@article{46573, abstract = {{An ultra-fast change of the absorption onset for zincblende gallium-nitride (zb-GaN) (fundamental bandgap: 3.23 eV) is observed by investigating the imaginary part of the dielectric function using time-dependent femtosecond pump–probe spectroscopic ellipsometry between 2.9 and 3.7 eV. The 266 nm (4.66 eV) pump pulses induce a large electron–hole pair concentration up to 4×1020cm−3, which shift the transition energy between conduction and valence bands due to many-body effects up to ≈500 meV. Here, the absorption onset increases due to band filling while the bandgap renormalization at the same time decreases the bandgap. Additionally, the absorption of the pump-beam creates a free-carrier profile within the 605 nm zb-GaN layer with high free-carrier concentrations at the surface, and low concentrations at the interface to the substrate. This leads to varying optical properties from the sample surface (high transition energy) to substrate (low transition energy), which are taken into account by grading analysis for an accurate description of the experimental data. For this, a model describing the time- and position-dependent free-carrier concentration is formulated by considering the relaxation, recombination, and diffusion of those carriers. We provide a quantitative analysis of optical experimental data (ellipsometric angles Ψ and Δ) as well as a plot for the time-dependent change of the imaginary part of the dielectric function.}}, author = {{Baron, Elias and Goldhahn, Rüdiger and Espinoza, Shirly and Zahradník, Martin and Rebarz, Mateusz and Andreasson, Jakob and Deppe, Michael and As, Donat Josef and Feneberg, Martin}}, issn = {{0021-8979}}, journal = {{Journal of Applied Physics}}, keywords = {{General Physics and Astronomy}}, number = {{7}}, publisher = {{AIP Publishing}}, title = {{{Time-resolved pump–probe spectroscopic ellipsometry of cubic GaN. I. Determination of the dielectric function}}}, doi = {{10.1063/5.0153091}}, volume = {{134}}, year = {{2023}}, } @article{49117, author = {{Scharwald, D. and Meier, T. and Sharapova, P. R.}}, issn = {{2643-1564}}, journal = {{Physical Review Research}}, keywords = {{General Physics and Astronomy}}, number = {{4}}, publisher = {{American Physical Society (APS)}}, title = {{{Phase sensitivity of spatially broadband high-gain SU(1,1) interferometers}}}, doi = {{10.1103/physrevresearch.5.043158}}, volume = {{5}}, year = {{2023}}, } @article{49609, abstract = {{The alignment of liquid crystals on surfaces plays a central role in optimizing their performances. In this work, a cutting-edge nano-lithography-based method to control the local orientation of a thermotropic liquid crystal is applied to easily available commercial standard materials and evaluated. Parallel nanogrooves on a substrate, created through 3D nanoprinting in a negative-tone photoresin optimized for two-photon polymerization are used for this purpose. Azimuthal anchoring energies of the order from 10−6 J/m2 to 10−5 J/m2 are found, depending on the spacing, width and depth of the grooves. In part, these values are larger than those reported previously for another photopolymer. Both uniform alignment and spatial patterns of different alignment directions can be realized. Electro-optic studies confirm the suitability of the method for electrically addressable photonic applications and indicate strong polar anchoring.}}, author = {{Zhang, Bingru and Plidschun, Malte and Schmidt, Markus A. and Kitzerow, Heinz-Siegfried}}, issn = {{2159-3930}}, journal = {{Optical Materials Express}}, keywords = {{Electronic, Optical and Magnetic Materials}}, number = {{12}}, publisher = {{Optica Publishing Group}}, title = {{{Anchoring and electro-optic switching of liquid crystals on nano-structured surfaces fabricated by two-photon based nano-printing}}}, doi = {{10.1364/ome.503100}}, volume = {{13}}, year = {{2023}}, } @article{43440, author = {{Zhang, Bingru and Nguyen, Linh and Martens, Kevin and Heuer-Jungemann, Amelie and Philipp, Julian and Kempter, Susanne and Rädler, Joachim O. and Liedl, Tim and Kitzerow, Heinz-Siegfried}}, issn = {{0267-8292}}, journal = {{Liquid Crystals}}, keywords = {{Condensed Matter Physics, General Materials Science, General Chemistry}}, number = {{7-10}}, pages = {{1243--1251}}, publisher = {{Informa UK Limited}}, title = {{{Luminescent DNA-origami nano-rods dispersed in a lyotropic chromonic liquid crystal}}}, doi = {{10.1080/02678292.2023.2188494}}, volume = {{50}}, year = {{2023}}, } @article{48599, abstract = {{AbstractThe biexciton‐exciton emission cascade commonly used in quantum‐dot systems to generate polarization entanglement yields photons with intrinsically limited indistinguishability. In the present work, it focuses on the generation of pairs of photons with high degrees of polarization entanglement and simultaneously high indistinguishability. It achieves this goal by selectively reducing the biexciton lifetime with an optical resonator. It demonstrates that a suitably tailored circular Bragg reflector fulfills the requirements of sufficient selective Purcell enhancement of biexciton emission paired with spectrally broad photon extraction and twofold degenerate optical modes. The in‐depth theoretical study combines (i) the optimization of realistic photonic structures solving Maxwell's equations from which model parameters are extracted as input for (ii) microscopic simulations of quantum‐dot cavity excitation dynamics with full access to photon properties. It reports non‐trivial dependencies on system parameters and use the predictive power of the combined theoretical approach to determine the optimal range of Purcell enhancement that maximizes indistinguishability and entanglement to near unity values, here specifically for the telecom C‐band at 1550 nm.}}, author = {{Bauch, David and Siebert, Dustin and Jöns, Klaus and Förstner, Jens and Schumacher, Stefan}}, issn = {{2511-9044}}, journal = {{Advanced Quantum Technologies}}, keywords = {{tet_topic_qd}}, publisher = {{Wiley}}, title = {{{On‐Demand Indistinguishable and Entangled Photons Using Tailored Cavity Designs}}}, doi = {{10.1002/qute.202300142}}, year = {{2023}}, } @unpublished{43246, abstract = {{The biexciton-exciton emission cascade commonly used in quantum-dot systems to generate polarization entanglement yields photons with intrinsically limited indistinguishability. In the present work we focus on the generation of pairs of photons with high degrees of polarization entanglement and simultaneously high indistinguishibility. We achieve this goal by selectively reducing the biexciton lifetime with an optical resonator. We demonstrate that a suitably tailored circular Bragg reflector fulfills the requirements of sufficient selective Purcell enhancement of biexciton emission paired with spectrally broad photon extraction and two-fold degenerate optical modes. Our in-depth theoretical study combines (i) the optimization of realistic photonic structures solving Maxwell's equations from which model parameters are extracted as input for (ii) microscopic simulations of quantum-dot cavity excitation dynamics with full access to photon properties. We report non-trivial dependencies on system parameters and use the predictive power of our combined theoretical approach to determine the optimal range of Purcell enhancement that maximizes indistinguishability and entanglement to near unity values in the telecom C-band at $1550\,\mathrm{nm}$.}}, author = {{Bauch, David and Siebert, Dustin and Jöns, Klaus and Förstner, Jens and Schumacher, Stefan}}, keywords = {{tet_topic_phc, tet_topic_qd}}, title = {{{On-demand indistinguishable and entangled photons at telecom frequencies using tailored cavity designs}}}, year = {{2023}}, } @article{52122, author = {{Ali, Usman and Holthaus, Martin and Meier, Torsten}}, issn = {{2643-1564}}, journal = {{Physical Review Research}}, keywords = {{General Physics and Astronomy}}, number = {{4}}, publisher = {{American Physical Society (APS)}}, title = {{{Chirped Bloch-harmonic oscillations in a parametrically forced optical lattice}}}, doi = {{10.1103/physrevresearch.5.043152}}, volume = {{5}}, year = {{2023}}, } @article{49607, abstract = {{In this work, we utilize thin dielectric meta-atoms placed on a silver substrate to efficiently enhance and manipulate the third-harmonic generation. We theoretically and experimentally reveal that when the structural symmetry of the meta-atom is incompatible with the lattice symmetry of an array, some generalized nonlinear geometric phases appear, which offers new possibilities for harmonic generation control beyond the accessible symmetries governed by the selection rule. The underlying mechanism is attributed to the modified rotation of the effective principal axis of a dense meta-atom array, where the strong coupling among the units gives rise to a generalized linear geometric phase modulation of the pump light. Therefore, nonlinear geometric phases carried by third-harmonic emissions are the natural result of the wave-mixing process among the modes excited at the fundamental frequency. This mechanism further points out a new strategy to predict the nonlinear geometric phases delivered by the nanostructures according to their linear responses. Our design is simple and efficient and offers alternatives for the nonlinear meta-devices that are capable of flexible photon generation and manipulation.}}, author = {{Liu, Bingyi and Geromel, René and Su, Zhaoxian and Guo, Kai and Wang, Yongtian and Guo, Zhongyi and Huang, Lingling and Zentgraf, Thomas}}, issn = {{2330-4022}}, journal = {{ACS Photonics}}, keywords = {{Electrical and Electronic Engineering, Atomic and Molecular Physics, and Optics, Biotechnology, Electronic, Optical and Magnetic Materials}}, number = {{12}}, pages = {{4357--4366}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Nonlinear Dielectric Geometric-Phase Metasurface with Simultaneous Structure and Lattice Symmetry Design}}}, doi = {{10.1021/acsphotonics.3c01163}}, volume = {{10}}, year = {{2023}}, } @article{42679, abstract = {{The Saharan desert ant Cataglyphis bombycina is densely covered with shiny silver setae (hair-like structures). Their appearance was explained by geometric optics and total internal reflection. The setae also increase the emissivity of the ant, as they form an effective medium. This work provides additional data on microstructural details of the setae that are used to simulate the scattering of an individual seta to explain their influence on the optical properties. This is achieved by characterization of their structure using light microscopy and scanning/transmission electron microscopy. How the microstructural features influence scattering is investigated wave-optically within the limits of finite-difference time-domain simulations from the ultraviolet to the mid-infrared spectral range to elucidate the optical effects beyond ray optics and effective medium theory. The results show that Mie scattering plays an important role in protecting the ant from solar radiation and could be relevant for its thermal tolerance.}}, author = {{Schwind, Bertram and Wu, Xia and Tiemann, Michael and Fabritius, Helge-Otto}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, keywords = {{Atomic and Molecular Physics, and Optics, Statistical and Nonlinear Physics}}, number = {{3}}, pages = {{B49 -- B58}}, publisher = {{Optica Publishing Group}}, title = {{{Broadband Mie scattering effects by structural features of setae from the Saharan silver ant Cataglyphis bombycina}}}, doi = {{10.1364/josab.474899}}, volume = {{40}}, year = {{2023}}, } @article{54852, abstract = {{The crystal family of potassium titanyl phosphate (KTiOPO4) is a promising material group for applications in quantum and nonlinear optics. The fabrication of low-loss optical waveguides, as well as high-grade periodically poled ferroelectric domain structures, requires a profound understanding of the material properties and crystal structure. In this regard, Raman spectroscopy offers the possibility to study and visualize domain structures, strain, defects, and the local stoichiometry, which are all factors impacting device performance. However, the accurate interpretation of Raman spectra and their changes with respect to extrinsic and intrinsic defects requires a thorough assignment of the Raman modes to their respective crystal features, which to date is only partly conducted based on phenomenological modelling. To address this issue, we calculated the phonon spectra of potassium titanyl phosphate and the related compounds rubidium titanyl phosphate (RbTiOPO4) and potassium titanyl arsenate (KTiOAsO4) based on density functional theory and compared them with experimental data. Overall, this allows us to assign various spectral features to eigenmodes of lattice substructures with improved detail compared to previous assignments. Nevertheless, the analysis also shows that not all features of the spectra can unambigiously be explained yet. A possible explanation might be that defects or long range fields not included in the modeling play a crucial rule for the resulting Raman spectrum. In conclusion, this work provides an improved foundation into the vibrational properties in the KTiOPO4 material family.}}, author = {{Neufeld, Sergej and Gerstmann, Uwe and Padberg, Laura and Eigner, Christof and Berth, Gerhard and Silberhorn, Christine and Eng, Lukas M. and Schmidt, Wolf Gero and Rüsing, Michael}}, issn = {{2073-4352}}, journal = {{Crystals}}, number = {{10}}, publisher = {{MDPI AG}}, title = {{{Vibrational Properties of the Potassium Titanyl Phosphate Crystal Family}}}, doi = {{10.3390/cryst13101423}}, volume = {{13}}, year = {{2023}}, } @article{54854, abstract = {{Batteries based on heavier alkali ions are considered promising candidates to substitute for current Li-based technologies. In this theoretical study, we characterize the structural properties of a novel material, i.e., F-doped RbTiOPO4 (RbTiPO4F, RTP:F), and discuss aspects of its electrochemical performance in Rb-ion batteries (RIBs) using density functional theory (DFT). According to our calculations, RTP:F is expected to retain the so-called KTiOPO4 (KTP)-type structure, with lattice parameters of 13.236 Å, 6.616 Å, and 10.945 Å. Due to the doping with F, the crystal features eight extra electrons per unit cell, whereby each of these electrons is trapped by one of the surrounding Ti atoms in the cell. Notably, the ground state of the system corresponds to a ferromagnetic spin configuration (i.e., S=4). The deintercalation of Rb leads to the oxidation of the Ti atoms in the cell (i.e., from Ti3+ to Ti4+) and to reduced magnetic moments. The material promises interesting electrochemical properties for the cathode: rather high average voltages above 2.8 V and modest volume shrinkages below 13% even in the fully deintercalated case are predicted.}}, author = {{Bocchini, Adriana and Xie, Yingjie and Schmidt, Wolf Gero and Gerstmann, Uwe}}, issn = {{2073-4352}}, journal = {{Crystals}}, number = {{1}}, publisher = {{MDPI AG}}, title = {{{Structural and Electrochemical Properties of F-Doped RbTiOPO4 (RTP:F) Predicted from First Principles}}}, doi = {{10.3390/cryst14010005}}, volume = {{14}}, year = {{2023}}, } @article{54853, abstract = {{The nitrogen-vacancy (NV) centers (NCVSi)− in 4H silicon carbide (SiC) constitute an ensemble of spin S = 1 solid state qubits interacting with the surrounding 14N and 29Si nuclei. As quantum applications based on a polarization transfer from the electron spin to the nuclei require the knowledge of the electron–nuclear interaction parameters, we have used high-frequency (94 GHz) electron–nuclear double resonance spectroscopy combined with first-principles density functional theory to investigate the hyperfine and nuclear quadrupole interactions of the basal and axial NV centers. We observed that the four inequivalent NV configurations (hk, kh, hh, and kk) exhibit different electron–nuclear interaction parameters, suggesting that each NV center may act as a separate optically addressable qubit. Finally, we rationalized the observed differences in terms of distinctions in the local atomic structures of the NV configurations. Thus, our results provide the basic knowledge for an extension of quantum protocols involving the 14N nuclear spin.}}, author = {{Murzakhanov, F. F. and Sadovnikova, M. A. and Mamin, G. V. and Nagalyuk, S. S. and von Bardeleben, H. J. and Schmidt, Wolf Gero and Biktagirov, Timur and Gerstmann, Uwe and Soltamov, V. A.}}, issn = {{0021-8979}}, journal = {{Journal of Applied Physics}}, number = {{12}}, publisher = {{AIP Publishing}}, title = {{{14N Hyperfine and nuclear interactions of axial and basal NV centers in 4H-SiC: A high frequency (94 GHz) ENDOR study}}}, doi = {{10.1063/5.0170099}}, volume = {{134}}, year = {{2023}}, } @article{54851, abstract = {{Composites of different graphene oxide types, TiO2 materials, and especially synthetic routes influence the photocatalytic activity of the resulting material.}}, author = {{Rosenthal, Marta and Biktagirov, Timur and Schmidt, Wolf Gero and Wilhelm, René}}, issn = {{2044-4753}}, journal = {{Catalysis Science & Technology}}, number = {{15}}, pages = {{4367--4377}}, publisher = {{Royal Society of Chemistry (RSC)}}, title = {{{Synthesis of new graphene oxide/TiO2 and TiO2/SiO2 nanocomposites and their evaluation as photocatalysts}}}, doi = {{10.1039/d3cy00461a}}, volume = {{13}}, year = {{2023}}, } @article{54850, author = {{Meier, Lukas and Schmidt, Wolf Gero}}, issn = {{1932-7447}}, journal = {{The Journal of Physical Chemistry C}}, number = {{4}}, pages = {{1973--1980}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Adsorption of Cyclic (Alkyl) (Amino) Carbenes on Monohydride Si(001) Surfaces: Interface Bonding and Electronic Properties}}}, doi = {{10.1021/acs.jpcc.2c07316}}, volume = {{127}}, year = {{2023}}, } @misc{54407, abstract = {{Dataset of the publication "Quantum-optical excitations of semiconductor nanostructures in a microcavity using a two-band model and a single-mode quantum field" H. Rose, A. N. Vasil’ev, O. V. Tikhonova, T. Meier, and P. R. Sharapova, Phys. Rev. A 107, 013703 (2023). ( https://doi.org/10.1103/PhysRevA.107.013703 ). The zip file includes the data on which the plots shown in figures 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 are based.}}, author = {{Rose, Hendrik and Vasil'ev, Andrey N. and Tikhonova, Olga V. and Meier, Torsten and Sharapova, Polina}}, publisher = {{LibreCat University}}, title = {{{Quantum-optical excitations of semiconductor nanostructures in a microcavity using a two-band model and a single-mode quantum field}}}, doi = {{10.5281/ZENODO.7554556}}, year = {{2023}}, } @misc{54398, abstract = {{Dataset of the publication “Analysis of the nonlinear optical response of excitons in type-I and type-II quantum wells including many-body correlations”, A. Trautmann, M. Stein, F. Schäfer, D. Anders, C. Ngo, J. T. Steiner, M. Reichelt, S. Chatterjee, and T. Meier, Proc. SPIE 12419, Ultrafast Phenomena and Nanophotonics XXVII, 124190A (2023) ( https://doi.org/10.1117/12.2650169 ). The zip file includes the data on which the plots are based.}}, author = {{Trautmann, Alexander and Stein, Markus and Schäfer, Felix and Anders, Daniel and Ngo, Cong and Steiner, Johannes Tilmann and Reichelt, Matthias and Chatterjee, Sangam and Meier, Torsten}}, publisher = {{LibreCat University}}, title = {{{Analysis of the nonlinear optical response of excitons in type-I and type-II quantum wells including many-body correlations}}}, doi = {{10.5281/ZENODO.7757178}}, year = {{2023}}, } @misc{54395, abstract = {{Dataset of the publication “Control of the electron dynamics in solid-state high harmonic generation on ultrafast time scales by a polarization-skewed laser pulse”, by X. Song, S. Yang, G. Wang, J. Lin, L. Wang, T. Meier, and W. Yang, published in Optics Express 31, 18862 (2023) , https://doi.org/10.1364/OE.491418 .
The zip file includes a brief description, the data on which the plot of figures 1 – 3 are based, and matlab figure files.}}, author = {{Song, Xiaohong and Yang, Shidong and Wang, Guifang and Lin, Jianpeng and Wang, Liang and Meier, Torsten and Yang, Weifeng}}, publisher = {{LibreCat University}}, title = {{{Control of the electron dynamics in solid-state high harmonic generation on ultrafast time scales by a polarization-skewed laser pulse}}}, doi = {{10.5281/ZENODO.8001856}}, year = {{2023}}, } @misc{54394, abstract = {{Dataset of the publication “Excitonic anomalous currents in semiconductor quantum wells”, by C. Ngo, S. Priyadarshi, H. T. Duc, M. Bieler, and T. Meier, published in Physical Review B 108, 165302 (2023) ( https://doi.org/10.1103/PhysRevB.108.165302 )
The zip file includes a brief description and the data on which the plots of figures 2 – 10 are based, and the codes used for the numerical evaluations (k.p and semiconductor Bloch equations).}}, author = {{Ngo, Cong and Priyadarshi, Shekhar and Duc, Huynh Thanh and Bieler, Mark and Meier, Torsten}}, publisher = {{LibreCat University}}, title = {{{Excitonic anomalous currents in semiconductor quantum wells}}}, doi = {{10.5281/ZENODO.8175324}}, year = {{2023}}, } @misc{53287, abstract = {{Dataset of the publication “Terahertz-induced anomalous currents following the optical excitation of excitons in semiconductor quantum wells“, C. Ngo, S. Priyadarshi, H. T. Duc, M. Bieler, and T. Meier, Proc. SPIE 12419, Ultrafast Phenomena and Nanophotonics XXVII, 124190G (2023) ( https://doi.org/10.1117/12.2646022 ). The zip file includes the data on which the plots are based.
}}, author = {{Ngo, C. and Priyadarshi, S and Duc, H. T. and Meier, Torsten}}, publisher = {{LibreCat University}}, title = {{{Terahertz-induced anomalous currents following the optical excitation of excitons in semiconductor quantum wells}}}, doi = {{10.5281/ZENODO.7804463}}, year = {{2023}}, } @misc{54396, abstract = {{Dataset of the publication “Revealing the nonadiabatic tunneling dynamics in solid-state high harmonic generation“, by Ruixin Zuo, Xiaohong Song, Shuai Ben, Torsten Meier, and Weifeng Yang, published in PHYSICAL REVIEW RESEARCH 5, L022040 (2023) ( https://doi.org/10.1103/PhysRevResearch.5.L022040 )
The zip file includes the data on which the plots 2 – 9 are based.}}, author = {{Zuo, Ruixin and Song, Xiaohong and Ben, Shuai and Meier, Torsten and Yang, Weifeng}}, publisher = {{LibreCat University}}, title = {{{Revealing the nonadiabatic tunneling dynamics in solid-state high harmonic generation}}}, doi = {{10.5281/ZENODO.7967260}}, year = {{2023}}, }