Gradual Evolution (Advanced)

For advanced users Gradual Evolution procedure (alone or in combination with other OptiLayer tools) provides a variety of design options, especially for problems with specific requirements. Here we present only one example. We design multilayer coatings reflecting different colors from their front and back sides (see upper and lower rows of the right pane picture).

optical coatings with color properties
 metal-dielectric coating

Materials: TiO2, SiO2 and SiO2-Ag sandwich (see left pane).

Due to specific optical properties of SiO2-Ag sandwiches and technological reasons, design is to satisfy the following requirements:

  • Only one Ag layer;
  • Thicknesses of SiO2 layers surrounding SiO2-Ag layers are not less than 40 nm.

Starting design - 3-layer sandwich with thicknesses of SiO2 layers are 78 nm and thickness of Ag layer is 12 nm. The choice of the starting design is explained by the fact that we carefully characterized Ag layers in such sandwiches and knew dependencies of their refractive index and extinction coefficients not only on the wavelength but on film thickness.

Thicknesses of layers in the starting design have status F (Fixed).


 design metal-dielectric coatings
 design metal-dielectric coatings

In the course of the Gradual Evolution the layers can be inserted either near the substrate or near the incidence medium, but not into the sandwich (put the mouse on the picture)

design metal dielectric coatings

metal dielectric coatings 

After Constrained Optimization step the color performance is improved (see the picture on the left).

constrained optimization

See the details in our publications:

  1. V. Janicki, T.V. Amotchkina, J. Sancho-Parramon, H. Zorc, M.K. Trubetskov, and A.V. Tikhonravov. "Design and production of bicolour reflecting coatings with Au metal island fims." Opt. Express 19, 25521-25527 (2011).
  2. T. V. Amotchkina, J. Sancho-Parramon, V. Janicki, M. K. Trubetskov, H. Zorc, A.V. Tikhonravov, Design of multilayer coatings containing metal island films, Proc. SPIE. 8168, Advances in Optical Thin Films IV 816809 (2011)