This article shows how to create a coating file in Speos based on raw measurement data. Speos coatings are only defined and valid for rays crossing an interface in one direction.
Overview
The Speos *.coated format models a simple coating by defining the S and P polarization in :
- Reflection [%]
- Transmission [%]
- Absorption [%]
Each of these values are expressed in function of the wavelength [nm] and the incident angle [deg] without scattering.
The data can either be processed in the Coated Editor, requiring a Speos license, in plain text format *.txt in any text or spreadsheet editor. Any change in the text file will appear in the Coated Editor interface when saved with the *.coated file extension.
Structure of the file
Each line of the text file requires specific information to fit the format:
- Line 1 is compulsory to define the format.
- Line 2 either contains an optional comment or is left empty.
- Line 3 contains the number of incident angles and the number of wavelengths, separated by a single space.
Note: there should be no TABs in the first 3 lines.
- Line 4 starts with a TAB, and contains all wavelengths separated by a TAB
- Line 5 contains the first incident angle, a TAB, then each P polarised R and T values
- Line 6 starts with a TAB and contains each S polarised R and T value
- Continued for each incident angle:
Practical Tips
When creating the file without Speos license, the recommended workflow is to use a spreadsheet editor.
The example below can be copied and pasted into a spreadsheet or a text editor. The same file is available to download at the top right of this article:
| OPTIS - Coated surface file v1.0 | ||||||
| Coating File Example | ||||||
| 4 3 | ||||||
| 480 | 580 | 780 | ||||
| 0 | 31.9 | 68.1 | 1.5 | 98.5 | 25.7 | 74.3 |
| 31.9 | 68.1 | 1.5 | 98.5 | 25.7 | 74.3 | |
| 50 | 11.3 | 88.7 | 11.4 | 88.6 | 23.3 | 76.7 |
| 11.3 | 88.7 | 11.4 | 88.6 | 23.3 | 76.7 | |
| 70 | 15 | 85 | 15.2 | 84.8 | 26.3 | 73.7 |
| 15 | 85 | 15.2 | 84.8 | 26.3 | 73.7 | |
| 90 | 100 | 0 | 100 | 0 | 100 | 0 |
| 100 | 0 | 100 | 0 | 100 | 0 | |
Note: there should be no TABs in the first 3 lines. This is a common error when importing data from spreadsheets.
Once the correct number of incident angles and wavelengths is entered in the 3rd line, and all R & T values have been filled in for their respective P, S polarisation and wavelength, the file can be saved as text format. The file extension can then be changed to .coated
Ignore the warning about changing the filename extension by clicking "Yes".
The resulting .coated file can be opened in Speos using the Coated Surface Editor:
Using the Coated Surface Editor in Speos
This editor requires a Speos license. Enter "Coated Surface Editor" in the Window search bar to open the application.
Data can be directly pasted in the table:
Options:
The options tab allows to change the value automatically calculated based on the other two: by default the Absorption coefficient is derived from the Reflection and Transmission coefficient:
It is also possible to force the S and P values to be the same:
Taking the model further
Since Speos coatings are only defined and valid for rays crossing an interface in one direction, a coating working in both directions can be achieved by defining a second coating to build a BSDF180 Surface (ansys.com)
Lumerical solvers are the tools of choice to design, model and optimize coatings. The following article shows an example coating creation in Lumerical, exported to .coated format to be used in Speos :
Zemax OpticStudio designs can now be imported directly in Speos using Optical Design Exchange (ansys.com) Coatings defined in Zemax OpticStudio will be automatically converted in Speos.