The Pulsed Nonresonant Optical Stark Effect and the Urbach Tail in Semiconductors

The theory of the intrinsic Urbach tail absorption in semiconductors is discussed. Some recent results of a cumulant expansion up to second order are presented which fit experimental observations excellently. The results can be simulated with a frequency‐dependent broadening which gives rise to memory effects for the optically induced polarization. The importance of these effects for the understanding of the pulsed nonresonant optical Stark effect is discussed.