Planet radius distribution as a function of orbital period. The grey circles denote the planet sample obtained from the CKS sample (Fulton et al. 2017). The blue dot-dashed line and the green dashed line indicate the peak of the bimodal distribution of the planet radius distribution, where planets tend to favour radii of ~ 1.3 R_⊕ and ~ 2.4 R_⊕ due to the photoevaporation mechanism. The red dotted line indicates the lower limit of the photoevaporation valley derived from Owen & Wu (2017).