W. Hoyer

Philipps-Universität Marburg, Marburg, Hesse, Germany

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Publications (55)103.1 Total impact

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    ABSTRACT: In this paper we present a numerical method for solving a three-dimensional cold-plasma system that describes electron gas dynamics driven by an external electromagnetic wave excitation. The nonlinear Drude dispersion model is derived from the cold-plasma fluid equations and is coupled to the Maxwell's field equations. The Finite-Difference Time-Domain (FDTD) method is applied for solving the Maxwell's equations in conjunction with the time-split semi-implicit numerical method for the nonlinear dispersion and a physics based treatment of the discontinuity of the electric field component normal to the dielectric-metal interface. The application of the proposed algorithm is illustrated by modeling light pulse propagation and second-harmonic generation (SHG) in metallic metamaterials (MMs), showing good agreement between computed and published experimental results.
    Journal of Computational Physics 01/2010; 229:5921-5932. · 2.14 Impact Factor
  • J. Comput. Phys. 01/2010; 229(17):5921-5932.
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    ABSTRACT: In a recent publication [Phys. Rev. Lett. 97, 227402 (2006)], it has been demonstrated numerically that a long-range disorder potential in a semiconductor quantum well can be reconstructed reliably via single-photon interferometry of spontaneously emitted light. In the present paper, a simplified analytical model of independent two-level systems is presented in order to study the reconstruction procedure in more detail. With the help of this model, the measured photon correlations can be calculated analytically and the influence of parameters, such as the disorder length scale, the wavelength of the used light, or the spotsize can be investigated systematically. Furthermore, the relation between the proposed angle-resolved single-photon correlations and the disorder potential can be understood and the measured signal is expected to be closely related to the characteristic strength and length scale of the disorder.
    Journal of Materials Science Materials in Electronics 12/2008; 20:23-29. · 1.49 Impact Factor
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    ABSTRACT: We present experiments on second-harmonic generation from arrays of magnetic split-ring resonators and arrays of complementary split-ring resonators. In both cases, the fundamental resonance is excited by the incident femtosecond laser pulses under normal incidence, leading to comparably strong second-harmonic signals. These findings are discussed in terms of Babinet's principle and in terms of a recently developed microscopic classical theory that leads to good agreement regarding the relative and the absolute nonlinear signal strengths. The hydrodynamic convective contribution is found to be the dominant source of second-harmonic generation--in contrast to a previous assignment [Science 313, 502 (2006)].
    Optics Letters 10/2008; 33(17):1975-7. · 3.39 Impact Factor
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    ABSTRACT: In this article, we develop a classical electrodynamic theory to study the optical nonlinearities of metallic nanoparticles. The quasi-free electrons inside the metal are approximated as a classical Coulomb-interacting electron gas, and their motion under the excitation of an external electromagnetic field is described by the plasma equations. This theory is further tailored to study second-harmonic generation. Through detailed experiment-theory comparisons, we validate this classical theory as well as the associated numerical algorithm. It is demonstrated that our theory not only provides qualitative agreement with experiments, it also reproduces the overall strength of the experimentally observed second-harmonic signals.
    Physical Review B 08/2008; · 3.66 Impact Factor
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    ABSTRACT: Strong second-harmonic generation has recently been experimentally observed from metamaterials consisting of periodic arrays of metal split ring resonators with an effective negative magnetic permeability [Science, 313, 502 (2006)]. To explore the underlying physical mechanism, a classical model derived from microscopic theory is employed here. The quasi-free electrons inside the metal are approximated as a classical Coulomb-interacting electron gas, and their motion under the excitation of an external electromagnetic field is described by the cold-plasma wave equations. Through numerical simulations, it is demonstrated that the microscopic theory includes the dominant physical mechanisms bothqualitatively and quantitatively.
    08/2008;
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    ABSTRACT: A fully microscopical theory for the photoluminescence of a quantum-well in an arbitrary one-dimensional stack structure is presented. For strong-coupling configurations, the full semiconductor luminescence equations are solved. For the weak-coupling regime, a frequency-dependent filter function is directly derived from the semiconductor luminescence equations with the knowledge of the dielectric structure. Via that filter function, the detected luminescence can be related to the pure quantum-well emission in vacuum. The approach is generalized to include corrections to the emitted peak width due to the photonic-environment-dependent radiative decay, and the corrections are shown to be obtainable from the mode functions alone. The applicability of the method is thoroughly tested up to the onset of normal-mode coupling.
    Journal of the Optical Society of America B 01/2008; 25(2). · 2.21 Impact Factor
  • 12/2007: pages 255-351;
  • W. Hoyer, M. Kira, S. W. Koch
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    ABSTRACT: Quantum optical effects in semiconductors are studied using a density-matrix approach which takes into account the many-body Coulomb interaction among the charge carriers, coupling to lattice vibrations, and the quantum nature of light. The theory provides a consistent set of equations which is used to compute photoluminescence spectra, predict the emission of squeezed light, investigate correlations between photons emitted by quantum-well structures, and to show examples where light-matter entanglement influences experiments done with classical optical fields.
    10/2007: pages 55-66;
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    ABSTRACT: It is well known that electromagnetic waves with frequencies below the plasma frequency cannot propagate inside an electron plasma. For plasmas with infinite extensions, this property can be mathematically described by a Bogoliubov transformation of the photonic operators. More generally, the presence of finite-size electron plasmas such as laser-induced atmospheric light strings or metallic nano structures including metamaterials leads to a modification of the light–matter interaction. It is shown how this geometric property can be fully accounted for with the help of adapted mode functions used for the quantization of the electromagnetic field. In addition to the analytical derivations, numerical results for luminescence spectra out of quasi-two-dimensional, planar plasma sheets are presented. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (b) 08/2007; 244(10):3540 - 3557. · 1.49 Impact Factor
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    ABSTRACT: Angle and energy resolved single-photon correlation measurements of luminescence emitted from semiconductor nanostructures are modeled. A simple reconstruction procedure is shown to yield the long-range disorder fluctuations with high fidelity.
    05/2007;
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    ABSTRACT: The method of angular photonic correlations of spontaneous emission is introduced as an experimental, purely optical scheme to characterize disorder in semiconductor nanostructures. The theoretical expression for the angular correlations is derived and numerically evaluated for a model system. The results demonstrate how the proposed experimental method yields direct information about the spatial distribution of the relevant states and thus on the disorder present in the system.
    Physical Review Letters 01/2007; 97(22):227402. · 7.73 Impact Factor
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    ABSTRACT: A microscopic theory based on Bloch electrons and holes in a two-band approximation is applied in order to compute absorption and luminescence spectra for GaAs-type quantum wells at room temperature. Special focus is set to investigate the effect of the Coulomb interaction on the linewidth of the luminescence spectra and on the radiative recombination rates.
    Journal of the Optical Society of America B 01/2007; 24(6). · 2.21 Impact Factor
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    ABSTRACT: The quantum emission in radiatively coupled semiconductor multiple-quantum-well structures is investigated theoretically. It is shown that coupling effects can lead to a subradiant suppression of the emission compared to the emission of a single quantum well (QW). The suppression strength depends on the number and spacing of the QWs as well as on the homogeneous broadening and leads to an enhancement of the radiative lifetime of excitons in the structure. The strongest lifetime enhancement is found for Bragg-arranged QWs with small homogeneous broadening. Additionally, the radiative coupling between the QWs provides an exciton pumping mechanism such that excitons can directly be created into the state that has vanishing center-of-mass momentum.
    Physical Review B 10/2006; · 3.66 Impact Factor
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    ABSTRACT: We study optical second-harmonic generation from planar arrays of magnetic split-ring resonators at 1.5 microns resonance wavelength. We obtain by far the largest signals when exciting the magnetic-dipole resonance.
    06/2006;
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    ABSTRACT: We discuss second-harmonic generation experiments on planar arrays of magnetic split-ring resonators, using 150 fs pulses at 1.5 microns wavelength. Lithographic tuning reveals by far the largest signals when exciting the magnetic-dipole resonance.
    05/2006;
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    W. Hoyer, M. Kira, S. W. Koch
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    ABSTRACT: A fully microscopic theory for the spontaneous emission from semiconductors is discussed. The theory is evaluated for a quantum-well system and the role of excitonic and unbound electron-hole-pair contributions to the emission is analyzed. Simplifying aproximations to the full theory and their range of validity are discussed. Numerical solutions are presented for experimentally relevant situations and it is shown that a detailed analysis of measured spectra requires the knowledge of both absorption and emission under identical conditions.
    05/2006;
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    ABSTRACT: We study the angular correlation of single photons emitted from excited semiconductor quantum wells. The considered physical system is described in terms of two subsystems, the electronic part constituting the bath and the photonic part constituting the bathed subsystem, both being coupled by the light-matter interaction. From the master equations describing the coarse-grained Markovian evolution of the photonic subsystem, we derive the corresponding equations of motion for the photonic angular correlation functions. These equations are solved in the stationary, low-density limit. Experimentally, the angular correlations can be assessed by studying the interference of light emitted in different directions. In agreement with recent experimental results, we find that for ordered quantum wells angular correlations exist only in emission directions for which the projections of the photon momenta onto the plane of the quantum well are equal. This feature is a direct consequence of the Bloch character of the electronic states in an ordered quantum well. Thus the experimental study of the angular correlations of emitted photons may provide an interesting diagnostic tool to reveal the presence of disorder in semiconductor heterostructures and to characterize its influence on the electronic states near the band edges.
    Journal of Luminescence 01/2006; 121(1):21-31. · 2.14 Impact Factor
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    ABSTRACT: Starting from a general microscopic model for an interacting two-component plasma including the interaction with a quantized light field, the equations of motion in the Wigner representation are derived. In contrast to the case of strongly focused laser beams which are known to leave behind so called wakefield oscillations of the electron plasma, thermal wakefield oscillations dominate the dynamics of a femtosecond laser generated plasma rod. It is shown that the photoluminescence from the resulting electron-ion plasma bears spectral features related to the plasma frequency due to these thermal radial wakefield oscillations.
    Journal of Physics Conference Series 07/2005; 11(1):153.
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    ABSTRACT: A microscopic theory for the luminescence of ordered semiconductors is modified to describe photoluminescence of strongly disordered semiconductors. The approach includes both diagonal disorder and the many-body Coulomb interaction. As a case study, the light emission of a correlated plasma is investigated numerically for a one-dimensional two-band tight-binding model. The band structure of the underlying ordered system is assumed to correspond to either a direct or an indirect semiconductor. In particular, luminescence and absorption spectra are computed for various levels of disorder and sample temperature to determine thermodynamic relations, the Stokes shift, and the radiative lifetime distribution.
    Journal of Luminescence 06/2005; · 2.14 Impact Factor

Publication Stats

511 Citations
103.10 Total Impact Points

Institutions

  • 1970–2010
    • Philipps-Universität Marburg
      • Faculty of Physics
      Marburg, Hesse, Germany
  • 1999–2005
    • The University of Arizona
      • • Department of Mathematics
      • • College of Optical Sciences
      Tucson, AZ, United States
  • 2003
    • University of Rostock
      • Institut für Physik
      Rostock, Mecklenburg-Vorpommern, Germany
  • 2001
    • KTH Royal Institute of Technology
      • Department of Physics
      Tukholma, Stockholm, Sweden