@article{63827, abstract = {{Light-emitting diodes (LEDs) are becoming increasingly important across various sectors of the lighting industry and are being used more frequently. In the field of symbolic projection, research is increasingly focusing on implementing light modulation using energy-efficient, incoherent LEDs rather than lasers. Since light modulation in micro- and nano-optics is typically achieved through phase modulation, Finite-Difference Time-Domain (FDTD) simulations are employed for analysis. The objective of this article is to investigate different approaches for approximating incoherent monochromatic light sources within FDTD simulations. To this end, two approaches based on dipole sources are considered, as well as a method involving plane waves with modulated wavefronts based on Cosine–Fourier functions and a method based on the superposition of Gaussian beams. These methods are evaluated in terms of their accuracy using a two-dimensional double-slit configuration and are compared against a fully incoherent analytical reference.}}, author = {{Metzner, Dominik and Potthoff, Jens and Zentgraf, Thomas and Förstner, Jens}}, issn = {{2304-6732}}, journal = {{Photonics}}, keywords = {{tet_topic_opticalantenna, tet_topic_numerics, tet_topic_meta}}, number = {{2}}, publisher = {{MDPI AG}}, title = {{{Approximating Incoherent Monochromatic Light Sources in FDTD Simulations}}}, doi = {{10.3390/photonics13020128}}, volume = {{13}}, year = {{2026}}, } @article{64864, abstract = {{Probing novel properties, arising from twisted interfaces, has traditionally relied on the stacking of exfoliated two-dimensional materials and the spontaneous formation of van der Waals bonds. So far, investigations involving intimate covalent or ionic bonds have not been a focus. Yet, we show here that an established technique, involving thermocompressional wafer bonding, works well for creating twisted non-van der Waals interfaces. We have successfully bonded z-cut lithium niobate single crystals to create ferroelectric oxide interfaces with strong polar discontinuities and have mapped the associated emergent interfacial conductivity. In some instances, a dramatic change in microstructure occurs, involving local dipolar switching. A twist-induced collapse in the capability of the system to effec8tively screen interfacial bound charge is implied. Importantly, this only occurs around specific moiré twist angles with sparse coincident lattices and associated short-range aperiodicity. In quasicrystals, aperiodicity is known to induce pseudo-bandgaps and we suspect a similar phenomenon here.}}, author = {{Rogers, Andrew and Holsgrove, Kristina and Schäfer, Nils A. and Koppitz, Boris and McCluskey, Conor J. and Yedama, Shivani and Lynch, Ronan and Sloan, Keelan and Porter, Barry and Sykes, Adam and Catalan Daniels, Alex and Silva, Romualdo S. and Bruno, Flavio Y. and Seddon, Sam D. and Lu, Haidong and Rüsing, Michael and Fink, Christa and Fahler-Muenzer, Philipp and Fearn, Sarah and Heutz, Sandrine E. M. and Hadjimichael, Marios and Ramasse, Quentin M. and Alexe, Marin and Kumar, Amit and McQuaid, Raymond G. P. and Gruverman, Alexei and Sanna, Simone and Eng, Lukas M. and Gregg, J. Marty}}, issn = {{2041-1723}}, journal = {{Nature Communications}}, number = {{1}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{Polar discontinuities, emergent conductivity, and critical twist-angle-dependent behaviour at wafer-bonded ferroelectric interfaces}}}, doi = {{10.1038/s41467-026-68553-7}}, volume = {{17}}, year = {{2026}}, } @article{64873, abstract = {{Continuous flow catalysis utilizing gel-bound organocatalysts within a microfluidic reactor represents a compelling strategy in the realm of organic synthesis. In this study, a quinuclidine-based catalytic monomer (QMA) was synthesized to create polymer gel dots through the process of photopolymerization that serve as a support for the catalyst. The resulting gel-bound organocatalysts were assembled within a continuous microfluidic reactor to facilitate the Baylis–Hillman reaction between various aldehydes and acrylonitrile at a temperature of 50 °C. The conversion of the product was assessed using 1H NMR spectroscopy as an offline analytical method over a duration of 8 h. The findings indicated that highly reactive aldehydes achieved conversion rates exceeding 90%, in contrast to their less reactive counterparts. Furthermore, these results were juxtaposed with previously published data derived from alternative synthetic methodologies, revealing that the continuous microfluidic reactions employing integrated organocatalysts within polymer networks exhibited significantly higher conversions with reduced reaction times (8 h) at the same temperature (50 °C). Additionally, the influence of different geometries (round, triangular, and square) of the gel dots on catalytic activity was investigated, with round and square gel dots demonstrating slightly superior performance compared with triangular gel dots, attributed to their increased surface area. Moreover, an extended reaction period of 6 days was conducted using 4-bromobenzaldehyde and acrylonitrile, resulting in a conversion rate exceeding 70%, which remained stable for 5 days before experiencing a slight decline due to product accumulation on the gel dots.}}, author = {{Killi, Naresh and Kumar, Amit and Nebhani, Leena and Obst, Franziska and Richter, Andreas and Reineke Matsudo, Bernhard and Zentgraf, Thomas and Kuckling, Dirk}}, issn = {{2470-1343}}, journal = {{ACS Omega}}, number = {{9}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Integrating an Organocatalyst into a Polymeric Gel Framework for the Continuous Microflow Baylis–Hillman Reaction}}}, doi = {{10.1021/acsomega.5c09476}}, volume = {{11}}, year = {{2026}}, } @article{61523, abstract = {{AbstractMetasurface holography offers a powerful approach for manipulating wavefronts at the nano and micro scale. Extensive research has been conducted to enhance the multiplexing capacity for diverse wavefronts. However, the independence of multiplexed channels is fundamentally restricted in techniques using single‐layer metasurfaces, resulting in unavoidable crosstalk and the need for post‐filtering of the output wavefronts. Here, a universal wavefront multiplexing concept is presented based on non‐injective transformation. By employing joint optimization on two metasurfaces, different channels can be independently designed without any constraints on the output wavefronts. To validate this approach, ultra‐compact orbital angular momentum (OAM) sorters are designed. In these experiments, the output beams from different channels can be independently mapped to 2D positions with high fineness. In another application of wavefront‐multiplexed holography, 10‐channel multiplexing is experimentally achieved with minimal crosstalk and without the need for post‐processing. These results demonstrate the independence between channels enabled by the non‐injective transformation in the method. The precise wavefront control and high multiplexing capacity underscore its potential for scalable wavefront manipulation devices.}}, author = {{Jin, Xiao and Zentgraf, Thomas}}, issn = {{0935-9648}}, journal = {{Advanced Materials}}, publisher = {{Wiley}}, title = {{{Independent Wavefront Multiplexing with Metasurfaces via Non‐Injective Transformation}}}, doi = {{10.1002/adma.202511823}}, volume = {{38}}, year = {{2026}}, } @article{64978, abstract = {{The degrees of freedom (DoFs) of light determine the maximum number of independent signal channels an optical system can support. However, the polarization DoF is intrinsically limited to two by orthogonality, which causes unavoidable crosstalk and often forces position multiplexing, where different channels are assigned to distinct spatial locations to suppress crosstalk. This research introduces a multilayer synchronous polarization projection method that fundamentally increases the DoF for polarization multiplexing. The DoF equals twice the number of projection layers. We experimentally demonstrate six- channel polarization multiplexing holography without position multiplexing. The six-channel multiplexing results indicate that our approach exceeds the conventional polarization multiplexing method, yielding an average 3.79 dB improvement in extinction ratio across the six channels. Compared with the theoretical limit of traditional polarization multiplexing, our method reduces crosstalk by an average of 6.52 dB across all channels in a seven-channel design. The polarization projection method breaks the DoF limitation of polarization multiplexing, opening a path toward high-dimensional photonic information encoding for communication, encryption, and imaging.}}, author = {{Jin, Xiao and Zentgraf, Thomas}}, issn = {{2577-5421}}, journal = {{Advanced Photonics}}, number = {{02}}, publisher = {{SPIE-Intl Soc Optical Eng}}, title = {{{Increasing the design degree of freedom for polarization through multilayer synchronous polarization projection}}}, doi = {{10.1117/1.ap.8.2.026010}}, volume = {{8}}, year = {{2026}}, } @article{65094, abstract = {{ The development of practical sensors for optical coherence tomography (OCT) with undetected photons requires miniaturization via integration. To be practical, these sensors must exhibit a large spectral bandwidth and a high brightness, which are linked to a high axial resolution and a sufficient signal-to-noise ratio, respectively. Here, we combine these requirements in a scheme for OCT measurements with undetected photons based on nonlinear Ti : Li Nb O 3 waveguides. We investigate the performance benchmarks of the commonly used SU(1,1) scheme in comparison to an induced-coherence scheme and find that the latter is actually better suited when implementing measurements with undetected photons in integrated systems. In both schemes, we perform pump-gain optimization and OCT measurements with undetected photons with an axial resolution as low as 28 μ m . }}, author = {{Roeder, Franz and Pollmann, René and Quiring, Viktor and Eigner, Christof and Brecht, Benjamin and Silberhorn, Christine}}, issn = {{2331-7019}}, journal = {{Physical Review Applied}}, number = {{3}}, publisher = {{American Physical Society (APS)}}, title = {{{Toward integrated sensors for optimized optical coherence tomography with undetected photons}}}, doi = {{10.1103/cwsx-42c4}}, volume = {{25}}, year = {{2026}}, } @article{65096, abstract = {{ Precise measurements of both the arrival time and carrier frequency of light pulses are essential for time–frequency-encoded quantum technologies. Quantum mechanics, however, imposes fundamental limits on the simultaneous determination of these quantities. In this work, we derive and experimentally verify the quantum uncertainty bounds governing joint time–frequency measurements. We show that when detection is restricted to finite time windows, the problem is naturally described by a quantum rotor, rendering the commonly used Heisenberg uncertainty relation inapplicable. We further propose an optimal detection scheme that saturates these fundamental limits. By sampling the Q -function, we demonstrate the reconstruction of the Wigner function beyond the harmonic oscillator. Using an experimental implementation based on a quantum pulse gate, we confirm that the proposed scheme approaches the ultimate quantum limit for simultaneous time–frequency measurements. These results provide a framework for joint time–frequency detection with direct implications for precision measurements and quantum information processing. }}, author = {{Folge, Patrick Fabian and Serino, Laura Maria and Mišta, Ladislav and Brecht, Benjamin and Silberhorn, Christine and Řeháček, Jaroslav and Hradil, Zdeněk}}, issn = {{2334-2536}}, journal = {{Optica}}, number = {{3}}, publisher = {{Optica Publishing Group}}, title = {{{Quantum-limited detection of the arrival time and the carrier frequency of time-dependent signals}}}, doi = {{10.1364/optica.579459}}, volume = {{13}}, year = {{2026}}, } @article{63451, abstract = {{Superconducting nanowire single-photon detectors (SNSPDs) can enable photon-number resolution (PNR) based on accurate measurements of the detector’s response time to few-photon optical pulses. In this work, we investigate the impact of the optical pulse shape and duration on the accuracy of this method. We find that Gaussian temporal pulse shapes yield cleaner arrival-time histograms and, thus, more accurate PNR, compared to bandpass-filtered pulses of equal bandwidth. For low system jitter and an optical pulse duration comparable to the other jitter contributions, photon numbers can be discriminated in our system with a commercial SNSPD. At 60 ps optical pulse duration, photon-number discrimination is significantly reduced. Furthermore, we highlight the importance of using the correct arrival-time histogram model when analyzing photon-number assignment. Using exponentially modified Gaussian distributions, instead of the commonly used Gaussian distributions, we can more accurately determine photon-number misidentification probabilities. Finally, we reconstruct the positive operator-valued measures of the detector, revealing sharp features that indicate the intrinsic PNR capabilities.}}, author = {{Schapeler, Timon and Mischke, Isabell and Schlue, Fabian and Stefszky, Michael and Brecht, Benjamin and Silberhorn, Christine and Bartley, Tim}}, issn = {{2835-0103}}, journal = {{APL Quantum}}, number = {{1}}, publisher = {{AIP Publishing}}, title = {{{Practical considerations for assignment of photon numbers with SNSPDs}}}, doi = {{10.1063/5.0304127}}, volume = {{3}}, year = {{2026}}, } @article{65095, abstract = {{ We provide experimental validation of tight entropic uncertainty relations for the Shannon entropies of observables with mutually unbiased eigenstates in high dimensions. In particular, we address the cases of dimensions d = 3 , 4, and 5 and consider from 2 to d + 1 mutually unbiased bases. The experiment is based on pulsed frequency bins measured with a multioutput quantum pulse gate, which can perform projective measurements on a complete high-dimensional basis in the time-frequency domain. Our results fit the theoretical predictions: the bound on the sum of the entropies is never violated and is saturated by the states that minimize the uncertainty relations. }}, author = {{Serino, Laura Maria and Chesi, Giovanni and Brecht, Benjamin and Maccone, Lorenzo and Macchiavello, Chiara and Silberhorn, Christine}}, issn = {{2469-9926}}, journal = {{Physical Review A}}, number = {{3}}, publisher = {{American Physical Society (APS)}}, title = {{{Experimental entropic uncertainty relations in dimensions three to five}}}, doi = {{10.1103/f6c4-jtlc}}, volume = {{113}}, year = {{2026}}, } @inproceedings{65357, author = {{Kim, Minjun and Devaraj, Vasanthan and Seo, Hyeon-Seok and Eom, Seongjae and Lee, Jeong-Su and Lee, Donghan and Zentgraf, Thomas and Lee, Jong-Min and Jeon, Min Yong}}, booktitle = {{Quantum Sensing and Nano Electronics and Photonics XXII}}, editor = {{Razeghi, Manijeh and Khodaparast, Giti A. and Vitiello, Miriam S.}}, publisher = {{SPIE}}, title = {{{Fabrication of uniform, high-field-enhanced plasmonic satellite clusters using multidewetting}}}, doi = {{10.1117/12.3095416}}, year = {{2026}}, } @article{65460, abstract = {{Beamsplitters represent fundamental components in both classical and quantum optical systems, enabling the distribution of light, as well as the generation of interference, superposition, and entanglement. However, optical networks constructed from conventional bulk 2 × 2-beamsplitters encounter inherent scalability issues, as the number of required beamsplitters scales quadratically with the number of optical modes for a fully connected network. Metasurfaces offer a promising route to overcome these constraints. By manipulating light at the wavelength scale, compact optical components with advanced functionalities can be constructed, which address several modes simultaneously. In this work, we design and experimentally utilize a metasurface as a multiport beamsplitter. Furthermore, we realized a multimode interferometer composed of two cascaded metasurfaces. We characterize the individual and cascaded metasurfaces by using classical light, showing controllable splitting ratios through tunable phase relations. We then expand the approach to quantum light, employing single photons to demonstrate second- and third-order photon correlations as well as single photon interference across multiple spatial paths. These results establish metasurface-based multiport beamsplitters as a scalable and reconfigurable platform bridging classical and quantum photonics. }}, author = {{Aschwanden, Rebecca and Claro-Rodríguez, Nicolás and Zhao, Ruizhe and Kallert, Patricia Anna Maria and Krieger, Tobias and Buchinger, Quirin and Covre da Silva, Saimon F. and Stroj, Sandra and Rota, Michele and Höfling, Sven and Huber-Loyola, Tobias and Rastelli, Armando and Trotta, Rinaldo and Huang, Lingling and Bartley, Tim and Jöns, Klaus and Zentgraf, Thomas}}, issn = {{2330-4022}}, journal = {{ACS Photonics}}, keywords = {{metasurface, beamsplitter, interferometer, quantum network, single photons, nanophotonics}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Cascaded Metasurface Interferometer for Multipath Interference with Classical and Quantum Light}}}, doi = {{10.1021/acsphotonics.6c00096}}, year = {{2026}}, } @article{65316, abstract = {{Metasurfaces are powerful tools for manipulating light using small structures on the nanoscale. In most metasurfaces, near-field couplings are treated as being unfavorable perturbations. Here, we experimentally investigate a structure consisting of sinusoidally modulated silicon waveguides where near-field coupling of local resonances leads to negative coupling, i.e., a negative coupling constant. This gives rise to wave-vector-dependent eigenstates of elliptical, linear, and circular polarizations. In particular, fully circular polarization states are not only present at a single point in momentum space (k-space) but also along a line. This circular polarization line, as well as a linear polarization line, emanates from a polarization degeneracy at the Dirac point. We experimentally validate the existence of these eigenstates and demonstrate the energy-, polarization-, and wave vector dependence of this metasurface as well as its sensitivity to fabrication tolerances. By tuning the incident k-vector, certain polarization-energy eigenstates are strongly reflected, allowing for uses in angle-tunable polarization filters and light sources.}}, author = {{Wetter, Helene and Wingenbach, Jan and Rehberg, Falk and Gao, Wenlong and Schumacher, Stefan and Zentgraf, Thomas}}, issn = {{2330-4022}}, journal = {{ACS Photonics}}, keywords = {{metasurface, waveguides, Dirac point, polarization, negative coupling}}, pages = {{2128--2133}}, publisher = {{American Chemical Society (ACS)}}, title = {{{Polarization- and Wave-Vector Selective Optical Metasurface with Near-Field Coupling}}}, doi = {{10.1021/acsphotonics.5c02865}}, volume = {{13}}, year = {{2026}}, } @article{58493, author = {{Zietlow, Christian and Lindner, Jörg K. N.}}, issn = {{2045-2322}}, journal = {{Scientific Reports}}, number = {{1}}, publisher = {{Springer Science and Business Media LLC}}, title = {{{An applied noise model for scintillation-based CCD detectors in transmission electron microscopy}}}, doi = {{10.1038/s41598-025-85982-4}}, volume = {{15}}, year = {{2025}}, } @article{58178, author = {{Lindner, Jörg K. N. and Zietlow, Christian}}, issn = {{0304-3991}}, journal = {{Ultramicroscopy}}, publisher = {{Elsevier BV}}, title = {{{An applied noise model for low-loss EELS maps}}}, doi = {{10.1016/j.ultramic.2024.114101}}, year = {{2025}}, } @inproceedings{60022, author = {{Brauckmann, Michael and Narvaez Castaneda, Emmanuel and Siebert, Dustin and Brecht, Benjamin and Förstner, Jens and Zentgraf, Thomas}}, booktitle = {{Proceedings of The 15th International Conference on Metamaterials, Photonic Crystals and Plasmonics}}, location = {{Malaga, Spain}}, title = {{{Enhancement Of Light-matter Interaction In Topological Waveguides And Resonators}}}, year = {{2025}}, } @article{63734, abstract = {{Quantum dots (QDs) are a promising source of single photons mainly due to their on-demand operation. However, their emission wavelength depends on their size and immediate surroundings in the solid-state environment. By applying a serrodyne electro-optic phase modulation, we achieve a spectral shift up to 0.01 nm (3.5 GHz) while preserving the purity and indistinguishability of the photons. This method provides an efficient and scalable approach for tuning the emission wavelength of QDs without relying on nonlinear frequency mixing or probabilistic processes. Our results show that the electro-optic phase modulation enables stable and tunable spectral shifts, making it suitable for applications such as quantum communication, quantum key distribution, and primarily integrating remote quantum dot sources into large-scale quantum networks.}}, author = {{Kapoor, Sanjay and Rodek, Aleksander and Mikołajczyk, Michał and Szuniewicz, Jerzy and Sośnicki, Filip Maksymilian and Kazimierczuk, Tomasz and Kossacki, Piotr and Karpiński, Michał}}, issn = {{2192-8614}}, journal = {{Nanophotonics}}, number = {{11}}, pages = {{1775--1782}}, publisher = {{Walter de Gruyter GmbH}}, title = {{{Electro-optic frequency shift of single photons from a quantum dot}}}, doi = {{10.1515/nanoph-2024-0550}}, volume = {{14}}, year = {{2025}}, } @article{63732, abstract = {{Time lenses have been recognized as crucial components for manipulating ultrafast optical pulses in various applications, from ultrafast spectroscopy to the interfacing of optical quantum systems. A time lens is characterized by its chirp rate, which determines the focusing strength of the time lens, and accurate knowledge of this chirp is critical for precise dispersion compensation and minimizing aberrations. Here, we introduce a tunable time aperture model for sinusoidal time lenses that provides a more accurate estimate of the effective chirp rate without modifying the device. We derive a closed-form expression for the maximum phase error and show how it depends on the time aperture. We experimentally demonstrate a 1.6-fold improvement in spectral bandwidth compression of Gaussian pulses compared to the conventional approach. Our framework offers a practical tool for designing efficient temporal optical systems, benefiting applications in both classical and quantum optics where accurate spectro-temporal shaping is essential.}}, author = {{Kapoor, Sanjay and Sośnicki, Filip Maksymilian and Karpiński, Michał}}, issn = {{2378-0967}}, journal = {{APL Photonics}}, number = {{9}}, publisher = {{AIP Publishing}}, title = {{{Aberration-optimized electro-optic time lens model using a tunable aperture}}}, doi = {{10.1063/5.0270904}}, volume = {{10}}, year = {{2025}}, } @article{60001, author = {{Zietlow, Christian and Lindner, Jörg}}, journal = {{Ultramicroscopy}}, number = {{275}}, publisher = {{Elsevier}}, title = {{{An unbiased ADMM-TGV algorithm for the deconvolution of STEM-EELS maps}}}, doi = {{10.1016/j.ultramic.2025.114159}}, year = {{2025}}, } @article{59069, abstract = {{Stable and bright single photon sources are key components for future quantum applications. A simple fabrication method is an important requirement for such sources. Here, we present a single photon source based on diced ridge waveguides in titanium indiffused LiNbO3. These waveguides can be easily fabricated by combining planar titanium in-diffusion without lithographic patterning and easy-to-handle precision dicing. Such devices have the potential to generate high single photon rates because ridge structures are typically less prone to the photorefractive effect. We achieve waveguide propagation losses <0.4dBcm and a SHG conversion efficiency of about 81%Wcm2. Harnessing a type-0 SPDC process to generate 1550 nm photons, we obtain a SPDC brightness of 3⋅1051s⋅mW⋅nm, with a heralding efficiency of ηh=45% (ηh,wg=77.5% for the waveguide itself excluded setup losses) and a heralded second-order correlation function of gh2(0)<0.003 at low pump powers.}}, author = {{Kießler, Christian and Kirsch, Michelle and Lengeling, Sebastian and Herrmann, Harald and Silberhorn, Christine}}, issn = {{2770-0208}}, journal = {{Optics Continuum}}, number = {{3}}, publisher = {{Optica Publishing Group}}, title = {{{SPDC single-photon source in Ti-indiffused diced ridge LiNbO3 waveguides}}}, doi = {{10.1364/optcon.557439}}, volume = {{4}}, year = {{2025}}, } @article{59276, abstract = {{Stress plays a crucial role in thin films and layered systems, and thus significantly influences the material's electrical, mechanical and (nonlinear) optical responses. Despite lithium niobate's wide applicability as a nonlinear optical material, the impact of mechanical stress on its nonlinear optical properties is not well characterized. In this work, we systematically study both experimentally and theoretically, the nonlinear optical responses of thin film lithium niobate (TFLN) single crystals. Compressive and tensile stress is applied in our experiment using a piezodriven strain cell. We then record the second-harmonic-generated (SHG) response in back-reflection geometry, and compare these results to theoretical modeling using density functional theory (DFT). Both methods consistently reveal that uniaxial stress induces changes of the nonlinear optical susceptibility of certain tensor elements on the order of up to 1 pm/(V GPa). The exact value depends on the tensor element that is addressed in our SHG analysis, on the crystal orientation, and also whether using compressive or tensile stresses. Furthermore, a lowering of the crystal symmetry when applying stress along the x or y crystallographic axes is observed by the appearance of new nonlinear optical tensor elements within the strained crystals.}}, author = {{Pionteck, Mike N. and Roeper, Matthias and Koppitz, Boris and Seddon, Samuel D. and Rüsing, Michael and Padberg, Laura and Eigner, Christof and Silberhorn, Christine and Sanna, Simone and Eng, Lukas M.}}, issn = {{2469-9950}}, journal = {{Physical Review B}}, number = {{6}}, publisher = {{American Physical Society (APS)}}, title = {{{Second-order nonlinear piezo-optic properties of single crystal lithium niobate thin films}}}, doi = {{10.1103/physrevb.111.064109}}, volume = {{111}}, year = {{2025}}, }