Fig. furhter presents the peak value of k/k 0 (at ω c = ω 0 ) as a function of cavity lifetime τ c . One can see that the k/k 0 increase as the cavity lifetime increase, and then decrease, giving rise to a turnover when increasing τ c , and In Ref. 25, For τ c > 200 fs (toward the lossless limit of τ c → ∞), the cavity modification effects gradually decrease, agreeing with the previous results in Ref. 25. The trend of k/k 0 increase as τ c increase for τ c ∈ [0, 100] fs was not discussed in the previous literature. The current results bring a more complete picture of how k/k 0 depends on τ c .