The correlation between the optical properties and composition of lithium niobate films is investigated in films deposited by laser ablation of single‐crystal LiNbO3and Li enriched LiNbO3sintered targets under different oxygen pressures and laser fluences. The results show that the variation of the film refractive index is in many cases related to the deposition process itself, rather than to a variation of the film composition. The experimental conditions to produce stoichiometric films with optical properties similar to those of the bulk material are discussed. ©1995 American Institute of Physics.