Defining and Applying Coatings in ZEMAX is a topic unto itself, and is covered in detail in the “Defining coatings in ZEMAX” section of Chapter 20 in the ZEMAX User’s Guide.  ZEMAX can model any type of thin-film coating, including multilayer dielectric and metallic coatings.  However, we will limit our discussion in this article to constructing and applying simple, ideal coatings in ZEMAX. 

Like all coatings in ZEMAX, ideal coatings are created in a coating file consisting of sections of data defining materials, tapers, and coatings.  For one ideal coating, the syntax is simply:

IDEAL <name> <Transmitted Intensity> <Reflected Intensity>

IDEAL coatings are defined by only the intensity transmission and reflection coefficients, and are independent of ray wavelength or angle of incidence.  The absorption coefficient is computed automatically via A = 1.0 – R – T, to conserve energy.

IDEAL 60Reflect 40 60

will transmit 40% of the ray energy and reflect 60% of the energy, independent of the wavelength, incident angle; etc. 

The coatings made available in any single design in ZEMAX are defined in the “Coating File” as listed in the System General dialog.



The COATING.DAT file, which is the default coating file, is simply an ASCII text file which consists of sections of data relative to various types of coatings in ZEMAX.  This file may be modified to include other user-defined coatings.  If any additions or changes are made, it is always recommended that the file be saved under a different name.  Otherwise, updated installations of ZEMAX can overwrite the default coating file. 

Open the COATING.DAT file via a text editor/viewer (such as Notepad).  There are several simple ideal coatings which currently exist in the file, but none of which match the reflection/transmission ratio that we wish to model in this demonstration.



In the current example, we want 60% reflection from a mirrored surface.  Thus, the transmission is 40%.  We need to insert an ideal coating which represents these percentages:


Once the new ideal coating has been entered into the coating file, save the file under an appropriate filename, such as MYCOATING.DAT.  Note that the extension MUST end in .DAT and saved into the same directory as the COATING.DAT file.