Excited Wannier-Stark states in the optical absorption of a superlattice in an electric field

We calculate the optical absorption of a multiple quantum well in a perpendicular electric field, including Coulomb interaction, with no restriction in the number of minibands. Both below- and above-barrier states are taken into account. It is shown that higher-order miniband transitions significantly contribute to the optical absorption. We predict a clear and distinct Stark ladder from the (2,2) transition that is more pronounced than the one from the (1,1) transition.