Physics and applications of III-Sb based type-I QW diode lasers

We present recent progress achieved in the development of type-I GalnAsSb/AIGaAsSb quantum-well (QW) lasers covering the 1.74 - 2.34 µm spectral range. Diode lasers based on the broadened waveguide design comprising 3 QWs have been studied in detail. Laser structures emitting at 2.23 µm exhibited a record high internal quantum efficiency of 89%, internal loss of 6.8 cm-1, and threshold current density at infinite cavity length as low as 120 A/cm2, indicating the superior quality of these devices. For the 2 µm lasers a high characteristic temperature of 179 K for the threshold current was achieved for temperatures between 250 and 280 K. In order to investigate the heterobarrier leakage associated with thermally activated carriers, laser structures emitting at 2.23 µm with different Al-concentrations in the barriers and separate confinement regions have been studied. While the structure with 40% Al revealed the highest T (ind O) of 103 K, the laser with 20% Al yielded the best power efficiency, with a maximum value of 30%. 1.7 W in cw mode at room temperature has been achieved for broad area single emitters at Lambda = 2 µm, with high-reflection/antireflection coated mirror facets, mounted epi-side down. As an application, tunable diode lasers absorption spectroscopy (TDLAS) sensing small concentrations of methane has been demonstrated using our 2.3 µm diode laser.