]︀ (c.f. Eq. 26), and 𝜉 is expressed in Eq. 25. Note that this expression also peaks at 𝜔 c = 𝜔 0 (as indicated in Fig. ), when 𝜏 ‖ → ∞. In Eq. 35, 𝜔 c is the lower limit of the integral with respect to 𝑑𝜔 k , as well as appearing explicitly in 𝜏 ‖ . The result of this definite integral in Eq. 35 is not as simple as replacing 𝜔 k with 𝜔 c as in the single-mode approximation (Eq. 32). VSC (Eq. 32) for the single mode case (or the many modes case inside a 1D FP cavity) calculated using Eq. 32 (same as the solid lines in Fig. ). (b) FGR rate profiles 𝑘 2D VSC (Eq. 35 for many mode cases inside a 2D FP cavity. Here, we use 𝒟/𝑐 = 1 fs, which corresponds to the cavity diameter 𝒟 = 0.3 𝜇m. Note that both 𝑘 1D VSC and 𝑘 2D VSC are rescaled by a factor of 0.4 to be consistent with Fig. .