@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{54852,
  abstract     = {{<jats:p>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.</jats:p>}},
  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     = {{<jats:p>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.</jats:p>}},
  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}},
}

@misc{53298,
  abstract     = {{Dataset of the publication "Theoretical analysis of four-wave mixing on semiconductor quantum dot ensembles with quantum light" H. Rose, S. Grisard, A. V. Trifonov, R. Reichhardt, M. Reichelt, M. Bayer, I. A. Akimov, and T. Meier, Proc. SPIE 12419, Ultrafast Phenomena and Nanophotonics XXVII, 124190H (2023). ( https://doi.org/10.1117/12.2647700 ). The zip file includes the data on which the plots shown in figures 1 and 2 are based.}},
  author       = {{Rose, Hendrik and Grisard, Stefan and Trifonov, Artur V. and Reichhardt, Rilana and Reichelt, Matthias and Bayer, Manfred and Akimov, Ilya A. and Meier, Torsten}},
  publisher    = {{LibreCat University}},
  title        = {{{Theoretical analysis of four-wave mixing on semiconductor quantum dot ensembles with quantum light}}},
  doi          = {{10.5281/ZENODO.7755761}},
  year         = {{2023}},
}

@article{50012,
  abstract     = {{Silicon photonics, in conjunction with complementary metal-oxide-semiconductor (CMOS) fabrication, has greatly enhanced the development of integrated optical phased arrays. This facilitates a dynamic control of light in a compact form factor that enables the synthesis of arbitrary complex wavefronts in the infrared spectrum. We numerically demonstrate a large-scale two-dimensional silicon-based optical phased array (OPA) composed of nanoantennas with circular gratings that are balanced in power and aligned in phase, required for producing elegant radiation patterns in the far-field. For a wavelength of 1.55 μm, we optimize two antennas for the OPA exhibiting an upward radiation efficiency as high as 90%, with almost 6.8% of optical power concentrated in the field of view. Additionally, we believe that the proposed OPAs can be easily fabricated and would have the ability to generate complex holographic images, rendering them an attractive candidate for a wide range of applications like LiDAR sensors, optical trapping, optogenetic stimulation, and augmented-reality displays.}},
  author       = {{Farheen, Henna and Strauch, Andreas and Scheytt, J. Christoph and Myroshnychenko, Viktor and Förstner, Jens}},
  issn         = {{1569-4410}},
  journal      = {{Photonics and Nanostructures - Fundamentals and Applications}},
  keywords     = {{tet_topic_opticalantenna}},
  pages        = {{101207}},
  publisher    = {{Elsevier BV}},
  title        = {{{Optimized, Highly Efficient Silicon Antennas for Optical Phased Arrays}}},
  doi          = {{10.1016/j.photonics.2023.101207}},
  volume       = {{58}},
  year         = {{2023}},
}

@article{43245,
  abstract     = {{High-contrast slab waveguide Bragg gratings with 1D periodicity are investigated. For specific oblique excitation by semi-guided waves at sufficiently high angles of incidence, the idealized structures do not exhibit any radiative losses, such that reflectance and transmittance for the single port mode add strictly up to one. We consider a series of symmetric, fully and partly etched finite gratings, for parameters found in integrated silicon photonics. These can act as spectral filters with a reasonably flattop response. Apodization can lead to more box shaped reflectance and transmittance spectra. Together with a narrowband Fabry–Perot filter, these configurations are characterized by reflection bands, or transmittance peaks, with widths that span three orders of magnitude.}},
  author       = {{Hammer, Manfred and Farheen, Henna and Förstner, Jens}},
  issn         = {{0740-3224}},
  journal      = {{Journal of the Optical Society of America B}},
  keywords     = {{tet_topic_waveguide}},
  number       = {{4}},
  pages        = {{862}},
  publisher    = {{Optica Publishing Group}},
  title        = {{{How to suppress radiative losses in high-contrast integrated Bragg gratings}}},
  doi          = {{10.1364/josab.485725}},
  volume       = {{40}},
  year         = {{2023}},
}

@inproceedings{43052,
  abstract     = {{We demonstrate a large-scale two dimensional silicon-based optical phased array (OPA) composed of nanoantennas with circular gratings that are balanced in power and aligned in phase, required for producing desired radiation patterns in the far-field. The OPAs are numerically optimized to have an upward efficiency of up to 90%, targeting radiation concentration mainly in the field of view. We envision that our OPAs have the ability of generating complex holographic images, rendering them an attractive candidate for a wide range of applications like LiDAR sensors, optical trapping, optogenetic stimulation and augmented-reality displays.}},
  author       = {{Farheen, Henna and Strauch, Andreas and Scheytt, J. Christoph and Myroshnychenko, Viktor and Förstner, Jens}},
  booktitle    = {{Integrated Optics: Devices, Materials, and Technologies XXVII}},
  editor       = {{García-Blanco, Sonia M. and Cheben, Pavel}},
  keywords     = {{tet_topic_opticalantenna}},
  pages        = {{124241D }},
  publisher    = {{SPIE}},
  title        = {{{Optimized silicon antennas for optical phased arrays}}},
  doi          = {{10.1117/12.2658716}},
  year         = {{2023}},
}

@inproceedings{50466,
  abstract     = {{A key challenge in designing efficient optical phased arrays is the lack of a well-designed radiator. This work explores horn antennas numerically optimized to target high upward radiation efficiency to be employed in silicon-based phased arrays capable of producing elegant radiation patterns in the far-field.}},
  author       = {{Farheen, Henna and Joshi, S. and Scheytt, J. Christoph and Myroshnychenko, Viktor and Förstner, Jens}},
  booktitle    = {{2023 IEEE Photonics Conference (IPC)}},
  keywords     = {{tet_topic_opticalantenna}},
  publisher    = {{IEEE}},
  title        = {{{Increasing the upward radiation efficiency of optical phased arrays using asymmetric silicon horn antennas}}},
  doi          = {{10.1109/ipc57732.2023.10360519}},
  year         = {{2023}},
}

@article{55901,
  author       = {{Grisard, Stefan and Trifonov, Artur V. and Rose, Hendrik and Reichhardt, Rilana and Reichelt, Matthias and Schneider, Christian and Kamp, Martin and Höfling, Sven and Bayer, Manfred and Meier, Torsten and Akimov, Ilya A.}},
  issn         = {{2330-4022}},
  journal      = {{ACS Photonics}},
  number       = {{9}},
  pages        = {{3161--3170}},
  publisher    = {{American Chemical Society (ACS)}},
  title        = {{{Temporal Sorting of Optical Multiwave-Mixing Processes in Semiconductor Quantum Dots}}},
  doi          = {{10.1021/acsphotonics.3c00530}},
  volume       = {{10}},
  year         = {{2023}},
}

@article{37280,
  author       = {{Rose, Hendrik and Vasil'ev, A. N. and Tikhonova, O. V. and Meier, Torsten and Sharapova, Polina}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Quantum-optical excitations of semiconductor nanostructures in a microcavity using a two-band model and a single-mode quantum field}}},
  doi          = {{10.1103/physreva.107.013703}},
  volume       = {{107}},
  year         = {{2023}},
}

@unpublished{43132,
  author       = {{Meier, Torsten and Grisard, S. and Trifonov, A.V. and Rose, Hendrik and Reichhardt, R. and Reichelt, Matthias and Schneider, C. and Kamp, M. and Höfling, S. and Bayer, M. and Akimov, I.A}},
  booktitle    = {{arxiv:2302.02480}},
  title        = {{{Temporal sorting of optical multi-wave-mixing processes in semiconductor quantum dots}}},
  year         = {{2023}},
}

@article{44050,
  author       = {{Sperling, Jan and Agudelo, Elizabeth}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{4}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Entanglement of particles versus entanglement of fields: Independent quantum resources}}},
  doi          = {{10.1103/physreva.107.042420}},
  volume       = {{107}},
  year         = {{2023}},
}

@article{40477,
  author       = {{Sperling, Jan and Gianani, Ilaria and Barbieri, Marco and Agudelo, Elizabeth}},
  issn         = {{2469-9926}},
  journal      = {{Physical Review A}},
  number       = {{1}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Detector entanglement: Quasidistributions for Bell-state measurements}}},
  doi          = {{10.1103/physreva.107.012426}},
  volume       = {{107}},
  year         = {{2023}},
}

@article{42973,
  author       = {{Lüders, Carolin and Pukrop, Matthias and Barkhausen, Franziska and Rozas, Elena and Schneider, Christian and Höfling, Sven and Sperling, Jan and Schumacher, Stefan and Aßmann, Marc}},
  issn         = {{0031-9007}},
  journal      = {{Physical Review Letters}},
  keywords     = {{General Physics and Astronomy}},
  number       = {{11}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Tracking Quantum Coherence in Polariton Condensates with Time-Resolved Tomography}}},
  doi          = {{10.1103/physrevlett.130.113601}},
  volume       = {{130}},
  year         = {{2023}},
}

@article{44097,
  abstract     = {{We present strong enhancement of third harmonic generation in an amorphous silicon metasurface consisting of elliptical nano resonators. We show that this enhancement originates from a new type of multi-mode Fano mechanism. These ‘Super-Fano’ resonances are investigated numerically in great detail using full-wave simulations. The theoretically predicted behavior of the metasurface is experimentally verified by linear and nonlinear transmission spectroscopy. Moreover, quantitative nonlinear measurements are performed, in which an absolute conversion efficiency as high as ηmax ≈ 2.8 × 10−7 a peak power intensity of 1.2 GW cm−2 is found. Compared to an unpatterned silicon film of the same thickness amplification factors of up to ~900 are demonstrated. Our results pave the way to exploiting a strong Fano-type multi-mode coupling in metasurfaces for high THG in potential applications.}},
  author       = {{Hähnel, David and Golla, Christian and Albert, Maximilian and Zentgraf, Thomas and Myroshnychenko, Viktor and Förstner, Jens and Meier, Cedrik}},
  issn         = {{2047-7538}},
  journal      = {{Light: Science & Applications}},
  keywords     = {{tet_topic_meta}},
  number       = {{1}},
  pages        = {{97}},
  publisher    = {{Springer Nature}},
  title        = {{{A multi-mode super-fano mechanism for enhanced third harmonic generation in silicon metasurfaces}}},
  doi          = {{https://doi.org/10.1038/s41377-023-01134-1}},
  volume       = {{12}},
  year         = {{2023}},
}

@article{44044,
  abstract     = {{Dispersion is present in every optical setup and is often an undesired effect, especially in nonlinear-optical experiments where ultrashort laser pulses are needed. Typically, bulky pulse compressors consisting of gratings or prisms are used
to address this issue by precompensating the dispersion of the optical components. However, these devices are only able to compensate for a part of the dispersion (second-order dispersion). Here, we present a compact pulse-shaping device that uses plasmonic metasurfaces to apply an arbitrarily designed spectral phase delay allowing for a full dispersion control. Furthermore, with specific phase encodings, this device can be used to temporally reshape the incident laser pulses into more complex pulse forms such as a double pulse. We verify the performance of our device by using an SHG-FROG measurement setup together with a retrieval algorithm to extract the dispersion that our device applies to an incident laser pulse.}},
  author       = {{Geromel, René and Georgi, Philip and Protte, Maximilian and Lei, Shiwei and Bartley, Tim and Huang, Lingling and Zentgraf, Thomas}},
  issn         = {{1530-6984}},
  journal      = {{Nano Letters}},
  keywords     = {{Mechanical Engineering, Condensed Matter Physics, General Materials Science, General Chemistry, Bioengineering}},
  number       = {{8}},
  pages        = {{3196 -- 3201}},
  publisher    = {{American Chemical Society (ACS)}},
  title        = {{{Compact Metasurface-Based Optical Pulse-Shaping Device}}},
  doi          = {{10.1021/acs.nanolett.2c04980}},
  volume       = {{23}},
  year         = {{2023}},
}

@article{45596,
  abstract     = {{Dielectric metasurfaces provide a unique platform for efficient harmonic generation and optical wavefront manipulation at the nanoscale. Tailoring phase and amplitude of a nonlinearly generated wave with a high emission efficiency using resonance-based metasurfaces is a challenging task that often requires state-of-the-art numerical methods. Here, we propose a simple yet effective approach combining a sampling method with a Monte Carlo approach to design the third-harmonic wavefront generated by all-dielectric metasurfaces composed of elliptical silicon nanodisks. Using this approach, we theoretically demonstrate the full nonlinear 2π phase control with a uniform and highest possible amplitude in the considered parameter space, allowing us to design metasurfaces operating as third harmonic beam deflectors capable of steering light into a desired direction with high emission efficiency. The TH beam deflection with a record calculated average conversion efficiency of 1.2 × 10–1 W–2 is achieved. We anticipate that the proposed approach will be widely applied as alternative to commonly used optimization algorithms with higher complexity and implementation effort for the design of metasurfaces with other holographic functionalities.}},
  author       = {{Hähnel, David and Förstner, Jens and Myroshnychenko, Viktor}},
  issn         = {{2330-4022}},
  journal      = {{ACS Photonics}},
  keywords     = {{tet_topic_meta}},
  publisher    = {{American Chemical Society (ACS)}},
  title        = {{{Efficient Modeling and Tailoring of Nonlinear Wavefronts in Dielectric Metasurfaces}}},
  doi          = {{10.1021/acsphotonics.2c01967}},
  year         = {{2023}},
}

@inproceedings{43192,
  abstract     = {{The nonlinear optical response of an ensemble of semiconductor quantum dots is analyzed by wave-mixing processes, where we focus on four-wave mixing with two incident pulses. Wave-mixing experiments are often described with semiclassical models, where the light is modeled classically and the material quantum mechanically. Here, however, we use a fully quantized model, where the light is given by a quantum state of light. Quantum light involves more degrees of freedom than classical light as e.g., its photon statistics and quantum correlations, which is a promising resource for quantum devices, such as quantum memories. The light-matter interaction is treated with a Jaynes-Cummings type model and the quantum field is given by a single mode since the quantum dots are embedded in a microcavity. We present numerical simulations of the four-wave-mixing response of a homogeneous system for pulse sequences and find a significant dependence of the result on the photon statistics of the incident pulses. The model constitutes a problem with a large state space which arises from the frequency distribution of the transition energies of the inhomogeneously broadened quantum dot ensemble that is coupled with a quantum light mode. Here we approximate the dynamics by summing over individual quantum dot-microcavity systems. Photon echoes arising from the excitation with different quantum states of light are simulated and compared.}},
  author       = {{Rose, Hendrik and Grisard, S. and Trifonov, A. V. and Reichhardt, R. and Reichelt, Matthias and Bayer, M. and Akimov, I. A.  and Meier, Torsten}},
  booktitle    = {{Ultrafast Phenomena and Nanophotonics XXVII}},
  publisher    = {{SPIE}},
  title        = {{{Theoretical analysis of four-wave mixing on semiconductor quantum dot ensembles with quantum light}}},
  doi          = {{10.1117/12.2647700}},
  volume       = {{12419}},
  year         = {{2023}},
}

@article{45704,
  abstract     = {{<jats:p>Since high-order harmonic generation (HHG) from atoms depends sensitively on the polarization of the driving laser field, the polarization gating (PG) technique was developed and applied successfully to generate isolated attosecond pulses from atomic gases. The situation is, however, different in solid-state systems as it has been demonstrated that due to collisions with neighboring atomic cores of the crystal lattice strong HHG can be generated even by elliptically- and circularly-polarized laser fields. Here we apply PG to solid-state systems and find that the conventional PG technique is inefficient for the generation of isolated ultrashort harmonic pulse bursts. In contrast, we demonstrate that a polarization-skewed laser pulse is able to confine the harmonic emission to a time window of less than one-tenth of the laser cycle. This method provides a novel way to control HHG and to generate isolated attosecond pulses in solids.</jats:p>}},
  author       = {{Song, Xiaohong and Yang, Shidong and Wang, Guifang and Lin, Jianpeng and Wang, Liang and Meier, Torsten and Yang, Weifeng}},
  issn         = {{1094-4087}},
  journal      = {{Optics Express}},
  keywords     = {{Atomic and Molecular Physics, and Optics}},
  number       = {{12}},
  publisher    = {{Optica Publishing Group}},
  title        = {{{Control of the electron dynamics in solid-state high harmonic generation on ultrafast time scales by a polarization-skewed laser pulse}}},
  doi          = {{10.1364/oe.491418}},
  volume       = {{31}},
  year         = {{2023}},
}

@article{45703,
  author       = {{Zuo, Ruixin and Song, Xiaohong and Ben, Shuai and Meier, Torsten and Yang, Weifeng}},
  issn         = {{2643-1564}},
  journal      = {{Physical Review Research}},
  keywords     = {{General Physics and Astronomy}},
  number       = {{2}},
  publisher    = {{American Physical Society (APS)}},
  title        = {{{Revealing the nonadiabatic tunneling dynamics in solid-state high harmonic generation}}},
  doi          = {{10.1103/physrevresearch.5.l022040}},
  volume       = {{5}},
  year         = {{2023}},
}