@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{63532,
abstract = {{Room-temperature lasing is a key milestone in the development of miniaturized optoelectronic and photonic devices. We present a simple approach to synthesize phase-pure quasi-2D layered tin perovskite nanowires with varying quantum well thicknesses (n = 1 to 4). By incorporating a new organic spacer capable of forming a hydrogen-bonded organic framework, this method promoted anisotropic crystal growth and enhanced lattice rigidity. Furthermore, introducing molecular intercalants enabled controlled crystallization into well-defined nanowires that function as Fabry–Pérot cavities. Cavities made from n = 2 to 4 perovskites support efficient and robust near-infrared, room-temperature optically pumped lasing with the threshold as low as 75.8 μJ/cm2, cavity quality factor over 3000, and negligible degradation over 106 pulses. A cleaved coupled nanolaser was fabricated as a proof-of-concept device for photonic applications.}},
author = {{Kim, Jeong Hui and Simon, Jeffrey and Shao, Wenhao and Nian, Zhichen and Yang, Hanjun and Chen, Peigang and Triplett, Brandon and Li, Zhixu and Wu, Pengfei and Chen, Yuheng and Farheen, Henna and Pagadala, Karthik and Choi, Kyu Ri and Fruhling, Colton B. and Förstner, Jens and Boltasseva, Alexandra and Savoie, Brett M. and Shalaev, Vladimir M. and Dou, Letian}},
issn = {{0002-7863}},
journal = {{Journal of the American Chemical Society}},
keywords = {{tet_topic_opticalantenna}},
pages = {{jacs.5c14431}},
publisher = {{American Chemical Society (ACS)}},
title = {{{Hydrogen-Bonded Organic Framework Enables Phase-Pure Layered Tin Perovskite Nanowires for Room-Temperature Lasing}}},
doi = {{10.1021/jacs.5c14431}},
year = {{2026}},
}
@article{64877,
author = {{Taheri, Behnood and Kopylov, Denis and Hammer, Manfred and Meier, Torsten and Förstner, Jens and Sharapova, Polina R.}},
journal = {{arXiv}},
title = {{{Gain-induced spectral non-degeneracy in type-II parametric down-conversion}}},
doi = {{10.48550/ARXIV.2603.01656}},
year = {{2026}},
}
@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}},
}
@inproceedings{62296,
author = {{Spieker, Carsten and Förstner, Jens and Hölscher, Jonas and Claes, Leander and Henning, Bernd}},
booktitle = {{2025 International Congress on Ultrasonics}},
pages = {{126–129}},
publisher = {{AMA Service GmbH}},
title = {{{Modeling and simulation of the behavior of piezoceramics with the discontinuous Galerkin method}}},
doi = {{10.5162/ultrasonic2025/a18-a1}},
year = {{2025}},
}
@inproceedings{62297,
author = {{Hölscher, Jonas and Friesen, Olga and Claes, Leander and Spieker, Carsten and Förstner, Jens and Henning, Bernd}},
booktitle = {{2025 International Congress on Ultrasonics}},
pages = {{130–133}},
publisher = {{AMA Service GmbH}},
title = {{{Multiscale thermo-piezoelectric simulations using the finite element method}}},
doi = {{10.5162/ultrasonic2025/a18-a2}},
year = {{2025}},
}
@article{60891,
abstract = {{Straight dielectric waveguide channels made from slabs of thin-film lithium niobate (TFLN), or lithium niobate on insulator (LNOI), are investigated in the linear regime, for channels of rib and strip type with common trapezoidal cross sections, in Z-cut and X-cut samples at varying on-chip orientation. We clarify the theoretical basis for the waveguides with potentially non-diagonal core permittivity. Symmetry classes can be distinguished that differ in their consequences for potential modal degeneracy and polarization conversion. Our rigorous numerical analysis by means of a finite-element solver takes the anisotropy of the lithium niobate cores rigorously into account. We discuss extensive data for effective indices, polarization properties, and hybridization of guided modes, in single- and multimode channels. Scans over the waveguide width and orientation as primary parameters are complemented by a series of illustrations of vectorial mode profiles. These turn out to be essentially complex in cases of X-cut channels at non-crystal-axis-aligned orientations.}},
author = {{Hammer, Manfred and Khan, Shahriar and Taheri, Behnood and Farheen, Henna and Förstner, Jens}},
issn = {{2770-0208}},
journal = {{Optics Continuum}},
keywords = {{tet_topic_waveguide}},
number = {{10}},
pages = {{2356}},
publisher = {{Optica Publishing Group}},
title = {{{TFLN channel waveguides of rib and strip type: Properties of guided modes}}},
doi = {{10.1364/optcon.569959}},
volume = {{4}},
year = {{2025}},
}
@inproceedings{61760,
abstract = {{We present a topology-optimized silicon nitride (Si3N4) coupler designed to enhance the coupling efficiency between integrated single-photon emitters and photonic waveguide modes. By leveraging inverse design techniques, we optimize the coupler’s geometry to maximize power transfer while maintaining fabrication feasibility by improving mode overlap and directional emission, addressing the challenge of low coupling efficiency caused by size mismatch and material incompatibility. Simulations demonstrate a substantial enhancement in photon extraction and waveguide coupling. This approach can be extended to other photonic devices, offering a versatile framework for improving quantum light-matter interactions in integrated photonics.}},
author = {{Farheen, Henna and Chen, Yuheng and Chen, Peigang and Kryvobok, Artem and Peana, Samuel and Senichev, Alexander and Shalaev, Vladimir M. and Boltasseva, Alexandra and Förstner, Jens and Kildishev, Alexander V.}},
booktitle = {{Photonic Computing: From Materials and Devices to Systems and Applications II}},
editor = {{Ni, Xingjie and Cai, Wenshan}},
keywords = {{tet_topic_waveguide}},
publisher = {{SPIE}},
title = {{{Topology-optimized silicon nitride coupler for integrated single-photon emitters}}},
doi = {{10.1117/12.3065734}},
year = {{2025}},
}
@article{54668,
abstract = {{Samples of dielectric optical waveguides of rib or strip type in thin-film lithium niobate (TFLN) technology are characterized with respect to their optical loss using the Fabry-Pérot method. Attributing the losses mainly to sidewall roughness, we employ a simple perturbational procedure, based on rigorously computed mode profiles of idealized channels, to estimate the attenuation for waveguides with different cross sections. A single fit parameter suffices for an adequate modelling of the effect of the waveguide geometry on the loss levels.}},
author = {{Hammer, Manfred and Babel, Silia and Farheen, Henna and Padberg, Laura and Scheytt, J. Christoph and Silberhorn, Christine and Förstner, Jens}},
issn = {{1094-4087}},
journal = {{Optics Express}},
keywords = {{tet_topic_waveguide}},
number = {{13}},
pages = {{22878}},
publisher = {{Optica Publishing Group}},
title = {{{Estimation of losses caused by sidewall roughness in thin-film lithium niobate rib and strip waveguides}}},
doi = {{10.1364/oe.521766}},
volume = {{32}},
year = {{2024}},
}
@article{52700,
abstract = {{We explore the polarization hysteretic behaviour and field-dependent permittivity of ferroelectric-dielectric 2D materials formed by random dispersions of low permittivity inclusions in a ferroelectric matrix, using finite element simulations. We show how the degree of impenetrability of dielectric inclusions plays a substantial role in controlling the coercive field, remnant and saturation polarizations of the homogenized materials. The results highlight the significance of the degree of impenetrability of inclusion in tuning the effective polarization properties of such ferroelectric composites: coercive field drops significantly as percolation threshold is attained and remnant polarization decreases faster than a linear decay.}},
author = {{Myroshnychenko, Viktor and Mulavarickal Jose, Pious Mathews and Farheen, Henna and Ejaz, Shafaq and Brosseau, Christian and Förstner, Jens}},
issn = {{0031-8949}},
journal = {{Physica Scripta}},
keywords = {{tet_topic_ferro}},
number = {{4}},
pages = {{045952}},
publisher = {{IOP Publishing}},
title = {{{From Swiss-cheese to discrete ferroelectric composites: assessing the ferroelectric butterfly shape in polarization loops}}},
doi = {{10.1088/1402-4896/ad3172}},
volume = {{99}},
year = {{2024}},
}
@article{55751,
abstract = {{Lateral leakage of TM modes in dielectric optical waveguides of rib/ridge or strip-loaded types can be fully suppressed, if the waveguide core is formed not through a strip that protrudes at one side (up) from the remaining lateral guiding slab, but through parallel strips on both sides (up and down), such that the resulting cross section becomes vertically symmetric. The fairly general arguments underlying the leakage suppression apply to TM modes of all orders simultaneously, and are independent of wavelength. These plus-shaped waveguides support strictly guided, non-leaky TM modes for, in principle, arbitrarily shallow etching.}},
author = {{Üstün, Necati and Farheen, Henna and Hammer, Manfred and Förstner, Jens}},
issn = {{0740-3224}},
journal = {{Journal of the Optical Society of America B}},
keywords = {{tet_topic_waveguide}},
number = {{9}},
pages = {{2077}},
publisher = {{Optica Publishing Group}},
title = {{{Symmetry-protected TM modes in rib-like, plus-shaped optical waveguides with shallow etching}}},
doi = {{10.1364/josab.528729}},
volume = {{41}},
year = {{2024}},
}
@article{55989,
abstract = {{Phased arrays are vital in communication systems and have received significant interest in the field of optoelectronics and photonics, enabling a wide range of applications such as LiDAR, holography, wireless communication, etc. In this work, we present a blazed grating antenna that is optimized to have upward radiation efficiency as high as 80% with a compact footprint of 3.5 μm × 2 μm at an operational wavelength of 1.55 μm. Our numerical investigations demonstrate that this antenna in a 64 × 64 phased array configuration is capable of producing desired far-field radiation patterns. Additionally, our antenna possesses a low side lobe level of -9.7 dB and a negligible reflection efficiency of under 1%, making it an attractive candidate for integrated optical phased arrays.}},
author = {{Farheen, Henna and Joshi, Suraj and Scheytt, J. Christoph and Myroshnychenko, Viktor and Förstner, Jens}},
issn = {{2515-7647}},
journal = {{Journal of Physics: Photonics}},
keywords = {{tet_topic_opticalantenna}},
pages = {{045010}},
publisher = {{IOP Publishing}},
title = {{{An efficient compact blazed grating antenna for optical phased arrays}}},
doi = {{10.1088/2515-7647/ad6ed4}},
volume = {{6}},
year = {{2024}},
}
@article{56193,
abstract = {{Dielectric slab waveguides made of thin-film-lithium-niobate (TFLN) media are consid-ered, for operation in the linear regime. We outline and implement a largely analytic procedure forrigorous modal analysis of three-layer slabs with birefringent, anisotropic core. For Z-cut wave-guides, the slab eigenmode problem separates into uncoupled sets of scalar equations for TE andTM modes. Slabs in X-cut configuration support mostly mildly hybrid eigenmodes, with clear pre-dominant TE or TM polarization, and with effective indices that depend on the propagation directionof the modes, relative to the crystal axes. Strong hybridization can be observed for near degeneratemodes in singular configurations without vertical symmetry, or in symmetric slabs where two nearlydegenerate modes are of the same symmetry class. Dispersion curves for slab thickness and propa-gation angle are discussed, for slabs with oxide and air cover. }},
author = {{Hammer, Manfred and Farheen, Henna and Förstner, Jens}},
issn = {{2770-0208}},
journal = {{Optics Continuum}},
keywords = {{tet_topic_waveguide}},
pages = {{532822}},
publisher = {{Optica Publishing Group}},
title = {{{Guided modes of thin-film lithium niobate slabs}}},
doi = {{10.1364/optcon.532822}},
year = {{2024}},
}
@inproceedings{57528,
abstract = {{Based on the surface equivalence principle an equivalent near-field source can be determined by measurements with a near-field scanner. One application is to use the source to simulate the interferences of the device-under-test with other objects in its close environment. Due to a limited signal-to-noise ratio in practical applications, noise adds to the near-field source. Hence, noise effects affect the quality of the simulation results and cause uncertainties. The influence of the noise effects is investigated by a simulative approach with artificially added noise. Two test devices with different a geometric dimension, operating frequency and excited power are evaluated for different characteristics and signal-to-noise ratios to assess the impact of the simulation results. Finally, in a combined simulation an equivalent near-field source will disturb an IoT-device and the voltages at two resistors on the device are examined.}},
author = {{Schröder, Dominik and Kiefner, Ulrich and Hedayat, Christian and Förstner, Jens}},
booktitle = {{2024 International Symposium on Electromagnetic Compatibility – EMC Europe}},
keywords = {{tet_topic_hf, tet_enas}},
publisher = {{IEEE}},
title = {{{Evaluation of Measurement Noise Effects in the Close Environment of Equivalent Near-Field Sources}}},
doi = {{10.1109/emceurope59828.2024.10722220}},
year = {{2024}},
}
@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{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}},
}