OptiLayer supports color targets in all existing color coordinates systems:

• CIE xyz 1931,

• CIE UCS 1976,

• CIE H^oLC,

• CIE C*hs(uv),

• CIE L*a*b*,

• Hunter Lab,

• CIE YU’V’ (1976)

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.

• 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.

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:

Learn more in our publications:

• T. Amotchkina, M. Trubetskov, A.Tikhonravov, J. Kruschwitz, Optical Design: Advanced thin-film software techniques improve design-to-fabrication workflow, Laser Focus World, January 2015
• 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).
• 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, Vol. 8168, 816809 (2011), in Marseille, France.

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;

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

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).

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

OptiLayer allows evaluating integral values of spectral and color characteristics:

•  Color target:

OptiLayer allows specifying color targets in all existing color coordinates systems.

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

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

• 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° ≤ h_ab ≤ 180°

n_sub = 1.52, n_inc = 1.0

Layer Materials:

F = 1.38

L = 1.45

B = 1.65

M = 1.8

T = 2.15

H = 2.45

• 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.

• 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!

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

Learn more: https://www.osapublishing.org/ao/abstract.cfm?uri=ao-53-4-A360&origin=search