  In this review we focus on electronic transport through semiconductor
nanostructures which are driven by ac fields. Along the review we describe the
available experimental information on different nanostructures, like resonant
tunneling diodes, superlattices or quantum dots, together with the theoretical
tools needed to describe the observed features. These theoretical tools such
as, for instance, the Floquet formalism, the non-equilibrium Green's function
technique or the density matrix technique, are suitable for tackling with
photon-assisted transport problems where the interplay of different aspects
like nonequilibrium, nonlinearity, quantum confinement or electron-electron
interactions gives rise to many intriguing new phenomena. Along the review we
give many examples which demonstrate the possibility of using appropriate ac
fields to control/manipulate coherent quantum states in semiconductor
nanostructures.
