SUBPICOSECOND SPECTROSCOPY OF THE OPTICAL NONLINEARITIES OF CUCL QUANTUM DOTS

We have observed of ultrafast time-resolved nonlinear optical absorption spectra of confined excitons in CuCl quantum dots embedded in a NaCl matrix. The main part of the nonlinear change consisted of blueshifts of the ${\mathit{Z}}_{3}$ and ${\mathit{Z}}_{12}$ exciton bands, and their decay had two time constants that coincide with the luminescence lifetimes of excitons and of excitonic molecules. A microscopic mechanism for the optical nonlinearities of confined excitons is discussed.