Our results suggest that by considering many modes, the FGR rate constant inside a 1D FP cavity (1-dimension along the k ∥ direction) reduces back to the single mode case, because of the van-Hove-type singularity in the photonic DOS . As a result, inside a 1D FP cavity, VSC modification occurs only at the normal incidence ω c = ω 0 . For molecules coupled inside a 2D FP cavity, the FGR rate constant is expressed as follows