Resonant tunneling in the presence of two electric fields: One static and the other oscillating

The transmissivity of an electron incident on a nanostructure such as met in semiconductor devices is affected when the particle is interacting with an oscillating field. Since most experiments are done by applying also a static field (the `bias'), the two fields have to be simultaneously introduced in the wave equation to determine the probabilities of absorption and emission of quanta in both transmission and reflection. We review and extend the formalism needed to treat this situation. Appropriate Airy functions provide a very efficient way for calculating the probabilities for absorption or emission of photons, either in reflection or in transmission. An application is made to resonant tunneling through a system of two barriers.