Pulsed laser deposition (PLD) is a very efficient technique for the fabrication of thin films and multilayer heterostructure of various materials. In this study, KrF excimer laser (248 nm) is used to ablate the target, the desired plume is produced during this ablation. The pure and Al doped ZnO thin films on the glass substrate are prepared at different substrate temperatures. From the transmission data by spectrophotometer, we get the band gap energy E-g, the refractive index n, and the thickness of the thin film t. Interestingly, the dependences of E-g on the fabrication temperatures of the pure ZnO and Al doped ZnO are different. It shows that the band gap energy of the pure ZnO thin films increases and saturates with temperatures, however, E-g of Al doped ZnO thin films show an exponential decrease behaviour. The refractive index and the thickness of the thin films determined by the ellipsometer data are also presented and discussed. (C) 2003 Elsevier Science B.V. All rights reserved.