Heavy-hole and light-hole excitons in nonlinear absorption spectra of colloidal nanoplatelets

We study the nonlinear optical response of CdSe/CdS nanoplatelets (NPLs) in the vicinity of heavy hole (hh) and light hole (lh) exciton resonances by means of the two color pump-probe technique. The population of hh and lh excitonic states leads to the decrease of the light absorption at both resonances under resonant excitation of one of them. Increase of the pump power leads to the saturation of the absorption. This effect allows us to estimate the exciton total lifetime.