Quantum wells and superlattices in strong time-dependent fields

The behavior of electrons in quantum semiconductor structures interacting with strong far-infrared laser radiation is discussed, under circumstances where quantum tunneling is important. The systematic appearance of avoided crossings in the quasienergy spectrum of a two-state system is related to the frequency spectrum of radiation scattered from a laser-driven double well. The application of the adiabatic approximation to a periodically forced superlattice explains the collapse of quasienergy minibands and leads to the prediction of a possible inhibition of wave-packet spreading.