Phase transition and storage of quantum optical information using polaritons in spatially-periodical structures

In the paper we discuss various aspects both of phase transition and Bose–Einstein condensation (BEC) problems for 2D gas for polaritons forming in semiconductor and atomic micro- and nanostructures. The consideration is carried out taking into account current experimental facilities and technological achievements. We offer new type of spatiallyperiodical structure – polaritonic crystal (PolC), formed be 2D lattice of trapped two level atoms interacting with e.m. field in the lattice of tunnel-coupled microcavities. The main accent made on investigation of mechanisms of coherent polariton formation, which are defined as coupled states of optical field and atomic medium for low branch polaritons. We analyze different cases of variation (reduction) of group velocity of optical wave packets under the condition of quasi-condensation (or true condensation) phenomenon for polaritons. We have shown that PolC structure admits complete localization of polaritons which can be used for low branch polariton quasi-condensation as well as for recording and storage of quantum optical information for spreading optical irradiation.