Ultrafast optical processes in nitrides

We discuss here so-called 'propagation phenomena' in nitrides, i.e. the phenomena of light-matter coupling at the femtosecond and picosecond time-scales. Specifics of nitrides, namely, giant oscillator strengths of A and B excitons and extremely important potential disorder in GaN and related structures makes the elastic scattering of light by excitons a dominant process that has a huge influence on all kinds of coherent optical spectrum. We show how to extract the oscillator strength and inhomogeneous broadening from the reflection and resonant Rayleigh scattering spectra of GaN-based QWs. Finally, we discuss the stability of excitonic complexes like charged trions in nitrides and the effect of the free electron-hole plasma on their optical properties. (author)