@article{64662,
  abstract     = {{<jats:p>
                    In this study, we investigate the impact of chromium-induced point defects on the nonlinear optical properties and electric-field-induced second harmonic generation (EFISH) in rutile titanium dioxide (TiO
                    <jats:sub>2</jats:sub>
                    ). Chromium thin films were deposited by electron beam evaporation on (001)-oriented bulk TiO
                    <jats:sub>2</jats:sub>
                    substrates and subsequently diffused into the lattice in a tube furnace under a nitrogen atmosphere at 900 °C. The introduction of chromium significantly enhanced the third harmonic generation (THG) of a 1560 nm laser, with an amplification factor of up to 8.3, indicative of an enhanced third-order nonlinear susceptibility,
                    <jats:italic>χ</jats:italic>
                    <jats:sup>(3)</jats:sup>
                    . Moreover, the application of an external voltage induced a pronounced EFISH signal in the chromium-doped samples, further confirming the enhanced nonlinear response. These results demonstrate that defect engineering via chromium doping in rutile TiO
                    <jats:sub>2</jats:sub>
                    offers a promising pathway for the development of high-performance nonlinear optical devices.
                  </jats:p>}},
  author       = {{Brinkmann, Marius and Meier, Falco and Spedt, Vladimir and Meier, Cedrik}},
  issn         = {{1094-4087}},
  journal      = {{Optics Express}},
  number       = {{26}},
  publisher    = {{Optica Publishing Group}},
  title        = {{{Boosting third-order nonlinearities in rutile TiO<sub>2</sub> by chromium doping}}},
  doi          = {{10.1364/oe.572063}},
  volume       = {{33}},
  year         = {{2025}},
}

@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{29716,
  author       = {{Widhalm, Alex and Golla, Christian and Weber, Nils and Mackwitz, Peter and Zrenner, Artur and Meier, Cedrik}},
  issn         = {{1094-4087}},
  journal      = {{Optics Express}},
  keywords     = {{Atomic and Molecular Physics, and Optics}},
  number       = {{4}},
  publisher    = {{The Optical Society}},
  title        = {{{Electric-field-induced second harmonic generation in silicon dioxide}}},
  doi          = {{10.1364/oe.443489}},
  volume       = {{30}},
  year         = {{2022}},
}

@article{29790,
  abstract     = {{The free exciton transition (near-band-edge emission, NBE) of ZnO at ≈388 nm can be strongly enhanced and even stimulated by an underlying photonic structure. 1D Photonic crystals, so-called distributed Bragg reflectors, are utilized to suppress the deep-level emission of ZnO (DLE, ≈500–530 nm). The reflector stacks are fabricated in a layer-by-layer procedure by wet-chemical synthesis. They consist of low-ε porous SiO2 layers and high-ε TiO2 layers. Varying the thickness of the SiO2 layers allows tuning the optical bandgap in a wide range between ≈420 and 800 nm. A ZnO layer is deposited on top of the reflector stacks by sol–gel synthesis. The spontaneous photoluminescence (PL) emission of the ZnO film is modulated by the photonic structure. When the optical bandgap of the reflector is in resonance with the deep-level emission of ZnO (DLE, ≈500–530 nm), then this defect-related emission mode is suppressed. Strong NBE emission is observed even when the ZnO layer does not show any NBE emission (due to low crystallinity) in the absence of the photonic structure. With this cost-efficient synthesis method, emitters for, e.g., luminescent gas sensors can be fabricated.}},
  author       = {{Kothe, Linda and Albert, Maximilian and Meier, Cedrik and Wagner, Thorsten and Tiemann, Michael}},
  issn         = {{2196-7350}},
  journal      = {{Advanced Materials Interfaces}},
  keywords     = {{Mechanical Engineering, Mechanics of Materials}},
  publisher    = {{Wiley}},
  title        = {{{Stimulation and Enhancement of Near‐Band‐Edge Emission in Zinc Oxide by Distributed Bragg Reflectors}}},
  doi          = {{10.1002/admi.202102357}},
  volume       = {{9}},
  year         = {{2022}},
}

@article{30210,
  abstract     = {{Lithium niobate on insulator (LNOI) has a great potential for photonic integrated circuits, providing substantial versatility in design of various integrated components. To properly use these components in the implementation of different quantum protocols, photons with different properties are required. In this paper, we theoretically demonstrate a flexible source of correlated photons built on the LNOI waveguide of a special geometry. This source is based on the parametric down-conversion (PDC) process, in which the signal and idler photons are generated at the telecom wavelength and have different spatial profiles and polarizations, but the same group velocities. Distinguishability in polarizations and spatial profiles facilitates the routing and manipulating individual photons, while the equality of their group velocities leads to the absence of temporal walk-off between photons. We show how the spectral properties of the generated photons and the number of their frequency modes can be controlled depending on the pump characteristics and the waveguide length. Finally, we discuss special regimes, in which narrowband light with strong frequency correlations and polarization-entangled Bell states are generated at the telecom wavelength.}},
  author       = {{Ebers, Lena and Ferreri, Alessandro and Hammer, Manfred and Albert, Maximilian and Meier, Cedrik and Förstner, Jens and Sharapova, Polina R.}},
  issn         = {{2515-7647}},
  journal      = {{Journal of Physics: Photonics}},
  keywords     = {{tet_topic_waveguide}},
  pages        = {{025001}},
  publisher    = {{IOP Publishing}},
  title        = {{{Flexible source of correlated photons based on LNOI rib waveguides}}},
  doi          = {{10.1088/2515-7647/ac5a5b}},
  volume       = {{4}},
  year         = {{2022}},
}

@article{23815,
  abstract     = {{In this paper, silicon oxynitride films (SiON) grown by plasma-enhanced chemical vapor deposition are investigated. As precursor gases silane (SiH4), nitrous oxide (N2O), nitrogen (N2) and ammonia (NH3) are used with different compositions. We find that for achieving high nitrogen content adding ammonia to the precursor mix is most efficient. Moreover, we investigate the balance between adsorption and desorption processes during film growth by investigating the film growth rate as a function of the substrate temperature. From these data we are able to determine an effective activation energy for the film growth, corresponding to the difference between adsorption and desorption energy. Finally, we have thoroughly investigated the optical properties of the films using spectroscopic ellipsometry. From these measurements, we suggest a parametrized model for the refractive index and extinction coefficient in a wide range of compositions based on a Cauchy- and a Lorentz-fit.}},
  author       = {{Aschwanden, R. and Köthemann, R. and Albert, M. and Golla, C. and Meier, Cedrik}},
  issn         = {{0040-6090}},
  journal      = {{Thin Solid Films}},
  title        = {{{Optical properties of silicon oxynitride films grown by plasma-enhanced chemical vapor deposition}}},
  doi          = {{10.1016/j.tsf.2021.138887}},
  volume       = {{736}},
  year         = {{2021}},
}

@article{20592,
  abstract     = {{GaAs-(111)-nanostructures exhibiting second harmonic generation are new building blocks in nonlinear optics. Such structures can be fabricated through epitaxial lift-off using selective etching of Al-containing layers and subsequent transfer to glass substrates. Herein, the selective etching of (111)B-oriented AlxGa1−xAs sacrificial layers (10–50 nm thick) with different aluminum concentrations (x = 0.5–1.0) in 10\% hydrofluoric acid is investigated and compared with standard (100)-oriented structures. The thinner the sacrificial layer and the lower the aluminum content, the lower the lateral etch rate. For both orientations, the lateral etch rates are in the same order of magnitude, but some quantitative differences exist. Furthermore, the epitaxial lift-off, the transfer, and the nanopatterning of thin (111)B-oriented GaAs membranes are demonstrated. Atomic force microscopy and high-resolution X-ray diffraction measurements reveal the high structural quality of the transferred GaAs-(111) films.}},
  author       = {{Henksmeier, Tobias and Eppinger, Martin and Reineke, Bernhard and Zentgraf, Thomas and Meier, Cedrik and Reuter, Dirk}},
  journal      = {{physica status solidi (a)}},
  keywords     = {{epitaxial lift-off, GaAs/AlxGa1−xAs heterostructures, selective etching}},
  number       = {{3}},
  pages        = {{2000408}},
  title        = {{{Selective Etching of (111)B-Oriented AlxGa1−xAs-Layers for Epitaxial Lift-Off}}},
  doi          = {{https://doi.org/10.1002/pssa.202000408}},
  volume       = {{218}},
  year         = {{2021}},
}

@article{20900,
  author       = {{Albert, M. and Golla, C. and Meier, Cedrik}},
  issn         = {{0022-0248}},
  journal      = {{Journal of Crystal Growth}},
  title        = {{{Optical in-situ temperature management for high-quality ZnO molecular beam epitaxy}}},
  doi          = {{10.1016/j.jcrysgro.2020.126009}},
  volume       = {{557}},
  year         = {{2021}},
}

@article{22214,
  author       = {{Mund, Johannes and Yakovlev, Dmitri R. and Sadofev, Sergey and Meier, Cedrik and Bayer, Manfred}},
  issn         = {{2469-9950}},
  journal      = {{Physical Review B}},
  title        = {{{Second harmonic generation on excitons in ZnO/(Zn,Mg)O quantum wells with built-in electric fields}}},
  doi          = {{10.1103/physrevb.103.195311}},
  volume       = {{103}},
  year         = {{2021}},
}

@article{20644,
  abstract     = {{Plasmonic nanoantennas for visible and infrared radiation strongly improve the interaction of light with the matter on the nanoscale due to their strong near-field enhancement. In this study, we investigate a double-resonant plasmonic nanoantenna, which makes use of plasmonic field enhancement, enhanced outcoupling of second harmonic light, and resonant lattice effects. Using this design, we demonstrate how the efficiency of second harmonic generation can be increased significantly by fully embedding the nanoantennas into nonlinear dielectric material ZnO, instead of placing them on the surface. Investigating two different processes, we found that the best fabrication route is embedding the gold nanoantennas in ZnO using an MBE overgrowth process where a thin ZnO layer was deposited on nanoantennas fabricated on a ZnO substrate. In addition, second harmonic generation measurements show that the embedding leads to an enhancement compared to the emission of nanoantennas placed on the ZnO substrate surface. These promising results facilitate further research to determine the influence of the periodicity of the nanoantenna arrangement of the resulting SHG signal.}},
  author       = {{Volmert, Ruth and Weber, Nils and Meier, Cedrik}},
  issn         = {{1089-7550}},
  journal      = {{Journal of Applied Physics}},
  number       = {{4}},
  title        = {{{Nanoantennas embedded in zinc oxide for second harmonic generation enhancement}}},
  doi          = {{10.1063/5.0012813}},
  volume       = {{128}},
  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{8797,
  abstract     = {{Free from phase-matching constraints, plasmonic metasurfaces have contributed significantly to the control of optical nonlinearity and enhancement of nonlinear generation efficiency by engineering subwavelength meta-atoms. However, high dissipative losses and inevitable thermal heating limit their applicability in nonlinear nanophotonics. All-dielectric metasurfaces, supporting both electric and magnetic Mie-type resonances in their nanostructures, have appeared as a promising alternative to nonlinear plasmonics. High-index dielectric nanostructures, allowing additional magnetic resonances, can induce magnetic nonlinear effects, which, along with electric nonlinearities, increase the nonlinear conversion efficiency. In addition, low dissipative losses and high damage thresholds provide an extra degree of freedom for operating at high pump intensities, resulting in a considerable enhancement of the nonlinear processes. We discuss the current state of the art in the intensely developing area of all-dielectric nonlinear nanostructures and metasurfaces, including the role of Mie modes, Fano resonances, and anapole moments for harmonic generation, wave mixing, and ultrafast optical switching. Furthermore, we review the recent progress in the nonlinear phase and wavefront control using all-dielectric metasurfaces. We discuss techniques to realize all-dielectric metasurfaces for multifunctional applications and generation of second-order nonlinear processes from complementary metal–oxide–semiconductor-compatible materials.}},
  author       = {{Sain, Basudeb and Meier, Cedrik and Zentgraf, Thomas}},
  issn         = {{2577-5421}},
  journal      = {{Advanced Photonics}},
  number       = {{2}},
  pages        = {{024002}},
  title        = {{{Nonlinear optics in all-dielectric nanoantennas and metasurfaces: a review}}},
  doi          = {{10.1117/1.ap.1.2.024002}},
  volume       = {{1}},
  year         = {{2019}},
}

@article{9698,
  author       = {{Golla, C. and Weber, N. and Meier, Cedrik}},
  issn         = {{0021-8979}},
  journal      = {{Journal of Applied Physics}},
  number       = {{7}},
  title        = {{{Zinc oxide based dielectric nanoantennas for efficient nonlinear frequency conversion}}},
  doi          = {{10.1063/1.5082720}},
  volume       = {{125}},
  year         = {{2019}},
}

@article{9897,
  author       = {{Protte, Maximilian and Weber, Nils and Golla, Christian and Zentgraf, Thomas and Meier, Cedrik}},
  issn         = {{0021-8979}},
  journal      = {{Journal of Applied Physics}},
  title        = {{{Strong nonlinear optical response from ZnO by coupled and lattice-matched nanoantennas}}},
  doi          = {{10.1063/1.5093257}},
  volume       = {{125}},
  year         = {{2019}},
}

@article{12930,
  author       = {{Köthemann, Ronja and Weber, Nils and Lindner, Jörg K N and Meier, Cedrik}},
  issn         = {{0268-1242}},
  journal      = {{Semiconductor Science and Technology}},
  number       = {{9}},
  title        = {{{High-precision determination of silicon nanocrystals: optical spectroscopy versus electron microscopy}}},
  doi          = {{10.1088/1361-6641/ab3536}},
  volume       = {{34}},
  year         = {{2019}},
}

@article{14544,
  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}},
}

@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}},
}

@article{1430,
  author       = {{Hoffmann, Sandro P. and Albert, Maximilian and Weber, Nils and Sievers, Denis and Förstner, Jens and Zentgraf, Thomas and Meier, Cedrik}},
  issn         = {{2330-4022}},
  journal      = {{ACS Photonics}},
  keywords     = {{tet_topic_phc}},
  pages        = {{1933--1942}},
  publisher    = {{American Chemical Society (ACS)}},
  title        = {{{Tailored UV Emission by Nonlinear IR Excitation from ZnO Photonic Crystal Nanocavities}}},
  doi          = {{10.1021/acsphotonics.7b01228}},
  volume       = {{5}},
  year         = {{2018}},
}

@article{1327,
  author       = {{Weber, N. and Hoffmann, S. P. and Albert, M. and Zentgraf, Thomas and Meier, Cedrik}},
  issn         = {{0021-8979}},
  journal      = {{Journal of Applied Physics}},
  number       = {{10}},
  publisher    = {{AIP Publishing}},
  title        = {{{Efficient frequency conversion by combined photonic–plasmonic mode coupling}}},
  doi          = {{10.1063/1.5017010}},
  volume       = {{123}},
  year         = {{2018}},
}