SIZE SELECTIVE NONLINEAR OPTICAL SPECTROSCOPY OF EXCITONS IN CUCL QUANTUM DOTS

A size selective pump-and-probe method was applied to the Z3 exciton absorption spectra of CuCl microcrystals. Observation of the spectral hole-burning gave us the size-dependent homogenous linewidth at 2 K. The size-dependent part of the homogeneous linewidth is inversely proportional to the square of the radius of microcrystals. This dependence is explained by the scattering of excitons at the irregular surface of microcrystals. With the increase in the excitation density, the lower energy absorption is bleached and the higher energy absorption is enhanced. The high density excitation effect is explained by both the radiative energy transfer between microcrystals and the exchange interaction of excitons in microcrystals.