Polaritonic devices

We review the current hopes for applications of exciton–polaritons in semiconductor microcavities. These quasi-particles have become distinguished in recent years for a variety of different effects including Bose–Einstein condensation, ballistic spin current propagation and polarisation sensitive bistability. Bose–Einstein condensation is related to ultra low-threshold lasing, which has been demonstrated at room temperature and currently captures a significant research effort towards electrical carrier injection. Inspired by spintronics, the spin structure of polaritons gives rise to the field of spinoptronics, which presents optical analogues of the Datta and Das transistor and Aharonov–Bohm ring interferometer. Bistability, enhanced with the polarisation degree of freedom, gives rise to long-living spin memory elements, spin logic gates and polariton neurons for the construction of all-optical and hybrid optoelectronic circuits.