We have found that seconds of 100 mW Ar laser exposure produces more than 100 times an increase in infrared photoluminescence (PL) intensity in thin‐film polycrystalline silicon (poly‐Si). The change of PL intensity on laser exposed film areas (minimum spot size of 20 &mgr;m) and the variation in film surface morphology measured by atomic force microscope are compared. The effect of PL enhancement strongly correlates to two distinctive processes: (a) the increase of a grain size due to poly‐Si recrystallization, and (b) the oxygen incorporation into the film from glass or quartz substrates or/and from ambient gas. ©1995 American Institute of Physics.