Optically pumped four-level infrared laser based on intersubband transitions in multiple quantum wells: feasibility study

The feasibility of optically pumped infrared laser based on the intersubband transitions in multiple quantum wells is studied theoretically. The criteria for population inversion and efficient lasing operations are established. A system consisting of a superlattice with four quantum wells per period is proposed and shown to satisfy the criteria. The relaxation processes are investigated, giving the electron-phonon interaction a rigorous theoretical treatment. It is shown that in the proposed structure, optical gain in excess of 300 cm ^-1 can be realized under practical pumping conditions. Modification and optimization of the proposed laser are discussed