A theoretical treatment of the subband population in the intersubband staircase laser

A theoretical study of the subband occupation in an intersubband staircase laser has been performed within the density-matrix approach by applying a canonical transformation to a tight-binding model of a superlattice with four quantum wells per unit cell. The field-induced carrier redistribution in a superlattice structure is investigated, for which recently mid-infrared laser operation has been demonstrated. An intrinsic population inversion occurs, which is due to resonant tunneling.