TY - JOUR AB - A series of new organic donor–π–acceptor dyes incorporating a diquat moiety as a novel electron-acceptor unit have been synthesized and characterized. The analytical data were supported by DFT calculations. These dyes were explored in the aerobic thiocyanation of indoles and pyrroles. Here they showed a high photocatalytic activity under visible light, giving isolated yields of up to 97 %. In addition, the photocatalytic activity of standalone diquat and methyl viologen through formation of an electron donor acceptor complex is presented. AU - Meier, Armin AU - Badalov, Sabuhi AU - Biktagirov, Timur AU - Schmidt, Wolf Gero AU - Wilhelm, René ID - 43827 IS - 22 JF - Chemistry – A European Journal KW - General Chemistry KW - Catalysis KW - Organic Chemistry SN - 0947-6539 TI - Diquat Based Dyes: A New Class of Photoredox Catalysts and Their Use in Aerobic Thiocyanation VL - 29 ER - TY - JOUR AB - Perfect vector vortex beams (PVVBs) have attracted considerable interest due to their peculiar optical features. PVVBs are typically generated through the superposition of perfect vortex beams, which suffer from the limited number of topological charges (TCs). Furthermore, dynamic control of PVVBs is desirable and has not been reported. We propose and experimentally demonstrate hybrid grafted perfect vector vortex beams (GPVVBs) and their dynamic control. Hybrid GPVVBs are generated through the superposition of grafted perfect vortex beams with a multifunctional metasurface. The generated hybrid GPVVBs possess spatially variant rates of polarization change due to the involvement of more TCs. Each hybrid GPVVB includes different GPVVBs in the same beam, adding more design flexibility. Moreover, these beams are dynamically controlled with a rotating half waveplate. The generated dynamic GPVVBs may find applications in the fields where dynamic control is in high demand, including optical encryption, dense data communication, and multiple particle manipulation. AU - Ahmed, Hammad AU - Ansari, Muhammad Afnan AU - Li, Yan AU - Zentgraf, Thomas AU - Mehmood, Muhammad Qasim AU - Chen, Xianzhong ID - 45868 IS - 1 JF - Nature Communications KW - General Physics and Astronomy KW - General Biochemistry KW - Genetics and Molecular Biology KW - General Chemistry KW - Multidisciplinary SN - 2041-1723 TI - Dynamic control of hybrid grafted perfect vector vortex beams VL - 14 ER - TY - JOUR AB - Interference between single photons is key for many quantum optics experiments and applications in quantum technologies, such as quantum communication or computation. It is advantageous to operate the systems at telecommunication wavelengths and to integrate the setups for these applications in order to improve stability, compactness and scalability. A new promising material platform for integrated quantum optics is lithium niobate on insulator (LNOI). Here, we realise Hong-Ou-Mandel (HOM) interference between telecom photons from an engineered parametric down-conversion source in an LNOI directional coupler. The coupler has been designed and fabricated in house and provides close to perfect balanced beam splitting. We obtain a raw HOM visibility of (93.5 ± 0.7) %, limited mainly by the source performance and in good agreement with off-chip measurements. This lays the foundation for more sophisticated quantum experiments in LNOI. AU - Babel, Silia AU - Bollmers, Laura AU - Massaro, Marcello AU - Luo, Kai Hong AU - Stefszky, Michael AU - Pegoraro, Federico AU - Held, Philip AU - Herrmann, Harald AU - Eigner, Christof AU - Brecht, Benjamin AU - Padberg, Laura AU - Silberhorn, Christine ID - 45850 IS - 14 JF - Optics Express KW - Atomic and Molecular Physics KW - and Optics SN - 1094-4087 TI - Demonstration of Hong-Ou-Mandel interference in an LNOI directional coupler VL - 31 ER - TY - JOUR AU - Bopp, Frederik AU - Schall, Johannes AU - Bart, Nikolai AU - Vögl, Florian AU - Cullip, Charlotte AU - Sbresny, Friedrich AU - Boos, Katarina AU - Thalacker, Christopher AU - Lienhart, Michelle AU - Rodt, Sven AU - Reuter, Dirk AU - Ludwig, Arne AU - Wieck, Andreas D. AU - Reitzenstein, Stephan AU - Müller, Kai AU - Finley, Jonathan J. ID - 46133 IS - 16 JF - Physical Review B SN - 2469-9950 TI - Coherent driving of direct and indirect excitons in a quantum dot molecule VL - 107 ER - TY - JOUR AU - Littmann, Mario AU - Reuter, Dirk AU - As, Donat Josef ID - 46132 IS - 7 JF - physica status solidi (b) KW - Condensed Matter Physics KW - Electronic KW - Optical and Magnetic Materials SN - 0370-1972 TI - Remote Epitaxy of Cubic Gallium Nitride on Graphene‐Covered 3C‐SiC Substrates by Plasma‐Assisted Molecular Beam Epitaxy VL - 260 ER - TY - JOUR AB - This work reports a fully guided setup for single-mode squeezing on integrated titanium-indiffused periodically poled nonlinear resonators. A continuous-wave laser beam is delivered and the squeezed field is collected by single-mode fibers; up to −3.17(9) dB of useful squeezing is available in fibers. To showcase the usefulness of such a fiber-coupled device, we applied the generated squeezed light in a fiber-based phase sensing experiment, showing a quantum enhancement in the signal-to-noise ratio of 0.35 dB. Moreover, our investigation of the effect of photorefraction on the cavity resonance condition suggests that it causes system instabilities at high powers. AU - Domeneguetti, Renato AU - Stefszky, Michael AU - Herrmann, Harald AU - Silberhorn, Christine AU - Andersen, Ulrik L. AU - Neergaard-Nielsen, Jonas S. AU - Gehring, Tobias ID - 46138 IS - 11 JF - Optics Letters KW - Atomic and Molecular Physics KW - and Optics SN - 0146-9592 TI - Fully guided and phase locked Ti:PPLN waveguide squeezing for applications in quantum sensing VL - 48 ER - TY - JOUR AB - Site-controlled Ga droplets on AlGaAs substrates are fabricated using area-selective deposition of Ga through apertures in a mask during molecular beam epitaxy (MBE). The Ga droplets can be crystallized into GaAs quantum dots using a crystallization step under As flux. In order to model the complex process, including the masked deposition of the droplets and a reduction of their number during a thermal annealing step, a multiscale kinetic Monte Carlo (mkMC) simulation of self-assembled Ga droplet formation on AlGaAs is expanded for area-selective deposition. The simulation has only two free model parameters: the activation energy for surface diffusion and the activation energy for thermal escape of adatoms from a droplet. Simulated droplet numbers within the opening of the aperture agree quantitatively with the experimental results down to the perfect site-control, with one droplet per aperture. However, the model parameters are different compared to those of the self-assembled droplet growth. We attribute this to the presence of the mask in close proximity to the surface, which modifies the local process temperature and the As background. This approach also explains the dependence of the model parameters on the size of the aperture. AU - Feddersen, Stefan AU - Zolatanosha, Viktoryia AU - Alshaikh, Ahmed AU - Reuter, Dirk AU - Heyn, Christian ID - 46278 IS - 3 JF - Nanomaterials KW - General Materials Science KW - General Chemical Engineering SN - 2079-4991 TI - Modeling of Masked Droplet Deposition for Site-Controlled Ga Droplets VL - 13 ER - TY - JOUR AU - Lange, Nina Amelie AU - Schapeler, Timon AU - Höpker, Jan Philipp AU - Protte, Maximilian AU - Bartley, Tim ID - 46468 IS - 2 JF - Physical Review A SN - 2469-9926 TI - Degenerate photons from a cryogenic spontaneous parametric down-conversion source VL - 108 ER - TY - CONF AB - We present a miniaturized pulse shaping device that creates an arbitrary dispersion through the interaction of multiple metasurfaces on less than 2 mm3 volume. For this, a metalens and a grating-metasurface between two silver mirrors are fabricated. The grating contains further phase information to achieve the device's pulse shaping functionality. AU - Geromel, René AU - Georgi, Philip AU - Protte, Maximilian AU - Bartley, Tim AU - Huang, Lingling AU - Zentgraf, Thomas ID - 46485 T2 - CLEO: Fundamental Science 2023 TI - Dispersion control with integrated plasmonic metasurfaces ER - TY - JOUR AB - We present the fabrication of strain-free quantum dots in the In0.53Ga0.47As/In0.52Al0.48As-system lattice matched to InP, as future sources for single and entangled photons for long-haul fiber-based quantum communication in the optical C-band. We achieved these quantum dots by local droplet etching via InAl droplets in an In0.52Al0.48As layer and subsequent filling of the holes with In0.53Ga0.47As. Here, we present detailed investigations of the hole morphologies measured by atomic force microscopy. Statistical analysis of a set of nanoholes reveals a high degree of symmetry for nearly half of them when etched at optimized temperatures. Overgrowth with 50–150 nm In0.52Al0.48As increases their diameter and elongates the holes along the [01̄1]-direction. By systematically scanning the parameter space, we were able to fill the holes with In0.53Ga0.47As, and by capping the filled holes and performing photoluminescence measurements, we observe photoluminescence emission in the O-band up into the C-band depending on the filling height of the nanoholes. AU - Deutsch, D. AU - Buchholz, C. AU - Zolatanosha, V. AU - Jöns, K. D. AU - Reuter, D. ID - 44851 IS - 5 JF - AIP Advances KW - General Physics and Astronomy SN - 2158-3226 TI - Telecom C-band photon emission from (In,Ga)As quantum dots generated by filling nanoholes in In0.52Al0.48As layers VL - 13 ER - TY - CONF AU - Elsner, Julia AU - Tenberge, Claudia AU - Fechner, Sabine ED - van Vorst, Helena ID - 45371 T2 - Lernen, Lehren und Forschen in einer digital geprägten Welt TI - Videoanalyse des Modellierprozesses von Grundschüler*innen VL - 43 ER - TY - JOUR AU - Zscherp, Mario Fabian AU - Jentsch, Silas Aurel AU - Müller, Marius Johannes AU - Lider, Vitalii AU - Becker, Celina AU - Chen, Limei AU - Littmann, Mario AU - Meier, Falco AU - Beyer, Andreas AU - Hofmann, Detlev Michael AU - As, Donat Josef AU - Klar, Peter Jens AU - Volz, Kerstin AU - Chatterjee, Sangam AU - Schörmann, Jörg ID - 46741 IS - 33 JF - ACS Applied Materials & Interfaces KW - General Materials Science SN - 1944-8244 TI - Overcoming the Miscibility Gap of GaN/InN in MBE Growth of Cubic InxGa1–xN VL - 15 ER - TY - JOUR AU - Schubatzky, Thomas AU - Burde, Jan-Philipp AU - Große-Heilmann, Rike Isabel AU - Haagen-Schützenhöfer, Claudia AU - Riese, Josef AU - Weiler, David ID - 47085 JF - Computers & Education KW - Education KW - General Computer Science SN - 0360-1315 TI - Predicting the development of digital media PCK/TPACK: The role of PCK, motivation to use digital media, interest in and previous experience with digital media VL - 206 ER - TY - JOUR AU - Zhai, Xiaokun AU - Ma, Xuekai AU - Gao, Ying AU - Xing, Chunzi AU - Gao, Meini AU - Dai, Haitao AU - Wang, Xiao AU - Pan, Anlian AU - Schumacher, Stefan AU - Gao, Tingge ID - 40274 IS - 13 JF - Physical Review Letters TI - Electrically controlling vortices in a neutral exciton polariton condensate at room temperature VL - 131 ER - TY - GEN AB - In planar microcavities, the transverse-electric and transverse-magnetic (TE-TM) mode splitting of cavity photons arises due to their different penetration into the Bragg mirrors and can result in optical spin-orbit coupling (SOC). In this work, we find that in a liquid crystal (LC) microcavity filled with perovskite microplates, the pronounced TE-TM splitting gives rise to a strong SOC that leads to the spatial instability of microcavity polariton condensates under single-shot excitation. Spatially varying hole burning and mode competition occurs between polarization components leading to different condensate profiles from shot to shot. The single-shot polariton condensates become stable when the SOC vanishes as the TE and TM modes are spectrally well separated from each other, which can be achieved by application of an electric field to our LC microcavity with electrically tunable anisotropy. Our findings are well reproduced and traced back to their physical origin by our detailed numerical simulations. With the electrical manipulation our work reveals how the shot-to-shot spatial instability of spatial polariton profiles can be engineered in anisotropic microcavities at room temperature, which will benefit the development of stable polariton-based optoeletronic and light-emitting devices. AU - Gao, Ying AU - Ma, Xuekai AU - Zhai, Xiaokun AU - Xing, Chunzi AU - Gao, Meini AU - Dai, Haitao AU - Wu, Hao AU - Liu, Tong AU - Ren, Yuan AU - Wang, Xiao AU - Pan, Anlian AU - Hu, Wei AU - Schumacher, Stefan AU - Gao, Tingge ID - 47532 T2 - arXiv:2305.01368 TI - Single-shot spatial instability and electric control of polariton condensates at room temperature ER - TY - GEN AB - The control and active manipulation of spin-orbit coupling (SOC) in photonic systems is fundamental in the development of modern spin optics and topological photonic devices. Here, we demonstrate the control of an artificial Rashba-Dresselhaus (RD) SOC mediated by photochemical reactions in a microcavity filled with an organic single-crystal of photochromic phase-change character. Splitting of the circular polarization components of the optical modes induced by photonic RD SOC is observed experimentally in momentum space. By applying an ultraviolet light beam, we control the spatial molecular orientation through a photochemical reaction and with that we control the energies of the photonic modes. This way we realize a reversible conversion of spin-splitting of the optical modes with different energies, leading to an optically controlled switching between circularly and linearly polarized emission from our device. Our strategy of in situ and reversible engineering of SOC induced by a light field provides a promising approach to actively design and manipulate synthetic gauge fields towards future on-chip integration in photonics and topological photonic devices. AU - Liang, Qian AU - Ma, Xuekai AU - Ren, Jiahuan AU - Long, Teng AU - Gu, Chunling AU - An, Cunbin AU - Fu, Hongbing AU - Schumacher, Stefan AU - Liao, Qing ID - 47533 T2 - arXiv:2309.07652 TI - Photochemical reaction enabling the engineering of photonic spin-orbit coupling in organic-crystal optical microcavities ER - TY - GEN AB - Topological states have been widely investigated in different types of systems and lattices. In the present work, we report on topological edge states in double-wave (DW) chains, which can be described by a generalized Aubry-Andr\'e-Harper (AAH) model. For the specific system of a driven-dissipative exciton polariton system we show that in such potential chains, different types of edge states can form. For resonant optical excitation, we further find that the optical nonlinearity leads to a multistability of different edge states. This includes topologically protected edge states evolved directly from individual linear eigenstates as well as additional edge states that originate from nonlinearity-induced localization of bulk states. Extending the system into two dimensions (2D) by stacking horizontal DW chains in the vertical direction, we also create 2D multi-wave lattices. In such 2D lattices multiple Su-Schrieffer-Heeger (SSH) chains appear along the vertical direction. The combination of DW chains in the horizontal and SSH chains in the vertical direction then results in the formation of higher-order topological insulator corner states. AU - Schneider, Tobias AU - Gao, Wenlong AU - Zentgraf, Thomas AU - Schumacher, Stefan AU - Ma, Xuekai ID - 47531 T2 - arXiv:2303.12593 TI - Topological edge and corner states in coupled wave lattices in nonlinear polariton condensates ER - TY - GEN AB - Exceptional points (EPs) with their intriguing spectral topology have attracted considerable attention in a broad range of physical systems, with potential sensing applications driving much of the present research in this field. Here we theoretically demonstrate the realization of EPs in a system with significant nonlinearity, a non-equilibrium exciton-polariton condensate. With the possibility to control loss and gain and nonlinearity by optical means, this system allows for a comprehensive analysis of the interplay of nonlinearities (Kerr-type and saturable gain) and non-Hermiticity. Not only do we find that EPs can be intentionally shifted in parameter space by the saturable gain, we also observe intriguing rotations and intersections of Riemann surfaces, and find nonlinearity-enhanced sensing capabilities. Our results are quite general in nature and illustrate the potential of tailoring spectral topology and related phenomena in non-Hermitian systems by nonlinearity. AU - Wingenbach, Jan AU - Schumacher, Stefan AU - Ma, Xuekai ID - 47529 T2 - arXiv:2305.04855 TI - Tweaking Spectral Topology and Exceptional Points by Nonlinearity in Non-Hermitian Polariton Systems ER - TY - CHAP AU - Zentgraf, Thomas ED - Panoiu, Nicoae C. ID - 47543 SN - 978-0-323-90614-2 T2 - Fundamentals and Applications of Nonlinear Nanophotonics TI - Symmetry governed nonlinear selection rules in nanophotonics ER - TY - JOUR AU - Tenberge, Claudia ID - 47868 JF - Grundschule Sachunterricht TI - Ungeliebte Tiere in der Stadt VL - 98 ER -