AG Kampfrath: Terahertz Physics

The Terahertz Physics Group studies phenomena that occur at extremely high frequencies in the so-called terahertz (THz) region from about 1 to 30 THz. This spectral range is still quite unexplored although it coincides with numerous fundamental resonances and relaxation processes in condensed matter. Important examples are crystal-lattice vibrations (phonons), spin waves (magnons), excitons (bound electron-hole pairs) and the scattering of conduction electrons (velocity relaxation).

To study and ultimately control these motions, we develop new and sensitive optical methods based on ultrashort electromagnetic THz fields and optical laser pulses. To better understand our experimental results, we work out simple theoretical models.

Examples of important questions we address are:

  • How do lattice vibrations affect the state of the electrons and their spins?
  • How can we control the ultrafast transport of electrons or spins through nanostructures?
  • How are dynamics modified close to interfaces?
  • How do molecules in liquids and soft matter react to strong pulsed THz electric fields?

A better understanding of the dynamics of complex materials at their natural (THz) frequencies is relevant for future applications because bit rates in information technology are gradually approaching the THz range, for instance in wireless networks and field effect transistors. We also explore our results directly for applications in THz photonics, including the development of novel emitters, detectors and modulators of broadband THz radiation.

We participate in national and international research collaborations: the DFG-funded Collaborative Research Center/Transregio 227 on Ultrafast Spin Dynamics and the EU-funded project ASPIN-FET on Antiferromagnetic Spintronics.