Thin Al2O3 films are grown and in situ doped with erbium by pulsed laser deposition in a single step process, by alternate ablation from Al2O3 and Er targets. The as‐deposited films have an Er step dopant profile throughout the film thickness, whose concentration depends on the number of pulses at the Er target. The as‐grown films are optically active, as evidenced by the photoluminescence spectrum centered at 1.533 μm, corresponding to intra‐4f transitions in Er3+. The photoluminescence intensity increases upon annealing due to an increase of the luminescence lifetime. This is most likely a result of a decrease in the nonradiative decay channels, related to annealing of defects in the Al2O3 film. © 1996 American Institute of Physics.