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Krozer, V. (author), Leone, B. (author), Roskos, H. (author), Löffler, T. (author), Loata, G. (author), Döhler, G. (author), Renner, F. (author), Eckardt, S. (author), Klaassen, T.O. (author), Adam, A. (author)A recent study initiated by the European Space Agency aimed at identifying the most promising technologies to significantly improve on the generation of coherent electromagnetic radiation in the THz regime. The desired improvements include, amongst others, higher output powers and efficiencies at increasingly higher frequencies, wider tunability...conference paper 2004
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Vermolen, F.J. (author), E. van Baaren, E. (author), Adam, J.A. (author)A mathematical model is developed for the rate of healing of a circular wound in a spherical skull. In this paper the regeneration, decay and transport of a generic "growth factor, which induces the healing of the wound, is taken into account. Further, an equation of motion is derived for the actual healing of the wound. The expressions for the...report 2005
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Gao, J.R. (author), Hovenier, J.N. (author), Yang, Z.Q. (author), Baselmans, J.J.A. (author), Baryshev, A. (author), Hajenius, M. (author), Klapwijk, T.M. (author), Adam, A.J.L. (author), Klaassen, T.O. (author), Williams, B.S. (author), Kumar, S. (author), Hu, Q. (author), Reno, J.L. (author)We report the first demonstration of an all solid-state heterodyne receiver that can be used for high-resolution spectroscopy above 2?THz suitable for space-based observatories. The receiver uses a NbN superconducting hot-electron bolometer as mixer and a quantum cascade laser operating at 2.8?THz as local oscillator. We measure a double...journal article 2005
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- Orlova, E.E. (author), Hovenier, J.N. (author), Klaassen, T.O. (author), Kasalynas, I. (author), Adam, A.J.L. (author), Gao, J.R. (author), Klapwijk, T.M. (author), Williams, B.S. (author), Kumar, S. (author), Hu, Q. (author), Reno, J.L. (author) journal article 2006
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Adam, A.J.L. (author), Kaalynas, I. (author), Hovenier, J.N. (author), Klaassen, T.O. (author), Gao, J.R. (author), Orlova, E.E. (author), Williams, B.S. (author), Kumar, S. (author), Hu, Q. (author), Reno, J.L. (author)The need to reach single-mode lasing and minimize at the same time the electrical dissipation of cryogenically operated terahertz quantum cascade lasers may result in small and subwavelength cavity dimensions. To assess the influence of such dimensions on the shape of the laser emission, we have measured the beam pattern of two metal-metal...journal article 2006
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Baryshev, A. (author), Hovenier, J.N. (author), Adam, A.J.L. (author), Kaalynas, I. (author), Gao, J.R. (author), Klaassen, T.O. (author), Williams, B.S. (author), Kumar, S. (author), Hu, Q. (author), Reno, J.L. (author)We have studied the phase locking and spectral linewidth of an ? 2.7?THz quantum cascade laser by mixing its two lateral lasing modes. The beat signal at about 8?GHz is compared with a microwave reference by applying conventional phase lock loop circuitry with feedback to the laser bias current. Phase locking has been demonstrated, resulting in...journal article 2006
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Kasalynas, I. (author), Adam, A.J.L. (author), Klaassen, T.O. (author), Hovenier, N.J. (author), Panraud, G. (author), Iordanov, V.P. (author), Sarro, P.M. (author)Detection peculiarities of an un-cooled (room temperature) 8×8 pixel array designed to image broadband THz radiation were investigated. Each pixel consists of a thin conductive film absorber on a dielectric membrane with thermopile temperature readout. It was designed and tested for four combinations of two different types of absorber and...conference paper 2007
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Adam, A.J.L. (author), Van der Valk, N.C.J. (author), Planken, P.C.M. (author)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 the features observed in the measurements,...journal article 2007
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Seo, M.A. (author), Adam, A.J.L. (author), Kang, J.H. (author), Lee, J.W. (author), Jeoung, S.C. (author), Park, Q.H. (author), Planken, P.C.M. (author), Kim, D.S. (author)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 measurements we are able to reconstruct the magnetic...journal article 2007
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- Ahn, K.J. (author), Lee, K.G. (author), Kihm, H.W. (author), Seo, M.A. (author), Adam, A.J.L. (author), Planken, P.C.M. (author), Kim, D.S. (author) journal article 2008
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Adam, A.J.L. (author), Brok, J.M. (author), Seo, M.A. (author), Ahn, K.J. (author), Kim, D.S. (author), Kang, J.H. (author), Park, Q.H. (author), Nagel, M. (author), Planken, P.C.M. (author)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 near the hole edges, we observe, that holes...journal article 2008
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Kihm, H.W. (author), Lee, K.G. (author), Seo, M.A. (author), Ahn, K.J. (author), Adam, A.J.L. (author), Kang, J.H. (author), Park, Q.H. (author), Planken, P.C.M. (author), Kim, D.S. (author)We study the dielectric constant dependent diffraction phenomena of single slit apertures, both theoretically and experimentally. We experimentally simulate perfect metal and real metal cases by investigating subwavelength diffraction by a single slit, both in nano-optical and in terahertz regimes, keeping the slit-width/wavelength ratio...conference paper 2008
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Seo, M.A. (author), Adam, A.J.L. (author), Kang, J.H. (author), Lee, J.W. (author), Ahn, K.J. (author), Park, Q.H. (author), Planken, P.C.M. (author), Kim, D.S. (author)We performed terahertz near-field experiments on single rectangular holes with various lengths grown on an electro-optic crystal substrate with ?/100 resolution. We find that the near-field amplitude becomes proportionally larger as the rectangle becomes narrower, strongly suggesting that a constant energy passes through even for a very narrow...journal article 2008
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Adam, A.J.L. (author), Brok, J.M. (author), Seo, M.A. (author), Ahn, K.J. (author), Kim, D.S. (author), Kang, J.H. (author), Park, Q.H. (author), Nagel, M. (author), Planken, P.C.M. (author)An erratum is presented to correct an error in the discussion section of [Opt. Express. 16, 7407-7417 (2008)] and to add a relevant reference on earlier work.journal article 2008
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Adam, A.J.L. (author), Planken, P.C.M. (author), Meloni, S. (author), Dik, J. (author)We show terahertz reflection images of hidden paint layers in a painting on canvas and compare the results with X-ray Radiography and Infrared 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...journal article 2009
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Nielsen, K. (author), Rasmussen, H.K. (author), Adam, A.J.L. (author), Planken, P.C.M. (author), Bang, O. (author), Jepsen, P.U. (author)We report on a new class of polymer photonic crystal fibers for low-loss guidance of THz radiation. The use of the cyclic olefin copolymer Topas, in combination with advanced fabrication technology, results in bendable THz fibers with unprecedented low loss and low material dispersion in the THz regime.We demonstrate experimentally how the...journal article 2009
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Knab, J.R. (author), Adam, A.J.L. (author), Nagel, M. (author), Shaner, E. (author), Seo, M.A. (author), Kim, D.S. (author), Planken, P.C.M. (author)We present measurements of the complete terahertz (THz) electric near-field distribution, Ex, Ey and Ez, in both the time- and frequency-domains, for subwavelength apertures and subsections of subwavelength aperture arrays. Measuring the individual components of the THz near-field with subwavelength spatial resolution, as they emerge from these...journal article 2009
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Guestin, L. (author), Adam, A.J.L. (author), Knab, J.R. (author), Nagel, M. (author), Planken, P.C.M. (author)We have studied theoretically and experimentally the influence of a dielectric substrate on the frequency-dependent terahertz electric near-field of a small hole in a metal layer. We find that the near-field transmission spectrum and the two-dimensional field distribution of an empty hole in a thin metal layer on a substrate are almost identical...journal article 2009
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Vuong, L.T. (author), Adam, A.J.L. (author), Brok, J.M. (author), Planken, P.C.M. (author), Urbach, H.P. (author)Circularly polarized electric fields incident on subwavelength apertures produce near-field phase singularities with phase vorticity ±1 depending on the polarization handedness. These near-field phase singularities combine with those associated with orbital angular momentum and result in polarization-dependent transmission. We produce arbitrary...journal article 2010
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Knab, J.R. (author), Adam, A.J.L. (author), Chakkittakandy, R. (author), Planken, P.C.M. (author)Using near-field, terahertz time-domain spectroscopy (THz-TDS), we investigate how the addition of a dielectric material into a subwavelength-diameter, cylindrical waveguide affects its transmission properties. The THz electric near-field is imaged with deep subwavelength resolution as it emerges from filled and unfilled waveguides....journal article 2010