@article{BeierleinEgorovHarderetal.2021, author = {Beierlein, J. and Egorov, O. A. and Harder, T. H. and Gagel, P. and Emmerling, M. and Schneider, C. and H{\"o}fling, S. and Peschel, U. and Klembt, S.}, title = {Bloch Oscillations of Hybrid Light-Matter Particles in a Waveguide Array}, series = {Advanced Optical Materials}, volume = {9}, journal = {Advanced Optical Materials}, number = {13}, doi = {10.1002/adom.202100126}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-239814}, year = {2021}, abstract = {Bloch oscillations are a phenomenon well known from quantum mechanics where electrons in a lattice experience an oscillatory motion in the presence of an electric field gradient. Here, the authors report on Bloch oscillations of hybrid light-matter particles, called exciton-polaritons (polaritons), being confined in an array of coupled microcavity waveguides. To this end, the waveguide widths and their mutual couplings are carefully designed such that a constant energy gradient is induced perpendicular to the direction of motion of the propagating polaritons. This technique allows us to directly observe and study Bloch oscillations in real- and momentum-space. Furthermore, the experimental findings are supported by numerical simulations based on a modified Gross-Pitaevskii approach. This work provides an important transfer of basic concepts of quantum mechanics to integrated solid state devices, using quantum fluids of light.}, language = {en} } @article{SyperekAndrzejewskiRudnoRudzińskietal.2017, author = {Syperek, M. and Andrzejewski, J. and Rudno-Rudziński, W. and Maryński, A. and Sȩk, G. and Misiewicz, J. and Reithmaier, J. P. and Somers, A. and H{\"o}fling, S.}, title = {The issue of 0D-like ground state isolation in GaAs- and InP-based coupled quantum dots-quantum well systems}, series = {Journal of Physics: Conference Series}, volume = {906}, journal = {Journal of Physics: Conference Series}, number = {1}, issn = {1742-6588}, doi = {10.1088/1742-6596/906/1/012019}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-262876}, year = {2017}, abstract = {The issue of quantum mechanical coupling between a semiconductor quantum dot and a quantum well is studied in two families of GaAs- and InP- based structures at cryogenic temperatures. It is shown that by tuning the quantum well parameters one can strongly disturb the 0D-character of the coupled system ground state, initially located in a dot. The out-coupling of either an electron or a hole state from the quantum dot confining potential is viewed by a significant elongation of the photoluminescence decay time constant. Band structure calculations show that in the GaAs-based coupled system at its ground state a hole remains isolated in the dot, whereas an electron gets delocalized towards the quantum well. The opposite picture is built for the ground state of a coupled system based on InP.}, language = {en} } @article{SuchomelBrodbeckLiewetal.2017, author = {Suchomel, H. and Brodbeck, S. and Liew, T. C. H. and Amthor, M. and Klaas, M. and Klembt, S. and Kamp, M. and H{\"o}fling, S. and Schneider, C.}, title = {Prototype of a bistable polariton field-effect transistor switch}, series = {Scientific Reports}, volume = {7}, journal = {Scientific Reports}, number = {5114}, doi = {10.1038/s41598-017-05277-1}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-158323}, year = {2017}, abstract = {Microcavity exciton polaritons are promising candidates to build a new generation of highly nonlinear and integrated optoelectronic devices. Such devices range from novel coherent light emitters to reconfigurable potential landscapes for electro-optical polariton-lattice based quantum simulators as well as building blocks of optical logic architectures. Especially for the latter, the strongly interacting nature of the light-matter hybrid particles has been used to facilitate fast and efficient switching of light by light, something which is very hard to achieve with weakly interacting photons. We demonstrate here that polariton transistor switches can be fully integrated in electro-optical schemes by implementing a one-dimensional polariton channel which is operated by an electrical gate rather than by a control laser beam. The operation of the device, which is the polariton equivalent to a field-effect transistor, relies on combining electro-optical potential landscape engineering with local exciton ionization to control the scattering dynamics underneath the gate. We furthermore demonstrate that our device has a region of negative differential resistance and features a completely new way to create bistable behavior.}, language = {en} } @article{RudnoRudzińskiSyperekAndrezejewskietal.2017, author = {Rudno-Rudziński, W. and Syperek, M. and Andrezejewski, J. and Maryński, A. and Misiewicz, J. and Somers, A. and H{\"o}fling, S. and Reithmaier, J. P. and Sęk, G.}, title = {Carrier delocalization in InAs/InGaAlAs/InP quantum-dash-based tunnel injection system for 1.55 μm emission}, series = {AIP Advances}, volume = {7}, journal = {AIP Advances}, number = {1}, doi = {10.1063/1.4975634}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-181787}, year = {2017}, abstract = {We have investigated optical properties of hybrid two-dimensional-zero-dimensional (2D-0D) tunnel structures containing strongly elongated InAs/InP(001) quantum dots (called quantum dashes), emitting at 1.55 μm. These quantum dashes (QDashes) are separated by a 2.3 nm-width barrier from an InGaAs quantum well (QW), lattice matched to InP. We have tailored quantum-mechanical coupling between the states confined in QDashes and a QW by changing the QW thickness. By combining modulation spectroscopy and photoluminescence excitation, we have determined the energies of all relevant optical transitions in the system and proven the carrier transfer from the QW to the QDashes, which is the fundamental requirement for the tunnel injection scheme. A transformation between 0D and mixed-type 2D-0D character of an electron and a hole confinement in the ground state of the hybrid system have been probed by time-resolved photoluminescence that revealed considerable changes in PL decay time with the QW width changes. The experimental discoveries have been explained by band structure calculations in the framework of the eight-band k·p model showing that they are driven by delocalization of the lowest energy hole state. The hole delocalization process from the 0D QDash confinement is unfavorable for optical devices based on such tunnel injection structures.}, language = {en} } @article{LaihoPresslSchlageretal.2016, author = {Laiho, K. and Pressl, B. and Schlager, A. and Suchomel, H. and Kamp, M. and H{\"o}fling, S. and Schneider, C. and Weihs, G.}, title = {Uncovering dispersion properties in semiconductor waveguides to study photon-pair generation}, series = {Nanotechnology}, volume = {27}, journal = {Nanotechnology}, number = {43}, doi = {10.1088/0957-4484/27/43/434003}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-187025}, pages = {434003}, year = {2016}, abstract = {We investigate the dispersion properties of ridge Bragg-reflection waveguides to deduce their phasematching characteristics. These are crucial for exploiting them as sources of parametric down-conversion (PDC). In order to estimate the phasematching bandwidth we first determine the group refractive indices of the interacting modes via Fabry-Perot experiments in two distant wavelength regions. Second, by measuring the spectra of the emitted PDC photons, we gain access to their group index dispersion. Our results offer a simple approach for determining the PDC process parameters in the spectral domain, and provide important feedback for designing such sources, especially in the broadband case.}, language = {en} } @article{MotykaDyksikRyczkoetal.2016, author = {Motyka, M. and Dyksik, M. and Ryczko, K. and Weih, R. and Dallner, M. and H{\"o}fling, S. and Kamp, M. and Sęk, G. and Misiewicz, J.}, title = {Type-II quantum wells with tensile-strained GaAsSb layers for interband cascade lasers with tailored valence band mixing}, series = {Applied Physics Letters}, volume = {108}, journal = {Applied Physics Letters}, number = {10}, doi = {10.1063/1.4943193}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-189795}, year = {2016}, abstract = {Optical properties of modified type II W-shaped quantum wells have been investigated with the aim to be utilized in interband cascade lasers. The results show that introducing a tensely strained GaAsSb layer, instead of a commonly used compressively strained GaInSb, allows employing the active transition involving valence band states with a significant admixture of the light holes. Theoretical predictions of multiband k.p theory have been experimentally verified by using photoluminescence and polarization dependent photoreflectance measurements. These results open a pathway for practical realization of mid-infrared lasing devices with uncommon polarization properties including, for instance, polarization-independent midinfrared light emitters.}, language = {en} } @article{DyksikMotykaKurkaetal.2016, author = {Dyksik, M. and Motyka, M. and Kurka, M. and Ryczo, K. and Dallner, M. and H{\"o}fling, S. and Kamp, M. and Sęk, G. and Misiwicz, J.}, title = {Photoluminescence quenching mechanisms in type IIInAs/GaInSb QWs on InAs substrates}, series = {Optical and Quantum Electronics}, volume = {48}, journal = {Optical and Quantum Electronics}, number = {401}, doi = {10.1007/s11082-016-0667-y}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204672}, year = {2016}, abstract = {Optical properties of AlSb/InAs/GaInSb/InAs/AlSb quantum wells (QWs) grown on an InAs substrate were investigated from the point of view of room temperature emission in the mid- and long-wavelength infrared ranges. By means of two independent techniques of optical spectroscopy, photoreflectance and temperature-dependent photoluminescence, it was proven that the main process limiting the performance of such InAs substrate-based type II structures is related to the escape of carriers from the hole ground state of the QW. Two nonradiative recombination channels were identified. The main process was attributed to holes tunneling to the valence band of the GaAsSb spacing layer and the second one with trapping of holes by native defects located in the same layer.}, language = {en} } @article{EstrechoGaoBrodbecketal.2016, author = {Estrecho, E. and Gao, T. and Brodbeck, S. and Kamp, M. and Schneider, C. and H{\"o}fling, S. and Truscott, A. G. and Ostrovskaya, E. A.}, title = {Visualising Berry phase and diabolical points in a quantum exciton-polariton billiard}, series = {Scientific Reports}, volume = {6}, journal = {Scientific Reports}, number = {37653}, doi = {10.1038/srep37653}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-167496}, year = {2016}, abstract = {Diabolical points (spectral degeneracies) can naturally occur in spectra of two-dimensional quantum systems and classical wave resonators due to simple symmetries. Geometric Berry phase is associated with these spectral degeneracies. Here, we demonstrate a diabolical point and the corresponding Berry phase in the spectrum of hybrid light-matter quasiparticles—exciton-polaritons in semiconductor microcavities. It is well known that sufficiently strong optical pumping can drive exciton-polaritons to quantum degeneracy, whereby they form a macroscopically populated quantum coherent state similar to a Bose-Einstein condensate. By pumping a microcavity with a spatially structured light beam, we create a two-dimensional quantum billiard for the exciton-polariton condensate and demonstrate a diabolical point in the spectrum of the billiard eigenstates. The fully reconfigurable geometry of the potential walls controlled by the optical pump enables a striking experimental visualization of the Berry phase associated with the diabolical point. The Berry phase is observed and measured by direct imaging of the macroscopic exciton-polariton probability densities.}, language = {en} } @article{CzerniukBrueggemannTepperetal.2014, author = {Czerniuk, T. and Br{\"u}ggemann, C. and Tepper, J. and Brodbeck, S. and Schneider, C. and Kamp, M. and H{\"o}fling, S. and Glavin, B. A. and Yakovlev, D. R. and Akimov, A. V. and Bayer, M.}, title = {Lasing from active optomechanical resonators}, series = {Nature Communications}, volume = {5}, journal = {Nature Communications}, doi = {10.1038/ncomms5038}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-121559}, pages = {4038}, year = {2014}, abstract = {Planar microcavities with distributed Bragg reflectors (DBRs) host, besides confined optical modes, also mechanical resonances due to stop bands in the phonon dispersion relation of the DBRs. These resonances have frequencies in the 10- to 100-GHz range, depending on the resonator's optical wavelength, with quality factors exceeding 1,000. The interaction of photons and phonons in such optomechanical systems can be drastically enhanced, opening a new route towards the manipulation of light. Here we implemented active semiconducting layers into the microcavity to obtain a vertical-cavity surface-emitting laser (VCSEL). Thereby, three resonant excitations--photons, phonons and electrons--can interact strongly with each other providing modulation of the VCSEL laser emission: a picosecond strain pulse injected into the VCSEL excites long-living mechanical resonances therein. As a result, modulation of the lasing intensity at frequencies up to 40 GHz is observed. From these findings, prospective applications of active optomechanical resonators integrated into nanophotonic circuits may emerge.}, language = {en} } @article{BraunSchneiderMaieretal.2014, author = {Braun, T. and Schneider, C. and Maier, S. and Igusa, R. and Iwamoto, S. and Forchel, A. and H{\"o}fling, S. and Arakawa, Y. and Kamp, M.}, title = {Temperature dependency of the emission properties from positioned In(Ga)As/GaAs quantum dots}, series = {AIP Advances}, volume = {4}, journal = {AIP Advances}, number = {9}, issn = {2158-3226}, doi = {10.1063/1.4896284}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-115448}, year = {2014}, abstract = {In this letter we study the influence of temperature and excitation power on the emission linewidth from site-controlled InGaAs/GaAs quantum dots grown on nanoholes defined by electron beam lithography and wet chemical etching. We identify thermal electron activation as well as direct exciton loss as the dominant intensity quenching channels. Additionally, we carefully analyze the effects of optical and acoustic phonons as well as close-by defects on the emission linewidth by means of temperature and power dependent micro-photoluminescence on single quantum dots with large pitches. (C) 2014 Author(s).}, language = {en} } @article{KasprzakSivalertpornAlbertetal.2013, author = {Kasprzak, J. and Sivalertporn, K. and Albert, F. and Schneider, C. and H{\"o}fling, S. and Kamp, M. and Forchel, A. and Muljarov, E. A. and Langbein, W.}, title = {Coherence dynamics and quantum-to-classical crossover in an exciton-cavity system in the quantum strong coupling regime}, series = {New Journal of Physics}, volume = {15}, journal = {New Journal of Physics}, number = {045013}, issn = {1367-2630}, doi = {10.1088/1367-2630/15/4/045013}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-123005}, year = {2013}, abstract = {Interaction between light and matter generates optical nonlinearities, which are particularly pronounced in the quantum strong coupling regime. When a single bosonic mode couples to a single fermionic mode, a Jaynes-Cummings (JC) ladder is formed, which we realize here using cavity photons and quantum dot excitons. We measure and model the coherent anharmonic response of this strongly coupled exciton-cavity system at resonance. Injecting two photons into the cavity, we demonstrate a \(\sqrt 2\) larger polariton splitting with respect to the vacuum Rabi splitting. This is achieved using coherent nonlinear spectroscopy, specifically four-wave mixing, where the coherence between the ground state and the first (second) rung of the JC ladder can be interrogated for positive (negative) delays. With increasing excitation intensity and thus rising average number of injected photons, we observe spectral signatures of the quantum-to-classical crossover of the strong coupling regime.}, language = {en} } @article{KimKusudoLoeffleretal.2013, author = {Kim, N. Y. and Kusudo, K. and L{\"o}ffler, A. and H{\"o}fling, S. and Forchel, A. and Yamamoto, Y.}, title = {Exciton-polariton condensates near the Dirac point in a triangular lattice}, series = {New Journal of Physics}, volume = {15}, journal = {New Journal of Physics}, number = {035032}, issn = {1367-2630}, doi = {10.1088/1367-2630/15/3/035032}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-123103}, year = {2013}, abstract = {Dirac particles, massless relativistic entities, obey linear energy dispersions and hold important implications in particle physics. The recent discovery of Dirac fermions in condensed matter systems including graphene and topological insulators has generated a great deal of interest in exploring the relativistic properties associated with Dirac physics in solid-state materials. In addition, there are stimulating research activities to engineer Dirac particles, elucidating their exotic physical properties in a controllable setting. One of the successful platforms is the ultracold atom-optical lattice system, whose dynamics can be manipulated and probed in a clean environment. A microcavity exciton-polariton-lattice system offers the advantage of forming high-orbital condensation in non-equilibrium conditions, which enables one to explore novel quantum orbital order in two dimensions. In this paper, we experimentally construct the band structures near Dirac points, the vertices of the first hexagonal Brillouin zone with exciton-polariton condensates trapped in a triangular lattice. Due to the finite spectral linewidth, the direct map of band structures at Dirac points is elusive; however, we identify the linear part above Dirac points and its associated velocity value is similar to ~0.9-2 x \(10^8 cm s^{-1}\), consistent with the theoretical estimate \(1 x 10^8 cm s^{-1}\) with a \(2 \mu m\) lattice constant. We envision that the exciton-polariton condensates in lattices would be a promising solid-state platform, where the system order parameter can be accessed in both real and momentum spaces.}, language = {en} } @article{HopfmannAlbertSchneideretal.2013, author = {Hopfmann, C. and Albert, F. and Schneider, C. and H{\"o}fling, S. and Kamp, M. and Forchel, A. and Kanter, I. and Reizenstein, S.}, title = {Nonlinear emission characteristics of quantum dot-micropillar lasers in the presence of polarized optical feedback}, series = {New Journal of Physics}, volume = {15}, journal = {New Journal of Physics}, number = {025030}, issn = {1367-2630}, doi = {10.1088/1367-2630/15/2/025030}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-123127}, year = {2013}, abstract = {We report on electrically pumped quantum dot-microlasers in the presence of polarized self-feedback. The high-\(\beta\) microlasers show two orthogonal, linearly polarized emission modes which are coupled via the common gain medium. This coupling is explained in terms of gain competition between the two lasing modes and leads to distinct differences in their input-output characteristics. By applying polarized self-feedback via an external mirror, we are able to control the laser characteristics of the emission modes in terms of the output power, the coherence time and the photon statistics. We find that linearly polarized self-feedback stabilizes the lasing of a given mode, while cross-polarized feedback between the two modes reduces strongly the intensity of the other emission mode showing particular high-intensity fluctuations and even super-thermal values of the photon autocorrelation function \(g^{(2)} (\tau)\) at zero delay. Measurements of \(g^{(2)} (\tau)\) under external feedback also allow us to detect revival peaks associated with the round trip time of the external cavity. Analyzing the damping and shape of the \(g^{(2)} (\tau)\) revival peaks by a phenomenological model provides us insight into the underlying physics such as the effective exciton lifetime and gain characteristics of the quantum dots in the active region of these microlasers.}, language = {en} }