We present result of optical studies on InAs/GaIn(As)Sb/InAs type II quantum wells predicted for the active region in interband cascade lasers, and further for laser-based gas sensors operating at room temperature in a broad wavelength range of mid infrared. Using photoreflectance spectroscopy supported by electronic structure calculations we determine the oscillator strength of the fundamental optical transition in structures with GaIn(As)Sb material of various compositions hole confinement layer. We show that incorporation of arsenic into this layer can affect several crucial properties significantly like transition wavelength and its probability, but also the structural material quality affecting the radiative efficiency. Also, by using photoluminescence we investigate one of the crucial parameters for the performance of interband cascade lasers, the spectral emission width of type II quantum wells constituting the laser active region.
There are reviewed the optical properties of two kind of active regions of mid infrared laser devices both grown on GaSb
substrates: GaInAsSb/AlGaInAsSb type I QWs for laser diodes and InAs/GaInAsSb type II QWs for interband cascade
lasers. There are presented their crucial optical properties and the related current challenges with respect to the device
performances. This covers such issues as spectral tenability of the emission via the structure parameters, the band gap
discontinuities, carrier loss mechanisms and oscillator strengths. For that, spectroscopic techniques have been used
(photoluminescence and its temperature dependence, and photoreflectance) and combined with the energy level
calculations based on effective mass approximation and kp theory. Eventually, the potential for further material
optimization and prospects for the improved device performances are also discussed.