@article{22053,
  author       = {{Spychala, K. J. and Mackwitz, P. and Widhalm, A. and Berth, G. and Zrenner, A.}},
  issn         = {{0021-8979}},
  journal      = {{Journal of Applied Physics}},
  title        = {{{Spatially resolved light field analysis of the second-harmonic signal of χ(2)-materials in the tight focusing regime}}},
  doi          = {{10.1063/1.5133476}},
  year         = {{2020}},
}

@article{22054,
  author       = {{Spychala, K. J. and Mackwitz, P. and Widhalm, A. and Berth, Gerhard and Zrenner, Artur}},
  issn         = {{0021-8979}},
  journal      = {{Journal of Applied Physics}},
  title        = {{{Spatially resolved light field analysis of the second-harmonic signal of χ(2)-materials in the tight focusing regime}}},
  doi          = {{10.1063/1.5133476}},
  year         = {{2020}},
}

@article{16839,
  author       = {{Sain, Basudeb and Zentgraf, Thomas}},
  issn         = {{2047-7538}},
  journal      = {{Light: Science & Applications}},
  pages        = {{67}},
  title        = {{{Metasurfaces help lasers to mode-lock}}},
  doi          = {{10.1038/s41377-020-0312-1}},
  volume       = {{9}},
  year         = {{2020}},
}

@article{16931,
  author       = {{Zhou, Hongqiang and Sain, Basudeb and Wang, Yongtian and Schlickriede, Christian and Zhao, Ruizhe and Zhang, Xue and Wei, Qunshuo and Li, Xiaowei and Huang, Lingling and Zentgraf, Thomas}},
  issn         = {{1936-0851}},
  journal      = {{ACS Nano}},
  number       = {{5}},
  pages        = {{5553–5559}},
  title        = {{{Polarization-Encrypted Orbital Angular Momentum Multiplexed Metasurface Holography}}},
  doi          = {{10.1021/acsnano.9b09814}},
  volume       = {{14}},
  year         = {{2020}},
}

@article{16944,
  author       = {{Schlickriede, Christian and Kruk, Sergey S. and Wang, Lei and Sain, Basudeb and Kivshar, Yuri and Zentgraf, Thomas}},
  issn         = {{1530-6984}},
  journal      = {{Nano Letters}},
  number       = {{6}},
  pages        = {{4370–4376}},
  title        = {{{Nonlinear imaging with all-dielectric metasurfaces}}},
  doi          = {{10.1021/acs.nanolett.0c01105}},
  volume       = {{20}},
  year         = {{2020}},
}

@article{15480,
  abstract     = {{<jats:p>The nonlinear processes of frequency conversion such as second harmonic generation (SHG) usually obey certain selection rules, resulting from the preservation of different kinds of physical quantities, e.g. the angular momentum. For the SHG created by a monolayer of transition-metal dichalcogenides (TMDCs) such as WS<jats:sub>2</jats:sub>, the valley-exciton locked selection rule predicts an SHG signal in the cross-polarization state. By combining plasmonic nanostructures with a monolayer of TMDC, a hybrid metasurface is realized, which affects this nonlinear process because of an additional polarization conversion process. Here, we observe that the plasmonic metasurface modifies the light-matter interaction with the TMDC, resulting in an SHG signal that is co-polarized with respect to the incident field, which is usually forbidden for the monolayers of TMDC. We fabricate such hybrid metasurfaces by placing plasmonic nanorods on top of a monolayer WS<jats:sub>2</jats:sub> and study the valley-exciton locked SHG emission from such system for different parameters, such as wavelength and polarization. Furthermore, we show the potential of the hybrid metasurface for tailoring nonlinear processes by adding additional phase information to the SHG signal using the Pancharatnam-Berry phase effect. This allows direct tailoring of the SHG emission to the far-field.</jats:p>}},
  author       = {{Spreyer, Florian and Zhao, Ruizhe and Huang, Lingling and Zentgraf, Thomas}},
  issn         = {{2192-8614}},
  journal      = {{Nanophotonics}},
  number       = {{2}},
  pages        = {{351–360}},
  title        = {{{Second harmonic imaging of plasmonic Pancharatnam-Berry phase metasurfaces coupled to monolayers of WS2}}},
  doi          = {{10.1515/nanoph-2019-0378}},
  volume       = {{9}},
  year         = {{2020}},
}

@article{15714,
  author       = {{Riedl, T. and Kunnathully, V. S. and Trapp, A. and Langer, T. and Reuter, D. 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}},
}

@article{16197,
  abstract     = {{Nonlinear Pancharatnam–Berry phase metasurfaces facilitate the nontrivial phase modulation for frequency conversion processes by leveraging photon‐spin dependent nonlinear geometric‐phases. However, plasmonic metasurfaces show some severe limitation for nonlinear frequency conversion due to the intrinsic high ohmic loss and low damage threshold of plasmonic nanostructures. Here, the nonlinear geometric‐phases associated with the third‐harmonic generation process occurring in all‐dielectric metasurfaces is studied systematically, which are composed of silicon nanofins with different in‐plane rotational symmetries. It is found that the wave coupling among different field components of the resonant fundamental field gives rise to the appearance of different nonlinear geometric‐phases of the generated third‐harmonic signals. The experimental observations of the nonlinear beam steering and nonlinear holography realized in this work by all‐dielectric geometric‐phase metasurfaces are well explained with the developed theory. This work offers a new physical picture to understand the nonlinear optical process occurring at nanoscale dielectric resonators and will help in the design of nonlinear metasurfaces with tailored phase properties.}},
  author       = {{Liu, Bingyi and Sain, Basudeb and Reineke, Bernhard and Zhao, Ruizhe and Meier, Cedrik and Huang, Lingling and Jiang, Yongyuan and Zentgraf, Thomas}},
  issn         = {{2195-1071}},
  journal      = {{Advanced Optical Materials}},
  number       = {{9}},
  publisher    = {{Wiley}},
  title        = {{{Nonlinear Wavefront Control by Geometric-Phase Dielectric Metasurfaces: Influence of Mode Field and Rotational Symmetry}}},
  doi          = {{10.1002/adom.201902050}},
  volume       = {{8}},
  year         = {{2020}},
}

@inproceedings{21719,
  abstract     = {{We fabricate silicon tapers to increase the mode overlap of superconducting detectors on Ti:LiNbO3 waveguides. Mode images show a reduction in mode size from 6 µm to 2 µm FWHM, agreeing with beam propagation simulations.}},
  author       = {{Protte, Maximilian and Ebers, Lena and Hammer, Manfred and Höpker, Jan Philipp and Albert, Maximilian and Quiring, Viktor and Meier, Cedrik and Förstner, Jens and Silberhorn, Christine and Bartley, Tim}},
  booktitle    = {{OSA Quantum 2.0 Conference}},
  isbn         = {{9781943580811}},
  keywords     = {{tet_topic_waveguide}},
  title        = {{{Towards Semiconductor-Superconductor-Crystal Hybrid Integration for Quantum Photonics}}},
  doi          = {{10.1364/quantum.2020.qth7a.8}},
  year         = {{2020}},
}

@article{34092,
  abstract     = {{<jats:p>Block copolymer (BCP) self-assembly is a promising tool for next generation lithography as microphase separated polymer domains in thin films can act as templates for surface nanopatterning with sub-20 nm features. The replicated patterns can, however, only be as precise as their templates. Thus, the investigation of the morphology of polymer domains is of great importance. Commonly used analytical techniques (neutron scattering, scanning force microscopy) either lack spatial information or nanoscale resolution. Using advanced analytical (scanning) transmission electron microscopy ((S)TEM), we provide real space information on polymer domain morphology and interfaces between polystyrene (PS) and polymethylmethacrylate (PMMA) in cylinder- and lamellae-forming BCPs at highest resolution. This allows us to correlate the internal structure of polymer domains with line edge roughnesses, interface widths and domain sizes. STEM is employed for high-resolution imaging, electron energy loss spectroscopy and energy filtered TEM (EFTEM) spectroscopic imaging for material identification and EFTEM thickness mapping for visualisation of material densities at defects. The volume fraction of non-phase separated polymer species can be analysed by EFTEM. These methods give new insights into the morphology of polymer domains the exact knowledge of which will allow to improve pattern quality for nanolithography.</jats:p>}},
  author       = {{Bürger, Julius and Kunnathully, Vinay and Kool, Daniel and Lindner, Jörg and Brassat, Katharina}},
  issn         = {{2079-4991}},
  journal      = {{Nanomaterials}},
  keywords     = {{General Materials Science, General Chemical Engineering}},
  number       = {{1}},
  publisher    = {{MDPI AG}},
  title        = {{{Characterisation of the PS-PMMA Interfaces in Microphase Separated Block Copolymer Thin Films by Analytical (S)TEM}}},
  doi          = {{10.3390/nano10010141}},
  volume       = {{10}},
  year         = {{2020}},
}

@article{34093,
  author       = {{Riedl, Thomas and Kunnathully, V. S. and Trapp, A. and Langer, T. and Reuter, Dirk and Lindner, Jörg}},
  issn         = {{2475-9953}},
  journal      = {{Physical Review Materials}},
  keywords     = {{Physics and Astronomy (miscellaneous), General Materials Science}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Strain-driven InAs island growth on top of GaAs(111) nanopillars}}},
  doi          = {{10.1103/physrevmaterials.4.014602}},
  volume       = {{4}},
  year         = {{2020}},
}

@article{34088,
  author       = {{Bürger, Julius and Riedl, Thomas and Lindner, Jörg}},
  issn         = {{0304-3991}},
  journal      = {{Ultramicroscopy}},
  keywords     = {{Instrumentation, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials}},
  publisher    = {{Elsevier BV}},
  title        = {{{Influence of lens aberrations, specimen thickness and tilt on differential phase contrast STEM images}}},
  doi          = {{10.1016/j.ultramic.2020.113118}},
  volume       = {{219}},
  year         = {{2020}},
}

@article{34091,
  author       = {{Kunnathully, Vinay S. and Riedl, Thomas and Trapp, Alexander and Langer, Timo and Reuter, Dirk and Lindner, Jörg}},
  issn         = {{0022-0248}},
  journal      = {{Journal of Crystal Growth}},
  keywords     = {{Materials Chemistry, Inorganic Chemistry, Condensed Matter Physics}},
  publisher    = {{Elsevier BV}},
  title        = {{{InAs heteroepitaxy on nanopillar-patterned GaAs (111)A}}},
  doi          = {{10.1016/j.jcrysgro.2020.125597}},
  volume       = {{537}},
  year         = {{2020}},
}

@article{34090,
  author       = {{Riedl, Thomas and Lindner, Jörg}},
  issn         = {{0038-1098}},
  journal      = {{Solid State Communications}},
  keywords     = {{Materials Chemistry, Condensed Matter Physics, General Chemistry}},
  publisher    = {{Elsevier BV}},
  title        = {{{Applicability of molecular statics simulation to partial dislocations in GaAs}}},
  doi          = {{10.1016/j.ssc.2020.113927}},
  volume       = {{314-315}},
  year         = {{2020}},
}

@article{34089,
  author       = {{Riedl, Thomas and Lindner, Jörg}},
  issn         = {{0038-1098}},
  journal      = {{Solid State Communications}},
  keywords     = {{Materials Chemistry, Condensed Matter Physics, General Chemistry}},
  publisher    = {{Elsevier BV}},
  title        = {{{Applicability of molecular statics simulation to partial dislocations in GaAs}}},
  doi          = {{10.1016/j.ssc.2020.113927}},
  volume       = {{314-315}},
  year         = {{2020}},
}

@inproceedings{24020,
  abstract     = {{Novel analog-to-digital converter (ADC) architectures are motivated by the demand for rising sampling rates and effective number of bits (ENOB). The main limitation on ENOB in purely electrical ADCs lies in the relatively high jitter of oscillators, in the order of a few tens of fs for state-of-the-art components. When compared to the extremely low jitter obtained with best-in-class Ti:sapphire mode-locked lasers (MLL), in the attosecond range, it is apparent that a mixed electrical-optical architecture could significantly improve the converters' ENOB. We model and analyze the ENOB limitations arising from optical sources in optically enabled, spectrally sliced ADCs, after discussing the system architecture and implementation details. The phase noise of the optical carrier, serving for electro-optic signal transduction, is shown not to propagate to the reconstructed digitized signal and therefore not to represent a fundamental limit. The optical phase noise of the MLL used to generate reference tones for individual slices also does not fundamentally impact the converted signal, so long as it remains correlated among all the comb lines. On the other hand, the timing jitter of the MLL, as also reflected in its RF linewidth, is fundamentally limiting the ADC performance, since it is directly mapped as jitter to the converted signal. The hybrid nature of a photonically enabled, spectrally sliced ADC implies the utilization of a number of reduced bandwidth electrical ADCs to convert parallel slices, resulting in the propagation of jitter from the electrical oscillator supplying their clock. Due to the reduced sampling rate of the electrical ADCs, as compared to the overall system, the overall noise performance of the presented architecture is substantially improved with respect to a fully electrical ADC.}},
  author       = {{Zazzi, Andrea and Müller, Juliana and Gudyriev, Sergiy and Marin-Palomo, Pablo and Fang, Dengyang and Scheytt, Christoph and Koos, Christian and Witzens, Jeremy}},
  booktitle    = {{21. ITG-Fachtagung Photonische Netze}},
  publisher    = {{VDE-Verlag}},
  title        = {{{Mode-locked laser timing jitter limitation in optically enabled frequency-sliced ADCs}}},
  year         = {{2020}},
}

@article{24025,
  abstract     = {{The effect of phase noise introduced by optical sources in spectrally-sliced optically enabled DACs and ADCs is modeled and analyzed in detail. In both data converter architectures, a mode-locked laser is assumed to provide an optical comb whose lines are used to either synthesize or analyze individual spectral slices. While the optical phase noise of the central MLL line as well as of other optical carriers used in the analyzed system architectures have a minor impact on the system performance, the RF phase noise of the MLL fundamentally limits it. In particular, the corresponding jitter of the MLL pulse train is transferred almost one-to-one to the system-level timing jitter of the data converters. While MLL phase noise can in principle be tracked and removed by electronic signal processing, this results in electric oscillator phase noise replacing the MLL jitter and is not conducive in systems leveraging the ultra-low jitter of low-noise mode-locked lasers. Precise analytical models are derived and validated by detailed numerical simulations.}},
  author       = {{Zazzi, Andrea and Müller, Juliana and Gudyriev, Sergiy and Marin-Palomo, Pablo and Fang, Dengyang and Scheytt, Christoph and Koos, Christian and Witzens, Jeremy}},
  journal      = {{Opt. Express}},
  title        = {{{Fundamental limitations of spectrally-sliced optically enabled data converters arising from MLL timing jitter}}},
  doi          = {{10.1364/OE.382832}},
  volume       = {{28}},
  year         = {{2020}},
}

@inproceedings{24028,
  abstract     = {{A 28 Gbps NRZ bang-bang clock and data recovery (CDR) chip for 100G PSM4 is presented. It exhibits an adaptable loop filter transfer function with independently tunable proportional and integral parameters. This allows to optimize the jitter transfer, jitter tolerance, and locking range of the CDR according to system requirements. The CDR represents a key component for a single-chip 8-channel electronic-photonic PSM4 transceiver. A CDR chip was manufactured in a 0.25 μm monolithic photonic BiCMOS technology. The core chip area is 0.51 mm 2 and it dissipates 330 mW from 2.5 V and 3.3 V power supplies.}},
  author       = {{Iftekhar, Mohammed and Gudyriev, Sergiy and Scheytt, Christoph}},
  booktitle    = {{2020 IEEE 20th Topical Meeting on Silicon Monolithic Integrated Circuits in RF Systems (SiRF)}},
  publisher    = {{IEEE}},
  title        = {{{28 Gbps Bang-Bang CDR for 100G PSM4 with Independently Tunable Proportional and Integral Parameters of the Loop Filter in 0.25 µm Photonic BiCMOS Technology}}},
  doi          = {{10.1109/SIRF46766.2020.9040190}},
  year         = {{2020}},
}

@article{16301,
  author       = {{Atorf, Bernhard and Mühlenbernd, Holger and Zentgraf, Thomas and Kitzerow, Heinz-Siegfried}},
  issn         = {{1094-4087}},
  journal      = {{Optics Express}},
  number       = {{6}},
  pages        = {{8898--8908}},
  title        = {{{All-optical switching of a dye-doped liquid crystal plasmonic metasurface}}},
  doi          = {{10.1364/oe.383877}},
  volume       = {{28}},
  year         = {{2020}},
}

@inproceedings{24024,
  abstract     = {{Recently it has been demonstrated that an optoelectronic phase-locked loop (OEPLL) using a mode-locked laser as a reference oscillator achieves significantly lower phase noise than conventional electronic frequency synthesizers. In this paper a concept for an OEPLL-based frequency synthesizer is presented and it is investigated how it can be used as a local oscillator (LO) for THz transceivers in order to improve the signal quality in THz wireless communications. The concept of the OEPLL is presented and it's measured phase noise is compared to the phase noise of a laboratory-grade electronic frequency synthesizer. The measured phase noise spectra of both synthesizers at 10 GHz are then used to model LO phase noise at 320 GHz. Based on models of generic zero-IF transmit and receive frontends, THz signals with different modulation formats and Baud rates are simulated at system level using the modeled LO phase noise for the two LO approaches. Finally, the results are compared.}},
  author       = {{Scheytt, Christoph and Wrana, Dominik and Bahmanian, Meysam and Kallfass, Ingmar}},
  booktitle    = {{2020 Third International Workshop on Mobile Terahertz Systems (IWMTS)}},
  location     = {{Essen, Germany }},
  title        = {{{Ultra-Low Phase Noise Frequency Synthesis for THz Communications Using Optoelectronic PLLs}}},
  doi          = {{10.1109/IWMTS49292.2020.9166347}},
  year         = {{2020}},
}