We propose a novel spin-optronic device based on the interference of
polaritonic waves traveling in opposite directions and gaining topological
Berry phase. It is governed by the ratio of the TE-TM and Zeeman splittings,
which can be used to control the output intensity. Because of the peculiar
orientation of the TE-TM effective magnetic field for polaritons, there is no
analogue of the Aharonov- Casher phase shift existing for electrons.Comment: 4 page