@article{20900,
  author       = {{Albert, M. and Golla, C. and Meier, Cedrik}},
  issn         = {{0022-0248}},
  journal      = {{Journal of Crystal Growth}},
  title        = {{{Optical in-situ temperature management for high-quality ZnO molecular beam epitaxy}}},
  doi          = {{10.1016/j.jcrysgro.2020.126009}},
  volume       = {{557}},
  year         = {{2021}},
}

@article{22215,
  abstract     = {{Topological states of light represent counterintuitive optical modes localized at boundaries of finite-size optical structures that originate from the properties of the bulk. Being defined by bulk properties, such boundary states are insensitive to certain types of perturbations, thus naturally enhancing robustness of photonic circuitries. Conventionally, the N-dimensional bulk modes correspond to (N – 1)-dimensional boundary states. The higher-order bulk-boundary correspondence relates N-dimensional bulk to boundary states with dimensionality reduced by more than 1. A special interest lies in miniaturization of such higher-order topological states to the nanoscale. Here, we realize nanoscale topological corner states in metasurfaces with C6-symmetric honeycomb lattices. We directly observe nanoscale topology-empowered edge and corner localizations of light and enhancement of light–matter interactions via a nonlinear imaging technique. Control of light at the nanoscale empowered by topology may facilitate miniaturization and on-chip integration of classical and quantum photonic devices.}},
  author       = {{Kruk, Sergey S. and Gao, Wenlong and Choi, Duk-Yong and Zentgraf, Thomas and Zhang, Shuang and Kivshar, Yuri}},
  issn         = {{1530-6984}},
  journal      = {{Nano Letters}},
  number       = {{11}},
  pages        = {{4592–4597}},
  publisher    = {{ACS}},
  title        = {{{Nonlinear Imaging of Nanoscale Topological Corner States}}},
  doi          = {{10.1021/acs.nanolett.1c00449}},
  volume       = {{21}},
  year         = {{2021}},
}

@article{22450,
  abstract     = {{We realize and investigate a nonlinear metasurface taking advantage of intersubband transitions in ultranarrow GaN/AlN multi-quantum well heterostructures. Owing to huge band offsets, the structures offer resonant transitions in the telecom window around 1.55 µm. These heterostructures are functionalized with an array of plasmonic antennas featuring cross-polarized resonances at these near-infrared wavelengths and their second harmonic. This kind of nonlinear metasurface allows for substantial second-harmonic generation at normal incidence which is completely absent for an antenna array without the multi-quantum well structure underneath. While the second harmonic is originally radiated only into the plane of the quantum wells, a proper geometrical arrangement of the plasmonic elements permits the redirection of the second-harmonic light to free-space radiation, which is emitted perpendicular to the surface.}},
  author       = {{Mundry, Jan and Spreyer, Florian and Jmerik, Valentin and Ivanov, Sergey and Zentgraf, Thomas and Betz, Markus}},
  issn         = {{2159-3930}},
  journal      = {{Optical Materials Express}},
  number       = {{7}},
  publisher    = {{OSA}},
  title        = {{{Nonlinear metasurface combining telecom-range intersubband transitions in GaN/AlN quantum wells with resonant plasmonic antenna arrays}}},
  doi          = {{10.1364/ome.426236}},
  volume       = {{11}},
  year         = {{2021}},
}

@article{22533,
  author       = {{Meier, F. and Protte, M. and Baron, E. and Feneberg, M. and Goldhahn, R. and Reuter, Dirk and As, D. J.}},
  issn         = {{2158-3226}},
  journal      = {{AIP Advances}},
  title        = {{{Selective area growth of cubic gallium nitride on silicon (001) and 3C-silicon carbide (001)}}},
  doi          = {{10.1063/5.0053865}},
  year         = {{2021}},
}

@article{22723,
  author       = {{Yoon, Gwanho and Tanaka, Takuo and Zentgraf, Thomas and Rho, Junsuk}},
  issn         = {{0022-3727}},
  journal      = {{Journal of Physics D: Applied Physics}},
  title        = {{{Recent progress on metasurfaces: applications and fabrication}}},
  doi          = {{10.1088/1361-6463/ac0faa}},
  volume       = {{54}},
  year         = {{2021}},
}

@unpublished{22807,
  abstract     = {{Photonic quantum technologies [1] with applications in quantum
communication, sensing as well as quantum simulation and computing, are on the
verge of becoming commercially available. One crucial building block are
tailored nanoscale integratable quantum light sources, matching the specific
needs of use-cases. Several different approaches to realize solid-state quantum
emitters [2] with high performance [3] have been pursued. However, the
properties of the emitted single photons are always defined by the individual
quantum light source and despite numerous quantum emitter tuning
techniques [4-7], scalability is still a major challenge. Here we show an
emitter-independent method to tailor and control the properties of the single
photon emission. We demonstrate a laser-controlled down-conversion process from
an excited state of a quantum three-level system [8]. Starting from a biexciton
state, a tunable control laser field defines a virtual state in a stimulated
process. From there, spontaneous emission to the ground state leads to
optically controlled single photon emission. Based on this concept, we
demonstrate energy tuning of the single photon emission with a control laser
field. The nature of the involved quantum states furthermore provides a unique
basis for the future control of polarization and bandwidth, as predicted by
theory [9,10]. Our demonstration marks an important step towards tailored
single photon emission from a photonic quantum system based on quantum optical
principles.}},
  author       = {{Jonas, B. and Heinze, D. and Schöll, E. and Kallert, P. and Langer, T. and Krehs, S. and Widhalm, A. and Jöns, K. D. and Reuter, D. and Schumacher, S. and Zrenner, Artur}},
  booktitle    = {{arXiv:2105.12393}},
  title        = {{{Nonlinear down-conversion in a single quantum dot}}},
  year         = {{2021}},
}

@article{21932,
  abstract     = {{Gaussian-beam-like bundles of semi-guided waves propagating in a dielectric slab can excite modes with high-order optical angular momentum supported by a circular fiber. We consider a multimode step-index fiber with a high-index coating, where the waves in the slab are evanescently coupled to the modes of the fiber. Conditions for effective resonant interaction are identified. Based on a hybrid analytical–numerical coupled mode model, our simulations predict that substantial fractions of the input power can be focused into waves with specific orbital angular momentum, of excellent purity, with a clear distinction between degenerate modes with opposite vorticity.}},
  author       = {{Hammer, Manfred and Ebers, Lena and Förstner, Jens}},
  issn         = {{0740-3224}},
  journal      = {{Journal of the Optical Society of America B}},
  keywords     = {{tet_topic_waveguides}},
  number       = {{5}},
  pages        = {{1717}},
  title        = {{{Resonant evanescent excitation of guided waves with high-order optical angular momentum}}},
  doi          = {{10.1364/josab.422731}},
  volume       = {{38}},
  year         = {{2021}},
}

@article{22003,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>The coherent electron spin dynamics of an ensemble of singly charged (In,Ga)As/GaAs quantum dots in a transverse magnetic field is driven by periodic optical excitation at 1 GHz repetition frequency. Despite the strong inhomogeneity of the electron <jats:italic>g</jats:italic> factor, the spectral spread of optical transitions, and the broad distribution of nuclear spin fluctuations, we are able to push the whole ensemble of excited spins into a single Larmor precession mode that is commensurate with the laser repetition frequency. Furthermore, we demonstrate that an optical detuning of the pump pulses from the probed optical transitions induces a directed dynamic nuclear polarization and leads to a discretization of the total magnetic field acting on the electron ensemble. Finally, we show that the highly periodic optical excitation can be used as universal tool for strongly reducing the nuclear spin fluctuations and preparation of a robust nuclear environment for subsequent manipulation of the electron spins, also at varying operation frequencies.</jats:p>}},
  author       = {{Evers, E. and Kopteva, N. E. and Yugova, I. A. and Yakovlev, D. R. and Reuter, Dirk and Wieck, A. D. and Bayer, M. and Greilich, A.}},
  issn         = {{2056-6387}},
  journal      = {{npj Quantum Information}},
  title        = {{{Suppression of nuclear spin fluctuations in an InGaAs quantum dot ensemble by GHz-pulsed optical excitation}}},
  doi          = {{10.1038/s41534-021-00395-1}},
  year         = {{2021}},
}

@article{22004,
  author       = {{Schall, Johannes and Deconinck, Marielle and Bart, Nikolai and Florian, Matthias and Helversen, Martin and Dangel, Christian and Schmidt, Ronny and Bremer, Lucas and Bopp, Frederik and Hüllen, Isabell and Gies, Christopher and Reuter, Dirk and Wieck, Andreas D. and Rodt, Sven and Finley, Jonathan J. and Jahnke, Frank and Ludwig, Arne and Reitzenstein, Stephan}},
  issn         = {{2511-9044}},
  journal      = {{Advanced Quantum Technologies}},
  title        = {{{Bright Electrically Controllable Quantum‐Dot‐Molecule Devices Fabricated by In Situ Electron‐Beam Lithography}}},
  doi          = {{10.1002/qute.202100002}},
  year         = {{2021}},
}

@article{28255,
  abstract     = {{Topological photonic crystals (TPhCs) provide robust manipulation of light with built-in immunity to fabrication tolerances and disorder. Recently, it was shown that TPhCs based on weak topology with a dislocation inherit this robustness and further host topologically protected lower-dimensional localized modes. However, TPhCs with weak topology at optical frequencies have not been demonstrated so far. Here, we use scattering-type scanning near-field optical microscopy to verify mid-bandgap zero-dimensional light localization close to 100 THz in a TPhC with nontrivial Zak phase and an edge dislocation. We show that because of the weak topology, differently extended dislocation centers induce similarly strong light localization. The experimental results are supported by full-field simulations. Along with the underlying fundamental physics, our results lay a foundation for the application of TPhCs based on weak topology in active topological nanophotonics, and nonlinear and quantum optic integrated devices because of their strong and robust light localization.}},
  author       = {{Lu, Jinlong and Wirth, Konstantin G. and Gao, Wenlong and Heßler, Andreas and Sain, Basudeb and Taubner, Thomas and Zentgraf, Thomas}},
  issn         = {{2375-2548}},
  journal      = {{Science Advances}},
  number       = {{49}},
  title        = {{{Observing 0D subwavelength-localized modes at ~100 THz protected by weak topology}}},
  doi          = {{10.1126/sciadv.abl3903}},
  volume       = {{7}},
  year         = {{2021}},
}

@article{28196,
  abstract     = {{We show that narrow trenches in a high-contrast silicon-photonics slab can act as lossless power dividers for semi-guided waves. Reflectance and transmittance can be easily configured by selecting the trench width. At sufficiently high angles of incidence, the devices are lossless, apart from material attenuation and scattering due to surface roughness. We numerically simulate a series of devices within the full 0-to-1-range of splitting ratios, for semi-guided plane wave incidence as well as for excitation by focused Gaussian wave bundles. Straightforward cascading of the trenches leads to concepts for 1×M-power dividers and a polarization beam splitter.}},
  author       = {{Hammer, Manfred and Ebers, Lena and Förstner, Jens}},
  issn         = {{2578-7519}},
  journal      = {{OSA Continuum}},
  keywords     = {{tet_topic_waveguide}},
  number       = {{12}},
  pages        = {{3081}},
  title        = {{{Configurable lossless broadband beam splitters for semi-guided waves in integrated silicon photonics}}},
  doi          = {{10.1364/osac.437549}},
  volume       = {{4}},
  year         = {{2021}},
}

@article{26987,
  abstract     = {{Optical metasurfaces are perfect candidates for the phase and amplitude modulation of light, featuring an excellent basis for holographic applications. In this work, we present a dual amplitude holographic scheme based on the photon sieve principle, which is then combined with a phase hologram by utilizing the Pancharatnam–Berry phase. We demonstrate that two types of apertures, rectangular and square shapes in a gold film filled with silicon nanoantennas are sufficient to create two amplitude holograms at two different wavelengths in the visible, multiplexed with an additional phase-only hologram. The nanoantennas are tailored to adjust the spectral transmittance of the apertures, enabling the wavelength sensitivity. The phase-only hologram is implemented by utilizing the anisotropic rectangular structure. Interestingly, such three holograms have quantitative mathematical correlations with each other. Thus, the flexibility of polarization and wavelength channels can be utilized with custom-tailored features to achieve such amplitude and phase holography simultaneously without sacrificing any space-bandwidth product. The present scheme has the potential to store different pieces of information which can be displayed separately by switching the wavelength or the polarization state of the reading light beam.}},
  author       = {{Frese, Daniel and Sain, Basudeb and Zhou, Hongqiang and Wang, Yongtian and Huang, Lingling and Zentgraf, Thomas}},
  issn         = {{2192-8614}},
  journal      = {{Nanophotonics}},
  number       = {{18}},
  pages        = {{4543--4550}},
  publisher    = {{De Gruyter}},
  title        = {{{A wavelength and polarization selective photon sieve for holographic applications}}},
  doi          = {{10.1515/nanoph-2021-0440}},
  volume       = {{10}},
  year         = {{2021}},
}

@article{23728,
  abstract     = {{We demonstrate the integration of amorphous tungsten silicide superconducting nanowire single-photon detectors on titanium in-diffused lithium niobate waveguides. We show proof-of-principle detection of evanescently coupled photons of 1550 nm wavelength using bidirectional waveguide coupling for two orthogonal polarization directions. We investigate the internal detection efficiency as well as detector absorption using coupling-independent characterization measurements. Furthermore, we describe strategies to improve the yield and efficiency of these devices.}},
  author       = {{Höpker, Jan Philipp and Verma, Varun B and Protte, Maximilian and Ricken, Raimund and Quiring, Viktor and Eigner, Christof and Ebers, Lena and Hammer, Manfred and Förstner, Jens and Silberhorn, Christine and Mirin, Richard P and Woo Nam, Sae and Bartley, Tim}},
  issn         = {{2515-7647}},
  journal      = {{Journal of Physics: Photonics}},
  pages        = {{034022}},
  title        = {{{Integrated superconducting nanowire single-photon detectors on titanium in-diffused lithium niobate waveguides}}},
  doi          = {{10.1088/2515-7647/ac105b}},
  volume       = {{3}},
  year         = {{2021}},
}

@article{34054,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>Colloidal nanosphere monolayers—used as a lithography mask for site-controlled material deposition or removal—offer the possibility of cost-effective patterning of large surface areas. In the present study, an automated analysis of scanning electron microscopy (SEM) images is described, which enables the recognition of the individual nanospheres in densely packed monolayers in order to perform a statistical quantification of the sphere size, mask opening size, and sphere-sphere separation distributions. Search algorithms based on Fourier transformation, cross-correlation, multiple-angle intensity profiling, and sphere edge point detection techniques allow for a sphere detection efficiency of at least 99.8%, even in the case of considerable sphere size variations. While the sphere positions and diameters are determined by fitting circles to the spheres edge points, the openings between sphere triples are detected by intensity thresholding. For the analyzed polystyrene sphere monolayers with sphere sizes between 220 and 600 nm and a diameter spread of around 3% coefficients of variation of 6.8–8.1% for the opening size are found. By correlating the mentioned size distributions, it is shown that, in this case, the dominant contribution to the opening size variation stems from nanometer-scale positional variations of the spheres.</jats:p>}},
  author       = {{Riedl, Thomas and Lindner, Jörg}},
  issn         = {{1431-9276}},
  journal      = {{Microscopy and Microanalysis}},
  keywords     = {{Instrumentation}},
  number       = {{1}},
  pages        = {{185--195}},
  publisher    = {{Cambridge University Press (CUP)}},
  title        = {{{Automated SEM Image Analysis of the Sphere Diameter, Sphere-Sphere Separation, and Opening Size Distributions of Nanosphere Lithography Masks}}},
  doi          = {{10.1017/s1431927621013866}},
  volume       = {{28}},
  year         = {{2021}},
}

@article{26221,
  author       = {{Bartnick, Moritz and Santandrea, Matteo and Höpker, Jan Philipp and Thiele, Frederik and Ricken, Raimund and Quiring, Viktor and Eigner, Christof and Herrmann, Harald and Silberhorn, Christine and Bartley, Tim}},
  issn         = {{2331-7019}},
  journal      = {{Physical Review Applied}},
  title        = {{{Cryogenic Second-Harmonic Generation in Periodically Poled Lithium Niobate Waveguides}}},
  doi          = {{10.1103/physrevapplied.15.024028}},
  year         = {{2021}},
}

@article{25227,
  abstract     = {{<jats:title>Abstract</jats:title><jats:p>Quantum well (QW) heterostructures have been extensively used for the realization of a wide range of optical and electronic devices. Exploiting their potential for further improvement and development requires a fundamental understanding of their electronic structure. So far, the most commonly used experimental techniques for this purpose have been all-optical spectroscopy methods that, however, are generally averaging in momentum space. Additional information can be gained by angle-resolved photoelectron spectroscopy (ARPES), which measures the electronic structure with momentum resolution. Here we report on the use of extremely low-energy ARPES (photon energy ~ 7 eV) to increase depth sensitivity and access buried QW states, located at 3 nm and 6 nm below the surface of cubic-GaN/AlN and GaAs/AlGaAs heterostructures, respectively. We find that the QW states in cubic-GaN/AlN can indeed be observed, but not their energy dispersion, because of the high surface roughness. The GaAs/AlGaAs QW states, on the other hand, are buried too deep to be detected by extremely low-energy ARPES. Since the sample surface is much flatter, the ARPES spectra of the GaAs/AlGaAs show distinct features in momentum space, which can be reconducted to the band structure of the topmost surface layer of the QW structure. Our results provide important information about the samples’ properties required to perform extremely low-energy ARPES experiments on electronic states buried in semiconductor heterostructures.</jats:p>}},
  author       = {{Hajlaoui, Mahdi and Ponzoni, Stefano and Deppe, Michael and Henksmeier, Tobias and As, Donat Josef and Reuter, Dirk and Zentgraf, Thomas and Springholz, Gunther and Schneider, Claus Michael and Cramm, Stefan and Cinchetti, Mirko}},
  issn         = {{2045-2322}},
  journal      = {{Scientific Reports}},
  title        = {{{Extremely low-energy ARPES of quantum well states in cubic-GaN/AlN and GaAs/AlGaAs heterostructures}}},
  doi          = {{10.1038/s41598-021-98569-6}},
  volume       = {{11}},
  year         = {{2021}},
}

@article{23843,
  author       = {{Meier, F. and Protte, M. and Baron, E. and Feneberg, M. and Goldhahn, R. and Reuter, Dirk and As, Donat Josef}},
  issn         = {{2158-3226}},
  journal      = {{AIP Advances}},
  title        = {{{Selective area growth of cubic gallium nitride on silicon (001) and 3C-silicon carbide (001)}}},
  doi          = {{10.1063/5.0053865}},
  year         = {{2021}},
}

@techreport{53290,
  abstract     = {{In this report, we consider a semiconductor nanostructure in an optical cavity that is coupled to quantum light. We describe the semiconductor nanostructure with a parabolic band structure in a 1D k-space, while we assume a single-mode quantum field. The 1D<br> system is chosen for simplicity in both the analytical and the numerical treatment and paves the way for the description of 2D structures in the future. Therefore, instead of using parameters which are realistic for 1D systems, we rather use parameters which qualitatively correspond to 2D GaAs structures.}},
  author       = {{Rose, H. and Vasil'ev, A.N. and Tikhonova, O.V. and Meier, Torsten and Sharapova, Polina R.}},
  publisher    = {{LibreCat University}},
  title        = {{{Excitation of an electronic band structure by a single-photon Fock state}}},
  doi          = {{10.5281/ZENODO.5774985}},
  year         = {{2021}},
}

@misc{54403,
  abstract     = {{Dataset of the publication “Theoretical analysis and simulations of two-dimensional Fourier transform spectroscopy performed on exciton-polaritons of a quantum-well microcavity system“, H. Rose, J. Paul, J. K. Wahlstrand, A. Bristow, and T. Meier, Proceedings of the SPIE 11684, 1168414 (2021) ( https://doi.org/10.1117/12.2576696 ). The zip file includes the data on which the plots shown in figure 2 are based.}},
  author       = {{Rose, Hendrik and Paul, Jagannath and Wahlstrand, Jared K. and Bristow, Alan D. and Meier, Torsten}},
  publisher    = {{LibreCat University}},
  title        = {{{Theoretical analysis and simulations of two-dimensional Fourier transform spectroscopy performed on exciton-polaritons of a quantum-well microcavity system}}},
  doi          = {{10.5281/ZENODO.5153619}},
  year         = {{2021}},
}

@misc{54408,
  abstract     = {{Dataset of the publication “Accurate photon echo timing by optical freezing of exciton dephasing and rephasing in quantum dots“, ( https://doi.org/10.1038/s42005-020-00491-2 ). The zip file includes the data on which the plots shown in figures 2-5 of the main text, and supplementary figures S1-S5 are based.}},
  author       = {{Kosarev, Alexander and Rose, Hendrik and Poltavtsev, Sergey and Reichelt, Matthias and Schneider, Christian and Kamp, Martin and Höfling, Sven and Bayer, Manfred and Meier, Torsten and Akimov, Ilya}},
  publisher    = {{LibreCat University}},
  title        = {{{Accurate photon echo timing by optical freezing of exciton dephasing and rephasing in quantum dots}}},
  doi          = {{10.5281/ZENODO.5226662}},
  year         = {{2021}},
}