Nonlinear optical spectra of the confined excitons in stress induced nanostructures in bii₃

We report the optical nonlinear response of the confined excitons in nanostructures induced by external stress in a layered crystal BiI₃. The absorption intensity of the confined excitons is saturated by intense laser excitation. We clarify the size dependence of the saturation density which reflects the nanostructure size. The saturation density of the confined exciton in large domains is lower than the the case of small domains. By pump-probe measurements using a sub-picosecond laser pulse, we examine the dynamical process of the confined excitons in the disks with various sizes. From the temporal behavior of the absorption saturation, it becomes clear that the exciton life times in small disks are shorter than the large ones. A new nonlinearly growing luminescence due to the process by a inelastic recoiling of excitons is detected.