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De Visser, P.J. (author), Yates, S.J.C. (author), Guruswamy, T. (author), Goldie, D.J. (author), Withington, S. (author), Neto, A. (author), Llombart, N. (author), Baryshev, A.M. (author), Klapwijk, T.M. (author), Baselmans, J.J.A. (author)We have measured the absorption of terahertz radiation in a BCS superconductor over a broad range of frequencies from 200 GHz to 1.1 THz, using a broadband antenna-lens system and a tantalum microwave resonator. From low frequencies, the response of the resonator rises rapidly to a maximum at the gap edge of the superconductor. From there on,...journal article 2015
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Wiedenmann, J. (author), Bocquillon, E. (author), Deacon, R.S. (author), Hartinger, S. (author), Hermann, O. (author), Klapwijk, T.M. (author), Maier, L. (author), Ames, C. (author), Brüne, C. (author), Gould, C. (author), Oiwa, A. (author), Ishibashi, K. (author), Tarucha, S. (author), Buhmann, H. (author), Molenkamp, L.W. (author)The Josephson effect describes the generic appearance of a supercurrent in a weak link between two superconductors. Its exact physical nature deeply influences the properties of the supercurrent. In recent years, considerable efforts have focused on the coupling of superconductors to the surface states of a three-dimensional topological...journal article 2016
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Ren, Y. (author), Hovenier, J.N. (author), Cui, M. (author), Hayton, D.J. (author), Gao, J.R. (author), Klapwijk, T.M. (author), Shi, S.C. (author), Kao, T.Y. (author), Hu, Q. (author), Reno, J.L. (author)We report frequency locking of two 3.5-THz third-order distributed feedback (DFB) quantum cascade lasers (QCLs) by using methanol molecular absorption lines, a proportional-integral-derivative controller, and a NbN bolometer. We show that the free-running linewidths of the QCLs are dependent on the electrical and temperature tuning coefficients....journal article 2012
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Vercruyssen, N. (author), Verhagen, T.G.A. (author), Flokstra, M.G. (author), Pekola, J.P. (author), Klapwijk, T.M. (author)We study the nonlinear response of current transport in a superconducting diffusive nanowire between normal reservoirs. We demonstrate theoretically and experimentally the existence of two different superconducting states appearing when the wire is driven out of equilibrium by an applied bias, called the global and bimodal superconducting states...journal article 2012
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Janssen, R.M.J. (author), Endo, A. (author), Baselmans, J.J.A. (author), De Visser, P.J. (author), Barends, R. (author), Klapwijk, T.M. (author)The sensitivity of microwave kinetic inductance detectors (MKIDs) based on coplanar waveguides (CPWs) needs to be improved by at least an order of magnitude to satisfy the requirements for space-based terahertz astronomy. Our aim is to investigate if this can be achieved by reducing the width of the CPW to much below what has typically been made...journal article 2012
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- Smit, G.D.J. (author), Rogge, S. (author), Caro, J. (author), Klapwijk, T.M. (author) journal article 2003
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Ren, Y. (author), Hovenier, J.N. (author), Higgins, R. (author), Gao, J.R. (author), Klapwijk, T.M. (author), Shi, S.C. (author), Bell, A. (author), Klein, B. (author), Williams, B.S. (author), Kumar, S. (author), Hu, Q. (author), Reno, J.L. (author)A terahertz (THz) heterodyne spectrometer is demonstrated based on a quantum cascade laser (QCL) as a local oscillator (LO) and an NbN hot electron bolometer as a mixer, and it is used to measure high-resolution molecular spectral lines of methanol (CH3OH) between 2.913–2.918 THz. The spectral lines are taken from a gas cell containing methanol...journal article 2010
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Ren, Y. (author), Hovenier, J.N. (author), Higgins, R. (author), Gao, J.R. (author), Klapwijk, T.M. (author), Shi, S.C. (author), Klein, B. (author), Kao, T.Y. (author), Hu, Q. (author), Reno, J.L. (author)A frequency tunable terahertz heterodyne spectrometer, based on a third-order distributed feedback quantum cascade laser as a local oscillator, has been demonstrated by measuring molecular spectral lines of methanol (CH3OH) gas at 3.5 THz. By varying the bias voltage of the laser, we achieved a tuning range of ? 1?GHz of the lasing frequency,...journal article 2011
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- Mena, F.P. (author), Kooi, J.W. (author), Baryshev, A.M. (author), Lodewijk, C.F.J. (author), Hesper, R. (author), Wild, W. (author), Klapwijk, T.M. (author) journal article 2008
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Janssen, R.M.J. (author), Baselmans, J.J.A. (author), Endo, A. (author), Ferrari, L. (author), Yates, S.J.C. (author), Baryshev, A.M. (author), Klapwijk, T.M. (author)We demonstrate photon noise limited performance in both phase and amplitude readout in microwave kinetic inductance detectors (MKIDs) consisting of NbTiN and Al, down to 100 fW of optical power. We simulate the far field beam pattern of the lens-antenna system used to couple radiation into the MKID and derive an aperture efficiency of 75%. This...journal article 2013
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- van Gorkom, R.P. (author), Caro, J. (author), Klapwijk, T.M. (author), Radelaar, S. (author) journal article 2001
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- Keizer, R.S. (author), Flokstra, M.G. (author), Aarts, J. (author), Klapwijk, T.M. (author) journal article 2006
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- Wilms Fleet, D. (author), Gao, J.R. (author), Klapwijk, T.M. (author), de Eorte, P.A.J. (author) journal article 2001
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- Boogaard, G.R. (author), Verbruggen, A.H. (author), Belzig, W. (author), Klapwijk, T.M. (author) journal article 2004
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Driessen, E.F.C. (author), Coumou, P.C.J.J. (author), Tromp, R.R. (author), De Visser, P.J. (author), Klapwijk, T.M. (author)We probe the effects of strong disorder (2.4<kFl<8.6) on superconductivity in thin films of niobium titanium nitride and titanium nitride by measuring the microwave electrodynamics in coplanar waveguide resonators. We find a gradual evolution of the electromagnetic response with disorder, deviating from BCS theory, for both materials. This...journal article 2012
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- Kravchenko, S.V. (author), Klapwijk, T.M. (author) journal article 2000
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- Smit, G.D.J. (author), Rogge, S. (author), Caro, J. (author), Klapwijk, T.M. (author) journal article 2004
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Smit, G.D.J. (author), Rogge, S. (author), Klapwijk, T.M. (author)We have measured electrical transport across epitaxial, nanometer-sized metal–semiconductor interfaces by contacting CoSi2 islands grown on Si(111) with the tip of a scanning tunneling microscope. The conductance per unit area was found to increase with decreasing diode area. Indeed, the zero-bias conductance was found to be ? 104 times larger...journal article 2002
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Khosropanah, P. (author), Gao, J.R. (author), Laauwen, W.M. (author), Hajenius, M. (author), Klapwijk, T.M. (author)We have studied the sensitivity of a superconducting NbN hot electron bolometer mixer integrated with a spiral antenna at 4.3?THz. Using hot/cold blackbody loads and a beam splitter all in vacuum, we measured a double sideband receiver noise temperature of 1300?K at the optimum local oscillator (LO) power of 330?nW, which is about 12 times the...journal article 2007
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- Morpurgo, A.F. (author), Heida, J.P. (author), Klapwijk, T.M. (author), van Wees, B.J. (author), Borghs, G. (author) journal article 1999