Surface emitting quantum cascade lasers

We present single mode surface emitting quantum cascade lasers (QCLs). Efficient surface emission of QCLs is obtained by a second-order surface grating. More complicated structures, e.g. photonic crystals, require very high aspect ratio dry etching. We provide a short overview of chlorine based plasma etching and discuss the limitations on accuracy and the impact of different process parameters on etch profiles and depths.