Characterization of e-beam evaporated Ge, YbF 3 , ZnS, and LaF 3 thin films for laser-oriented coatings

Thin films of Ge, ZnS, ${{\rm YbF}_3}$YbF3, and ${{\rm LaF}_3}$LaF3 produced using e-beam evaporation on ZnSe and Ge substrates were characterized in the range of 0.4–12 µm. It was found that the Sellmeier model provides the best fit for refractive indices of ZnSe substrate, ZnS, and ${{\rm LaF}_3}$LaF3 films; the Cauchy model provides the best fit for ${{\rm YbF}_3}$YbF3 film. Optical constants of Ge substrate and Ge film as well as extinction coefficients of ZnS, ${{\rm YbF}_3}$YbF3, ${{\rm LaF}_3}$LaF3, and ZnSe substrate are presented in the frame of a non-parametric model. For the extinction coefficient of ZnS, the exponential model is applicable. Stresses in Ge, ZnS, ${{\rm YbF}_3}$YbF3, and ${{\rm LaF}_3}$LaF3 were estimated equal to $( - {50})\,\,{\rm MPa}$(−50)MPa, $( - {400})\,\,{\rm MPa}$(−400)MPa, 140 MPa, and 380 MPa, respectively. The surface roughness does not exceed 5 nm for all films and substrates.