Patent ID: 8493654

Claim:
An interband cascade gain medium, comprising: an active gain region, the active gain region having a first end and a second end opposite the first end and having a cladding layer at each of the first and second ends, the active gain region comprising a plurality of cascading stages, each of the cascading stages including: an active gain quantum well region; a hole injector region adjacent the active gain quantum well region; and an electron injector region adjacent the hole injector region; each of the active gain quantum well region, the hole injector region, and the electron injector region comprising a plurality of electron barriers and at least one of an electron quantum well and a hole quantum well, the active gain region having an active gain quantum well region of a first stage at the first end thereof and an electron injector region of a last stage at the second end thereof; and further comprising at least one high-refractive-index separate confinement layer comprising one of GaSb, GaInSb, GaAlSb, GaAsSb, GaAlAsSb, GaInAsSb, GaAlInSb, and GaAlInAsSb and having a total thickness of at least about 0.8 μm disposed at at least one of the first and second ends of the gain medium between the active gain region and a corresponding cladding layer.