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Welcome to the Theoretical Electrical Engineering group (TET)

Our main research interest is the theoretical description of photonic and optoelectronic systems like optical nanoantennas, dielectric waveguides, photonic crystals, metamaterials, plasmonic systems, or biological photonic structures. Our speciality is the combinations of advanced material models with state-of-the-art numerical methods for the simulation of electromagnetic fields. For students we offer a wide range of courses ranging from the theoretical foundation of electromagnetism and numerics to advanced courses on field simulation and photonics. 

Research: Topics, Publications, Team

Teaching: Course Portfolio, Current Courses, Current Projects


The five most recent publications

Open list in Research Information System

Resonant evanescent excitation of guided waves with high-order optical angular momentum

M. Hammer, L. Ebers, J. Förstner, Journal of the Optical Society of America B (2021), 38(5)

Gaussian-beam-like bundles of semi-guided waves propagating in a dielectric slab can excite modes with high-order optical angular momentum supported by a circular fiber. We consider a multimode step-index fiber with a high-index coating, where the waves in the slab are evanescently coupled to the modes of the fiber. Conditions for effective resonant interaction are identified. Based on a hybrid analytical–numerical coupled mode model, our simulations predict that substantial fractions of the input power can be focused into waves with specific orbital angular momentum, of excellent purity, with a clear distinction between degenerate modes with opposite vorticity.

Dielectric travelling wave antennas for directional light emission

T. Leuteritz, H. Farheen, S. Qiao, F. Spreyer, C. Schlickriede, T. Zentgraf, V. Myroshnychenko, J. Förstner, S. Linden, Optics Express (2021), 29(10)

We present a combined experimental and numerical study of the far-field emission properties of optical travelling wave antennas made from low-loss dielectric materials. The antennas considered here are composed of two simple building blocks, a director and a reflector, deposited on a glass substrate. Colloidal quantum dots placed in the feed gap between the two elements serve as internal light source. The emission profile of the antenna is mainly formed by the director while the reflector suppresses backward emission. Systematic studies of the director dimensions as well as variation of antenna material show that the effective refractive index of the director primarily governs the far-field emission pattern. Below cut off, i.e., if the director’s effective refractive index is smaller than the refractive index of the substrate, the main lobe results from leaky wave emission along the director. In contrast, if the director supports a guided mode, the emission predominately originates from the end facet of the director.

    HighPerMeshes – A Domain-Specific Language for Numerical Algorithms on Unstructured Grids

    S. Alhaddad, J. Förstner, S. Groth, D. Grünewald, Y. Grynko, F. Hannig, T. Kenter, F. Pfreundt, C. Plessl, M. Schotte, T. Steinke, J. Teich, M. Weiser, F. Wende, in: Euro-Par 2020: Parallel Processing Workshops, 2021

    Solving partial differential equations on unstructured grids is a cornerstone of engineering and scientific computing. Nowadays, heterogeneous parallel platforms with CPUs, GPUs, and FPGAs enable energy-efficient and computationally demanding simulations. We developed the HighPerMeshes C++-embedded Domain-Specific Language (DSL) for bridging the abstraction gap between the mathematical and algorithmic formulation of mesh-based algorithms for PDE problems on the one hand and an increasing number of heterogeneous platforms with their different parallel programming and runtime models on the other hand. Thus, the HighPerMeshes DSL aims at higher productivity in the code development process for multiple target platforms. We introduce the concepts as well as the basic structure of the HighPerMeshes DSL, and demonstrate its usage with three examples, a Poisson and monodomain problem, respectively, solved by the continuous finite element method, and the discontinuous Galerkin method for Maxwell’s equation. The mapping of the abstract algorithmic description onto parallel hardware, including distributed memory compute clusters, is presented. Finally, the achievable performance and scalability are demonstrated for a typical example problem on a multi-core CPU cluster.

      Towards Semiconductor-Superconductor-Crystal Hybrid Integration for Quantum Photonics

      M. Protte, L. Ebers, M. Hammer, J.P. Höpker, M. Albert, V. Quiring, C. Meier, J. Förstner, C. Silberhorn, T.J. Bartley, in: OSA Quantum 2.0 Conference, 2020

      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.

        Light backscattering from large clusters of densely packed irregular particles

        Y. Grynko, Y. Shkuratov, J. Förstner, Journal of Quantitative Spectroscopy and Radiative Transfer (2020), 255, pp. 107234

        We numerically simulate multiple light scattering in discrete disordered media represented by large clusters of irregular non-absorbing particles. The packing density of clusters is 0.5. With such conditions diffuse scattering is significantly reduced and light transport follows propagation channels that are determined by the particle size and topology of the medium. This kind of localization produces coherent backscattering intensity surge and enhanced negative polarization branch if compared to lower density samples.

        Max number of publications reached - all publications can be found in our Research Infomation System.

        Open list in Research Information System

        Head of the group

        Prof. Dr. Jens Förstner

        Theoretical Electrical Engineering

        Jens Förstner
        +49 5251 60-3013
        +49 5251 60-3524

        Office hours:

        on request (during lecture break)

        TET courses & projects

        Frequently asked questions (FAQ)

        Course Portfolio

        SoSe 2021: Courses, projects

        WS 2020/2021: Courses, projects

        SoSe 2020: Courses, projects

        WS 2019/2020:Courses, projects

        SoSe 2019: Courses, projects

        WS 2018/2019: Courses, projects

        SoSe 2018: Courses, projects

        WS 2017/2018: Courses, projects

        The University for the Information Society