Random semiconductor lasers: scattered versus Fabry-Perot feedback.

As a result of growth imperfections, (Zn,Cd)O/ZnO quantum well structures exhibit random laser action. Fabrication of microresonators allows us to study and to compare directly cavity and scattered feedback. Our experimental and theoretical analysis shows that (i) pure random lasing generally requires a larger gain than in the standard Fabry-Perot regime, (ii) the presence of Mie scatterers in the semiconductor-based cavity does not substantially increase the lasing threshold, and (iii) the random feedback creates a subtle modal gain distribution that might be of particular importance for the dynamical properties, both with and without Fabry-Perot cavity.