg-Papoulis iterative algorithm used to extrapolate band-limited functions and it is able to extend the valid region of the calculatedfar-field pattern up to the whole forward...

  4. Superdirective narrowband first-order probe versus wideband higher-order probe for spherical near-field antenna measurements at P-band

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Kim, Oleksiy S.; Breinbjerg, Olav

    2013-01-01

    A comparative study of the wideband 400-1200 MHz higher-order probe and the narrowband 431 MHz first-order probe, in terms of their advantages and disadvantages for spherical near-field antenna measurements at P-band, is presented. The comparison is based on the experimental data and focused...

  5. On the truncation of the azimuthal mode spectrum of high-order probes in probe-corrected spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Laitinen, Tommi

    2011-01-01

    Azimuthal mode (m mode) truncation of a high-order probe pattern in probe-corrected spherical near-field antenna measurements is studied in this paper. The results of this paper provide rules for appropriate and sufficient m-mode truncation for non-ideal first-order probes and odd-order probes wi...

  6. Design and experimental verification of near-field Ka-band probe based on wideband OMJ with minimum higher-order spherical mode content

    DEFF Research Database (Denmark)

    Foged, L. J.; Giacomini, A.; Morbidini, R;

    2012-01-01

    A desired feature of modern field probes is that the useable bandwidth should exceed that of the Antenna Under Test (AUT) [1]. Recent developments in probe and orthomode junctions (OMJ) technology has shown that bandwidths of up to 4:1 are achievable [2-5]. The probes are based on inverted ridge...... technology capable of maintaining the same high performance standards of traditional probes However, in typical Spherical Near Field (SNF) measurement scenarios, the applicable frequency range of the single probe can also be limited by the content of μ≠1 spherical modes in the probe pattern [6...

  7. Near-field investigation of the explosive dispersal of radioactive material based on a reconstructed spherical blast-wave flow.

    Science.gov (United States)

    Hummel, David; Ivan, Lucian

    2017-03-15

    A "dirty bomb" is a type of radiological dispersal device (RDD) that has been the subject of significant safety and security concerns given the disruption that would result from a postulated terrorist attack. Assessing the risks of radioactive dose in a hypothetical scenario requires models that can accurately predict dispersion in a realistic environment. Modelling a RDD is complicated by the fact that the most important phenomena occur over vastly disparate spatial and temporal length scales. Particulate dispersion in the air is generally considered on scales of hundreds to thousands of meters, and over periods of minutes and hours. Dispersion models are extremely sensitive, however, to the particle size and source characterization, which are determined in distances measured in micrometers to meters, over milliseconds or less. This study examines the extent to which the explosive blast determines the transport of contaminant particles relative to the atmospheric wind over distances relevant to "near-field" dispersion problems (i.e., hundreds of meters), which are relevant to urban environments. Our results indicate that whether or not the effect of the blast should be included in a near-field dispersion model is largely dependent on the size of the contaminant particle. Relatively large particles (i.e., >40 μm in diameter), which are most likely to be produced by a RDD, penetrate the leading shock front, thereby avoiding the reverse blast wind. Consequently, they travel much farther than suspended aerosols (<10 μm) before approaching the ambient wind velocity. This suggests that, for these "near-field" dispersion problems in urban environments, the transport of contaminants from the blast wave may be integral to accurately predicting their dispersion.

  8. Comparison of the FFT/matrix inversion and system matrix techniques for higher-order probe correction in spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Nielsen, Jeppe Majlund; Breinbjerg, Olav

    2011-01-01

    Two higher-order probe-correction techniques for spherical near-field antenna measurements are compared in details for the accuracy they provide and their computational cost. The investigated techniques are the FFT/matrix inversion and the system matrix inversion. Each of these techniques allows...... and a higher-order probe....... correction of general high-order probes, including non-symmetric dual-polarized antennas with independent ports. The investigation was carried out by processing with each technique the same measurement data for a challenging case with an antenna under test significantly offset from the center of rotation...

  9. Superdirective Magnetic Dipole Array as a First-Order Probe for Spherical Near-Field Antenna Measurements

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Pivnenko, Sergey; Breinbjerg, Olav

    2012-01-01

    The theory as well as numerical and experimental results are presented for a superdirective array composed of closely spaced electrically small resonant magnetic dipole elements. The array operates on a metal ground plane and can exhibit a maximum directivity of 11.5 dBi, 15.2 dBi, and 17.8 d......Bi (including 3 dB due to the ground plane), for 2, 3, and 4 magnetic dipoles, respectively. The array is self-resonant and is directly excited by a 50-ohm coaxial cable through the ground plane. The array radiates essentially the $\\vert\\mu\\vert=1$ spherical modes, which, despite a narrow bandwidth, makes...

  10. Experimental Testing of Nonredundant Near-Field to Far-Field Transformations with Spherical Scanning Using Flexible Modellings for Nonvolumetric Antennas

    Directory of Open Access Journals (Sweden)

    Francesco D'Agostino

    2013-01-01

    Full Text Available This paper deals with the experimental testing of effective probe compensated near-field-far-field (NF-FF transformations with spherical scanning requiring a minimum number of NF data. They rely on nonredundant sampling representations of the voltage measured by the probe, based on very flexible source modellings suitable for nonvolumetric antennas characterized by two dimensions very different from the other one. In particular, a cylinder ended in two half-spheres is adopted for modelling long antennas, whereas the quasi-planar ones are considered as enclosed in a rotational surface formed by two circular “bowls” having the same aperture diameter, but eventually different bending radii. The NF data needed to perform the classical spherical NF-FF transformation are then accurately and efficiently retrieved from the acquired nonredundant ones via optimal sampling interpolation formulas. A remarkable reduction of the number of the required NF data and, as a consequence, a significant measurement time saving can be so obtained. The experimental tests have been carried out at Antenna Characterization Lab of the University of Salerno and both the NF and FF reconstructions are resulted to be very good, thus confirming the accuracy and reliability of these NF-FF transformations from the experimental viewpoint too.

  11. Near Field Communication

    National Research Council Canada - National Science Library

    Nagashree R N; Vibha Rao; Aswini N

    2014-01-01

    Near Field Communication (NFC), an emerging short-range wireless point to point interconnection technology, with the combination of handheld electronic device has become a potential tool for the two devices to exchange various...

  12. Near Field Communication

    Directory of Open Access Journals (Sweden)

    Nagashree R N

    2014-03-01

    Full Text Available Near Field Communication (NFC, an emerging short-range wireless point to point interconnection technology, with the combination of handheld electronic device has become a potential tool for the two devices to exchange various information when in close range. NFC unites various standards and proprietary technologies. This paper presents a brief introduction about the NFC and various applications and security issues.

  13. Near Field Communication

    OpenAIRE

    Nagashree R N; Vibha Rao; Aswini N

    2014-01-01

    Near Field Communication (NFC), an emerging short-range wireless point to point interconnection technology, with the combination of handheld electronic device has become a potential tool for the two devices to exchange various information when in close range. NFC unites various standards and proprietary technologies. This paper presents a brief introduction about the NFC and various applications and security issues.

  14. Securing Near Field Communication

    OpenAIRE

    Kortvedt, Henning Siitonen

    2009-01-01

    Near Field Communication (NFC) specifies a standard for a wireless communication protocol enabling data transfer by keeping two devices close together, about 10 cm maximum. NFC is designed for integration with mobile phones, which can communicate with other NFC phones (peer-to-peer) or read information on tags and cards (reader). An NFC device can also be put in card emulation mode, to offer compatibility with other contactless smart card standards. This enables NFC devices to replace traditi...

  15. The Near Field Refractor

    CERN Document Server

    Gutierrez, Cristian E

    2013-01-01

    We present an abstract method in the setting of compact metric spaces which is applied to solve a number of problems in geometric optics. In particular, we solve the one source near field refraction problem. That is, we construct surfaces separating two homogenous media with different refractive indices that refract radiation emanating from the origin into a target domain contained in an n-1 dimensional hypersurface. The input and output energy are prescribed. This implies the existence of lenses focusing radiation in a prescribed manner.

  16. Near field communications handbook

    CERN Document Server

    Ahson, Syed A; Furht, Borko

    2011-01-01

    Near Field Communication, or NFC, is a short-range high frequency wireless communication technology that enables the exchange of data between devices over about a decimeter. The technology is a simple extension of the ISO 14443 proximity-card standard (contact less card, RFID) that combines the interface of a smart card and a reader into a single device with practical implications. A complete reference for NFC, this handbook provides technical information about all aspects of NFC, as well as applications. It covers basic concepts as well as research grade material and includes a discussion of

  17. Diagnostics of the BIOMASS feed array prototype

    DEFF Research Database (Denmark)

    Cappellin, Cecilia; Pivnenko, Sergey; Pontoppidan, Kennie Nybo

    2013-01-01

    The 3D reconstruction algorithm is applied to the prototype feed array of the BIOMASS synthetic aperture radar, recently measured at the DTU-ESA Spherical Near-Field Antenna Test Facility in Denmark. Careful analysis of the measured feed array data has shown that the test support structure...

  18. Calibration of the DH6500-MG02 and DH6500-MG03 antennas

    DEFF Research Database (Denmark)

    Nielsen, Jeppe Majlund; Pivnenko, Sergey

    frequencies. For the DH6500-MG03 horn the measurement comprises on-axis gain, and on-axis polarization at 601 frequencies. For both horns, the input reection coecient was measured at 601 frequencies. The measurement was carried out at the DTU-ESA Spherical Near-Field Antenna Test Facility in April 2013...

  19. An Accurate and Efficient Design Tool for Large Contoured Beam Reflectarrays

    DEFF Research Database (Denmark)

    Zhou, Min; Sørensen, Stig B.; Jørgensen, Erik;

    2012-01-01

    illuminations. Two offset contoured beam reflectarrays that radiate a highgain beam on an European coverage have been designed, manufactured, and measured at the DTU-ESA Spherical Near-Field Antenna Test Facility. An excellent agreement is obtained for the simulated and measured patterns. To show the design...

  20. Near-field Optical Microscopy

    NARCIS (Netherlands)

    Ruiter, A.G.T.

    1997-01-01

    Near-field scanning optical microscopy (NSOM) is one of the most recent scanning probe techniques. In this technique, an optical probe is brought in the vicinity of the sample surface, in the near-field zone. The microscope can either work in illumination mode, in which the probe consists of a

  1. Near-field Optical Microscopy

    NARCIS (Netherlands)

    Ruiter, Anthonius Gerardus Theodorus

    1997-01-01

    Near-field scanning optical microscopy (NSOM) is one of the most recent scanning probe techniques. In this technique, an optical probe is brought in the vicinity of the sample surface, in the near-field zone. The microscope can either work in illumination mode, in which the probe consists of a sub-w

  2. Optical Near-Field Plates

    Science.gov (United States)

    2015-04-08

    color filtering and spectral imaging ,” Nat. Comm. 1, 59 (2010). 3. H.-F. Shi and L. J. Guo, “Design of Plasmonic Near Field Plate at Opitical...AFRL-OSR-VA-TR-2015-0085 OPTICAL NEAR-FILED PLATES Roberto Merlin UNIVERSITY OF MICHIGAN Final Report 04/08/2015 DISTRIBUTION A: Distribution...03-2015 Final 09/01/2009-12/31/2014 Optical Near-Field Plates FA9550-09-1-0636 erlin, Roberto, D. The University of Michigan Ann Arbor, MI 48109

  3. Heterodyne Near-Field Scattering

    CERN Document Server

    Brogioli, D; Giglio, M; Giglio, Marzio

    2002-01-01

    We describe an optical technique based on the statistical analysis of the random intensity distribution due to the interference of the near-field scattered light with the strong transmitted beam. It is shown that, from the study of the two-dimensional power spectrum of the intensity, one derives the scattered intensity as a function of the scattering wave vector. Near-field conditions are specified and discussed. The substantial advantages over traditional scattering technique are pointed out, and is indicated that the technique could be of interest for wave lengths other than visible light.

  4. Near-field light scattering by parallel glass fibers

    Science.gov (United States)

    Benincasa, Daniel S.; Tsuei, Tak-Goa; Barber, Peter W.

    1987-09-01

    Single glass fibers whose radius-to-wavelength ratio is large, for example, r/λ=100, strongly focus normally incident laser light to give greatly enhanced intensities both within and in the near field of the fiber, even when the fiber is not at resonance. Calculated results show that the enhancement is dependent on the radius-to-wavelength ratio and on the fiber index of refraction. Even greater enhancements are observed for spherical particles. The near-field intensity for a single fiber is greatly modified when a second fiber is moved into its near field. Calculations of the near-field intensities for two coupled fibers provide insight into the coupling mechanism, especially the dependence of the coupling on the fiber separation and on the orientation of the two fibers relative to the incident wave.

  5. Near field optics and nanoscopy

    CERN Document Server

    Fillard, J P

    1996-01-01

    This book contains the most recent information on optical nanoscopy. Far-Field and Near-Field properties on e.m. waves are presented which illustrate how optical images can be obtained from sub-micron objects. Scanning Probe techniques and computer processing are covered here. An explanation is given on how propagating photons or evanescent waves can behave over distances shorter than the wavelength, taking into account the presence of small objects. Quantum tunneling of photons is explained comparatively with the electron mechanism. Technical details are given on photon tunneling microscopes.

  6. Nanomanipulation using near field photonics.

    Science.gov (United States)

    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.

  7. Near-field single molecule spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    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.

  8. Chiral near fields generated from plasmonic lattices

    CERN Document Server

    Canaguier-Durand, Antoine

    2014-01-01

    Plasmonic fields are usually considered non-chiral because of the transverse magnetic polarization of surface plasmon modes. We however show here that plasmonic lattices built from coherent superpositions of surface plasmons can generate optical chirality in the interfering near field. We reveal in particular the emergence of plasmonic potentials relevant to the generation of near-field chiral forces. This draws promising perspectives for performing enantiomeric separation schemes within the near field.

  9. Array antenna diagnostics with the 3D reconstruction algorithm

    DEFF Research Database (Denmark)

    Cappellin, Cecilia; Meincke, Peter; Pivnenko, Sergey;

    2012-01-01

    The 3D reconstruction algorithm is applied to a slotted waveguide array measured at the DTU-ESA Spherical Near-Field Antenna Test Facility. One slot of the array is covered by conductive tape and an error is present in the array excitation. Results show the accuracy obtainable by the 3D...... reconstruction algorithm. Considerations on the measurement sampling, the obtainable spatial resolution, and the possibility of taking full advantage of the reconstruction geometry are provided....

  10. Electromagnetic measurements in the near field

    CERN Document Server

    Bienkowski, Pawel

    2012-01-01

    This book is devoted to the specific problems of electromagnetic field (EMF) measurements in the near field and to the analysis of the main factors which impede accuracy in these measurements. It focuses on careful and accurate design of systems to measure in the near field based on a thorough understanding of the fundamental engineering principles and on an analysis of the likely system errors. Beginning with a short introduction to electromagnetic fields with an emphasis on the near field, it them presents methods of EMF measurements in near field conditions. It details the factors limiting

  11. Near Field Communication: Introduction and Implications

    Science.gov (United States)

    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,…

  12. Antenna Diagnostics using Near Field Techniques

    NARCIS (Netherlands)

    Paquay, M.H.A.

    1996-01-01

    The radiation characteristics of an antenna are fully determined by its aperture distribution. Measured Near Field data gives an impression but this is not good enough to detect small anomalies. For good antenna diagnostics, the field at the aperture plane is required. The Near Field Measurement Tec

  13. Attosecond nanoscale near-field sampling

    Science.gov (United States)

    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

  14. The Survey on Near Field Communication

    National Research Council Canada - National Science Library

    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...

  15. Ideal near-field thermophotovoltaic cells

    CERN Document Server

    Molesky, Sean

    2015-01-01

    We ask the question, what are the ideal characteristics of a near-field thermophotovoltaic cell? Our search leads us to a reexamination of near-field photonic heat transfer in terms of the joint density of electronic states. This form reveals that the presence of matched van Hove singularities resulting from quantum-confinement in the emitter and converter of a thermophotovoltaic cell boosts both the magnitude and spectral selectivity of photonic heat transfer; dramatically improving energy conversion efficiency. We provide a model near-field thermophotovoltaic design making use of this idea by employing the van Hove singularities present in carbon nanotubes. Shockely 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, carbon nanotubes and two-dimensional materials as future materials for thermophotovoltaic near-field energy conversion devices.

  16. Sampling Criterion for EMC Near Field Measurements

    DEFF Research Database (Denmark)

    Franek, Ondrej; Sørensen, Morten; Ebert, Hans;

    2012-01-01

    An alternative, quasi-empirical sampling criterion for EMC near field measurements intended for close coupling investigations is proposed. The criterion is based on maximum error caused by sub-optimal sampling of near fields in the vicinity of an elementary dipole, which is suggested as a worst......-case representative of a signal trace on a typical printed circuit board. It has been found that the sampling density derived in this way is in fact very similar to that given by the antenna near field sampling theorem, if an error less than 1 dB is required. The principal advantage of the proposed formulation is its...... parametrization with respect to the desired maximum error in measurements. This allows the engineer performing the near field scan to choose a suitable compromise between accuracy and measurement time....

  17. The near-field acoustic levitation of high-mass rotors.

    Science.gov (United States)

    Hong, Z Y; Lü, P; Geng, D L; Zhai, W; Yan, N; Wei, B

    2014-10-01

    Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope.

  18. The near-field acoustic levitation of high-mass rotors

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Z. Y.; Lü, P.; Geng, D. L.; Zhai, W.; Yan, N.; Wei, B., E-mail: bbwei@nwpu.edu.cn [Department of Applied Physics, Northwestern Polytechnical University, Xi' an 710072 (China)

    2014-10-15

    Here we demonstrate that spherical rotors with 40 mm diameter and 0-1 kg mass can be suspended more than tens of micrometers away from an ultrasonically vibrating concave surface by near-field acoustic radiation force. Their rotating speeds exceed 3000 rpm. An acoustic model has been developed to evaluate the near-field acoustic radiation force and the resonant frequencies of levitation system. This technique has potential application in developing acoustic gyroscope.

  19. Attosecond nanoscale near-field sampling

    CERN Document Server

    Förg, Benjamin; Suessmann, Frederik; Foerster, Michael; Krueger, Michael; Ahn, Byung-Nam; Wintersperger, Karen; Zherebtsov, Sergey; Guggenmos, Alexander; Pervak, Vladimir; Kessel, Alexander; Trushin, Sergei; Azzeer, Abdallah; Stockman, Mark; Kim, Dong-Eon; Krausz, Ferenc; Hommelhoff, Peter; Kling, Matthias

    2015-01-01

    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 nearfields from light interaction with nanostructures with sub cycle resolution. Here, we experimentally demonstrate attosecond nearfield retrieval with a gold nanotip using streaking spectroscopy. By comparison of the results from gold nanotips to those obtained for a noble gas, the spectral response of the nanotip near field arising from laser excitation can be extracted. Monte Carlo MC trajectory simulations in near fields obtained with the macroscopic Maxwells equations elucidate the streaking mechanism on the nanoscale.

  20. Near-Field Enhanced Negative Luminescent Refrigeration

    Science.gov (United States)

    Chen, Kaifeng; Santhanam, Parthiban; Fan, Shanhui

    2016-08-01

    We consider a near-field enhanced negative luminescent refrigeration system made of a polar material supporting surface-phonon polariton resonances and a narrow-band-gap semiconductor under a reverse bias. We show that in the near-field regime, such a device yields significant cooling power density and a high efficiency close to the Carnot limit. In addition, the performance of our system still persists even in the presence of strong nonidealities such as Auger recombination and sub-band-gap thermal radiation from free carriers.

  1. Near-field optical thin microcavity theory

    Science.gov (United States)

    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.

  2. Antenna Near-Field Probe Station Scanner

    Science.gov (United States)

    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.

  3. Sampling Criterion for EMC Near Field Measurements

    DEFF Research Database (Denmark)

    Franek, Ondrej; Sørensen, Morten; Ebert, Hans

    2012-01-01

    -case representative of a signal trace on a typical printed circuit board. It has been found that the sampling density derived in this way is in fact very similar to that given by the antenna near field sampling theorem, if an error less than 1 dB is required. The principal advantage of the proposed formulation is its...

  4. Computational lens for the near field

    DEFF Research Database (Denmark)

    Carney, P. Scott; Franzin, Richard A.; Bozhevolnyi, Sergey I.;

    2004-01-01

    A method is presented to reconstruct the structure of a scattering object from data acquired with a photon scanning tunneling microscope . The data may be understood to form a Gabor type near-field hologram and are obtained at a distance from the sample where the field is defocused and normally u...

  5. Structural Design of the DTU-ESA MM-Wave Validation Standard Antenna

    DEFF Research Database (Denmark)

    Branner, Kim; Berring, Peter; Markussen, Christen Malte;

    2015-01-01

    A new specially designed antenna to be used for inter-comparisons and validation of antenna test facilities is under development in cooperation between DTU and TICRA under a contract from the European Space Agency. The antenna is designed to be extremely thermally and mechanically stable in the r...... to verify that they can be met. The paper also discusses the challenges of integrating an aluminum feed cluster with high thermal expansion coefficient in a CFRP support frame with very low thermal expansion coefficient.......A new specially designed antenna to be used for inter-comparisons and validation of antenna test facilities is under development in cooperation between DTU and TICRA under a contract from the European Space Agency. The antenna is designed to be extremely thermally and mechanically stable...

  6. DTU-ESA millimeter-wave VAlidation STandard antenna (mm-VAST) - detailed design

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Pivnenko, Sergey; Breinbjerg, Olav;

    2015-01-01

    A design of a well-characterized, mechanically and thermally stable multi-frequency VAlidation STandard antenna for mm-wave frequencies (mm-VAST) developed in an ESA project is presented. The antenna will facilitate inter-comparison and validation of antenna measurement ranges at K/Ka and Q/V bands...... in response to on-going deployment of satellite communication services at 20/30 GHz (K/Ka-band) as well as future commercial use of the 40/50 GHz bands (Q/V-band)....

  7. DTU-ESA millimeter-wave validation standard antenna – requirements and design

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Kim, Oleksiy S.; Breinbjerg, Olav;

    2014-01-01

    stability over a given operational temperature range. In addition, VAST antennas must possess electrical characteristics that are typical for satellite antennas and challenging to measure. A multi-band millimeter-wave VAST (mm-VAST) antenna for the K/Ka-bands and Q/V bands is currently under development......Inter-comparisons and validations of antenna measurement ranges are useful tools allowing the detection of various problems in the measurement procedures, thus leading to improvements of the measurement accuracy and facilitating better understanding of the measurement techniques. The maximum value...... from a validation campaign is achieved when a dedicated Validation Standard (VAST) antenna specifically designed for this purpose is available. The driving requirements to VAST antennas are their mechanical stability with respect to any orientation of the antenna in the gravity field and thermal...

  8. DTU-ESA millimeter-wave validation standard antenna (mm-vast) – performance verification

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Kim, Oleksiy S.; Breinbjerg, Olav;

    2015-01-01

    A new multi-frequency Validation Standard (VAST) antenna covering upper microwave (K/Ka) and millimeter wave (Q/V) bands, and thus called mmVAST, was developed in cooperation between DTU and TICRA under contract from the European Space Agency. In this paper, the mechanical and electrical requirem......A new multi-frequency Validation Standard (VAST) antenna covering upper microwave (K/Ka) and millimeter wave (Q/V) bands, and thus called mmVAST, was developed in cooperation between DTU and TICRA under contract from the European Space Agency. In this paper, the mechanical and electrical...... requirements as well as the design and manufacturing of the mm-VAST antenna are briefly presented. The focus is then given to the details of conducted mechanical and electrical tests aimed at verifying the performance of the manufactured antenna and to the obtained measurement results....

  9. Near-Field/Far-Field Transformation with Helicoidal Scanning from Irregularly Spaced Data

    Directory of Open Access Journals (Sweden)

    Francesco D'Agostino

    2010-01-01

    Full Text Available A fast and accurate technique for the compensation of the probe positioning errors in the near-field/far-field transformation with helicoidal scanning is proposed in this paper. It relies on a nonredundant sampling representation using a spherical modelling of the antenna under test and employs an iterative scheme to evaluate the near-field data at the points fixed by the helicoidal nonredundant representation from the acquired irregularly distributed ones. Once these helicoidal data have been recovered, those required by a classical cylindrical near-field/far-field transformation are efficiently determined by using an optimal sampling interpolation algorithm. Some numerical tests assessing the effectiveness of the proposed approach and its stability with respect to random errors affecting the near-field data are shown.

  10. Review of near-field optical microscopy

    Institute of Scientific and Technical Information of China (English)

    WU Shi-fa

    2006-01-01

    This review has introduced a new near-field optical microscope (NOM)-atomic force microscope combined with photon scanning tunneling microscope (AF/PSTM).During scanning,AF/PSTM could get two optical images of refractive index image and transmissivity image,and two AFM images of topography image and phase image.A reflected near-field optical microscope (AF/RSNOM) has also been developed on AF/PSTM platform.The NOM has been reviewed in this paper and the comparison between AF/PSTM & RSNOM and the commercial A-SNOM & RNOM has also been discussed.The functions of AF/PSTM & RSNOM are much better than A-SNOM & RNOM.

  11. Near-field thermal electromagnetic transport

    CERN Document Server

    Edalatpour, Sheila

    2015-01-01

    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 into 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 exchanging thermal radiation, 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. The forma...

  12. A near-field optical microscopy nanoarray

    Energy Technology Data Exchange (ETDEWEB)

    Semin, D.J.; Ambrose, W.P.; Goodwin, P.M.; Kwller, A. [Los Alamos National Lab., NM (United States); Wendt, J.R. [Sandia National Labs., Albuquerque, NM (United States)

    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.

  13. Characterization of near-field optical probes

    DEFF Research Database (Denmark)

    Vohnsen, Brian; Bozhevolnyi, Sergey I.

    1999-01-01

    Radiation and collection characteristics of four different near-field optical-fiber probes, namely, three uncoated probes and an aluminium-coated small-aperture probe, are investigated and compared. Their radiation properties are characterized by observation of light-induced topography changes...... in a photo-sensitive film illuminated with the probes, and it is confirmed that the radiated optical field is unambigiously confined only for the coated probe. Near-field optical imaging of a standing evanescent-wave pattern is used to compare the detection characteristics of the probes, and it is concluded...... that, for the imaging of optical-field intensity distributions containing predominantly evanescent-wave components, a sharp uncoated tip is the probe of choice. Complementary results obtained with optical phase-conjugation experiments with he uncoated probes are discussed in relation to the probe...

  14. Mapping Nanoscale Electromagnetic Near-Field Distributions Using Optical Forces

    CERN Document Server

    Huang, Fei; Mardy, Zahra; Burdett, Jonathan; Wickramasinghe, H Kumar

    2014-01-01

    We demonstrate the application of Atomic Force Microscopy (AFM) based optical force microscopy to map the optical near-fields with nanometer resolution, limited only by the AFM probe geometry. We map the electric field distributions of tightly focused laser beams with different polarizations and show that the experimentally measured data agrees well with the theoretical predictions from a dipole-dipole interaction model, thereby validating our approach. We further validate the proposed technique by evaluating the optical electric field scattered by a spherical nanoparticle by measuring the optical forces between the nanoparticle and gold coated AFM probe. The technique allows for wavelength independent, background free, thermal noise limited mechanical imaging of optical phenomenon with sensitivity limited by AFM performance. Optical forces due to both electric and magnetic dipole-dipole interactions can be measured using this technique.

  15. Evaluation of near-field earthquake effects

    Energy Technology Data Exchange (ETDEWEB)

    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.

  16. Near-field radiofrequency electromagnetic exposure assessment.

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    2014-12-10

    near-field plates possible. A linear near-field plate is shown in Fig. 1, which can create a subwavelength line (1D) focus when excited by an...concentric annular slots on a circular grounded dielectric slab. The plate is excited through a coaxial cable and its rim is short circuited. The slots are...standard printed circuit board technology. The plates consist of concentric annular slots on a circular grounded dielectric slab excited through a coaxial

  18. The near-field scanning thermal microscope

    Science.gov (United States)

    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.

  19. Near-field characterization of plasmonic waveguides

    DEFF Research Database (Denmark)

    Zenin, Volodymyr

    2014-01-01

    This PhD thesis presents investigation of plasmonic waveguides and waveguiding components by means of scanning near-field optical microscopy characterizations, far-field optical observations, and numerical simulations. The plasmonic waveguiding attracts huge interest due to several reasons: 1...... simply by changing geometric parameters of the waveguide, keeping in mind the trade-off between confinement and propagation losses. A broad variety of plasmonic waveguides and waveguide components, including antennas for coupling the light in/out of the waveguide, requires correspondent characterization...

  20. Near Field Communication: Technology and Market Trends

    Directory of Open Access Journals (Sweden)

    Gabriella Arcese

    2014-09-01

    Full Text Available Among the different hi-tech content domains, the telecommunications industry is one of the most relevant, in particular for the Italian economy. Moreover, Near Field Communication (NFC represents an example of innovative production and a technological introduction in the telecommunications context. It has a threefold function: card emulator, peer-to-peer communication and digital content access, and it could be pervasively integrated in many different domains, especially in the mobile payment one. The increasing attention on NFC technology from the academic community has improved an analysis on the changes and the development perspective about mobile payments. It has considered the work done by the GSMA (Global System for Mobile Communications Association and the NFC Forum in recent years. This study starts from an analysis of the scientific contributions to Near Field Communication and how the main researches on this topic were conceived. Our focus is on the diffusion rates, the adoption rates and the technology life cycle. After that, we analyze the technical-economical elements of NFC. Finally, this work presents the state of art of the improvements to this technology with a deeper focus on NFC technologies applied to the tourism industry. In this way, we have done a case analysis that shows some of the NFC existent applications linked to each stage of the tourism value chain.

  1. Near Field Environment Process Model Report

    Energy Technology Data Exchange (ETDEWEB)

    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.

  2. Study on the near-field recording spot

    Science.gov (United States)

    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.

  3. Measurement of the Waveguide Near-field Optical Spot

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The characteristic of near-field spots is analyzed.The size of the near field and the heat response time of the hybrid record medium to overcome super paramagnetic effect are calculated based on 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,near-field optical lithography can be accomplished with the aid of atomic force microscope (AFM).The diameter of near-field recording spot can be obtained by specifically designed computer.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.

  4. Numerical Simulations of Blast Loads from Near-Field Ground Explosions in Air

    Science.gov (United States)

    Dobrociński, Stanisław; Flis, Leszek

    2015-12-01

    Numerical simulations of air blast loading in the near-field acting on the ground have been performed. A simplified blast model based on empirical blast loading data representing spherical and hemispherical explosive shapes has been simulated. Conwep is an implementation of the empirical blast models presented by Kingery and Bulmash, which is also implemented in the commercial code LS-DYNA based on work done by Rahnders-Pehrson and Bannister. This makes it possible to simulate blast loads acting on structures representing spherical and hemispherical explosive shapes of TNT with reasonable computational effort as an alternative to the SPH and Eulerian model. The CPU time for the simplified blast model is however considerably shorter and may still be useful in time consuming concept studies. Reasonable numerical results using reasonable model sizes can be achieved not only for modelling near-field explosions in air but most areas of geotechnical. Calculation was compared with blast SPH and Eulerian model.

  5. Effect of Sound Source Scattering on Measurement of Near-Field Head-Related Transfer Functions

    Institute of Scientific and Technical Information of China (English)

    YU Guang-Zheng; XIE Bo-Sun; RAO Dan

    2008-01-01

    @@ A simple spherical head and pulsating spherical sound source model are proposed to investigate the effect of multiple scattering between the head and the sound source on near-field head-related transfer function (HRTF) measurement. Multipole expansion method is used to calculate HRTFs of the model, then the relationships among the magnitude error of HRTF with frequency, source direction, source size, and the distance between the head centre and the sound source are analysed. The results show that to ensure the magnitude error of HRTF within 1.0 dB up to 20 kHz, for source distance not less than 0.15m or 0.20 m, the radius of the sound source should not exceed 0.03 m or 0.05 m, respectively. The conclusion suggests an appropriate size of sound source in near-field HRTF measurement.

  6. Numerical Simulations of Blast Loads from Near-Field Ground Explosions in Air

    Directory of Open Access Journals (Sweden)

    Dobrociński Stanisław

    2015-12-01

    Full Text Available Numerical simulations of air blast loading in the near-field acting on the ground have been performed. A simplified blast model based on empirical blast loading data representing spherical and hemispherical explosive shapes has been simulated. Conwep is an implementation of the empirical blast models presented by Kingery and Bulmash, which is also implemented in the commercial code LS-DYNA based on work done by Rahnders-Pehrson and Bannister. This makes it possible to simulate blast loads acting on structures representing spherical and hemispherical explosive shapes of TNT with reasonable computational effort as an alternative to the SPH and Eulerian model. The CPU time for the simplified blast model is however considerably shorter and may still be useful in time consuming concept studies. Reasonable numerical results using reasonable model sizes can be achieved not only for modelling near-field explosions in air but most areas of geotechnical. Calculation was compared with blast SPH and Eulerian model.

  7. Near field acoustic holography with microphones mounted on a rigid sphere

    DEFF Research Database (Denmark)

    Jacobsen, Finn; Moreno, Guillermo; Fernandez Grande, Efren;

    2008-01-01

    . This is potentially very useful for source identification. On the other hand a rigid sphere is somewhat more practical than an open sphere, and it is possible to modify the existing spherical NAH theory so that a similar sound field reconstruction can be made with an array of microphones flush-mounted on a rigid...... sphere. Rigid spheres with flush-mounted microphones are also used for beamforming, and it is known that they are advantageous compared with open spheres for this application. However, whereas beamforming is a far field technique NAH is a near field technique, and spherical NAH based on a rigid sphere...

  8. The Survey on Near Field Communication.

    Science.gov (United States)

    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.

  9. The Survey on Near Field Communication

    Directory of Open Access Journals (Sweden)

    Vedat Coskun

    2015-06-01

    Full Text Available 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. Strains of scattering of near-field of a point source

    Indian Academy of Sciences (India)

    M D Sharma

    2004-06-01

    Three dimensional scattering of near-field is studied for dilatation and rotation in the time domain. The perturbation method is applied to solve the equation of motion for the first order scattering from a weak inhomogeneity in an otherwise homogeneous medium. The inhomogeneity is assumed close enough to the point source so that the near-field intermediate wave is dominating over the far-field spherical and pulses. The integral expressions are derived to relate dilatation and rotation of scattering to the radial fluctuations of velocities and density in the inhomogeneity. These integrals are solved to calculate the strains of scattering from (a part of) an inhomogeneous spherical shell of arbitrary curvature. Variable curvature may allow the shape of inhomogeneity volume element to change uniformly from spherical to rectangular. Rotation of scattering from a spherical shell is independent of wave velocity inhomogeneity. Dilatation of scattering does not involve wave velocity inhomogeneity but its gradient. The back scattering results are obtained as a special case. Strains are computed numerically, for hypothetical models to study the effects of various parameters viz., velocity inhomogeneity, distance of source from inhomogeneity and from receiver, and thickness of inhomogeneity. The curvature of the spherical shell is varied to study the effects of the shape of inhomogeneous volume element on scattering.

  11. Near-field/altered-zone models report

    Energy Technology Data Exchange (ETDEWEB)

    Hardin, E. L., LLNL

    1998-03-01

    nonlithophysal and lower 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

  12. Near-field/altered-zone models report

    Energy Technology Data Exchange (ETDEWEB)

    Hardin, E. L., LLNL

    1998-03-01

    nonlithophysal and lower 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

  13. Near-Field Magnetic Dipole Moment Analysis

    Science.gov (United States)

    Harris, Patrick K.

    2003-01-01

    This paper describes the data analysis technique used for magnetic testing at the NASA Goddard Space Flight Center (GSFC). Excellent results have been obtained using this technique to convert a spacecraft s measured magnetic field data into its respective magnetic dipole moment model. The model is most accurate with the earth s geomagnetic field cancelled in a spherical region bounded by the measurement magnetometers with a minimum radius large enough to enclose the magnetic source. Considerably enhanced spacecraft magnetic testing is offered by using this technique in conjunction with a computer-controlled magnetic field measurement system. Such a system, with real-time magnetic field display capabilities, has been incorporated into other existing magnetic measurement facilities and is also used at remote locations where transport to a magnetics test facility is impractical.

  14. 0.4-1.2 GHz hybrid Al-CFRP open-boundary quad-ridge horn

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Pivnenko, Sergey; Breinbjerg, Olav

    2011-01-01

    We present a 0.4-1.2 GHz open-boundary quad-ridge horn to be used as a wide-band probe at the DTU-ESA Spherical Near-Field Antenna Test Facility at the Technical University of Denmark (DTU). Due to adopted hybrid Al-CFRP fabrication technology, the weight of the probe is reduced by a factor of 2.......3 as compared to the case of the same probe fabricated of solid aluminum. Measured characteristics of the probe as well as its performance with respect to the higher-order probe correction technique are presented and discussed....

  15. 60 GHz antenna measurement setup using a VNA without external frequency conversion

    DEFF Research Database (Denmark)

    Popa, Paula Irina; Pivnenko, Sergey; Nielsen, Jeppe Majlund;

    2014-01-01

    and phase, 0.06 dB and 6 degrees peak-to-peak deviations over 4 hours. A PNF measurement of a 25 dBi Standard Gain Horn was carried out and the results were compared to those from the DTU-ESA Spherical Near-Field Facility with a good agreement in the validity region. Uncertainty investigations regarding...... cable flexing effects at 60 GHz have shown that these introduce an uncertainty of about 0.02 dB (1 sigma) around the main beam region indicating a very good performance of the PNF setup....

  16. Phase Radiation Characteristics of an Open-Ended Circular Waveguide

    DEFF Research Database (Denmark)

    Shishkova, A.V.; Pivnenko, Sergiy; Kim, O.S.

    2002-01-01

    Analytic expressions for phase radiation characteristics of a semi-infinite open-ended circular waveguide regardless of its aperture size and operating frequency have been obtained making use of the rigorous Weinstein's theory. The analysis of phase radiation patterns has been carried out...... for the dominant mode (TE11) as well as for the high order modes TM01 and TE01, both for a single and multimode propagation. The measurement of radiation characteristics of an open-ended circular waveguide has been carried out at the DTU-ESA Spherical Near-Field Antenna Test Facility. It is shown...

  17. 3D printed 20/30-GHz dual-band offset stepped-reflector antenna

    DEFF Research Database (Denmark)

    Menendez, Laura G.; Kim, Oleksiy S.; Persson, Frank

    2015-01-01

    with a peak directivity of 36.7 dB and 40.4 dB at 20 and 30 GHz, respectively; this corresponds to an aperture efficiency of 61 % and 64 %, respectively. These results demonstrate that 3D printing is a viable manufacturing technology for medium-sized high-frequency antennas.......This paper documents the manufacturing by selective laser sintering of a 20/30 GHz dual-band circularly polarized offset stepped-reflector antenna for K- and Ka-band satellite communication. The manufactured antenna has been measured at the DTU-ESA Spherical Near-Field Antenna Test Facility...

  18. Ultrafast infrared near-field molecular nano-spectroscopy

    Directory of Open Access Journals (Sweden)

    Rang Matthias

    2013-03-01

    Full Text Available 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.

  19. Near-Field Optical Microscopy of Fractal Structures

    DEFF Research Database (Denmark)

    Coello, Victor; Bozhevolnyi, Sergey I.

    1999-01-01

    Using a photon scanning tunnelling microscope combined with a shear-force feedback system, we image both topographical and near-field optical images (at the wavelengths of 633 and 594 nm) of silver colloid fractals. Near-field optical imaging is calibrated with a standing evanescent wave pattern...

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

    Science.gov (United States)

    2014-01-01

    performing near-field measurement using an array of probes for antenna and bistatic radar cross section (RCS) applications. 15. SUBJECT TERMS...electromagnetic near-field measurement, antenna measurement, bistatic RCS measurement 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT... SAR 18. NUMBER OF PAGES 84 19a. NAME OF RESPONSIBLE PERSON (Monitor) a. REPORT Unclassified b. ABSTRACT Unclassified c. THIS PAGE

  1. Perturbation of near-field scan from connected cables

    DEFF Research Database (Denmark)

    Sørensen, Morten; Franek, Ondrej; Pedersen, Gert Frølund;

    2012-01-01

    The perturbation of near-fields scan from connected cables are investigated and how to handle the cables is discussed. A connected cable induced small but theoretical detectable changes in the near-field. This change can be seen in Huygens’ box simulations (equivalent source currents on a box...

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  4. Near-field acoustic holography with sound pressure and particle velocity measurements

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren

    of particle velocity measurements and combined pressure-velocity measurements in NAH, the relation between the near-field and the far-field radiation from sound sources via the supersonic acoustic intensity, and finally, the reconstruction of sound fields using rigid spherical microphone arrays. Measurement...... of the particle velocity has notable potential in NAH, and furthermore, combined measurement of sound pressure and particle velocity opens a new range of possibilities that are examined in this study. On this basis, sound field separation methods have been studied, and a new measurement principle based on double...... layer measurements of the particle velocity has been proposed. Also, the relation between near-field and far-field radiation from sound sources has been examined using the concept of the supersonic intensity. The calculation of this quantity has been extended to other holographic methods, and studied...

  5. Near-field probing of photonic crystal directional couplers

    DEFF Research Database (Denmark)

    Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo

    2006-01-01

    . By comparing the near-field optical images recorded in and after the directional coupler area, the features of light distribution are analyzed. Finally, the scanning near-field optical microscope observations are found to be in agreement with the transmission measurements conducted with the same sample.......We report the design, fabrication and characterization of a photonic crystal directional with a size of ~20 x 20 mm2 fabricated in silicon-on-insulator material. Using a scanning near-field optical microscope we demonstrate a high coupling efficiency for TM polarized light at telecom wavelengths...

  6. Transfer functions in collection scanning near-field optical microscopy

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Vohnsen, Brian; Bozhevolnaya, Elena A.

    1999-01-01

    It is generally accepted that, if in collection near-field optical microscopy the probe-sample coupling can be disregarded, a fiber probe can be considered as a detector of the near-field intensity whose size can be accounted for via an intensity transfer function. We show that, in general...... are considered with respect to the relation between near-field optical images and the corresponding intensity distributions. Our conclusions are supported with numerical simulations and experimental results obtained by using a photon scanning tunneling microscope with an uncoated fiber tip....

  7. Principles of planar near-field antenna measurements

    CERN Document Server

    Gregson, Stuart; Parini, Clive

    2007-01-01

    This single volume provides a comprehensive introduction and explanation of both the theory and practice of 'Planar Near-Field Antenna Measurement' from its basic postulates and assumptions, to the intricacies of its deployment in complex and demanding measurement scenarios.

  8. Integration and Evaluation of Nanophotonic Devices Using Optical Near Field

    Science.gov (United States)

    Yatsui, Takashi; Nomura, Wataru; Yi, Gyu-Chul; Ohtsu, Motoichi

    In this chapter, we review the optical near-field phenomena and their applications to realize the nanophotonic device. To realize the nanometer-scale controllability in size and position, we demonstrate the feasibility of nanometer-scale chemical vapor deposition using optical near-field techniques (see Sect. 15.2). In which, the probe-less fabrication method for mass production is also demonstrated. To confirm the promising optical properties of individual ZnO for realizing nanophotonic devices, we performed the near-field evaluation of the ZnO quantum structure (see Sect. 15.3). To drive the nanophotonic device with external conventional diffraction-limited photonic device, the far-/near-field conversion device is required. Section 15.4 reviews nanometer-scale waveguide to be used as such a conversion device of the nanophotonic ICs.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  11. FGG-NUFFT-Based Method for Near-Field 3-D Imaging Using Millimeter Waves.

    Science.gov (United States)

    Kan, Yingzhi; Zhu, Yongfeng; Tang, Liang; Fu, Qiang; Pei, Hucheng

    2016-09-19

    In this paper, to deal with the concealed target detection problem, an accurate and efficient algorithm for near-field millimeter wave three-dimensional (3-D) imaging is proposed that uses a two-dimensional (2-D) plane antenna array. First, a two-dimensional fast Fourier transform (FFT) is performed on the scattered data along the antenna array plane. Then, a phase shift is performed to compensate for the spherical wave effect. Finally, fast Gaussian gridding based nonuniform FFT (FGG-NUFFT) combined with 2-D inverse FFT (IFFT) is performed on the nonuniform 3-D spatial spectrum in the frequency wavenumber domain to achieve 3-D imaging. The conventional method for near-field 3-D imaging uses Stolt interpolation to obtain uniform spatial spectrum samples and performs 3-D IFFT to reconstruct a 3-D image. Compared with the conventional method, our FGG-NUFFT based method is comparable in both efficiency and accuracy in the full sampled case and can obtain more accurate images with less clutter and fewer noisy artifacts in the down-sampled case, which are good properties for practical applications. Both simulation and experimental results demonstrate that the FGG-NUFFT-based near-field 3-D imaging algorithm can have better imaging performance than the conventional method for down-sampled measurements.

  12. FGG-NUFFT-Based Method for Near-Field 3-D Imaging Using Millimeter Waves

    Directory of Open Access Journals (Sweden)

    Yingzhi Kan

    2016-09-01

    Full Text Available In this paper, to deal with the concealed target detection problem, an accurate and efficient algorithm for near-field millimeter wave three-dimensional (3-D imaging is proposed that uses a two-dimensional (2-D plane antenna array. First, a two-dimensional fast Fourier transform (FFT is performed on the scattered data along the antenna array plane. Then, a phase shift is performed to compensate for the spherical wave effect. Finally, fast Gaussian gridding based nonuniform FFT (FGG-NUFFT combined with 2-D inverse FFT (IFFT is performed on the nonuniform 3-D spatial spectrum in the frequency wavenumber domain to achieve 3-D imaging. The conventional method for near-field 3-D imaging uses Stolt interpolation to obtain uniform spatial spectrum samples and performs 3-D IFFT to reconstruct a 3-D image. Compared with the conventional method, our FGG-NUFFT based method is comparable in both efficiency and accuracy in the full sampled case and can obtain more accurate images with less clutter and fewer noisy artifacts in the down-sampled case, which are good properties for practical applications. Both simulation and experimental results demonstrate that the FGG-NUFFT-based near-field 3-D imaging algorithm can have better imaging performance than the conventional method for down-sampled measurements.

  13. Scanning near-field infrared microscopy on semiconductor structures

    Energy Technology Data Exchange (ETDEWEB)

    Jacob, Rainer

    2011-01-15

    Near-field optical microscopy has attracted remarkable attention, as it is the only technique that allows the investigation of local optical properties with a resolution far below the diffraction limit. Especially, the scattering-type near-field optical microscopy allows the nondestructive examination of surfaces without restrictions to the applicable wavelengths. However, its usability is limited by the availability of appropriate light sources. In the context of this work, this limit was overcome by the development of a scattering-type near-field microscope that uses a widely tunable free-electron laser as primary light source. In the theoretical part, it is shown that an optical near-field contrast can be expected when materials with different dielectric functions are combined. It is derived that these differences yield different scattering cross-sections for the coupled system of the probe and the sample. Those cross-sections define the strength of the near-field signal that can be measured for different materials. Hence, an optical contrast can be expected, when different scattering cross-sections are probed. This principle also applies to vertically stacked or even buried materials, as shown in this thesis experimentally for two sample systems. In the first example, the different dielectric functions were obtained by locally changing the carrier concentration in silicon by the implantation of boron. It is shown that the concentration of free charge-carriers can be deduced from the near-field contrast between implanted and pure silicon. For this purpose, two different experimental approaches were used, a non-interferometric one by using variable wavelengths and an interferometric one with a fixed wavelength. As those techniques yield complementary information, they can be used to quantitatively determine the effective carrier concentration. Both approaches yield consistent results for the carrier concentration, which excellently agrees with predictions from

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  15. A new method to reduce truncation errors in partial spherical near-field measurements

    DEFF Research Database (Denmark)

    Cano-Facila, F J; Pivnenko, Sergey

    2011-01-01

    angular sector as well as a truncation error is present in the calculated far-field pattern within this sector. The method is based on the Gerchberg-Papoulis algorithm used to extrapolate functions and it is able to extend the valid region of the calculated far-field pattern up to the whole forward...

  16. Metamaterial-Inspired First-Order Probe for Spherical Near-Field Antenna Measurements

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Breinbjerg, Olav

    2011-01-01

    A first-order probe based on a two-element split ring resonator (SRR) array is presented. The probe is applicable at low frequencies due to its small size and excellent mode content.......A first-order probe based on a two-element split ring resonator (SRR) array is presented. The probe is applicable at low frequencies due to its small size and excellent mode content....

  17. A new method to reduce truncation errors in partial spherical near-field measurements

    DEFF Research Database (Denmark)

    Cano-Facila, F J; Pivnenko, Sergey

    2011-01-01

    angular sector as well as a truncation error is present in the calculated far-field pattern within this sector. The method is based on the Gerchberg-Papoulis algorithm used to extrapolate functions and it is able to extend the valid region of the calculated far-field pattern up to the whole forward...

  18. Near-field thermodynamics: Useful work, efficiency, and energy harvesting

    Energy Technology Data Exchange (ETDEWEB)

    Latella, Ivan, E-mail: ilatella@ffn.ub.edu; Pérez-Madrid, Agustín, E-mail: agustiperezmadrid@ub.edu [Departament de Física Fonamental, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona (Spain); Lapas, Luciano C., E-mail: luciano.lapas@pq.cnpq.br [Universidade Federal da Integração Latino-Americana, Caixa Postal 2067, 85867-970 Foz do Iguaçu (Brazil); Miguel Rubi, J., E-mail: mrubi@ub.edu [Departament de Física Fonamental, Facultat de Física, Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona (Spain); Department of Chemistry, Imperial College London, SW7 2AZ London (United Kingdom)

    2014-03-28

    We show that the maximum work that can be obtained from the thermal radiation emitted between two planar sources in the near-field regime is much larger than that corresponding to the blackbody limit. This quantity, as well as an upper bound, for the efficiency of the process is computed from the formulation of thermodynamics in the near-field regime. The case when the difference of temperatures of the hot source and the environment is small, relevant for energy harvesting, is studied in detail. We also show that thermal radiation energy conversion can be more efficient in the near-field regime. These results open new possibilities for the design of energy converters that can be used to harvest energy from sources of moderate temperature at the nanoscale.

  19. Field of view for near-field aperture synthesis imaging

    CERN Document Server

    Buscher, David F

    2015-01-01

    Aperture synthesis techniques are increasingly being employed to provide high angular resolution images in situations where the object of interest is in the near field of the interferometric array. Previous work has showed that an aperture synthesis array can be refocused on an object in the near field of an array, provided that the object is smaller than the effective Fresnel zone size corresponding to the array-object range. We show here that, under paraxial conditions, standard interferometric techniques can be used to image objects which are substantially larger than this limit. We also note that interferometric self-calibration and phase-closure image reconstruction techniques can be used to achieve near-field refocussing without requiring accurate object range information. We use our results to show that the field of view for high-resolution aperture synthesis imaging of geosynchronous satellites from the ground can be considerably larger than the largest satellites in Earth orbit.

  20. Near-Field Cross Section Imaging of Wideband Millimeter Wave

    Directory of Open Access Journals (Sweden)

    Kan Yingzhi

    2016-01-01

    Full Text Available Near-field millimeter wave imaging has been a hot topic recent years for its importance applications in the area of anti-terrorism. The penetrating characteristic of millimeter wave is of significant importance to security, such as the concealed weapons detection, ground-penetrating radar imaging, through-barrier imaging and so on. Cross section imaging is a basic aspect for near-field millimeter wave imaging, which includes antenna array distribution and wideband signal processing. This paper utilizes back projection method in space area to realize ultra-band nearfield cross section imaging. We induce two dimensional direction integral formulas to obtain the reconstruction image of the near-field imaging area, and the simulation results validate the effectiveness of this imaging algorithm.

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

    Science.gov (United States)

    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.

  2. Near-field energy extraction with hyperbolic metamaterials.

    Science.gov (United States)

    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.

  3. Near-field second-harmonic generation from gold nanoellipsoids

    Energy Technology Data Exchange (ETDEWEB)

    Celebrano, M.; Zavelani-Rossi, M.; Polli, D.; Cerullo, G. [Istituto di Fotonica e Nanotecnologie, CNR, Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Biagioni, P.; Finazzi, M.; Duo, L. [LNESS - Dipartimento di Fisica, Politecnico di Milano, Piazza Leonardo Da Vinci 32, 20133 Milano (Italy); Labardi, M.; Allegrini, M. [CNR-INFM, polyLab, Dipartimento di Fisica ' Enrico Fermi' , Universita di Pisa, Largo Pontecorvo 3, 56127 Pisa (Italy); Grand, J.; Adam, P.M.; Royer, P. [Laboratoire de Nanotechnologie et d' Instrumentation Optique, Universite de Technologie de Troyes, 12 rue Marie Curie, BP 2060 10010 Troyes cedex (France)

    2008-07-01

    Second-harmonic generation from single gold nanofabricated particles is experimentally investigated by a nonlinear scanning near-field optical microscope (SNOM). High peak power femtosecond polarized light pulses at the output of a hollow pyramid aperture allow for efficient second-harmonic imaging, with sub-100-nm spatial resolution and high contrast. The near-field nonlinear response is found to be directly related to both local surface plasmon resonances and particle morphology. The combined analysis of linear and second-harmonic SNOM images allows one to discriminate among near-field scattering, absorption and re-emission processes, which would not be possible with linear techniques alone. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  4. Single-ion microwave near-field quantum sensor

    Science.gov (United States)

    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.

  5. Near-field environment/processes working group summary

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, W.M. [Center for Nuclear Waste Regulatory Analyses, San Antonio, TX (United States)

    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.

  6. Laser terahertz emission microscopy with near-field probes

    DEFF Research Database (Denmark)

    Pedersen, Pernille Klarskov; Mittleman, Daniel M.

    2016-01-01

    Using an AFM, an optical near-field image at 800 nm of a dipole antenna for THz emission is measured, and by simultaneously collecting the emitted THz radiation, the laser light confined under the AFM probe gives a THz emission resolution of less than 50 nm.......Using an AFM, an optical near-field image at 800 nm of a dipole antenna for THz emission is measured, and by simultaneously collecting the emitted THz radiation, the laser light confined under the AFM probe gives a THz emission resolution of less than 50 nm....

  7. Image Formation in Second-Harmonic Near-Field Microscopy

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Lozovski, Valeri Z.; Pedersen, Kjeld

    1999-01-01

    A macroscopic self-consistent approach that enables one to rigorously describe image formation in scanning near-field optical second-harmonic generation microscopy is developed. The self-consistent second-harmonic field is determined by taking into account both the linear and nonlinear contributi......A macroscopic self-consistent approach that enables one to rigorously describe image formation in scanning near-field optical second-harmonic generation microscopy is developed. The self-consistent second-harmonic field is determined by taking into account both the linear and nonlinear...

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

    CERN Document Server

    Naruse, Makoto; Takahashi, Taiki; Aono, Masashi; Akahane, Kouichi; D'Acunto, Mario; Hori, Hirokazu; Thylen, Lars; Katori, Makoto; Ohtsu, Motoichi

    2016-01-01

    Optical excitation transfer in nanostructured matter has been intensively studied in various material systems for versatile applications. Herein, we 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 distance when the light localization is strong. The results provide fundamental insights into optical excitation transfer and will facilitate the design and analysis of nanoscale signal-transfer characteristics.

  9. Transfer function and near-field detection of evanescent waves

    DEFF Research Database (Denmark)

    Radko, Ylia P.; Bozhevolnyi, Sergey I.; Gregersen, Niels

    2006-01-01

    for the transfer function, which is derived by introducing an effective pointof (dipolelike) detection inside the probe tip. It is found to be possible to fit reasonably well both the experimental and the simulation data for evanescent field components, implying that the developed approximation of the near......-field transfer function can serve as a simple, rational, and sufficiently reliable means of fiber probe characterization....... of collection and illumination modes. Making use of a collection near-field microscope with a similar fiber tip illuminated by an evanescent field, we measure the collected power as a function of the field spatial frequency in different polarization configurations. Considering a two-dimensional probe...

  10. Near field communication recent developments and library implications

    CERN Document Server

    McHugh, Sheli

    2014-01-01

    Near Field Communication is a radio frequency technology that allows objects, such as mobile phones, computers, tags, or posters, to exchange information wirelessly across a small distance. This report on the progress of Near Field Communication reviews the features and functionality of the technology and summarizes the broad spectrum of its current and anticipated applications. We explore the development of NFC technology in recent years, introduce the major stakeholders in the NFC ecosystem, and project its movement toward mainstream adoption. Several examples of early implementation of NFC

  11. Efficient Calculation of Near Fields in the FDTD Method

    DEFF Research Database (Denmark)

    Franek, Ondrej

    2011-01-01

    When calculating frequency-domain near fields by the FDTD method, almost 50 % reduction in memory and CPU operations can be achieved if only E-fields are stored during the main time-stepping loop and H-fields computed later. An improved method of obtaining the H-fields from Faraday's Law...

  12. Electro-Anatomical Characterization by Cardiac Electric Near-Fields

    Science.gov (United States)

    2007-11-02

    CHARACTERIZATION BY CARDIAC ELECTRIC NEAR-FIELDS E. Hofer1, G. Plank2, I. Schafferhofer1, D. Sanchez-Quintana3 1Institute of Medical Physics and...Project Number Task Number Work Unit Number Performing Organization Name(s) and Address(es) Institute of Medical Physics and Biophysics Karl-Frazens

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

    Science.gov (United States)

    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.

  14. Graphene-on-Silicon Near-Field Thermophotovoltaic Cell

    NARCIS (Netherlands)

    Svetovoy, V. B.; Palasantzas, G.

    2014-01-01

    A graphene layer on top of a dielectric can dramatically influence the ability of the material for radiative heat transfer. This property of graphene is used to improve the performance and reduce costs of near-field thermophotovoltaic cells. Instead of low-band-gap semiconductors it is proposed to u

  15. A combined near field optical and force microscope

    NARCIS (Netherlands)

    Moers, M.H.P.; Tack, R.G.; Hulst, van N.F.; Bölger, B.

    1993-01-01

    Scanning near field optical microscopy (SNOM) is the optical alternative of the scanning probe microscopical techniques which enables a lateral resolution down to about 10 nm, unlimited by diffraction. Moreover, the potential of non- destructive imaging of chemical and biological samples with nanome

  16. THz near-field Faraday imaging in hybrid metamaterials

    NARCIS (Netherlands)

    Kumar, N.; Strikwerda, A.C.; Fan, K.; Zhang, X.; Averitt, R.D.; Planken, P.C.M.; Adam, A.J.L.

    2012-01-01

    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.

  17. Photon-induced near-field electron microscopy.

    Science.gov (United States)

    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.

  18. Planar Near-Field Measurements of Ground Penetrating Radar Antennas

    DEFF Research Database (Denmark)

    Meincke, Peter; Hansen, Thorkild

    2004-01-01

    Planar near-field measurements are formulated for a general ground penetrating radar (GPR) antenna. A total plane-wave scattering matrix is defined for the system consisting of the GPR antenna and the planar air-soil interface. The transmitting spectrum of the GPR antenna is expressed in terms...

  19. Graphene-on-Silicon Near-Field Thermophotovoltaic Cell

    NARCIS (Netherlands)

    Svetovoy, V. B.; Palasantzas, G.

    2014-01-01

    A graphene layer on top of a dielectric can dramatically influence the ability of the material for radiative heat transfer. This property of graphene is used to improve the performance and reduce costs of near-field thermophotovoltaic cells. Instead of low-band-gap semiconductors it is proposed to u

  20. Near-Field Spectroscopy with Nanoparticles Deposited by AFM

    Science.gov (United States)

    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.

  1. THz near-field Faraday imaging in hybrid metamaterials

    NARCIS (Netherlands)

    Kumar, N.; Strikwerda, A.C.; Fan, K.; Zhang, X.; Averitt, R.D.; Planken, P.C.M.; Adam, A.J.L.

    2012-01-01

    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. Normall

  2. Radiative heat transfer in the extreme near field.

    Science.gov (United States)

    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

    2015-12-17

    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 4-6), 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.

  3. Near-field thermal imaging of nanostructured surfaces

    Science.gov (United States)

    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.

  4. Near-Field Nanolasers based on Nonradiating Anapole Modes

    KAUST Repository

    Gongora, J. S. Totero

    2016-05-31

    By employing ab-initio simulations of Maxwell-Bloch equations with a source of quantum noise, we study a new laser concept based on photonic dark-matter nanostructures that emit only in the near-field, with no far-field radiation pattern.

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

    Energy Technology Data Exchange (ETDEWEB)

    Gisler, Galen R [Los Alamos National Laboratory; Weaver, Robert P [Los Alamos National Laboratory; Gittings, Michael L [Los Alamos National Laboratory

    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.

  6. Use of Near Field Communication in emergency Rescue situations

    DEFF Research Database (Denmark)

    Kramp, Gunnar

    2006-01-01

    Near Field Communication (NFC) where the placement of two devices in close proximity of each other makes it possible for two devices to exhange and share information, opens up for a variety of transparent and intuitive interaction possibilities. However, as we have identified in the palcom projec...... [1], instant and appropriate feedback regarding state of the connection and identification of which devices are connected to each other, is crucial for use.......Near Field Communication (NFC) where the placement of two devices in close proximity of each other makes it possible for two devices to exhange and share information, opens up for a variety of transparent and intuitive interaction possibilities. However, as we have identified in the palcom project...

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

    Science.gov (United States)

    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.

  8. Near-field model of ultrasonic array data

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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. THz near-field Faraday imaging in hybrid metamaterials.

    Science.gov (United States)

    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.

  11. Thermal excitation of plasmons for near-field thermophotovoltaics

    CERN Document Server

    Guo, Yu; Hu, Huan; Cortes, Cristian L; Jacob, Zubin

    2014-01-01

    The traditional approaches of exciting plasmons consist of using electrons (eg: 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. Exp. 21.101, A96-A110, (2013). Here, we show how the long-standing search for a high temperature narrow band near-field emitter for thermophotovoltaics can be fulfilled by high temperature plasmonics. We also describe how 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.

  12. Near-field mapping by laser ablation of PMMA coatings

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Maibohm, Christian; Kostiucenko, Oksana

    The optical near-field of lithography-defined gold nanostructures, arranged into regular arrays on a gold film, is characterized via ablation of a polymer coating by laser illumination. The method utilizes femto-second laser pulses from a laser scanning microscope which induces electrical field...... that the different stages in the ablation process can be controlled and characterized making the technique suitable for characterizing optical near-fields of metal nanostructures....... enhancements on and around the gold nanostructures. At the positions of the enhancements, the ablation threshold of the polymer coating is significantly lowered creating subdiffractional topographic modifications on the surface which are quantified via scanning electron microscopy and atomic force microscopy...

  13. Near-field mapping by laser ablation of PMMA coatings

    DEFF Research Database (Denmark)

    Fiutowski, Jacek; Maibohm, Christian; Kostiucenko, Oksana

    The optical near-field of lithography-defined gold nanostructures, arranged into regular arrays on a gold film, is characterized via ablation of a polymer coating by laser illumination. The method utilizes femto-second laser pulses from a laser scanning microscope which induces electrical field...... that the different stages in the ablation process can be controlled and characterized making the technique suitable for characterizing optical near-fields of metal nanostructures....... enhancements on and around the gold nanostructures. At the positions of the enhancements, the ablation threshold of the polymer coating is significantly lowered creating sub-diffractional topographic modifications on the surface which are quantified via scanning electron microscopy and atomic force microscopy...

  14. Rewritable organic films for near-field recording

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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. Near-Field Loop Antenna for the UHF RFID Reader

    Institute of Scientific and Technical Information of China (English)

    Peng Yang; Yan Li; Li-Jun Jiang; Feng Yang

    2011-01-01

    A loop antenna for near field readers is proposed.Through periodic interdigital capacitors,the phase of the current on the loop is compensated and kept in phase.Hence,a loop with a perimeter of one wavelength at 900 MHz achieves a uniform near magnetic field distribution inside the loop.A novel method is proposed to evaluate the performance of the coplanar waveguide (CPW) to coplanar stripline (CPS) transition,which is used as a balun for the feeding network in this paper.This loop antenna has a 70 MHz operating bandwidth and 12 cm maximum reading range when the output power is 24 dBm,which is suitable for most near field radio frequency identification (RFID) applications.

  18. Near-field heat transfer between gold nanoparticle arrays

    Energy Technology Data Exchange (ETDEWEB)

    Phan, Anh D., E-mail: anhphan@mail.usf.edu [Department of Physics, University of South Florida, Tampa, Florida 33620 (United States); Institute of Physics, Vietnam Academy of Science and Technology, 10 Dao Tan, Ba Dinh, Hanoi 10000 (Viet Nam); Phan, The-Long, E-mail: ptlong2512@yahoo.com [Department of Physics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Woods, Lilia M. [Department of Physics, University of South Florida, Tampa, Florida 33620 (United States)

    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.

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

    Directory of Open Access Journals (Sweden)

    Reza K. Amineh

    2012-01-01

    Full Text Available 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.

  20. Parameterization of the Near-Field Internal Wave Field Generated by a Submarine

    CERN Document Server

    Rottman, James W; Dommermuth, Douglas; Broutman, Dave

    2014-01-01

    We attempt to gain some insight into the modeling of the generation of internal waves produced by submarines traveling in the littoral regions of the ocean with the use of high fidelity numerical simulations. These numerical simulations are shown to be capable of simulating high Reynolds number flow around bodies, including the effects of stable stratification. In addition, we use the results of these detailed numerical studies to test and revise the source distribution parameterizations of the near-field waves that have been used in analytical studies based on linear theory. Such parameterizations have been shown to be useful in initializing ray-tracing schemes that can be used for computing wave propagation through realistic oceans with variable background properties. For simplicity, we focus on the idealized case of a spherical body traveling horizontally at constant speed through a uniformly stratified fluid.

  1. Medicines identification for African illiterate patients using near field communication

    OpenAIRE

    2014-01-01

    This paper presents the application of Near Field Communication (NFC) to the healthcare sector. Although a number of papers have been written to discuss different NFC applications in the healthcare sector, none of them address the potential challenges facing illiterate patients worldwide. According to UNESCO institute for statistics, the Sub-Saharan African region has the highest percentage of illiterate people compared to other regions in the world. NFC can be used in conjunction with other ...

  2. Thermal Diodes Based on Near-Field Radiation

    Science.gov (United States)

    2015-10-01

    rectifiers and switches. 21 Approved for public release; distribution unlimited. 1. E. Rousseau , A. Siria, G. Jourdan, S. Volz, F. Comin, J. Chevrier...4. A. Narayanaswamy and G. Chen, "Surface modes for near field thermophotovoltaics," Applied Physics Letters 82, 3544-3546 (2003). 5. E. Rousseau , A...Lett. 2008, 93 (4), 043109. (7) Rousseau , E.; Siria, A.; Jourdan, G.; Volz, S.; Comin, F.; Chevrier, J.; Greffet, J.-J. Nat. Photon. 2009, 3 (9

  3. Near-field Electrodynamics of Atomically Doped Carbon Nanotubes

    OpenAIRE

    Bondarev, Igor V.; Lambin, Philippe

    2005-01-01

    We develop a quantum theory of near-field electrodynamical properties of carbon nanotubes and investigate spontaneous decay dynamics of excited states and van der Waals attraction of the ground state of an atomic system close to a single-wall nanotube surface. Atomic spontaneous decay exhibits vacuum-field Rabi oscillations -- a principal signature of strong atom-vacuum-field coupling. The strongly coupled atomic state is nothing but a 'quasi-1D cavity polariton'. Its stability is mainly dete...

  4. Near-Field Heat Transfer between Multilayer Hyperbolic Metamaterials

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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

  6. Near-field acoustic imaging based on Laplacian sparsity

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Daudet, Laurent

    2016-01-01

    We present a sound source identification method for near-field acoustic imaging of extended sources. The methodology is based on a wave superposition method (or equivalent source method) that promotes solutions with sparse higher order spatial derivatives. Instead of promoting direct sparsity......, and the validity of the wave extrapolation used for the reconstruction is examined. It is shown that this methodology can overcome conventional limits of spatial sampling, and is therefore valid for wide-band acoustic imaging of extended sources....

  7. Generation and near-field imaging of Airy surface plasmons

    CERN Document Server

    Minovich, Alexander; Janunts, Norik; Pertsch, Thomas; Neshev, Dragomir N; Kivshar, Yuri S

    2011-01-01

    We demonstrate experimentally the generation and near-field imaging of nondiffracting surface waves - plasmonic Airy beams, propagating on the surface of a gold metal film. The Airy plasmons are excited by an engineered nanoscale phase grating, and demonstrate significant beam bending over their propagation. We show that the observed Airy plasmons exhibit self-healing properties, suggesting novel applications in plasmonic circuitry and surface optical manipulation.

  8. Near-field heat transfer between multilayer hyperbolic metamaterials

    Energy Technology Data Exchange (ETDEWEB)

    Biehs, Svend-Age [Oldenburg Univ. (Germany). Inst. fuer Physik; Ben-Abdallah, Philippe [Univ. Paris-Sud 11, Palaiseau (France). Lab. Charles Fabry; Univ. Sherbrooke, PQ (Canada). Dept. of Mechanical Engineering

    2017-05-01

    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.

  9. Electromagnetic and transient shielding effectiveness for near-field sources

    Directory of Open Access Journals (Sweden)

    C. Möller

    2007-06-01

    Full Text Available The contribution deals with an investigation of the recently proposed definitions for the electromagnetic and transient shielding effectiveness (SE in the case of an electric-dipole near-field source. To this end, new factors are introduced which depend on the distance between the dipole source and the measurement point inside the shield and which are valid for perpendicularly (with respect to the distance vector polarized dipoles. Numerical results support and confirm the theoretical derivations.

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

    Science.gov (United States)

    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.

  11. Phased Array Excitations For Efficient Near Field Wireless Power Transmission

    Science.gov (United States)

    2016-09-01

    in Handbook of Reflector Antennas and Feed Systems Volume I: Theory and Design of Reflectors , Boston, MA: Artech House, 2013, pp. 31–32. 48...distribution in the near-field environment of the antenna , allowing for an optimum rectenna design . B. PREVIOUS WORK Previous work has been done in the...calculations involving bodies of arbitrary shape .” Zhang and Cheng [13] experimented with two efficient, electrically small planar antennas and found that

  12. Near-field acoustic holography analysis of modulated sound source

    Institute of Scientific and Technical Information of China (English)

    MAO Rongfu; ZHU Haichao; DU Xianghua; ZHU Haipeng

    2011-01-01

    When conventional near-field acoustic holography (NAH) technique is appliedto sound field induced by modulated signal, the modulating frequency can not be revealed by the reconstructed results. To solve the problem, a NAH analysis methodology for modulated sound source was proposed. Firstly, Hilbert transform was introduced to demodulate the signal, and then modulating component was reconstructed by NAH technique. Both numerical simulation and experiment results demonstrate that accurate reconstruction analysis can be obtained by the proposed method.

  13. Near-Field Acoustic Holography of Chladni Plate

    Science.gov (United States)

    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. High RF Magnetic Field Near-Field Microwave Microscope

    Science.gov (United States)

    Tai, Tamin; Mircea, Dragos I.; Anlage, Steven M.

    2010-03-01

    Near-field microwave microscopes have been developed to quantitatively image RF and microwave properties of a variety of materials on deep sub-wavelength scales [1]. Microscopes that develop high-RF magnetic fields on short length scales are useful for examining the fundamental electrodynamic properties of superconductors [2]. We are creating a new class of near-field microwave microscopes that develop RF fields on the scale of 1 Tesla on sub-micron length scales. These microscopes will be employed to investigate defects that limit the RF properties of bulk Nb materials used in accelerator cavities, and the nonlinear Meissner effect in novel superconductors. Work funded by the US Department of Energy. [1] S. M. Anlage, V. V. Talanov, A. R. Schwartz, ``Principles of Near-Field Microwave Microscopy,'' in Scanning Probe Microscopy: Electrical and Electromechanical Phenomena at the Nanoscale, Volume 1, edited by S. V. Kalinin and A. Gruverman (Springer-Verlag, New York, 2007), pp. 215-253. [2] D. I. Mircea, H. Xu, S. M. Anlage, ``Phase-sensitive Harmonic Measurements of Microwave Nonlinearities in Cuprate Thin Films,'' Phys. Rev. B 80, 144505 (2009).

  15. Near-Field Fluorescence and Topography Characterization of a Single Nanometre Fluorophore by Apertureless Tip-Enhanced Scanning Near-Field Microscopy

    Institute of Scientific and Technical Information of China (English)

    WU Xiao-Bin; WANG Jia; XU Ji-Ying; WANG Rui; TIAN Qian; YU Jian-Yuan

    2007-01-01

    Tip-enhanced near-field fluorescence and topography characterization of a single nanometre fluorophore is conducted by using an apertureless scanning near-field microscopy system. A fluorophore with size 80nm is mapped with a spatial resolution of 10nm. The corresponding near-field fluorescence data shows significant signal enhancement due to the apertureless tip-enhanced effect. With the nanometre spatial resolution capability and nanometre local tip-enhanced effect, the apertureless tip-enhanced scanning near-field microscopy may be further used to characterize a single molecule by realizing the local near-field spectrum assignment corresponding to topography at nanometre scale.

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

    Science.gov (United States)

    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.

  17. Near field communication (NFC) from theory to practice

    CERN Document Server

    Coskun, Vedat; Ozdenizci, Busra

    2011-01-01

    This book provides the technical essentials, state-of-the-art knowledge, business ecosystem and standards of Near Field Communication (NFC)by NFC Lab - Istanbul research centre which conducts intense research on NFC technology. In this book, the authors present the contemporary research on all aspects of NFC, addressing related security aspects as well as information on various business models. In addition, the book provides comprehensive information a designer needs to design an NFC project, an analyzer needs to analyze requirements of a new NFC based system, and a programmer needs to implem

  18. Planar Near-Field Measurements of Ground Penetrating Radar Antennas

    DEFF Research Database (Denmark)

    Meincke, Peter; Hansen, Thorkild

    2004-01-01

    Planar near-field measurements are formulated for a general ground penetrating radar (GPR) antenna. A total plane-wave scattering matrix is defined for the system consisting of the GPR antenna and the planar air-soil interface. The transmitting spectrum of the GPR antenna is expressed in terms...... of measurements obtained with a buried probe as the GPR antenna moves over a scan plane on the ground. A numerical example in which the scan plane is finite validates the expressions for the spectrum of the GPR antenna....

  19. Near-Field Optical control of Doughnut-Shaped Nanostructures

    CERN Document Server

    Dubrovkin, A M; Ortyl, E; Zielinska, S

    2014-01-01

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

  20. Near-field Optical Imagigng and Chemical Analysis

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  2. Near-field characterization of photonic crystal Y-splitters

    DEFF Research Database (Denmark)

    Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo

    2005-01-01

    -1570 nm. The recorded intensity distribution exhibit highly wavelength (and polarization) dependent intensity variations along the propagation direction, especially around the fork and bend regions. By comparing the SNOM images recorded in and after the PC Y-splitter area, the features of light......A scanning near-field optical microscope (SNOM) is used to directly map the propagation of light in a specially designed 50/50 photonic crystal (PC) Y-splitter fabricated on silicon-on-insulator (SOI) wafers. SNOM images are obtained for TE- and TM-polarized light in the wavelength range 1425...

  3. Near Field Imaging at Microwave and Millemeter Wave Frequencies

    Energy Technology Data Exchange (ETDEWEB)

    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.

  4. Near-Field to Far-Field Transformation Techniques with Spiral Scannings: A Comprehensive Review

    Directory of Open Access Journals (Sweden)

    Renato Cicchetti

    2014-01-01

    Full Text Available An overview of the near-field-far-field (NF-FF transformation techniques with innovative spiral scannings, useful to derive the radiation patterns of the antennas commonly employed in the modern wireless communication systems, is provided in this paper. The theoretical background and the development of a unified theory of the spiral scannings for quasi-spherical and nonspherical antennas are described, and an optimal sampling interpolation expansion to evaluate the probe response on a quite arbitrary rotational surface from a nonredundant number of its samples, collected along a proper spiral wrapping it, is presented. This unified theory can be applied to spirals wrapping the conventional scanning surfaces and makes it possible to accurately reconstruct the NF data required by the NF-FF transformation employing the corresponding classical scanning. A remarkable reduction of the measurement time is so achieved, due to the use of continuous and synchronized movements of the positioning systems and to the reduced number of needed NF measurements. Some numerical and experimental results relevant to the spherical spiral scanning case when dealing with quasi-planar and electrically long antennas are shown.

  5. Near-field Approaches to Subcellular Tissue Abalation

    Science.gov (United States)

    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.

  6. Cryogenic apparatus for study of near-field heat transfer

    Science.gov (United States)

    Kralik, T.; Hanzelka, P.; Musilova, V.; Srnka, A.; Zobac, M.

    2011-05-01

    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 100 to 103 μm. The heat transferred from the hot (10 - 100 K) to the cold sample (˜5 K) sinks into a liquid helium bath through a thermal resistor, serving as a heat flux meter. Transferred heat power within ˜2 nW/cm2 and ˜30 μW/cm2 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.

  7. 4D Near-Field Source Localization Using Cumulant

    Directory of Open Access Journals (Sweden)

    Zhao Feng

    2007-01-01

    Full Text Available This paper proposes a new cumulant-based algorithm to jointly estimate four-dimensional (4D source parameters of multiple near-field narrowband sources. Firstly, this approach proposes a new cross-array, and constructs five high-dimensional Toeplitz matrices using the fourth-order cumulants of some properly chosen sensor outputs; secondly, it forms a parallel factor (PARAFAC model in the cumulant domain using these matrices, and analyzes the unique low-rank decomposition of this model; thirdly, it jointly estimates the frequency, two-dimensional (2D directions-of-arrival (DOAs, and range of each near-field source from the matrices via the low-rank three-way array (TWA decomposition. In comparison with some available methods, the proposed algorithm, which efficiently makes use of the array aperture, can localize sources using sensors. In addition, it requires neither pairing parameters nor multidimensional search. Simulation results are presented to validate the performance of the proposed method.

  8. 4D Near-Field Source Localization Using Cumulant

    Directory of Open Access Journals (Sweden)

    Junying Zhang

    2007-01-01

    Full Text Available This paper proposes a new cumulant-based algorithm to jointly estimate four-dimensional (4D source parameters of multiple near-field narrowband sources. Firstly, this approach proposes a new cross-array, and constructs five high-dimensional Toeplitz matrices using the fourth-order cumulants of some properly chosen sensor outputs; secondly, it forms a parallel factor (PARAFAC model in the cumulant domain using these matrices, and analyzes the unique low-rank decomposition of this model; thirdly, it jointly estimates the frequency, two-dimensional (2D directions-of-arrival (DOAs, and range of each near-field source from the matrices via the low-rank three-way array (TWA decomposition. In comparison with some available methods, the proposed algorithm, which efficiently makes use of the array aperture, can localize N−3 sources using N sensors. In addition, it requires neither pairing parameters nor multidimensional search. Simulation results are presented to validate the performance of the proposed method.

  9. Near-Field Diffraction from a Binary Microaxicon

    Directory of Open Access Journals (Sweden)

    Victor V. Kotlyar

    2012-01-01

    Full Text Available We study binary axicons of period 4, 6, and 8 μm fabricated by photolithography with a 1 μm resolution, 500 nm depth, and 4 mm diameter. Near-field diffraction focal spots varying in diameter from 3.5λ to 4.5λ (for the axicon of period T=4 μm and from 5λ to 8λ (for the axicon with T=8 μm are experimentally found on the optical axis at a distance of up to 40 μm from the axicon for the wavelength λ=0.532 μm. The first focal spot is found at distance 2 μm (T=4 μm, with the period of the focal spots being 2 μm (T=4 μm and 4 μm (T=8 μm. Diffraction of linearly polarized plane and diverging waves is simulated using FullWAVE (RSoft and a proprietary program BOR-FDTD, which implement finite-difference schemes to solve three-dimensional Maxwell's equations in the Cartesian and cylindrical coordinates. The numerically simulated values for diameters of the near-field focal spots for the axicon of period T=4 μm are in good agreement with the experimental values.

  10. Near-Field Based Communication and Electrical Systems

    Science.gov (United States)

    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

  11. Application of the SWE-to-PWE antenna diagnostics technique to an offset reflector antenna

    DEFF Research Database (Denmark)

    Cappellin, Cecilia; Frandsen, A; Breinbjerg, Olav

    2007-01-01

    A new antenna diagnostics technique has been developed for the DTU-ESA Spherical Near-Field Antenna Test Facility at the Technical University of Denmark. The technique is based on the transformation of the Spherical Wave Expansion (SWE) of the radiated field, obtained from a spherical near...... will be detected in the antenna far-field pattern, and the accuracy and ability of the diagnostics technique to subsequently identify them will be investigated. Real measurement data will be employed for each test case....... measurement accuracy, have been reported previously, we validate here the new antenna diagnostics technique through an experimental investigation of a commercially available offset reflector antenna, where a tilt of the feed and surface distortions are intentionally introduced. The effects of these errors...

  12. Acoustic source localization in mixed field using spherical microphone arrays

    Science.gov (United States)

    Huang, Qinghua; Wang, Tong

    2014-12-01

    Spherical microphone arrays have been used for source localization in three-dimensional space recently. In this paper, a two-stage algorithm is developed to localize mixed far-field and near-field acoustic sources in free-field environment. In the first stage, an array signal model is constructed in the spherical harmonics domain. The recurrent relation of spherical harmonics is independent of far-field and near-field mode strengths. Therefore, it is used to develop spherical estimating signal parameter via rotational invariance technique (ESPRIT)-like approach to estimate directions of arrival (DOAs) for both far-field and near-field sources. In the second stage, based on the estimated DOAs, simple one-dimensional MUSIC spectrum is exploited to distinguish far-field and near-field sources and estimate the ranges of near-field sources. The proposed algorithm can avoid multidimensional search and parameter pairing. Simulation results demonstrate the good performance for localizing far-field sources, or near-field ones, or mixed field sources.

  13. Study of Near Field Communication Technology in University Scenarios

    Science.gov (United States)

    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.

  14. Multi-mode Scanning Near-field Optical Microscope

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    A scanning near-field optical microscope using uncoated fiber tip is described, which can work in transmission and reflection configurations, both capable of working in illumination and collection-mode, so that either transparent or opaque sample can be investigated. Depending on different applications, either constant-gap or constant-height images can be achieved. A compact homemade translator permits to select interested area of sample in the range of 4mm×4mm. Working in the constant-height as well as transmission and collection-mode configuration, several kinds of samples such as holographic grating, liposome and zeolite were investigated. The experimental results revealed the dependence of the optical resolution of the SNOM on the tip-sample separation.

  15. Photocurrent mapping of near-field optical antenna resonances.

    Science.gov (United States)

    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 radiative heat transfer between two nonlocal dielectrics

    CERN Document Server

    Singer, F; Joulain, Karl

    2015-01-01

    We explore in the present work the near-field radiative heat transfer between two semi-infinite parallel nonlocal dielectric planes by means of fluctuational electrodynamics. We use atheory for the nonlocal dielectric permittivityfunction proposed byHalevi and Fuchs. This theory has the advantage to includedifferent models performed in the literature. According to this theory, the nonlocal dielectric function is described by a Lorenz-Drude like single oscillator model, in which the spatial dispersion effects are represented by an additional term depending on the square of the total wavevector k. The theory takes into account the scattering of the electromagneticexcitation at the surface of the dielectric material, which leads to the need of additional boundary conditions in order to solve Maxwell's equations and treat the electromagnetic transmission problem. The additional boundary conditions appear as additional surface scattering parameters in the expressions of the surface impedances. It is shown that the...

  17. Experimental studies on near-field holographic antenna measurement

    Science.gov (United States)

    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.

  18. Utilization of Near Field Communication Technology for Loyalty Management

    Directory of Open Access Journals (Sweden)

    Ferina Ferdianti

    2013-09-01

    Full Text Available Near Field Communication (NFC is one of wireless technology developed at this time. We can use a mobile phone to do many transactions with NFC. Mobile developments have created to provide convenience for users in all aspects. However, at this time the function of NFC just limited for payment and micropayment. Beside it, there are assets that support to increase sales with attention of loyality management system. In this system, discounts or prizes are given based on data mining for every transaction costumers. Loyalty management has three concept, those are Frequency, Recency and Quantity. The goals are minimizing the cost, making purchase process faster, and managing data obtained through the NFC technology more simple. The result of this paper is the procedure to use data mining of NFC for loyalty management and system design using Unified Modeling Language approach.

  19. Near-Field Cosmology with Metal-Poor Stars

    CERN Document Server

    Frebel, Anna

    2015-01-01

    The oldest, most metal-poor stars in the Galactic halo and satellite dwarf galaxies present an opportunity to explore the chemical and physical conditions of the earliest star forming environments in the Universe. We review the fields of stellar archaeology and dwarf galaxy archaeology by examining the chemical abundance measurements of various elements in extremely metal-poor stars. Focus on the carbon-rich and carbon-normal halo star populations illustrates how these provide insight into the Population III star progenitors responsible for the first metal enrichment events. We extend the discussion to near-field cosmology, which is concerned with the formation of the first stars and galaxies and how metal-poor stars can be used to constrain these processes. Complementary abundance measurements in high-redshift gas clouds further help to establish the early chemical evolution of the Universe. The data appear consistent with the existence of two distinct channels of star formation at the earliest times.

  20. Eavesdropping near-field contactless payments: a quantitative analysis

    Directory of Open Access Journals (Sweden)

    Thomas P. Diakos

    2013-10-01

    Full Text Available This paper presents an assessment of how successful an eavesdropping attack on a contactless payment transaction can be in terms of bit and frame error rates, using an easily concealable antenna and low-cost electronics. Potential success of an eavesdropping attack largely depends on the correct recovery of the data frames used in the ISO 14443 standard. A near-field communication inductive loop antenna was used to emulate an ISO 14443 transmission. For eavesdropping, an identical inductive loop antenna as well as a shopping trolley modified to act like an antenna were used. The authors present and analyse frame error rates obtained with the authors equipment over a range of distances, up to 100 cm, well above the official maximum operating distance depending on the magnetic field strength.

  1. Measurement of incident sound power using near field acoustic holography

    DEFF Research Database (Denmark)

    Jacobsen, Finn; Tiana Roig, Elisabet

    2009-01-01

    ; and it has always been regarded as impossible to measure the sound power that is incident on a wall directly. This paper examines a new method of determining this quantity from sound pressure measurements at positions on the wall using ‘statistically optimised near field acoustic holography’ (SONAH......The conventional method of measuring the insertion loss of a partition relies on an assumption of the sound field in the source room being diffuse and the classical relation between the spatial average of the mean square pressure in the source room and the incident sound power per unit area......). The purpose is to examine whether one should use a correction similar to the well-known ‘Waterhouse correction’ when the incident sound power is deduced from the sound pressure in the source room....

  2. Scanning near field microwave microscopy based on an active resonator

    Science.gov (United States)

    Qureshi, Naser; Kolokoltsev, Oleg; Ordonez-Romero, Cesar Leonardo

    2014-03-01

    A large number of recent implementations of near field scanning microwave microscopy (NFSMM) have been based on the perturbation of a resonant cavity connected to a sharp scanning probe. In this work we present results from an alternative approach: the perturbation of a microwave source connected to a scanning tip. Based on a yittrium iron garnet (YIG) cavity ring resonator this scanning probe system has a quality factor greater than 106, which allows us to detect very small frequency shifts, which translates to a very high sensitivity in sample impedance measurements. Using a selection of representative semiconductor, metal and biological samples we show how this approach leads to unusually high sensitivity and spatial resolution. Work supported by a grant from PAPIIT, UNAM 104513.

  3. Approaches to eliminate near field artifact of MURA

    Institute of Scientific and Technical Information of China (English)

    WANG Ren-Song; RONG Jun-Yan; WEI Long

    2008-01-01

    Since the coded aperture technique has been successfully applied on X-ray imaging space telescopes, attentions of its development have also been cast on the application in medical imaging, for it has a very tempting quality to greatly enhance the detection sensitivity without gravely lowering the spacial resolution. But when the coded aperture technique is applied to image a nearby object, the so called "near-field artifact"comes up, that is, the reconstructed image has a sort of distortion. Among types of coded apertures the MURA (Modified Uniformly Redundant Array) is one of the most discussed. Roberto Arrcosi came up with the solution to remove the artifacts utilizing mask and antimask. In this article we present two ways to eliminate the second order aberration based on his work.

  4. Near-field scanning microwave microscopy of microwave devices

    Science.gov (United States)

    Vlahacos, C. P.; Steinhauer, David E.; Dutta, S.; Anlage, S. M.; Wellstood, F. C.; Newman, H.

    1997-03-01

    We have developed a scanning microwave microscope which can presently image features with a spatial resolution of 10-100 μm in the frequency range 5-15 GHz.(C. P. Vlahacos, et al.), Appl. Phys. Lett. 69, 3272 (1996).^,(S. M. Anlage, et al.), IEEE. Trans. Appl. Supercond. (1997). The microscope consists of a resonant section of a coaxial cable which is terminated with a small-diameter open-ended coaxial probe. Images are made by scanning the sample under the probe while recording the induced near-field microwave voltage as a function of sample position. We will present images for several microwave devices, including an X-band microstrip planar ferrite circulator and a high-temperature superconducting microstrip YBa_2Cu_3O_7-δ resonator, and compare them to the calculated field profiles.

  5. Near-Field, On-Chip Optical Brownian Ratchets.

    Science.gov (United States)

    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.

  6. Discrete and continuum simulations of near-field ground motion from Source Physics Experiments (SPE) (Invited)

    Science.gov (United States)

    Ezzedine, S. M.; Vorobiev, O.; Herbold, E. B.; Glenn, L. A.; Antoun, T.

    2013-12-01

    This work is focused on analysis of near-field measurements (up to 100 m from the source) recorded during Source Physics Experiments in a granitic formation. One of the main goals of these experiments is to investigate the possible mechanisms of shear wave generation in the nonlinear source region. SPE experiments revealed significant tangential motion (up to 30 % of the magnitude in the radial direction) at many locations. Furthermore, azimuthal variations in radial velocities were also observed which cannot be generated by a spherical source in isotropic materials. Understanding the nature of this non-radial motion is important for discriminating between the natural seismicity and underground explosions signatures. Possible mechanisms leading to such motion include, but not limited to, heterogeneities in the rock such as joints, faults and geologic layers as well as surface topography and vertical motion at the surface caused by material spall and gravity. We have performed a three dimensional computational studies considering all these effects. Both discrete and continuum methods have been employed to model heterogeneities. In the discrete method, the joints and faults were represented by cohesive contact elements. This enables us to examine various friction laws at the joints which include softening, dilatancy, water saturation and rate-dependent friction. Yet this approach requires the mesh to be aligned with joints, which may present technical difficulties in three dimensions when multiple non-persistent joints are present. In addition, the discrete method is more computationally expensive. The continuum approach assumes that the joints are stiff and the dilatancy and shear softening can be neglected. In this approach, the joints are modeled as weakness planes within the material, which are imbedded into and pass through many finite elements. The advantage of this approach is that it requires neither sophisticated meshing algorithms nor contact detection

  7. Spherical models

    CERN Document Server

    Wenninger, Magnus J

    2012-01-01

    Well-illustrated, practical approach to creating star-faced spherical forms that can serve as basic structures for geodesic domes. Complete instructions for making models from circular bands of paper with just a ruler and compass. Discusses tessellation, or tiling, and how to make spherical models of the semiregular solids and concludes with a discussion of the relationship of polyhedra to geodesic domes and directions for building models of domes. "". . . very pleasant reading."" - Science. 1979 edition.

  8. Near-field chemistry of the spent nuclear fuel repository; Kemialliset vuorovaikutukset kaeytetyn ydinpolttoaineen loppusijoitustilan laehialueella

    Energy Technology Data Exchange (ETDEWEB)

    Kumpulainen, H.; Lehikoinen, J.; Muurinen, A.; Ollila, K. [VTT Chemical Technology, Espoo (Finland). Industrial Physics

    1998-07-01

    Factors affecting near-field chemistry of the spent nuclear fuel repository as well as the involved mutual interactions are described on the basis of literature. The most important processes in the near-field (spent-fuel, canister and bentonite) are presented. The related examples on near-field chemistry models shed light on the extensive problematics of near-field chemistry. (authors) 80 refs.

  9. Near-field for electrodynamics at sub-wavelength scales: generalizing to an arbitrary number of dielectrics.

    Science.gov (United States)

    Li, Shaohong; Gao, Yi; Neuhauser, Daniel

    2012-06-21

    We extend the recently developed near-field (NF) method to include an arbitrary number of dielectrics. NF assumes that the dipoles and fields respond instantaneously to the density, without retardation. The central task in NF is the solution of the Poisson equation for every time step, which is here done by a conjugate gradient method which handles any dielectric distribution. The optical response of any metal-dielectric system can now be studied very efficiently in the near field region. The improved NF method is first applied to simple benchmark systems: a gold nanoparticle in vacuum and embedded in silica. The surface plasmons in these systems and their dependence on the dielectrics are reproduced in the new NF approach. As a further application, we study a silver nanoparticle-based structure for the optical detection of a "lipid" (i.e., dielectric) layer in water, where the layer is wrapping around part of the metallic nanostructure. We show the ~0.1-0.15 eV shift in the spectrum due to the presence of the layer, for both spherical and non-spherical (sphere+rod) systems with various polarizations.

  10. Flexible Passive near Field Communication Tag for Multigas Sensing.

    Science.gov (United States)

    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.

  11. Application of Near Field Communication Technology for Mobile Airline Ticketing

    Directory of Open Access Journals (Sweden)

    Wayan Suparta

    2012-01-01

    Full Text Available Problem statement: Near Field Communication (NFC technology opens up exciting new usage scenarios for mobile devices based platform. Users of NFC-enabled devices can simply point or touch their devices to other NFC-enabled elements in the environment to communicate with them (‘contactless’, making application and data usage easy and convenient. Approach: The study describes the characteristics and advantages of NFC technology offers for the development of mobile airline ticketing. This scenario describes the potential to overcome the conventional systems that are not gated and use study tickets. In such a system, today a transport application can be loaded on a NFC-enabled phone. To study such a case, Yogyakarta International Airport was taken as an example for a discussion. Results: NFC technology which consisting of three modes of operation and with international standardization can be applied as contactless to simplicity transactions, content delivery and information sharing on a mobile based platform. Conclusion: The idea of NFC application for mobile airline ticketing has been discussed for Yogyakarta International Airport."

  12. Viscoacoustic model for near-field ultrasonic levitation.

    Science.gov (United States)

    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.

  13. Photocurrent mapping of near-field optical antenna resonances

    KAUST Repository

    Barnard, Edward S.

    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 (∼50nm) and wavelength-scale (∼1μm) 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. © 2011 Macmillan Publishers Limited. All rights reserved.

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

    Directory of Open Access Journals (Sweden)

    Changhai Ru

    2014-01-01

    Full Text Available 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.

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

    Energy Technology Data Exchange (ETDEWEB)

    Ru, Changhai, E-mail: rchhai@gmail.com, E-mail: luojun@shu.edu.cn [College of Automation, Harbin Engineering University, Harbin 150001 (China); Robotics and Microsystems Center, Soochow University, Suzhou 215021 (China); Chen, Jie; Shao, Zhushuai [Robotics and Microsystems Center, Soochow University, Suzhou 215021 (China); Pang, Ming [College of Automation, Harbin Engineering University, Harbin 150001 (China); Luo, Jun, E-mail: rchhai@gmail.com, E-mail: luojun@shu.edu.cn [School of Mechatronics Engineering and Automation, Shanghai University, Shanghai 200072 (China)

    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.

  16. Entropic and Near-Field Improvements of Thermoradiative Cells

    Science.gov (United States)

    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.

  17. Wearable near-field communication antennas with magnetic composite films

    Science.gov (United States)

    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.

  18. 3D manipulation with a scanning near field optical nanotweezers

    CERN Document Server

    Berthelot, J; Juan, M L; Kreuzer, M P; Renger, J; Quidant, R

    2013-01-01

    Recent advances in Nanotechnologies have prompted the need for tools to accurately and non-invasively manipulate individual nano-objects. Among possible strategies, optical forces have been foreseen to provide researchers with nano-optical tweezers capable to trap a specimen and move it in 3D. In practice though, the combination of weak optical forces involved and photothermal issues have thus far prevented their experimental realization. Here, we demonstrate first 3D optical manipulation of single 50 nm dielectric objects with near field nano-tweezers. The nano-optical trap is built by engineering a bowtie plasmonic aperture at the extremity of a tapered metal-coated optical fiber. Both the trapping operation and monitoring are performed through the optical fiber making these nano-tweezers totally autonomous and free of bulky optical elements. The achieved trapping performances allow for the trapped specimen to be moved over tens of micrometers during several minutes with very low in-trap intensities. This n...

  19. Effects of Boundary Conditions on Near Field Plasma Plume Simulations

    Science.gov (United States)

    Boyd, Iain

    2004-11-01

    The successful development of various types of electric propulsion devices is providing the need for accurate assessment of integration effects generated by the interaction of the plasma plumes of these thrusters with the host spacecraft. Assessment of spacecraft interaction effects in ground based laboratory facilities is inadequate due to the technical difficulties involved in accurately recreating the near vacuum ambient conditions experienced in space. This situation therefore places a heavy demand on computational modeling of plasma plume phenomena. Recently (Boyd and Yim, Journal of Applied Physics, Vol. 95, 2004, pp. 4575-5484) a hybrid model of the near field of the plume of a Hall thruster was reported in which the heavy species are modeled using particles and the electrons are modeled using a detailed fluid description. The present study continues the model development and assessment by considering the sensitivity of computed results to different types of boundary conditions that must be formulated for the thruster exit, for the cathode exit, for the thruster walls, and for the plume far field. The model is assessed through comparison of its predictions with several sets of experimental data measured in the plume of the BHT-200 Hall thruster.

  20. Interfacing external sensors with Android smartphones through near field communication

    Science.gov (United States)

    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.

  1. Imaging Biological Systems using Dielectric Near-Field Microscopy

    Science.gov (United States)

    Brown, Keith; Issadore, David; Hunt, Tom; Westervelt, Robert

    2007-03-01

    We have developed a dielectric spectrometer for use on biological systems. The spectrum of dielectric response to RF electric fields is analogous to color as an optical response. Measurement of the dielectric spectrum from ˜ 10 kHz to ˜ 3 GHz will reveal information about the structure and conditions of protein solutions, protein crystals and biological tissues. We designed and built a system to test biological samples in a microfluidic chamber mounted on a circuit board. The apparatus measures the RF dielectric spectrum directly, or by analyzing the pulse response in the time domain. We have constructed several versions of the hardware for sensitive capacitive measurements, including two types of capacitive bridges, and a transmission line, incorporating precision electronics and local generation of pulses. A goal is to scale the system down and implement many dielectric spectrometers as an array of pixels on a CMOS chip for dielectric near-field microscopy of biological samples. This work made possible by NSEC NSF grant PHY-0117795 and the NCI MIT-Harvard CCNE.

  2. Heterodyne method of apertureless near-field scanning optical microscopy on periodic gold nanowells.

    Energy Technology Data Exchange (ETDEWEB)

    Hall, J. E.; Wiederrecht, G. P.; Gray, S. K.; Chang, S.-H.; Jeon, S.; Rogers, J. A.; Bachelot, R.; Royer, P.; Univ. of Illinois; Univ. of Technology at Troyes; Inst. of Electro-Optical Science and Engineering

    2007-04-02

    Heterodyne detection for apertureless near-field scanning optical microscopy was used to study periodic gold nanowell arrays. Optical near-field amplitude and phase signals were obtained simultaneously with the topography of the gold nanowells and with different polarizations. Theoretical calculations of the near-fields were consistent with the experiments; in particular, the calculated amplitudes were in especially good agreement. The heterodyne method is shown to be particularly effective for these types of periodic photonic structures and other highly scattering media, which can overwhelm the near-field scattered signal when conventional apertureless near-field scanning optical microscopy is used.

  3. Mie calculation of electromagnetic near-field for a multilayered sphere

    Science.gov (United States)

    Ladutenko, Konstantin; Pal, Umapada; Rivera, Antonio; Peña-Rodríguez, Ovidio

    2017-05-01

    We have developed an algorithm to calculate electric and magnetic fields inside and around a multilayered sphere. The algorithm includes explicit expressions for Mie expansion coefficients inside the sphere and calculation of the vector spherical harmonics in terms of the Riccati-Bessel functions and their logarithmic derivatives. This novel approach has been implemented in the new version of our program scattnlay. Scattnlay 2.0 will be the first publicly available (at GitHub, https://github.com/ovidiopr/scattnlay) program, based on the Mie theory, which can calculate near-fields for the general case of a multilayer sphere. Several tests were designed to verify that the results obtained with our code match literature results and those obtained through similar programs (limited to core-shell structures) or full-wave 3D simulations. These tests demonstrate that the implementation is effective, yielding accurate values of electric and magnetic fields for a wide range of size parameters, number of layers, and refractive indices.

  4. Near-Field Acoustic Resonance Scattering of a Finite Bessel Beam by an Elastic Sphere

    CERN Document Server

    Mitri, F G

    2014-01-01

    The near-field acoustic scattering from a sphere centered on the axis of a finite Bessel acoustic beam is derived stemming from the Rayleigh-Sommerfeld diffraction surface integral and the addition theorems for the spherical wave and Legendre functions. The beam emerges from a finite circular disk vibrating according to one of its radial modes corresponding to the fundamental solution of a Bessel beam J0. The incident pressure field's expression is derived analytically as a partial-wave series expansion taking into account the finite size and the distance from the center of the disk transducer. Initially, the scattered pressure by a rigid sphere is evaluated, and backscattering pressure moduli plots as well as 3-D directivity patterns for an elastic PMMA sphere centered on a finite Bessel beam with appropriate tuning of its half-cone angle, reveal possible resonance suppression of the sphere only in the zone near the Bessel transducer. Moreover, the analysis is extended to derive the mean spatial incident and...

  5. Far- and near-field optical properties of gold nanoparticle ensembles

    Energy Technology Data Exchange (ETDEWEB)

    Nedyalkov, N N; Dikovska, A O; Dimitrov, I; Nikov, Ru; Atanasov, P A; Toshkova, R A; Gardeva, E G; Yossifova, L S; Alexandrov, M T

    2012-12-31

    The optical properties of gold nanoparticle clusters are presented from the point of view of their applications in biophotonics, where the absorption and scattering spectra are crucial. Generalised multiparticle Mie theory and finite difference time domain (FDTD) technique are used for theoretical description of the far- and nearfield optical properties of two dimensional nanoparticle ensembles. The system under consideration consists of spherical gold nanoparticles from 20 to 200 nm in diameter, forming 2D clusters in water. The properties of the far-field absorption and scattering spectra as a function of the cluster size, particle dimensions, and interparticle distance are investigated for ordered hexagonal structure of the particle arrays. It is found that the absorption efficiency can be shifted to the IR spectral range by increasing array size and decreasing interparticle distance. The increase in the array size also results in enhancement of the scattering efficiency while the absorption is reduced. The near-field intensity distribution is inhomogeneous over the array, as formation of zones with intensity enhancement of about two orders of magnitude is observed in specific areas. The optical properties of an ensemble whose configuration is reproduced from real experiments of gold nanoparticle deposition onto cancer cells are also presented. The results obtained can be used in designing of nanoparticle arrays with applications in biophotonics, bioimaging and photothermal therapy. (nanosystems)

  6. Design of Scattering Scanning Near-Field Optical Microscope

    Science.gov (United States)

    Schrecongost, Dustin

    The primary objective of this work is to construct a fully functional scattering type Scanning Near-field Optical Microscope (s-SNOM), and to understand the working mechanisms behind it. An s-SNOM is an instrument made up of two separate instruments working in unison. One instrument is a scanning optical microscope focusing light onto a raster scanning sample surface combined with an interferometer set up. The second instrument is an Atomic Force Microscope (AFM) operating in noncontact mode. The AFM uses a small probe that interacts with the raster scanning sample surface to map out the topography of the of the sample surface. An s-SNOM uses both of these instruments simultaneously by focusing the light of the optical microscope onto the probe of the AFM. This probe acts as a nano-antenna and confines the light allowing for light-matter interaction to be inferred far below the resolution of the diffraction limit of light. This specific s-SNOM system is unique to others by having a controllable environment. It is high vacuum compatible and variable temperature. In addition, it is efficient at collecting scattered light due to the focusing objective being a partial elliptical mirror which collects 360° of light around the major axis. This s-SNOM system will be used for direct imaging of surface plasmons. Intended works are inducing surface plasmons on InSe thin films, and seeing the enhancement effect of introducing Au nano-rods. Also dielectric properties of materials will be interpreted such as the metal to insulator phase transition of NbO2.

  7. Near Field Communication-based telemonitoring with integrated ECG recordings.

    Science.gov (United States)

    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.

  8. Review of near-field optics and superlenses for sub-diffraction-limited nano-imaging

    Directory of Open Access Journals (Sweden)

    Wyatt Adams

    2016-10-01

    Full Text Available Near-field optics and superlenses for imaging beyond Abbe’s diffraction limit are reviewed. A comprehensive and contemporary background is given on scanning near-field microscopy and superlensing. Attention is brought to recent research leveraging scanning near-field optical microscopy with superlenses for new nano-imaging capabilities. Future research directions are explored for realizing the goal of low-cost and high-performance sub-diffraction-limited imaging systems.

  9. Generalized spectral method for near-field optical microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, B.-Y.; Zhang, L. M.; Basov, D. N.; Fogler, M. M. [Department of Physics, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093 (United States); Castro Neto, A. H. [Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215 (United States); Centre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore 117542 (Singapore)

    2016-02-07

    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 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 on the surface reflectivity of the material. Calculation of such resonances is carried out for several types of axisymmetric probes: spherical, spheroidal, and pear-shaped. For spheroids, an efficient numerical method is developed, capable of handling cases of large or strongly momentum-dependent surface reflectivity. Application of the method to highly resonant materials, such as aluminum oxide (by itself or covered with graphene), reveals a rich structure of multi-peak spectra and nonmonotonic approach curves, i.e., the probe-sample distance dependence. These features also strongly depend on the probe shape and optical constants of the model. For less resonant materials such as silicon oxide, the dependence is weak, so that the spheroidal model is reliable. The calculations are done within the quasistatic approximation with radiative damping included perturbatively.

  10. Super-Resolution Imaging on Microfluidic Super-Resolution Near-Field Structure

    Institute of Scientific and Technical Information of China (English)

    WANG Pei; TANG Lin; ZHANG Dou-Guo; LU Yong-Hua; JIAO Xiao-Jin; XIE Jian-Ping; MING Hai

    2005-01-01

    @@ We present a new concept of the microfluidic super-resolution near-field structure (MSRENS) based on a microfluidic structure and a super-resolution near-field structure. The near-field distance control, "nano-probe"and scanning can be realized simultaneously using the MSRENS, which is similar to a near-field scanning optical microscope. The design and simulation results are presented. Numerical simulation has demonstrated that the MSRENS with spatial resolution beyond the diffraction limit could be applicable in chemistry, biologics, and many other fields.

  11. Polarization resolved imaging with a reflection near-field optical microscope

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Xiao, Mufei; Hvam, Jørn Märcher

    1999-01-01

    Using a rigorous microscopic point-dipole description of probe-sample interactions, we study imaging with a reflection scanning near-field optical microscope. Optical content, topographical artifacts, sensitivity window-i.e., the scale on which near-field optical images represent mainly optical...... configuration is preferable to the cross-linear one, since it ensures more isotropic (in the surface plane) near-field imaging of surface features. The numerical results are supported with experimental near-field images obtained by using a reflection microscope with an uncoated fiber tip....

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

    Science.gov (United States)

    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.

  13. Three Dimensional Subwavelength focus by a near-field plate lens

    CERN Document Server

    Lan, Lu; Ma, Yungui

    2013-01-01

    We implemented the inverse design method to build a thin near-field lens that could produce a desired subwavelength focus by manipulating the near fields of a magnetic dipole source. The flat near-field lens represented by an artificial impedance surface was fabricated by lumped reactive elements (capacitor and inductor) with spatially varying values. In the experiment a desired annular focusing spot with a characteristic size nearly three times smaller than that allowed by the diffraction limit was obtained. Besides high-resolution imaging, the proposed near-field plate could be extended for other interesting applications, such as wireless power transfer or complex wavefront/beam shaper.

  14. Very high-accuracy calibration of radiation pattern and gain of a near-field probe

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Nielsen, Jeppe Majlund; Breinbjerg, Olav

    2014-01-01

    In this paper, very high-accuracy calibration of the radiation pattern and gain of a near-field probe is described. An open-ended waveguide near-field probe has been used in a recent measurement of the C-band Synthetic Aperture Radar (SAR) Antenna Subsystem for the Sentinel 1 mission of the Europ......In this paper, very high-accuracy calibration of the radiation pattern and gain of a near-field probe is described. An open-ended waveguide near-field probe has been used in a recent measurement of the C-band Synthetic Aperture Radar (SAR) Antenna Subsystem for the Sentinel 1 mission...

  15. Numerical Modeling of a Near-Field Scanning Optical System

    Science.gov (United States)

    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

  16. Electric and magnetic surface polariton mediated near-field radiative heat transfer between metamaterials made of silicon carbide particles.

    Science.gov (United States)

    Francoeur, Mathieu; Basu, Soumyadipta; Petersen, Spencer J

    2011-09-26

    Near-field radiative heat transfer between isotropic, dielectric-based metamaterials is analyzed. A potassium bromide host medium comprised of silicon carbide (SiC) spheres with a volume filling fraction of 0.4 is considered for the metamaterial. The relative electric permittivity and relative magnetic permeability of the metamaterial are modeled via the Clausius-Mossotti relations linking the macroscopic response of the medium with the polarizabilities of the spheres. We show for the first time that electric and magnetic surface polariton (SP) mediated near-field radiative heat transfer occurs between dielectric-based structures. Magnetic SPs, existing in TE polarization, are physically due to strong magnetic dipole resonances of the spheres. We find that spherical inclusions with radii of 1 μm (or greater) are needed in order to induce SPs in TE polarization. On the other hand, electric SPs existing in TM polarization are generated by surface modes of the spheres, and are thus almost insensitive to the size of the inclusions. We estimate that the total heat flux around SP resonance for the metamaterial comprised of SiC spheres with radii of 1 μm is about 35% greater than the flux predicted between two bulks of SiC, where only surface phonon-polaritons in TM polarization are excited. The results presented in this work show that the near-field thermal spectrum can be engineered via dielectric-based metamaterials, which is crucial in many emerging technologies, such as in nanoscale-gap thermophotovoltaic power generation. © 2011 Optical Society of America

  17. Near-field microscopy with a microfabricated solid immersion lens

    Science.gov (United States)

    Fletcher, Daniel Alden

    2001-07-01

    Diffraction of focused light prevents optical microscopes from resolving features in air smaller than half the wavelength, λ Spatial resolution can be improved by passing light through a sub-wavelength metal aperture scanned close to a sample, but aperture-based probes suffer from low optical throughput, typically below 10-4. An alternate and more efficient technique is solid immersion microscopy in which light is focused through a high refractive index Solid Immersion Lens (SIL). This work describes the fabrication, modeling, and use of a microfabricated SIL to obtain spatial resolution better than the diffraction limit in air with high optical throughput for infrared applications. SILs on the order of 10 μm in diameter are fabricated from single-crystal silicon and integrated onto silicon cantilevers with tips for scanning. We measure a focused spot size of λ/5 with optical throughput better than 10-1 at a wavelength of λ = 9.3 μm. Spatial resolution is improved to λ/10 with metal apertures fabricated directly on the tip of the silicon SIL. Microlenses have reduced spherical aberration and better transparency than large lenses but cannot be made arbitrarily small and still focus. We model the advantages and limitations of focusing in lenses close to the wavelength in diameter using an extension of Mie theory. We also investigate a new contrast mechanism unique to microlenses resulting from the decrease in field-of-view with lens diameter. This technique is shown to achieve λ/4 spatial resolution. We explore applications of the microfabricated silicon SIL for high spatial resolution thermal microscopy and biological spectroscopy. Thermal radiation is collected through the SIL from a heated surface with spatial resolution four times better than that of a diffraction- limited infrared microscope. Using a Fourier-transform infrared spectrometer, we observe absorption peaks in bacteria cells positioned at the focus of the silicon SIL.

  18. Accurate Modeling of Advanced Reflectarrays

    DEFF Research Database (Denmark)

    Zhou, Min

    Analysis and optimization methods for the design of advanced printed re ectarrays have been investigated, and the study is focused on developing an accurate and efficient simulation tool. For the analysis, a good compromise between accuracy and efficiency can be obtained using the spectral domain...... to the POT. The GDOT can optimize for the size as well as the orientation and position of arbitrarily shaped array elements. Both co- and cross-polar radiation can be optimized for multiple frequencies, dual polarization, and several feed illuminations. Several contoured beam reflectarrays have been designed...... using the GDOT to demonstrate its capabilities. To verify the accuracy of the GDOT, two offset contoured beam reflectarrays that radiate a high-gain beam on a European coverage have been designed and manufactured, and subsequently measured at the DTU-ESA Spherical Near-Field Antenna Test Facility...

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

    Energy Technology Data Exchange (ETDEWEB)

    Codell, R.B.; Baca, R.G.; Ahola, M.P. [and others

    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.

  20. STATISTICALLY OPTIMISED NEAR FIELD ACOUSTIC HOLOGRAPHYAND THE HELMHOLTZ EQUATION LEAST SQUARESMETHOD: A COMPARISON

    DEFF Research Database (Denmark)

    Gomes, Jesper Skovhus; Jacobsen, Finn

    Several variants of near field acoustic holography (NAH) that do not require measurement areas larger than the source have been proposed. This paper examines and compares two such methods, statistically optimised near field acoustic holography (SONAH) and the Helmholtz equation least squares method...

  1. Optimization of s-Polarization Sensitivity in Apertureless Near-Field Optical Microscopy

    Directory of Open Access Journals (Sweden)

    Yuika Saito

    2012-01-01

    Full Text Available It is a general belief in apertureless near-field microscopy that the so-called p-polarization configuration, where the incident light is polarized parallel to the axis of the probe, is advantageous to its counterpart, the s-polarization configuration, where the incident light is polarized perpendicular to the probe axis. While this is true for most samples under common near-field experimental conditions, there are samples which respond better to the s-polarization configuration due to their orientations. Indeed, there have been several reports that have discussed such samples. This leads us to an important requirement that the near-field experimental setup should be equipped with proper sensitivity for measurements with s-polarization configuration. This requires not only creation of effective s-polarized illumination at the near-field probe, but also proper enhancement of s-polarized light by the probe. In this paper, we have examined the s-polarization enhancement sensitivity of near-field probes by measuring and evaluating the near-field Rayleigh scattering images constructed by a variety of probes. We found that the s-polarization enhancement sensitivity strongly depends on the sharpness of the apex of near-field probes. We have discussed the efficient value of probe sharpness by considering a balance between the enhancement and the spatial resolution, both of which are essential requirements of apertureless near-field microscopy.

  2. A Monopole Antenna at Optical Frequencies: Single-Molecule Near-Field Measurements

    NARCIS (Netherlands)

    Taminiau, Tim H.; Segerink, Franciscus B.; van Hulst, N.F.

    2007-01-01

    We present a monopole antenna for optical frequencies (~600 THz) and discuss near-field measurements with single fluorescent molecules as a technique to characterize such antennas. The similarities and differences between near-field antenna measurements at optical and radio frequencies are discussed

  3. Design and performance verification of a wideband scalable dual-polarized probe for spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Kim, Oleksiy S.; Nielsen, Jeppe Majlund;

    2012-01-01

    A wideband scalable dual-polarized probe designed by the Electromagnetic Systems group at the Technical University of Denmark is presented. The design was scaled and two probes were manufactured for the frequency bands 1-3 GHz and 0.4-1.2 GHz. The results of the acceptance tests of the 0.4-1.2 GH...

  4. Extending the Bandwidth of a Superdirective First-Order Probe for Spherical Near-Field Antenna Measurements

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.

    2015-01-01

    . This contribution shows that a very narrow frequency bandwidth peculiar to superdirective antennas can be extended to practical values by the proper design of the array elements as well as by relaxing the maximum directivity condition, while keeping |µ| = 1 modes dominating in the radiation spectrum of the antenna...

  5. On the applicability of the spherical wave expansion with a single origin for near-field acoustical holography

    DEFF Research Database (Denmark)

    Gomes, J.; Hald, J.; Juhl, P.

    2009-01-01

    regularization (the truncated singular value decomposition) is introduced. Important differences between applying the method when using a microphone array surrounding the source completely and an array covering only a part of the source are described. Another relevant issue is the scaling of the wave functions...... the sound field model to the measured pressure close to the source. This problem is ill posed, and therefore regularization is required. The present paper investigates the consequence of using only the expansion truncation as regularization approach and compares it with results obtained when additional...

  6. A Novel Algorithm Based on 3D-MUSIC Algorithm for Localizing Near-Field Source

    Institute of Scientific and Technical Information of China (English)

    SHAN Zhi-yong; ZHOU Xi-lang; PEN Gen-jiang

    2005-01-01

    A novel 3-D MUSIC algorithm based on the classical 3D-MUSIC algorithm for the location of near-field source was presented. Under the far-field assumption of actual near-field, two algebraic relations of the location parameters between the actual near-field sources and the far-field ones were derived. With Fourier transformation and polynomial-root methods, the elevation and the azimuth of the far-field were obtained, the tracking paths can be developed, and the location parameters of the near-field source can be determined, then the more accurate results can be estimated using an optimization method. The computer simulation results p rove that the algorithm for the location of the near-fields is more accurate, effective and suitable for real-time applications.

  7. A High-Resolution Antenna Diagnostics Technique for Spherical Nesr-Field Measurements

    DEFF Research Database (Denmark)

    Cappellin, Cecilia; Breinbjerg, Olav; Frandsen, Aksel

    2005-01-01

    A new diagnostics technique for spherical near-field antenna measurements, that can provide a high spatial resolution of the reconstructed aperture field, is presented. This technique is realized by transforming the spherical wave expansion (SWE) of the radiated field into the corresponding plane...

  8. Far-field DOA estimation and near-field localization for multipath signals

    Science.gov (United States)

    Elbir, Ahmet M.; Tuncer, T. Engin

    2014-09-01

    In direction finding and localization applications, multipath signals are important sources of error for parameter estimation. When the antenna array receives multipath reflections which are coherent with the far-field line-of-sight signal, estimating the far- and near-field components becomes an important problem. In this paper, a new method is proposed to estimate the direction-of-arrival (DOA) of the far-field source and to localize its near-field multipaths. Far-field source DOA is estimated using calibration of the antenna array. A near-to-far transformation is proposed for the estimation of the near-field source DOA angles. In order to estimate the near-field range parameters, a compressive sensing approach is presented where a dictionary with near-field sources with different ranges is employed. As a result, the proposed method estimates the far-field and near-field source DOAs as well as the range and the signal amplitudes of the near-field sources. This method is evaluated using close-to-real world data generated by a numerical electromagnetic tool, where the array and transmitter are placed in an irregular terrain and array data are generated using full 3-D propagation model. It is shown that unknown source parameters can be estimated effectively showing the potential of the proposed approach in applications involving high-frequency direction finding and indoor localization.

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

    Science.gov (United States)

    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.

  10. Near-field radiative thermal control with graphene covered on different materials

    Science.gov (United States)

    Wang, Ao; Zheng, Zhiheng; Xuan, Yimin

    2016-09-01

    Based on the structure of double-layer parallel plates, this paper demonstrates that thermal radiation in near field is greatly enhanced due to near-field effects, exceeding Planck‧s blackbody radiation law. To study the effect of graphene on thermal radiation in near field, the authors add graphene layer into the structure and analyze the ability of graphene to control near-field thermal radiation with different materials. The result indicates that the graphene layer effectively suppresses the near-field thermal radiation between metal plates or polar-dielectric plates, having good ability of thermal insulation. But for doped-silicon plates, depending on the specific models, graphene has different control abilities, suppressing or enhancing, and the control abilities mainly depend on the material graphene is attached to. The authors also summarize some common rules about the different abilities of graphene to control the near-field thermal radiation. In consideration of the thickness of 0.34 nm of monolayer graphene, this paper points out that graphene plays a very important role in controlling the near-field thermal radiation.

  11. Near-field optics and quantum optics: an assignation arranged by four kinds of photons.

    Science.gov (United States)

    Keller, O

    2003-03-01

    In the process of emergence a photon emitted from an atom (or a molecule) is usually no better localized in space than to the near-field zone of the source. Near-field optics therefore is of central importance for understanding fundamental statistical aspects related to single-photon tunnelling, the space-time description of photon dynamics, and the photon position-operator problem. In the present work an attempt is made to study the microscopic near-field optical interaction from a quantum statistical point of view. In near-field quantum electrodynamics (QED) scalar and longitudinal photons always are involved and this makes the covariant formulation of QED attractive also in the low-energy regime. We show that the Lorenz gauge condition on the global state vector relates to the near-field electrodynamics of the d-photons. The gauge photon is shown to be of no importance in near-field interactions. To understand the role of the lack of photon localizability we finally study near-field quantum optical correlations in a new so-called propagator gauge.

  12. Electrically small circularly polarized spherical antenna with air core

    DEFF Research Database (Denmark)

    Kim, O. S.

    2013-01-01

    An electrically small circularly polarized self-resonant spherical antenna with air core is presented. The antenna is a modified multiarm spherical helix exciting TM10 and TE10 spherical modes with equal radiated power, and thus yielding perfect circular polarization over the entire far......-field sphere (except the polar regions, where the radiation is low). The self-resonance is achieved by exciting higher-order TM modes, which provide the necessary electric stored energy in the near-field, while contributing negligibly to the far-field radiation of the antenna. The antenna has electrical size...

  13. Surface Plasmon mediated near-field imaging and optical addressing in nanoscience

    CERN Document Server

    Drezet, A; Krenn, J R; Brun, M; Huant, S

    2007-01-01

    We present an overview of recent progress in plasmonics. We focus our study on the observation and excitation of surface plasmon polaritons (SPPs) with optical near-field microscopy. We discuss in particular recent applications of photon scanning tunnelling microscope (PSTM) for imaging of SPP propagating in metal and dielectric wave guides. We show how near-field scanning optical microscopy (NSOM) can be used to optically and actively address remotely nano-objects such as quantum dots. Additionally we compare results obtained with near-field microscopy to those obtained with other optical far-field methods of analysis such as leakage radiation microscopy (LRM).

  14. Fluorescence near-field microscopy of DNA at sub-10 nm resolution.

    Science.gov (United States)

    Ma, Ziyang; Gerton, Jordan M; Wade, Lawrence A; Quake, Stephen R

    2006-12-31

    We demonstrate apertureless near-field microscopy of single molecules at sub-10 nm resolution. With a novel phase filter, near-field images of single organic fluorophores were obtained with approximately sixfold improvement in the signal-to-noise ratio. The improvement allowed pairs of molecules separated by approximately 15 nm to be reliably and repeatedly resolved, thus demonstrating the first true Rayleigh resolution test for near-field images of single molecules. The potential of this technique for biological applications was demonstrated with an experiment that measured the helical rise of A-form DNA.

  15. Supersonic acoustic intensity with statistically optimized near-field acoustic holography

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Jacobsen, Finn

    2011-01-01

    and circulating energy in the near-field of the source. This quantity is of concern because it makes it possible to identify the regions of a source that contribute to the far field radiation, which is often the ultimate concern in noise control. Therefore, this is a very useful analysis tool complementary...... to the information provided by the near-field acoustic holography technique. This study proposes a version of the supersonic acoustic intensity applied to statistically optimized near-field acoustic holography (SONAH). The theory, numerical results and an experimental study are presented. The possibility of using...

  16. Generation of nearly 3D-unpolarized evanescent optical near fields using total internal reflection.

    Science.gov (United States)

    Hassinen, Timo; Popov, Sergei; Friberg, Ari T; Setälä, Tero

    2016-07-01

    We analyze the time-domain partial polarization of optical fields composed of two evanescent waves created in total internal reflection by random electromagnetic beams with orthogonal planes of incidence. We show that such a two-beam configuration enables to generate nearly unpolarized, genuine three-component (3D) near fields. This result complements earlier studies on spectral polarization, which state that at least three symmetrically propagating beams are required to produce a 3D-unpolarized near field. The degree of polarization of the near field can be controlled by adjusting the polarization states and mutual correlation of the incident beams.

  17. Optical near-field microscopy of light focusing through a photonic crystal flat lens.

    Science.gov (United States)

    Fabre, Nathalie; Lalouat, Loïc; Cluzel, Benoit; Mélique, Xavier; Lippens, Didier; de Fornel, Frédérique; Vanbésien, Olivier

    2008-08-15

    We report here the direct observation by using a scanning near-field microscopy technique of the light focusing through a photonic crystal flat lens designed and fabricated to operate at optical frequencies. The lens is fabricated using a III-V semiconductor slab, and we directly visualize the propagation of the electromagnetic waves by using a scanning near-field optical microscope. We directly evidence spatially, as well as spectrally, the focusing operating regime of the lens. At last, in light of the experimental scanning near-field optical microscope pictures, we discuss the lens ability to focus light at a subwavelength scale.

  18. Near-field second-harmonic generation in single gold nanoparticles

    Science.gov (United States)

    Zavelani-Rossi, M.; Celebrano, M.; Biagioni, P.; Polli, D.; Finazzi, M.; Duò, L.; Cerullo, G.; Labardi, M.; Allegrini, M.; Grand, J.; Adam, P.-M.

    2008-03-01

    Second-harmonic generation from single gold elliptical nanoparticles is experimentally investigated by a nonlinear scanning near-field optical microscope (SNOM). The near-field nonlinear response is found to be directly related to local surface plasmon resonances and to particle morphology. The combined analysis of linear and second-harmonic SNOM images provides discrimination among different light extinction particle behaviors, not achievable just with linear techniques. The polarization state of the emitted second harmonic is also investigated, providing experimental evidence of second-harmonic particle emission modes peculiar to near-field excitation.

  19. Enhanced near-field heat flow of a monolayer dielectric island.

    Science.gov (United States)

    Worbes, Ludwig; Hellmann, David; Kittel, Achim

    2013-03-29

    We have investigated the influence of thin films of a dielectric material on the near-field mediated heat transfer at the fundamental limit of single monolayer islands on a metallic substrate. We present spatially resolved measurements by near-field scanning thermal microscopy showing a distinct enhancement in heat transfer above NaCl islands compared to the bare Au(111) film. Experiments at this subnanometer scale call for a microscopic theory beyond the macroscopic fluctuational electrodynamics used to describe near-field heat transfer today. The method facilitates the possibility of developing designs of nanostructured surfaces with respect to specific requirements in heat transfer down to a single atomic layer.

  20. Near-field to far-field characterization of speckle patterns generated by disordered nanomaterials.

    Science.gov (United States)

    Parigi, Valentina; Perros, Elodie; Binard, Guillaume; Bourdillon, Céline; Maître, Agnès; Carminati, Rémi; Krachmalnicoff, Valentina; De Wilde, Yannick

    2016-04-04

    We study the intensity spatial correlation function of optical speckle patterns above a disordered dielectric medium in the multiple scattering regime. The intensity distributions are recorded by scanning near-field optical microscopy (SNOM) with sub-wavelength spatial resolution at variable distances from the surface in a range which spans continuously from the near-field (distance ≪ λ) to the far-field regime (distance ≫ λ). The non-universal behavior at sub-wavelength distances reveals the connection between the near-field speckle pattern and the internal structure of the medium.

  1. Near-field to far-field characterization of speckle patterns generated by disordered nanomaterials

    CERN Document Server

    Parigi, Valentina; Binard, Guillaume; Bourdillon, Céline; Maître, Agnès; Carminati, Rémi; Krachmalnicoff, Valentina; De Wilde, Yannick

    2016-01-01

    We study the intensity spatial correlation function of optical speckle patterns above a disordered dielectric medium in the multiple scattering regime. The intensity distributions are recorded by scanning near-field optical microscopy (SNOM) with sub-wavelength spatial resolution at variable distances from the surface in a range which spans continuously from the near-field (distance $ \\ll \\lambda $) to the far-field regime (distance $\\gg \\lambda $). The non-universal behavior at sub-wavelength distances reveals the connection between the near-field speckle pattern and the internal structure of the medium.

  2. Enhanced Near-Field Heat Flow of a Monolayer Dielectric Island

    Science.gov (United States)

    Worbes, Ludwig; Hellmann, David; Kittel, Achim

    2013-03-01

    We have investigated the influence of thin films of a dielectric material on the near-field mediated heat transfer at the fundamental limit of single monolayer islands on a metallic substrate. We present spatially resolved measurements by near-field scanning thermal microscopy showing a distinct enhancement in heat transfer above NaCl islands compared to the bare Au(111) film. Experiments at this subnanometer scale call for a microscopic theory beyond the macroscopic fluctuational electrodynamics used to describe near-field heat transfer today. The method facilitates the possibility of developing designs of nanostructured surfaces with respect to specific requirements in heat transfer down to a single atomic layer.

  3. Estimate on the uncertainty of predicting radiated emission from near-field scan caused by insufficient or inaccurate near-field data

    DEFF Research Database (Denmark)

    Sørensen, Morten; Radchenko, Andriy; Kam, Keong;

    2012-01-01

    Near-field scan on a Huygens’ box can be used in order to predict the maximal radiated emission from a Printed Circuit Board. The significance of step size and phase accuracy, and the importance of a full Huygens’ box are investigated by simulation of two different models with two different numer...

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

    Energy Technology Data Exchange (ETDEWEB)

    Peragut, Florian; De Wilde, Yannick, E-mail: yannick.dewilde@espci.fr [ESPCI ParisTech, PSL Research University, CNRS, Institut Langevin, 1 rue Jussieu, F-75005, Paris (France); Brubach, Jean-Blaise; Roy, Pascale [Société Civile Synchrotron SOLEIL, L' Orme des Merisiers, St-Aubin BP48, 91192 Gif-sur-Yvette Cedex (France)

    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.

  5. Near field communications technology and the potential to reduce medication errors through multidisciplinary application

    LENUS (Irish Health Repository)

    O’Connell, Emer

    2016-07-01

    Patient safety requires optimal management of medications. Electronic systems are encouraged to reduce medication errors. Near field communications (NFC) is an emerging technology that may be used to develop novel medication management systems.

  6. Imaging of apoptotic HeLa cells by using scanning near-field optical microscopy

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    By using scanning near-field optical microscopy (SNOM), HeLa cells in apoptosis process are imaged with a higher optical resolution beyond the diffraction limit. Since SNOM provides both topographic and transmitted light intensity information of a cell, it can correlate the structural characteristics and optical properties with the spatial position of the apoptotic cells. Wavelength imaging by using near-field spectroscopy shows that there is a great difference in light propagation and absorption in the cell. This unique technique can be applied to the super high resolution imaging of different components in the cell. The observations by near-field optical imaging and near-field spectroscopy indicate an inhomogeneous aggregation of the inner structure in the apoptotic HeLa cells and the change of transmission intensity of light with the apoptosis status.

  7. Nanohybrids Near-Field Optical Microscopy: From Image Shift to Biosensor Application

    Directory of Open Access Journals (Sweden)

    Nayla El-Kork

    2016-01-01

    Full Text Available Near-Field Optical Microscopy is a valuable tool for the optical and topographic study of objects at a nanometric scale. Nanoparticles constitute important candidates for such type of investigations, as they bear an important weight for medical, biomedical, and biosensing applications. One, however, has to be careful as artifacts can be easily reproduced. In this study, we examined hybrid nanoparticles (or nanohybrids in the near-field, while in solution and attached to gold nanoplots. We found out that they can be used for wavelength modulable near-field biosensors within conditions of artifact free imaging. In detail, we refer to the use of topographic/optical image shift and the imaging of Local Surface Plasmon hot spots to validate the genuineness of the obtained images. In summary, this study demonstrates a new way of using simple easily achievable comparative methods to prove the authenticity of near-field images and presents nanohybrid biosensors as an application.

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

    Science.gov (United States)

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

    2016-10-01

    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.

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

    Science.gov (United States)

    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.

  10. Near-field enhanced thermionic energy conversion for renewable energy recycling

    Science.gov (United States)

    Ghashami, Mohammad; Cho, Sung Kwon; Park, Keunhan

    2017-09-01

    This article proposes a new energy harvesting concept that greatly enhances thermionic power generation with high efficiency by exploiting the near-field enhancement of thermal radiation. The proposed near-field enhanced thermionic energy conversion (NETEC) system is uniquely configured with a low-bandgap semiconductor cathode separated from a thermal emitter with a subwavelength gap distance, such that a significant amount of electrons can be photoexcited by near-field thermal radiation to contribute to the enhancement of thermionic current density. We theoretically demonstrate that the NETEC system can generate electric power at a significantly lower temperature than the standard thermionic generator, and the energy conversion efficiency can exceed 40%. The obtained results reveal that near-field photoexcitation can enhance the thermionic power output by more than 10 times, making this hybrid system attractive for renewable energy recycling.

  11. Near-field thermal radiative emission of materials demonstrating near infrared surface polariton resonance

    Science.gov (United States)

    Petersen, Spencer Justin

    Surface polariton mediated near-field radiative transfer exceeds the blackbody limit by orders of magnitude and is quasimonochromatic. Thermophotovoltaic (TPV) power generation consists of converting thermal radiation into useful electrical energy and exhibits a peak performance near the TPV cell bandgap, which is typically located within the near infrared bandwidth. Therefore, an ideal emission source for a nanoscale gap TPV device, in which the emitter and cell are separated by no more than one peak emitted wavelength, will sustain surface polariton resonance at or near the TPV cell bandgap in the near infrared. To date, few materials have been identified that satisfy this requirement. The first objective of this dissertation is to theoretically explore dielectric Mie resonance-based (DMRB) electromagnetic metamaterials for the potential to sustain near infrared surface polariton resonance. Electromagnetic metamaterials are composite media, consisting of subwavelength, repeating unit structures called "meta-atoms." The microscopic configuration of the meta-atom can be engineered, dictating the effective macroscale electromagnetic properties of the bulk metamaterial, including the surface polariton resonance wavelength. DMRB metamaterials consist of dielectric nanoparticles within a host medium and are analyzed using an effective medium theory. The local density of electromagnetic states, an indicator of possibly harvestable energy near an emitting surface, is calculated for two DMRB metamaterials: spherical nanoparticles of 1) silicon carbide, and 2) silicon embedded in a host medium. Results show that the surface polariton resonance of these metamaterials is tunable and, for the silicon metamaterial only, is found in the near infrared bandwidth, making it a viable candidate for use in a nano-TPV device. In order to demonstrate the practicality thereof, the second objective is to fabricate and characterize DMRB metamaterials. Specimens are fabricated by hand

  12. Nanoscale Heat Transfer Due to Near Field Radiation and Nanofluidic Flows

    Science.gov (United States)

    2015-07-21

    AFRL-OSR-VA-TR-2015-0205 Nanoscale heat transfer due to near field radiation and nanofluidic flows Peter Taborek UNIVERSITY OF CALIFORNIA IRVINE...TITLE AND SUBTITLE Nanoscale heat transfer due to near field radiation and nanofluidic flows 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-12-1-0065...liquid flows through the pipe would spontaneously form a liquid/vapor interface either inside the pie or near the exit. We developed a model which

  13. Resolution of Internal Total Reflection Scanning Near-field Optical Microscopy

    Institute of Scientific and Technical Information of China (English)

    GE Huayong; GUO Qizhi; TAN Weihan

    2002-01-01

    In this paper, the probe-sample interaction equation based on Mie′s scattering theory is derived, and the resolution of scanning near field optical microscopy is calculated numerically. The results show that the offset of far-field component to near-field component in total field plays an important role in the resolution and the size of samples also has influence on resolution.

  14. Chiral-field microwave antennas (Chiral microwave near fields for far-field radiation)

    CERN Document Server

    Kamenetskii, E O; Shavit, R

    2015-01-01

    In a single-element structure we obtain a radiation pattern with a squint due to chiral microwave near fields originated from a magnetostatic-mode ferrite disk. At the magnetostatic resonances, one has strong subwavelength localization of energy of microwave radiation. Magnetostatic oscillations in a thin ferrite disk are characterized by unique topological properties: the Poynting-vector vortices and the field helicity. The chiral-topology near fields allow obtaining unique phase structure distribution for far-field microwave radiation.

  15. Hyperbolic waveguide for long-distance transport of near-field heat flux

    Science.gov (United States)

    Messina, Riccardo; Ben-Abdallah, Philippe; Guizal, Brahim; Antezza, Mauro; Biehs, Svend-Age

    2016-09-01

    Heat flux exchanged between two hot bodies at subwavelength separation distances can exceed the limit predicted by the blackbody theory. However, this super-Planckian transfer is restricted to these separation distances. Here we demonstrate the possible existence of a super-Planckian transfer at arbitrary large separation distances if the interacting bodies are connected in the near field with weakly dissipating hyperbolic waveguides. This result opens the way to long-distance transport of near-field thermal energy.

  16. Near-Field Radiative Heat Transfer between Metamaterials coated with Silicon Carbide Film

    OpenAIRE

    Basu, Soumyadipta; YANG, YUE; Wang, Liping

    2014-01-01

    In this letter, we study the near-field radiative heat transfer between two metamaterial substrates coated with silicon carbide (SiC) thin films. It is known that metamaterials can enhance the near-field heat transfer over ordinary materials due to excitation of magnetic plasmons associated with s polarization, while strong surface phonon polariton exists for SiC.By careful tuning of the optical properties of metamaterial it is possible to excite electrical and magnetic resonance for the meta...

  17. Unidirectional light propagation through two-layer nanostructures based on optical near-field interactions

    CERN Document Server

    Naruse, Makoto; Ishii, Satoshi; Drezet, Aurélien; Huant, Serge; Hoga, Morihisa; Ohyagi, Yasuyuki; Matsumoto, Tsutomu; Tate, Naoya; Ohtsu, Motoichi

    2014-01-01

    We theoretically demonstrate direction-dependent polarization conversion efficiency, yielding unidirectional light transmission, through a two-layer nanostructure by using the angular spectrum representation of optical near-fields. The theory provides results that are consistent with electromagnetic numerical simulations. This study reveals that optical near-field interactions among nanostructured matter can provide unique optical properties, such as the unidirectionality observed here, and offers fundamental guiding principles for understanding and engineering nanostructures for realizing novel functionalities.

  18. Validation of EMC near-field scanning amplitude and phase measurement data

    DEFF Research Database (Denmark)

    Mynster, Anders P.; Sørensen, Morten

    2012-01-01

    A frequency selection and data validation procedure is presented. It shows that using data from the reference channel it makes possible to estimate the validity of the measured data from an EMC near-field scan with phase on active circuits.......A frequency selection and data validation procedure is presented. It shows that using data from the reference channel it makes possible to estimate the validity of the measured data from an EMC near-field scan with phase on active circuits....

  19. Far-field Noise and Near-field Flow Validation of Tandem Cylinder Flow Simulations

    OpenAIRE

    今村, 太郎; Imamura, Taro; 平井, 亨; Hirai, Toru; 榎本, 俊治; Enomoto, Shunji; 山本, 一臣; Yamamoto, Kazuomi

    2012-01-01

    In this paper, flow around tandem cylinder is solved using UPACS-LES code developed in JAXA. Several key issues for unsteady flow simulation are investigated by changing the parameters, such as turbulence modeling and grid density. The flow field is compared with the experiment for both far- and near- field. Current results indicate that the calculation of the boundary layer and the shear layer around the cylinders plays important role especially to the near field flow structure while it is l...

  20. When to Perform Antenna Measurements in a Near-Field Range or a Short Tapered Chamber

    Science.gov (United States)

    2017-03-01

    ARL-TR-7963 ● MAR 2017 US Army Research Laboratory When to Perform Antenna Measurements in a Near-Field Range or a Short Tapered...Antenna Measurements in a Near-Field Range or a Short Tapered Chamber by Theodore K Anthony Sensors and Electron Devices Directorate, ARL...comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE

  1. Asymmetric active nano-particles for directive near-field radiation

    DEFF Research Database (Denmark)

    Arslanagic, Samel; Thorsen, Rasmus O.

    2016-01-01

    In this work, we demonstrate the potential of cylindrical active coated nano-particles with certain geometrical asymmetries for the creation of directive near-field radiation. The particles are excited by a near-by magnetic line source, and their performance characteristics are reported in terms...... of radiated power, near-field and power flow distributions as well as the far-field directivity....

  2. PCB current identification based on near-field measurements using preconditioning and regularization

    Science.gov (United States)

    Rinas, Denis; Ahl, Patrick; Frei, Stephan

    2016-09-01

    Radiated electromagnetic fields from a PCB can be estimated when the source current distribution is known. From a measured near-field distribution, the PCB source current distribution can be found. Accuracy depends on the measurement method and its limitations, the radiation model and the choice of the observation area. Many known methods are based on optimization algorithms for inverse problems that vary a set of elementary radiation sources and create a radiation model. However, apart from the time-consuming optimization process, such methods find one possible solution for a near-field distribution. As this distribution might not reflect the real current distribution, accuracy outside of near-field scan area can be low. Furthermore numerical problems can often be observed. Solving the given inverse problem with a system of linear equations and complex near-field data it can be very sensitive to noise. Regularization methods and an adjusted preconditioning can increase the accuracy. In this paper, an improved radiation model creation approach based on complex near-field data is presented. This approach is based on regularization methods and extended by current estimations from near-field data. Preconditioning is done considering some physical properties of the PCB and its possible current paths. Accuracy and stability of the method are investigated in the presence of noisy data.

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

    Science.gov (United States)

    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.

  4. Near-field imaging and spectroscopy of plasmonic cavities (Conference Presentation)

    Science.gov (United States)

    Kilbane, Deirdre

    2016-09-01

    Photoemission electron microscopy (PEEM) is an attractive and advantageous technique in the field of plasmonics. Whilst surface plasmons are excited at the metal dielectric interface by light, it is the near-field photoelectron distribution that is imaged, with optical diffraction limit is overcome. Additionally parallel acquisitioning makes time-resolved (TR) PEEM1 possible. PEEM therefore allows us to investigate light-matter interactions in localized, propagating and hybridized surface plasmons leading to advances in fundamental research and technological applications. In addition to near-field imaging it is also possible to perform near-field spectroscopy. A tunable short pulse optical parametric oscillator (OPO) light source can be combined with PEEM. We demonstrate this technique with arrays of whispering gallery mode (WGM) cavities2 fabricated with focused ion beam milling (FIB) on gold surfaces. Characteristic spectral peaks and near-field mode distributions result from the coherent excitation of different plasmon resonances. This near-field interference of modes allows us to control the emission from these WGM cavities3. Additionally recent advances in ultrafast near-field microscopy and spectroscopy will be discussed. [1] M. Bauer, C. Wiemann, J. Lange, D. Bayer, M. Rohmer and M. Aeschlimann, Appl. Phys. A 88 473 (2007) [2] E. J. Vesseur, F. J. García de Abajo and A. Polman Nano Letters 9 3147 (2009) [3] P. Melchior, D. Kilbane, E. J. Vesseur, A. Polman and M. Aeschlimann Optics Express 23, 31619 (2015)

  5. Point-by-point near-field optical energy deposition around plasmonic nanospheres in absorbing media.

    Science.gov (United States)

    Harrison, R K; Ben-Yakar, Adela

    2015-08-01

    Here we investigate the effects of absorbing media on plasmon-enhanced near-field optical energy deposition. We find that increasing absorption by the medium results in increased particle scattering at the expense of particle absorption, and that much of this increased particle scattering is absorbed by the medium close to the particle surface. We present an analytical method for evaluating the spatial distribution of near-field enhanced absorption surrounding plasmonic metal nanospheres in absorbing media using a new point-by-point method. We propose criteria to define relevant near-field boundaries and calculate the properties of the local absorption enhancement, which redistributes absorption to the near-field and decays asymptotically as a function of the distance from the particle to background levels. Using this method, we performed a large-scale parametric study to understand the effect of particle size and wavelength on the near-field absorption for gold nanoparticles in aqueous media and silicon, and identified conditions that are relevant to enhanced local infrared absorption in silicon. The presented approach provides insight into the local energy transfer around plasmonic nanoparticles for predicting near-field effects for advanced concepts in optical sensing, thin-film solar cells, nonlinear imaging, and photochemical applications.

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

    Science.gov (United States)

    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.

  7. Geochemical evolution of the near field of a KBS-3 repository

    Energy Technology Data Exchange (ETDEWEB)

    Arcos, David; Grandia, Fidel; Domenech, Cristina [Enviros Spain S.L., Barcelona (Spain)

    2006-09-15

    The Swedish concept developed by SKB for deep radioactive waste disposal, envisages an engineered multi-barrier system surrounding the nuclear waste (near field). In the present study we developed a numerical model to assess the geochemical evolution of the near field in the frame of the SKB's safety assessment SR-Can. These numerical models allow us to predict the long-term geochemical evolution of the near field system by means of reactive-transport codes and the information gathered in underground laboratory experiments and natural analogues. Two different scenarios have been defined to model this near field evolution, according to the pathway used by groundwater to contact the near field: a) through a fracture in the host rock intersecting the deposition hole; and b) through the material used to backfill the deposition tunnel. Moreover, we also modelled the effect of different groundwater compositions reaching the near field, as the up-rise of deep-seated brines and the intrusion of ice-melting derived groundwater. We also modelled the effect of the thermal stage due to the heat generated by spent fuel on the geochemical evolution of the bentonite barrier.

  8. Precision Near-Field Reconstruction in the Time Domain via Minimum Entropy for Ultra-High Resolution Radar Imaging

    Directory of Open Access Journals (Sweden)

    Jiwoong Yu

    2017-05-01

    Full Text Available Ultra-high resolution (UHR radar imaging is used to analyze the internal structure of objects and to identify and classify their shapes based on ultra-wideband (UWB signals using a vector network analyzer (VNA. However, radar-based imaging is limited by microwave propagation effects, wave scattering, and transmit power, thus the received signals are inevitably weak and noisy. To overcome this problem, the radar may be operated in the near-field. The focusing of UHR radar signals over a close distance requires precise geometry in order to accommodate the spherical waves. In this paper, a geometric estimation and compensation method that is based on the minimum entropy of radar images with sub-centimeter resolution is proposed and implemented. Inverse synthetic aperture radar (ISAR imaging is used because it is applicable to several fields, including medical- and security-related applications, and high quality images of various targets have been produced to verify the proposed method. For ISAR in the near-field, the compensation for the time delay depends on the distance from the center of rotation and the internal RF circuits and cables. Required parameters for the delay compensation algorithm that can be used to minimize the entropy of the radar images are determined so that acceptable results can be achieved. The processing speed can be enhanced by performing the calculations in the time domain without the phase values, which are removed after upsampling. For comparison, the parameters are also estimated by performing random sampling in the data set. Although the reduced data set contained only 5% of the observed angles, the parameter optimization method is shown to operate correctly.

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

    Science.gov (United States)

    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.

  10. Scattering-type scanning near-field optical microscopy with reconstruction of vertical interaction

    Science.gov (United States)

    Wang, Le; Xu, Xiaoji G.

    2015-11-01

    Scattering-type scanning near-field optical microscopy provides access to super-resolution spectroscopic imaging of the surfaces of a variety of materials and nanostructures. In addition to chemical identification, it enables observations of nano-optical phenomena, such as mid-infrared plasmons in graphene and phonon polaritons in boron nitride. Despite the high lateral spatial resolution, scattering-type near-field optical microscopy is not able to provide characteristics of near-field responses in the vertical dimension, normal to the sample surface. Here, we present an accurate and fast reconstruction method to obtain vertical characteristics of near-field interactions. For its first application, we investigated the bound electromagnetic field component of surface phonon polaritons on the surface of boron nitride nanotubes and found that it decays within 20 nm with a considerable phase change in the near-field signal. The method is expected to provide characterization of the vertical field distribution of a wide range of nano-optical materials and structures.

  11. Probing the Near-Field of Second-Harmonic Light around Plasmonic Nanoantennas.

    Science.gov (United States)

    Metzger, Bernd; Hentschel, Mario; Giessen, Harald

    2017-03-08

    We introduce a new concept that enables subwavelength polarization-resolved probing of the second-harmonic near-field distribution of plasmonic nanostructures. As a local sensor, this method utilizes aluminum nanoantennas, which are resonant to the second-harmonic wavelength and which allow to efficiently scatter the local second-harmonic light to the far-field. We place these sensors into the second-harmonic near-field generated by plasmonic nanostructures and carefully vary their position and orientation. Observing the second-harmonic light resonantly scattered by the aluminum nanoantennas provides polarization-resolved information about the local second-harmonic near-field distribution. We then investigate the polarization-resolved second-harmonic near-field of inversion symmetric gold dipole nanoantennas. Interestingly, we find strong evidence that the second-harmonic dipole is predominantly oriented perpendicular to the gold nanoantenna long axis, although the excitation laser is polarized parallel to the nanoantennas. We believe that our investigations will help to disentangle the highly debated origin of the second-harmonic response of inversion symmetric plasmonic structures. Furthermore, we believe that our new method, which enables the measurement of local nonlinear electric fields, will find widespread implementation and applications in nonlinear near-field optical microscopy.

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

    Energy Technology Data Exchange (ETDEWEB)

    Koya, Alemayehu Nana; Ji, Boyu; Hao, Zuoqiang; Lin, Jingquan, E-mail: linjingquan@cust.edu.cn [School of Science, Changchun University of Science and Technology, Changchun 130022 (China)

    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.

  13. Exposure to chemicals in consumer products: The role of the near-field environment

    DEFF Research Database (Denmark)

    Fantke, Peter; Csiszar, S.A.; Huang, L.;

    2016-01-01

    Humans can be exposed to chemicals in consumer products during product use and environmental releases with inhalation, ingestion, and dermal uptake as typical exposure routes. Nevertheless, chemical exposure modeling has traditionally focused on the far-field with near-field indoor models only......F, the fraction of the chemical in a product that is taken in by humans via each exposure pathway, considering specific compartments of entry into the near-field environment (releases of chemicals encapsulated in articles, indoor air spray, etc.). To est imate PiFs, we combined far-field environmental...... compartments with near -field compartments and exposure pathways in a multimedia matrix of transfer fractions, with columns and rows for each compartment and exposure pathway. The multiple transfers and PiFs (e.g. from chemicals encapsulated in articles to inhalation of indoor air and dermal uptake via skin...

  14. Ultra thin metallic coatings to control near field radiative heat transfer

    Directory of Open Access Journals (Sweden)

    R. Esquivel-Sirvent

    2016-09-01

    Full Text Available We present a theoretical calculation of the changes in the near field radiative heat transfer between two surfaces due to the presence of ultra thin metallic coatings on semiconductors. Depending on the substrates, the radiative heat transfer is modulated by the thickness of the ultra thin film. In particular we consider gold thin films with thicknesses varying from 4 to 20 nm. The ultra-thin film has an insulator-conductor transition close to a critical thickness of dc = 6.4 nm and there is an increase in the near field spectral heat transfer just before the percolation transition. Depending on the substrates (Si or SiC and the thickness of the metallic coatings we show how the near field heat transfer can be increased or decreased as a function of the metallic coating thickness. The calculations are based on available experimental data for the optical properties of ultrathin coatings.

  15. Local circular polarizations in nanostructures induced by linear polarization via optical near-fields

    CERN Document Server

    Naruse, Makoto; Inoue, Tetsuya; Yasuda, Hideki; Hori, Hirokazu; Naya, Masayuki

    2015-01-01

    We previously reported [Naruse, et al. Sci. Rep. 4, 6077, 2014] that the geometrical randomness of disk-shaped silver nanoparticles, which exhibit high reflection at near-infrared wavelengths, serves as the origin of a particle-dependent localization and hierarchical distribution of optical near-fields in the vicinity of the nanostructure. In this study, we show that the induced polarizations are circular, particularly at resonant wavelengths. We formulate optical near-field processes between nanostructures, accounting for their polarizations and geometries, and attribute circular polarization to the layout-dependent phase difference between the electrical susceptibilities associated with longitudinal and transverse-electric components. This study clarifies the fundamental optical properties of random nanostructured matter and offers generic theoretical concepts for implementing nanoscale polarizations of optical near-fields.

  16. Natural geochemical analogues of the near field of high-level nuclear waste repositories

    Energy Technology Data Exchange (ETDEWEB)

    Apps, J.A. [Lawrence Berkeley Lab., CA (United States)

    1995-09-01

    United States practice has been to design high-level nuclear waste (HLW) geological repositories with waste densities sufficiently high that repository temperatures surrounding the waste will exceed 100{degrees}C and could reach 250{degrees}C. Basalt and devitrified vitroclastic tuff are among the host rocks considered for waste emplacement. Near-field repository thermal behavior and chemical alteration in such rocks is expected to be similar to that observed in many geothermal systems. Therefore, the predictive modeling required for performance assessment studies of the near field could be validated and calibrated using geothermal systems as natural analogues. Examples are given which demonstrate the need for refinement of the thermodynamic databases used in geochemical modeling of near-field natural analogues and the extent to which present models can predict conditions in geothermal fields.

  17. Sub-nanosecond time-resolved near-field scanning magneto-optical microscope.

    Science.gov (United States)

    Rudge, J; Xu, H; Kolthammer, J; Hong, Y K; Choi, B C

    2015-02-01

    We report on the development of a new magnetic microscope, time-resolved near-field scanning magneto-optical microscope, which combines a near-field scanning optical microscope and magneto-optical contrast. By taking advantage of the high temporal resolution of time-resolved Kerr microscope and the sub-wavelength spatial resolution of a near-field microscope, we achieved a temporal resolution of ∼50 ps and a spatial resolution of microscope, the magnetic field pulse induced gyrotropic vortex dynamics occurring in 1 μm diameter, 20 nm thick CoFeB circular disks has been investigated. The microscope provides sub-wavelength resolution magnetic images of the gyrotropic motion of the vortex core at a resonance frequency of ∼240 MHz.

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  19. Optical Field Measurement of Nano-Apertures with a Scanning Near-Field Optical Microscope

    Institute of Scientific and Technical Information of China (English)

    XU Tie-Jun; XU Ji-Ying; WANG Jia; TIAN Qian

    2004-01-01

    @@ We investigate optical near-field distributions of the unconventional C-apertures and the conventional square apertures in preliminary experiment with an aperture scanning near-field optical microscope. These nano-apertures are fabricated in Au film on a glass substrate with focused ion beam technology. The experimental results indicate the uptrend of output light intensity that a C-aperture enables the intensity maximum to increase at least 10times more than a square aperture with same unit length. The measured near-field light spot sizes of C-apertureand square aperture with 200-nm unit length are 439nm × 500nm and 245nm × 216nm, respectively.

  20. Near Field Heat Transfer between Random Composite Materials: Applications and Limitations

    Science.gov (United States)

    Santiago, Eva Yazmin; Esquivel-Sirvent, Raul

    2017-02-01

    We present a theoretical study of the limits and bounds of using effective medium approximations in the calculation of the near field radiative heat transfer between a composite system made of Au nanoparticles in a SiC host and an homogeneous SiC slab. The effective dielectric function of the composite slab is calculated using three different approximations: Maxwell-Garnett, Bruggeman, and Looyenga's. In addition, we considered an empirical fit to the effective dielectric function by Grundquist and Hunderi. We show that the calculated value of the heat flux in the near field is dependent on the model, and the difference in the effective dielectric function is larger around the plasmonic response of the Au nanoparticles. This, in turn, accounts for the difference in the near field radiative heat flux. For all values of filling fractions, the Looyenga approximation gives a lower bound for the heat flux.

  1. Near field heat transfer between random composite materials. Applications and limitations

    Energy Technology Data Exchange (ETDEWEB)

    Santiago, Eva Yazmin; Esquivel-Sirvent, Raul [Univ. Nacional Autonoma de Mexico (Mexico). Inst. de Fisica

    2017-05-01

    We present a theoretical study of the limits and bounds of using effective medium approximations in the calculation of the near field radiative heat transfer between a composite system made of Au nanoparticles in a SiC host and an homogeneous SiC slab. The effective dielectric function of the composite slab is calculated using three different approximations: Maxwell-Garnett, Bruggeman, and Looyenga's. In addition, we considered an empirical fit to the effective dielectric function by Grundquist and Hunderi. We show that the calculated value of the heat flux in the near field is dependent on the model, and the difference in the effective dielectric function is larger around the plasmonic response of the Au nanoparticles. This, in turn, accounts for the difference in the near field radiative heat flux. For all values of filling fractions, the Looyenga approximation gives a lower bound for the heat flux.

  2. Antenna diagnostics for power flow in extreme near-field of a standard gain horn

    DEFF Research Database (Denmark)

    Popa, Paula Irina; Breinbjerg, Olav

    2016-01-01

    The plane wave spectrum of an aperture antenna can be calculated from a complex measurement of the radiated near- or far-field and it facilitates antenna diagnostics for the extreme near-field of the antenna. While antenna diagnostics often concerns the magnitude of the co-polar field, the plane...... wave spectrum actually allows for determination of both magnitude and phase of all three components of the electric as well as the magnetic field - and thus also the Poynting vector. In this work we focus on the Poynting vector and thus the power flow in the extreme near-field; as an example we employ...... that these oscillations are not merely a “Gibbs-like” phenomenon due to the availability of only the visible region of the plane wave spectrum and they are not caused by multiple reflections between the horn and the near-field probe - but resulted from the interference between the direct field and the edge...

  3. Near Field Radiation Characteristics of Implantable Square Spiral Chip Inductor Antennas for Bio-Sensors

    Science.gov (United States)

    Nessel, James A.; Simons, Rainee N.; Miranda, Felix A.

    2007-01-01

    The near field radiation characteristics of implantable Square Spiral Chip Inductor Antennas (SSCIA) for Bio-Sensors have been measured. Our results indicate that the measured near field relative signal strength of these antennas agrees with simulated results and confirm that in the near field region the radiation field is fairly uniform in all directions. The effects of parameters such as ground-plane, number of turns and microstrip-gap width on the performance of the SSCIA are presented. Furthermore, the SSCIA antenna with serrated ground plane produce a broad radiation pattern, with a relative signal strength detectable at distances within the range of operation of hand-held devices for self-diagnosis.

  4. Near-field lithography on the azobenzene polymer liquid crystal films

    Institute of Scientific and Technical Information of China (English)

    Douguo Zhang; Jian Liu; Zebo Zhang; Li Cao; Anlian Pan; Pei Wang; Yonghua Lu; Ming Bai; Jun Yang; Lin Tang; Jiangying Zhang; Hai Ming; Qijin Zhang

    2005-01-01

    @@ In this article, we reported near-field research on azobenzene polymer liquid crystal films using scanning near-field optical microscopy (SNOM). Optical writing and subsequently topographic reading of the patterns with subwavelength resolution were carried out in our experiments. Nanometer scale dots and lines were successfully fabricated on the films and the smallest dot diameter is about 120 nm. The width of the line fabricated is about 250 nm. This method is also a choice for nanolithography. The mechanism of the surface deformation on the polymer films was briefly analyzed from the viewpoint of gradient force in the optical near field. The intensity distribution of the electric field near the tip aperture was numerically simulated using finite-difference time-domain (FDTD) method and the numerical simulation results were consistent with the experimental results.

  5. Tunable resonance cavity control in a near-field scanning microwave microscope

    Energy Technology Data Exchange (ETDEWEB)

    Hong, Sung Hyuk; Kim, Joo Young; Lee, Kre Jin [Sogang Univ., Seoul (Korea, Republic of); Kim, Jin Tae [KRISS, Daejon (Korea, Republic of); Cha, Deok Joon [Kunsan National Univ., Kunsan (Korea, Republic of); Lee, Yong San [Daejin Univ., Pochon (Korea, Republic of)

    2002-05-01

    We report a microwave surface imaging technique using a near-field scanning microwave microscope with a tunable resonance cavity. By tuning the resonance cavity, we could demonstrate improved sensitivity and spatial resolution of the near-field image of YBa{sub 2}Cu{sub 3}O{sub y} thin films on MgO substrates. By measuring the shift in the resonant frequency and the change in the quality factor, we obtained near-field scanning microwave images with a spatial resolution better than 4 {mu}m at an operating frequency of f=1-1.5 GHz. The principal of operation can be explained by using the perturbation theory of a coaxial resonant cavity, considering the radius of the probe tip and the sample-tip distance.

  6. High energy photoelectron emission from gases using plasmonics enhanced near-fields

    CERN Document Server

    Ciappina, M F; Guichard, R; Pérez-Hernández, J A; Roso, L; Arnold, M; Siegel, T; Zaïr, A; Lewenstein, M

    2013-01-01

    We study theoretically the photoelectron emission in noble gases using plasmonic enhanced near-fields. We demonstrate that these fields have a great potential to generate high energy electrons by direct mid-infrared laser pulses of the current femtosecond oscillator. Typically, these fields appear in the surroundings of plasmonic nanostructures, having different geometrical shape such as bow-ties, metallic waveguides, metal nanoparticles and nanotips, when illuminated by a short laser pulse. In here, we consider metal nanospheres, in which the spatial decay of the near-field of the isolated nanoparticle can be approximated by an exponential function according to recent attosecond streaking measurements. We establish that the strong nonhomogeneous character of the enhanced near-field plays an important role in the above threshold ionization (ATI) process and leads to a significant extension in the photoelectron spectra. In this work, we employ the time dependent Schr\\"odinger equation in reduced dimensions to ...

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

    Science.gov (United States)

    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.

  8. The effectiveness of thin films in lieu of hyperbolic metamaterials in the near field

    CERN Document Server

    Miller, Owen D; Rodriguez, Alejandro W

    2013-01-01

    We show that the near-field functionality of hyperbolic metamaterials (HMM), typically proposed for increasing the photonic local density of states (LDOS), can be achieved with thin metal films. Essentially, relative to thin films, HMMs have a broader but weaker coupling to the high-wavevector states of near-field emitters, such that when integrated over wavevector the overall coupling of the two is essentially equivalent. We show analytically that properly designed thin films, of thicknesses comparable to the metal size of a hyperbolic metamaterial, yield a LDOS as high as (if not higher than) that of HMMs. We illustrate these ideas by performing exact numerical computations of the LDOS of multilayer HMMs, along with their application to the problem of maximizing near-field heat transfer, to show that thin films are suitable replacements in both cases.

  9. Near-field mapping of plasmonic antennas by multiphoton absorption in poly(methyl methacrylate).

    Science.gov (United States)

    Volpe, Giorgio; Noack, Monika; Aćimović, Srdjan S; Reinhardt, Carsten; Quidant, Romain

    2012-09-12

    Mapping the optical near-field response around nanoantennas is a challenging yet indispensable task to engineer light-matter interaction at the nanometer scale. Recently, photosensitive molecular probes, which undergo morphological or chemical changes induced by the local optical response of the nanostructures, have been proposed as a handy alternative to more cumbersome optical and electron-based techniques. Here, we report four-photon absorption in poly(methyl methacrylate) (PMMA) as a very promising tool for nanoimaging the optical near-field around nanostructures over a broad range of near-infrared optical wavelengths. The high performance of our approach is demonstrated on single-rod antennas and coupled gap antennas by comparing experimental maps with 3D numerical simulations of the electric near-field intensity.

  10. A review of models for near-field exposure pathways of chemicals in consumer products

    DEFF Research Database (Denmark)

    Huang, Lei; Ernstoff, Alexi; Fantke, Peter;

    2017-01-01

    Exposure to chemicals in consumer products has been gaining increasing attention, with multiple studies showing that near-field exposures from products is high compared to far-field exposures. Regarding the numerous chemical-product combinations, there is a need for an overarching review of models...... able to quantify the multiple transfers of chemicals from products used near-field to humans. The present review therefore aims at an in-depth overview of modeling approaches for near-field chemical release and human exposure pathways associated with consumer products. It focuses on lower...... in a “human receptor compartment”. We first focus on models of physical mass transfers from the product to ‘near-field’ compartments. For transfers of chemicals from article interior, adequate modeling of in-article diffusion and of partitioning between article surface and air/skin/food is key. Modeling...

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

    Energy Technology Data Exchange (ETDEWEB)

    Elliott, Stephen J.; Ni, Guangjian [Institute of Sound and Vibration Research, University of Southampton, Southampton (United Kingdom)

    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.

  12. Temporal and Spectral Properties of Subcycle THz Pulses in Near-Field Zone

    Institute of Scientific and Technical Information of China (English)

    YANG Yu-Ping; YAN Wei; XU Xin-Long; SHI Yu-Lei; WANG Li

    2005-01-01

    @@ In a novel generation and detection configuration of terahertz (THz) radiation, we investigate experimentally and numerically the properties of sub-cycle THz pulses in the near field. It is found that the sub-cycle THz pulses experience significant spectral and temporal deformation in the near-field zone. The variations of both the pulse waveform and spectral distribution of the THz electric field are clearly observed in our experiments when the spot size of source is changed. Numerical simulations based on Gaussian distribution are performed to explain the details of the data and lead to an excellent agreement with the experimental results.

  13. Near field and altered zone environmental report Volume I: technical bases for EBS design

    Energy Technology Data Exchange (ETDEWEB)

    Wilder, D. G., LLNL

    1997-08-01

    This report presents an updated summary of results for the waste package (WP) and engineered barrier system (EBS) evaluations, including materials testing, waste-form characterization, EBS performance assessments, and near-field environment (NFE) characterization. Materials testing, design criteria and concept development, and waste-form characterization all require an understanding of the environmental conditions that will interact with the WP and EBS. The Near-Field Environment Report (NFER) was identified in the Waste Package Plan (WPP) (Harrison- Giesler, 1991) as the formal means for transmitting and documenting this information.

  14. Mie scattering of Laguerre-Gaussian beams: photonic nanojets and near-field optical vortices

    CERN Document Server

    Kiselev, Alexei D

    2014-01-01

    We study Mie scattering of Laguerre-Gaussian (LG) light beams remodelled using the method of far-field matching. The theoretical results are used to analyze the optical field in the near-field region for purely azimuthal LG beams characterized by a nonzero azimuthal mode number $m_{LG}$. The mode number $m_{LG}$ is found to have a profound effect on the morphology of photonic nanojets and the near-field structure of optical vortices associated with the components of the electric field.

  15. Fast Near-Field Calculation for Volume Integral Equations for Layered Media

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Meincke, Peter; Breinbjerg, Olav

    2005-01-01

    An efficient technique based on the Fast Fourier Transform (FFT) for calculating near-field scattering by dielectric objects in layered media is presented. A higher or-der method of moments technique is employed to solve the volume integral equation for the unknown induced volume current density....... Afterwards, the scattered electric field can be easily computed at a regular rectangular grid on any horizontal plane us-ing a 2-dimensional FFT. This approach provides significant speedup in the near-field calculation in comparison to a straightforward numerical evaluation of the ra-diation integral since...

  16. Theory of the thermal radiation from optical antennas in far- and near-fields

    CERN Document Server

    Liu, Baoan

    2015-01-01

    We develop a general theory from the first principles to describe the thermal emission from optical antennas in both far- and near-fields. Thermal emission from optical antennas is quasi-monochromatic because of the modulation by antenna resonance modes, and the thermal emission rate has a theoretical limit, which can be achieved when the resonance mode losses are equally distributed to the emitter and the absorber. We then revisit the thermal emission from metal nanorods and propose a new methodology to realize reasonant near-field metamaterials with monochromatic and super-Planckian thermal emission.

  17. Frequency-domain electromagnetic sounding with combination wave in near-field zone

    Institute of Scientific and Technical Information of China (English)

    苏发; 何继善

    1996-01-01

    By analysing the propagation law of electromagnetic wave,the distribution pattern of the field and the theory of frequency electromagnetic sounding,the physical mechanisms that make the frequency electromagnetic sounding in near-field zone difficult are discussed.Based on the theory of near source field,a new method of dual-frequency electromagnetic sounding of combination wave in near-field zone is advanced.Meanwhile,the method of measurement of fields,the definition of apparent resistivity and the numerical algorithm are approached.

  18. Polarization contrast in reflection near-field optical microscopy with uncoated fibre tips

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Langbein, Wolfgang; Hvam, Jørn Märcher

    1999-01-01

    Using cross-hatched, patterned semiconductor surfaces and round 20-nm-thick gold pads on semiconductor wafers, we investigate the imaging characteristics of a reflection near-field optical microscope with an uncoated fibre tip for different polarization configurations and light wavelengths....... Is is shown that cross-polarized detection allows one to effectively suppress far-field components in the detected signal and to realise imaging of optical contrast on the sub-wavelength scale. The sensitivity window of our microscope, i.e. the scale on which near-field optical images represent mainly optical...

  19. Near-Field Ultrasonic Phased Array Deflection Focusing Based CFRP Wing Box Structural Health Monitoring

    OpenAIRE

    Yajie Sun; Yonghong Zhang; Chengshan Qian; Zijia Zhang

    2013-01-01

    Near-field ultrasonic phased array theory is researched and utilized in the carbon-fiber wing box to identify the damage in the structure. Near-field ultrasonic phased array based structural health monitoring is researched to overcome the limitation of the far-field ultrasonic phased array in monitoring scope. The time delay of the theory and the process of the damage identification method are researched in detail. The recognition result is shown in a mapped image. The proposed method is appl...

  20. A novel optical lithography implement utilizing third harmonic generation via metallic tip enhanced near field

    Science.gov (United States)

    Zhang, Hui; Zhu, Ning; Mei, Ting; He, Miao; Li, Hao; Chen, Zhenshi

    2017-01-01

    A novel scheme for near-field optical lithography utilizing a metallic tip illuminated by femtosecond laser pulses with proper polarization has been presented. The strongly enhanced near field at the metallic tip offers a localized excitation source for the third harmonic generation in the nonlinear material. The generated third harmonic via excitation of nonlinear photoresist provides good exposure contrast due to the cubic intensity dependence. The spatial resolution of this novel lithography scheme is shown to be better than that of the conventional lithography technique.

  1. Near field evidence of backward surface plasmon polaritons on negative index material boundaries

    Energy Technology Data Exchange (ETDEWEB)

    Cuevas, Mauro, E-mail: cuevas@df.uba.ar [Facultad de Ingeniería y Tecnología Informática, Universidad de Belgrano, Villanueva 1324, C1426BMJ, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Grunhut, Vivian [Facultad de Ingeniería, Universidad Austral (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Depine, Ricardo A. [Grupo de Electromagnetismo Aplicado, Departamento de Física, FCEN, Universidad de Buenos Aires and IFIBA, Ciudad Universitaria, Pabellón I, C1428EHA, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina)

    2016-12-09

    Highlights: • Electromagnetic scattering from a localized defect on a NIM surface is presented. • The electromagnetic response strongly depends on the SPPs excited. • Near field distribution reveals the forward or backward character of SPPs excited. - Abstract: We present a detailed analysis about the electromagnetic response of a metamaterial surface with a localized defect. The excitation of electromagnetic surface waves leads to a near-field distribution showing a periodic dependence along the metamaterial surface. We find that this periodic pattern provides a direct demonstration of the forward or backward surface wave propagation.

  2. Near-field x-ray phase contrast imaging and phase retrieval algorithm

    Institute of Scientific and Technical Information of China (English)

    Zhu Hua-Feng; Xie Hong-Lan; Gao Hong-Yi; Chen Jian-Wen; Li Ru-Xin; Xu Zhi-Zhan

    2005-01-01

    Theoretical analyses of x-ray diffraction phase contrast imaging and near field phase retrieval method are presented.A new variant of the near field intensity distribution is derived with the optimal phase imaging distance and spatial frequency of object taken into account. Numerical examples of phase retrieval using simulated data are also given. On the above basis, the influence of detecting distance and polychroism of radiation on the phase contrast image and the retrieved phase distribution are discussed. The present results should be useful in the practical application of in-line phase contrast imaging.

  3. Near-field ablation threshold of cellular samples at mid-IR wavelengths

    CERN Document Server

    Raghu, Deepa; Gamari, Benjamin; Reeves, M E

    2012-01-01

    We report the near-field ablation of material from cellulose acetate coverslips in water and my- oblast cell samples in growth media, with a spot size as small as 1.5 {\\mu}m under 3 {\\mu}m wavelength radiation. The power dependence of the ablation process has been studied and comparisons have been made to models of photomechanical and plasma-induced ablation. The ablation mechanism is mainly dependent on the acoustic relaxation time and optical properties of the materials. We find that for all near-field experiments, the ablation thresholds are very high, pointing to plasma-induced ablation as the dominant mechanism.

  4. Far- and near-field second harmonic imaging of ferroelectric domain walls

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Pedersen, Kjeld; Skettrup, Torben

    1998-01-01

    Domain walls in periodically poled ferroelectric LiNbO3 crystals are observed with both far- and near-field imaging techniques that make use of second harmonic generation in the transition regions between neighbouring domains. Second harmonic images of domain walls represent bright lines of about.......5 micrometers in width (as measured with the near-field microscope) for the polarization of the second harmonic radiation perpendicular to the domain walls. Origin and selection rules for the constrast in second harmonic images of domain walls are discussed....

  5. Near-field dynamics of broad area diode laser at very high pump levels

    Directory of Open Access Journals (Sweden)

    Martin Hempel

    2011-12-01

    Full Text Available Near-field properties of the emission of broad area semiconductor diode lasers under extremely high pumping of up to ∼50 times the threshold are investigated. A transition from a gain to thermally-induced index guiding is shown under operation with single pulses of 300 ns duration. At highest output powers, catastrophic optical damage is observed which is studied in conjunction with the evolution of time-averaged filamentary near-field properties. Dynamics of the process is resolved on a picosecond time scale.

  6. A sparse equivalent source method for near-field acoustic holography

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Xenaki, Angeliki; Gerstoft, Peter

    2017-01-01

    This study examines a near-field acoustic holography method consisting of a sparse formulation of the equivalent source method, based on the compressive sensing (CS) framework. The method, denoted Compressive–Equivalent Source Method (C-ESM), encourages spatially sparse solutions (based...... on the superposition of few waves) that are accurate when the acoustic sources are spatially localized. The importance of obtaining a non-redundant representation, i.e., a sensing matrix with low column coherence, and the inherent ill-conditioning of near-field reconstruction problems is addressed. Numerical...

  7. Thermal supercurrent in non-reciprocal many-body near field electromagnetic heat transfer

    CERN Document Server

    Zhu, Linxiao

    2016-01-01

    We consider the consequence of non-reciprocity in near-field heat transfer by studying systems consisting of magneto-optical nanoparticles. We demonstrate that in thermal equilibrium, non-reciprocal many-body system can support a persistent directional heat current, i.e. thermal supercurrent, without violating the second law of thermodynamics. Such a thermal supercurrent can not occur in reciprocal systems, and can only arise in many-body systems. The use of non-reciprocity therefore points to a new regime of near-field heat transfer for the control of heat flow in the nanoscale.

  8. Persistent Directional Current at Equilibrium in Nonreciprocal Many-Body Near Field Electromagnetic Heat Transfer

    Science.gov (United States)

    Zhu, Linxiao; Fan, Shanhui

    2016-09-01

    We consider the consequence of nonreciprocity in near-field heat transfer by studying systems consisting of magneto-optical nanoparticles. We demonstrate that, in thermal equilibrium, a nonreciprocal many-body system in heat transfer can support a persistent directional heat current, without violating the second law of thermodynamics. Such a persistent directional heat current cannot occur in reciprocal systems, and can only arise in many-body systems in heat transfer. The use of nonreciprocity therefore points to a new regime of near-field heat transfer for the control of heat flow in the nanoscale.

  9. Three-dimensional radar imaging techniques and systems for near-field applications

    Energy Technology Data Exchange (ETDEWEB)

    Sheen, David M.; Hall, Thomas E.; McMakin, Douglas L.; Jones, Anthony M.; Tedeschi, Jonathan R.

    2016-05-12

    The Pacific Northwest National Laboratory has developed three-dimensional holographic (synthetic aperture) radar imaging techniques and systems for a wide variety of near-field applications. These applications include radar cross-section (RCS) imaging, personnel screening, standoff concealed weapon detection, concealed threat detection, through-barrier imaging, ground penetrating radar (GPR), and non-destructive evaluation (NDE). Sequentially-switched linear arrays are used for many of these systems to enable high-speed data acquisition and 3-D imaging. In this paper, the techniques and systems will be described along with imaging results that demonstrate the utility of near-field 3-D radar imaging for these compelling applications.

  10. Near-Field Ultrasonic Phased Array Deflection Focusing Based CFRP Wing Box Structural Health Monitoring

    OpenAIRE

    Yajie Sun; Yonghong Zhang; Chengshan Qian; Zijia Zhang

    2013-01-01

    Near-field ultrasonic phased array theory is researched and utilized in the carbon-fiber wing box to identify the damage in the structure. Near-field ultrasonic phased array based structural health monitoring is researched to overcome the limitation of the far-field ultrasonic phased array in monitoring scope. The time delay of the theory and the process of the damage identification method are researched in detail. The recognition result is shown in a mapped image. The proposed method is appl...

  11. Wideband Phase Retrieval Technique from Amplitude-Only Near-Field Data

    Directory of Open Access Journals (Sweden)

    G. D. Massa

    2008-12-01

    Full Text Available A wideband frequency behavior is demonstrated for a phaseless near-field technique of basically interferometric approach, which uses two identical probes interfering each other through a microstrip circuit and performing amplitude-only near-field measurements on a single scanning surface. The phase retrieval procedure is properly formulated to take into account the frequency dependence without changing neither the microstrip circuit nor the distance between the probes. Numerical simulations on a linear array of elementary sources are presented to validate the theoretical results.

  12. Shape matters: Near-field fluid mechanics dominate the collective motions of ellipsoidal squirmers.

    Science.gov (United States)

    Kyoya, K; Matsunaga, D; Imai, Y; Omori, T; Ishikawa, T

    2015-12-01

    Microswimmers show a variety of collective motions. Despite extensive study, questions remain regarding the role of near-field fluid mechanics in collective motion. In this paper, we describe precisely the Stokes flow around hydrodynamically interacting ellipsoidal squirmers in a monolayer suspension. The results showed that various collective motions, such as ordering, aggregation, and whirls, are dominated by the swimming mode and the aspect ratio. The collective motions are mainly induced by near-field fluid mechanics, despite Stokes flow propagation over a long range. These results emphasize the importance of particle shape in collective motion.

  13. A comparison of inverse boundary element method and near-field acoustical holography

    DEFF Research Database (Denmark)

    Schuhmacher, Andreas; Hald, Jørgen; Saemann, E.-U.

    1999-01-01

    An inverse boundary element method (IBEM) is used to estimate the surface velocity of a rolling tyre from measurements of the near-field pressure. Subsequently, the sound pressure is calculated over a finite plane surface next to the tyre from the reconstructed velocity field on the tyre surface........ In order to verify the reconstruction process, part of the measurement data is used together with Near-Field Acoustical Holography (NAH). Estimated distributions of sound pressure and particle velocity over a plane surface obtained from the two methods are compared....

  14. Direct analysis of dispersive wave fields from near-field pressure measurements

    NARCIS (Netherlands)

    Horchens, L.

    2011-01-01

    Flexural waves play a significant role for the radiation of sound from plates. The analysis of flexural wave fields enables the detection of sources and transmission paths in plate-like structures. The measurement of these wave fields can be carried out indirectly by means of near-field acoustic hol

  15. The ACE-DTU Planar Near-Field Ground Penetrating Radar Antenna Test Facility

    DEFF Research Database (Denmark)

    Lenler-Eriksen, Hans-Rudolph; Meincke, Peter

    2004-01-01

    The ACE-DTU planar near-field ground penetrating radar (GPR) antenna test facility is used to measure the plane-wave transmitting spectrum of a GPR loop antenna close to the air-soil interface by means of a probe buried in soil. Probe correction is implemented using knowledge about the complex...

  16. Reconstruction of an object shape from the near-field intensity of a reflected paraxial beam.

    Science.gov (United States)

    Vdovin, G

    1997-08-01

    Experimental reconstruction of an object shape from the near-field intensity of reflected or transmitted light is reported. The method of reconstruction is based on the direct numerical solution of the finite-difference representation of the paraxial irradiance-transport equation. Practical applications and limitations of the method are discussed.

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

    Science.gov (United States)

    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.

  18. Single molecule mapping of the optical field distribution of probes for near-field microscopy

    NARCIS (Netherlands)

    Veerman, J.A.; Garcia Parajo, M.F.; Kuipers, L.; van Hulst, N.F.

    1999-01-01

    The most difficult task in near-field scanning optical microscopy (NSOM) is to make a high quality subwavelength aperture probe, Recently we have developed high definition NSOM probes by focused ion beam (FIB) milling. These probes have a higher brightness, better polarization characteristics,

  19. Simulation, Fabrication and Near-Field Characterization of Nanoantenna Couplers for Telecom Range

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Zenin, Vladimir A.; Malureanu, Radu;

    2014-01-01

    We report a modified bow - tie antenna for light coupling to subwavelength plasmonic slot waveguide . Its effective area is 15 times larger than that of the bare waveguide terminatio n at the wavelength 1.55 μm . We demonstrate numerical simulation, fabrication and , for the first time, full ampl...... amplitude - phase near - field optical characterization of nanocoupler in telecom range ....

  20. A comparison of inverse boundary element method and near-field acoustical holography

    DEFF Research Database (Denmark)

    Schuhmacher, Andreas; Hald, Jørgen; Saemann, E.-U.

    1999-01-01

    An inverse boundary element method (IBEM) is used to estimate the surface velocity of a rolling tyre from measurements of the near-field pressure. Subsequently, the sound pressure is calculated over a finite plane surface next to the tyre from the reconstructed velocity field on the tyre surface...

  1. Direct measurement of the near-field super resolved focused spot in InSb

    NARCIS (Netherlands)

    Assafrao, A.C.; Wachters, A.J.H.; Verheijen, M.; Nugrowati, A.M.; Pereira, S.F.; Urbach, H.P.; Armand, M.F.; Olivier, S.

    2012-01-01

    Under appropriate laser exposure, a thin film of InSb exhibits a sub-wavelength thermally modified area that can be used to focus light beyond the diffraction limit. This technique, called Super-Resolution Near-Field Structure, is a potential candidate for ultrahigh density optical data storage and

  2. Weighted near-field focusing in an array-based GPR

    NARCIS (Netherlands)

    Savelyev, T.G.; Yarovoy, A.G.; Ligthart, L.P.

    2008-01-01

    This paper presents a 3-D imaging technique for an ultra-wideband (UWB) ground penetrating radar (GPR) with a single transmit antenna and a linear receive array. The video impulse GPR working in the frequency band of 0.3–3 GHz has been designed in IRCTR for landmine detection, i.e., for a near-field

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

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Jui-Yung; Basu, Soumyadipta; Yang, Yue; Wang, Liping, E-mail: liping.wang@asu.edu [School for Engineering of Matter, Transport and Energy, Arizona State University, Tempe, Arizona 85287 (United States)

    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.

  4. Near field phased array DOA and range estimation of UHF RFID tags

    NARCIS (Netherlands)

    Huiting, Jordy; Kokkeler, André B.J.; Smit, Gerard J.M.

    2015-01-01

    This paper presents a near field localization system based on a phased array for UHF RFID tags. To estimate angle and range the system uses a two-dimensional MUSIC algorithm. A four channel phased array is used to experimentally verify the estimation of angle and range for an EPC gen2 tag. The syste

  5. Near field phased array DOA and range estimation of UHF RFID tags

    NARCIS (Netherlands)

    Huiting, J.; Kokkeler, Andre B.J.; Smit, Gerardus Johannes Maria

    2015-01-01

    This paper presents a near field localization system based on a phased array for UHF RFID tags. To estimate angle and range the system uses a two-dimensional MUSIC algorithm. A four channel phased array is used to experimentally verify the estimation of angle and range for an EPC gen2 tag. The

  6. Polarization contrast in fluorescence scanning near-field optical microscopy in reflection

    NARCIS (Netherlands)

    Jalocha, A.; Hulst, van N.F.

    1995-01-01

    Polarization contrast is presented in fluorescence images of a Langmuir-Blodgett monolayer obtained with a scanning near-field optical microscope operated in reflection. A tapered optical fiber is used both to excite and to collect the fluorescence. The lateral resolution in the reflection fluoresce

  7. The ACE-DTU Planar Near-Field Ground Penetrating Radar Antenna Test Facility

    DEFF Research Database (Denmark)

    Lenler-Eriksen, Hans-Rudolph; Meincke, Peter

    2004-01-01

    The ACE-DTU planar near-field ground penetrating radar (GPR) antenna test facility is used to measure the plane-wave transmitting spectrum of a GPR loop antenna close to the air-soil interface by means of a probe buried in soil. Probe correction is implemented using knowledge about the complex...

  8. Minimal BRDF Sampling for Two-Shot Near-Field Reflectance Acquisition

    DEFF Research Database (Denmark)

    Xu, Zexiang; Nielsen, Jannik Boll; Yu, Jiyang

    2016-01-01

    We develop a method to acquire the BRDF of a homogeneous flat sample from only two images, taken by a near-field perspective camera, and lit by a directional light source. Our method uses the MERL BRDF database to determine the optimal set of lightview pairs for data-driven reflectance acquisition...

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  11. Optical near-field lithography on hydrogen-passivated silicon surfaces

    DEFF Research Database (Denmark)

    Madsen, Steen; Müllenborn, Matthias; Birkelund, Karen

    1996-01-01

    We report on a novel lithography technique for patterning of hydrogen-passivated amorphous silicon surfaces. A reflection mode scanning near-field optical microscope with uncoated fiber probes has been used to locally oxidize a thin amorphous silicon layer. Lines of 110 nm in width, induced...

  12. Single molecule mapping of the optical field distribution of probes for near-field microscopy

    NARCIS (Netherlands)

    Veerman, J.A.; Garcia-Parajo, M.F.; Kuipers, L.; Hulst, van N.F.

    1999-01-01

    The most difficult task in near-field scanning optical microscopy (NSOM) is to make a high quality subwavelength aperture probe, Recently we have developed high definition NSOM probes by focused ion beam (FIB) milling. These probes have a higher brightness, better polarization characteristics, bette

  13. Detection of reflector surface error from near-field data: Effect of edge diffracted field

    Science.gov (United States)

    Cherrette, Alan R.; Lee, Shong W.; Acosta, Roberto J.

    1987-01-01

    The surface accuracy of large reflector antennas must be maintained within certain tolerances if high gain/low sidelobe performance is to be achieved. Thus the measurement of the surface profile is an important part of the quality control procedure when constructing antennas of this type. An efficient method for surface profile measurement has been proposed, i.e., the reflector surface is calculated from the measured near-field phase data using the theory of geometric optics. For a surface profile calculation of this kind, it is necessary to know the margin of error built into the method of calculation. This will enable a specification of the tolerance from which the surface profile can be determined. When calculating the surface profile from near-field phase data, there are two main sources of error. The first is the measurement error in near-field phase data. The second arises from the edge diffracted fields that are superimposed on the reflected fields in the measured near-field data. The error in the calculated surface profile produced by the edge diffracted fields is examined.

  14. Characterization of viscous biofuel sprays using digital imaging in the near field region

    NARCIS (Netherlands)

    Sallevelt, J.L.H.P.; Pozarlik, A.K.; Brem, G.

    2015-01-01

    The atomization of biodiesel, vegetable oil and glycerin has been studied in an atmospheric spray rig by using digital imaging (PDIA). Images of the spray were captured in the near field, just 18 mm downstream of the atomizer, and processed to automatically determine the size of both ligaments and d

  15. Induced Light Emission from Quantum Dots: The Directional Near-Field Pattern

    DEFF Research Database (Denmark)

    Iezhokin, Igor; Keller, Ole; Lozovski, Valeri

    2010-01-01

    The optical Lippmann-Schwinger equation, supplemented by the microscopic conductivity tensor, is used to establish a near-field radiation theory for a mesoscopic particle. The present theory deviates from previous ones in that it allows one to take into account the finite size of the particle in ...

  16. Effects of the near field on source-independent q estimation

    NARCIS (Netherlands)

    Shigapov, R.; Kashtan, B.; Droujinine, A.; Mulder, W.A.

    2013-01-01

    We consider the problem of Q estimation from microseismic and from perforation shot data. Assuming that the source wavelet is not well known, we focused on the spectral ratio method and on source-independent viscoelastic full waveform inversion. We derived 3-D near-field approximations of monopole a

  17. Room-temperature near-field reflection spectrocopy of semiconductor nanostructures

    DEFF Research Database (Denmark)

    Langbein, Wolfgang; Hvam, Jørn Märcher; Madsen, Steen

    1999-01-01

    We investigate the properties of near-field reflection spectroscopy in different polarization and detection modes using uncoated fiber probes. The results show, that cross-polarized detection suppresses to a large extent far-field contributions. Using the fiber dithering as a modulation source fo...

  18. Near-field imaging of out-of-plane light scattering in photonic crystal slabs

    DEFF Research Database (Denmark)

    Volkov, Valentyn; Bozhevolnyi, Sergey; Taillaert, Dirk

    2003-01-01

    A collection scanning near-field optical microscope (SNOM) is used to image the propagating of light at telecommunication wavelengths (1520-1570 nm) along photonic crystal (PC) slabs, which combine slab waveguides with in-plane PCs consisting of one- and two-dimensional gratings. The efficient out...

  19. A New Method for Analyzing Near-Field Faraday Probe Data in Hall Thrusters

    Science.gov (United States)

    Huang, Wensheng; Shastry, Rohit; Herman, Daniel A.; Soulas, George C.; Kamhawi, Hani

    2013-01-01

    This paper presents a new method for analyzing near-field Faraday probe data obtained from Hall thrusters. Traditional methods spawned from far-field Faraday probe analysis rely on assumptions that are not applicable to near-field Faraday probe data. In particular, arbitrary choices for the point of origin and limits of integration have made interpretation of the results difficult. The new method, called iterative pathfinding, uses the evolution of the near-field plume with distance to provide feedback for determining the location of the point of origin. Although still susceptible to the choice of integration limits, this method presents a systematic approach to determining the origin point for calculating the divergence angle. The iterative pathfinding method is applied to near-field Faraday probe data taken in a previous study from the NASA-300M and NASA-457Mv2 Hall thrusters. Since these two thrusters use centrally mounted cathodes the current density associated with the cathode plume is removed before applying iterative pathfinding. A procedure is presented for removing the cathode plume. The results of the analysis are compared to far-field probe analysis results. This paper ends with checks on the validity of the new method and discussions on the implications of the results.

  20. The effect of electronically steering a phased array ultrasound transducer on near-field tissue heating

    Science.gov (United States)

    Payne, Allison; Vyas, Urvi; Todd, Nick; Bever, Joshua de; Christensen, Douglas A.; Parker, Dennis L.

    2011-01-01

    Purpose: This study presents the results obtained from both simulation and experimental techniques that show the effect of mechanically or electronically steering a phased array transducer on proximal tissue heating. Methods: The thermal response of a nine-position raster and a 16-mm diameter circle scanning trajectory executed through both electronic and mechanical scanning was evaluated in computer simulations and experimentally in a homogeneous tissue-mimicking phantom. Simulations were performed using power deposition maps obtained from the hybrid angular spectrum (HAS) method and applying a finite-difference approximation of the Pennes’ bioheat transfer equation for the experimentally used transducer and also for a fully sampled transducer to demonstrate the effect of acoustic window, ultrasound beam overlap and grating lobe clutter on near-field heating. Results: Both simulation and experimental results show that electronically steering the ultrasound beam for the two trajectories using the 256-element phased array significantly increases the thermal dose deposited in the near-field tissues when compared with the same treatment executed through mechanical steering only. In addition, the individual contributions of both beam overlap and grating lobe clutter to the near-field thermal effects were determined through comparing the simulated ultrasound beam patterns and resulting temperature fields from mechanically and electronically steered trajectories using the 256-randomized element phased array transducer to an electronically steered trajectory using a fully sampled transducer with 40 401 phase-adjusted sample points. Conclusions: Three distinctly different three distinctly different transducers were simulated to analyze the tradeoffs of selected transducer design parameters on near-field heating. Careful consideration of design tradeoffs and accurate patient treatment planning combined with thorough monitoring of the near-field tissue temperature will

  1. Numerical simulations of flame dynamics in the near-field of high-Reynolds number jets

    Science.gov (United States)

    Venugopal, Rishikesh

    Recent experiments in diesel jet flames show that flame lift-off has a significant influence on pollutant formation. Lift-off occurs in the near-field of the jet, which is characterized by complex interactions between turbulence and chemistry. Commonly employed modeling approaches based on Reynolds-averaged Navier-Stokes (RANS) simulations are limited in their capability to predict transient and steady lift-off phenomena, as they ignore effects due to unsteadiness and curvature that are inherent in the near-field. In the present work, we perform numerical investigations of localized flame dynamics in the near-field (x/d diesel engine applications. The primary focus is on the exploration of unsteady extinction/reignition phenomena. A dual approach involving large-eddy simulation (LES) of a 70,000-Re variable-density isothermal gaseous fuel jet, and studies of flame-vortex interactions and unsteady flamelets, under diesel engine conditions, is employed in this work. Results from flame-vortex interaction studies show that in the near-field (x/d 1.0) in the jet near-field,temporary flame weakening/recovery events are likely to occur. Steady flamelet models provide reasonable estimates of the mean temperature, and mean mass fractions of the major species and unburned hydrocarbons (UHCs), but are inadequate for the prediction of mean NO mass fractions. Extrapolation of the analysis to jets with higher global strain rates shows that unsteady effects on the localized flame dynamics are important for the prediction of transient and steady lift-off behavior.

  2. The effect of electronically steering a phased array ultrasound transducer on near-field tissue heating.

    Science.gov (United States)

    Payne, Allison; Vyas, Urvi; Todd, Nick; de Bever, Joshua; Christensen, Douglas A; Parker, Dennis L

    2011-09-01

    This study presents the results obtained from both simulation and experimental techniques that show the effect of mechanically or electronically steering a phased array transducer on proximal tissue heating. The thermal response of a nine-position raster and a 16-mm diameter circle scanning trajectory executed through both electronic and mechanical scanning was evaluated in computer simulations and experimentally in a homogeneous tissue-mimicking phantom. Simulations were performed using power deposition maps obtained from the hybrid angular spectrum (HAS) method and applying a finite-difference approximation of the Pennes' bioheat transfer equation for the experimentally used transducer and also for a fully sampled transducer to demonstrate the effect of acoustic window, ultrasound beam overlap and grating lobe clutter on near-field heating. Both simulation and experimental results show that electronically steering the ultrasound beam for the two trajectories using the 256-element phased array significantly increases the thermal dose deposited in the near-field tissues when compared with the same treatment executed through mechanical steering only. In addition, the individual contributions of both beam overlap and grating lobe clutter to the near-field thermal effects were determined through comparing the simulated ultrasound beam patterns and resulting temperature fields from mechanically and electronically steered trajectories using the 256-randomized element phased array transducer to an electronically steered trajectory using a fully sampled transducer with 40 401 phase-adjusted sample points. Three distinctly different three distinctly different transducers were simulated to analyze the tradeoffs of selected transducer design parameters on near-field heating. Careful consideration of design tradeoffs and accurate patient treatment planning combined with thorough monitoring of the near-field tissue temperature will help to ensure patient safety during an MRg

  3. Analysis of Waves in the Near-Field of Wave Energy Converter Arrays through Stereo Video

    Science.gov (United States)

    Black, C.; Haller, M. C.

    2013-12-01

    Oregon State University conducted a series of laboratory experiments to measure and quantify the near-field wave effects caused within arrays of 3 and 5 Wave Energy Converters (WEC). As the waves and WECs interact, significant scattering and radiation occurs increasing/decreasing the wave heights as well as changing the direction the wave is traveling. These effects may vary based on the number of WECs within an array and their respective locations. The findings of this analysis will assist in selecting the WEC farm location and in improving WEC design. Analyzing the near-field waves will help determine the relative importance of absorption, scattering, and radiation as a function of the incident wave conditions and device performance. The WEC mooring system design specifications may also be impacted if the wave heights in the near-field are greater than expected. It is imperative to fully understand the near-field waves before full-scale WEC farms can be installed. Columbia Power Technologies' Manta served as the test WEC prototype on a 1 to 33 scale. Twenty-three wave gages measured the wave heights in both regular and real sea conditions at locations surrounding and within the WEC arrays. While these gages give a good overall picture of the water elevation behavior, it is difficult to resolve the complicated wave field within the WEC array using point gages. Here stereo video techniques are applied to extract the 3D water surface elevations at high resolution in order to reconstruct the multi-directional wave field in the near-field of the WEC array. The video derived wave information will also be compared against the wave gage data.

  4. Relativistic spherical plasma waves

    Science.gov (United States)

    Bulanov, S. S.; Maksimchuk, A.; Schroeder, C. B.; Zhidkov, A. G.; Esarey, E.; Leemans, W. P.

    2012-02-01

    Tightly focused laser pulses that diverge or converge in underdense plasma can generate wake waves, having local structures that are spherical waves. Here we study theoretically and numerically relativistic spherical wake waves and their properties, including wave breaking.

  5. Diamond nanocrystals hosting single nitrogen-vacancy color centers sorted by photon-correlation near-field microscopy.

    Science.gov (United States)

    Sonnefraud, Yannick; Cuche, Aurélien; Faklaris, Orestis; Boudou, Jean-Paul; Sauvage, Thierry; Roch, Jean-François; Treussart, François; Huant, Serge

    2008-03-15

    Diamond nanocrystals containing highly photoluminescent color centers are attractive, nonclassical, and near-field light sources. For near-field applications, the size of the nanocrystal is crucial, since it defines the optical resolution. Nitrogen-vacancy (NV) color centers are efficiently created by proton irradiation and annealing of a nanodiamond powder. Using near-field microscopy and photon statistics measurements, we show that nanodiamonds with sizes down to 25 nm can hold a single NV color center with bright and stable photoluminescence.

  6. Novel microwave near-field sensors for material characterization, biology, and nanotechnology

    CERN Document Server

    Joffe, R; Shavit, R

    2015-01-01

    The wide range of interesting electromagnetic behavior of contemporary materials requires that experimentalists working in this field master many diverse measurement techniques and have a broad understanding of condensed matter physics and biophysics. Measurement of the electromagnetic response of materials at microwave frequencies is important for both fundamental and practical reasons. In this paper, we propose a novel near-field microwave sensor with application to material characterization, biology, and nanotechnology. The sensor is based on a subwavelength ferrite-disk resonator with magnetic-dipolar-mode (MDM) oscillations. Strong energy concentration and unique topological structures of the near fields originated from the MDM resonators allow effective measuring material parameters in microwaves, both for ordinary structures and objects with chiral properties.

  7. Polymer nanofibers prepared by low-voltage near-field electrospinning

    Institute of Scientific and Technical Information of China (English)

    Zheng Jie; Long Yun-Ze; Sun Bin; Zhang Zhi-Hua; Shao Feng; Zhang Hong-Di; Zhang Zhi-Ming; Huang Jia-Yin

    2012-01-01

    Electrospinning is a straightforward method to produce micro/nanoscale fibers from polymer solutions typically using an operating voltage of 10 kV-30 kV and spinning distance of 10 cm-20 cm.In this paper,polyvinyl pyrrolidone (PVP) non-woven nanofibers with diameters of 200 nm-900 nm were prepared by low-voltage near-field electrospinning with a working voltage of less than 2.8 kV and a spinning distance of less than 10 mm.Besides the uniform fibers,beaded-fibers were also fabricated and the formation mechanism was discussed.Particularly,a series of experiments were carried out to explore the influence of processing variables on the formation of near-field electrospun PVP nanofibers,including concentration,humidity,collecting position,and spinning distance.

  8. Modelling and closed loop control of near-field acoustically levitated objects

    CERN Document Server

    Ilssar, Dotan; Flashner, Henryk

    2016-01-01

    The present paper introduces a novel approach for modelling the governing, slow dynamics of near-field acoustically levitated objects. This model is sufficiently simple and concise to enable designing a closed-loop controller, capable of accurate vertical positioning of a carried object. The near-field acoustic levitation phenomenon exploits the compressibility, the nonlinearity and the viscosity of the gas trapped between a rapidly oscillating surface and a freely suspended planar object, to elevate its time averaged pressure above the ambient pressure. By these means, the vertical position of loads weighing up to several kilograms can be varied between dozens and hundreds of micrometers. The simplified model developed in this paper is a second order ordinary differential equation where the height-dependent stiffness and damping terms of the gas layer are derived explicitly. This simplified model replaces a traditional model consisting of the equation of motion of the levitated object, coupled to a nonlinear...

  9. Sparse Multi-Static Arrays for Near-Field Millimeter-Wave Imaging

    Energy Technology Data Exchange (ETDEWEB)

    Sheen, David M.

    2013-12-31

    This paper describes a novel design technique for sparse multi-static linear arrays. The methods described allow the development of densely sampled linear arrays suitable for high-resolution near-field imaging that require dramatically fewer antenna and switch elements than the previous state of the art. The techniques used are related to sparse array techniques used in radio astronomy applications, but differ significantly in design due to the transmit-receive nature of the arrays, and the application to linear arrays that achieve dense uniform sampling suitable for high-resolution near-field imaging. As many as 3 to 5 or more samples per antenna can be obtained, compared to 1 sample per antenna for the current state of the art. This could dramatically reduce cost and improve performance over current active millimeter-wave imaging systems.

  10. Scanning near-field infrared micro-spectroscopy on buried InAs quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Fehrenbacher, Markus; Jacob, Rainer; Winnerl, Stephan; Schneider, Harald; Helm, Manfred [Institut fuer Ionenstrahlphysik und Materialforschung, Helmholtz-Zentrum Dresden-Rossendorf (Germany); Wenzel, Marc Tobias; Krysztofinski, Anja; Ribbeck, Hans-Georg von; Eng, Lukas M. [Institut fuer Angewandte Photophysik, TU Dresden (Germany)

    2012-07-01

    Providing an optical resolution on the nanometer length scale, scanning near-field optical microscopy (SNOM) turned out to be a capable technique to investigate the optical properties of perovskites, buried semiconductors and single quantum dots. Thereby, the line-width of the observed resonances (5 - 8 meV) is significantly smaller than the inhomogeneously broadened line-width of other spectroscopic measurements. Using a scattering-type-SNOM (s-SNOM) combined with a tunable free-electron laser (FEL) light source we investigated the electronic structure of single InAs quantum dots, capped under a 70 nm thick GaAs layer. Spectroscopic near-field scans clearly identified two inter-sublevel transitions within the quantum dots at 85 meV and 120 meV, contrasting from the surrounding medium. Moreover, spatially scanning the s-SNOM tip at fixed excitation energies allowed mapping the 3D distribution of such buried quantum dots.

  11. Prediction and near-field observation of skull-guided acoustic waves

    CERN Document Server

    Estrada, Héctor; Razansky, Daniel

    2016-01-01

    Ultrasound waves propagating in water or soft biological tissue are strongly reflected when encountering the skull, which limits the use of ultrasound-based techniques in transcranial imaging and therapeutic applications. Current knowledge on the acoustic properties of the cranial bone is restricted to far-field observations, leaving its near-field properties unexplored. We report on the existence of skull-guided acoustic waves, which was herein confirmed by near-field measurements of optoacoustically-induced responses in ex-vivo murine skulls immersed in water. Dispersion of the guided waves was found to reasonably agree with the prediction of a multilayered flat plate model. It is generally anticipated that our findings may facilitate and broaden the application of ultrasound-mediated techniques in brain diagnostics and therapy.

  12. Far-field and near-field investigation of plasmonic-photonic hybrid laser mode

    CERN Document Server

    Zhang, Taiping; Callard, Ségolène; jamois, Cecile; Letartre, Xavier; Chevalier, Celine; Rojo-Romeo, Pedro; Devif, Brice; Viktorovitch, Pierre

    2014-01-01

    We report an approach to achieve this goal via build a plasmonic-dielectric photonic hybrid system. We induce a defect mode based photonic crystal (PC) cavity to work as a intermedium storage as well as a near-field light source to excite a plasmonic nanoantenna (NA). In this way, a plasmonic-photonic nano-laser source is created in present experiment. The coupling condition between the two elements is investigated in far-field and near-field level. We found that the NA reduces the Q-factor of the PC-cavity. Meanwhile, the NA concentrates and enhances the laser emission of the PC-cavity. This novel hybrid dielectric-plasmonic structure may open a new avenue in the generation of nano-light sources, which can be applied in areas such as optical information storage, non-linear optics, optical trapping and detection, integrated optics, etc.

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

    Science.gov (United States)

    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.

  14. Tunable narrow-band near-field thermal emitters based on resonant metamaterials

    Science.gov (United States)

    Li, Jiayu; Liu, Baoan; Shen, Sheng

    2017-08-01

    In the near field, Planck's law of blackbody radiation breaks down, and radiative heat transfer can be enhanced by orders of magnitude when surface polaritons are supported by interacting materials. However, such thermal radiation enhancement is strongly material dependent, thus difficult to control. Here, we propose a metamaterial-based structure consisting of patterned doped silicon nanorods that exhibits tunable narrow-band thermal emission. Direct numerical simulation based on the Wiener chaos expansion (WCE) method is performed to accurately investigate the heat transfer mechanism of metamaterials in the near field. The fundamental principle of the WCE method is elucidated, and an algorithm for symmetric and periodic structures is discussed. Implementation of the WCE method with the finite-difference time-domain method using the discrete dipole approximation (DDA) is also addressed in this paper.

  15. Near-Field Radiative Heat Transfer between Metamaterials coated with Silicon Carbide Film

    CERN Document Server

    Basu, Soumyadipta; Wang, Liping

    2014-01-01

    In this letter, we study the near-field radiative heat transfer between two metamaterial substrates coated with silicon carbide (SiC) thin films. It is known that metamaterials can enhance the near-field heat transfer over ordinary materials due to excitation of magnetic plasmons associated with s polarization, while strong surface phonon polariton exists for SiC.By careful tuning of the optical properties of metamaterial it is possible to excite electrical and magnetic resonance for the metamaterial and surface phonon polaritons for SiC at different spectral regions, resulting in the enhanced heat transfer. The effect of the SiC film thickness at different vacuum gaps is investigated. Results obtained from this study will be beneficial for application of thin film coatings for energy harvesting.

  16. Strong Near-Field Enhancement of Radiative Heat Transfer between Metallic Surfaces

    Science.gov (United States)

    Kralik, Tomas; Hanzelka, Pavel; Zobac, Martin; Musilova, Vera; Fort, Tomas; Horak, Michal

    2012-11-01

    Near-field heat transfer across a gap between plane-parallel tungsten layers in vacuo was studied experimentally with the temperature of the cold sample near 5 K and the temperature of the hot sample in the range 10-40 K as a function of the gap size d. At gaps smaller than one-third of the peak wavelength λm given by Wien’s displacement law, the near-field effect was observed. In comparison with blackbody radiation, hundred times higher values of heat flux were achieved at d≈1μm. Heat flux normalized to the radiative power transferred between black surfaces showed scaling (λm/d)n, where n≈2.6. This Letter describes the results of experiment and a comparison with present theory over 4 orders of magnitude of heat flux.

  17. The Mathematical Basis of the Inverse Scattering Problem for Cracks from Near-Field Data

    Directory of Open Access Journals (Sweden)

    Yao Mao

    2015-01-01

    Full Text Available We consider the acoustic scattering problem from a crack which has Dirichlet boundary condition on one side and impedance boundary condition on the other side. The inverse scattering problem in this paper tries to determine the shape of the crack and the surface impedance coefficient from the near-field measurements of the scattered waves, while the source point is placed on a closed curve. We firstly establish a near-field operator and focus on the operator’s mathematical analysis. Secondly, we obtain a uniqueness theorem for the shape and surface impedance. Finally, by using the operator’s properties and modified linear sampling method, we reconstruct the shape and surface impedance.

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

    Science.gov (United States)

    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.

  19. Patch near-field acoustic holography: The influence of acoustic contributions from outside the source

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Jacobsen, Finn; Zhang, Yong-Bin

    2009-01-01

    is of particular interest (known as the “patch” or “source patch”). The area of the source beyond this patch is not of interest in the analysis. However, its acoustic output may nevertheless contribute to the total sound field in the measurement plane, and influence the reconstruction of the field close...... that an acceptable reconstruction of the normal velocity can be achieved if the contributions from beyond the patch area are accounted for.......It is a requirement of conventional Near-field Acoustic Holography that the measurement area covers the entire surface of the source. In the case of Patch Near-field Acoustic Holography (patch NAH), the measurement area can be reduced to cover only a specific area of the source which...

  20. An Analysis of Near Fields of 34m Antennas of JPL/NASA Deep Space Network

    Science.gov (United States)

    Jamnejad, Vahraz; Juan, Nuria Llombart

    2011-01-01

    This paper addresses the issue of calculating near fields of the 34m Beam Waveguide (BWG) antennas of the NASA/JPL Deep Space Network (DSN). Calculating the near fields of DSN antennas are of interest in receive mode where the transmitting signals from nearby flying objects such as helicopters and airplanes could interfere with the operation of sensitive RF receiving system of DSN antennas, and in the transmit mode where fields from high-powered DSN antennas interfere with receivers on nearby flying objects, as well as safety considerations for the operators and visitors to the grounds surrounding the antenna sites. A complete and detailed analysis has been performed using PO/PTD techniques, including surface errors and support struts effects. Some results are presented, including comparisons with preliminary field tests.

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

    CERN Document Server

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

    2014-01-01

    Optical near-field interactions between nanostructured matter, 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.

  2. Transport of an arbitrary near-field component with an array of tilted wires

    Energy Technology Data Exchange (ETDEWEB)

    Morgado, Tiago A; Silveirinha, Mario G [Departamento de Engenharia Electrotecnica, Universidade de Coimbra, Instituto de Telecomunicacoes, Polo II, 3030 Coimbra (Portugal)], E-mail: mario.silveirinha@co.it.pt

    2009-08-15

    In this work, we investigate the possibility of near-field transport using an array of tilted metallic wires. It is demonstrated that consistent with the results reported in Belov et al (2006 Phys. Rev. B 73 033108), which describes subwavelength imaging by an array of metallic wires normal to the interface, the setup considered here may enable the transport of the subwavelength details of a given source through an oblique projection. The array of tilted wires permits the transfer of the electric field component parallel to the wires at the image plane, even when there is no electric field normal to interface, and thus the manipulation of other near-field components (i.e. other wave polarizations) that are not accessible with the usual setup of wires normal to the interface. The emergence of negative refraction due to the extreme anisotropy of structured material is also demonstrated.

  3. Bowtie nano-aperture as interface between near-fields and a single-mode fiber.

    Science.gov (United States)

    Mivelle, M; Ibrahim, I A; Baida, F; Burr, G W; Nedeljkovic, D; Charraut, D; Rauch, J-Y; Salut, R; Grosjean, T

    2010-07-19

    We present the development and study of a single bowtie nano-aperture (BNA) at the end of a monomode optical fiber as an interface between near-fields/nano-optical objects and the fiber mode. To optimize energy conversion between BNA and the single fiber mode, the BNA is opened at the apex of a specially designed polymer fiber tip which acts as an efficient mediator (like a horn optical antenna) between the two systems. As a first application, we propose to use our device as polarizing electric-field nanocollector for scanning near-field optical microscopy (SNOM). However, this BNA-on-fiber probe may also find applications in nanolithography, addressing and telecommunications as well as in situ biological and chemical probing and trapping.

  4. Electromagnetically induced transparency and absorption in plasmonic metasurfaces based on near-field coupling

    Energy Technology Data Exchange (ETDEWEB)

    Wan, Ming-li, E-mail: mlwan@pdsu.edu.cn [College of Electric and Information Engineering, Pingdingshan University, Pingdingshan 467000 (China); He, Jin-na [College of Electric and Information Engineering, Pingdingshan University, Pingdingshan 467000 (China); Song, Yue-li [College of Electric and Information Engineering, Pingdingshan University, Pingdingshan 467000 (China); New PV-energy Engineering Research Center, Pingdingshan University, Pingdingshan 467000 (China); Zhou, Feng-qun [College of Electric and Information Engineering, Pingdingshan University, Pingdingshan 467000 (China)

    2015-09-04

    We theoretically investigate optical properties of a plasmonic metasurface consisting of a dipolar wire as the bright antenna stacked above a quadrupolar wire as the dark antenna. It is demonstrated that by adjusting the lateral displacement between the two resonators, the spectral feature of the metasurface can be evolved from the plasmonic electromagnetically-induced transparency to electromagnetically-induced absorption. The extracted physical parameters based on the two-coupled-oscillator model reveal that the near-field coupling strength plays a key role for the transition behavior in the plasmonic metasurface. - Highlights: • We study spectral response of metamaterial in dependence on near-field coupling. • Coupled two-oscillator is adopted to explain the spectral behavior. • For weak coupling, metamaterials exhibit an EIA-like feature. • For strong coupling, metamaterials exhibit an EIT-like profile.

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

    Energy Technology Data Exchange (ETDEWEB)

    Roy Chowdhury, Dibakar, E-mail: dibakar.roychowdhury@anu.edu.au [Center for Sustainable Energy Systems, College of Engineering and Computer Science, Australian National University, Canberra 0200 (Australia); College of Engineering, Mahindra Ecole Centrale, Jeedimetla, Hyderabad, 500043 (India); Xu, Ningning; Zhang, Weili [School of Electrical Engineering and Computer Science, Oklahoma State University, Stillwater, Oklahoma 87074 (United States); Singh, Ranjan, E-mail: ranjans@ntu.edu.sg [Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore); Centre for Disruptive Photonic Technologies, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 (Singapore)

    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.

  6. A study on regularization parameter choice in near-field acoustical holography

    DEFF Research Database (Denmark)

    Gomes, Jesper; Hansen, Per Christian

    2008-01-01

    Cumulative Periodogram (NCP). The latter method is new within NAH and it is based on the Fourier transform of the residual vector. The methods are used in connection with three NAH methods: Statistically Optimized Near-field Acoustical Holography (SONAH), the Inverse Boundary Element Method (IBEM......Regularization plays an important role in Near-field Acoustical Holography (NAH), and choosing the right amount of regularization is crucial in order to get a meaningful solution. An automated method such as the L-curve or Generalized Cross-Validation (GCV) is often used in NAH to choose...... a regularization parameter. These parameter choice methods (PCMs) are attractive, since they require no a priori knowledge about the noise. However, there seems to be no clear understanding of when one PCM is better than the other. This paper presents comparisons of three PCMs: GCV, L-curve and Normalized...

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

    Science.gov (United States)

    Lee, Hongki; Kim, Chulhong; Kim, Donghyun

    2015-12-02

    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.

  8. Near-field optical microscopy and spectroscopy of few-layer black phosphorous

    Science.gov (United States)

    Frenzel, A. J.; Tran, S.; Hinton, J. P.; Sternbach, A. J.; Yang, J.; Gillgren, N.; Lau, C. N.; Basov, D. N.

    Few-layer black phosphorous is a recent addition to the family of two-dimensional (2D) materials which exhibits strongly anisotropic transport and optical properties due to its puckered honeycomb structure. It was recently predicted that this intrinsic anisotropy should manifest in the plasmon dispersion. Additionally, tuning layer number and carrier density can control the dispersion of these collective modes. Scanning near-field optical microscopy (SNOM) has been demonstrated as a powerful method to probe electronic properties, including propagating collective modes, in layered 2D materials. We used SNOM to investigate anisotropic carrier response in few-layer black phosphorous encapsulated by hexagonal boron nitride. In addition to exploring gate-voltage tunability of the electronic response, we demonstrate effective modulation of the near-field signal by ultrafast photoexcitation.

  9. Temperature and microwave near field imaging by thermo-elastic optical indicator microscopy

    Science.gov (United States)

    Lee, Hanju; Arakelyan, Shant; Friedman, Barry; Lee, Kiejin

    2016-12-01

    A high resolution imaging of the temperature and microwave near field can be a powerful tool for the non-destructive testing of materials and devices. However, it is presently a very challenging issue due to the lack of a practical measurement pathway. In this work, we propose and demonstrate experimentally a practical method resolving the issue by using a conventional CCD-based optical indicator microscope system. The present method utilizes the heat caused by an interaction between the material and an electromagnetic wave, and visualizes the heat source distribution from the measured photoelastic images. By using a slide glass coated by a metal thin film as the indicator, we obtain optically resolved temperature, electric, and magnetic microwave near field images selectively with a comparable sensitivity, response time, and bandwidth of existing methods. The present method provides a practical way to characterize the thermal and electromagnetic properties of materials and devices under various environments.

  10. Light concentration in the near-field of dielectric spheroidal particles with mesoscopic sizes

    Science.gov (United States)

    Mendes, Manuel J.; Tobías, Ignacio; Martí, Antonio; Luque, Antonio

    2011-08-01

    This paper presents a numerical study of the light focusing properties of dielectric spheroids with sizes comparable to the illuminating wavelength. An analytical separation-of-variables method is used to determine the electric field distribution inside and in the near-field outside the particles. An optimization algorithm was implemented in the method to determine the particles' physical parameters that maximize the forward scattered light in the near-field region. It is found that such scatterers can exhibit pronounced electric intensity enhancement (above 100 times the incident intensity) in their close vicinity, or along wide focal regions extending to 10 times the wavelength. The results reveal the potential of wavelength-sized spheroids to manipulate light beyond the limitations of macroscopic geometrical optics. This can be of interest for several applications, such as light management in photovoltaics.

  11. High-rectification near-field thermal diode using phase change periodic nanostructure

    Science.gov (United States)

    Ghanekar, Alok; Ji, Jun; Zheng, Yi

    2016-09-01

    We theoretically demonstrate workings of a near-field thermal rectification device that uses a phase change material to achieve asymmetry in radiative heat transfer. We exploit the temperature dependent dielectric properties of VO2 due to metal-insulator transition near 341 K. Analogous to an electrical diode, heat transfer coefficient is high in one direction while it is considerably small when the polarity of temperature gradient is reversed. We show that thermal rectification can be greatly enhanced by using 1-D rectangular and triangular VO2 surface gratings. With the introduction of periodic grating, rectification ratio is dramatically enhanced in the near-field due to reduced tunneling of surface waves across the interfaces for negative polarity. Our calculations predict that for minimal temperature difference of 20 K, the rectification ratio as high as 16 can be obtained, and it is maximum in existing literature for comparable operating temperatures and separation.

  12. Study of Near-Field Vibration Sources for the NLC Linac Components

    CERN Document Server

    Le Pimpec, F

    2003-01-01

    The vibration stability requirements for the Next Linear Collider (NLC) are far more stringent than for the previous generation of Colliders. To meet these goals, it is imperative that the effects of vibration on NLC Linac components from near-field sources (e.g. compressors, high vacuum equipment, klystrons, modulators, pumps, fans, etc) be well understood. The civil construction method, whether cut-and-cover or parallel bored tunnels, can determine the proximity and possible isolation of noise sources. This paper presents a brief summary and analysis of recently completed and planned studies for characterization of near-field vibration sources under either construction method. The results of in-situ vibration measurements will also be included.

  13. Heating rate and spin flip lifetime due to near field noise in layered superconducting atom chips

    CERN Document Server

    Fermani, Rachele; Zhang, Bo; Lim, Michael J; Dumke, Rainer

    2009-01-01

    We theoretically investigate the heating rate and spin flip lifetimes due to near field noise for atoms trapped close to layered superconducting structures. In particular, we compare the case of a gold layer deposited above a superconductor with the case of a bare superconductor. We study a niobium-based and a YBCO-based chip. For both niobium and YBCO chips at a temperature of 4.2 K, we find that the deposition of the gold layer can have a significant impact on the heating rate and spin flip lifetime, as a result of the increase of the near field noise. At a chip temperature of 77 K, this effect is less pronounced for the YBCO chip.

  14. Energy modulation of nonrelativistic electrons in an optical near field on a metal microslit

    Science.gov (United States)

    Ishikawa, R.; Bae, J.; Mizuno, K.

    2001-04-01

    Energy modulation of nonrelativistic electrons with a laser beam using a metal microslit as an interaction circuit has been investigated. An optical near field is induced in the proximity of the microslit by illumination of the laser beam. The electrons passing close to the slit are accelerated or decelerated by an evanescent wave contained in the near field whose phase velocity is equal to the velocity of the electrons. The electron-evanescent wave interaction in the microslit has been analyzed theoretically and experimentally. The theory has predicted that electron energy can be modulated at optical frequencies. Experiments performed in the infrared region have verified theoretical predictions. The electron-energy changes of more than ±5 eV with a 10 kW CO2 laser pulse at the wavelength of 10.6 μm has been successfully observed for an electron beam with an energy of less than 80 keV.

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

    Science.gov (United States)

    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).

  16. Near-field manipulation of spectroscopic selection rules on the nanoscale.

    Science.gov (United States)

    Jain, Prashant K; Ghosh, Debraj; Baer, Roi; Rabani, Eran; Alivisatos, A Paul

    2012-05-22

    In conventional spectroscopy, transitions between electronic levels are governed by the electric dipole selection rule because electric quadrupole, magnetic dipole, and coupled electric dipole-magnetic dipole transitions are forbidden in a far field. We demonstrated that by using nanostructured electromagnetic fields, the selection rules of absorption spectroscopy could be fundamentally manipulated. We also show that forbidden transitions between discrete quantum levels in a semiconductor nanorod structure are allowed within the near-field of a noble metal nanoparticle. Atomistic simulations analyzed by an effective mass model reveal the breakdown of the dipolar selection rules where quadrupole and octupole transitions are allowed. Our demonstration could be generalized to the use of nanostructured near-fields for enhancing light-matter interactions that are typically weak or forbidden.

  17. Dynamic Analyses of Isolated Structures under Bi-Directional Excitations of Near-Field Ground Motions

    Directory of Open Access Journals (Sweden)

    Gokhan Ozdemir

    2012-01-01

    Full Text Available Nonlinear response history analyses (NRHA of a 3-story isolated reinforced concrete (RC building are carried out under both uni- and bi-directional earthquake excitations of near-field records. NRHA are conducted for a wide range of yield strength (Q/W of lead rubber bearings (LRB, and isolation period (T. Selected near-field records are used to investigate both the contribution of orthogonal components on maximum isolator displacements and accuracy of equivalent lateral force (ELF procedure on estimation of maximum isolator displacements. Analyses results show that both the contribution of orthogonal components and accuracy of ELF procedure depend on the soil condition where isolation system is implemented.

  18. Near-field characterization of low-loss photonic crystal waveguides

    DEFF Research Database (Denmark)

    Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo

    2005-01-01

    A scanning near-field optical microscope is used to directly map the propagation of light in the wavelength range of 1500-1630 nm along straight photonic crystal waveguides (PCWs) fabricated on silicon-on-insulator wafers. The PVWs were formed by removing a single row of holes in the triangular 428......-nm-period lattices with different filling factors (0.76 and 0.82) and connected to access ridge waveguides. Using the near-field optical images we investigate the light propagation along PCWs for TM and TE polarization (the electric field is perpendicular/parallel to the sample surface). Efficient...... guiding (for both samples) of the TM-polarized radiation is observed in the whole range of laser tunability. For TE polarization, the efficient guiding is limited to the wavelengths shorter than 1552 or 1570 nm for the PCW with the filling factor of 0.76 or 0.82, respectively. For longer wavelengths, we...

  19. Dielectric properties characterization of saline solutions by near-field microwave microscopy

    Science.gov (United States)

    Gu, Sijia; Lin, Tianjun; Lasri, Tuami

    2017-01-01

    Saline solutions are of a great interest when characterizations of biological fluids are targeted. In this work a near-field microwave microscope is proposed for the characterization of liquids. An interferometric technique is suggested to enhance measurement sensitivity and accuracy. The validation of the setup and the measurement technique is conducted through the characterization of a large range of saline concentrations (0-160 mg ml-1). Based on the measured resonance frequency shift and quality factor, the complex permittivity is successfully extracted as exhibited by the good agreement found when comparing the results to data obtained from Cole-Cole model. We demonstrate that the near field microwave microscope (NFMM) brings a great advantage by offering the possibility to select a resonance frequency and a quality factor for a given concentration level. This method provides a very effective way to largely enhance the measurement sensitivity in high loss materials.

  20. Mechanical and hydrological characterization of the near-field surrounding excavations in a geologic salt formation

    Energy Technology Data Exchange (ETDEWEB)

    Howard, Clifford L. [Sandia National Laboratories, Albuquerque, NM (United States)

    2014-09-01

    The technical basis for salt disposal of nuclear waste resides in salt’s favorable physical, mechanical and hydrological characteristics. Undisturbed salt formations are impermeable. Upon mining, the salt formation experiences damage in the near-field rock proximal to the mined opening and salt permeability increases dramatically. The volume of rock that has been altered by such damage is called the disturbed rock zone (DRZ).

  1. A Huygens Surface Approach to Antenna Implementation in Near-Field Radar Imaging System Simulations

    Science.gov (United States)

    2015-08-01

    critical geometrical details; re- casting the FDTD update equations on a grid conformal to a curvilinear coordinate system (e.g., cylindrical); and...Imaging System Simulations by Traian Dogaru and DaHan Liao Approved for public release; distribution unlimited...A Huygens Surface Approach to Antenna Implementation in Near-Field Radar Imaging System Simulations by Traian Dogaru and DaHan Liao Sensors

  2. Reconstruction of the shape of object with near field measurements in a half-plane

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    We consider a mathematical problem modelling some characteristics of near field optical microscope.We take a monofrequency line source to illuminate a sample with constant index of refraction and use the scattered field data measured near the sample to reconstruct the shape of it. Mixed reciprocity relation and factorization method are applied to solve our problem.Some numerical examples to show the feasibility of the method are presented.

  3. Reconstruction of the shape of object with near field measurements in a half-plane

    Institute of Scientific and Technical Information of China (English)

    DONG HePing; MA FuMing

    2008-01-01

    We consider a mathematical problem modelling some characteristics of near field optical microscope. We take a monofrequency line source to illuminate a sample with constant index of refraction and use the scattered field data measured near the sample to reconstruct the shape of it.Mixed reciprocity relation and factorization method are applied to solve our problem. Some numerical examples to show the feasibility of the method are presented.

  4. Near-Field Terahertz Transmission Imaging at 0.210 Terahertz Using a Simple Aperture Technique

    Science.gov (United States)

    2015-10-01

    6. AUTHOR(S) Martin S. Heimbeck, Henry O. Everitt, and Amy E. Frees 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Commander...U.S. Army Research, Development, and Engineering Command ATTN: RDMR-WDI Redstone Arsenal, AL 35898-5000 8. PERFORMING ORGANIZATION ...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

  5. Comparison of Numerical and Experimental Time-Resolved Near-Field Hall Thruster Plasma Properties

    Science.gov (United States)

    2012-07-20

    divergence in cooling phase of the cycle may be due to: – Non - maxwellian EEDF • Low emission signal (SNR=1.9 dB) in low Id portion of cycle...Intensity ratio- Te – Absolute Intensity - Density – Doppler Shift - velocity • Non -intrusive- capable of near field measurements • Line of...Ions- uniform velocity, LIF • e- - Maxwellian EDF=f(Te) Empirical excitation cross sections9,10 1 2 = (α,1,

  6. Near-field investigation of a plasmonic-photonic hybrid nanolaser

    CERN Document Server

    Zhang, Taiping; Callard, Ségolène; jamois, Cecile; Letartre, Xavier; Chevalier, Celine; Rojo-Romeo, Pedro; Devif, Brice; Viktorovitch, Pierre

    2014-01-01

    We report an approach of realization and characterization of a novel plasmonic-photonic hybrid nanodevice. The device comprises a plasmonic nano-antenna (NA) and a defect mode based PC cavity, and were fabricated based on a multi-step electron-beam lithography. The laser emission of the devices was demonstrated and the coupling conditions between the NA and PC cavity were investigated in near-field level.

  7. Photon sorting in the near field using subwavelength cavity arrays in the near-infrared

    Energy Technology Data Exchange (ETDEWEB)

    Mandel, Isroel M., E-mail: imandel@gc.cuny.edu; Lansey, Eli [Department of Physics, Graduate Center and City College of the City University of New York, New York 10016 (United States); Gollub, Jonah N.; Sarantos, Chris H.; Akhmechet, Roman [Phoebus Optoelectronics, New York, New York 10013 (United States); Golovin, Andrii B.; Crouse, David T. [Department of Electrical Engineering, The City College of New York, New York, New York 10031 (United States)

    2013-12-16

    A frequency selective metasurface capable of sorting photons in the near-infrared spectral range is designed, fabricated, and characterized. The metasurface, a periodic array of dielectric cylindrical cavities in a gold film, localizes and transmits light of two spectral frequency bands into spatially separated cavities, resulting in near-field light splitting. The design and fabrication methodologies of the metasurface are discussed. The transmittance and photon sorting properties of the designed structure is simulated numerically and the measured transmission is presented.

  8. Near-field nonlinear optical spectroscopy of Langmuir-Blodgett films

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Geisler, T.

    1998-01-01

    Using an uncoated fiber tip as a light source and a multilayer Langmuir-Blodgett film of 2-docosylamino-5-nitropyridine as a sample, we obtain near-field images at the fundamental-harmonic (FH) and second-harmonic (SH) wavelengths for different polarizations and wavelengths of the pump light...... differently but predominantly in the dipping direction and whose SH efficiency is maximum for pump wavelengths in the range of 770-800 nm. (C) 1998 Optical Society of America....

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

    OpenAIRE

    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 imag...

  10. Development of the near field geochemistry model; Desarrollo de un modelo geoquimico de campo proximo

    Energy Technology Data Exchange (ETDEWEB)

    Arcos, D.; Bruno, J.; Duro, L.; Grive, M.

    2000-07-01

    This report discusses in a quantitative manner the evolution of the near field geochemistry as a result of the interactions between two different introducing granitic groundwaters and the FEBEX bentonite as a buffer material. The two granitic groundwaters considered are: SR-5 water, sampled in a borehole at 500 m depth in Mina Ratones, and a mean composition of different granitic groundwaters from the iberian Massif. The steel canister has also been introduced by considering the iron corrosion in anoxic conditions. (Author)

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

    Science.gov (United States)

    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.

  12. Disorder fingerprint: Intensity distributions in the near field of random media

    Science.gov (United States)

    Naraghi, R. Rezvani; Sukhov, S.; Dogariu, A.

    2016-11-01

    The structural morphology of complex dielectric media determines their functionalities by driving the statistical properties of the electromagnetic fields. Our controlled experiments and full electromagnetic calculations that go beyond common dipolar approximations demonstrate that the specific characteristics of disorder lead to non-Rayleigh statistics of detected intensity, which can be directly accessed in the near field of random media and can be unambiguously related to the short-range correlations of disorder.

  13. Thermodynamics and energy conversion of near-field thermal radiation: Maximum work and efficiency bounds

    Directory of Open Access Journals (Sweden)

    Latella Ivan

    2014-01-01

    Full Text Available We analyse the process of conversion of near-field thermal radiation into usable work by considering the radiation emitted between two planar sources supporting surface phonon-polaritons. The maximum work flux that can be extracted from the radiation is obtained taking into account that the spectral flux of modes is mainly dominated by these surface modes. The thermodynamic efficiencies are discussed and an upper bound for the first law efficiency is obtained for this process.

  14. Strong near-field optical localization on an array of gold nanodisks

    OpenAIRE

    Aigouy, Lionel; Prieto Vizán, Patricia; Vitrey, Alan; Anguita, José Virgilio; Cebollada, Alfonso; González Sagardoy, María Ujué

    2011-01-01

    By scanning near-field optical microscopy, we measured the localization of the electromagnetic field on an array of gold nanodisks illuminated in a transmission mode. We experimentally observed that the field is localized between the disks, with a pattern oriented along the incident polarization direction. We also observed that the electromagnetic field rapidly decays above the nanodisks, showing a strong vertical localization. The experimental results are in good agreement with numerical sim...

  15. Cost-Effective, Cognitive Undersea Network for Timely and Reliable Near-Field Tsunami Warning

    Directory of Open Access Journals (Sweden)

    X. Xerandy

    2015-07-01

    Full Text Available The focus of this paper is on developing an early detection and warning system for near-field tsunami to mitigate its impact on communities at risk. This a challenging task, given the stringent reliability and timeliness requirements, the development of such an infrastructure entails. To address this challenge, we propose a hybrid infrastructure, which combines cheap but unreliable undersea sensors with expensive but highly reliable fiber optic, to meet the stringent constraints of this warning system. The derivation of a low-cost tsunami detection and warning infrastructure is cast as an optimization problem, and a heuristic approach is used to determine the minimum cost network configuration that meets the targeted reliability and timeliness requirements. To capture the intrinsic properties of the environment and model accurately the main characteristics of the sound wave propagation undersea, the proposed optimization framework incorporates the Bellhop propagation model and accounts for significant environment factors, including noise, varying undersea sound speed and sea floor profile. We apply our approach to a region which is prone to near-field tsunami threats to derive a cost-effective under sea infrastructure for detection and warning. For this case study, the results derived from the proposed framework show that a feasible infrastructure, which operates with a carrier frequency of 12-KHz, can be deployed in calm, moderate and severe environments and meet the stringent reliability and timeliness constraints, namely 20 minutes warning time and 99 % data communication reliability, required to mitigate the impact of a near-field tsunami. The proposed framework provides useful insights and guidelines toward the development of a realistic detection and warning system for near-field tsunami.

  16. Comparison of two numerical modelling codes for hydraulic and transport calculations in the near-field

    Energy Technology Data Exchange (ETDEWEB)

    Kalin, J., E-mail: jan.kalin@zag.s [Slovenian National Building and Civil Engineering Institute, Dimiceva 12, SI-1000 Ljubljana (Slovenia); Petkovsek, B., E-mail: borut.petkovsek@zag.s [Slovenian National Building and Civil Engineering Institute, Dimiceva 12, SI-1000 Ljubljana (Slovenia); Montarnal, Ph., E-mail: philippe.montarnal@cea.f [CEA/Saclay, DM2S/SFME/LSET, Gif-sur-Yvette, 91191 cedex (France); Genty, A., E-mail: alain.genty@cea.f [CEA/Saclay, DM2S/SFME/LSET, Gif-sur-Yvette, 91191 cedex (France); Deville, E., E-mail: estelle.deville@cea.f [CEA/Saclay, DM2S/SFME/LSET, Gif-sur-Yvette, 91191 cedex (France); Krivic, J., E-mail: jure.krivic@geo-zs.s [Geological Survey of Slovenia, Dimiceva 14, SI-1000 Ljubljana (Slovenia); Ratej, J., E-mail: joze.ratej@geo-zs.s [Geological Survey of Slovenia, Dimiceva 14, SI-1000 Ljubljana (Slovenia)

    2011-04-15

    In the past years the Slovenian Performance Analysis/Safety Assessment team has performed many generic studies for the future Slovenian low and intermediate level waste repository, most recently a Special Safety Analysis for the Krsko site. The modelling approach was to split the problem into three parts: near-field (detailed model of the repository), far-field (i.e., geosphere) and biosphere. In the Special Safety Analysis the code used to perform the near-field calculations was Hydrus2D. Recently the team has begun a cooperation with the French Commisariat al'Energie Atomique/Saclay (CEA/Saclay) and, as a part of this cooperation, began investigations into using the Alliances numerical platform for near-field calculations in order to compare the overall approach and calculated results. The article presents the comparison between these two codes for a silo-type repository that was considered in the Special Safety Analysis. The physical layout and characteristics of the repository are presented and a hydraulic and transport model of the repository is developed and implemented in Alliances. Some analysis of sensitivity to mesh fineness and to simulation timestep has been preformed and is also presented. The compared quantity is the output flux of radionuclides on the boundary of the model. Finally the results from Hydrus2D and Alliances are compared and the differences and similarities are commented.

  17. Vortex rings and jets recent developments in near-field dynamics

    CERN Document Server

    Yu, Simon

    2015-01-01

    In this book, recent developments in our understanding of fundamental vortex ring and jet dynamics will be discussed, with a view to shed light upon their near-field behaviour which underpins much of their far-field characteristics. The chapters provide up-to-date research findings by their respective experts and seek to link near-field flow physics of vortex ring and jet flows with end-applications in mind. Over the past decade, our knowledge on vortex ring and jet flows has grown by leaps and bounds, thanks to increasing use of high-fidelity, high-accuracy experimental techniques and numerical simulations. As such, we now have a much better appreciation and understanding on the initiation and near-field developments of vortex ring and jet flows under many varied initial and boundary conditions. Chapter 1 outlines the vortex ring pinch-off phenomenon and how it relates to the initial stages of jet formations and subsequent jet behaviour, while Chapter 2 takes a closer look at the behaviour resulting from vor...

  18. High-efficiency and high-resolution apertureless plasmonic near-field probe under internal illumination

    Science.gov (United States)

    Jiang, R. H.; Chou, H. C.; Chu, J. Y.; Chen, C.; Yen, T. J.

    2016-09-01

    Near-field scanning optical microscopy (NSOM) offers subwavelength optical resolution beyond the diffraction limit, enabling practical applications in optical imaging, sensing and nanolithography. However, due to the sub-100 nm size of apertures, conventional NSOM aperture probes suffer from the constrains of the strong attenuation of the throughput and limited the spatial resolution. To solve the problem, we designed a novel scheme for apertureless plasmonic probes with radial internal illumination. Employing non-periodic multi-rings geometry for plasmonic excitations, surface plasmons adiabatically nanofocuse energy at tip and the full width at half maximum of the optimal design is 18 nm. The proposed probe was optimized with 2D finite-difference time-domain (FDTD) analysis and realistic parabolic probe geometries. Comprehensive electromagnetic simulation shows that the optimal probe feature obeys Fabry-Pérot condition on the plasmonic metallic wall, giving rise to substantial field enhancement up to 6 orders of magnitude greater than conventional aperture probes without degrading its spatial resolution. We fabricated the proposed probe which possesses apex angle ( 22 degree) and tip radius ( 30 nm). Finally, the proposed near field plasmonic probe effectively combining the high resolution of apertureless probes with high throughput can enable the proposed plasmonic NSOM probe as a practical tool for applications in near field optical microscopy.

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

    Science.gov (United States)

    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.

  20. Electromagnetic absorption in a multilayered slab model of tissue under near-field exposure conditions

    Energy Technology Data Exchange (ETDEWEB)

    Chatterjee, I.; Hagmann, M.J.; Gandhi, O.P.

    1980-01-01

    The electromagnetic energy deposited in a semi-infinite slab model consisting of skin, fat, and muscle layers is calculated for both plane-wave and near-field exposures. The plane-wave spectrum (PWS) approach is used to calculate the energy deposited in the model by fields present due to leakage from equipment using electromagnetic energy. This analysis applies to near-field exposures where coupling of the target to the leakage source can be neglected. Calculations were made for 2,450 MHz, at which frequency the layered slab adequately models flat regions of the human body. Resonant absorption due to layering is examined as a function of the skin and fat thicknesses for plane-wave exposure and as a function of the physical extent of the near-field distribution. Calculations show that for fields that are nearly constant over at least a free-space wavelength, the energy deposition (for skin, fat, and muscle combination that gives resonant absorption) is equal to or less than that resulting from plane-wave exposure, but is appreciably greater than that obtained for a homogeneous muscle slab model.

  1. Coherent regime and far-to-near-field transition for radiative heat transfer

    Science.gov (United States)

    Tsurimaki, Yoichiro; Chapuis, Pierre-Olivier; Okajima, Junnosuke; Komiya, Atsuki; Maruyama, Shigenao; Vaillon, Rodolphe

    2017-01-01

    Radiative heat transfer between two semi-infinite parallel media is analyzed in the transition zone between the near-field and the classical macroscopic, i.e. incoherent far-field, regimes of thermal radiation, first for model gray materials and then for real metallic (Al) and dielectric (SiC) materials. The presence of a minimum in the flux-distance curve is observed for the propagative component of the radiative heat transfer coefficient, and in some cases for the total coefficient, i.e. the sum of the propagative and evanescent components. At best this reduction can reach 15% below the far-field limit in the case of aluminum. The far-to-near-field regime taking place for the distance range between the near-field and the classical macroscopic regime involves a coherent far-field regime. One of its limits can be practically defined by the distance at which the incoherent far-field regime breaks down. This separation distance below which the standard theory of incoherent thermal radiation cannot be applied anymore is found to be larger than the usual estimate based on Wien's law and varies as a function of temperature. The aforementioned effects are due to coherence, which is present despite the broadband spectral nature of thermal radiation, and has a stronger impact for reflective materials.

  2. Near-field enhancement of the nanostructure on the fused silica with rigorous method.

    Science.gov (United States)

    Wang, Hu; Qi, Hongji; Wang, Bin; Cui, Yanyan; Chai, Yingjie; Jin, Yunxia; Yi, Kui; Shao, Jianda

    2015-05-10

    A rigorous electromagnetic method is developed to analyze the resonance effect of near field caused by nanoscale subsurface defects, which play a key role in describing absorption enhancement during laser-matter interaction for transparent dielectric materials. The total electric field calculated with this new method is consistent with the result of finite-difference time-domain simulation. The concept of mode amplitude density spectrum is developed to analyze the specific modes of the total field. A new mode parameter is proposed to demarcate the contribution of the resonance. The frequency space is divided into four parts and the resonance effect is analyzed as well as the contributions of different modes to the total field. The influence of the structure parameters on the near-field modulation and energy transference is also discussed. It is found that the enhancement mechanism of the near-field and local absorption is the resonance effect caused by the total internal reflection on the sidewall of the nanostructure. In addition, the surrounding energy is mainly guided into the structure by the root of the structure via the energy flow analysis.

  3. High-fidelity spatial addressing of 43Ca+ qubits using near-field microwave control

    Science.gov (United States)

    Prado Lopes Aude Craik, Diana; Linke, Norbert; Allcock, David; Sepiol, Martin; Harty, Thomas; Ballance, Christopher; Stacey, Derek; Steane, Andrew; Lucas, David

    2016-05-01

    Individual addressing of qubits is essential for scalable quantum computation. Spatial addressing allows unlimited numbers of qubits to share the same frequency, whilst enabling arbitrary parallel operations. We present the latest experimental results obtained using a two-zone microfabricated surface trap designed to perform spatial, near-field microwave addressing of long-lived 43Ca+ ``atomic clock'' qubits held in separate trap zones (each of which feature four integrated microwave electrodes). Microwave near fields generated by multi-electrode chip ion traps are often difficult to faithfully simulate and a simple method of characterizing and testing trap chips before placement under ultra-high vacuum would significantly speed up trap design optimization. We describe a printed circuit board antenna for use in mapping microwave near-fields generated by ion-trap electrodes. The antenna is designed to measure fields down to 100 μ m away from trap electrodes and to be impedance matched at a desired spot frequency for an improved signal to noise ratio in field measurements. This work is supported by the US Army Research Office, EPSRC (UK) and the UK National Quantum Technologies Programme.

  4. Near-field radiation between graphene-covered carbon nanotube arrays

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Richard Z.; Liu, Xianglei; Zhang, Zhuomin M., E-mail: zhuomin.zhang@me.gatech.edu [George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

    2015-05-15

    It has been shown that at small separation distances, thermal radiation between hyperbolic metamaterials is enhanced over blackbodies. This theoretical study considers near-field radiation when graphene is covered on the surfaces of two semi-infinite vertically aligned carbon nanotube (VACNT) arrays separated by a sub-micron vacuum gap. Doped graphene is found to improve photon tunneling in a broad hyperbolic frequency range, due to the interaction with graphene-graphene surface plasmon polaritons (SPP). In order to elucidate the SPP resonance between graphene on hyperbolic substrates, vacuum-suspended graphene sheets separated by similar gap distances are compared. Increasing the Fermi energy through doping shifts the spectral heat flux peak toward higher frequencies. Although the presence of graphene on VACNT does not offer huge near-field heat flux enhancement over uncovered VACNT, this study identifies conditions (i.e., gap distance and doping level) that best utilize graphene to augment near-field radiation. Through the investigation of spatial Poynting vectors, heavily doped graphene is found to increase penetration depths in hyperbolic modes and the result is sensitive to the frequency regime. This study may have an impact on designing carbon-based vacuum thermophotovoltaics and thermal switches.

  5. Near-field radiation between graphene-covered carbon nanotube arrays

    Directory of Open Access Journals (Sweden)

    Richard Z. Zhang

    2015-05-01

    Full Text Available It has been shown that at small separation distances, thermal radiation between hyperbolic metamaterials is enhanced over blackbodies. This theoretical study considers near-field radiation when graphene is covered on the surfaces of two semi-infinite vertically aligned carbon nanotube (VACNT arrays separated by a sub-micron vacuum gap. Doped graphene is found to improve photon tunneling in a broad hyperbolic frequency range, due to the interaction with graphene-graphene surface plasmon polaritons (SPP. In order to elucidate the SPP resonance between graphene on hyperbolic substrates, vacuum-suspended graphene sheets separated by similar gap distances are compared. Increasing the Fermi energy through doping shifts the spectral heat flux peak toward higher frequencies. Although the presence of graphene on VACNT does not offer huge near-field heat flux enhancement over uncovered VACNT, this study identifies conditions (i.e., gap distance and doping level that best utilize graphene to augment near-field radiation. Through the investigation of spatial Poynting vectors, heavily doped graphene is found to increase penetration depths in hyperbolic modes and the result is sensitive to the frequency regime. This study may have an impact on designing carbon-based vacuum thermophotovoltaics and thermal switches.

  6. Near-field radiation between graphene-covered carbon nanotube arrays

    Science.gov (United States)

    Zhang, Richard Z.; Liu, Xianglei; Zhang, Zhuomin M.

    2015-05-01

    It has been shown that at small separation distances, thermal radiation between hyperbolic metamaterials is enhanced over blackbodies. This theoretical study considers near-field radiation when graphene is covered on the surfaces of two semi-infinite vertically aligned carbon nanotube (VACNT) arrays separated by a sub-micron vacuum gap. Doped graphene is found to improve photon tunneling in a broad hyperbolic frequency range, due to the interaction with graphene-graphene surface plasmon polaritons (SPP). In order to elucidate the SPP resonance between graphene on hyperbolic substrates, vacuum-suspended graphene sheets separated by similar gap distances are compared. Increasing the Fermi energy through doping shifts the spectral heat flux peak toward higher frequencies. Although the presence of graphene on VACNT does not offer huge near-field heat flux enhancement over uncovered VACNT, this study identifies conditions (i.e., gap distance and doping level) that best utilize graphene to augment near-field radiation. Through the investigation of spatial Poynting vectors, heavily doped graphene is found to increase penetration depths in hyperbolic modes and the result is sensitive to the frequency regime. This study may have an impact on designing carbon-based vacuum thermophotovoltaics and thermal switches.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

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

    Science.gov (United States)

    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.

  10. PIV study of near-field tip vortex behind perforated Gurney flaps

    Science.gov (United States)

    Lee, T.

    2011-02-01

    The impact of Gurney flaps, of different heights and perforations, on the growth and development of a tip vortex, both along the tip and in the near field of a finite NACA 0012 wing, at Re = 1.05 × 105 was investigated by using particle image velocimetry (PIV). Wind-tunnel force balance measurements were also made to supplement the PIV results. This study is a continuation of the work of Lee and Ko (Exp Fluids 46(6):1005-1019, 2009) on the near-wake measurements behind perforated Gurney flaps. The present results show that along the tip, the overall behavior of the secondary vortices and their interaction with the primary, or tip, vortex remained basically unchanged, regardless of flap height and perforation. The peak vorticity of the tip vortex, however, increased with flap height and always exhibited a local maximum at x/ c = 0.8 (from the leading edge). In the near field, the strength and structure of the near-field tip vortex were found to vary greatly with the flap height and perforation. The small flaps produced a more concentrated tip vortex with an increased circulation, while the large Gurney flaps caused a disruption of the tip vortex. The disrupted vortex can, however, be re-established by the addition of flap perforation. The larger the flap perforation the more organized the tip vortex. The Gurney flaps have the potential to serve as an alternative off-design wake vortex control device.

  11. NEAR-FIELD SOURCE LOCALIZATION METHOD AND APPLICATION USING THE TIME REVERSAL MIRROR TECHNIQUE

    Institute of Scientific and Technical Information of China (English)

    Fu Yongqing; Jiang Yulei; Liu Zhanya

    2011-01-01

    In order to develop the acoustic keyboard for Personal Computer (PC),it is necessary to seek high-precision near-field source localization algorithm for identifying the keyboard characters.First of all,the focusing property of Time Reversal Mirror (TRM) is introduced,and then a mathematical model of microphone array receiving typing sound is established according to the realization of acoustic keyboard from which the TRM localization algorithm is carried out.The results through computer simulation show that the localization Root Mean Square Error (RMSE) performance of the algorithm can reach 10-3,which demonstrates that the algorithm possesses a high accuracy for the actual near-field acoustic source localization,with potential of developing the computer acoustic keyboard.Furthermore,for the purpose of testing its effect on actual near-field source localization,we organize three experiments for acoustic keyboard characters localization.The experiment results show that the positioning error of TRM algorithm is less than 1 cm within a provided acoustic keyboard region.This will provide theoretical guidance for the further research of computer acoustic keyboard.

  12. Profiling the Near field of Nanoshells Using Surface Enhanced Raman Spectroscopy

    Science.gov (United States)

    Lal, Surbhi

    2005-03-01

    There is tremendous interest in the enhancement of electromagnetic fields near metal surfaces. The spatial extent of the near field as a function of distance from the metal surface is of particular interest for applications such as surface enhanced Raman spectroscopy. By using specially designed molecular scaffolds with Raman-active constituents, we measure the profile of this fringing field at a nanoshell surface. Nanoshells are colloidal particles composed of a silica core covered by a gold shell, which exhibit a tunable plasmon resonance; close to this resonance there is a strong enhancement of the electromagnetic near field. The molecular scaffolds consist of polyadenine DNA strands as tethers with a terminal fluorescein molecule. By varying the length of the DNA strand, the fluorescein molecule is placed at controlled distances from the nanoshell surface. Both the DNA scaffold and the terminal fluorescein molecule provide us with independent SERS Stokes modes whose relative intensities permit us to map the average spatial decay length of the near field of the nanoparticle at its plasmon resonance.

  13. Optical near-field studies of waveguiding organic nanofibers by angular dependent excitation

    DEFF Research Database (Denmark)

    Maibohm, Christian

      Optical near-field studies of waveguiding organic nanofibers by angular dependent excitation.   Authors: Christian Maibohm¹, Tomasz Kawalec¹, Vladimir G. Bordo² and Horst-Günter Rubahn¹. Institutions: 1) NanoSYD, MCI, University of southern Denmark, DK- 6400         Sønderborg Denmark .        ......  Optical near-field studies of waveguiding organic nanofibers by angular dependent excitation.   Authors: Christian Maibohm¹, Tomasz Kawalec¹, Vladimir G. Bordo² and Horst-Günter Rubahn¹. Institutions: 1) NanoSYD, MCI, University of southern Denmark, DK- 6400         Sønderborg Denmark...... .                    2) Institute of General Physics, Russian Academy of Science, 119991 Moscow, Russia. Abstract:   Single crystalline organic nanofibers of para-phenylene are grown in UHV by MBE and dipole assisted self-assembly. In the optical far-field the fluorescence from a single nanofiber is spectrally well...... defined and highly polarized. By UV excitation in a fluorescence microscope it has also been shown that nanofibers have waveguiding properties. To further characterize the waveguiding properties the optical near-field has to be investigated. This is done by transferring nanofibers to an quartz half sphere...

  14. Near-Field Optical Drilling of Sub-λ Pits in Thin Polymer Films.

    Science.gov (United States)

    Ding, Tao; Chikkaraddy, Rohit; Mertens, Jan; Baumberg, Jeremy J

    2017-06-21

    Under UV illumination, polymer films can undergo chain scission and contract. Using this effect, tightly focused laser light is shown to develop runaway near-field concentration that drills sub-100 nm pits through a thin film. This subwavelength photolithography can be controlled in real time by monitoring laser scatter from the evolving holes, allowing systematic control of the void diameter. Our model shows how interference between the substrate and film together with near-field focusing by the evolving crevice directs this formation and predicts minimum pit sizes in films of 100 nm thickness on gold substrates. The smallest features so far are 60 nm diameter pits using 447 nm light focused onto polystyrene through a ×100 objective (NA = 0.8). Such arrays of pits can be easily used as masks for fabricating more complex nanostructures, such as plasmonic nanostructures and biomicrofluidic devices. This demonstration shows the potential for harnessing near-field feedback in optical direct-writing for nanofabrication.

  15. Novel Scanning Near-Field Microwave Microscopes Capable of Imaging Semiconductors and Metals

    Science.gov (United States)

    Imtiaz, Atif; Tselev, Alexander; Anlage, Steven

    2003-03-01

    To study novel physics in condensed matter and materials science, experimental techniques of probing the high frequency electrical properties of materials are limited in resolution to the wavelength of the incident electromagnetic wave. We report here a novel near-field microscope that is capable of operation at radio and microwave frequencies[1]. The spatial resolution is comparable to NSOM in the scanning capacitance mode of the microscope[2]. Our objective is to image materials contrast at microwave frequencies and improve the spatial resolution. The microscope is sensitive to losses in materials, and we will present evidence of sheet resistance contrast in a Boron-doped Silicon sample. These experiments are performed with two versions of the near-field microwave microscope: one has integrated STM-feedback for distance control and the second one maintains a constant frequency shift through Distance Following technique. We will discuss the data on these films in light of a transmission line and lumped element model of the microscope. The microscope is an attractive platform for measuring local losses and local nonlinear properties of a rich variety of semiconducting and correlated-electron materials. [1] D.E. Steinhauer, et.al, "Quantitative Imaging of Sheet Resistance with a Scanning Near-Field Microwave Microscope", Appl. Phys. Lett. 72, 861 (1998) [2] Atif Imtiaz and Steven M. Anlage, "A novel STM-assisted microwave microscope with capacitance and loss imaging capability", Ultramicroscopy (in press); cond-mat/0203540

  16. A Novel Scanning Near-Field Microwave Microscope Capable of High Resolution Loss Imaging

    Science.gov (United States)

    Imtiaz, Atif

    2005-03-01

    To study novel physics in condensed matter and materials science, experimental techniques need to be pushed for better sensitivity and higher spatial resolution. Classical techniques of probing the high frequency electrical properties of materials are limited in resolution to the wavelength of the incident electromagnetic wave. We report here a novel near-field microwave microscope to image materials contrast, with 2.5 nm spatial resolution in capacitance. Our objective is to improve the spatial resolution in local loss imaging. We will present evidence of sheet resistance contrast in a Boron-doped Silicon sample on sub- micron length scales. We will present quantitative analysis of the data on the Boron-doped Silicon sample in light of evanescent wave model of the microscope that we have developed. In addition, the probe to sample interaction on nanometer length scales will be discussed [1]. This work has been supported by an NSF IMR Grant DMR-9802756, and the University of Maryland/Rutgers NSF-MRSEC through the Near Field Microwave Microscope Shared Experimental Facility Grant DMR-00-80008. [1] Atif Imtiaz, Marc Pollak, Steven M. Anlage, John D. Barry and John Melngailis, ``Near-Field Microwave Microscopy on nanometer length scales'', to be published in J. Appl. Phys. (Feb. 1, 2005).

  17. Electromagnetic power flow between opposite sides of a lossy dielectric sphere using spherical vector wave expansion

    DEFF Research Database (Denmark)

    Nour, Baqer; Breinbjerg, Olav

    2010-01-01

    This article addresses the problem of communication in near field region. The proposed example is the communication between two small antennas, which are modelled as an electric dipole antenna (transmitter) and a small box (receiver), near a sphere that models a head. Spherical vector wave...

  18. Sub-wavelength imaging by depolarization in a reflection near-field optical microscope using an uncoated fiber probe

    DEFF Research Database (Denmark)

    Madsen, Steen; Bozhevolnyi, Sergey I.; Hvam, Jørn Märcher

    1998-01-01

    We present a reflection scanning near-field optical microscope utilizing counter-directional light propagation in an uncoated fiber probe, cross-polarized detection and shear-force feedback. Topographical and near-field optical imaging with a scanning speed of up to 10 mu m/s and a lateral...

  19. Analysis of near-field components of a plasmonic optical antenna and their contribution to quantum dot infrared photodetector enhancement.

    Science.gov (United States)

    Gu, Guiru; Vaillancourt, Jarrod; Lu, Xuejun

    2014-10-20

    In this paper, we analyze near-field vector components of a metallic circular disk array (MCDA) plasmonic optical antenna and their contribution to quantum dot infrared photodetector (QDIP) enhancement. The near-field vector components of the MCDA optical antenna and their distribution in the QD active region are simulated. The near-field overlap integral with the QD active region is calculated at different wavelengths and compared with the QDIP enhancement spectrum. The x-component (E(x)) of the near-field vector shows a larger intensity overlap integral and stronger correlation with the QDIP enhancement than E(z) and thus is determined to be the major near-field component to the QDIP enhancement.

  20. Real-Space Mapping of the Chiral Near-Field Distributions in Spiral Antennas and Planar Metasurfaces.

    Science.gov (United States)

    Schnell, M; Sarriugarte, P; Neuman, T; Khanikaev, A B; Shvets, G; Aizpurua, J; Hillenbrand, R

    2016-01-13

    Chiral antennas and metasurfaces can be designed to react differently to left- and right-handed circularly polarized light, which enables novel optical properties such as giant optical activity and negative refraction. Here, we demonstrate that the underlying chiral near-field distributions can be directly mapped with scattering-type scanning near-field optical microscopy employing circularly polarized illumination. We apply our technique to visualize, for the first time, the circular-polarization selective nanofocusing of infrared light in Archimedean spiral antennas, and explain this chiral optical effect by directional launching of traveling waves in analogy to antenna theory. Moreover, we near-field image single-layer rosette and asymmetric dipole-monopole metasurfaces and find negligible and strong chiral optical near-field contrast, respectively. Our technique paves the way for near-field characterization of optical chirality in metal nanostructures, which will be essential for the future development of chiral antennas and metasurfaces and their applications.

  1. Evaluation of seismic performance of reinforced concrete (RC) buildings under near-field earthquakes

    Science.gov (United States)

    Moniri, Hassan

    2017-03-01

    Near-field ground motions are significantly severely affected on seismic response of structure compared with far-field ground motions, and the reason is that the near-source forward directivity ground motions contain pulse-long periods. Therefore, the cumulative effects of far-fault records are minor. The damage and collapse of engineering structures observed in the last decades' earthquakes show the potential of damage in existing structures under near-field ground motions. One important subject studied by earthquake engineers as part of a performance-based approach is the determination of demand and collapse capacity under near-field earthquake. Different methods for evaluating seismic structural performance have been suggested along with and as part of the development of performance-based earthquake engineering. This study investigated the results of illustrious characteristics of near-fault ground motions on the seismic response of reinforced concrete (RC) structures, by the use of Incremental Nonlinear Dynamic Analysis (IDA) method. Due to the fact that various ground motions result in different intensity-versus-response plots, this analysis is done again under various ground motions in order to achieve significant statistical averages. The OpenSees software was used to conduct nonlinear structural evaluations. Numerical modelling showed that near-source outcomes cause most of the seismic energy from the rupture to arrive in a single coherent long-period pulse of motion and permanent ground displacements. Finally, a vulnerability of RC building can be evaluated against pulse-like near-fault ground motions effects.

  2. Evaluation of seismic performance of reinforced concrete (RC) buildings under near-field earthquakes

    Science.gov (United States)

    Moniri, Hassan

    2017-01-01

    Near-field ground motions are significantly severely affected on seismic response of structure compared with far-field ground motions, and the reason is that the near-source forward directivity ground motions contain pulse-long periods. Therefore, the cumulative effects of far-fault records are minor. The damage and collapse of engineering structures observed in the last decades' earthquakes show the potential of damage in existing structures under near-field ground motions. One important subject studied by earthquake engineers as part of a performance-based approach is the determination of demand and collapse capacity under near-field earthquake. Different methods for evaluating seismic structural performance have been suggested along with and as part of the development of performance-based earthquake engineering. This study investigated the results of illustrious characteristics of near-fault ground motions on the seismic response of reinforced concrete (RC) structures, by the use of Incremental Nonlinear Dynamic Analysis (IDA) method. Due to the fact that various ground motions result in different intensity-versus-response plots, this analysis is done again under various ground motions in order to achieve significant statistical averages. The OpenSees software was used to conduct nonlinear structural evaluations. Numerical modelling showed that near-source outcomes cause most of the seismic energy from the rupture to arrive in a single coherent long-period pulse of motion and permanent ground displacements. Finally, a vulnerability of RC building can be evaluated against pulse-like near-fault ground motions effects.

  3. Focussed ion beam machined cantilever aperture probes for near-field optical imaging.

    Science.gov (United States)

    Jin, E X; Xu, X

    2008-03-01

    Near-field optical probe is the key element of a near-field scanning optical microscopy (NSOM) system. The key innovation in the first two NSOM experiments (Pohl et al., 1984; Lewis et al., 1984) is the fabrications of a sub-wavelength optical aperture at the apex of a sharply pointed transparent probe tip with a thin metal coating. This paper discusses the routine use of focussed ion beam (FIB) to micro-machine NSOM aperture probes from the commercial silicon nitride cantilevered atomic force microscopy probes. Two FIB micro-machining approaches are used to form a nanoaperture of controllable size and shape at the apex of the tip. The FIB side slicing produces a silicon nitride aperture on the flat-end tips with controllable sizes varying from 120 nm to 30 nm. The FIB head-on drilling creates holes on the aluminium-coated tips with sizes down to 50 nm. Nanoapertures in C and bow tie shapes can also be patterned using the FIB head-on milling method to possibly enhance the optical transmission. A transmission-collection NSOM system is constructed from a commercial atomic force microscopy to characterize the optical resolution of FIB-micro-machined aperture tips. The optical resolution of 78 nm is demonstrated by an aperture probe fabricated by FIB head-on drilling. Simultaneous topography imaging can also be realized using the same probe. By mapping the optical near-field from a bow-tie aperture, optical resolution as small as 59 nm is achieved by an aperture probe fabricated by the FIB side slicing method. Overall, high resolution and reliable optical imaging of routinely FIB-micro-machined aperture probes are demonstrated.

  4. Modeling of the 2011 Japan Tsunami: Lessons for Near-Field Forecast

    Science.gov (United States)

    Wei, Yong; Chamberlin, Christopher; Titov, Vasily V.; Tang, Liujuan; Bernard, Eddie N.

    2013-06-01

    During the devastating 11 March 2011 Japanese tsunami, data from two tsunami detectors were used to determine the tsunami source within 1.5 h of earthquake origin time. For the first time, multiple near-field tsunami measurements of the 2011 Japanese tsunami were used to demonstrate the accuracy of the National Oceanic and Atmospheric Administration (NOAA) real-time flooding forecast system in the far field. To test the accuracy of the same forecast system in the near field, a total of 11 numerical models with grids telescoped to 2 arcsec (~60 m) were developed to hindcast the propagation and coastal inundation of the 2011 Japanese tsunami along the entire east coastline of Japan. Using the NOAA tsunami source computed in near real-time, the model results of tsunami propagation are validated with tsunami time series measured at different water depths offshore and near shore along Japan's coastline. The computed tsunami runup height and spatial distribution are highly consistent with post-tsunami survey data collected along the Japanese coastline. The computed inundation penetration also agrees well with survey data, giving a modeling accuracy of 85.5 % for the inundation areas along 800 km of coastline between Ibaraki Prefecture (north of Kashima) and Aomori Prefecture (south of Rokkasho). The inundation model results highlighted the variability of tsunami impact in response to different offshore bathymetry and flooded terrain. Comparison of tsunami sources inferred from different indirect methods shows the crucial importance of deep-ocean tsunami measurements for real-time tsunami forecasts. The agreement between model results and observations along Japan's coastline demonstrate the ability and potential of NOAA's methodology for real-time near-field tsunami flooding forecasts. An accurate tsunami flooding forecast within 30 min may now be possible using the NOAA forecast methodology with carefully placed tsunameters and large-scale high-resolution inundation

  5. Predicting benzene vapor concentrations with a near field/far field model.

    Science.gov (United States)

    Nicas, Mark; Neuhaus, John

    2008-09-01

    Published data on benzene vapor concentrations in work simulation settings were used to examine the predictive ability of a near field/far field vapor dispersion model with an exponentially decreasing vapor emission rate. A given simulation involved two 15-min periods of applying a known volume of benzene-containing liquid to equipment on a worktable in a room with a measured air exchange rate. Replicate personal breathing zone (15-min time-weighted average, TWA) and room area (1-hr TWA) air samples were collected. In our modeling, the benzene vapor concentration in the near field zone (at the worktable) represented the personal breathing zone exposure level, and the benzene vapor concentration in the far field zone represented the room area concentration. Across 10 simulation combinations of two factors (the mass of benzene applied and the room air exchange rate), the mean of the personal breathing zone exposure levels ranged from 0.2 to 9.9 mg m(-3), and the mean of the room area concentrations ranged from 0.05 to 5.05 mg m(-3). Our model provided reasonably accurate estimates of the measured benzene vapor concentrations. Linear regression of the mean measured personal breathing zone exposure versus the predicted near field concentration yielded slope = 0.93 and r(2) = 0.94; the null hypothesis that the true slope equals one was not rejected (p-value = 0.39). Linear regression of the mean measured room area concentration versus the predicted far field concentration yielded slope = 0.90 and r(2) = 0.94; the null hypothesis that the true slope equals one was not rejected (p-value = 0.20). Other statistical tests showed no significant differences between measured and predicted values. In addition, most predicted concentrations fell within an approximate range of one-half to twofold the respective measured concentrations.

  6. Distinct sensory representations of wind and near-field sound in the Drosophila brain

    Science.gov (United States)

    Yorozu, Suzuko; Wong, Allan; Fischer, Brian J.; Dankert, Heiko; Kernan, Maurice J.; Kamikouchi, Azusa; Ito, Kei; Anderson, David J.

    2009-01-01

    Behavioral responses to wind are thought to play a critical role in controlling the dispersal and population genetics of wild Drosophila species1,2, as well as their navigation in flight3, but their underlying neurobiological basis is unknown. We show that Drosophila melanogaster, like wild-caught Drosophila strains4, exhibits robust wind-induced suppression of locomotion (WISL), in response to air currents delivered at speeds normally encountered in nature1,2. Here we identify wind-sensitive neurons in Johnston’s Organ (JO), an antennal mechanosensory structure previously implicated in near-field sound detection (reviewed in5,6). Using Gal4 lines targeted to different subsets of JO neurons7, and a genetically encoded calcium indicator8, we show that wind and near-field sound (courtship song) activate distinct populations of JO neurons, which project to different regions of the antennal and mechanosensory motor center (AMMC) in the central brain. Selective genetic ablation of wind-sensitive JO neurons in the antenna abolishes WISL behavior, without impairing hearing. Different neuronal subsets within the wind-sensitive population, moreover, respond to different directions of arista deflection caused by airflow and project to different regions of the AMMC, providing a rudimentary map of wind-direction in the brain. Importantly, sound- and wind-sensitive JO neurons exhibit different intrinsic response properties: the former are phasically activated by small, bi-directional, displacements of the aristae, while the latter are tonically activated by unidirectional, static deflections of larger magnitude. These different intrinsic properties are well suited to the detection of oscillatory pulses of near-field sound and laminar airflow, respectively. These data identify wind-sensitive neurons in JO, a structure that has been primarily associated with hearing, and reveal how the brain can distinguish different types of air particle movements, using a common sensory organ

  7. Second harmonic generation at the probe tip for background-free near-field optical imaging.

    Science.gov (United States)

    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.

  8. Near-field tsunami early warning and emergency planning in the Mediterranean Sea

    Directory of Open Access Journals (Sweden)

    Gerassimos A. Papadopoulos

    2013-04-01

    Full Text Available The new European project Near-field Tsunami Early Warning and Emergency Planning in the Mediterranean Sea (NEARTOWARN faces the need to develop operational tsunami early warning systems in near-field (local conditions where the travel time of the first tsunami wave is very short, that is less than 30 min, which is a typical case in the North East Atlantic and the Mediterranean Sea region but also elsewhere around the globe. The operational condition that should be fulfilled is that the time of tsunami detection, plus the time of warning transmitting, plus the time of evacuation should not exceed the travel time of the first tsunami wave from its source to the closest evacuation zone. To this goal the time to detect of the causative earthquake should be compressed at the very minimum. In this context the core of the proposed system is a network of seismic early warning devices, which activate and send alert in a few seconds after the generation of a near-field earthquake, when a seismic ground motion exceeding a prescribed threshold is detected. Then civil protection mobilizes to manage the earthquake crisis but also to detect and manage a possible tsunami through a geographical risk management system. For the tsunami detection the system is supported by tide-gauges of radar type, a database of presimulated tsunami scenarios, and a local tsunami decision matrix. The island of Rhodes in the eastern termination of the Hellenic Arc and Trench has been selected for a pilot and operational development of the local tsunami warning system given that the island is a highly popular tourist destination, historically it was hit by large tsunamigenic earthquakes and was recently the master test-site for the pan-European FP6 tsunami research project Tsunami Risk ANd Strategies For the European Region (TRANSFER.

  9. An Algorithm for Joint Estimating Range, DOA and Frequency of Near-Field Sources

    Institute of Scientific and Technical Information of China (English)

    CHENJianfeng; ZHANGXianda; WUYuntao

    2004-01-01

    Most of the existing eigen-decomposition based localization methods make the plane wave assumption in order to estimate the signal parameters of multiple sources. This paper proposes a novel joint algorithm for ranges, DOA's and frequencies of multiple narrow-band sources with the sources in the near field. This algorithm uses the Estimating signal parameters via rotational invariance technique (ESPRIT) based on cumulant-domain signal subspaces. The new algorithm does not require searching spectral peak or pairing among parameters, and has the power to resist an additive Gaussian noise due to use of the fourth-order cumulants. The performance of the new algorithm is confirmed by computer simulations.

  10. Engineering complex nanolasers: from spaser quantum information sources to near-field anapole lasers

    KAUST Repository

    Gongora, J. S. Totero

    2017-02-16

    In this invited contribution I will review recent results of our research in the field of complex nanolasers. I will begin by discussing recent experimental results from a new type of ultra-dark nanoparticles, which behave as an ideal black-body and spontaneously produce single color pulses thanks to an equivalent Bose-Einstein Condensation of light. I will then discuss new quantum information sources from core-shell spaser nanoparticles. Finally, I will illustrate a new type of laser source that emits only in the near field, discussing applications in integrated optical circuits.

  11. Bow-tie optical antenna probes for single-emitter scanning near-field optical microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Farahani, Javad N [Nano-Optics Group, National Center of Competence for Research in Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Eisler, Hans-Juergen [Nano-Optics Group, National Center of Competence for Research in Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Pohl, Dieter W [Nano-Optics Group, National Center of Competence for Research in Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Pavius, Michael [Center of MicroNanoTechnology (CMI), Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Flueckiger, Philippe [Center of MicroNanoTechnology (CMI), Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Gasser, Philippe [EMPA, Swiss Federal Laboratories for Materials Testing and Research, Electronics/Metrology Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Hecht, Bert [Nano-Optics Group, National Center of Competence for Research in Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)

    2007-03-28

    A method for the fabrication of bow-tie optical antennas at the apex of pyramidal Si{sub 3}N{sub 4} atomic force microscopy tips is described. We demonstrate that these novel optical probes are capable of sub-wavelength imaging of single quantum dots at room temperature. The enhanced and confined optical near-field at the antenna feed gap leads to locally enhanced photoluminescence (PL) of single quantum dots. Photoluminescence quenching due to the proximity of metal is found to be insignificant. The method holds promise for single quantum emitter imaging and spectroscopy at spatial resolution limited by the engineered antenna gap width exclusively.

  12. Concept study of radar sensors for near-field tsunami early warning

    Directory of Open Access Journals (Sweden)

    T. Börner

    2010-09-01

    Full Text Available Off-shore detection of tsunami waves is a critical component of an effective tsunami early warning system (TEWS. Even more critical is the off-shore detection of local tsunamis, namely tsunamis that strike coastal areas within minutes after generation. In this paper we propose new concepts for near-field tsunami early detection, based on innovative and up-to-date microwave remote sensing techniques. We particularly introduce the NESTRAD (NEar-Space Tsunami RADar concept, which consists of a real aperture radar accommodated inside a stationary stratospheric airship providing continuous monitoring of tsunamigenic oceanic trenches.

  13. Near-Field Analysis of Bright and Dark Modes on Plasmonic Metasurfaces Showing Extraordinary Suppressed Transmission

    CERN Document Server

    Dobmann, Sabine; Ploss, Daniel; Peschel, Ulf

    2014-01-01

    Plasmonic metasurfaces are investigated that consist of a sub wavelength line pattern in an ultrathin (~ 10 nm) silver film, designed for extraordinarily suppressed transmission (EOST) in the visible spectral range. Measurements with a near-field scanning optical microscope (NSOM) demonstrate that far field irradiation creates resonant excitations of antenna like (bright) modes that are localized on the metal ridges. In contrast, bound (dark) surface plasmon polaritons (SPPs) launched from an NSOM tip propagate well across the metasurface, preferentially perpendicular to the grating lines.

  14. Creating optical near-field orbital angular momentum in a gold metasurface.

    Science.gov (United States)

    Chen, Ching-Fu; Ku, Chen-Ta; Tai, Yi-Hsin; Wei, Pei-Kuen; Lin, Heh-Nan; Huang, Chen-Bin

    2015-04-01

    Nanocavities inscribed in a gold thin film are optimized and designed to form a metasurface. We demonstrate both numerically and experimentally the creation of surface plasmon (SP) vortex carrying orbital angular momentum in the metasurface under linearly polarized optical excitation that carries no optical angular momentum. Moreover, depending on the orientation of the exciting linearly polarized light, we show that the metasurface is capable of providing dynamic switching between SP vortex formation or SP subwavelength focusing. The resulting SP intensities are experimentally measured using a near-field scanning optical microscope and are found in excellent quantitative agreements as compared to the numerical results.

  15. Burying of channel optical waveguides: relation between near-field measurement and Ag concentration profile

    Science.gov (United States)

    Tsai, Wan-Shao; Liu, Yen-Huang; Barkman, Ondrej; Prajzler, Vaclav; Stanek, Stanislav; Nekvindova, Pavla

    2015-01-01

    Two-step field-assisted ion-exchanged waveguides have been fabricated on a glass substrate. The concentration profiles of the exchanged ions were measured with electron microprobe. The waveguides were characterized under scanning electron microscope and optical microscope for the investigation of burying structures. Guiding mode patterns were characterized with near-field measurement, where symmetric profiles were observed for the burying-type waveguide. The refractive index profiles were also measured with a modified end-fire coupling method. The relation between ion concentration profiles and index profiles were compared for the waveguides with different fabrication process.

  16. Nonlinear chemical imaging microscopy: near-field third harmonic generation imaging of human red blood cells.

    Science.gov (United States)

    Schaller, R D; Johnson, J C; Saykally, R J

    2000-11-01

    Third harmonic generation (THG) imaging using a near-field scanning optical microscope (NSOM) is demonstrated for the first time. A femtosecond, tunable near-infrared laser was used to generate both nonresonant and resonantly enhanced third harmonic radiation in human red blood cells. We show that resonantly enhanced THG is a chemically specific bulk probe in NSOM imaging by tuning the excitation source onto and off of resonance with the Soret transition of oxyhemoglobin. Additionally, we provide evidence that tightly focused, nonresonant, far-field THG imaging experiments do not produce contrast that is truly surface specific.

  17. Anomalous spectral behaviour of diffracted chirped Gaussian pulses in the near field

    Institute of Scientific and Technical Information of China (English)

    Pan Liu-Zhan; L(u) Bai-Da

    2004-01-01

    By using the Fourier transform method, analytical expressions for the axial power spectrum and near-field intensity in the spacetime domain of chirped Gaussian pulses diffracted at an aperture are derived, which permit us to study changes in spectral and temporal profiles of the chirped Gaussian pulses both analytically and numerically. Detailed numerical results and physical analysis show that spectral anomalies take place in the neighbourhood of certain critical distances, and the shifting of maximum and splitting of temporal intensity profiles appear. In particular, for ultrashort chirped pulses, there exists also spectral switch. Besides the truncation parameter, the chirp parameter and pulse duration affect the behaviour of spectral switches.

  18. Comparison of Numerical and Experimental Time-Resolved Near-Field Hall Thruster Plasma Properties

    Science.gov (United States)

    2014-03-06

    RESOLVED NEAR-FIELD HALL THRUSTER PLASMA PROPERTIES 807 TABLE I BHT -600 HALL THRUSTER AT NOMINAL XENON OPERATING CONDITIONS AND PERFORMANCE [21] 1.2-m...is a 600 W BHT -600 with a 3.2-mm hollow cathode manufactured by the Busek Company (Natick, MA). This thruster has been studied previously using both...electrostatic probes and various opti- cal diagnostics [17]–[20]. The BHT -600 has an acceleration channel outer radius of 32 mm, inner radius of 24 mm

  19. Electrical alignment of antenna coordinate system in a planar near-field setup

    DEFF Research Database (Denmark)

    Mynster, Anders P.; Nielsen, Jeppe Majlund; Pivnenko, Sergey

    2011-01-01

    In this paper, a simple and efficient electrical alignment procedure known as flip-test is adapted and applied to check and correct two errors in the mechanical setup of a planar near-field system: the mis-pointing of the z-axis of the antenna coordinate system with respect to the scan plane...... and the displacement of the center point of the scan plane with respect to the z-axis of the antenna coordinate system. Simulations of the errors and their correction algorithms were carried out with different models of antennas composed of Hertzian dipoles and an optimum algorithm was then selected. The proposed...

  20. Field enhancement analysis of an apertureless near field scanning optical microscope probe with finite element method

    Institute of Scientific and Technical Information of China (English)

    Weibin Chen; Qiwen Zhan

    2007-01-01

    Plasmonic field enhancement in a fully coated dielectric near field scanning optical microscope (NSOM)probe under radial polarization illumination is analyzed using an axially symmetric three-dimensional (3D)finite element method (FEM) model. The enhancement factor strongly depends on the illumination spot size, taper angle of the probe, and the metal film thickness. The tolerance of the alignment angle is investigated. Probe designs with different metal coatings and their enhancement performance are studied as well. The nanometric spot size at the tip apex and high field enhancement of the apertureless NSOM probe have important potential application in semiconductor metrology.

  1. Meta-instrument: high speed positioning and tracking platform for near-field optical imaging microscopes

    CERN Document Server

    Bijster, R J F; Spierdijk, J P F; Dekker, A; Klop, W A; Kramer, G F IJ; Cheng, L K; Hagen, R A J; Sadeghian, H

    2016-01-01

    High resolution and high throughput imaging are typically mutually exclusive. The meta-instrument pairs high resolution optical concepts such as nano-antennas, superoscillatory lenses and hyperlenses with a miniaturized opto-mechatronic platform for precise and high speed positioning of the optical elements at lens-to-sample separations that are measured in tens of nanometers. Such platform is a necessary development for bringing near-field optical imaging techniques to their industrial application. Towards this purpose, we present two designs and proof-of-principle instruments that are aimed at realizing sub-nanometer positional precision with a 100 kHz bandwidth.

  2. Opto-mechatronics issues in solid immersion lens based near-field recording

    Science.gov (United States)

    Park, No-Cheol; Yoon, Yong-Joong; Lee, Yong-Hyun; Kim, Joong-Gon; Kim, Wan-Chin; Choi, Hyun; Lim, Seungho; Yang, Tae-Man; Choi, Moon-Ho; Yang, Hyunseok; Rhim, Yoon-Chul; Park, Young-Pil

    2007-06-01

    We analyzed the effects of an external shock on a collision problem in a solid immersion lens (SIL) based near-field recording (NFR) through a shock response analysis and proposed a possible solution to this problem with adopting a protector and safety mode. With this proposed method the collision between SIL and media can be avoided. We showed possible solution for contamination problem in SIL based NFR through a numerical air flow analysis. We also introduced possible solid immersion lens designs to increase the fabrication and assembly tolerances of an optical head with replicated lens. Potentially, these research results could advance NFR technology for commercial product.

  3. Near-field speckle-scanning-based x-ray imaging

    OpenAIRE

    Berujon, Sebastien; Ziegler, Eric

    2015-01-01

    The x-ray near-field speckle-scanning concept is an approach recently introduced to obtain absorption, phase, and dark-field images of a sample. In this paper, we present ways of recovering from a sample its ultrasmall-angle x-ray scattering distribution using numerical deconvolution. We also show how to access the 2D phase gradient signal from random step scans, the latter having the potential to elude the flat-field correction error. Each feature is explained theoretically and demonstrated ...

  4. Near-field wireless sensing of single and multiple open-ended micro coils

    Directory of Open Access Journals (Sweden)

    A. Yousaf

    2013-05-01

    Full Text Available In this work we present near-field wireless sensing of single and multiple open-ended micro coils using an electrically small loop antenna. Wirelessly characterized parameters of open-ended micro coils include its resonance frequency, quality factor and inductance. Moreover a wireless frequency-dependent analytical model was developed. Micro coil inductance was extracted from the wirelessly measured signal using a constraint-based least-squares approach. Wireless measurements and analytical fit of micro coils are in strong agreement which validates the analytical model. Finite element method (FEM simulations of the coupled system were done in COMSOL Multiphysics.

  5. Polarization of near-field light induced with a plasmonic nanoantenna

    Science.gov (United States)

    Kharintsev, Sergey S.; Fishman, Alexander I.; Kazarian, Sergei G.; Salakhov, Myakzyum Kh.

    2015-09-01

    Evaluation and control of a polarization state of optical near fields are of tremendous advantage for locally probing intrinsic molecular orientations of highly anisotropic molecules with a plasmonic (metallic) nanoantenna. In this paper, we report on a physical mechanism of reading a dipole orientation at the apex of a rough cone-shaped gold tip illuminated with radially and azimuthally polarized light. In-plane and out-of-plane arrangement of nonlinear optical chromophores embedded into a glassy polymer is probed with tip-enhanced Raman scattering.

  6. A New Algorithm for Joint Range-DOA-Frequency Estimation of Near-Field Sources

    Directory of Open Access Journals (Sweden)

    Jian-Feng Chen

    2004-03-01

    Full Text Available This paper studies the joint estimation problem of ranges, DOAs, and frequencies of near-field narrowband sources and proposes a new computationally efficient algorithm, which employs a symmetric uniform linear array, uses eigenvalues together with the corresponding eigenvectors of two properly designed matrices to estimate signal parameters, and does not require searching for spectral peak or pairing among parameters. In addition, the proposed algorithm can be applied in arbitrary Gaussian noise environment since it is based on the fourth-order cumulants, which is verified by extensive computer simulations.

  7. Near Field Screech Noise Computation for an Underexpanded Supersonic Jet by the CE/SE Method

    Science.gov (United States)

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

    2001-01-01

    The space-time conservation element and solution element (CE/SE) method is employed to numerically study the near-field axisymmetric screech-tone noise of a typical underexpanded circular jet issuing from a sonic nozzle. For the computed cases, corresponding to fully expanded Mach numbers of 1.10, 1.15 and 1.19, the self-sustained feedback loop is automatically established. The computed shock-cell structure, acoustic wave length, screech tone frequencies, and sound pressure levels are in good agreement with experimental results.

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

    Science.gov (United States)

    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.

  9. Transient waves generated by a moving bottom obstacle: a new near-field solution

    DEFF Research Database (Denmark)

    Madsen, Per A.; Hansen, Asger Bendix

    2012-01-01

    in the region over the obstacle dispersion can be ignored while nonlinearity cannot. The relevant governing equations for the near-field solution are therefore the nonlinear shallow water (NSW) equations. These are bidirectional and can be formulated in terms of a two-family system of characteristics. We...... analytically integrate and eliminate the backward-going family and achieve a versatile unidirectional single-family formulation, which covers subcritical, transcritical and supercritical conditions with relatively high accuracy. The formulation accounts for the temporal and spatial evolution of the bound waves...

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

    Science.gov (United States)

    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.

  11. Transverse and longitudinal characterization of electron beams using interaction with optical near-fields

    CERN Document Server

    Kozák, Martin; Leedle, Kenneth J; Deng, Huiyang; Schönenberger, Norbert; Ruehl, Axel; Hartl, Ingmar; Hoogland, Heinar; Holzwarth, Ronald; Harris, James S; Byer, Robert L; Hommelhoff, Peter

    2016-01-01

    We demonstrate an experimental technique for both transverse and longitudinal characterization of bunched femtosecond free electron beams. The operation principle is based on monitoring of the current of electrons that obtained an energy gain during the interaction with the synchronized optical near-field wave excited by femtosecond laser pulses. The synchronous accelerating/decelerating fields confined to the surface of a silicon nanostructure are characterized using a highly focused sub-relativistic electron beam. Here the transverse spatial resolution of 450 nm and femtosecond temporal resolution achievable by this technique are demonstrated.

  12. The Optical Chirality Flux as a Useful Far-Field Probe of Chiral Near Fields

    CERN Document Server

    Poulikakos, Lisa V; McPeak, Kevin M; Burger, Sven; Niegemann, Jens; Hafner, Christian; Norris, David J

    2016-01-01

    To optimize the interaction between chiral matter and highly twisted light, quantities that can help characterize chiral electromagnetic fields near nanostructures are needed. Here, by analogy with Poynting's theorem, we formulate the time-averaged conservation law of optical chirality in lossy dispersive media and identify the optical chirality flux as an ideal far-field observable for characterizing chiral optical near fields. Bounded by the conservation law, we show that it provides precise information, unavailable from circular dichroism spectroscopy, on the magnitude and handedness of highly twisted fields near nanostructures.

  13. Manipulating quantum dot fluorescence by utilizing Brownian induced near-field interactions with plasmonic nanoparticles

    Science.gov (United States)

    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

  14. Attosecond physics at a nanoscale metal tip: strong field physics meets near-field optics

    Science.gov (United States)

    Krüger, M.; Thomas, S.; Förster, M.; Maisenbacher, L.; Wachter, G.; Lemell, Chr.; Burgdörfer, J.; Hommelhoff, P.

    2013-03-01

    Attosecond physics, centering on the control of electronic matter waves within a single cycle of the optical laser's driving field, has led to tremendously successful experiments with atoms and molecules in the gas phase. We show that pivotal phenomena such as elastic electron rescattering at the parent matter, a strong carrier-evenlope phase sensitivity and electronic matter wave intereference also show up in few-cycle laser driven electron emission from nanometric sharp metal tips. Furthermore, we utilize spectral signatures to measure the enhanced near-field with a spatial resolution of 1nm.

  15. Effects of a Near Field Pyroshock on the Performance of a Nitramine Nitrocellulose Propellant

    Science.gov (United States)

    Baca, Arcenio

    2016-01-01

    The purpose of this study is to investigate the effects of a pyroshock environment on the performance characteristics of a propellant used in pyrotechnic devices such as guillotine cutters. A heritage pressure cartridge assembly which uses a nitramine nitrocellulose propellant with a known performance baseline will be exposed to a near field pyroshock event. The pressure cartridge will then be fired in an ambient closed bomb firing to collect pressure time history. This data will be compared to the baseline data to evaluate the effects of the shock on the performance of the propellant.

  16. Near-field imaging of interference pattern of counterpropagating evanescent waves

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Bozhevolnaya, Elena A.

    1999-01-01

    It is generally accepted that measurement of of the contrast of the intensity interference pattern formed by two counterpropagating evanescent waves can be used to characterize the resolving power of a collection near-field microscope. We argue that, if the light collected by a fiber probe...... propagates toward a detector in the form of guided fiber modes, then this perception is wrong. Using symmetry arguments and simple calculations, we show that, if an extended fiber probe is axially symmetric and oriented perpendicular to the propagation direction, then the measured contrast should always...

  17. Electronic data capture platform for clinical research based on mobile phones and near field communication technology.

    Science.gov (United States)

    Morak, Jürgen; Schwetz, Verena; Hayn, Dieter; Fruhwald, Friedrich; Schreier, Gunter

    2008-01-01

    Electronic data capture systems support data acquisition for clinical research and enable the evaluation of new investigational medical devices. In case of evaluating a device the most challenging part is the user interface i.e. the solution how to acquire the data within a clinical setting and to synchronize them with a web-based data centre. The aim of this paper is to describe the development of an electronic data capture system with a mobile data input solution based on mobile phones and Near Field Communication technology. This system was evaluated within a real clinical setting and demonstrated high usability, security and reliability.

  18. Planar near-field acoustical holography based on equivalent source method and its experimental investigation

    Institute of Scientific and Technical Information of China (English)

    ZHANG Yongbin; CHEN Xinzhao; BI Chuanxing; CHEN Jian

    2008-01-01

    The current main approach to reconstruct and predict the acoustic field of a planar source is Near-field Acoustical Holography (NAH) based on FFT. But this method has some disadvantages such as wraparound error and edge Gibbs phenomena which will contaminate the results badly. A planar NAH based on equivalent source approach is developed, which has no wraparound error and edge Gibbs phenomena, and it is beneficial for engineering application.The experimental results of acoustic radiation generated by a point-driven plate with clamped boundaries validate the correctness and availability of the method.

  19. Finite dipole model for extreme near-field thermal radiation between a tip and planar SiC substrate

    Science.gov (United States)

    Jarzembski, Amun; Park, Keunhan

    2017-04-01

    Recent experimental studies have measured the infrared (IR) spectrum of tip-scattered near-field thermal radiation for a SiC substrate and observed up to a 50cm-1 redshift of the surface phonon polariton (SPhP) resonance peak [1,2]. However, the observed spectral redshift cannot be explained by the conventional near-field thermal radiation model based on the point dipole approximation. In the present work, a heated tip is modeled as randomly fluctuating point charges (or fluctuating finite dipoles) aligned along the primary axis of a prolate spheroid, and quasistatic tip-substrate charge interactions are considered to formulate the effective polarizability and self-interaction Green's function. The finite dipole model (FDM), combined with fluctuational electrodynamics, allows the computation of tip-plane thermal radiation in the extreme near-field (i.e., H / R ≲ 1 , where H is the tip-substrate gap distance and R is the tip radius), which cannot be calculated with the point dipole approximation. The FDM provides the underlying physics on the spectral redshift of tip-scattered near-field thermal radiation as observed in experiments. In addition, the SPhP peak in the near-field thermal radiation spectrum may split into two peaks as the gap distance decreases into the extreme near-field regime. This observation suggests that scattering-type spectroscopic measurements may not convey the full spectral features of tip-plane extreme near-field thermal radiation.

  20. Reciprocity theory of apertureless scanning near-field optical microscopy with point-dipole probes.

    Science.gov (United States)

    Esslinger, Moritz; Vogelgesang, Ralf

    2012-09-25

    Near-field microscopy offers the opportunity to reveal optical contrast at deep subwavelength scales. In scanning near-field optical microscopy (SNOM), the diffraction limit is overcome by a nanoscopic probe in close proximity to the sample. The interaction of the probe with the sample fields necessarily perturbs the bare sample response, and a critical issue is the interpretation of recorded signals. For a few specific SNOM configurations, individual descriptions have been modeled, but a general and intuitive framework is still lacking. Here, we give an exact formulation of the measurable signals in SNOM which is easily applicable to experimental configurations. Our results are in close analogy with the description Tersoff and Hamann have derived for the tunneling currents in scanning tunneling microscopy. For point-like scattering probe tips, such as used in apertureless SNOM, the theory simplifies dramatically to a single scalar relation. We find that the measured signal is directly proportional to the field of the coupled tip-sample system at the position of the tip. For weakly interacting probes, the model thus verifies the empirical findings that the recorded signal is proportional to the unperturbed field of the bare sample. In the more general case, it provides guidance to an intuitive and faithful interpretation of recorded images, facilitating the characterization of tip-related distortions and the evaluation of novel SNOM configurations, both for aperture-based and apertureless SNOM.

  1. Near-Field Sound Localization Based on the Small Profile Monaural Structure

    Directory of Open Access Journals (Sweden)

    Youngwoong Kim

    2015-11-01

    Full Text Available The acoustic wave around a sound source in the near-field area presents unconventional properties in the temporal, spectral, and spatial domains due to the propagation mechanism. This paper investigates a near-field sound localizer in a small profile structure with a single microphone. The asymmetric structure around the microphone provides a distinctive spectral variation that can be recognized by the dedicated algorithm for directional localization. The physical structure consists of ten pipes of different lengths in a vertical fashion and rectangular wings positioned between the pipes in radial directions. The sound from an individual direction travels through the nearest open pipe, which generates the particular fundamental frequency according to the acoustic resonance. The Cepstral parameter is modified to evaluate the fundamental frequency. Once the system estimates the fundamental frequency of the received signal, the length of arrival and angle of arrival (AoA are derived by the designed model. From an azimuthal distance of 3–15 cm from the outer body of the pipes, the extensive acoustic experiments with a 3D-printed structure show that the direct and side directions deliver average hit rates of 89% and 73%, respectively. The closer positions to the system demonstrate higher accuracy, and the overall hit rate performance is 78% up to 15 cm away from the structure body.

  2. Brighter near-field optical probes by means of improving the optical destruction threshold.

    Science.gov (United States)

    Stöckle, R M; Schaller, N; Deckert, V; Fokas, C; Zenobi, R

    1999-01-01

    The optical destruction thresholds of conventionally etched and tube-etched near-field optical probes were measured. One of the main advantages of tube-etched tips is their smooth glass surface after taper formation. Presumably for this reason, a destruction limit of over 120 microJ was obtained, almost twice as large as that of the rougher, conventionally etched fibre probes. The use of additional adhesion layers (Ti. Cr, Co and Ni) between the glass surface and the aluminium coating produced, especially for tube-etched tips, a significant increase in the optical destruction threshold. With increasingly thin metal coatings, the use of a protection coating that prevents corrosion during aging is recommended. An additional increase in optical stability was achieved by applying mixed-metal coatings: alternating thin titanium and thick aluminium layers yielded fibre probes with superior properties that achieved average optical destruction thresholds of > 270 microJ. This is an increase in stability of > 400% compared with conventionally fabricated near-field optical tips.

  3. Military jet noise source imaging using multisource statistically optimized near-field acoustical holography.

    Science.gov (United States)

    Wall, Alan T; Gee, Kent L; Neilsen, Tracianne B; McKinley, Richard L; James, Michael M

    2016-04-01

    The identification of acoustic sources is critical to targeted noise reduction efforts for jets on high-performance tactical aircraft. This paper describes the imaging of acoustic sources from a tactical jet using near-field acoustical holography techniques. The measurement consists of a series of scans over the hologram with a dense microphone array. Partial field decomposition methods are performed to generate coherent holograms. Numerical extrapolation of data beyond the measurement aperture mitigates artifacts near the aperture edges. A multisource equivalent wave model is used that includes the effects of the ground reflection on the measurement. Multisource statistically optimized near-field acoustical holography (M-SONAH) is used to reconstruct apparent source distributions between 20 and 1250 Hz at four engine powers. It is shown that M-SONAH produces accurate field reconstructions for both inward and outward propagation in the region spanned by the physical hologram measurement. Reconstructions across the set of engine powers and frequencies suggests that directivity depends mainly on estimated source location; sources farther downstream radiate at a higher angle relative to the inlet axis. At some frequencies and engine powers, reconstructed fields exhibit multiple radiation lobes originating from overlapped source regions, which is a phenomenon relatively recently reported for full-scale jets.

  4. Ocean-bottom Pressure Signals as Potential Identifiers of Tsunami Earthquakes in the Near Field

    Science.gov (United States)

    Salaree, A.; Okal, E. A.

    2015-12-01

    The real-time detection of "tsunami earthquakes" remains a challenge, especially in the near field. These events are characterized by an anomalously slow seismic rupture, with their true long-period seismic moment, and hence, tsunami potential, deceptively concealed from short-period waves and in particular felt accelerations. In the context of the deployment of long-period ocean-bottom sensors in epicentral areas, we explore simple but robust ways to quantify source parameters which could potentially lead to the real-time identification of tsunami earthquakes in the near field. We use records of 2011 Tohoku aftershocks on the JAMSTEC stations deployed off the coast of Japan in the wake of the mainshock. Because seismic phases are not resolvable at short distances, we simply consider an integrated measurement Ω of the square of pressure variations, sharing the philosophy of Boatwright and Choy's (1986) seismic energy, and compare this parameter, scaled to seismic moment, with other discriminants, such as Newman and Okal's (1998) energy-to-moment ratio, Θ, Okal et al.'s (2002) T-wave parameter Γ, or Okal's (2013) parameter Φ combining (in the far field) body-wave duration and energy. We also consider the duration of the pressure signal, and examine its relation to Ω.

  5. Disentangling time in a near-field approach to scanning probe microscopy

    Science.gov (United States)

    Farina, Marco; Lucesoli, Agnese; Pietrangelo, Tiziana; di Donato, Andrea; Fabiani, Silvia; Venanzoni, Giuseppe; Mencarelli, Davide; Rozzi, Tullio; Morini, Antonio

    2011-09-01

    Microwave microscopy has recently attracted intensive effort, owing to its capability to provide quantitative information about the local composition and the electromagnetic response of a sample. Nonetheless, the interpretation of microwave images remains a challenge as the electromagnetic waves interact with the sample and the surrounding in a multitude of ways following different paths: microwave images are a convolution of all contributions. In this work we show that examining the time evolution of the electromagnetic waves allows us to disentangle each contribution, providing images with striking quality and unexplored scenarios for near-field microscopy.Microwave microscopy has recently attracted intensive effort, owing to its capability to provide quantitative information about the local composition and the electromagnetic response of a sample. Nonetheless, the interpretation of microwave images remains a challenge as the electromagnetic waves interact with the sample and the surrounding in a multitude of ways following different paths: microwave images are a convolution of all contributions. In this work we show that examining the time evolution of the electromagnetic waves allows us to disentangle each contribution, providing images with striking quality and unexplored scenarios for near-field microscopy. Electronic supplementary information (ESI) available: Materials and methods, Fig. S1-S7, Table 1, and Videos S1-S4. See DOI: 10.1039/c1nr10491h

  6. Near-field scanning optical microscopy in cell biology and cytogenetics.

    Science.gov (United States)

    Hausmann, Michael; Perner, Birgit; Rapp, Alexander; Wollweber, Leo; Scherthan, Harry; Greulich, Karl-Otto

    2006-01-01

    Light microscopy has proven to be one of the most versatile analytical tools in cell biology and cytogenetics. The growing spectrum of scientific knowledge demands a continuous improvement of the optical resolution of the instruments. In far-field light microscopy, the attainable resolution is dictated by the limit of diffraction, which, in practice, is about 250 nm for high-numerical-aperture objective lenses. Near-field scanning optical microscopy (NSOM) was the first technique that has overcome this limit up to about one order of magnitude. Typically, the resolution range below 100 nm is accessed for biological applications. Using appropriately designed scanning probes allows for obtaining an extremely small near-field light excitation volume (some tens of nanometers in diameter). Because of the reduction of background illumination, high contrast imaging becomes feasible for light transmission and fluorescence microscopy. The height of the scanning probe is controlled by atomic force interactions between the specimen surface and the probe tip. The control signal can be used for the production of a topographic (nonoptical) image that can be acquired simultaneously. In this chapter, the principle of NSOM is described with respect to biological applications. A brief overview of some requirements in biology and applications described in the literature are given. Practical advice is focused on instruments with aperture-type illumination probes. Preparation protocols focussing on NSOM of cell surfaces and chromosomes are presented.

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

    Energy Technology Data Exchange (ETDEWEB)

    Kelkar, Sharad M. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Stauffer, Philip H. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Robinson, Bruce Alan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    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).

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

    Energy Technology Data Exchange (ETDEWEB)

    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.

  9. Femtosecond-resolved ablation dynamics of Si in the near field of a small dielectric particle

    Directory of Open Access Journals (Sweden)

    Paul Kühler

    2013-09-01

    Full Text Available In this work we analyze the ablation dynamics of crystalline Si in the intense near field generated by a small dielectric particle located at the material surface when being irradiated with an infrared femtosecond laser pulse (800 nm, 120 fs. The presence of the particle (7.9 μm diameter leads to a strong local enhancement (ca. 40 times of the incoming intensity of the pulse. The transient optical response of the material has been analyzed by means of fs-resolved optical microscopy in reflection configuration over a time span from 0.1 ps to about 1 ns. Characteristic phenomena like electron plasma formation, ultrafast melting and ablation, along with their characteristic time scales are observed in the region surrounding the particle. The use of a time resolved imaging technique allows us recording simultaneously the material response at ordinary and large peak power densities enabling a direct comparison between both scenarios. The time resolved images of near field exposed regions are consistent with a remarkable temporal shift of the ablation onset which occurs in the sub-picosend regime, from about 500 to 800 fs after excitation.

  10. Prediction and near-field observation of skull-guided acoustic waves.

    Science.gov (United States)

    Estrada, Hector; Rebling, Johannes; Razansky, Daniel

    2017-03-01

    Ultrasound waves propagating in water or soft biological tissue are strongly reflected when encountering the skull, which limits the use of ultrasound-based techniques in transcranial imaging and therapeutic applications. Current knowledge on the acoustic properties of the cranial bone is restricted to far-field observations, leaving its near-field unexplored. We report on the existence of skull-guided acoustic waves, which was herein confirmed by near-field measurements of optoacoustically-induced responses in ex-vivo murine skulls immersed in water. Dispersion of the guided waves was found to reasonably agree with the prediction of a multilayered flat plate model. We observed a skull-guided wave propagation over a lateral distance of at least 3 mm, with a half-decay length in the direction perpendicular to the skull ranging from 35 to 300 μm at 6 and 0.5 MHz, respectively. Propagation losses are mostly attributed to the heterogenous acoustic properties of the skull.. It is generally anticipated that our findings may facilitate and broaden the application of ultrasound-mediated techniques in brain diagnostics and therapy.

  11. ALGERIA’S VULNERABILITY TO TSUNAMIS FROM NEAR-FIELD SEISMIC SOURCES

    Directory of Open Access Journals (Sweden)

    ALGERIA’S VULNERABILITY TO TSUNAMIS FROM NEAR-FIELD SEISMIC SOURCES

    2012-01-01

    Full Text Available Evaluation of the effects of tsunami damage relative to earthquake damage may help to identify critical coastal zone structures and exposed populations for near field tsunami risk. In this work, we propose to define the ratio between tsunami intensity and earthquake intensity as a measure of near field tsunami vulnerability for coastal communities. This parameter is estimated for 13 tsunami events reported in North Algeria from the 14th century to present. Although the results show that there are no tsunamis that are unusually large for the size of the earthquake that generated them, coastal communities remain at risk from these periodic hazards.We also use tsunami modelling and published information to estimate maximum inundation in Northern Algeria. Then, we generate a flooding map, which reveals the communities, buildings and infrastructure that are exposed to the tsunami hazard. This map shows that the majority of the people in Algiers and Oran live above 5 meters in elevation, and are hence not exposed to the hazard. Despite this, the coastline remains vulnerable to tsunami as earthquakes can damage poorly constructed buildings and other infrastructure, weakening it prior to the arrival of the tsunami. To increase resilience in the coastal zone, tsunami and earthquake awareness, education and preparedness must become a priority in the context of regional early warning programs.

  12. High-Throughput Near-Field Optical Nanoprocessing of Solution-Deposited Nanoparticles

    KAUST Repository

    Pan, Heng

    2010-07-27

    The application of nanoscale electrical and biological devices will benefit from the development of nanomanufacturing technologies that are highthroughput, low-cost, and flexible. Utilizing nanomaterials as building blocks and organizing them in a rational way constitutes an attractive approach towards this goal and has been pursued for the past few years. The optical near-field nanoprocessing of nanoparticles for high-throughput nanomanufacturing is reported. The method utilizes fluidically assembled microspheres as a near-field optical confinement structure array for laserassisted nanosintering and nanoablation of nanoparticles. By taking advantage of the low processing temperature and reduced thermal diffusion in the nanoparticle film, a minimum feature size down to ≈i100nm is realized. In addition, smaller features (50nm) are obtained by furnace annealing of laser-sintered nanodots at 400 °C. The electrical conductivity of sintered nanolines is also studied. Using nanoline electrodes separated by a submicrometer gap, organic field-effect transistors are subsequently fabricated with oxygen-stable semiconducting polymer. © 2010 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim.

  13. Near-Field Thermometry Sensor Based on the Thermal Resonance of a Microcantilever in Aqueous Medium

    Directory of Open Access Journals (Sweden)

    Kenneth David Kihm

    2007-12-01

    Full Text Available A new concept using a near-field thermometry sensor is presented, employing atipless microcantilever experimentally validated for an aqueous medium within approximatelyone cantilever width from the solid interface. By correlating the thermal Brownian vibratingmotion of the microcantilever with the surrounding liquid temperature, the near-fieldmicroscale temperature distributions at the probing site are determined at separation distancesof z = 5, 10, 20, and 40 μm while the microheater temperature is maintained at 50°C, 70°C, or90°C. In addition, the near-field correction of the correlation is discussed to account for thequenched cantilever vibration frequencies, which are quenched due to the no-slip solid-wallinterference. Higher thermal sensitivity and spatial resolution is expected when the vibrationfrequencies increase with a relatively short and thick cantilever and the dimensions of themicrocantilever are reduced. Use of the microcantilever thermometry sensor can also reduce thecomplexity and mitigate the high cost associated with existing microfabricated thermocouplesor thermoresistive sensors.

  14. Low Power Near Field Communication Methods for RFID Applications of SIM Cards

    Science.gov (United States)

    Chen, Yicheng; Zheng, Zhaoxia; Gong, Mingyang; Yu, Fengqi

    2017-01-01

    Power consumption and communication distance have become crucial challenges for SIM card RFID (radio frequency identification) applications. The combination of long distance 2.45 GHz radio frequency (RF) technology and low power 2 kHz near distance communication is a workable scheme. In this paper, an ultra-low frequency 2 kHz near field communication (NFC) method suitable for SIM cards is proposed and verified in silicon. The low frequency transmission model based on electromagnetic induction is discussed. Different transmission modes are introduced and compared, which show that the baseband transmit mode has a better performance. The low-pass filter circuit and programmable gain amplifiers are applied for noise reduction and signal amplitude amplification. Digital-to-analog converters and comparators are used to judge the card approach and departure. A novel differential Manchester decoder is proposed to deal with the internal clock drift in range-controlled communication applications. The chip has been fully implemented in 0.18 µm complementary metal-oxide-semiconductor (CMOS) technology, with a 330 µA work current and a 45 µA idle current. The low frequency chip can be integrated into a radio frequency SIM card for near field RFID applications. PMID:28420104

  15. Graphene-based tunable hyperbolic metamaterials and enhanced near-field absorption.

    Science.gov (United States)

    Othman, Mohamed A K; Guclu, Caner; Capolino, Filippo

    2013-03-25

    We investigate a novel implementation of hyperbolic metamaterial (HM) at far-infrared frequencies composed of stacked graphene sheets separated by thin dielectric layers. Using the surface conductivity model of graphene, we derive the homogenization formula for the multilayer structure by treating graphene sheets as lumped layers with complex admittances. Homogenization results and limits are investigated by comparison with a transfer matrix formulation for the HM constituent layers. We show that infrared iso-frequency wavevector dispersion characteristics of the proposed HM can be tuned by varying the chemical potential of the graphene sheets via electrostatic biasing. Accordingly, reflection and transmission properties for a film made of graphene-dielectric multilayer are tunable at terahertz frequencies, and we investigate the limits in using the homogenized model compared to the more accurate transfer matrix model. We also propose to use graphene-based HM as a super absorber for near-fields generated at its surface. The power emitted by a dipole near the surface of a graphene-based HM is increased dramatically (up to 5 × 10(2) at 2 THz), furthermore we show that most of the scattered power is directed into the HM. The validity and limits of the homogenized HM model are assessed also for near-fields and show that in certain conditions it overestimates the dipole radiated power into the HM.

  16. Fabrication of conjugated polymers nanostructures via direct near-field optical lithography

    Energy Technology Data Exchange (ETDEWEB)

    Cacialli, F.; Riehn, Robert; Downes, A.; Latini, G.; Charas, Ana; Morgado, Jorge

    2004-08-15

    We report our investigations into the fabrication of nanostructures of poly(p-phenylene vinylene) via direct scanning near-field lithography of its soluble precursor. Our technique is based on the spatially selective inhibition of the precursor solubility by exposure to the ultraviolet optical field present at the apex of commercially available, Au-coated near-field probes with aperture diameters between 40 and 80 nm ({+-}5 nm). After development in methanol and thermal conversion under vacuum we obtain features with a minimum dimension of 160 nm. We analyse our results via tapping-mode atomic force microscopy, and find a clear phase contrast between the core and the centre of the lithographed features, corroborating the hypothesis that hard, fully insolubilised regions are surrounded by a gel-like phase, which we estimate of the order of 110-130 nm for the smallest features, by comparing our experiments with simulations carried out using a Bethe-Bouwkamp model. Use of such model also allows us to discuss the influence of probe size, tip-sample distance, and film thickness on the resolution of the lithographic process. We demonstrate the use of the technique for the direct writing of two-dimensional periodic structures with intentional defects and a periodicity relevant to applications in the visible range.

  17. Near-field nonuniformities in angularly multiplexed KrF fusion lasers with induced spatial incoherence

    Science.gov (United States)

    Lehmberg, Robert H.; Chan, Yung

    2005-05-01

    Induced spatial incoherence (ISI) has been proposed for KrF laser drivers to achieve the high degree of spatial beam uniformity required for direct-drive inertial confinement fusion. Although ISI provides ultrasmooth illumination at the far field of the laser, where the target is located, it can still allow the beams in the quasi-near field to develop a time-averaged spatial structure. This speckle, which arises primarily from random-phase aberration, builds up as the laser beams propagate away from the pupil plane located at the final amplifier stage; it is distinct from any structure imposed by gain nonuniformities in the amplifiers. Because of the spatial incoherence, the speckle is significantly smaller than that experienced by coherent beams. Nevertheless, it remains a damage issue, especially for the long beam delay paths required in angularly multiplexed KrF lasers. We develop a novel algorithm for calculating the time-integrated intensities; compare simulations and measurements of the near-field speckle in the Nike KrF laser; and explore options, such as aberration reduction and optical relaying, for controlling the problem in future angularly multiplexed KrF drivers. © Optical Society of America

  18. Numerical Investigation of Near-Field Plasma Flows in Magnetic Nozzles

    Science.gov (United States)

    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.

  19. Underwater hybrid near-field acoustical holography based on the measurement of vector hydrophone array

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Hybrid near-field acoustical holography(NAH) is developed for reconstructing acoustic radiation from a cylindrical source in a complex underwater environment. In hybrid NAH,we combine statistically optimized near-field acoustical holography(SONAH) and broadband acoustical holography from intensity measurements(BAHIM) to reconstruct the underwater cylindrical source field. First,the BAHIM is utilized to regenerate as much acoustic pressures on the hologram surface as necessary,and then the acoustic pressures are taken as input to the formulation implemented numerically by SONAH. The main advantages of this technology are that the complex pressure on the hologram surface can be reconstructed without reference signal,and the measurement array can be smaller than the source,thus the practicability and efficiency of this technology are greatly enhanced. Numerical examples of a cylindrical source are demonstrated. Test results show that hybrid NAH can yield a more accurate reconstruction than conventional NAH. Then,an experiment has been carried out with a vector hydrophone array. The experimental results show the advantage of hybrid NAH in the reconstruction of an acoustic field and the feasibility of using a vector hydrophone array in an underwater NAH measurement,as well as the identification and localization of noise sources.

  20. Near-field radiative heat transfer between arbitrarily-shaped objects and a surface

    CERN Document Server

    Edalatpour, Sheila

    2016-01-01

    A fluctuational electrodynamics-based formalism for calculating near-field radiative heat transfer between objects of arbitrary size and shape and an infinite surface is presented. The surface interactions are treated analytically via Sommerfeld's theory of electric dipole radiation above an infinite plane. The volume integral equation for the electric field is discretized using the thermal discrete dipole approximation (T-DDA). The framework is verified against exact results in the sphere-surface configuration, and is applied to analyze near-field radiative heat transfer between a complex-shaped probe and an infinite plane both made of silica. It is found that when the probe tip size is approximately equal to or smaller than the gap d separating the probe and the surface, coupled localized surface phonon (LSPh)-surface phonon-polariton (SPhP) mediated heat transfer occurs. In this regime, the net spectral heat rate exhibits four resonant modes due to LSPhs along the minor axis of the probe while the net tota...