TY  - JOUR
A1  - Yu, Leo
A1  - Natarajan, Chandra M.
A1  - Horikiri, Tomoyuki
A1  - Langrock, Carsten
A1  - Pelc, Jason S.
A1  - Tanner, Michael G.
A1  - Abe, Eisuke
A1  - Maier, Sebastian
A1  - Schneider, Christian
A1  - Höfling, Sven
A1  - Kamp, Martin
A1  - Hadfield, Robert H.
A1  - Fejer, Martin M.
A1  - Yamamoto, Yoshihisa
T1  - Two-photon interference at telecom wavelengths for time-bin-encoded single photons from quantum-dot spin qubits
JF  - Nature Communications
N2  - Practical quantum communication between remote quantum memories rely on single photons at telecom wavelengths. Although spin-photon entanglement has been demonstrated in atomic and solid-state qubit systems, the produced single photons at short wavelengths and with polarization encoding are not suitable for long-distance communication, because they suffer from high propagation loss and depolarization in optical fibres. Establishing entanglement between remote quantum nodes would further require the photons generated from separate nodes to be indistinguishable. Here, we report the observation of correlations between a quantum-dot spin and a telecom single photon across a 2-km fibre channel based on time-bin encoding and background-free frequency downconversion. The downconverted photon at telecom wavelengths exhibits two-photon interference with another photon from an independent source, achieving a mean wavepacket overlap of greater than 0.89 despite their original wavelength mismatch (900 and 911 nm). The quantum-networking operations that we demonstrate will enable practical communication between solid-state spin qubits across long distances.
KW  - atom
KW  - 1550 nm
KW  - up-conversion
KW  - heralded entanglement
KW  - emission
KW  - interface
KW  - generation
KW  - communication
KW  - downconversion
Y1  - 2015
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-138677
VL  - 6
ER  - 
TY  - JOUR
A1  - Schlottmann, Elisabeth
A1  - Schicke, David
A1  - Krüger, Felix
A1  - Lingnau, Benjamin
A1  - Schneider, Christian
A1  - Höfling, Sven
A1  - Lüdge, Kathy
A1  - Porte, Xavier
A1  - Reitzenstein, Stephan
T1  - Stochastic polarization switching induced by optical injection in bimodal quantum-dot micropillar lasers
JF  - Optics Express
N2  - Mutual coupling and injection locking of semiconductor lasers is of great interest in non-linear dynamics and its applications for instance in secure data communication and photonic reservoir computing. Despite its importance, it has hardly been studied in microlasers operating at mu W light levels. In this context, vertically emitting quantum dot micropillar lasers are of high interest. Usually, their light emission is bimodal, and the gain competition of the associated linearly polarized fundamental emission modes results in complex switching dynamics. We report on selective optical injection into either one of the two fundamental mode components of a bimodal micropillar laser. Both modes can lock to the master laser and influence the non-injected mode by reducing the available gain. We demonstrate that the switching dynamics can be tailored externally via optical injection in very good agreement with our theory based on semi-classical rate equations. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
KW  - Nonlinear Dynamics
KW  - Bistability
KW  - Generation
KW  - Subject
KW  - Regimes
KW  - Physics
KW  - Vcsels
Y1  - 2019
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-228603
VL  - 27
IS  - 20
ER  - 
TY  - JOUR
A1  - Nitsche, Wolfgang H.
A1  - Kim, Na Young
A1  - Roumpos, Georgios
A1  - Schneider, Christian
A1  - Höfling, Sven
A1  - Forchel, Alfred
A1  - Yamamoto, Yoshihisa
T1  - Spatial correlation of two-dimensional bosonic multimode condensates
JF  - Physical Review A
N2  - The Berezinskii-Kosterlitz-Thouless (BKT) theorem predicts that two-dimensional bosonic condensates exhibit quasi-long-range order which is characterized by a slow decay of the spatial coherence. However previous measurements on exciton-polariton condensates revealed that their spatial coherence can decay faster than allowed under the BKT theory, and different theoretical explanations have already been proposed. Through theoretical and experimental study of exciton-polariton condensates, we show that the fast decay of the coherence can be explained through the simultaneous presence of multiple modes in the condensate.
KW  - Exciton-polariton condensate
KW  - Long-range order
KW  - Microcavity
KW  - Vortices
KW  - Systems
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-188897
VL  - 93
IS  - 5
ER  - 
TY  - JOUR
A1  - Lundt, Nils
A1  - Klembt, Sebastian
A1  - Cherotchenko, Evgeniia
A1  - Betzold, Simon
A1  - Iff, Oliver
A1  - Nalitov, Anton V.
A1  - Klaas, Martin
A1  - Dietrich, Christof P.
A1  - Kavokin, Alexey V.
A1  - Höfling, Sven
A1  - Schneider, Christian
T1  - Room-temperature Tamm-plasmon exciton-polaritons with a WSe\(_{2}\) monolayer
JF  - Nature Communications
N2  - Solid-state cavity quantum electrodynamics is a rapidly advancing field, which explores the frontiers of light–matter coupling. Metal-based approaches are of particular interest in this field, as they carry the potential to squeeze optical modes to spaces significantly below the diffraction limit. Transition metal dichalcogenides are ideally suited as the active material in cavity quantum electrodynamics, as they interact strongly with light at the ultimate monolayer limit. Here, we implement a Tamm-plasmon-polariton structure and study the coupling to a monolayer of WSe\(_{2}\), hosting highly stable excitons. Exciton-polariton formation at room temperature is manifested in the characteristic energy–momentum dispersion relation studied in photoluminescence, featuring an anti-crossing between the exciton and photon modes with a Rabi-splitting of 23.5 meV. Creating polaritonic quasiparticles in monolithic, compact architectures with atomic monolayers under ambient conditions is a crucial step towards the exploration of nonlinearities, macroscopic coherence and advanced spinor physics with novel, low-mass bosons.
KW  - optics and photonics
KW  - two-dimensional materials
KW  - electronic properties and materials
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-169470
VL  - 7
ER  - 
TY  - JOUR
A1  - Wurdack, Matthias
A1  - Lundt, Nils
A1  - Klaas, Martin
A1  - Baumann, Vasilij
A1  - Kavokin, Alexey V.
A1  - Höfling, Sven
A1  - Schneider, Christian
T1  - Observation of hybrid Tamm-plasmon exciton-polaritons with GaAs quantum wells and a MoSe\(_{2}\) monolayer
JF  - Nature Communications
N2  - Strong light matter coupling between excitons and microcavity photons, as described in the framework of cavity quantum electrodynamics, leads to the hybridization of light and matter excitations. The regime of collective strong coupling arises, when various excitations from different host media are strongly coupled to the same optical resonance. This leads to a well-controllable admixture of various matter components in three hybrid polariton modes. Here, we study a cavity device with four embedded GaAs quantum wells hosting excitons that are spectrally matched to the A-valley exciton resonance of a MoSe\(_{2}\) monolayer. The formation of hybrid polariton modes is evidenced in momentum resolved photoluminescence and reflectivity studies. We describe the energy and k-vector distribution of exciton-polaritons along the hybrid modes by a thermodynamic model, which yields a very good agreement with the experiment.
KW  - two-dimensional materials
KW  - microresonators
KW  - nanophotonics and plasmonics
KW  - cavity device
KW  - strong coupling
Y1  - 2017
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-170480
VL  - 8
IS  - 259
ER  - 
TY  - JOUR
A1  - Redlich, Christoph
A1  - Lingnau, Benjamin
A1  - Holzinger, Steffen
A1  - Schlottmann, Elisabeth
A1  - Kreinberg, Sören
A1  - Schneider, Christian
A1  - Kamp, Martin
A1  - Höfling, Sven
A1  - Wolters, Janik
A1  - Reitzenstein, Stephan
A1  - Lüdge, Kathy
T1  - Mode-switching induced super-thermal bunching in quantum-dot microlasers
JF  - New Journal of Physics
N2  - The super-thermal photon bunching in quantum-dot (QD) micropillar lasers is investigated both experimentally and theoretically via simulations driven by dynamic considerations. Using stochastic multi-mode rate equations we obtain very good agreement between experiment and theory in terms of intensity profiles and intensity-correlation properties of the examined QD micro-laser's emission. Further investigations of the time-dependent emission show that super-thermal photon bunching occurs due to irregular mode-switching events in the bimodal lasers. Our bifurcation analysis reveals that these switchings find their origin in an underlying bistability, such that spontaneous emission noise is able to effectively perturb the two competing modes in a small parameter region. We thus ascribe the observed high photon correlation to dynamical multistabilities rather than quantum mechanical correlations.
KW  - microlaser
KW  - nonlinear dynamics
KW  - correlation properties
KW  - photon statistics
KW  - noise and multimode dynamics
KW  - quantum dot laser
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-166286
VL  - 18
IS  - 063011
ER  - 
TY  - THES
A1  - Schneider, Christian
T1  - Konzepte zur skalierbaren Realisierung von effizienten, halbleiterbasierten Einzelphotonenquellen
T1  - Concepts for the scalable realization of efficient semiconductor single photon sources
N2  - Dem Einsatz niederdimensionaler Nanostrukturen als optisch aktives Medium wird enormes Potential vorausgesagt sowohl in den klassischen optoelektronischen Bauteilen (wie z.B. Halbleiterlasern) als auch in optischen Bauteilen der näachsten Generation (z.B. Einzelphotonenquellen oder Quellen verschränkter Photonenpaare). Dennoch konnten sich quantenpunktbasierte Halbleiterlaser, abgesehen von einigen wenigen Ausnahmen (QDLaser inc.), im industriellen Maßstab bisher nicht gegen Bauelemente mit höherdimensionalen Quantenfilmen als optisch aktivem Element durchsetzen. Deshalb scheint der Einsatz von Quantenpunkten (QPen) in nichtklassischen Lichtquellen gegenwärtig vielversprechender. Um jedoch solche Bauteile bis zur letztendlichen Marktreife zu bringen, müssen neben der starken Unterdrückung von Multiphotonenemission noch wesentliche Grundvoraussetzungen erfüllt werden: In dieser Arbeit wurden grundlegende Studien durchgeführt, welche insbesondere dem Fortschritt und den Problemen der Effizienz, des elektrischen Betriebs und der Skalierbaren Herstellung der Photonenqullen dienen sollte. Zum Einen wurden hierfür elektrisch betriebene Einzelphotonenquellen basierend auf gekoppelten QP-Mikroresonatoren realisiert und de ren Bauteileffizienz gezielt optimiert, wobei konventionelle selbstorganisierte InAs-QPe als aktives Medium eingesetzt wurden. Für die skalierbare Integration einzelner QPe in Mikroresonatoren wurde des Weiteren das gesteuerte QP-Wachstum auf vorstrukturierten Substraten optimiert und auf diese Art ortskontrollierte QPe in Bauteile integriert. Für die Realisierung hocheffizienter, elektrisch gepumpter inzelphotonenquellen wurde zunächst das Wachstum von binären InAs-QPen im Stranski-Krastanov-Modus optimiert und deren optische Eigenschaften im Detail untersucht. Durch das Einbringen einer Schicht von Siliziumatomen nahe der QP-Schicht konnten die Emitter negativ geladen werden und der helle Trionenzustand der QPe als energetischer Eigenzustand des Systems zur effizienten Extraktion einzelner Photonen ausgenutzt werden. Durch die Integration dieser geladenen QPe in elektrisch kontaktierte, auf Braggspiegel basierte Mikrotürmchen konnten Einzelphotonenquellen realisiert werden, in denen gezielt Licht-Materie- Wechselwirkungseffekte zur Steigerung der Bauteileffizienz ausgenutzt wurden. Basierend auf theoretischen Überlegungen wurde die Schichtstruktur soweit optimiert, dass letztendlich experimentell eine elektrisch gepumpte Einzelphotonenquelle mit einer Photonenemissionsrate von 47 MHz sowie einer zuvor unerreichten Bauteileffizienz von 34 % im Regime der schwachen Licht-Materie-Kopplung demonstriert werden konnte. Da Effekte der Licht-Materie-Wechselwirkung zwischen QP und Resonator neben der spektralen Resonanz ebenfalls von der relativen Position von Resonator und QP zueinander abhängen, ist eine Kombination von positionierten QPen und Bauteilausrichtung nahezu unumg¨anglich für die skalierbare, deterministische Herstellung von Systemen aus perfekt angeordnetem Emitter und Resonator. Deshalb wurden bestehende Konzepte zum geordneten Wachstum von QPen weiterentwickelt: Hierbei wurde geordnetes InAs-QP-Wachstum mit Perioden realisiert, die vergleichbare Abmessungen wie optische Resonatoren aufweisen, also Nukleationsperioden zwischen 500 nm und 4 μm. Durch ein genaues Anpassen der Wachstums- und Prozessbedingungen konnte des Weiteren die Bildung von QP-Molekülen auf den Nukleationsplätzen nahezu unterdrückt beziehungsweise gesteuert werden. Durch eine systematische Optimierung der optischen Eigenschaften der QPe konnten Emitter mit Einzelquantenpunktlinienbreiten um 100 μeV realisiert werden, was eine Grundvoraussetzung zur Studie ausgeprägter Licht-Materie-Wechselwirkungseffekte in Mikroresonatoren darstellt. Letztendlich konnten durch die Integration derartiger QPe in optisch sowie elektrisch betriebene Mikroresonatoren erstmals Bauteile realisiert werden, welche einige der prinzipiellen, an eine Einzelphotonenquelle gestellten Anforderungen erfüllen. Insbesondere konnten deutliche Signaturen der schwachen Licht-Materie-Kopplung einzelner positionierter QPe in photonische Kristallresonatoren, Mikroscheibenresonatoren sowie Mikrotürmchenresonatoren festgestellt werden. Darüberhinaus konnte an einem spektral resonanten System aus einem positionierten QP und der Grundmode eines Mikrotürmchenresonators eindeutig Einzelphotonenemission unter optischer Anregung demonstriert werden. Ebenfalls konnten Mikrotürmchenresonatoren mit integrierten positionierten QPen erstmals elektrisch betrieben werden und somit die Grundvoraussetzung für eine der skalierbaren Herstellung effizienter Einzelphotonenquellen geschaffen werden.
N2  - Employing low dimensional nanostructures as active medium in classical optoelectronic devices (for instance semiconductor laser diodes) as well as optical devices of the next generation (such as single photon sources or sources of entangled photon pairs promises enormous potential. Yet, despite some exceptions (for example QDLasers inc.), quantum dot (QD)-based semiconductor lasers can hardly compete with devices exploiting higher dimensional gain material so far. Hence, using QDs as single photon emitters seems very promising. In order to achieve compatibility on the market, some urgent pre-requisites still need to be met in such devices besides the surpression of multiphoton emission: • Efficiency: Only a highly efficient single photon source can be reasonably employed in applications. • Electrical operation: In order to achieve a high integration density and for reasons of user friendlyness, the device needs to be driven electrically. • Scalability: The scalable fabrication of single photon sources is pre-requisite and one of the greatest technological challenges. • Temperature: Eventually, single photon sources will only be established in the wide field of secure data transmission if their operation at room temperature can be assured. In this work, basic studies were carried out especially devoted to the progress in the first three challenges. On the one hand, electrically driven single photon sources based on coupled QD-microcavities were realized and optimized by employing conventional self organized InAs QDs as active material. On the other hand, in order to facilitate a scalable integration of single QDs into microcavities, directed QD nucleation on pre-patterned substrate was optimized. These site-controlled QDs were at last integrated into resonator devices. In order to realize highly efficient, electrically driven single photon sources, at first the growth of binary Stranski-Krastanov InAs QDs was optimized and their emission properties were investigated in detail. By introducing Silicon atoms in the vicinity of the QD-layer, the emitters could be negatively charged. The resulting bright trion state of the QDs can subsequently be exploited as the energetic eigenstate of the system for the extraction of single photons. By integrating these charged QDs in contacted, Bragg-reflector based micropillars, single photon sources were realized exploiting light-matter coupling to enhance the device’s efficiency. Based on theoretical considerations, the grown layer sequence was optimized to an extent that eventually an electrically driven single photon source with an emission rate of 47 MHz and an unprecedented device efficiency of 34 % in the weak coupling regime could be demonstrated. Since the effects of light-matter coupling between QD and resonator rely on the QD’s position in the device, a combination of site-controlled QD-growth and device alignment is almost inevitable for a scalable, deterministic fabrication of perfectly aligned emittercavity systems. Therefore, existing concepts for ordered QD-growth were adapted and improved [KH07]: Ordered QD-growth on periods comparable to dimensions of optical resonators between 500 nm und 4 μm was realized. By carefully adjusting the growth and process conditions, formation of QD-molecules on nucleation sites could be controlled and supressed almost entirely. Carrying out a systematic optimization of the QD’s optical properties, emitters with single QD-linewidth around 100 μeV were realized. This is pre-requsite for the study of pronounced light-matter interaction in microcavities. Finally, the integration of such QDs in optically and electrically driven microresonators resulted in devices demonstrating some of the fundamental properties requested from a single photon source. Pronounced signatures of the weak light-matter coupling between a site-controlled QD in a photonic crystal cavity, a microdisk cavity and micropillar cavities were observed. Furthermore, single photon emission of a spectrally resonant system of sitecontrolled QD and micropillar cavity under pulsed optical excitation was unambigiously demonstrated. Beyond this, micropillar cavities with site-controlled QDs were electrically driven for the first time, which is pre-requisite for the scalable fabrication of efficient single photon sources.
KW  - Einzelphotonenemission
KW  - Quantenpunkt
KW  - Positionierung
KW  - Drei-Fünf-Halbleiter
KW  - Optischer Resonator
KW  - Mikrokavität
KW  - Single photon emission
KW  - quantum dot
KW  - site-controlled
KW  - semiconductor
KW  - microcavity
Y1  - 2011
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-73506
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  - 
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  - Rau, Markus
A1  - Heindel, Tobias
A1  - Unsleber, Sebastian
A1  - Braun, Tristan
A1  - Fischer, Julian
A1  - Frick, Stefan
A1  - Nauerth, Sebastian
A1  - Schneider, Christian
A1  - Vest, Gwenaelle
A1  - Reitzenstein, Stephan
A1  - Kamp, Martin
A1  - Forchel, Alfred
A1  - Höfling, Sven
A1  - Weinfurter, Harald
T1  - Free space quantum key distribution over 500 meters using electrically driven quantum dot single-photon sources-a proof of principle experiment
JF  - New Journal of Physics
N2  - Highly efficient single-photon sources (SPS) can increase the secure key rate of quantum key distribution (QKD) systems compared to conventional attenuated laser systems. Here we report on a free space QKD test using an electrically driven quantum dot single-photon source (QD SPS) that does not require a separate laser setup for optical pumping and thus allows for a simple and compact SPS QKD system. We describe its implementation in our 500 m free space QKD system in downtown Munich. Emulating a BB84 protocol operating at a repetition rate of 125 MHz, we could achieve sifted key rates of 5-17 kHz with error ratios of 6-9% and g((2))(0)-values of 0.39-0.76.
KW  - QKD
KW  - electrically driven
KW  - free space
KW  - quantum dots
KW  - quantum key distribution
Y1  - 2014
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-116760
VL  - 16
IS  - 043003
ER  -