where c n,0 is the eigenstate expansion coefficient of the nth polariton state for |G, 1⟩ and c n, j is the eigenstate expansion coefficient of the nth polariton state for |D j , 0⟩. For the case λ D = 0, the donor state energies are identical for all R and consequentially the polariton states can be separated into bright and dark states. This also holds for the case λ D ̸ = 0 and R = 0 (more generally, when all R j are identical). The bright polariton states are the upper polariton (UP) and lower polariton (LP) states