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 -