@article{36471,
abstract = {{Superconducting nanowire single-photon detectors (SNSPDs) show near unity efficiency, low dark count rate, and short recovery time. Combining these characteristics with temporal control of SNSPDs broadens their applications as in active de-latching for higher dynamic range counting or temporal filtering for pump-probe spectroscopy or LiDAR. To that end, we demonstrate active gating of an SNSPD with a minimum off-to-on rise time of 2.4 ns and a total gate length of 5.0 ns. We show how the rise time depends on the inductance of the detector in combination with the control electronics. The gate window is demonstrated to be fully and freely, electrically tunable up to 500 ns at a repetition rate of 1.0 MHz, as well as ungated, free-running operation. Control electronics to generate the gating are mounted on the 2.3 K stage of a closed-cycle sorption cryostat, while the detector is operated on the cold stage at 0.8 K. We show that the efficiency and timing jitter of the detector is not altered during the on-time of the gating window. We exploit gated operation to demonstrate a method to increase in the photon counting dynamic range by a factor 11.2, as well as temporal filtering of a strong pump in an emulated pump-probe experiment.}},
author = {{Hummel, Thomas and Widhalm, Alex and Höpker, Jan Philipp and Jöns, Klaus and Chang, Jin and Fognini, Andreas and Steinhauer, Stephan and Zwiller, Val and Zrenner, Artur and Bartley, Tim}},
issn = {{1094-4087}},
journal = {{Optics Express}},
keywords = {{Atomic and Molecular Physics, and Optics}},
number = {{1}},
publisher = {{Optica Publishing Group}},
title = {{{Nanosecond gating of superconducting nanowire single-photon detectors using cryogenic bias circuitry}}},
doi = {{10.1364/oe.472058}},
volume = {{31}},
year = {{2023}},
}
@article{41035,
author = {{Sharapova, Polina R. and Kruk, Sergey S. and Solntsev, Alexander S.}},
issn = {{1863-8880}},
journal = {{Laser & Photonics Reviews}},
keywords = {{Condensed Matter Physics, Atomic and Molecular Physics, and Optics, Electronic, Optical and Magnetic Materials}},
publisher = {{Wiley}},
title = {{{Nonlinear Dielectric Nanoresonators and Metasurfaces: Toward Efficient Generation of Entangled Photons}}},
doi = {{10.1002/lpor.202200408}},
year = {{2023}},
}
@article{58091,
author = {{Li, Changxiu and Scherbakov, Alexey V. and Soubelet, Pedro and Samusev, Anton K. and Ruppert, Claudia and Balakrishnan, Nilanthy and Gusev, Vitalyi E. and Stier, Andreas V. and Finley, Jonathan J. and Bayer, Manfred and Akimov, Andrey V. }},
journal = {{Nano Letters}},
number = {{17}},
title = {{{Coherent Phonons in van der Waals MoSe2/WSe2 Heterobilayers}}},
doi = {{10.1021/acs.nanolett.3c02316}},
volume = {{23}},
year = {{2023}},
}
@article{58093,
author = {{Nitschke, Jonah Elias and Esteras, Dorye L. and Gutnikov, Michael and Schiller, Karl and Mañas-Valero, Samuel and Coronado, Eugenio and Stupar, Matija and Zamborlini, Giovanni and Ponzoni, Stefano and Baldoví, José J. and Cinchetti, Mirko }},
journal = {{Materials Today Electronics}},
title = {{{Valence band electronic structure of the van der Waals antiferromagnet FePS3}}},
doi = {{10.1016/j.mtelec.2023.100061}},
volume = {{6}},
year = {{2023}},
}
@inproceedings{30387,
abstract = {{Resonant evanescent coupling can be utilized to selectively excite orbital angular momentum (OAM) modes of high angular order supported by a thin circular dielectric rod. Our 2.5-D hybrid-analytical coupled mode model combines the vectorial fields associated with the fundamental TE- and TM-modes of a standard silicon photonics slab waveguide, propagating at oblique angles with respect to the rod axis, and the hybrid modes supported by the rod. One observes an efficient resonant interaction in cases where the common axial wavenumber of the waves in the slab matches the propagation constant of one or more modes of the rod. For certain modes of high angular order, the incident wave is able to transfer its directionality to the field in the fiber, exciting effectively only one of a pair of degenerate OAM modes}},
author = {{Hammer, Manfred and Ebers, Lena and Förstner, Jens}},
booktitle = {{Complex Light and Optical Forces XVI}},
editor = {{Andrews, David L. and Galvez, Enrique J. and Rubinsztein-Dunlop, Halina}},
keywords = {{tet_topic_waveguide}},
pages = {{120170F}},
publisher = {{SPIE}},
title = {{{Resonant evanescent excitation of OAM modes in a high-contrast circular step-index fiber}}},
doi = {{10.1117/12.2612179}},
year = {{2022}},
}
@inbook{33466,
abstract = {{We review our results of numerical simulations of light scattering from different systems of densely packed irregular particles. We consider spherical clusters, thick layers and monolayers with realistic topologies and dimensions much larger than the wavelength of light. The maximum bulk packing density of clusters is 0.5. A numerically exact solution of the electromagnetic problem is obtained using the Discontinuous Galerkin Time Domain method and with application of high- performance computing. We show that high packing density causes light localization in such structures which makes an impact on the opposition phenomena: backscattering intensity surge and negative linear polarization feature. Diffuse multiple scattering is significantly reduced in the case of non-absorbing particles and near-field interaction results in a percolation-like light transport determined by the topology of the medium. With this the negative polarization feature caused by single scattering gets enhanced if compared to lower density samples. We also confirm coherent double scattering mechanism of negative polarization for light scattered from dense absorbing slabs. In this case convergent result for the scattering angle polarization dependency at backscattering can be obtained for a layer of just a few tens of particles if they are larger than the wavelength.}},
author = {{Grynko, Yevgen and Shkuratov, Yuriy and Alhaddad, Samer and Förstner, Jens}},
booktitle = {{Springer Series in Light Scattering - Volume 8: Light Polarization and Multiple Scattering in Turbid Media}},
editor = {{Kokhanovsky, Alexander}},
isbn = {{9783031102974}},
issn = {{2509-2790}},
keywords = {{tet_topic_scattering}},
publisher = {{Springer International Publishing}},
title = {{{Light Scattering by Large Densely Packed Clusters of Particles}}},
doi = {{10.1007/978-3-031-10298-1_4}},
volume = {{8}},
year = {{2022}},
}
@article{54849,
abstract = {{The third‐order susceptibility of lithium niobate (LiNbO3) is calculated within a Berry‐phase formulation of the dynamical polarization based on the electronic structure obtained within density‐functional theory (DFT). Maximum values of the order of m V are calculated for photon energies between 1.2 and 2 eV, i.e., in the lower half of the optical bandgap of lithium niobate. Both free and bound electron (bi)polarons are found to lead to a remarkable enhancement of the third‐order susceptibility for photon energies below 1 eV.}},
author = {{Kozub, Agnieszka L. and Gerstmann, Uwe and Schmidt, Wolf Gero}},
issn = {{0370-1972}},
journal = {{physica status solidi (b)}},
number = {{2}},
publisher = {{Wiley}},
title = {{{Third‐Order Susceptibility of Lithium Niobate: Influence of Polarons and Bipolarons}}},
doi = {{10.1002/pssb.202200453}},
volume = {{260}},
year = {{2022}},
}
@article{28413,
abstract = {{Optical traveling wave antennas offer unique opportunities to control and selectively guide light into a specific direction, which renders them excellent candidates for optical communication and sensing. These applications require state-of-the-art engineering to reach optimized functionalities such as high directivity and radiation efficiency, low sidelobe levels, broadband and tunable capabilities, and compact design. In this work, we report on the numerical optimization of the directivity of optical traveling wave antennas made from low-loss dielectric materials using full-wave numerical simulations in conjunction with the particle swarm optimization algorithm. The antennas are composed of a reflector and a director deposited on a glass substrate, and an emitter placed in the feed gap between them serves as an internal source of excitation. In particular, we analyze antennas with rectangular- and horn-shaped directors made of either hafnium dioxide or silicon. The optimized antennas produce highly directional emissions due to the presence of two dominant guided TE modes in the director in addition to leaky modes. These guided modes dominate the far-field emission pattern and govern the direction of the main lobe emission, which predominately originates from the end facet of the director. Our work also provides a comprehensive analysis of the modes, radiation patterns, parametric influences, and bandwidths of the antennas, which highlights their robust nature.}},
author = {{Farheen, Henna and Leuteritz, Till and Linden, Stefan and Myroshnychenko, Viktor and Förstner, Jens}},
issn = {{0740-3224}},
journal = {{Journal of the Optical Society of America B}},
keywords = {{tet_topic_opticalantenna}},
number = {{1}},
pages = {{83}},
title = {{{Optimization of optical waveguide antennas for directive emission of light}}},
doi = {{10.1364/josab.438514}},
volume = {{39}},
year = {{2022}},
}
@article{29075,
abstract = {{We study a double-scattering coherent mechanism of negative polarization (NP) near opposition that is observed for powder-like surfaces. The problem is solved numerically for absorbing structures with irregular constituents, cubes, spheres, and ellipsoids larger than the wavelength of incident light. Our simulations show that double scattering between two random irregular particles shows weak NP. Adding one more particle significantly increases the relative contribution of double scattering which enhances NP. Simulations with regular shapes and controlled geometric parameters show that the interference mechanism is sensitive to the geometry of the scattering system and can also result in no polarization or even strong enhancement of positive polarization at backscattering.}},
author = {{Alhaddad, Samer and Grynko, Yevgen and Farheen, Henna and Förstner, Jens}},
issn = {{0146-9592}},
journal = {{Optics Letters}},
keywords = {{tet_topic_scattering}},
number = {{1}},
pages = {{58}},
title = {{{Numerical analysis of the coherent mechanism producing negative polarization at backscattering from systems of absorbing particles}}},
doi = {{10.1364/ol.444953}},
volume = {{47}},
year = {{2022}},
}
@article{31329,
abstract = {{Highly directive antennas with the ability of shaping radiation patterns in desired directions are essential for efficient on-chip optical communication with reduced cross talk. In this paper, we design and optimize three distinct broadband traveling-wave tantalum pentoxide antennas exhibiting highly directional characteristics. Our antennas contain a director and reflector deposited on a glass substrate, which are excited by a dipole emitter placed in the feed gap between the two elements. Full-wave simulations in conjunction with global optimization provide structures with an enhanced linear directivity as high as 119 radiating in the substrate. The high directivity is a result of the interplay between two dominant TE modes and the leaky modes present in the antenna director. Furthermore, these low-loss dielectric antennas exhibit a near-unity radiation efficiency at the operational wavelength of 780 nm and maintain a broad bandwidth. Our numerical results are in good agreement with experimental measurements from the optimized antennas fabricated using a two-step electron-beam lithography, revealing the highly directive nature of our structures. We envision that our antenna designs can be conveniently adapted to other dielectric materials and prove instrumental for inter-chip optical communications and other on-chip applications.}},
author = {{Farheen, Henna and Yan, Lok-Yee and Quiring, Viktor and Eigner, Christof and Zentgraf, Thomas and Linden, Stefan and Förstner, Jens and Myroshnychenko, Viktor}},
issn = {{1094-4087}},
journal = {{Optics Express}},
keywords = {{tet_topic_opticalantenna}},
number = {{11}},
pages = {{19288}},
publisher = {{Optica Publishing Group}},
title = {{{Broadband optical Ta2O5 antennas for directional emission of light}}},
doi = {{10.1364/oe.455815}},
volume = {{30}},
year = {{2022}},
}
@article{37319,
author = {{Grisard, S. and Rose, Hendrik and Trifonov, A. V. and Reichhardt, R. and Reiter, D. E. and Reichelt, Matthias and Schneider, C. and Kamp, M. and Höfling, S. and Bayer, M. and Meier, Torsten and Akimov, I. A.}},
issn = {{2469-9950}},
journal = {{Physical Review B}},
number = {{20}},
publisher = {{American Physical Society (APS)}},
title = {{{Multiple Rabi rotations of trions in InGaAs quantum dots observed by photon echo spectroscopy with spatially shaped laser pulses}}},
doi = {{10.1103/physrevb.106.205408}},
volume = {{106}},
year = {{2022}},
}
@inproceedings{37329,
author = {{Trautmann, Alexander and Zuo, Ruixin and Wang, Guifang and Hannes, Wolf-Rüdiger and Yang, Shidong and Thong, Le Huu and Ngo, Cong and Steiner, Johannes and Ciappina, Marcelo and Reichelt, Matthias and Duc, Huynh Thanh and Song, Xiaohong and Yang, Weifeng and Meier, Torsten}},
booktitle = {{Ultrafast Phenomena and Nanophotonics XXVI}},
editor = {{Betz, Markus and Elezzabi, Abdulhakem Y.}},
title = {{{Microscopic simulations of high harmonic generation from semiconductors}}},
doi = {{10.1117/12.2607447}},
volume = {{11999}},
year = {{2022}},
}
@article{37323,
author = {{Paul, J. and Rose, Hendrik and Swagel, E. and Meier, Torsten and Wahlstrand, J. K. and Bristow, A. D.}},
issn = {{2469-9950}},
journal = {{Physical Review B}},
number = {{11}},
publisher = {{American Physical Society (APS)}},
title = {{{Coherent contributions to population dynamics in a semiconductor microcavity}}},
doi = {{10.1103/physrevb.105.115307}},
volume = {{105}},
year = {{2022}},
}
@article{40523,
abstract = {{AbstractTailored nanoscale quantum light sources, matching the specific needs of use cases, are crucial building blocks for photonic quantum technologies. Several different approaches to realize solid-state quantum emitters with high performance have been pursued and different concepts for energy tuning have been established. However, the properties of the emitted photons are always defined by the individual quantum emitter and can therefore not be controlled with full flexibility. Here we introduce an all-optical nonlinear method to tailor and control the single photon emission. We demonstrate a laser-controlled down-conversion process from an excited state of a semiconductor quantum three-level system. Based on this concept, we realize energy tuning and polarization control of the single photon emission with a control-laser field. Our results mark an important step towards tailored single photon emission from a photonic quantum system based on quantum optical principles.}},
author = {{Jonas, B. and Heinze, Dirk Florian and Schöll, E. and Kallert, P. and Langer, T. and Krehs, S. and Widhalm, A. and Jöns, Klaus and Reuter, Dirk and Schumacher, Stefan and Zrenner, Artur}},
issn = {{2041-1723}},
journal = {{Nature Communications}},
keywords = {{General Physics and Astronomy, General Biochemistry, Genetics and Molecular Biology, General Chemistry, Multidisciplinary}},
number = {{1}},
publisher = {{Springer Science and Business Media LLC}},
title = {{{Nonlinear down-conversion in a single quantum dot}}},
doi = {{10.1038/s41467-022-28993-3}},
volume = {{13}},
year = {{2022}},
}
@article{40431,
author = {{Praschan, Tom and Heinze, Dirk and Breddermann, Dominik and Zrenner, Artur and Walther, Andrea and Schumacher, Stefan}},
issn = {{2469-9950}},
journal = {{Physical Review B}},
number = {{4}},
publisher = {{American Physical Society (APS)}},
title = {{{Pulse shaping for on-demand emission of single Raman photons from a quantum-dot biexciton}}},
doi = {{10.1103/physrevb.105.045302}},
volume = {{105}},
year = {{2022}},
}
@misc{40428,
author = {{Jonas, Björn and Heinze, Dirk Florian and Schöll, Eva and Kallert, Patricia and Langer, Timo and Krehs, Sebastian and Widhalm, Alex and Jöns, Klaus and Reuter, Dirk and Zrenner, Artur}},
publisher = {{LibreCat University}},
title = {{{Nonlinear down-conversion in a single quantum dot}}},
doi = {{10.5281/ZENODO.6024228}},
year = {{2022}},
}
@article{37711,
abstract = {{AbstractPolarons influence decisively the performance of lithium niobate for optical applications. In this work, the formation of (defect) bound polarons in lithium niobate is studied by ab initio molecular dynamics. The calculations show a broad scatter of polaron formation times. Rising temperature increases the share of trajectories with long formation times, which leads to an overall increase of the average formation time with temperature. However, even at elevated temperatures, the average formation time does not exceed the value of 100 femtoseconds, i.e., a value close to the time measured for free, i.e., self-trapped polarons. Analyzing individual trajectories, it is found that the time required for the structural relaxation of the polarons depends sensitively on the excitation of the lithium niobate high-frequency phonon modes and their phase relation.}},
author = {{Krenz, Marvin and Gerstmann, Uwe and Schmidt, Wolf Gero}},
issn = {{0947-8396}},
journal = {{Applied Physics A}},
keywords = {{General Materials Science, General Chemistry}},
pages = {{480}},
publisher = {{Springer Science and Business Media LLC}},
title = {{{Bound polaron formation in lithium niobate from ab initio molecular dynamics}}},
doi = {{10.1007/s00339-022-05577-y}},
volume = {{128}},
year = {{2022}},
}
@article{33484,
abstract = {{We study the DC conductivity in potassium titanyl phosphate (KTiOPO4, KTP) and its isomorphs KTiOAsO4 (KTA) and Rb1%K99%TiOPO4 (RKTP) and introduce a method by which to reduce the overall ionic conductivity in KTP by a potassium nitrate treatment. Furthermore, we create so-called gray tracking in KTP and investigate the ionic conductivity in theses areas. A local unintended reduction of the ionic conductivity is observed in the gray-tracked regions, which also induce additional optical absorption in the material. We show that a thermal treatment in an oxygen-rich atmosphere removes the gray tracking and brings the ionic conductivity as well as the optical transmission back to the original level. These studies can help to choose the best material and treatment for specific applications.}},
author = {{Padberg, Laura and Quiring, Viktor and Bocchini, Adriana and Santandrea, Matteo and Gerstmann, Uwe and Schmidt, Wolf Gero and Silberhorn, Christine and Eigner, Christof}},
issn = {{2073-4352}},
journal = {{Crystals}},
pages = {{1359}},
title = {{{DC Ionic Conductivity in KTP and Its Isomorphs: Properties, Methods for Suppression, and Its Connection to Gray Tracking}}},
doi = {{10.3390/cryst12101359}},
volume = {{12}},
year = {{2022}},
}
@inproceedings{30389,
abstract = {{Online solvers for a series of standard 1-D or 2-D problems in integrated optics will be discussed. Implemented on the basis of HTML/JavaScript/SVG with core routines compiled from well tested C++-sources, the quasi-analytical algorithms require a computational load that can be handled easily even by current mobile devices. So far the series covers the 1-D guided modes of dielectric multilayer slab waveguides and the oblique plane wave reflection from these, the modes of rectangular channel waveguides (in an approximation of effective indices), bend modes of curved multilayer slabs, whispering-gallery resonances (“Quasi-Normal-Modes”) supported by circular dielectric cavities, the hybrid modes of circular multi-step-index optical fibers, bound and leaky modes of 1-D complex multilayers, including plasmonic surface modes, and, with restrictions, quite general rectangular scattering problems in 2-D.}},
author = {{Hammer, Manfred}},
booktitle = {{Integrated Optics: Devices, Materials, and Technologies XXVI}},
editor = {{García-Blanco, Sonia M. and Cheben, Pavel}},
keywords = {{tet_topic_waveguide}},
pages = {{1200414}},
publisher = {{SPIE}},
title = {{{Small-scale online simulations in guided-wave photonics}}},
doi = {{10.1117/12.2612208}},
year = {{2022}},
}
@article{26627,
abstract = {{Many-body perturbation theory based on density-functional theory calculations is used to determine the quasiparticle band structures and the dielectric functions of the isomorphic ferroelectrics rubidium titanyl phosphate (RbTiOPO4) and potassium titanyl arsenide (KTiOAsO4). Self-energy corrections of more than 2 eV are found to widen the transport band gaps of both materials considerably to 5.3 and 5.2 eV, respectively. At the same time, both materials are characterized by strong exciton binding energies of 1.4 and 1.5 eV, respectively. The solution of the Bethe-Salpeter equation based on the quasiparticle energies results in onsets of the optical absorption within the range of the measured data.}},
author = {{Neufeld, Sergej and Schindlmayr, Arno and Schmidt, Wolf Gero}},
issn = {{2515-7639}},
journal = {{Journal of Physics: Materials}},
number = {{1}},
publisher = {{IOP Publishing}},
title = {{{Quasiparticle energies and optical response of RbTiOPO4 and KTiOAsO4}}},
doi = {{10.1088/2515-7639/ac3384}},
volume = {{5}},
year = {{2022}},
}