Near-field characteristics of broad area diode lasers during catastrophic optical damage failure

One of the failure mechanisms preventing diode lasers in reaching ultra high optical output powers is the catastrophic optical damage (COD). It is a sudden degradation mechanism which impairs the device functionality completely. COD is caused by a positive feedback loop of absorbing laser light and increasing temperature at a small portion of the active material, leading to a thermal runaway on a nanosecond timescale. We analyze commercial gain-guided AlGaAs/GaAs quantum well broad area diode lasers in single pulse step tests. The near-field emission on the way to and at the COD is resolved on a picosecond time scale by a streak-camera combined with a microscope. In the final phase of the step tests the COD is occurring at ~50 times threshold current. The growth of the COD defect site is monitored and defect propagation velocities between 30 and 190 m/s are determined. The final shape of the damage is verified by opening the device and taking a micro-photoluminescence m ap of the active layer.