@unpublished{HenkelPieplow2014, author = {Henkel, Carsten and Pieplow, Gregor}, title = {Reply to Comment on 'Fully covariant radiation force on a polarizable particle'}, series = {New journal of physics : the open-access journal for physics}, volume = {16}, journal = {New journal of physics : the open-access journal for physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {1367-2630}, doi = {10.1088/1367-2630/16/11/118002}, pages = {8}, year = {2014}, abstract = {We argue that the theories of Volokitin and Persson (2014 New J. Phys. 16 118001), Dedkov and Kyasov (2008 J. Phys.: Condens. Matter 20 354006), and Pieplow and Henkel (2013 New J. Phys. 15 023027) agree on the electromagnetic force on a small, polarizable particle that is moving parallel to a planar, macroscopic body, as far as the contribution of evanescent waves is concerned. The apparent differences are discussed in detail and explained by choices of units and integral transformations. We point out in particular the role of the Lorentz contraction in the procedure used by Volokitin and Persson, where a macroscopic body is 'diluted' to obtain the force on a small particle. Differences that appear in the contribution of propagating photons are briefly mentioned.}, language = {en} } @article{FolmanKruegerSchmiedmayeretal.2002, author = {Folman, R. and Kr{\"u}ger, P. and Schmiedmayer, J{\"o}rg and Denschlag, J. H. and Henkel, Carsten}, title = {Microscopic atom optics : from wires to an atom chip}, year = {2002}, abstract = {We review the 10 year long journey into the miniaturization and integration of matter wave optics resulting in devices mounted on surfaces, so called atom chips. The first experiments started with the guiding of atoms with free standing wires and investigated the trapping potentials in simple geometries. Atom optical elements can now be micro fabricated down to 1 um size on atom chips. The creation of a Bose-Einstein condensate miniaturized in surface traps was recently achieved, and the first attempts to integrate light optics are in progress. In this review, we describe microscopic atom optics elements using current carrying and charged structures. Experiments with free standing structures (atom wires)are reviewed, investigating the basic principles of microscopic atom optics. We then discuss the miniaturization on the atom chip. One of the open central questions is dealt with: what happens with cold atoms close to a warm surface, how fast will they heat up or lose their coherence? The review concludes with an outlook of what we believe the future directions to be, and what can be hoped for.}, language = {en} } @article{HenkelWallisWestbrooketal.1999, author = {Henkel, Carsten and Wallis, H. and Westbrook, N. and Aspect, Alain and Sengstock, K. and Ertmer, W.}, title = {Theory of atomic diffraction from evanescent waves}, year = {1999}, abstract = {We review recent theoretical models and experiments dealing with the diffraction of neutral atoms by a reflection grating, formed by a standing evanescent wave. We analyze diffraction mechanisms proposed for confront the theory with experiment.}, language = {en} } @article{RogobeteSchnieppSandoghdaretal.2003, author = {Rogobete, Lavinia and Schniepp, H. and Sandoghdar, Vahid and Henkel, Carsten}, title = {Spontaneous emission in nanoscopic dielectric particles}, issn = {0030-3992}, year = {2003}, language = {en} } @phdthesis{Henkel2004, author = {Henkel, Carsten}, title = {Coherence theory of atomic de Broglie waves and electromagnetic near fields}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-0001272}, school = {Universit{\"a}t Potsdam}, year = {2004}, abstract = {Die Arbeit untersucht theoretisch die Wechselwirkung neutraler Teilchen (Atome, Molek{\"u}le) mit Oberfl{\"a}chen, soweit sie durch das elektromagnetische Feld vermittelt wird. Spektrale Energiedichten und Koh{\"a}renzfunktionen werden hergeleitet und liefern eine umfassende Charakterisierung des Felds auf der sub-Wellenl{\"a}ngen-Skala. Die Ergebnisse finden auf zwei Teilgebieten Anwendung: in der integrierten Atomoptik, wo ultrakalte Atome an thermische Oberfl{\"a}chen koppeln, und in der Nahfeldoptik, wo eine Aufl{\"o}sung unterhalb der Beugungsbegrenzung mit einzelnen Molek{\"u}len als Sonden und Detektoren erzielt werden kann.}, language = {en} } @misc{HenkelSteaneKaiseretal.1994, author = {Henkel, Carsten and Steane, Andrew M. and Kaiser, Robin and Dalibard, Jean}, title = {A modulated mirror for atomic interferometry}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-42279}, year = {1994}, abstract = {A novel atomic beam splitter, using reflection of atoms off an evanescent light wave, is investigated theoretically. The intensity or frequency of the light is modulated in order to create sidebands on the reflected de Broglie wave. The weights and phases of the various sidevands are calculated using three different approaches: the Born approximation, a semiclassical path integral approach, and a numerical solution of the time-dependent Schrdinger equation. We show how this modulated mirror could be used to build practical atomic interferometers.}, language = {en} } @misc{HenkelCourtoisAspect1994, author = {Henkel, Carsten and Courtois, Jean-Yves and Aspect, Alain}, title = {Atomic diffraction by a thin phase grating}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-42269}, year = {1994}, abstract = {We present a semiclassical perturbation method for the description of atomic diffraction by a weakly modulated potential. It proceeds in a way similar to the treatment of light diffraction by a thin phase grating, and consists in calculating the atomic wavefunction by means of action integrals along the classical trajectories of the atoms in the absence of the modulated part of the potential. The capabilities and the validity condition of the method are illustrated on the well-known case of atomic diffraction by a Gaussian standing wave. We prove that in this situation the perturbation method is equivalent to the Raman-Nath approximation, and we point out that the usually-considered Raman-Nath validity condition can lead to inaccuracies in the evaluation of the phases of the diffraction amplitudes. The method is also applied to the case of an evanescent wave reflection grating, and an analytical expression for the diffraction pattern at any incidence angle is obtained for the first time. Finally, the application of the method to other situations is briefly discussed.}, language = {en} } @article{PuhlmannHenkelHeueretal.2016, author = {Puhlmann, Dirk and Henkel, Carsten and Heuer, Axel and Pieplow, Gregor and Menzel, Ralf}, title = {Characterization of a remote optical element with bi-photons}, series = {Physica scripta : an international journal for experimental and theoretical physics}, volume = {91}, journal = {Physica scripta : an international journal for experimental and theoretical physics}, publisher = {IOP Publ. Ltd.}, address = {Bristol}, issn = {0031-8949}, doi = {10.1088/0031-8949/91/2/023006}, pages = {113 -- 114}, year = {2016}, abstract = {We present a simple setup that exploits the interference of entangled photon pairs. 'Signal' photons are sent through a Mach-Zehnder-like interferometer, while 'idlers' are detected in a variable polarization state. Two-photon interference (in coincidence detection) is observed with very high contrast and for significant time delays between signal and idler detection events. This is explained by quantum erasure of the polarization tag and a delayed choice protocol involving a non-local virtual polarizer. The phase of the two-photon fringes is scanned by varying the path length in the signal beam or by rotating a birefringent crystal in the idler beam. We exploit this to characterize one beam splitter of the signal photon interferometer (reflection and transmission amplitudes including losses), using only information about coincidences and control parameters in the idler path. This is possible because our bi-photon state saturates the Greenberger-Yelin-Englert inequality between contrast and predictability.}, language = {en} } @article{HannemannWegnerHenkel2021, author = {Hannemann, Mandy and Wegner, Gino and Henkel, Carsten}, title = {No-slip boundary conditions for electron hydrodynamics and the thermal Casimir pressure}, series = {Universe : open access journal}, volume = {7}, journal = {Universe : open access journal}, number = {4}, publisher = {MDPI}, address = {Basel}, issn = {2218-1997}, doi = {10.3390/universe7040108}, pages = {20}, year = {2021}, abstract = {We derive modified reflection coefficients for electromagnetic waves in the THz and far infrared range. The idea is based on hydrodynamic boundary conditions for metallic conduction electrons. The temperature-dependent part of the Casimir pressure between metal plates is evaluated. The results should shed light on the "thermal anomaly," where measurements deviate from the standard fluctuation electrodynamics for conducting metals.}, language = {en} } @article{DikovskySokolovskyZhangetal.2009, author = {Dikovsky, Valery and Sokolovsky, Vladimir and Zhang, Bin and Henkel, Carsten and Folman, Ron}, title = {Superconducting atom chips : advantages and challenges}, issn = {1434-6060}, doi = {10.1140/epjd/e2008-00261-5}, year = {2009}, abstract = {Superconductors are considered in view of applications to atom chip devices. The main features of magnetic traps based on superconducting wires in the Meissner and mixed states are discussed. The former state may mainly be interesting for improved atom optics, while in the latter, cold atoms may provide a probe of superconductor phenomena. The properties of a magnetic side guide based on a single superconducting strip wire placed in an external magnetic field are calculated analytically and numerically. In the mixed state of type II superconductors, inhomogeneous trapped magnetic flux, relaxation processes and noise caused by vortex motion are posing specific challenges for atom trapping.}, language = {en} } @misc{HenkelCourtoisKaiseretal.1994, author = {Henkel, Carsten and Courtois, Jean-Yves and Kaiser, Robin and Westbrook, C. and Aspect, Alain}, title = {Phase shifts of atomic de Broglie waves at an evanescent wave mirror}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-42289}, year = {1994}, abstract = {A detailed theoretical investigation of the reflection of an atomic de Broglie wave at an evanescent wave mirror is presented. The classical and the semiclassical descriptions of the reflection process are reviewed, and a full wave-mechanical approach based on the analytical soution of the corresponding Schr{\"o}dinger equation is presented. The phase shift at reflection is calculated exactly and interpreted in terms of instantaneous reflection of the atom at an effective mirror. Besides the semiclassical regime of reflection describable by the WKB method, a pure quantum regime of reflection is identified in the limit where the incident de Broglie wavelength is large compared to the evanescent wave decay length.}, language = {en} } @article{ZuritaSanchezHenkel2006, author = {Zurita-S{\´a}nchez, Jorge R. and Henkel, Carsten}, title = {Lossy electrical transmission lines: Thermal fluctuations and quantization}, issn = {1050-2947}, doi = {10.1103/Physreva.73.063825}, year = {2006}, abstract = {We present a theoretical framework for the analysis of the statistical properties of thermal fluctuations on a lossy transmission line. A quantization scheme of the electrical signals in the transmission line is formulated. We discuss two applications in detail. Noise spectra at finite temperature for voltage and current are shown to deviate significantly from the Johnson-Nyquist limit, and they depend on the position on the transmission line. We analyze the spontaneous emission, at low temperature, of a Rydberg atom and its resonant enhancement due to vacuum fluctuations in a capacitively coupled transmission line. The theory can also be applied to study the performance of microscale and nanoscale devices, including high-resolution sensors and quantum information processors}, language = {en} } @article{HenkelJoulain2006, author = {Henkel, Carsten and Joulain, Karl}, title = {Electromagnetic field correlations near a surface with a nonlocal optical response}, issn = {0946-2171}, doi = {10.1007/s00340-006-2219-9}, year = {2006}, abstract = {The coherence length of the thermal electromagnetic field near a planar surface has a minimum value related to the nonlocal dielectric response of the material. We perform two model calculations of the electric energy density and the field's degree of spatial coherence. Above a polar crystal, the lattice constant gives the minimum coherence length. It also gives the upper limit to the near field energy density, cutting off its 1/z(3) divergence. Near an electron plasma described by the semiclassical Lindhard dielectric function, the corresponding length scale is fixed by plasma screening to the Thomas-Fermi length. The electron mean free path, however, sets a larger scale where significant deviations from the local description are visible}, language = {en} } @article{DikovskyJaphaHenkeletal.2005, author = {Dikovsky, V. and Japha, Y. and Henkel, Carsten and Folman, R.}, title = {Reduction of magnetic noise in atom chips by material optimization}, year = {2005}, abstract = {We discuss the influence of the material type in metal wires to the electromagnetic fluctuations in magnetic microtraps close to the surface of an atom chip. We show that significant reduction of the magnetic noise can be achieved by replacing the pure noble metal wires with their dilute alloys. The alloy composition provides an additional degree of freedom which enables a, controlled reduction of both magnetic noise and resistivity if the atom chip is cooled. In addition, we provide a careful re-analysis of the magnetically induced trap loss observed by Yu-Ju Lin et al. [Phys. Rev. Lett. 92 050404 (2004)] and find good agreement with an improved theory}, language = {en} } @article{Henkel2005, author = {Henkel, Carsten}, title = {Nanometer scala electromagnetic field fluctuations accepted for publication}, isbn = {1-588-83042-X}, year = {2005}, language = {en} } @article{HenkelGardinerNegretti2004, author = {Henkel, Carsten and Gardiner, Simon A. and Negretti, Antonio}, title = {(De)coherence physics with condensates in microtraps}, issn = {1054-660X}, year = {2004}, abstract = {We discuss the dynamics of a condensate in a miniaturized electromagnetic trap formed above a microstructured substrate. Recent experiments have found that trap lifetimes get reduced when approaching the substrate because atoms couple to thermally excited near fields. The data agree quantitatively with our theory [Appl. Phys. B 69, 379 (1999)]. We focus on the decoherence of a quantum degenerate gas in a quasi-one-dimensional trap. Monte Carlo simulations indicate that atom interactions reduce the condensate decoherence rate. This is explained by a simple theory in terms of the suppression of long-wavelength excitations. We present preliminary simulation results for the adiabatic generation of dark solitons}, language = {en} } @article{ZhangHenkelHalleretal.2005, author = {Zhang, B. and Henkel, Carsten and Haller, E. and Wildermuth, S. and Hofferberth, S. and Kruger, P. and Schmiedmayer, J{\"o}rg}, title = {Relevance of sub-surface chip layers for the lifetime of magnetically trapped atoms}, year = {2005}, abstract = {We investigate the lifetime of magnetically trapped atoms above a planar, layered atom chip structure. Numerical calculations of the thermal magnetic noise spectrum are performed, based on the exact magnetic Green function and multi layer reflection coefficients. We have performed lifetime measurements where the center of a side guide trap is laterally shifted with respect to the current carrying wire using additional bias fields. Comparing the experiment to theory, we find a fair agreement and demonstrate that for a chip whose topmost layer is metallic, the magnetic noise depends essentially on the thickness of that layer, as long as the layers below have a, much smaller conductivity; essentially the same magnetic noise would be obtained with a metallic membrane suspended in vacuum. Based on our theory we give general scaling laws of how to reduce the effect of surface magnetic noise on the trapped atoms}, language = {en} } @article{KalkbrennerHakansonSchadleetal.2005, author = {Kalkbrenner, T. and Hakanson, U. and Schadle, A. and Burger, S. and Henkel, Carsten and Sandoghdar, Vahid}, title = {Optical microscopy via spectral modifications of a nanoantenna}, issn = {0031-9007}, year = {2005}, abstract = {The existing optical microscopes form an image by collecting photons emitted from an object. Here we report on the experimental realization of microscopy without the need for direct optical communication with the sample. To achieve this, we have scanned a single gold nanoparticle acting as a nanoantenna in the near field of a sample and have studied the modification of its intrinsic radiative properties by monitoring its plasmon spectrum}, language = {en} } @article{Henkel2005, author = {Henkel, Carsten}, title = {Magnetostatic field noise near metallic surfaces}, year = {2005}, abstract = {We develop an effective low-frequency theory of the electromagnetic field in equilibrium with thermal objects. The aim is to compute thermal magnetic noise spectra close to metallic microstructures. We focus on the limit where the material response is characterised by the electric conductivity. At the boundary between empty space and metallic microstructures, a large jump occurs in the dielectric function which leads to a partial screening of low-frequency magnetic fields generated by thermal current fluctuations. We resolve a, discrepancy between two approaches used in the past to compute magnetic field noise spectra close to microstructured materials}, language = {en} } @article{HenkelJoulain2005, author = {Henkel, Carsten and Joulain, Karl}, title = {Casimir force between designed materials : what is possible and what not}, issn = {0295-5075}, year = {2005}, abstract = {We establish strict upper limits for the Casimir interaction between multilayered structures of arbitrary dielectric or diamagnetic materials. We discuss the appearance of different power laws due to frequency-dependent material constants. Simple analytical expressions are in good agreement with numerical calculations based on Lifshitz theory. We discuss the improvements required for current ( meta) materials to achieve a repulsive Casimir force}, language = {en} } @article{RogobeteHenkel2004, author = {Rogobete, Lavinia and Henkel, Carsten}, title = {Spontaneous emission in a subwavelength environment characterized by boundary integral equations}, year = {2004}, abstract = {We discuss the impact of a dielectric nanoparticle on the fluorescence light from an emitter embedded in the particle. Numerical and analytical calculations predict a slower radiative decay compared to a bulk dielectric due to electrostatic screening. We assess the relevance of the nanoparticle shape and size and the position and orientation of the molecule. The numerical results are obtained from a rigorous solution of the Maxwell equations, formulated as boundary integral equations}, language = {en} } @article{HenkelGardiner2004, author = {Henkel, Carsten and Gardiner, Simon A.}, title = {Decoherence of Bose-Einstein condensates in microtraps}, year = {2004}, abstract = {We discuss the impact of thermally excited near fields on the coherent expansion of a condensate in a miniaturized electromagnetic trap. Monte Carlo simulations are compared with a kinetic two-component theory and indicate that atom interactions can slow down decoherence. This is explained by a simple theory in terms of the condensate dynamic structure factor}, language = {en} } @article{BoedeckerHenkelHermannetal.2004, author = {Boedecker, Geesche and Henkel, Carsten and Hermann, Christian and Hess, Ortwin}, title = {Spontaneous emission in photonic structures : theory and simulation}, isbn = {3-527-40432-5}, year = {2004}, language = {en} } @article{Henkel2004, author = {Henkel, Carsten}, title = {The rhysics of Atom-Surface interactions}, year = {2004}, language = {en} } @article{NegrettiHenkel2004, author = {Negretti, Antonio and Henkel, Carsten}, title = {Enhanced phase sensitivity and soliton formation in an integrated BEC interferometer}, issn = {0953-4075}, year = {2004}, abstract = {We study the dynamics of Bose-Einstein condensates in time-dependent microtraps for the purpose of understanding the influence of the mean field interaction on the performance of interferometers. We identify conditions where the nonlinearity due to atom interactions increases the sensitivity of interferometers to a phase shift. This feature is connected with the adiabatic generation of a dark soliton. We analyse the robustness of this phenomenon with respect to thermal fluctuations, due to excited near fields in an electromagnetic surface trap}, language = {en} } @article{HenkelJoulainMuletetal.2004, author = {Henkel, Carsten and Joulain, Karl and Mulet, J. P. and Greffet, Jean-Jacques}, title = {Coupled surface polaritons and the Casimir force}, year = {2004}, abstract = {The Casimir force between metallic plates made of realistic materials is evaluated for distances in the nanometer range. A spectrum over real frequencies is introduced and shows narrow peaks due to surface resonances (plasmon polaritons or phonon polaritons) that are coupled across the vacuum gap. We demonstrate that the Casimir force originates from the attraction (repulsion) due to the corresponding symmetric (antisymmetric) eigenmodes, respectively. This picture is used to derive a simple analytical estimate of the Casimir force at short distances. We recover the result known for Drude metals without absorption and compute the correction for weakly absorbing materials}, language = {en} } @article{HenkelNestDomokosetal.2004, author = {Henkel, Carsten and Nest, Mathias and Domokos, P. and Folman, R.}, title = {Optical discrimination between spatial decoherence and thermalization of a massive object}, year = {2004}, abstract = {We propose an optical ring interferometer to observe environment-induced spatial decoherence of massive objects. The object is held in a harmonic trap and scatters light between degenerate modes of a ring cavity. The output signal of the interferometer permits to monitor the spatial width of the object's wave function. It shows oscillations that arise from coherences between energy eigenstates and that reveal the difference between pure spatial decoherence and that coinciding with energy transfer and heating. Our method is designed to work with a wide variety of masses, ranging from the atomic scale to nanofabricated structures. We give a thorough discussion of its experimental feasibility}, language = {en} } @article{HenkelJoulainMuletetal.2002, author = {Henkel, Carsten and Joulain, Karl and Mulet, J. P. and Greffet, Jean-Jacques}, title = {Radiation forces on small particles in thermal near fields}, year = {2002}, abstract = {We study the optical forces due to the radiation of a thermal source. Our model consists of a particle modelled by a dipole above a half-space at temperature T. The fluctuating fields are computed using the Lifshitz model. We find two contributions to the force: a repulsive "wind" component and a dispersive force mainly due to the contribution of thermally excited surface waves. It is found that for SIC material, the latter is repulsive in the very near field. The usual van der Waals force is larger by a factor of approximately ten for submicron size particles.}, language = {en} } @article{HenkelPoetting2001, author = {Henkel, Carsten and P{\"o}tting, Sierk}, title = {Coherent transport of matter waves}, year = {2001}, abstract = {A transport theory for atomic matter waves in low-dimensional waveguides is outlined. The thermal fluctuation spectrum of magnetic near fields leaking out of metallic microstructures is estimated. The corresponding scattering rate for paramagnetic atoms turns out to be quite large in micrometer-sized waveguides (approx. 100/s). Analytical estimate for the heating and decoherence of a cold atom cloud are given. We finally discuss numerical and analytical results for the scattering from static potential imperfections and the ensuing spatial diffusion process.}, language = {en} } @article{Henkel2001, author = {Henkel, Carsten}, title = {Coherent transport}, issn = {1296-2147}, year = {2001}, abstract = {We discuss the transport of matter waves in low-dimensional waveguides. Due to scattering from uncontrollable noise fields, the spatial coherence gets reduced and eventually lost. We develop a description of this decoherence process in terms of transport equations for the atomic Wigner function. We outline its derivation and discuss the special case of white noise where an analytical solution can be found.}, language = {en} } @article{GreffetCarminatiJoulainetal.2003, author = {Greffet, Jean-Jacques and Carminati, R{\´e}mi and Joulain, Karl and Mulet, J. P. and Henkel, Carsten and Mainguy, S.}, title = {Coherent spontaneous emission of light due to surface waves}, issn = {0303-4216}, year = {2003}, language = {en} } @article{BoedeckerHenkel2003, author = {Boedecker, Geesche and Henkel, Carsten}, title = {All-frequency effective medium theory of a photonic crystal}, issn = {1094-4087}, year = {2003}, language = {en} } @article{HenkelKruegerFolmanetal.2003, author = {Henkel, Carsten and Kr{\"u}ger, P. and Folman, R. and Schmiedmayer, J{\"o}rg}, title = {Fundamental limits for coherent manipulation on atom chips}, issn = {0946-2171}, year = {2003}, language = {en} } @article{GreffetCarminatiJoulainetal.2001, author = {Greffet, Jean-Jacques and Carminati, R{\´e}mi and Joulain, Karl and Mulet, J. P. and Henkel, Carsten}, title = {Coherence properties of thermal near fields : implications for nanometer-scale radiative transfer}, year = {2001}, abstract = {With the recent development of local (optical and thermal) probe microscopy and the advent of nanotechnology, it seems necessary to revisit the old subject of coherence properies of thermal sources of light. Concerning temporal coherence, we show that thermal sources may produce quasi-monochromatic near fields. In light of this result, the possibility of perfoming near-field solid-state spectroscopy and of designing near-field infrared sources is discussed. The problem of radiative transfer between two thermal sources held at subwavelength distance is studied. The radiative flux may be enhanced by several orders of magnitude due to the excitation of resonant surface waves, and this may occur at particular frequencies. Finally, we study the spatial coherence of thermal sources and the substantial influence of the near field. Surface waves may induce long-range spatial correlation, on a scale much larger than the wavelength. Conversely, quasi-static contributions, as well as skin-layer currents, induce arbitary small correlations. With the recent development of local (optical and thermal) probe microscopy and the advent of nanotechnology, it seems necessary to revisit the old subject of coherence of thermal fields.}, language = {en} } @article{HenkelWilkens1999, author = {Henkel, Carsten and Wilkens, Martin}, title = {Heating of trapped atoms near thermal surfaces}, year = {1999}, abstract = {We study the electromagnetic coupling and concomitant heating of a particle in a miniaturized trap close to a solid surface. Two dominant heating mechanisms are identified: proximity fields generated by thermally exicted currents in the absorbing solid and timedependent image potentials due to elastic surfaces distortions (Rayleigh phonons. Estimates for the lifetime of the trap ground state are given. Ions are paricularly sinsitive to electric proximity fields: for a silver substrate, we find a lifetime below one second at distrances closer than some ten 10^-6m to the surfaces. Neutral atoms may approach the surface more closely: if they have a magnetic moment, a minimum distance of one 10^-6m is estimatied in tight traps, the heat being transferred via magnetic proximity fields. For spinless atoms, heat is transferred by inelastic scattering of virtual photons off sorface phonons. The corresponding lifetime, however, is estimated to be extremely long compared to the timescale of typical experiments.}, language = {en} } @article{HenkelCourtois1998, author = {Henkel, Carsten and Courtois, J.-Y.}, title = {Recoil and momentum diffusion of an atom close to a vacuum-dielectric interface}, year = {1998}, abstract = {We derive the quantum-mechanical master equation (generalized optical Bloch equation) for an atom in the vicinity of a flat dielectric surface. This equation gives access to the semiclassical radiation pressure force and the atomic momentum diffusion tensor, that are expressed in terms of the vacuum field correlation function (electromagnetic field susceptibility). It is demonstrated that the atomic center-of-mass motion provides a nonlocal probe of the electromagnetic vacuum fluctuations. We show in particular that in a circularly polarized evanescent wave, the radiation pressure force experienced by the atoms is not colinear with the evanescent wave's propagation vector. In a linearly polarized evanescent wave, the recoil per fluorescence cycle leads to a net magnetization for a Jg = 1/2 ground state atom.}, language = {en} } @article{HenkelWilkens2000, author = {Henkel, Carsten and Wilkens, Martin}, title = {Heating of trapped particles close to surfaces-blackbody and beyond}, year = {2000}, abstract = {We discuss heating and decoherencw in traps fpr ions and neutral paricles close to metallic surfaces. We focus on simple trap geometries and compute noise spectra of thermally excited electromagnetic fields. If the trap is located in the near field of the substrate, the field fluctuations are largely increased compared to the level of the blackbody field, leading to much shorter coherence and life times of the trapped atoms. The correspinding time constants are computed for ion traps and magnetic traps. Analytical estimates for the size dependence of the noise spectrum are given. We finally discuss prospects for the coherent transport of matter waves in integrated surface waveguides.}, language = {en} } @article{HenkelSandoghdar1998, author = {Henkel, Carsten and Sandoghdar, Vahid}, title = {Single-molecule sprectroscopy near structured dielectrics}, year = {1998}, abstract = {We present an analytical approach to the calculation of the linewidth and lineshift of an atom or molecule in the near field of a structured dielectric surface. For soft surface corrugations with amplitude lambda/50, we find variations of the linewidth in the ten percent region. More strikingly, the shift of the molecular resonance can reach several natural linewidths. We demonstrate that the lateral resolution is of the order of the molecule-surface distance. We give a semiquantitative explanation of the outcome of our calculations that is based on simple intuitive models.}, language = {en} } @article{HenkelPoettingWilkens1999, author = {Henkel, Carsten and Poetting, Sierk and Wilkens, Martin}, title = {Loss and heating of particles in small and noisy traps}, year = {1999}, abstract = {We derive the time and loss rate for a trapped atom that is coupled to fluctuating fields in the vicinity of a room-temperature metallic and/or dielectric surface. Our results indicate a clear predominance of near-field effects over ordinary blackbody radiation. We develop a theoretical framework for both charged ions and neutral atoms with and without spin. Loss processes that are due to a transition to an untrapped internal state are included.}, language = {en} } @article{HenkelJoulainCarminatietal.2000, author = {Henkel, Carsten and Joulain, Karl and Carminati, R{\´e}mi and Greffet, Jean-Jacques}, title = {Spatial coherence of thermal near fields}, year = {2000}, abstract = {We analyze the spatial coherence of the electromagnetic field emitted by a half-space at temperature T close to the interface. An asymptotic analysis allows to identify three different contributions to the cross-spectral density tensor in the near-field regime. It is shown that the coherence length can be either much larger or much shorter than the wavelength depending on the dominant contribution.}, language = {en} } @article{HenkelChinLangeretal.1999, author = {Henkel, Carsten and Chin, Y. and Langer, Norbert and Mauersberger, R.}, title = {Detection of extragalactic 15N : Nitrogen nucleosynthesis and chemical evolution}, year = {1999}, language = {en} } @article{ChinHenkelLangeretal.1999, author = {Chin, Y. and Henkel, Carsten and Langer, Norbert and Mauersberger, R.}, title = {The detection of extragalactic 15N : consequences for nitrogeen nucleosynthesis and chemical evolution}, year = {1999}, language = {en} } @article{MarzoliTombesiCiaramicolietal.2009, author = {Marzoli, Irene and Tombesi, Paolo and Ciaramicoli, Giacomo and Werth, Guenther and Bushev, Pavel and Stahl, S. and Schmidt-Kaler, Ferdinand and Hellwig, Michael and Henkel, Carsten and Marx, Gerrit and Jex, Igor and Stachowska, Ewa and Szawiola, Gustaw and Walaszyk, Adrian}, title = {Experimental and theoretical challenges for the trapped electron quantum computer}, issn = {0953-4075}, doi = {10.1088/0953-4075/42/15/154010}, year = {2009}, abstract = {We discuss quantum information processing with trapped electrons. After recalling the operation principle of planar Penning traps, we sketch the experimental conditions to load, cool and detect single electrons. Here we present a detailed investigation of a scalable scheme including feasibility studies and the analysis of all important elements, relevant for the experimental stage. On the theoretical side, we discuss different methods to couple electron qubits. We estimate the relevant qubit coherence times and draw implications for the experimental setting. A critical assessment of quantum information processing with trapped electrons concludes the paper.}, language = {en} } @article{CarminatiGreffetHenkeletal.2006, author = {Carminati, R{\´e}mi and Greffet, Jean-Jacques and Henkel, Carsten and Vigoureux, Jean-Marie}, title = {Radiative and non-radiative decay of a single molecule close to a metallic nanoparticle}, issn = {0030-4018}, doi = {10.1016/j.optcom.2005.12.009}, year = {2006}, abstract = {We study the spontaneous emission of a single emitter close to a metallic nanoparticle, with the aim to clarify the distance dependence of the radiative and non-radiative decay rates. We derive analytical formulas based on a dipole- dipole model, and show that the nonradiative decay rate follows a R-6 dependence at short distance, where R is the distance between the emitter and the center of the nanoparticle, as in Forster's energy transfer. The distance dependence of the radiative decay rate is more subtle. It is chiefly dominated by a R-3 dependence, a R-6 dependence being visible at plasmon resonance. The latter is a consequence of radiative damping in the effective dipole polarizability of the nanoparticle. The different distance behavior of the radiative and non-radiative decay rates implies that the apparent quantum yield always vanishes at short distance. Moreover, non-radiative decay is strongly enhanced when the emitter radiates at the plasmon-resonance frequency of the nanoparticle.}, language = {en} } @article{WestbrookHenkelWestbrooketal.1998, author = {Westbrook, N. and Henkel, Carsten and Westbrook, C. I. and Landragin, A. and Labeyrie, G. and Cognet, L. and Savalli, V. and Horvath, G. and Aspect, Alain and Moelmer, Klaus and Courtois, J.-Y. and Phillips, W. D. and Kaiser, Rolf and Bagnato, V.}, title = {New physics with evanescent wave atomic mirrors : the van der Waals force and atomic diffraction}, year = {1998}, abstract = {After a brief introduction to the field of atom optics and to atomic mirrors, we present experimental results obtained in our group during the last two years while studying the reflection of rubidium atoms by an evanescent wave. These involve the first measurement of the van der Waals force between an atom in its ground state and a dielectric wall, as well as the demonstration of a reflection grating for atoms at normal incidence. We also consider the influence of quantum reflection and tunnelling phenomena. Further studies using the atomic mirror as a probe of the van der Waals interaction, and of very small surface roughness are briefly discussed.}, language = {en} } @article{ZhangHenkel2007, author = {Zhang, Bo and Henkel, Carsten}, title = {Magnetic noise around metallic microstructures}, issn = {0021-8979}, doi = {10.1063/1.2800174}, year = {2007}, abstract = {We compute the local spectrum of the magnetic field near a metallic microstructure at finite temperature. Our main focus is on deviations from a plane-layered geometry for which we review the main properties. Arbitrary geometries are handled with the help of numerical calculations based on surface integral equations. The magnetic noise shows a significant polarization anisotropy above flat wires with finite lateral width, in stark contrast to an infinitely wide wire. Within the limits of a two-dimensional setting, our results provide accurate estimates for loss and dephasing rates in so-called `atom chip traps' based on metallic wires. A simple approximation based on the incoherent summation of local current elements gives qualitative agreement with the numerics, but fails to describe current correlations among neighboring objects.}, language = {en} } @article{GreffetHenkel2006, author = {Greffet, Jean-Jacques and Henkel, Carsten}, title = {Rayonnement thermique coh{\´e}rent}, issn = {0290-0041}, year = {2006}, abstract = {Le rayonnement {\´e}lectromagn{\´e}tique produit par un corps {\`a} temp{\´e}rature T est g{\´e}n{\´e}ralement consid{\´e}r{\´e} comme l'exemple type du rayonnement incoh{\´e}rent que l'on oppose au rayonnement laser. L'un est quasi isotrope tandis que l'autre est tr{\`e}s directionnel, l'un a un large spectre tandis que l'autre est quasi-monochromatique. Aussi surprenant que cela puisse para{\^i}tre, le rayonnement thermique de bon nombre de corps est coh{\´e}rent lorsque l'on se place {\`a} une distance inf{\´e}rieure {\`a} la longueur d'onde de la surface {\´e}mettrice. Nous verrons que ces effets peuvent {\^e}tre pr{\´e}dits {\`a} l'aide d'une approche {\´e}lectromagn{\´e}tique du rayonnement thermique. Plusieurs exp{\´e}riences r{\´e}centes ont confirm{\´e} ces propri{\´e}t{\´e}s inattendues.}, language = {fr} } @article{IntravaiaHenkelLambrecht2007, author = {Intravaia, Francesco and Henkel, Carsten and Lambrecht, Astrid}, title = {Role of surface plasmons in the Casimir effect}, year = {2007}, abstract = {In this paper we study the role of surface plasmon modes in the Casimir effect. The Casimir energy can be written as a sum over the modes of a real cavity and one may identify two sorts of modes, two evanescent surface plasmon modes and propagative modes. As one of the surface plasmon modes becomes propagative for some choice of parameters we adopt an adiabatic mode definition where we follow this mode into the propagative sector and count it together with the surface plasmon contribution, calling this contribution ``plasmonic''. We evaluate analytically the contribution of the plasmonic modes to the Casimir energy. Surprisingly we find that this becomes repulsive for intermediate and large mirror separations. The contribution of surface plasmons to the Casimir energy plays a fundamental role not only at short but also at large distances. This suggests possibilities to taylor the Casimir force via a manipulation of the surface plasmon properties.}, language = {en} } @article{GreffetHenkel2007, author = {Greffet, Jean-Jacques and Henkel, Carsten}, title = {Coherent thermal radiation}, issn = {0010-7514}, year = {2007}, abstract = {The radiation emitted by a heated body is generally quoted as a typical example of incoherent radiation, in distinction to laser radiation. One is nearly isotropic, the other highly directional; one is spectrally broad, the other quasi-monochromatic. It may come as a surprise that the thermal radiation of a large number of substances is coherent, both in space and time, when it is observed at a distance from the body that is shorter than the wavelength. This behaviour can be understood within an electromagnetic approach to thermal emission. Several recent experiments have confirmed these unexpected properties.}, language = {en} } @article{Henkel2007, author = {Henkel, Carsten}, title = {Laser theory in manifest Lindblad form}, issn = {0953-4075}, year = {2007}, abstract = {We discuss the laser theory for a single-mode laser with nonlinear gain. We focus in particular on a micromaser which is pumped with a dilute beam of excited atoms crossing the laser cavity. In the weak-coupling regime, an expansion in the coupling strength is developed that preserves the Lindblad form of the master equation, securing the positivity of the density matrix. This can be improved with an alternative approach, not restricted to weak coupling: the Lindblad operators are expanded in orthogonal polynomials adapted to the probability distribution for the atom-laser interaction time. Results for the photon statistics and the laser linewidth illustrate the theory.}, language = {en} }