We study the effects of a laser beam from the laser diode operating at 980nm on the violet-excited ZnS:Cu and SrAl2 O4:Eu phosphor powders. Two contrary phenomena, i.e., infrared-induced permanent quenching and short-lived enhancement of phosphorescence, are observed. The defect levels play a significant role in both the processes. It is demonstrated that the phosphorescence induced by the violet beam can be controlled by another infrared beam. The tu-offand tu-on behaviour means that doping luminescent centres into host materials is a considerable way to design a new all-optical switch and may control the output of laser beams in the fibre lasers and optical communications.