Experimental determination of optical constants in the vacuum ultra violet wavelength region between 80 and 140nm: A reflectance versus thickness method and its application to ZnSe

Experimental determination of optical constants of MgF2 and AlF3 thin films in the vacuum ultra-violet wavelength region (60–124nm), and its application to optical designs

“…The first part of this paper is devoted to the determination of (n, k) index values in the VUV domain of thin films of two materials particularly relevant in this spectral range: MgF 2 and AlF 3 . We use a method we have developed [3] and present it in the next section.…”

“…6. The n(k) and k(k) values selected in Palik's tables for MgF 2 crystals are given for comparison [2] (no values in Palik's tables for AlF 3 ). An absolute uncertainty varying from 10 À2 to some 10 À2 affects values of n and k obtained by graphical determination in the range 60-124 nm.…”

“…The reflectivity finally measured on the real mirror may be then found very different from that calculated from the model. In order to prevent such failures, we have developed a method particularly suited to the determination of optical constants in the VUV region which we detailed in a previous paper [3]. This two media reflectance method at normal incidence provides a graphic determination of the complex index (n, k) of thin films of the material analyzed, versus wavelength.…”

Polarizing and non-polarizing mirrors in far UV for the Hydrogen Lyman-α radiation (λ = 121.6 nm)

“…This technique was then used to control the actual value of the thickness of each of the successive layers forming the mirror coating. Indices were determined by using the graphical method we developed [3,4]. It is briefly described in the next paragraph.…”

“…For this reason, optical constant values are often either unknown or very dependent on the measurement conditions [1,2], thus making it difficult to design a desired component. We have developed a method particularly suited to the determination of optical constants in the VUV region [3,4] which enabled us to model and optimize reliably polarizing and non polarizing mirrors to be used at = 121.6 nm.…”