Seminars Archive

THz light-matter interaction of 2D systems in the linear and non-perturbative regime.

Abstract
The development of THz technologies in particular emitters and detectors gave access to many new interesting physics of light-matter interaction in the linear and nonlinear regimes. Semiconductors such as graphene or 2D systems in heterostructures have been studied intensively within THz spectroscopy providing insights in phonon, exciton and electron resonances and lead for example to new applications such as modulators inevitable for THz communication. In particular strong THz pulses, which are typically generated by sources such as free-electron lasers [2], provide access towards fundamental effects, e.g. the AC-Stark effect [1] and electromagnetic induced transparency [3] in the low THz range. The first part of this talk is dedicated to the design and fabrication of a THz modulator based on metasurfaces and a single layer of graphene as a tunable absorber. The linear absorption properties of the device can be modulated electrically by gating graphene, while the absorption is probed with broadband THz pulses. The second part presents a THz pump-probe experiment of a single GaAs/AlGaAs quantum well, where pump pulses are generated by the free-electron laser FELBE in Dresden-Rossendorf. Strong THz-pump pulses induce a splitting of the second and third subbands, while weak, broadband THz pulses probe an Autler-Townes doublet as well as a Mollow triplet. [1] J. Schmidt, et al., Rev. Sci. Instrum., vol. 86, p. 063103, 2015 [2] M. Wagner et al. Phys. Rev. Lett., vol. 105, p. 167401, 2010 [3] M. Fleischhauer et al., Rev. Mod. Phys., vol. 77, pp. 633–673, 2005