Intersubband stimulated emission and optical gain by ‘‘phonon pumping’’ in quantum wires

We present an analysis of the optical gain for stimulated emission between subbands in quasione-dimensional structures. The population inversion is induced by a new pumping mechanism involving phonon absorption during transport in quantum wires. The population inversion threshold for far infrared stimulated emission is calculated in a generic GaAs quantum wires laser structure and shows a quite reasonable minimum value of Δn=3×105/cm at λ=100 μm. For longer wavelengths, free carrier absorption is the main limitation to stimulated emission.