Optical characterization of materials deposited by different processes:: the LaF3 in the UV-visible region.

The optical characterization of materials in thin film phase is a standard task in the field of coating technology. There are experimental circumstances where the accurate comparison between several deposition processes (for the same material) is important. In these cases, several sets of substrates are coated at the different deposition plants. The samples will be subsequently analyzed using, if the plants are at different locations, different spectrophotometers and finally the results of all the optical characterizations will be compared. The aim of this work is to present the results of a global procedure for the optical characterization of LaF3 in the W-visible region, deposited at three different plants. We have used R and T spectrophotometric data and we have assumed the following model for the optical characterization: n(lambda)=n(0)+ n(1)/lambda (2), k(lambda)=k(0) exp(k(1)/lambda). Our method characterizes all the samples from the same deposition process by a single set of parameters (instead of a set for each sample), using all the available measurements to determine them in a single numerical fitting, without a significant loss in the quality of the fittings. This procedure reduces the number of parameters and makes the comparison between different deposition processes more clear. By using similar results obtained for MgF2, the optical characterization of stacks (manufactured using MgF2 and LaF3) is also presented.