A novel class of coherent light emitters: polariton lasers

The specificities of polariton lasers-a new generation of coherent light-emitting devices where the relaxation of the bosonic quasiparticles responsible for the light emission, the polaritons, is stimulated whereas the photon emission process issued from the radiative decay of those polaritons is purely spontaneous-are reviewed. It is shown that the practical realization of such devices able to operate at room temperature would most likely rely on wide bandgap semiconductors (inorganic or organic ones) exhibiting highly stable excitons/polaritons. Using III-nitrides, the most advanced of the candidates to date, an electrically driven multiple quantum well polariton laser would display a threshold current density down to similar to 100 A cm(-2), a value more than one order of magnitude lower than that of state of the art GaN-based edge-emitting laser diodes. For the sake of comparison, the main features of optically pumped polariton lasers available that differ from those of their conventional counterparts, namely vertical cavity surface-emitting lasers, are also discussed.