Gradual degradation in 980 nm InGaAs/AlGaAs pump lasers

High temperature (140 °C) and high current density (17 kA cm−2) aging tests have been applied to InGaAs/AlGaAs 980 nm single-mode pump lasers. The use of low reflectivity (≅1%, AR) coatings on both facets leads to a symmetrical cavity configuration with relatively low power per facet emission (≈50–60 mW per facet). In this way, a quasi-uniform strongly accelerated stress is applied to the laser cavity and the normally very low gradual degradation rate becomes observable after a few hundreds hours of operation as a strong threshold current shift, while the external efficiency of the laser is almost unaffected. The degradation of the laser structure has been studied by low level I(V) curves analysis, Low Temperature (80 K) Spectrally Resolved Cathodoluminescence (LT-SRCL) and Electrical/Optical Noise (EON) techniques; the degradation seems to be longitudinally uniform and localized in the vicinity of the QW. Some laser thus degraded has been subsequently aged in more standard conditions, after applying a high reflection coating (HR) on the back facet; preliminary results of these tests are discussed.