New developments in mid-infrared Sb-based lasers

A number of different approaches are being investigated to obtain high-performance mid-infrared (2-5 mu m) diode lasers for applications such as infrared lidar, remote sensing and environmental monitoring. They include laser heterostructures based on interband transitions in quantum-well or superlattice active region, and quantum cascade structures based on unipolar intersubband transitions. The Sb-containing structures, employing GaSb, InAs, AlSb and related alloys, are focusing actually much attention. Significant improvements in the molecular beam epitaxy of these alloys make possible now the growth of laser antimonide structures of high structural quality. Excellent performances have been reported at approximate to 2 mu m from GaInAsSb/AlGaAsSb and at approximate to 3.5 mu m from InAsSb/InAlAsSb type-I quantum-well diode lasers. Type-II (staggered alignment) GaInAsSb/GaSb and type-III (broken gap alignment) InAs/Ga(In)Sb strained multiquantum-well lasers are promising material systems for midinfrared sources, due to their large conduction and valence band offsets, the potential of Auger process suppression and the enhancement of the electron-hole optical coupling by wave function engineering. Besides high performance interband quantum cascade lasers operating at room temperature with negligible current leakage and high output power can be designed from Sb-containing type-III structures.