WorldWideScience

Sample records for contrast terahertz near-field

  1. Direct Measurements of Terahertz Meta-atoms with Near-Field Emission of Terahertz Waves

    Science.gov (United States)

    Serita, Kazunori; Darmo, Juraj; Kawayama, Iwao; Murakami, Hironaru; Tonouchi, Masayoshi

    2017-09-01

    We present the direct measurements of terahertz meta-atoms, an elementary unit of metamaterials, by using locally generated terahertz waves in the near-field region. In contrast to a conventional far-field terahertz spectroscopy or imaging, our technique features the localized emission of coherent terahertz pulses on a sub-wavelength scale, which has a potential for visualizing details of dynamics of each meta-atom. The obtained data show the near-field coupling among the meta-atoms and the impact of the electric field distribution from the excited meta-atom to neighbor meta-atoms. The observable LC resonance response is enhanced with an increase of numbers of meta-atoms. Furthermore, our approach also has a potential for visualizing the individual mode of meta-atom at different terahertz irradiation spots. These data can help us to understand the important role of the meta-atom in metamaterials and develop the novel terahertz components and devices such as active terahertz metamaterial and compact, high-sensitive bio-sensor devices.

  2. Measurement and calculation of the near field of a terahertz apertureless scanning optical microscope

    NARCIS (Netherlands)

    Adam, A.J.L.; Van der Valk, N.C.J.; Planken, P.C.M.

    2007-01-01

    We present measurements and calculations of the terahertz (THz) electric field measured in the near field of a metal tip used in THz apertureless near-field optical microscopy (THz-ANSOM). An analytical model in which we treat the metal tip as a linear wire antenna allows us to predict almost all of

  3. Tailoring Terahertz Near-Field Enhancement via Two-Dimensional Plasmons

    Science.gov (United States)

    Davoyan, Arthur R.; Popov, Vyacheslav V.; Nikitov, Sergei A.

    2012-03-01

    We suggest a novel possibility for electrically tunable terahertz near-field enhancement in flatland electronic materials supporting two-dimensional plasmons, including recently discovered graphene. We employ electric-field effect modulation of electron density in such materials and induce a periodic plasmonic lattice with a defect cavity. We demonstrate that the plasmons resonantly excited in such a periodic plasmonic lattice by an incident terahertz radiation can strongly pump the cavity plasmon modes leading to a deep subwavelength concentration of terahertz energy, beyond λ/1000, with giant electric-field enhancement factors up to 104, which is 2 orders of magnitude higher than achieved previously in metal-based terahertz field concentrators.

  4. 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....

  5. Near-field terahertz imaging of ferroelectric domains in barium titanate

    Czech Academy of Sciences Publication Activity Database

    Berta, Milan; Kadlec, Filip

    2010-01-01

    Roč. 83, 10-11 (2010), 985-993 ISSN 0141-1594 R&D Projects: GA MŠk LC512 Institutional research plan: CEZ:AV0Z10100520 Keywords : singular value decomposition * domain structure imaging * near-field terahertz microscopy * subwavelength resolution Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.006, year: 2010

  6. Macroscopic Magnetization Control by Symmetry Breaking of Photoinduced Spin Reorientation with Intense Terahertz Magnetic Near Field

    Science.gov (United States)

    Kurihara, Takayuki; Watanabe, Hiroshi; Nakajima, Makoto; Karube, Shutaro; Oto, Kenichi; Otani, YoshiChika; Suemoto, Tohru

    2018-03-01

    We exploit an intense terahertz magnetic near field combined with femtosecond laser excitation to break the symmetry of photoinduced spin reorientation paths in ErFeO3 . We succeed in aligning macroscopic magnetization reaching up to 80% of total magnetization in the sample to selectable orientations by adjusting the time delay between terahertz and optical pump pulses. The spin dynamics are well reproduced by equations of motion, including time-dependent magnetic potential. We show that the direction of the generated magnetization is determined by the transient direction of spin tilting and the magnetic field at the moment of photoexcitation.

  7. Electro-optic detection of subwavelength terahertz spot sizes in the near field of a metal tip

    NARCIS (Netherlands)

    Van der Valk, N.C.J.; Planken, P.C.M.

    2002-01-01

    We report on a method to obtain a subwavelength resolution in terahertz time-domain imaging. In our method, a sharp copper tip is used to locally distort and concentrate the THz electric field. The distorted electric field, present mainly in the near field of the tip, is electro-optically measured

  8. Near-field probing of Mie resonances in single TiO.sub.2./sub. microspheres at terahertz frequencies

    Czech Academy of Sciences Publication Activity Database

    Mitrofanov, O.; Dominec, Filip; Kužel, Petr; Reno, J.L.; Brener, I.; Chung, U.-C.; Elissalde, C.; Maglione, M.; Mounaix, P.

    2014-01-01

    Roč. 22, č. 19 (2014), s. 23034-23042 ISSN 1094-4087 R&D Projects: GA ČR(CZ) GA14-25639S EU Projects: European Commission(XE) 607521 - NOTEDEV Institutional support: RVO:68378271 Keywords : metamaterials * near-field microscopy * resonators * terahertz imaging Subject RIV: BH - Optics, Masers, Lasers Impact factor: 3.488, year: 2014

  9. Advanced terahertz electric near-field measurements at sub-wavelength diameter metallic apertures

    NARCIS (Netherlands)

    Adam, A.J.L.; Brok, J.M.; Seo, M.A.; Ahn, K.J.; Kim, D.S.; Kang, J.H.; Park, Q.H.; Nagel, M.; Planken, P.C.M.

    2008-01-01

    Using terahertz-light excitation, we have measured with sub-wavelength spatial, and sub-cycle temporal resolution the time- and frequency-dependent electric-field and surface-charge density in the vicinity of small metallic holes. In addition to a singularity like concentration of the electric field

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

    NARCIS (Netherlands)

    Jalocha, A.; Jalocha, A.; van Hulst, 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

  11. A metal-dielectric antenna for terahertz near-field imaging

    Czech Academy of Sciences Publication Activity Database

    Klein, N.; Lahl, P.; Poppe, U.; Kadlec, Filip; Kužel, Petr

    2005-01-01

    Roč. 98, - (2005), 014910/1-014910/5 ISSN 0021-8979 R&D Projects: GA MŠk(CZ) LC512 Institutional research plan: CEZ:AV0Z10100522 Keywords : near-field imaging Subject RIV: BH - Optics, Masers, Lasers Impact factor: 2.498, year: 2005

  12. 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...

  13. Electro-optic detection of subwavelength terahertz spot sizes in the near field of a metal tip

    Science.gov (United States)

    van der Valk, N. C. J.; Planken, P. C. M.

    2002-08-01

    We report on a method to obtain a subwavelength resolution in terahertz time-domain imaging. In our method, a sharp copper tip is used to locally distort and concentrate the THz electric field. The distorted electric field, present mainly in the near field of the tip, is electro-optically measured in an (100) oriented GaP crystal. By raster scanning the tip along the surface of the crystal, we find the smallest THz spot size of 18 μm for frequencies from 0.1 to 2.5 THz. For our peak frequency of 0.15 THz, this corresponds to a resolution of λ/110. Our setup has the potential to reach a resolution down to a few μm.

  14. Simulations of multi-contrast x-ray imaging using near-field speckles

    Energy Technology Data Exchange (ETDEWEB)

    Zdora, Marie-Christine [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom and Department of Physics & Astronomy, University College London, London, WC1E 6BT (United Kingdom); Thibault, Pierre [Department of Physics & Astronomy, University College London, London, WC1E 6BT (United Kingdom); Herzen, Julia; Pfeiffer, Franz [Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany); Zanette, Irene [Diamond Light Source, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE (United Kingdom); Lehrstuhl für Biomedizinische Physik, Physik-Department & Institut für Medizintechnik, Technische Universität München, 85748 Garching (Germany)

    2016-01-28

    X-ray dark-field and phase-contrast imaging using near-field speckles is a novel technique that overcomes limitations inherent in conventional absorption x-ray imaging, i.e. poor contrast for features with similar density. Speckle-based imaging yields a wealth of information with a simple setup tolerant to polychromatic and divergent beams, and simple data acquisition and analysis procedures. Here, we present a simulation software used to model the image formation with the speckle-based technique, and we compare simulated results on a phantom sample with experimental synchrotron data. Thorough simulation of a speckle-based imaging experiment will help for better understanding and optimising the technique itself.

  15. Optical image contrast enhancement in near-field optics induced by water condensation.

    Science.gov (United States)

    Douas, Maysoun; Marqués, Manuel I; Serena, Pedro A

    2013-12-01

    In surface science, water adsorption on hydrophilic samples is usually invoked, addressing their nanoscale experimental effects in scanning probe microscopy, especially when water condensates between tip and sample. Here we study by means of a numerical hybrid method the effect of water bridge formation in near field imaging. We show how this nanometric water neck plays an important role not only in the optical image, producing a high contrast at hydrophilic patches, but also in the tip-sample distance control. This work contributes with a new methodology able to retrieve the original application of SNOM, using it as an instrument to study the optical properties of matter overcoming the diffraction limit. It extends the application of SNOM to study the hydrophilic character of polymeric and biological samples, taking advantage of ubiquitous effect of humidity when operating in ambient condition. © 2013 Elsevier B.V. All rights reserved.

  16. Mapping an on-chip terahertz antenna by a scanning near-field probe and a fixed field-effect transistor

    International Nuclear Information System (INIS)

    Lü Li; Sun Jian-Dong; Wu Dong-Min; Cai Yong; Qin Hua; Lewis, Roger A.; Sun Yun-Fei

    2015-01-01

    In the terahertz (THz) regime, the active region for a solid-state detector usually needs to be implemented accurately in the near-field region of an on-chip antenna. Mapping of the near-field strength could allow for rapid verification and optimization of new antenna/detector designs. Here, we report a proof-of-concept experiment in which the field mapping is realized by a scanning metallic probe and a fixed AlGaN/GaN field-effect transistor. Experiment results agree well with the electromagnetic-wave simulations. The results also suggest a field-effect THz detector combined with a probe tip could serve as a high sensitivity THz near-field sensor. (paper)

  17. Metamaterial near-field sensor for deep-subwavelength thickness measurements and sensitive refractometry in the terahertz frequency range

    International Nuclear Information System (INIS)

    Reinhard, Benjamin; Schmitt, Klemens M.; Neu, Jens; Wollrab, Viktoria; Beigang, Rene; Rahm, Marco

    2012-01-01

    We present a metamaterial-based terahertz (THz) sensor for thickness measurements of subwavelength-thin materials and refractometry of liquids and liquid mixtures. The sensor operates in reflection geometry and exploits the frequency shift of a sharp Fano resonance minimum in the presence of dielectric materials. We obtained a minimum thickness resolution of 12.5 nm (1/16 000 times the wavelength of the THz radiation) and a refractive index sensitivity of 0.43 THz per refractive index unit. We support the experimental results by an analytical model that describes the dependence of the resonance frequency on the sample material thickness and the refractive index.

  18. Metamaterial near-field sensor for deep-subwavelength thickness measurements and sensitive refractometry in the terahertz frequency range

    Energy Technology Data Exchange (ETDEWEB)

    Reinhard, Benjamin; Schmitt, Klemens M.; Neu, Jens [Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern (Germany); Wollrab, Viktoria; Beigang, Rene; Rahm, Marco [Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, 67663 Kaiserslautern (Germany); Fraunhofer Institute for Physical Measurement Techniques IPM, 79110 Freiburg (Germany)

    2012-05-28

    We present a metamaterial-based terahertz (THz) sensor for thickness measurements of subwavelength-thin materials and refractometry of liquids and liquid mixtures. The sensor operates in reflection geometry and exploits the frequency shift of a sharp Fano resonance minimum in the presence of dielectric materials. We obtained a minimum thickness resolution of 12.5 nm (1/16 000 times the wavelength of the THz radiation) and a refractive index sensitivity of 0.43 THz per refractive index unit. We support the experimental results by an analytical model that describes the dependence of the resonance frequency on the sample material thickness and the refractive index.

  19. Solvothermally Synthesized Sb2Te3 Platelets Show Unexpected Optical Contrasts in Mid-Infrared Near-Field Scanning Microscopy.

    Science.gov (United States)

    Hauer, Benedikt; Saltzmann, Tobias; Simon, Ulrich; Taubner, Thomas

    2015-05-13

    We report nanoscale-resolved optical investigations on the local material properties of Sb2Te3 hexagonal platelets grown by solvothermal synthesis. Using mid-infrared near-field microscopy, we find a highly symmetric pattern, which is correlated to a growth spiral and which extends over the entire platelet. As the origin of the optical contrast, we identify domains with different densities of charge carriers. On Sb2Te3 samples grown by other means, we did not find a comparable domain structure.

  20. Review of Near-Field Terahertz Measurement Methods and Their Applications : How to Achieve Sub-Wavelength Resolution at THz Frequencies

    NARCIS (Netherlands)

    Adam, A.J.L.

    2011-01-01

    In the last decades, many research teams working at Terahertz frequencies focused their efforts on surpassing the diffraction limit. Numerous techniques have been investigated, combining methods existing at optic wavelength with THz system such as Time Domain Spectroscopy. The actual development led

  1. Quasi-near field terahertz spectroscopy

    NARCIS (Netherlands)

    Chakkittakandy, R.

    2010-01-01

    Everyday we see around us many materials that are different from one another. We identify them on the basis of their shape, texture, smell, taste, color, etc with the help of our senses. Many times it is almost impossible to identify materials only with our senses. Then, one has to look into more

  2. 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

  3. Mode profiling of THz fibers with dynamic aperture near-field imaging

    DEFF Research Database (Denmark)

    Stecher, Matthias; Dürrschmidt, Stefan F.; Nielsen, Kristian

    2011-01-01

    We present terahertz near-field mode profiling of different polymer THz fibers. Images with a resolution below the THz wavelength show the fundamental mode profile and higher order modes appearing at higher frequencies.......We present terahertz near-field mode profiling of different polymer THz fibers. Images with a resolution below the THz wavelength show the fundamental mode profile and higher order modes appearing at higher frequencies....

  4. 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

  5. Near-field flat focusing mirrors

    Science.gov (United States)

    Cheng, Yu-Chieh; Staliunas, Kestutis

    2018-03-01

    This article reviews recent progress towards the design of near-field flat focusing mirrors, focusing/imaging light patterns in reflection. An important feature of such flat focusing mirrors is their transverse invariance, as they do not possess any optical axis. We start with a review of the physical background to the different focusing mechanisms of near- and far-field focusing. These near-field focusing devices like flat lenses and the reviewed near-field focusing mirrors can implement planar focusing devices without any optical axis. In contrast, various types of far-field planar focusing devices, such as high-contrast gratings and metasurfaces, unavoidably break the transverse invariance due to their radially symmetrical structures. The particular realizations of near-field flat focusing mirrors including Bragg-like dielectric mirrors and dielectric subwavelength gratings are the main subjects of the review. The first flat focusing mirror was demonstrated with a chirped mirror and was shown to manage an angular dispersion for beam focusing, similar to the management of chromatic dispersion for pulse compression. Furthermore, the reviewed optimized chirped mirror demonstrated a long near-field focal length, hardly achieved by a flat lens or a planar hyperlens. Two more different configurations of dielectric subwavelength gratings that focus a light beam at normal or oblique incidence are also reviewed. We also summarize and compare focusing performance, limitations, and future perspectives between the reviewed flat focusing mirrors and other planar focusing devices including a flat lens with a negative-index material, a planar hyperlens, a high-contrast grating, and a metasurface.

  6. 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.

  7. Biological applications of near-field scanning optical microscopy

    NARCIS (Netherlands)

    Moers, Marco H.P.; Moers, M.H.P.; Ruiter, A.G.T.; Jalocha, A.; Jalocha, Alain; van Hulst, N.F.

    1995-01-01

    Near-field Scanning Optical Microscopy (NSOM) is a true optical microscopic technique allowing fluorescence, absorption, reflection and polarization contrast with the additional advantage of nanometer lateral resolution, unlimited by diffraction and operation at ambient conditions. NSOM based on

  8. Thermodynamics of the near field

    International Nuclear Information System (INIS)

    Apps, J.A.

    1985-01-01

    The near field is normally taken to mean the part of the geologic setting of a repository that is affected by mechanical or thermal perturbations resulting from repository excavations and emplacement of radioactive waste. The near-field host rocks, the waste package, and the intervening backfill constitute a series of engineered and natural barriers that should be designed to initially prevent and subsequently control radionuclide release. Nuclear Regulatory Commission regulations 10 CFR part 60 specify that the waste package must not allow any release of radionuclides for at least 300 years, and preferably 1000 years. Thereafter, the release rate of any radionuclide is not to exceed on part in 100,000 per year of the inventory that is calculated to be present 1000 years after closure. In this paper, the author briefly outlines recent developments and identifies important fundamental research in thermodynamics and related areas that is needed to resolve some of the current uncertainties

  9. Near field communication in orienteering

    OpenAIRE

    Lisovski, Dominik Gabriel

    2017-01-01

    Near Field Communication (NFC) – radio-based communication technology that is rapidly gaining in popularity, although its potential is still not fully utilized. The aim of this thesis is to improve orienteering sports using NFC technology. Firstly, in this final work orienteering sport is analysed. It is identified how punching happens at control points and what are the main problems of orienteering sports. Secondly, operating principles of the technology, usage perspectives at the present an...

  10. EDITORIAL: Terahertz nanotechnology Terahertz nanotechnology

    Science.gov (United States)

    Demming, Anna; Tonouchi, Masayoshi; Reno, John L.

    2013-05-01

    A useful synergy is being established between terahertz research and nanotechnology. High power sources [1-3] and detectors [4] in what was once considered the terahertz 'frequency gap' [5] in the electromagnetic spectrum have stimulated research with huge potential benefits in a range of industries including food, medicine and security, as well as fundamental physics and astrophysics. This special section, with guest editors Masayoshi Tonouchi and John Reno, gives a glimpse of the new horizons nanotechnology is broaching in terahertz research. While the wavelengths relevant to the terahertz domain range from hundreds of micrometres to millimetres, structures at the nanoscale reveal interesting low energy dynamics in this region. As a result terahertz spectroscopy techniques are becoming increasingly important in nanomaterial characterization, as demonstrated in this special section by colleagues at the University of Oxford in the UK and the Australian National University. They use terahertz spectroscopy to identify the best nanostructure parameters for specific applications [6]. The low energy dynamics in nanostructures also makes them valuable tools for terahertz detection [7]. In addition the much sought after terahertz detection over broadband frequency ranges has been demonstrated, providing versatility that has been greatly in demand, particularly in spectroscopy applications [8, 9]. Also in this special section, researchers in Germany and China tackle some of the coupling issues in terahertz time domain spectroscopy with an emitter specifically well suited for systems operated with an amplified fibre [3]. 'In medical imaging, the advantage of THz radiation is safety, because its energy is much lower than the ionization energy of biological molecules, in contrast to hazardous x-ray radiation,' explains Joo-Hiuk Son from the University of Seoul in Korea in his review [10]. As he also points out, the rotational and vibrational energies of water molecules are

  11. 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.

  12. 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. This journal is © The Royal Society of Chemistry 2011

  13. Near-field solubility studies

    International Nuclear Information System (INIS)

    Thomason, H.P.; Williams, S.J.

    1992-02-01

    Experimental determinations of the solubilities of americium, plutonium, neptunium, protactinium, thorium, radium, lead, tin, palladium and zirconium are reported. These elements have radioactive isotopes of concern in assessments of radioactive waste disposal. All measurements were made under the highly alkaline conditions typical of the near field of a radioactive waste repository which uses cementitious materials for many of the immobilisation matrices, the backfill and the engineered structures. Low redox potentials, typical of those resulting from the corrosion of iron and steel, were simulated for those elements having more than one accessible oxidation state. The dissolved concentrations of the elements were defined using ultrafiltration. In addition, the corrosion of iron and stainless steel was shown to generate low redox potentials in solution and the solubility of iron(II) at high pH was measured and found to be sufficient for it to act as a redox buffer with respect to neptunium and plutonium. (author)

  14. Report of near field group

    Energy Technology Data Exchange (ETDEWEB)

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

    1985-04-01

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

  15. Report of near field group

    International Nuclear Information System (INIS)

    Palmer, R.B.; Baggett, N.; Claus, J.

    1985-04-01

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

  16. Scanning near-field infrared microscopy on semiconductor structures

    International Nuclear Information System (INIS)

    Jacob, Rainer

    2011-01-01

    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

  17. 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

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

    Science.gov (United States)

    Morozov, Yevhenii M; Lapchuk, Anatoliy S

    2016-05-01

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

  19. 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,…

  20. 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.)

  1. Near-field edge fringes at sharp material boundaries.

    Science.gov (United States)

    Babicheva, V E; Gamage, S; Stockman, M I; Abate, Y

    2017-10-02

    We have studied the formation of near-field fringes when sharp edges of materials are imaged using scattering-type scanning near-field optical microscope (s-SNOM). The materials we have investigated include dielectrics, metals, a near-perfect conductor, and those that possess anisotropic permittivity and hyperbolic dispersion. For our theoretical analysis, we use a technique that combines full-wave numerical simulations of tip-sample near-field interaction and signal demodulation at higher orders akin to what is done in typical s-SNOM experiments. Unlike previous tip-sample interaction near-field models, our advanced technique allows simulation of the realistic tip and sample structure. Our analysis clarifies edge imaging of recently emerged layered materials such as hexagonal boron nitride and transition metal dichalcogenides (in particular, molybdenum disulfide), as well as traditional plasmonic materials such as gold. Hexagonal boron nitride is studied at several wavelengths, including the wavelength where it possesses excitation of phonon-polaritons and hyperbolic dispersion. Based on our results of s-SNOM imaging in different demodulation orders, we specify resonant and non-resonant types of edges and describe the edge fringes for each case. We clarify near-field edge-fringe formation at material sharp boundaries, both outside bright fringes and the low-contrast region at the edge, and elaborate on the necessity of separating them from propagating waves on the surface of polaritonic materials.

  2. 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...

  3. Terahertz physics

    CERN Document Server

    Lewis, R A

    2012-01-01

    Terahertz physics covers one of the least explored but richest regions of the electromagnetic spectrum. Designed for independent learning, this is the first book to open up this exciting new field to students of science and engineering. Written in a clear and consistent style, the textbook focuses on an understanding of fundamental physical principles at terahertz frequencies and their applications. Part I outlines the foundations of terahertz science, starting with the mathematical representation of oscillations before exploring terahertz-frequency light, terahertz phenomena in matter and the terahertz interactions between light and matter. Part II covers components of terahertz technology, from sources of terahertz frequency radiation, through the manipulation of the radiation, to its detection. Part III deals with applications, including time-domain spectroscopy. Highlighting modern developments and concepts, the book is ideal for self-study. It features precise definitions, clear explanations, instructive...

  4. Terahertz technology

    CERN Document Server

    Rostami, Ali; Baghban, Hamed

    2010-01-01

    This book presents information about Terahertz science, Terahertz photodetectors and Terahertz Lasers. A special emphasis is given to room temperature operation of long wavelength photodetectors based on novel quantum dots (Centered Defect Spherical Quantum Dots). Moreover, a complete analysis of systems based on Quantum Cascade structures to detect far infrared wavelengths is provided. Finally, the book presents Terahertz laser principles considering multi-color lasers in this range of wavelengths. It is written as a background for graduate students in the Optics field.

  5. THz near-field imaging of biological tissues employing synchrotron radiation

    International Nuclear Information System (INIS)

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

    2004-01-01

    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

  6. Terahertz surface plasmon polariton waveguiding with periodic metallic cylinders

    KAUST Repository

    Zhang, Ying

    2017-06-15

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

  7. 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...

  8. Near field cosmology from Dwarf Galaxies

    Indian Academy of Sciences (India)

    First page Back Continue Last page Graphics. Near field cosmology from Dwarf Galaxies. Extremely faint dwarfs are particularly interesting in the context of hierarchical galaxy formation models. The smallest objects collapse first, larger galaxies from by merger of smaller ones. The process of galaxy formation via merger s is ...

  9. Development of the near field geochemistry model

    International Nuclear Information System (INIS)

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

    2000-01-01

    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)

  10. 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.

  11. Optical near fields of multipolar particle plasmons

    International Nuclear Information System (INIS)

    Hohenau, A.; Ditlbacher, H.; Schider, G.; Krenn, J.R.; Leitner, A.; Aussenegg, F.R.; Schaich, W.L.

    2004-01-01

    Nanoscale noble metal particles are well known for their ability to sustain resonant electron plasma oscillations, so-called particle plasmons. This phenomenon gives rise to spectrally selective light absorption and to an enhancement of the local electric field. Due to these properties, metal nanoparticles are of high current interest for applications and fundamental research in fields as surface enhanced Raman scattering or nanoscale waveguides. Most investigations and applications focus on the dipolar resonances of such particles. However, the particular near-field profiles and far-field scattering patterns of higher order excitations are of interest as well and might be advantageous for specific applications. In this presentation, we report on experimental and theoretical studies of multipolar optical excitations in prolate metal nanoparticles. The results of optical far-field extinction spectroscopy and optical near-field measurements on such particles can be qualitatively understood in a physical picture of standing plasmon-waves. The specific properties of the optical near-fields of the multipolar excitations compared to dipolar excitations are emphasized. (author)

  12. Terahertz spoof surface-plasmon-polariton subwavelength waveguide

    KAUST Repository

    Zhang, Ying

    2017-12-11

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

  13. Near-field optical microscopy with a scanning tunneling microscope

    International Nuclear Information System (INIS)

    Barbara, A.; Lopez-Rios, T.; Quemerais, P.

    2005-01-01

    A homemade apertureless near-field optical microscope using a scanning tunneling microscope (STM) is described. The experimental set-up simultaneously provides optical and topographic images of the sample. Technical details and features of the set-up are presented, together with results demonstrating the sub-wavelength resolution achieved as well as its sensitivity to dielectric contrasts. We show that the use of a STM permits to precisely control very small distances between the tip and the sample which is a great advantage to excite localized optical resonances between the tip and the surface

  14. 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...... results calculated for a rectangular object are presented and compared with experimental observations. It is demonstrated that the optical contrast and the spatial resolution are significantly better in the second-harmonic images than in the images obtained at the fundamental frequency....

  15. 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.

  16. 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.

  17. Convergence analysis in near-field imaging

    International Nuclear Information System (INIS)

    Bao, Gang; Li, Peijun

    2014-01-01

    This paper is devoted to the mathematical analysis of the direct and inverse modeling of the diffraction by a perfectly conducting grating surface in the near-field regime. It is motivated by our effort to analyze recent significant numerical results, in order to solve a class of inverse rough surface scattering problems in near-field imaging. In a model problem, the diffractive grating surface is assumed to be a small and smooth deformation of a plane surface. On the basis of the variational method, the direct problem is shown to have a unique weak solution. An analytical solution is introduced as a convergent power series in the deformation parameter by using the transformed field and Fourier series expansions. A local uniqueness result is proved for the inverse problem where only a single incident field is needed. On the basis of the analytic solution of the direct problem, an explicit reconstruction formula is presented for recovering the grating surface function with resolution beyond the Rayleigh criterion. Error estimates for the reconstructed grating surface are established with fully revealed dependence on such quantities as the surface deformation parameter, measurement distance, noise level of the scattering data, and regularity of the exact grating surface function. (paper)

  18. Plasmonic Terahertz Amplification in Graphene-Based Asymmetric Hyperbolic Metamaterial

    Directory of Open Access Journals (Sweden)

    Igor Nefedov

    2015-05-01

    Full Text Available We propose and theoretically explore terahertz amplification, based on stimulated generation of plasmons in graphene asymmetric hyperbolic metamaterials (AHMM, strongly coupled to terahertz radiation. In contrast to the terahertz amplification in resonant nanocavities, AHMM provides a wide-band THz amplification without any reflection in optically thin graphene multilayers.

  19. Terahertz metamaterials

    Science.gov (United States)

    Peralta, Xomalin Guaiuli; Brener, Igal; O'Hara, John; Azad, Abul; Smirnova, Evgenya; Williams, John D.; Averitt, Richard D.

    2014-08-12

    Terahertz metamaterials comprise a periodic array of resonator elements disposed on a dielectric substrate or thin membrane, wherein the resonator elements have a structure that provides a tunable magnetic permeability or a tunable electric permittivity for incident electromagnetic radiation at a frequency greater than about 100 GHz and the periodic array has a lattice constant that is smaller than the wavelength of the incident electromagnetic radiation. Microfabricated metamaterials exhibit lower losses and can be assembled into three-dimensional structures that enable full coupling of incident electromagnetic terahertz radiation in two or three orthogonal directions. Furthermore, polarization sensitive and insensitive metamaterials at terahertz frequencies can enable new devices and applications.

  20. Terahertz Techniques

    CERN Document Server

    Bründermann, Erik; Kimmitt, Maurice FitzGerald

    2012-01-01

    Research and development in the terahertz portion of the electromagnetic spectrum has expanded very rapidly during the past fifteen years due to major advances in sources, detectors and instrumentation. Many scientists and engineers are entering the field and this volume offers a comprehensive and integrated treatment of all aspects of terahertz technology. The three authors, who have been active researchers in this region over a number of years, have designed Terahertz Techniques to be both a general introduction to the subject and a definitive reference resource for all those involved in this exciting research area.

  1. Scanning Near-Field Optical Microscopy

    Directory of Open Access Journals (Sweden)

    Dušan Vobornik

    2008-02-01

    Full Text Available An average human eye can see details down to 0,07 mm in size. The ability to see smaller details of the matter is correlated with the development of the science and the comprehension of the nature. Today’s science needs eyes for the nano-world. Examples are easily found in biology and medical sciences. There is a great need to determine shape, size, chemical composition, molecular structure and dynamic properties of nano-structures. To do this, microscopes with high spatial, spectral and temporal resolution are required. Scanning Near-field Optical Microscopy (SNOM is a new step in the evolution of microscopy. The conventional, lens-based microscopes have their resolution limited by diffraction. SNOM is not subject to this limitation and can offer up to 70 times better resolution.

  2. Terahertz scanning probe microscope

    NARCIS (Netherlands)

    Klapwijk, T.M.

    2014-01-01

    The invention provides aterahertz scanning probe microscope setup comprising (i) a terahertz radiation source configured to generate terahertz radiation; (ii) a terahertz lens configured to receive at least part of the terahertz radiation from the terahertz radiation source; (iii) a cantilever unit

  3. 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...... contrast-and symmetry properties are considered for optical images obtained in constant-distance mode for different polarization configurations. We demonstrate that images obtained in cross-polarized detection mode are free of background and topographical artifacts and that the cross-circular polarization...... 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....

  4. Migration model for the near field

    International Nuclear Information System (INIS)

    Andersson, G.; Rasmusson, A.; Neretnieks, I.

    1982-11-01

    The near field model describes the transport of substances dissolved in the groundwater to and from a canister in which radioactive materials are stored. The migration of substances that can cause corrosion (oxidants) of the canister is described by means of a mathematical model. The model takes into account diffusion through the buffer material and water flow in the rock fractures. Two distinct transport resistances can be distinguished in this transport process. The first consists of the diffusion resistance in the buffer material and the second arises due to diffusion resistance in the flowing water in the thin fractures in the rock. The model can also be used to calculate the non-steady-state phase of the inward or outward transport of dissolved species. The model has also been used to calculate how a redox front caused by radiolytically produced oxidants moves out through the clay and into the rock. It has been shown that the migration rate of the redox front can be calculated with good accuracy by means of simple mass balance computations. The transport of radiolytically formed hydrogen away from the fuel has been calculated. When dissolved in the water, hydrogen can be transported through the clay barrier by means of diffusion without the partial pressure of the hydrogen exceeding the hydrostatic pressure. (author)

  5. 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

  6. Sub-wavelength terahertz beam profiling of a THz source via an all-optical knife-edge technique.

    Science.gov (United States)

    Phing, Sze Ho; Mazhorova, Anna; Shalaby, Mostafa; Peccianti, Marco; Clerici, Matteo; Pasquazi, Alessia; Ozturk, Yavuz; Ali, Jalil; Morandotti, Roberto

    2015-02-25

    Terahertz technologies recently emerged as outstanding candidates for a variety of applications in such sectors as security, biomedical, pharmaceutical, aero spatial, etc. Imaging the terahertz field, however, still remains a challenge, particularly when sub-wavelength resolutions are involved. Here we demonstrate an all-optical technique for the terahertz near-field imaging directly at the source plane. A thin layer (terahertz generation crystal, which acts as an all-optical, virtual blade for terahertz near-field imaging via a knife-edge technique. Remarkably, and in spite of the fact that the proposed approach does not require any mechanical probe, such as tips or apertures, we are able to demonstrate the imaging of a terahertz source with deeply sub-wavelength features (<30 μm) directly in its emission plane.

  7. Exploiting optical near fields for phase change memories

    OpenAIRE

    Leiprecht, P.; Kühler, P.; Longo, M.; Leiderer, P.; Afonso, Carmen N.; Siegel, Jan

    2011-01-01

    We apply a recently developed technique based on optical near fields to achieve reversible phase switching in Ge2 Sb2 Te 5 films. By placing dielectric microspheres at the film surface and exposing them to pulsed laser light, a complex intensity distribution due to the optical near field can be created at the film surface. We demonstrate writing and erasing operations of patterns through phase switching. Spheres can be removed after an operation by optical near fields without ablation. Data e...

  8. Detection of Terahertz Radiation

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a system for detecting terahertz radiation, a camera device, and a method for detecting terahertz radiation.......The present invention relates to a system for detecting terahertz radiation, a camera device, and a method for detecting terahertz radiation....

  9. 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...

  10. Subwavelength micropillar array terahertz lasers.

    Science.gov (United States)

    Krall, Michael; Brandstetter, Martin; Deutsch, Christoph; Detz, Hermann; Andrews, Aaron Maxwell; Schrenk, Werner; Strasser, Gottfried; Unterrainer, Karl

    2014-01-13

    We report on micropillar-based terahertz lasers with active pillars that are much smaller than the emission wavelength. These micropillar array lasers correspond to scaled-down band-edge photonic crystal lasers forming an active photonic metamaterial. In contrast to photonic crystal lasers which use significantly larger pillar structures, lasing emission is not observed close to high-symmetry points in the photonic band diagram, but in the effective medium regime. We measure stimulated emission at 4 THz for micropillar array lasers with pillar diameters of 5 µm. Our results not only demonstrate the integration of active subwavelength optics in a terahertz laser, but are also an important step towards the realization of nanowire-based terahertz lasers.

  11. Survey and review of near-field performance assessment

    International Nuclear Information System (INIS)

    Apted, M.J.

    1993-01-01

    Chemical reactions control the performance, stability, and rate of degradation of natural and engineered barriers to waste repositories of the near field. Chemical processes are overviewed in this context. Temperature, and associated temperature gradients, are also important parameters in near-field performance assessment. The mechanical conditions of the near-field rock will be perturbed by construction of the underground repository. Mechanical analysis in the near field is further complicated by the introduction of HLW canisters and associated engineered barrier materials. Hydrological processes important to near-field performance include those associated with fluid transport. Considerable discussions and studies have been conducted on the issue of coupling among chemical-thermal-mechanical-hydrological processes; they are overviewed. (R.P.) 2 figs., 2 tabs

  12. CONTRAST

    DEFF Research Database (Denmark)

    Kristensen, Thomas Krogsgaard

    2007-01-01

    Dette er en afrapportering fra den årlige CONTRAST workshop, der i 2007 blev afholdt i Yaoundé, Cameroon.......Dette er en afrapportering fra den årlige CONTRAST workshop, der i 2007 blev afholdt i Yaoundé, Cameroon....

  13. Terahertz ptychography.

    Science.gov (United States)

    Valzania, Lorenzo; Feurer, Thomas; Zolliker, Peter; Hack, Erwin

    2018-02-01

    We realized a phase retrieval technique using terahertz (THz) radiation as an alternative to THz digital holography, named THz ptychography. Ptychography has been used in x-ray imaging as a groundbreaking improvement of conventional coherent diffraction imaging. Here we show that ptychography can be performed at THz frequencies too. We reconstructed an amplitude and a phase object with both simulated and real data. Lateral resolution accounts to <2λ, while depth variations as low as λ/30 can be assessed.

  14. 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.

  15. Simulations for printing contacts with near field x-rays

    International Nuclear Information System (INIS)

    Bourdillon, Antony J; Boothroyd, Chris B

    2005-01-01

    In ultra high resolution lithography, sometimes called near field x-ray lithography, Fresnel diffraction is deliberately used to increase resolution: the contraction in current occurring beyond a clear mask feature has, further, important experimentally beneficial effects that were previously overlooked. All the key features of the technique have, by now, been demonstrated and previously reported. The technique is also an enhancement of the most-developed next generation lithography. The enhancement has fundamental advantages, including an increase in mask-wafer Gap (the Gap scales as the square of the width of a clear mask feature); reduced exposure times; more easily fabricated masks; high density prints by multiple exposures; high contrast; elimination of sidebands; reduction in the effects of mask defects, compact masks, etc. We have, previously reported experimental and simulated prints from lines and more complex flag and bridge structures; here we report simulations for symmetrical contacts. More particularly, in the printing of circular features, it is shown that a demagnification factor around 7 can be routinely used to optimize mask-wafer Gap. Although the Gap is significantly extended by using larger clear mask features, finer prints can still be developed

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

    DEFF Research Database (Denmark)

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

    1999-01-01

    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.......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...

  17. 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....... Near-field optical images exhibit spatially localized (within 150-250 nm) intensity enhancement (by up to 20 times) in the form of round bright spots, whose positions and brightness are found to be sensitive to the light wavelength, polarization and angle of incidence. The observed phenomenon...

  18. 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....

  19. Tutorial: Terahertz beamforming, from concepts to realizations

    Science.gov (United States)

    Headland, Daniel; Monnai, Yasuaki; Abbott, Derek; Fumeaux, Christophe; Withayachumnankul, Withawat

    2018-05-01

    The terahertz range possesses significant untapped potential for applications including high-volume wireless communications, noninvasive medical imaging, sensing, and safe security screening. However, due to the unique characteristics and constraints of terahertz waves, the vast majority of these applications are entirely dependent upon the availability of beam control techniques. Thus, the development of advanced terahertz-range beam control techniques yields a range of useful and unparalleled applications. This article provides an overview and tutorial on terahertz beam control. The underlying principles of wavefront engineering include array antenna theory and diffraction optics, which are drawn from the neighboring microwave and optical regimes, respectively. As both principles are applicable across the electromagnetic spectrum, they are reconciled in this overview. This provides a useful foundation for investigations into beam control in the terahertz range, which lies between microwaves and infrared light. Thereafter, noteworthy experimental demonstrations of beam control in the terahertz range are discussed, and these include geometric optics, phased array devices, leaky-wave antennas, reflectarrays, and transmitarrays. These techniques are compared and contrasted for their suitability in applications of terahertz waves.

  20. 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.

  1. 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.

  2. Scanning near-field optical microscopy on rough surfaces: Applications in chemistry, biology, and medicine

    OpenAIRE

    Kaupp, Gerd

    2006-01-01

    Shear-force apertureless scanning near-field optical microscopy (SNOM) with very sharp uncoated tapered waveguides relies on the unexpected enhancement of reflection in the shear-force gap. It is the technique for obtaining chemical (materials) contrast in the optical image of “real world” surfaces that are rough and very rough without topographical artifacts, and it is by far less complicated than other SNOM techniques that can only be used for very flat surfaces. The ex...

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

    Science.gov (United States)

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

    2010-10-01

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

  4. Chemical and microbiological effects in the near field: current status

    International Nuclear Information System (INIS)

    Ewart, F.T.; Pugh, S.Y.R.; Wisbey, S.J.; Woodwark, D.R.

    1988-12-01

    The radionuclide inventory of a radioactive waste repository, influenced by the chemical conditions in the near-field, determines the source term for radionuclides entering the geosphere. The research described in this report is focussed on providing the information necessary to quantify this source term. The processes which interact to determine near field behaviour over a long period of time are complex and a simplified representation is required for radiological assessment modelling. The assumptions made in formulating the near field assessment methodology are discussed and justified in this report. The techniques for acquiring the necessary large body of data for a wide range of relevant radionuclides are also described and the values used in the CASCADE I exercise are given. (author)

  5. 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...... 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......We consider characterization of a near-field optical probe in terms of detection efficiency of different spatial frequencies associated with propagating and evanescent field components. The former are both detected with and radiated from an etched single-mode fibertip, showing reciprocity...

  6. Near-field three-terminal thermoelectric heat engine

    Science.gov (United States)

    Jiang, Jian-Hua; Imry, Yoseph

    2018-03-01

    We propose a near-field inelastic thermoelectric heat engine where quantum dots are used to effectively rectify the charge flow of photocarriers. The device converts near-field heat radiation into useful electrical power. Heat absorption and inelastic transport can be enhanced by introducing two continuous spectra separated by an energy gap. The thermoelectric transport properties of the heat engine are studied in the linear-response regime. Using a small band-gap semiconductor as the absorption material, we show that the device achieves very large thermopower and thermoelectric figure of merit, as well as considerable power factor. By analyzing thermal-photocarrier generation and conduction, we reveal that the Seebeck coefficient and the figure of merit have oscillatory dependence on the thickness of the vacuum gap. Meanwhile, the power factor, the charge, and thermal conductivity are significantly improved by near-field radiation. Conditions and guiding principles for powerful and efficient thermoelectric heat engines are discussed in details.

  7. 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

  8. Near-Field Effects in Mesoscopic Light Transport.

    Science.gov (United States)

    Rezvani Naraghi, R; Sukhov, S; Sáenz, J J; Dogariu, A

    2015-11-13

    In dense multiple scattering media, optical fields evolve through both homogeneous and evanescent waves. New regimes of light transport emerge because of the near-field coupling between individual scattering centers at mesoscopic scales. We present a novel propagation model that is developed in terms of measurable far- and near-field scattering cross sections. Our quantitative description explains the increase of total transmission in dense scattering media and its accuracy is established through both full-scale numerical calculations and enhanced backscattering experiments.

  9. Tailoring the slow light behavior in terahertz metasurfaces

    International Nuclear Information System (INIS)

    Manjappa, Manukumara; Cong, Longqing; Singh, Ranjan; Chiam, Sher-Yi; Bettiol, Andrew A.; Zhang, Weili

    2015-01-01

    We experimentally study the effect of near field coupling on the transmission of light in terahertz metasurfaces. Our results show that tailoring the coupling between the resonators modulates the amplitude of resulting electromagnetically induced transmission, probed under different types of asymmetries in the coupled system. Observed change in the transmission amplitude is attributed to the change in the amount of destructive interference between the resonators in the vicinity of strong near field coupling. We employ a two-particle model to theoretically study the influence of the coupling between bright and quasi-dark modes on the transmission properties of the system and we find an excellent agreement with our observed results. Adding to the enhanced transmission characteristics, our results provide a deeper insight into the metamaterial analogues of atomic electromagnetically induced transparency and offer an approach to engineer slow light devices, broadband filters, and attenuators at terahertz frequencies

  10. 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.

  11. 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, as...

  12. 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...

  13. 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

  14. 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.

  15. Measurements of near-field blast effects using kinetic plates

    Science.gov (United States)

    Manner, V. W.; Pemberton, S. J.; Brown, G. W.; Tappan, B. C.; Hill, L. G.; Preston, D. N.; Neuscamman, S. J.; Glascoe, L. G.

    2014-05-01

    Few tests have been designed to measure the near-field blast impulse of ideal and non-ideal explosives, mostly because of the inherent experimental difficulties due to non-transparent fireballs and thermal effects on gauges. In order to measure blast impulse in the near-field, a new test has been developed by firing spherical charges at 152 mm (6 in) from steel plates and probing acceleration using laser velocimetry. Tests measure the velocity imparted to the steel plate in the 50 - 300 μs timeframe, and are compared with free-field overpressure measurements at 1.52 m (5 ft) and ms timescales using piezoelectric pencil gauges. Specifically, tests have been performed with C4 to probe the contributions of ideal explosives and charge size effects. Non-ideal aluminized explosive formulations have been studied to explore the role of aluminum in near-field blast effects and far-field pressure, and are compared with formulations using LiF as an inert surrogate replacement for Al. The results are compared with other near-field blast tests and cylinder tests, and the validity of this test is explored with modeling and basic theory.

  16. 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.

  17. 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...

  18. Near field acoustic holography with microphones on a rigid sphere

    DEFF Research Database (Denmark)

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

    2011-01-01

    Spherical near field acoustic holography (spherical NAH) is a technique that makes it possible to reconstruct the sound field inside and just outside a spherical surface on which the sound pressure is measured with an array of microphones. This is potentially very useful for source identification...

  19. Patch near field acoustic holography based on particle velocity measurements

    DEFF Research Database (Denmark)

    Zhang, Yong-Bin; Jacobsen, Finn; Bi, Chuan-Xing

    2009-01-01

    Patch near field acoustic holography (PNAH) based on sound pressure measurements makes it possible to reconstruct the source field near a source by measuring the sound pressure at positions on a surface. that is comparable in size to the source region of concern. Particle velocity is an alternative...

  20. Near-field ptychography: phase retrieval for inline holography using a structured illumination.

    Science.gov (United States)

    Stockmar, Marco; Cloetens, Peter; Zanette, Irene; Enders, Bjoern; Dierolf, Martin; Pfeiffer, Franz; Thibault, Pierre

    2013-01-01

    Inline holography is a common phase-contrast imaging method which uses free-space propagation to encode the phase signal into measured intensities. However, quantitative retrieval of the sample's image remains challenging, imposing constraints on the nature of the sample or on the propagation distance. Here, we present a way of simultaneously retrieving the sample's complex-valued transmission function and the incident illumination function from near-field diffraction patterns. The procedure relies on the measurement diversity created by lateral translations of the sample with respect to a structured illumination. The reconstruction approach, in essence identical to that employed in ptychography, is applied to hard X-ray synchrotron measurements and to simulations. Compared to other inline holography techniques, we expect near-field ptychography to reduce reconstruction artefacts by factoring out wavefront imperfections and relaxing constraints on the sample's scattering properties, thus ultimately improving the robustness of propagation-based X-ray phase tomography.

  1. Terahertz imaging of sub-wavelength particles with Zenneck surface waves

    Czech Academy of Sciences Publication Activity Database

    Navarro-Cia, M.; Natrella, M.; Dominec, Filip; Delagnes, J.C.; Kužel, Petr; Mounaix, P.; Graham, C.; Renaud, C.C.; Seeds, A.J.; Mitrofanov, O.

    2013-01-01

    Roč. 103, č. 22 (2013), "221103-1"-"221103-5" ISSN 0003-6951 Institutional support: RVO:68378271 Keywords : terahertz * near-field * Zenneck plasmon * sub-wavelength * imaging Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 3.515, year: 2013

  2. Near-field strong coupling of single quantum dots.

    Science.gov (United States)

    Groß, Heiko; Hamm, Joachim M; Tufarelli, Tommaso; Hess, Ortwin; Hecht, Bert

    2018-03-01

    Strong coupling and the resultant mixing of light and matter states is an important asset for future quantum technologies. We demonstrate deterministic room temperature strong coupling of a mesoscopic colloidal quantum dot to a plasmonic nanoresonator at the apex of a scanning probe. Enormous Rabi splittings of up to 110 meV are accomplished by nanometer-precise positioning of the quantum dot with respect to the nanoresonator probe. We find that, in addition to a small mode volume of the nanoresonator, collective coherent coupling of quantum dot band-edge states and near-field proximity interaction are vital ingredients for the realization of near-field strong coupling of mesoscopic quantum dots. The broadband nature of the interaction paves the road toward ultrafast coherent manipulation of the coupled quantum dot-plasmon system under ambient conditions.

  3. Near-field optical spectroscopy of semiconductor quantum wires

    Science.gov (United States)

    Gershoni, D.; Harris, T. D.; Pfeiffer, L. N.

    1997-09-01

    We discuss low temperature near-field scanning optical spectroscopical studies of single, nanometer dimension, cleaved edge overgrown quantum wires. We use the enhanced spatial resolution of near-field microscopy, to spectroscopically investigate these single wires, which are inaccessible to conventional far-field optical spectroscopy. We thus performed a direct experimental comparison between a two-dimensional quantum system and a single genuine one-dimensional quantum system. We show that the photoluminescence of a single quantum wire is easily distinguished from that of the surrounding quantum well. Emission from localized centers is shown to dominate the photoluminescence from both wires and wells at low temperatures. A factor of three enhancement in the optical absorption of a wire, in comparison with that of a similar well, is concluded from the photoluminescence excitation data.

  4. 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.

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

    DEFF Research Database (Denmark)

    Fiutowski, J.; Maibohm, C.; Kostiucenko, O.

    2011-01-01

    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......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....... The obtained experimental results for different polymer coating thicknesses and nanostructure geometries are in good agreement with theoretical calculations of the near field distribution for corresponding enhancement mechanisms. The developed method and its tunable experimental parameters show...

  6. 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.

  7. Application of near field communication in hotel industry

    OpenAIRE

    Trikšys, Gerimantas

    2016-01-01

    Today, NFC technology can be used not only to pay products in store. In this paperwork aims to explore other payment areas using NFC technology. The selected area – hotels. In the first part of this thesis explains Near Field Communication and Host Card Emulation technologies. Also describes the comparison between Host Card Emulation and Secure element. Furthermore analyzed most popular NFC payment systems for mobile devices and their weaknesses and general comparison. In the second part of t...

  8. 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. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  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. Characterization of burn injuries using terahertz time-domain spectroscopy

    Science.gov (United States)

    Arbab, M. Hassan; Dickey, Trevor C.; Winebrenner, Dale P.; Chen, Antao; Mourad, Pierre D.

    2011-03-01

    The accuracy rates of the clinical assessment techniques used in grading burn injuries remain significantly low for partial thickness burns. In this paper, we present experimental results from terahertz characterization of 2nd and 3rd degree burn wounds induced on a rat model. Reflection measurements were obtained from the surface of both burned and normal skin using pulsed terahertz spectroscopy. Signal processing techniques are described for interpretation of the acquired terahertz waveform and differentiation of burn wounds. Furthermore, the progression of burn injuries is shown by comparison between acute characterization and 72-hours survival studies. While the water content of healthy and desiccated skin has been considered as a source of terahertz signal contrast, it is demonstrated that other biological effects such as formation of post-burn interstitial edema as well as the density of the discrete scattering structures in the skin (such as hair follicles, sweat glands, etc.) play a significant role in the terahertz response of the burn wounds.

  11. Acousto-optic interactions for terahertz waves using phoxonic quasicrystals

    Science.gov (United States)

    Wang, Zhong; Yu, Tianbao; Wang, Tongbiao; Liu, Wenxing; Liu, Nianhua; Liao, Qinghua

    2018-03-01

    Phoxonic quasicrystals possess abundant localized modes and low-index-contrast bandgaps, thus showing much advantage over periodic counterparts. We calculated the modulation of photonic modes for terahertz waves by phononic modes in defect-free phoxonic quasicrystals (FDQs) and quasicrystals having center point defects (PDQs). Both the moving interface (MI) and photoelastic effects are considered in acousto-optic coupling. Terahertz modes can be efficiently modified by acoustic modes due to the simultaneous confinement of electromagnetic and elastic fields both inside and outside the bandgaps. The acousto-optic coupling strength depends on the selection of the acoustic and terahertz defect modes. The predominant coupling mechanism is determined by the overlapping between the terahertz and acoustic modes in PDQs, while the MI effect becomes predominant in FDQs. Our results are important for terahertz wave modulation with ultra-small footprint size.

  12. Microarrays of near-field optical probes with adjustable dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Chovin, A. [Laboratoire d' Analyse Chimique par Reconnaissance Moleculaire, Universite Bordeaux I, ENSCPB, 16 avenue Pey-Berland, 33607 Pessac (France); Garrigue, P. [Laboratoire d' Analyse Chimique par Reconnaissance Moleculaire, Universite Bordeaux I, ENSCPB, 16 avenue Pey-Berland, 33607 Pessac (France); Pecastaings, G. [Centre de Recherche Paul Pascal-CNRS, 115 avenue du Dr Schweitzer, 33600 Pessac (France); Saadaoui, H. [Centre de Recherche Paul Pascal-CNRS, 115 avenue du Dr Schweitzer, 33600 Pessac (France); Manek-Hoenninger, I. [Centre Lasers Intenses et Applications, Universite Bordeaux I, 351 Cours de la Liberation, 33405 Talence (France)]. E-mail: manek@celia.u-bordeaux1.fr; Sojic, N. [Laboratoire d' Analyse Chimique par Reconnaissance Moleculaire, Universite Bordeaux I, ENSCPB, 16 avenue Pey-Berland, 33607 Pessac (France)]. E-mail: sojic@enscpb.fr

    2006-01-15

    We present the fabrication and the characterization of high-density microarrays comprising thousands of near-field optical probes. Two types of microarrays have been prepared by adapting the SNOM methodology: arrays of uncoated fiber nanotips (i.e. apertureless probes) and arrays of apertures with adjustable subwavelength dimensions. Such arrays were fabricated by retaining the coherent structure of monomode optical fiber bundles and therefore keeping their imaging properties. The size of the apertures in a microarray was tuned at the nanometer scale by modifying the fabrication parameters. Far-field characterization of these near-field probe arrays shows completely different behavior depending both on their architecture and on their characteristic size. The angular distribution of the far-field intensity transmitted through the aperture arrays is used to determine the optical size of such diffracting apertures. Aperture radii ranging from 95 to 250 nm were found in good agreement with SEM data. Furthermore, each nanoaperture of the array is optically independent in the far-field regime. Eventually, this study demonstrates potential applications of these imaging arrays as parallel near-field optical probes in both configurations (apertureless and with apertures)

  13. Microarrays of near-field optical probes with adjustable dimensions.

    Science.gov (United States)

    Chovin, A; Garrigue, P; Pecastaings, G; Saadaoui, H; Manek-Hönninger, I; Sojic, N

    2006-01-01

    We present the fabrication and the characterization of high-density microarrays comprising thousands of near-field optical probes. Two types of microarrays have been prepared by adapting the SNOM methodology: arrays of uncoated fiber nanotips (i.e. apertureless probes) and arrays of apertures with adjustable subwavelength dimensions. Such arrays were fabricated by retaining the coherent structure of monomode optical fiber bundles and therefore keeping their imaging properties. The size of the apertures in a microarray was tuned at the nanometer scale by modifying the fabrication parameters. Far-field characterization of these near-field probe arrays shows completely different behavior depending both on their architecture and on their characteristic size. The angular distribution of the far-field intensity transmitted through the aperture arrays is used to determine the optical size of such diffracting apertures. Aperture radii ranging from 95 to 250 nm were found in good agreement with SEM data. Furthermore, each nanoaperture of the array is optically independent in the far-field regime. Eventually, this study demonstrates potential applications of these imaging arrays as parallel near-field optical probes in both configurations (apertureless and with apertures).

  14. Exergy in near-field electromagnetic heat transfer

    Science.gov (United States)

    Iizuka, Hideo; Fan, Shanhui

    2017-09-01

    The maximum amount of usable work extractable from a given radiative heat flow defines the exergy. It was recently noted that the exergy in near-field radiative heat transfer can exceed that in the far-field. Here, we derive a closed form formula of exergy in the near-field heat transfer between two parallel surfaces. This formula reveals that, for a given resonant frequency, the maximum exergy depends critically on the resonant linewidth, and there exists an optimal choice of the linewidth that maximizes the exergy. Guided by the analytical result, we show numerically that with a proper choice of doping concentration, the heat flow between two properly designed SiC-coated heavily doped silicon regions can possess exergy that is significantly higher compared to the heat flow between two SiC regions where the heat flow is carried out by phonon-polaritons. Our work indicates significant opportunities for either controlling material properties or enhancing the fundamental potential for near-field heat transfer in thermal energy conversion through the approach of meta-material engineering.

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

    International Nuclear Information System (INIS)

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

    1996-01-01

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

  16. Near-Field Source Localization by Using Focusing Technique

    Directory of Open Access Journals (Sweden)

    Joseph Saillard

    2008-12-01

    Full Text Available We discuss two fast algorithms to localize multiple sources in near field. The symmetry-based method proposed by Zhi and Chia (2007 is first improved by implementing a search-free procedure for the reduction of computation cost. We present then a focusing-based method which does not require symmetric array configuration. By using focusing technique, the near-field signal model is transformed into a model possessing the same structure as in the far-field situation, which allows the bearing estimation with the well-studied far-field methods. With the estimated bearing, the range estimation of each source is consequently obtained by using 1D MUSIC method without parameter pairing. The performance of the improved symmetry-based method and the proposed focusing-based method is compared by Monte Carlo simulations and with Crammer-Rao bound as well. Unlike other near-field algorithms, these two approaches require neither high-computation cost nor high-order statistics

  17. Short presentation on some researches activities about near field earthquakes

    International Nuclear Information System (INIS)

    Donald, John

    2002-01-01

    The major hazard posed by earthquakes is often thought to be due to moderate to large magnitude events. However, there have been many cases where earthquakes of moderate and even small magnitude have caused very significant destruction when they have coincided with population centres. Even though the area of intense ground shaking caused by such events is generally small, the epicentral motions can be severe enough to cause damage even in well-engineered structures. Two issues are addressed here, the first being the identification of the minimum earthquake magnitude likely to cause damage to engineered structures and the limits of the near-field for small-to-moderate magnitude earthquakes. The second issue addressed is whether features of near-field ground motions such as directivity, which can significantly enhance the destructive potential, occur in small-to-moderate magnitude events. The accelerograms from the 1986 San Salvador (El Salvador) earthquake indicate that it may be non conservative to assume that near-field directivity effects only need to be considered for earthquakes of moment magnitude M 6.5 and greater. (author)

  18. Maximal near-field radiative heat transfer between two plates

    Science.gov (United States)

    Nefzaoui, Elyes; Ezzahri, Younès; Drévillon, Jérémie; Joulain, Karl

    2013-09-01

    Near-field radiative transfer is a promising way to significantly and simultaneously enhance both thermo-photovoltaic (TPV) devices power densities and efficiencies. A parametric study of Drude and Lorentz models performances in maximizing near-field radiative heat transfer between two semi-infinite planes separated by nanometric distances at room temperature is presented in this paper. Optimal parameters of these models that provide optical properties maximizing the radiative heat flux are reported and compared to real materials usually considered in similar studies, silicon carbide and heavily doped silicon in this case. Results are obtained by exact and approximate (in the extreme near-field regime and the electrostatic limit hypothesis) calculations. The two methods are compared in terms of accuracy and CPU resources consumption. Their differences are explained according to a mesoscopic description of nearfield radiative heat transfer. Finally, the frequently assumed hypothesis which states a maximal radiative heat transfer when the two semi-infinite planes are of identical materials is numerically confirmed. Its subsequent practical constraints are then discussed. Presented results enlighten relevant paths to follow in order to choose or design materials maximizing nano-TPV devices performances.

  19. Broadband X-ray Imaging in the Near-Field Region of an Airblast Atomizer

    Science.gov (United States)

    Li, Danyu; Bothell, Julie; Morgan, Timothy; Heindel, Theodore

    2017-11-01

    The atomization process has a close connection to the efficiency of many spray applications. Examples include improved fuel atomization increasing the combustion efficiency of aircraft engines, or controlled droplet size and spray angle enhancing the quality and speed of the painting process. Therefore, it is vital to understand the physics of the atomization process, but the near-field region is typically optically dense and difficult to probe with laser-based or intrusive measurement techniques. In this project, broadband X-ray radiography and X-ray computed tomography (CT) imaging were performed in the near-field region of a canonical coaxial airblast atomizer. The X-ray absorption rate was enhanced by adding 20% by weight of Potassium Iodide to the liquid phase to increase image contrast. The radiographs provided an estimate of the liquid effective mean path length and spray angle at the nozzle exit for different flow conditions. The reconstructed CT images provided a 3D map of the time-average liquid spray distribution. X-ray imaging was used to quantify the changes in the near-field spray characteristics for various coaxial airblast atomizer flow conditions. Office of Naval Research.

  20. Integrated heterodyne terahertz transceiver

    Science.gov (United States)

    Lee, Mark [Albuquerque, NM; Wanke, Michael C [Albuquerque, NM

    2009-06-23

    A heterodyne terahertz transceiver comprises a quantum cascade laser that is integrated on-chip with a Schottky diode mixer. An antenna connected to the Schottky diode receives a terahertz signal. The quantum cascade laser couples terahertz local oscillator power to the Schottky diode to mix with the received terahertz signal to provide an intermediate frequency output signal. The fully integrated transceiver optimizes power efficiency, sensitivity, compactness, and reliability. The transceiver can be used in compact, fieldable systems covering a wide variety of deployable applications not possible with existing technology.

  1. Anti-reflection coating design for metallic terahertz meta-materials

    Science.gov (United States)

    Pancaldi, Matteo; Freeman, Ryan; Hudl, Matthias; Hoffmann, Matthias C.; Urazhdin, Sergei; Vavassori, Paolo; Bonetti, Stefano

    2018-02-01

    We demonstrate a silicon-based, single-layer anti-reflection coating that suppresses the reflectivity of metals at near-infrared frequencies, enabling optical probing of nano-scale structures embedded in highly reflective surroundings. Our design does not affect the interaction of terahertz radiation with metallic structures that can be used to achieve terahertz near-field enhancement. We have verified the functionality of the design by calculating and measuring the reflectivity of both infrared and terahertz radiation from a silicon/gold double layer as a function of the silicon thickness. We have also fabricated the unit cell of a terahertz meta-material, a dipole antenna comprising two 20-nm thick extended gold plates separated by a 2 $\\mu$m gap, where the terahertz field is locally enhanced. We used the time-domain finite element method to demonstrate that such near-field enhancement is preserved in the presence of the anti-reflection coating. Finally, we performed magneto-optical Kerr effect measurements on a single 3-nm thick, 1-$\\mu$m wide magnetic wire placed in the gap of such a dipole antenna. The wire only occupies 2\\% of the area probed by the laser beam, but its magneto-optical response can be clearly detected. Our design paves the way for ultrafast time-resolved studies, using table-top femtosecond near-infrared lasers, of dynamics in nano-structures driven by strong terahertz radiation.

  2. Anti-reflection coating design for metallic terahertz meta-materials.

    Science.gov (United States)

    Pancaldi, Matteo; Freeman, Ryan; Hudl, Matthias; Hoffmann, Matthias C; Urazhdin, Sergei; Vavassori, Paolo; Bonetti, Stefano

    2018-02-05

    We demonstrate a silicon-based, single-layer anti-reflection coating that suppresses the reflectivity of metals at near-infrared frequencies, enabling optical probing of nano-scale structures embedded in highly reflective surroundings. Our design does not affect the interaction of terahertz radiation with metallic structures that can be used to achieve terahertz near-field enhancement. We have verified the functionality of the design by calculating and measuring the reflectivity of both infrared and terahertz radiation from a silicon/gold double layer as a function of the silicon thickness. We have also fabricated the unit cell of a terahertz meta-material, a dipole antenna comprising two 20-nm thick extended gold plates separated by a 2 μm gap, where the terahertz field is locally enhanced. We used the time-domain finite element method to demonstrate that such near-field enhancement is preserved in the presence of the anti-reflection coating. Finally, we performed magneto-optical Kerr effect measurements on a single 3-nm thick, 1-μm wide magnetic wire placed in the gap of such a dipole antenna. The wire only occupies 2% of the area probed by the laser beam, but its magneto-optical response can be clearly detected. Our design paves the way for ultrafast time-resolved studies, using table-top femtosecond near-infrared lasers, of dynamics in nano-structures driven by strong terahertz radiation.

  3. Graphene hyperlens for terahertz radiation

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Lavrinenko, Andrei

    2012-01-01

    We propose the structured graphene terahertz hyperlens that allows overcoming natural diffraction limit and resolving subwavelength features. The proposed hyperlens can have applications in terahertz spectroscopy and imaging.......We propose the structured graphene terahertz hyperlens that allows overcoming natural diffraction limit and resolving subwavelength features. The proposed hyperlens can have applications in terahertz spectroscopy and imaging....

  4. Convergence of Mie theory series: criteria for far-field and near-field properties.

    Science.gov (United States)

    Allardice, Jesse R; Le Ru, Eric C

    2014-11-01

    We investigate the convergence of the series arising in Mie theory for the solution of electromagnetic scattering by a sphere. In contrast with previous studies that focused only on the scattering cross section, we here consider a wide spectrum of relevant properties, including scattering, extinction, and absorption cross sections, complex scattering amplitudes (i.e., radiation profile), and near-field properties such as surface electric field and average surface field intensity. The scattering cross section is shown to exhibit the fastest convergence, indicating that existing convergence criteria based on this property are not suitable for the majority of other relevant characteristics computed from Mie theory. Criteria are therefore proposed for those properties.

  5. Evaluation of long-term mechanical stability of near field

    International Nuclear Information System (INIS)

    Takaji, Kazuhiko; Sugino, Hiroyuki; Okutsu, Kazuo; Miura, Kazuhiko; Tabei, Kazuto; Noda, Masaru; Takahashi, Shinichi; Sugie, Shigehiko

    1999-11-01

    In the near field, as tunnels and pits are excavated, a redistribution of stresses in the surrounding rock will occur. For a long period of time after the emplacement of waste packages various events will take place, such as the swelling of the buffer, sinking of the overpack under its own weight, deformation arising from expansion of overpack corrosion products and the creep deformation of the rock mass. The evaluation of what effects these changes in the stress-state will have on the buffer and rock mass is a major issue from the viewpoint of safety assessment. Therefore, rock creep analysis, overpack corrosion expansion analysis and overpack sinking analysis have been made in order to examine the long-term mechanical stability of the near field and the interaction of various events that may affect the stability of the near field over a long period of time. As the results, rock creep behavior, the variations of the stress-state and the range of the influence zone differ from the rock strength, strength of buffer in the tunnel and side pressure coefficient etc. about the hard rock system and soft rock system established as basic cases. And the magnitude of the stress variations for buffer by the overpack sinking and rock creep deformation is negligible compared with it by the overpack corrosion expansion. Furthermore, though very limited zone of buffer around the overpack is close to the critical state by the overpack corrosion expansion, the engineered barrier system attains a comparatively stable state for a long period of time. (author)

  6. 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.

  7. Geochemical evolution of the L/ILW near-field

    International Nuclear Information System (INIS)

    Kosakowski, G.; Berner, U.; Wieland, E.; Glaus, M.; Degueldre, C.

    2014-10-01

    The deep geological repository for low- and intermediate-level radioactive waste (L/ILW) contains large amounts of cement based materials used for waste conditioning, tunnel support and the backfill of cavities. The waste inventory is composed of a wide range of organic and inorganic materials. This study describes the spatial and temporal geochemical evolution of the cementitious near-field, and the interactions with the technical barriers and the surrounding host rock. This evolution is governed by several coupled processes, an important one being the development of saturation by groundwater ingress from the host rock. Saturation of the near-field is controlled by the inflow of water from the host rock, by the transport of dissolved gases from the near-field into the host rock and in the engineered gas transport system, and by the transport of humidity in the gas phase. The production of gas by anoxic corrosion of metals and by microbial degradation of organic wastes consumes water. The mineral reactions which give rise to concrete degradation, such as carbonation or alkali-silica-aggregate reactions may also consume or produce water. The first phase of cementitious near-field degradation, which persists only for a short period of time, is related to the hydration of cement minerals. The pore water has a pH of 13 or even higher because of the high content of dissolved alkali hydroxides. A constant pH of 12.5 determines the second phase of the cement degradation. The alkali concentration is reduced by mineral reactions and/or solute transport. This phase persists for a long time. In the third phase the portlandite is completely dissolved due to the reaction with silicates/aluminates present in the near-field and carbonate in the groundwater of the host rock or associated with reactive waste materials. The pore water is in equilibrium with calcium-silicate-hydrates (C-S-H) which gives rise to a pH value near 11 or lower. The Ca/Si ratio of C-S-H changes towards

  8. Geochemical evolution of the L/ILW near-field

    Energy Technology Data Exchange (ETDEWEB)

    Kosakowski, G.; Berner, U.; Wieland, E.; Glaus, M.; Degueldre, C.

    2014-10-15

    The deep geological repository for low- and intermediate-level radioactive waste (L/ILW) contains large amounts of cement based materials used for waste conditioning, tunnel support and the backfill of cavities. The waste inventory is composed of a wide range of organic and inorganic materials. This study describes the spatial and temporal geochemical evolution of the cementitious near-field, and the interactions with the technical barriers and the surrounding host rock. This evolution is governed by several coupled processes, an important one being the development of saturation by groundwater ingress from the host rock. Saturation of the near-field is controlled by the inflow of water from the host rock, by the transport of dissolved gases from the near-field into the host rock and in the engineered gas transport system, and by the transport of humidity in the gas phase. The production of gas by anoxic corrosion of metals and by microbial degradation of organic wastes consumes water. The mineral reactions which give rise to concrete degradation, such as carbonation or alkali-silica-aggregate reactions may also consume or produce water. The first phase of cementitious near-field degradation, which persists only for a short period of time, is related to the hydration of cement minerals. The pore water has a pH of 13 or even higher because of the high content of dissolved alkali hydroxides. A constant pH of 12.5 determines the second phase of the cement degradation. The alkali concentration is reduced by mineral reactions and/or solute transport. This phase persists for a long time. In the third phase the portlandite is completely dissolved due to the reaction with silicates/aluminates present in the near-field and carbonate in the groundwater of the host rock or associated with reactive waste materials. The pore water is in equilibrium with calcium-silicate-hydrates (C-S-H) which gives rise to a pH value near 11 or lower. The Ca/Si ratio of C-S-H changes towards

  9. Near-field optical spectroscopy of single quantum wires

    Science.gov (United States)

    Harris, T. D.; Gershoni, D.; Grober, R. D.; Pfeiffer, L.; West, K.; Chand, N.

    1996-02-01

    Low temperature near-field scanning optical microscopy is used for spectroscopic studies of single, nanometer dimension, cleaved edge overgrown quantum wires. A direct experimental comparison between a two dimensional system and a single genuinely one dimensional quantum wire system, inaccessible to conventional far field optical spectroscopy, is enabled by the enhanced spatial resolution. We show that the photoluminescence of a single quantum wire is easily distinguished from that of the surrounding quantum well. Emission from localized centers is shown to dominate the photoluminescence from both wires and wells at low temperatures. A factor of 3 absorption enhancement for these wires compared to the wells is concluded from the photoluminescence excitation data.

  10. Near-field acoustic imaging based on Laplacian sparsity

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Daudet, Laurent

    2016-01-01

    , as in standard compressive sensing or basis pursuit approaches, solutions with a piecewise constant gradient or curvature are promoted, suitable for modeling extended sources that are subject to smooth spatial variations. The obtained results are compared to Least Squares and Compressive Sensing solutions......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...

  11. 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....

  12. Near field acoustic holography with particle velocity transducers

    DEFF Research Database (Denmark)

    Jacobsen, Finn; Liu, Yang

    2005-01-01

    Near field acoustic holography is usually based on measurement of the pressure. This paper describes an investigation of an alternative technique that involves measuring the normal component of the acoustic particle velocity. A simulation study shows that there is no appreciable difference between...... in a plane further away, high spatial frequency components are reduced by the reciprocal wave number ratio (k/kz). For the same reason holography based on the particle velocity is less sensitive to transducer mismatch than the conventional technique based on the pressure. These findings are confirmed...

  13. Towards terahertz microscopy

    NARCIS (Netherlands)

    Van der Valk, N.C.J.

    2005-01-01

    Terahertz (=1012 Hz) radiation is a form of electromagnetic radiation that is at this moment used rarely for imaging purposes. However, there are indeed reasons to assume that imaging with terahertz radiation could be very useful. First, many materials, such as paper, plastics and clothing are

  14. Terahertz polarization imaging

    NARCIS (Netherlands)

    Van der Valk, N.C.J.; Van der Marel, W.A.M.; Planken, P.C.M.

    2005-01-01

    We present a new method to measure the polarization state of a terahertz pulse by using a modified electrooptic sampling setup. To illustrate the power of this method, we show two examples in which the knowledge of the polarization of the terahertz pulse is essential for interpreting the results:

  15. Terahertz pulse imaging in reflection geometry of human skin cancer and skin tissue

    International Nuclear Information System (INIS)

    Woodward, Ruth M; Cole, Bryan E; Wallace, Vincent P; Pye, Richard J; Arnone, Donald D; Linfield, Edmund H; Pepper, Michael

    2002-01-01

    We demonstrate the application of terahertz pulse imaging (TPI) in reflection geometry for the study of skin tissue and related cancers both in vitro and in vivo. The sensitivity of terahertz radiation to polar molecules, such as water, makes TPI suitable for studying the hydration levels in the skin and the determination of the lateral spread of skin cancer pre-operatively. By studying the terahertz pulse shape in the time domain we have been able to differentiate between diseased and normal tissue for the study of basal cell carcinoma (BCC). Basal cell carcinoma has shown a positive terahertz contrast, and inflammation and scar tissue a negative terahertz contrast compared to normal tissue. In vivo measurements on the stratum corneum have enabled visualization of the stratum corneum-epidermis interface and the study of skin hydration levels. These results demonstrate the potential of terahertz pulse imaging for the study of skin tissue and its related disorders, both in vitro and in vivo

  16. Terahertz Spectroscopy and Imaging

    CERN Document Server

    Zeitler, Axel; Kuwata-Gonokami, Makoto

    2013-01-01

    "This book presents the current state of knowledge in the field of terahertz spectroscopy, providing a comprehensive source of information for beginners and experienced researchers alike whose interests lie in this area. The book aims to explain the fundamental physics that underpins terahertz  technology and to describe its key applications. Highlights of scientific research in the field of terahertz science are also outlined in some chapters, providing an overview as well as giving an insight into future directions for research.  Over the past decade terahertz spectroscopy has developed into one of the most rapidly growing areas of its kind, gaining an important impact across a wide range of scientific disciplines. Due to substantial advances in femtosecond laser technology, terahertz time-domain spectroscopy (THz-TDS) has established itself as the dominant spectroscopic technique for experimental scientists interested in measurements at this frequency range. In solids and liquids THz radiation is in reso...

  17. Near field ice detection using infrared based optical imaging technology

    Science.gov (United States)

    Abdel-Moati, Hazem; Morris, Jonathan; Zeng, Yousheng; Corie, Martin Wesley; Yanni, Victor Garas

    2018-02-01

    If not detected and characterized, icebergs can potentially pose a hazard to oil and gas exploration, development and production operations in arctic environments as well as commercial shipping channels. In general, very large bergs are tracked and predicted using models or satellite imagery. Small and medium bergs are detectable using conventional marine radar. As icebergs decay they shed bergy bits and growlers, which are much smaller and more difficult to detect. Their low profile above the water surface, in addition to occasional relatively high seas, makes them invisible to conventional marine radar. Visual inspection is the most common method used to detect bergy bits and growlers, but the effectiveness of visual inspections is reduced by operator fatigue and low light conditions. The potential hazard from bergy bits and growlers is further increased by short detection range (<1 km). As such, there is a need for robust and autonomous near-field detection of such smaller icebergs. This paper presents a review of iceberg detection technology and explores applications for infrared imagers in the field. Preliminary experiments are performed and recommendations are made for future work, including a proposed imager design which would be suited for near field ice detection.

  18. 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.

  19. 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.

  20. Surface wave multipath signals in near-field microwave imaging.

    Science.gov (United States)

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

    2012-01-01

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

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

    Directory of Open Access Journals (Sweden)

    Paul M. Meaney

    2012-01-01

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

  2. Literature survey of redox reactions in the near field

    International Nuclear Information System (INIS)

    Miki, Takahito; Chiba, Tamotsu; Inagaki, Manabu; Sasamoto, Hiroshi; Yui, Mikazu

    2000-01-01

    This report presents a summary of literature survey about geochemical reactions which are important to evaluate the redox conditions in the near field rock mass and buffer. The results of literature survey are summarized as follows; Minerals including ferrous iron and organic materials in the rock mass are important reductants. Initial stage after closure of repository, oxygen will be consumed by pyrite, because the reaction rate between pyrite and oxygen is relatively fast. It is possible to estimate the redox capacity for reductants by rock (mineral)-water interaction experiment in a laboratory. And it is expected that the ferrous iron-rich rock and higher porosity rock may have bigger redox capacity. It is impossible to estimate the oxygen consumption rate by reductants such as minerals including ferrous iron. The rate law and rate constant for the oxidation reaction of ferrous iron in the solution are also determined. As a conclusion, it seems that we can evaluate kinetically the evolution of geochemical conditions in the near field rock mass and buffer by excavation of drifts, based on data derived from these existing literatures. (author)

  3. Near-field NanoThermoMechanical memory

    International Nuclear Information System (INIS)

    Elzouka, Mahmoud; Ndao, Sidy

    2014-01-01

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

  4. Unidirectional wireless power transfer using near-field plates

    Energy Technology Data Exchange (ETDEWEB)

    Imani, Mohammadreza F., E-mail: mohamad.imani@gmail.com [Center for Metamaterials and Integrated Plasmonics, Department of Electrical and Computer Engineering, Duke University, Durham, North Carolina 27708 (United States); Grbic, Anthony [Radiation Laboratory, Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, Michigan 48109 (United States)

    2015-05-14

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

  5. Imaging with terahertz radiation

    International Nuclear Information System (INIS)

    Chan, W L; Deibel, Jason; Mittleman, Daniel M

    2007-01-01

    Within the last several years, the field of terahertz science and technology has changed dramatically. Many new advances in the technology for generation, manipulation, and detection of terahertz radiation have revolutionized the field. Much of this interest has been inspired by the promise of valuable new applications for terahertz imaging and sensing. Among a long list of proposed uses, one finds compelling needs such as security screening and quality control, as well as whimsical notions such as counting the almonds in a bar of chocolate. This list has grown in parallel with the development of new technologies and new paradigms for imaging and sensing. Many of these proposed applications exploit the unique capabilities of terahertz radiation to penetrate common packaging materials and provide spectroscopic information about the materials within. Several of the techniques used for terahertz imaging have been borrowed from other, more well established fields such as x-ray computed tomography and synthetic aperture radar. Others have been developed exclusively for the terahertz field, and have no analogies in other portions of the spectrum. This review provides a comprehensive description of the various techniques which have been employed for terahertz image formation, as well as discussing numerous examples which illustrate the many exciting potential uses for these emerging technologies

  6. Performance of visible and mid-infrared scattering-type near-field optical microscopes.

    Science.gov (United States)

    Taubner, T; Hillenbrand, R; Keilmann, F

    2003-06-01

    We describe the principles of two scattering-type near-field optical microscopes (s-SNOMs), one operating at 633 nm wavelength, the other at selectable wavelengths in the range 7.3-11.3 micro m, and compare the measurement experience. Both use interferometric detection of scattered radiation, and are therefore capable of amplitude and phase-contrast imaging. In this study both instruments use the same or even identical commercial probe tips, and measure a single, three-component, test sample. Our results show that the imaging process of s-SNOM is wavelength-independent, namely, that the resolution is determined by the properties of the tip only, and that the contrast is given by the complex refractive index of the sample, predictable from a simple, analytical model of tip-sample interaction. A novel, 'edge-darkening' artefact is described which may appear in s-SNOM and that is wavelength-independent.

  7. Deep underground disposal of radioactive wastes: Near field effects

    International Nuclear Information System (INIS)

    1985-01-01

    This report reviews the important near-field effects of the disposal of wastes in deep rock formations. The basic characteristics of waste form, container and package, buffer and backfill materials and potential host-rock types are discussed from the perspective of the performance requirements of the total repository system. Effects of waste emplacement on the separate system components and on the system as a whole are discussed. The effects include interactions between groundwater and brines and the other system components, thermal and thermo-mechanical effects, and chemical and geochemical reactions. Special consideration is given to the radiation field that exists in proximity to the waste containers and also to the coupled effects of different phenomena

  8. Near-field recording for small form factor optical disks

    Science.gov (United States)

    Kim, Jin-Hong

    2007-02-01

    Small form factor optical disk (SFFOD) with a diameter of 27.4mm was prepared for a mobile application. Near-field recording (NFR) technology with a flying optical head is applied to SFFOD for high density and small volume. A problem of contamination was observed at the head-disk interface(HDI) for first-surface recording. As a solution of the problem, a cover-layer was laminated onto the disk to move the focal plane into the media, which could solve the contamination problem. An edge bead free cover-layer could be coated with UVcurable resin by using an outer-ring technique during the spin coating process. A diamond-like carbon(DLC) film and a lubricant film were coated on the disk to reduce the HDI problems.

  9. Engineering two-wire optical antennas for near field enhancement

    Science.gov (United States)

    Yang, Zhong-Jian; Zhao, Qian; Xiao, Si; He, Jun

    2017-07-01

    We study the optimization of near field enhancement in the two-wire optical antenna system. By varying the nanowire sizes we obtain the optimized side-length (width and height) for the maximum field enhancement with a given gap size. The optimized side-length applies to a broadband range (λ = 650-1000 nm). The ratio of extinction cross section to field concentration size is found to be closely related to the field enhancement behavior. We also investigate two experimentally feasible cases which are antennas on glass substrate and mirror, and find that the optimized side-length also applies to these systems. It is also found that the optimized side-length shows a tendency of increasing with the gap size. Our results could find applications in field-enhanced spectroscopies.

  10. Numerical calculations of ultrasonic fields. 1: Transducer near fields

    Science.gov (United States)

    Johnson, J. A.

    1982-04-01

    A computer code for the calculation of linear acoustic wave propagation in homogeneous fluid and solid materials has been derived from the thermal hydraulics code STEALTH. The code uses finite difference techniques in a two dimensional mesh made up of arbitrarily shaped quadrilaterals. Problems with two dimensional plane strain or two dimensional axial symmetries can be solved. Free, fixed or stressed boundaries can be used. Transducers can be modeled by time dependent boundary conditions or by moving pistons. A brief description of the method is given and the results of the calculation of the near fields of circular flat and focused transducers are shown. These results agree with analytic theory along the axis of symmetry and with other codes that use a Huygens' reconstruction technique off axis.

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

    Science.gov (United States)

    Svetovoy, V. B.; Palasantzas, G.

    2014-09-01

    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 use graphene-on-silicon Schottky photovoltaic cells. One layer of graphene absorbs around 90% of incoming radiation and increases the heat transfer. This strong absorption is due to the excitation of plasmons in graphene, which are automatically tuned in resonance with the emitted light in the midinfrared range. The absorbed radiation excites electron-hole pairs in graphene, which are separated by the surface field induced by the Schottky barrier. For a quasimonochromatic source the generated power is one order of magnitude larger and the efficiency is on the same level as for semiconductor photovoltaic cells.

  12. Utilization of Near Field Communication Technology for Loyalty Management

    Directory of Open Access Journals (Sweden)

    Ferina Ferdianti

    2013-11-01

    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.

  13. Near-Field Ground Motion Modal versus Wave Propagation Analysis

    Directory of Open Access Journals (Sweden)

    Artur Cichowicz

    2010-01-01

    Full Text Available The response spectrum generally provides a good estimate of the global displacement and acceleration demand of far-field ground motion on a structure. However, it does not provide accurate information on the local shape or internal deformation of the response of the structure. Near-field pulse-like ground motion will propagate through the structure as waves, causing large, localized deformation. Therefore, the response spectrum alone is not a sufficient representation of near-field ground motion features. Results show that the drift-response technique based on a continuous shear-beam model has to be employed here to estimate structure-demand parameters when structure is exposed to the pulse like ground motion. Conduced modeling shows limited applicability of the drift spectrum based on the SDOF approximation. The SDOF drift spectrum approximation can only be applied to structures with smaller natural periods than the dominant period of the ground motion. For periods larger than the dominant period of ground motion the SDOF drift spectra model significantly underestimates maximum deformation. Strong pulse-type motions are observed in the near-source region of large earthquakes; however, there is a lack of waveforms collected from small earthquakes at very close distances that were recorded underground in mines. The results presented in this paper are relevant for structures with a height of a few meters, placed in an underground excavation. The strong ground motion sensors recorded mine-induced earthquakes in a deep gold mine, South Africa. The strongest monitored horizontal ground motion was caused by an event of magnitude 2 at a distance of 90 m with PGA 123 m/s2, causing drifts of 0.25%–0.35%. The weak underground motion has spectral characteristics similar to the strong ground motion observed on the earth's surface; the drift spectrum has a maximum value less than 0.02%.

  14. Terahertz plasmonic Bessel beamformer

    International Nuclear Information System (INIS)

    Monnai, Yasuaki; Shinoda, Hiroyuki; Jahn, David; Koch, Martin; Withayachumnankul, Withawat

    2015-01-01

    We experimentally demonstrate terahertz Bessel beamforming based on the concept of plasmonics. The proposed planar structure is made of concentric metallic grooves with a subwavelength spacing that couple to a point source to create tightly confined surface waves or spoof surface plasmon polaritons. Concentric scatterers periodically incorporated at a wavelength scale allow for launching the surface waves into free space to define a Bessel beam. The Bessel beam defined at 0.29 THz has been characterized through terahertz time-domain spectroscopy. This approach is capable of generating Bessel beams with planar structures as opposed to bulky axicon lenses and can be readily integrated with solid-state terahertz sources

  15. Synthetic aperture in terahertz in-line digital holography for resolution enhancement.

    Science.gov (United States)

    Huang, Haochong; Rong, Lu; Wang, Dayong; Li, Weihua; Deng, Qinghua; Li, Bin; Wang, Yunxin; Zhan, Zhiqiang; Wang, Xuemin; Wu, Weidong

    2016-01-20

    Terahertz digital holography is a combination of terahertz technology and digital holography. In digital holography, the imaging resolution is the key parameter in determining the detailed quality of a reconstructed wavefront. In this paper, the synthetic aperture method is used in terahertz digital holography and the in-line arrangement is built to perform the detection. The resolved capability of previous terahertz digital holographic systems restricts this technique to meet the requirement of practical detection. In contrast, the experimental resolved power of the present method can reach 125 μm, which is the best resolution of terahertz digital holography to date. Furthermore, the basic detection of a biological specimen is conducted to show the practical application. In all, the results of the proposed method demonstrate the enhancement of experimental imaging resolution and that the amplitude and phase distributions of the fine structure of samples can be reconstructed by using terahertz digital holography.

  16. 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.

  17. Nanoscale Terahertz Emission Spectroscopy

    DEFF Research Database (Denmark)

    Pedersen, Pernille Klarskov; Kim, Hyewon; Colvin, Vicki L.

    By utilizing plasmonic coupling to an AFM probe, we demonstrate Laser Terahertz Emission Nanoscopy (LTEN) with sub-20 nm resolution. We demonstrate the resolution by imaging a single gold nanorod on an InAs substrate....

  18. The potential of terahertz imaging for cancer diagnosis: A review of investigations to date.

    Science.gov (United States)

    Yu, Calvin; Fan, Shuting; Sun, Yiwen; Pickwell-Macpherson, Emma

    2012-03-01

    The terahertz region lies between the microwave and infrared regions of the electromagnetic spectrum such that it is strongly attenuated by water and very sensitive to water content. Terahertz radiation has very low photon energy and thus it does not pose any ionization hazard for biological tissues. Because of these characteristic properties, there has been an increasing interest in terahertz imaging and spectroscopy for biological applications within the last few years and more and more terahertz spectra are being reported, including spectroscopic studies of cancer. The presence of cancer often causes increased blood supply to affected tissues and a local increase in tissue water content may be observed: this acts as a natural contrast mechanism for terahertz imaging of cancer. Furthermore the structural changes that occur in affected tissues have also been shown to contribute to terahertz image contrast. This paper introduces terahertz technology and provides a short review of recent advances in terahertz imaging and spectroscopy techniques. In particular investigations relating to the potential of terahertz imaging and spectroscopy for cancer diagnosis will be highlighted.

  19. Spherical near-field scanning at the Technical University of Denmark

    DEFF Research Database (Denmark)

    Hansen, J. E.; Jensen, F.

    1988-01-01

    The early work (1969-79) on spherical near-field antenna measurements at the Technical University of Denmark (TUD) is outlined. A spherical near-field transmission formula is described and the first probe-corrected spherical near-field measurements are discussed. The TUD-ESA (European Space Agency...

  20. Excitation Of A Funnel-Shape Optical Near Field By The Laguarre-Gaussian Doughnut Beam

    OpenAIRE

    Iftiquar, S. M.; Ito, Haruhiko; Takamizawa, Akifumi; Ohtsu, Motoichi

    2003-01-01

    Optical near field has been generated by Laguarre-Gaussian doughnut beam on inner surface of "atom funnel". The resulting optical near field has been measured with the help of fiber probe and a consequent effect on cold atoms- released from MOT, has been estimated. Atoms with temperature less than 10 micro_kelvin can be reflected by the optical near field.

  1. TeraHertz imaging of hidden paint layers on canvas.

    Science.gov (United States)

    Adam, Aurèle J L; Planken, Paul C M; Meloni, Sabrina; Dik, Joris

    2009-03-02

    We show terahertz reflection images of hidden paint layers in a painting on canvas and compare the results with X-ray Radiography and In-frared Reflectography. Our terahertz measurements show strong reflections from both the canvas/paint interface and from the raw umber/lead white interface, indicating sufficient refractive-index contrast. Our results show that X-rays cannot be used to image through the lead white pigment which effectively blocks the X-rays. Although Infrared Reflectography is capable of vaguely observing the hidden paint strokes from the canvas side, we show that only terahertz imaging is capable of providing information on the thickness of the hidden paint layers. Terahertz imaging is thus shown to be a powerful imaging method for art historians, conservators and conservation scientists.

  2. Precision deposition of a nanofibre by near-field electrospinning

    International Nuclear Information System (INIS)

    Zheng Gaofeng; Li Wenwang; Wang Xiang; Wu Dezhi; Sun Daoheng; Lin Liwei

    2010-01-01

    The deposition behaviour of an individual nanofibre on planar and patterned silicon substrates is studied using near-field electrospinning (NFES). A high-speed camera was utilized to investigate the formation and motion process of a liquid jet. Thanks to the shorter distance from the spinneret to the collector, bending instability and splitting of the charged jet in electrospinning were overcome. In NFES, a straight-line jet between the spinneret and the collector can be utilized to direct-write an orderly nanofibre. Perturbation stemming from residual charges on the collector caused the oscillation of the charged jet, and the deposition of the non-woven nanofibre on the planar substrate. With increasing collector speed, the impact of residual charges was weakened by the strong drag force from the collector and a straight-line nanofibre could be obtained. In addition, the nanofibre can be direct-written in a special pattern by controlling the motion track of the collector. Therefore, it can be concluded that a micro-strip pattern was a good guidance for nanofibre deposition, and the nanofibre deposition track followed well along the top surface of the micro-strip pattern. The position-controlled deposition of a single nanofibre provides a new aspect for applications of electrospinning.

  3. Near-field tsunami edge waves and complex earthquake rupture

    Science.gov (United States)

    Geist, Eric L.

    2013-01-01

    The effect of distributed coseismic slip on progressive, near-field edge waves is examined for continental shelf tsunamis. Detailed observations of edge waves are difficult to separate from the other tsunami phases that are observed on tide gauge records. In this study, analytic methods are used to compute tsunami edge waves distributed over a finite number of modes and for uniformly sloping bathymetry. Coseismic displacements from static elastic theory are introduced as initial conditions in calculating the evolution of progressive edge-waves. Both simple crack representations (constant stress drop) and stochastic slip models (heterogeneous stress drop) are tested on a fault with geometry similar to that of the M w = 8.8 2010 Chile earthquake. Crack-like ruptures that are beneath or that span the shoreline result in similar longshore patterns of maximum edge-wave amplitude. Ruptures located farther offshore result in reduced edge-wave excitation, consistent with previous studies. Introduction of stress-drop heterogeneity by way of stochastic slip models results in significantly more variability in longshore edge-wave patterns compared to crack-like ruptures for the same offshore source position. In some cases, regions of high slip that are spatially distinct will yield sub-events, in terms of tsunami generation. Constructive interference of both non-trapped and trapped waves can yield significantly larger tsunamis than those that produced by simple earthquake characterizations.

  4. Superresolution near-field imaging with surface waves

    Science.gov (United States)

    Fu, Lei; Liu, Zhaolun; Schuster, Gerard

    2018-02-01

    We present the theory for near-field superresolution imaging with surface waves and time reverse mirrors (TRMs). Theoretical formulae and numerical results show that applying the TRM operation to surface waves in an elastic half-space can achieve superresolution imaging of subwavelength scatterers if they are located less than about 1/2 of the shear wavelength from the source line. We also show that the TRM operation for a single frequency is equivalent to natural migration, which uses the recorded data to approximate the Green's functions for migration, and only costs O(N4) algebraic operations for post-stack migration compared to O(N6) operations for natural pre-stack migration. Here, we assume the sources and receivers are on an N × N grid and there are N2 trial image points on the free surface. Our theoretical predictions of superresolution are validated with tests on synthetic data. The field-data tests suggest that hidden faults at the near surface can be detected with subwavelength imaging of surface waves by using the TRM operation if they are no deeper than about 1/2 the dominant shear wavelength.

  5. Near-field performance of the advanced cold process canister

    International Nuclear Information System (INIS)

    Werme, L.

    1991-12-01

    A near-field performance evaluation of an advanced cold process canister for spent fuel disposal has been performed jointly by TVO, Finland and SKB, Sweden. The canister consists of a steel canister as a load bearing element, with an outer corrosion shield of copper. In the analysis, as well internal (ie corrosion processes from the inside of the canister) as external processes (mechanical and chemical) have been considered both prior to and after canister breach. The major conclusions for the evaluation are: Internal processes cannot cause the canister breach under foreseen conditions, ie local-iced corrosion for the steel or copper canisters can be dismissed as a failure mechanism; The evaluation of the effects of processed outside the canister indicate that there is no rapid mechanism to endanger the integrity of the canister. Consequently the service life of the canister will be several million years. For completeness also evaluation of post-failure behaviour was carried out. Analyses were focussed on low probability phenomena from faults in canisters. Some items were identified where further research is justified in order to increase knowledge of the phenomena and thus strengthen the confidence of safety margins. However, it can be concluded that the risks of these scenarios can be judged to be acceptable. This is due to the fact that firstly, the probability of occurrence of most of these scenarios can be controlled to a large extent through technical measures. Secondly, these analyses indicated that the consequences would not be severe

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

    International Nuclear Information System (INIS)

    Leikanger, Tore; Häkkinen, Juha; Schuss, Christian

    2017-01-01

    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. (paper)

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

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

    Science.gov (United States)

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

    2014-01-01

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

  9. 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.

  10. 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.

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

    Directory of Open Access Journals (Sweden)

    Bihong Zhan

    2017-06-01

    Full Text Available 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.

  12. 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.

  13. Superresolution Near-field Imaging with Surface Waves

    KAUST Repository

    Fu, Lei

    2017-10-21

    We present the theory for near-field superresolution imaging with surface waves and time reverse mirrors (TRMs). Theoretical formulas and numerical results show that applying the TRM operation to surface waves in an elastic half-space can achieve superresolution imaging of subwavelength scatterers if they are located less than about 1/2 of the shear wavelength from the source line. We also show that the TRM operation for a single frequency is equivalent to natural migration, which uses the recorded data to approximate the Green’s functions for migration, and only costs O(N4) algebraic operations for poststack migration compared to O(N6) operations for natural prestack migration. Here, we assume the sources and receivers are on an N × N grid and there are N2 trial image points on the free surface. Our theoretical predictions of superresolution are validated with tests on synthetic data. The field-data tests suggest that hidden faults at the near surface can be detected with subwavelength imaging of surface waves by using the TRM operation if they are no deeper than about 1/2 the dominant shear wavelength.

  14. Enhancing usability using Near Field Communication for mobile application

    Directory of Open Access Journals (Sweden)

    Wihidayat Endar

    2018-01-01

    Full Text Available Near Field Communication (NFC as relatively new wireless communication technology pushes new challenges to application developers to make their applications easier to use and simpler to operate. This point of view known as usability element. Usability is one of the elements for creating good quality applications. This study aims to analyse the usability of mobile-based application embeds with NFC. We also try to evaluate usability in applications used by children. We developed an application called Receptionist which has a primary function as a communication tool between students, teachers and parents at a middle school. To know the impact of the NFC, the Receptionist input system is designed with two methods, via conventional navigation (using buttons and via NFC. To understand the usability of each method, we do user testing and questioners on students. The results show, using the NFC there is a significant increase in usability attributes: efficiency, effectiveness, and learnability. On the other hand, there is decreases of user satisfaction comparing to conventional method. In general, this study demonstrates the potential of new input device technologies that can improve the usability of mobile-based applications.

  15. Terahertz imaging of subjects with concealed weapons

    Science.gov (United States)

    Dickinson, Jason C.; Goyette, Thomas M.; Gatesman, Andrew J.; Joseph, Cecil S.; Root, Zachary G.; Giles, Robert H.; Waldman, Jerry; Nixon, William E.

    2006-05-01

    In response to the growing interest in developing terahertz imaging systems for concealed weapons detection, the Submillimeter-Wave Technology Laboratory (STL) at the University of Massachusetts Lowell has produced full-body terahertz imagery using coherent active radar measurement techniques. The proof-of-principle results were readily obtained utilizing the compact radar range resources at STL. Two contrasting techniques were used to collect the imagery. Both methods made use of in-house transceivers, consisting of two ultra-stable far-infrared lasers, terahertz heterodyne detection systems, and terahertz anechoic chambers. The first technique involved full beam subject illumination with precision azimuth and elevation control to produce high resolution images via two axis Fourier transforms. Imagery collected in this manner is presented at 1.56THz and 350GHz. The second method utilized a focused spot, moved across the target subject in a high speed two dimensional raster pattern created by a large two-axis positioning mirror. The existing 1.56THz compact radar range was modified to project a focused illumination spot on the target subject several meters away, and receive the back-reflected intensity. The process was repeated across two dimensions, and the resultant image was assembled and displayed utilizing minimal on-the-fly processing. Imagery at 1.56THz of human subjects with concealed weapons are presented and discussed for this scan type.

  16. Calculation of near-field concentrations of hydrogen sulphide

    International Nuclear Information System (INIS)

    Baynes, C.J.

    1985-03-01

    This report provides simulations of the near-field dispersion in the atmosphere of postulated releases of hydrogen sulphide gas (H2S) at a heavy water plant. The size and extent of the flammable or detonable gas clouds which might result are estimated. This work was undertaken to support experimental studies of the detonability of H2S releases. Thirty-six different cases were simulated involving the catastrophic failure of a liquid H2S storage tank or tank car of H2S. The major variables were the size of the release, the initial mixing ratio of gas with ambient air, and the wind speed. Since the gas/air mixture is initially heavier than air, an existing heavy gas mathematical model (DENZ) was used for these simulations. The model was modified to provide the outputs needed to support the experimental studies. The outputs were the mass of H2S in the cloud, the mass and volume of the cloud, its radius at ground level and its temperature, all as functions of distance and time from release. The edge of the cloud was defined by a given concentration of H2S in air. The simulations were repeated for ten different values of this parameter, ranging between 3% and 40% H2S by volume. Simulations were also performed using a simple 'top-hat' mixing model to predict the length of the flammable or detonable jet formed at the break in a pipe carrying H2S vapour under pressure. The analysis was conducted for four postulated pipe break diameters and repeated for the same ten concentration levels used in the storage tank studies. The report presents a summary of the results. The complete outputs from the 36 storage tank failure simulations are available on floppy disks in a format suitable for detailed examination using any IBM-PC compatible microcomputer system

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

    International Nuclear Information System (INIS)

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

    1996-12-01

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

  18. Optical Near-field Interactions and Forces for Optoelectronic Devices

    Science.gov (United States)

    Kohoutek, John Michael

    Throughout history, as a particle view of the universe began to take shape, scientists began to realize that these particles were attracted to each other and hence came up with theories, both analytical and empirical in nature, to explain their interaction. The interaction pair potential (empirical) and electromagnetics (analytical) theories, both help to explain not only the interaction between the basic constituents of matter, such as atoms and molecules, but also between macroscopic objects, such as two surfaces in close proximity. The electrostatic force, optical force, and Casimir force can be categorized as such forces. A surface plasmon (SP) is a collective motion of electrons generated by light at the interface between two mediums of opposite signs of dielectric susceptibility (e.g. metal and dielectric). Recently, surface plasmon resonance (SPR) has been exploited in many areas through the use of tiny antennas that work on similar principles as radio frequency (RF) antennas in optoelectronic devices. These antennas can produce a very high gradient in the electric field thereby leading to an optical force, similar in concept to the surface forces discussed above. The Atomic Force Microscope (AFM) was introduced in the 1980s at IBM. Here we report on its uses in measuring these aforementioned forces and fields, as well as actively modulating and manipulating multiple optoelectronic devices. We have shown that it is possible to change the far field radiation pattern of an optical antenna-integrated device through modification of the near-field of the device. This modification is possible through change of the local refractive index or reflectivity of the "hot spot" of the device, either mechanically or optically. Finally, we have shown how a mechanically active device can be used to detect light with high gain and low noise at room temperature. It is the aim of several of these integrated and future devices to be used for applications in molecular sensing

  19. Detection of internal fields in double-metal terahertz resonators

    DEFF Research Database (Denmark)

    Mitrofanov, Oleg; Han, Zhanghua; Ding, Fei

    2017-01-01

    Terahertz (THz) double-metal plasmonic resonators enable enhanced light-matter coupling by exploiting strong field confinement. The double-metal design however restricts access to the internal fields. We propose and demonstrate a method for spatial mapping and spectroscopic analysis of the internal...... electromagnetic fields in double-metal plasmonic resonators. We use the concept of image charges and aperture-type scanning near-field THz time-domain microscopy to probe the fields confined within the closed resonator. The experimental method opens doors to studies of light-matter coupling in deeply sub...

  20. Near field scanning optical microscopy of polycrystalline semiconductors

    Science.gov (United States)

    Herndon, Mary Kay

    1999-09-01

    Photovoltaic devices are commonly used for space applications and remote terrestrial power requirements. Polycrystalline solar cell devices often have much lower efficiencies than their crystalline counterparts, but because they can be fabricated much more cheaply, they can still be cost-effective when compared to single crystal devices. The long term goal of this work is to provide information that will lead to higher quality devices with improved cost efficiency. In order to do this, a better understanding of the mechanisms that take place in these materials is needed. The goal of this thesis was to improve our understanding of these devices by adapting a novel characterization technique, Near Field Scanning Optical Microscopy (NSOM), to the study of polycrystalline films. Visible light NSOM is a relatively new technique that allows for optical characterization of materials with resolution beyond the far-field diffraction limit. By using NSOM to study the physical and electrical properties of polycrystalline solar cells, individual grains can be studied and more insight can be gained as to how various properties of the thin films affect the device efficiency. For this research, an NSOM was designed and built to be versatile enough to handle the sorts of samples and measurements required for studying a variety of photovoltaic devices. As a first step, the NSOM was used to characterize single crystal GaAs solar cell devices. Measurements of topography and NSOM-induced photocurrent were obtained simultaneously on cross sections of the material, allowing the p-n junction to be probed. Because the NSOM data could be compared to an expected result, this allowed verification of the new microscope's imaging capabilities and ensured accurate data interpretation. Effects of surface recombination were detected on the cleaved edges. The NSOM was used to characterize surface quality and study the effects of surface passivation treatments. Of the polycrystalline materials

  1. Terahertz radiation mixer

    Science.gov (United States)

    Wanke, Michael C [Albuquerque, NM; Allen, S James [Santa Barbara, CA; Lee, Mark [Albuquerque, NM

    2008-05-20

    A terahertz radiation mixer comprises a heterodyned field-effect transistor (FET) having a high electron mobility heterostructure that provides a gatable two-dimensional electron gas in the channel region of the FET. The mixer can operate in either a broadband pinch-off mode or a narrowband resonant plasmon mode by changing a grating gate bias of the FET. The mixer can beat an RF signal frequency against a local oscillator frequency to generate an intermediate frequency difference signal in the microwave region. The mixer can have a low local oscillator power requirement and a large intermediate frequency bandwidth. The terahertz radiation mixer is particularly useful for terahertz applications requiring high resolution.

  2. Near-field scanning microwave microscopy and its applications in characterization of dielectric materials

    Science.gov (United States)

    Zhang, Qinxin

    Dielectric properties of materials are related to their microstructure, defects and compositional variations. Traditional impedance measurement of dielectric properties is an average performed on the length scale of the microwave wavelength, which is not sensitive to local structure and compositional variations. The nondestructive mapping technique of near-field scanning microwave microscopy (SMM) has been shown to be an effective technique for investigating the local dielectric properties variation. The development of near-field SMM and its application in characterization of dielectric ceramics are presented in this work. The local surface dielectric properties of a variety of bulk specimens were characterized with SMM, while their microstructures were characterized with backscattered electron scanning electron microscopy (SEM) and polarized optical microscopy. The compositions and phases were identified by energy dispersive spectroscopy (EDS) analysis and X-ray powder diffraction (XRD). The local dielectric properties variations causing the contrast in SMM images were correlated to the local microstructures and chemical variations, such as defects, nonstoichiometric compositions, solid-solution, phase separations, and so on. SMM characterization has been used to detect defects in single crystals, such as twinning structure in a LaAlO3 single crystal; to present topographic and grain boundary effects in bulk polycrystalline yttria stabilized zirconia (YSZ); to differentiate chemical variations, such as oxygen-deficient "cored" titania crystal, and Zn/Co varied BZCN312 matrices; to characterize inhomogeneities of dielectric properties in a co-fired CMT30/CMT40 ceramic; to discover a new phase with unknown dielectric properties, such as BZCN816 phase in BZCN312 matrices; to investigate stabilized components, such as La 2/3TiO3 phase stabilized by LaAlO3 phase; to study solid solution, such as LT3-LAO solid solution and LAO-STO solid solution; to study phase

  3. Tunable terahertz radiation source

    Science.gov (United States)

    Boulaevskii, Lev; Feldmann, David M; Jia, Quanxi; Koshelev, Alexei; Moody, Nathan A

    2014-01-21

    Terahertz radiation source and method of producing terahertz radiation, said source comprising a junction stack, said junction stack comprising a crystalline material comprising a plurality of self-synchronized intrinsic Josephson junctions; an electrically conductive material in contact with two opposing sides of said crystalline material; and a substrate layer disposed upon at least a portion of both the crystalline material and the electrically-conductive material, wherein the crystalline material has a c-axis which is parallel to the substrate layer, and wherein the source emits at least 1 mW of power.

  4. Terahertz spectroscopy of plasmonic fractals.

    Science.gov (United States)

    Agrawal, A; Matsui, T; Zhu, W; Nahata, A; Vardeny, Z V

    2009-03-20

    We use terahertz time-domain spectroscopy to study the transmission properties of metallic films perforated with aperture arrays having deterministic or stochastic fractal morphologies ("plasmonic fractals"), and compare them with random aperture arrays. All of the measured plasmonic fractals show transmission resonances and antiresonances at frequencies that correspond to prominent features in their structure factors in k space. However, in sharp contrast to periodic aperture arrays, the resonant transmission enhancement decreases with increasing array size. This property is explained using a density-density correlation function, and is utilized for determining the underlying fractal dimensionality, D(fractals relative to the transmission of the corresponding random aperture arrays is obtained, and is shown to be universal.

  5. 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.

  6. Terahertz-frequency dielectric response of liquids

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd; Møller, Uffe; Cooke, David

    The dielectric response of liquids spans many decades in frequency. The dielectric response of a polar liquid is typically determined by relaxational dynamics of the dipolar moments of the liquid. In contrast, the dielectric response of a nonpolar liquid is determined by much weaker collision-ind...... function of liquids at terahertz frequencies. We will review the current understanding of the high-frequency dielectric spectrum of water, and discuss the relation between the dielectric spectrum and the thermodynamic properties of certain aqueous solutions.......The dielectric response of liquids spans many decades in frequency. The dielectric response of a polar liquid is typically determined by relaxational dynamics of the dipolar moments of the liquid. In contrast, the dielectric response of a nonpolar liquid is determined by much weaker collision......-induced dipole moments. In the polar liquid water the fastest relaxational dynamics is found at terahertz frequencies, just below the first intermolecular vibrational and librational modes. In this presentation we will discuss optical terahertz spectroscopic techniques for measurement of the full dielectric...

  7. High Reliability Oscillators for Terahertz Systems Project

    Data.gov (United States)

    National Aeronautics and Space Administration — Terahertz sources based on lower frequency oscillators and amplifiers plus a chain of frequency multipliers are the workhorse technology for NASA's terahertz...

  8. 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...

  9. Terahertz radiography of hazardous substances without radiation hazard; Terahertz-Radiographie riskanter Substanzen ohne Strahlengefaehrdung

    Energy Technology Data Exchange (ETDEWEB)

    Kupsch, A.; Beckmann, J.; Ewert, U.; Hentschel, M.P.; Lange, A. [Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin (Germany)

    2007-07-01

    A femto seconds laser pumped time-resolving terahertz spectrometer opens up completely new options in the radiographic testing of objects of unknown composition or with unknown internals. There is a wide range of applications that will improve safety and availability of the technological and staff infrastructure, from dielectric characterisation of nonmetals to the detection of the internals of nonconventional blasting and incendiary compositions. With scanning rates of currently 10 Hz and a local resolution of up to 0.3 mm, transmission radiographs with high spectral resolution can be generated in the frequency range of 0.1 - 2.2 THz. This makes it possible to distinguish between different materials, e.g. explosives, polymer composites, ceramics, and nonmetal powders. The terahertz images can be generated even through packagings. For a demonstration of the novel radiographic technique, THz topographs, e.g. for a mockup letter bomb, are discussed and compared with conventional soft X-ray radiographs. As the terahertz are not harmful physiologically, in contrast to X-rays, the are now being used by way of trial for security checks in airports. In view of the increasing technological importance of polymers and mineral materials, the use of terahertz spectroscopic imaging in non-destructive testing and characterisation is explored here. (orig.)

  10. Compensation for the phase-type spatial periodic modulation of the near-field beam at 1053 nm

    Science.gov (United States)

    Gao, Yaru; Liu, Dean; Yang, Aihua; Tang, Ruyu; Zhu, Jianqiang

    2017-10-01

    A phase-only spatial light modulator is used to provide and compensate for the spatial periodic modulation (SPM) of the near-field beam at the near infrared at 1053nm wavelength with an improved iterative weight-based method. The transmission characteristics of the incident beam has been changed by a spatial light modulator (SLM) to shape the spatial intensity of the output beam. The propagation and reverse propagation of the light in free space are two important processes in the iterative process. The based theory is the beam angular spectrum transmit formula (ASTF) and the principle of the iterative weight-based method. We have made two improvements to the originally proposed iterative weight-based method. We select the appropriate parameter by choosing the minimum value of the output beam contrast degree and use the MATLAB built-in angle function to acquire the corresponding phase of the light wave function. The required phase that compensates for the intensity distribution of the incident SPM beam is iterated by this algorithm, which can decrease the magnitude of the SPM of the intensity on the observation plane. The experimental results show that the phase-type SPM of the near-field beam is subject to a certain restriction. We have also analyzed some factors that make the results imperfect. The experiment results verifies the possible applicability of this iterative weight-based method to compensate for the SPM of the near-field beam.

  11. Terahertz Radome Inspection

    Directory of Open Access Journals (Sweden)

    Fabian Friederich

    2018-01-01

    Full Text Available Radomes protecting sensitive radar, navigational, and communications equipment of, e.g., aircraft, are strongly exposed to the environment and have to withstand harsh weather conditions and potential impacts. Besides their significance to the structural integrity of the radomes, it is often crucial to optimize the composite structures for best possible radio performance. Hence, there exists a significant interest in non-destructive testing techniques, which can be used for defect inspection of radomes in field use as well as for quality inspection during the manufacturing process. Contactless millimeter-wave and terahertz imaging techniques provide millimeter resolution and have the potential to address both application scenarios. We report on our development of a three-dimensional (3D terahertz imaging system for radome inspection during industrial manufacturing processes. The system was designed for operation within a machining center for radome manufacturing. It simultaneously gathers terahertz depth information in adjacent frequency ranges, from 70 to 110 GHz and from 110 to 170 GHz by combining two frequency modulated continuous-wave terahertz sensing units into a single measurement device. Results from spiraliform image acquisition of a radome test sample demonstrate the successful integration of the measurement system.

  12. Bridging the terahertz gap

    International Nuclear Information System (INIS)

    Davies, Giles; Linfield, Edmund

    2004-01-01

    Over the last century or so, physicists and engineers have progressively explored and conquered the electromagnetic spectrum. Starting with visible light, we have encroached outwards, developing techniques for generating and detecting radiation at both higher and lower frequencies. And as each successive region of the spectrum has been colonized, we have developed technology to exploit the radiation found there. X-rays, for example, are routinely used to image hidden objects. Near-infrared radiation is used in fibre-optic communications and in compact-disc players, while microwaves are used to transmit signals from your mobile phone. But there is one part of the electromagnetic spectrum that has steadfastly resisted our advances. This is the terahertz region, which ranges from frequencies of about 300 GHz to 10 THz (10 x 10 sup 1 sup 2 Hz). This corresponds to wavelengths of between about 1 and 0.03 mm, and lies between the microwave and infrared regions of the spectrum. However, the difficulties involved in making suitably compact terahertz sources and detectors has meant that this region of the spectrum has only begun to be explored thoroughly over the last decade. A particularly intriguing feature of terahertz radiation is that the semiconductor devices that generate radiation at frequencies above and below this range operate in completely different ways. At lower frequencies, microwaves and millimetre- waves can be generated by 'electronic' devices such as those found in mobile phones. At higher frequencies, near-infrared and visible light are generated by 'optical' devices such as semiconductor laser diodes, in which electrons emit light when they jump across the semiconductor band gap. Unfortunately, neither electronic nor optical devices can conveniently be made to work in the terahertz region because the terahertz frequency range sits between the electronic and optical regions of the electromagnetic spectrum. Developing a terahertz source is therefore a

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

    International Nuclear Information System (INIS)

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

    1996-01-01

    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

  14. Near-field optical microscope using a silicon-nitride probe

    NARCIS (Netherlands)

    van Hulst, N.F.; Moers, M.H.P.; Moers, M.H.P.; Noordman, O.F.J.; Noordman, O.F.J.; Tack, R.G.; Segerink, Franciscus B.; Bölger, B.; Bölger, B.

    1993-01-01

    Operation of an alternative near-field optical microscope is presented. The microscope uses a microfabricated silicon- nitride probe with integrated cantilever, as originally developed for force microscopy. The cantilever allows routine close contact near-field imaging o­n arbitrary surfaces without

  15. 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 c...

  16. 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

  17. 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.

  18. A line array based near field imaging technique for characterising acoustical properties of elongated targets

    NARCIS (Netherlands)

    Driessen, F.P.G.

    1995-01-01

    With near field imaging techniques the acoustical pressure waves at distances other than the recorded can be calculated. Normally, acquisition on a two dimensional plane is necessary and extrapolation is performed by a Rayleigh integral. A near field single line instead of two dimensional plane

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

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren; Jacobsen, Finn

    2011-01-01

    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...

  20. Observation of multilayer graphene sheets using terahertz phase ...

    Indian Academy of Sciences (India)

    2016-12-02

    Dec 2, 2016 ... DOI 10.1007/s12043-016-1308-5. Observation of multilayer graphene sheets using terahertz phase contrast microscopy. ZHIKUN LIU, YANAN XIE. ∗. , LI GENG, DENGKE PAN and PAN SONG. School of Communication and Information Engineering, Key Laboratory of Specialty Fibre Optics and Optical.

  1. Observation of multilayer graphene sheets using terahertz phase ...

    Indian Academy of Sciences (India)

    Based on this fact, a simple route is presented for identifying the single or few layers of graphene sheets by using terahertz phase contrast microscopy (TPCM). ... School of Communication and Information Engineering, Key Laboratory of Specialty Fibre Optics and Optical Access Networks, Shanghai University, Shanghai ...

  2. Recent advances in terahertz technology for biomedical applications.

    Science.gov (United States)

    Sun, Qiushuo; He, Yuezhi; Liu, Kai; Fan, Shuting; Parrott, Edward P J; Pickwell-MacPherson, Emma

    2017-06-01

    Terahertz instrumentation has improved significantly in recent years such that THz imaging systems have become more affordable and easier to use. THz systems can now be operated by non-THz experts greatly facilitating research into many potential applications. Due to the non-ionising nature of THz light and its high sensitivity to soft tissues, there is an increasing interest in biomedical applications including both in vivo and ex vivo studies. Additionally, research continues into understanding the origin of contrast and how to interpret terahertz biomedical images. This short review highlights some of the recent work in these areas and suggests some future research directions.

  3. Terahertz spectroscopic investigation of human gastric normal and tumor tissues.

    Science.gov (United States)

    Hou, Dibo; Li, Xian; Cai, Jinhui; Ma, Yehao; Kang, Xusheng; Huang, Pingjie; Zhang, Guangxin

    2014-09-21

    Human dehydrated normal and cancerous gastric tissues were measured using transmission time-domain terahertz spectroscopy. Based on the obtained terahertz absorption spectra, the contrasts between the two kinds of tissue were investigated and techniques for automatic identification of cancerous tissue were studied. Distinctive differences were demonstrated in both the shape and amplitude of the absorption spectra between normal and tumor tissue. Additionally, some spectral features in the range of 0.2~0.5 THz and 1~1.5 THz were revealed for all cancerous gastric tissues. To systematically achieve the identification of gastric cancer, principal component analysis combined with t-test was used to extract valuable information indicating the best distinction between the two types. Two clustering approaches, K-means and support vector machine (SVM), were then performed to classify the processed terahertz data into normal and cancerous groups. SVM presented a satisfactory result with less false classification cases. The results of this study implicate the potential of the terahertz technique to detect gastric cancer. The applied data analysis methodology provides a suggestion for automatic discrimination of terahertz spectra in other applications.

  4. An Entropy-Based Propagation Speed Estimation Method for Near-Field Subsurface Radar Imaging

    Directory of Open Access Journals (Sweden)

    Pistorius Stephen

    2010-01-01

    Full Text Available During the last forty years, Subsurface Radar (SR has been used in an increasing number of noninvasive/nondestructive imaging applications, ranging from landmine detection to breast imaging. To properly assess the dimensions and locations of the targets within the scan area, SR data sets have to be reconstructed. This process usually requires the knowledge of the propagation speed in the medium, which is usually obtained by performing an offline measurement from a representative sample of the materials that form the scan region. Nevertheless, in some novel near-field SR scenarios, such as Microwave Wood Inspection (MWI and Breast Microwave Radar (BMR, the extraction of a representative sample is not an option due to the noninvasive requirements of the application. A novel technique to determine the propagation speed of the medium based on the use of an information theory metric is proposed in this paper. The proposed method uses the Shannon entropy of the reconstructed images as the focal quality metric to generate an estimate of the propagation speed in a given scan region. The performance of the proposed algorithm was assessed using data sets collected from experimental setups that mimic the dielectric contrast found in BMI and MWI scenarios. The proposed method yielded accurate results and exhibited an execution time in the order of seconds.

  5. An Entropy-Based Propagation Speed Estimation Method for Near-Field Subsurface Radar Imaging

    Science.gov (United States)

    Flores-Tapia, Daniel; Pistorius, Stephen

    2010-12-01

    During the last forty years, Subsurface Radar (SR) has been used in an increasing number of noninvasive/nondestructive imaging applications, ranging from landmine detection to breast imaging. To properly assess the dimensions and locations of the targets within the scan area, SR data sets have to be reconstructed. This process usually requires the knowledge of the propagation speed in the medium, which is usually obtained by performing an offline measurement from a representative sample of the materials that form the scan region. Nevertheless, in some novel near-field SR scenarios, such as Microwave Wood Inspection (MWI) and Breast Microwave Radar (BMR), the extraction of a representative sample is not an option due to the noninvasive requirements of the application. A novel technique to determine the propagation speed of the medium based on the use of an information theory metric is proposed in this paper. The proposed method uses the Shannon entropy of the reconstructed images as the focal quality metric to generate an estimate of the propagation speed in a given scan region. The performance of the proposed algorithm was assessed using data sets collected from experimental setups that mimic the dielectric contrast found in BMI and MWI scenarios. The proposed method yielded accurate results and exhibited an execution time in the order of seconds.

  6. Intense terahertz excitation of semiconductors

    CERN Document Server

    Ganichev, S D

    2006-01-01

    This work presents the first comprehensive treatment of high-power terahertz applications to semiconductors and low-dimensional semiconductor structures. Terahertz properties of semiconductors are in the centre of scientific activities because of the need of high-speed electronics.

  7. Superconductor terahertz metamaterial

    OpenAIRE

    Gu, Jianqiang; Singh, Ranjan; Tian, Zhen; Cao, Wei; Xing, Qirong; Han, Jiaguang; Zhang, Weili

    2010-01-01

    We characterize the behaviour of split ring resonators made up of high-transition temperature YBCO superconductor using terahertz time domain spectroscopy. The superconductor metamaterial shows sharp change in the transmission spectrum at the fundamental inductive-capacitive resonance and the dipole resonance as the temperature dips below the transition temperature. Our results reveal that the high performance of such a metamaterial is limited by material imperfections and defects such as cra...

  8. 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.

  9. Imaging of phase change materials below a capping layer using correlative infrared near-field microscopy and electron microscopy

    Science.gov (United States)

    Lewin, M.; Hauer, B.; Bornhöfft, M.; Jung, L.; Benke, J.; Michel, A.-K. U.; Mayer, J.; Wuttig, M.; Taubner, T.

    2015-10-01

    Phase Change Materials (PCM) show two stable states in the solid phase with significantly different optical and electronic properties. They can be switched reversibly between those two states and are promising candidates for future non-volatile memory applications. The development of phase change devices demands characterization tools, yielding information about the switching process at high spatial resolution. Scattering-type Scanning Near-field Optical Microscopy (s-SNOM) allows for spectroscopic analyses of the different optical properties of the PCMs on the nm-scale. By correlating the optical s-SNOM images with transmission electron microscopy images of the same sample, we unambiguously demonstrate the correlation of the infrared optical contrast with the structural state of the phase change material. The investigated sample consists of sandwiched amorphous and crystalline regions of Ag 4 In 3 Sb 67 Te 26 below a 100 nm thick ( ZnS ) 80 - ( SiO2 ) 20 capping layer. Our results demonstrate the sensitivity of s-SNOM to small dielectric near-field contrasts even below a comparably thick capping layer ( 100 nm ).

  10. Performance analysis of near-field thermophotovoltaic devices considering absorption distribution

    International Nuclear Information System (INIS)

    Park, K.; Basu, S.; King, W.P.; Zhang, Z.M.

    2008-01-01

    This paper elucidates the energy transfer and conversion processes in near-field thermophotovoltaic (TPV) systems, considering local radiation absorption and photocurrent generation in the TPV cell. Radiation heat transfer in a multilayered structure is modeled using the fluctuation-dissipation theorem, and the electric current generation is evaluated based on the photogeneration and recombination of electron-hole pairs in different regions of the TPV cell. The effects of near-field radiation on the photon penetration depth, photocurrent generation, and quantum efficiency are examined in the spectral region of interest. The detailed analysis performed in the present work demonstrates that, while the near-field operation can enhance the power throughput, the conversion efficiency is not much improved and may even be reduced. Subsequently, a modified design of near-field TPV systems is proposed to improve the efficiency

  11. 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.

  12. 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.

  13. Near-Field Performance Evaluations of Alex Effect in Metallised Explosives

    National Research Council Canada - National Science Library

    Lu, Jing

    2003-01-01

    .... To characterise Alex, and evaluate its influence upon near-field performance of explosive formulations, a series of velocity of detonation measurements and plate dent depth tests (detonation pressure...

  14. 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...

  15. 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.

  16. Effects of a power and photon energy of incident light on near-field etching properties

    Science.gov (United States)

    Yatsui, T.; Saito, H.; Nishioka, K.; Leuschel, B.; Soppera, O.; Nobusada, K.

    2017-12-01

    We developed a near-field etching technique for realizing an ultra-flat surfaces of various materials and structures. To elucidate the near-field etching properties, we have investigated the effects of power and the photon energy of the incident light. First, we established theoretically that an optical near-field with photon energy lower than the absorption edge of the molecules can induce molecular vibrations. We used nanodiamonds to study the power dependence of the near-field etching properties. From the topological changes of the nanodiamonds, we confirmed the linear-dependence of the etching volume with the incident power. Furthermore, we studied the photon energy dependence using TiO2 nanostriped structures, which revealed that a lower photon energy results in a lower etching rate.

  17. Investigation of lasers based on coupled waveguides by near-field scanning optical microscopy

    Science.gov (United States)

    Polubavkina, Yu S.; Gordeev, N. Yu; Payusov, A. S.; Kryzhanovskaya, N. V.; Moiseev, E. I.; Zubov, F. I.; Mintairov, S. A.; Kalyuzhnyy, N. A.; Kulagina, M. M.; Shernyakov, Yu M.; Maximov, M. V.; Zhukov, A. E.

    2017-11-01

    We have investigated near field intensity distributions of InGaAs/GaAs/AlGaAs lasers possessing broadened waveguides based on coupled large optical cavity structures (CLOC) by scanning near-field optical microscopy (SNOM). The concept allows effective suppressing of the transverse high-order mode lasing. The obtained results can be considered to be the direct proof of pure transverse single-mode emission of the CLOC lasers.

  18. Near-field marking of gold nanostars by ultrashort pulsed laser irradiation: experiment and simulations

    Science.gov (United States)

    Møller, Søren H.; Vester-Petersen, Joakim; Nazir, Adnan; Eriksen, Emil H.; Julsgaard, Brian; Madsen, Søren P.; Balling, Peter

    2018-02-01

    Quantitative measurements of the electric near-field distribution of star-shaped gold nanoparticles have been performed by femtosecond laser ablation. Measurements were carried out on and off the plasmon resonance. A detailed comparison with numerical simulations of the electric fields is presented. Semi-quantitative agreement is found, with slight systematic differences between experimentally observed and simulated near-field patterns close to strong electric-field gradients. The deviations are attributed to carrier transport preceding ablation.

  19. 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.

  20. 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.

  1. 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....

  2. A MEMS Device Capable of Measuring Near-Field Thermal Radiation between Membranes

    OpenAIRE

    Changyu Sun; Jun Yu; Chong Feng; Zhenan Tang

    2013-01-01

    For sensors constructed by freestanding membranes, when the gap between a freestanding membrane and the substrate or between membranes is at micron scale, the effects of near-field radiative heat transfer on the sensors' thermal performance should be considered during sensor design. The radiative heat flux is transferred from a membrane to a plane or from a membrane to a membrane. In the current study of the near-field thermal radiation, the scanning probe technology has difficulty in making ...

  3. 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....

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

    OpenAIRE

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

    2001-01-01

    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 analy...

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

    Science.gov (United States)

    Malyuskin, Oleksandr; Fusco, Vincent

    2017-12-01

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

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

    International Nuclear Information System (INIS)

    Arcos, David; Grandia, Fidel; Domenech, Cristina

    2006-09-01

    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

  7. Evaluation of human hairs with terahertz wave

    Science.gov (United States)

    Serita, Kazunori; Murakami, Hironaru; Kawayama, Iwao; Takahashi, Yoshinori; Yoshimura, Masashi; Mori, Yusuke; Tonouchi, Masayoshi

    2014-03-01

    Single human hairs using a scanning laser terahertz (THz) imaging system are evaluated. The system features near-field THz emission and far-field THz detection. A sample is set in the vicinity of a two-dimensional THz emitter, and an excitation laser beam is scanned over the emitter via a galvanometer. By detecting the transmitted THz wave pulses that are locally generated at the irradiation spots of the excitation laser, we can obtain the THz transmission image and the spectrum of the sample with imaging time of 47 s for 512×512 pixels and maximum resolution of ˜27 μm. Using the system, we succeeded in observing the specific features of single human hairs in both the THz transmittance spectra and transmission images; it was found that the THz transmittance spectrum of gray hair shows a tendency of increase while that of black hair shows a decrease with increasing frequency above 1.2 THz. We could also observe the change of the moisture retention in the hair, and it is found that cuticles play one of the important roles in keeping moisture inside the hair. Those obtained data indicate that our system can be useful for evaluating single human hairs and those kinds of microscale samples.

  8. Nano metamaterials for ultrasensitive Terahertz biosensing.

    Science.gov (United States)

    Lee, Dong-Kyu; Kang, Ji-Hun; Kwon, Junghoon; Lee, Jun-Seok; Lee, Seok; Woo, Deok Ha; Kim, Jae Hun; Song, Chang-Seon; Park, Q-Han; Seo, Minah

    2017-08-15

    As a candidate for a rapid detection of biomaterials, terahertz (THz) spectroscopy system can be considered with some advantage in non-destructive, label-free, and non-contact manner. Because protein-ligand binding energy is in the THz range, especially, most important conformational information in molecular interactions can be captured by THz electromagnetic wave. Based on the THz time-domain spectroscopy system, THz nano-metamaterial sensing chips were prepared for great enhancing of detection sensitivity. A metamaterial sensing chip was designed for increasing of absorption cross section of the target sample, related to the transmitted THz near field enhancement via the composition of metamaterial. The measured THz optical properties were then analyzed in terms of refractive index and absorption coefficient, and compared with simulation results. Also, virus quantification regarding various concentrations of the viruses was performed, showing a clear linearity. The proposed sensitive and selective THz detection method can provide abundant information of detected biomaterials to help deep understanding of fundamental optical characteristics of them, suggesting rapid diagnosis way especially useful for such dangerous and time-sensitive target biomaterials.

  9. Near-field and far-field modeling of scattered surface waves. Application to the apertureless scanning near-field optical microscopy

    International Nuclear Information System (INIS)

    Muller, J.; Parent, G.; Fumeron, S.; Jeandel, G.; Lacroix, D.

    2011-01-01

    The detection of surface waves through scanning near-field optical microscopy (SNOM) is a promising technique for thermal measurements at very small scales. Recent studies have shown that electromagnetic waves, in the vicinity of a scattering structure such as an atomic force microscopy (AFM) tip, can be scattered from near to far-field and thus detected. In the present work, a model based on the finite difference time domain (FDTD) method and the near-field to far-field (NFTFF) transformation for electromagnetic waves propagation is presented. This model has been validated by studying the electromagnetic field of a dipole in vacuum and close to a dielectric substrate. Then simulations for a tetrahedral tip close to an interface are presented and discussed.

  10. Terahertz substance imaging by waveform shaping.

    Science.gov (United States)

    Yi, Minwoo; Kim, Hyosub; Jin, Kyong Hwan; Ye, Jong Chul; Ahn, Jaewook

    2012-08-27

    Terahertz pulse shaping technique is used to adaptively design terahertz waveforms of enhanced spectral correlation to particular materials among a given set of materials. In a proof-of-principle experiment performed with a two-dimensional image target consisted of meta-materials of distinctive resonance frequencies, the as-designed waveforms are used to demonstrate terahertz substance imaging. It is hoped that this material-specific terahertz waveforms may enable single- or few-shot terahertz material classification when being used in conjunction with terahertz power measurement.

  11. Seawater-sediment interaction at elevated temperatures and pressures: implications for the near field chemical environment

    International Nuclear Information System (INIS)

    Seyfried, W.E. Jr.; Thornton, E.C.; Janecky, D.R.

    1981-01-01

    Results of four experiments are reported which document chemical exchange and mineralogic modification during seawater-sediment interaction at 200 0 to 300 0 C, 500 bars. Sediments used for this study are from MPG-1 (central North Pacific). Experimental conditions (T, P, W/R) were chosen to be reasonably analogous to conditions which will characterize the near field environment; that is a zone within approximately 1 m of the buried waste canister. In general, the major element chemistry of seawater was similarly modified in all experiments. The aqueous concentrations of Ca, Mg, Sr, and SO 4 decreased and SiO 2 /sub (aq)/, Na, K, and ΣCO 2 increased relative to values in seawater prior to reaction with sediments. pH decreased and remained distinctly acid. Con comitantly significant concentrations of heavy metals entered seawater from the sediments during reaction. Dissolution of Mn-rich phases profoundly affected alteration processes. For example, reaction of MnO 2 components of the smectite-rich sediment (Pacific smectite) with seawater created an unusually oxidizing milieu (fO 2 = 10 -7 74 ), and resulted in dissolution of significant quantities of Au from the reaction cell. Although illite-quartz-Fe-chlorite (sediment B)-seawater interaction also created a relatively oxidizing environment, this environment was not capable of oxidizing Au. Thus, in this regard (oxidation potential) sediment mineralogy exerts a strong influence. Mineralogic modification of sediment B at 200 0 and 300 0 C was minor and characterized by partial dissolution of illite and exchange of Fe for Mg in chlorite. In contrast the smectite-rich sediment, which, prior to reaction with seawater contained a poorly crystalline smectite phase, clinoptilolite, and amorphous material, recrystallized totally to a well defined smectite mineral. Anhydrite was abundantly present amongst the alteration products of all experiments

  12. Scanning near-field optical microscopy on rough surfaces: applications in chemistry, biology, and medicine

    Directory of Open Access Journals (Sweden)

    2006-01-01

    Full Text Available Shear-force apertureless scanning near-field optical microscopy (SNOM with very sharp uncoated tapered waveguides relies on the unexpected enhancement of reflection in the shear-force gap. It is the technique for obtaining chemical (materials contrast in the optical image of “real world” surfaces that are rough and very rough without topographical artifacts, and it is by far less complicated than other SNOM techniques that can only be used for very flat surfaces. The experimental use of the new photophysical effect is described. The applications of the new technique are manifold. Important mechanistic questions in solid-state chemistry (oxidation, diazotization, photodimerization, surface hydration, hydrolysis are answered with respect to simultaneous AFM (atomic force microscopy and detailed crystal packing. Prehistoric petrified bacteria and concomitant pyrite inclusions are also investigated with local RAMAN SNOM. Polymer beads and unstained biological objects (rabbit heart, shrimp eye allow for nanoscopic analysis of cell organelles. Similarly, human teeth and a cancerous tissue are analyzed. Bladder cancer tissue is clearly differentiated from healthy tissue without staining and this opens a new highly promising diagnostic tool for precancer diagnosis. Industrial applications are demonstrated at the corrosion behavior of dental alloys (withdrawal of a widely used alloy, harmless substitutes, improvement of paper glazing, behavior of blood bags upon storage, quality assessment of metal particle preparations for surface enhanced RAMAN spectroscopy, and determination of diffusion coefficient and light fastness in textile fiber dyeing. The latter applications include fluorescence SNOM. Local fluorescence SNOM is also used in the study of partly aggregating dye nanoparticles within resin/varnish preparations. Unexpected new insights are obtained in all of the various fields that cannot be obtained by other techniques.

  13. Laser heating of scanning probe tips for thermal near-field spectroscopy and imaging

    Directory of Open Access Journals (Sweden)

    Brian T. O’Callahan

    2017-02-01

    Full Text Available Spectroscopy and microscopy of the thermal near-field yield valuable insight into the mechanisms of resonant near-field heat transfer and Casimir and Casimir-Polder forces, as well as providing nanoscale spatial resolution for infrared vibrational spectroscopy. A heated scanning probe tip brought close to a sample surface can excite and probe the thermal near-field. Typically, tip temperature control is provided by resistive heating of the tip cantilever. However, this requires specialized tips with limited temperature range and temporal response. By focusing laser radiation onto AFM cantilevers, we achieve heating up to ∼1800 K, with millisecond thermal response time. We demonstrate application to thermal infrared near-field spectroscopy (TINS by acquiring near-field spectra of the vibrational resonances of silicon carbide, hexagonal boron nitride, and polytetrafluoroethylene. We discuss the thermal response as a function of the incident excitation laser power and model the dominant cooling contributions. Our results provide a basis for laser heating as a viable approach for TINS, nanoscale thermal transport measurements, and thermal desorption nano-spectroscopy.

  14. Some variations of the Kristallin-I near-field model

    International Nuclear Information System (INIS)

    Smith, P.A.; Curti, E.

    1995-11-01

    The Kristallin-I project is an integrated analysis of the final disposal of vitrified high-level radioactive waste (HLW) in the crystalline basement of Northern Switzerland. It includes an analysis of the radiological consequences of radionuclide release from a repository. This analysis employs a chain of independent models for the near-field, geosphere and biosphere. In constructing these models, processes are incorporated that are believed to be relevant to repository safety, while other processes are neglected. In the present report, a set of simplified, steady-state models of the near-field is developed to investigate the possible effects of specific processes which are neglected in the time-dependent Kristallin-I near-field model. These processes are neglected, either because (i) they are thought unlikely to occur to a significant degree, or because (ii) they are likely to make a positive contribution to the performance of the near-field barrier to radionuclide migration, but are insufficiently understood to justify incorporating them in a safety assessment. The aim of this report is to investigate whether the arguments for neglecting these processes in the Kristallin-I near-field model can be justified. This work addresses the following topics: - radionuclide transport at the bentonite-host rock interface, - canister settlement, -chemical conditions and radionuclide transport at the glass-bentonite interface. (author) figs., tabs., refs

  15. Prediction of Near-Field Wave Attenuation Due to a Spherical Blast Source

    Science.gov (United States)

    Ahn, Jae-Kwang; Park, Duhee

    2017-11-01

    Empirical and theoretical far-field attenuation relationships, which do not capture the near-field response, are most often used to predict the peak amplitude of blast wave. Jiang et al. (Vibration due to a buried explosive source. PhD Thesis, Curtin University, Western Australian School of Mines, 1993) present rigorous wave equations that simulates the near-field attenuation to a spherical blast source in damped and undamped media. However, the effect of loading frequency and velocity of the media have not yet been investigated. We perform a suite of axisymmetric, dynamic finite difference analyses to simulate the propagation of stress waves induced by spherical blast source and to quantify the near-field attenuation. A broad range of loading frequencies, wave velocities, and damping ratios are used in the simulations. The near-field effect is revealed to be proportional to the rise time of the impulse load and wave velocity. We propose an empirical additive function to the theoretical far-field attenuation curve to predict the near-field range and attenuation. The proposed curve is validated against measurements recorded in a test blast.

  16. Terahertz imaging for styrofoam inspection

    Science.gov (United States)

    Pradarutti, B.; Riehemann, S.; Notni, G.; Tünnermann, A.

    2007-09-01

    Imaging of styrofoam with the help of ultrashort Terahertz pulses is investigated. With a combination of pulse amplitude and time delay imaging it is possible to speed up the measurement about two orders of magnitudes.

  17. Plasma Wave Electronic Terahertz Technology

    National Research Council Canada - National Science Library

    Shur, Michael

    2003-01-01

    Plasma waves are oscillations of electron density in time and space. In deep submicron field effect transistors plasma wave frequencies lie in the terahertz range and can be tuned by applied gate bias...

  18. Gelatin embedding: a novel way to preserve biological samples for terahertz imaging and spectroscopy

    International Nuclear Information System (INIS)

    Fan, Shuting; Ung, Benjamin; Parrott, Edward P J; Pickwell-MacPherson, Emma

    2015-01-01

    Sample dehydration has traditionally been a challenging problem in ex vivo terahertz biomedical experiments as water content changes significantly affect the terahertz properties and can diminish important contrast features. In this paper, we propose a novel method to prevent sample dehydration using gelatin embedding. By looking at terahertz image data and calculating the optical properties of the gelatin-embedded sample, we find that our method successfully preserves the sample for at least 35 h, both for imaging and spectroscopy. Our novel preservation method demonstrates for the first time the capability to simultaneously maintain sample structural integrity and prevent dehydration at room temperature. This is particularly relevant for terahertz studies of freshly excised tissues but could be beneficial for other imaging and spectroscopy techniques. (paper)

  19. Resonant metallic nanostructures for enhanced terahertz spectroscopy

    KAUST Repository

    Toma, A.

    2015-11-12

    We present our recent studies on terahertz resonant dipole nanoantennas. Exploiting the localization and enhancement capabilities of these devices, we introduce an effective method to perform terahertz spectroscopy on an extremely small number of nano-objects.

  20. High-Accuracy Spherical Near-Field Measurements for Satellite Antenna Testing

    DEFF Research Database (Denmark)

    Breinbjerg, Olav

    2017-01-01

    The spherical near-field antenna measurement technique is unique in combining several distinct advantages and it generally constitutes the most accurate technique for experimental characterization of radiation from antennas. From the outset in 1970, spherical near-field antenna measurements have...... matured into a well-established technique that is widely used for testing antennas for many wireless applications. In particular, for high-accuracy applications, such as remote sensing satellite missions in ESA's Earth Observation Programme with uncertainty requirements at the level of 0.05dB - 0.10d......B, the spherical near-field antenna measurement technique is generally superior. This paper addresses the means to achieving high measurement accuracy; these include the measurement technique per se, its implementation in terms of proper measurement procedures, the use of uncertainty estimates, as well as facility...

  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. Near-field light design with colloidal quantum dots for photonics and plasmonics.

    Science.gov (United States)

    Kress, Stephan J P; Richner, Patrizia; Jayanti, Sriharsha V; Galliker, Patrick; Kim, David K; Poulikakos, Dimos; Norris, David J

    2014-10-08

    Colloidal quantum-dots are bright, tunable emitters that are ideal for studying near-field quantum-optical interactions. However, their colloidal nature has hindered their facile and precise placement at desired near-field positions, particularly on the structured substrates prevalent in plasmonics. Here, we use high-resolution electro-hydrodynamic printing (quantum dots on both flat and structured substrates with a few nanometer precision. We also demonstrate that the autofocusing capability of the printing method enables placement of quantum dots preferentially at plasmonic hot spots. We exploit this control and design diffraction-limited photonic and plasmonic sources with arbitrary wavelength, shape, and intensity. We show that simple far-field illumination can excite these near-field sources and generate fundamental plasmonic wave-patterns (plane and spherical waves). The ability to tailor subdiffraction sources of plasmons with quantum dots provides a complementary technique to traditional scattering approaches, offering new capabilities for nanophotonics.

  3. Near-field thermal radiation transfer controlled by plasmons in graphene

    Science.gov (United States)

    Ilic, Ognjen; Jablan, Marinko; Joannopoulos, John D.; Celanovic, Ivan; Buljan, Hrvoje; Soljačić, Marin

    2012-04-01

    It is shown that thermally excited plasmon-polariton modes can strongly mediate, enhance, and tune the near-field radiation transfer between two closely separated graphene sheets. The dependence of near-field heat exchange on doping and electron relaxation time is analyzed in the near infrared within the framework of fluctuational electrodynamics. The dominant contribution to heat transfer can be controlled to arise from either interband or intraband processes. We predict maximum transfer at low doping and for plasmons in two graphene sheets in resonance, with orders-of-magnitude enhancement (e.g., 102 to 103 for separations between 0.1 μm and 10 nm) over the Stefan-Boltzmann law, known as the far-field limit. Strong, tunable, near-field transfer offers the promise of an externally controllable thermal switch as well as a novel hybrid graphene-graphene thermoelectric/thermophotovoltaic energy conversion platform.

  4. 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...

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

    International Nuclear Information System (INIS)

    Apps, J.A.

    1995-01-01

    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

  6. Ultrathin high efficiency photodetectors based on subwavelength grating and near-field enhanced absorption.

    Science.gov (United States)

    Zohar, Moshe; Auslender, Mark; Hava, Shlomo

    2015-03-12

    Optical absorbers, comprising a thin semiconductor layer placed between two transparent ones in close proximity to a subwavelength grating, are considered. With no back mirror, these structures only mimic the resonant cavity enhanced photodetector, being an order of magnitude thinner. It is argued that the grating can assist the light confinement by near field microcavity resonance rather than by far field mirroring. Tolerant designs to attain nearly 100% optical absorption at a predefined wavelength are demonstrated, and the near-field enhancement of the absorption is confirmed. The results obtained indicate that the proposed near field enhanced photodetectors meet the combined challenges of significantly increasing the efficiency and reducing the complexity and size of the entire device as compared to the resonant cavity enhanced photodetectors, which may be useful for integrated multi-detector arrays.

  7. Proceedings from the technical workshop on near-field performance assessment for high-level waste

    International Nuclear Information System (INIS)

    Sellin, P.; Apted, M.; Gago, J.

    1991-12-01

    This report contains the proceedings of 'Technical workshop of near-filed performance assessment for high-level waste' held in Madrid October 15-17, 1990. It includes the invited presentations and summaries of the scientific discussions. The workshop covered several topics: * post-emplacement environment, * benchmarking of computer codes, * glass release, * spent-fuel release, * radionuclide solubility, * near-field transport processes, * coupled processes in the near-field, * integrated assessments, * sensitivity analyses and validation. There was an invited presentation on each topic followed by an extensive discussion. One of the points highlighted in the closing discussion of the workshop was the need for international cooperation in the field of near-field performance assessment. The general opinion was that this was best achieved in smaller groups discussing specific questions. (au) Separate abstracts were prepared for 9 papers in this volume

  8. Model development to evaluate evolution of redox conditions in the near field

    International Nuclear Information System (INIS)

    Chiba, Tamotsu; Miki, Takahito; Inagaki, Manabu; Sasamoto, Hiroshi; Yui, Mikazu

    1999-02-01

    Deep underground is thought to be a potential place for high level radioactive waste repository. It is believed that the chemical condition of deep groundwater is generally anoxic and reducing. However, during construction and operation phase of repository, oxygen will diffuse some distance into the surrounding rock mass, and diffused oxygen may remain in the surrounding rock mass even after repository closure. In such a case, the transitional redox condition around the drift is not preferable in view point of safety assessment for HLW disposal. Hence, it is very important to evaluate evolution of redox conditions in the near field. This report describes the status of model development to evaluate evolution of redox conditions in the near field. We use the commercial solver to equate the mathematical equations which mean evolution of redox condition in the near field. The target area modeled in this report are near field rock mass and engineered barrier (buffer). In case of near field rock mass, we consider the following two geological media: (1) porous media for sedimentary rock, (2) fractured media for crystalline rock. In case of the engineered barrier, we regard the buffer as porous media. We simulate the behavior of dissolved oxygen and Fe 2+ in groundwater during evolution of redox condition in the near field rock mass and the buffer. In case of the porous media, we consider diffusion of chemical species as dominant transport mechanism. On the other hand, in case of the fractured media, we consider diffusion of chemical species in rock matrix and advection of that (only dissolved oxygen considered in this model) in fracture as transport mechanism. We also use the rate law of iron oxidation reaction and dissolution of Fe-bearing minerals in this model besides. (author)

  9. Preliminary analysis for evolution of redox conditions in the near field

    International Nuclear Information System (INIS)

    Chiba, Tamotsu; Miki, Takahito; Inagaki, Manabu; Sasamoto, Hiroshi; Yui, Mikazu

    1999-06-01

    It is planned that high level radioactive waste is going to be disposed under deep geological environment. It is believed that the chemical condition of deep groundwater is generally anoxic and reducing. However, during construction and operation phase of repository, oxygen will diffuse some distance into the surrounding rock mass, and diffused oxygen may remain in the surrounding rock mass even after repository closure. In such a case, the transitional redox condition around the drift is not preferable in view point of safety assessment for HLW disposal. Hence, it is very important to evaluate evolution of redox conditions in the near field. This report describes results of preliminary analysis for evolution of redox conditions in the near field rock mass and buffer after repository closure based on the model developed by Chiba et al. (1999). The results of preliminary analysis are summarized as follows: The decrease of oxygen in the near field rock mass and buffer are affected by pH of groundwater and surface area of iron-bearing minerals. The decrease of oxygen in the near field rock mass takes place at time scales lower than 500 years in considering the hypothetical reference groundwater pH range for H12 report. It is implicated that the redox conditions in the near field rock mass will recover to reducing conditions. The decrease of oxygen in the buffer takes place at time scales lower several tens years under neutral to weakly alkaline pH values of porewater in the buffer, even if it is assumed that residual oxygen in the near field rock mass after repository closure will diffuse into the buffer. On the other hand, under weakly acid pH values of porewater in the buffer, it may be presumed that oxygen remain in the buffer at time scale more than 500 years. (author)

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

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.; Pedersen, K.; 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 0.......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....

  11. 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...

  12. Near-Field Spectroscopy of the Quantum Constituents of a Luminescent System

    Science.gov (United States)

    Hess, H. F.; Betzig, E.; Harris, T. D.; Pfeiffer, L. N.; West, K. W.

    1994-06-01

    Luminescent centers with sharp (<0.07 millielectron volt), spectrally distinct emission lines were imaged in a GaAs/AlGaAs quantum well by means of low-temperature near-field scanning optical microscopy. Temperature, magnetic field, and linewidth measurements establish that these centers arise from excitons laterally localized at interface fluctuations. For sufficiently narrow wells, virtually all emission originates from such centers. Near-field microscopy/spectroscopy provides a means to access energies and homogeneous line widths for the individual eigenstates of these centers, and thus opens a rich area of physics involving quantum resolved systems.

  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. Development of a backscattering type ultraviolet apertureless near-field scanning optical microscope.

    Science.gov (United States)

    Kwon, Sangjin; Jeong, Hyun; Jeong, Mun Seok; Jeong, Sungho

    2011-08-01

    A backscattering type ultraviolet apertureless near-field scanning optical microscope (ANSOM) for the correlated measurement of topographical and optical characteristics of photonic materials with high optical resolution was developed. The near-field Rayleigh scattering image of GaN covered with periodic submicron Cr dots showed that optical resolution around 40 nm was achievable. By measuring the tip scattered photoluminescence of InGaN/GaN multi quantum wells, the applicability of the developed microscope for high resolution fluorescence measurement was also demonstrated.

  15. Group velocity measurement using spectral interference in near-field scanning optical microscopy

    International Nuclear Information System (INIS)

    Mills, John D.; Chaipiboonwong, Tipsuda; Brocklesby, William S.; Charlton, Martin D. B.; Netti, Caterina; Zoorob, Majd E.; Baumberg, Jeremy J.

    2006-01-01

    Near-field scanning optical microscopy provides a tool for studying the behavior of optical fields inside waveguides. In this experiment the authors measure directly the variation of group velocity between different modes of a planar slab waveguide as the modes propagate along the guide. The measurement is made using the spectral interference between pulses propagating inside the waveguide with different group velocities, collected using a near-field scanning optical microscope at different points down the guide and spectrally resolved. The results are compared to models of group velocities in simple guides

  16. 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...... by the optical near field, were observed after etching in potassium hydroxide. The uncoated fibers can also induce oxidation without light exposure, in a manner similar to an atomic force microscope, and linewidths of 50 nm have been achieved this way. (C) 1996 American Institute of Physics....

  17. Cancer cell imaging by stable wet near-field scanning optical microscope with resonance tracking method

    International Nuclear Information System (INIS)

    Park, Kyoung-Duck; Park, Doo-Jae; Jeong, Mun-Seok; Choi, Geun-Chang; Lee, Seung-Gol; Byeon, Clare-Chisu; Choi, Soo-Bong

    2014-01-01

    We report on a successful topographical and optical imaging of various cancer cells in liquid and in air by using a stable wet near-field scanning optical microscope that utilizes a resonance tracking method. We observed a clear dehydration which gives rise to a decrease in the cell volume down to 51%. In addition, a micro-ball lens effect due to the round-shaped young cancer cells was observed from near-field imaging, where the refractive index of young cancer cells was deduced.

  18. 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.

  19. Cancer cell imaging by stable wet near-field scanning optical microscope with resonance tracking method

    Energy Technology Data Exchange (ETDEWEB)

    Park, Kyoung-Duck [Sungkyunkwan University, Suwon (Korea, Republic of); Inha University, Incheon (Korea, Republic of); Park, Doo-Jae; Jeong, Mun-Seok [Sungkyunkwan University, Suwon (Korea, Republic of); Choi, Geun-Chang [Seoul National University, Seoul (Korea, Republic of); Lee, Seung-Gol [Inha University, Incheon (Korea, Republic of); Byeon, Clare-Chisu [Kyungpook National University, Daegu (Korea, Republic of); Choi, Soo-Bong [Incheon National University, Incheon (Korea, Republic of)

    2014-05-15

    We report on a successful topographical and optical imaging of various cancer cells in liquid and in air by using a stable wet near-field scanning optical microscope that utilizes a resonance tracking method. We observed a clear dehydration which gives rise to a decrease in the cell volume down to 51%. In addition, a micro-ball lens effect due to the round-shaped young cancer cells was observed from near-field imaging, where the refractive index of young cancer cells was deduced.

  20. 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.

  1. 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.

  2. 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.

  3. 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....

  4. 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 su......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...

  5. Multilayer Graphene for Waveguide Terahertz Modulator

    DEFF Research Database (Denmark)

    Khromova, I.; Andryieuski, Andrei; Lavrinenko, Andrei

    2014-01-01

    We study terahertz to infrared electromagnetic properties of multilayer graphene/dielectric artificial medium and present a novel concept of terahertz modulation at midinfrared wavelengths. This approach allows the realization of high-speed electrically controllable terahertz modulators based...... on hollow waveguide sections filled with multilayer graphene....

  6. X-ray near-field holography. Beyond idealized assumptions of the probe

    International Nuclear Information System (INIS)

    Hagemann, Johannes

    2017-01-01

    The work at hand considers the imperfect, often neglected, aspects of X-ray nearfield phase-contrast propagation imaging, or in short: X-ray near-field holography (NFH). NFH is a X-ray microscopy technique able to yield high resolution, yet low dose imaging of a wide range of specimen. Derived from wave optical theory, propagation-based imaging methods rely on assumptions for the illuminating wave field. These are for example the assumptions of a perfect plane wave or spherical wave emanating from a point source or monochromaticity. Violation of the point source assumption implies for example at the same time the occurrence of a distorted wave front and a finite degree of coherence, both crucial for NFH. With the advances in X-ray focusing, instrumentation and X-ray wave guiding, NFH has become of high interest, since the barriers for practical implementation have been overcome. The idea of holography originates from electron microscopy to overcome the lack of high-quality electron lenses. With holography the need for optics between the specimen and detector is circumvented. The drawback, however, is that the measurement obtained at the detector is not a direct image of the specimen under survey but a ''propagated version'' of it, the so-called hologram. The problem with the optics is replaced by another problem, also referred to as the phase problem. The phase problem is caused by the fact that only the intensities of a wave field can be measured but not the phase information. The phase information is crucial for obtaining the image of the specimen and thus needs to be reconstructed. In recent years the methodology, sometimes also mythology, has been developed to reconstruct the specimen from the measured hologram. For a long time, the standard approach to deal with deviations from the ideal assumptions in real world holography experiments has been to simply ignore these. The prime example for this is the method of the standard flat

  7. [Application of terahertz technology in medical testing and diagnosis].

    Science.gov (United States)

    Qi, Na; Zhang, Zhuo-Yong; Xiang, Yu-Hong

    2013-08-01

    Terahertz science and technology is increasingly emphasized in science and industry, and has progressed significantly in recent years. There is an important aspect of attention in the application of terahertz technology to medicine. The overview of the terahertz characters, terahertz spectroscopy and terahertz imaging technology is introduced. This paper focuses on reviewing the use of and research progress in terahertz spectroscopy and terahertz imaging technology in medical testing and diagnosis. Furthermore, the problems to be solved and development directions of terahertz spectroscopy and terahertz imaging technology are discussed.

  8. Nonlinear terahertz superconducting plasmonics

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Jingbo; Liang, Lanju; Jin, Biaobing, E-mail: bbjin@nju.edu.cn, E-mail: tonouchi@ile.osaka-u.ac.jp, E-mail: phwu@nju.edu.cn; Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng, E-mail: bbjin@nju.edu.cn, E-mail: tonouchi@ile.osaka-u.ac.jp, E-mail: phwu@nju.edu.cn [Research Institute of Superconductor Electronics (RISE), School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); Zhang, Caihong; Kawayama, Iwao; Murakami, Hironaru; Tonouchi, Masayoshi, E-mail: bbjin@nju.edu.cn, E-mail: tonouchi@ile.osaka-u.ac.jp, E-mail: phwu@nju.edu.cn [Institute of Laser Engineering, Osaka University, 2-6 Yamadaoka, Suita, Osaka 565-0871 (Japan); Wang, Huabing [Research Institute of Superconductor Electronics (RISE), School of Electronic Science and Engineering, Nanjing University, Nanjing 210093 (China); National Institute for Materials Science, Tsukuba 305-0047 (Japan)

    2014-10-20

    Nonlinear terahertz (THz) transmission through subwavelength hole array in superconducting niobium nitride (NbN) film is experimentally investigated using intense THz pulses. The good agreement between the measurement and numerical simulations indicates that the field strength dependent transmission mainly arises from the nonlinear properties of the superconducting film. Under weak THz pulses, the transmission peak can be tuned over a frequency range of 145 GHz which is attributed to the high kinetic inductance of 50 nm-thick NbN film. Utilizing the THz pump-THz probe spectroscopy, we study the dynamic process of transmission spectra and demonstrate that the transition time of such superconducting plasmonic device is within 5 ps.

  9. Active terahertz metamaterial devices

    Science.gov (United States)

    Chen, Houtong; Padilla, Willie John; Averitt, Richard Douglas; O'Hara, John F.; Lee, Mark

    2010-11-02

    Metamaterial structures are taught which provide for the modulation of terahertz frequency signals. Each element within an array of metamaterial (MM) elements comprises multiple loops and at least one gap. The MM elements may comprise resonators with conductive loops and insulated gaps, or the inverse in which insulated loops are present with conductive gaps; each providing useful transmissive control properties. The metamaterial elements are fabricated on a semiconducting substrate configured with a means of enhancing or depleting electrons from near the gaps of the MM elements. An on to off transmissivity ratio of about 0.5 is achieved with this approach. Embodiments are described in which the MM elements incorporated within a Quantum Cascade Laser (QCL) to provide surface emitting (SE) properties.

  10. New reversing freeform lens design method for LED uniform illumination with extended source and near field

    Science.gov (United States)

    Zhao, Zhili; Zhang, Honghai; Zheng, Huai; Liu, Sheng

    2018-03-01

    In light-emitting diode (LED) array illumination (e.g. LED backlighting), obtainment of high uniformity in the harsh condition of the large distance height ratio (DHR), extended source and near field is a key as well as challenging issue. In this study, we present a new reversing freeform lens design algorithm based on the illuminance distribution function (IDF) instead of the traditional light intensity distribution, which allows uniform LED illumination in the above mentioned harsh conditions. IDF of freeform lens can be obtained by the proposed mathematical method, considering the effects of large DHR, extended source and near field target at the same time. In order to prove the claims, a slim direct-lit LED backlighting with DHR equal to 4 is designed. In comparison with the traditional lenses, illuminance uniformity of LED backlighting with the new lens increases significantly from 0.45 to 0.84, and CV(RMSE) decreases dramatically from 0.24 to 0.03 in the harsh condition. Meanwhile, luminance uniformity of LED backlighting with the new lens is obtained as high as 0.92 at the condition of extended source and near field. This new method provides a practical and effective way to solve the problem of large DHR, extended source and near field for LED array illumination.

  11. Atomic force and scanning near-field optical microscopy study of carbocyanine dye J-aggregates

    Czech Academy of Sciences Publication Activity Database

    Prokhorov, V.V.; Petrova, M.G.; Kovaleva, Natalia; Demikhov, E.I.

    2014-01-01

    Roč. 10, č. 5 (2014), s. 700-704 ISSN 1573-4137 Institutional support: RVO:68378271 Keywords : carbocyanine dye * elementary fibri * high-resolution atomic force microscopy * J-aggregate * probe microscopy * scanning near-field optical microscopy Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.096, year: 2014

  12. The influence of organic materials on the near field of an intermediate level radioactive waste repository

    International Nuclear Information System (INIS)

    Wilkins, J.D.

    1988-01-01

    The influence of organic materials which are present in some intermediate level wastes on the chemistry of the near field of a radioactive waste repository is discussed. Particular attention is given to the possible formation of water soluble complexing agents as a result of the radiation field and chemical conditions. The present state of the research is reviewed. (author)

  13. 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

    A new and effective method for reduction of truncation errors in partial spherical near-field (SNF) measurements is proposed. The method is useful when measuring electrically large antennas, where the measurement time with the classical SNF technique is prohibitively long and an acquisition over...

  14. 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

  15. 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...

  16. Magnetic anisotropy in a permalloy microgrid fabricated by near-field optical lithography

    International Nuclear Information System (INIS)

    Li, S. P.; Lebib, A.; Peyrade, D.; Natali, M.; Chen, Y.; Lew, W. S.; Bland, J. A. C.

    2001-01-01

    We report the fabrication and magnetic properties of permalloy microgrids prepared by near-field optical lithography and characterized using high-sensitivity magneto-optical Kerr effect techniques. A fourfold magnetic anisotropy induced by the grid architecture is identified. [copyright] 2001 American Institute of Physics

  17. Topography characterization of a deep grating using near-field imaging

    DEFF Research Database (Denmark)

    Gregersen, Niels; Tromborg, Bjarne; Volkov, Valentyn S.

    2006-01-01

    Using near-field optical microscopy at the wavelength of 633 nm, we image light intensity distributions at several distances above an ~2-mm deep and a 1-mm-period glass grating illuminated from below under the condition of total internal reflection. The intensity distributions are numerically mod...

  18. Rigorous numerical modeling of scattering-type scanning near-field optical microscopy and spectroscopy

    Science.gov (United States)

    Chen, Xinzhong; Lo, Chiu Fan Bowen; Zheng, William; Hu, Hai; Dai, Qing; Liu, Mengkun

    2017-11-01

    Over the last decade, scattering-type scanning near-field optical microscopy and spectroscopy have been widely used in nano-photonics and material research due to their fine spatial resolution and broad spectral range. A number of simplified analytical models have been proposed to quantitatively understand the tip-scattered near-field signal. However, a rigorous interpretation of the experimental results is still lacking at this stage. Numerical modelings, on the other hand, are mostly done by simulating the local electric field slightly above the sample surface, which only qualitatively represents the near-field signal rendered by the tip-sample interaction. In this work, we performed a more comprehensive numerical simulation which is based on realistic experimental parameters and signal extraction procedures. By directly comparing to the experiments as well as other simulation efforts, our methods offer a more accurate quantitative description of the near-field signal, paving the way for future studies of complex systems at the nanoscale.

  19. Control strategies for active noise barriers using near-field error sensing

    NARCIS (Netherlands)

    Berkhoff, Arthur P.

    In this paper active noise control strategies for noise barriers are presented which are based on the use of sensors near the noise barrier. Virtual error signals are derived from these near-field sensor signals such that reductions of the far-field sound pressure are obtained with the active

  20. Near-field optical microscopy of localized excitations on rough surfaces: influence of a probe

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.

    1999-01-01

    Starting from the general principles of near-field optical microscopy. I consider the influence of a probe when being used to image localized dipolar excitations and suggest a way of evaluating the perturbation thus introduced. Using the rigorous microscopic (electric) point-dipole description, I...

  1. Poly(diacetylene) Monolayers Studied with a Fluorescence Scanning Near-Field Optical Microscope

    NARCIS (Netherlands)

    Moers, Marco H.P.; Moers, M.H.P.; Gaub, Hermann E.; van Hulst, N.F.

    1994-01-01

    A novel and powerful method to study the optical properties of thin lipid films which a resolution superior to confocal microscopy is presented. With a scanning near-field optical microscope, fluorescence images of a Langmuir-Blodgett film of diethylene glycol diamine pentacosadiynoic amide are

  2. 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

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

    DEFF Research Database (Denmark)

    Iezhokin, Igor; Keller, Ole; Lozovski, Valeri

    2010-01-01

    in a selfconsistent local-field calculation. The main result of the basic theory is illustrated by a number of numerical calculations on box-shaped quantum dots keeping only two optically mobile electrons. Particular attendance is paid to the distance and angular dependences of the near-field radiation pattern When...

  4. Near field plasmonic gradient effects on high vacuum tip-enhanced Raman spectroscopy.

    Science.gov (United States)

    Fang, Yurui; Zhang, Zhenglong; Chen, Li; Sun, Mengtao

    2015-01-14

    Near field gradient effects in high vacuum tip-enhanced Raman spectroscopy (HV-TERS) are a recent developing ultra-sensitive optical and spectral analysis technology on the nanoscale, based on the plasmons and plasmonic gradient enhancement in the near field and under high vacuum. HV-TERS can not only be used to detect ultra-sensitive Raman spectra enhanced by surface plasmon, but also to detect clear molecular IR-active modes enhanced by strongly plasmonic gradient. Furthermore, the molecular overtone modes and combinational modes can also be experimentally measured, where the Fermi resonance and Darling-Dennison resonance were successfully observed in HV-TERS. Theoretical calculations using electromagnetic field theory firmly supported experimental observation. The intensity ratio of the plasmon gradient term over the linear plasmon term can reach values greater than 1. Theoretical calculations also revealed that with the increase in gap distance between tip and substrate, the decrease in the plasmon gradient was more significant than the decrease in plasmon intensity, which is the reason that the gradient Raman can be only observed in the near field. Recent experimental results of near field gradient effects on HV-TERS were summarized, following the section of the theoretical analysis.

  5. 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,

  6. Nanostructure enhanced near-field radiative heat transfer and designs for energy conversion devices

    Science.gov (United States)

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

    2017-09-01

    Near-field radiative heat transfer can exceed the blackbody limit, and this property has been explored toward energy transfer and conversion applications, such as thermophtovoltaic (TPV) devices, radiative cooling devices, and thermoradiative (TR) devices. The coupling of resonant modes between two surfaces is important in near- field heat transfer and near-field TPV and TR systems. It was shown that the coupling of resonant modes enhances the transmissivity between two coupled objects, which further determines the radiative heat transfer and energy conversion. Surface plasmon polaritons (SPPs), which are surface resonances existing on metal surfaces, are commonly used for such systems. While the frequency of SPP resonance is fixed for a planar emitter, a nanostructured emitter supports additional resonances such as SPP or cavity modes with lower frequencies that are closer to the bandgap energy of a typical PV cell. We show that the nanostructured designs significantly improves the near-field radiative power transfer, and electric power output for a TR system.

  7. 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...

  8. A MEMS device capable of measuring near-field thermal radiation between membranes.

    Science.gov (United States)

    Feng, Chong; Tang, Zhenan; Yu, Jun; Sun, Changyu

    2013-02-04

    For sensors constructed by freestanding membranes, when the gap between a freestanding membrane and the substrate or between membranes is at micron scale, the effects of near-field radiative heat transfer on the sensors' thermal performance should be considered during sensor design. The radiative heat flux is transferred from a membrane to a plane or from a membrane to a membrane. In the current study of the near-field thermal radiation, the scanning probe technology has difficulty in making a membrane separated at micron scale parallel to a plane or another membrane. A novel MEMS (micro electromechanical system) device was developed by sacrificial layer technique in this work to realize a double parallel freestanding membrane structure. Each freestanding membrane has a platinum thin-film resistor and the distance between the two membranes is 1 m. After evaluating the electrical and thermal characteristics of the lower freestanding membrane, experimental measurements of near-field radiative heat transfer between the lower membrane and the upper membrane were carried out by setting the lower membrane as a heat emitter and the upper membrane as a heat receiver. The near-field radiative heat transfer between the two membranes was validated by finding a larger-than-blackbody radiative heat transfer based on the experimental data.

  9. A MEMS Device Capable of Measuring Near-Field Thermal Radiation between Membranes

    Directory of Open Access Journals (Sweden)

    Changyu Sun

    2013-02-01

    Full Text Available For sensors constructed by freestanding membranes, when the gap between a freestanding membrane and the substrate or between membranes is at micron scale, the effects of near-field radiative heat transfer on the sensors’ thermal performance should be considered during sensor design. The radiative heat flux is transferred from a membrane to a plane or from a membrane to a membrane. In the current study of the near-field thermal radiation, the scanning probe technology has difficulty in making a membrane separated at micron scale parallel to a plane or another membrane. A novel MEMS (micro electromechanical system device was developed by sacrificial layer technique in this work to realize a double parallel freestanding membrane structure. Each freestanding membrane has a platinum thin-film resistor and the distance between the two membranes is 1 m. After evaluating the electrical and thermal characteristics of the lower freestanding membrane, experimental measurements of near-field radiative heat transfer between the lower membrane and the upper membrane were carried out by setting the lower membrane as a heat emitter and the upper membrane as a heat receiver. The near-field radiative heat transfer between the two membranes was validated by finding a larger-than-blackbody radiative heat transfer based on the experimental data.

  10. 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...... amplitude - phase near - field optical characterization of nanocoupler in telecom range ....

  11. Characterization of aniosotropic nano-particles by using depolarized dynamic light scattering in the near field

    NARCIS (Netherlands)

    Brogioli, D.; Salerno, D.; Cassina, V.; Sacanna, S.; Philipse, A.P.; Croccolo, F.; Mantegazza, F.

    2009-01-01

    Light scattering techniques are widely used in many fields of condensed and soft matter physics. Usually these methods are based on the study of the scattered light in the far field. Recently, a new family of near field detection schemes has been developed, mainly for the study of small angle light

  12. Investigation of whispering gallery modes in microlasers by scanning near-field optical microscopy

    Science.gov (United States)

    Polubavkina, Yu S.; Kryzhanovskaya, N. V.; Nadtochiy, A. M.; Mintairov, A. M.; Lipovsky, A. A.; Scherbak, S. A.; Kulagina, M. M.; Maximov, M. V.; Zhukov, A. E.

    2017-11-01

    Near-field scanning optical microscopy (NSOM) with a spatial resolution below the light diffraction limit was used to study intensity distributions of the whispering gallery modes (WGMs) in quantum dot-based microdisk and microring lasers on GaAs with different outer diameters. Room temperature microphotoluminescence study (μPL) reveal lasing in microlasers of both geometries.

  13. 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

  14. Analysis of near-field of diffractive gratings used in inertial confinement fusion driver

    Science.gov (United States)

    Tang, Xionggui; Gao, Fuhua; Gao, Feng; Zhang, Yixiao; Du, Jinglei; Guo, Yongkang; Du, Chunlei

    2005-02-01

    Diffractive gratings, such as 1 grating and beam sampling grating (BSG), are used in the inertial confinement fusion (ICF) driver because of their high diffractive efficiency. Under high power laser condition, it demands that near fields of the diffractive gratings, mainly affected by input laser energy and beam modulation, must be less than their damage threshold, otherwise the diffractive gratings will be damaged. In this paper, Fourier modal method based on the rigorous electromagnetic theory is introduced to rapidly and accurately analyze the distribution of near fields of the diffractive gratings. Its physical concept is clear and concise, and computation cost is small. Through numerical simulation, it indicates that the results calculated by Fourier modal method are accurate and effective, compared with those calculated by other method. The near fields of 1 grating used in final optical system of ICF driver are obtained. In addition, fabrication errors effects on the near field modulation are simulated. It shows that the sidewall slope errors are the main cause of optical field modulation. With theoretical analysis and numerical simulation, it is useful to understand mechanism of damage and help how to control fabrication process errors of the optical elements used in the optical system of ICF.

  15. Spectral tuning of near-field radiative heat transfer by graphene-covered metasurfaces

    Science.gov (United States)

    Zheng, Zhiheng; Wang, Ao; Xuan, Yimin

    2018-03-01

    When two gratings are respectively covered by a layer of graphene sheet, the near-field radiative heat transfer between two parallel gratings made of silica (SiO2) could be greatly improved. As the material properties of doped silicon (n-type doping concentration is 1020 cm-3, marked as Si-20) and SiO2 differ greatly, we theoretically investigate the near-field radiative heat transfer between two parallel graphene-covered gratings made of Si-20 to explore some different phenomena, especially for modulating the spectral properties. The radiative heat flux between two parallel bulks made of Si-20 can be enhanced by using gratings instead of bulks. When the two gratings are respectively covered by a layer of graphene sheet, the radiative heat flux between two gratings made of Si-20 can be further enhanced. By tuning graphene chemical potential μ and grating filling factor f, due to the interaction between surface plasmon polaritons (SPPs) of graphene sheets and grating structures, the spectral properties of the radiative heat flux between two parallel graphene-covered gratings can be effectively regulated. This work will develop and supplement the effects of materials on the near-field radiative heat transfer for this kind of system configuration, paving a way to modulate the spectral properties of near-field radiative heat transfer.

  16. Near-Field Antenna Measurements Using Photonic Sensor of Mach-Zehnder Interferometer

    Directory of Open Access Journals (Sweden)

    Masanobu Hirose

    2012-01-01

    Full Text Available We have been developing a photonic sensor system to measure the electric near-field distribution at a distance shorter than one wavelength from the aperture of an antenna. The photonic sensor is a type of Mach-Zehnder interferometer and consists of an array antenna of 2.4 mm height and 2 mm width on a LiNbO3 substrate (0.5 mm thickness, 8 mm length, and 3 mm width supported by a glass pipe. The photonic sensor can be considered to be a receiving infinitesimal dipole antenna that is a tiny metallic part printed on a small dielectric plate at microwave frequency. Those physical and electrical features make the photonic sensor attractive when used as a probe for near-field antenna measurements. We have demonstrated that the system can be applied to planar, spherical, and cylindrical near-field antenna measurements without any probe compensation approximately below 10 GHz. We show the theories and the measurements using the photonic sensor in the three near-field antenna measurement methods.

  17. Editorial 6th International Conference on Near-field Optics and Related Techniques

    NARCIS (Netherlands)

    van Hulst, N.F.

    2001-01-01

    This topical issue of the Journal of Microscopy contains all of the papers are based on work presented at NFO-6, the 6th International Conference on Near-field Optics and Related Techniques, held at the University of Twente, Enschede, the Netherlands, 27-31 August 2000.

  18. Dielectric and fluorescent samples imaged by scanning near-field optical microscopy in reflection

    NARCIS (Netherlands)

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

    1995-01-01

    Dielectric fluorescent samples are imaged by scanning near- field optical microscopy in reflection. A non-metallized tapered fibre tip is used both as an emitter and a detector. Shear force feedback controls the distance between the tip and the sample and gives simultaneously a topographic image of

  19. 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

  20. 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

    -tier, mechanistic models suitable for life cycle assessments (LCA), chemical alternative assessment (CAA) and high-throughput screening risk assessment (HTS). Chemicals in a product enter the near-field via a defined “compartment of entry”, are transformed or transferred to adjacent compartments, and eventually end...

  1. A total generalized variation approach for near-field acoustic holography

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren

    2017-01-01

    Near-field methods based on microphone array measurements are useful to understand how a source radiates sound. Due to discretization errors, these methods are typically restricted to low frequencies. Sparse approaches have gained considerable attention, as they can potentially recover a seemingl...

  2. Near field acoustic holography based on the equivalent source method and pressure-velocity transducers

    DEFF Research Database (Denmark)

    Zhang, Y.-B.; Chen, X.-Z.; Jacobsen, Finn

    2009-01-01

    The advantage of using the normal component of the particle velocity rather than the sound pressure in the hologram plane as the input of conventional spatial Fourier transform based near field acoustic holography (NAH) and also as the input of the statistically optimized variant of NAH has...

  3. 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

    Spherical near field acoustic holography (spherical NAH) is a technique that makes it pos-sible to reconstruct the sound field inside and just outside an acoustically transparent spherical surface on which the sound pressure is measured with an array of microphones with negligible scattering...

  4. Spherical near field acoustic holography with microphones on a rigid sphere

    DEFF Research Database (Denmark)

    Jacobsen, Finn; Hald, Jørgen; Fernandez Grande, Efren

    2008-01-01

    Spherical near field acoustic holography (SNAH) is a recently developed technique that makes it possible to reconstruct the sound field inside and just outside an acoustically transparent spherical surface on which the sound pressure is measured with an array of microphones with negligible...

  5. 6.2-GHz modulated terahertz light detection using fast terahertz quantum well photodetectors.

    Science.gov (United States)

    Li, Hua; Wan, Wen-Jian; Tan, Zhi-Yong; Fu, Zhang-Long; Wang, Hai-Xia; Zhou, Tao; Li, Zi-Ping; Wang, Chang; Guo, Xu-Guang; Cao, Jun-Cheng

    2017-06-14

    The fast detection of terahertz radiation is of great importance for various applications such as fast imaging, high speed communications, and spectroscopy. Most commercial products capable of sensitively responding the terahertz radiation are thermal detectors, i.e., pyroelectric sensors and bolometers. This class of terahertz detectors is normally characterized by low modulation frequency (dozens or hundreds of Hz). Here we demonstrate the first fast semiconductor-based terahertz quantum well photodetectors by carefully designing the device structure and microwave transmission line for high frequency signal extraction. Modulation response bandwidth of gigahertz level is obtained. As an example, the 6.2-GHz modulated terahertz light emitted from a Fabry-Pérot terahertz quantum cascade laser is successfully detected using the fast terahertz quantum well photodetector. In addition to the fast terahertz detection, the technique presented in this work can also be used for optically characterizing the frequency stability of terahertz quantum cascade lasers, heterodyne detections and photomixing applications.

  6. 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.

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

    Science.gov (United States)

    Dawidowicz, Karol; Baryła, Radosław

    2017-06-01

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

  8. Detection of Ionic liquid using terahertz time-domain spectroscopy

    Science.gov (United States)

    Wang, Cuicui; Zhao, Xiaojing; Liu, Shangjian; Zuo, Jian; Zhang, Cunlin

    2018-01-01

    Terahertz (THz, THz+1012Hz) spectroscopy is a far-infrared analytical technology with spectral bands locating between microware and infrared ranges. Being of excellent transmission, non-destruction and high discrimination, this technology has been applied in various fields such as physics, chemistry, nondestructive detection, communication, biomedicine public security. Terahertz spectrum is corresponding with vibration and rotation of liquid molecules, which is suitable to identify and study the liquid molecular dynamics. It is as a powerful spectral detection technology, terahertz time-domain spectroscopy is widely used in solution detection. can enable us to extract the material parameters or dielectric spectrum that show material micro-structure and dynamics by measuring amplitude and phase from coherent terahertz pulses. Ionic liquid exists in most biological tissues, and it is very important for life. It has recently been suggested that near-fired terahertz ionic contrast microscopy can be employed to image subtle changes in ionic concentrations arising from neuronal activity. In this paper, we detected Ionic liquid with different concentrations at room temperature by THz-TDS technique in the range of 0.2-1.5 THz. The liquid cell with a thickness of 0.2mm is made of quartz. The absorption coefficient, refractive index and dielectric function of solutions can be extracted based on THz-TDS. We use an expanded model for fitting the dielectric function based on a combination of a Debye relation for the anions and cations. We find A linear increase of the real and imaginary part of the dielectric function compared with pure water with increasing ion concentrations. A good agreement between the model and the experimental results is obtained. By means of dielectric relaxation process, it was found that the characteristic time of molecular movement and the information related to the liquid molecular structure and movement was obtained.

  9. High-resolution reconstruction for terahertz imaging.

    Science.gov (United States)

    Xu, Li-Min; Fan, Wen-Hui; Liu, Jia

    2014-11-20

    We present a high-resolution (HR) reconstruction model and algorithms for terahertz imaging, taking advantage of super-resolution methodology and algorithms. The algorithms used include projection onto a convex sets approach, iterative backprojection approach, Lucy-Richardson iteration, and 2D wavelet decomposition reconstruction. Using the first two HR reconstruction methods, we successfully obtain HR terahertz images with improved definition and lower noise from four low-resolution (LR) 22×24 terahertz images taken from our homemade THz-TDS system at the same experimental conditions with 1.0 mm pixel. Using the last two HR reconstruction methods, we transform one relatively LR terahertz image to a HR terahertz image with decreased noise. This indicates potential application of HR reconstruction methods in terahertz imaging with pulsed and continuous wave terahertz sources.

  10. Terahertz Science, Technology, and Communication

    Science.gov (United States)

    Chattopadhyay, Goutam

    2013-01-01

    The term "terahertz" has been ubiquitous in the arena of technology over the past couple of years. New applications are emerging every day which are exploiting the promises of terahertz - its small wavelength; capability of penetrating dust, clouds, and fog; and possibility of having large instantaneous bandwidth for high-speed communication channels. Until very recently, space-based instruments for astrophysics, planetary science, and Earth science missions have been the primary motivator for the development of terahertz sensors, sources, and systems. However, in recent years the emerging areas such as imaging from space platforms, surveillance of person-borne hidden weapons or contraband from a safe stand-off distance and reconnaissance, medical imaging and DNA sequencing, and in the world high speed communications have been the driving force for this area of research.

  11. 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.......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....

  12. Terahertz superconducting plasmonic hole array.

    Science.gov (United States)

    Tian, Zhen; Singh, Ranjan; Han, Jiaguang; Gu, Jianqiang; Xing, Qirong; Wu, Judy; Zhang, Weili

    2010-11-01

    We demonstrate a superconductor array of subwavelength holes with active thermal control over the resonant transmission induced by surface plasmon polaritons. The array was lithographically fabricated on a high-temperature yttrium barium copper oxide superconductor and characterized by terahertz time-domain spectroscopy. We observe a clear transition from a virtual excitation of the surface plasmon mode to a real surface plasmon mode. The highly controllable superconducting plasmonic crystals may find promising applications in the design of low-loss, large- dynamic-range amplitude modulation and surface-plasmon-based terahertz devices.

  13. Broadband terahertz fiber directional coupler

    DEFF Research Database (Denmark)

    Nielsen, Kristian; Rasmussen, Henrik K.; Jepsen, Peter Uhd

    2010-01-01

    We present the design of a short broadband fiber directional coupler for terahertz (THz) radiation and demonstrate a 3 dB coupler with a bandwidth of 0:6 THz centered at 1:4 THz. The broadband coupling is achieved by mechanically downdoping the cores of a dual-core photonic crystal fiber by micro......We present the design of a short broadband fiber directional coupler for terahertz (THz) radiation and demonstrate a 3 dB coupler with a bandwidth of 0:6 THz centered at 1:4 THz. The broadband coupling is achieved by mechanically downdoping the cores of a dual-core photonic crystal fiber...

  14. Nanoscale Laser Terahertz Emission Microscopy

    DEFF Research Database (Denmark)

    Klarskov, Pernille; Kim, Hyewon; Colvin, Vicki L.

    2017-01-01

    Laser terahertz emission microscopy (LTEM) has become a powerful tool for studying ultrafast dynamics and local fields in many different types of materials. This technique, which relies on acceleration of charge carriers in a material upon femtosecond excitation, can provide insight into the phys......Laser terahertz emission microscopy (LTEM) has become a powerful tool for studying ultrafast dynamics and local fields in many different types of materials. This technique, which relies on acceleration of charge carriers in a material upon femtosecond excitation, can provide insight...

  15. Terahertz imaging applied to cancer diagnosis

    Science.gov (United States)

    Brun, M.-A.; Formanek, F.; Yasuda, A.; Sekine, M.; Ando, N.; Eishii, Y.

    2010-08-01

    We report on terahertz (THz) time-domain spectroscopy imaging of 10 µm thick histological sections. The sections are prepared according to standard pathological procedures and deposited on a quartz window for measurements in reflection geometry. Simultaneous acquisition of visible images enables registration of THz images and thus the use of digital pathology tools to investigate the links between the underlying cellular structure and specific THz information. An analytic model taking into account the polarization of the THz beam, its incidence angle, the beam shift between the reference and sample pulses as well as multiple reflections within the sample is employed to determine the frequency-dependent complex refractive index. Spectral images are produced through segmentation of the extracted refractive index data using clustering methods. Comparisons of visible and THz images demonstrate spectral differences not only between tumor and healthy tissues but also within tumors. Further visualization using principal component analysis suggests different mechanisms as to the origin of image contrast.

  16. 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.

  17. Longitudinal Near-Field Coupling between Acoustic Resonators Grafted onto a Waveguide

    Directory of Open Access Journals (Sweden)

    Yan-Feng Wang

    2017-10-01

    Full Text Available We investigate longitudinal near-field coupling between acoustic resonators grafted along a waveguide. Experiments are performed in the audible range with a simple acoustic system composed of a finite aperiodic sequence of air resonators. Transmission typically shows a zero around a resonance frequency of a single resonator, as is well known. When two identical resonators are brought in close proximity, however, we observe that longitudinal near-field coupling strongly influences the acoustic transmission. When the separation between resonators is increased so that they can be considered in the far field of one another, we further observe the appearance of Fano-like transmission profiles. We explain this observation by the formation of locally resonant Fabry-Perot interferometers from every pair of resonators. All experimental results are compared to three-dimensional finite element analysis of the acoustic system.

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

    International Nuclear Information System (INIS)

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

    2014-01-01

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

  19. Three-dimensional propagation in near-field tomographic X-ray phase retrieval

    International Nuclear Information System (INIS)

    Ruhlandt, Aike; Salditt, Tim

    2016-01-01

    An extension of phase retrieval algorithms for near-field X-ray (propagation) imaging to three dimensions is presented, enhancing the quality of the reconstruction by exploiting previously unused three-dimensional consistency constraints. This paper presents an extension of phase retrieval algorithms for near-field X-ray (propagation) imaging to three dimensions, enhancing the quality of the reconstruction by exploiting previously unused three-dimensional consistency constraints. The approach is based on a novel three-dimensional propagator and is derived for the case of optically weak objects. It can be easily implemented in current phase retrieval architectures, is computationally efficient and reduces the need for restrictive prior assumptions, resulting in superior reconstruction quality

  20. A Compact RFID Reader Antenna for UHF Near-Field and Far-Field Operations

    Directory of Open Access Journals (Sweden)

    Lai Xiao zheng

    2013-01-01

    Full Text Available A compact loop antenna is presented for mobile ultrahigh frequency (UHF radio frequency identification (RFID application. This antenna, printed on a 0.8 mm thick FR4 substrate with a small size of 31 mm × 31 mm, achieves good impedance bandwidth from 897 to 928 MHz, which covers USA RFID Band (902–928 MHz. The proposed loop configuration, with a split-ring resonator (SRR coupled inside it, demonstrates strong and uniform magnetic field distribution in the near-field antenna region. Its linearly polarized radiation pattern provides available far-field gain. Finally, the reading capabilities of antenna are up to 56 mm for near-field and 1.05 m for far-field UHF RFID operations, respectively.

  1. 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

    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......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...... recently gaining attention. Further, models that are mostly emissions-based, may not necessarily be applicable to all types of chemical release from consumer products. To address this gap, we (1) define a framework to simultaneously account for exposure to chemicals in the near- and far-field, (2...

  2. Observation of nanostructure by scanning near-field optical microscope with small sphere probe

    Directory of Open Access Journals (Sweden)

    Yasushi Oshikane, Toshihiko Kataoka, Mitsuru Okuda, Seiji Hara, Haruyuki Inoue and Motohiro Nakano

    2007-01-01

    Full Text Available Step and terrace structure has been observed in an area of 1 μm×1 μm on the cleaved surface of KCl–KBr solid-solution single crystal by scanning near-field optical microscope (SNOM with a small sphere probe of 500 nm diameter. Lateral spatial resolution of the SNOM system was estimated to be 20 nm from the observation of step width and the scanning-step interval. Vertical spatial resolution was estimated to be 5–2 nm from the observation of step height and noise level of photomultiplier tube (PMT. With applying a dielectric dipole radiation model to the probe surface, the reason why such a high spatial resolution was obtained in spite of the 500 nm sphere probe, was understood as the effect of the near-field term appeared in the radiation field equations.

  3. CALIBRE and CRYSTAL: Near-field and geosphere models for Project-90

    International Nuclear Information System (INIS)

    Robinson, P.C.; Worgan, K.J.; Shaw, W.T.; Wingefors, S.

    1991-01-01

    A new near-field model (CALIBRE) and a fractured geosphere model (CRYSTAL) have been developed in support of the Swedish Nuclear Power Inspectorate's Project-90 safety assessment of a reference repository for spent nuclear fuel. CALIBRE calculates in two dimensions the twin problems of oxidant and radionuclide migration through a bentonite buffer and fractured host rock, with redox front formation and precipitation of nuclides at the redox front. The output from CALIBRE can be input directly to the CRYSTAL code, which is a fast, one-dimensional contaminant transport model of a fractured rock geosphere. This paper describes the main features of the models and illustrates how certain processes can have a significant impact on the flux of radionuclides emerging from the near field to the geosphere, and from the geosphere to the biosphere

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

    International Nuclear Information System (INIS)

    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 head-related 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 0.035m 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 suitable for the near-field HRTF measurements. (fundamental areas of phenomenology(including applications))

  5. Near field analysis of CSG and BSG combined element under high power laser condition

    Science.gov (United States)

    Yao, Xin; Gao, Fuhua; Zhang, Yixiao; Wang, Lei; Guo, Yongkang; Hou, Xi

    2006-08-01

    In high power laser system, it is of great interest to combine two or more diffractive structures, in particular, the beam-sampling gratings (BSG) and the color separation gratings (CSG), onto one element. However, the combined element with diffractive structure on both surfaces, may cause serious laser induced damage to the element itself. So, this paper use Fourier modal method to analyze the near field characteristic of CSG and BSG combined element. Through theoretically analysis and numerical calculation, amplitude and phase distribution of electric field are present both inside and outside the diffractive structural region, and the maximum peak-to-average modulation in near field is also given. Based on this study, the most possibility of optical damage induced by beam modulation of CSG and BSG combined element appears in the neighborhood of the interface.

  6. Three-dimensional propagation in near-field tomographic X-ray phase retrieval

    Energy Technology Data Exchange (ETDEWEB)

    Ruhlandt, Aike, E-mail: aruhlan@gwdg.de; Salditt, Tim [Institut für Röntgenphysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, Göttingen (Germany)

    2016-01-29

    An extension of phase retrieval algorithms for near-field X-ray (propagation) imaging to three dimensions is presented, enhancing the quality of the reconstruction by exploiting previously unused three-dimensional consistency constraints. This paper presents an extension of phase retrieval algorithms for near-field X-ray (propagation) imaging to three dimensions, enhancing the quality of the reconstruction by exploiting previously unused three-dimensional consistency constraints. The approach is based on a novel three-dimensional propagator and is derived for the case of optically weak objects. It can be easily implemented in current phase retrieval architectures, is computationally efficient and reduces the need for restrictive prior assumptions, resulting in superior reconstruction quality.

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

    International Nuclear Information System (INIS)

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

    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. (rapid communication)

  8. Near Field Observations of Seismicity in Volcanic Environments: A Read-Made Field Laboratory

    Science.gov (United States)

    Bean, C. J.; Thun, J.; Eibl, E. P. S.; Benson, P. M.; Rowley, P.; Lokmer, I.; Cauchie, L.

    2017-12-01

    Volcanic environments experience periods of rapid stress fluctuations and consequent seismicity. This volcano seismicity is diverse in character, spanning the range from discrete high frequency events through low-frequency earthquakes and tremor. The inter-relationships between these events appear to be controlled by edifice rheology, stress state and the presence of fluids (which help modulate the stress field). In general volcanoes are accessible to instrumentation, allowing near-field access to the seismicity at play. Here we present results from a range of field, numerical and laboratory experiments that demonstrate the controls that rheology and strain rate play on seismicity type. In particular we demonstrate the role played by internal friction angles on the initiation and evolution of seismicity, in dry weak-compliant volcanic materials. Furthermore we show the importance of near field observation in constraining details of the seismic source, in a meso-scale field setting.

  9. 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.

  10. 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....

  11. Development of Near-Field Microwave Microscope with the Functionality of Scanning Tunneling Spectroscopy

    Science.gov (United States)

    Machida, Tadashi; Gaifullin, Marat B.; Ooi, Shuuich; Kato, Takuya; Sakata, Hideaki; Hirata, Kazuto

    2010-11-01

    We describe the details of an original near-field scanning microwave microscope, developed for simultaneous measurements of local density-of-states (LDOS) and local ohmic losses (LOL). Improving microwave detection systems, we have succeeded in distinguishing the LDOS and LOL even between two low resistance materials; gold and highly orientated pyrolitic graphite. The experimental data indicate that our microscope holds a capability to investigate both LDOS and LOL in nanoscale.

  12. 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)

  13. Overcoming the black body limit in plasmonic and graphene near-field thermophotovoltaic systems.

    Science.gov (United States)

    Ilic, Ognjen; Jablan, Marinko; Joannopoulos, John D; Celanovic, Ivan; Soljacić, Marin

    2012-05-07

    Near-field thermophotovoltaic (TPV) systems with carefully tailored emitter-PV properties show large promise for a new temperature range (600 – 1200K) solid state energy conversion, where conventional thermoelectric (TE) devices cannot operate due to high temperatures and far-field TPV schemes suffer from low efficiency and power density. We present a detailed theoretical study of several different implementations of thermal emitters using plasmonic materials and graphene. We find that optimal improvements over the black body limit are achieved for low bandgap semiconductors and properly matched plasmonic frequencies. For a pure plasmonic emitter, theoretically predicted generated power density of 14 W/cm2 and efficiency of 36% can be achieved at 600K (hot-side), for 0.17eV bandgap (InSb). Developing insightful approximations, we argue that large plasmonic losses can, contrary to intuition, be helpful in enhancing the overall near-field transfer. We discuss and quantify the properties of an optimal near-field photovoltaic (PV) diode. In addition, we study plasmons in graphene and show that doping can be used to tune the plasmonic dispersion relation to match the PV cell bangap. In case of graphene, theoretically predicted generated power density of 6(120) W/cm2 and efficiency of 35(40)% can be achieved at 600(1200)K, for 0.17eV bandgap. With the ability to operate in intermediate temperature range, as well as high efficiency and power density, near-field TPV systems have the potential to complement conventional TE and TPV solid state heat-to-electricity conversion devices.

  14. Quantitative topographic imaging using a near-field scanning microwave microscope

    Science.gov (United States)

    Vlahacos, C. P.; Steinhauer, D. E.; Dutta, S. K.; Feenstra, B. J.; Anlage, Steven M.; Wellstood, F. C.

    1998-04-01

    We describe a technique for extracting topographic information using a scanning near-field microwave microscope. By monitoring the shift of the system's resonant frequency, we obtain quantitative topographic images of uniformly conducting metal surfaces. At a frequency of 9.572 GHz, our technique allows a height discrimination of about 55 nm at a separation of 30 μm. We present topographic images of uneven, conducting samples and compare the height response and sensitivity of the system with theoretical expectations.

  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 pe...... permittivity of the soil and the current distribution of the probe....

  16. Dielectric and fluorescent samples imaged by scanning near-field optical microscopy in reflection

    OpenAIRE

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

    1995-01-01

    Dielectric fluorescent samples are imaged by scanning near- field optical microscopy in reflection. A non-metallized tapered fibre tip is used both as an emitter and a detector. Shear force feedback controls the distance between the tip and the sample and gives simultaneously a topographic image of the surface. A direct correlation with the optical image is obtained. We demonstrate that this reflection setup is suitable for dielectric samples. Images in fluorescence have been obtained o­n Lan...

  17. 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).

  18. Fast near-field calculation for volume integral equations for layered media

    OpenAIRE

    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 nea...

  19. Geometrical optics in the near field: local plane-interface approach with evanescent waves.

    Science.gov (United States)

    Bose, Gaurav; Hyvärinen, Heikki J; Tervo, Jani; Turunen, Jari

    2015-01-12

    We show that geometrical models may provide useful information on light propagation in wavelength-scale structures even if evanescent fields are present. We apply a so-called local plane-wave and local plane-interface methods to study a geometry that resembles a scanning near-field microscope. We show that fair agreement between the geometrical approach and rigorous electromagnetic theory can be achieved in the case where evanescent waves are required to predict any transmission through the structure.

  20. High Reliability Oscillators for Terahertz Systems, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Terahertz sources based on lower frequency oscillators and amplifiers plus a chain of frequency multipliers are the workhorse technology for NASA's terahertz...

  1. Near-field radiative heat transfer in graphene plasmonic nanodisk dimers

    Science.gov (United States)

    Ramirez, Francisco V.; Shen, Sheng; McGaughey, Alan J. H.

    2017-10-01

    Near-field thermal radiation mediated by surface plasmons in parallel graphene nanodisk dimers is studied using a semianalytical model under the electrostatic approximation. The radiative heat transfer between two disks as a function of the distance between them in coaxial and coplanar configurations is first considered. Three regimes are identified and their extents determined using nondimensional analysis. When the edge-to-edge separation is smaller than the disk diameter, near-field coupling and surface plasmon hybridization lead to an enhancement of the radiative heat transfer by up to four orders of magnitude compared to the Planck blackbody limit. A mismatch in the disk diameters affects the plasmonic mode hybridization and can either diminish or enhance the near-field radiation. Destructive interference between eigenmodes that emerge when the relative orientation between disks is varied can induce a twofold reduction in the radiative heat transfer. In all configurations, the radiative heat transfer properties can be controlled by tuning the disk size/orientation, the substrate optical properties, and graphene's doping concentration and electron mobility.

  2. Near field communication (NFC) model for arduino uno based security systems office system

    Science.gov (United States)

    Chairunnas, A.; Abdurrasyid, I.

    2018-03-01

    Currently, many offices or companies that start growing rapidly in a company or office should have a very limited room to enter only people entitled to enter the room and use the facilities contained in it, for example, Files in it must have many files and documents very important because to reduce the abuse of files and irresponsible person. Because it will be made room door security system by using Near Field Communication on android smartphone. Software used is Arduino IDE. The tools used in this system are Arduino Uno R3, NFC shield, pear sensor, bell, led, servo, 16 × 2 LCD, and Near Field Communication (NFC) in android smartphone. This system runs based on 2 inputs of a new technology that is Near Field Communication (NFC) in android smartphone. And also use pear sensor to detect unauthorized person entering the room. If the correct password is entered then the door will open and the pear sensor will light off if wrong then the bell will light up.

  3. 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...

  4. Near-field thermophotovoltaic system design and calculation based on coupled-mode analysis

    Science.gov (United States)

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

    2017-10-01

    The coupling of resonant modes between two surfaces is important in near-field heat transfer and near-field thermophotovoltaic (TPV) systems. Recently, coupled-mode theory (CMT) has been developed for the analysis and optimal design of TPV systems. We use CMT to analyze the "emitter-vacuum-PV cell" configuration and quantitatively show how the emitter of a nanostructure can drastically improve the near-field TPV device performance. The key feature of the nanostructure is the additional geometry-induced resonant mode, whose energy is lower than the original surface plasmon polariton resonant frequency and much closer to the bandgap of the PV cell. Specifically, we show that, with a simple grating structure, the generated power density of a TPV cell is increased from 13 to 34 W/cm2 when the PV cell is fixed at 300 K and the emitter is at 1000 K. The increase is over 20 times higher when both planar and grating emitters are at a lower temperature of 500 K.

  5. Laminar and turbulent nozzle-jet flows and their acoustic near-field

    International Nuclear Information System (INIS)

    Bühler, Stefan; Obrist, Dominik; Kleiser, Leonhard

    2014-01-01

    We investigate numerically the effects of nozzle-exit flow conditions on the jet-flow development and the near-field sound at a diameter-based Reynolds number of Re D = 18 100 and Mach number Ma = 0.9. Our computational setup features the inclusion of a cylindrical nozzle which allows to establish a physical nozzle-exit flow and therefore well-defined initial jet-flow conditions. Within the nozzle, the flow is modeled by a potential flow core and a laminar, transitional, or developing turbulent boundary layer. The goal is to document and to compare the effects of the different jet inflows on the jet flow development and the sound radiation. For laminar and transitional boundary layers, transition to turbulence in the jet shear layer is governed by the development of Kelvin-Helmholtz instabilities. With the turbulent nozzle boundary layer, the jet flow development is characterized by a rapid changeover to a turbulent free shear layer within about one nozzle diameter. Sound pressure levels are strongly enhanced for laminar and transitional exit conditions compared to the turbulent case. However, a frequency and frequency-wavenumber analysis of the near-field pressure indicates that the dominant sound radiation characteristics remain largely unaffected. By applying a recently developed scaling procedure, we obtain a close match of the scaled near-field sound spectra for all nozzle-exit turbulence levels and also a reasonable agreement with experimental far-field data

  6. Optimization of a near-field thermophotovoltaic system operating at low temperature and large vacuum gap

    Science.gov (United States)

    Lim, Mikyung; Song, Jaeman; Kim, Jihoon; Lee, Seung S.; Lee, Ikjin; Lee, Bong Jae

    2018-05-01

    The present work successfully achieves a strong enhancement in performance of a near-field thermophotovoltaic (TPV) system operating at low temperature and large-vacuum-gap width by introducing a hyperbolic-metamaterial (HMM) emitter, multilayered graphene, and an Au-backside reflector. Design variables for the HMM emitter and the multilayered-graphene-covered TPV cell are optimized for maximizing the power output of the near-field TPV system with the genetic algorithm. The near-field TPV system with the optimized configuration results in 24.2 times of enhancement in power output compared with that of the system with a bulk emitter and a bare TPV cell. Through the analysis of the radiative heat transfer together with surface-plasmon-polariton (SPP) dispersion curves, it is found that coupling of SPPs generated from both the HMM emitter and the multilayered-graphene-covered TPV cell plays a key role in a substantial increase in the heat transfer even at a 200-nm vacuum gap. Further, the backside reflector at the bottom of the TPV cell significantly increases not only the conversion efficiency, but also the power output by generating additional polariton modes which can be readily coupled with the existing SPPs of the HMM emitter and the multilayered-graphene-covered TPV cell.

  7. Sequencing of acoustic events in the near field of subsonic jets

    Science.gov (United States)

    Lewalle, Jacques; Kan, Pinqing

    2013-11-01

    Our group has developed several pattern recognition algorithms to identify short events common to near-and far-field signals. Here we are treating far-field and near-field pressure data as well as TR-PIV (10kHz) sections through the near jet. Our algorithms are based on wavelet transforms (band-pass filtering) and cross-correlations, identifying short excerpts in the time-frequency-lag domain that contribute most to the correlations. Matching such events between multiple signal pairs exposes the sequencing of near-field activity. We consider only near-field events (NFEs) matched with a loud far-field event (FFE). The NFEs are based on the correlation of velocity, vorticity, 2-D divergence, Q-index and Kulite signals with far-field pressure. The timing of the NFEs maps out possible sequences of events related to loud coherent noise emission. Results at several subsonic Mach numbers are compared. This work is supported in part by Spectral Energies LLC, under an SBIR grant from AFRL; by a Syracuse University Graduate Fellowship; and by the Department of Mechanical and Aerospace Engineering at SU.

  8. Meshed doped silicon photonic crystals for manipulating near-field thermal radiation

    Science.gov (United States)

    Elzouka, Mahmoud; Ndao, Sidy

    2018-01-01

    The ability to control and manipulate heat flow is of great interest to thermal management and thermal logic and memory devices. Particularly, near-field thermal radiation presents a unique opportunity to enhance heat transfer while being able to tailor its characteristics (e.g., spectral selectivity). However, achieving nanometric gaps, necessary for near-field, has been and remains a formidable challenge. Here, we demonstrate significant enhancement of the near-field heat transfer through meshed photonic crystals with separation gaps above 0.5 μm. Using a first-principle method, we investigate the meshed photonic structures numerically via finite-difference time-domain technique (FDTD) along with the Langevin approach. Results for doped-silicon meshed structures show significant enhancement in heat transfer; 26 times over the non-meshed corrugated structures. This is especially important for thermal management and thermal rectification applications. The results also support the premise that thermal radiation at micro scale is a bulk (rather than a surface) phenomenon; the increase in heat transfer between two meshed-corrugated surfaces compared to the flat surface (8.2) wasn't proportional to the increase in the surface area due to the corrugations (9). Results were further validated through good agreements between the resonant modes predicted from the dispersion relation (calculated using a finite-element method), and transmission factors (calculated from FDTD).

  9. Spatial Terahertz Modulator

    Science.gov (United States)

    Xie, Zhenwei; Wang, Xinke; Ye, Jiasheng; Feng, Shengfei; Sun, Wenfeng; Akalin, Tahsin; Zhang, Yan

    2013-11-01

    Terahertz (THz) technology is a developing and promising candidate for biological imaging, security inspection and communications, due to the low photon energy, the high transparency and the broad band properties of the THz radiation. However, a major encountered bottleneck is lack of efficient devices to manipulate the THz wave, especially to modulate the THz wave front. A wave front modulator should allow the optical or electrical control of the spatial transmission (or reflection) of an input THz wave and hence the ability to encode the information in a wave front. Here we propose a spatial THz modulator (STM) to dynamically control the THz wave front with photo-generated carriers. A computer generated THz hologram is projected onto a silicon wafer by a conventional spatial light modulator (SLM). The corresponding photo-generated carrier spatial distribution will be induced, which forms an amplitude hologram to modulate the wave front of the input THz beam. Some special intensity patterns and vortex beams are generated by using this method. This all-optical controllable STM is structure free, high resolution and broadband. It is expected to be widely used in future THz imaging and communication systems.

  10. SITE-94. Modelling of near-field chemistry for SITE-94

    International Nuclear Information System (INIS)

    Arthur, R.; Apted, M.

    1996-12-01

    This report evaluates methods for the incorporation of site data into models simulating the long-term chemical evolution of the near field. The models are based on limiting conditions at equilibrium, or steady state, in three closed systems representing fully saturated bentonite, Fe o corrosion products of the canister and spent fuel. A l kg reference mass of site groundwater is assumed to equilibrate first with bentonite and then with the canister's corrosion products. A third closed system representing spent fuel is modeled in terms of spent-fuel dissolution in 1 kg of water evolved from the canister, coupled with steady-state constraints on the rate of oxidant production by α radiolysis of H 2 O(l). Precipitation of secondary minerals controlling the solubilities of radioelements dissolved from spent fuel is also simulated in this model. Version 7.2 of the EQ3/6 geochemical software package and its supporting composite thermodynamic database, dataO.com.R22, are used to carry out these calculations. It is concluded that chemical models of near-field evolution combined with thermodynamic models of radionuclide speciation-solubility behavior can assist efforts to assimilate site characterization data into the performance assessment process, and to deal with uncertainties that are inherent in both site properties and in concepts of near field chemistry. It is essential, however, that expert judgement and prudence should be exercised such that model results are conservative with respect to acknowledged and documented uncertainties. Most importantly, it must be recognized that it is probably not possible to model with a high-level of accuracy the complex chemical environments and long timescales involved in disposal technologies for nuclear wastes. For performance assessment, however, only bounding values are needed, and modeling approaches such as described in this report are useful for this purpose. Technical peer review and cross-comparisons of near-field modeling

  11. Electromagnetic model of a near-field cable-free impedance and gain measurement technique for electrically small antennas

    DEFF Research Database (Denmark)

    Zhang, Jiaying; Pivnenko, Sergey; Breinbjerg, Olav

    2011-01-01

    In this paper, a novel near-field cable-free impedance and gain measurement technique for electrically small antennas is proposed. In this technique, with the electrically small antenna placed in the near-field region of the probe, the properties of this antenna are extracted by measuring...

  12. Terahertz antenna technology for space applications

    CERN Document Server

    Choudhury, Balamati; Jha, Rakesh Mohan

    2016-01-01

    This book explores the terahertz antenna technology towards implementation of compact, consistent and cheap terahertz sources, as well as the high sensitivity terahertz detectors. The terahertz EM band provides a transition between the electronic and the photonic regions thus adopting important characteristics from these regimes. These characteristics, along with the progress in semiconductor technology, have enabled researchers to exploit hitherto unexplored domains including satellite communication, bio-medical imaging, and security systems. The advances in new materials and nanostructures such as graphene will be helpful in miniaturization of antenna technology while simultaneously maintaining the desired output levels. Terahertz antenna characterization of bandwidth, impedance, polarization, etc. has not yet been methodically structured and it continues to be a major research challenge. This book addresses these issues besides including the advances of terahertz technology in space applications worldwide,...

  13. Terahertz technology for imaging and spectroscopy

    Science.gov (United States)

    Crowe, T. W.; Porterfield, D. W.; Hesler, J. L.; Bishop, W. L.; Kurtz, D. S.; Hui, K.

    2006-05-01

    The terahertz region of the electromagnetic spectrum has unique properties that make it especially useful for imaging and spectroscopic detection of concealed weapons, explosives and chemical and biological materials. However, terahertz energy is difficult to generate and detect, and this has led to a technology gap in this frequency band. Nonlinear diodes can be used to bridge this gap by translating the functionality achieved at microwave frequencies to the terahertz band. Basic building blocks include low-noise mixers, frequency multipliers, sideband generators and direct detectors. These terahertz components rely on planar Schottky diodes and recently developed integrated diode circuits make them easier to assemble and more robust. The new generation of terahertz sources and receivers requires no mechanical tuning, yet achieves high efficiency and broad bandwidth. This paper reviews the basic design of terahertz transmitters and receivers, with special emphasis on the recent development of systems that are compact, easy to use and have excellent performance.

  14. Terahertz Nanofocusing with Cantilevered Terahertz-Resonant Antenna Tips.

    Science.gov (United States)

    Mastel, Stefan; Lundeberg, Mark B; Alonso-González, Pablo; Gao, Yuanda; Watanabe, Kenji; Taniguchi, Takashi; Hone, James; Koppens, Frank H L; Nikitin, Alexey Y; Hillenbrand, Rainer

    2017-11-08

    We developed THz-resonant scanning probe tips, yielding strongly enhanced and nanoscale confined THz near fields at their tip apex. The tips with length in the order of the THz wavelength (λ = 96.5 μm) were fabricated by focused ion beam (FIB) machining and attached to standard atomic force microscopy (AFM) cantilevers. Measurements of the near-field intensity at the very tip apex (25 nm radius) as a function of tip length, via graphene-based (thermoelectric) near-field detection, indicate their first and second order geometrical antenna resonances for tip length of 33 and 78 μm, respectively. On resonance, we find that the near-field intensity is enhanced by one order of magnitude compared to tips of 17 μm length (standard AFM tip length), which is corroborated by numerical simulations that further predict remarkable intensity enhancements of about 10 7 relative to the incident field. Because of the strong field enhancement and standard AFM operation of our tips, we envision manifold and straightforward future application in scattering-type THz near-field nanoscopy and THz photocurrent nanoimaging, nanoscale nonlinear THz imaging, or nanoscale control and manipulation of matter employing ultrastrong and ultrashort THz pulses.

  15. 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.

  16. Near-Field Imaging of Free Carriers in ZnO Nanowires with a Scanning Probe Tip Made of Heavily Doped Germanium

    Science.gov (United States)

    Sakat, Emilie; Giliberti, Valeria; Bollani, Monica; Notargiacomo, Andrea; Pea, Marialilia; Finazzi, Marco; Pellegrini, Giovanni; Hugonin, Jean-Paul; Weber-Bargioni, Alexander; Melli, Mauro; Sassolini, Simone; Cabrini, Stefano; Biagioni, Paolo; Ortolani, Michele; Baldassarre, Leonetta

    2017-11-01

    A novel scanning probe tip made of heavily doped semiconductor is fabricated and used instead of standard gold-coated tips in infrared scattering-type near-field microscopy. Midinfrared near-field microscopy experiments are conducted on ZnO nanowires with a lateral resolution better than 100 nm, using tips made of heavily electron-doped germanium with a plasma frequency in the midinfrared (plasma wavelength of 9.5 μ m ). Nanowires embedded in a dielectric matrix are imaged at two wavelengths, 11.3 and 8.0 μ m , above and below the plasma wavelength of the tips. An opposite sign of the imaging contrasts between the nanowire and the dielectric matrix is observed at the two infrared wavelengths, indicating a clear role of the free-electron plasma in the heavily doped germanium tip in building the imaging contrast. Electromagnetic simulations with a multispherical dipole model accounting for the finite size of the tip are well consistent with the experiments. By comparison of the simulated and measured imaging contrasts, an estimate for the local free-carrier density in the investigated ZnO nanowires in the low 1019 cm-3 range is retrieved. The results are benchmarked against the scattering intensity and phase maps obtained on the same sample with a gold-coated probe tip in pseudoheterodyne detection mode.

  17. 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.

  18. Buried shallow fault slip from the South Napa earthquake revealed by near-field geodesy.

    Science.gov (United States)

    Brooks, Benjamin A; Minson, Sarah E; Glennie, Craig L; Nevitt, Johanna M; Dawson, Tim; Rubin, Ron; Ericksen, Todd L; Lockner, David; Hudnut, Kenneth; Langenheim, Victoria; Lutz, Andrew; Mareschal, Maxime; Murray, Jessica; Schwartz, David; Zaccone, Dana

    2017-07-01

    Earthquake-related fault slip in the upper hundreds of meters of Earth's surface has remained largely unstudied because of challenges measuring deformation in the near field of a fault rupture. We analyze centimeter-scale accuracy mobile laser scanning (MLS) data of deformed vine rows within ±300 m of the principal surface expression of the M (magnitude) 6.0 2014 South Napa earthquake. Rather than assuming surface displacement equivalence to fault slip, we invert the near-field data with a model that allows for, but does not require, the fault to be buried below the surface. The inversion maps the position on a preexisting fault plane of a slip front that terminates ~3 to 25 m below the surface coseismically and within a few hours postseismically. The lack of surface-breaching fault slip is verified by two trenches. We estimate near-surface slip ranging from ~0.5 to 1.25 m. Surface displacement can underestimate fault slip by as much as 30%. This implies that similar biases could be present in short-term geologic slip rates used in seismic hazard analyses. Along strike and downdip, we find deficits in slip: The along-strike deficit is erased after ~1 month by afterslip. We find no evidence of off-fault deformation and conclude that the downdip shallow slip deficit for this event is likely an artifact. As near-field geodetic data rapidly proliferate and will become commonplace, we suggest that analyses of near-surface fault rupture should also use more sophisticated mechanical models and subsurface geomechanical tests.

  19. Near-field electromagnetic holography for high-resolution analysis of network interactions in neuronal tissue.

    Science.gov (United States)

    Kjeldsen, Henrik D; Kaiser, Marcus; Whittington, Miles A

    2015-09-30

    Brain function is dependent upon the concerted, dynamical interactions between a great many neurons distributed over many cortical subregions. Current methods of quantifying such interactions are limited by consideration only of single direct or indirect measures of a subsample of all neuronal population activity. Here we present a new derivation of the electromagnetic analogy to near-field acoustic holography allowing high-resolution, vectored estimates of interactions between sources of electromagnetic activity that significantly improves this situation. In vitro voltage potential recordings were used to estimate pseudo-electromagnetic energy flow vector fields, current and energy source densities and energy dissipation in reconstruction planes at depth into the neural tissue parallel to the recording plane of the microelectrode array. The properties of the reconstructed near-field estimate allowed both the utilization of super-resolution techniques to increase the imaging resolution beyond that of the microelectrode array, and facilitated a novel approach to estimating causal relationships between activity in neocortical subregions. The holographic nature of the reconstruction method allowed significantly better estimation of the fine spatiotemporal detail of neuronal population activity, compared with interpolation alone, beyond the spatial resolution of the electrode arrays used. Pseudo-energy flow vector mapping was possible with high temporal precision, allowing a near-realtime estimate of causal interaction dynamics. Basic near-field electromagnetic holography provides a powerful means to increase spatial resolution from electrode array data with careful choice of spatial filters and distance to reconstruction plane. More detailed approaches may provide the ability to volumetrically reconstruct activity patterns on neuronal tissue, but the ability to extract vectored data with the method presented already permits the study of dynamic causal interactions

  20. Multipass laser amplification with near-field far-field optical separation

    Science.gov (United States)

    Hagen, Wilhelm F.

    1979-01-01

    This invention discloses two classes of optical configurations for high power laser amplification, one allowing near-field and the other allowing far-field optical separation, for the multiple passage of laser pulses through one or more amplifiers over an open optical path. These configurations may reimage the amplifier or any other part of the cavity on itself so as to suppress laser beam intensity ripples that arise from diffraction and/or non-linear effects. The optical cavities combine the features of multiple passes, spatial filtering and optical reimaging and allow sufficient time for laser gain recovery.

  1. Near-field antenna testing using the Hewlett Packard 8510 automated network analyzer

    Science.gov (United States)

    Kunath, Richard R.; Garrett, Michael J.

    1990-01-01

    Near-field antenna measurements were made using a Hewlett-Packard 8510 automated network analyzer. This system features measurement sensitivity better than -90 dBm, at measurement speeds of one data point per millisecond in the fast data acquisition mode. The system was configured using external, even harmonic mixers and a fiber optic distributed local oscillator signal. Additionally, the time domain capability of the HP8510, made it possible to generate far-field diagnostic results immediately after data acquisition without the use of an external computer.

  2. 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.

  3. Apertureless near-field optical microscopy with differential and close-proximity detection

    Science.gov (United States)

    Fukuzawa, Kenji; Tanaka, Yuriko

    1997-07-01

    A new method of apertureless near-field optical microscopy that combines laterally differential detection with close-proximity detection has been developed. The laterally differential detection allows the light scattered from the probe apex to be distinguished from the background light. The close-proximity detection is done using a microfabricated photosensitive cantilever; it is thought to be a form of heterodyne detection, which provides a high signal level. This method makes it possible to detect the light scattered from the probe apex, which depends on the coupling between the probe apex dipole and the sample feature dipole.

  4. Superconducting Material - A study on the near field of a superconducting antenna

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Soon Chil; Lee, Seung Chul; Doe, Joong Hoe; Hoe, Mi Ra [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

    1996-07-01

    The pulse spectroscopy in combination with piezoelectric resonance makes an ideal non-disturbing tool for the measurement of electric field near an antenna. This new field sensing technique was used to investigate the field of a ring antenna the near field of which is widely used such as the plasma generation and NMR. The superconducting wire also have the dominant capacitive AC field in near regions, meaning that the net charge on the ring surface is not due to the ohm`s law as in DC. 23 refs., 8 figs. (author)

  5. Ballistic near-field heat transport in dense many-body systems

    Science.gov (United States)

    Latella, Ivan; Biehs, Svend-Age; Messina, Riccardo; Rodriguez, Alejandro W.; Ben-Abdallah, Philippe

    2018-01-01

    Radiative heat transport mediated by near-field interactions is known to be superdiffusive in dilute, many-body systems. Here we use a generalized Landauer theory of radiative heat transfer in many-body planar systems to demonstrate a nonmonotonic transition from superdiffusive to ballistic transport in dense systems. We show that such a transition is associated to a change of the polarization of dominant modes. Our findings are complemented by a quantitative study of the relaxation dynamics of the system in the different regimes of heat transport. This result could have important consequences on thermal management at nanoscale of many-body systems.

  6. Parallel alignment of bacteria using near-field optical force array for cell sorting

    Science.gov (United States)

    Zhao, H. T.; Zhang, Y.; Chin, L. K.; Yap, P. H.; Wang, K.; Ser, W.; Liu, A. Q.

    2017-08-01

    This paper presents a near-field approach to align multiple rod-shaped bacteria based on the interference pattern in silicon nano-waveguide arrays. The bacteria in the optical field will be first trapped by the gradient force and then rotated by the scattering force to the equilibrium position. In the experiment, the Shigella bacteria is rotated 90 deg and aligned to horizontal direction in 9.4 s. Meanwhile, 150 Shigella is trapped on the surface in 5 min and 86% is aligned with angle < 5 deg. This method is a promising toolbox for the research of parallel single-cell biophysical characterization, cell-cell interaction, etc.

  7. 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

  8. 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......-of-plane light scattering is directly observed for both 1D and 2D gratings (period 590 nm) fabricated on silicon-on-insulator wafers and the corresponding SNOM images are presented. Using the obtained SNOM images, we analyze light intensity distributions along PC gratings measured at different wavelengths and...

  9. Room-temperature near-field reflection spectroscopy of single quantum wells

    DEFF Research Database (Denmark)

    Langbein, Wolfgang Werner; Hvam, Jørn Marcher; Madsen, Steen

    1997-01-01

    . This technique suppresses efficiently the otherwise dominating far-field background and reduces topographic artifacts. We demonstrate its performance on a thin, strained near-surface CdS/ZnS single quantum well at room temperature. The optical structure of these topographically flat samples is due to Cd......We report on a novel optical near-field technique to measure the local polarizability of a topographically flat sample with a spatial resolution better than 100 nm. Using an uncoated fiber probe, we implement a cross-polarization detection of the optical signal at the fiber dither frequency...

  10. Circularly polarized near-field optical mapping of spin-resolved quantum Hall chiral edge states.

    Science.gov (United States)

    Mamyouda, Syuhei; Ito, Hironori; Shibata, Yusuke; Kashiwaya, Satoshi; Yamaguchi, Masumi; Akazaki, Tatsushi; Tamura, Hiroyuki; Ootuka, Youiti; Nomura, Shintaro

    2015-04-08

    We have successfully developed a circularly polarized near-field scanning optical microscope (NSOM) that enables us to irradiate circularly polarized light with spatial resolution below the diffraction limit. As a demonstration, we perform real-space mapping of the quantum Hall chiral edge states near the edge of a Hall-bar structure by injecting spin polarized electrons optically at low temperature. The obtained real-space mappings show that spin-polarized electrons are injected optically to the two-dimensional electron layer. Our general method to locally inject spins using a circularly polarized NSOM should be broadly applicable to characterize a variety of nanomaterials and nanostructures.

  11. Apoptosis study of the macrophage via near-field scanning optical microscope

    International Nuclear Information System (INIS)

    Wang, D-C; Chen, K-Y; Chen, G-Y; Chen, S-H; Wun, S-J

    2008-01-01

    The cell apoptosis phenomenon was studied by traditional optical microscope with much lower resolution and also observed by Atomic Force Microscope (AFM) with nano-resolution recently. They both detect the cell apoptosis through the change of cell topography. In this study, the cell apoptosis was investigated via Near-Field Scanning Optical Microscope (NSOM). The cell topography, with nano-scaled resolution, and its optical characteristics were observed by NSOM at the same measurement scanning. The macrophage was chosen as the cell investigated. To understand the cell apoptosis process is the goal set for the research. The apoptosis process was related to the variations of the optical characteristics of the cell

  12. Cathodoluminescence-activated nanoimaging: noninvasive near-field optical microscopy in an electron microscope.

    Science.gov (United States)

    Bischak, Connor G; Hetherington, Craig L; Wang, Zhe; Precht, Jake T; Kaz, David M; Schlom, Darrell G; Ginsberg, Naomi S

    2015-05-13

    We demonstrate a new nanoimaging platform in which optical excitations generated by a low-energy electron beam in an ultrathin scintillator are used as a noninvasive, near-field optical scanning probe of an underlying sample. We obtain optical images of Al nanostructures with 46 nm resolution and validate the noninvasiveness of this approach by imaging a conjugated polymer film otherwise incompatible with electron microscopy due to electron-induced damage. The high resolution, speed, and noninvasiveness of this "cathodoluminescence-activated" platform also show promise for super-resolution bioimaging.

  13. 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.

  14. 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.

  15. Near-field shock formation in noise propagation from a high-power jet aircraft.

    Science.gov (United States)

    Gee, Kent L; Neilsen, Tracianne B; Downing, J Micah; James, Michael M; McKinley, Richard L; McKinley, Robert C; Wall, Alan T

    2013-02-01

    Noise measurements near the F-35A Joint Strike Fighter at military power are analyzed via spatial maps of overall and band pressure levels and skewness. Relative constancy of the pressure waveform skewness reveals that waveform asymmetry, characteristic of supersonic jets, is a source phenomenon originating farther upstream than the maximum overall level. Conversely, growth of the skewness of the time derivative with distance indicates that acoustic shocks largely form through the course of near-field propagation and are not generated explicitly by a source mechanism. These results potentially counter previous arguments that jet "crackle" is a source phenomenon.

  16. Radiation Pattern Reconstruction from the Near-Field Amplitude Measurement on Two Planes Using PSO

    Directory of Open Access Journals (Sweden)

    Z. Novacek

    2005-12-01

    Full Text Available The paper presents a new approach to the radiation patternreconstruction from near-field amplitude only measurement over a twoplanar scanning surfaces. This new method for antenna patternreconstruction is based on the global optimization PSO (Particle SwarmOptimization. The paper presents appropriate phaseless measurementrequirements and phase retrieval algorithm together with a briefdescription of the particle swarm optimization method. In order toexamine the methodologies developed in this paper, phaselessmeasurement results for two different antennas are presented andcompared to results obtained by a complex measurement (amplitude andphase.

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

    Science.gov (United States)

    Elzouka, Mahmoud

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

  18. Fibre-top atomic force microscope probe with optical near-field detection capabilities.

    Science.gov (United States)

    Tiribilli, B; Margheri, G; Baschieri, P; Menozzi, C; Chavan, D; Iannuzzi, D

    2011-04-01

    We present a fibre-top probe fabricated by carving a tipped cantilever on an optical fibre, with the tip machined in correspondence of the fibre core. When approached to an optical prism illuminated under total internal reflection conditions, the tip of the cantilever detects the optical tunnelling signal, while the light coupled from the opposite end of the fibre measures the deflection of the cantilever. Our results suggest that fibre-top technology can be used for the development of a new generation of hybrid probes that can combine atomic force microscopy with scanning near field optical microscopy. © 2010 The Authors Journal of Microscopy © 2010 Royal Microscopical Society.

  19. 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......-field pattern calculated from a truncated SNF measurement up to the whole forward hemisphere. The method is useful when measuring electrically large antennas and the measurement over the whole sphere is very time consuming. Therefore, a solution is considered to take samples over a portion of the spherical...

  20. 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.

  1. Computations with near-field coupled plasmon particles interacting with phase-change materials

    Science.gov (United States)

    Kanazawa, Shohei; Kuwamura, Kenta; Kihara, Yuya; Hirukawa, Yusuke; Saiki, Toshiharu

    2015-12-01

    The computing functionality emerging from spatial correlations due to near-field interactions between local processing and memory elements is discussed. In particular, we investigate the possibility of solving a problem analogous to the spin-glass problem by using a coupled dipole system, in which the individual coupling strengths can be modified to optimize the system so that the exact solution can be easily reached. For this algorithm, we propose an implementation based on a coupled plasmon-particle system interacting with a phase-change material; this system exhibits threshold behavior and plasticity to provide processing and memory functions, respectively.

  2. Gallium nitride nanowire probe for near-field scanning microwave microscopy

    Science.gov (United States)

    Weber, J. C.; Blanchard, P. T.; Sanders, A. W.; Imtiaz, A.; Wallis, T. M.; Coakley, K. J.; Bertness, K. A.; Kabos, P.; Sanford, N. A.; Bright, V. M.

    2014-01-01

    We report on the fabrication of a GaN nanowire probe for near-field scanning microwave microscopy. A single nanowire was Pt-bonded to a commercial Si cantilever prior to evaporation of a Ti/Al coating to provide a microwave signal pathway. Testing over a microcapacitor calibration sample shows the probe to have capacitance resolution of at least 0.7 fF with improved sensitivity and reduced uncertainty compared with a commercial microwave probe. High wear resistance of the defect-free nanowire enabled it to maintain a tip radius of 150 nm after multiple contact-mode scans while demonstrating nanometer-scale topographical resolution.

  3. Preparation of non-spherical particles by shell-shield etching for near-field nanopatterning

    International Nuclear Information System (INIS)

    Ye, Jian; Liesbet, Lagae

    2014-01-01

    The shape of polymer particles plays an important role in determining their function. In this paper, we describe a simple and unconventional method called shell-shield etching (SSE) that allows us to prepare freestanding submicrometer- or micrometer-sized polymer particles with various shapes. By precisely varying the time of ultraviolet ozone treatment under the partial shielding effect of the silica shell, we controllably reshape polymer spheres into symmetry-reduced polymer peaches, mushrooms, bowls, and plates. Finite difference time domain simulations indicate that the non-spherical particles obtained from the SSE method might have potential for near-field nanopatterning applications. (papers)

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

    DEFF Research Database (Denmark)

    Fernandez Grande, Efren

    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. Inspection of plastic weld joints with terahertz imaging

    Science.gov (United States)

    Wietzke, S.; Krumbholz, N.; Jördens, C.; Baudrit, B.; Bastian, M.; Koch, M.

    2007-06-01

    Polymers cover the whole range from commodities to high-tech applications. Plastic products have also gained in importance for construction purposes. This draws the attention to joining techniques like welding. Common evaluation of the weld quality is mostly mechanical and destructive. Existing non-destructive techniques are mostly not entirely reliable or economically inefficient. Here, we demonstrate the potential of terahertz time-domain spectroscopy imaging as a non-destructive testing tool for the inspection of plastic weld joints. High-density polyethylene sheets welded in a lap joint with varying quality serve as samples for terahertz transmission measurements. Imperfections within the weld contact area can clearly be detected by displaying the transmitted intensity in a limited frequency range. Contaminations such as metal or sand are identified since they differ significantly from the polymer in the terahertz image. Furthermore, this new and promising technique is capable of detecting the boundaries of a weld contact area. Aside from revealing a contrast between a proper weld joint and no material connection, the size of an air gap between two plastic sheets can be determined by considering the characteristic frequency-dependent transmission through the structure: The spectral positions of the maxima and minima allow for the calculation of the air layer thickness.

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

    Science.gov (United States)

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

    2016-11-01

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

  7. 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.

  8. Near-field hazard assessment of March 11, 2011 Japan Tsunami sources inferred from different methods

    Science.gov (United States)

    Wei, Y.; Titov, V.V.; Newman, A.; Hayes, G.; Tang, L.; Chamberlin, C.

    2011-01-01

    Tsunami source is the origin of the subsequent transoceanic water waves, and thus the most critical component in modern tsunami forecast methodology. Although impractical to be quantified directly, a tsunami source can be estimated by different methods based on a variety of measurements provided by deep-ocean tsunameters, seismometers, GPS, and other advanced instruments, some in real time, some in post real-time. Here we assess these different sources of the devastating March 11, 2011 Japan tsunami by model-data comparison for generation, propagation and inundation in the near field of Japan. This study provides a comparative study to further understand the advantages and shortcomings of different methods that may be potentially used in real-time warning and forecast of tsunami hazards, especially in the near field. The model study also highlights the critical role of deep-ocean tsunami measurements for high-quality tsunami forecast, and its combination with land GPS measurements may lead to better understanding of both the earthquake mechanisms and tsunami generation process. ?? 2011 MTS.

  9. REFREP: a near-field model for a spent fuel repository

    International Nuclear Information System (INIS)

    Hautojaervi, A.; Vieno, T.

    1988-05-01

    A code package for near-field performance analysis of spent fuel disposal has been programmed. The conceptual models used are shortly described in connection with th model presentations. For more comprehensive descriptions the previous safety analysis and references therein are referred. The REFREP package consists of nine individual modules performing the following tasks: viewing and updating of the data files (UPDATE), calculating of the breaching times of canisters (CORRFLUX), calculating of stationary nuclide release rates using solubility values (MASSFLUX), calculating of actinide inventories from chain decay (INVENT), calculating of elemental inventories of actinides (ELEMENT), calculating of nuclide release rates according to congruent release (CONGRUNT), performing of sensitivity analysis for one variable (SENSIT), summing of release rates from individual canisters according to given probability distributions of canister breaching times (PROBREL), and forming a compact data file including all the input values (DATAOUT). The results have been shown to agree very well with the results of the previous safety analysis where near-field analysis was performed by means of separate codes and manual calculation. The REFREP model offers already at this stage some additional features to the old procedures and more versatile capabilities can easyly be added into the modular structure of the package. REFREP has been developed in a VAX-environment. Some changes in file handling might be necessary if the code is transferred to another computer

  10. Optical security based on near-field processes at the nanoscale

    International Nuclear Information System (INIS)

    Naruse, Makoto; Tate, Naoya; Ohtsu, Motoichi

    2012-01-01

    Optics has been playing crucial roles in security applications ranging from authentication and watermarks to anti-counterfeiting. However, since the fundamental physical principle involves optical far-fields, or propagating light, diffraction of light causes severe difficulties, for example in device scaling and system integration. Moreover, conventional security technologies in use today have been facing increasingly stringent demands to safeguard against threats such as counterfeiting of holograms, requiring innovative physical principles and technologies to overcome their limitations. Nanophotonics, which utilizes interactions between light and matter at the nanometer scale via optical near-field interactions, can break through the diffraction limit of conventional propagating light. Moreover, nanophotonics has some unique physical attributes, such as localized optical energy transfer and the hierarchical nature of optical near-field interactions, which pave the way for novel security functionalities. This paper reviews the physical principles and describes some experimental demonstrations of systems based on nanophotonics with respect to security applications such as tamper resistance against non-invasive and invasive attacks, hierarchical information retrieval, hierarchical holograms, authentication, and traceability. (paper)

  11. A Study of a Powder Coating Gun near Field: A Case of Staggered Concentric Jet Flow

    Directory of Open Access Journals (Sweden)

    Edward Grandmaison

    2013-11-01

    Full Text Available This paper examines, experimentally and numerically, an isothermal coaxial air jet, created by an innovative nozzle design for an air propane torch, used for the thermal deposition of polymers. This design includes staggering the origins of the central and annular jets and creating an annular air jet with an inward radial velocity component. The experimental work used a Pitot tube to measure axial velocity on the jet centerline and in the fully developed flow. The static gauge pressure in the near field was also measured and found to be positive, an unexpected result. The numerical work used Gambit and Fluent. An extensive grid sensitivity study was conducted and it was found that results from a relatively coarse mesh were substantially the same as results from a mesh with almost 11 times the number of control volumes. A thorough evaluation of all of the RANS models in Fluent 6.3.26 found that the flow fields they calculated showed at most partial agreement with the experimental results. The greatest difference between numerical and experimental results was the incorrect prediction by all RANS models of a recirculation zone in the near field on the jet axis. Experimental work showed it did not exist.

  12. Effect of condensed water on scanning near-field optical microscope measurement

    International Nuclear Information System (INIS)

    Douas, M; Serena, P A; Marqués, M I

    2013-01-01

    The relevance of the scanning near-field optical microscope (SNOM), for near-field characterization, is often shaded by the appearance of artifacts, especially when geometrical characterization is intended. Artifacts are related to many features such as the feedback system or the scanning mode. For non-vacuum environmental conditions, artifact sources may be related to tip geometry and the pollutants attached, either on the tip or on the studied surfaces, altering the optical image. As an environmental element, water vapor could be treated as a source for artifacts, but could also be used as a tool for chemical characterization of hydrophilic patches. Spontaneous meniscus formation between hydrophilic surfaces, such as the tip and the sample, may guide light from the tip to the sample, enhancing the transmitted signal. This study focuses on the effects that water condensation at the nanoscale has on the signals achieved by SNOM, combining two computational methods (Monte Carlo and finite difference time domain) in order to deal with light propagation through heterogeneous media and water condensation. (paper)

  13. Near-field enhanced femtosecond laser nano-drilling of glass substrate

    International Nuclear Information System (INIS)

    Zhou, Y.; Hong, M.H.; Fuh, J.Y.H.; Lu, L.; Lukyanchuk, B.S.; Wang, Z.B.

    2008-01-01

    Particle mask assisted near-field enhanced femtosecond laser nano-drilling of transparent glass substrate was demonstrated in this paper. A particle mask was fabricated by self-assembly of spherical 1 μm silica particles on the substrate surface. Then the samples were exposed to femtosecond laser (800 nm, 100 fs) and characterized by field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). The nano-hole array was found on the glass surface. The hole sizes were measured from 200 to 300 nm with an average depth of 150 nm and increased with laser fluence. Non-linear triple-photon absorption and near-field enhancement were the main mechanisms of the nano-feature formation. Calculations based on Mie theory shows an agreement with experiment results. More debris, however, was found at high laser fluence. This can be attributed to the explosion of silica particles because the focusing point is inside the 1 μm particle. The simulation predicts that the focusing point will move outside the particle if the particle size increases. The experiment performed under 6.84 μm silica particles verified that no debris was formed. And for all the samples, no cracks were found on the substrate surface because of ultra-short pulse width of femtosecond laser. This method has potential applications in nano-patterning of transparent glass substrate for nano-structure device fabrication

  14. A Numerical Study of Near-Field Dispersion within and above Forest Canopies

    Science.gov (United States)

    Edburg, Steven; Stock, David; Lamb, Brian; Thistle, Harold

    2004-11-01

    Pine beetle infestations have impacted recreational uses, wildlife habitat, and silvicultural practice in forest stands throughout the US and Canada. Pheromone releases are used by forest managers as an anti-aggregation technique to protect high value forest stands against the pine beetle. As a result, near-field pheromone dispersion patterns are needed to develop effective forest management techniques. Recent field experiments have shown a strong link between tracer gas dispersion, meteorological data and canopy density. However, field experiments are limited by cost, location, meteorological conditions etc. Analytical and numerical models are a cost effective solution to study multiple cases, while having control over meteorological parameters. In this research, numerical simulations were conducted, and the Reynolds stress model, RSM, and large eddy simulation, LES, were used to predict near-field concentrations of a tracer gas in a pine canopy. The canopy was represented with porous media based on leaf area index and basal area. Unstable atmospheric conditions were prescribed with solar radiation absorption in the canopy. Results were compared with meteorological data and thirty minute concentration averages from a field experiment. The steady RSM solution showed reasonable comparison with experimental data, although it did not capture the dynamics of the flow. Unsteady LES captured the time dependency of the flow and dispersion patterns. Future work will consist of modeling canopies that are not continuous and dispersion during stable atmospheric conditions. Bursting and sweeping affects on dispersion will also be investigated.

  15. 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.

  16. A novel phase-sensitive scanning near-field optical microscope

    International Nuclear Information System (INIS)

    Wu Xiao-Yu; Lin Sun; Tan Qiao-Feng; Wang Jia

    2015-01-01

    Phase is one of the most important parameters of electromagnetic waves. It is the phase distribution that determines the propagation, reflection, refraction, focusing, divergence, and coupling features of light, and further affects the intensity distribution. In recent years, the designs of surface plasmon polariton (SPP) devices have mostly been based on the phase modulation and manipulation. Here we demonstrate a phase sensitive multi-parameter heterodyne scanning near-field optical microscope (SNOM) with an aperture probe in the visible range, with which the near field optical phase and amplitude distributions can be simultaneously obtained. A novel architecture combining a spatial optical path and a fiber optical path is employed for stability and flexibility. Two kinds of typical nano-photonic devices are tested with the system. With the phase-sensitive SNOM, the phase and amplitude distributions of any nano-optical field and localized field generated with any SPP nano-structures and irregular phase modulation surfaces can be investigated. The phase distribution and the interference pattern will help us to gain a better understanding of how light interacts with SPP structures and how SPP waves generate, localize, convert, and propagate on an SPP surface. This will be a significant guidance on SPP nano-structure design and optimization. (paper)

  17. 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.

  18. Analysis of near-field thermal energy transfer within the nanoparticles

    Science.gov (United States)

    Yuksel, Anil; Yu, Edward T.; Cullinan, Michael; Murthy, Jayathi

    2017-08-01

    Nanoscale size effects bring additional near-field thermal considerations when heating nanoparticles under high laser power. Scanning electron micrographs of a typical copper nanoparticle powder bed reveal that the nanoparticles are distributed log-normally with 116 nm mean radius and 48 nm standard deviation. In this paper, we solve Maxwell's equations in frequency domain to understand near-field thermal energy effects for different standard deviations. Log-normally distributed copper nanoparticle packings which have 116 nm mean radius with 3 different standard deviations (12, 48 and 84 nm) are created by using Discrete Element Model (DEM) in which certain number of particles are generated, specifying a position and radius for each. The solid particles interacting with the neighbouring particles are to be distributed randomly into the bed domain with an initial velocity and a boundary condition, which creates the particle packing within a defined time range under gravitational and weak van der Waals forces. Finite Difference Frequency Domain analysis, which yields the electromagnetic field distribution, is applied by solving Maxwell's equations to obtain absorption, scattering and extinction coefficients. We show that different particle distributions create different plasmonic effects in the bed domain which results in non-local heat transport. We calculate the surface plasmon effect due to the electromagnetic coupling between the nanoparticles and the dielectric medium under the different distributions. This analysis helps to reveal how sintering quality can be enhanced by creating stronger laser-particle interactions for specific groups of nanoparticles.

  19. Study on the near-field non-linearity (SMILE) of high power diode laser arrays

    Science.gov (United States)

    Zhang, Hongyou; Jia, Yangtao; Li, Changxuan; Zah, Chung-en; Liu, Xingsheng

    2018-02-01

    High power laser diodes have been found a wide range of industrial, space, medical applications, characterized by high conversion efficiency, small size, light weight and a long lifetime. However, due to thermal induced stress, each emitter in a semiconductor laser bar or array is displaced along p-n junction, resulting of each emitter is not in a line, called Near-field Non-linearity. Near-field Non-linearity along laser bar (also known as "SMILE") determines the outcome of optical coupling and beam shaping [1]. The SMILE of a laser array is the main obstacle to obtain good optical coupling efficiency and beam shaping from a laser array. Larger SMILE value causes a larger divergence angle and a wider line after collimation and focusing, respectively. In this letter, we simulate two different package structures based on MCC (Micro Channel Cooler) with Indium and AuSn solders, including the distribution of normal stress and the SMILE value. According to the theoretical results, we found the distribution of normal stress on laser bar shows the largest in the middle and drops rapidly near both ends. At last, we did another experiment to prove that the SMILE value of a laser bar was mainly affected by the die bonding process, rather than the operating condition.

  20. Caroli formalism in near-field heat transfer between parallel graphene sheets

    Science.gov (United States)

    Jiang, Jia-Huei; Wang, Jian-Sheng

    2017-10-01

    In this work we conduct a close-up investigation into the nature of near-field heat transfer (NFHT) of two graphene sheets in parallel-plate geometry. We develop a fully microscopic and quantum approach using the nonequilibrium Green's function method. A Caroli formula for heat flux is proposed and numerically verified. We show that our near-field-to-black-body heat flux ratios generally exhibit 1 /dα dependence, with an effective exponent α ≈2.2 , at long distances exceeding 100 nm and up to one micron; in the opposite d →0 limit, the values converge to a range within an order of magnitude. We justify this feature by noting it is owing to the breakdown of local conductivity theory, which predicts a 1 /d dependence. Furthermore, from the numerical result, we find that in addition to thermal wavelength λt h a shorter distance scale ˜10 -100 nm, comparable to the graphene thermal length (ℏ vF/kBT ) or Fermi wavelength (kF-1), marks the transition point between the short- and long-distance transfer behaviors; within that point, a relatively large variation of heat flux in response to doping level becomes a typical characteristic. The emergence of such large variation is tied to relative NFHT contributions from the intra- and interband transitions. Beyond that point, scaling of thermal flux ∝1 /dα can be generally observed.

  1. Nuclide release calculation in the near-field of a reference HLW repository

    International Nuclear Information System (INIS)

    Lee, Youn Myoung; Hwang, Yong Soo; Kang, Chul Hyung

    2004-01-01

    The HLW-relevant R and D program for disposal of high-level radioactive waste has been carried out at Korea Atomic Energy Research Institute (KAERI) since early 1997 in order to develop a conceptual Korea Reference Repository System for direct disposal of nuclear spent fuel by the end of 2007. A preliminary reference geologic repository concept considering such established criteria and requirements as waste and generic site characteristics in Korea was roughly envisaged in 2003 focusing on the near-field components of the repository system. According to above basic repository concept, which is similar to that of Swedish KBS-3 repository, the spent fuel is first encapsulated in corrosion resistant canisters, even though the material has not yet been determined, and then emplaced into the deposition holes surrounded by high density bentonite clay in tunnels constructed at a depth of about 500 m in a stable plutonic rock body. Not only to demonstrate how much a reference repository is safe in the generic point of view with several possible scenarios and cases associated with a preliminary repository concept by conducting calculations for nuclide release and transport in the near-field components of the repository, even though enough information has not been available that much yet, but also to show a methodology by which a generic safety assessment could be performed for further development of Korea reference repository concept, nuclide release calculation study strongly seems to be necessary

  2. Near-Field Coupling Communication Technology For Human-Area Networking

    Directory of Open Access Journals (Sweden)

    Ryoji Nagai

    2012-12-01

    Full Text Available We propose a human-area networking technology that uses the surface of the human body as a data transmission path and uses near-field coupling TRXs. This technology aims to achieve a "touch and connect" form of communication and a new concept of "touch the world" by using a quasi-electrostatic field signal that propagates along the surface of the human body. This paper explains the principles underlying near-field coupling communication. Special attention has been paid to common-mode noise since our communication system is strongly susceptible to this. We designed and made a common-mode choke coil and a transformer to act as common-mode noise filters to suppress common-mode noise. Moreover, we describe how we evaluated the quality of communication using a phantom model with the same electrical properties as the human body and present the experimental results for the packet error rate (PER as a function of the signal to noise ratio (SNR both with the common-mode choke coil or the transformer and without them. Finally, we found that our system achieved a PER of less than 10-2 in general office rooms using raised floors, which corresponded to the quality of communication demanded by communication services in ordinary office spaces.

  3. Development of Spherical Near Field Model for Geological Radioactive Waste Repository

    International Nuclear Information System (INIS)

    Kim, S. Y.; Lee, K. J.; Chang, S. H.; Lee, K. J.; Chang, S. H.

    2012-01-01

    Modeling for geological radioactive waste repository can be divided into 3 parts. They are near field modeling related to engineered barrier, far field modeling related to natural barrier and biosphere modeling. In order to make the general application for safety assessment of geological waste repository, spherical geometry near field model has been developed. This model can be used quite extensively when users calculate equivalent spherical geometry for specific engineered barrier like equivalent waste radius, equivalent barrier radius and etc. Only diffusion was considered for general purpose but advection part can be updated. Goldsim and Goldsim Radionuclide Transport (RT) module were chosen and used as developing tool for the flexible modeling. Developer can freely make their own model with developer friendly graphic interface by using Goldsim. Furthermore, model with user friendly graphic interface can be developed by using Goldsim Dashboard Authoring module. The model has been validated by comparing the result with that of another model, inserting similar inputs and conditions. The model has been proved to be reasonably operating from the comparison result by validation process. Cylindrical model can be developed as a further work based on the knowledge and experience from this research

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

    International Nuclear Information System (INIS)

    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

  5. Polarimetic near-field backpropagation algorithm for application to GPR imaging of mines and minelike objects

    Science.gov (United States)

    Morrow, Ivor L.; van Genderen, Piet

    2001-10-01

    This paper presents a novel polarimetric near-field two-dimension (2D) synthetic aperture focusing technique (SAFT) suitable for ground penetrating radar (GPR) application. The imaging algorithm is intended for locating metallic and non-metallic anti-personnel (AP's) mines using an ultra-wide-band stepped frequency radar. A radar image can be formed by coherently integrating the backscattered field over the measured frequency spectrum and cross-range scan. The coherent integration is essentially a convolution of the collected data and a focusing (test) function, which only depends on the geometry of the measurement. Wavefront curvature must be taken account of when attempting to image an object within 1-2 wavelengths off an antenna(s) phase center. Applying conventional far-field SAR imaging using a direct Fourier inversion may result in images which are increasingly blurred and shifted at points more distant from the point of rotation of the focusing function. Here, a focusing function is first derived based on a conventional far-field geometrical optic propagator for a two-media problem. Then to correct for geometric distortion in the focusing function when applied in the near-field zone we introduce higher order terms to the range function. In order to verify and augment the technique described two field studies were conducted, over different frequency spectrums, the finding of which demonstrates the utility of the technique and the experimental practices.

  6. Sub-microanalysis of solid samples with near-field enhanced atomic emission spectroscopy

    Science.gov (United States)

    Wang, Xiaohua; Liang, Zhisen; Meng, Yifan; Wang, Tongtong; Hang, Wei; Huang, Benli

    2018-03-01

    A novel approach, which we have chosen to name it as near-field enhanced atomic emission spectroscopy (NFE-AES), was proposed by introducing a scanning tunnelling microscope (STM) system into a laser-induced breakdown spectrometry (LIBS). The near-field enhancement of a laser-illuminated tip was utilized to improve the lateral resolution tremendously. Using the hybrid arrangement, pure metal tablets were analyzed to verify the performance of NFE-AES both in atmosphere and in vacuum. Due to localized surface plasmon resonance (LSPR), the incident electromagnetic field is enhanced and confined at the apex of tip, resulting in sub-micron scale ablation and elemental emission signal. We discovered that the signal-to-noise ratio (SNR) and the spectral resolution obtained in vacuum condition are better than those acquired in atmospheric condition. The quantitative capability of NFE-AES was demonstrated by analyzing Al and Pb in Cu matrix, respectively. Submicron-sized ablation craters were achieved by performing NFE-AES on a Si wafer with an Al film, and the spectroscopic information from a crater of 650 nm diameter was successfully obtained. Due to its advantage of high lateral resolution, NFE-AES imaging of micro-patterned Al lines on an integrated circuit of a SIM card was demonstrated with a sub-micron lateral resolution. These results reveal the potential of the NFE-AES technique in sub-microanalysis of solids, opening an opportunity to map chemical composition at sub-micron scale.

  7. 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...

  8. 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.

  9. RFID Antenna Near-field Characterization Using a New 3D Magnetic Field Probe

    Directory of Open Access Journals (Sweden)

    Kassem Jomaa

    2017-05-01

    Full Text Available In this paper the design of a new 3D magnetic field (H-field probe with a near-field scanning system is presented, then the near electromagnetic fields radiated by a Library RFID system is characterized. The proposed system is developed in order to determine the magnetic near-field emitted by electronic devices. The designed isotropic H-field probe consists of three orthogonal and identical loops each of diameter of 6 mm having 3 turns. The antenna factor of the designed probe is presented for a frequency range from 10 MHz to 1 GHz. The designed probe is tested and validated using a standard passive circuit as a device under test. An RFID reader antenna is also designed and simulated on HFSS (high frequency structural simulator and the radiated magnetic field, obtained by simulations, is then compared to the real measured one above the fabricated circuit. The obtained levels are checked if they satisfy the European and ICNIRP Electromagnetic Fields Guidelines.

  10. Illuminated up close: near-field optical microscopy of cell surfaces.

    Science.gov (United States)

    Czajkowsky, Daniel M; Sun, Jielin; Shao, Zhifeng

    2015-01-01

    Invented in the 1990s, near-field optical microscopy (NSOM) was the first optical microscopy method to hold the promise of finally breaking the diffraction barrier in studies of biological samples. This promise, though, failed to materialize at that time, largely owing to the inability to image soft samples, such as cell surfaces, without damage. However, steady technical improvements have now produced NSOM devices that can routinely achieve images of cell surfaces with sub-100nm resolution in aqueous solution. Further, beyond just optical information, these instruments can also provide simultaneous topographic, mechanical, and/or chemical details of the sample, an ability not yet matched by any other optics-based methodology. With the long recognized important roles of many biological processes at cell surfaces in human health and disease, near-field probing of cell surfaces is indeed now well poised to directly illume in biomedicine what has, until recently, been unknowable with classic light microscopy. Copyright © 2015 Elsevier Inc. All rights reserved.

  11. Design and fabrication of two probes for Near Field THz imaging .

    Science.gov (United States)

    Garcia, Angelica; Paz, Gaudencio; Perez, Joel; Qureshi, Naser; Microwave photonics Team

    THz imaging has gained attention due to the potential applications in medicine, security, inspections on semiconductor devices, etc. Until now, systems devoted to Near Field THz imaging consist of two basic parts: generation of THz radiation and a sensing probe system. In this work we present two approaches to make a probe for near field THz imaging. The first one is a novel device capable of integrate in a single chip the THz source with the sensing system. The device is fabricated in a GaAs substrate, on one side a photoconductive gold antenna is printed using microfabrication techniques; on the opposite side a specifically designed bow tie sub-wavelength sized bow-tie aperture is placed centered to the gap of the antenna. According to our simulations, the aperture exhibits field enhancement at the metal tips when it is illuminated from the substrate side by the THz radiation emitted from the antenna. The second device is a tapered conical waveguide with micrometrical aperture size at the end. A commercial silicon lens is used to focus the THz radiation emitted from a photoconductive antenna on the aperture. Simulation in COMSOL is used to find the best taper angle where reflection and loss are reduced. PAPIIT 106316 and CONACYT Fronteras 344.

  12. Low Power Near Field Communication Methods for RFID Applications of SIM Cards.

    Science.gov (United States)

    Chen, Yicheng; Zheng, Zhaoxia; Gong, Mingyang; Yu, Fengqi

    2017-04-14

    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.

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

    Science.gov (United States)

    Estrada, Héctor; Rebling, Johannes; Razansky, Daniel

    2017-06-01

    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.

  14. Fourier-transform terahertz near-field imaging of one-dimensional slit arrays : Mapping of electric-field-, magnetic-field-, and Poynting vectors

    NARCIS (Netherlands)

    Seo, M.A.; Adam, A.J.L.; Kang, J.H.; Lee, J.W.; Jeoung, S.C.; Park, Q.H.; Planken, P.C.M.; Kim, D.S.

    2007-01-01

    We present 2D measurements of the full THz electric field behind a sample consisting of multiple slits in a metal foil. Our measurements, which have a sub-wavelength spatial, and a sub-period temporal resolution, reveal electric field lines, electric field vortices and saddle points. From our

  15. Application of autofocusing methods in continuous-wave terahertz in-line digital holography

    Science.gov (United States)

    Huang, Haochong; Wang, Dayong; Rong, Lu; Zhou, Xun; Li, Zeyu; Wang, Yunxin

    2015-07-01

    Terahertz digital holography is a combination of terahertz imaging and digital holography. During reconstruction, the key point is to find accurately the propagation distance from which the distribution of focused samples can be reconstructed. In this paper, we use a continuous-wave terahertz in-line digital holographic imaging system to record holograms. Moreover, the autofocusing algorithms through which the reconstructed distance can be calculated are applied to the reconstruction. The in-line schematic is beneficial to the terahertz wave imaging, which, however, inevitably produces the object's twin image. In the refocusing process, both the reconstructed image with low signal-to-noise ratio and contrast and the twin image induce the formation of false peaks corresponding to improper distances on the autofocusing curves. To restrain the disturbance factors and improve the accuracy of the judgment, a phase retrieval method is implemented in the reconstruction. The results demonstrate the feasibility of the autofocusing method with phase retrieval in terahertz in-line digital holographic imaging system. The proposed method provides an automated and efficient evaluation which helps to obtain the optimized propagation distance.

  16. Terahertz in-line digital holography of human hepatocellular carcinoma tissue.

    Science.gov (United States)

    Rong, Lu; Latychevskaia, Tatiana; Chen, Chunhai; Wang, Dayong; Yu, Zhengping; Zhou, Xun; Li, Zeyu; Huang, Haochong; Wang, Yunxin; Zhou, Zhou

    2015-02-13

    Terahertz waves provide a better contrast in imaging soft biomedical tissues than X-rays, and unlike X-rays, they cause no ionisation damage, making them a good option for biomedical imaging. Terahertz absorption imaging has conventionally been used for cancer diagnosis. However, the absorption properties of a cancerous sample are influenced by two opposing factors: an increase in absorption due to a higher degree of hydration and a decrease in absorption due to structural changes. It is therefore difficult to diagnose cancer from an absorption image. Phase imaging can thus be critical for diagnostics. We demonstrate imaging of the absorption and phase-shift distributions of 3.2 mm × 2.3 mm × 30-μm-thick human hepatocellular carcinoma tissue by continuous-wave terahertz digital in-line holography. The acquisition time of a few seconds for a single in-line hologram is much shorter than that of other terahertz diagnostic techniques, and future detectors will allow acquisition of meaningful holograms without sample dehydration. The resolution of the reconstructions was enhanced by sub-pixel shifting and extrapolation. Another advantage of this technique is its relaxed minimal sample size limitation. The fibrosis indicated in the phase distribution demonstrates the potential of terahertz holographic imaging to obtain a more objective, early diagnosis of cancer.

  17. Time-resolved ultraviolet near-field scanning optical microscope for characterizing photoluminescence lifetime of light-emitting devices.

    Science.gov (United States)

    Park, Kyoung-Duck; Jeong, Hyun; Kim, Yong Hwan; Yim, Sang-Youp; Lee, Hong Seok; Suh, Eun-Kyung; Jeong, Mun Seok

    2013-03-01

    We developed a instrument consisting of an ultraviolet (UV) near-field scanning optical microscope (NSOM) combined with time-correlated single photon counting, which allows efficient observation of temporal dynamics of near-field photoluminescence (PL) down to the sub-wavelength scale. The developed time-resolved UV NSOM system showed a spatial resolution of 110 nm and a temporal resolution of 130 ps in the optical signal. The proposed microscope system was successfully demonstrated by characterizing the near-field PL lifetime of InGaN/GaN multiple quantum wells.

  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...... resolution better than 40 nm are demonstrated with a latex projection test sample. Determination of the optical resolution as well as correlation between topographical and near-field optical images are discussed. (C) 1998 Elsevier Science B.V....

  19. Fluctuational electrodynamics calculations of near-field heat transfer in non-planar geometries: A brief overview

    Science.gov (United States)

    Otey, Clayton R.; Zhu, Linxiao; Sandhu, Sunil; Fan, Shanhui

    2014-01-01

    Near-field electromagnetic heat transfer is of interest for a variety of applications, including energy conversion, and precision heating, cooling and imaging of nano-structures. This past decade has seen considerable progress in the study of near-field electromagnetic heat transfer, but it is only very recently that numerically exact methods have been developed for treating near-field heat transfer in the fluctuational electrodynamics formalism for non-trivial geometries. In this paper we provide a tutorial review of these exact methods, with an emphasis on the computational aspects of three important methods, which we compare in the context of a canonical example, the coupled dielectric sphere problem.

  20. Terahertz applications: trends and challenges

    Science.gov (United States)

    Robin, Thierry; Bouye, Clementine; Cochard, Jacques

    2014-03-01

    The objective of our work [1] was to determine the opportunities and challenges for Terahertz application development for the next years with a focus on systems: for homeland security and for Non Destructive Testing (NDT). Terahertz radiation has unique abilities and has been the subject of extensive research for many years. Proven concepts have emerged for numerous applications including Industrial NDT, Security, Health, Telecommunications, etc. Nevertheless, there has been no widely deployed application and Businesses based on THz technologies are still in their infancy. Some technological, market and industrial barriers are still to be broken. We summarize the final analysis and data: study of the technology trends and major bottlenecks per application segment, main challenges to be addressed in the next years, key opportunities for THz technologies based on market needs and requirements.

  1. Intense Terahertz Fields for Fast Energy Release

    Science.gov (United States)

    2016-11-01

    6201 Fort Belvoir, VA 22060-6201 T E C H N IC A L R E P O R T DTRA-TR-17-10 Intense Terahertz Fields for Fast Energy Release...customary unit. Grant #  HDTRA 1-12-1-0044 Intense Terahertz Fields for Fast Energy Release Final Report PI: Keith A. Nelson 617-253-1423 kanelson

  2. Ultrabroadband terahertz conductivity of Si nanocrystal films

    DEFF Research Database (Denmark)

    Cooke, D. G.; Meldrum, A.; Jepsen, P. Uhd

    2012-01-01

    The terahertz conductivity of silicon nanoparticles embedded in glass with varying density is studied with ultra-broadband terahertz spectroscopy on picosecond time scales following fs optical excitation. The transition from relatively isolated charge carriers to densities which allow inter...... the applicability of this simple model to the conductivity of nanoparticle ensembles over the entire THz spectral window....

  3. High efficiency optoelectronic terahertz sources

    Science.gov (United States)

    Lampin, Jean-François; Peytavit, Emilien; Akalin, Tahsin; Ducournau, G.; Hindle, Francis; Mouret, Gael

    2010-08-01

    We have developed a new generation of optoelectronic large bandwidth terahertz sources based on TEM horn antennas monolithically integrated with several types of photodetectors: low-temperature grown GaAs (LTG-GaAs) planar photoconductors, vertically integrated LTG-GaAs photoconductors on silicon substrate and uni-travelling-carrier photodiodes. Results of pulsed (time-domain) and photomixing (CW, frequency domain) experiments are presented.

  4. Terahertz superconducting plasmonic hole array

    OpenAIRE

    Tian, Zhen; Singh, Ranjan; Han, Jiaguang; Gu, Jianqiang; Xing, Qirong; Zhang, Weili

    2010-01-01

    We demonstrate thermally tunable superconductor hole array with active control over their resonant transmission induced by surface plasmon polaritons . The array was lithographically fabricated on high temperature YBCO superconductor and characterized by terahertz-time domain spectroscopy. We observe a clear transition from the virtual excitation of the surface plasmon mode to the real surface plasmon mode. The highly tunable superconducting plasmonic hole arrays may have promising applicatio...

  5. Terahertz radar cross section measurements

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Heiselberg, Henning; Jepsen, Peter Uhd

    2010-01-01

    We perform angle- and frequency-resolved radar cross section (RCS) measurements on objects at terahertz frequencies. Our RCS measurements are performed on a scale model aircraft of size 5-10 cm in polar and azimuthal configurations, and correspond closely to RCS measurements with conventional rad...... information and also allows for identification of scattering points such as weaponry attached to the aircraft. The shapes of the models and positions of reflecting parts are retrieved by the filtered back projection algorithm....

  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. Progress in nano-electro optics characterization of nano-optical materials and optical near-field interactions

    CERN Document Server

    Ohtsu, Motoichi

    2005-01-01

    This volume focuses on the characterization of nano-optical materials and optical-near field interactions. It begins with the techniques for characterizing the magneto-optical Kerr effect and continues with methods to determine structural and optical properties in high-quality quantum wires with high spatial uniformity. Further topics include: near-field luminescence mapping in InGaN/GaN single quantum well structures in order to interpret the recombination mechanism in InGaN-based nano-structures; and theoretical treatment of the optical near field and optical near-field interactions, providing the basis for investigating the signal transport and associated dissipation in nano-optical devices. Taken as a whole, this overview will be a valuable resource for engineers and scientists working in the field of nano-electro-optics.

  8. Plasmonic antenna resonance pinning and suppression of near-field coupling from epsilon-near-zero substrate

    DEFF Research Database (Denmark)

    DeVault, C.; Zenin, V. A.; Pors, A.

    2017-01-01

    The resonance wavelength of single gold nanorods patterned on an epsilon-near-zero substrate is observed to be independent of antenna length. Additionally, the near-field coupling between dimer antennas is suppressed at the epsilon-near-zero wavelength.......The resonance wavelength of single gold nanorods patterned on an epsilon-near-zero substrate is observed to be independent of antenna length. Additionally, the near-field coupling between dimer antennas is suppressed at the epsilon-near-zero wavelength....

  9. Conference Paper NFO-7:7th International Conference on Near-Field Optics and Related Technologies

    Energy Technology Data Exchange (ETDEWEB)

    Novotny, Lukas [Univ. of Rochester, NY (United States)

    2004-10-18

    The seventh conference in the NFO conference series, held here in Rochester, provided to be the principal forum for advances in sub-wavelength optics, near-field optical microscopy, local field enhancement, instrumental developments and the ever-increasing range of applications. This conference brought together the diverse scientific communities working on the theory and application of near-field optics (NFO) and related techniques.

  10. [Terahertz Spectroscopic Identification with Deep Belief Network].

    Science.gov (United States)

    Ma, Shuai; Shen, Tao; Wang, Rui-qi; Lai, Hua; Yu, Zheng-tao

    2015-12-01

    Feature extraction and classification are the key issues of terahertz spectroscopy identification. Because many materials have no apparent absorption peaks in the terahertz band, it is difficult to extract theirs terahertz spectroscopy feature and identify. To this end, a novel of identify terahertz spectroscopy approach with Deep Belief Network (DBN) was studied in this paper, which combines the advantages of DBN and K-Nearest Neighbors (KNN) classifier. Firstly, cubic spline interpolation and S-G filter were used to normalize the eight kinds of substances (ATP, Acetylcholine Bromide, Bifenthrin, Buprofezin, Carbazole, Bleomycin, Buckminster and Cylotriphosphazene) terahertz transmission spectra in the range of 0.9-6 THz. Secondly, the DBN model was built by two restricted Boltzmann machine (RBM) and then trained layer by layer using unsupervised approach. Instead of using handmade features, the DBN was employed to learn suitable features automatically with raw input data. Finally, a KNN classifier was applied to identify the terahertz spectrum. Experimental results show that using the feature learned by DBN can identify the terahertz spectrum of different substances with the recognition rate of over 90%, which demonstrates that the proposed method can automatically extract the effective features of terahertz spectrum. Furthermore, this KNN classifier was compared with others (BP neural network, SOM neural network and RBF neural network). Comparisons showed that the recognition rate of KNN classifier is better than the other three classifiers. Using the approach that automatic extract terahertz spectrum features by DBN can greatly reduce the workload of feature extraction. This proposed method shows a promising future in the application of identifying the mass terahertz spectroscopy.

  11. Visualization and classification in biomedical terahertz pulsed imaging

    International Nuclear Information System (INIS)

    Loeffler, Torsten; Siebert, Karsten; Czasch, Stephanie; Bauer, Tobias; Roskos, Hartmut G

    2002-01-01

    'Visualization' in imaging is the process of extracting useful information from raw data in such a way that meaningful physical contrasts are developed. 'Classification' is the subsequent process of defining parameter ranges which allow us to identify elements of images such as different tissues or different objects. In this paper, we explore techniques for visualization and classification in terahertz pulsed imaging (TPI) for biomedical applications. For archived (formalin-fixed, alcohol-dehydrated and paraffin-mounted) test samples, we investigate both time- and frequency-domain methods based on bright- and dark-field TPI. Successful tissue classification is demonstrated

  12. Vectorial near-field imaging of a GaN based photonic crystal cavity

    International Nuclear Information System (INIS)

    La China, F.; Intonti, F.; Caselli, N.; Lotti, F.; Vinattieri, A.; Gurioli, M.; Vico Triviño, N.; Carlin, J.-F.; Butté, R.; Grandjean, N.

    2015-01-01

    We report a full optical deep sub-wavelength imaging of the vectorial components of the electric local density of states for the confined modes of a modified GaN L3 photonic crystal nanocavity. The mode mapping is obtained with a scanning near-field optical microscope operating in a resonant forward scattering configuration, allowing the vectorial characterization of optical passive samples. The optical modes of the investigated cavity emerge as Fano resonances and can be probed without the need of embedded light emitters or evanescent light coupling into the nanocavity. The experimental maps, independently measured in the two in-plane polarizations, turn out to be in excellent agreement with numerical predictions

  13. Penerapan Kartu Elektronis Berbasis Near Field Communication (NFC Pada Sistem Keamanan Pintu Rumah Cerdas

    Directory of Open Access Journals (Sweden)

    Danny Kurnianto

    2017-02-01

    Full Text Available Berdasarkan data laporan Badan Pusat Statistik (BPS tahun 2015  bahwa angka kejadian tindak pencurian di Indonesia sampai tahun 2014 masih tergolong tinggi. Salah satu faktor yang menyebabkan hal ini adalah kurangnya penerapan sistem keamanan pintu elektronis di rumah-rumah penduduk. Penggunaan kartu elektronis berbasis Near Field Communication (NFC menjadi pilihan yang sesuai karena teknologi NFC memberikan jaminan keamanan yang lebih baik untuk teknologi yang sejenis dengan konsumsi daya yang rendah. Proses otentifikasi sistem keamanan pintu elektronis dilakukan dengan membaca kode unik dari kartu NFC Tag yang akan dicocokkan dengan kode unik kartu NFC di basis data sistem. Jika hasil otentifikasi telah benar, Arduino sebagai pusat pengendali akan mengaktifkan solenoid lock door sehingga pintu akan terbuka. Hasil pengujian sistem menunjukkan bahwa jarak pembacaan sesungguhnya dari kartu NFC Tag sebesar 7 cm dengan jangkauan sudut pembacaan antara 0o - 85o. Tingkat keberhasilan sistem dalam melakukan proses otentifikasi sebesar 100%.

  14. Spectroscopic infrared scanning near-field optical microscopy (IR-SNOM)

    International Nuclear Information System (INIS)

    Vobornik, D.; Margaritondo, G.; Sanghera, J.S.; Thielen, P.; Aggarwal, I.D.; Ivanov, B.; Tolk, N.H.; Manni, V.; Grimaldi, S.; Lisi, A.; Rieti, S.; Piston, D.W.; Generosi, R.; Luce, M.; Perfetti, P.; Cricenti, A.

    2005-01-01

    Scanning near-field optical microscopy (SNOM or NSOM) is the technique with the highest lateral optical resolution available today, while infrared (IR) spectroscopy has a high chemical specificity. Combining SNOM with a tunable IR source produces a unique tool, IR-SNOM, capable of imaging distributions of chemical species with a 100 nm spatial resolution. We present in this paper boron nitride (BN) thin film images, where IR-SNOM shows the distribution of hexagonal and cubic phases within the sample. Exciting potential applications in biophysics and medical sciences are illustrated with SNOM images of the distribution of different chemical species within cells. We present in this article images with resolutions of the order of λ/60 with SNOM working with infrared light. With our SNOM setup, we routinely get optical resolutions between 50 and 150 nm, regardless of the wavelength of the light used to illuminate the sample

  15. Exposure to Chemicals in Consumer Products: The Role of the Near-Field Environment

    DEFF Research Database (Denmark)

    Fantke, Peter; Ernstoff, Alexi; Huang, L.

    2016-01-01

    contact) were obtained by inverting the transfer fractions matrix, yielding cumulative multimedia transfer fractions. PiFs for various chemicals in products were found to be on the order of 1x10-7 for semi-volatile organic compounds (SVOCs) in thick flooring, 5x10 -3 for VOCs in indoor air spray, and up......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...... recently gaining attention. Further, models that are mostly emissions-based, may not necessarily be applicable to all types of chemical release from consumer products. To address this gap, we (1) define a framework to simultaneously account for exposure to chemicals in the near- and far-field, (2...

  16. New test techniques to evaluate near field effects for supersonic store carriage and separation

    Science.gov (United States)

    Sawyer, Wallace C.; Stallings, Robert L., Jr.; Wilcox, Floyd J., Jr.; Blair, A. B., Jr.; Monta, William J.; Plentovich, Elizabeth B.

    1989-01-01

    Store separation and store carriage drag studies were conducted. A primary purpose is to develop new experimental methods to evaluate near field effects of store separation and levels of store carriage drag associated with a variety of carriage techniques for different store shapes and arrangements. Flow field measurements consisting of surface pressure distributions and vapor screen photographs are used to analyze the variations of the store separation characteristics with cavity geometry. Store carriage drag measurements representative of tangent, semi-submerged, and internal carriage installations are presented and discussed. Results are included from both fully metric models and models with only metric segments (metric pallets) and the relative merits of the two are discussed. Carriage drag measurements for store installations on an aircraft parent body are compared both with prediction methods and with installations on a generic parent body.

  17. Application of near field communication for health monitoring in daily life.

    Science.gov (United States)

    Strömmer, Esko; Kaartinen, Jouni; Pärkkä, Juha; Ylisaukko-Oja, Arto; Korhonen, Ilkka

    2006-01-01

    We study the possibility of applying an emerging RFID-based communication technology, NFC (Near Field Communication), to health monitoring. We suggest that NFC is, compared to other competing technologies, a high-potential technology for short-range connectivity between health monitoring devices and mobile terminals. We propose practices to apply NFC to some health monitoring applications and study the benefits that are attainable with NFC. We compare NFC to other short-range communication technologies such as Bluetooth and IrDA, and study the possibility of improving the usability of health monitoring devices with NFC. We also introduce a research platform for technical evaluation, applicability study and application demonstrations of NFC.

  18. Graphene-based photovoltaic cells for near-field thermal energy conversion.

    Science.gov (United States)

    Messina, Riccardo; Ben-Abdallah, Philippe

    2013-01-01

    Thermophotovoltaic devices are energy-conversion systems generating an electric current from the thermal photons radiated by a hot body. While their efficiency is limited in far field by the Schockley-Queisser limit, in near field the heat flux transferred to a photovoltaic cell can be largely enhanced because of the contribution of evanescent photons, in particular for a source supporting a surface mode. Unfortunately, in the infrared where these systems operate, the mismatch between the surface-mode frequency and the semiconductor gap reduces drastically the potential of this technology. In this paper we propose a modified thermophotovoltaic device in which the cell is covered by a graphene sheet. By discussing the transmission coefficient and the spectral properties of the flux, we show that both the cell efficiency and the produced current can be enhanced, paving the way to promising developments for the production of electricity from waste heat.

  19. Fibers and Conductive Films Using Silver Nanoparticles and Nanowires by Near-Field Electrospinning Process

    Directory of Open Access Journals (Sweden)

    Cheng-Tang Pan

    2015-01-01

    Full Text Available The silver nanowires (AgNWs and silver nanoparticles (AgNPs were synthesized. With near-field electrospinning (NFES process, fibers and thin films with AgNPs and AgNWs were fabricated. In the NFES process, 10 k voltage was applied and the AgNPs and AgNWs fibers can be directly orderly collected without breaking and bending. Then, the characteristics of the fibers were analyzed by four-point probe and EDS. The conductive film was analyzed. When the thickness of films with AgNWs and AgNPs was 1.6 µm, the sheet resistance of films was 0.032 Ω/sq which was superior to that of the commercial ITO. The transmissivity of films was analyzed. The transmissivity was inversely proportional to sheet resistance of the films. In the future, the fibers and films can be used as transparent conductive electrodes.

  20. Nanoscale domains in thin-film pentacene seen by mid-infrared near-field spectroscopy

    Science.gov (United States)

    Keilmann, Fritz; Nickel, Bert; Westermeier, Christian; Liewald, Clemens; Amarie, Sergiu; Cernescu, Adrian

    2015-03-01

    The coexistence of structural phases in thin-film pentacene was known from X-ray diffraction, yet the scale of domain sizes remained unknown due to large-scale averaging. Infrared spectroscopy (classical FTIR) can distinguish different structural phases by slightly shifted molecular vibrational resonances but with spatial resolution not better than about 10 micrometer. When FTIR is paired with near-field microscopy performed by back-scattering infrared radiation from an AFM tip (``nano-FTIR'' allowing 20 nm resolution), Bulk-Phase (BP) domains were readily observed to form cost of the surrounding Thin-Film-Phase (TFP) pentacene. Both the domain interfaces and their continuing dimensional evolution may point to hidden problems for solar conversion systems development, possibly also with molecular materials beyond pentacene.

  1. Effect of aircraft exhaust sulfur emissions on near field plume aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Brown, R.C.; Miake-Lye, R.C.; Anderson, M.R.; Kolb, C.E. [Aerodyne Research, Inc., Billerica, MA (United States). Center for Chemical and Environmental Physics

    1997-12-31

    Based on estimated exit plane sulfur speciation, a two dimensional, axisymmetric flow field model with coupled gas phase oxidation kinetics and aerosol nucleation and growth dynamics is used to evaluate the effect of fuel sulfur oxidation in the engine on the formation and growth of volatile H{sub 2}SO{sub 4}/H{sub 2}O aerosols in the near field plume. The conversion of fuel sulfur to sulfur trioxide and sulfuric acid in the engine is predicted to significantly increase the number density and surface area density of volatile H{sub 2}SO{sub 4}/H{sub 2}O aerosols and the chemical activation of exhaust soot particulates. This analysis indicates the need for experimental measurements of exhaust SO{sub x} emissions to fully assess the atmospheric impact of aircraft emissions. (author) 18 refs.; Submitted to Geophysical Research Letters

  2. Reactive near field electromagnetic axonal communication channels and their role in neurodegenerative diseases.

    Science.gov (United States)

    Morgera, Salvatore Domenic

    2015-01-01

    Research focus is on the micron-scale subsystem of the human nervous system known as the axon, or nerve fibre. In studying what has been traditionally treated as an electrochemical subsystem, we find that the axon is both an electrochemical and electromagnetic link in an intricately designed network. This work offers a game changing look at phenomena which enable interaction among millions of fibres tightly packed in bundles and tracts in the human peripheral and central nervous systems, respectively. We maintain that these fibres do not act independently as generally believed, but form intricate spatial and temporal near-field networks. An understanding of these networks will lead to improved diagnostics and therapeutics for neurodegenerative diseases.

  3. An internet of things example: classrooms access control over near field communication.

    Science.gov (United States)

    Palma, Daniel; Agudo, Juan Enrique; Sánchez, Héctor; Macías, Miguel Macías

    2014-04-21

    The Internet of Things is one of the ideas that has become increasingly relevant in recent years. It involves connecting things to the Internet in order to retrieve information from them at any time and from anywhere. In the Internet of Things, sensor networks that exchange information wirelessly via Wi-Fi, Bluetooth, Zigbee or RF are common. In this sense, our paper presents a way in which each classroom control is accessed through Near Field Communication (NFC) and the information is shared via radio frequency. These data are published on the Web and could easily be used for building applications from the data collected. As a result, our application collects information from the classroom to create a control classroom tool that displays access to and the status of all the classrooms graphically and also connects this data with social networks.

  4. 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

    A new and effective method for reduction of truncation errors in partial spherical near-field (SNF) measurements is proposed. The method is useful when measuring electrically large antennas, where the measurement time with the classical SNF technique is prohibitively long and an acquisition over...... the whole spherical surface is not practical. Therefore, to reduce the data acquisition time, partial sphere measurement is usually made, taking samples over a portion of the spherical surface in the direction of the main beam. But in this case, the radiation pattern is not known outside the measured...... 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...

  5. An Internet of Things Example: Classrooms Access Control over Near Field Communication

    Directory of Open Access Journals (Sweden)

    Daniel Palma

    2014-04-01

    Full Text Available The Internet of Things is one of the ideas that has become increasingly relevant in recent years. It involves connecting things to the Internet in order to retrieve information from them at any time and from anywhere. In the Internet of Things, sensor networks that exchange information wirelessly via Wi-Fi, Bluetooth, Zigbee or RF are common. In this sense, our paper presents a way in which each classroom control is accessed through Near Field Communication (NFC and the information is shared via radio frequency. These data are published on the Web and could easily be used for building applications from the data collected. As a result, our application collects information from the classroom to create a control classroom tool that displays access to and the status of all the classrooms graphically and also connects this data with social networks.

  6. The near-field geochemistry of HLW disposal in an argilleous host rock

    International Nuclear Information System (INIS)

    McKinley, I.G.

    1989-04-01

    Current concepts in Switzerland envisage the disposal of vitrified high-level waste (HLW) , encapsulated in massive steel canisters, horizontally into tunnels which are backfilled with compacted bentonite. In the Project Gewaehr 1985 study, the geochemical aspects of the performance of these barriers in a repository situated at a depth of approx 1300 m in a crystalline host-rock were evaluated. This report extends that analysis to consider an alternative repository concept at a depth of approx 850 m in an argilleous host rock. In general, the longevity of the engineered barriers is little affected by the choice of host rock - the analysis predicts that bentonite will retain its favourable physical and chemical properties for more than 10 6 years, the canister will last more than 10 3 years and the complete degradation of the glass matrix will take over 10 5 years. These components also ensure that most of the near-field is chemically buffered in reducing, mildly alkaline conditions. After failure of the mechanical integrity of the canister, the release of many important nuclides is further constrained by their low solubilities. Transport of dissolved radionuclides occurs in the benonite only by diffusion, which is limited by various retardation mechanisms. One of the key roles of the bentonite in this regard is to act as a filter, preventing migration of particulate or colloidal species. In conclusion, the expected radionuclide release rates from the near-field are very low, even with fairly conservative assumptions on the performance of various barriers. There are indications that a more realistic analysis would demonstrate negligible releases of almost all key nuclides. The justification of such a treatment depends, however, on building up a more fundamental understanding of some of the processes involved and validation of the models/databases used by a variety of methods, possibly including natural analogue studies. (author) 7 figs., 12 tabs., 99 refs

  7. The interaction of the near-field plasma with antennas used in magnetic fusion research

    Science.gov (United States)

    Caughman, John

    2015-09-01

    Plasma heating and current drive using antennas in the Ion Cyclotron Range of Frequencies (ICRF) are important elements for the success of magnetic fusion. The antennas must operate in a harsh environment, where local plasma densities can be >1018/m3, magnetic fields can range from 0.2-5 Tesla, and antenna operating voltages can be >40 kV. This environment creates operational issues due to the interaction of the near-field of the antenna with the local plasma. In addition to parasitic losses in this plasma region, voltage and current distributions on the antenna structure lead to the formation of high electric fields and RF plasma sheaths, which can lead to enhanced particle and energy fluxes on the antenna and on surfaces intersected by magnetic field lines connected to or passing near the antenna. These issues are being studied using a simple electrode structure and a single-strap antenna on the Prototype Materials Plasma EXperiment (Proto-MPEX) at ORNL, which is a linear plasma device that uses an electron Bernstein wave heated helicon plasma source to create a high-density plasma suitable for use in a plasma-material interaction test stand. Several diagnostics are being used to characterize the near-field interactions, including double-Langmuir probes, a retarding field energy analyzer, and optical emission spectroscopy. The RF electric field is being studied utilizing Dynamic Stark Effect spectroscopy and Doppler-Free Saturation Spectroscopy. Recent experimental results and future plans will be presented. ORNL is managed by UT-Battelle, LLC, for the U.S. DOE under Contract DE-AC-05-00OR22725.

  8. Analysis of near-field thermal and psychometric waste package environment using ventilation

    International Nuclear Information System (INIS)

    Danko, G.

    1995-03-01

    The ultimate objective of the Civilian Radioactive Waste Management System (CRWMS) Program is to safely emplace and isolate the nations' spent nuclear fuel (SNF) and radioactive wastes in a geologic repository. Radioactive waste emplaced in a geologic repository will generate heat, increasing the temperature in the repository. The magnitude of this temperature increase depends upon (1) the heat source, i.e. the thermal loading of the repository, and (2) the geologic and engineered heat transport characteristics of the repository. Thermal management techniques currently under investigation include ventilation of the emplacement drifts during the preclosure period which could last as long as 100 years. Understanding the amount of heat and moisture removed from the emplacement drifts and near-field rock by ventilation, are important in determining performance of the engineered barrier system (EBS), as well as the corrosive environment of the waste packages, and the interaction of the EBS with the near-field host rock. Since radionuclide releases and repository system performance are significantly affected by the corrosion rate related to the psychometric environment, it is necessary to predict the amount of heat and moisture that are removed from the repository horizon using a realistic model for a wide range of thermal loading. This can be realized by coupling the hydrothermal model of the rock mass to a ventilation/climate model which includes the heat and moisture transport on the rock-air interface and the dilution of water vapor in the drift. This paper deals with the development of the coupled model concept, and determination of the boundary conditions for the calculations

  9. Near-Field Hydrology Data Package for the Immobilized Low-Activity Waste 2001 Performance Assessment

    Energy Technology Data Exchange (ETDEWEB)

    PD Meyer; RJ Serne

    1999-12-21

    Lockheed Martin Hanford Company (LMHC) is designing and assessing the performance of disposal facilities to receive radioactive wastes that are currently stored in single- and double-shell tanks at the Hanford Site. The preferred method for disposing of the portion that is classified as immobilized low-activity waste (ILAW) is to vitrify the waste and place the product in new-surface, shallow land burial facilities. The LMHC project to assess the performance of these disposal facilities is the Hanford ILAW Performance Assessment (PA) Activity. The goal of this project is to provide a reasonable expectation that the disposal of the waste is protective of the general public, groundwater resources, air resources, surface water resources, and inadvertent intruders. Achieving this goal will require prediction of contaminant migration from the facilities. This migration is expected to occur primarily via the movement of water through the facilities and the consequent transport of dissolved contaminants in the pore water of the vadose zone. Pacific Northwest National Laboratory (PNNL) assists LMHC in its performance assessment activities. One of PNNL's tasks is to provide estimates of the physical, hydraulic, and transport properties of the materials comprising the disposal facilities and the disturbed region around them. These materials are referred to as the near-field materials. Their properties are expressed as parameters of constitutive models used in simulations of subsurface flow and transport. In addition to the best-estimate parameter values, information on uncertainty in the parameter values and estimates of the changes in parameter values over time are required to complete the PA. These parameter estimates and information are contained in this report, the Near-Field Hydrology Data Package.

  10. High energy multi-cycle terahertz generation

    International Nuclear Information System (INIS)

    Ahr, Frederike Beate

    2017-10-01

    Development of compact electron accelerators and free-electron lasers requires novel acceleration schemes at shorter driving wavelengths. The Axsis project seeks to develop terahertz based electron acceleration as well as the high energy terahertz sources required. This thesis explores the methods and optical material required for the generation of highenergy multi-cycle terahertz pulses. Two experimental concepts to generate high energy terahertz radiation are presented. In addition the theoretical background and the optical properties of pertinent optical materials in the terahertz range are discussed. Investigations of the materials are performed with a terahertz time domain spectrometer and a Fourier transform infrared spectrometer. The nonlinear optical crystal lithium niobate as well as other crystals suitable for the terahertz generation and in addition polymers and other radiation attenuators are characterized in the range from 0.2 to 1 THz. The theory describing the generation of narrowband terahertz radiation is evaluated. The experimental setups to generate terahertz radiation and to characterize its properties are described. The specific crystals - periodically poled lithium niobate (PPLN) - used in the experiments to generate the multi-cycle terahertz radiation are examined to determine e.g. the poling period. The first experimental concept splits the ultra fast, broadband pump pulses into a pulse train in order to pump the PPLN at a higher fluence while increasing the damage limit. The measurements confirm that a pulse train of ultra short, broadband pump pulses increases not only the terahertz energy but also the energy conversion efficiency. The second experimental concept utilizes chirped and delayed infrared laser pulses. This pulse format makes it possible to pump the crystal with high energy pulses resulting in high energy terahertz radiation. The concept is optimized to reach energies up to 127 μJ exceeding the existing results of narrowband

  11. High energy multi-cycle terahertz generation

    Energy Technology Data Exchange (ETDEWEB)

    Ahr, Frederike Beate

    2017-10-15

    Development of compact electron accelerators and free-electron lasers requires novel acceleration schemes at shorter driving wavelengths. The Axsis project seeks to develop terahertz based electron acceleration as well as the high energy terahertz sources required. This thesis explores the methods and optical material required for the generation of highenergy multi-cycle terahertz pulses. Two experimental concepts to generate high energy terahertz radiation are presented. In addition the theoretical background and the optical properties of pertinent optical materials in the terahertz range are discussed. Investigations of the materials are performed with a terahertz time domain spectrometer and a Fourier transform infrared spectrometer. The nonlinear optical crystal lithium niobate as well as other crystals suitable for the terahertz generation and in addition polymers and other radiation attenuators are characterized in the range from 0.2 to 1 THz. The theory describing the generation of narrowband terahertz radiation is evaluated. The experimental setups to generate terahertz radiation and to characterize its properties are described. The specific crystals - periodically poled lithium niobate (PPLN) - used in the experiments to generate the multi-cycle terahertz radiation are examined to determine e.g. the poling period. The first experimental concept splits the ultra fast, broadband pump pulses into a pulse train in order to pump the PPLN at a higher fluence while increasing the damage limit. The measurements confirm that a pulse train of ultra short, broadband pump pulses increases not only the terahertz energy but also the energy conversion efficiency. The second experimental concept utilizes chirped and delayed infrared laser pulses. This pulse format makes it possible to pump the crystal with high energy pulses resulting in high energy terahertz radiation. The concept is optimized to reach energies up to 127 μJ exceeding the existing results of narrowband

  12. Nonlinear terahertz coherent excitation of vibrational modes of liquids.

    Science.gov (United States)

    Allodi, Marco A; Finneran, Ian A; Blake, Geoffrey A

    2015-12-21

    We report the first coherent excitation of intramolecular vibrational modes via the nonlinear interaction of a TeraHertz (THz) light field with molecular liquids. A terahertz-terahertz-Raman pulse sequence prepares the coherences with a broadband, high-energy, (sub)picosecond terahertz pulse, that are then measured in a terahertz Kerr effect spectrometer via phase-sensitive, heterodyne detection with an optical pulse. The spectrometer reported here has broader terahertz frequency coverage, and an increased sensitivity relative to previously reported terahertz Kerr effect experiments. Vibrational coherences are observed in liquid diiodomethane at 3.66 THz (122 cm(-1)), and in carbon tetrachloride at 6.50 THz (217 cm(-1)), in exact agreement with literature values of those intramolecular modes. This work opens the door to 2D spectroscopies, nonlinear in terahertz field, that can study the dynamics of condensed-phase molecular systems, as well as coherent control at terahertz frequencies.

  13. Terahertz Technology: A Boon to Tablet Analysis

    Science.gov (United States)

    Wagh, M. P.; Sonawane, Y. H.; Joshi, O. U.

    2009-01-01

    The terahertz gap has a frequency ranges from ∼0.3 THz to ∼10 THz in the electromagnetic spectrum which is in between microwave and infrared. The terahertz radiations are invisible to naked eye. In comparison with x-ray they are intrinsically safe, non-destructive and non-invasive. Terahertz spectroscopy enables 3D imaging of structures and materials, and the measurement of the unique spectral fingerprints of chemical and physical forms. Terahertz radiations are produced by a dendrimer based high power terahertz source and spectroscopy technologies. It resolves many of the questions left unanswered by complementary techniques, such as optical imaging, Raman and infrared spectra. In the pharmaceutical industries it enables nondestructive, internal, chemical analysis of tablets, capsules, and other dosage forms. Tablet coatings are a major factor in drug bioavailability. Therefore tablet coatings integrity and uniformity are of crucial importance to quality. Terahertz imaging gives an unparalleled certainty about the integrity of tablet coatings and the matrix performance of tablet cores. This article demonstrates the potential of terahertz pulse imaging for the analysis of tablet coating thickness by illustrating the technique on tablets. PMID:20490288

  14. Evaluating Multiple Levels of an Interaction Fidelity Continuum on Performance and Learning in Near-Field Training Simulations.

    Science.gov (United States)

    Bhargava, Ayush; Bertrand, Jeffrey W; Gramopadhye, Anand K; Madathil, Kapil C; Babu, Sabarish V

    2018-04-01

    With costs of head-mounted displays (HMDs) and tracking technology decreasing rapidly, various virtual reality applications are being widely adopted for education and training. Hardware advancements have enabled replication of real-world interactions in virtual environments to a large extent, paving the way for commercial grade applications that provide a safe and risk-free training environment at a fraction of the cost. But this also mandates the need to develop more intrinsic interaction techniques and to empirically evaluate them in a more comprehensive manner. Although there exists a body of previous research that examines the benefits of selected levels of interaction fidelity on performance, few studies have investigated the constituent components of fidelity in a Interaction Fidelity Continuum (IFC) with several system instances and their respective effects on performance and learning in the context of a real-world skills training application. Our work describes a large between-subjects investigation conducted over several years that utilizes bimanual interaction metaphors at six discrete levels of interaction fidelity to teach basic precision metrology concepts in a near-field spatial interaction task in VR. A combined analysis performed on the data compares and contrasts the six different conditions and their overall effects on performance and learning outcomes, eliciting patterns in the results between the discrete application points on the IFC. With respect to some performance variables, results indicate that simpler restrictive interaction metaphors and highest fidelity metaphors perform better than medium fidelity interaction metaphors. In light of these results, a set of general guidelines are created for developers of spatial interaction metaphors in immersive virtual environments for precise fine-motor skills training simulations.

  15. Enhancement of spatial resolution of terahertz imaging systems based on terajet generation by dielectric cube

    Directory of Open Access Journals (Sweden)

    Hai Huy Nguyen Pham

    2017-05-01

    Full Text Available The terahertz (THz, 0.1–10 THz region has been attracting tremendous research interest owing to its potential in practical applications such as biomedical, material inspection, and nondestructive imaging. Those applications require enhancing the spatial resolution at a specific frequency of interest. A variety of resolution-enhancement techniques have been proposed, such as near-field scanning probes, surface plasmons, and aspheric lenses. Here, we demonstrate for the first time that a mesoscale dielectric cube can be exploited as a novel resolution enhancer by simply placing it at the focused imaging point of a continuous wave THz imaging system. The operating principle of this enhancer is based on the generation—by the dielectric cuboid—of the so-called terajet, a photonic jet in the THz region. A subwavelength hotspot is obtained by placing a Teflon cube, with a 1.46 refractive index, at the imaging point of the imaging system, regardless of the numerical aperture (NA. The generated terajet at 125 GHz is experimentally characterized, using our unique THz-wave visualization system. The full width at half maximum (FWHM of the hotspot obtained by placing the enhancer at the focal point of a mirror with a measured NA of 0.55 is approximately 0.55λ, which is even better than the FWHM obtained by a conventional focusing device with the ideal maximum numerical aperture (NA = 1 in air. Nondestructive subwavelength-resolution imaging demonstrations of a Suica integrated circuit card, which is used as a common fare card for trains in Japan, and an aluminum plate with 0.63λ trenches are presented. The amplitude and phase images obtained with the enhancer at 125 GHz can clearly resolve both the air-trenches on the aluminum plate and the card’s inner electronic circuitry, whereas the images obtained without the enhancer are blurred because of insufficient resolution. An increase of the image contrast by a factor of 4.4 was also obtained using

  16. Electrically continuous graphene from single crystal copper verified by terahertz conductance spectroscopy and micro four-point probe

    DEFF Research Database (Denmark)

    Buron, Jonas Christian Due; Pizzocchero, Filippo; Jessen, Bjarke Sørensen

    2014-01-01

    . Micro four-point probe resistance values measured on graphene grown on single crystalline copper in two different voltage-current configurations show close agreement with the expected distributions for a continuous 2D conductor, in contrast with previous observations on graphene grown on commercial...... noninvasive conductance characterization methods: ultrabroadband terahertz time-domain spectroscopy and micro four-point probe, which probe the electrical properties of the graphene film on different length scales, 100 nm and 10 μm, respectively. Ultrabroadband terahertz time-domain spectroscopy allows...... copper foil. The terahertz and micro four-point probe conductance values of the graphene grown on single crystalline copper shows a close to unity correlation, in contrast with those of the graphene grown on commercial copper foil, which we explain by the absence of extended defects on the microscale...

  17. Anomalous extinction in index-matched terahertz nanogaps

    Science.gov (United States)

    Jeong, Jeeyoon; Kim, Dasom; Park, Hyeong-Ryeol; Kang, Taehee; Lee, Dukhyung; Kim, Sunghwan; Bahk, Young-Mi; Kim, Dai-Sik

    2018-01-01

    Slot-type nanogaps have been widely utilized in transmission geometry because of their advantages of exclusive light funneling and exact quantification of near-field enhancement at the gap. For further application of the nanogaps in electromagnetic interactions with various target materials, complementary studies on both transmission and reflection properties of the nanogaps are necessary. Here, we observe an anomalous extinction of terahertz waves interacting with rectangular ring-shaped sub-30 nm wide gaps. Substrate works as an index matching layer for the nanogaps, leading to a stronger field enhancement and increased nonlinearity at the gap under substrate-side illumination. This effect is expressed in reflection as a larger dip at the resonance, caused by destructive interference of the diffracted field from the gap with the reflected beam from the metal. The resulting extinction at the resonance is larger than 60% of the incident power, even without any absorbing material in the whole nanogap structure. The extinction even decreases in the presence of an absorbing medium on top of the nanogaps, suggesting that transmission and reflection from nanogaps might not necessarily represent the absorption of the whole structure.

  18. Anomalous extinction in index-matched terahertz nanogaps

    Directory of Open Access Journals (Sweden)

    Jeong Jeeyoon

    2018-01-01

    Full Text Available Slot-type nanogaps have been widely utilized in transmission geometry because of their advantages of exclusive light funneling and exact quantification of near-field enhancement at the gap. For further application of the nanogaps in electromagnetic interactions with various target materials, complementary studies on both transmission and reflection properties of the nanogaps are necessary. Here, we observe an anomalous extinction of terahertz waves interacting with rectangular ring-shaped sub-30 nm wide gaps. Substrate works as an index matching layer for the nanogaps, leading to a stronger field enhancement and increased nonlinearity at the gap under substrate-side illumination. This effect is expressed in reflection as a larger dip at the resonance, caused by destructive interference of the diffracted field from the gap with the reflected beam from the metal. The resulting extinction at the resonance is larger than 60% of the incident power, even without any absorbing material in the whole nanogap structure. The extinction even decreases in the presence of an absorbing medium on top of the nanogaps, suggesting that transmission and reflection from nanogaps might not necessarily represent the absorption of the whole structure.

  19. Modeling coupled thermal, flow, transport and geochemical processes controlling near field long-term evolution

    International Nuclear Information System (INIS)

    Zhou, W.; Arthur, R.; Xu, T.; Pruess, K.

    2005-01-01

    Full text of publication follows: Bentonite is planned for use as a buffer material in the Swedish nuclear waste disposal concept (KBS-3). Upon emplacement, the buffer is expected to experience a complex set of coupled processes involving heating, re-saturation, reaction and transport of groundwater imbibed from the host rock. The effect of these processes may eventually lead to changes in desirable physical and rheological properties of the buffer, but these processes are not well understood. In this paper, a new quantitative model is evaluated to help improve our understanding of the long-term performance of buffer materials. This is an extension of a previous study [1] that involved simple thermal and chemical models applied to a fully saturated buffer. The thermal model in the present study uses heating histories for spent fuel in a single waste package [2]. The model uses repository dimensions, such as borehole and tunnel spacings [2], which affect the temperature distribution around the waste package. At the time of emplacement, bentonite is partially saturated with water having a different composition than the host-rock groundwater. The present model simulates water imbibition from the host rock into the bentonite under capillary and hydraulic pressure gradients. The associated chemical reactions and solute transport are simulated using Aespoe water composition [3]. The initial mineralogy of bentonite is assumed to be dominated by Na-smectite with much smaller amounts of anhydrite and calcite. Na-smectite dissolution is assumed to be kinetically-controlled while all other reactions are assumed to be at equilibrium controlled. All equilibrium and kinetic constants are temperature dependent. The modeling tool used is TOUGHREACT, developed by Lawrence Berkeley National Laboratory [4]. TOUGHREACT is a numerical model that is well suited for near-field simulations because it accounts for feedback between porosity and permeability changes from mineral

  20. Experimental Validation of UTDefect: Scattering in Anisotropic Media and Near-field Behavior

    International Nuclear Information System (INIS)

    Pecorari, Claudio

    2002-11-01

    Theoretical models that simulate measurements of ultrasonic waves undergoing scattering by material defects have been developed by Prof. Bostroem and co-workers at Chalmers Univ. of Tech. for a variety of experimental configurations and defects. A software program named UTDefect has been developed at the same time, which gathers the theoretical results obtained so far in a single package. A discussion of the motivations behind such an effort and details concerning UTDefect can be found in articles by Bostroem. Following an initial effort to validate some of the theoretical predictions available at the time, the present project has been conceived as a support to the on-going theoretical work. In fact, the goal of the project described in this report has been the experimental validation of two aspects of the above theory that have not yet been tested: the scattering of a finite ultrasonic beam by a surface-breaking crack in an anisotropic medium, and an improved model of the behaviour of a finite ultrasonic beam in the near-field region of the source. In the last case, the supporting medium is supposed to be isotropic. To carry out the first task, a single crystal, silicon sample was employed. A surface-breaking notch with a depth of approximately 1.8 mm was introduced by means of a wire-cutting saw to simulate a scattering defect. Two kinds of measurements were performed of this sample. The first one considered the signal amplitude as a function of the transducer position. To this end, three wedges generating beams propagating in different directions were used. The second series of measurements concerned the frequency content of the backscattered signals at the position where the amplitude was maximum. All three wedges mentioned above were used also in this part of the work. The experimental results were compared to the values of the physical quantities of interest as predicted by UTDefect, with the only difference that UTDefect was run for a sub-surface rectangular

  1. Terahertz Tools Advance Imaging for Security, Industry

    Science.gov (United States)

    2010-01-01

    Picometrix, a wholly owned subsidiary of Advanced Photonix Inc. (API), of Ann Arbor, Michigan, invented the world s first commercial terahertz system. The company improved the portability and capabilities of their systems through Small Business Innovation Research (SBIR) agreements with Langley Research Center to provide terahertz imaging capabilities for inspecting the space shuttle external tanks and orbiters. Now API s systems make use of the unique imaging capacity of terahertz radiation on manufacturing floors, for thickness measurements of coatings, pharmaceutical tablet production, and even art conservation.

  2. Handbook of terahertz technologies devices and applications

    CERN Document Server

    Song, Ho-Jin

    2015-01-01

    Terahertz waves, which lie in the frequency range of 0.1-10 THz, have long been investigated in a few limited fields, such as astronomy, because of a lack of devices for their generation and detection. Several technical breakthroughs made over the last couple of decades now allow us to radiate and detect terahertz waves more easily, which has triggered the search for new uses of terahertz waves in many fields, such as bioscience, security, and information and communications technology. The book covers some of the technical breakthroughs in terms of device technologies. It discusses not only th

  3. EDITORIAL: Photonic terahertz technology

    Science.gov (United States)

    Lisauskas, Alvydas; Löffler, Torsten; Roskos, Hartmut G.

    2005-07-01

    In recent years, when reading newspapers and journals or watching TV, one has been able to find feature presentations dealing with the prospects of terahertz (THz) technology and its potential impact on market applications. THz technology aims to fill the THz gap in the electro-magnetic spectrum in order to make the THz frequency regime, which spans the two orders of magnitude from 100 GHz to 10 THz, accessible for applications. From the lower-frequency side, electronics keeps pushing upwards, while photonic approaches gradually improve our technological options at higher frequencies. The popular interest reflects the considerable advances in research in the THz field, and it is mainly advances in the photonic branch, with the highlight being the development of the THz quantum cascade laser, which in recent years have caught the imagination of the public, and of potential users and investors. This special issue of Semiconductor Science and Technology provides an overview of key scientific developments which currently represent the cutting edge of THz photonic technology. In order to be clear about the implications, we should define exactly what we mean by 'THz photonic technology', or synonymously 'THz photonics'. It is characterized by the way in which THz radiation (or a guided THz wave) is generated, namely by the use of lasers. This may be done in one of two fundamentally different schemes: (i) by laser action in the terahertz frequency range itself (THz lasers), or (ii) by down-conversion processes (photomixing) involving the radiation of lasers which operate in the visible, near-infrared or infrared spectral ranges, either in pulsed or continuous-wave mode. The field of THz photonics has grown so considerably that it is out of the question to cover all its aspects in a single special issue of a journal. We have elected, instead, to focus our attention on two types of development with a potentially strong impact on the THz field: first, on significant advances

  4. Switching terahertz wave with grating-coupled Kretschmann configuration.

    Science.gov (United States)

    Jiu-Sheng, Li

    2017-08-07

    We present a terahertz wave switch utilizing Kretschmann configuration which consists of high-refractive-index prism-liquid crystal-periodically grooved metal grating. The switching mechanism of the terahertz switch is based on spoof surface plasmon polariton (SSPP) excitation in the attenuated total reflection regime by changing the liquid crystal refractive index. The results highlighted the fact that the feasibility to "tune" the attenuated total reflection terahertz wave intensity by using the external applied bias voltage. The extinction ratio of the terahertz switch reaches 31.48dB. The terahertz switch has good control ability and flexibility, and can be used in potential terahertz free space device systems.

  5. Contrast in terahertz conductivity of phase-change materials

    Czech Academy of Sciences Publication Activity Database

    Kadlec, Filip; Kadlec, Christelle; Kužel, Petr

    2012-01-01

    Roč. 152, č. 10 (2012), s. 852-855 ISSN 0038-1098 R&D Projects: GA ČR GC202/09/J045 Institutional research plan: CEZ:AV0Z10100520 Keywords : thin films * electronic transport * phonons * light absorption and reflection Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 1.534, year: 2012 http://www.sciencedirect.com/science/article/pii/S0038109812001093

  6. In situ experiments on the performance of near-field for nuclear waste repository at KURT

    International Nuclear Information System (INIS)

    Cho, Won-Jin; Kim, Jin-Sub; Lee, Changsoo; Kwon, Sangki; Choi, Jong-Won

    2012-01-01

    Highlights: ► Results of in situ experiments on the near-field of a repository are summarized. ► In BHT, the rock temperatures at 0.3 m from heater showed 40–50 °C increase. ► EDZ size measured from the in situ test was in the range of 0.6–1.8 m. ► Maximum errors in estimating the location of AE source were 0.6–1.0 m. ► Permeability in the EDZ increased up to 2 orders compared with the intact rock. - Abstract: To obtain the information on the design and performance assessment of a geological repository for nuclear waste, several in situ experiments on the performance of the near-field have been conducted for 5 years in the small-scale underground research laboratory, KURT. This paper summarizes the results from the in situ experiments. In the borehole heater test, the rock temperature at 0.3 m distance from the heater hole with 90 °C showed a 40 °C increase over initial temperature. After heating with 120 °C, the rock temperature at 0.3 m distance from the heater hole increased up to 50 °C over initial temperature. The EDZ size measured from the in situ test was in the range of 0.6–1.8 m, and was higher than that from the laboratory tests, which was estimated to be around 1.1–1.5 m. The maximum errors in estimating the location of acoustic emission source were 1.0 m in EDZ and 0.6 m in an intact rock zone, respectively. The damping ratios of the EDZ and intact rock were 0.091 and 0.005, respectively. The permeability of rock increased with decreasing distance from the tunnel wall because of the EDZ. The permeability in the EDZ seems to be increased up to 2 orders compared with that in the intact rock.

  7. The Aleutian Tsunami of 1946: the Compound Earthquake-Landslide Source and Near-Field Modeling

    Science.gov (United States)

    Fryer, G. J.; Yamazaki, Y.; McMurtry, G. M.

    2015-12-01

    The tsunami of April 1, 1946, spread death and destruction throughout the Pacific from the Aleutians to Antarctica, and produced exceptional runup, 42 m, at Scotch Cap on Unimak Island in the near field. López & Okal (2006) showed that the triggering earthquake was at least MW = 8.6, large enough to explain the far-field tsunami but still requiring a landslide or other secondary source to achieve the local runup. No convincing landslide was found until von Huene, et al (2014) merged all available multibeam data and reprocessed a old multichannel line to show that a feature on the Aleutian Terrace they call Lone Knoll (LK) is the displaced block of a translational slide. From 210Pb dating of push cores taken near the summit of LK, we find that a disruption in sedimentation occurred in 1946 at one site, but sedimentation was not disrupted at another site nearby. We infer that the slide block moved coherently at a speed close to the threshold for erosion of the hemipelagic clays. From GLORIA sidescan, Fryer, et al (2004) had earlier tentatively identified LK as a landslide deposit, but if the tsunami crossed the shallow Aleutian Shelf at the long-wave speed, that landslide had to extend up to the shelf edge to satisfy the known 48-min travel time to Scotch Cap. The resulting landslide was enormous, and a multibeam survey later in 2004 showed that it could not exist. The slide imaged by von Huene, et al is far smaller, with a headwall 30 km downslope at a depth of 3 km. The greater distance demands that the tsunami travel much faster across the shelf. The huge runup, however, suggests that wave height was a significant fraction of the water depth (only 80 m), so the tsunami probably crossed the Aleutian Shelf as a bore. From modeling the landslide-generated tsunami with a shock-capturing dispersive code we infer that it did indeed cross the shelf as a bore traveling at roughly twice the long-wave speed. We are still exploring the dependence of the tsunami on slide

  8. Near-Field Population Response During the 2 April 2007 Solomon Islands Tsunami

    Science.gov (United States)

    McAdoo, B. G.; Moore, A. L.; Baumwoll, J.

    2007-12-01

    When the magnitude 8.1 earthquake and subsequent tsunami hit the Solomon Islands on 2 April 2007 it killed 52 people. On Ghizo Island, home of the capital of the Western Province, Gizo, waves approaching 4 m in height inundated the south coast villages. Eyewitness accounts supported by geologic data from the offshore coral reef and sediment deposited on land suggest a wave that came in as the shaking stopped as a rapidly-rising tide rather than a turbulent bore- vehicles and houses were floated inland with very little damage. Those that survived in villages affected by the tsunami had indigenous knowledge of prior events, whereas immigrant populations died in higher proportions. While buoy-based early warning systems are necessary to mitigate the effects of teletsunamis, they would have done little good in this near-field environment. In Pailongge, a village of 76 indigenous Solomon Islanders on Ghizo's south coast, there were no deaths. Village elders directed the people inland following the shaking and the almost immediate withdrawal of water from the lagoon, and heads of household made sure that children were accounted for and evacuated. Of the 366 Gilbertese living in Titiana, however, 13 people died, 8 of which were children who were exploring the emptied lagoon. A large proportion of the dead were children (24) as they were likely too weak to swim against the non-bore flow. The Gilbertese migrated from Kiribati in the 1950"s, and had not experienced a major earthquake and tsunami, hence had no cultural memory. In the case of the Solomon Islands tsunami, as was the case in the 2004 Indian Ocean tsunami, indigenous knowledge served the people in the near-field well. In the case of the Indian Ocean where there was 10-20 minutes separation between the time the shaking began and the waves arrived, the combination of an in-place plan and a suitable physical geography allowed the population of Simeulue Island and the Moken people of Thailand to escape before the

  9. Rock mechanical, thermomechanical and hydraulic behaviour of the near field for spent nuclear fuel

    International Nuclear Information System (INIS)

    Johansson, E.; Hakala, M.; Lorig, L.J.

    1991-10-01

    Teollisuuden Voima Oy (TVO) is investigating the feasibility of disposing high level nuclear waste in crystalline rock at depths of 400 to 600 meters below the ground surface. Two explicit distinct element computer codes UDEC and 3DEC were used to simulate the mechanical response associated with excavation and the thermomechanical response associated with waste emplacement. Model input data are mostly based on preliminary design of the repository and on field data from on-going site investigations in Finland. The results showed that the overall stability of the repository near-field appears to be good during the studied time period 0 - 900 years. The maximum displacements after excavation are about 2 mm on the walls of the disposal tunnel. Joint openings are only a few micrometers. The hydraulic conductivity increases by 4 to 6 times within the zone of 0,3 m around the tunnel and emplacement hole, and farther away the average increase in conductivity is 1,2 to 1,7 times. After 60 years the heating increases the stresses in the vicinity of the excavated rooms, and closes the joints decreasing the hydraulic conductivity by 93 - 99 % when assuming 10 μm in-situ hydraulic aperture. However, when assuming 50 μm in-situ hydraulic aperture the hydraulic conductivity increases 10 - 40 % because the change in dynamic viscosity of water has a larger effect than the joint aperture change. After 900 years in the cooling stage the stresses and displacements come back almost to the same level as after the excavation. Some permanent displacements remain in the joints due to the shearing. The hydraulic conductivity at 900 years is 10 - 70 % of the conductivity after the excavation. The comparisons between the 2-D and 3-D results show that the two-dimensional modeling, if sufficient cross-sections have been analyzed, is enough to describe mechanical behaviour of the near-field, whereas the three-dimensional modeling is needed in some cases to assess the thermomechanical behaviour

  10. In vivo terahertz reflection imaging of human scars during and after the healing process.

    Science.gov (United States)

    Fan, Shuting; Ung, Benjamin S Y; Parrott, Edward P J; Wallace, Vincent P; Pickwell-MacPherson, Emma

    2017-09-01

    We use terahertz imaging to measure four human skin scars in vivo. Clear contrast between the refractive index of the scar and surrounding tissue was observed for all of the scars, despite some being difficult to see with the naked eye. Additionally, we monitored the healing process of a hypertrophic scar. We found that the contrast in the absorption coefficient became less prominent after a few months post-injury, but that the contrast in the refractive index was still significant even months post-injury. Our results demonstrate the capability of terahertz imaging to quantitatively measure subtle changes in skin properties and this may be useful for improving scar treatment and management. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Aspheric lenses for terahertz imaging.

    Science.gov (United States)

    Lo, Yat Hei; Leonhardt, Rainer

    2008-09-29

    We present novel designs for aspheric lenses used in terahertz (THz) imaging. As different surfaces result in different beam shaping properties and in different losses from reflection and absorption, the resultant imaging resolution (i.e. the focal spot size) depends critically on the design approach. We evaluate the different lens designs using Kirchhoff's scalar diffraction theory, and test the predictions experimentally. We also show that our lenses can achieve sub-wavelength resolution. While our lens designs are tested with THz radiation, the design considerations are applicable also to other regions of the electro-magnetic spectrum.

  12. Terahertz Spectroscopy of Novel Superconductors

    OpenAIRE

    Lupi, Stefano

    2011-01-01

    Through the coupling of Synchrotron Radiation and Michelson interferometry, one may obtain in the terahertz (THz) range transmittance and reflectivity spectra with a signal-to-noise ratio (S/N) up to 103. In this paper we review the application of this spectroscopic technique to novel superconductors with an increasing degree of complexity: the single-gap boron-doped diamond; the isotropic multiband V3Si, where superconductivity opens two gaps at the Fermi energy; the CaAlSi superconductor, i...

  13. Terahertz Spectroscopy of Novel Superconductors

    Directory of Open Access Journals (Sweden)

    Stefano Lupi

    2011-01-01

    Full Text Available Through the coupling of Synchrotron Radiation and Michelson interferometry, one may obtain in the terahertz (THz range transmittance and reflectivity spectra with a signal-to-noise ratio (S/N up to 103. In this paper we review the application of this spectroscopic technique to novel superconductors with an increasing degree of complexity: the single-gap boron-doped diamond; the isotropic multiband V3Si, where superconductivity opens two gaps at the Fermi energy; the CaAlSi superconductor, isostructural to MgB2, with a single gap in the hexagonal ab plane and two gaps along the orthogonal c axis.

  14. Terahertz sensing in corneal tissues

    OpenAIRE

    Bennett, David B.; Taylor, Zachary D.; Tewari, Pria; Singh, Rahul S.; Culjat, Martin O.; Grundfest, Warren S.; Sassoon, Daniel J.; Johnson, R. Duncan; Hubschman, Jean-Pierre; Brown, Elliott R.

    2011-01-01

    This work introduces the potential application of terahertz (THz) sensing to the field of ophthalmology, where it is uniquely suited due to its nonionizing photon energy and high sensitivity to water content. Reflective THz imaging and spectrometry data are reported on ex-vivo porcine corneas prepared with uniform water concentrations using polyethylene glycol (PEG) solutions. At 79% water concentration by mass, the measured reflectivity of the cornea was 20.4%, 14.7%, 11.7%, 9.6%, and 7.4% a...

  15. Graphene hyperlens for terahertz radiation

    DEFF Research Database (Denmark)

    Andryieuski, Andrei; Lavrinenko, Andrei; Chigrin, Dmitry N.

    2012-01-01

    We propose a graphene hyperlens for the terahertz (THz) range. We employ and numerically examine a structured graphene-dielectric multilayered stack that is an analog of a metallic wire medium. As an example of the graphene hyperlens in action, we demonstrate an imaging of two point sources...... separated by a distance λ0/5. An advantage of such a hyperlens as compared to a metallic one is the tunability of its properties by changing the chemical potential of graphene. We also propose a method to retrieve the hyperbolic dispersion, check the effective medium approximation, and retrieve...

  16. Near-field and high-resolution cylindrical noise source location method based on vector sound pressure array

    Directory of Open Access Journals (Sweden)

    ZUO Xiang

    2017-08-01

    Full Text Available The existing underwater noise source near-field location method usually assumes that the measurement plane is flat, which increases the difficulty of applying the underwater noise target test for cylindrical distribution. Simultaneously, the conventional near-field focused beam has a lower spatial resolution when used to locate an underwater noise source with cylindrical distribution. Moreover, the near-field underwater noise source location method based on the sound pressure array has a left and right side fuzzy problem. In order to solve these problems, by establishing the near-field measurement model of the noise source with cylindrical distribution as the measurement surface, and combining the unilateral directivity of the vector hydrophone and the high resolution characteristics of the MUSIC algorithm, a near-field and high resolution location method is proposed for cylindrical distribution based on vector sound pressure, and a computer simulation is carried out. The results show that the method can use a smaller array aperture to locate the underwater noise source, enabling it to be used to locate and recognize the noise sources of complex and large-scale cylindrical systems.

  17. Markov chain Monte Carlo sampling based terahertz holography image denoising.

    Science.gov (United States)

    Chen, Guanghao; Li, Qi

    2015-05-10

    Terahertz digital holography has attracted much attention in recent years. This technology combines the strong transmittance of terahertz and the unique features of digital holography. Nonetheless, the low clearness of the images captured has hampered the popularization of this imaging technique. In this paper, we perform a digital image denoising technique on our multiframe superposed images. The noise suppression model is concluded as Bayesian least squares estimation and is solved with Markov chain Monte Carlo (MCMC) sampling. In this algorithm, a weighted mean filter with a Gaussian kernel is first applied to the noisy image, and then by nonlinear contrast transform, the contrast of the image is restored to the former level. By randomly walking on the preprocessed image, the MCMC-based filter keeps collecting samples, assigning them weights by similarity assessment, and constructs multiple sample sequences. Finally, these sequences are used to estimate the value of each pixel. Our algorithm shares some good qualities with nonlocal means filtering and the algorithm based on conditional sampling proposed by Wong et al. [Opt. Express18, 8338 (2010)10.1364/OE.18.008338OPEXFF1094-4087], such as good uniformity, and, moreover, reveals better performance in structure preservation, as shown in numerical comparison using the structural similarity index measurement and the peak signal-to-noise ratio.

  18. Inducing superconductivity at a nanoscale: photodoping with a near-field scanning optical microscope.

    Science.gov (United States)

    Decca, R S; Drew, H D; Maiorov, B; Guimpel, J; Osquiguil, E J

    1999-01-01

    The local modification of an insulating GdBa2Cu3O6.5 thin film, made superconducting by illumination with a near-field scanning optical microscope (NSOM), is reported. A 100-nm aperture NSOM probe acts as a sub-wavelength light source of wavelength lambda(exc) = 480-650 nm, locally generating photocarriers in an otherwise insulating GdBa2-Cu3O6.5 thin film. Of the photogenerated electron-hole pairs, electrons are trapped in the crystallographic lattice, defining an electrostatic confining potential to enable the holes to move. Reflectance measurements at lambda = 1.55 microm at room temperature show that photocarriers can be induced and constrained to move on a approximately 200 nm scale for all investigated lambda(exc). Photogenerated wires present a superconducting critical temperature Tc= 12 K with a critical current density Jc = 10(4) A cm(-2). Exploiting the flexibility provided by photodoping through a NSOM probe, a junction was written by photodoping a wire with a narrow (approximately 50 nm) under-illuminated gap. The strong magnetic field modulation of the critical current provides a clear signature of the existence of a Josephson effect in the junction.

  19. EARLY DETECTION OF NEAR-FIELD TSUNAMIS USING UNDERWATER SENSOR NETWORKS

    Directory of Open Access Journals (Sweden)

    L. E. Freitag

    2012-01-01

    Full Text Available We propose a novel approach for near-field tsunami detection, specifically for the area near the city of Padang, Indonesia. Padang is located on the western shore of Sumatra, directly across from the Mentawai segment of the Sunda Trench, where accumulated strain has not been released since the great earthquake of 1797. Consequently, the risk of a major tsunamigenic earthquake on this segment is high. Currently, no ocean-bottom pressure sensors are deployed in the Mentawai basin to provide a definitive tsunami warning for Padang. Timely warnings are essential to initiate evacuation procedures and minimize loss of human life. Our approach augments existing technology with a network of underwater sensors to detect tsunamis generated by an earthquake or landslide fast enough to provide at least 15 minutes of warning. Data from the underwater sensor network would feed into existing decision support systems that accept input from land and sea-based sensors and provide warning information to city and regional authorities.

  20. 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)

  1. The near-field transport in a repository for high-level nuclear waste

    International Nuclear Information System (INIS)

    Aranguiz, L.R.

    1995-05-01

    The thesis is focused on the modelling of a redox front which is created when the oxidants produced by a radiolytic process in a damaged canister escape to the surroundings, and on a fast and flexible model to calculate the radionuclide transport in the repository. In addition, the thesis includes an attempt to validate the processes involved in the redox front model and a sensitivity analysis of the uncertainties in the parameter values regarding the release of radionuclides from the Swedish KBS-3 repository. The redox front model considers that the transport of oxidants in the clay surrounding the canister is by diffusion and that the transport in the fractures in the rock is by flow with diffusion into the rock matrix.The assumed radiolysis rates denoted high and low in the thesis are probably not realistic, but can be seen as upper limits. thus it is unlikely that the redox front will ever move past the bentonite clay surrounding the canister, and if it does, the front may move less than 100 m. The model to calculate the transport of radionuclides in the near-field uses a coarse compartmentalization of the repository by embedding analytical solutions in zones where other techniques, such as finite difference methods, would need a very fine discretization. Only a few compartments are required to obtain a good accuracy in the calculated release. 34 refs, 17 figs

  2. Steady and oscillatory plasma properties in the near-field plume of a hollow cathode

    Science.gov (United States)

    Zun, ZHANG; Kan, XIE; Jiting, OUYANG; Ning, GUO; Yu, QIN; Qimeng, XIA; Song, BAI; Xianming, WU; Zengjie, GU

    2018-02-01

    Hollow cathodes serve as electron sources in Hall thrusters, ion thrusters and other electric propulsion systems. One of the vital problems in their application is the cathode erosion. However, the basic erosion mechanism and the source of high-energy ions cause of erosion are not fully understood. In this paper, both potential measurements and simulation analyses were performed to explain the formation of high-energy ions. A high-speed camera, a single Langmuir probe and a floating emissive probe were used to determine the steady and oscillatory plasma properties in the near-field plume of a hollow cathode. The temporal structure, electron temperature, electron density, and both static and oscillation of plasma potentials of the plume have been obtained by the diagnostics mentioned above. The experimental results show that there exists a potential hill (about 30 V) and also severe potential oscillations in the near-plume region. Moreover, a simple 2D particle-in-cell model was used to analyze the energy transition between the potential hill and/or its oscillations and the ions. The simulation results show that the energy of ions gained from the static potential background is about 20 eV, but it could reach to 60 eV when the plasma oscillates.

  3. Near-field soil-structure interaction analysis using nonlinear hybrid modeling

    International Nuclear Information System (INIS)

    Katayama, I.; Chen, C.; Lee, Y.J.; Jean, W.Y.; Penzien, J.

    1989-01-01

    The hybrid modeling method (Gupta and Penzien 1980) and associated analysis procedure for solving a three-dimensional soil-structure interaction problem was developed by Gupta and Penzien (1981) and Gupta et al.(1982). Subsequently, successive modifications have been made to the original modeling method and analysis procedure allowing more general treatment of the SSI problem (Penzien, 1988). Through many correlation studies of field test data obtained under forced-vibration and earthquake-excitation conditions, it has been shown that the HASSI programs can effectively predict the dynamic response of a soil-structure system, if realistic soil parameters are adopted. In the above, the entire structure-foundation system is considered to respond in a linear fashion. Since the reflected three-dimensional waves at the soil-structure interface decays very rapidly with distance away from the structure (Katayama, 1987 (a)), the response of the soil close to the base of the structure may greatly affect its response; therefore, proper modeling of the non-linear soil behavior characteristic is essential. The nonlinear behavior of near-field soil has been taken into consideration in HASSI-7 by the standard equivalent linearization procedures used in programs SHAKE and FLUSH

  4. Campanile Near-Field Probes Fabricated by Nanoimprint Lithography on the Facet of an Optical Fiber.

    Science.gov (United States)

    Calafiore, Giuseppe; Koshelev, Alexander; Darlington, Thomas P; Borys, Nicholas J; Melli, Mauro; Polyakov, Aleksandr; Cantarella, Giuseppe; Allen, Frances I; Lum, Paul; Wong, Ed; Sassolini, Simone; Weber-Bargioni, Alexander; Schuck, P James; Cabrini, Stefano; Munechika, Keiko

    2017-05-10

    One of the major challenges to the widespread adoption of plasmonic and nano-optical devices in real-life applications is the difficulty to mass-fabricate nano-optical antennas in parallel and reproducible fashion, and the capability to precisely place nanoantennas into devices with nanometer-scale precision. In this study, we present a solution to this challenge using the state-of-the-art ultraviolet nanoimprint lithography (UV-NIL) to fabricate functional optical transformers onto the core of an optical fiber in a single step, mimicking the 'campanile' near-field probes. Imprinted probes were fabricated using a custom-built imprinter tool with co-axial alignment capability with sub optical coupling between the fiber and the imprinted optical transformer. The imprinted optical transformer probe was used in an actual NSOM measurement performing hyperspectral photoluminescence mapping of standard fluorescent beads. The calibration scans confirmed that imprinted probes enable sub-diffraction limited imaging with a spatial resolution consistent with the gap size. This novel nano-fabrication approach promises a low-cost, high-throughput, and reproducible manufacturing of advanced nano-optical devices.

  5. Near-field microwave detection of corrosion precursor pitting under thin dielectric coatings in metallic substrate

    International Nuclear Information System (INIS)

    Hughes, D.; Zoughi, R.; Austin, R.; Wood, N.; Engelbart, R.

    2003-01-01

    Detection of corrosion precursor pitting on metallic surfaces under various coatings and on bare metal is of keen interest in evaluation of aircraft fuselage. Near-field microwave nondestructive testing methods, utilizing open-ended rectangular waveguides and coaxial probes, have been used extensively for detection of surface flaws in metals, both on bare metal and under a dielectric coating. This paper presents the preliminary results of using microwave techniques to detect corrosion precursor pitting under paint and primer, applique and on bare metal. Machined pits of 500 μm diameter were detected using open-ended rectangular waveguides at V-Band under paint and primer and applique, and on bare metal. Using coaxial probes, machined pits with diameters down to 150 μm on bare metal were also detected. Relative pit size and density were shown on a corrosion-pitted sample using open-ended rectangular waveguides at frequencies of 35 GHz to 70 GHz. The use of Boeing's MAUS TM scanning systems provided improved results by alleviating standoff variation and scanning artifact. Typical results of this investigation are also presented

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

    International Nuclear Information System (INIS)

    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

    2012-01-01

    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)

  7. Safety Assessment of a Hypothetical Near Surface Disposal at PPTN Serpong Site: Near-Field Modeling

    International Nuclear Information System (INIS)

    Lubis, Erwansyah

    2000-01-01

    The near field modeling of a hypothetical surface disposal at Serpong site has been performed. Considering a realistic downward water flux of 10 -1 0 m/s through the conditioned waste zone and the concrete barriers, transport of radionuclide by advection and dispersion below the bottom of the repository was calculated using PORFLOW computer code. The result shows that the highest fluxes were observed H-3, Cs-135, Nb-94 and Ni-59, all about 10 4 Bq/a/m 2 . Intermediate fluxes were obtained for Cs-137, I-129 and Co-60. Lowest were due to Ni-63 and C-14. The effect on radionuclide fluxes by having an unsaturated soil of 1.0-m depth below the bottom of the repository also was investigated. The results indicate that the highest fluxes are due to Cs-135, Nb-94 and Ni- 59, approximately 10 4 Bq/a/m 2 . The fluxes owing to H-3 has decreased to 10 -9 Bq/a/m 2 owing to decay. Radionuclides that are not absorbed onto lateritic clay soil, C-14 and I-129 are not decreased in flux. All other radionuclides has significantly smaller fluxes compared to the ones calculated at the bottom of the repository. This indicates that the lateric clay soil at Serpong site plays an important role in retarding and dispersing the radionuclide migration towards the ground water. (author)

  8. Live endothelial cells imaged by Scanning Near-field Optical Microscopy (SNOM): capabilities and challenges.

    Science.gov (United States)

    Bulat, Katarzyna; Rygula, Anna; Szafraniec, Ewelina; Ozaki, Yukihiro; Baranska, Malgorzata

    2017-06-01

    The scanning near-field optical microscopy (SNOM) shows a potential to study details of biological samples, since it provides the optical images of objects with nanometric spatial resolution (50-200 nm) and the topographic information at the same time. The goal of this work is to demonstrate the capabilities of SNOM in transmission configuration to study human endothelial cells and their morphological changes, sometimes very subtle, upon inflammation. Various sample preparations were tested for SNOM measurements and promising results are collected to show: 1) the influence of α tumor necrosis factor (TNF-α) on EA.hy 926 cells (measurements of the fixed cells); 2) high resolution images of various endothelial cell lines, i.e. EA.hy 926 and HLMVEC (investigations of the fixed cells in buffer environment); 3) imaging of live endothelial cells in physiological buffers. The study demonstrate complementarity of the SNOM measurements performed in air and in liquid environments, on fixed as well as on living cells. Furthermore, it is proved that the SNOM is a very useful method for analysis of cellular morphology and topography. Changes in the cell shape and nucleus size, which are the symptoms of inflammatory reaction, were noticed in TNF-α activated EA.hy 926 cells. The cellular structures of submicron size were observed in high resolution optical images of cells from EA.hy 926 and HLMVEC lines. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Casimir friction and near-field radiative heat transfer in graphene structures

    International Nuclear Information System (INIS)

    Volokitin, A.I.; Samara State Technical Univ.

    2017-01-01

    The dependence of the Casimir friction force between a graphene sheet and a (amorphous) SiO 2 substrate on the drift velocity of the electrons in the graphene sheet is studied. It is shown that the Casimir friction is strongly enhanced for the drift velocity above the threshold velocity when the friction is determined by the resonant excitation of the surface phonon-polaritons in the SiO 2 substrate and the electron-hole pairs in graphene. The theory agrees well with the experimental data for the current-voltage dependence for unsuspended graphene on the SiO 2 substrate. The theories of the Casimir friction and the near-field radiative energy transfer are used to study the heat generation and dissipation in graphene due to the interaction with phonon-polaritons in the (amorphous) SiO 2 substrate and acoustic phonons in graphene. For suspended graphene, the energy transfer coefficient at nanoscale gap is ∝ three orders of magnitude larger than the radiative heat transfer coefficient of the blackbody radiation limit.

  10. Study on Transient Properties of Levitated Object in Near-Field Acoustic Levitation

    Science.gov (United States)

    Jia, Bing; Chen, Chao; Zhao, Chun-Sheng

    2011-12-01

    A new approach to the study on the transient properties of the levitated object in near-field acoustic levitation (NFAL) is presented. In this article, the transient response characteristics, including the levitated height of an object with radius of 24 mm and thickness of 5 mm, the radial velocity and pressure difference of gas at the boundary of clearance between the levitated object and radiating surface (squeeze film), is calculated according to several velocity amplitudes of radiating surface. First, the basic equations in fluid areas on Arbitrary Lagrange—Euler (ALE) form are numerically solved by using streamline upwind petrov galerkin (SUPG) finite elements method. Second, the formed algebraic equations and solid control equations are solved by using synchronous alternating method to gain the transient messages of the levitated object and gas in the squeeze film. Through theoretical and numerical analyses, it is found that there is a oscillation time in the transient process and that the response time does not simply increase with the increasing of velocity amplitudes of radiating surface. More investigations in this paper are helpful for the understanding of the transient properties of levitated object in NFAL, which are in favor of enhancing stabilities and responsiveness of levitated object.

  11. Design of Prototype Payment Application System With Near Field Communication (NFC Technology based on Android

    Directory of Open Access Journals (Sweden)

    Huda Ubaya

    2012-06-01

    Full Text Available Since the late 1990s, people have enjoyed a comfortable lifestyle. Mobile devices supported by the development of wireless networks have spread throughout the world. People can get information, order tickets, download songs and perform commercial transactions, called mobile commerce. Mobile commerce applications become the most popular application for mobile device users who want to do business and financial transactions easily and securely, anytime and anywhere they are. Today the use of physical cash is experiencing a decline in popularity in the business world, because it is being replaced by non-physical payments are often called electronic money (e-money. An important technology behind mobile payments is called Near Field Communication (NFC. As an indication that the NFC has tremendous business potential, leading companies like Nokia, Microsoft, Visa Inc., and MasterCard Worldwide and NXP Semiconductors, is actively engaged on them. Payment processing integrated with NFC technology based mobile operating system that is a trend today is Android that support NFC technology is version 2.3.3 Gingerbread. The prototype application is designed to pay for 2 on the user side of the user as consumer and the merchant side as a trader or seller by using the handset that already have NFC technology is Google Samsung Nexus S. Pay an application prototype also implements the concept of security in e-commerce transactions by using the protocol-to-Tag Tag so that the user needs for security and comfort during the financial transaction are met.

  12. Coherent interaction with two-level fluctuators using near field scanning microwave microscopy.

    Science.gov (United States)

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

    2015-11-24

    Near field Scanning Microwave Microscopy (NSMM) is a scanning probe technique that non-invasively can obtain material properties on the nano-scale at microwave frequencies. While focus has been on developing room-temperature systems it was recently shown that this technique can potentially reach the quantum regime, opening up for applications in materials science and device characterization in solid state quantum information processing. In this paper we theoretically investigate this new regime of NSMM. Specifically we show that interaction between a resonant NSMM probe and certain types of two-level systems become possible when the NSMM probe operates in the (sub-) single photon regime, and we expect a high signal-to-noise ratio if operated under the right conditions. This would allow to detect single atomic material defects with energy splittings in the GHz range with nano-scale resolution, provided that individual defects in the material under study are well enough separated. We estimate that this condition is fulfilled for materials with loss tangents below tan δ ∼ 10(-3) which holds for materials used in today's quantum circuits and devices where typically tan δ microscopes operating in a high power regime.

  13. Characterization of Line Nanopatterns on Positive Photoresist Produced by Scanning Near-Field Optical Microscope

    Directory of Open Access Journals (Sweden)

    Sadegh Mehdi Aghaei

    2015-01-01

    Full Text Available Line nanopatterns are produced on the positive photoresist by scanning near-field optical microscope (SNOM. A laser diode with a wavelength of 450 nm and a power of 250 mW as the light source and an aluminum coated nanoprobe with a 70 nm aperture at the tip apex have been employed. A neutral density filter has been used to control the exposure power of the photoresist. It is found that the changes induced by light in the photoresist can be detected by in situ shear force microscopy (ShFM, before the development of the photoresist. Scanning electron microscope (SEM images of the developed photoresist have been used to optimize the scanning speed and the power required for exposure, in order to minimize the final line width. It is shown that nanometric lines with a minimum width of 33 nm can be achieved with a scanning speed of 75 µm/s and a laser power of 113 mW. It is also revealed that the overexposure of the photoresist by continuous wave laser generated heat can be prevented by means of proper photoresist selection. In addition, the effects of multiple exposures of nanopatterns on their width and depth are investigated.

  14. A compact combined ultrahigh vacuum scanning tunnelling microscope (UHV STM) and near-field optical microscope

    International Nuclear Information System (INIS)

    Woolley, R A J; Hayton, J A; Cavill, S; Ma, Jin; Beton, P H; Moriarty, P

    2008-01-01

    We have designed and constructed a hybrid scanning near-field optical microscope (SNOM)–scanning tunnelling microscope (STM) instrument which operates under ultrahigh vacuum (UHV) conditions. Indium tin oxide (ITO)-coated fibre-optic tips capable of high quality STM imaging and tunnelling spectroscopy are fabricated using a simple and reliable method which foregoes the electroless plating strategy previously employed by other groups. The fabrication process is reproducible, producing robust tips which may be exchanged under UHV conditions. We show that controlled contact with metal surfaces considerably enhances the STM imaging capabilities of fibre-optic tips. Light collection (from the cleaved back face of the ITO-coated fibre-optic tip) and optical alignment are facilitated by a simple two-lens arrangement where the in-vacuum collimation/collection lens may be adjusted using a slip-stick motor. A second in-air lens focuses the light (which emerges from the UHV system as a parallel beam) onto a cooled CCD spectrograph or photomultiplier tube. The application of the instrument to combined optical and electronic spectroscopy of Au and GaAs surfaces is discussed

  15. The near-field transport in a repository for high-level nuclear waste

    Energy Technology Data Exchange (ETDEWEB)

    Aranguiz, L.R.

    1995-05-01

    The thesis is focused on the modelling of a redox front which is created when the oxidants produced by a radiolytic process in a damaged canister escape to the surroundings, and on a fast and flexible model to calculate the radionuclide transport in the repository. In addition, the thesis includes an attempt to validate the processes involved in the redox front model and a sensitivity analysis of the uncertainties in the parameter values regarding the release of radionuclides from the Swedish KBS-3 repository. The redox front model considers that the transport of oxidants in the clay surrounding the canister is by diffusion and that the transport in the fractures in the rock is by flow with diffusion into the rock matrix.The assumed radiolysis rates denoted high and low in the thesis are probably not realistic, but can be seen as upper limits. thus it is unlikely that the redox front will ever move past the bentonite clay surrounding the canister, and if it does, the front may move less than 100 m. The model to calculate the transport of radionuclides in the near-field uses a coarse compartmentalization of the repository by embedding analytical solutions in zones where other techniques, such as finite difference methods, would need a very fine discretization. Only a few compartments are required to obtain a good accuracy in the calculated release. 34 refs, 17 figs.

  16. Near Field UHF RFID Antenna System Enabling the Tracking of Small Laboratory Animals

    Directory of Open Access Journals (Sweden)

    Luca Catarinucci

    2013-01-01

    Full Text Available Radio frequency identification (RFID technology is more and more adopted in a wide range of applicative scenarios. In many cases, such as the tracking of small-size living animals for behaviour analysis purposes, the straightforward use of commercial solutions does not ensure adequate performance. Consequently, both RFID hardware and the control software should be tailored for the particular application. In this work, a novel RFID-based approach enabling an effective localization and tracking of small-sized laboratory animals is proposed. It is mainly based on a UHF Near Field RFID multiantenna system, to be placed under the animals’ cage, and able to rigorously identify the NF RFID tags implanted in laboratory animals (e.g., mice. Once the requirements of the reader antenna have been individuated, the antenna system has been designed and realized. Moreover, an algorithm based on the measured Received Signal Strength Indication (RSSI aiming at removing potential ambiguities in data captured by the multiantenna system has been developed and integrated. The animal tracking system has been largely tested on phantom mice in order to verify its ability to precisely localize each subject and to reconstruct its path. The achieved and discussed results demonstrate the effectiveness of the proposed tracking system.

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

    Science.gov (United States)

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

    2015-03-01

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

  18. Spacecraft Communications System Verification Using On-Axis Near Field Measurement Techniques

    Science.gov (United States)

    Keating, Thomas; Baugh, Mark; Gosselin, R. B.; Lecha, Maria C.; Krebs, Carolyn A. (Technical Monitor)

    2000-01-01

    Determination of the readiness of a spacecraft for launch is a critical requirement. The final assembly of all subsystems must be verified. Testing of a communications system can mostly be done using closed-circuits (cabling to/from test ports), but the final connections to the antenna require radiation tests. The Tropical Rainfall Measuring Mission (TRMM) Project used a readily available 'near-fleld on-axis' equation to predict the values to be used for comparison with those obtained in a test program. Tests were performed in a 'clean room' environment at both Goddard Space Flight Center (GSFC) and in Japan at the Tanegashima Space Center (TnSC) launch facilities. Most of the measured values agreed with the predicted values to within 0.5 dB. This demonstrates that sometimes you can use relatively simple techniques to make antenna performance measurements when use of the 'far field ranges, anechoic chambers, or precision near-field ranges' are neither available nor practical. Test data and photographs are provided.

  19. Modelling exhaust plume mixing in the near field of an aircraft

    Directory of Open Access Journals (Sweden)

    F. Garnier

    Full Text Available A simplified approach has been applied to analyse the mixing and entrainment processes of the engine exhaust through their interaction with the vortex wake of an aircraft. Our investigation is focused on the near field, extending from the exit nozzle until about 30 s after the wake is generated, in the vortex phase. This study was performed by using an integral model and a numerical simulation for two large civil aircraft: a two-engine Airbus 330 and a four-engine Boeing 747. The influence of the wing-tip vortices on the dilution ratio (defined as a tracer concentration shown. The mixing process is also affected by the buoyancy effect, but only after the jet regime, when the trapping in the vortex core has occurred. In the early wake, the engine jet location (i.e. inboard or outboard engine jet has an important influence on the mixing rate. The plume streamlines inside the vortices are subject to distortion and stretching, and the role of the descent of the vortices on the maximum tracer concentration is discussed. Qualitative comparison with contrail photograph shows similar features. Finally, tracer concentration of inboard engine centreline of B-747 are compared with other theoretical analyses and measured data.

  20. Experimental and modelling studies of the near-field chemistry for Nirex repository concepts

    International Nuclear Information System (INIS)

    Atkinson, A.; Ewart, F.T.; Pugh, S.Y.R.; Rees, J.H.; Sharland, S.M.; Tasker, P.W.; Wilkins, J.D.

    1988-02-01

    A research programme is described which is designed to investigate the chemical conditions in the near field of a concrete based repository and the behaviour of the radiologically important nuclides under these conditions. The chemical conditions are determined by the corrosion of the iron components of the repository and by the soluble components of the concrete. Both of these have been investigated experimentally and models developed which have been validated by further experiment. The effect of these reactions on the repository pH and Eh, and how these develop in time and space have been modelled using a coupled chemical equilibrium and transport code. The solubility of the important nuclides are being studied experimentally under these conditions, and under sensible variations. These data have been used to refine the thermodynamic data base used for the geochemical code PHREEQE. The sorption behaviour of plutonium and americium, under the same conditions, have been studied; the sorption coefficients were found to be large and independent of the concrete formulation, particle size and solid liquid ratio. Recent experimental results from sorption/exchange experiments with lead and 14-carbon are also reported. The programme has also investigated experimentally the possible perturbation of the repository chemistry by microbial action and by natural and added organic material. A final set of experiments combine all the repository components and the waste in a long term equilibration experiment. (author)