Cavity polaritons for new photonic devices

In high finesse semiconductor microcavities containing quantum wells, photons emitted by the quantum well excitons can oscillate long enough inside the cavity to be reabsorbed reemitted again and so forth. The system enters the so-called strong coupling regime, with the formation of entangled exciton-photon eigenstates, named cavity polaritons, which governs all the physics of the system. After an introduction to cavity polaritons, we will review in this paper some of their original physical properties and discuss their potential in terms of new photonic devices. In a first part, we will show how polaritons can massively occupy a single quantum state, thus acquiring spatial and temporal coherence reflected in the emitted light. Such polariton laser could provide a low threshold source of coherent light. Then the properties of polariton diodes will be addressed and in particular we will describe a new optical bistability based on the control of the light matter coupling via the intra cavity electric field.