Type II W, interband cascade and vertical-cavity surface-emitting mid-IR lasers

The authors review recent demonstrations of improved mid-IR laser performan ce when a type II 'W-well' structure is incorporated into the active region . The W configuration consists of a hole quantum well (e.g. GaSb or GaInSb) between electron quantum wells (e.g. InAs) in order to maximise the gain w hile suppressing nonradiative Auger losses. Optically pumped W lasers recen tly produced more than 1.4 W per facet peak power for pulsed operation at 3 00 K. An interband cascade laser with a W active region (W-ICL) has operate d up to 286 K. The first III-V mid-IR VCSEL (lambda = 2.9 mu m) with a W ac tive region has lased up to 280 K for pulsed operation and to 160 K for cw, with a cw threshold of only 4 mW for a 6 mu m spot at 78 K.