Dark-state polaritons in a degenerate two-level system

Abstract

We investigate the formation of dark-state polaritons in an ensemble of degenerate two-level atoms admitting electromagnetically induced transparency. Using a generalization of microscopic equation-of-motion technique, multiple collective polariton modes are identified depending on the polarizations of two coupling fields. For each mode, the polariton dispersion relation and composition are obtained in a closed form out of a matrix eigenvalue problem for arbitrary control field strengths. We illustrate the algorithm by considering the Fg = 2 → Fe = 1 transition of the D1 line in 87Rb atomic vapor. In addition, an application of dark-state polaritons to the frequency and/or polarization conversion, using D1 and D2 transitions in cold Rb atoms, is given.