Novel infrared band-aligned superlattice laser

Abstract

A novel infrared laser is proposed which uses the intersubband optical transition in a band-aligned superlattice. In this band-aligned superlattice laser, the miniband discontinuity within the conduction of valence band functions as a band offset in the heterojunction structure, and the population inversion is achieved by current injection as in the conventional heterojunction laser. It is more flexible than a heterojunction laser of a quantum well laser since one may tailor the bandwidth and band structures as well as the band gap of the minibands. Also indirect band-gap materials like Si and Ge can be used for lasing in the intersubband transitions. The intersubband optical transition is similar to an atomic two-level system which exhibits low threshold current, and a gain coefficient with weak temperature dependence and a narrow spectrum which is determined only by the line-shape function. These special features make the band-aligned superlattice laser competitive with and perhaps superior to the quantum well dot laser which is not presently feasible.