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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

The HighPerMeshes framework 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, Concurrency and Computation: Practice and Experience (2021), pp. e6616

Ultrafast electric control of cavity mediated single-photon and photon-pair generation with semiconductor quantum dots

D. Bauch, D.F. Heinze, J. Förstner, K.D. Jöns, S. Schumacher, Physical Review B (2021), 104, pp. 085308

Employing the ultrafast control of electronic states of a semiconductor quantum dot in a cavity, we introduce an approach to achieve on-demand emission of single photons with almost perfect indistinguishability and photon pairs with near ideal entanglement. Our scheme is based on optical excitation off resonant to a cavity mode followed by ultrafast control of the electronic states using the time-dependent quantum-confined Stark effect, which then allows for cavity-resonant emission. Our theoretical analysis considers cavity-loss mechanisms, the Stark effect, and phonon-induced dephasing, allowing realistic predictions for finite temperatures.

Integrated superconducting nanowire single-photon detectors on titanium in-diffused lithium niobate waveguides

J.P. Höpker, V.B. Verma, M. Protte, R. Ricken, V. Quiring, C. Eigner, L. Ebers, M. Hammer, J. Förstner, C. Silberhorn, R.P. Mirin, S. Woo Nam, T. Bartley, Journal of Physics: Photonics (2021), 3, pp. 034022

We demonstrate the integration of amorphous tungsten silicide superconducting nanowire single-photon detectors on titanium in-diffused lithium niobate waveguides. We show proof-of-principle detection of evanescently coupled photons of 1550 nm wavelength using bidirectional waveguide coupling for two orthogonal polarization directions. We investigate the internal detection efficiency as well as detector absorption using coupling-independent characterization measurements. Furthermore, we describe strategies to improve the yield and efficiency of these devices.

Optimization of optical waveguide antennas for directive emission of light

H. Farheen, T. Leuteritz, S. Linden, V. Myroshnychenko, J. Förstner, in: arXiv:2106.02468, 2021

Optical travelling wave antennas offer unique opportunities to control and selectively guide light into a specific direction which renders them as excellent candidates for optical communication and sensing. These applications require state of the art engineering to reach optimized functionalities such as high directivity and radiation efficiency, low side lobe level, broadband and tunable capabilities, and compact design. In this work we report on the numerical optimization of the directivity of optical travelling wave antennas made from low-loss dielectric materials using full-wave numerical simulations in conjunction with a particle swarm optimization algorithm. The antennas are composed of a reflector and a director deposited on a glass substrate and an emitter placed in the feed gap between them serves as an internal source of excitation. In particular, we analysed antennas with rectangular- and horn-shaped directors made of either Hafnium dioxide or Silicon. The optimized antennas produce highly directional emission due to the presence of two dominant guided TE modes in the director in addition to leaky modes. These guided modes dominate the far-field emission pattern and govern the direction of the main lobe emission which predominately originates from the end facet of the director. Our work also provides a comprehensive analysis of the modes, radiation patterns, parametric influences, and bandwidths of the antennas that highlights their robust nature.

    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), pp. 1717

    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.

    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

    WS 2021/2022: Courses, projects

    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