NONLINEAR-OPTICAL SPECTRA OF CONFINED AND LOCALIZED EXCITONS IN MESOSCOPIC DOMAIN AND QUASI-2D STACKING-FAULT INTERFACE IN BII3 CRYSTALS

Saturation spectra of the excitons confined and localized at several k inds of stacking disorders in layered crystal BiI3 are studied. The qu asi-two dimensional exciton localized at the stacking fault interface does not saturate its absorption strength below the density of 10(5)W/ cm2 due to the large binding energy and the lateral center-of-mass mot ion along the interface. On the exciton system associated with some po lytypic structures contained in a very small region, an obvious absorp tion saturation is observed. The behaviour of absorption saturation is well described by a saturation effect on a simplified two-level syste m having a homogeneous line broadening. An absorption saturation is al so observed on the confined excitons in mesoscopic domains induced by the external deformation of the crystal. The pumping-laser photon-ener gy dependence of the saturation density characterizes this exciton sys tem to be inhomogeneous.