Enhanced stimulated emission of excited states in quantum wells by resonant tunneling

Although lasing involving transitions between higher lying subbands in quantum well structures has been observed, it usually occurs in lasers with short cavities (L<1 mm). In typically QW lasers with long cavities (L>1 mm), the ground state transition is almost always the dominant lasing process. To study the feasibility of selective injection of carriers into a higher lying subbands, we investigated the electroluminescence properties of some resonant tunneling GaAs single quantum well structures. We observed lasing via higher lying subbands instead of the ground state in 1 mm long lasers