Patent ID: 7403552

Claim:
A semiconductor laser comprising a plurality of coupled laser stages, each stage comprising a multiple semiconductor layer structure including an electron injector, an active region coupled to the electron injector and an electron reflector coupled to the active region opposite the electron injector, wherein: (a) the electron injector has an upper miniband, a lower miniband, and a minigap; (b) the active region comprises at least one quantum well having associated therewith an upper energy level and a lower energy level, characterized in that electrons injected into the upper energy level of the active region from the lower miniband of the electron injector undergo a radiative transition to emit a photon as they decay from the upper energy level to the lower energy level; and (c) the electron reflector comprises an upper miniband, a lower minband, and a minigap, characterized in that the minigap acts as a reflector for electrons in the upper energy level of the active region and the lower miniband acts as a transmitter of the electrons that have decayed to the lower energy level of the active region to the lower miniband of the injector in the adjacent laser stage; wherein the electron injectors and electron reflectors between active regions are of different structure.