Achtung:

Sie haben Javascript deaktiviert!
Sie haben versucht eine Funktion zu nutzen, die nur mit Javascript möglich ist. Um sämtliche Funktionalitäten unserer Internetseite zu nutzen, aktivieren Sie bitte Javascript in Ihrem Browser.

Snow on campus. Show image information

Snow on campus.

Photo: Paderborn University, Johannes Pauly

Prof. Dr. Torsten Meier

Contact
Publications
Prof. Dr. Torsten Meier

Computational Optoelectronics and Photonics

Head - Professor

Paderborn University

Vice President - Professor - Vice-President for International Relations

Center for Optoelectronics and Photonics (CeOPP)

Member - Professor

Institute for photonic quantum systems (PhoQS)

Professor

Paderborn Center for Parallel Computing (PC2) >Vorstand

Member - Professor

Sonderforschungsbereich Transregio 142

Member - Professor

Phone:
+49 5251 60-2336
Fax:
+49 5251 60-3435
Office:
N3.338
Visitor:
Pohlweg 55
33098 Paderborn

Open list in Research Information System

2020

Strongly nonresonant four-wave mixing in semiconductors

W. Hannes, A. Trautmann, M. Stein, F. Sch\, M. Koch, T. Meier, Phys. Rev. B (2020), 101, pp. 075203


Enhanced high-order harmonic generation in semiconductors by excitation with multicolor pulses

X. Song, S. Yang, R. Zuo, T. Meier, W. Yang, Physical Review A (2020), 101


Accurate photon echo timing by optical freezing of exciton dephasing and rephasing in quantum dots

A.N. Kosarev, H. Rose, S.V. Poltavtsev, M. Reichelt, C. Schneider, M. Kamp, S. Höfling, M. Bayer, T. Meier, I.A. Akimov, Communications Physics (2020), 3

<jats:title>Abstract</jats:title><jats:p>Semiconductor quantum dots are excellent candidates for ultrafast coherent manipulation of qubits by laser pulses on picosecond timescales or even faster. In inhomogeneous ensembles a macroscopic optical polarization decays rapidly due to dephasing, which, however, is reversible in photon echoes carrying complete information about the coherent ensemble dynamics. Control of the echo emission time is mandatory for applications. Here, we propose a concept to reach this goal. In a two-pulse photon echo sequence, we apply an additional resonant control pulse with multiple of 2<jats:italic>π</jats:italic> area. Depending on its arrival time, the control slows down dephasing or rephasing of the exciton ensemble during its action. We demonstrate for self-assembled (In,Ga)As quantum dots that the photon echo emission time can be retarded or advanced by up to 5 ps relative to its nominal appearance time without control. This versatile protocol may be used to obtain significantly longer temporal shifts for suitably tailored control pulses.</jats:p>


    k.p-based multiband simulations of non-degenerate two-photon absorption in bulk GaAs

    W. Hannes, T. Meier, in: Ultrafast Phenomena and Nanophotonics XXIV, 2020


    Realization of all-optical vortex switching in exciton-polariton condensates

    X. Ma, B. Berger, M. Aßmann, R. Driben, T. Meier, C. Schneider, S. Höfling, S. Schumacher, Nature Communications (2020), 11


    Strongly nonresonant four-wave mixing in semiconductors

    W. Hannes, A. Trautmann, M. Stein, F. Schäfer, M. Koch, T. Meier, Physical Review B (2020), 101(7)


    2019

    Higher-order contributions and nonperturbative effects in the nondegenerate nonlinear optical absorption of semiconductors using a two-band model

    W. Hannes, T. Meier, Physical Review B (2019), 99(12)


    Attosecond temporal confinement of interband excitation by intraband motion

    X. Song, R. Zuo, S. Yang, P. Li, T. Meier, W. Yang, Optics Express (2019), 27


    Nonlinear integrated quantum electro-optic circuits

    K. Luo, S. Brauner, C. Eigner, P.R. Sharapova, R. Ricken, T. Meier, H. Herrmann, C. Silberhorn, Science Advances (2019)

    <jats:p>Future quantum computation and networks require scalable monolithic circuits, which incorporate various advanced functionalities on a single physical substrate. Although substantial progress for various applications has already been demonstrated on different platforms, the range of diversified manipulation of photonic states on demand on a single chip has remained limited, especially dynamic time management. Here, we demonstrate an electro-optic device, including photon pair generation, propagation, electro-optical path routing, as well as a voltage-controllable time delay of up to ~12 ps on a single Ti:LiNbO<jats:sub>3</jats:sub> waveguide chip. As an example, we demonstrate Hong-Ou-Mandel interference with a visibility of more than 93 ± 1.8%. Our chip not only enables the deliberate manipulation of photonic states by rotating the polarization but also provides precise time control. Our experiment reveals that we have full flexible control over single-qubit operations by harnessing the complete potential of fast on-chip electro-optic modulation.</jats:p>


      Intensity-dependent degenerate and non-degenerate nonlinear optical absorption of direct-gap semiconductors

      W. Hannes, L. Krauß-Kodytek, C. Ruppert, M. Betz, T. Meier, in: Ultrafast Phenomena and Nanophotonics XXIII, 2019


      Realization of all-optical vortex switching in exciton-polariton condensates

      X. Ma, B. Berger, M. Assmann, R. Driben, T. Meier, C. Schneider, S. Höfling, S. Schumacher, in: arXiv:1907.03171, 2019

      Vortices are topological objects representing the circular motion of a fluid. With their additional degree of freedom, the 'vorticity', they have been widely investigated in many physical systems and different materials for fundamental interest and for applications in data storage and information processing. Vortices have also been observed in non-equilibrium exciton-polariton condensates in planar semiconductor microcavities. There they appear spontaneously or can be created and pinned in space using ring-shaped optical excitation profiles. However, using the vortex state for information processing not only requires creation of a vortex but also efficient control over the vortex after its creation. Here we demonstrate a simple approach to control and switch a localized polariton vortex between opposite states. In our scheme, both the optical control of vorticity and its detection through the orbital angular momentum of the emitted light are implemented in a robust and practical manner.


        Bloch oscillations of multidimensional dark soliton wave packets and light bullets

        R. Driben, X. Ma, S. Schumacher, T. Meier, Optics Letters (2019), 44(6)


        Spatially asymmetric transients of propagating exciton-polariton modes in a planar CdZnTe/CdMgTe guiding structure

        J. Vondran, F. Spitzer, M. Bayer, I.A. Akimov, A. Trautmann, M. Reichelt, C. Meier, N. Weber, T. Meier, R. André, H. Mariette, Physical Review B (2019)


        Ballistic photocurrents in semiconductor quantum wells caused by the excitation of asymmetric excitons

        H.T. Duc, C. Ngo, T. Meier, Physical Review B (2019), 100(4)


        Bloch oscillations of multidimensional dark soliton wave packets and light bullets

        R. Driben, X. Ma, S. Schumacher, T. Meier, Optics Letters (2019)


        2018

        Coherent optical spectroscopy of charged exciton complexes in semiconductor nanostructures

        I. Akimov, S.V. Poltavtsev, M. Salewski, I.A. Yugova, G. Karczewski, T. Wojtowicz, W. Maciej, M. Reichelt, T. Meier, D. Yakovlev, M. Bayer, in: Ultrafast Phenomena and Nanophotonics XXII, 2018, pp. 105300G


        Nonlinearity-induced localization in a periodically driven semidiscrete system

        R. Driben, V.V. Konotop, B.A. Malomed, T. Meier, A.V. Yulin, Physical Review E (2018), 97(6)


        Signatures of transient Wannier-Stark localization in bulk gallium arsenide

        C. Schmidt, J. Bühler, A. Heinrich, J. Allerbeck, R. Podzimski, D. Berghoff, T. Meier, W.G. Schmidt, C. Reichl, W. Wegscheider, D. Brida, A. Leitenstorfer, Nature Communications (2018), 9(1)


        Observation and Uses of Position-Space Bloch Oscillations in an Ultracold Gas

        Z.A. Geiger, K.M. Fujiwara, K. Singh, R. Senaratne, S.V. Rajagopal, M. Lipatov, T. Shimasaki, R. Driben, V.V. Konotop, T. Meier, D.M. Weld, Physical Review Letters (2018), 120(21)


        Observation and Uses of Position-Space Bloch Oscillations in an Ultracold Gas

        Z.A. Geiger, K.M. Fujiwara, K. Singh, R. Senaratne, S.V. Rajagopal, M. Lipatov, T. Shimasaki, R. Driben, V.V. Konotop, T. Meier, D.M. Weld, Physical Review Letters (2018), 120(21)


        Nonlinearity-induced localization in a periodically driven semidiscrete system

        R. Driben, V.V. Konotop, B.A. Malomed, T. Meier, A.V. Yulin, Physical Review E (2018), 97(6)


        Exotic complexes in one-dimensional Bose-Einstein condensates with spin-orbit coupling

        D.B. Belobo, T. Meier, Scientific Reports (2018), 8(1)


        Coherent optical spectroscopy of charged exciton complexes in semiconductor nanostructures

        I. Akimov, S.V. Poltavtsev, M. Salewski, I.A. Yugova, G.. Karczewski, T. Wojtowicz, W.. Maciej , M. Reichelt, T. Meier, D. Yakovlev, M. Bayer, in: Ultrafast Phenomena and Nanophotonics XXII, SPIE, 2018


        Signatures of transient Wannier-Stark localization in bulk gallium arsenide

        C. Schmidt, J. Bühler, A. Heinrich, J. Allerbeck, R. Podzimski, D. Berghoff, T. Meier, W.G. Schmidt, C. Reichl, W. Wegscheider, D. Brida, A. Leitenstorfer, Nature Communications (2018), 9, pp. 2890


        2017

        Bloch oscillations and resonant radiation of light propagating in arrays of nonlinear fibers with high-order dispersion

        A. Yulin, R. Driben, T. Meier, Physical Review A (2017), 96(3)


        Modified two-photon interference achieved by the manipulation of entanglement

        P. Sharapova, K. Luo, H. Herrmann, M. Reichelt, C. Silberhorn, T. Meier, Physical Review A (2017), 96, pp. 043857


        Toolbox for the design of LiNbO3-based passive and active integrated quantum circuits

        P. Sharapova, K.H. Luo, H. Herrmann, M. Reichelt, T. Meier, C. Silberhorn, New Journal of Physics (2017), 19


        Anisotropic excitons and their contributions to shift current transients in bulk GaAs

        R. Podzimski, H.T. Duc, T. Meier, Physical Review B (2017), 96(20)


        Towards integrated superconducting detectors on lithium niobate waveguides

        J.P. Höpker, M. Bartnick, E. Meyer-Scott, F. Thiele, T. Meier, T. Bartley, S. Krapick, N.M. Montaut, M. Santandrea, H. Herrmann, S. Lengeling, R. Ricken, V. Quiring, A.E. Lita, V.B. Verma, T. Gerrits, S.W. Nam, C. Silberhorn, in: Quantum Photonic Devices, 2017, pp. 1035809


        Damping of Rabi oscillations in intensity-dependent photon echoes from exciton complexes in a CdTe/(Cd,Mg)Te single quantum well

        S.V. Poltavtsev, M. Reichelt, I.A. Akimov, G. Karczewski, M. Wiater, T. Wojtowicz, D.R. Yakovlev, T. Meier, M. Bayer, Physical Review B (2017), 96, pp. 075306


        Bloch oscillations sustained by nonlinearity

        R. Driben, V.V. Konotop, T. Meier, A.V. Yulin, Scientific Reports (2017)


        A microscopic approach to ultrafast near band gap photocurrents in bulk semiconductors

        R. Podzimski, H.T. Duc, T. Meier, in: Ultrafast Phenomena and Nanophotonics XXI, 2017


        High-Resolution Two-Dimensional Optical Spectroscopy of Electron Spins

        M. Salewski, S. Poltavtsev, I. Yugova, G. Karczewski, M. Wiater, T. Wojtowicz, D. Yakovlev, I. Akimov, T. Meier, M. Bayer, Physical Review X (2017), 7, pp. 031030


        Time-resolved photon echoes from donor-bound excitons in ZnO epitaxial layers

        S.V. Poltavtsev, A.N. Kosarev, I.A. Akimov, D.R. Yakovlev, S. Sadofev, J. Puls, S.P. Hoffmann, M. Albert, C. Meier, T. Meier, M. Bayer, Physical Review B (2017), 96(3)


        2016

        Ultrafast shift and rectification photocurrents in GaAs quantum wells: Excitation intensity dependence and the importance of band mixing

        H.T. Duc, R. Podzimski, S. Priyadarshi, M. Bieler, T. Meier, Physical Review B (2016), 94(8)


        Indium oxide inverse opal films synthesized by structure replication method

        S. Amrehn, D. Berghoff, A. Nikitin, M. Reichelt, X. Wu, T. Meier, T. Wagner, Photonics and Nanostructures - Fundamentals and Applications (2016), 19, pp. 55-63


        Photocurrents in semiconductors and semiconductor quantum wells analyzed by k.p-based Bloch equations

        R. Podzimski, H.T. Duc, S. Priyadarshi, C. Schmidt, M. Bieler, T. Meier, in: Ultrafast Phenomena and Nanophotonics XX, 2016


        Ultrafast dynamical response of the lower exciton-polariton branch in CdZnTe

        J. Lohrenz, S. Melzer, C. Ruppert, I.A. Akimov, H. Mariette, M. Reichelt, A. Trautmann, T. Meier, M. Betz, Physical Review B (2016), 93(7)


        Quantum interference control of electrical currents in GaAs microstructures: physics and spectroscopic applications

        E. Sternemann, T. Jostmeier, C. Ruppert, S. Thunich, H.T. Duc, R. Podzimski, T. Meier, M. Betz, Applied Physics B (2016), 122(44)


        Simulations of high harmonic generation from plasmonic nanoparticles in the terahertz region

        Y. Grynko, T. Zentgraf, T. Meier, J. Förstner, Applied Physics B (2016), 122(9), pp. 242


        Two-dimensional symbiotic solitons and vortices in binary condensates with attractive cross-species interaction

        X. Ma, R. Driben, B.A. Malomed, T. Meier, S. Schumacher, Scientific Reports (2016), 6, pp. 34847


        Dynamics of dipoles and vortices in nonlinearly coupled three-dimensional field oscillators

        R. Driben, V.V. Konotop, B.A. Malomed, T. Meier, Physical Review E (2016), 94(1)


        Precession and nutation dynamics of nonlinearly coupled non-coaxial three-dimensional matter wave vortices

        R. Driben, V.V. Konotop, T. Meier, Scientific Reports (2016), 6, pp. 22758


        Advanced optical manipulation of carrier spins in (In,Ga)As quantum dots

        S. Varwig, E. Evers, A. Greilich, D.R. Yakovlev, D. Reuter, A.D. Wieck, T. Meier, A. Zrenner, M. Bayer, Applied Physics B (2016), 122(1)

        Spins in semiconductor quantum dots have been considered as prospective quantum bit excitations. Their coupling to the crystal environment manifests itself in a limitation of the spin coherence times to the microsecond range, both for electron and hole spins. This rather short-lived coherence compared to atomic states asks for manipulations on timescales as short as possible. Due to the huge dipole moment for transitions between the valence and conduction band, pulsed laser systems offer the possibility to perform manipulations within picoseconds or even faster. Here, we report on results that show the potential of optical spin manipulations with currently available pulsed laser systems. Using picosecond laser pulses, we demonstrate optically induced spin rotations of electron and hole spins. We further realize the optical decoupling of the hole spins from the nuclear surrounding at the nanosecond timescales and demonstrate an all-optical spin tomography for interacting electron spin sub-ensembles.


          2015

          Multipoles and vortex multiplets in multidimensional media with inhomogeneous defocusing nonlinearity

          R. Driben, N. Dror, B.A. Malomed, T. Meier, New Journal of Physics (2015), 17


          Multipoles and vortex multiplets in multidimensional media with inhomogeneous defocusing nonlinearity

          R. Driben, N. Dror, B.A. Malomed, T. Meier, New Journal of Physics (2015), 17


          Sub-cycle control of multi-THz high-harmonic generation and all-coherent charge transport in bulk semiconductors

          C. Lange, O. Schubert, M. Hohenleutner, F. Langer, S. Baierl, T. Maag, B. Urbanek, E.R.J. Edwards, G. Woltersdorf, D. Bougeard, U. Huttner, D. Golde, T. Meier, M. Kira, S.W. Koch, R. Huber, in: Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XIV, 2015


          Curvature effects in the band structure of carbon nanotubes including spin–orbit coupling

          H. Liu, D.F. Heinze, H. Thanh Duc, S. Schumacher, T. Meier, Journal of Physics: Condensed Matter (2015), 27


          Sub-cycle control of multi-THz high-harmonic generation and all-coherent charge transport in bulk semiconductors

          C. Lange, O. Schubert, M. Hohenleutner, F. Langer, S. Baierl, T. Maag, B. Urbanek, E.R.J. Edwards, G. Woltersdorf, D. Bougeard, U. Huttner, D. Golde, T. Meier, M. Kira, S.W. Koch, R. Huber, in: Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XIV, 2015


          Time-domain calculations of shift currents in bulk GaAs

          R. Podzimski, H.T. Duc, T. Meier, in: Ultrafast Phenomena and Nanophotonics XIX, 2015


          Time-domain calculations of shift currents in bulk GaAs

          R. Podzimski, H.T. Duc, T. Meier, in: Ultrafast Phenomena and Nanophotonics XIX, 2015


          Creation of vortices by torque in multidimensional media with inhomogeneous defocusing nonlinearity

          R. Driben, T. Meier, B.A. Malomed, Scientific Reports (2015), 5, pp. 9420


          2014

          Engineering plasmonic and dielectric directional nanoantennas

          A. Hildebrandt, M. Reichelt, T. Meier, J. Förstner, in: Ultrafast Phenomena and Nanophotonics XVIII, SPIE, 2014, pp. 89841G-8941G-6

          Optical and infrared antennas provide a promising way to couple photons in and out of nanoscale structures. As counterpart to conventional radio antennas, they are able to increase optical felds in sub-wavelength volumes, to enhance excitation and emission of quantum emitters or to direct light, radiated by quantum emitters. The directed emission of these antennas has been mainly pursued by surface plasmon based devices, e.g. Yagi-Uda like antennas, which are rather complicated due to the coupling of several metallic particles. Also, like all metallic structures in optical or infrared regime, these devices are very sensitive to fabrication tolerances and are affected by strong losses. It has been shown recently, that such directed emission can be accomplished by dielectric materials as well. In this paper we present an optimization of nanoscopic antennas in the near infrared regime starting from a metallic Yagi-Uda structure. The optimization is done via a particle-swarm algorithm, using full time domain finite integration simulations to obtain the characteristics of the investigated structure, also taking into account substrates. Furthermore we present a dielectric antenna, which performs even better, due to the lack of losses by an appropriate choice of the dielectric material. These antennas are robust concerning fabrication tolerances and can be realized with different materials for both the antenna and the substrate, without using high index materials.


            Influence of Coulomb-induced band couplings on linear excitonic absorption spectra of semiconducting carbon nanotubes

            H. Liu, S. Schumacher, T. Meier, Physical Review B (2014)


            2013

            Collective effects in second-harmonic generation from split-ring-resonator arrays

            F.B. Niesler, S. Linden, J. Förstner, Y. Grynko, T. Meier, M. Wegener, in: Conference on Lasers and Electro-Optics 2012, OSA, 2013

            We perform experiments on resonant second-harmonic generation from planar gold split-ring-resonator arrays under normal incidence of light as a function of the lattice constant. Optimum nonlinear conversion occurs at intermediate lattice constants.


              Optimal second-harmonic generation in split-ring resonator arrays

              Y. Grynko, T. Meier, S. Linden, F.B.P. Niesler, M. Wegener, J. Förstner, in: Ultrafast Phenomena and Nanophotonics XVII, SPIE, 2013, pp. 86230L-86230L-9

              Previous experimental measurements and numerical simulations give evidence of strong electric and magnetic field interaction between split-ring resonators in dense arrays. One can expect that such interactions have an influence on the second harmonic generation. We apply the Discontinuous Galerkin Time Domain method and the hydrodynamic Maxwell-Vlasov model to simulate the linear and nonlinear optical response from SRR arrays. The simulations show that dense placement of the constituent building blocks appears not always optimal and collective effects can lead to a significant suppression of the near fields at the fundamental frequency and, consequently, to the decrease of the SHG intensity. We demonstrate also the great role of the symmetry degree of the array layout which results in the variation of the SHG efficiency in range of two orders of magnitude.


                Selection rules and linear absorption spectra of carbon nanotubes in axial magnetic fields

                H. Liu, S. Schumacher, T. Meier, Physical Review B (2013)


                2012

                Optimization of the intensity enhancement in plasmonic nanoantennas

                A. Hildebrandt, M. Reichelt, T. Meier, J. Förstner, AIP AIP Conference Proceedings 1475, 2012

                We design the geometrical shape of plasmonic nanostructures to achieve field patterns with desired properties. For this, we combine Maxwell simulations and automatic optimization techniques. By allowing variations of the geometrical shape, which can be based on either boxes or arbitrary polygons, we maximize the desired objective.


                  Photonic crystal waveguides intersection for resonant quantum dot optical spectroscopy detection

                  X. Song, S. Declair, T. Meier, A. Zrenner, J. Förstner, Optics Express (2012), 20(13)

                  Using a finite-difference time-domain method, we theoretically investigate the optical spectra of crossing perpendicular photonic crystal waveguides with quantum dots embedded in the central rod. The waveguides are designed so that the light mainly propagates along one direction and the cross talk is greatly reduced in the transverse direction. It is shown that when a quantum dot (QD) is resonant with the cavity, strong coupling can be observed via both the transmission and crosstalk spectrum. If the cavity is far off-resonant from the QD, both the cavity mode and the QD signal can be detected in the transverse direction since the laser field is greatly suppressed in this direction. This structure could have strong implications for resonant excitation and in-plane detection of QD optical spectroscopy.


                    Engineering high harmonic generation in semiconductors via pulse shaping

                    M. Reichelt, A. Hildebrandt, A. Walther, J. Förstner, T. Meier, in: Ultrafast Phenomena and Nanophotonics XVI, Proc. SPIE 8260, 2012, pp. 82601L

                    Paper Abstract High harmonic generation is investigated for a two-band model of a semiconductor nanostructure. Similar to an atomic two-level system, the semiconductor emits high harmonic radiation. We show how one can specifically enhance the emission for a given frequency by applying a non-trivially shaped laser pulse. Therefore, the semiconductor Bloch equations including the interband and additionally the intraband dynamics are solved numerically and the spectral shape of the input pulse is computed via an optimization algorithm. It is demonstrated that desired emission frequencies can be favored even though the overall input power is kept constant. We also suggest special metallic nano geometries to achieve enhanced localized optical fields. They are found by geometric optimization.


                      Near-field coupling and second-harmonic generation in split-ring resonator arrays

                      Y. Grynko, T. Meier, S. Linden, F.B.P. Niesler, M. Wegener, J. Förstner, AIP Conference Proceedings 1475, 2012, pp. 128-130

                      We simulate the linear and nonlinear optical response from split-ring resonator (SRR) arrays to study collective effects between the constituent SRRs that determine spectral properties of the second harmonic generation (SHG). We apply the Discontinuous Galerkin Time Domain (DGTD) method and the hydrodynamic Maxwell-Vlasov model to calculate the SHG emission. Our model is able to qualitatively reproduce and explain the non-monotonic dependence of the spectral SHG transmission measured experimentally for SRR arrays with different lattice constants


                        Collective Effects in Second-Harmonic Generation from Split-Ring-Resonator Arrays

                        S. Linden, F.B.P. Niesler, J. Förstner, Y. Grynko, T. Meier, M. Wegener, Physical Review Letters (2012), 109(1), pp. 015502

                        Optical experiments on second-harmonic generation from split-ring-resonator square arrays show a nonmonotonic dependence of the conversion efficiency on the lattice constant. This finding is interpreted in terms of a competition between dilution effects and linewidth or near-field changes due to interactions among the individual elements in the array.


                        2011

                        Injection currents in (110)-oriented GaAs/AlGaAs quantum wells: recent progress in theory and experiment

                        H.T. Duc, M. Pochwala, J. Förstner, T. Meier, S. Priyadarshi, A.M. Racu, K. Pierz, U. Siegner, M. Bieler, in: Ultrafast Phenomena in Semiconductors and Nanostructure Materials XV, SPIE, 2011

                        We experimentally and theoretically investigate injection currents generated by femtosecond single-color circularly-polarized laser pulses in (110)-oriented GaAs quantum wells. The current measurements are performed by detecting the emitted Terahertz radiation at room temperature. The microscopic theory is based on a 14 x 14 k • p band-structure calculation in combination with the multi-subband semiconductor Bloch equations. For symmetric GaAs quantum wells grown in (110) direction, an oscillatory dependence of the injection currents on the exciting photon energy is obtained. The results of the microscopic theory are in good agreement with the measurements.


                          Numerical analysis of coupled photonic crystal cavities

                          S. Declair, T. Meier, A. Zrenner, J. Förstner, Photonics and Nanostructures - Fundamentals and Applications (2011), 9(4), pp. 345-350

                          We numerically investigate the interaction dynamics of coupled cavities in planar photonic crystal slabs in different configurations. The single cavity is optimized for a long lifetime of the fundamental mode, reaching a Q-factor of ≈43, 000 using the method of gentle confinement. For pairs of cavities we consider several configurations and present a setup with strongest coupling observable as a line splitting of about 30 nm. Based on this configuration, setups with three cavities are investigated.


                            Intensity dependence of optically-induced injection currents in semiconductor quantum wells

                            M. Pochwala, H.T. Duc, J. Förstner, T. Meier, in: CLEO:2011 - Laser Applications to Photonic Applications, OSA, 2011

                            The intensity dependence of optically-induced injection currents in semiconductor quantum wells is investigated numerically. Oscillatory behavior of the electron charge current transients as function of intensity and time is predicted and explained.


                              Electrong-factor anisotropy in symmetric (110)-oriented GaAs quantum wells

                              J. Hübner, S. Kunz, S. Oertel, D. Schuh, M. Pochwała, H.T. Duc, J. Förstner, T. Meier, M. Oestreich, Physical Review B (2011), 84(4), pp. 041301 (R)

                              We demonstrate by spin quantum beat spectroscopy that in undoped symmetric (110)-oriented GaAs/AlGaAs single quantum wells, even a symmetric spatial envelope wave function gives rise to an asymmetric in-plane electron Land´e g-factor. The anisotropy is neither a direct consequence of the asymmetric in-plane Dresselhaus splitting nor a direct consequence of the asymmetric Zeeman splitting of the hole bands, but rather it is a pure higher-order effect that exists as well for diamond-type lattices. The measurements for various well widths are very well described within 14 × 14 band k·p theory and illustrate that the electron spin is an excellent meter variable for mapping out the internal—otherwise hidden—symmetries in two-dimensional systems. Fourth-order perturbation theory yields an analytical expression for the strength of the g-factor anisotropy, providing a qualitative understanding of the observed effects.


                              Simulation of the ultrafast nonlinear optical response of metal slabs

                              M. Wand, A. Schindlmayr, T. Meier, J. Förstner, Physica Status Solidi B (2011), 248(4), pp. 887-891

                              WoS

                              We present a nonequilibrium ab initio method for calculating nonlinear and nonlocal optical effects in metallic slabs with a thickness of several nanometers. The numerical analysis is based on the full solution of the time‐dependent Kohn–Sham equations for a jellium system and allows to study the optical response of metal electrons subject to arbitrarily shaped intense light pulses. We find a strong localization of the generated second‐harmonic current in the surface regions of the slabs.


                                Application of the Discontinuous Galerkin Time Domain Method to the Optics of Bi-Chiral Plasmonic Crystals

                                Y. Grynko, J. Förstner, T. Meier, A. Radke, T. Gissibl, P.V. Braun, H. Giessen, D.N. Chigrin, AIP, 2011, pp. 76-78

                                A simulation environment for metallic nanostructures based on the Discontinuous Galerkin Time Domain method is presented. It is used to model optical transmission by silver bi‐chiral plasmonic crystals. The results of simulations qualitatively and quantitavely agree with experimental measurements of transmitted circular polarization.


                                  Numerical investigation of the coupling between microdisk modes and quantum dots

                                  S. Declair, T. Meier, J. Förstner, physica status solidi (c) (2011), 8(4), pp. 1254-1257

                                  We numerically investigate the coupling between circular resonators and study strong light‐matter coupling of single as well as multiple circular resonators to quantum‐mechanical resonators in two dimensional model simulations. For all cases, the computed resonances of the coupled system as function of the detuning show anti‐crossings. The obtained mode splittings of coupled optical resonators are strongly depending on distance and cluster in almost degenerate eigenstates for large distances, as is known from coupled resonator optical waveguides. Vacuum Rabi splitting is observed for a quantum dot strongly coupled to eigenmodes of single perfectly cylindrical resonators.


                                    Intensity-dependent ultrafast dynamics of injection currents in unbiased GaAs quantum wells

                                    M. Pochwała, H.T. Duc, J. Förstner, T. Meier, physica status solidi (RRL) - Rapid Research Letters (2011), 5(3), pp. 119-121

                                    The intensity dependence of optically-induced injection currents in unbiased GaAs semiconductor quantum wells grown in [110] direction is investigated theoretically for a number of well widths. Our microscopic analysis is based on a 14 x 14 band k . p method in combination with the multisubband semiconductor Bloch equations. An oscillatory dependence of the injection current transients as function of intensity and time is predicted and explained. It is demonstrated that optical excitations involving different subbands and Rabi flopping are responsible for this complex dynamics.


                                      Theoretical approach to the ultrafast nonlinear optical response of metal slabs

                                      M. Wand, A. Schindlmayr, T. Meier, J. Förstner, in: CLEO:2011 - Laser Applications to Photonic Applications , Optical Society of America, 2011

                                      WoS

                                      We present an ab-initio method for calculating nonlinear and nonlocal optical effects in metallic slabs with sub-wavelength thickness. We find a strong localization of the second-harmonic current at the metal-vacuum interface.


                                        Application of the discontinous Galerkin time domain method to the optics of metallic nanostructures

                                        Y. Grynko, J. Förstner, T. Meier, AAPP | Atti della Accademia Peloritana dei Pericolanti (2011), 89(1)

                                        A simulation environment for metallic nanostructures based on the Discontinuous Galerkin Time Domain method is presented. The model is used to compute the linear and nonlinear optical response of split ring resonators and to study physical mechanisms that contribute to second harmonic generation.


                                        Oscillatory excitation energy dependence of injection currents in GaAs/AlGaAs quantum wells

                                        H. Thanh Duc, J. Förstner, T. Meier, S. Priyadarshi, A.M. Racu, K. Pierz, U. Siegner, M. Bieler, physica status solidi (c) (2011), 8(4), pp. 1137-1140

                                        The injection of photocurrents by femtosecond laser pulses in (110)-orientedGaAs/AlGaAs quantum wells is investigated theoretically and experimentally. The roomtemperature measurements show an oscillatory dependence of the injection current amplitude and direction on the excitation photon energy. Microscopic calculations using the semiconductor Bloch equations that are set up on the basis of k.p band structure calculations provide a detailed understanding of the experimental findings.


                                          2010

                                          Microscopic analysis of charge and spin photocurrents injected by circularly polarized one-color laser pulses in GaAs quantum wells

                                          H.T. Duc, J. Förstner, T. Meier, Physical Review B (2010), 82(11), pp. 115316-1

                                          The dynamics of charge and spin injection currents excited by circularly polarized, one-color laser beams in semiconductor quantum wells is analyzed. Our microscopic approach is based on a 14x14 k · p band-structure theory in combination with multisubband semiconductor Bloch equations which allows a detailed analysis of the photogenerated carrier distributions and coherences in k space. Charge and spin injection currents are numerically calculated for [110]- and [001]-grown GaAs quantum wells including dc population contributions and ac contributions that arise from intersubband coherences. The dependencies of the injection currents on the excitation conditions, in particular, the photon energy are computed and discussed.


                                            Tuning quantum-dot based photonic devices with liquid crystals

                                            K.A. Piegdon, S. Declair, J. Förstner, T. Meier, H. Matthias, M. Urbanski, H. Kitzerow, D. Reuter, A.D. Wieck, A. Lorke, C. Meier, Optics Express (2010), 18(8)

                                            Microdisks made from GaAs with embedded InAs quantum dots are immersed in the liquid crystal 4-cyano-4’-pentylbiphenyl (5CB). The quantum dots serve as emitters feeding the optical modes of the photonic cavity. By changing temperature, the liquid crystal undergoes a phase transition from the isotropic to the nematic state, which can be used as an effective tuning mechanism of the photonic modes of the cavity. In the nematic state, the uniaxial electrical anisotropy of the liquid crystal molecules can be exploited for orienting the material in an electric field, thus externally controlling the birefringence of the material. Using this effect, an electric field induced tuning of the modes is achieved. Numerical simulations using the finite-differences time-domain (FDTD) technique employing an anisotropic dielectric medium allow to understand the alignment of the liquid crystal molecules on the surface of the microdisk resonator.


                                            Modeling excitonic line shapes in weakly disordered semiconductor nanostructures

                                            I. Kuznetsova, N. Gőgh, J. Förstner, T. Meier, S.T. Cundiff, I. Varga, P. Thomas, Physical Review B (2010), 81(7)

                                            Excitonic spectra of weakly disordered semiconductor heterostructures are simulated on the basis of a one-dimensional tight-binding model. The influence of the length scale of weak disorder in quantum wells on the redshift of the excitonic peak and its linewidth is studied. By calculating two-dimensional Fouriertransform spectra we are able to determine the contribution of disorder to inhomogeneous and also to homogeneous broadenings separately. This disorder-induced dephasing is related to a Fano-type coupling and leads to contributions to the homogeneous linewidth that depends on energy within the inhomogeneously broadened line. The model includes heavy- and light-hole excitons and yields smaller inhomogeneous broadening for the light-hole exciton if compared to the heavy-hole exciton, which agrees qualitatively with the experiment.


                                              Self-assembled quantum dots in a liquid-crystal-tunable microdisk resonator

                                              K.A. Piegdon, M. Offer, A. Lorke, M. Urbanski, A. Hoischen, H. Kitzerow, S. Declair, J. Förstner, T. Meier, D. Reuter, A.D. Wieck, C. Meier, Physica E: Low-dimensional Systems and Nanostructures (2010), 42(10), pp. 2552-2555

                                              GaAs-based semiconductor microdisks with high quality whispering gallery modes (Q44000) have been fabricated.A layer of self-organized InAs quantumdots (QDs) served as a light source to feed the optical modes at room temperature. In order to achieve frequency tuning of the optical modes, the microdisk devices have been immersed in 4 – cyano – 4´-pentylbiphenyl (5CB), a liquid crystal(LC) with a nematic phase below the clearing temperature of TC≈34°C .We have studied the device performance in the temperature rangeof T=20-50°C, in order to investigate the influence of the nematic–isotropic phase transition on the optical modes. Moreover,we havea pplied an AC electric field to the device,which leads in the nematic phase to a reorientation of the anisotropic dielectric tensor of the liquid crystal.This electrical anisotropy can be used to achieve electrical tunability of the optical modes.Using the finite-difference time domain (FDTD) technique with an anisotropic material model, we are able to describe the influence of the liquid crystal qualitatively.


                                                Enhanced FDTD edge correction for nonlinear effects calculation

                                                C. Classen, J. Förstner, T. Meier, R. Schuhmann, in: 2010 IEEE Antennas and Propagation Society International Symposium, IEEE, 2010

                                                The electromagnetic field in the vicinity of sharp edges needs a special treatment in numeric calculation whenever accurate, fast converging results are necessary. One of the fundamental works concerning field singularities has been proposed in 1972 [1] and states that the electromagnetic energy density must be integrable over any finite domain, even if this domain contains singularities. It is shown, that the magnetic field H(, ϕ) and electric field E(, ϕ) are proportional to ∝ (t−1) for  → 0. The variable  is the distance to the edge and t has to fulfill the integrability condition and thus is restricted to 0 < t < 1. This result is often used to reduce the error corresponding to the singularity without increasing the numerical effort [2 - 5]. For this purpose, a correction factor K is estimated by inserting the proportionality into the wave equation. It is shown, that this method improves the accuracy of the result significantly, however the order of convergence is often not studied. In [4] a method to modify the material parameters in order to use analytic results to improve the numeric calculation is presented. In this contribution we will - inspired by the scheme given in [4] - develop a new method to estimate a correction factor for perfect conducting materials (PEC) and demonstrate the improvement of the results compared to the standard edge correction. Therefore analytic results (comparable to [1]) are consequently merged with the scheme in [4]. The main goal of this work is the calculation of the second harmonic generation (SHG) in the wave response of so-called metamaterials [6]. Frequently these structures contain sharp metallic edges with field singularities at the interfaces which have a strong impact on the SHG signals. Thus, an accurate simulation of singularities is highly important. However, the following approach can also be applied to many other setups, and one of them is shown in the example below.


                                                Coherent control of a single exciton qubit by optoelectronic manipulation

                                                S. Michaelis de Vasconcellos, S. Gordon, M. Bichler, T. Meier, A. Zrenner, Nature Photonics (2010), 4(8), pp. 545-548

                                                The coherent state manipulation of single quantum systems is a fundamental requirement for the implementation of quantum information processors. Exciton qubits are of particular interest for coherent optoelectronic applications, in particular due to their excellent coupling to photons. Until now, coherent manipulations of exciton qubits in semiconductor quantum dots have been performed predominantly by pulsed laser fields. Coherent control of the population of excitonic states with a single laser pulse, observed by Rabi oscillations, has been demonstrated by several groups using different techniques1,2,3. By using two laser pulses, more general state control can be achieved4, and coupling of two excitons has been reported5,6. Here, we present a conceptually new approach for implementing the coherent control of an exciton two-level system (qubit) by means of a time-dependent electric interaction. The new scheme makes use of an optical clock signal and a synchronous electric gate signal, which controls the coherent manipulation.


                                                  Anticrossing of Whispering Gallery Modes in microdisk resonators embedded in an anisotropic environment

                                                  S. Declair, C. Meier, T. Meier, J. Förstner, Photonics and Nanostructures - Fundamentals and Applications (2010), 8(4), pp. 273-277

                                                  We numerically investigate the behavior of Whispering Gallery Modes (WGMs) in circularly shaped resonators like microdisks, with diameters in the range of optical vacuum wavelengths. The microdisk is embedded in an uniaxial anisotropic dielectric environment. By changing the optical anisotropy, one obtains spectral tunability of the optical modes. The degree of tunability strongly depends on the radial (azimuthal) mode order M (N). As the modes approach each other spectrally, anticrossing is observed, leading to a rearrangement of the optical states.


                                                    Reversal of Coherently Controlled Ultrafast Photocurrents by Band Mixing in Undoped GaAs Quantum Wells

                                                    S. Priyadarshi, A.M. Racu, K. Pierz, U. Siegner, M. Bieler, H.T. Duc, J. Förstner, T. Meier, Physical Review Letters (2010), 104(21)

                                                    It is demonstrated that valence-band mixing in GaAs quantum wells tremendously modifies electronic transport. A coherent control scheme in which ultrafast currents are optically injected into undoped GaAs quantum wells upon excitation with femtosecond laser pulses is employed. An oscillatory dependence of the injection current amplitude and direction on the excitation photon energy is observed. A microscopic theoretical analysis shows that this current reversal is caused by the coupling of the light- and heavy-hole bands and that the hole currents dominate the overall current response. These surprising consequences of band mixing illuminate fundamental physics as they are unique for experiments which are able to monitor electronic transport resulting from carriers with relatively large momenta.


                                                      Microscopic theoretical analysis of optically generated injection currents in semiconductor quantum wells

                                                      H.T. Duc, J. Förstner, T. Meier, in: Ultrafast Phenomena in Semiconductors and Nanostructure Materials XIV, SPIE, 2010, pp. 76000S-76000S-9

                                                      A microscopic theory that describes injection currents in GaAs quantum wells is presented. 14 × 14 band k.p theory is used to compute the band structure including anisotropy and spin-orbit interaction. Transient injection currents are obtained via numerical solutions of the semiconductor Bloch equations. Depending on the growth direction of the considered quantum well system and the propagation and polarization directions of the incident light beam, it is possible to generate charge and/or spin photocurrents on ultrashort time scales. The dependence of the photocurrents on the excitation conditions is computed and discussed.


                                                        2009

                                                        Generation of injection currents in (110)-oriented GaAs quantum wells: experimental observation and development of a microscopic theory

                                                        M. Bieler, K. Pierz, U. Siegner, P. Dawson, H.T. Duc, J. Förstner, T. Meier, in: Ultrafast Phenomena in Semiconductors and Nanostructure Materials XIII, SPIE, 2009, pp. 721404-721404-13

                                                        We have experimentally investigated injection currents generated by all-optical excitation of GaAs/AlGaAs quantum wells excited with 130 fs optical pulses. The currents have been detected via free-space THz experiments at room temperature. Our experiments prove that Coulomb effects strongly influence injection currents. This becomes most prominently visible when exciting light-hole exciton transitions. At this photon energy we observe a pronounced phase shift of the current transients which is due to oppositely oriented heavy-hole and light-hole type contributions. We are currently developing a microscopic theory based on a 14×14 k.p model in combination with the semiconductor Bloch equations to describe the observed features quantitatively. The combined theoretical and experimental approach will allow us to analyze the influence of the bandstructure and interaction effects on the injection current amplitude and current dynamics.


                                                          Anticrossing of Whispering Gallery Modes in Microdisk Resonators Embedded in a Liquid Crystal

                                                          J. Förstner, S. Declair, C. Meier, T. Meier, in: AIP Conference Proceedings, AIP Conference Proceedings , 2009, pp. 60-62

                                                          We numerically investigate Whispering Gallery Modes (WGM) in a subwavelength microdisk resonator [1] embedded in an uniaxial anisotropic liquid crystal environment. It is shown that the WGMs have anticrossing behavior when modes of different radial mode order M or azimuthal order N approach each other spectrally.


                                                            Coupling Dynamics of Quantum Dots in a Liquid-Crystal-Tunable Microdisk Resonator

                                                            J. Förstner, C. Meier, K. Piegdon, S. Declair, A. Hoischen, M. Urbanski, T. Meier, H. Kitzerow, in: Advances in Optical Sciences Congress, OSA Technical Digest (CD) (Optical Society of America, 2009), paper NTuC2, 2009

                                                            We experimentally and theoretically investigate microdisk resonators with embedded quantum dots immersed in a liquid crystal in its nematic phase, showing the tunabililty of the photonic modes via external parameters like temperature or electric field.


                                                              2006

                                                              Optical Experiments on Second-Harmonic Generation with Metamaterials Composed of Split-Ring Resonators

                                                              M.W. Klein, C. Enkrich, M. Wegener, J. Förstner, J.V. Moloney, W. Hoyer, T. Stroucken, T. Meier, S.W. Koch, S. Linden, in: Photonic Metamaterials: From Random to Periodic, OSA, 2006

                                                              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.


                                                                Optical experiments on second-harmonic generation from metamaterials consisting of split-ring resonators

                                                                M.W. Klein, C. Enkrich, M. Wegener, J. Förstner, J.V. Moloney, W. Hoyer, T. Stroucken, T. Meier, S.W. Koch, S. Linden, in: 2006 Conference on Lasers and Electro-Optics and 2006 Quantum Electronics and Laser Science Conference, IEEE, 2006

                                                                We discuss second-harmonic generation experiments on planar arrays of magnetic split-ring resonators, using 150 fs pulses at 1.5 mum wavelength. Lithographic tuning reveals by far the largest signals when exciting the magnetic-dipole resonance.


                                                                  Open list in Research Information System

                                                                  The University for the Information Society