Polariton dispersion of periodic quantum well structures

We studied polariton dispersion relations of a periodic quantum well structure with a period in the vicinity of half the exciton resonance wavelength, i.e. Bragg structure. We classified polariton modes using an approximation of large quantum well number. The polariton effective masses are found to be very small, $10^{-3} - 10^{-4}$ of the free electron mass.