where g c = µ LL ′ 1/(2ℏϵ 0 V) is the Jaynes-Cummings type light-matter coupling strength that does not depend on ω k . Note that in the literature, Ω R = 4g 2 c ω c for the resonance condition. When there is only one mode, Eq. 29 reduces back to Eq. 17. Further, ϕ k describes the angle between the molecular dipole and the k th cavity mode. For the 1D FP cavity (one dimensional for the k ∥ direction), cos ϕ k = 1. For the 2D FP cavity (two dimensional for the k ∥ direction), we assume an isotropic average cos 2 ϕ k → ⟨cos 2 ϕ k ⟩ = 1/2. As such, the rate constant in Eq. 29 can be evaluated by replacing the summation with an integral as follows