Photon echo studies of biexcitons and coherences in colloidal CdSe quantum dots

Nonlinear optical properties of colloidal quantum dots are studied to elucidate the significance and nature of many-body effects. Two-pulse photon echo studies of nanocrystalline CdSe quantum dots are reported for samples dispersed in a poly(butylmethacrylate) film (4.4 K). Oscillations are observed in the experimental data that are attributed to 1S(3/2)1S(e)-2S(3/2)1S(e) biexciton cohererences. Signals are simulated using a phenomenological model based on the many-body description of the dynamics (the average polarization model). It is found that the electronic coherences and the nonlinear response originating from biexciton source terms are important, but their manifestation in the photon echo signals is strongly influenced by the interplay between homogeneous and inhomogeneous line broadening. (c) 2005 WILEY-VCH Verlag GmbH & Co.