Modelling the interaction between terahertz radiation and semiconductors

In the last few years, the interaction of terahertz (THz) radiation with many-electron systems in semiconductors, metals, graphene, or other materials has attracted significant attention worldwide. After our original suggestion to used THz radiation to identify excitonic populations in semiconductors, our group proceeded to developed a microscopic many-body approach that allows us to quantitatively model and explain a large variety of experiments. This theory goes well beyond the widely used Drude model by systematically including the full quantum nature of the Fermionic electrons and their Coulombic interaction effects. The ponderomotive and the intrinsic THz contributions to the measured THz response are clearly identified and their often intricate interplay is analyzed. So far, the theory has been used to successfully describe excitonic population effects in laser excited semiconductors, the generation of THz gain via non-resonant optical pumping, the ultrafast response of semiconductors to single-cycle THz pulses, as well as the coherent THz control of optically dark excitonic populations. The interaction of electron plasmas with THz radiation has been studied and the detection of THz radiation with diode lasers has been analyzed. Recent work includes the study of Fano signatures in the intersubband THz response of optically excited quantum wells, the THz-detection of plasmonic resonances in quantum wells and high-mobility transistor structures, the THz response of grapheme, as well as extreme nonlinear optical effects of semiconductors and metals under intense THz irradiation.