Tracing Ultrafast Phenomena with Infrared Electric Fields

Abstract

This presentation reviews efforts of my group to investigate the dynamical properties of matter and light at the most fundamental level, namely at the spatio-temporal scales defined by the oscillation periods of relevant elementary excitations and the related wavelengths. There are several reasons why the infrared turned out as an extremely exciting and rewarding region for carrying out this kind of research. Right from the beginning, it was clear that many collective excitations of matter like e.g. phonons or magnons, the resonances of weakly coupled few- or many-body entities like e.g. excitons or superconducting condensates but also single-particle excitations in semiconductor nanostructures reside in this frequency range. Their dynamics and interactions play a functional role for the nature and technology surrounding us. Also, in all dielectric systems, there exist wide intervals which are far from any resonances. On the one hand, this fact provides us with the ability to investigate the properties of the electromagnetic field itself with subcycle resolution and at an extreme sensitivity in the quantum regime. On the other side, it allows to manipulate matter in an adiabatic and non-perturbative way as soon as short transients with adequate peak fields are available.