TY - JOUR A1 - Amthor, Matthias A1 - Weißenseel, Sebastian A1 - Fischer, Julian A1 - Kamp, Martin A1 - Schneider, Christian A1 - Höfling, Sven T1 - Electro-optical switching between polariton and cavity lasing in an InGaAs quantum well microcavity N2 - We report on the condensation of microcavity exciton polaritons under optical excitation in a microcavity with four embedded InGaAs quantum wells. The polariton laser is characterized by a distinct nonlinearity in the input-output-characteristics, which is accompanied by a drop of the emission linewidth indicating temporal coherence and a characteristic persisting emission blueshift with increased particle density. The temporal coherence of the device at threshold is underlined by a characteristic drop of the second order coherence function to a value close to 1. Furthermore an external electric field is used to switch between polariton regime, polariton condensate and photon lasing. KW - Quantum-well, -wire and -dot devices KW - Scattering KW - stimulated KW - Resonators KW - Microcavity devices Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-111130 ER - TY - JOUR A1 - Dietrich, Christof P. A1 - Steude, Anja A1 - Tropf, Laura A1 - Schubert, Marcel A1 - Kronenberg, Nils M. A1 - Ostermann, Kai A1 - Höfling, Sven A1 - Gather, Malte C. T1 - An exciton-polariton laser based on biologically produced fluorescent protein JF - Science Advances N2 - Under adequate conditions, cavity polaritons form a macroscopic coherent quantum state, known as polariton condensate. Compared to Wannier-Mott excitons in inorganic semiconductors, the localized Frenkel excitons in organic emitter materials show weaker interaction with each other but stronger coupling to light, which recently enabled the first realization of a polariton condensate at room temperature. However, this required ultrafast optical pumping, which limits the applications of organic polariton condensates. We demonstrate room temperature polariton condensates of cavity polaritons in simple laminated microcavities filled with biologically produced enhanced green fluorescent protein (eGFP). The unique molecular structure of eGFP prevents exciton annihilation even at high excitation densities, thus facilitating polariton condensation under conventional nanosecond pumping. Condensation is clearly evidenced by a distinct threshold, an interaction-induced blueshift of the condensate, long-range coherence, and the presence of a second threshold at higher excitation density that is associated with the onset of photon lasing. KW - polarition condensate KW - enhanced green fluorescent protein KW - photon lasing KW - quantum physics Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-171305 VL - 2 IS - 8 ER - TY - JOUR A1 - Dyksik, Mateusz A1 - Motyka, Marcin A1 - Sęk, Grzegorz A1 - Misiewicz, Jan A1 - Dallner, Matthias A1 - Weih, Robert A1 - Kamp, Martin A1 - Höfling, Sven T1 - Submonolayer Uniformity of Type II InAs/GaInSb W-shaped Quantum Wells Probed by Full-Wafer Photoluminescence Mapping in the Mid-infrared Spectral Range JF - Nanoscale Research Letters N2 - The spatial uniformity of GaSb- and InAs substrate-based structures containing type II quantum wells was probed by means of large-scale photoluminescence (PL) mapping realized utilizing a Fourier transform infrared spectrometer. The active region was designed and grown in a form of a W-shaped structure with InAs and GaInSb layers for confinement of electrons and holes, respectively. The PL spectra were recorded over the entire 2-in. wafers, and the parameters extracted from each spectrum, such as PL peak energy position, its linewidth and integrated intensity, were collected in a form of two-dimensional spatial maps. Throughout the analysis of these maps, the wafers' homogeneity and precision of the growth procedure were investigated. A very small variation of PL peak energy over the wafer indicates InAs quantum well width fluctuation of only a fraction of a monolayer and hence extraordinary thickness accuracy, a conclusion further supported by high uniformity of both the emission intensity and PL linewidth. KW - interband cascade lasers KW - fourier transform spectroscopy KW - mid-infrared KW - type II quantum wells KW - spatially resolved photoluminescence Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-139733 VL - 10 IS - 402 ER - TY - JOUR A1 - He, Yu-Ming A1 - Iff, Oliver A1 - Lundt, Nils A1 - Baumann, Vasilij A1 - Davanco, Marcelo A1 - Srinivasan, Kartik A1 - Höfling, Sven A1 - Schneider, Christian T1 - Cascaded emission of single photons from the biexciton in monolayered WSe\(_{2}\) JF - Nature Communications N2 - Monolayers of transition metal dichalcogenide materials emerged as a new material class to study excitonic effects in solid state, as they benefit from enormous Coulomb correlations between electrons and holes. Especially in WSe\(_{2}\), sharp emission features have been observed at cryogenic temperatures, which act as single photon sources. Tight exciton localization has been assumed to induce an anharmonic excitation spectrum; however, the evidence of the hypothesis, namely the demonstration of a localized biexciton, is elusive. Here we unambiguously demonstrate the existence of a localized biexciton in a monolayer of WSe\(_{2}\), which triggers an emission cascade of single photons. The biexciton is identified by its time-resolved photoluminescence, superlinearity and distinct polarization in micro-photoluminescence experiments. We evidence the cascaded nature of the emission process in a cross-correlation experiment, which yields a strong bunching behaviour. Our work paves the way to a new generation of quantum optics experiments with two-dimensional semiconductors. KW - lasers KW - LED KW - quantum dots KW - light sources Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-169363 VL - 7 ER - TY - JOUR A1 - Horikiri, Tomoyuki A1 - Yamaguchi, Makoto A1 - Kamide, Kenji A1 - Matsuo, Yasuhiro A1 - Byrnes, Tim A1 - Ishida, Natsuko A1 - Löffler, Andreas A1 - Höfling, Sven A1 - Shikano, Yutaka A1 - Ogawa, Tetsuo A1 - Forchel, Alfred A1 - Yamamoto, Yoshihisa T1 - High-energy side-peak emission of exciton-polariton condensates in high density regime JF - Scientific Reports N2 - In a standard semiconductor laser, electrons and holes recombine via stimulated emission to emit coherent light, in a process that is far from thermal equilibrium. Exciton-polariton condensates–sharing the same basic device structure as a semiconductor laser, consisting of quantum wells coupled to a microcavity–have been investigated primarily at densities far below the Mott density for signatures of Bose-Einstein condensation. At high densities approaching the Mott density, exciton-polariton condensates are generally thought to revert to a standard semiconductor laser, with the loss of strong coupling. Here, we report the observation of a photoluminescence sideband at high densities that cannot be accounted for by conventional semiconductor lasing. This also differs from an upper-polariton peak by the observation of the excitation power dependence in the peak-energy separation. Our interpretation as a persistent coherent electron-hole-photon coupling captures several features of this sideband, although a complete understanding of the experimental data is lacking. A full understanding of the observations should lead to a development in non-equilibrium many-body physics. KW - side-peak emission KW - exciton-polariton condensates KW - standard semiconductor laser Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-167711 VL - 6 IS - 25655 ER - TY - JOUR A1 - Jahnke, Frank A1 - Gies, Christopher A1 - Aßmann, Marc A1 - Bayer, Manfred A1 - Leymann, H.A.M. A1 - Foerster, Alexander A1 - Wiersig, Jan A1 - Schneider, Christian A1 - Kamp, Martin A1 - Höfling, Sven T1 - Giant photon bunching, superradiant pulse emission and excitation trapping in quantum-dot nanolasers JF - Nature Communications N2 - Light is often characterized only by its classical properties, like intensity or coherence. When looking at its quantum properties, described by photon correlations, new information about the state of the matter generating the radiation can be revealed. In particular the difference between independent and entangled emitters, which is at the heart of quantum mechanics, can be made visible in the photon statistics of the emitted light. The well-studied phenomenon of superradiance occurs when quantum–mechanical correlations between the emitters are present. Notwithstanding, superradiance was previously demonstrated only in terms of classical light properties. Here, we provide the missing link between quantum correlations of the active material and photon correlations in the emitted radiation. We use the superradiance of quantum dots in a cavity-quantum electrodynamics laser to show a direct connection between superradiant pulse emission and distinctive changes in the photon correlation function. This directly demonstrates the importance of quantum–mechanical correlations and their transfer between carriers and photons in novel optoelectronic devices. KW - photon bunching KW - quantum mechanics KW - superradiant pulse emission Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-166144 VL - 7 IS - 11540 ER - TY - JOUR A1 - Kim, Seonghoon A1 - Zhang, Bo A1 - Wang, Zhaorong A1 - Fischer, Julian A1 - Brodbeck, Sebastian A1 - Kamp, Martin A1 - Schneider, Christian A1 - Höfling, Sven A1 - Deng, Hui T1 - Coherent Polariton Laser JF - Physical Review X N2 - The semiconductor polariton laser promises a new source of coherent light, which, compared to conventional semiconductor photon lasers, has input-energy threshold orders of magnitude lower. However, intensity stability, a defining feature of a coherent state, has remained poor. Intensity noise many times the shot noise of a coherent state has persisted, attributed to multiple mechanisms that are difficult to separate in conventional polariton systems. The large intensity noise, in turn, limits the phase coherence. Thus, the capability of the polariton laser as a source of coherence light is limited. Here, we demonstrate a polariton laser with shot-noise-limited intensity stability, as expected from a fully coherent state. This stability is achieved by using an optical cavity with high mode selectivity to enforce single-mode lasing, suppress condensate depletion, and establish gain saturation. Moreover, the absence of spurious intensity fluctuations enables the measurement of a transition from exponential to Gaussian decay of the phase coherence of the polariton laser. It suggests large self-interaction energies in the polariton condensate, exceeding the laser bandwidth. Such strong interactions are unique to matter-wave lasers and important for nonlinear polariton devices. The results will guide future development of polariton lasers and nonlinear polariton devices. KW - polariton laser KW - condensed matter physics KW - photonics KW - quantum physics KW - coherent light Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-166597 VL - 6 IS - 011026 ER - TY - JOUR A1 - Lee, Chang-Min A1 - Lim, Hee-Jin A1 - Schneider, Christian A1 - Maier, Sebastian A1 - Höfling, Sven A1 - Kamp, Martin A1 - Lee, Yong-Hee T1 - Efficient single photon source based on \(\mu\)-fibre-coupled tunable microcavity JF - Scientific Reports N2 - Efficient and fast on-demand single photon sources have been sought after as critical components of quantum information science. We report an efficient and tunable single photon source based on an InAs quantum dot (QD) embedded in a photonic crystal cavity coupled with a highly curved \(\mu\)-fibre. Exploiting evanescent coupling between the \(\mu\)-fibre and the cavity, a high collection efficiency of 23% and Purcell-enhanced spontaneous emissions are observed. In our scheme, the spectral position of a resonance can be tuned by as much as 1.5 nm by adjusting the contact position of the \(\mu\)-fibre, which increases the spectral coupling probability between the QD and the cavity mode. Taking advantage of the high photon count rate and the tunability, the collection efficiencies and the decay rates are systematically investigated as a function of the QD-cavity detuning. KW - tapers KW - semiconductor quantum dots KW - crystal KW - nanowire KW - generation KW - nanoactivity KW - mode KW - emission Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-145835 VL - 5 IS - 14309 ER - TY - JOUR A1 - Lee, Eun-Hye A1 - Song, Jin-Dong A1 - Han, Il-Ki A1 - Chang, Soo-Kyung A1 - Langer, Fabian A1 - Höfling, Sven A1 - Forchel, Alfred A1 - Kamp, Martin A1 - Kim, Jong-Su T1 - Structural and optical properties of position-retrievable low-density GaAs droplet epitaxial quantum dots for application to single photon sources with plasmonic optical coupling JF - Nanoscale Research Letters N2 - The position of a single GaAs quantum dot (QD), which is optically active, grown by low-density droplet epitaxy (DE) (approximately 4 QDs/μm\(^{2}\)), was directly observed on the surface of a 45-nm-thick Al\(_{0.3}\)Ga\(_{0.7}\)As capping layer. The thin thickness of AlGaAs capping layer is useful for single photon sources with plasmonic optical coupling. A micro-photoluminescence for GaAs DE QDs has shown exciton/biexciton behavior in the range of 1.654 to 1.657 eV. The direct observation of positions of low-density GaAs DE QDs would be advantageous for mass fabrication of devices that use a single QD, such as single photon sources. KW - quantum dot KW - droplet epitaxy KW - micro-photoluminescence KW - single photon KW - GaAs Y1 - 2015 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-143692 VL - 10 IS - 114 ER - TY - JOUR A1 - Li, Donghai A1 - Shan, Hangyong A1 - Rupprecht, Christoph A1 - Knopf, Heiko A1 - Watanabe, Kenji A1 - Taniguchi, Takashi A1 - Qin, Ying A1 - Tongay, Sefaattin A1 - Nuß, Matthias A1 - Schröder, Sven A1 - Eilenberger, Falk A1 - Höfling, Sven A1 - Schneider, Christian A1 - Brixner, Tobias T1 - Hybridized exciton-photon-phonon states in a transition-metal-dichalcogenide van-der-Waals heterostructure microcavity JF - Physical Review Letters N2 - Excitons in atomically thin transition-metal dichalcogenides (TMDs) have been established as an attractive platform to explore polaritonic physics, owing to their enormous binding energies and giant oscillator strength. Basic spectral features of exciton polaritons in TMD microcavities, thus far, were conventionally explained via two-coupled-oscillator models. This ignores, however, the impact of phonons on the polariton energy structure. Here we establish and quantify the threefold coupling between excitons, cavity photons, and phonons. For this purpose, we employ energy-momentum-resolved photoluminescence and spatially resolved coherent two-dimensional spectroscopy to investigate the spectral properties of a high-quality-factor microcavity with an embedded WSe\(_2\) van-der-Waals heterostructure at room temperature. Our approach reveals a rich multi-branch structure which thus far has not been captured in previous experiments. Simulation of the data reveals hybridized exciton-photon-phonon states, providing new physical insight into the exciton polariton system based on layered TMDs. KW - strong coupling KW - laser spectroscopy KW - transition metal dichalcogenide KW - coherent multidimensional spectroscopy KW - exciton Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-351303 UR - https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.128.087401 SN - 1079-7114 ET - accepted version ER -