@article{13284, author = {{Hannes, Wolf-Rüdiger and Meier, Torsten}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{12}}, title = {{{Higher-order contributions and nonperturbative effects in the nondegenerate nonlinear optical absorption of semiconductors using a two-band model}}}, doi = {{10.1103/physrevb.99.125301}}, volume = {{99}}, year = {{2019}}, } @article{13365, abstract = {{The KTiOPO4 (KTP) band structure and dielectric function are calculated on various levels of theory starting from density-functional calculations. Within the independent-particle approximation an electronic transport gap of 2.97 eV is obtained that widens to about 5.23 eV when quasiparticle effects are included using the GW approximation. The optical response is shown to be strongly anisotropic due to (i) the slight asymmetry of the TiO6 octahedra in the (001) plane and (ii) their anisotropic distribution along the [001] and [100] directions. In addition, excitonic effects are very important: The solution of the Bethe–Salpeter equation indicates exciton binding energies of the order of 1.5 eV. Calculations that include both quasiparticle and excitonic effects are in good agreement with the measured reflectivity.}}, author = {{Neufeld, Sergej and Bocchini, Adriana and Gerstmann, Uwe and Schindlmayr, Arno and Schmidt, Wolf Gero}}, issn = {{2515-7639}}, journal = {{Journal of Physics: Materials}}, pages = {{045003}}, publisher = {{IOP Publishing}}, title = {{{Potassium titanyl phosphate (KTP) quasiparticle energies and optical response}}}, doi = {{10.1088/2515-7639/ab29ba}}, volume = {{2}}, year = {{2019}}, } @article{26300, author = {{Sperling, Jan and Meyer-Scott, E. and Barkhofen, Sonja and Brecht, Benjamin and Silberhorn, Christine}}, issn = {{0031-9007}}, journal = {{Physical Review Letters}}, title = {{{Experimental Reconstruction of Entanglement Quasiprobabilities}}}, doi = {{10.1103/physrevlett.122.053602}}, year = {{2019}}, } @inproceedings{43748, abstract = {{The fundamental interband absorption in gallium arsenide shows a strong blue shift when biased by mid-infrared transients exceeding 10 MV/cm. This subcycle feature is induced by the localization of electronic wavefunctions from 3D to 2D.}}, author = {{Meier, Torsten and Bühler, Johannes and Schmidt, Christian and Heinrich, Alexander-Cornelius and Allerbeck, Jonas and Podzimski, Reinold and Berghoff, Daniel and Schmidt, Wolf Gero and Reichl, Christian and Wegscheider, Werner and Brida, Daniele and Leitenstorfer, Alfred}}, booktitle = {{XXI International Conference on Ultrafast Phenomena 2018 (UP 2018)}}, publisher = {{EDP Sciences}}, title = {{{Subcycle Wannier-Stark Localization by Mid-Infrared Bias in Gallium Arsenide}}}, doi = {{10.1051/epjconf/201920505001}}, volume = {{205}}, year = {{2019}}, } @article{22887, author = {{Vondran, J. and Spitzer, F. and Bayer, M. and Akimov, I. A. and Trautmann, Alexander and Reichelt, Matthias and Meier, Cedrik and Weber, N. and Meier, Torsten and André, R. and Mariette, H.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{15}}, pages = {{155308}}, title = {{{Spatially asymmetric transients of propagating exciton-polariton modes in a planar CdZnTe/CdMgTe guiding structure}}}, doi = {{10.1103/physrevb.100.155308}}, volume = {{100}}, year = {{2019}}, } @unpublished{22884, abstract = {{Measurement-induced nonclassical effects in a two-mode interferometer are investigated theoretically using numerical simulations and analytical results. We demonstrate that for certain parameters measurements within the interferometer lead to the occurrence of two-mode squeezing. The results strongly depend on the detection probability, the phase inside the interferometer, and the choice of the input states. The appropriate parameters for maximized squeezing are obtained. We analyze the influence of losses and confirm that the predicted effects are within reach of current experimental techniques.}}, author = {{Riabinin, Matvei and Sharapova, Polina and Bartley, Tim and Meier, Torsten}}, booktitle = {{arXiv:1912.09097}}, title = {{{Generating two-mode squeezing with multimode measurement-induced nonlinearity}}}, year = {{2019}}, } @article{13429, author = {{Bocchini, Adriana and Neufeld, Sergej and Gerstmann, Uwe and Schmidt, Wolf Gero}}, issn = {{0953-8984}}, journal = {{Journal of Physics: Condensed Matter}}, pages = {{385401}}, title = {{{Oxygen and potassium vacancies in KTP calculated from first principles}}}, doi = {{10.1088/1361-648x/ab295c}}, volume = {{31}}, year = {{2019}}, } @article{20578, author = {{Driben, R and Ma, Xuekai and Schumacher, Stefan and Meier, Torsten}}, issn = {{0146-9592}}, journal = {{Optics Letters}}, number = {{6}}, pages = {{1327--1330}}, title = {{{Bloch oscillations of multidimensional dark soliton wave packets and light bullets}}}, doi = {{10.1364/ol.44.001327}}, volume = {{44}}, year = {{2019}}, } @article{15851, author = {{Ma, Xuekai and Kartashov, Yaroslav Y and Gao, Tingge and Schumacher, Stefan}}, issn = {{1367-2630}}, journal = {{New Journal of Physics}}, title = {{{Controllable high-speed polariton waves in a PT-symmetric lattice}}}, doi = {{10.1088/1367-2630/ab5a9b}}, volume = {{21}}, year = {{2019}}, } @unpublished{13340, abstract = {{Spontaneous formation of transverse patterns is ubiquitous in nonlinear dynamical systems of all kinds. An aspect of particular interest is the active control of such patterns. In nonlinear optical systems this can be used for all-optical switching with transistor-like performance, for example realized with polaritons in a planar quantum-well semiconductor microcavity. Here we focus on a specific configuration which takes advantage of the intricate polarization dependencies in the interacting optically driven polariton system. Besides detailed numerical simulations of the coupled light-field exciton dynamics, in the present paper we focus on the derivation of a simplified population competition model giving detailed insight into the underlying mechanisms from a nonlinear dynamical systems perspective. We show that such a model takes the form of a generalized Lotka-Volterra system for two competing populations explicitly including a source term that enables external control. We present a comprehensive analysis both of the existence and stability of stationary states in the parameter space spanned by spatial anisotropy and external control strength. We also construct phase boundaries in non-trivial regions and characterize emerging bifurcations. The population competition model reproduces all key features of the switching observed in full numerical simulations of the rather complex semiconductor system and at the same time is simple enough for a fully analytical understanding of the system dynamics.}}, author = {{Pukrop, Matthias and Schumacher, Stefan}}, booktitle = {{arXiv:1903.12534}}, title = {{{Externally Controlled Lotka-Volterra Dynamics in a Linearly Polarized Polariton Fluid}}}, year = {{2019}}, } @unpublished{13347, abstract = {{<div> <div> <div> <p>Molecular doping in conjugated polymers is a crucial process for their application in organic photovoltaics and optoelectronics. In the present work we theoretically investigate p-type molecu- lar doping in a series of (poly[2,6-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b;3,4-b”]dithiophene)-alt- 4,7-(2,1,3-benzothiadiazole)] (PCPDT-BT) conjugated oligomers with different lengths and three widely-used dopants with different electron affinities, namely F4TCNQ, F6TCNNQ, and CN6-CP. We study in detail the molecular geometry of possible oligomer-dopant complexes and its influence on the doping mechanisms and electronic system properties. We find that the mechanisms of dop- ing and charge transfer observed sensitively depend on the specific geometry of the oligomer-dopant complexes. For a given complex different geometries may exist, some of which show transfer of an entire electron from the oligomer chain onto the dopant molecule resulting in an integer-charge transfer complex, leaving the system in a ground state with broken spin symmetry. In other ge- ometries merely hybridization of oligomer and dopant frontier orbitals occurs with partial charge transfer but spin-symmetric ground state. Considering the resulting electronic density of states both cases may well contribute to an increased electrical conductivity of corresponding film samples while the underlying physical mechanisms are entirely different. </p> </div> </div> </div>}}, author = {{Dong, Chuan-Ding and Schumacher, Stefan}}, title = {{{Molecular Doping of PCPDT-BT Copolymers: Comparison of Molecular Complexes with and Without Integer Charge Transfer}}}, year = {{2019}}, } @article{13343, author = {{Vollbrecht, Joachim and Wiebeler, Christian and Bock, Harald and Schumacher, Stefan and Kitzerow, Heinz-Siegfried}}, issn = {{1932-7447}}, journal = {{The Journal of Physical Chemistry C}}, number = {{7}}, pages = {{4483--4492}}, title = {{{Curved Polar Dibenzocoronene Esters and Imides versus Their Planar Centrosymmetric Homologs: Photophysical and Optoelectronic Analysis}}}, doi = {{10.1021/acs.jpcc.8b10730}}, volume = {{123}}, year = {{2019}}, } @article{40384, author = {{Ferreri, Alessandro and Ansari, V. and Silberhorn, Christine and Sharapova, Polina R.}}, issn = {{2469-9926}}, journal = {{Physical Review A}}, number = {{5}}, publisher = {{American Physical Society (APS)}}, title = {{{Temporally multimode four-photon Hong-Ou-Mandel interference}}}, doi = {{10.1103/physreva.100.053829}}, volume = {{100}}, year = {{2019}}, } @article{13282, author = {{Lin, Zemeng and Huang, Lingling and Xu, Zhen Tao and Li, Xiaowei and Zentgraf, Thomas and Wang, Yongtian}}, issn = {{2195-1071}}, journal = {{Advanced Optical Materials}}, number = {{21}}, pages = {{1900782}}, title = {{{Four‐Wave Mixing Holographic Multiplexing Based on Nonlinear Metasurfaces}}}, doi = {{10.1002/adom.201900782}}, volume = {{7}}, year = {{2019}}, } @article{24056, abstract = {{Source-free all optical sampling, based on the convolution of the signal spectrum with a frequency comb in an electronic-photonic, co-integrated silicon device will be presented for the first time, to the best of our knowledge. The method has the potential to achieve very high precision, requires only low power and can be fully tunable in the electrical domain. Sampling rates of three and four times the RF bandwidths of the photonics and electronics can be achieved. Thus, the presented method might lead to low-footprint, fully-integrated, precise, electrically tunable, photonic ADCs with very high-analog bandwidths for the digital infrastructure of tomorrow.}}, author = {{Misra, Arijit and Kress, Christian and Singh, Karanveer and Preussler, Stefan and Scheytt, Christoph and Schneider, Thomas}}, journal = {{Opt. Express}}, number = {{21}}, pages = {{29972--29984}}, title = {{{Integrated source-free all optical sampling with a sampling rate of up to three times the RF bandwidth of silicon photonic MZM}}}, doi = {{10.1364/OE.27.029972}}, volume = {{27}}, year = {{2019}}, } @inproceedings{24054, abstract = {{Optical sampling of pseudo random microwave signals with sinc-shaped Nyquist pulse sequences has been demonstrated in an integrated silicon photonics platform. An electronic-photonic, co-integrated depletion type silicon intensity modulator with high extinction ratio has been used to sample the microwave signal with a sampling rate, which corresponds to three times its RF bandwidth. Thus, a sampling rate of 21 GSa/s is achieved with a 7 GHz modulator, with 3 dBm of differential input power.}}, author = {{Misra, Arijit and Kress, Christian and Singh, Karanveer and Preussler, Stefan and Scheytt, Christoph and Schneider, Thomas}}, booktitle = {{2019 International Topical Meeting on Microwave Photonics (MWP)}}, pages = {{1--4}}, title = {{{Integrated All Optical Sampling of Microwave Signals in Silicon Photonics}}}, doi = {{10.1109/MWP.2019.8892128}}, year = {{2019}}, } @article{1765, author = {{Huang, Lingling and Zhang, Shuang and Zentgraf, Thomas}}, issn = {{2192-8614}}, journal = {{Nanophotonics}}, number = {{6}}, pages = {{1169--1190}}, publisher = {{Walter de Gruyter GmbH}}, title = {{{Metasurface holography: from fundamentals to applications}}}, doi = {{10.1515/nanoph-2017-0118}}, volume = {{7}}, year = {{2018}}, } @article{5916, author = {{Zhao, Ruizhe and Sain, Basudeb and Wei, Qunshuo and Tang, Chengchun and Li, Xiaowei and Weiss, Thomas and Huang, Lingling and Wang, Yongtian and Zentgraf, Thomas}}, issn = {{2047-7538}}, journal = {{Light: Science & Applications}}, number = {{1}}, publisher = {{Springer Nature America, Inc}}, title = {{{Multichannel vectorial holographic display and encryption}}}, doi = {{10.1038/s41377-018-0091-0}}, volume = {{7}}, year = {{2018}}, } @inproceedings{4579, abstract = {{Semi-guided waves confined in dielectric slab waveguides are being considered for oblique angles of propagation. If the waves encounter a linear discontinuity of (mostly) arbitrary shape and extension, a variant of Snell's law applies, separately for each pair of incoming and outgoing modes. Depending on the effective indices involved, and on the angle of incidence, power transfer to specific outgoing waves can be allowed or forbidden. In particular, critical angles of incidence can be identified, beyond which any power transfer to non-guided waves is forbidden, i.e. all radiative losses are suppressed. In that case the input power is carried away from the discontinuity exclusively by reflected semi-guided waves in the input slab, or by semi-guided waves that are transmitted into other outgoing slab waveguides. Vectorial equations on a 2-D cross sectional domain apply. These are formally identical to the equations that govern the eigenmodes of 3-D channel waveguides. Here, however, these need to be solved not as an eigenvalue problem, but as an inhomogeneous problem with a right-hand-side that is given by the incoming semi-guided wave, and subject to transparent boundary conditions. The equations resemble a standard 2-D Helmholtz problem, with an effective permittivity in place of the actual relative permittivity. Depending on the properties of the incoming wave, including the angle of incidence, this effective permittivity can become locally negative, causing the suppression of propagating outgoing waves. A series of high-contrast example configurations are discussed, where these effects lead to - in some respects - quite surprising transmission characteristics.}}, author = {{Hammer, Manfred and Ebers, Lena and Hildebrandt, Andre and Alhaddad, Samer and Förstner, Jens}}, booktitle = {{2018 IEEE 17th International Conference on Mathematical Methods in Electromagnetic Theory (MMET)}}, isbn = {{9781538654385}}, keywords = {{tet_topic_waveguides}}, publisher = {{IEEE}}, title = {{{Oblique Semi-Guided Waves: 2-D Integrated Photonics with Negative Effective Permittivity}}}, doi = {{10.1109/mmet.2018.8460455}}, year = {{2018}}, } @article{7008, author = {{Evers, E. and Belykh, V. V. and Kopteva, N. E. and Yugova, I. A. and Greilich, A. and Yakovlev, D. R. and Reuter, Dirk and Wieck, A. D. and Bayer, M.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{7}}, publisher = {{American Physical Society (APS)}}, title = {{{Decay and revival of electron spin polarization in an ensemble of (In,Ga)As quantum dots}}}, doi = {{10.1103/physrevb.98.075309}}, volume = {{98}}, year = {{2018}}, }