We have made quantum wells laser diodes by Molecular Beam Epitaxy with emission wavelengths from 2.3 mu m to 3.1 mu m. With growing wavelength, threshold current densities increase almost exponentially. We obtained threshold values as low as 65 A/cm(2) at 2.3 mu m and 156 A/cm(2) at 2.62 mu m. At the same time, the valence-band offset decrease from 132 meV (at 2.3 mu m) to 78 meV (at 2.6 mu m). A threshold current density study shows that Auger effect is not the only responsible for the augmentation of J(th). The reduction of internal efficiency eta(i) has a greater impact on the increase of J(th). The diminution of the holes confinement is incriminated for the degradation of eta(i) with growing wavelength. Therefore, to improve J(th) at higher wavelengths another kind of barrier has to be utilized (for example, thanks to the use of the quinary material AlGaInAsSb).

GaInAsSb/GaAlAsSb/GaSb distributed-feedback (DFB) laser diodes based on a type I active region were fabricated by molecular beam epitaxy at the Centre d'Electronique et de Micro-Optoélectronique de Montpellier (CEM2). The DFB processing was done by Nanoplus Nanosystems and Technologies GmbH. The devices work in the continuous-wave regime above room temperature around an emission wavelength of 2.3 microm with a side-mode suppression ratio greater than 25 dB and as great as 10 mW of output power. The laser devices are fully characterized in terms of optical and electrical properties. Their tuning properties made them adaptable to tunable diode laser absorption spectroscopy because they exhibit more than 220 GHz of continuous tuning by temperature or current. The direct absorption of CH4 is demonstrated to be possible with high spectral selectivity.