@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}}, } @inproceedings{4581, author = {{Grynko, Yevgen and Förstner, Jens}}, booktitle = {{2018 IEEE 17th International Conference on Mathematical Methods in Electromagnetic Theory (MMET)}}, isbn = {{9781538654385}}, keywords = {{tet_topic_numerics, tet_topic_shg}}, publisher = {{IEEE}}, title = {{{Application of the Discontinuous Galerkin Time Domain Method in Nonlinear Nanoplasmonics}}}, doi = {{10.1109/mmet.2018.8460261}}, year = {{2018}}, } @inbook{3743, abstract = {{Frequently, optical integrated circuits combine elements (waveguide channels, cavities), the simulation of which is well established through mature numerical eigenproblem solvers. It remains to predict the interaction of these modes. We address this task by a general, “Hybrid” variant (HCMT) of Coupled Mode Theory. Using methods from finite-element numerics, the properties of a circuit are approximated by superpositions of eigen-solutions for its constituents, leading to quantitative, computationally cheap, and easily interpretable models.}}, author = {{Hammer, Manfred}}, booktitle = {{Recent Trends in Computational Photonics}}, editor = {{Agrawal, Arti}}, isbn = {{978-3-319-55438-9}}, keywords = {{tet_topic_waveguide, tet_topic_numerics}}, pages = {{77--105}}, publisher = {{Springer}}, title = {{{Guided Wave Interaction in Photonic Integrated Circuits — A Hybrid Analytical/Numerical Approach to Coupled Mode Theory}}}, volume = {{204}}, year = {{2017}}, } @article{3828, abstract = {{The 3D implementation of a hybrid analytical/numerical variant of the coupled-mode theory is discussed. Eigenmodes of the constituting dielectric channels are computed numerically. The frequency-domain coupled-mode models then combine these into fully vectorial approximations for the optical electromagnetic fields of the composite structure. Following a discretization of amplitude functions by 1D finite elements, pro- cedures from the realm of finite-element numerics are applied to establish systems of linear equations for the then- discrete modal amplitudes. Examples substantiate the functioning of the technique and allow for some numerical assessment. The full 3D simulations are highly efficient in memory consumption, moderately demanding in com- putational time, and, in regimes of low radiative losses, sufficiently accurate for practical design. Our results include the perturbation of guided modes by changes of the refractive indices, the interaction of waves in parallel, horizontally or vertically coupled straight waveguides, and a series of crossings of potentially overlapping channels with fairly arbitrary relative positions and orientations.}}, author = {{Hammer, Manfred and Alhaddad, Samer and Förstner, Jens}}, issn = {{0740-3224}}, journal = {{Journal of the Optical Society of America B}}, keywords = {{tet_topic_waveguide, tet_topic_numerics}}, number = {{3}}, pages = {{613--624}}, publisher = {{The Optical Society}}, title = {{{Hybrid coupled-mode modeling in 3D: perturbed and coupled channels, and waveguide crossings}}}, doi = {{10.1364/josab.34.000613}}, volume = {{34}}, year = {{2017}}, } @inbook{3836, abstract = {{We apply the Discontinuous Galerkin Time Domain (DGTD) method for numerical simulations of the second harmonic generation from various metallic nanostructures. A Maxwell–Vlasov hydrodynamic model is used to describe the nonlinear effects in the motion of the excited free electrons in a metal. The results are compared with the corresponding experimental measurements for split-ring resonators and plasmonic gap antennas.}}, author = {{Grynko, Yevgen and Förstner, Jens}}, booktitle = {{Recent Trends in Computational Photonics}}, editor = {{Agrawal, Arti}}, isbn = {{9783319554372}}, issn = {{0342-4111}}, keywords = {{tet_topic_numerics, tet_topic_shg, tet_topic_meta}}, pages = {{261--284}}, publisher = {{Springer International Publishing}}, title = {{{Simulation of Second Harmonic Generation from Photonic Nanostructures Using the Discontinuous Galerkin Time Domain Method}}}, doi = {{10.1007/978-3-319-55438-9_9}}, year = {{2017}}, } @inproceedings{3934, abstract = {{Typical optical integrated circuits combine elements, like straight and curved waveguides, or cavities, the simulation and design of which is well established through numerical eigenproblem-solvers. It remains to predict the interaction of these modes. We address this task by a ”Hybrid” variant (HCMT) of Coupled Mode Theory. Using methods from finite-element numerics, the optical properties of a circuit are approximated by superpositions of eigen-solutions for its constituents, leading to quantitative, low-dimensional, and interpretable models in the frequency domain. Spectral scans are complemented by the direct computation of supermode properties (spectral positions and linewidths, coupling-induced phase shifts). This contribution outlines the theoretical background, and discusses briefly limitations and implementational details, with the help of an example of a 2-D coupled-resonator-optical-waveguide configuration.}}, author = {{Hammer, Manfred}}, booktitle = {{Integrated Optics: Devices, Materials, and Technologies XX}}, editor = {{Broquin, Jean-Emmanuel and Nunzi Conti, Gualtiero}}, keywords = {{tet_topic_waveguide, tet_topic_numerics}}, location = {{San Francisco, USA}}, number = {{9750}}, pages = {{975018--975018--8 }}, publisher = {{SPIE}}, title = {{{Wave interaction in photonic integrated circuits: Hybrid analytical / numerical coupled mode modeling}}}, doi = {{10.1117/12.2214331}}, year = {{2016}}, } @article{3890, abstract = {{The incidenceofthin-film-guided, in-planeunguidedwavesatobliqueanglesonstraightdiscontinuities of dielectricslabwaveguides,anearlyproblemofintegratedoptics,isbeingre-considered.The3-D frequencydomainMaxwellequationsreducetoaparametrizedinhomogeneousvectorialproblemona 2-D computationaldomain,withtransparent-influx boundaryconditions.Weproposearigorousvec- torial solverbasedonsimultaneousexpansionsintopolarizedlocalslabeigenmodesalongthetwo orthogonal crosssectioncoordinates(quadridirectionaleigenmodepropagationQUEP).Thequasi-ana- lytical schemeisapplicabletoconfigurations with — in principle — arbitrary crosssectiongeometries. Examples forahigh-contrastfacetofanasymmetricslabwaveguide,forthelateralexcitationofa channel waveguide,andforastepdiscontinuitybetweenslabwaveguidesofdifferentthicknessesare discussed.}}, author = {{Hammer, Manfred}}, issn = {{0030-4018}}, journal = {{Optics Communications}}, keywords = {{tet_topic_waveguide, tet_topic_numerics}}, pages = {{447--456}}, publisher = {{Elsevier BV}}, title = {{{Oblique incidence of semi-guided waves on rectangular slab waveguide discontinuities: A vectorial QUEP solver}}}, doi = {{10.1016/j.optcom.2014.09.087}}, volume = {{338}}, year = {{2014}}, } @article{4044, abstract = {{A simulation environment for metallic nanostructures based on the Discontinuous Galerkin Time Domain method is presented. The model is used to compute the linear and nonlinear optical response of split ring resonators and to study physical mechanisms that contribute to second harmonic generation.}}, author = {{Grynko, Yevgen and Förstner, Jens and Meier, Torsten}}, issn = {{1825-1242}}, journal = {{AAPP | Atti della Accademia Peloritana dei Pericolanti}}, keywords = {{tet_topic_numerics, tet_topic_shg, tet_topic_meta}}, number = {{1}}, title = {{{Application of the discontinous Galerkin time domain method to the optics of metallic nanostructures}}}, doi = {{10.1478/C1V89S1P041}}, volume = {{89}}, year = {{2011}}, } @inproceedings{4167, abstract = {{The electromagnetic field in the vicinity of sharp edges needs a special treatment in numeric calculation whenever accurate, fast converging results are necessary. One of the fundamental works concerning field singularities has been proposed in 1972 [1] and states that the electromagnetic energy density must be integrable over any finite domain, even if this domain contains singularities. It is shown, that the magnetic field H(, ϕ) and electric field E(, ϕ) are proportional to ∝ (t−1) for  → 0. The variable  is the distance to the edge and t has to fulfill the integrability condition and thus is restricted to 0 < t < 1. This result is often used to reduce the error corresponding to the singularity without increasing the numerical effort [2 - 5]. For this purpose, a correction factor K is estimated by inserting the proportionality into the wave equation. It is shown, that this method improves the accuracy of the result significantly, however the order of convergence is often not studied. In [4] a method to modify the material parameters in order to use analytic results to improve the numeric calculation is presented. In this contribution we will - inspired by the scheme given in [4] - develop a new method to estimate a correction factor for perfect conducting materials (PEC) and demonstrate the improvement of the results compared to the standard edge correction. Therefore analytic results (comparable to [1]) are consequently merged with the scheme in [4]. The main goal of this work is the calculation of the second harmonic generation (SHG) in the wave response of so-called metamaterials [6]. Frequently these structures contain sharp metallic edges with field singularities at the interfaces which have a strong impact on the SHG signals. Thus, an accurate simulation of singularities is highly important. However, the following approach can also be applied to many other setups, and one of them is shown in the example below.}}, author = {{Classen, C and Förstner, Jens and Meier, Torsten and Schuhmann, R}}, booktitle = {{2010 IEEE Antennas and Propagation Society International Symposium}}, isbn = {{9781424449675}}, keywords = {{tet_topic_numerics}}, location = {{Toronto, ON, Canada}}, publisher = {{IEEE}}, title = {{{Enhanced FDTD edge correction for nonlinear effects calculation}}}, doi = {{10.1109/aps.2010.5562017}}, year = {{2010}}, }