Optical gain appearance in the CdSe/CdS nanoplatelets colloidal solution

Abstract

The experimental investigations of the colloidal heterostructured CdSe/CdS nanoplatelets transient absorption in the regime of one-photon stationary excitation of excitons by high-intensity nanosecond laser pulses are presented. A strong dependence of exciton’s transitions behavior on nanoplatelets concentration in colloidal solution and pump intensities was studied for the first time. The revealed nonlinear transmission changes of the nanoplatelets solutions with different optical density were explained by the presence of phase space filling effect, energy exchange between exciton states, reabsorption processes and exciton–exciton interaction. The most vital result of the paper is the identification of conditions for the existence of the optical gain in colloidal solutions of nanoplatelets.