Ultrashort Pulse Spectroscopy and Terahertz Physics

Prof. Dr. Hartmut G. Roskos

Profile of the group

The central research topic of the working group is the time-resolved investigation of elementary excitations in semiconductors, superconductors and magnetic materials using ultrashort light pulses. Suitable laser systems, frequency conversion methods and measurement methods are being developed for this purpose. Particular attention is paid to the development of the terahertz frequency range (10-10,000 GHz), which is of particular research relevance due to its proximity to the electronically developed megahertz and gigahertz range on the one hand and to optics on the other, and which uses methods from both areas ("optoelectronic" methods).

The measurement techniques are mainly used for time-resolved spectroscopy of coherent phenomena in solid state physics. Examples are quantum suspensions of charge carrier wave packets (such as Bloch oscillations) and spin excitations, coherent lattice oscillations (phonons) as well as collective excitations such as plasmons. The excitation mechanisms as well as the interaction of the excitations with the environment are investigated.

  • Essential leitmotifs of the work are:
  • a) Understanding the dynamics of the quantum mechanical phase in scattering processes, determining the conditions for phase preservation during scattering;
  • b) Investigation of couplings, e.g. between coherent carrier wave packets and phonons or of spin and carrier density excitations in superconductors and spin systems;
  • c) Development of fundamentals for the realization of an electrically pumped, continuously tunable, coherent radiation source in the terahertz frequency range ("THz laser") based on semiconductor structures of reduced dimensionality (quantum well structures).