MECHANISMS AND SIZE DEPENDENCE OF RESONAN T OPTICAL NONLINEARITIES OFGLASSES DOPED WITH CD(S,SE) NANOCRYSTALS

The mechanisms leading to the resonant optical Kerr effect in CdSe-dop ed glasses have been studied by time resolving the nonlinear response in samples having experienced various degrees of photodarkening. The r esponse is generally comprised of two components: a slow one due to tr apped carriers in particles with traps and a fast one due to free carr iers in particles without traps. Trapped carriers act through the stat ic electric field they create. The free carrier component is itself th e sum of two contributions: bleaching of the ground state to one-pair excited state transition and induced absorption between the one-pair a nd a two-pair state. The figure of merit associated with the fast comp onent decreases when the particle size decreases.