@article{29202,
  author       = {{De, Souvaraj and Singh, Karanveer and Kress, Christian and Das, Ranjan and Schwabe, Tobias and Preußler, Stefan and Kleine-Ostmann, Thomas and Scheytt, J. Christoph and Schneider, Thomas}},
  journal      = {{IEEE Photonics Technology Letters}},
  number       = {{21}},
  pages        = {{1189--1192}},
  title        = {{{Roll-Off Factor Analysis of Optical Nyquist Pulses Generated by an On-Chip Mach-Zehnder Modulator}}},
  doi          = {{10.1109/LPT.2021.3112485}},
  volume       = {{33}},
  year         = {{2021}},
}

@article{20189,
  abstract     = {{A dielectric step-index optical fiber with tube-like profile is considered, being positioned with a small gap on top of a dielectric slab waveguide. We propose a 2.5-D hybrid analytical/numerical coupled mode model for the evanescent excitation of the tube through semi-guided waves propagating in the slab at oblique angles. The model combines the directional polarized modes supported by the slab with analytic solutions for the TE-, TM-, and orbital-angular-momentum (OAM) modes of the tube-shaped fiber. Implementational details of the scheme are discussed, complemented by finite-element simulations for verification purposes. Our results include configurations with resonant in-fiber excitation of OAM modes with large orbital angular momentum and strong field enhancement.}},
  author       = {{Hammer, Manfred and Ebers, Lena and Förstner, Jens}},
  issn         = {{0306-8919}},
  journal      = {{Optical and Quantum Electronics}},
  keywords     = {{tet_topic_waveguides}},
  title        = {{{Hybrid coupled mode modelling of the evanescent excitation of a dielectric tube by semi-guided waves at oblique angles}}},
  doi          = {{10.1007/s11082-020-02595-z}},
  volume       = {{52}},
  year         = {{2020}},
}

@article{20233,
  abstract     = {{The challenge of designing new tunable nonlinear dielectric materials with tailored properties has attracted an increasing amount of interest recently. Herein, we study the effective nonlinear dielectric response of a stochastic paraelectric-dielectric composite consisting of equilibrium distributions of circular and partially penetrable disks (or parallel, infinitely long, identical, partially penetrable, circular cylinders) of a dielectric phase randomly dispersed in a continuous matrix of a paraelectric phase. The random microstructures were generated using the Metropolis Monte Carlo algorithm. The evaluation of the effective permittivity and tunability were carried out by employing either a Landau thermodynamic model or its Johnson’s approximation to describe the field-dependent permittivity of the paraelectric phase and solving continuum-electrostatics equations using finite element calculations. We reveal that the percolation threshold in this composite governs the critical behavior of the effective permittivity and tunability. For microstructures below the percolation threshold, our simulations demonstrate a strong nonlinear behaviour of the field-dependent effective permittivity and very high tunability that increases as a function of dielectric phase concentration. Above the percolation threshold, the effective permittivity shows the tendency to linearization and the tunability dramatically drops down. The highly reduced permittivity and extraordinarily high tunability are obtained for the composites with dielectric impenetrable disks at high concentrations, in which the triggering of the percolation transition is avoided. The reported results cast light on distinct nonlinear behaviour of 2D and 3D stochastic composites and can guide the design of novel composites with the controlled morphology and tailored permittivity and tunability.}},
  author       = {{Myroshnychenko, Viktor and Smirnov, Stanislav and Jose, Pious Mathews Mulavarickal and Brosseau, Christian and Förstner, Jens}},
  issn         = {{1359-6454}},
  journal      = {{Acta Materialia}},
  pages        = {{116432}},
  title        = {{{Nonlinear dielectric properties of random paraelectric-dielectric composites}}},
  doi          = {{10.1016/j.actamat.2020.10.051}},
  volume       = {{203}},
  year         = {{2020}},
}

@article{17390,
  author       = {{Chantakit, Teanchai and Schlickriede, Christian and Sain, Basudeb and Meyer, Fabian and Weiss, Thomas and Chattham, Nattaporn and Zentgraf, Thomas}},
  issn         = {{2327-9125}},
  journal      = {{Photonics Research}},
  number       = {{9}},
  pages        = {{1435--1440}},
  publisher    = {{OSA}},
  title        = {{{All-dielectric silicon metalens for two-dimensional particle manipulation in optical tweezers}}},
  doi          = {{10.1364/prj.389200}},
  volume       = {{8}},
  year         = {{2020}},
}

@article{17433,
  author       = {{Wang, D. Q. and Reuter, Dirk and Wieck, A. D. and Hamilton, A. R. and Klochan, O.}},
  issn         = {{0003-6951}},
  journal      = {{Applied Physics Letters}},
  title        = {{{Two-dimensional lateral surface superlattices in GaAs heterostructures with independent control of carrier density and modulation potential}}},
  doi          = {{10.1063/5.0009462}},
  year         = {{2020}},
}

@article{17434,
  author       = {{Kunnathully, Vinay S. and Riedl, Thomas and Trapp, Alexander and Langer, Timo and Reuter, Dirk and Lindner, Jörg K.N.}},
  issn         = {{0022-0248}},
  journal      = {{Journal of Crystal Growth}},
  title        = {{{InAs heteroepitaxy on nanopillar-patterned GaAs (111)A}}},
  doi          = {{10.1016/j.jcrysgro.2020.125597}},
  year         = {{2020}},
}

@article{17435,
  author       = {{Geier, M. and Freudenfeld, J. and Silva, J. T. and Umansky, V. and Reuter, Dirk and Wieck, A. D. and Brouwer, P. W. and Ludwig, S.}},
  issn         = {{2469-9950}},
  journal      = {{Physical Review B}},
  title        = {{{Electrostatic potential shape of gate-defined quantum point contacts}}},
  doi          = {{10.1103/physrevb.101.165429}},
  year         = {{2020}},
}

@article{17436,
  abstract     = {{<jats:p>The study of electron transport in low-dimensional systems is of importance, not only from a fundamental point of view, but also for future electronic and spintronic devices. In this context heterostructures containing a two-dimensional electron gas (2DEG) are a key technology. In particular GaAs/AlGaAs heterostructures, with a 2DEG at typically 100 nm below the surface, are widely studied. In order to explore electron transport in such systems, low-resistance ohmic contacts are required that connect the 2DEG to macroscopic measurement leads at the surface. Here we report on designing and measuring a dedicated device for unraveling the various resistance contributions in such contacts, which include pristine 2DEG series resistance, the 2DEG resistance under a contact, the contact resistance itself, and the influence of pressing a bonding wire onto a contact. We also report here a recipe for contacts with very low resistance values that remain below 10 Ω for annealing times between 20 and 350 s, hence providing the flexibility to use this method for materials with different 2DEG depths. The type of heating, temperature ramp rate and gas forming used for annealing is found to strongly influence the annealing process and hence the quality of the resulting contacts.</jats:p>}},
  author       = {{Javaid Iqbal, Muhammad and Reuter, Dirk and Wieck, Andreas Dirk and van der Wal, Caspar}},
  issn         = {{1286-0042}},
  journal      = {{The European Physical Journal Applied Physics}},
  title        = {{{Characterization of low-resistance ohmic contacts to a two-dimensional electron gas in a GaAs/AlGaAs heterostructure}}},
  doi          = {{10.1051/epjap/2020190202}},
  year         = {{2020}},
}

@article{17437,
  author       = {{Ebler, C. and Labud, P. A. and Rai, A. K. and Reuter, Dirk and Wieck, A. D. and Ludwig, A.}},
  issn         = {{2469-9950}},
  journal      = {{Physical Review B}},
  title        = {{{Electrical detection of excitonic states by time-resolved conductance measurements}}},
  doi          = {{10.1103/physrevb.101.125303}},
  year         = {{2020}},
}

@article{17523,
  abstract     = {{<jats:p>Compact and robust cold atom sources are increasingly important for quantum research, especially for transferring cutting-edge quantum science into practical applications. In this study, we report on a novel scheme that uses a metasurface optical chip to replace the conventional bulky optical elements used to produce a cold atomic ensemble with a single incident laser beam, which is split by the metasurface into multiple beams of the desired polarization states. Atom numbers ~10<jats:sup>7</jats:sup> and temperatures (about 35 μK) of relevance to quantum sensing are achieved in a compact and robust fashion. Our work highlights the substantial progress toward fully integrated cold atom quantum devices by exploiting metasurface optical chips, which may have great potential in quantum sensing, quantum computing, and other areas.</jats:p>}},
  author       = {{Zhu, Lingxiao and Liu, Xuan and Sain, Basudeb and Wang, Mengyao and Schlickriede, Christian and Tang, Yutao and Deng, Junhong and Li, Kingfai and Yang, Jun and Holynski, Michael and Zhang, Shuang and Zentgraf, Thomas and Bongs, Kai and Lien, Yu-Hung and Li, Guixin}},
  issn         = {{2375-2548}},
  journal      = {{Science Advances}},
  number       = {{31}},
  publisher    = {{American Association for the Advancement of Science}},
  title        = {{{A dielectric metasurface optical chip for the generation of cold atoms}}},
  doi          = {{10.1126/sciadv.abb6667}},
  volume       = {{6}},
  year         = {{2020}},
}

@article{17803,
  abstract     = {{We numerically simulate multiple light scattering in discrete disordered media represented by large clusters of irregular non-absorbing particles. The packing density of clusters is 0.5. With such conditions diffuse scattering is significantly reduced and light transport follows propagation channels that are determined by the particle size and topology of the medium. This kind of localization produces coherent backscattering intensity surge and enhanced negative polarization branch if compared to lower density samples.}},
  author       = {{Grynko, Yevgen and Shkuratov, Yuriy and Förstner, Jens}},
  issn         = {{0022-4073}},
  journal      = {{Journal of Quantitative Spectroscopy and Radiative Transfer}},
  keywords     = {{tet_topic_scattering}},
  pages        = {{107234}},
  title        = {{{Light backscattering from large clusters of densely packed irregular particles}}},
  doi          = {{10.1016/j.jqsrt.2020.107234}},
  volume       = {{255}},
  year         = {{2020}},
}

@article{23838,
  author       = {{Beloufa, Abbes and Bouguenna, Driss and Kermas, Nawel and As, Donat Josef}},
  issn         = {{0361-5235}},
  journal      = {{Journal of Electronic Materials}},
  pages        = {{2008--2017}},
  title        = {{{A Physics-Based Compact Static and Dynamic Characteristics Model for Al2O3/InxAl1−xN/AlN/GaN MOS-HEMTs}}},
  doi          = {{10.1007/s11664-019-07927-8}},
  year         = {{2020}},
}

@article{23840,
  author       = {{Baron, Elias and Goldhahn, Rüdiger and Deppe, Michael and As, Donat Josef and Feneberg, Martin}},
  issn         = {{0370-1972}},
  journal      = {{physica status solidi (b)}},
  title        = {{{Photoluminescence Line‐Shape Analysis of Highly n‐Type Doped Zincblende GaN}}},
  doi          = {{10.1002/pssb.201900522}},
  year         = {{2020}},
}

@article{23841,
  author       = {{Deppe, Michael and Henksmeier, Tobias and Gerlach, Jürgen W. and Reuter, Dirk and As, Donat Josef}},
  issn         = {{0370-1972}},
  journal      = {{physica status solidi (b)}},
  title        = {{{Molecular Beam Epitaxy Growth and Characterization of Germanium‐Doped Cubic Al                          x                        Ga            1−                          x                        N}}},
  doi          = {{10.1002/pssb.201900532}},
  year         = {{2020}},
}

@article{20372,
  abstract     = {{A stepwise angular spectrum method (SASM) for curved interfaces is presented to calculate the wave propagation in planar lens-like integrated optical structures based on photonic slab waveguides. The method is derived and illustrated for an effective 2D setup first and then for 3D slab waveguide lenses. We employ slab waveguides of different thicknesses connected by curved surfaces to realize a lens-like structure. To simulate the wave propagation in 3D including reflection and scattering losses, the stepwise angular spectrum method is combined with full vectorial finite element computations for subproblems with lower complexity. Our SASM results show excellent agreement with rigorous numerical simulations of the full structures with a substantially lower computational effort and can be utilized for the simulation-based design and optimization of complex and large scale setups.}},
  author       = {{Ebers, Lena and Hammer, Manfred and Förstner, Jens}},
  issn         = {{1094-4087}},
  journal      = {{Optics Express}},
  keywords     = {{tet_topic_waveguides}},
  number       = {{24}},
  pages        = {{36361}},
  title        = {{{Light diffraction in slab waveguide lenses simulated with the stepwise angular spectrum method}}},
  doi          = {{10.1364/oe.409612}},
  volume       = {{28}},
  year         = {{2020}},
}

@article{20644,
  abstract     = {{Plasmonic nanoantennas for visible and infrared radiation strongly improve the interaction of light with the matter on the nanoscale due to their strong near-field enhancement. In this study, we investigate a double-resonant plasmonic nanoantenna, which makes use of plasmonic field enhancement, enhanced outcoupling of second harmonic light, and resonant lattice effects. Using this design, we demonstrate how the efficiency of second harmonic generation can be increased significantly by fully embedding the nanoantennas into nonlinear dielectric material ZnO, instead of placing them on the surface. Investigating two different processes, we found that the best fabrication route is embedding the gold nanoantennas in ZnO using an MBE overgrowth process where a thin ZnO layer was deposited on nanoantennas fabricated on a ZnO substrate. In addition, second harmonic generation measurements show that the embedding leads to an enhancement compared to the emission of nanoantennas placed on the ZnO substrate surface. These promising results facilitate further research to determine the influence of the periodicity of the nanoantenna arrangement of the resulting SHG signal.}},
  author       = {{Volmert, Ruth and Weber, Nils and Meier, Cedrik}},
  issn         = {{1089-7550}},
  journal      = {{Journal of Applied Physics}},
  number       = {{4}},
  title        = {{{Nanoantennas embedded in zinc oxide for second harmonic generation enhancement}}},
  doi          = {{10.1063/5.0012813}},
  volume       = {{128}},
  year         = {{2020}},
}

@inbook{20847,
  author       = {{Zentgraf, Thomas and Chen, Shumei and Li, Guixin and Zhang, Shuang}},
  booktitle    = {{Nanoantennas and Plasmonics: Modelling, design and fabrication}},
  editor       = {{Werner, Douglas H. and Campbell, Sawyer D. and Kang, Lei}},
  publisher    = {{The Institution of Engineering and Technology}},
  title        = {{{Plasmonic metasurfaces for controlling harmonic generations}}},
  doi          = {{10.1049/SBEW540E_ch8}},
  year         = {{2020}},
}

@article{17995,
  author       = {{Riha, Christian and Buchholz, Sven S. and Chiatti, Olivio and Wieck, Andreas D. and Reuter, Dirk and Fischer, Saskia F.}},
  issn         = {{0003-6951}},
  journal      = {{Applied Physics Letters}},
  title        = {{{Excess noise in      Al x   Ga  1 − xAs/GaAs based quantum rings}}},
  doi          = {{10.1063/5.0002247}},
  year         = {{2020}},
}

@article{21796,
  author       = {{Schuster, J and Kim, T Y and Batke, E and Reuter, Dirk and Wieck, A D}},
  issn         = {{0268-1242}},
  journal      = {{Semiconductor Science and Technology}},
  title        = {{{Two-dimensional electron bound hole photoluminescence in GaAs in perpendicular magnetic fields}}},
  doi          = {{10.1088/1361-6641/ab89e1}},
  year         = {{2020}},
}

@article{21797,
  author       = {{Riedl, T. and Kunnathully, V. S. and Trapp, A. and Langer, T. and Reuter, Dirk and Lindner, J. K. N.}},
  issn         = {{2475-9953}},
  journal      = {{Physical Review Materials}},
  title        = {{{Strain-driven InAs island growth on top of GaAs(111) nanopillars}}},
  doi          = {{10.1103/physrevmaterials.4.014602}},
  year         = {{2020}},
}