Quantum cascade lasers with double-quantum-well superlattices

A quantum-cascade laser using a double-quantum-well graded superlattice as the active region is presented. Each SL period consists of two strongly cou pled quantum wells resulting in the splitting of the lowest miniband into t wo minibands, These two minibands can be designed to be pat and to contain delocalized, spatially symmetric wavefunctions under an applied electric fi eld which in turn leads to a high optical dipole for the interminiband tran sition. In addition, the new design allows independent control of the energ y levels of the lowest two minibands, their width and the splitting separat ing them, enhancing design flexibility. Using a cascade design of 55 pairs of alternated active regions and injectors, pulsed laser action is achieved at lambda = 11.6 mum, Peak output powers reach 120 mW at 7 K and approxima tely 12 mW at the maximum operating temperature of 195 K.