Microscopic analysis of extreme nonlinear optics in semiconductors

Extreme nonlinear optics denotes the regime where the Rabi frequency is comparable to or even larger than the band gap frequency. This regime can be reached experimentally by using intense ultrashort laser pulses which have a duration of just a few femtoseconds, see, e.g., [1]. As shown in [2] for the case of a two-level system, a theoretical analysis of extreme nonlinear optics requires one to describe the dynamics on ultrashort time scales beyond the rotating-wave approximation. Such calculations describe, e.g., the generation of higher harmonics and Mollow tripletts [1,2]. Here, we use a microscopic model of a two-band semiconductor with Coulomb interaction to analyze the regime of extreme nonlinear optics. It is, in particular, shown that the importance of excitonic effects which are known to dominate the nonlinear optical response at moderate excitation intensities become less important at largely elevated intensities