Femtosecond two-pulse photon echo due to quantum-size excitons in nanocrystals

Time dependences of the signal of two-pulse photon echo excited through quantum-size excitonic transitions in CdSe nanocrystals with the use of femtosecond laser pulses are calculated for the regime of simultaneous excitation of two excitonic transitions. The presence of quantum beats is revealed both in the time dependence of the echo signal and in the dependence of the maximum echo intensity on the delay time between the pumping laser pulses. The presented plots indicate that the revealed beats are highly sensitive to the mean size of nanocrystals and the type of the distribution of nanocrystals in radii.