  We have theoretically investigated the tunneling current induced by a
terahertz (THz) field applied to an asymmetric double quantum well. The
excitation couples an initially localized state to a nearby continuum of
extended states. We have shown that the calculated current has similar features
as those present in the optical spectra, such as interference effects due to
the interaction between the continuum and the localized states, in addition to
many-photon transition effects. The induced current is calculated as a function
of the intensity of the THz field. A second THz field is used to yield
non-linear processes, useful to control the interference effects. We believe
that part of the issues studied here can be usefull for the integration of
novel switching mechanisms based on optics (THz) and electronic current.
