Save time using maths: analytical tool designs corkscrew-shaped nano-antennae

The nano-antennae werde produced in an electron microscope by direct electron-beam writing.

The nano-antennae werde produced in an electron microscope by direct electron-beam writing. © HZB

For the first time, an HZB team has derived analytically how corkscrew-shaped nano-antennas interact with light. The mathematical tool can be used to calculate the geometry that a nano-antenna must have for specific applications in sensor technology or information technology.

The nanostructures from Katja Höflich's HZB team are shaped like corkscrews and made of silver. Mathematically, such a nano antenna can be regarded as an one-dimensional line that forms a helix, characterized by parameters such as diameter, length, number of turns per unit length, and handedness.

The nano corkscrews are highly sensitive to light: depending on frequency and polarisation, they can strongly enhance it. Because helical antennas have a handedness, they can select light quanta according to their handedness, i.e. their spin. This results in novel applications in information technology based on the spin quantum number of light. Another application may lay in sensor technology in detecting chiral molecular species down to the single molecule level.

Usually, the interaction of such nano-antennas with an electromagnetic field is determined using numerical methods. Each helix geometry, however, requires a new numerically expensive calculation.

For the first time, Höflich and her team have now derived an analytically exact solution of the problem. “We now have a formula that tells us how a nano-antenna with specific parameters responds to light”, says Höflich. This analytical description can be used as a design tool, as it specifies the required geometrical parameters of a nano-helix to amplify electromagnetic fields of desired frequencies or polarisation.

The HZB researchers were able to  fabricate nano-antennae in an electron microscope at the CCMS corelab of HZB by using direct electron-beam writing. The electron beam first writes a helix-shaped carbon structure one point at a time. This structure is subsequently coated with silver. The actual measurements of the optical properties for these silver nano-antennae are in good agreement with the calculated properties predicted by the analytical model.

Optica  (2019, Vol. 6, Issue 9): “Resonant behavior of a single plasmonic helix”; Katja Höflich, Thorsten Feichtner, Enno Hansjürgen, Caspar Haverkamp, Heiko Kollmann, Christoph Lienau, Martin Siles.

 

DOI: 10.1364/OPTICA.6.001098

arö

You might also be interested in

  • Rhombohedral graphite as a model for quantum magnetism
    Science Highlight
    27.09.2022
    Rhombohedral graphite as a model for quantum magnetism
    Graphene is an extremely exciting material. Now a graphene variant shows another talent: rhombohedral graphite made of several layers slightly offset from each other could enlighten the hidden physics in quantum magnets.
  • 8th World Conference on PV Energy Conversion
    News
    19.09.2022
    8th World Conference on PV Energy Conversion
    The WCPEC-8 woll take place from 26 – 30 September 2022 in the Milano Convention Centre in Milan, Italy.
    Also scientists from PVcomB will present latest results about their research work to photovoltaics.

  • 40 years of research with synchrotron light in Berlin
    News
    14.09.2022
    40 years of research with synchrotron light in Berlin
    Press release _ Berlin, 14 September: For decades, science in Berlin has been an important driver of innovation and progress. Creative, talented people from all over the world come together here and develop new ideas from which we all benefit as a society. Many discoveries – from fundamental insights to marketable products – are made by doing research with synchrotron light. Researchers have had access to this intense light in Berlin for 40 years. It inspires many scientific disciplines and is an advantage for Germany.