Giant dynamical Stark shift in germanium quantum wells

We report a strong dynamical (ac) Stark shift of the direct gap transitions in Ge quantum wells at both cryogenic and room temperature. A blueshift of 67 meV is observed, exceeding values reported for III-V materials by about an order of magnitude. The fast intervalley scattering in the Ge material system leads to short dephasing times which in return causes larger shifts. (C) 2011 American Institute of Physics. [doi:10.1063/1.3580630]