Feedback induced instabilities in a quantum dot semiconductor laser.

We analyse the properties of GaAs based quantum dot semiconductor lasers emitting near 1310 nm. The line-width enhancement factor is shown to depend strongly on device temperature, ranging from 1.5 at 20 degrees C to 5 at 50 degrees C. With optical feedback from a distant reflector, devices remained stable at 20 degrees C but displayed a range of instabilities at 50 degrees C, including irregular power drop--outs and periodic pulsations, before entering a chaotic regime. Such dynamical features are unique to quantum dot lasers -- quantum well lasers are significantly more unstable under optical feedback making such a clear route to chaos difficult to observe.