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

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Abstract
The authors review recent demonstrations of improved mid-IR laser performance 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 while suppressing nonradiative Auger losses. Optically pumped W lasers recently produced more than 1.4 W per facet peak power for pulsed operation at 300 K. An interband cascade laser with a W active region (W-ICL) has operated up to 286 K. The first III–V mid-IR VCSEL (λ = 2.9 µm) with a W active 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 µm spot at 78 K.