@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{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} }