Fig. 5. Representations of polariton-assisted remote energy transfer (PARET), where donor–acceptor separation Δz approaches 1 µm for various cases of strong coupling to surface plasmons (in a realistic setup, a spacer separates donor and acceptor layers). (a) PARET from dense slab of donors (strongly coupled to SPs) to dilute monolayer of acceptors. (b) “Carnival effect” (i.e., role-reversed) PARET from dense slab of acceptors (strongly coupled to surface plasmons) to dilute monolayer of donors. Inset: cartoon highlighting the “carnival effect”, or role reversal, between donors and acceptors. (c) PARET from dense slab of donors to dense slab of acceptors (both are strongly coupled to SPs). Inset: cartoon illustrating the vibrational relaxation that mediates PARET in this case.