Resonance tunneling in the presence of external field W(x,t)=W(x)cos( omega t) is investigated within the framework of the classical perturbation theory. This approach is applied to a quantum-well structure in a superposition of a DC and sufficiently small AC (laser) field. Rigorous expressions for the shape of the tunneling spectra are obtained in a number of physically important cases. An AC field of the frequency omega large compared to the resonance width Gamma is shown to split the resonance peak into a family of well-separated peaks with spacing between them equal to omega . In the limit of weak, slowly varying fields the form of the resonance peak is determined by the mean value of the time-dependent potential in the well only.
 

Physical Review B, 37 4201-8, 1988.