Heterodyne-detected accumulated photon echo in CdSe quantum dots

The homogeneous optical spectra of CdSe quantum dots were investigated under very low excitation density of 10−3 photons per dot by using the heterodyne-detected accumulated photon echo. The photon echo decay is composed of two exponential decays in femto- and picosecond time domains. The fast decay component comes from the confined acoustic phonon sideband, while the slow one comes from the zero-phonon line. The linewidth of the zero-phonon line at 0 K is inversely proportional to the radius of the dots and ranges from 0.1 to 0.2 meV, suggesting the dominant contribution of the surface scattering. It increases linearly with the temperature rise. The temperature broadening linear coefficient is inversely proportional to the square of the radius of the dots consistence with the theory based on the deformation potential coupling to the confined acoustic phonon modes.