Color Coatings

OptiLayer allows designing of all types of optical coatings with specified color properties.

OptiLayer supports color targets in all existing color coordinates systems:

  • CIE xyz 1931,
  • CIE UCS 1976,
  • CIE HoLC,
  • CIE C*hs(uv),
  • CIE L*a*b*,
  • Hunter Lab,
  • CIE YU'V' (1976)


Example: Coating changing color of the reflected light from Violet (at normal incidence) to Yellow (at AOI=50o)

multilayer color design

Example: Coating changing color of the reflected light from Red (at normal incidence) to Violet (at AOI=50o)

design optical coatings for color applications

Color Patch represents color variations in another way:

color patch

multilayer color design




Metal-dielectric Color Coatings

OptiLayer allows designing all types of metal-dielectric coatings. Even design with metal-island films is possible.

Example: One of the building blocks in such coatings is a metal island film (for example, Ag, Au) embedded into SiOe environment. Metal-dielectric composite Ag-SiO2 (Au-SiO2) can be represented as s thin layer with effective thickness \(\delta\).

Refractive index \(n(\lambda)\) and extinction coefficient \(k(\lambda)\) can be found from thin film characterization based on ellipsometric/photometric experimental data related to test samples (sandwiches of SiO2-Ag-SiO2 or SiO2-Au-SiO2). For this purpose, an unique non-parametric characterization approach of OptiLayer can be applied.

Schematic representation of a metal-dielectric sandwich.

color coatings

 refractive index metal dielectric film

extinction coefficient metal dielectric film


  • Layer combination SiO2-Ag-SiO2 should be kept unchanged in the course of the design process;
  • Thicknesses of SiO2 layers should be not less than 40 nm due to technological reasons;
  • Effective thickness of Ag layer is fixed because optical constants \(n(\lambda)\) and \(k(\lambda)\) are determined for each particular mass thickness of the metal layer. Example (left pane): refractive index and extinction coefficient of 12-nm Ag-SiO2 composite film.

Design Example: Coatings reflected light of different colors from their front and back sides. Transmittance of the sample should be more than 50%.

Many combinations of colors of the reflected light from front and back sides can be considered, for example:

  • Violet and Yellow;
  • Yellow and Green;
  • Violet and Pink;
  • Violet and Orange and so on.

Such coatings can be easily designed with the help of OptiLayer. Color coordinates of such coatings are shown on the chromaticity diagram on the right pane.

Number of layers is from 7 to 12

With effective thickness of Ag-SiO2 layer of 12 nm, averaged transmittance in the visible spectral range is about 60-65%.

Similar samples can be produced:

coatings for color applications

Learn more in our publications:

 chromaticity diagram

Coatings for Architectural Glass

Modern buildings and houses are often clad in double panes (double glazing) or triple panes (triple glazing) to enhance views and daylight. The optical qualities of the glass and its multilayer coatings are important from both practical and aesthetic pints of views.

Panes are manufactured with glass in range of thickness from 3 mm to 10 mm. Laminated or tempered glass may also be used as part of the construction.

OptiLayer allows designing all types of panes-coatings combinations and achieving any specified target specifications with the help of the powerful stack tool.

Simplified example: two glass panes with antireflection coatings on both of them.  

Target specifications:

  • maximize light transmittance (visible light); 
  • maximize solar transmittance;
  • provide colors of the reflected light in the range: -3<a*<2, -3<b*<2;
  • maximal Color Rendering Index (CRI);
  • working angular range is from 0 to 60 degrees;

coatings for architecture glass

OptiLayer allows simultaneous specifications of targets of different types: conventional, color, integral and electrical-field. In this particular design problem three types of targets are involved:

  • Conventional target (T=100% in the range from 300 nm to 2500 nm);
  • Integral Target: Light Transmittance=100%, Solar Transmittance=100%;

GlassPanes IntegralTarget

Spectral luminous efficiency \(V(\lambda)\) and spectral distribution of solar radiation \(S(\lambda)\), which are necessary for calculations, are built in OptiLayer (F1, F2). Of course, you can define and use your own spectral distributions (F3, F4, etc).

coatings for architecture glass coatings for architecture glass

Possible thin film materials: TiO2, SiO2, Silver.

Result: a double glazing with 8-layer metal-dielectric coatings on the internal surfaces.

OptiLayer allows evaluating integral values of spectral and color characteristics:

coatings double glazing


  •  Color target:

coatings for double glazed windows OptiLayer allows specifying color targets in all existing color coordinates systems.

One of the results:

Transmittance of the double glazing in the spectral range from 300 nm to 2500 nm for different angles of incidence.

coatings for windows

OptiLayer allows specifying targets weights. It means that depending on your preferences you will achieve a required balance between target specifications of different types.

Color coordinates for different incidence angles are plotted on the chromaticity diagram:

coatings for double glazed windows

Color Rendering Index is 90-95% in the whole angular range!

 Angle-Independent Color Mirror (Contest Problem)

In conjunction with the 2013 Optical Interference Coatings (OIC) topical meeting of the Optical Society of America (Tucson, Arizona), an angle-independent color mirror was a subject of a design contest held. Michael Trubetskov (developer of OptiLayer Software) and Weidong Shen (user of the OptiLayer Software) won this contest by submitting color mirror designs with a zero color difference between normal incidence and all other incidence angles up to 60° as well as the thinnest design. Many designers used OptiLayer Software in order to solve design contest problems. Learn more about the contest...
  • In the design problem it is required to design a greenish-color mirror that maintains the same perceived specular reflected color, under D65 source.
  • Polarization of averaged, angular range is from normal incidence to 60 degrees.
  • In order to determine if the reflected color at oblique incidence is perceptually similar to the reflected color at normal incidence, each angular color difference is calculated from normal incidence (referred to as the “anchor color”) using a CIE color difference equation, CIEDE2000.
  • Layer Thickness ≥ 3nm, Number of Layers ≤ 2000.
  • Lightness: L* ≥ 30.
  • Chroma: Cab* ≥ 100.
  • Hue Angle: 120° ≤ hab ≤ 180°

multilayers color coordinates

All-Dielectric Solution:

nsub = 1.52, ninc = 1.0

Layer Materials:

F = 1.38

L = 1.45

B = 1.65

M = 1.8

T = 2.15

H = 2.45

 coating designs color properties
 OIC design contest

Design tricks and approaches:

  • The breaker condition and the most complicated part – minimization of the design total physical thickness;
  • It can be done with standard Gradual Evolution, Needle Optimization techniques
    in OptiLayer; 
  • A special additional experimental target for minimization of total thickness was implemented in OptiLayer.
  • Additional simplex-type fine tuning based on GPU (Graphics Processor Unit) computations was applied. NVidia GTX 580 was used. GPU code was about 5-8 times faster than code running at two six-core Xeon 3.8 GHz CPUs.


Metal-Dielectric Solutions:

  • Main problem with metal layers – if used at the beginning of computations they become too thick and “shield” the rest of the stack.
  • To prevent this, special Trapping option of OptiLayer has been applied. 
  • When layer thickness appears within trapping limits – it becomes constrained automatically!

OIC design contest

 OIC design contest

A winning result: Design has 121 layers, total physical thickness of 4782.80003 nm, DE2000 = 0; 13 thin Ag layers.


Learn more: