This seminar gives an overview on our recent experimental studies involving terahertz (THz) and mid-infrared radiation from the free-electron laser facility FELBE in Dresden, Germany. In particular, cyclotron resonance spectroscopy and aperture-less near-field microscopy will be addressed as examples for linear measurements. Moreover, nonlinear THz photocurrents originating from two-photon excitation between subbands in semiconductor quantum wells allow for measurements of intersubband relaxation and dephasing times and for quadratic autocorrelation of THz pulses. The final part of my talk will concentrate on nonlinear two-color THz spectroscopy, in particular THz sideband generation and coherent dynamics involving excitons dressed by strong THz beams.
Harald Schneider did his Ph. D. at the Max-Planck Institute for Solid-State Research, Stuttgart, Germany, in 1988. In 1989 he moved to the Fraunhofer-Institute for Solid State Physics, Freiburg, Germany, and in 2005 to the Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany, where he is currently working as a department head. He is a faculty member at the University of Freiburg, Germany, since 2003. In 2010 he became Visiting Overseas Chair Professor at the Shanghai Jiao Tong University. His research interests include optoelectronic properties of semiconductors, ultrafast and free-electron laser based spectroscopy, and detectors for the infrared and THz regimes. For the development of infrared cameras of highest thermal resolution, he and his colleagues were awarded the 2001 German Science Foundation Award. He has co-authored more than 200 publications.