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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

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.

Light diffraction in slab waveguide lenses simulated with the stepwise angular spectrum method

L. Ebers, M. Hammer, J. Förstner, Optics Express (2020), 28(24), pp. 36361

A stepwise angular spectrum method (SASM) for curved interfaces is presented to calculate the wave propagation in planar lens-like integrated optical structures based on photonic slab waveguides. The method is derived and illustrated for an effective 2D setup first and then for 3D slab waveguide lenses. We employ slab waveguides of different thicknesses connected by curved surfaces to realize a lens-like structure. To simulate the wave propagation in 3D including reflection and scattering losses, the stepwise angular spectrum method is combined with full vectorial finite element computations for subproblems with lower complexity. Our SASM results show excellent agreement with rigorous numerical simulations of the full structures with a substantially lower computational effort and can be utilized for the simulation-based design and optimization of complex and large scale setups.

    Electrically controlled rapid adiabatic passage in a single quantum dot

    A. Mukherjee, A. Widhalm, D. Siebert, S. Krehs, N. Sharma, A. Thiede, D. Reuter, J. Förstner, A. Zrenner, Applied Physics Letters (2020), 116, pp. 251103

    Hybrid coupled mode modelling of the evanescent excitation of a dielectric tube by semi-guided waves at oblique angles

    M. Hammer, L. Ebers, J. Förstner, Optical and Quantum Electronics (2020), 52

    A dielectric step-index optical fiber with tube-like profile is considered, being positioned with a small gap on top of a dielectric slab waveguide. We propose a 2.5-D hybrid analytical/numerical coupled mode model for the evanescent excitation of the tube through semi-guided waves propagating in the slab at oblique angles. The model combines the directional polarized modes supported by the slab with analytic solutions for the TE-, TM-, and orbital-angular-momentum (OAM) modes of the tube-shaped fiber. Implementational details of the scheme are discussed, complemented by finite-element simulations for verification purposes. Our results include configurations with resonant in-fiber excitation of OAM modes with large orbital angular momentum and strong field enhancement.

      Nonlinear dielectric properties of random paraelectric-dielectric composites

      V. Myroshnychenko, S. Smirnov, P.M.M. Jose, C. Brosseau, J. Förstner, Acta Materialia (2020), 203, pp. 116432

      The challenge of designing new tunable nonlinear dielectric materials with tailored properties has attracted an increasing amount of interest recently. Herein, we study the effective nonlinear dielectric response of a stochastic paraelectric-dielectric composite consisting of equilibrium distributions of circular and partially penetrable disks (or parallel, infinitely long, identical, partially penetrable, circular cylinders) of a dielectric phase randomly dispersed in a continuous matrix of a paraelectric phase. The random microstructures were generated using the Metropolis Monte Carlo algorithm. The evaluation of the effective permittivity and tunability were carried out by employing either a Landau thermodynamic model or its Johnson’s approximation to describe the field-dependent permittivity of the paraelectric phase and solving continuum-electrostatics equations using finite element calculations. We reveal that the percolation threshold in this composite governs the critical behavior of the effective permittivity and tunability. For microstructures below the percolation threshold, our simulations demonstrate a strong nonlinear behaviour of the field-dependent effective permittivity and very high tunability that increases as a function of dielectric phase concentration. Above the percolation threshold, the effective permittivity shows the tendency to linearization and the tunability dramatically drops down. The highly reduced permittivity and extraordinarily high tunability are obtained for the composites with dielectric impenetrable disks at high concentrations, in which the triggering of the percolation transition is avoided. The reported results cast light on distinct nonlinear behaviour of 2D and 3D stochastic composites and can guide the design of novel composites with the controlled morphology and tailored permittivity and tunability.

      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

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