Facilities

Equipment for characterization of optical films

To study optical anisotropy of LC layers and functional films, 3D orientational molecular ordering in the films, we actively use transmission null ellepsometry (TNE) technique based on Senarmont method.

The optical scheme of this method is presented below. The probe beam (628 nm) linearly polarized at 45° with respect to vertical line is directed to anisotropic sample. The sample is oriented so that its x or y in-plane axis is vertical. Passing the sample, the testing beam becomes elliptically polarized. The elliptical polarization is transformed back to linear by a quarter wave plate with a slow axis parallel to that of the polarizer. The angle ϕ of output polarization, determined by rotation of a linear analyzer, gives the in-plane retardation (ny-nx)d. Then the sample is rotated around the x axis vertically aligned and the polarization angle ϕ is measured as a function of the incidence angle θ. The out-of-plane retardation (nz-nx)d is determined by fitting a theoretical expression of ϕ(θ).

Scheme of null ellipsometry setup

Photograph of null ellipsometry setup